JPS6092956A - Steering device for car - Google Patents

Abstract

PURPOSE:To improve positional freedom for arranging a pump, in a steering system having front/rear steering means where the rear wheel steering means will utilize the pressurized fluid to be fed from a pump to perform steering of rear wheel, by driving the pump with a motor. CONSTITUTION:Upon rotation of a steering handle 19, knuckle arms 14R, 14L will rotate through a steering gear mechanism 20 while being assisted by a power cylinder 32 thus to steer the front wheel 12. The pressurized fluid corresponding to the steering force will cause function of actuators 46a-46d to steer the rear wheel 13 through rotation around a pin 27 of rear wheel suspension member 22. The pressurized fluid to be fed/discharged against each actuator 46a-46d is controlled of its flow and direction by means of a control valve 45 provided on the steering shaft 18 then discharged from a pump 39. Said pump 39 is driven by a motor 49 to improve the positional freedom for arranging the pressurized fluid feeding system including the pump 39.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) This invention relates to a steering system for a vehicle, specifically, a pump that supplies pressurized fluid to a rear wheel steering system, which is driven by an electric motor.
The present invention relates to a vehicle steering device that aims to provide simple control and a large degree of freedom in installation location.

(Prior Art) For vehicles in recent years, steering devices capable of steering both front wheels and rear wheels have been proposed for the purpose of improving turning performance. Conventionally, as this type of steering device, for example, a compliance steer control device described in Japanese Unexamined Patent Publication No. 57-99470 is known.

This compliance steer control value H is determined by providing a hydraulic actuating means to an elastic band interposed between the rear wheel suspension device and the vehicle body, and supplying hydraulic pressure to the power cylinder of the power steering mechanism to the hydraulic actuating means. By doing so, control is performed to reduce or increase the compliance steer that occurs when the vehicle is turning.

That is, the rear wheels are steered by decreasing or increasing compliance steer.

This kind of compliance steer control device steers the rear wheels in the same direction as the front wheels when steering the steering wheel, setting the turning characteristics to the understeer side, and mainly aims to improve turning performance when driving at high speeds. It is.

By the way, as is well known, in the power steering mechanism, in order to give the driver an appropriate steering feeling, the steering assist force generated by the power cylinder is controlled to be small in a high vehicle speed range. Therefore, low-pressure hydraulic pressure is supplied to the power cylinder of the power steering mechanism in a high vehicle speed range. However, when controlling compliance steer for the rear wheels, in order to achieve more stable high-speed cornering, it is necessary to generate a large compliance steer in the high vehicle speed range, causing the rear wheels to deviate significantly in the same direction as the front wheels. desirable. For this reason, it is difficult to control the compliance steer control device with the best characteristics in terms of cornering performance when the hydraulic actuation means of the compliance steer control device is supplied with the hydraulic pressure directly to the power cylinder of the power steering mechanism. there were. Therefore, in order to control both the compliance steer control device and the power steering mechanism with the best characteristics, a pump that supplies pressure oil to the compliance steer control device and a pump that supplies pressure oil to the power steering mechanism are separately provided. It was necessary to control these pumps separately.

However, since there is little free space in the engine room of a vehicle, it is difficult to connect the two pumps mentioned above to the engine crankshaft and drive them. A control fluid device is required to control the pressure oil discharged by the pump, which has the disadvantage that the control device becomes complicated.

(Object of the Invention) The present invention has been made in view of the above-mentioned drawbacks, and provides simple control of the pump that supplies pressure fluid to the power steering device and the pump that supplies pressure fluid to the rear wheel steering device with simple and separate characteristics. The purpose is to prevent interference with other equipment by increasing the degree of freedom in its installation position.

(Structure of the Invention) A steering device for a vehicle according to the present invention includes a front wheel steering means that deflects a front wheel by transmitting a steering force applied to a steering handle, and a front wheel steering unit that deflects a front wheel by transmitting a steering force applied to a steering handle; A steering system for a vehicle includes a rear wheel steering means for biasing a rear wheel, and a pump for supplying pressurized fluid to the rear wheel steering means, and the pump is configured to be driven by an electric motor.

According to this vehicle steering system, the position of the pump is not restricted by the position of the engine crankshaft, so it has a large degree of freedom in its position. Since the discharge amount of the pump is controlled, the control is easy.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a diagram showing a first embodiment of the present invention, and shows an outline of a vehicle steering system.

First, to explain the configuration, 11 is the vehicle body, 12R112L
indicates the front wheels, and 13R and 13L indicate the rear wheels.

The front wheels 12p and 12L each have a knuckle arm 14.
It is connected to the end of the rack 16 via Q, 14L and side rods 15R and 115L. A pinion 17 meshes with the rank l6, and the pinion 17 is connected to a steering wheel 19 via a steering shaft 18. The rank 16 and the pinion 7 constitute a steering gear mechanism 20.

The rear wheels 131q and 13shi are each swingably supported by the rear wheel suspension member 22 via a semi-trailing arm 21R12]L.

The rear wheel suspension member 22 has both ends connected to a pin 24R124L via an insulator rubber 23R123L.
The differential gear housing 25 is elastically supported by the vehicle body 11, and the differential gear housing 25 is fixed by bolts (not shown). This differential gear housing 25 is also elastically supported to the vehicle body 11 by a pin 27 via an insulator rubber 26. In addition,
28R128 is differential gear housing 2
This is a drive shaft that connects the differential gear in 5 and the rear wheels 13q and 13shi.

29 is a first pump that pressurizes and discharges the working fluid in the reservoir 30; 31 is provided on the steering shaft 18 and is connected to the first pump 29 via piping P; and to the reservoir 29 via piping P2. The first control valve 31 is also connected to a power cylinder 32 provided in the rack 16 via pipes P3 and P-4. The first control valve 31 includes four variable orifices 31 whose flow path area changes according to the steering force applied to the steering handle 19 (in the embodiment, the steering force is applied to the steering handle 19).
a, 31b, 31c, and 31d, and controls the pressure fluid discharged by the first pump 29 according to the steering of the steering handle 19 and supplies it to the power cylinder 32.

In the power cylinder 32, a piston 33 fixed to the rank 16 is slidably fitted into a cylinder body 34 provided to the vehicle body 11, thereby defining two fluid chambers 35 and 36. This power cylinder 32 generates a steering assist force corresponding to the pressure difference between the fluid chambers 35 and 36 supplied with pressure fluid from the first control valve 31, and presses the rank 16 in accordance with the steering direction. These first pump 29, reservoir 30, first control valve 31, and power cylinder 32 constitute a well-known power steering device 37. Further, this power steering device 37 constitutes a front wheel steering means 38 together with the aforementioned steering gear mechanism 20.

39 is a second pump that pressurizes and discharges the working fluid in the reservoir 40; 49 is an electric motor that drives the second pump 39; the electric motor 49 is connected to the control circuit 42; The control circuit 42 includes a vehicle speed sensor 43 that detects the vehicle speed V.
, the steering status of the steering wheel 19 (steering force T, steering angle ω,
A steering sensor 50 that detects a steering angular velocity 2, etc.) and an operation switch 48 that can be manually operated are connected, and an electric motor 49 is controlled based on the output signals of these sensors 43 and 50 and the operation of the operation switch 48. These control circuit 42, vehicle speed sensor 43, and operation switch 48 constitute a control means 44.

The discharge boat of the second pump 39 is connected to the second control valve 45 via a pipe P5. The second control valve 45 also
Piping P. is connected to the reservoir 4o via a pair of pipes P? , PB to four actuators 46a, 46b, 46C146d interposed between the rear wheel suspension member 22 and the vehicle body 11.

Similarly to the first control valve 31, this second control valve 45 also has the following features:
The pressure fluid supplied from the flow control valve 41 is controlled in accordance with the steering of the steering handle 19 to drive the actuators 46a, 46.
b, supply to 46C146d. The actuator is connected to the vehicle body 11 and the rear wheel suspension member 22 by a pin joint, and deforms the insulator rubber 23R123L by the action of the supplied pressure fluid to rotate the rear wheel suspension member 22 around the pin 27. That is, these actuators 46a, 46b,
46c and 46d rotate the rear wheels 13p, 13 by rotating the rear wheel suspension member 22 by the action of pressure fluid.
Bias L.

The second pump 39, control means 44, and second control valve 4 described above
5 and actuators 46a, 46b, 46c.

46d constitutes a compliance steering control device (rear wheel steering means) 47.

Next, the effect will be explained.

The steering device of this vehicle biases the front wheels 12R112L and the rear wheels 13R113 of the vehicle in accordance with the steering of the steering handle 19.The power steering device 37 generates a steering assist force to deflect the front wheels 12P and 13R by the steering handle 19.
The compliance steer control device 47 assists the steering of the rear wheels 13H and 12L in accordance with the steering of the steering handle 19.
13 in the same direction as the front wheels 12R112L. In the compliance steer control device 47, the deflection angle of the rear wheels 13H, 13 with respect to the steering of the steering handle 19 is determined by the steering force T applied to the steering handle 19,
Control is performed according to the steering angle ω of the steering wheel 19, the steering angular velocity product, and the vehicle speed ■. For this reason, the control circuit 42
The motor 49 is controlled by controlling the energization to the motor 49 according to the vehicle speed.
The rotational speed of the motor 49 is set to have the characteristics shown in FIG. 2, and the motor 49 is energized in accordance with the above characteristics only when the steering handle 19 is steered.

When the steering handle 19 is not being steered now, the first control valve 31 is operated by the variable orifices 31a, 31b, 31c,
31d have the same opening degree, and the pressure fluid discharged by the first pump 29 flows through each variable orifice 31a of the first control valve 31.
, 31b, 31c, and 31d to the reservoir 30. Therefore, the power cylinder 32 does not generate any steering assist force, and the vehicle moves straight. Similarly, the pressure fluid discharged by the second pump 39 is returned to the reservoir 4o via the second control valve 45, so that the rear wheels 13R and 13L do not deviate, and the straightness of the vehicle is maintained. Furthermore, when the steering handle 19 is not being steered, the motor 49 is not energized and does not drive the pump 39. Therefore, the load on the engine is reduced and the fuel efficiency of the vehicle is improved.

Next, a steering force is applied to the steering handle 19, and the steering handle 19 moves, for example, to the right (the same applies in the following description).
When the first control valve 31 is steered to the variable orifice 31
a, 31d are narrowed and the variable orifice 31b,
31C is opened, and a pressure difference is created in the pressure fluid flowing out into each pipe P, PT. That is, the first control valve 31 is
One fluid chamber 3 of the power cylinder 32 via piping P'4
In order to supply high pressure fluid to the power cylinder 3
2 generates a steering assist force to press the rack 16. Therefore, the front wheels 12R112 are connected to the steering gear mechanism 2.
0 from the steering wheel 19 and the steering assist force generated by the power cylinder 32.

Similarly, when the steering handle 19 is steered, the motor 49
is energized to drive the second pump 39, and the second
The variable orifices 45b and 45c of the control valve 45 are opened, and the variable orifices 45a and 45d are narrowed. Therefore, the pressure fluid discharged by the pump 39 is transferred to each variable orifice 45a, 45b, 45 of the second control valve 45.
It flows out with a pressure difference into the pipes P 7 and P B through C145d, and the pipe P flows into the actuators 46b and 46c.
High pressure fluid is supplied via 8. Therefore, the actuators 46a, 46b, 46c, and 46d deform the insulator rubbers 23R, 23L-t, rotate the rear wheel suspension member 22 clockwise in the figure, and rotate the rear wheels 13q, 13L to the right. In other words, it is biased in the same direction as the front wheels 12s and 12L.

Here, the rotation speed R of the electric motor 49 is controlled by the control circuit 42 in accordance with the vehicle speed V, and has vehicle speed dependent characteristics as shown in FIG. That is, the electric motor 49 stops in a low vehicle speed range below the first set vehicle speed V, and also in a medium vehicle speed range between the first set vehicle speed ■ and the second set vehicle speed v2 (V+ ≦■≦V2). The rotational speed R increases at a predetermined ratio in the second set vehicle speed (2), and the second set vehicle speed (2) rotates at a constant rotational speed R in a high vehicle speed range of 2 or more.

Therefore, the flow rate characteristics of the pressure fluid supplied by the second pump 39 to the compliance steer control device 47 have characteristics that are substantially reciprocal to the rotation speed characteristics of the motor 49 shown in FIG. Therefore, in a low vehicle speed range where cornering stability is not relatively important, even if the steering wheel 19 is steered, the rear wheels 19
3B and 13L do not deviate, and the vehicle has agile maneuverability. In addition, in a vehicle speed range exceeding the first set vehicle speed ■, when the steering force T applied to the steering wheel 19 is constant (each variable orifice 45a of the second control valve 45
, 45b, 45c, and 45d maintain a predetermined opening degree), the piping P? by the second control valve 45? , pm increases with vehicle speed ■, causing actuators 46a,'
46b, 46c, and 46d deform the insulator rubbers 23R and 23L with larger force. That is, since the second control valve 45 utilizes well-known orifice characteristics, when the flow rate of the pressure fluid supplied to the second control valve 45 increases, the actuators 46a, 46b, 46C146
d, supplying higher pressure fluid to the actuator 46
a, 46b, 46c, 46d are insulator rubber 23F with great force? , 23L is deformed more greatly. Therefore, the rear wheels 13R113L are thicker (biased) and have a larger sideslip angle in a high vehicle speed range, thereby stabilizing the turning of the vehicle.

Further, this steering device is configured such that its control circuit 42 can change the rotation speed of the motor 49 within the range between the solid line and the broken line in FIG. 2 according to the operating position of the operation switch 48. .

Therefore, it is possible to set the turning characteristics of the vehicle to desired characteristics, and it is also possible to set the turning characteristics of the vehicle to desired characteristics.
If the friction coefficient, etc.) has changed, it is possible to set turning characteristics suitable for the driving road surface.

Furthermore, in this steering device, the mounting position of the second pump 49 is not restricted by the engine mounting position of the vehicle and can be mounted at any position, so that the mounting is easy. That is, since the pump 39 is driven by the motor 49, the pump 39 can be installed at any position simply by wiring the motor 49.

Furthermore, with this steering device, the deflection angle of the rear wheels 13R, 13L can be controlled simply by controlling the energization of the motor 49, so the control is easy, and there is no need to provide fluid equipment for control. Since there is no such thing, manufacturing costs are reduced.

Note that the rotational speed control characteristics of the motor 49 are not limited to the characteristics shown in FIG. 2; for example, the characteristics shown in FIG. 3, the characteristics shown in FIG. 4, or the characteristics shown in FIG. It is also easily possible to control the motor 49 according to its characteristics.

The characteristics shown in FIG. 3 are such that the motor 49 is energized to drive the pump 39 in a vehicle speed range of first predetermined vehicle speed ■1 or more, and the rotation speed characteristic is changed to the entire vehicle speed range of first predetermined vehicle speed V□ or more. It can be adjusted between the solid line and the broken line in the figure using the operation switch 48. If the motor 49 is controlled to have such characteristics, the discharge amount of the pump 39 will be increased in the entire vehicle speed range above the first predetermined vehicle speed v1, and more stable turning will be achieved, especially when the friction coefficient of the road surface is small, such as during rainy weather. It is possible to obtain performance.

In addition, the characteristics shown in FIGS. 4 and 5 are such that the rotation speed characteristics of the motor 49 in the vehicle speed range below the second set vehicle speed ■2 can be adjusted between the solid line and the broken line in the figures using the operation switch 48. It is something.

If the motor 49 is controlled with such characteristics, the discharge amount of the pump 39 can be reduced and agile performance can be obtained, especially when the vehicle makes sharp turns at low speeds, such as when driving on a winding road. I can do it.

(Effects of the Invention) As described above, according to the present invention, since the pump that supplies pressurized fluid to a rear wheel steering device such as a compliance steer control device is driven by an electric motor, the location of the pump, etc. Greater freedom in decision-making, and
Its control becomes easy.

In addition, in the above-described embodiment, since the rotation speed of the motor is controlled according to the vehicle speed, the deflection angle of the rear wheels in response to the steering wheel has a characteristic that depends on the vehicle speed, resulting in good turning performance. In particular, since the motor is stopped in the low speed range where stability is not a problem when turning below a predetermined vehicle speed, the vehicle's dynamic performance becomes agile and the power consumption of the motor is reduced, resulting in improved fuel efficiency. Improvements can be made. Furthermore, in the embodiments described above, since the rotation speed characteristics of the motor are manually changed, it is possible to obtain the turning characteristics desired by the driver, and it is also possible to obtain characteristics according to the road surface conditions.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a vehicle steering system according to an embodiment of the present invention, and FIGS. 2 to 5 are diagrams each showing a mode of controlling an electric motor. 11-----Vehicle body, 12R1+2--Front wheel, 13R113L--One rear wheel, 19-----One steering handle, 20--Steering gear mechanism, 37- ---
Power steering device, 38------1 front wheel steering means, 39---1 second pump, 42---Control circuit, 43---111 Vehicle speed sensor, Wing----- - Control means, 47 - Compliance steer control device (rear wheel steering means) 48 - Operation switch, 49 - Electric motor, 50 - Steering sensor. Patent Applicant Nissan Motor Co., Ltd. Representative Patent Attorney Ugagun Part Figure 1 Figure 2 Figure 3

Claims (4)

[Claims] (1) A front wheel steering means for deflecting the front wheels by transmitting the steering force applied to the steering handle; and a rear wheel steering means for deflecting the rear wheels in response to the steering of the steering handle by the action of pressure fluid; 1. A vehicle steering device comprising: a pump for supplying pressurized fluid to rear wheel steering means, wherein the pump is driven by an electric motor. (2) The vehicle steering system according to claim 1, further comprising a control means for controlling energization of the electric motor, and controlling the rotational speed of the electric motor in accordance with vehicle speed. (3) The vehicle steering device according to claim 2, wherein the control means energizes the electric motor only when the steering handle is being steered. (4) The control means according to claim 2, wherein the control means stops energizing the electric motor and stops driving the pump in a low vehicle speed range where the vehicle speed is below a predetermined vehicle speed. Vehicle steering system.