JP2841774B2 - Caster angle control device for vehicles - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a caster angle control device for a vehicle suspension, and in particular, to a caster angle control device for a vehicle that can appropriately control the caster angle when the steering angle increases or decreases. About.

2. Description of the Related Art It is known that the running characteristics of a vehicle can be changed by adjusting the suspension alignment in an automobile, and a caster angle (hereinafter simply referred to as a caster), which is one of suspension elements, is adjusted. do it,
Means for improving the running performance of a vehicle have also been proposed.

With respect to such casters, when the angle is increased, the straight running stability is improved, and when the angle is reduced, the steering performance (turnability) is improved. For example, the caster is controlled so as to increase in accordance with the vehicle speed to improve the straight running performance. To make
It has been proposed to improve the steering performance (turning performance) by controlling the casters to be smaller in accordance with the magnitude of the steering angle.

[Problems to be Solved by the Invention] However, in the conventional caster control as described above, since the caster control is merely performed according to the magnitude of the steering angle, the steering performance is improved over the entire turning operation. I have not been able to.

In other words, when the caster is enlarged, the straight running stability is improved while the steering wheel is heavy during the turning operation, and when the caster is reduced, the straight running stability is reduced while the steering wheel is lightened during the turning operation.

Therefore, when the vehicle is steered from a straight running state to a turning state, that is, when the steering wheel is increased at the start of steering, reducing the casters facilitates the steering,
When returning the vehicle from the turning state to the straight running state, that is, when turning back the steering wheel at the end of steering, it is easier to return to the straight running state by making the caster larger than making the caster smaller, and when returning straight, It is more effective to make the caster larger than to make it smaller.

The present invention has been devised in view of such a problem, and has a caster angle control for a vehicle in which caster control can be appropriately performed at the time of additional turning or turning back during steering so that turning performance can be improved. It is intended to provide a device.

[Means for Solving the Problems] Therefore, a caster angle control device for a vehicle according to the present invention includes a caster angle adjusting mechanism capable of adjusting a caster angle in a vehicle suspension by driving a component of the suspension; Caster angle setting means for setting a reference caster angle according to the traveling state; and control means for controlling the caster angle adjusting mechanism so that the caster angle of the vehicle takes the caster angle set by the caster angle setting means. The caster angle setting means sets a caster angle smaller than the reference caster angle when the steering angle is in the increased turning state based on the steering angle information, and sets the caster angle smaller than the reference caster angle when the steering angle is in the returning state. It is characterized in that it is configured to set a large caster angle.

[Operation] In the vehicle caster angle control device of the present invention described above, the caster angle setting means sets the caster angle smaller than the reference caster angle when the steering angle is in a state of being increased based on the steering angle information. When the steering angle is in the turning back state, a caster angle larger than the reference caster angle is set. Then, under the control of the control means, the caster angle adjusting mechanism adjusts the caster angle of the vehicle to the caster angle set by the caster angle setting means while driving the components of the suspension.

[Embodiment] Hereinafter, a vehicle caster angle control device as an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart showing the contents of the caster angle control, and FIGS. FIG. 5 is a graph showing the characteristics of the coefficient relating to the setting of the caster angle, FIG. 5 is an exploded perspective view showing the caster angle adjusting mechanism, FIG. 6 is a perspective view showing the suspension provided with the caster angle adjusting mechanism, and FIG. FIG. 8 is a graph showing another example of a coefficient characteristic relating to the setting of the caster angle.

First, the suspension of a vehicle equipped with this device will be described. The suspension of this embodiment is a strut-type front suspension for a passenger car as shown in FIG. As is well known, a shock absorber 2 and a coil spring 3 are combined, and the head of each strut 1, 1 is fixed to the vehicle body 4 side. A front wheel 7 is rotatably mounted on the lower end of each strut 1, 1 via a knuckle 5 and a hub 6.

The lower end of the strut 1 is connected via a lower arm 8 to a cross member 9 provided between the front wheels so as to also serve as a subframe, and constitutes a suspension using the shock absorber 2 as a part of a suspension link. ing.

Reference numeral 10 denotes a center member provided on the cross member 9, and reference numeral 11 denotes a disc brake.

A caster angle adjustment mechanism (slide) that allows the caster angle to be freely adjusted by sliding the heads 1A, 1A in the front-rear direction of the vehicle body 4 to the mounting portions of the heads 1A, 1A of the struts 1, 1 respectively. Mechanism) 12,12 are provided.

In FIG. 6, reference numeral 27 denotes a drive shaft, and 28 denotes a stabilizer.

Each of the caster angle adjusting mechanisms 12, 12 has the same configuration, and as shown in FIG. 5, a slide base 14 attached to the vehicle body 4 on the upper surface of the strut tower;
Slide base 14 attached to the upper end of strut 1
And a slide plate 13 that can slide with respect to.

The slide base 14, for example, has a structure in which a substantially rectangular through hole 16 parallel to the vehicle longitudinal direction is provided in the center of a plate member 15 whose longitudinal side faces the vehicle longitudinal direction.
A pair of rail portions 17, 17 each having a substantially triangular cross section are provided upright on two sides corresponding to the vehicle width direction side 16 in parallel. Each of the rails 17, 17 is arranged inward, and the head 1A of the strut 1 penetrates between the opposed rails 17, 17 and inside the through hole 16. 17a is a rib for supporting the rail portion 17.

On the other hand, the slider plate 13 is
Substantially rectangular plate member 1 with dimensions corresponding to the distance between 17,17
8 and sliding walls 19, 19 which are provided on two parallel sides on the rail portion side of the plate member 18 and have a wedge shape which can be inserted into the rail portions 17, 17 respectively.

The sliding wall portions 19, 19 have a wedge-shaped cross section, for example, the plate member 1
A symmetrical triangular wall with the side of 8 as the top is integrally provided on the side of the plate member 18 and slides on the rails 17, 17 without rattling, whereby the slide plate
The rail 13 is guided by the rails 17, 17 between the rails 17, 17 and can slide in a certain direction.

In addition, between each sliding wall portion 19 and the rail portion 17 facing the same, for example, a needle roller bearing 20 in which a plurality of roller bearings are arranged in parallel is interposed along the sliding direction, and the slider plate 13 is Stable and smooth sliding along the direction. In FIG. 5, reference numeral 21 denotes a bearing rolling surface provided on each of four outer surfaces of the sliding wall portion 19, and is formed of a rectangular recess.

The upper end of the strut 1 penetrates through the slide base 14 and is inserted into a circular opening 13a provided at the center of the slide plate 13. Also, fixed holes are provided before and after the opening 13a.
On the other hand, a pair (two) of mounting bolts 23, 2 is provided on the head portion 1A of the strut 1, for example, on the insulator portion 1a.
3 are projected, and these fixing bolts 23,2 are
By fastening 3, the head 1 </ b> A of the strut 1 is integrated with the slider plate 13. Thus, the casters of the front suspension can be made variable by sliding the slider plate 13 in the front-rear direction.
Numeral 24 indicates a nut for fastening the strut head.

And each slide plate 1 of such a slide mechanism 12,12
An actuator (drive device) 25 for moving the strut head in the longitudinal direction of the vehicle body is directly connected to 3. As the actuator 25, for example, a hydraulic actuator that drives a hydraulic cylinder 25B through a hydraulic supply / discharge system 25A having a hydraulic switching valve such as an electromagnetic valve as illustrated is conceivable.

In this case, for example, a hydraulic circuit configuration as shown in FIG. 7 is conceivable. In FIG. 7, 25a is a tank for storing hydraulic oil, 25b is a pump, 25c is a pump accumulator,
25d and 25e are main accumulator, 25f is filter, 25g
Is a relief valve, 25h is a check valve, 25i, 25j, 25
k and 25l are control valves, 25m and 25n are position sensors, and other symbols are the same as those described above.

The actuator 25 is connected to a controller (comprising a microcomputer and its peripheral circuits) 26 as control means, and information from various sensors (for example, a vehicle speed sensor and a steering angle sensor) 29 taken into the controller 26. , The angle of the casters can be varied according to the vehicle speed V, the steering angle θ, and the magnitude of the steering angular velocity.

In particular, the controller 26 has a caster angle setting section (caster angle setting means) for setting an optimum caster angle based on detection information from each sensor, and a caster angle set by the caster angle setting section. It has a controller for controlling the caster angle adjusting mechanism.

The caster angle setting unit first sets a reference caster angle, and when the vehicle is traveling straight, the reference caster angle is used as it is as a caster angle, but the steering angle is increased based on information from the steering angle sensor. In some cases, a small caster correction is applied to the reference caster angle to set a smaller caster angle (small caster angle) than the reference caster angle, and a large caster correction is applied to the reference caster angle when the steering angle is in the return state. The caster angle is set to be larger than the reference caster angle (large caster angle). Further, among the controls by the control unit, the control performed at the time of small caster correction is called caster small control, and the control performed at the time of large caster correction is called caster large control.

The reference caster angle is used as it is during straight running or turning at a constant steering angle. The value C of the reference caster angle is: C = C ₀ + ΔC (1) where C ₀ = caster assist Set value ΔC = correction auxiliary set value Further, the correction auxiliary set value ΔC in this case can be set as ΔC = 0.

Of these, as for the caster auxiliary set value C ₀ , as shown in FIG. 2, the auxiliary set value C ₀ is set to a larger value as the vehicle speed V increases, corresponding to the vehicle speed V.

At the time of small caster correction (during small caster control),
The above-described correction auxiliary set value ΔC is as follows: ΔC = −KV ₁ · Kθ ₁ · C ′ (2) At the time of large caster correction (during large caster control), ΔC = KV ₂ · Kθ ₂ · C ′ ... (3)

However, KV ₁ , KV ₂ = vehicle speed correction coefficient Kθ ₁ , Kθ ₂ = steering angular velocity correction coefficient C ′ = correction auxiliary constant This correction auxiliary constant C ′ is an appropriately small constant value.

Note that the vehicle speed correction coefficients KV ₁ and KV ₂ are coefficients that decrease as the vehicle speed V increases, as shown in FIG. 3, and the steering angular velocity correction coefficients Kθ ₁ , Kθ ₂ become large as shown in FIG. Is a coefficient that increases as the value || In FIGS. 3 and 4, KV corresponds to KV ₁ and KV ₂ , and Kθ is Kθ ₁ and KV
corresponds to θ _2.

In this manner, when the small caster angle correction at the time the steering wheel widening, is it coefficient to reduce the vehicle speed correction coefficient KV ₁ as the vehicle speed V increases, in order to lightly perform so the handle operation during turning-increasing At low speeds, the steering wheel is generally heavy, so the correction amount (in this case, the correction amount on the caster decreasing side) is increased to relatively reduce the caster angle so that the steering wheel becomes light enough. On the other hand, at high speeds, the steering wheel is generally light, so that the correction amount is small and the caster angle is not reduced so much that the steering wheel does not become too light.

Also, when the large caster angle is corrected at the time of turning back the steering wheel, the vehicle speed correction coefficient KV _{2 is set} to a coefficient that decreases as the vehicle speed V increases. In general, the steering wheel is heavy at low speeds, so the amount of correction (in this case, the amount of correction toward the caster increase side) is increased so that the wheels quickly return to the neutral position. Sometimes the steering wheel is generally light, so if the correction amount is the same as at low speeds, the wheels will return to the straight side too lightly and the steering feeling will be impaired, and in order to prevent this, the control amount of increasing the caster at higher speeds will be reduced. It is made smaller.

Furthermore, the reason that the steering angular velocity correction coefficients Kθ ₁ and Kθ ₂ are both set to increase as the magnitude of the steering angular velocity || increases, is that the driver demands sharper steering as the magnitude of the steering angular velocity increases. Therefore, the larger the steering angular speed, the larger the control amount, the smaller the caster angle when turning, the lighter the steering wheel to facilitate the turning start operation, and when turning further, return to the straight running side with a larger caster angle. They can do it quickly.

Since the caster angle control device for a vehicle according to one embodiment of the present invention is configured as described above, the caster angle control is performed as shown in FIG.

That is, first, the like immediately after the ignition switch is turned on the motor vehicle, the parameters relating to the control initially set (step S1), the vehicle speed V, the reads the steering angle θ and the lateral velocity G _Y from each sensor (step S2).

Then, in a succeeding step S3, a caster angle (reference caster angle) is set.

That is, the caster auxiliary set value C ₀ is set from the map (FIG. 2) in accordance with the vehicle speed V, and the correction auxiliary set value ΔC is set to Δ
Assuming that C = 0, the caster angle C (= C ₀ ) obtained by substituting these values into the above equation (1) is set as the reference caster angle.

In the next step S4, it is determined whether or not the handle is turned right. If the handle is turned right, the process proceeds to step S5. If the handle is not turned right, the process proceeds to step S8.

In step S8, it is determined whether or not the steering wheel is turned left.
Proceeding to S9, if the steering wheel is not turned left, it is determined that the vehicle is traveling straight, and the aforementioned reference caster angle C is set to the target caster angle.

The determinations in steps S4 and S8 can be made by determining whether the steering angle θ detected by the steering angle sensor is positive or negative (however, one of the left and right directions is positive).

In step S5 or step S9, it is determined whether or not the steering wheel is in the further turning state. This determination can be made based on whether the steering angular velocity is positive, that is, whether the steering angle θ is increasing with the neutral position as the reference (0), and if the steering angle θ is increasing, it can be said that the steering angle is increased.

If it is in the further turning state, the process proceeds to step S6, in which the caster is small-sized, that is, the caster angle is reduced.

Specifically, a vehicle speed correction coefficient KV ₁ and a steering angular velocity correction coefficient Kθ ₁ are determined from each map (see FIGS. 3 and 4) based on the vehicle velocity V and the steering angular velocity, and these coefficients KV ₁ and Kθ ₁ are determined. A correction auxiliary set value ΔC is calculated from the above-described equation (2) based on the above, and this correction auxiliary set value ΔC is substituted into the equation (1). In other words, this correction auxiliary set value is added to the reference caster angle C (= C ₀ ). The caster value C subjected to the small caster correction is set to the target caster angle by adding ΔC.

If it is determined in step S5 or S9 that the steering wheel is not in the further turning state, the process proceeds to step S7 or step S10, respectively, to determine whether the steering wheel is in the returning state. This determination can be made based on whether the steering angular velocity is negative, that is, whether the steering angle θ has decreased with the neutral position as the reference (0), and if it has decreased, it can be said that the steering wheel is in the return state.

In the case of the cutback state, the process proceeds to step S11, and the caster large control, that is, the control is performed so as to increase the caster angle.

Specifically, a vehicle speed correction coefficient KV ₁ and a steering angular velocity correction coefficient Kθ ₁ are determined from each map (see FIGS. 3 and 4) based on the vehicle velocity V and the steering angular velocity, and these coefficients KV ₁ and Kθ ₁ are determined. A correction auxiliary set value ΔC is calculated based on the above-described equation (3), and the correction auxiliary set value ΔC is substituted into the equation (1). In other words, this correction auxiliary set value is added to the reference caster angle C (= C ₀ ). The caster value C subjected to the large caster correction is set to the target caster angle by adding ΔC.

On the other hand, if it is determined in step S7 or step S10 that the steering wheel is not in the turning back state, that is, when the steering wheel is in a constant steering angle state in which the steering wheel is not turning back or turning back,
The aforementioned reference caster angle C is set to a target caster angle.

Then, the control unit of the controller 26 controls the operation of the actuator 25 of the caster angle adjusting mechanism 12 so as to obtain the caster angles set as described above.

As a result, when the steering wheel is turned further at the start of steering, the caster is controlled to be small, and the steering operation at the start of steering becomes lighter and can be easily performed. Also, when returning the vehicle from the turning state to the straight running state, that is, when turning back the steering wheel at the end of steering, the casters are largely controlled, and the large casters allow the vehicle to go straight without using a large force for steering operation. Will return quickly.

As described above, at the time of the turning operation, the caster control is appropriately performed appropriately from the start operation to the straight-line return operation.
The turning performance of the vehicle is improved, the turning operation is facilitated, and the driving at the time of turning can be performed with a margin.

In order to prevent a sudden change in the caster angle from affecting the steering and the like, a means for appropriately adjusting the speed at which the actual caster angle reaches the set caster angle may be added to the present apparatus. .

Furthermore, in this embodiment, in both the small caster correction and the large caster correction, the control amount is set to be large at low speeds and small at high speeds according to the vehicle speed. When the handle is slow and heavy,
The handle has become light enough to prevent the handle from becoming too light when the handle is light and at high speed.

In other words, when correcting small casters, reducing the casters makes turning easier and reducing the handle at the start of turning, but when correcting large casters, increasing the casters makes it easier to return to the straight running state. The steering wheel when returning straight ahead will be lighter. Therefore, in any case, the steering wheel becomes lighter as the correction amount (control amount) increases. Therefore, reducing the control amount at high speed prevents the steering wheel from becoming too light.

Thereby, the turning performance of the vehicle is further improved over a wide traveling state from a low speed to a high speed, and the steering operation during the turning is further facilitated.

The flowchart of FIG. 1 is intended showing an example of the operation, also, the characteristics of the coefficient of the second to fourth diagrams are merely examples thereof, for example, the characteristics of the steering angular velocity correction coefficient K [theta ₁ In place of FIG. 4, instead of FIG. 4, as shown in FIG. 8, the caster angular velocity is set to be positive, negative, or zero, that is, applicable to all cases where the steering angle is increased, returned, or fixed. , the vehicle speed correction coefficient KV ₁ is set to substantially the same characteristics as FIG. 3, the reference caster and small casters and large _{casters, C = C 0 -KV '·} Kθ' · C "...... (1) ' However , KV ′ = vehicle speed correction coefficient Kθ ′ = steering angular velocity correction coefficient C ″ = correction auxiliary constant. Regarding the control flow in this case, in the flowchart of FIG. 1, the contents of step S3 are set by calculating and setting the casters (reference casters, small casters, and large casters) by the above-described calculation. It can be omitted and only steps S1 to S3 can be performed.

Further, the application of the caster angle control device is not limited to the suspension and the caster angle adjusting mechanism (slide mechanism) 12 having the configuration as in the present embodiment, but may be applied to the caster angle external force correction as described above. For example, the responsiveness adjustment of the caster control is not limited to the caster control as in the present embodiment, and the responsiveness adjustment of the caster control can be applied only to the vehicle speed corresponding control and the steering angle corresponding control conventionally proposed. It is also applicable to caster control and the like, and has an effect of improving driving feeling.

[Effects of the Invention] As described in detail above, according to the vehicle caster angle control device of the present invention, in a vehicle suspension, a caster angle adjustment mechanism capable of adjusting a caster angle by driving a component of the suspension. Caster angle setting means for setting a reference caster angle according to the traveling state; and control means for controlling the caster angle adjusting mechanism so that the caster angle of the vehicle takes the caster angle set by the caster angle setting means. The caster angle setting means sets a caster angle smaller than the reference caster angle when the steering angle is increased based on the steering angle information, and sets the reference caster angle when the steering angle is returned. It is configured to set a larger caster angle, so that caster control is always performed appropriately from the start of steering to the end of steering. As a result, there is an advantage that the turning performance of the vehicle is improved, and especially the steering operation can be performed appropriately and lightly, so that the driving at the time of turning can be easily performed.

[Brief description of the drawings]

1 to 8 show a caster angle control device for a vehicle as an embodiment of the present invention. FIG. 1 is a flowchart showing the contents of the caster angle control, and FIGS. Graph showing the characteristics of the coefficient according to the setting of
5 is an exploded perspective view showing the caster angle adjusting mechanism, FIG. 6 is a perspective view showing a suspension provided with the caster angle adjusting mechanism, FIG. 7 is a hydraulic circuit configuration diagram of the actuator, and FIG. 9 is a graph showing another example of the coefficient characteristics related to the setting of the caster angle. 1 ... Strut, 1A ... Head of strut 1, 1a ...
Insulator part, 2 ... Shock absorber, 3 ...
... Coil spring, 4 ... Vehicle, 5 ... Knuckle, 6
… Hub, 7… Front wheel, 8… Lower arm, 9… Cross member, 10… Center member, 11… Disc brake, 12… Caster angle adjustment mechanism (slide mechanism),
13 ... slide plate, 13a ... opening, 14 ... slide base, 15 ... plate member, 16 ... through hole, 17 ... rail part, 17
a ... rail part, 18 ... plate member, 19 ... sliding wall part, 20 ...
... Needle roller bearing, 22 ... Fixed hole, 23 ... Mounting bolt, 24 ... Nut, 25 ... Actuator (drive unit), 25A ... Hydraulic supply / discharge system, 25B ... Hydraulic cylinder, 25a
…… Tank, 25b …… Pump, 25c …… Pump accumulator, 25d, 25e …… Main accumulator, 25f …… Filter, 25g …… Relief valve, 25h …… Check valve, 25i, 25j, 25k, 25l …… Control Valve, 25m, 25n
... Position sensors, 26 ... Controllers, 27 ... Drive shafts, 28 ... Stabilizers, 29 ... Various sensors (for example, vehicle speed sensors, steering angle sensors, and lateral acceleration sensors).

Continuation of the front page (72) Inventor Takao Morita 5-33-8 Shiba, Minato-ku, Tokyo Inside Mitsubishi Motors Corporation (56) References JP-A-1-197109 (JP, A) 67441 (JP, B2) JP-B 62-9449 (JP, B2)

Claims (1)

(57) [Claims] In a vehicle suspension, a caster angle adjusting mechanism capable of adjusting a caster angle by driving a component of the suspension, a caster angle setting means for setting a reference caster angle according to a traveling state, and a vehicle. Control means for controlling the caster angle adjusting mechanism so that the caster angle of the caster angle takes the caster angle set by the caster angle setting means, and the caster angle setting means cuts the steering angle based on the steering angle information. It is configured to set a caster angle smaller than the reference caster angle when in the increased state and to set a caster angle larger than the reference caster angle when the steering angle is in the turning back state. A caster angle control device for vehicles.