JP4370501B2 - Vehicle steering system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicle steering apparatus that generates a steering force or a steering assist force for changing the direction of a wheel using a hydraulic actuator.
[0002]
[Prior art]
The vehicle steering apparatus includes a link type in which a steering member such as a steering wheel is mechanically connected to a steering mechanism via a transmission member such as a steering shaft, and the steering member is mechanically connected to the steering mechanism. It is roughly divided into a steer-by-wire system that is not used.
In the former link type, in a power steering device using hydraulic pressure, the control valve is controlled by the torsion between the input shaft and the output shaft that are coaxially connected via a torsion bar, and the control valve is operated on the left and right sides of the hydraulic actuator (power cylinder). The inflow / discharge of hydraulic oil into the chamber is controlled, and steering is assisted by the hydraulic pressure generated by the hydraulic actuator.
[0003]
As the latter steer-by-wire system, a hydraulic actuator is provided as a steering actuator in the middle of the steering mechanism, and when an abnormality occurs in the drive of the regular valve that controls the supply and discharge of hydraulic fluid to this hydraulic actuator, the emergency valve There is a vehicle steering apparatus provided with oil supply means for supplying hydraulic oil from a hydraulic actuator to a hydraulic actuator (for example, Patent Document 1).
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 2002-137748
[Problems to be solved by the invention]
In the former link-type hydraulic power steering apparatus, the opening degree of a rotary control valve that is normally used depends on the amount of twist of the steering shaft. In other words, hydraulic oil is supplied to the hydraulic actuator via the control valve after the steering shaft is twisted. For this reason, when a steering member such as a steering wheel is operated quickly, there is a problem that the rising of the assist force is delayed with respect to this operation and the operation of the steering member becomes heavy. In addition, there is a possibility that it may not be adapted to active steering, for example, when running on a counter on a snowy road.
[0006]
In the latter, the steer-by-wire hydraulic vehicle steering apparatus disclosed in Patent Document 1, when the valve (normal valve) is opened in proportion to the steering angle of the steering member, the steering member rotates at the required steering angle. Even after stopping, the hydraulic oil may flow into the hydraulic actuator and the steering may continue. This is because a time lag occurs between the operation of the steering member and the inflow of hydraulic oil to the hydraulic actuator.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a vehicle steering apparatus in which there is no delay in supplying and discharging hydraulic oil to and from a hydraulic actuator with respect to operation of a steering member.
[0007]
[Means for Solving the Problems and Effects of the Invention]
In order to achieve the above object, the present invention provides a vehicle steering apparatus in which a steering member and a steering mechanism are not mechanically coupled and a steering force is generated by a hydraulic actuator in accordance with an operation of the steering member. A flow control valve as a valve that controls the flow of hydraulic oil into and out of the actuator, a drive means for operating the flow control valve, a steering angle sensor for detecting the steering angle of the steering member, and the rotation of the steered wheels A steering angle sensor for detecting a steering angle, a vehicle speed sensor for detecting a vehicle speed, a steering speed detecting means for detecting a steering speed related to a steering member, and a steering speed detected by the steering speed detecting means the larger so that the flow rate of the flow control valve is increased, and a control means for controlling the operation of the flow control valve through the drive means, the opening B of the flow control valve, satisfies the following formula It is characterized in that that.
B = B1 (C−A, R) + k · | Va |
Here, B1 (C-A, R) is detected by the deviation (C-A) between the steering angle A detected by the steering angle sensor and the turning angle C detected by the turning angle sensor, and by the vehicle speed sensor. The reference opening is set based on the vehicle speed R. Further, k · | Va | is a factor that increases with an increase in the magnitude of the steering speed Va, where k is a coefficient.
[0008]
In the present invention, when applied to, for example, a hydraulic power steering device, it is possible to detect that steering by a steering member has been performed earlier than when the steering shaft is twisted and to obtain an assist force corresponding thereto. Therefore, even if the steering member is operated quickly, the operation of the steering member does not become heavy. Further, even when applied to a steer-by-wire system using a hydraulic actuator, it is possible to realize turning without delay with respect to the operation of the steering member.
[0009]
Further, the valve consists of the flow control valve, the control means, the flow rate of as the flow rate control valve is large steering speed detected by the steering speed detecting means for controlling the flow rate control valve so as to increase, the following advantages There is. That is , when a wheel is steered by a hydraulic actuator, the steered amount is proportional to the volume of hydraulic oil flowing into the hydraulic actuator. In the present invention, when the steering speed is high, the flow rate of the hydraulic oil to the hydraulic actuator can be increased by the flow rate control valve, which is a speed control valve, so that the steering force is not delayed with respect to the operation of the steering member. Can be generated.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof. FIG. 1 is a schematic diagram showing an overall configuration of a vehicle steering apparatus according to a reference embodiment.
In this reference embodiment will be described with reference to the example vehicle steering system is a hydraulic power steering apparatus, the present invention will be described below, the vehicle steering apparatus of steer-by-wire type using the hydraulic actuator for steering Is also applicable.
[0011]
Referring to FIG. 1, a vehicle steering apparatus 1 includes an input shaft 3 coupled to a steering member 2 made of, for example, a steering wheel so as to be integrally rotatable, and a rack and pinion mechanism provided coaxially with the input shaft 3. An output shaft 5 connected to the steering mechanism 4 such as a torsion bar 6 that connects the input shaft 3 and the output shaft 5 so that they can rotate relative to each other, and a hydraulic actuator 7 including a power cylinder for generating a steering assist force. And a known control valve 10 that is interposed between the hydraulic actuator 7 and the hydraulic pump 8 and the oil tank 9 and that controls the supply and discharge of the hydraulic oil to and from the hydraulic actuator 7 according to the torsion of the torsion bar 6.
[0012]
The steering mechanism 4 includes a pinion 4a that rotates integrally with the output shaft 5, and a rack shaft 4b that meshes with the pinion 4a and extends in the left-right direction of the vehicle. The steering wheel 11 is steered by moving the rack shaft 4b in the axial direction.
The control valve 10 is a valve body 10a that is held rotatably on the output shaft 5, and a valve rotor 10b that is fitted inside the valve body 10a so as to be rotatable relative to the valve shaft 10a. including. Between the valve body 10a and the valve rotor 10b, a pair of throttles (not shown) whose throttle areas change in different directions according to the relative angular displacements of the two 10a and 10b are provided.
[0013]
The hydraulic actuator 7 forms a cylinder chamber 12 by liquid-tightly sealing a part of a cylindrical rack housing (not shown) surrounding the outside of the rack shaft 4b. A piston 13 fixed to the middle portion of the rack shaft 4b is slidably fitted in the cylinder chamber 12, and is given to the rack shaft 4b by the differential pressure between the oil chambers 7a and 7b on both sides of the piston 13. The oil pressure directly assists the steering operation performed along the axial direction of the rack shaft 4b.
[0014]
Specifically, when the steering member 2 is operated, the input shaft 3 rotates about the axis, and this rotation is transmitted to the rack shaft 4b via the torsion bar 6, the output shaft 5 and the pinion 4a. The rack shaft 4b slides in the axial direction to steer. At this time, the torsion bar 6 that connects the input shaft 3 and the output shaft 5 is twisted according to the steering torque applied to the steering member 2. In response to this twisting, the valve body 10a and the valve rotor 10b of the control valve 10 are displaced relative to each other, and the pressure oil from the hydraulic pump 8 is supplied to the required oil chamber 7a or 7b of the hydraulic actuator 7. Yes.
[0015]
It is a feature of the present reference of the form is the following. In other words, a pair of paths 14 connecting the hydraulic pump 8 and the oil tank 9 and the hydraulic actuator 7 via the control valve 10 are provided with a pair of paths 15 serving as bypass paths that bypass the control valve 10. A flow rate control valve 16 for controlling the amount of hydraulic oil supplied to and discharged from the hydraulic actuator 7 is provided.
In the path 15, an electromagnetic direction control valve 17 is provided between the flow control valve 16 and the hydraulic pump 8 and the oil tank 9. The direction control valve 17 switches the pair of paths 15 to each other so as to selectively connect the hydraulic pump 8 to the oil chamber 7a or 7b of the hydraulic actuator 7 in accordance with the steering direction.
[0016]
Further, a steering angle sensor 18 for detecting the steering angle of the steering member 2 is provided. The steering angle sensor 18 is connected to a control unit 19, and a signal detected from the steering angle sensor 18 is supplied to the control unit 19 including a CPU, a ROM, a RAM, and the like.
The controller 19 differentiates the steering angle A detected by the steering angle sensor 18 to detect the steering speed (steering angular speed) Va, and drives the flow control valve 16 in accordance with the detected steering speed Va. The motor 20 is controlled via the drive circuit 21. As the motor 20, for example, a step motor can be used.
[0017]
Further, the control unit 19 detects the steering direction of the steering member 2 based on the steering angle A detected by the steering angle sensor 18, and controls the direction control valve 17 via the drive circuit 22 according to the detected steering direction. Control.
FIG. 2 shows the flow of steering control by the control unit 19. The control unit 19 reads the steering angle A detected by the steering angle sensor 18 (step S1), and obtains the steering speed (steering angular velocity) Va by differentiating the read steering angle A (step S2).
[0018]
When the steering speed Va is not zero (actually, when deviating from an error region near zero) (NO in step S3), the magnitude of the steering speed Va is multiplied by a predetermined coefficient k, that is, an arithmetic expression. The opening degree B of the flow control valve 16 is obtained using B = k · | Va | (step S4).
Next, if necessary according to the steering direction, the pair of paths 15 are switched to each other by the direction control valve 17 (steps S5 and S6), so that the flow rate control valve 16 has the opening B obtained in step S4. The motor 20 is driven and controlled (step S7), and the flow control valve 16 is closed with the end of steering.
[0019]
On the other hand, when the steering speed Va obtained in step S2 is zero (actually, in the error region near zero) (YES in step S3), steps S1 to S3 are repeated, and the steering speed is repeated. Continue to monitor Va.
According to the present embodiment, in the vehicle steering apparatus 1 including the hydraulic power steering apparatus, when the operation of the steering member 2 is started, the steering angle sensor 18 immediately detects the steering angle A, and accordingly. The steering speed Va is detected, and the hydraulic oil can be supplied to and discharged from the hydraulic actuator 7 with a supply / discharge amount corresponding to the steering speed Va. Therefore, the steering assist force can be generated without delay and with good responsiveness. After a little delay, the torsion bar 6 is twisted, and pressure oil is supplied via the control valve 10 in response to the twist, and the steering assistance is further supplemented.
[0020]
Further, when the steering speed Va is high, the inflow speed of the hydraulic oil to the hydraulic actuator 7 can be increased, so that steering assistance with better response can be achieved.
Then, FIG. 3 is a schematic sectional view showing an overall configuration of a vehicle steering system of the embodiment of the present onset Ming embodiment. In the present embodiment, a steer-by-wire vehicle steering apparatus 1A using a steering hydraulic actuator will be described.
Steering shaft 4c is removed by mechanical pressure between steering member 2 such as a steering wheel and steering mechanism 4 and hydraulic pressure of hydraulic actuator 7 as a steering actuator driven according to, for example, a rotation operation of steering member 2. Is moved in the axial direction to steer the steered wheel 11 for steering.
[0021]
The steering member 2 is connected to a steering shaft 30 that is rotatably supported with respect to the vehicle. The steering shaft 30 is provided with a reaction force actuator 31 for applying an operation reaction force to the steering member 2. The reaction force actuator 31 includes an electric motor such as a brushless motor having an output shaft integral with the steering shaft 30.
An elastic member 32 made of a spiral spring or the like is connected to the end of the steering shaft 30 opposite to the steering member 2. When the reaction force actuator 31 does not apply torque to the steering member 2, the elastic member 32 returns the steering member 2 to the straight steering position by the elastic force.
[0022]
In order to detect an operation input value of the steering member 2, a steering angle sensor 18 for detecting the steering angle of the steering member 2 is provided in association with the steering shaft 30. The steering shaft 30 is provided with a torque sensor 33 for detecting torque applied to the steering member 2. On the other hand, in relation to the steered shaft 4c, a steered angle detection sensor 34 for detecting the steered angle of the steered steered wheels 11 is provided.
A steering angle sensor 18, a torque sensor 33, a turning angle sensor 34, and a vehicle speed sensor 35 are connected to the control unit 36.
[0023]
A flow control valve 16 for controlling the supply and discharge amount of hydraulic oil to the hydraulic actuator 7 and an electromagnetic direction control valve 17 are provided in a pair of paths 37 connecting the oil path pump 8 and the oil tank 9 and the hydraulic actuator 7. The control unit 36 drives and controls the motor 20 for adjusting the opening degree of the flow rate control valve 16 via the drive circuit 21 and switches and controls the direction control valve 17 via the drive circuit 22. Is the same as the reference embodiment of FIG. Further, the control unit 36 controls the reaction force actuator 31 via the drive circuit 38.
[0024]
FIG. 4 shows the flow of steering control by the control unit 36. The control unit 36 reads the steering angle A detected by the steering angle sensor 18, the turning angle C detected by the turning angle sensor 34, and the vehicle speed R detected by the vehicle speed sensor 35 (step S1), and the read steering The steering speed (steering angular speed) Va is obtained by differentiating the angle A (step S2).
When the steering speed Va is not zero (actually, when deviating from an error region near zero) (NO in step S3), the arithmetic expression B = B1 (C−A, R) + k · | Va | is used. Then, the opening degree B of the flow control valve 16 is obtained (step S4).
[0025]
B1 (C-A, R) is detected by the deviation (C-A) between the steering angle A detected by the steering angle sensor 18 and the turning angle C detected by the turning angle sensor 34, and by the vehicle speed sensor 35. The reference opening is set based on the vehicle speed R. On the other hand, k · | Va | is a factor that increases as the magnitude of the steering speed Va increases.
Next, if necessary according to the steering direction, the pair of paths 37 are switched to each other by the direction control valve 17 (steps S5 and S6), so that the flow rate control valve 16 has the opening B obtained in step S4. The motor 20 is driven and controlled (step S7).
[0026]
Further, based on the detected steering angle A, the steering torque detected by the torque sensor 33, and the detected vehicle speed R, an appropriate reaction force in the direction opposite to the operation direction of the steering member 2 is generated. The reaction force actuator 31 is driven and controlled via the drive circuit 38. Note that the flow control valve 16 is closed with the end of steering.
On the other hand, when the steering speed Va obtained in step S2 is zero (actually, in the error region near zero) (YES in step S3), steps S1 to S3 are repeated, and the steering speed is repeated. Continue to monitor Va.
[0027]
In the present embodiment, in the steer-by-wire vehicle steering apparatus 1A for obtaining a steering force by the hydraulic actuator 7, when the operation of the steering member 2 is started, the steering angle sensor 18 immediately detects the steering angle A. Accordingly, the steering speed Va is detected, and hydraulic oil can be supplied to and discharged from the hydraulic actuator 7 with a supply / discharge amount including an increment corresponding to the steering speed Va, so that there is no delay with respect to the operation of the steering member 2. Steering can be realized. In particular, when the steering speed Va is high, the inflow speed of the hydraulic oil to the hydraulic actuator 7 can be increased, so that steering with better response can be achieved.
[0028]
Further, by adding an increment k · | Va | depending on the steering speed Va to the reference opening B1 as the opening B of the flow control valve 16, a sufficient supply / discharge amount to the hydraulic actuator 7 can be secured. Therefore, when the operation of the steering member 2 is stopped, the turning by the hydraulic actuator 7 is completed without time lag.
Incidentally, in the above shape state, using the motor 20 as a driving means and flow control valve 16, has been to increase the degree of opening in accordance with an increase of the steering speed Va, not limited to this. For example, in the reference form of FIG. 1, an electromagnetic on-off valve is used in place of the flow control valve 16, and a solenoid is used in place of the motor 20 as the driving means. When the steering speed Va is detected, the solenoid is turned on ( Alternatively, the on-off valve may be opened by turning it off, and when the steering speed Va is not detected, the solenoid may be turned off (or on) to switch the on-off valve to the closed state. Further, active steering can be made possible by controlling the opening degree and opening / closing time of the flow control valve according to the steering speed and load.
[0029]
In addition, various modifications can be made within the scope of the claims of the present invention.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a schematic configuration of a hydraulic power steering apparatus as one reference form.
FIG. 2 is a flowchart showing a flow of steering control.
3 is a schematic diagram showing a schematic configuration of a steer-by-wire type vehicle steering apparatus of the form of implementation of the present invention.
FIG. 4 is a flowchart showing a flow of steering control.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1,1A Steering device 2 for vehicles Steering member 3 Input shaft 4 Steering mechanism 5 Output shaft 6 Torsion bar 7 Hydraulic actuator 8 Hydraulic pump 9 Oil tank 10 Control valve 11 Wheels 14 and 15 Path 16 Flow control valve 17 Directional control valve 18 Steering Angle sensor 19 Control unit 20 Motor 31 Reaction force actuator 34 Steering angle sensor 35 Vehicle speed sensor 36 Control unit

Claims (1)

In the vehicle steering apparatus in which the steering member and the steering mechanism are not mechanically coupled, and the steering force is generated by the hydraulic actuator according to the operation of the steering member.
A flow control valve as a valve for controlling the flow of hydraulic oil into and out of the hydraulic actuator;
Drive means for operating the flow control valve;
A steering angle sensor for detecting the steering angle of the steering member;
A turning angle sensor for detecting the turning angle of the turning wheel;
A vehicle speed sensor for detecting the vehicle speed;
Steering speed detection means for detecting a steering speed related to the steering member;
Control means for controlling the operation of the flow control valve via the drive means so that the flow rate of the flow control valve increases as the steering speed detected by the steering speed detection means increases . The opening degree B satisfies the following formula: a vehicle steering apparatus.
B = B1 (C−A, R) + k · | Va |
Here, B1 (CA, R) is detected by a deviation (CA) between the steering angle A detected by the steering angle sensor and the turning angle C detected by the turning angle sensor, and by the vehicle speed sensor. The reference opening is set based on the vehicle speed R. Further, k · | Va | is a factor that increases with an increase in the steering speed Va, where k is a coefficient.

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