JP2014043199A - Suspension control device - Google Patents

Abstract

A suspension control device capable of suppressing vibrations is provided.
A suspension control device includes a suspension device that connects a sprung member and an unsprung member of a vehicle, and an actuator that can adjust a frictional force along a stroke direction of the suspension device. The actuator 3 is controlled based on the speed direction of the sprung member 5 along the stroke direction of the suspension device 2 and the stroke speed direction of the suspension device 2, and the frictional force along the stroke direction of the suspension device 2. And a control device 4 for adjusting the frequency.
[Selection] Figure 1

Description

  The present invention relates to a suspension control device.

  As a conventional suspension control device mounted on a vehicle, for example, Patent Document 1 discloses a rod guide and an oil seal provided on the cylinder side with the other end of a piston rod attached to one end of a piston slidably contacting a cylinder inner peripheral surface. There is disclosed a hydraulic shock absorber led out to the outside. This hydraulic shock absorber is provided with a bush in the space between the rod guide and the oil seal so that when the piston speed is very low, a constant friction is generated between the bush and the piston rod. Yes.

JP-A-10-141415

  By the way, the hydraulic shock absorber of the vehicle described in Patent Document 1 described above is intended to suppress fine vibrations generated after large vibrations when traveling on rough roads by the above configuration. There is room for further improvement.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a suspension control device capable of suppressing vibration.

  To achieve the above object, a suspension control device according to the present invention is capable of adjusting a suspension device that connects a sprung member and an unsprung member of a vehicle, and a frictional force along a stroke direction of the suspension device. The actuator is controlled based on a certain actuator, the speed direction of the sprung member along the stroke direction of the suspension device, and the stroke speed direction of the suspension device, and is along the stroke direction of the suspension device. And a control device that adjusts the frictional force.

  In the suspension control device, the control device controls the actuator, and when the speed direction of the sprung member and the stroke speed direction of the suspension device are the same direction, the speed direction of the sprung member The frictional force along the stroke direction of the suspension device can be increased compared to the case where the stroke speed direction of the suspension device is different.

  In the suspension control device, the control device is in a very low speed region where a stroke speed of the suspension device is equal to or lower than a predetermined speed set in advance, and a predetermined angle at which the steering angle of the vehicle is set in advance. In the following cases, the actuator is controlled based on the speed direction of the sprung member and the stroke speed direction of the suspension device to adjust the frictional force along the stroke direction of the suspension device. be able to.

  The suspension control device according to the present invention has an effect that vibration can be suppressed.

FIG. 1 is a schematic configuration diagram illustrating a schematic configuration of a suspension control device according to an embodiment. FIG. 2 is a diagram illustrating the generated force of the damping mechanism (shock absorber) of the suspension control device according to the embodiment. FIG. 3 is a schematic diagram for explaining a tendency of riding comfort performance due to a change in frictional force in the suspension control apparatus according to the embodiment. FIG. 4 is a schematic diagram illustrating the control logic of the friction force control in the suspension control device according to the embodiment. FIG. 5 is a flowchart for explaining an example of frictional force control by the suspension control device according to the embodiment. FIG. 6 is a diagram illustrating an example of sprung vibration when friction force control is performed in the suspension control device according to the embodiment.

  Embodiments according to the present invention will be described below in detail with reference to the drawings. In addition, this invention is not limited by this embodiment. In addition, constituent elements in the following embodiments include those that can be easily replaced by those skilled in the art or those that are substantially the same.

[Embodiment]
FIG. 1 is a schematic configuration diagram illustrating a schematic configuration of a suspension control device according to the embodiment, FIG. 2 is a diagram illustrating the generated force of a damping mechanism (shock absorber) of the suspension control device according to the embodiment, and FIG. FIG. 4 is a schematic diagram illustrating a tendency of riding comfort performance due to a change in frictional force in the suspension control device according to the embodiment. FIG. 4 is a schematic diagram illustrating control logic of frictional force control in the suspension control device according to the embodiment. FIG. 6 is a flowchart for explaining an example of frictional force control by the suspension control device according to the embodiment, and FIG. 6 is a diagram showing an example of sprung vibration when frictional force control is performed in the suspension control device according to the embodiment. is there.

FIG. 1 shows a single-wheel model of the vibration suppression control system according to the embodiment. The single-wheel model shown in FIG. 1 is a vehicle motion model including a suspension device. In FIG. 1, “c _s ” represents an attenuation coefficient of the later-described attenuation mechanism 8. “F _c ” represents a suspension friction force in the sliding portion 9 described later. “K _s ” represents a spring coefficient of the spring mechanism 7 described later. “K _t ” represents the rigidity (spring constant) of the wheel 50. “M _b ” represents the mass of the sprung member 5 described later (hereinafter, sometimes referred to as “sprung mass”). “M _w ” represents the mass of an unsprung member 6 to be described later (hereinafter sometimes referred to as “unsprung mass”). “X _b ” represents a displacement of a sprung member 5 described later (hereinafter, sometimes referred to as “sprung displacement”). “X _w ” represents a displacement of an unsprung member 6 to be described later (hereinafter sometimes referred to as “unsprung displacement”). “X _r ” represents the displacement of the road surface R (hereinafter sometimes referred to as “road surface displacement”). Here, the displacement is a displacement in the vertical direction of the vehicle with respect to each reference position, and can be, for example, a displacement in the vertical direction. In addition, it is good also considering the movement amount of the axial direction of the suspension apparatus 2 mentioned later as a displacement.

  In the suspension control apparatus 1 according to the present embodiment shown in FIG. 1, the suspension apparatus 2 is provided for each of the four wheels 50 of the vehicle, and each wheel 50 is supported on the vehicle body. The suspension control device 1 includes a suspension device 2, an actuator 3, and an ECU 4 as a control device. In the suspension control device 1, one suspension device 2 and one actuator 3 are provided for each of the four wheels 50, and one ECU 4 is provided in common for the four wheels 50. Hereinafter, one of the four wheels 50 will be described.

  The suspension device 2 is provided between the sprung member 5 and the unsprung member 6 of the vehicle, and connects the sprung member 5 and the unsprung member 6. The sprung member 5 is a member supported by the suspension device 2 and includes a vehicle body. The unsprung member 6 is a member disposed on the wheel 50 side of the suspension device 2 and includes a knuckle coupled to the wheel 50, a lower arm coupled to the knuckle, and the like.

  The suspension device 2 includes a spring mechanism 7 and a damping mechanism 8. The spring mechanism 7 and the damping mechanism 8 are provided in parallel.

The spring mechanism 7 connects the sprung member 5 and the unsprung member 6, generates a spring force corresponding to the relative displacement between the sprung member 5 and the unsprung member 6, and uses the spring force as the sprung member 5 and the unsprung member 5. It acts on the unsprung member 6. The spring mechanism 7 generates the spring force by, for example, a coil spring 7a attached to a piston rod 8c or the like of the later-described damping mechanism 8 or an air suspension mechanism (not shown). The relative displacement between the sprung member 5 and the unsprung member 6 is that the sprung member 5 and the unsprung member 6 approach each other in the direction of the stroke of the suspension device 2 (hereinafter sometimes referred to as “suspension stroke direction”). Or it is the relative displacement in the direction of separating. Here, although the suspension stroke direction is illustrated as being along the vertical direction, it may have a predetermined inclination with respect to the vertical direction. Further, the spring mechanism 7 may be configured to be able to variably control the spring coefficient k _s , that is, the spring force.

The damping mechanism 8 connects the sprung member 5 and the unsprung member 6 and generates a damping force that attenuates the relative motion between the sprung member 5 and the unsprung member 6. The relative motion between the sprung member 5 and the unsprung member 6 is a relative motion in a direction in which the sprung member 5 and the unsprung member 6 approach or separate in the suspension stroke direction. The damping mechanism 8 attenuates the relative motion by generating a damping force corresponding to the relative speed between the sprung member 5 and the unsprung member 6 in this relative motion. As the damping mechanism 8, for example, a shock absorber is used. The shock absorber is, for example, a piston having a cylinder 8a connected to one of the sprung member 5 or the unsprung member 6 and enclosing a differential fluid, and a piston portion 8b connected to the other and reciprocating in the cylinder 8a. A thing provided with the rod 8c can be used. The suspension device 2 strokes when the cylinder 8a and the piston rod 8c are relatively displaced, and the sprung member 5 and the unsprung member 6 are relatively displaced. In other words, the suspension stroke direction is the direction along the relative displacement between the cylinder 8a and the piston rod 8c, and is typically the direction along the relative displacement between the sprung member 5 and the unsprung member 6. The damping mechanism 8 may be configured to variably control the damping coefficient c _s , that is, the damping force. In this case, as the damping mechanism 8, for example, a shock absorber capable of variably controlling the damping coefficient c _s is used. The means for variably controlling the damping coefficient c _s can be, for example, a device that makes the flow passage area of the oil passage communicating the piston upper chamber and the lower chamber variable by rotating the rotary valve of the piston portion. . Note that. The attenuation mechanism 8 is not limited to this, and an attenuation mechanism having another configuration may be used, or the attenuation coefficient c _s may not be variably controllable.

The actuator 3 is capable of adjusting a frictional force (hereinafter sometimes referred to as “suspension frictional force”) F _c along the stroke direction of the suspension device 2.

Here, the suspension friction force F _c is a friction force acting on the sliding portion 9 of the suspension device 2. The sliding portion 9 of the suspension device 2 is a portion that slides with the stroke in the suspension device 2. For example, the sliding portion between the piston rod 8 c and the cylinder 8 a of the damping mechanism 8 (shock absorber), the piston rod 8 c. And a sliding portion of a seal member provided between the cylinder 8a and the cylinder 8a. That is, the suspension friction force F _c is a friction force generated along the stroke direction at these sliding portions 9 in accordance with the stroke of the suspension device 2.

The actuator 3 is configured to be able to variably control the suspension friction force F _c generated in the sliding portion 9. As the actuator 3, for example, a device that varies the tightening force of the sealing member that forms the sliding portion 9 by a piezoelectric element or the like, and in the sliding portion 9 between the piston rod 8 c and the cylinder 8 a, the piston rod 8 c or the cylinder 8 a Various devices can be used, such as a device that varies the pressing force that presses one against the other. The actuator 3 is not limited to this and may be adjustable device suspension frictional force F _c in other configurations.

ECU4 controls the actuator 3, and adjusts the suspension frictional force F _c. Here, the ECU 4 controls each part of the vehicle on which the suspension control device 1 is mounted. The ECU 4 is an electronic circuit mainly composed of a known microcomputer including a CPU, a ROM, a RAM, and an interface. The ECU 4 includes various sensors and suspension control devices such as an unsprung G sensor 10 as an unsprung acceleration detection unit, an unsprung G sensor 11 as an unsprung acceleration detection unit, and a steering angle sensor 12 as a steering angle detection unit. 1 is electrically connected to each part of the vehicle. The sprung G sensor 10 is disposed on the sprung member 5. The sprung G sensor 10 can detect acceleration in the vertical direction of the sprung member 5, typically in the suspension stroke direction (hereinafter sometimes referred to as “sprung acceleration”). The unsprung G sensor 11 is disposed on the unsprung member 6. The unsprung G sensor 11 can detect acceleration in the vertical direction of the unsprung member 6, typically in the suspension stroke direction (hereinafter sometimes referred to as “unsprung acceleration”). The steering angle sensor 12 detects a steering angle of a vehicle on which the suspension control device 1 is mounted, in this case, a steering wheel steering angle that is an operation amount of the steering wheel. The ECU 4 receives electrical signals (detection signals) corresponding to detection results from various sensors, and outputs a drive signal to each part of the vehicle according to the input detection results to control the driving of the suspension control device 1.

  FIG. 2 is a diagram for explaining the generated force of the damping mechanism (shock absorber) 8. The horizontal axis represents the speed (mm / s) of the piston portion 8b, the displacement (mm) of the piston portion 8b, and the vertical axis. Is the axial force (N). In FIG. 2, the speed of the stroke of the suspension device 2 (hereinafter sometimes referred to as “stroke speed”) is a very low speed input, for example, when the vehicle travels on a good road with relatively little unevenness on the road surface R. An example of a very low speed region is shown. Here, the stroke speed of the suspension apparatus 2 corresponds to the expansion / contraction speed of the suspension apparatus 2 (speed of relative displacement between the cylinder 8a and the piston rod 8c). The very low speed range is, for example, a speed range where the absolute value of the stroke speed is greater than 0 m / s and less than 0.002 m / s. FIG. 2 schematically shows, as an example, the generated force (total axial force) of the damping mechanism 8 in the case of a slight amplitude excitation of about 0.2 mm and 1.5 Hz (a very low speed less than 0.002 m / s). Represents.

In the suspension device 2, friction is generated at the sliding portion 9 with vertical vibration. As shown in FIG. 2, the generated force of the damping mechanism 8 of the suspension device 2 configured as described above is the Coulomb friction force (the Coulomb friction force (the suspension friction force F _c ) when the stroke speed is in the very low speed region. a) and elastic (viscoelastic) frictional force (b) are main, and there is almost no influence of the very low speed damping force (c) of the damping mechanism 8. Here, the Coulomb friction force (a) is typically static friction in the sliding portion 9, and the elastic (viscoelastic) friction force (b) is typically the sealing member of the sliding portion 9. This is the dynamic friction at the start of the stroke in

The suspension control device 1 relates to the riding comfort performance according to the relationship between the frequency of the road surface input acting on the suspension device 2 and the suspension friction force F _c in the above-described very low speed range of the stroke speed. The knowledge that there is a contradiction as shown in was obtained. That is, for example, the suspension control device 1 has the sliding portion 9 in order to improve the riding comfort performance with respect to the road surface input in the medium frequency range (hereinafter, sometimes referred to as “medium frequency vibration”) acting on the suspension device 2. If the suspension frictional force F _c of relatively small frictional force generated, road surface input of the low frequency range (hereinafter referred to as "low-frequency vibration".) ride comfort is deteriorated for so-called " There is a tendency to give a “feel of fluff”. On the other hand, the suspension control apparatus 1 is, for example, in order to improve the ride comfort for low-frequency vibration, when the suspension frictional force F _c generated in the sliding portion 9 relatively large frictional force, against medium-frequency vibration Riding comfort performance deteriorates, and there is a tendency to feel a so-called “growing feeling”. Therefore, the suspension control apparatus 1 simply keep relatively large suspension frictional force F _c, or simply be allowed to relatively small suspension frictional force F _c, ride comfort for the low-frequency vibration There is a possibility that the performance and the riding comfort performance with respect to medium frequency excitation cannot be compatible. In the above, the low frequency region is, for example, a region greater than 0 Hz and less than 1.5 Hz. On the other hand, the medium frequency region is, for example, a region between 1.5 Hz and 8 Hz.

Therefore, in the suspension control device 1 of the present embodiment, the ECU 4 controls the actuator 3 in accordance with the state of the suspension device 2 and executes the friction force control that adjusts the suspension friction force F _c , so Both comfort performance and ride comfort performance for medium frequency excitation are achieved, and sprung vibration can be appropriately suppressed.

Specifically, the ECU 4 is based on the speed direction of the sprung member 5 along the suspension stroke direction (hereinafter sometimes referred to as “sprung speed direction”) and the stroke speed direction of the suspension device 2. Friction force control for controlling the actuator 3 to adjust the suspension friction force F _c is executed. Thereby, the ECU 4 changes the friction characteristic of the damping mechanism (shock absorber) 8 according to the state of the suspension device 2.

  Here, the sprung speed direction is the direction of the speed vector of the sprung member 5 and is typically upward in the vertical direction (+ (positive)) or downward in the vertical direction (-(negative)). . The stroke speed direction is the direction of the stroke speed (extension / contraction speed) vector of the suspension device 2 and is typically upward in the vertical direction (extension direction, + (positive)) or downward in the vertical direction (contraction direction, − (Negative)).

  The ECU 4 according to the present embodiment executes the friction force control when the vehicle having a stroke speed in a very low speed region travels straight on a good road. Here, the ECU 4 is in a very low speed region where the stroke speed of the suspension device 2 is equal to or lower than a predetermined speed that is set in advance, and when the vehicle steering angle is equal to or lower than a predetermined angle that is set in advance, the friction force Execute control. Thereby, ECU4 improves the vehicle performance in case a stroke speed is a very low speed area | region.

Here, the ECU 4 can calculate the stroke speed of the suspension device 2 as follows, for example. In the following description, the symbol “′” represents a single differentiation, and the symbol “″” represents a double differentiation. The ECU 4 determines the sprung acceleration x _b ″ and the unsprung acceleration x _w ′ based on the sprung acceleration x _b ″ and the unsprung acceleration x _w ″ detected by the sprung G sensor 10 and the unsprung G sensor 11. 'Is integrated to calculate the sprung speed x _b ' and the unsprung speed x _w '. Then, the ECU 4 calculates the difference between the sprung speed x _b ′ and the unsprung speed x _w ′ based on the calculated sprung speed x _b ′ and unsprung speed x _w ′, that is, the sprung member 5 and the unsprung mass. A relative speed (x _b ′ −x _w ′) with respect to the member 6 is calculated, and this is set as a stroke speed (extension / contraction speed) of the suspension device 2. For example, the ECU 4 may calculate the stroke speed based on a detection result of a sensor that detects the amount of expansion / contraction (stroke displacement) of the suspension device 2. Further, the ECU 4 can acquire the steering angle of the vehicle based on the steering wheel steering angle detected by the steering angle sensor 12. Further, the predetermined speed is set in advance in accordance with, for example, the characteristics of the stroke of the suspension device 2 based on actual vehicle evaluation or the like. The predetermined speed is set to a speed at which the stroke speed can be determined to be in the very low speed region, and is typically a speed greater than 0 m / s and less than 0.002 m / s, for example, 0.015 m / s. It is set to about s. In addition, the predetermined angle is set in advance according to the straight traveling performance, steering characteristics, or the like of the vehicle based on, for example, actual vehicle evaluation. The predetermined angle is set to an angle at which it can be determined that the vehicle is traveling straight ahead, for example, about ± 5 °.

  In the case of the low-frequency excitation (first frequency excitation), the suspension device 2 as described above is an excitation with a relatively slow and long cycle. The knowledge that the velocity direction tends to be the same direction was obtained. On the other hand, in the case of the medium frequency excitation (second frequency excitation) higher than the low frequency excitation, the suspension device 2 is an excitation with a relatively short cycle, so It was found that the direction of stroke speed tends to be different.

Based on the above, the ECU 4 controls the actuator 3 in the friction force control, and when the sprung speed direction and the stroke speed direction are the same direction, the sprung speed direction and the stroke speed direction are different from each other (reverse direction). ), The suspension frictional force F _c is increased. That, ECU 4, when the on velocity direction and the stroke velocity direction the spring is the same direction, in other words, if it can be estimated to be oscillating low-frequency pressure, relatively large suspension frictional force F _c. Meanwhile, ECU 4, when the on velocity direction and the stroke velocity direction the spring is different directions, in other words, if it can be estimated that the medium is frequency excitation is relatively small suspension frictional force F _c.

  Here, in order to appropriately suppress the sprung vibration, an on / off control logic as shown in FIG. 4 is designed, and based on this, the ECU 4 performs the friction force control. In FIG. 4, illustration of the unsprung member 6 and the like is omitted, and the suspension device 2 is schematically illustrated.

That is, the ECU 4 is required to have a riding comfort performance with respect to low-frequency excitation (B) and (D) in the speed direction relationship, that is, the sprung speed direction and the stroke speed direction are the same direction. In some cases, the suspension friction force _Fc is relatively increased. In this case, in the state (B), the sprung speed direction is upward (+) and the stroke speed direction is the extension direction (+), and the ECU 4 controls the actuator 3 as indicated by the black arrow in FIG. A relatively large suspension frictional force _Fc is applied downward. In the state (D), the sprung speed direction is downward (−) and the stroke speed direction is the contraction direction (−), and the ECU 4 controls the actuator 3 as shown by the black arrow in FIG. A large suspension frictional force _Fc is applied upward.

On the other hand, the ECU 4 has a speed direction relationship as shown in (A) and (C) in which riding comfort performance is required for medium frequency excitation, that is, a direction in which the sprung speed direction and the stroke speed direction are different ( In the reverse direction), the suspension friction force _Fc is relatively reduced. In this case, in the state (A), the sprung speed direction is upward (+) and the stroke speed direction is the contraction direction (−), and the ECU 4 controls the actuator 3 as indicated by the black arrow in FIG. A relatively small suspension frictional force _Fc is applied upward. In the state of (C), the sprung speed direction is downward (−) and the stroke speed direction is the extension direction (+). The ECU 4 controls the actuator 3 as shown by the black arrow in FIG. A small suspension frictional force _Fc is applied downward.

The suspension friction force F _c can be expressed by, for example, the following mathematical formula (1). In the following formula (1), “f _c ” is an unsigned suspension friction force (that is, the absolute value of the suspension friction force F _c ). That is, the suspension frictional force F _c is the frictional force direction is determined according to the magnitude relation of speed sprung x _b 'and unsprung velocity x _w' and.

Here, for example, the ECU 4 calculates the product of the sprung speed x _b ′ and the stroke speed (x _b ′ −x _w ′), and this is referred to as a frictional force selection determination value (hereinafter referred to as “determination value”). And the high-friction force or the low-friction force is selected based on whether the determination value is equal to or greater than a threshold value, in this case “0”. The ECU 4 uses, for example, the following formula (2) to determine a determination value x _b ′ · (x _b ′ −x) that is a product of the sprung speed x _b ′ and the stroke speed (x _b ′ −x _w ′). Based on _w ′), the frictional force control value F _ccon is set. The frictional force control value F _ccon is a control value for controlling the suspension frictional force F _c by controlling the actuator 3.

That is, when the determination value x _b ′ · (x _b ′ −x _w ′) is a positive value (x _b ′ · (x _b ′ −x _w ′) ≧ 0), the ECU 4 Since the stroke speed direction is the same direction, the friction force control value F _ccon is set to a relatively large value. In this case, for example, the ECU 4 sets the friction force control value F _ccon to the friction force control value maximum value F _cmax that can be realized by the actuator 3. On the other hand, when the determination value x _b ′ · (x _b ′ −x _w ′) is a negative value (x _b ′ · (x _b ′ −x _w ′) <0), the ECU 4 Since the stroke speed direction is a different direction, the friction force control value F _ccon is set to a relatively small value. In this case, for example, the ECU 4 sets the friction force control value F _ccon to the friction force control value minimum value F _cmin that can be realized by the actuator 3.

The ECU 4 controls the actuator 3 based on the friction force control value F _ccon set as described above, and actually adjusts the suspension friction force F _c . That is, when the sprung speed direction and the stroke speed direction are the same direction and the riding comfort performance with respect to low frequency excitation is required, the ECU 4 sets the friction force control value F _ccon to the friction force control value maximum value F _cmax. As a result, the actuator 3 is controlled so that the suspension friction force F _c actually acting is relatively increased. In this case, the suspension friction force F _c is the maximum value that can be realized by the actuator 3. On the other hand, when the sprung speed direction and the stroke speed direction are different from each other and the riding comfort performance with respect to medium frequency excitation is required, the ECU 4 uses the friction force control value F _ccon as the friction force control value minimum value F _cmin. As a result, the suspension friction force F _c actually acting is relatively reduced by controlling the actuator 3. In this case, the suspension friction force F _c is a minimum value that can be realized by the actuator 3.

  Next, an example of frictional force control by the ECU 4 will be described with reference to the flowchart of FIG. Note that these control routines are repeatedly executed at a control cycle of several ms to several tens of ms.

  First, the ECU 4 determines whether or not the absolute value of the vehicle steering angle (steering wheel steering angle) is equal to or smaller than a predetermined angle (for example, 5 °) set based on the detection result by the steering angle sensor 12. (Step ST1). When the ECU 4 determines that the absolute value of the vehicle steering angle (steering wheel steering angle) is larger than the predetermined angle (step ST1: No), the ECU 4 ends the current control cycle and shifts to the next control cycle.

When the ECU 4 determines that the absolute value of the vehicle steering angle (steering wheel steering angle) is equal to or smaller than the predetermined angle (step ST1: Yes), the ECU 4 determines the sprung acceleration based on the detection result by the sprung G sensor 10. x _b ″ is integrated (step ST2).

Then, the ECU 4 calculates the sprung speed x _b ′ based on the integration result of the sprung acceleration x _b ″ calculated in step ST2 (step ST3).

Next, the ECU 4 integrates the unsprung acceleration x _w ″ based on the detection result by the unsprung G sensor 11 to calculate the unsprung speed x _w ′, and the sprung speed x _b ′ calculated in step ST3. And the unsprung speed x _w ′, the stroke speed (x _b ′ −x _w ′) is calculated. Then, the ECU 4 determines whether or not the absolute value of the stroke speed (x _b ′ −x _w ′) is equal to or lower than a predetermined speed (for example, 0.015 m / s) set in advance (step ST4). When the ECU 4 determines that the absolute value of the stroke speed (x _b ′ −x _w ′) is greater than the predetermined speed (step ST4: No), the ECU 4 ends the current control cycle and shifts to the next control cycle.

When the ECU 4 determines that the absolute value of the stroke speed (x _b ′ −x _w ′) is equal to or lower than the predetermined speed (step ST4: Yes), the sprung speed x _b ′ calculated in step ST3 and step ST4 The product of the calculated stroke speed (x _b ′ −x _w ′) is calculated, and this is set as a judgment value x _b ′ · (x _b ′ −x _w ′) (step ST5).

Then, the ECU 4 determines whether or not the determination value x _b ′ · (x _b ′ −x _w ′) calculated in step ST5 is 0 (threshold) or more (step ST6).

When the ECU 4 determines that the determination value x _b ′ · (x _b ′ −x _w ′) is equal to or greater than 0 (step ST6: Yes), the ECU 4 requests a high frictional force and relatively _{sets the} frictional force control value F _ccon . To a larger value, for example, the frictional force control value maximum value F _cmax (step ST7).

Then, ECU 4 is set frictional force control value F _CCON (here, the maximum value F _cmax frictional force control value) in step ST7 relative based on, controls the actuator 3, the suspension frictional force F _c acting actually (Step ST8), the current control cycle is terminated, and the next control cycle is started.

On the other hand, when it is determined that the determination value x _b ′ · (x _b ′ −x _w ′) calculated in step ST5 is smaller than 0 (step ST6: No), the ECU 4 requests a low frictional force and controls the frictional force. The value F _ccon is _set to a relatively small value, for example, the frictional force control value minimum value F _cmin (step ST9).

Then, the ECU 4 controls the actuator 3 based on the friction force control value F _ccon (here, the friction force control value minimum value F _cmin ) set in step ST9, and the suspension friction force F _c actually acting is relatively (Step ST8), the current control cycle is terminated, and the next control cycle is started.

FIG. 6 is a diagram showing an example of simulation of sprung vibration in a vehicle equipped with the suspension control device 1 configured as described above. In FIG. 6, the horizontal axis is the excitation frequency, the vertical axis is the power spectral density of the sprung vibration, and the stroke speed (x _b ′ −x _w ′) is about 0.015 m / s. An example of a simulation result at a low speed input is shown. In the drawing, a solid line L1 represents a case where the above-described frictional force control is performed in the suspension control device 1 of the present embodiment. A dotted line L2 represents a case where the suspension friction force F _c is fixed to a relatively small value (for example, F _c = 0N) in the suspension control device according to the comparative example. A dotted line L3 represents a case where the suspension friction force F _c is fixed to a relatively large value (for example, F _c = 20 N) in the suspension control device according to the comparative example.

As is clear from the solid line L1 in FIG. 6, the suspension control device 1 according to the present embodiment executes the friction force control that controls the actuator 3 and adjusts the suspension friction force F _c according to the state of the suspension device 2. Thus, compared to the dotted lines L2 and L3 representing the suspension control device according to the comparative example, the sprung vibration with respect to the low frequency excitation can be suppressed, and the sprung vibration with respect to the medium frequency excitation can be suppressed in a well-balanced manner. be able to. As a result, the suspension control device 1 can suppress both the “feel of fluff” due to low frequency excitation and the “feel of roughness” due to medium frequency excitation, and the riding comfort performance and medium frequency excitation against low frequency excitation. It is possible to achieve both a comfortable ride performance for the vehicle.

  The suspension control device 1 according to the embodiment described above includes the suspension device 2, the actuator 3, and the ECU 4. The suspension device 2 connects the sprung member 5 and the unsprung member 6 of the vehicle. The actuator 3 can adjust the frictional force along the direction of the stroke of the suspension device 2. The ECU 4 controls the actuator 3 based on the speed direction of the sprung member 5 along the stroke direction of the suspension device 2 and the stroke speed direction of the suspension device 2, and follows the stroke direction of the suspension device 2. Adjust the friction force.

  Therefore, for example, when the low-frequency performance is required, the suspension control device 1 relatively increases the frictional force along the stroke direction when the sprung speed direction and the stroke speed direction are the same direction. When medium frequency performance is required, when the sprung speed direction and the stroke speed direction are different directions, the frictional force along the stroke direction can be relatively reduced. As a result, the suspension control device 1 achieves both riding comfort performance with respect to low-frequency vibration and riding comfort performance with respect to medium-frequency vibration, and appropriately balances vehicle performance with a contradictory low-frequency performance and medium-frequency performance. Therefore, sprung vibration can be suppressed appropriately.

  Furthermore, according to the suspension control device 1 according to the embodiment described above, the ECU 4 is in a very low speed region where the stroke speed is equal to or less than a predetermined speed, and the steering angle of the vehicle is equal to or less than a predetermined angle set in advance. If so, the above frictional force control is executed. Therefore, the suspension control device 1 executes the frictional force control when the vehicle travels on a straight road on a good road that requires both ride comfort performance for low-frequency vibration and ride comfort performance for medium-frequency vibration. In other cases, the frictional force can be fixed, so that the sprung vibration can be more efficiently suppressed.

  The suspension control device according to the above-described embodiment of the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope described in the claims.

  In the above description, the control device has been described as being shared by the ECU 4, but is not limited thereto. For example, the control device may be configured separately from the ECU 4 and exchange information such as a detection signal, a drive signal, and a control command with each other.

  In the above description, the ECU 4 has been described as executing the friction force control when the vehicle having a stroke speed in the very low speed region is traveling straight on a good road. However, the present invention is not limited to this. Force control may be executed. That is, the ECU 4 is in a very low speed region where the stroke speed of the suspension device 2 is equal to or lower than a predetermined speed that is set in advance, and the frictional force is not limited to when the vehicle steering angle is equal to or lower than a predetermined angle. You may make it perform control.

In the above description, ECU 4, when setting the frictional force control value F _CCON relatively large value, for example, by using the frictional force control value maximum value F _cmax, relative frictional force control value F _CCON In the case of setting to a small value, for example, the frictional force control value minimum value F _cmin has been described as being used. ECU4, when the on velocity direction and the stroke velocity direction the spring is the same direction, as compared with the case and the sprung velocity direction and the stroke velocity direction are different directions, so the suspension frictional force F _c increases The frictional force control value F _ccon may be set to an arbitrary value. In other words, the suspension friction force F _c when the sprung speed direction and the stroke speed direction are the same direction may not be the maximum value that the actuator 3 can achieve, and the sprung speed direction and the stroke speed direction are different. The suspension friction force F _c in the case of the direction does not have to be the minimum value that can be realized by the actuator 3, and is arbitrary depending on the riding comfort performance for low-frequency excitation and the riding comfort performance for medium-frequency excitation, respectively. You may make it become a value.

DESCRIPTION OF SYMBOLS 1 Suspension control apparatus 2 Suspension apparatus 3 Actuator 4 ECU (control apparatus)
5 Sprung member 6 Unsprung member 7 Spring mechanism 7a Coil spring 8 Damping mechanism 8a Cylinder 8b Piston part 8c Piston rod 9 Sliding part 10 Sprung G sensor 11 Unsprung G sensor 12 Steering angle sensor 50 Wheel

Claims (3)

A suspension device for connecting the sprung member and the unsprung member of the vehicle;
An actuator capable of adjusting the frictional force along the direction of the stroke of the suspension device;
The actuator is controlled based on the speed direction of the sprung member along the stroke direction of the suspension device and the stroke speed direction of the suspension device, and the frictional force along the stroke direction of the suspension device is controlled. And a control device for adjusting,
Suspension control device. The control device controls the actuator, and when the speed direction of the sprung member and the stroke speed direction of the suspension device are the same direction, the speed direction of the sprung member and the stroke speed direction of the suspension device Increase the frictional force along the direction of the stroke of the suspension device as compared to the case where
The suspension control device according to claim 1. The control device includes the spring when the stroke speed of the suspension device is in a very low speed region that is equal to or lower than a predetermined speed that is set in advance and the steering angle of the vehicle is equal to or lower than a predetermined angle that is set in advance. Controlling the actuator based on the speed direction of the upper member and the stroke speed direction of the suspension device, and adjusting the frictional force along the stroke direction of the suspension device;
The suspension control device according to claim 1 or 2.

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