JP2005254843A - Power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent deterioration of steering feeling by friction of a stopped electric motor in a power steering device generating assistance force by a hydraulic cylinder and the electric motor. <P>SOLUTION: This power steering device is provided with the hydraulic cylinder 25 and the electric motor 33 arranged in a steering torque transmitting passage for transmitting steering torque inputted to a steering wheel 11 by a driver to a wheel W. When only the hydraulic cylinder 25 of the hydraulic cylinder 25 and the electric motor 33 is driven in order to assist steering operation of the driver, the steering feeling is deteriorated by the friction when the electric motor 33 is driven by the assistance force of the hydraulic cylinder 25 transmitted from the steering torque transmitting passage, friction offset torque for offsetting self-friction is generated in the electric motor 33, and thereby deterioration of the steering feeling by friction of the electric motor 33 can be prevented. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention arranges a hydraulic cylinder and an electric motor in a steering torque transmission path for transmitting a steering torque input by a driver to a steering wheel to a wheel, and assists the steering operation of the driver with an assist force generated by the hydraulic cylinder and the electric motor. The present invention relates to a power steering device.

In hydraulic power steering, where the rack bar housed in the steering gear box is driven by a hydraulic cylinder to assist the steering operation of the driver, the assist force generated by the hydraulic cylinder by connecting an electric motor to the pinion that meshes with the rack of the rack bar Is disclosed in Japanese Patent Application Laid-Open Publication No. 2004-228688, which controls the increase / decrease by the torque in the same direction and the opposite direction generated by the electric motor.
JP-A 63-64869

  By the way, when the hydraulic cylinder and the electric motor are arranged in the steering torque transmission path of the power steering device, if the assist force is generated by driving only the hydraulic cylinder with the electric motor stopped, the assist torque is transmitted from the steering torque transmission path. Since the electric motor may be driven from the outside by the assist force of the hydraulic cylinder, the steering feeling is reduced due to the friction of the electric motor.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent a reduction in steering feeling due to friction of a stopped electric motor in a power steering device that generates assist force by a hydraulic cylinder and an electric motor. .

  In order to achieve the above object, according to the first aspect of the present invention, a hydraulic cylinder and an electric motor are disposed in a steering torque transmission path for transmitting a steering torque input by a driver to a steering wheel to a wheel. In the power steering device that assists the driver's steering operation with the assist force generated by the electric motor, when the electric motor is driven by the assist force of the hydraulic cylinder, the electric motor generates a friction canceling torque that cancels its own friction. A power steering apparatus characterized by this is proposed.

  According to the invention described in claim 2, in addition to the configuration of claim 1, at least of the inertia compensation signal calculated based on the high-pass signal of the steering torque signal and the damper compensation signal calculated based on the motor angular velocity signal. On the other hand, a power steering device is proposed which corrects the friction canceling torque.

  According to the third aspect of the present invention, the hydraulic cylinder and the electric motor are arranged on the steering torque transmission path for transmitting the steering torque input by the driver to the steering handle to the wheel, and the hydraulic cylinder and the electric motor generate assistance. In a power steering apparatus that assists a driver's steering operation with force, a clutch is provided between the steering torque transmission path and an electric motor, and the clutch is released when the electric motor does not generate assist force. A power steering device is proposed.

  According to a fourth aspect of the present invention, in addition to the configuration of the third aspect, when a road surface reaction torque greater than a predetermined value is transmitted from a wheel to a steering handle via the steering torque transmission path, A power steering apparatus characterized by engaging a clutch is proposed.

  The friction of the electric motor referred to in the present invention is not limited to the mechanical frictional force of the electric motor, but the inertia of the rotor of the electric motor, the tensile force by the magnet of the electric motor, and the steering connected to the electric motor. A force acting in a direction that resists rotation of the steering system, such as a mechanical frictional force of the torque transmission path, is included.

  According to the configuration of the first aspect, the hydraulic pressure transmitted from the steering torque transmission path when assisting the steering operation of the driver by driving only the hydraulic cylinder among the hydraulic cylinder and the electric motor arranged in the steering torque transmission path. Even when the electric motor is driven from the outside by the assist force of the cylinder, the electric motor generates a friction canceling torque that cancels its own friction, thereby preventing a reduction in steering feeling due to the friction of the electric motor.

  According to the configuration of the second aspect, the friction canceling torque is corrected by the inertia compensation signal calculated based on the high-pass signal of the steering torque signal or the damper compensation signal calculated based on the motor angular velocity signal. It is possible to compensate for the influence and improve the convergence of the electric motor.

  According to the configuration of the third aspect, when driving only the hydraulic cylinder and assisting the driver's steering operation among the hydraulic cylinder and the electric motor arranged in the steering torque transmission path, the clutch is opened to release the steering torque transmission path. By preventing the electric motor from being driven by the assist force of the hydraulic cylinder transmitted from the motor, it is possible to prevent the steering feeling from being lowered due to the friction of the electric motor.

  According to the fourth aspect of the present invention, the clutch is engaged when a road surface reaction torque greater than a predetermined value is transmitted from the wheel to the steering handle via the steering torque transmission path. It is possible to suppress the steering and enhance the steering feeling.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on examples of the present invention shown in the accompanying drawings.

  1 to 3 show a first embodiment of the present invention. FIG. 1 is an overall configuration diagram of a power steering apparatus, FIG. 2 is a block diagram of an electric motor control system, and FIG. 3 is a steering torque and friction compensation. It is a graph which shows the relationship with an electric current.

  As shown in FIG. 1, the first steering shaft 12 connected to the steering handle 11 passes through a first universal joint 13, a second steering shaft 14, a second universal joint 15, a third steering shaft 16 and a torsion bar 17. To the pinion shaft 18. Both ends of the rack bar 19 supported by the vehicle body so as to be movable left and right are connected to the left and right wheels W, W via tie rods 20, 20 and knuckles 21, 21. A pinion 22 provided at the lower end of the pinion shaft 18 meshes with a rack 23 formed on the rack bar 19, and the steering torque input by the driver to the steering handle 11 is converted into a lateral thrust force by the pinion 22 and the rack 23. The left and right wheels W, W are steered.

  In order to assist the driver's steering operation, a hydraulic cylinder 25 is provided through which the rack bar 19 slidably passes through the seal members 24, 24. The hydraulic cylinder 25 is fixed to the rack bar 19 and slidable on the hydraulic cylinder 25. First and second hydraulic oil chambers 27 and 28 are defined on both sides of the piston 26 fitted into the first and second hydraulic fluids. A control valve 29 is provided between the third steering shaft 16 and the pinion shaft 18 to switch the oil passage according to the torsion bar 17 being twisted, and the four ports 29a, 29b, 29c, 29d of the control valve 29 are provided. The hydraulic oil tank 30, the hydraulic pump 31, and the first and second working chambers 27 and 28 are connected to the hydraulic oil tank 30 and the hydraulic pump 31, respectively.

  When the torsion bar 17 is twisted and deformed in one direction by the steering torque input by the driver to the steering handle 11, the first port 29a communicates with the third port 29c, the second port 29b communicates with the fourth port 29d, and the hydraulic pump The hydraulic oil pumped from 31 is supplied to the first hydraulic oil chamber 27 and the hydraulic oil in the second hydraulic oil chamber 28 is returned to the hydraulic oil tank 30, so that the piston 26 moves to the left side of the vehicle body in the hydraulic cylinder 25. Thus, the left turning of the wheels W and W is assisted. Conversely, when the torsion bar 17 is twisted and deformed in the other direction by the steering torque input by the driver to the steering handle 11, the first port 29a communicates with the fourth port 29d and the second port 29b communicates with the third port 29c. The hydraulic oil pumped from the hydraulic pump 31 is supplied to the second hydraulic oil chamber 28, and the hydraulic oil in the first hydraulic oil chamber 27 is returned to the hydraulic oil tank 30. Moving to the right side, the right steering of the wheels W, W is assisted.

  A worm wheel 32 is provided on the third steering shaft 16, and a worm 34 provided on an output shaft 33 a of an electric motor 33 formed of a DC brush motor meshes with the worm wheel 32. Accordingly, when the electric motor 33 is driven, the rotation of the output shaft 33a is transmitted to the third steering shaft 16 via the worm 34 and the worm wheel 32, and the steering operation of the driver is assisted by the assist force generated by the electric motor 33. be able to. The worm 34 and the worm wheel 32 have a relatively small reduction ratio, and can reversely transmit power from the worm wheel 32 side to the worm 34 side.

  The steering assist by the hydraulic cylinder 25 is performed when the torsion bar 17 is twisted and deformed, that is, when the driver's steering torque is input to the steering handle 11, but the steering assist by the electric motor 33 is performed when necessary. Is performed based on a command from

  As shown in FIG. 2, the electronic control unit U that controls the operation of the electric motor 33 includes a steering torque sensor Sa that detects the steering torque from the torsion angle of the torsion bar 17, and a vehicle speed that detects the vehicle speed from the rotation speed of the wheels W. The sensor Sb is connected to a current sensor Sc and a voltage sensor Sd that detect the current and voltage of the electric motor 33. The electronic control unit U includes a friction compensation unit 35, an inertia compensation unit 36, and a damper compensation unit 37. The current command values output from the friction compensation unit 35, the inertia compensation unit 36, and the damper compensation unit 37 are added. A control current of the electric motor 33 is used.

  The friction compensation means 35 receives the steering torque passing through the low-pass filter 38 and the phase compensation means 39 and the vehicle speed, and the inertia compensation means 36 receives the steering torque passed through the low-pass filter 38 and the high-pass filter 40 and the low-pass filter. The steering torque that has passed through the filter 38 and the vehicle speed are input, and the inertia compensation means 36 has the steering torque that has passed through the low-pass filter 38, the motor angular speed calculated by the motor angular speed calculation means 41 from the motor current and motor voltage, The vehicle speed is input.

  When the steering operation of the driver is assisted by the assist force generated by the hydraulic cylinder 25, the rotation of the third steering shaft 16 is transmitted to the electric motor 33 via the worm wheel 32 and the worm 34, and the electric motor 33 is externally connected. There is a possibility that the friction generated by the rotation of the wheel will reduce the steering feeling. However, according to this embodiment, the low-pass signal of the steering torque is passed through the phase compensation means 39, and the torque phase compensation signal that advances the phase by the amount delayed by the mechanical time constants of the worm wheel 32, worm 34, and electric motor 33. The friction compensation means 35 calculates the friction compensation current as shown in FIG. 3 based on the torque phase compensation signal and the vehicle speed and supplies it to the electric motor 33.

  In this way, when the electric motor 33 that is operated and stopped only by the hydraulic cylinder 25 is driven by an external force, the friction of the electric motor 33 itself and the friction of the worm wheel 32 and the worm 34 are canceled out. By driving the electric motor 33, it is possible to cancel the friction and prevent the steering feeling from being lowered.

  Further, when the steering torque changes suddenly due to the inertia of the electric motor 33 when the steering handle 11 is turned or turned back, a large torque high-pass signal is input from the high-pass filter 40 to the inertia compensation means 36. The compensation means 36 calculates the inertia compensation current proportional to the torque high-pass signal and supplies it to the electric motor 33, so that the influence of the inertia of the electric motor 33 can be compensated. Further, when the steering handle 11 is turned or returned, the motor angular speed calculated by the motor angular speed calculating means 41 from the motor current and the motor voltage is input to the damper compensating means 37, and the damper compensating means 37 is a damper compensating current proportional to the motor angular speed. Is calculated and supplied to the electric motor 33, whereby the convergence of the electric motor 33 can be improved.

  When the electric motor 33 is a direct current brush motor, the motor angular speed calculation means 41 calculates the motor angular speed from the motor current and the motor voltage. When the electric motor 33 is a direct current brushless motor, the motor angular speed is calculated. It can be calculated from the differential value of the output of a rotational position sensor such as a resolver.

  Next, a second embodiment of the present invention will be described with reference to FIG.

  In the second embodiment, a clutch 42 controlled by an electronic control unit U is provided between an output shaft 33 a of an electric motor 33 and a worm 34. When the hydraulic cylinder 25 is driven and the electric motor 33 is not driven, the clutch 42 is released to prevent torque from being transmitted from the steering torque transmission path to the electric motor 33, so that the friction of the electric motor 33 can be reduced. It is possible to prevent the ring from being lowered. Further, when the electric motor 33 is stopped, the clutch 42 is engaged when a large reaction force is input to the wheels W and W from the road surface, or when there is a possibility that shimmy is generated by traveling on the gravel road. As a result, the friction of the electric motor 33 is positively transmitted to the steering torque transmission path, and the steering handle 11 is prevented from being taken in one direction or generating vibration due to the load from the road surface. Can be increased.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the present invention described in the claims. It is.

  For example, although the clutch 42 is disposed between the electric motor 33 and the worm 34 in the second embodiment, the clutch 42 may be disposed between the steering torque transmission path and the worm wheel 32. This prevents the friction between the worm 34 and the worm wheel 32 from acting on the steering torque transmission path in addition to the friction of the electric motor 33 when the clutch is released, and both the frictions when the clutch is engaged. It is possible to act on the steering torque transmission path, which is more effective.

  In the embodiment, the electric motor 33 is connected to the third steering shaft 16, but the electric motor 33 can be connected to an arbitrary position on the steering torque transmission path between the steering handle 11 and the wheels W and W.

Overall configuration diagram of the power steering apparatus according to the first embodiment Block diagram of electric motor control system Graph showing the relationship between steering torque and friction compensation current Overall configuration diagram of a power steering apparatus according to a second embodiment

Explanation of symbols

11 Steering handle 25 Hydraulic cylinder 33 Electric motor 42 Clutch W Wheel

Claims (4)

The hydraulic cylinder (25) and the electric motor (33) are arranged on the steering torque transmission path for transmitting the steering torque input by the driver to the steering handle (11) to the wheels (W), and the hydraulic cylinder (25) and the electric motor (33) are arranged. In the power steering device that assists the driver's steering operation with the assist force generated by
When the electric motor (33) is driven by the assist force of the hydraulic cylinder (25), the electric motor (33) generates a friction canceling torque that cancels its own friction.   2. The power according to claim 1, wherein the friction canceling torque is corrected by at least one of an inertia compensation signal calculated based on a high-pass signal of a steering torque signal and a damper compensation signal calculated based on a motor angular velocity signal. Steering device. The hydraulic cylinder (25) and the electric motor (33) are arranged on the steering torque transmission path for transmitting the steering torque input by the driver to the steering handle (11) to the wheels (W), and the hydraulic cylinder (25) and the electric motor (33) are arranged. In the power steering device that assists the driver's steering operation with the assist force generated by
A power steering characterized in that a clutch (42) is provided between the steering torque transmission path and the electric motor (33), and the clutch (42) is released when the electric motor (33) does not generate assist force. apparatus. The clutch (42) is engaged when a road surface reaction force torque of a predetermined value or more is transmitted from the wheel (W) to the steering handle (11) through the steering torque transmission path. A power steering device according to claim 1.

Images