JP2006273061A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an electric power steering apparatus capable of performing steering assistance with a high degree of freedom of voltage, easy maintenance, long life of parts, little burden on a battery.
A battery 2 that supplies electric power to a motor via a control means inside an electric power steering apparatus 10, a boosting means 3 that boosts the output voltage of the battery and supplies the voltage to the motor via the control means, and a boosting means And a capacitor C that is provided on the output side of 3 and charges and discharges electric power output to the motor. The capacitor C is preferably connected to the output line of the booster 3 via a diode D.
[Selection] Figure 2

Description

  The present invention relates to an electric power steering apparatus having a booster as a power source.

  The electric power steering device detects a steering torque generated in the steering shaft when steering the steering handle, and generates a steering assist force by driving a motor when a large steering force is required based on the detection signal. , It operates to reduce the steering force of the steering handle. That is, when the steering handle is being steered, if the steering torque is large, a large steering force is required. Therefore, the target value of the motor current is set so as to supply a large steering assist force, and the motor The feedback control is performed so that the actual current value of the current value coincides with the target value. Further, when the steering torque is small, a large steering force is not required, so the target value of the motor current is set so as to supply a small steering assist force.

  By the way, in such a system, current does not always flow through the motor, and current does not flow through the motor unless the steering handle is driven. However, when the motor requires a current, a large current needs to flow. When stationary driving that requires the maximum steering assist force, the required power is about 600 watts to 800 watts for a normal 2000 cc class car. Current may be required.

  By the way, in order to control such a large current, a semiconductor switching element corresponding to the large current is required. The size of the semiconductor switching element is determined by the amount of current that can be passed. Moreover, in order to actually perform chopper control of a large current, a semiconductor switching element having a peak current value of 1.5 to 2 times the maximum current flowing through the motor is required, which increases the size and cost of the circuit. Inevitable. In order to pass a larger current, the wiring around the circuit is required to be thick enough to pass the current, and the weight and layout of the wiring become a problem. In addition, a phenomenon is also known in which the electromotive force from the motor increases and current does not easily flow when the motor rotates rapidly. In addition, if a large current is taken from the battery, the voltage of the battery will drop each time the steering wheel is steered, causing noise in the electrical system and causing fluctuations in the brightness of the headlamps during night driving. It was.

  In order to solve such a problem, the first battery, the booster connected to the first battery, the second battery connected to the output side of the booster, and the second battery An example of a power supply device for electric power steering, which is configured by a control circuit that supplies driving power of a steering motor corresponding to a steering torque signal connected to the steering wheel and a steering motor connected to the control circuit, has been reported. (See Patent Document 1).

As shown in FIG. 5, the power supply device 25 of Patent Document 1 boosts the voltage of the first battery 31 with the booster 32, stores electric power in the second battery 33, and the motor 19 and the like from the second battery 33. Since the power is supplied to the load, the booster 32 can be reduced in size, and the circuit weight and the price can be reduced. Moreover, since the voltage fluctuation of the 1st battery 31 does not arise even if an apparatus is used, the fluctuation | variation of the brightness of the lamp for illumination connected to the 1st battery 31 can be reduced.
Japanese Patent Publication No. 8-539

However, when connecting the second battery to the output of the booster in this way,
1) The voltage becomes a voltage that is an integral multiple of a unit battery that is generally used, and the voltage has a low degree of freedom and cannot take an arbitrary voltage value.
2) Since the boosted voltage is determined by the voltage of the second battery, it cannot be changed according to the situation.
3) Since a normal storage battery has a lifetime and is a regular replacement product, it becomes a system with a high maintenance cost in which maintenance is complicated.
4) The apparatus becomes large when a plurality of storage batteries are used to obtain a predetermined voltage. In addition, the use of a special battery increases the cost.
Problems such as are born.

  The present invention solves these problems, and it is an object of the present invention to realize an electric power steering device capable of performing steering assistance with a high degree of freedom in voltage, easy maintenance, long life of parts, and less burden on the battery. And

  In order to solve the above-mentioned problems, the present invention provides an electric power steering apparatus having control means for calculating a target current based on at least an output signal from a steering input detection means and controlling a current flowing in a motor that outputs a steering assist force A booster that boosts the output voltage of the battery and supplies power to the motor via the controller; and a capacity that is provided on the output side of the booster and charges and discharges the power output to the motor. Means. As a result, the electric power is output from the capacity means provided on the output side of the boosting means so as to supplement the electric power.

  In the electric power steering apparatus, the capacity means is connected to an output line of the boosting means via a diode, and when the output voltage of the boosting means becomes lower than a charging voltage of the capacity means, the capacity means It is preferable to supply electric power to the motor from the output side toward the output side of the boosting means. According to this, when the output voltage of the booster is higher than the charging voltage of the capacitor, the capacitor is charged from the booster. In addition, when the output voltage of the booster becomes lower than the charging voltage of the capacitor, power is supplied to the motor toward the output side of the booster.

  The electric power steering apparatus includes supply power monitoring means for monitoring a state of power supplied to the boosting means, and controls discharge of power from the capacity means based on a signal from the supply power monitoring means. can do. According to this configuration, the discharge of power from the capacity unit is controlled based on monitoring of the state of power supplied to the boosting unit.

  Furthermore, the discharge power from the capacity means can be increased as the voltage of the power supplied to the boosting means decreases.

  According to the present invention, sufficient electric power is output from the capacity means provided on the output side of the boosting means to the motor. In addition, it is possible to realize an electric power steering apparatus that has a high degree of freedom in voltage, is easy to maintain, has a long component life, and has a small burden on the battery and can perform steering assistance.

  Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a configuration of an electric power steering apparatus 10 according to an embodiment of the present invention. This device comprises a drive mechanism 5 and a power supply device 1. When a steering handle 11 of the drive mechanism 5 is rotated, a steering shaft 12 directly connected to the steering handle 11 is connected to a torque sensor 20 (steering input detection means). ) To rotate the pinion 13 constituting the rack and pinion mechanism 15, thereby moving the rack shaft 14 to change the direction of the front wheel 17 connected via a tie rod (not shown) and steering. At this time, the control circuit 22 (control means) supplies power from the power supply device 1 to the motor 19 according to the torque signal T detected by the torque sensor 20 and the vehicle speed signal V detected by the vehicle speed sensor 21, and the target motor current. Control to flow. With this supplied power, the motor 19 rotates the pinion 13 via the power transmission mechanism 18 and operates to reduce the steering torque of the steering handle 11.
The power supply apparatus 1 used for such an electric power steering apparatus 10 has a function of supplying electric power to a motor 19 that provides a steering assist force. The electric power steering device 10 of the present invention has a capacitor for holding a charge charge inside the power supply device 1, and the voltage of the battery (primary power supply) providing power to the input side of the booster circuit is reduced. When the current flowing through the motor 19 increases, the charging charge of the capacitor is given to the output side to compensate for the shortage.

  FIG. 2 is a block diagram of a power supply device 1a used in the electric power steering device 10 according to one embodiment of the present invention. In FIG. 2, reference numeral 2 is a battery, reference numeral 3 is a booster circuit (boosting means), reference numeral 10 is an electric power steering device, reference numeral C is a capacitor (capacitance means), reference numeral D is a diode (diode means), and reference numeral R is a resistor. It is. The booster circuit 3 boosts and outputs an input voltage, and a battery 2 is connected to the input side. An electric power steering device 10 is connected to the output side of the booster circuit 3, and a resistor R and a diode D connected in series are connected in parallel to the connection line. One end of the capacitor C is connected to the connection point between the resistor R and the diode D, and the other end is grounded.

In this embodiment, the output voltage of the battery 2 is boosted by the booster circuit 3, and the voltage boosted by the booster circuit 3 is applied to the motor 19 (see FIG. 5) that provides a steering assist force via the control circuit 22 in the electric power steering apparatus 10. 1). The output of the booster circuit 3 is also connected to a large-capacitance capacitor C through a resistor R to charge the capacitor C.
For example, the output of the booster circuit 3 is increased because the power usage from the battery 2 increases and the input voltage to the booster circuit 3 decreases, or the current flowing from the booster circuit 3 to the electric power steering device 10 increases. When the voltage drops below the charging voltage of the capacitor C, the diode D connected in the forward direction from the terminal of the capacitor C to the output of the booster circuit 3 is turned ON, and the capacitor C is charged instead of the output power of the booster circuit 3. Electric power is supplied to the electric power steering apparatus 10 side.

As described above, in the electric power steering device 10, when a large amount of power is required for driving the motor 19 (see FIG. 1), the charging power of the capacitor C supplements the power output from the booster circuit 3. Since it works, the voltage applied to the motor 19 does not decrease, and the steering assist can be performed efficiently, and even if the electric power steering device 10 works, the battery 2 does not fluctuate in voltage, so It is less likely that the brightness of the lamp fluctuates.
In the case of the capacitor C, the capacity can be selected widely according to the purpose. Therefore, the capacity is set small for a vehicle that can be steered with a relatively small thrust, and the power (current) is large for a vehicle that requires a relatively large thrust. Can be selected in accordance with the purpose, such as increasing the capacity so that is supplied to the motor 19. In the case of the capacitor C, the charge amount can be accurately grasped by the capacity and the charge voltage. Furthermore, since the charge voltage can be changed even during operation, the charge amount can be changed by changing the charge voltage. There is an advantage that can be controlled freely.

FIG. 3 shows a block diagram of a power supply apparatus 1b used in an electric power steering apparatus according to another embodiment of the present invention. In FIG. 3, reference numeral 2 is a battery, reference numeral 3 is a booster circuit (boost means), reference numeral 4 is a charge / discharge control circuit (supply power monitoring means), reference numeral 6 is a control signal, reference numeral 10 is an electric power steering device, and reference numeral C is A capacitor, symbol R is a resistor. Reference numeral S denotes a semiconductor switching element, and conduction / opening between the drain and the source is controlled by a gate voltage. To facilitate understanding, the same functions as those in FIG. 2 are denoted by the same reference numerals.
A control circuit 22 is connected to the output side of the booster circuit 3, and a resistor R and a semiconductor switching element S connected in series are connected in parallel to the connection line. One end of the capacitor C is connected to a connection point between the resistor R and the semiconductor switching element S, and the other end is grounded. The charge / discharge control circuit 4 monitors the input voltage and output voltage of the booster circuit 3 and controls the gate voltage of the semiconductor switching element S and the booster circuit 3. Further, the semiconductor switching element S may include a parasitic diode inside, or may include a diode between the charge / discharge control circuit 4 and the output line of the booster circuit.

  In this embodiment, the output voltage of the battery 2 is boosted by the booster circuit 3, and the voltage boosted by the booster circuit 3 is supplied to the motor 19 (which gives steering assist force via the control circuit 22 in the electric power steering device 10). 1). The output of the booster circuit 3 is connected to a large-capacitance capacitor C through a resistor R and charges the capacitor C. The charge / discharge control circuit 4 monitors the output voltage of the battery 2, and when the output voltage of the battery 2 decreases or is expected to decrease, the charge / discharge control circuit 4 sends a control signal 6 to the booster circuit 3. And increasing the charge voltage of the capacitor C to increase the amount of charge charged in the capacitor C. Furthermore, the charge / discharge control circuit 4 also monitors the output voltage of the booster circuit 3, and when the electric power steering device 10 is powered and the output voltage of the booster circuit 3 decreases, the semiconductor switching is performed. The element S is turned on to supply power from the capacitor C.

  Thus, since the capacitor C is used to hold the charge, the charge voltage can be varied even during operation. Therefore, the charge amount can be changed according to the situation to control the accumulated charge amount. For example, when the output voltage of the battery 2 is likely to decrease, such as when using an in-vehicle cooler or during night driving, the output of the booster circuit 3 is increased when there is room when the condition of the battery 2 is viewed. The charge voltage is increased to increase the amount of accumulated charge, and when necessary, a method is used to output (supply) the electric power steering device 10. As a result, when the electric power steering apparatus 10 requires a large amount of electric power, the discharge power of the capacitor C works to supplement the electric power from the booster circuit 3, so that the voltage applied to the motor 19 of the electric power steering apparatus 10 decreases. In addition, the steering assist can be performed efficiently, and even if the electric power steering apparatus 10 operates, the voltage fluctuation does not occur in the battery 2, and the load on the battery 2 when the load is maximum is greatly reduced. be able to.

FIG. 4 shows a block diagram of a power supply device 1c used in an electric power steering apparatus according to still another embodiment of the present invention. The reference numerals of the respective parts in FIG. 3 are the same as those in FIG. This embodiment differs from FIG. 3 in that two circuits are provided in the booster circuit 3 and output separately.
According to this configuration, since one output of the booster circuit 3 is used only for charging the capacitor C, separately from the power output to the control circuit 22, it is separate from the voltage supplied to the electric power steering device 10. The charging voltage can be set freely.
Further, as shown in FIG. 4, an inrush current to the semiconductor switching element S or the capacitor C may be prevented by inserting a relay Re on the output side of the capacitor. By providing the relay Re, a protective element such as a diode for protecting the capacitor C becomes unnecessary, and a voltage drop due to the protective element can be prevented. Therefore, the output voltage can be improved more efficiently.
As described above, regardless of the output of the booster circuit 3 to the electric power steering device 10, the accumulated charge amount can be changed by changing the charging voltage of the capacitor C as necessary. The output of the booster circuit 3 can be assisted by the charge of the capacitor C according to the required power. Furthermore, the present invention is also applicable to steer-by-wire (Steer_By_Wire) in which the steering wheel and the front wheels in the steering system S are mechanically separated.
In the present embodiment, the capacitor C is charged via the resistor R. However, the capacitor C may be charged with a constant current.

  As described above, the power supply devices 1a, 1b, and 1c used in the electric power steering devices of the respective embodiments are provided with the capacitor C that charges and discharges the output of the booster circuit on the output side, and the electric power steering device When a large amount of power is required, the charging power is discharged to assist the output of the booster circuit. Since the capacitor C is used, the capacity can be selected according to the purpose, and the charge charge amount can be accurately grasped and the charge voltage can be varied even during operation. Therefore, the charge charge amount can be varied by changing the charge voltage. Control according to the situation can be performed freely. Furthermore, the apparatus can be made small, inexpensive, long-life, and maintenance-free. By using the power supply devices 1a, 1b, and 1c, the burden on the battery 2 can be reduced, fluctuations in the output voltage of the battery and noise can be reduced, and current flowing to the electric power steering device can be reduced. Thus, the electric power steering device and the motor can be reduced in size and weight.

  Since the electric power steering apparatus according to the present invention is configured as described above, it can increase the effect particularly in terms of reduction in size and weight, and can be widely used for passenger vehicles and the like.

It is a block diagram which shows the structure of the electric power steering apparatus which is embodiment of this invention. It is a block diagram of the power supply device used for the electric power steering device which is one embodiment of this invention. It is a block diagram of the power supply device used for the electric power steering device which is other embodiment of this invention. It is a block diagram of the power supply device used for the electric power steering device which is further another embodiment of this invention. It is a block diagram which shows the structure of the step-up circuit of the conventional power supply device for electric power steering.

Explanation of symbols

1, 1a, 1b, 1c Power supply device 2 Battery 3 Booster circuit (Boosting means)
4 Charge / discharge control circuit (Supply power monitoring means)
DESCRIPTION OF SYMBOLS 5 Drive mechanism 6 Control signal 10 Electric power steering apparatus 11 Steering handle 12 Steering shaft 13 Pinion 14 Rack shaft 15 Rack pinion mechanism 17 Front wheel 18 Power transmission mechanism 19 Motor 20 Torque sensor (steering input detection means)
22 Control circuit (control means)
25 Power supply device 31 First battery 32 Booster device 33 Second battery C Capacitor (capacitance means)
D Diode (diode means)
R resistor S semiconductor switching element Re relay

Claims (4)

An electric power steering apparatus having a control means for calculating a target current based on at least an output signal from a steering input detection means and controlling a current flowing in a motor that outputs a steering assist force,
Boosting means for boosting the output voltage of the battery and supplying power to the motor via the control means; and capacity means for charging / discharging the power output to the motor provided on the output side of the boosting means An electric power steering device. The capacitor means is connected to the output line of the boost means via a diode,
2. The electric power is supplied to the motor from the capacity means toward the output side of the boost means when the output voltage of the boost means becomes lower than the charging voltage of the capacity means. Electric power steering device.   The power supply monitoring means for monitoring the state of the power supplied to the boosting means, and discharging of the power from the capacity means is controlled based on a signal from the supply power monitoring means. 2. The electric power steering apparatus according to 2.   4. The electric power steering apparatus according to claim 3, wherein the discharge power from the capacity means is increased as the voltage of power supplied to the boosting means decreases.

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