JPH05139137A - Caster angle control device for vehicle - Google Patents

Abstract

PURPOSE:To provide a caster angle control device which enables a caster angle to be widely controlled with a small amount of movement of the intermediate portion of a hub carrier for supporting the front wheel of the vehicle, enables the device itself to be in size, and requires no special complicated structure on the part of a vehicle body, by moving the intermediate portion of the hub carrier with a lower end portion thereof being fixed. CONSTITUTION:A lower link 12 is connected to the lower end portion of a hub carrier 11 for supporting a front wheel 10FL, 10FR of the vehicle while an upper link 14 is connected to the upper end portion thereof. Further, the intermediate portion of the hub carrier 11 is obliquely connected to a rear- vehicle portion of the lower link 12 by a variable-length wind-up link 15. This wind-up link is internally mounted with a hydraulic chamber and a piston to change the length of the wind-up link itself. A caster angle control device is thereby formed into a structure of causing a change in the position of a point of connection between the wind-up link and the hub carrier 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a caster angle control device for automatically controlling a caster angle of front wheels of a vehicle.

[0002]

2. Description of the Related Art A steered wheel of a vehicle, that is, a caster angle of a front wheel with respect to a traveling direction of a kingpin axis sets a ground contact point of a tire behind an intersection of the kingpin axis and a road surface. The effect of trying to go straight is obtained. Therefore, the larger the caster angle, the better the straight traveling property and the converging property, and the better the returning of the steering wheel, but the steering force becomes heavy. In particular, when the vehicle is stationary, the steering force at low speed is greatly affected.

In order to solve such a problem, the applicant of the present invention has previously proposed a caster angle control device described in Japanese Utility Model Publication No. 1-94108. This caster angle control device is a suspension device in which an upper link is connected to the upper end of a hub carrier and a transverse link is connected to the lower end of the hub carrier, and the transverse link is moved forward of the vehicle as the vehicle speed increases. By doing so, the caster angle is controlled to increase at high speed to improve the straight running stability, and the caster angle is controlled to decrease at low speed to reduce the stationary force.

[0004]

However, in the conventional caster angle control device, since the transverse link connected to the lower end of the hub carrier is directly moved in the front-rear direction of the vehicle, the caster angle can be largely changed. When controlling, the transverse link must be moved greatly. Therefore, the structure of the vehicle body becomes complicated because the size of the device itself becomes large and a large space for accommodating the device is required in the tire housing, for example. In addition, since the amount of movement of the transverse link is large, the mechanism for accurately moving it becomes complicated.

The present invention was developed in view of the above problems, and it is an object of the present invention to provide a caster angle control device which is compact in itself and does not require a complicated structure on the vehicle body side. Is.

[0006]

A caster angle control device for a vehicle according to the present invention is a caster angle control device for a vehicle capable of controlling the caster angle of a front wheel of the vehicle, and a hub carrier supporting each front wheel, and the hub carrier. An upper link connected to an upper end of the hub carrier, a lower link connected to a lower end of the hub carrier, a wind up link connecting an intermediate portion of the hub carrier and the lower link, and a connection between the wind up link and the hub carrier. An actuator for changing the position of a point is provided.

[0007]

In the caster angle control device for a vehicle according to the present invention, since the middle portion of the hub carrier and the lower link are connected by the windup link, the kingpin shaft is effectively the connecting point between the hub carrier and the lower link ( Hereinafter, a lower link connection point) and a connection point of the hub carrier and the wind uplink (hereinafter referred to as a wind uplink connection point) are connected to each other. Then, the caster angle is controlled by changing the position of the wind-up link connection point by the actuator to change the inclination angle of the kingpin shaft in the vehicle front-rear direction. The amount of movement of the wind up link connection point with the control angle of the caster angle is smaller than that in the case where only the lower link or the upper link is moved to obtain the same control angle in the suspension device without the wind up link. Corresponds to the ratio of the distance between the lower link connecting point and the wind upper link connecting point to the distance between the lower link connecting point and the upper link connecting point. Therefore, in the caster angle control device for a vehicle according to the present invention, a large caster angle control angle can be obtained by slightly moving the wind up link connecting point.

[0008]

1 is an embodiment of a caster angle control device of the present invention, which is applied to a vehicle equipped with a double wishbone type four-wheel independent suspension mechanism. First, the structure will be described. As shown in the figure, the front wheel 1 of the vehicle
A suspension device 1 having a drive means for changing the caster angle is attached to each of the wheels 0FL and 10FR. Of these, the hub carrier 11 that supports the front wheels 10FL and 10FR has a lower link 12 rotatably connected to a lower end thereof and a side rod 13 rotatably connected to an intermediate portion thereof as shown in FIGS. Further, the upper link 14 is connected to the upper end portion thereof, and the respective links 12, rods 13, and links 14 are connected to a vehicle body side (not shown) via a rubber bush or the like. The vehicle rear portion of the lower link 12 and the middle portion of the hub carrier 11 are diagonally connected by a variable length windup link 15, which improves the rigidity of the wheels in the vertical direction and, in fact, effectively. An ideal negative scrub is realized by increasing the kingpin inclination angle by moving the upper connection point of the hub carrier to the inner side in the vehicle width direction.
The lower end side of the variable length wind-up link 15 is rotatably connected to the lower link 12 via a rubber bush or the like, and the upper end side is rotatably connected to the hub carrier 11 via a universal joint mechanism or the like. There is.

A hydraulic chamber 16 and a piston 17 as shown in FIG. 4 are incorporated in the variable length windup link 15, and the length of the windup 15 itself is changed by expanding and contracting the piston 17. As shown in FIG. 5a, when the wind up link 15 is lengthened, the caster angle θ of the front wheels is decreased, and when the wind up link 15 is shortened, the caster angle θ is increased as shown in FIG. 5b. Changes to. A spring 18 is installed inside the hydraulic chamber 16 by a stop pin 19, and a control valve 21 for controlling the hydraulic pressure from a hydraulic source 20 is connected to the hydraulic chamber 16 and opens and closes the control valve 21. By doing so, the piston 17 is expanded and contracted.
Although this hydraulic circuit will not be described in detail here, for example, the hydraulic circuit described in Japanese Patent Laid-Open No. 60-15213 previously proposed by the present applicant can be diverted. In addition,
This variable length windup link 15 has a piston 17
A stroke sensor 22 for detecting the stroke length is attached, and the detection signal from the sensor 22 is output to the controller 2 shown in FIGS. In addition, the control valve 21
Is opened and closed by an output signal from the controller 2.

A vehicle speed sensor 3 is attached to the vehicle to detect a longitudinal speed (hereinafter referred to as vehicle speed) V of the vehicle and output a detection signal to the controller 2.
The controller 2 is provided with a computing unit 23C and a control unit 23F, of which the computing unit 23C includes the vehicle speed sensor 3
From the stroke sensor 22 of each of the front wheels 10FL and 10FR is input to the control unit 23F. The control valve 21 of each front wheel is opened / closed by the control signal from the control unit 23F based on the output signal from the arithmetic unit 23C. The computing unit 23C and the control unit 23F have a built-in microcomputer (not shown). Of these, the computing unit 23C has a microcomputer shown in FIG.
The program shown in the flowchart of a, the vehicle speed-target caster angle correlation (hereinafter referred to as the vehicle speed control map) shown in FIG. Each is stored in advance.

In the vehicle speed control map, as clearly shown in FIG. 6, the relationship between the vehicle speed V and the target caster angles θ _FL and θ _FR determined according to the vehicle speed V is shown. In this control map, the target caster angle is set to increase as the vehicle speed increases, which reduces the steering force at low speeds and improves straight running stability and steering performance at high speeds. By the way, the caster angle is set to remain slightly even when the vehicle speed becomes zero.

Next, the operation of the caster angle control device will be described. The process shown in FIG.
It is executed as a timer interrupt process every (for example, 5 msec). First, in step S1, the vehicle speed V is read from the detection signal of the vehicle speed sensor 3. Next, in step S2,
From the vehicle speed V, the target caster angles θ _FL and θ _FR are determined based on the vehicle speed control map shown in FIG.

Next, in step S3, the variable length wind-up 1 that satisfies the target caster angles θ _FL and θ _FR.
The length of 5, that is, the target output value from the stroke sensor 22 is calculated and output to the control unit 23F, and the program ends. On the other hand, the process shown in FIG.
Similar to the process shown in (1), it is executed as a timer interrupt process for each predetermined period ΔT (for example, 5 msec).

First, in step S4, the above-mentioned step S3 is performed.
In addition to reading the target output value from the stroke sensor 22 calculated in step 1, the detection signal of the stroke sensor 22 of each wheel 10FL, 10FR is read. Next, in step S5, it is compared whether or not the output value of the detection signal from the stroke sensor 22 of each wheel is equal to the target output value. If they are equal, the program is terminated, and if they are not equal. Moves to step S6.

In step S6, the front wheels 10FL, 10FL
The program is terminated by expanding and contracting the piston 17 of the FR variable length windup 15 to a stroke length that satisfies the target output value from the stroke sensor 22. By controlling the caster angle based on the processing of FIG. 7,
As the vehicle speed increases, the caster angle increases and the straight running stability of the vehicle increases, and as the vehicle speed decreases, the caster angle decreases and the steering force such as stationary steering is reduced.

By the way, in this embodiment, the variable length wind-up link 15 is provided obliquely with respect to the width direction of the vehicle as clearly shown in FIG. 3a. Therefore, when the wind-up link 15 is shortened, the front wheel The camber angle changes in the negative direction. For this reason, in this embodiment in which the wind-up link 15 is controlled to be shortened during high-speed traveling, for example, the canvas last of the front wheel outside the turning that changes to the positive side with the roll at the time of turning is reduced to reduce the cornering force. It is also possible to improve the turning efficiency and the turning stability of the vehicle by improving the steering effect.

In this embodiment, the caster angle of the wheel is controlled by the program stored in the microcomputer, but it may be controlled by using a theoretical circuit having the same function. Further, although the vehicle speed is directly detected by the sensor in the above-mentioned embodiment, it may be calculated by using an appropriate means such as integrating and estimating the vehicle acceleration.

Further, although the target caster angle is set to linearly increase as the vehicle speed increases in the vehicle speed control map, this correlation is arbitrarily set according to the characteristics of the vehicle and the desired target caster angle. It is possible.

[0019]

As described above, according to the caster angle control device of the present invention, the caster angle is controlled by changing the connecting point position of the wind up link connected to the intermediate portion of the hub carrier by the actuator. Therefore, compared with the conventional caster angle control device in which only the lower link or the upper link is moved to obtain the same control angle, the amount of movement is small, and the winding uplink connection point is slightly moved. By doing so, a large caster angle control angle can be obtained. Therefore, the entire apparatus can be made compact, and the vehicle body side does not require any specially complicated structure.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a caster angle control device of the present invention.

FIG. 2 is a perspective view of a suspension mechanism of a front wheel suspension device used in the caster angle control device of FIG.

3A and 3B are operation explanatory views of the suspension device of FIG. 2, where FIG. 3A is a front view and FIG. 3B is a side view.

FIG. 4 is a vertical cross-sectional view showing a caster angle changing actuator used in the caster angle control device of FIG.

FIG. 5 is an explanatory diagram of a change in caster angle by the suspension device of FIG.

FIG. 6 is a correlation diagram of a target caster angle according to a vehicle speed in the caster angle control device of FIG.

7 is a program for controlling a caster angle in the caster angle control device of FIG. 1, (a) is a flowchart showing arithmetic processing, and (b) is a flowchart showing control processing.

[Explanation of symbols]

 1 is a suspension device 2 is a controller 3 is a vehicle speed sensor 10FL, 10FR is a front wheel 11 is a hub carrier 12 is a lower link 13 is a side rod 14 is an upper link 15 is a variable length wind up link 16 is a hydraulic chamber 17 is a piston 22 is a stroke sensor 23C is a calculation unit. 23F is a control unit.

Claims (1)

[Claims] 1. A caster angle control device for a vehicle capable of controlling a caster angle of a front wheel of a vehicle, a hub carrier supporting each front wheel, an upper link connected to an upper end of the hub carrier, and a lower end of the hub carrier. A lower link that is connected to the lower carrier, a wind up link that connects the middle part of the hub carrier and the lower link, and an actuator that changes the position of the connection point between the wind up link and the hub carrier. Caster angle control device for vehicles.