JPH03114976A - Rear wheel steering angle control device for four-wheel steering vehicle - Google Patents

Abstract

PURPOSE:To ensure proper safety travel by fixing a steering angle limiting pin at a position relative to a steering angle limiting groove during a braking operation, and limiting a rear wheel steering angle to a steering amount at a braking start, even when a rear wheel steering angle control system fails upon braking slip during a high speed travel. CONSTITUTION:The more is the speed of a propeller shaft 10, the larger is a centrifugal force acting on a weight 13, and this weight 13 radially moves correspondingly to balance with an energizing force by a spring 16. Consequently, a steering angle limiting pin 17 comes to be located at a lower position as a vehicle speed rises, and a charge on a steering angle limiting groove 18 becomes large. Also, the larger is a charge on the aforesaid groove 18, the rod 6a of a rear wheel steering power cylinder 6 is subjected to the more limitation by the stroke range thereof, thereby giving a steering angle limit to a rear wheel 3. At the time of a braking operation, brake fluid pressure generated by a master cylinder works to press a piston 102 to the side of the steering angle limiting pin 17, and the charge of the pin 17 on the aforesaid groove 15 is thereby maintained at the same level as at a braking start.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a rear wheel steering angle control device for a four-wheel steering vehicle, and particularly to fail-safe technology thereof.

(Prior Art) Conventionally, as a rear wheel steering angle lll1l device for a four-wheel steering vehicle that steers the rear wheels when the front wheels are steered, for example, Japanese Patent Laid-Open No. 62-1
The one shown in Japanese Patent No. 66161 is known.

However, in such a conventional rear wheel steering angle control '@4 of a four-wheel steering vehicle, when a failure in the rear wheel steering angle ll1IlIII system is detected, after the failure is detected, the cylinder for restoring to the neutral position is The system is configured to activate and lock in the neutral position, and after a fail-safe operation is performed after the failure is detected, it is possible to drive at high speed using the rear wheel steering actuator that enables a large steering angle. If a failure occurs in the rear wheel steering angle control system, the restoring cylinder may start operating after the rear wheels have been steered to the maximum steering angle by - degrees.

For example, a rear wheel cylinder with a long stroke that enables a large steering angle in the opposite phase to the front wheels when turning at low speeds is used to control the rear wheel steering angle during high-speed driving when the front wheels are controlled to a small steering angle in the same phase. If a control system failure occurs, the rear power cylinder may stroke close to its maximum stroke even though the spring force to return it to the neutral position is acting, and a large turning angle may be given to the rear wheels, resulting in a large turning angle. If a corner is applied, the fail-safe function may be lost and sudden changes in vehicle behavior such as vehicle spin may occur.

In order to deal with this, a technology has been proposed, as shown in Japanese Utility Model Application Publication No. 60-150164, in which a solenoid controlled by an electrical signal is used to project a spacer at high speeds to regulate the rear wheel steering angle. . However, even with this configuration, since the appearance and retraction of the spacer is controlled based on electrical signals from the controller, there is a risk that some electrical abnormality may occur in the spacer appearance and retraction control device, and in this case, fail-safe There were concerns that the functions of the system would not be fully demonstrated.

Focusing on the above-mentioned problems, the present applicant has developed a rear wheel steering angle control device for a four-wheel steering vehicle that auxiliary turns the rear wheels during front wheel steering, which is advantageous in terms of cost and maintenance, and has a good performance. Although it has a high degree of freedom that allows a predetermined rear wheel steering angle necessary to obtain good turning performance regardless of the rear wheel steering angle control content, it can be used reliably if a failure occurs in the rear wheel steering angle control system at high speed. In order to ensure safe driving, a rear wheel steering angle control means has a rear wheel steering actuator that is driven to obtain a rear wheel steering angle according to vehicle conditions when the front wheels are steered, and a rear wheel steering actuator is used to steer the rear wheels. The rear steering mechanism includes a movable part of the rear steering mechanism, a steering angle limiting groove and a steering angle limiting pin provided at a position facing the movable part, and a steering angle limiting groove and a steering angle limiting pin provided at a position opposite to the movable part of the rear steering mechanism. A rear wheel steering angle control device for a four-wheel steered vehicle is proposed, which includes a rear wheel steering angle limiting mechanism that operates an angle limiting pin.

(Problem to be Solved by the Invention) However, even with this technology, the operation of the rear wheel steering angle limiting mechanism depends on the rotation speed of the drive shaft. If there is a difference between the vehicle speed and the wheel speed, and the rear wheel steering angle control system fails when the wheel speed is low even though the vehicle speed is high,
Since the rear wheel steering angle limiting mechanism limits the steering angle to an allowable amount corresponding to low wheel speeds, a large steering angle is applied to the rear wheels, which may cause a sudden change in vehicle behavior.

The present invention was made focusing on the above-mentioned problems.
In a rear wheel steering angle control device for a four-wheel steering vehicle that auxiliarily steers the rear wheels when the front wheels are steered, when the wheels slip due to braking during high-speed driving and a difference occurs between the vehicle body speed and the wheel speed, The purpose of the present invention is to ensure safe driving even when a failure occurs in the rear wheel steering angle control system.

(Means for Solving the Problems) In order to solve the above problems, a rear wheel steering angle control device for a four-wheel steering vehicle according to the present invention provides a rear wheel steering angle control device for a four-wheel steering vehicle that is driven to obtain a rear wheel steering angle according to vehicle conditions when front wheels are steered. a rear wheel steering angle control means having a wheel steering actuator; a rear steering mechanism that applies a steering angle to the rear wheels by the rear wheel steering actuator; a steering angle limiting groove provided at a movable part of the rear steering mechanism and a position opposite thereto; A rear wheel steering angle limiting mechanism that has a steering angle limiting pin and changes the relative position of the steering angle limiting pin and the steering angle limiting groove in a direction perpendicular to the movable part according to rotation of a drive shaft for driving the wheels. A rear wheel steering angle control mechanism for a four-wheel steered vehicle, comprising means for fixing the relative position of the steering angle limiting pin and the steering angle limiting groove when braking the vehicle. .

(Function) When the vehicle is running, in the rear wheel steering angle limiting mechanism, depending on the rotation speed of the drive shaft for driving the wheels, the rear steering mechanism, the movable part of the steering mechanism, and the steering angle limiting groove provided at the opposite position. The relative position of the steering angle limit pin is determined.

Therefore, by setting this relative position, the insertion amount of the steering angle limiting pin into the steering angle limiting groove can be freely determined, and this insertion amount is related to the vehicle speed by changing according to changes in the rotational speed of the drive shaft.

During braking, by fixing the relative position of the steering angle limiting pin and the steering angle limiting groove, the amount of insertion of the steering angle limiting pin into the steering angle limiting groove is maintained at the insertion amount at the start of braking, so that during braking slip during high speed driving, Even when a failure occurs in a rear wheel steering angle control system, the rear wheel steering angle is limited to the amount of steering at the time of starting braking.

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

First, the configuration will be explained.

FIG. 1 shows a rear wheel steering angle control HW of a four-wheel steering vehicle according to an embodiment of the invention, which is equipped with a rear wheel steering angle limiting mechanism (FIG. 2). ! FIG. 2 is an overall system diagram showing the system.

The rear wheel steering angle control device inputs vehicle information such as the front wheel steering angle θ and vehicle speed ■ from the steering angle sensor 1 and vehicle speed sensor 2, etc., and steers the rear wheels 3 largely in the opposite phase at low speeds and large steering angles. A rear wheel steering angle controller 4 that outputs an optimal rear wheel steering angle command according to vehicle conditions, such as turning the rear wheels 3 in the same phase and small at high speed and a small steering angle, and a valve from the rear wheel steering angle controller 4. A rear wheel steering power cylinder 6 (rear wheel steering actuator) that is driven according to a control pressure from a hydraulic control valve 5 that is driven in accordance with a drive command, and a tie rod 7 that gives a steering angle to the rear wheels 3 by the rear wheel steering power cylinder 6. and a spindle knuckle 8 (rear steering mechanism).

The hydraulic control valve 5 uses the pressurized hydraulic oil from the hydraulic pump 9 as an input pressure, and generates a control pressure to be sent to the left and right chambers of the rear wheel steering power cylinder 6.

Next, when the vehicle speed is low, the maximum steering angle of the rear wheels 3 is loosened, and the steering angle range in which the rear wheels 3 can be steered is set large in advance, and the maximum steering angle of the rear wheels 3 is set as the vehicle speed increases. The configuration of a vehicle speed-responsive rear wheel steering angle limiting mechanism A that gradually tightens the restriction to preliminarily narrow the steering angle range in which the rear wheels 3 can be steered will be described.

The rear wheel steering angle limiting mechanism A is a pure mechanical mechanism that limits the rear wheel steering angle by using the rotation of the propeller shaft 10, which rotates at a rotation speed that corresponds to the vehicle speed. Propeller shaft 10 (drive shaft)
a first rotor 11 that is rotated by a rotor; a weight 13 connected to the first rotor 11 via a first link 12; and a weight 13 connected to the weight 13 via a second link 14. 2
A steering angle limit provided on the rotor 15, a spring 16 (elastic body) that generates a force opposing the centrifugal force acting on the weight 13, and the second rotor 15 that is displaced in the axial direction as the link is displaced. The pin 17 and the rod 6a of the rear wheel steering power cylinder 6, which is located opposite the steering angle limiting pin 17 (
The steering angle limiting groove 18 is provided in the movable part.

The propeller shaft 10 transmits engine driving force to the rear wheels 3 via a rear differential 19 and a rear drive shaft 20, and also transmits engine driving force to the rear wheels 3 via a rear differential 19 and a rear drive shaft 20.
A crown gear 21, a first gear 22. The first rotor 11 is rotationally driven via the shaft 23 and the second gear 24.

The first rotor 11 has a cylindrical shape, and the housing 2
5 via a bearing 26 so as to be rotatable.

The first link 12 has both ends connected to the first rotor 11.
and the weight 13, and the second link 14 is
Its both ends are pin-coupled to the weight 13 and the second rotor 15, and both links 12 and 14 constitute a pantograph link mechanism, and the weight 1 is connected to the joint between both links 12 and 14.
3 is provided.

The second rotor 15 is provided through the cylindrical inner surface of the first rotor 11 through a seal ring 27 so as to be rotatable and movable in the axial direction.

The spring 16 is provided between the weight 13 and the second rotor 15 so as to apply an urging force that opposes the centrifugal force acting on the weight 13 due to rotation. That is, the spring 16 is fixed to an annular member 41 provided around the second rotor 15 and a spring support member 42 pin-coupled to the weight 13, and the spring 16 applies a tensile force against centrifugal force. It's starting to happen.

The steering angle limiting pin 17 is connected to the second rotor 15 via a bearing 28, and is provided so that it can only stroke in the axial direction and not rotate with respect to the housing 25 by a rotation prevention key 29. There is. The tip of the steering angle limiting pin 17 has a conical shape or a horizontal shape.

The steering angle limiting groove 18 is formed in a block 30 fixed to the rod 6a of the rear wheel steering/power cylinder 6, and the groove shape is conical or horizontal like the steering angle limiting pin 17. However, the steering angle limiting groove 18 is formed larger so as to allow a slight stroke of the O-rad 6a even when the steering angle limiting pin 17 is inserted to the deepest point.

Also, to explain the means for fixing the relative position of the steering angle limiting pin and the steering angle limiting groove in response to braking of the vehicle, a cylinder 101 is formed in the housing 25 in a direction perpendicular to the steering angle limiting pin 17, Inside the cylinder is a piston 102
and a spring 103 (elastic body) that generates a force that pushes the piston 102 against the steering angle limit pin 17 in the opposite direction.
It has an air vent hole 104. and the cylinder 10
1 is connected to the mask cylinder 10 via the brake pipe 105.
6, and brake pedal 107, front wheel 108, and rear wheel 3
It is connected to the wheel cylinder 109 of.

Next, the effect will be explained.

Stop.

(b) At the time of suspension When the vehicle is stopped, the propeller shaft 12 does not rotate.

Therefore, the weight 13 of the rear wheel steering angle limiting mechanism A is the spring 1.
6, and as shown in FIGS. 1 and 2, the steering angle limiting pin 17 is placed in a position where it is slightly inserted into the steering angle limiting groove 18.

(b) When the vehicle is running (when not braking) When the vehicle is running fi, the rear wheel steering angle limiting mechanism A uses the propeller shaft 10 to adjust the first rotor 11 according to the vehicle speed.
is rotated, and a centrifugal force acts on the weight 13 connected to the first rotor 11 via the first link 12.

When the centrifugal force acting on the weight 13 and the urging force by the spring 16 are not balanced, the weight 13 moves in the radial direction to a balanced position and stops moving 8 at the balanced position.

As the weight 13 moves, the first link 12 and the second link 14 are displaced, and the second rotor 15 connected to the second link 14 is also displaced in the axial direction, corresponding to the stop position of the weight 13. The second rotor 15 stops at the position.

This displacement operation of the second rotor 15 causes the second rotor 15 to
The relative position between the steering angle limiting pin 17 provided on the steering angle limiting pin 17 and the steering angle limiting groove 18 provided on the rod 6a of the rear wheel steering power cylinder 6 is determined.

That is, the higher the rotation speed of the propeller shaft 10 is, the greater the centrifugal force acting on the weight 13 becomes. The steering angle v1 limit pin 17 is disposed at a lower position as the vehicle speed increases from the position shown in FIG. 2, and the amount of insertion into the steering angle ill limit groove 18 increases.

The larger the insertion amount of the steering angle limiting pin 17 into the steering angle limiting FS 18, the more the O-rads 6a, 6b of the rear wheel steering power cylinder 6 are restricted in their stroke movable range, and this stroke restriction remains unchanged for the rear wheels. The steering angle is limited to 3.

(c) When the vehicle is running (braking) When the brake pedal 107 is depressed during braking, the mask cylinder 106 makes the brake fluid pressure high, and this brake fluid pressure moves the piston 102 toward the steering angle limiting pin 17 via the brake piping 105. As a result, the insertion amount of the steering angle limiting pin 17 into the steering angle limiting groove is maintained at the insertion amount at the start of braking.

As explained above, the rear wheel steering angle 1II111 installation of the embodiment has the following features.

■ Rear wheel steering angle limiting mechanism A does not prohibit rear wheel steering, but rather limits the maximum steering angle according to the vehicle speed, and at high vehicle speeds, the pre-limited maximum steering angle is severely restricted. Therefore, when the rear wheel steering angle control system is normal, it allows a predetermined rear wheel steering angle that provides good turning performance in all vehicle speed ranges from low to high speeds, but when the rear wheel steering angle control system fails while driving at high speed. If this occurs, the rear wheels are surely prevented from turning to a large turning angle, and safe driving is guaranteed.

■ As the steering angle limiting function by the rear wheel steering angle limiting mechanism A, the maximum steering angle is increased at low speeds (and a vehicle speed-responsive variable function that gradually reduces the maximum steering angle as the vehicle speed increases) is configured. Therefore, it has a degree of freedom in that the steering angle limit can be set to a desired amount according to each vehicle speed, and is compatible with rear wheel steering control devices with various control contents.

■ The rear wheel steering angle limiting mechanism A uses the rotation of the propeller shaft 10 to control the first rotor 11, the weight 13, and the second rotor 1.
5, it is a purely mechanical mechanism, compared to cases that include an electronic control system that obtains vehicle speed information from a vehicle speed sensor, etc., or cases that include an electric actuator such as an electric motor.
It has a simple configuration, is advantageous in terms of cost, and has fewer failures and malfunctions, which is advantageous in terms of maintenance.

■ The rear wheel steering angle control system and the rear wheel steering angle limiting system are completely separated and independent, so even in the event of a failure in which the rear wheel steering angle III is disabled, the rear wheel steering angle limiting system 8 provides a fail-safe function. can be demonstrated.

■ The rear wheel steering angle limiting system is equipped with a means for fixing the amount of insertion of the steering angle limiting pin 17 into the steering angle limiting groove 18 using a piston 102 that is activated by brake fluid pressure during braking, so that when braking while driving at high speed, the wheels are Even in the event of a failure in which the rear wheel steering angle control system is disabled due to slipping, the rear wheels will be reliably regulated from reaching a large steering angle in the same way as described in ■ above, and safe driving will be guaranteed. .

Although the embodiments of the present invention have been described above with reference to the drawings, the specific configuration is not limited to the illustrated example.

For example, as a rear wheel steering angle limiting mechanism, as shown in FIG.
It may be interposed between 5 and 5. In this case as well, spring 1
A spring 16 is provided between the housing 25 and the flange 17a of the steering angle limiting pin 17 so that a tensile force acts on the spring 16.

Further, the rear wheel steering actuator may be an actuator such as an electric motor instead of a hydraulic cylinder.

Further, in the rear wheel steering angle limiting mechanism of the embodiment, an example is shown in which rotation is received from the propeller shaft, but it may also be an example in which rotation is received from a drive shaft, transmission output shaft, etc. whose rotation speed is related to vehicle speed. In some cases, it can also be applied to front-wheel drive vehicles, mid-engine vehicles, etc. that do not have a propeller shaft.

In addition, in the rear wheel steering angle limiting mechanism of the embodiment, a steering angle limiting pin was provided on the second rotor side and a steering angle limiting groove was provided on the rod side of the power cylinder. A steering angle limiting groove may be provided on the slave side, and a steering angle limiting pin may be provided on the rod side of the power cylinder.

In addition, in the rear wheel steering angle control device of the embodiment, in order to fix the insertion amount of the steering angle limiting pin into the steering angle limiting groove, the relative position of the steering angle limiting pin and the steering angle limiting groove is adjusted according to the braking of the vehicle. Although we have shown an example in which the piston that fixes the steering angle limiting pin is actuated by brake fluid pressure as a fixing means, a switch that is actuated in response to a braking operation is provided, and the piston is actuated by a solenoid that is driven by a signal from this switch. You may let them.

Further, in the rear wheel steering angle limiting mechanism of the embodiment, rotation is given to the first rotor 11 in accordance with the rotation of the drive shaft, and the centrifugal force acting on the weight 13 and the biasing force by the spring 16 are balanced. An example of determining the position of the corner uniform pin was shown, but it is also possible to use a drive shaft to drive a hydraulic pump, and a piston operated by the hydraulic pressure generated in response to this to determine the position of the rudder angle limiting pin or rudder angle limiting groove. The present invention can also be applied to a rear wheel steering angle limiting mechanism.

(Effects of the Invention) As described above, in the present invention, in a rear wheel steering angle control device for a four-wheel steering vehicle that performs auxiliary steering of the rear wheels during front wheel steering, a mechanical rear wheel steering angle limiting mechanism is used. In addition to adopting a mechanism, the maximum steering angle at which the rear wheels can be steered is gradually limited in advance to a small steering angle as the vehicle speed increases from low vehicle speed to high vehicle speed.
Since it is iIg4, it is advantageous in terms of cost and maintenance, and has a high degree of freedom to allow the specified rear wheel steering angle necessary to obtain good turning performance regardless of the rear wheel steering angle control content. ``If a failure occurs in the rear wheel steering angle control system at high speed, the effect of ensuring safe driving can be obtained. Furthermore, even if a failure occurs in the rear wheel steering angle control system when the wheels slip due to braking during high-speed driving, it is possible to reliably guarantee safe driving.

[Brief explanation of drawings]

Fig. 1 is an overall system diagram showing the rear wheel steering angle control device of a four-wheel steering vehicle according to the embodiment, Fig. 2 is an enlarged view of main parts showing the rear wheel steering angle limiting mechanism of the embodiment device, and Fig. 3 is an illustration of other parts. FIG. 2 is an enlarged view of main parts showing a rear wheel steering angle limiting mechanism according to an embodiment of the present invention. A... Rear wheel steering angle limiting mechanism 3... Rear wheel 6... Rear wheel steering power cylinder (rear wheel steering actuator) 6a... Rod (movable part) 7... Tie rod 8... Knuckle spindle 0... Propeller shaft (drive shaft) 1... First rotor 2... First link 3... Weight 4... Second link 5... Second rotor 6. Spring (elastic body) 7 Rudder angle limiting pin 8 Rudder angle limiting groove 02 Piston 05 Brake pipe 07 Brake pedal

Claims (1)

[Claims] a rear wheel steering angle control means having a rear wheel steering actuator that is driven to obtain a rear wheel steering angle according to vehicle conditions during front wheel steering; and a rear steering mechanism that applies a steering angle to the rear wheels by the rear wheel steering actuator. The rear steering mechanism has a movable section, a steering angle limiting groove and a steering angle limiting pin provided at a position facing the movable section, and the steering angle relative to the movable section in a direction perpendicular to the movable section according to rotation of a drive shaft for driving wheels. A rear wheel steering angle control device for a four-wheel steered vehicle, comprising a rear wheel steering angle limiting mechanism that changes the relative position between a limiting pin and the steering angle limiting groove, wherein the steering angle limiting mechanism changes the relative position between the limiting pin and the steering angle limiting groove when the vehicle is braked. A rear wheel steering angle control device for a four-wheel steered vehicle, comprising means for fixing a relative position with an angle limiting groove.