JPS60213573A - Vehicle steering device - Google Patents

Abstract

PURPOSE:To aim at improving the steering function of rear wheels, by increasing the flow rate of fluid fed into a rear wheel control valve in proportion to increases in the pressure of a reaction force chamber in a front wheel control valve. CONSTITUTION:In the intermediate section of a hydraulic oil feed passage 28 for a rear wheel control valve 50, there is provided a solenoid type flow control valve 80 provided with a variable orifice passage, which energizes a solenoid 84 in association with a signal from a controller 100 to adjust the constriction degree of hydraulic oil so that the flow rate of hydraulic oil fed into a power cylinder 20 through a rear wheel control valve 50 is adjusted. A controller 100 in which desirable flow rates of hydraulic oil fed into the rear wheel power cylinder 20 in accordance with the running conditions of the vehicle are previously stored, controls the flow control valve 80 in accordance with input signals which are delivered from a steering angle sensor 102 and a reaction force pressure sensor 103, indicating the steered angle of the front wheels and the pressure in a reaction force chamber 71, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a vehicle steering system, and more particularly to a vehicle steering system suitable for simultaneously steering both front wheels and rear wheels.

[Background of the invention]

The power steering device of the vehicle steering equipment is equipped with a power cylinder to reduce the steering force. Vehicle steering is generally a front wheel system, and the power cylinder cylinder is used to steer the front wheels. There is. Recently, in order to improve small turning performance or to make slalom driving and parallel parking easier, a front and rear wheel steering system has been adopted in which the rear wheels are steered along with the front wheels. A cylinder is used (see Japanese Unexamined Patent Publication No. 112875/1987).
.

Therefore, in line with this trend, a reaction force control type speed-sensitive system has been adopted that reduces the steering reaction force to a large extent to maintain a constant steering feel and ensure stable operation.

However, in the conventional vehicle steering system as shown in the above-mentioned Japanese Patent Laid-Open No. 58-112875.

As shown in FIG. 1, in order to enable the rear wheels 2 to be steered in synchronization with the front wheels 1, pinions 3A and 3B are provided at both ends.
A rear wheel steering force transmission path 5 consisting of an operating shaft 4,
Crank member 6. Since a rear wheel steering mechanism 8 consisting of a connecting rod 7 and the like must be provided, there is a problem in that the entire device becomes complicated and large. Further, in this conventional system, it was not possible to accurately steer all of the front and rear wheels by the same amount due to mechanical errors in the transmission path 5° steering mechanism 8.

Therefore, in order to make the power cylinder operating mechanism completely compact and to prevent errors in the amount of steering of the front and rear wheels, instead of the mechanical rear wheel steering method described above, it is possible to move synchronously by rotating the five steering axes. A power steering device that can simultaneously steer the front and rear wheels using a dual control valve mechanism that has a built-in spool and a control valve that controls the direction of cylinder working fluid supply to both the front and rear power cylinders. has been proposed. In a power steering device using this dual control valve mechanism, the amount of steering for each front and rear wheel is exactly the same, which seems preferable.

However, when a vehicle turns, the vehicle does not necessarily turn with a constant turning radius, and generally the turning radius changes from moment to moment.
As a result, the turning radii of the front and rear wheels also differ, so it is desirable that the turning amount of one front and rear wheel be a turning angle that corresponds to each turning radius. In other words, in order to lengthen the steering followability of the rear wheels and achieve stable running, it is preferable to make the amount of rear wheel steering slightly wider than that of the front wheels. If the rear wheels and the rear wheels were steered by exactly the same amount, slippage would occur in the rear wheels, resulting in a new problem in that stable driving could not be achieved.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a vehicle steering device which has a compact device structure and which can realize stable driving under any driving conditions of the vehicle.

[Summary of the invention]

First, the principle of the present invention will be briefly explained.

Equipped with valve spools that move synchronously - When controlling both front and rear power cylinders using the fcZ linked control valve mechanism, the flow rate of pressure oil supplied to each power cylinder is the same, so the volume of both power cylinders can be made equal. if,
Although the steering amounts of the front and rear wheels can be made to be exactly the same, in reality, the cylinder volume, transmission link ratio, etc. are appropriately selected so that the steering amounts of the front and rear wheels are set in a predetermined proportional relationship.

However, the front wheel control valve is equipped with a reaction force control type speed sensitive system that keeps the steering torque constant by increasing the steering force in proportion to the increase in vehicle speed.
As the vehicle speed increases, the rear wheels are not steered by an amount equal to the amount of steering intended by the driver. Therefore, from the perspective of correcting the flow rate of fluid supplied to the rear wheel power cylinder so that the rear wheel steering matches the driver's intention and the amount of rear wheel steering is optimal for the amount of front wheel steering, the present invention was developed. This led to the invention.

For example, Fig. 2 is a diagram showing the characteristics of the fluid supply flow rate Q to the rear power cylinder with respect to the vehicle speed V of a power steering mechanism equipped with a dual control pulp mechanism, and in this figure, line X is the desired supply flow rate. The flow rate supplied to the power cylinder for the rear wheels is reduced as shown by line Y because the front wheel speed sensitive system works and exceeds the restriction of the valve mechanism, so the displacement of the control pulp is restricted. turn into. Therefore, if the supply flow rate characteristic to the rear wheel power cylinder is controlled as shown in line 2, the front wheel power steering will be equipped with a speed sensitive system (in the present invention, the reaction force pressure will be controlled proportionally to the increase in vehicle speed). Even if the valve is activated and the supply pressure to the reaction force chambers formed at both ends of the valve spool is increased (a system that increases the steering reaction force by suppressing the movement of the valve spool), the rear wheels will not move as intended by the driver. As expected, the steering is corrected to the desired steering amount.

In this manner, the vehicle steering system according to the present invention has valve spools that move in synchronization with the rotation of the steering shaft.
Built-in controls for front and rear wheels
k The power cylinders for the front and rear wheels can be operated simultaneously by using two parallel control pulp mechanisms.
The reaction pressure control valve suppresses the movement of the valve spool by increasing the pressure supplied to the reaction chamber in the front wheel side control valve mechanism at least in response to an increase in vehicle speed and/or steering angle, and also controls the movement of the valve spool. A flow control valve installed in the middle of the fluid supply path to the flow rate control valve performs correction control such that the amount of rear wheel turning becomes the optimum amount of turning with respect to the amount of front wheel turning, for example, it is proportional to the pressure rise in the reaction force chamber. , this achieves the above objective.

Furthermore, a directional control valve is installed in the working fluid return path to the rear wheel power cylinder, and when the speed exceeds a predetermined setting, the direction of the working fluid return path is reversed, so that the front and rear wheels are steered in the same direction at medium and high speeds, and at low speeds. It is also possible to improve the small turning performance at that time.

[Embodiments of the invention]

Next, an embodiment of the present invention will be described based on the drawings.

FIG. 3 shows a vehicle steering system according to this embodiment. In this figure, the vehicle steering system includes a front wheel power cylinder 1 that generates steering assist force for front wheels 12 and rear wheels 14.
The power cylinder 20 for the 0 and rear wheels, and the valve block 1 that moves in the same direction, are built in, and a control valve that controls the direction of pressure oil supply to both power cylinders 10 and 20 is installed in parallel. Valve mechanism 30 and each control valve (front wheel control valve 4O, rear wheel control valve 50)'
Oil pump 6 that supplies pressure oil pipes to both power cylinders via i
0 (60A, 60B) and a reaction pressure control valve 70 that controls the movement of the spool in the front wheel control valve 40.
, a flow control valve 8o provided in the pressure oil supply path to the rear wheel control valve, and a fiyv direction switching valve 90 provided in the middle of the pressure oil transmission path 92 to the rear wheel power cylinder 20.
, a pressure control valve 7o, a flow rate control valve 80. Directional switching valve 9 (
1 Controller 100 that sends control signals for operation
It consists of and.

Pistons (not shown) are inserted into the power cylinder 10 for the front wheels and the power cylinder 20 for the rear wheels, respectively, and both ends of both pistons are connected to tie rods 15 and 16 of the front and rear wheels, respectively. , the pressure oil is supplied into the cylinder, the piston slides, and the wheels 12.14
are designed to steer respectively.

A steering wheel 18 of the vehicle (the outer frame is indicated by reference numeral 17) is connected to a pinion shaft 21 via a steering shaft 19, and the pinion shaft 21 is connected to a pinion 21A as shown in FIG.
is integrally formed and rotatably supported by a bearing 22. A rack 23 that meshes with the pinion 21A is disposed perpendicular to the pinion shaft 21, and the rack 23 is connected to a piston that passes through the power cylinder 10 for the front wheels. It is now possible to steer the ship.

As shown in FIG. 4, the dual control valve mechanism 3o has independent valve spool insertion holes 41.
, front wheel control valve 40 with s 1 yt
The spool insertion holes 41 and 51 are formed perpendicularly to the pinion shaft 21, and the rear wheel control valve 5o is arranged in parallel and assembled to the rotation of the pinion shaft 21. In the insertion holes 41 and 51, there is a valve spool 42.52 which selectively supplies oil to the full power cylinder 10.20 from the pumps 60A and 60B via the pump boats 45 and 55. The arrangement is disgusting. In addition, in FIGS. 3 and 5, the reference numeral 61 (6
1A, 61B) indicate oil tanks. Pulp spool 42
．． As shown in FIGS. 5 and 6, annular grooves 43 and 44° 53 and 54 are provided on the outer periphery of the spool insertion holes 41 and 51 to form pressure oil passages with the inner peripheral walls of the spool insertion holes 41 and 51, respectively.
In addition, these grooves 4 are formed on the inner circumferential walls of the spool insertion holes 41 and 51.
3, 44゜53.54, respectively, to selectively communicate the hydraulic chamber of the power cylinder 10゜20 with the pump side or the tank side (pump port) 45.55 and cylinder bow)
46, 47.56.57% tank boat 48°58 is formed, and when the valve spool 42.52 moves from the neutral position to the right or left in the figure, the power cylinder 10. The direction in which the pressure oil is supplied to the pump 20 can be switched.

Further, the valve spool 42.52 is formed with a pin hole 49.59 orthogonal to the pinion shaft 21, and the swing lever 2 is connected to the pin hole 49.59 to the pinion shaft 21.
4 is placed through the opening 25 (25(11)A, 25B) separating the pulp spool 42.degree. 52 and the pinion shaft 21.

The swing lever 24 has a support pin 26 (26A
, 26B) and drive pins 27 (27A, 27B) are protruded, the drive pin 27 is fitted into the pin hole 49.59 of the pulp spool T2.52, and the swing lever 24 is attached to the fulcrum part of the support pin 26. FIG. 5 is centered around 28 (28A, 28B).

Figure 6: It is designed to be able to swing in the left and right directions.

The pulp spool 4 is compressed by a compression spring 72 installed inside.
2 is held in a neutral state (the position shown in FIG. 5).

On the other hand, a spring chamber 62 is formed at one end of the spool insertion hole 51, and a compression spring 6 is installed in this spring chamber 61.
3, the valve spool 52 is held in a neutral state (the position shown in FIG. 6).

Now the handle is 18′! ] l - Operate the pinion shaft 21
When rotated in either direction, tie rod 15 (1
2) Since the resistance of the rack 23 connected to the pinion shaft 23 is large, the pinion shaft 21 tends to be displaced along the rack 23 in this rotation direction in a direction opposite to the movement direction of the rack 23.

As a result, since the swing lever 24 is fitted to the pinion shaft 21, as the pinion shaft 21 swings in its displacement direction, the drive pin 27 swings in the same direction about the fulcrum portion 28. . Valve spool 42.
52 moves and Xie → 6!2 Horde 45 and 46 (or 47
), 55 and 56 (or 57) communicate with each other, pressure oil is supplied from the power cylinder xo and 2oi pumps 60A and 60B, and the rack 23 is driven in the rotational direction of the pinion shaft 21, so that both the front and rear wheels are steered. Ru.

A pressure control valve 70, which is an electromagnetic valve equipped with a variable throttle passage, is provided in the middle of the return circuit 73 of the front wheel control valve 40, and is connected to a controller 100 described later.
The solenoid 75 is actuated by a signal from the solenoid 75 to adjust the throttle amount P, and the entire pressure oil is supplied into the reaction oil chamber 71 of the control pulp 40 via the feed passage 76. This causes the valve spool 42 to move in the left-right direction in FIG. 5, thereby increasing the steering reaction force.

The controller 100K stores in advance the next desired reaction oil chamber pressure according to the driving situation (vehicle speed and front wheel steering angle) K, and further includes a vehicle speed sensor 101 that detects the rotational speed of the axle.
The vehicle speed when traveling is detected from the steering angle sensor 102 installed on the steering shaft 19, and the front wheel steering angle when traveling is detected from the steering angle sensor 102 installed on the steering shaft 19.
6, the pressure inside the reaction oil chamber 71 is constantly sent from the reaction pressure sensor 103 installed in the middle. Based on these input signals, the controller 100 increases the pressure in the reaction oil chamber 71 to increase the steering reaction force, for example, when the ground resistance becomes small (when traveling at high speed or when the steering angle is small). A valve opening degree control signal is sent to the pressure control valve 70. This causes the valve spool 42 to move.
The steering wheel 18 is not heavy and sudden steering at high speeds is prevented.

Note that 1 the pressure inside the reaction oil chamber 71 is increased and the valve spool 42
Instead of using a means to restrict the movement of the steering shaft 1, the steering shaft 1 is
Also, in the middle of the pressure oil supply path 82 (see FIG. 3) to the rear wheel control valve 50, there is a flow control valve 80 consisting of an electromagnetic valve equipped with a variable throttle passage. is installed, and the solenoid 84 is actuated by a signal from the controller 00 to adjust the throttle amount, and the flow rate supplied to the power cylinder 20 via the rear wheel control valve 50 is adjusted. . The controller 00 contains the driving status (reaction oil chamber 7
A desirable flow rate of pressure oil supplied to the rear wheel control valve 20 according to the internal pressure and front wheel steering angle) is stored in advance, and the front wheel steering angle and reaction force sent from the steering angle sensor 102 and reaction force pressure sensor-03 are stored in advance. Based on the input signal indicating the internal pressure of the oil chamber 71, the controller 00 determines the desired flow rate (desired supply flow rate to the power cylinder 20)
The flow rate control valve 80 is controlled by outputting a valve opening signal so that the following occurs. For example, when driving at high speed, the pressure control valve 70 works, and the reaction force mechanism on the front wheel side of the control valve mechanism 30 causes the valve spools 42 and 52 to move (the handlebar 18 operation becomes heavy), and the rear The flow rate of pressurized oil supplied to the wheel power cylinders 20 does not reach the amount of rear wheel steering intended by the driver. However, the flow rate control valve 80 operates in response to a signal from the controller 100 to correct the flow rate of pressure oil supplied to the rear wheel power cylinder 20, so that the amount of steering of the rear wheels 14 becomes the optimum amount.

In this way, in this embodiment, the flow control valve 80 allows the rear wheels to be steered by 14 degrees according to the driver's intention and to a desired amount of rear wheel turning relative to the amount of front wheel turning. Therefore, the followability of the rear wheel steering is maintained at an optimal level, and the rear wheels 14 do not slip, allowing stable running. In addition.

Since the structure of the flow control valve 80 is not new, its explanation will be omitted. Furthermore, in the above description, the flow rate of the pressure oil supplied to the control valve 50 is controlled, and the correction pressure oil is directly supplied by the flow rate control valve 80 to the pressure oil supply path from the control valve 50 to the power cylinder 50. It's okay.

t7c, a directional control valve 90 is provided in the middle of the pressure oil return path 92 between the control valve 50 and the power cylinder 20 for the rear wheels, and the front and rear wheels 12 and 14 are normally steered in opposite directions (at low speeds). However, at medium to high speeds, the pressure oil return direction is switched by a switching signal from the controller 100, and the front and rear wheels 12, 14 are steered in the same direction. That is, the controller 100 has
The traveling speed is always input from the vehicle speed sensor 101, but an arbitrary speed for sending a valve switching signal is set in advance, and when the traveling speed exceeds this set speed, the controller 100 switches the directional switching valve 90. A valve switching signal is sent and a solenoid 94 is operated to switch the pressure oil return direction.

In this way, when the vehicle is running at low speeds, the front and rear wheels are steered in opposite directions, which improves the turning radius with a small turning radius, while at medium and high speeds, the front and rear wheels are steered in the same direction, which improves performance during the change section. This allows the tracking ability of the rear wheels to be predictively adjusted to the steering direction.

You can change lanes and run slalom smoothly.

Furthermore, if the directional control valve 90 can be switched completely manually, it will be convenient for parallel parking.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, it is possible to obtain a vehicle steering system that has a compact device structure and can realize a stable running path under any driving conditions.

[Brief explanation of the drawing]

Fig. 1 is an overall plan view of a conventional vehicle steering system, and Fig. 2 is a diagram showing a change curve of the supply flow rate of the rear wheel power cylinder 5 with respect to speed when a speed-sensitive dual control knob mechanism is used. , FIG. 3 is a plan view of an embodiment of the present invention, and FIG. 4 is a plan view of an embodiment of the present invention.
5 is a sectional view taken along the line V--VK shown in FIG. 4, and FIG. 6 is a sectional view taken along the line ■--■ shown in FIG. 4. 10...Power cylinder for front wheel, 12°°° front wheel. 14... Rear wheel, 18... No S wheel, 19... Steering shaft, 20... Power cylinder for rear wheel, 21...
Pinion shaft, ' 21A... Hinion, 23... Rack, 24... Rocking lever, 27... Drive pin, 3
゛0...Control valve mechanism, 40...Front wheel control valve, 50...Rear wheel control valve. 42.52...Valve spool, 45. Claim-),
46.47, 56.57... cylinder port, 48.
58... Tank boat, 60 ('6' □A, 60
B)...Oil pump, 70...Reaction force pressure control valve, 71...Reaction force oil chamber, 75...Solenoid, 80...
...Flow rate control valve, 84...Solenoid, 90...Direction switching valve, 94...Tsure>id, 100...Controller, 101...Vehicle speed sensor, 102...Steering angle sensor, 103 ...W sensor ÷ 4-a-v-(19) @1 Figure 2

Claims (2)

[Claims] (1) Each power cylinder for front wheel steering and rear wheel steering has a built-in valve spool that moves in synchronization with the rotation of the steering shaft, and the movement of this valve spool causes working fluid to be supplied to both power cylinders. A dual control pulp mechanism in which a control valve for switching the supply direction is arranged in parallel, and a reaction force chamber formed at both ends of the valve spool in the front wheel control valve, the pressure of which is adjusted according to at least an increase in vehicle speed and/or steering angle. a reaction pressure control valve that completely suppresses the movement of this valve spool by increasing the pressure;
a flow rate control valve which is provided in the middle of the fluid supply path to the rear wheel control valve and acts to increase the fluid flow rate supplied to the control valve in proportion to the pressure increase in the reaction force chamber; A vehicle steering device characterized by comprising: (2) In the middle of the power cylinder working fluid return path between the rear wheel control valve and the rear wheel power cylinder,
2. The vehicle steering device according to claim 1, further comprising a direction switching valve that reverses the direction of supply of working fluid to the power cylinder after a predetermined set speed.