JP2011098688A - Vehicular suspension device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To expand a variable range of a damping force generated by an electromagnetic shock absorber 30.
An external circuit 100 is provided for causing a generated current to flow through a motor 40 by back electromotive force generated along with expansion and contraction of an electromagnetic shock absorber 30. The external circuit 100 includes a first connection path through which a generated current flows from the first terminal t1 to the second terminal t2 during the compression operation of the electromagnetic shock absorber 30, and a generated current from the second terminal t2 to the first terminal t1 during the extension operation. A second connection path that flows. The first connection path includes a parallel circuit of the first variable resistor VR1 and the first variable capacitor VC1, and the second connection path includes a parallel circuit of the second variable resistor VR2 and the second variable capacitor VC2.
[Selection] Figure 3

Description

  The present invention relates to a vehicle suspension device, and in particular, includes an electromagnetic shock absorber that damps the approaching / separating operation between the spring upper part and the unsprung part by generating a motor by the approaching / separating action between the spring upper part and the unsprung part. The present invention relates to a suspension device for a vehicle.

  Conventionally, an electromagnetic shock absorber driven by a motor is provided between an upper part and an unsprung part, and a vehicle suspension device that controls a motor so as to obtain a damping force according to a displacement input to the electromagnetic shock absorber. Is known from Patent Document 1 and the like. In the vehicle suspension apparatus proposed in Patent Document 1, an electrical damping element that passively generates damping force is connected in parallel with the motor, separately from the motor drive circuit that actively drives the motor, and the control target input While an active control is being performed for an input, an damping force is passively generated using an electrical damping element for an input other than the control target.

JP 2004-237824 A

  However, in order to drive the motor actively, the configuration becomes large and the cost is high. In addition, when generating a damping force passively, that is, when generating a damping force by passing a generated current to the motor, only a force proportional to the stroke speed between the spring top and the spring bottom can be generated. There is a limit to the damping force that can be produced. For example, when the stroke speed is slow, a large damping force cannot be generated.

  The present invention has been made to cope with the above-described problem, and an object of the present invention is to expand the variable range of the damping force in an electromagnetic shock absorber that generates a damping force by flowing a generated current to a motor.

  In order to achieve the above object, a feature of the present invention is that it includes a motor, and an operation conversion mechanism that converts an approach / separation operation between the spring upper portion and the spring unsprung into the operation of the motor, An electromagnetic shock absorber that generates a damping force with respect to the approaching / separating operation between the upper and lower springs by generating current flowing through the motor in accordance with the approaching / separating operation with the lower part; and An external circuit that is provided outside and connects between two energization terminals of the motor in order to flow a generated current to the motor, and a damping force that is generated by the electromagnetic shock absorber by controlling the generated current flowing in the external circuit A suspension system for a vehicle including a damping force control means for controlling the external circuit, wherein the external circuit includes a resistance circuit having a variable electric resistance, and a capacitor circuit having a variable capacitance. The damping force control means controls the damping force generated by the electromagnetic shock absorber by adjusting the electric resistance of the resistance circuit and the capacitance of the capacitor circuit. .

  In the present invention, the approach / separation operation (approach operation and separation operation) between the sprung portion and the unsprung portion is transmitted to the motor via the motion conversion mechanism. For example, a speed reducer such as a ball screw mechanism can be employed as the motion conversion mechanism. The motor generates an induced electromotive force in accordance with the approach / separation operation between the sprung portion and the unsprung portion. Therefore, by connecting the energization terminals of the motor to each other, a generated current flows through the motor, and a damping force can be generated with respect to the approach / separation operation between the spring upper part and the spring lower part. In order to flow this generated current, an external circuit is provided outside the motor. The damping force control means controls the damping force generated by the electromagnetic shock absorber by controlling the current flowing through the external circuit.

  The external circuit includes a resistor circuit having a variable electrical resistance (electric resistance value) and a capacitor circuit having a variable capacitance (capacitance value) in parallel. When the rotor of the motor is rotated by the approaching / separating operation of the upper and lower parts of the spring, an induced electromotive force is generated between the energization terminals, and a generated current flows to the motor via the external circuit. Therefore, the damping force can be controlled by adjusting the magnitude of the generated current by adjusting the electric resistance of the external circuit. In this case, the damping force adjusted by the electrical resistance is proportional to the stroke speed, which is the approach / separation speed between the sprung part and the unsprung part. I can't get it. Therefore, in the present invention, a capacitor circuit is provided in parallel with the resistor circuit in the external circuit, and the generated current flowing in the capacitor circuit is used for the damping force. The generated current flowing in the capacitor circuit is proportional to the stroke acceleration, which is the acceleration of the approach / separation operation between the sprung portion and the unsprung portion. The inertial force of the electromagnetic shock absorber is proportional to the stroke acceleration. Therefore, a force proportional to the inertial force of the electromagnetic shock absorber can be generated by the motor using the current component flowing in the capacitor circuit in the generated current flowing in the external circuit. That is, a part of the inertial force of the electromagnetic shock absorber can be converted into a damping force. This inertial force is advanced by 90 ° in phase with respect to the damping force. For this reason, the electromagnetic shock absorber can generate a damping force with high responsiveness.

  The damping force control means controls the damping force generated by the electromagnetic shock absorber by adjusting the electric resistance of the resistance circuit and the capacitance of the capacitor circuit. Therefore, the inertial force of the electromagnetic shock absorber can be variably controlled to generate a wide variable damping force with good responsiveness. As a result, the controllability of the damping force is improved even with a passive electromagnetic shock absorber that generates a damping force by flowing a generated current to the motor.

  Another feature of the present invention is that the external circuit is a first terminal that is one of the two current-carrying terminals of the motor and a second terminal that is the other when the sprung portion and the unsprung portion approach each other. A first connection path through which the generated current flows, and a second connection path through which the generated current flows from the second terminal to the first terminal during the separating operation of the spring upper part and the spring lower part, and the first connection A first resistance circuit having a variable electric resistance and a first capacitor circuit having a variable capacitance are provided in parallel on the path, and the second resistance circuit having a variable electric resistance and the capacitance are variable on the second connection path. A second capacitor circuit in parallel; and the damping force control means includes an electric resistance of the first resistor circuit and the second resistor circuit, and an electrostatic capacity of the first capacitor circuit and the second capacitor circuit. By adjusting the electromagnetic shock absolute It is to control the damping force generated by the server.

  In the present invention, circuits through which the generated current flows during the approaching operation and the separating operation of the sprung portion and the unsprung portion are separately provided. Each circuit (first connection path and second connection path) is provided with a resistor circuit and a capacitor circuit in parallel. Therefore, the damping force characteristic can be set independently for the approaching operation and the separating operation of the sprung portion and the unsprung portion.

  Another feature of the present invention is that stroke speed detecting means for detecting a stroke speed, which is a speed of an approach / separation operation between the spring upper part and the spring unsprung part, and an approach / separation between the spring upper part and the spring lower part. Stroke acceleration detecting means for detecting stroke acceleration which is an acceleration of operation, and the damping force control means adjusts the generated current flowing in the resistance circuit to a target damping within an adjustment range of damping force that can be generated. When a force is applied, the damping force is controlled by adjusting the electric resistance of the resistance circuit. When the target damping force is larger than the adjustment range of the damping force, the stroke speed and the stroke are controlled. When acceleration is in the same direction, in addition to the resistance circuit, a power generation current is supplied to the capacitor circuit to compensate for the deficiency of the damping force by adjusting the capacitance. A.

  In the present invention, the damping force control means adjusts the electric resistance of the resistance circuit when the target damping force falls within the adjustment range of the damping force that can be generated by adjusting the generated current flowing through the resistance circuit. Control the damping force. In this case, since the damping force that can be generated by the electromagnetic shock absorber is proportional to the stroke speed and inversely proportional to the electric resistance of the resistance circuit, the stroke speed detected by the stroke speed detecting means and the adjustment range of the electric resistance From this, it is possible to set the adjustment range of the damping force. The target damping force is arbitrarily set by the damping force control means. For example, the target damping force is set from the damping force control mode such as the ride comfort control mode, the steering stability (steering stability) control mode, the unsprung control mode, and the state of the vehicle.

  When the target damping force falls within the damping force adjustment range, the damping force control means can control the damping force to the target damping force without passing the generated current through the capacitor circuit. Control the damping force. In this case, for example, the capacitance of the capacitor circuit is zero, that is, the capacitor circuit is shut off, and the damping force is controlled only by adjusting the electric resistance of the resistor circuit.

  On the other hand, when the magnitude (absolute value) of the target damping force is larger than the adjustment range of the damping force, the damping force control means adds to the resistance circuit when the stroke speed and the stroke acceleration are in the same direction. The shortage of damping force is compensated for by adjusting the capacitance by passing the generated current through the capacitor circuit. Since the generated current flowing in the capacitor circuit is proportional to the stroke acceleration, when the stroke speed and the stroke acceleration are in the same direction (same sign), by passing the generated current through the capacitor circuit, this generated current is It acts as a damping force that attenuates the approach / separation operation with the unsprung part. Therefore, even when the stroke speed is slow, a force proportional to the stroke acceleration can be added as a damping force. At this time, since the damping force control means adjusts the capacitance of the capacitor circuit, an appropriate damping force can be generated.

  According to another aspect of the present invention, there is provided a moving direction detecting means for detecting a moving direction of the sprung part and a relative moving direction of the sprung part with respect to the unsprung part. When the movement direction of the upper part and the movement direction of the upper part of the spring relative to the lower part of the spring are opposite, the generated current is not passed through the resistance circuit, and the stroke speed and the stroke acceleration are The object is to control the propulsive force acting in the direction opposite to the damping force by adjusting the capacitance by passing a generated current through the capacitor circuit when the direction is opposite.

  The present invention can be used effectively when the sprung part is damped by skyhook control. In the skyhook control, a downward force is applied when the sprung portion moves upward, and an upward force is applied when the sprung portion moves downward to suppress vibration of the sprung portion. Therefore, when the movement direction of the sprung portion (the direction of the sprung absolute velocity) and the relative movement direction of the sprung portion with respect to the unsprung portion are opposite, a damping force is not generated by the electromagnetic shock absorber. . Therefore, the damping force control means prevents the generated current from flowing through the resistance circuit when the moving direction of the sprung portion is opposite to the relative moving direction of the sprung portion with respect to the unsprung portion. Minimizes the damping force generated by the shock absorber. In this case, when the stroke speed and the stroke acceleration are in opposite directions, if a generated current is passed through the capacitor circuit, a force in the direction opposite to the damping force, that is, a propulsive force can be generated by the generated current. Utilizing this fact, the damping force control means generates a propulsive force that works in the opposite direction to the damping force by causing the generated current to flow in the capacitor circuit when the stroke speed and the stroke acceleration are in the opposite directions. Propulsion is controlled by adjustment. As a result, it is possible to cause the electromagnetic shock absorber to generate a propulsive force that could not be achieved by passive control. As a result, the variable range of the damping force can be greatly expanded, and the controllability of the damping force is further improved.

  According to another aspect of the present invention, there is provided a notch detection means for detecting the start of turning of the steering wheel, and the damping force control means is normally attenuated by adjusting the electric resistance by flowing a generated current through the resistance circuit. The force is controlled, and at the start of the turning of the steering wheel, the generation force is supplied to the capacitor circuit in addition to the resistor circuit to increase the damping force.

  When the steering handle is cut, in order to ensure steering stability, it is necessary to generate a large damping force in the electromagnetic shock absorber so that the tire is in close contact with the road surface. Therefore, the present invention is provided with a notch detection means for detecting the start of turning of the steering handle. When the start of turning of the steering handle is detected by the notch detecting means, the damping force control means has a resistance at the start of the notch. In addition to the circuit, the generated current is passed through the capacitor circuit to increase the damping force. In other words, the damping force control means controls the damping force by adjusting the electric resistance by flowing a generated current through the resistance circuit in a normal time that is not at the start of the steering wheel turning. The generated current is supplied to both the circuit and the damping force is increased. Since the force that can be generated by the generated current flowing in the capacitor circuit is proportional to the stroke acceleration, the phase is advanced by 90 ° from the force that can be generated by the generated current flowing in the resistor circuit. Therefore, the damping force due to the generated current flowing in the capacitor circuit can be applied from the time when the stroke speed starts to increase, and the response is good. As a result, according to the present invention, good steering stability can be obtained with a simple configuration. Note that the incision detecting means may detect the start of incision of the steering wheel from the change in the steering angle of the steering wheel. For example, the incision of the steering wheel is indirectly based on a change in lateral acceleration or yaw rate acting on the vehicle. Start may be detected

  Another feature of the present invention is provided with a steering speed detecting means for detecting a steering speed, and the damping force control means has a low steering speed when a generated current is supplied to the capacitor circuit at the start of turning of the steering handle. The purpose is to increase the capacitance of the capacitor circuit.

  When the steering handle is turned slowly at the start of turning of the steering handle, the stroke speed that is the speed of the approaching / separating operation between the sprung portion and the unsprung portion is slow, so that the damping force is small and the generation of the damping force is also slowed. Therefore, in the present invention, when the generated current is supplied to the capacitor circuit at the start of turning of the steering wheel, the capacitance of the capacitor circuit is set to be larger as the steering speed is lower. Therefore, even when the steering speed is low, a generation current having an appropriate magnitude can be supplied to the capacitor circuit. As a result, an appropriate damping force according to the steering speed can be added, and good steering stability can be obtained.

1 is a system configuration diagram of a suspension device according to an embodiment of the present invention. It is sectional drawing showing schematic structure of a suspension main body. It is a circuit block diagram of an external circuit. It is a block diagram of a variable capacitor. It is a model figure of a suspension apparatus. It is a flowchart showing the damping force control routine of 1st Embodiment. It is a flowchart showing the damping force control routine of 2nd Embodiment. It is a flowchart showing the electrostatic capacitance control routine of 2nd Embodiment. It is a map showing the relationship between a steering speed and an electrostatic capacitance.

  Hereinafter, a vehicle suspension apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows a system configuration of a vehicle suspension apparatus according to the embodiment.

  This suspension device includes four sets of suspension bodies 10FL, 10FR, 10RL, 10RR provided between the wheels WFL, WFR, WRL, WRR and the vehicle body B, and the operations of the suspension bodies 10FL, 10FR, 10RL, 10RR. And an electronic control unit 50 for controlling. Hereinafter, the four sets of the suspension bodies 10FL, 10FR, 10RL, and 10RR and the wheels WFL, WFR, WRL, and WRR are simply collectively referred to as the suspension body 10 and the wheels W unless otherwise distinguished from front and rear. The electronic control unit 50 is referred to as an ECU 50.

  As shown in FIG. 2, the suspension body 10 is provided between the lower arm LA that supports the wheel W and the vehicle body B, absorbs the impact received from the road surface, enhances the riding comfort, and elastically supports the weight of the vehicle body B. A coil spring 20 as a suspension spring and an electromagnetic shock absorber 30 that generates a damping force against vertical vibration of the coil spring 20 are provided in parallel. Hereinafter, the upper side of the coil spring 20, that is, the vehicle body B side is referred to as “spring top”, and the lower side of the coil spring 20, that is, the wheel W side is referred to as “spring bottom”.

  The electromagnetic shock absorber 30 includes an outer cylinder 31 and an inner cylinder 32 that are arranged coaxially, a ball screw mechanism 35 that is a reduction gear provided inside the inner cylinder 32, and a rotor (illustrated) by the operation of the ball screw mechanism 35. An electric motor 40 (hereinafter simply referred to as the motor 40) that generates an induced electromotive force. In the present embodiment, a brushed DC motor is used as the motor 40.

  The outer cylinder 31 and the inner cylinder 32 are constituted by coaxial different diameter pipes, and the outer cylinder 31 is provided on the outer periphery of the inner cylinder 32 so as to be slidable in the axial direction. In the figure, reference numerals 33 and 34 denote bearings that slidably support the inner cylinder 32 in the outer cylinder 31.

  The ball screw mechanism 35 corresponds to the motion conversion mechanism of the present invention, and includes a ball screw 36 that rotates integrally with the rotor of the motor 40, and a female screw portion 38 that is screwed into a male screw portion 37 formed on the ball screw 36. And a ball screw nut 39 having The ball screw nut 39 is restricted by a rotation stopper (not shown) so that it cannot rotate. Therefore, in this ball screw mechanism 35, the linear motion of the ball screw nut 39 in the vertical axis direction is converted into the rotational motion of the ball screw 35. Conversely, the rotational motion of the ball screw 36 is converted into the vertical axis direction of the ball screw nut 39. Is converted into a linear motion.

  The lower end of the ball screw nut 39 is fixed to the bottom surface of the outer cylinder 31. When an external force is applied to the ball screw 36 to move the outer cylinder 31 in the axial direction, the ball screw 36 rotates. The motor 40 is rotated. At this time, the motor 40 generates an induced electromotive force in the electromagnetic coil by causing an electromagnetic coil (not shown) provided in the rotor to cross a magnetic flux generated from a permanent magnet (not shown) provided in the stator, thereby generating a generator. Work as.

  The upper end of the inner cylinder 32 is fixed to the mounting plate 41. The mounting plate 41 is fixed to the motor casing 42 of the motor 40, and the ball screw 36 is inserted through a through hole 43 formed at the center thereof. The ball screw 36 is connected to the rotor of the motor 40 in the motor casing 42 and is rotatably supported by a bearing 44 in the inner cylinder 32.

  The coil spring 20 is interposed in a compressed state between an annular retainer 45 provided on the outer peripheral surface of the outer cylinder 31 and a mounting plate 46 of the motor 40. The suspension body 10 configured in this manner is attached to the vehicle body B via the upper support 26 made of an elastic material on the upper surface of the attachment plate 46.

  When the lower part of the spring (wheel W) moves up and down while the vehicle is running, the outer cylinder 31 slides in the axial direction relative to the inner cylinder 32 and the coil spring 20 expands and contracts to absorb the impact received from the road surface. It enhances the ride comfort and supports the weight of the vehicle. At this time, the ball screw nut 39 moves up and down with respect to the ball screw 36 to rotate the ball screw 36. For this reason, the motor 40 generates a resistance force to stop the rotation of the rotor when the rotor rotates and an induced electromotive force is generated in the electromagnetic coil and a generated current flows through the external circuit 100 described later. This resistance force acts as a damping force of the electromagnetic shock absorber 30. The damping force can be adjusted by adjusting the magnitude of the current flowing in the electromagnetic coil of the motor 40 by the external circuit 100 provided for each electromagnetic shock absorber 30.

  Next, a configuration for controlling the operation of the electromagnetic shock absorber 30 will be described. The electromagnetic shock absorber 30 is controlled by the ECU 50 via an external circuit 100 provided outside the motor 40. The ECU 50 includes a microcomputer as a main part, and performs damping force control by adjusting the amount of current flowing through the motor 40 of the electromagnetic shock absorber 30 by switching control of the external circuit 100. As will be described later, this damping force control is performed independently for each electromagnetic shock absorber 30 at each wheel position by switching control of the external circuit 100 corresponding to the electromagnetic shock absorber 30.

  A stroke sensor 61, a sprung acceleration sensor 62, an unsprung acceleration sensor 63, and a lateral acceleration sensor 64 are connected to the ECU 50. The stroke sensor 61 is disposed in the vicinity of each electromagnetic shock absorber 30, and the vertical separation distance between the spring upper portion and the spring lower portion, that is, the expansion / contraction length of the electromagnetic shock absorber 30 (hereinafter referred to as stroke X). Is detected. The sprung acceleration sensor 62 is disposed at a position where the suspension bodies 10FL, 10FR, 10RL, 10RR are attached to the upper part of the spring, and the vertical acceleration of the upper part of the spring (hereinafter referred to as the sprung acceleration Gu). Detected). The unsprung acceleration sensor 63 is disposed on the unsprung portion (for example, the lower arm LA) connected to each suspension body 10FL, 10FR, 10RL, 10RR, and the unsprung acceleration in the vertical direction (hereinafter referred to as unsprung acceleration). Gd) is detected. The sprung acceleration sensor 62 and the unsprung acceleration sensor 63 detect an upward acceleration as a positive acceleration and a downward acceleration as a negative acceleration. The lateral acceleration sensor 64 is attached to the top of the spring and detects a lateral acceleration Gy that acts on the vehicle when the vehicle turns. The ECU 50 is connected to a CAN (Controller Area Network) communication system, and can acquire various types of vehicle information via a CAN communication line. In the present embodiment, the ECU 50 acquires information indicating the steering speed ωh of the steering wheel via the CAN communication line. Instead of the steering speed ωh, information representing the steering angle θh of the steering wheel may be acquired, and the steering speed ωh may be obtained by calculation by differentiating the steering angle θh.

  In the present embodiment, two embodiments (first embodiment and second embodiment) will be described for damping force control of the electromagnetic shock absorber 30. In the first embodiment, an unsprung acceleration sensor is used. 63, the lateral acceleration sensor 64 is not used.

  Next, the external circuit 100 will be described with reference to FIG. The external circuit 100 generates an induced electromotive force generated by the motor 40 when the rotor of the motor 40 is rotated through the ball screw mechanism 35 by the relative motion of the upper part of the spring (vehicle body B side) and the lower part of the spring (wheel W side). Therefore, when the induced electromotive force (induced voltage) of the motor 40 is large, the generated current is allowed to flow between the energization terminals of the motor 40 (between the first terminal t1 and the second terminal t2). Also, a part of the generated current flows through the power storage device 110 to charge the power storage device 110. In the figure, Rm represents the internal resistance of the motor 40 and Lm represents the motor inductance. In this figure, Rm and Lm are described outside the display symbol M of the motor 40, but in reality, Rm and Lm exist between the first terminal t1 and the second terminal t2. .

  The external circuit 100 includes a wiring ab that electrically connects the first terminal t1 and the second terminal t2 of the motor 40 at points a and b, and a wiring cd that electrically connects the points c and d. A wiring ef that electrically connects the point e and the point f is provided. In the figure, since the wiring is a line connecting the points (a, b, c...), The reference numerals are not shown. The wiring ab has a first diode D1 that allows a current flow in the direction from the point a to the point b and prevents a current flow in the direction from the point b to the point a, and a direction in the direction from the point b to the point a. A second diode D2 that allows current flow and blocks current flow in the direction from point a to point b is provided. In the wiring cd, a first switching element SW1, a first resistor R1, a second resistor R2, and a second switching element SW2 are provided in series in this order from the point c. The first resistor R1 and the second resistor R2 are fixed resistors that set a damping force. In the present embodiment, MOS-FETs are used as the first switching element SW1 and the second switching element SW2, but other switching elements can also be used. Each of the first switching element SW1 and the second switching element SW2 has a gate connected to the ECU 50, and is configured to be turned on / off at a duty ratio set by a PWM (Pulse Width Modulation) control signal from the ECU 50. The duty ratio in this specification represents an on-duty ratio, that is, a ratio of an on-time of the pulse signal to a time obtained by adding the on-time and off-time of the pulse signal.

A first variable capacitor VC1 and a second variable capacitor VC2 are provided in series on the wiring ef. As shown in FIG. 4, each of the first variable capacitor VC1 and the second variable capacitor VC2 includes three capacitors C1, C2, and C3 having fixed (known) capacitances connected in parallel. Switches SWC1, SWC2, and SWC3 (for example, semiconductor switches such as MOS-FETs) are provided in series with C1, C2, and C3. The switches SWC1, SWC2, and SWC3 have gates connected to the ECU 50, respectively, and are turned on / off by a signal from the ECU 50. Accordingly, the first variable capacitor VC1 and the second variable capacitor VC2 can change their capacitances in eight ways by switching the combination of the on / off states of the switches SWC1, SWC2, and SWC3, respectively. Hereinafter, the switches SWC1, SWC2, and SWC3 are referred to as capacitance adjustment switches SWC1, SWC2, and SWC3, and the capacitance of the first variable capacitor VC1 set by the capacitance adjustment switches SWC1, SWC2, and SWC3 is C _1x and the second variable. the capacitance of the capacitor VC2 and _{C 2x.} In this case, the capacitances C _1x and C _2x become zero when the capacitance adjustment switches SWC1, SWC2 and SWC3 are all turned off, and the capacitance C when the capacitance adjustment switches SWC1, SWC2 and SWC3 are all turned on. _1x and _C2x are maximized. The capacitances of the capacitors C1, C2, and C3 may be the same or different, and may be set according to the required variable width of the capacitance.

  Returning to the description of the external circuit 100 in FIG. The first terminal t1 and the point a are electrically connected by a wiring t1a, and the second terminal t2 and the point b are electrically connected by a wiring t2b. A current sensor 111 is provided in the wiring t1a. The current sensor 111 detects a current flowing through the motor 40 and outputs a detection signal representing a measured value ix (referred to as an actual current ix) including information indicating the energization direction to the ECU 50. The current sensor 111 is used for damping force control in the second embodiment.

  Further, the point g between the first diode D1 and the second diode D2 in the wiring ab, the point h between the first variable capacitor VC1 and the second variable capacitor VC2 in the wiring ef, and the first resistance in the wiring cd. The point i between the resistor R1 and the second resistor R2 is electrically connected by the wiring ghi. A first charging path jm that is a charging path to the power storage device 110 provided as an in-vehicle power supply battery is provided at a branch point j that is a connection point between the first switching element SW1 and the first resistor R1. It is done. Further, a second charging path km serving as a charging path to the power storage device 110 is branched and provided at a point k serving as a connection point between the second switching element SW2 and the second resistor R2. The first charging path jm and the second charging path km are connected to a main charging path mn that connects the point m and the positive electrode n of the power storage device 110. Further, the point i and the negative electrode o of the power storage device 110 are connected by a ground line oi. Note that various electric loads provided in the vehicle are connected to the power storage device 110.

  The first charging path jm is provided with a third diode D3 that allows a current flow in the direction from the j point to the m point and blocks a current flow in the direction from the m point to the j point. The second charging path km is provided with a fourth diode D4 that allows a current flow in the direction from the k point to the m point and blocks a current flow in the direction from the m point to the k point. That is, the charging circuit is configured to allow charging from the external circuit 100 to the power storage device 110 and to prevent discharging from the power storage device 110 to the external circuit 100.

  Next, the operation of the external circuit 100 will be described. When the rotor is rotated via the ball screw mechanism 35 by the relative movement between the spring top and the spring bottom, the motor 40 generates an induced electromotive force in a direction corresponding to the rotation direction. For example, during the compression operation in which the upper part of the spring and the lower part of the spring approach each other and the electromagnetic shock absorber 30 is compressed, the first terminal t1 of the motor 40 becomes a high potential and the second terminal t2 becomes a low potential. On the contrary, when the electromagnetic shock absorber 30 is extended by separating the sprung portion and the unsprung portion, the second terminal t2 of the motor 40 becomes a high potential and the first terminal t1 becomes a low potential.

  Therefore, during the compression operation in which the electromagnetic shock absorber 30 is compressed, the generated current flows from the first terminal t1 to the point e, and flows to the parallel circuit of the wiring eh and the wiring ecih at the point e. It returns to the second terminal t2 through the point b. A current path through which the generated current flows during the compression operation is referred to as a first connection path echgb. Further, during the extension operation in which the electromagnetic shock absorber 30 is extended, the generated current flows from the second terminal t2 to the point f, and flows to the parallel circuit of the wiring fh and the wiring fdih at the point f. , The point a is returned to the first terminal t1. A current path through which the generated current flows during the extension operation is referred to as a second connection path fdhga. As described above, the external circuit 100 is configured such that the circuit through which the generated current flows is different between the compression operation and the expansion operation of the electromagnetic shock absorber 30, as indicated by the thick broken line arrows in FIG.

In this example, the first resistor R1 becomes a resistance against the generated current flowing in the wiring ecih during the compression operation of the electromagnetic shock absorber 30, and the first switching element SW1 adjusts the magnitude (energization amount) of the generated current. Functions as a current regulator. Accordingly, a first variable resistor VR1 (corresponding to the first resistor circuit of the present invention) having a variable electric resistance is configured by a series circuit of the first resistor R1 and the first switching element SW1. Similarly, the second resistor R2 becomes a resistance to the generated current flowing through the wiring fdih during the extension operation of the electromagnetic shock absorber 30, and the second switching element SW2 is a current that adjusts the magnitude (energization amount) of the generated current. Functions as a regulator. Therefore, the series circuit of the second resistor R2 and the second switching element SW2 constitutes a second variable resistor VR2 (corresponding to the second resistor circuit of the present invention) whose electric resistance is variable. Hereinafter, the electrical resistance of the first variable resistor VR1 is R _1x , and the electrical resistance of the second variable resistor VR1 is R _2x .

As described above, in the external circuit 100, the first connection path echgb includes a parallel circuit of the first variable resistor VR1 and the first variable capacitor VC1 and the first diode D1 in series. The connection path fdhga has a configuration in which a parallel circuit of the second variable resistor VR2 and the second variable capacitor VC2 and a second diode D2 are provided in series. Thus, during the compression operation of the electromagnetic shock absorber 30, by adjusting the capacitance C _1x electrical resistance R _1x and first variable capacitor VC1 of the first variable resistor VR1, the generated current flowing through the motor 40 And adjusting the electric resistance R _2x of the second variable resistor VR2 and the capacitance C _2x of the second variable capacitor VC2 during the extension operation of the electromagnetic shock absorber 30. Thus, the magnitude of the generated current flowing through the motor 40 can be adjusted.

When a generated current flows through the electromagnetic coil of the motor 40, a power generation brake acts on the motor 40, thereby suppressing relative rotation between the ball screw nut 39 and the ball screw 36. That is, a damping force that suppresses the relative motion between the sprung portion and the unsprung portion is generated. Further, the damping force can be adjusted by adjusting the magnitude of the generated current. Therefore, the damping force for the compression operation can be set by adjusting the electric resistance R _1x of the first variable resistor VR1 and the capacitance C _1x of the first variable capacitor VC1, and the electric resistance R _{2x of} the second variable resistor VR2 The damping force for the extension operation can be set by adjusting the capacitance C _2x of the second variable capacitor VC2. For this reason, a damping force can be set independently for the compression operation direction and the extension operation direction of the electromagnetic shock absorber 30.

  Also, such adjustment of the damping force can be performed independently for each wheel by energization control of the external circuit 100 of the electromagnetic shock absorber 30.

  The induced electromotive force generated by the motor 40 increases as the motor rotation speed increases. When the induced electromotive force (induced voltage) exceeds the output voltage (storage voltage) of power storage device 110, a part of the power generated by motor 40 is regenerated in power storage device 110. For example, during the compression operation of the electromagnetic shock absorber 30, the generated current is divided in two directions at point j, one flows through the first connection path as it is, and the other flows through the first charging path jm. Therefore, the power storage device 110 is charged by the generated current that flows through the first charging path jm. Further, when the electromagnetic shock absorber 30 is extended, the generated current is divided in two directions at the point k, one flows through the second connection path as it is, and the other flows through the second charging path km. Therefore, the power storage device 110 is charged by the generated current that flows in the second charging path km.

Here, the damping force adjusted by the variable resistors VR1 and VR2 and the variable capacitors VC1 and VC2 will be described. Here, an example in which the electromagnetic shock absorber 30 is compressed will be described. When the electromagnetic shock absorber 30 is compressed and an induced electromotive force v (induced voltage v) is generated in the motor 40, a generated current flows through the first variable resistor VR1 and the first variable capacitor VC1. The current ir1 flowing through the first variable resistor VR1 and the current ic1 flowing through the first variable capacitor VC1 can be expressed by the following equations.
ir1 = v / R _1x (1)
ic1 = svC _1x (2)
R _1x is the electrical resistance of the first variable resistor VR1, C _1x is the capacitance of the first variable capacitor VC1, and s is a Laplace operator. Here, the motor internal resistance Rm and the motor inductance Lm are omitted as being small.

A current (ir1 + ic1) obtained by combining the current ir1 and the current ic1 flows through the electromagnetic coil of the motor 40. Therefore, the torque T generated by the motor 40 can be expressed as the following equation.
T = Km (ir1 + ic1) = Km (v / R _1x + svC _1x ) (3)
Km is a motor torque constant.

Further, the induced electromotive force v generated by the motor 40 can be expressed by the following equation.
v = (2π / N) X′Km (4)
Here, N is the lead of the ball screw 36, and X ′ is the stroke speed (differential value of the stroke X) of the electromagnetic shock absorber 30.
Further, the damping force F generated by the motor 40 can be expressed as the following equation.
F = (2π / N) T (5)
Accordingly, the damping force F is expressed as the following equation by substituting the equations (3) and (4) into the equation (5).
F = (2π / N) ² Km ² ((1 / R _1x ) X ′ + C _1x X ″) (6)
Here, X ″ is a stroke acceleration (second-order differential value of the stroke X).

As can be seen from this equation (6), (2π / N) ² Km ² (1 / R _1x ) X ′ is a damping force that can be varied by adjusting the electric resistance of the first variable resistor VR1, and (2π / N ) ² Km ² C _1x X ″ is a damping force that can be varied by adjusting the capacitance of the first variable capacitor VC1. The former is called R adjustment damping force, and the latter is called C adjustment damping force. Is generated with a magnitude proportional to the stroke speed X ′. On the other hand, the C adjustment damping force is generated with a magnitude proportional to the stroke acceleration X ″. Since the inertial force of the ball screw mechanism 35 (including the rotor of the motor 40) is generated with a magnitude proportional to the stroke acceleration X ″, this C adjustment damping force converts a part of the inertial force into a damping force. Therefore, by adjusting the capacitance of the first variable capacitor VC1, the amount for converting the inertial force into the damping force can be varied.

  When the electromagnetic shock absorber 30 is vibrating in a stroke, the stroke acceleration X ″ is advanced in phase by 90 ° with respect to the stroke speed X ′. For this reason, the stroke speed X ′ is small and the R adjustment damping force cannot be quickly increased. Even in the situation, it is possible to generate an appropriate damping force with good responsiveness by adding the previously generated C adjustment damping force.

Even when the electromagnetic shock absorber 30 is extended, the operating principle is the same as that during the compression operation described above. In this case, the generated current flows through the second connection path fdhga. Further, the damping force F can be expressed as the following equation.
F = (2π / N) ² Km ² ((1 / R _2x ) X ′ + C _2x X ″) (7)
Here, R _2x is the electric resistance of the second variable resistor VR2, and C _2x is the capacitance of the second variable capacitor VC2.

Next, two embodiments of the damping force control process executed by the ECU 50 will be described.
<First Embodiment>
In the first embodiment, the vibration of the sprung portion is damped based on the skyhook control. FIG. 5 is a conceptual diagram showing a suspension model based on the skyhook damper theory. In this model, the sprung portion is supported by a skyhook damper SD fixed to one point in absolute space. In the skyhook control, a downward force is applied when the sprung portion moves upward, and an upward force is applied when the sprung portion moves downward to suppress vibration of the sprung portion. If the damping coefficient of the skyhook damper SD (skyhook damping coefficient) is St, the damping force Fs generated by the skyhook damper SD is
Fs = −St · Xu ′
Represented as: Here, Xu ′ represents a sprung speed that is a vertical speed of the sprung portion. The sprung speed Xu ′ is calculated by time integration of the sprung acceleration Gu detected by the sprung acceleration sensor 62, and the speed at which the sprung heads upward is expressed as a positive value.

The ECU 50 causes the electric resistances R _1x and R _2x of the variable resistors VR1 and VR2 and the electrostatic capacitances of the variable capacitors VC1 and VC2 so that the motor 40 generates a damping force F corresponding to the skyhook damping force Fs. C _1x , C _2x is calculated, and the electric resistance R _1x , R _2x , and capacitance C _1x , C _2x are controlled within the range in which the duty ratios of the switching elements SW 1, SW ₂ are controlled, and the capacitance adjustment switch SWC1, SWC2, and SWC3 are switched on / off. Hereinafter, the damping force control process executed by the ECU 50 will be described with reference to the flowchart of FIG. The damping force control routine shown in FIG. 6 is stored as a control program in the ROM of the ECU 50 and is executed independently for each electromagnetic shock absorber 30 of each wheel. The damping force control routine is repeatedly executed at a predetermined short cycle from when the ignition switch is turned on to when it is turned off.

  When the damping force control routine is activated, the ECU 50 reads the stroke X detected by the stroke sensor 61 and the sprung acceleration Gu detected by the sprung acceleration sensor 62 in step S10. Subsequently, in step S11, the stroke speed X ′, the stroke acceleration X ″, and the sprung speed Xu ′ are calculated. The stroke speed X ′ is obtained by differentiating the stroke X, and the stroke acceleration X ″ is calculated by the stroke. X is obtained by second-order differentiation, and the sprung speed Xu ′ is obtained by integrating the sprung acceleration Gu. Subsequently, in step S12, the ECU 50 determines that the current state of the suspension pen device is based on the combination of the respective orientations (symbols) of the stroke speed X ′, the stroke acceleration X ″, and the sprung speed Xu ′. One of the states 1 to 8 classified as streets is selected, and the states 1 to 8 represent the moving direction of the sprung portion and the expansion / contraction state of the electromagnetic shock absorber 30.

State 1: Xu ′ ≧ 0 (rising on spring), X ′ ≧ 0 (extension), X ″ ≧ 0 (extension acceleration)
State 2: Xu ′ ≧ 0 (rising on spring), X ′ ≧ 0 (extension), X ″ <0 (extension deceleration)
State 3: Xu ′ ≧ 0 (sprung rise), X ′ <0 (compression), X ″ <0 (compression acceleration)
State 4: Xu ′ ≧ 0 (sprung rise), X ′ <0 (compression), X ″ ≧ 0 (compression deceleration)
State 5: Xu ′ <0 (down sprung), X ′ <0 (compression), X ″ <0 (compression acceleration)
State 6: Xu ′ <0 (sprung down), X ′ <0 (compression), X ″ ≧ 0 (compression deceleration)
State 7: Xu ′ <0 (down sprung), X ′ ≧ 0 (extension), X ″ ≧ 0 (extension acceleration)
State 8: Xu ′ <0 (down sprung), X ′ ≧ 0 (extension), X ″ <0 (extension deceleration)

Subsequently, in step S13, the ECU 50 calculates the electric resistances R _1x and R _2x of the variable resistors VR1 and VR2 and the electrostatic capacitances C of the variable capacitors VC1 and VC2 by a calculation formula set according to the selected state. _1x and _C2x are calculated. In this case, in the state 1, 2, 7, 8, since the generated current by extension operation of the electromagnetic shock absorber 30 flows through the second connection path Fdhga, the electrical resistance of the second variable resistor VR2 _{R 2x} and the second variable calculate the capacitance _{C 2x} capacitor VC2, in state 3, 4, 5 and 6, since the generated current by the compression operation of the electromagnetic shock absorber 30 flows through the first connection passage Echgb, the first variable resistor The electric resistance R _{1x of} VR1 and the capacitance C _1x of the first variable capacitor VC1 are calculated. This calculation will be described later.

Subsequently, in step S14, the ECU 50 sets the duty ratios Dr1 and Dr2 of the switching elements SW1 and SW2 based on the calculated electric resistances R _1x and R _2x and the electrostatic capacitances C _1x and C _2x and is variable. The on / off states of the capacitance adjusting switches SWC1, SWC2, and SWC3 of the capacitors VC1 and VC2 are set. ECU50, the electric resistance _{R 1x} and relation between the duty ratio Dr1 of the first switching element SW1, and prestored in the ROM relationship data representing the relationship between the duty ratio Dr2 electrical resistance _{R 2x} and the second switching element SW2 The duty ratios Dr1 and Dr2 are set from the electric resistances R _1x and R _2x with reference to the relation data. Further, the ECU 50 determines the relationship between the combination of the capacitance C _1x and the on / off state of the capacitance adjustment switches SWC1, SWC2, and SWC3 in the first variable capacitor VC1, and the capacitance C _2x and the second variable capacitor VC2. Relation data representing the relation of the combination of the on / off states of the capacity adjustment switches SWC1, SWC2 and SWC3 is stored in the ROM in advance, and the capacity adjustment is made from the capacitances C _1x and C _2x by referring to the relation data. The on / off states of the switches SWC1, SWC2, and SWC3 are set. The variable capacitors VC1 and VC2 can set the ON / OFF states of the capacitance adjustment switches SWC1, SWC2 and SWC3 in eight ways, respectively, so that the capacitances closest to the calculated capacitances C _1x and C _2x are The resulting combination of on / off states is set.

Subsequently, in step S15, the ECU 50 outputs the PWM control signal having the set duty ratios Dr1 and Dr2 to the switching elements SW1 and SW2, and adjusts the capacitance to the variable capacitors VC1 and VC2, respectively. A control signal for switching on / off states of the switches SWC1, SWC2, and SWC3 is output. When the ECU 50 performs the process of step S15, the damping force control routine is temporarily terminated. The ECU 50 repeatedly executes the damping force control routine at a predetermined short cycle. Accordingly, the electric resistances R _1x and R _2x of the variable resistors VR1 and VR2 and the electrostatic capacitances C _1x of the variable capacitors VC1 and VC2 are always determined according to the stroke speed X ′, the stroke acceleration X ″, and the sprung speed Xu ′. , C _2x are adjusted, and the generated current flowing in the motor 40 is controlled, whereby the damping force generated in the electromagnetic shock absorber 30 is controlled.

Next, calculation of the electric resistances R _1x and R _2x of the variable resistors VR1 and VR2 and the capacitances C _1x and C _2x of the variable capacitors VC1 and VC2 in step S13 will be described for each state. Note that states 5 to 8 are different from states 1 to 4 in that the sprung portion is lowered, and the relative operations of the sprung portion and the unsprung portion are common.

<State 1>
In the state 1, the sprung portion moves upward, and the electromagnetic shock absorber 30 is extended, and the extension speed is increased. In this state 1, a damping force is applied to the extension operation of the electromagnetic shock absorber 30 to suppress the upward movement of the spring top. Since the generated current flows through the second connection path fdhga when the electromagnetic shock absorber 30 is extended, power is generated by adjusting the electric resistance R _2x of the second variable resistor VR2 and the capacitance C _2x of the second variable capacitor VC2. The current can be adjusted. In the present embodiment, whether or not the skyhook damping force Fs can be generated by the motor 40 without passing the generated current through the second variable capacitor VC2 is determined by the following determination formula.
(2π / N) ² Km ² (1 / R _2x ) X ′ ≧ St · Xu ′ (8)
When the determination formula (8) is satisfied by setting the electric resistance R _2x to the minimum value (minimum value in the adjustment range), the generated current can be supplied to the second variable resistor VR2 without being supplied to the second variable capacitor VC2. For example, the skyhook damping force Fs can be generated by the motor 40 by adjusting the electric resistance _R2x . In this case, an electrical resistance R _2x that satisfies the following equation (9) may be calculated.
(2π / N) ² Km ² (1 / R _2x ) X ′ = St · Xu ′ (9)
Further, the capacitance C _2x of the second variable capacitor VC2 is set to zero (C _2x = 0).

On the other hand, when the electric resistance R _2x even determination expression to the minimum value (8) is not satisfied, the electrical resistance R _2x of the second variable resistor VR2 and the minimum value. In this case, the electric resistance R _2x is the electric resistance value of the second resistor R2 (electric resistance when the duty ratio Dr2 = 100%). Further, the capacitance C _2x of the second variable capacitor VC2 is calculated from the following equation (10).
C _2x X "
= (St · Xu ′ − (2π / N) ² Km ² (1 / R _2x ) X ′) / ((2π / N) ² Km ² )
... (10)
That is, when the damping force is insufficient with respect to the skyhook damping force Fs in the generated current flowing through the second variable resistor VR2, the shortage is compensated by flowing the generated current through the second variable capacitor VC2. The capacitance C _2x of the two variable capacitor VC2 is calculated.

<State 2>
In state 2, the sprung portion moves upward, and the electromagnetic shock absorber 30 is extended, and the extension speed is reduced. In this state 2, a damping force is applied to the extension operation of the electromagnetic shock absorber 30 to suppress the upward movement of the spring top. Since the generated current flows through the second connection path fdhga when the electromagnetic shock absorber 30 is extended, power is generated by adjusting the electric resistance R _2x of the second variable resistor VR2 and the capacitance C _2x of the second variable capacitor VC2. The current can be adjusted. In this case, since the stroke acceleration X ″ is a negative value, as can be seen from the equation (7), when the generated current is passed through the second variable capacitor VC2, the damping force is reduced. In state 2, the capacitance C _{2x is set} to zero (C _2x = 0).

In addition, regarding the electric resistance R _2x of the second variable resistor VR2, it is determined whether or not the determination formula (8) is satisfied. When the determination formula (8) is satisfied with the electric resistance R _2x as the minimum value, the electric resistance R _2x is calculated from the above expression (9). On the other hand, the electrical resistance R _2x minimum value and the determination expression even when the (8) In the case where not satisfied, the electrical resistance R _2x minimum value. In this case, the electric resistance R _2x is the electric resistance value of the second resistor R2 (electric resistance when the duty ratio Dr2 = 100%).

<State 3>
In state 3, the sprung portion moves upward, and the electromagnetic shock absorber 30 is compressing, and the compression speed is increasing. During compression operation of the electromagnetic shock absorber 30, because the generated current flows through the first connection passage Echgb, power generation by adjusting the capacitance _{C 1x} electrical resistance _{R 1x} and first variable capacitor VC1 of the first variable resistor VR1 The current can be adjusted. In this state 3, the spring top and the relative movement direction of the spring top with respect to the spring bottom are opposite. In this case, in the skyhook control, a damping force is not applied to the compression operation of the electromagnetic shock absorber 30. In state 3, since the direction (symbol) of the stroke acceleration X ″ is the same as the direction (symbol) of the stroke speed X ′, the generated current flowing through the first variable capacitor VC1 flows through the first variable resistor VR1. This acts in the direction of generating a damping force in the same way as the generated current, so that the damping force ((2π / N) ² Km ² (1 / R _1x ) X ′) due to the current component flowing in the first variable resistor VR1 1 A damping force ((2π / N) ² Km ² C _1x X ″) due to a current component flowing in the variable resistor VR1 is set to zero. In this case, the electric resistance R _1x of the first variable resistor VR1 is set to the maximum value, and the capacitance C _1x of the first variable capacitor VC1 is set to zero (C _1x = 0). Since the electric resistance R _1x of the first variable resistor VR1 is adjusted by the duty ratio Dr1 of the first switching element SW1, it can be made infinite by setting the duty ratio Dr1 to 0%. Further, since the capacitance C _1x of the first variable capacitor VC1 is determined by the combination of the on / off states of the capacitance adjustment switches SWC1, SWC2, and SWC3, all the capacitance adjustment switches SWC1, SWC2, and SWC3 are turned off. Can be reduced to zero. Therefore, in the state 3, the generation current is not supplied to the motor 40 so that the damping force is not generated.

<State 4>
In state 4, the sprung portion moves upward, and the electromagnetic shock absorber 30 is compressing, and the compression speed is reduced. During compression operation of the electromagnetic shock absorber 30, because the generated current flows through the first connection passage Echgb, power generation by adjusting the capacitance _{C 1x} electrical resistance _{R 1x} and first variable capacitor VC1 of the first variable resistor VR1 The current can be adjusted. In the state 4, the spring top and the relative movement direction of the spring top with respect to the spring bottom are opposite. In this case, in the skyhook control, a damping force is not applied to the compression operation of the electromagnetic shock absorber 30. In this state 4, since the direction (symbol) of the stroke acceleration X ″ is opposite to the direction (symbol) of the stroke speed X ′, the generated current flows through the first variable capacitor VC1 to act in the direction opposite to the damping force. The propulsive force to be generated can be generated in the electromagnetic shock absorber 30.

Therefore, the electric resistance R of the first variable resistor VR1 is such that no damping force is generated by the generated current flowing through the first variable resistor VR1, and that propulsive force is generated by the generated current flowing through the first variable capacitor VC1. _1x and the capacitance C _1x of the first variable capacitor VC1 are set. In this case, the damping force ((2π / N) ² Km ² (1 / R _1x ) X ′) due to the current component flowing through the first variable resistor VR1 is set to zero. That is, the duty ratio Dr1 of the first switching element SW1 is set to 0% so that the generated current does not flow through the first variable resistor VR1. Further, the damping force ((2π / N) ² Km ² C _1x X ″) due to the current component flowing through the first variable resistor VR1 is set to the skyhook damping force Fs. Accordingly, the electrostatic capacitance of the first variable capacitor VC1. The capacity C _1x is calculated from the following equation (11).
C _1x X ″ = St · Xu ′ / ((2π / N) ² Km ² ) (11)
Thereby, even if it is passive control which cannot drive the motor 40 actively, a propulsive force can be generated in the electromagnetic shock absorber 30. FIG.

<State 5>
In state 5, the sprung portion moves downward, and the electromagnetic shock absorber 30 is compressing, and the compression speed is increased. In this state 5, a damping force is applied to the compression operation of the electromagnetic shock absorber 30 to suppress the downward movement of the spring top. During compression operation of the electromagnetic shock absorber 30, because the generated current flows through the first connection passage Echgb, power generation by adjusting the capacitance _{C 1x} electrical resistance _{R 1x} and first variable capacitor VC1 of the first variable resistor VR1 The current can be adjusted. In this state 5, whether or not the skyhook damping force Fs can be generated by the motor 40 without flowing the generated current through the first variable capacitor VC1 is determined by the following determination formula.
(2π / N) ² Km ² (1 / R _1x ) X ′ ≦ St · Xu ′ (12)
Since this formula (12) is a negative value on both sides, the direction of the inequality sign in the judgment formula is opposite when considering the magnitude of the force (absolute value). When the determination formula (12) is established with the electric resistance R _1x being the minimum value, the electric resistance R _1x of the electric resistance R _1x can be obtained by flowing the generated current through the first variable resistor VR1 without flowing through the first variable capacitor VC1. By adjustment, the skyhook damping force Fs can be generated by the motor 40. In this case, it is only necessary to calculate an electrical resistance R _1x that satisfies the following expression (13).
(2π / N) ² Km ² (1 / R _1x ) X ′ = St · Xu ′ (13)
Further, the capacitance C _1x of the first variable capacitor VC2 is set to zero (C _1x = 0).

On the other hand, when the electric resistance R _1x even determination expression to the minimum value (12) is not satisfied, the electrical resistance R _1x of the first variable resistor VR1 and the minimum value. In this case, the electric resistance R _1x is the electric resistance value of the first resistor R ₁ (electric resistance when the duty ratio Dr 1 = 100%). Further, the capacitance C _1x of the first variable capacitor VC1 is calculated from the following equation (14).
C _1x X "
= (St · Xu ′ − (2π / N) ² Km ² (1 / R _1x ) X ′) / ((2π / N) ² Km ² )
(14)
That is, when the damping force is generated current flowing through the first variable resistor VR1 is insufficient relative to the skyhook damping force Fs is a generated current minute in shortage in the electrostatic capacitance C _2x of the first variable capacitor VC1 The capacitance C _1x of the first variable capacitor VC1 is calculated so as to compensate by flowing.

<State 6>
In state 6, the sprung portion moves downward, and the electromagnetic shock absorber 30 is compressing, and the compression speed is reduced. In this state 6, a damping force is applied to the compression operation of the electromagnetic shock absorber 30 to suppress the downward movement of the spring top. During compression operation of the electromagnetic shock absorber 30, because the generated current flows through the first connection passage Echgb, power generation by adjusting the capacitance _{C 1x} electrical resistance _{R 1x} and first variable capacitor VC1 of the first variable resistor VR1 The current can be adjusted. In this case, the direction (symbol) of the stroke acceleration X ″ is opposite to the direction (symbol) of the stroke speed X ′. Therefore, as can be seen from the equation (6), when the generated current flows through the first variable capacitor VC1, the damping is Therefore, in the state 6, the capacitance C _{1x is set} to zero (C _1x = 0).

Also, the electrical resistance R _1x of the first variable resistor VR1, it is determined whether the determination equation (12) is satisfied. When the determination formula (12) is satisfied with the electric resistance R _1x as the minimum value, the electric resistance R _1x is calculated from the above expression (13). On the other hand, the electrical resistance R _1x minimum value and the determination expression even when the (12) In the case where not satisfied, the electrical resistance R _1x and minimum value. In this case, the electric resistance R _1x is the electric resistance value of the first resistor R ₁ (electric resistance when the duty ratio Dr 1 = 100%).

<State 7>
In the state 7, the sprung portion moves downward, and the electromagnetic shock absorber 30 is extended, and the extension speed is increased. Since the generated current flows through the second connection path fdhga when the electromagnetic shock absorber 30 is extended, power is generated by adjusting the electric resistance R _2x of the second variable resistor VR2 and the capacitance C _2x of the second variable capacitor VC2. The current can be adjusted. In this state 7, the spring top and the relative movement direction of the spring top with respect to the spring bottom are opposite. In this case, in the skyhook control, a damping force is not applied to the extension operation of the electromagnetic shock absorber 30. In state 7, since the sign of stroke acceleration X ″ is the same as the sign of stroke speed X ′, the generated current flowing through the second variable capacitor VC2 is attenuated in the same manner as the generated current flowing through the second variable resistor VR2. Therefore, the damping force ((2π / N) ² Km ² (1 / R _2x ) X ′) due to the current component flowing in the second variable resistor VR2 and the second variable resistor VR2 Both damping force ((2π / N) ² Km ² C _2x X ″) due to the flowing current component is set to zero. In this case, the electric resistance R _2x of the second variable resistor VR2 is set to the maximum value, and the capacitance C _2x of the second variable capacitor VC2 is set to zero (C _2x = 0). Electrical resistance _{R 2x} of the second variable resistor VR2 is to be adjusted by the duty ratio Dr2 of the second switching element SW2, the duty ratio Dr2 can be infinite by 0%. Further, since the capacitance C _2x of the second variable capacitor VC2 is determined by the combination of the on / off states of the capacitance adjustment switches SWC1, SWC2, and SWC3, all the capacitance adjustment switches SWC1, SWC2, and SWC3 are turned off. Can be reduced to zero. Therefore, in the state 7, the generated current is not supplied to the motor 40 so that the damping force is not generated.

<State 8>
In state 8, the sprung portion moves downward, and the electromagnetic shock absorber 30 is extended, and the extension speed is reduced. Since the generated current flows through the second connection path fdhga when the electromagnetic shock absorber 30 is extended, power is generated by adjusting the electric resistance R _2x of the second variable resistor VR2 and the capacitance C _2x of the second variable capacitor VC2. The current can be adjusted. In this state 8, the spring top and the relative movement direction of the spring top with respect to the spring bottom are opposite. In this case, in the skyhook control, a damping force is not applied to the extension operation of the electromagnetic shock absorber 30. In this state 8, since the direction (symbol) of the stroke acceleration X ″ is opposite to the direction (symbol) of the stroke speed X ′, it acts in the direction opposite to the damping force by flowing the generated current through the second variable capacitor VC2. Propulsive force can be generated.

Therefore, the electric resistance R of the second variable resistor VR2 is such that no damping force is generated by the generated current flowing through the second variable resistor VR2, and propulsive force is generated by the generated current flowing through the second variable capacitor VC2. setting the electrostatic capacitance _{C 2x} of _2x and the second variable capacitor VC2. In this case, the damping force ((2π / N) ² Km ² (1 / R _2x ) X ′) due to the current component flowing through the second variable resistor VR2 is set to zero. That is, the duty ratio Dr2 of the second switching element SW1 is set to 0% so that the generated current does not flow through the second variable resistor VR2. Further, the damping force ((2π / N) ² Km ² C _2x X ″) due to the current component flowing through the second variable resistor VR2 is set to the skyhook damping force Fs. Accordingly, the electrostatic capacitance of the second variable capacitor VC2 is set. The capacity C _2x is calculated from the following equation (15).
C _2x X ″ = St · Xu ′ / ((2π / N) ² Km ² ) (15)
Thereby, even if it is passive control which cannot drive the motor 40 actively, a propulsive force can be generated in the electromagnetic shock absorber 30. FIG.

  The first variable capacitor VC1 and the second variable capacitor VC2 in the present embodiment change their capacitances in eight ways, so that the settable capacitance closest to the calculated capacitance can be set. Set to

  Further, the switching element SW2 (SW1) in the connection path on the side where the generated current does not flow, that is, in the second connection path fdhga when the electromagnetic shock absorber 30 is compressed, and in the first connection path echgb when the electromagnetic shock absorber 30 is extended. The capacitance adjusting switches SWC1, SWC2, and SWC3 may be turned off.

According to the damping force control routine of the first embodiment described above, when the moving direction of the sprung portion is the same as the relative moving direction of the sprung portion with respect to the unsprung portion (states 1, 2, 5, 6). When a damping force is generated in the electromagnetic shock absorber 30 and the movement direction of the sprung portion is opposite to the relative movement direction of the sprung portion with respect to the unsprung portion (states 3, 4, 7, and 8), A damping force is not generated in the electromagnetic shock absorber 30. In the case of the former (states 1, 2, 5, and 6), the Skyhook damping force Fs (within the adjustment range of the damping force that can be generated by adjusting the generated current flowing through the variable resistor VR1 (VR2). When the target damping force) is applied, the damping force is controlled by adjusting the electric resistance R _1x (R _2x ) of the variable resistor VR1 (VR2), and the magnitude of the skyhook damping force Fs (target damping force) is When the damping force adjustment range is larger, when the stroke speed X ′ and the stroke acceleration X ″ are in the same direction (symbol) (states 1 and 5), it is variable in addition to the variable resistor VR1 (VR2). Since the generated current is supplied to the capacitor VC1 (VC2) to compensate for the deficiency of the damping force, the inertia force proportional to the stroke acceleration can be converted into the damping force and added even when the stroke speed is small. Decay It can be generated.

On the other hand, if the moving direction of the sprung portion is opposite to the moving direction of the sprung portion relative to the unsprung portion (states 3, 4, 7, and 8), no damping force is generated in the electromagnetic shock absorber 30. In addition, when the stroke speed X ′ and the stroke acceleration X ″ are in opposite directions (states 4 and 8), the propulsion works in the opposite direction to the damping force by flowing the generated current through the variable capacitor VC1 (VC2). The force is generated and the propulsive force is controlled by adjusting the capacitance C _1x (C _2x ), thereby generating the propulsive force that could not be achieved by the passive control in the electromagnetic shock absorber 30. As a result, The variable range of the damping force can be greatly expanded, and the controllability of the damping force is further improved.

Next, the damping force control process of the second embodiment will be described. In the damping force control process of the second embodiment, a target current i * that is a target value of the generated current that flows to the motor 40 is calculated, and the variable resistor VR1 (VR2) is set so that the target current i * flows to the motor 40. ) Electric resistance R _1x (R _2x ) and a damping force that can be generated by the electromagnetic shock absorber 30 by flowing a generated current through the variable capacitor VC1 (VC2) at the start of turning of the steering handle (not shown). increase. FIG. 7 shows a damping force control routine executed by the ECU 50, and FIG. 8 shows a capacitance control routine executed by the ECU 50 in parallel with the damping force control routine. First, the damping force control routine shown in FIG. 7 will be described. This damping force control routine is stored as a control program in the ROM of the ECU 50, and is executed independently for each electromagnetic shock absorber 30 of each wheel. The damping force control routine is repeatedly executed at a predetermined short cycle from when the ignition switch is turned on to when it is turned off.

  When the damping force control routine is started, the ECU 50 causes the sprung acceleration Gu detected by the sprung acceleration sensor 62, the unsprung acceleration Gd detected by the unsprung acceleration sensor 63, and the lateral acceleration sensor 64 in step S21. The detected lateral acceleration Gy and the stroke X detected by the stroke sensor 61 are read. Subsequently, in step S22, it is determined whether or not the magnitude | Gu | of the sprung acceleration Gu is greater than a reference sprung acceleration Guo that is a preset magnitude of acceleration. The reference sprung acceleration Guo is an acceleration as a threshold value indicating whether it is better to suppress the vibration of the sprung portion.

  If it is determined in step S22 that the magnitude | Gu | of the sprung acceleration Gu is greater than the reference sprung acceleration Guo, the ride comfort control flag FLGu is set to “1” in step S23, and the processing is performed in step S22. Proceed to S25. On the other hand, if it is determined that the magnitude | Gu | of the sprung acceleration Gu is equal to or less than the reference sprung acceleration Guo, the ride comfort control flag FLGu is set to “0” in step S24, and the process proceeds to step S28. Proceed. The riding comfort control flag FLGu is a flag indicating whether or not the damping force control mode is set to the riding comfort control mode. When the damping comfort control flag FLGu is set to “1”, the control mode is set to the riding comfort control mode. When it is set to “0”, it indicates that the control mode is not set to the ride comfort control mode.

When the ride comfort control flag FLGu is set to “1” in step S23, that is, when the control mode of the damping force is set to the ride comfort control mode, the ECU 50 performs the target attenuation for ride comfort control in the subsequent step S25. The coefficient Ku * is calculated. The target damping coefficient Ku * for ride comfort control is a damping force coefficient that effectively suppresses vibration in the vicinity of the sprung resonance frequency (for example, 0.1 Hz to 3 Hz). Can be based on. In this case, the target damping coefficient Ku * for ride comfort control can be calculated from the following equation.
Ku * = Ks (Xu ′ / X ′)
Here, Ks represents a preset skyhook damping coefficient, Xu ′ represents a sprung speed, and X ′ represents a stroke speed of the electromagnetic shock absorber 30. However, the above equation is used when the product of the sprung speed Xu ′ and the stroke speed X ′ is positive. When the product is negative, the ride comfort control target damping coefficient Ku * is set to the minimum damping coefficient Kmin (for example, 0).

  After calculating the ride comfort control target damping coefficient Ku * in step S25, the ECU 50 multiplies the ride comfort control target damping coefficient Ku * by the stroke speed X 'to obtain the ride comfort control target damping force Fu. * Calculate. Subsequently, in step S27, a ride comfort control target current iu * is calculated. The ride comfort control target current iu * is a target value of the generated current necessary for the electromagnetic shock absorber 30 to generate the ride comfort control target damping force Fu *, and the ride comfort control target damping force Fu * is It is obtained by converting to motor torque and dividing the converted value by the motor torque constant. Note that the ride comfort control target current iu *, the unsprung control target current id *, and the stability control target current iy *, which will be described later, are applied to the motor 40 so as to give resistance to the expansion / contraction operation of the electromagnetic shock absorber 30. Therefore, the energization direction differs depending on the operation direction of the electromagnetic shock absorber 30. In other words, when the electromagnetic shock absorber 30 is in the compression operation, the generated current flows from the first terminal t1 of the motor 40 through the external circuit 100 to the second terminal t2, and when the electromagnetic shock absorber 30 is in the expansion operation, the generated current is the motor. The current flows from the second terminal t2 of 40 through the external circuit 100 to the first terminal t1.

  When the processing of step S27 or step S24 is performed, the ECU 50 determines in step S28 whether or not the magnitude | Gd | of the unsprung acceleration Gd is larger than a preset reference unsprung acceleration Gdo. The reference unsprung acceleration Gdo is an acceleration as a threshold value indicating whether it is better to suppress the vibration of the unsprung part.

  If it is determined in step S28 that the magnitude | Gd | of the unsprung acceleration Gd is larger than the reference unsprung acceleration Gdo, the unsprung control flag FLGd is set to “1” in step S29, and the processing is performed in step S28. Proceed to S31. On the other hand, if it is determined that the magnitude | Gd | of the unsprung acceleration Gd is equal to or less than the reference unsprung acceleration Gdo, the unsprung control flag FLGd is set to “0” in step S30, and the process proceeds to step S34. Proceed. The unsprung control flag FLGd is a flag indicating whether or not the damping force control mode is set to the unsprung control mode. When the unsprung force control mode is set to “1”, the control mode is set to the unsprung control mode. When it is set to “0”, it indicates that the control mode is not set to the unsprung control mode.

When the unsprung control flag FLGd is set to “1” in step S29, that is, when the damping force control mode is set to the unsprung control mode, the ECU 50 performs the unsprung control target damping in the following step S31. The coefficient Kd * is calculated. The unsprung control target damping coefficient Kd * is a damping force coefficient that effectively suppresses vibration in the vicinity of the unsprung resonance frequency (for example, 8 Hz to 15 Hz). For example, based on the ground hook control law Can be sought. In this case, the unsprung control target damping coefficient Kd * can be calculated from the following equation.
Kd * = Kg (Xd ′ / X ′)
Here, Kg represents a preset ground hook damping coefficient, and Xd ′ represents an unsprung speed. The unsprung speed Xd ′ is obtained by integrating the unsprung acceleration Gd. However, the above equation is used when the product of the unsprung speed Xd ′ and the stroke speed X ′ is positive. When the product is negative, the unsprung control target damping coefficient Kd * is set to the minimum damping coefficient Kmin (for example, 0).

  After calculating the unsprung control target damping coefficient Kd * in step S31, the ECU 50 multiplies the unsprung control target damping coefficient Kd * by the stroke speed X ′ in the subsequent step S32 to thereby obtain the unsprung control target damping force Fd. * Calculate. Subsequently, in step S33, the unsprung control target current id * is calculated. The unsprung control target current id * is a target value of the generated current required for the electromagnetic shock absorber 30 to generate the unsprung control target damping force Fd *, and the unsprung control target damping force Fd * is It is obtained by converting to motor torque and dividing the converted value by the motor torque constant.

When the processing of step S33 or step S30 is performed, the ECU 50 determines in step S34 whether the magnitude | Gy | of the lateral acceleration Gy is larger than a preset reference lateral acceleration Gyo. The reference lateral acceleration Gyo is an acceleration as a threshold value as to whether or not it is better to suppress vibration in the roll direction acting on the vehicle, and is set to about 10 (m / s ² ), for example.

  If it is determined in step S34 that the magnitude | Gy | of the lateral acceleration Gy is larger than the reference lateral acceleration Gyo, the controllability control flag FLGy is set to “1” in step S35, and the process is performed in step S37. Proceed to On the other hand, if it is determined that the magnitude | Gy | of the lateral acceleration Gy is equal to or less than the reference lateral acceleration Gyo, the controllability control flag FLGy is set to “0” in step S36, and the process proceeds to step S39. . This operability control flag FLGy is a flag indicating whether or not the damping force control mode is set to the operability control mode. When the control mode is set to “1”, the control mode is operability control. This indicates that the mode is set, and when “0” is set, the control mode is not set to the safety control mode.

  When the controllability control flag FLGy is set to “1” in step S35, that is, when the damping force control mode is set to the controllability control mode, the ECU 50 performs the controllability control in the following step S37. Target damping force Fy * is calculated. The target damping force Fy * for handling control is obtained by multiplying a preset control gain Ky by the lateral acceleration Gy. In this case, the control gain for the electromagnetic shock absorber 30 connected to the right wheel is different from the control gain for the electromagnetic shock absorber 30 connected to the left wheel. For example, when the control gain for the electromagnetic shock absorber 30 connected to the left wheel (left front wheel and left rear wheel) is Ky, the electromagnetic shock connected to the right wheel (right front wheel and right rear wheel) side. The control gain for the absorber 30 is -Ky. Alternatively, for example, with respect to the lateral acceleration generated when the vehicle turns to the left, the control gain KRy for the electromagnetic shock absorber 30 connected to the right wheel side is the same as that for the electromagnetic shock absorber 30 connected to the left wheel side. Is set to be larger than the control gain KLy. That is, the gain on the right wheel side and the gain on the left wheel side are set so that the roll of the vehicle is suppressed.

  Subsequently, in step S38, the ECU 50 calculates a steering control target current iy *. The target current iy * for operability control is a target value of the generated current necessary for the electromagnetic shock absorber 30 to generate the target damping force Fy * for operability control, and the target damping force for operability control. It is obtained by converting Fy * into motor torque and dividing the converted value by the motor torque constant.

  When the ECU 50 performs the process of step S38 or step S36, whether or not at least one of the ride comfort control flag FLGu, the unsprung control flag FLGd, and the stability control flag FLGy is set to “1” in step S39. Determine. If the determination result is “Yes”, that is, if the control mode is set to at least one of the ride comfort control mode, the unsprung control mode, and the stability control mode, in step S40, The largest current value is selected from each target current iu *, id *, iy *, and the selected current value is set as the final target current i *. On the other hand, if the determination in step S39 is “No”, that is, if the control mode is not set to any of the ride comfort control mode, the unsprung control mode, and the stability control mode, in step S41, A preset default current value idef is set as the final target current i *.

  When the final target current i * is set, the ECU 50 reads the actual current ix detected by the current sensor 111 in the subsequent step S42. Next, in step S43, the actual current ix becomes equal to the final target current i * by feedback control (for example, PID control) based on the deviation Δi (= i * −ix) between the final target current i * and the actual current ix. As described above, the duty ratio is adjusted by sending a PWM control signal to the first switching element SW1 or the second switching element SW2. In this case, the ECU 50 adjusts the duty ratio of the first switching element SW1 when the electromagnetic shock absorber 30 is being compressed, and by adjusting the duty ratio of the second switching element SW2 when the electromagnetic shock absorber 30 is being extended. By adjusting the duty ratio, the generated current flowing in the motor 40 is controlled to be equal to the final target current i *. For the switching element on the side where the duty ratio is not adjusted (the second switching element SW2 during the compression operation and the first switching element SW1 during the extension operation), the duty ratio may be fixed to 0%, for example. That's fine.

  The ECU 50 repeats such a damping force control routine at a predetermined short cycle. Accordingly, it is possible to generate a damping force having characteristics suitable for the compression direction and the extension direction of the electromagnetic shock absorber 30.

  The vehicle turns when the driver performs the turning operation of the steering wheel. When the vehicle turns, the ECU 50 sets the control mode to the safety control mode in order to ensure the steering stability. However, since the stroke speed of the electromagnetic shock absorber 30 is small at the start of the cutting, the ECU 50 is greatly attenuated. Cannot generate power. That is, the generated current that can be adjusted by the variable resistors VR1 and VR2 is proportional to the stroke speed X ′ of the electromagnetic shock absorber 30. Therefore, no matter how large the final target current i * is set, the stroke speed X ′ is small. Cannot generate a large damping force. Therefore, in the second embodiment, at the start of the turning operation of the steering wheel, the generated current is supplied to the variable capacitor VC1 (VC2) in addition to the variable resistor VR1 (VR2) to generate a damping force with high responsiveness.

  FIG. 8 shows a capacitance control routine executed by the ECU 50 in order to flow the generated current to the variable capacitor VC1 (VC2) at the start of the steering wheel turning operation. This capacitance control routine is stored as a control program in the ROM of the ECU 50, and is executed independently for each electromagnetic shock absorber 30 of each wheel. The capacitance control routine is repeatedly executed at a predetermined short period in parallel with the above-described damping force control routine from when the ignition switch is turned on until it is turned off.

  When the capacitance control routine is activated, the ECU 50 determines in step S51 whether or not the stability control flag FLGy is set to “1”. The steering control flag FLGy is set to “1” when it is determined that the magnitude | Gy | of the lateral acceleration Gy is larger than the reference lateral acceleration Gyo as described above. When the safety control flag FLGy is switched from “0” to “1”, it can be estimated that the turning operation of the steering wheel is started.

  If the steering control flag FLGy is not set to “1”, the ECU 50 clears the count value t (hereinafter referred to as timer value t) of the timekeeping timer to zero in step S52. As will be described later, this timer value t is incremented immediately after the controllability control flag FLGy is switched from “0” to “1”, and the time t after the steering wheel turning operation is started. Represents the corresponding value. The timer value t is set to zero (t = 0) when the electrostatic capacity control routine is started.

ECU50, when cleared to zero count value t, subsequently, in step S53, sets the capacitance _{C 2x} the capacitance _{C 1x} and second variable capacitor VC1 of the first variable capacitor VC1 to zero _(C 1x = 0 , C _2x = 0). Subsequently, in step S54, in order to make the capacitances C _1x and C _2x of the variable capacitors VC1 and VC2 zero, the capacitance adjusting switches SWC1, SWC2 of the first variable capacitor VC1 and the second variable capacitor VC2 are set. Each of the SWCs 3 is turned off, and the electrostatic capacity control routine is temporarily terminated. Since the capacitance control routine is repeatedly executed at a predetermined short cycle, the generated current does not flow through the variable capacitor VC1 (VC2) while the stability control flag FLGy is set to “0”. The capacitance adjusting switches SWC1, SWC2, SWC3 are maintained in the off state.

If the ECU 50 detects that the steering control flag FLGy is set to “1” while repeating such processing (S51: Yes), the ECU 50 advances the processing to step S55. In step S55, the ECU 50 increments the timer value t by the value “1”. Subsequently, it is determined whether or not the timer value t is equal to or greater than a preset reference time to. That is, it is determined whether or not the elapsed time since the stability control flag FLGy is set to “1” has reached the reference time to. If the timer value t has not reached the reference time to (S56: No), the steering speed ωh is read via the CAN communication line in step S57. Next, in step S58, the setting the electrostatic capacitance _{C 2x} the capacitance _{C 1x} and second variable capacitor VC1 of the first variable capacitor VC1 corresponding to the steering speed [omega] h.

In setting the capacitance, for example, as shown in FIG. 9, a map that associates the steering speed ωh with the capacitances C _1x and C _2x is stored in a memory such as a ROM, and this map is stored. Do it by reference. In this case, the capacitances C _1x and C _2x of the variable capacitors VC1 and VC2 are set larger as the steering speed ωh is smaller. In this example, the steering speed ωh (rotational speed of the steering wheel) is divided into three speed ranges, and when the steering speed ωh falls within the low speed steering range, the capacitances C _1x and C _2x are set to 0.1F. When the steering speed ωh falls within the medium speed steering range, the capacitances C _1x and C _2x are set to 0.01F, and when the steering speed ωh falls within the high speed steering range, the capacitance C _1x , C _2x is set to 0.001F. For example, the low speed steering range is a speed range in which the steering speed ωh is 5 deg / sec or less, and the medium speed steering range is a speed range in which the steering speed is greater than 5 deg / sec and is 10 deg / sec or less. Is set to a speed range in which the steering speed is greater than 10 deg / sec. The relationship between the steering speed ωh and the capacitances C _1x and C _2x of the variable capacitors VC1 and VC2 is not limited to these values, and can be set arbitrarily.

Subsequently, ECU 50, at step S59, the respective variable capacitors VC1, VC2 of the capacitance _{C 1x,} a _{C 2x} to the set capacity is the set, switch the respective capacity adjustment of the variable capacitors VC1, VC2 A control signal is output to SWC1, SWC2, and SWC3. For example, in the first variable capacitor VC1 and the second variable capacitor VC2, the capacitance of the capacitor C1 is 0.1F, the capacitance of the capacitor C2 is 0.01F, and the capacitance of the capacitor C3 is 0.001F, respectively. Set it. In step S59, when the steering speed ωh is in the low speed steering range, the capacity adjustment switches SWC1 of the variable capacitors VC1 and VC2 are turned on, and the other capacity adjustment switches SWC2 and SWC3 are turned off. To do. As a result, the capacitances C _1x and C _{2x of the} variable capacitors VC1 and VC2 are set to the set value (0.1F). When the steering speed ωh is in the middle speed steering range, the capacity adjustment switches SWC2 of the variable capacitors VC1 and VC2 are turned on, and the other capacity adjustment switches SWC1 and SWC3 are turned off. As a result, the capacitances C _1x and C _{2x of the} variable capacitors VC1 and VC2 are set to the set value (0.01F). When the steering speed ωh falls within the high speed steering range, the capacity adjustment switches SWC3 of the variable capacitors VC1 and VC2 are turned on, and the other capacity adjustment switches SWC1 and SWC2 are turned off. As a result, the capacitances C _1x and C _{2x of the} variable capacitors VC1 and VC2 are set to the set value (0.001F).

When the ECU 50 performs the process of step S59, the capacitance control routine is once ended, and then the capacitance control routine is repeated again at a predetermined short cycle. Therefore, until the elapsed time after the stability control flag FLGy is set to “1” reaches the reference time to, the capacitances C _1x and C _{2x of} the variable capacitors VC1 and VC2 correspond to the steering speed ωh. Controlled by value. As a result, at the start of turning of the steering wheel, the generated current flows through the variable capacitor VC1 (VC2) in addition to the variable resistor VR1 (VR2). In this case, the force that can be generated by the generated current flowing through the variable capacitor VC1 (VC2) is represented by (2π / N) ² Km ² C _1x X ″ or (2π / N) ² Km ² C _2x X ″. , The phase is 90 ° ahead of the force that can be generated by the generated current flowing through the variable resistor VR1 (VR2). Therefore, even if the stroke speed X is small, the stroke speed X is A damping force can be applied by the generated current flowing through the variable capacitor VC1 (VC2) from the time when the increase starts.

If the ECU 50 determines in step S56 that the timer value t has reached the reference time to, the ECU 50 regards that the steering handle turning start period has ended, and proceeds to step S53 to process the variable capacitor as described above. The capacitances C _1x and C _2x of VC1 and VC2 are set to zero. Accordingly, a normal state in which the generated current does not flow through the variable capacitor VC1 (VC2) is obtained. When a predetermined time elapses from the start of turning of the steering wheel, the stroke speed X ′ of the electromagnetic shock absorber 30 increases, and an appropriate damping force can be generated only by the generated current flowing through the variable resistor VR1 (VR2). Therefore, the damping force can be quickly generated by the electromagnetic shock absorber 30 by causing the generated current to flow through the variable capacitor VC1 (VC2) only after a predetermined time has elapsed since the start of turning of the steering wheel.

  When the ECU 50 detects that the maneuverability control flag FLGy is set to “0” while repeating these processes (S51: No), the ECU 50 clears the timer value t to zero and returns to the initial state in step S52.

According to the damping force control routine and the capacitance control routine of the second embodiment described above, an optimal damping force control mode is set based on the sprung acceleration Gu, the unsprung acceleration Gd, and the lateral acceleration Gy. . When the operability control mode is set, since the generated current is supplied to the variable capacitor VC1 (VC2) in addition to the variable resistor VR1 (VR2) for a predetermined period immediately after the setting, the electromagnetic shock is supplied. The damping force generated by the absorber 30 can be increased at an early stage. For this reason, the contact property between the tire and the road surface is improved, and good steering stability can be secured. In this case, since the electrostatic capacities C _1x and C _2x of the variable capacitors VC1 and VC2 are set larger as the steering speed ωh is smaller, an appropriate damping force can be added. That is, when the steering speed ωh is low, a large stroke speed X ′ cannot be obtained, and thus a large damping force cannot be generated with the generated current flowing through the variable resistor VR1 (VR2). By setting C _1x and C _2x large, a large generated current flows through the variable capacitor VC1 (VC2), and an appropriate damping force can be generated.

Further, according to the vehicle suspension apparatus of the present embodiment, the damping force control is performed with the characteristics independent of the compression operation and the extension operation using the low-cost electromagnetic shock absorber 30 using the brushed motor. Can do. For example, in the damping force control routine, even when the target damping coefficient (for example, Ku *, Kd *) is set to be different between the compression operation and the extension operation, the electric resistance R _1x and the second resistance R _{1x of} the first variable resistor VR 1 control the electric resistance R _2x and for the adjustable independently of the variable resistor VR2 is facilitated. In this case, the target attenuation coefficient in the compression operation may be set smaller than the target attenuation coefficient in the expansion operation. As for the damping force to be added at the beginning notch of the steering wheel, it is set to the electrostatic capacitance C _1x and different values and the electrostatic capacitance C _2x of the second variable capacitor VC2 of the first variable capacitor VC1, the compression operation and A damping force having a magnitude different from that of the extension operation can be applied. Therefore, good damping force control can be performed at low cost.

  Although the vehicle suspension device of the present embodiment has been described above, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the object of the present invention.

  For example, in this embodiment, the variable capacitors VC1 and VC2 are configured so that the capacitance is variable by combining three capacitors C1, C2 and C3. However, any number of variable capacitances can be used. It may be good or continuously variable. In the present embodiment, a configuration is adopted in which the electrical resistances of the variable resistors VR1, VR2 are made variable by duty ratio control of the switching elements SW1, SW2, but the configuration in which the electrical resistance is made variable is limited to this. For example, a combination of a plurality of fixed resistors may be switched. In the present embodiment, the coil spring 20 is used as the suspension spring, but another spring such as an air spring may be used instead of the coil spring 20.

  DESCRIPTION OF SYMBOLS 10 ... Suspension main body, 20 ... Coil spring, 30 ... Electromagnetic shock absorber, 40 ... Motor, 50 ... Electronic control unit (ECU), 61 ... Stroke sensor, 62 ... Sprung acceleration sensor, 63 ... Unsprung acceleration sensor, 64 ... lateral acceleration sensor, 100 ... external circuit, 110 ... power storage device, 111 ... current sensor, VR1 ... first variable resistor, VR2 ... second variable resistor, SW1, SW2 ... switching element, R1, R2 ... resistor, VC1: first variable capacitor, VC2: second variable capacitor, SWC1, SWC2, SWC3: capacitance adjusting switch, C1, C2, C3: capacitor, D1, D2, D3, D4: diode, t1: first terminal, t2 ... second terminal, B ... car body (upper spring), W ... wheel (lower spring), echgb ... first connection path, dfhga ... first Connection path.

Claims (6)

A motor and a motion conversion mechanism that converts the approach / separation operation between the spring upper portion and the spring unsprung into the operation of the motor, and generates electric power to the motor in accordance with the approach / separation operation between the spring upper portion and the spring lower portion. An electromagnetic shock absorber that generates a damping force with respect to an approaching / separating operation between the spring upper part and the spring lower part when an electric current flows;
An external circuit that is provided outside the motor and connects between two energization terminals of the motor in order to flow a generated current to the motor;
A vehicle suspension apparatus comprising: damping force control means for controlling a generated current flowing in the external circuit to control a damping force generated by the electromagnetic shock absorber;
The external circuit includes a resistor circuit having a variable electrical resistance and a capacitor circuit having a variable capacitance in parallel.
The vehicle suspension apparatus, wherein the damping force control means controls a damping force generated by the electromagnetic shock absorber by adjusting an electric resistance of the resistance circuit and a capacitance of the capacitor circuit. . The external circuit includes a first connection path through which a generated current flows from a first terminal that is one of the two energization terminals of the motor to a second terminal that is the other of the two spring terminals when the sprung portion and the unsprung portion are approaching each other. And a second connection path through which a generated current flows from the second terminal to the first terminal when the spring upper part and the spring lower part are separated from each other, and the electric resistance is variable in the first connection path A circuit and a first capacitor circuit having a variable capacitance are provided in parallel, and a second resistance circuit having a variable electric resistance and a second capacitor circuit having a variable capacitance are provided in parallel in the second connection path;
The damping force control means is the electromagnetic shock absorber by adjusting the electric resistance of the first resistance circuit and the second resistance circuit and the capacitance of the first capacitor circuit and the second capacitor circuit. The vehicle suspension device according to claim 1, wherein a damping force to be generated is controlled. Stroke speed detecting means for detecting a stroke speed which is a speed of an approach / separation operation between the sprung part and the unsprung part;
A stroke acceleration detecting means for detecting a stroke acceleration that is an acceleration of an approaching / separating operation between the sprung portion and the unsprung portion;
The damping force control means adjusts the attenuation by adjusting the electric resistance of the resistance circuit when the target damping force falls within an adjustment range of the damping force that can be generated by adjusting the generated current flowing through the resistance circuit. When the force is controlled and the magnitude of the target damping force is larger than the adjustment range of the damping force, the capacitor circuit is added to the resistance circuit when the stroke speed and the stroke acceleration are in the same direction. The vehicle suspension device according to claim 1, wherein a deficiency in damping force is compensated for by adjusting the electrostatic capacity by supplying a generated current to the vehicle. A moving direction detecting means for detecting a moving direction of the sprung portion and a relative moving direction of the sprung portion with respect to the unsprung portion;
The damping force control means prevents the generated current from flowing through the resistance circuit when the moving direction of the sprung portion and the relative moving direction of the sprung portion with respect to the unsprung portion are opposite to each other. The propulsive force acting in the direction opposite to the damping force is controlled by adjusting the capacitance by causing a generated current to flow through the capacitor circuit when the stroke speed and the stroke acceleration are in opposite directions. 4. The vehicle suspension device according to 3. Provided with a notch detecting means for detecting the start of turning of the steering wheel;
The damping force control means controls the damping force by adjusting the electric resistance by causing a generated current to flow through the resistor circuit in a normal state, and adds to the capacitor circuit in addition to the resistor circuit at the start of turning of the steering wheel. 3. The vehicle suspension apparatus according to claim 1, wherein a damping force is increased by flowing a generated current. A steering speed detecting means for detecting the steering speed;
The said damping force control means sets the electrostatic capacitance of the said capacitor circuit large, so that the said steering speed is small, when flowing an electric power generation current through the said capacitor circuit at the time of the start of the turning of the said steering wheel. The vehicle suspension apparatus described.

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