JP6166084B2 - Suspension device - Google Patents

Description

  The present invention relates to a suspension device for a rear wheel of an automobile, and more particularly to an apparatus capable of suppressing or canceling the influence of vertical force compliance steer generated at the beginning of turning.

A suspension device for a rear wheel of a vehicle such as an automobile has a hub bearing housing that supports the rear wheel so as to be rotatable with respect to the vehicle body via a suspension link (link) that is slidably attached to the vehicle body. It is supported so that it can be stroked.
As an example, such a rear-wheel suspension device is positioned in the camber direction of the rear wheel by a pair of upper and lower lateral links, and a pair of lower lateral links are arranged apart from each other in the front-rear direction, thereby Positioning is performed.
As an example of such a suspension device for a rear wheel, for example, Patent Document 1 discloses a front and rear lateral link (lower link) and a trailing link in which a hub bearing housing is slidably attached to a subframe attached to a lower floor of a vehicle body. What is positioned using is described.

One or both ends of each of these links are connected to a vehicle body or a hub bearing housing via a rubber bush for vibration isolation.
For example, when a lateral force is applied during turning of the vehicle, a lateral force compliance steer in which the rear wheels change toe-in or toe-out in the toe-in direction due to the difference in deformation amount of the rubber bushes of the front and rear lateral links occurs.
In general, when turning a vehicle, it is preferable that the turning outer wheel side tends to toe-in and the turning inner wheel side tends to toe-out.Therefore, when setting the rigidity of the rubber bush of the front and rear lateral links, the amount of displacement with respect to the lateral force is relative to the rear side. It is often set to be large on the front side.

  In addition, the geometrical arrangement (geometry) of each link constituting the suspension tends to toe-in on the turning outer ring side, that is, the bump side (contraction side), and toe-out tendency on the turning inner ring side, that is, the rebound side (extension side). In many cases, bump steer characteristics are given.

JP 2011-57021 A

However, as described above, in the case of a suspension that exhibits a lateral force compliance steer that is toe-in on the outer ring side and toe-out on the inner ring side due to the lateral force at the time of turning, the compliance steer (vertical force compliance) caused by the vertical force at the beginning of turning. Depending on the steering, there may be a tendency to toe out on the outer ring side and toe in on the inner ring side.
After that, when the lateral force increases and the suspension stroke starts and the lateral force compliance steer and bump steer occur, the outer ring side tends to toe in and the inner ring side tends to toe out. When the rear wheels are steered in the opposite phase, the steering stability is lowered.
In view of the above-described problems, an object of the present invention is to provide a rear wheel suspension device capable of suppressing or canceling the influence of vertical force compliance steer generated in the early stage of turning.

The present invention solves the above-described problems by the following means.
According to a first aspect of the present invention, there is provided a hub bearing housing that supports a rear wheel of a vehicle so as to be rotatable around an axle, and both ends of the hub bearing housing are slidably attached to a vehicle body and a hub bearing. A suspension link that supports the stroke, a suspension spring that generates a reaction force corresponding to a vertical displacement of the hub bearing housing with respect to the vehicle body, and a vertical speed of the hub bearing housing with respect to the vehicle body. A suspension device including a damper that generates a damping force, and having a vertical force compliance steering characteristic that steers the rear wheel on a toe-in side or a toe-out side by an increase in a vertical force acting on a tread surface of the rear wheel, The vertical force temporarily during the initial turning of the vehicle Toe change generating means for generating a toe change in a direction to cancel or suppress toe change caused by compliance steer characteristics, and the toe change generating means is provided in a part of the suspension link and changes a spring constant. Accordingly, the spring constant of the variable rigid bush capable of rotating the hub bearing housing in the toe-in direction or the toe-out direction is temporarily changed at the initial stage of turning , and the toe change generating means includes the suspension spring and the damper. The suspension device is characterized in that the generation of the toe change is terminated in response to the stroke of the valve being equal to or greater than a predetermined value .
According to this, the hub bearing housing is rotated so that the spring constant of the variable-rigidity bush provided on the suspension link is temporarily changed at the beginning of turning so that the toe-in direction is on the outer ring side and the toe-out direction is on the inner ring side. Accordingly, it is possible to prevent or suppress the outer wheel from being temporarily steered to the toe-out side and the inner ring from being steered to the toe-in side by the vertical force compliance steer, thereby improving the steering stability.

Further, when a sufficient toe change to the outer ring toe-in side and the inner ring toe-out side can be obtained by the bump steer or the lateral force compliance steer, an excessive toe change can be prevented and the steering stability can be further improved.

  As described above, according to the present invention, it is possible to provide a rear wheel suspension device capable of suppressing or canceling the influence of the vertical force compliance steer generated at the beginning of turning.

It is the perspective view which looked at Example 1 of the suspension device to which the present invention is applied from the front side. It is the perspective view which looked at the suspension apparatus of Example 1 from the back side. It is the figure which looked at the suspension apparatus of Example 1 from the front. It is the figure which looked at the suspension apparatus of Example 1 from back. It is the figure which looked at the suspension apparatus of Example 1 from upper direction. It is the figure which looked at the suspension apparatus of Example 1 from the downward direction. It is the figure which looked at the suspension apparatus of Example 1 from the side. 1 is a block diagram illustrating a configuration of a control system for a suspension device according to a first embodiment. 3 is a flowchart illustrating toe angle correction control of the suspension device according to the first embodiment. 3 is a graph schematically showing an example of transition of a rear wheel toe angle in the suspension device of the first embodiment.

  The present invention aims to provide a rear wheel suspension device capable of suppressing or canceling the influence of vertical force compliance steer generated at the beginning of turning, from immediately after the start of steering until the suspension stroke reaches a predetermined value or more. In the meantime, the problem was solved by changing the rigidity of the variable rigidity bush provided in each suspension link so that the hub bearing housing rotates in the toe-in direction on the turning outer ring side and the toe-out direction on the turning inner ring side.

Embodiment 1 of a suspension device to which the present invention is applied will be described below.
The suspension device of the embodiment is a double wishbone type suspension provided for the rear wheel of an automobile such as a four-wheel passenger car.
FIG. 1 is a perspective view of the suspension device according to the first embodiment as viewed from the front side.
FIG. 2 is a perspective view of the suspension device of the first embodiment when viewed from the rear side.
FIG. 3 is a front view of the suspension device according to the first embodiment.
FIG. 4 is a rear view of the suspension device according to the first embodiment.
FIG. 5 is a top view of the suspension device of the first embodiment.
FIG. 6 is a view of the suspension device of the first embodiment as viewed from below.
FIG. 7 is a side view of the suspension device according to the first embodiment.

  The suspension device 1 includes a subframe 10, a housing 20, a front lateral link 30, a rear lateral link 40, an upper link 50, a trailing link 60, a damper unit 70, a stabilizer device 80, and the like.

The sub-frame 10 is a structural member that serves as a base to which each link of the suspension device 1 is attached, and is attached to a lower floor of a vehicle body (not shown) via a sub-frame bush having anti-vibration rubber.
The sub frame 10 includes a front member 11, a rear member 12, a side member 13, and the like.
The front member 11 is a beam-like member that is provided at the front end of the sub-frame 10 and is disposed substantially along the vehicle width direction.
Both ends of the front member 11 are attached to the vehicle body via subframe bushes.
The rear member 12 is a beam-like member provided at the rear end portion of the subframe 10 and arranged substantially along the vehicle width direction.
Both end portions of the rear member 12 are attached to the vehicle body via subframe bushes.
The side member 13 is a beam-like member that connects a portion in the vicinity of the side end portion of the front member 11 and a portion in the vicinity of the side end portion of the rear member 12 substantially along the vehicle front-rear direction.
A pair of left and right side members 13 are provided apart from each other in the vehicle width direction.

The housing 20 is a member that houses a hub bearing that rotatably supports a hub to which wheels are attached.
The suspension device 1 supports the housing 20 with respect to the subframe 10 so as to allow a vertical stroke along a predetermined trajectory.

The front lateral link 30 and the rear lateral link 40 are provided between the lower part of the side member 13 and the lower part of the housing 20.
The front lateral link 30 and the rear lateral link 40 are disposed substantially along the vehicle width direction and separated from each other in the vehicle front-rear direction.
Both end portions of the front lateral link 30 and the rear lateral link 40 are swingably connected to the side member 13 and the housing 20 via rubber bushes for vibration isolation.

The upper link 50 is provided between the upper part of the side member 13 and the upper part of the housing 20.
The upper link 50 is disposed substantially along the vehicle width direction.
Both end portions of the upper link 50 are swingably connected to the side member 13 and the housing 20 via a rubber bush for vibration isolation and a ball joint, respectively.

The trailing link 60 is provided between the vicinity of the side end portion of the front member 11 and the lower portion of the housing 20.
The trailing link 60 is disposed substantially along the vehicle longitudinal direction.
Both ends of the trailing link 60 are swingably connected to the front member 11 and the housing 20 via rubber bushes for vibration isolation.

The damper unit 70 is a unit of a damper that generates a damping force corresponding to the expansion / contraction speed and a coil spring that generates a spring reaction force corresponding to the expansion / contraction amount.
The upper end portion of the damper unit 70 is attached to a vehicle body (not shown) via a top mount having a vibration proof rubber.
A lower end portion of the damper unit 70 is attached to the rear lateral link 40.

The stabilizer device 80 is an anti-roll device that generates a spring reaction force in a direction that reduces the left-right stroke difference when a stroke in the opposite direction (reverse phase) occurs on the left and right of the suspension device 1.
The stabilizer device 80 is connected to the left and right rear lateral links 40 via links at both ends of a stabilizer bar formed of spring steel and having an intermediate portion disposed substantially along the vehicle width direction.

In the suspension device 1 described above, the lateral force compliance steer characteristic that tends to toe-in on the turning outer wheel side and toe-out on the turning inner wheel side due to elastic deformation of the bushes of the front lateral link 30 and the rear lateral link 40 caused by the lateral force due to turning. The rigidity of each bush is set so that
Specifically, the lateral rigidity of the rubber bush of the front lateral link 30 is set lower than the lateral rigidity of the rubber bush of the rear lateral link 40.

Further, the suspension device 1 is steered to the toe-in side when the rear wheel strokes in the direction in which the rear wheel rises with respect to the vehicle body (bump side) due to the geometry of each link, and the rear wheel is When it strokes in the downward direction (rebound side), it has a bump steer characteristic that steers to the toe-out side.
Due to the above-described lateral force compliance steer characteristic and bump steer characteristic, the outer wheel is steered to the toe-in and the inner ring is steered to the toe-out side when the vehicle is in steady turning.

On the other hand, the front lateral link 30 and the rear lateral link 40 are subjected to a tensile load when the vehicle is traveling straight, due to the ground load on the rear wheels.
At the initial turning of the vehicle, a moment for rolling the vehicle body is generated, but there is a region where the stroke of the suspension does not start due to a stick of a damper or the like.
In such a region, the effects of lateral force compliance steer and bump steer are not substantially generated, but the ground load increases on the turning outer wheel side and the ground load decreases on the turning inner wheel side.
For this reason, the tensile load acting on the front lateral link 30 and the rear lateral link 40 increases on the turning outer ring side and decreases on the turning inner ring side.
Since the lateral stiffness of the rubber bushes of the front lateral link 30 and the rear lateral link 40 is lower on the front lateral link 30 side as described above, the displacement of the housing 20 due to such a change in tensile load is the rear side on the front side. Bigger than.
Therefore, a vertical force compliance steer characteristic occurs in which the turning outer wheel steers to the toe-out side and the turning inner wheel steers to the toe-in side.

As described above, at the beginning of turning, the influence of vertical force compliance steer appears strongly, but the influence of lateral force compliance steer and bump steer hardly appears, so the turning outer wheel is steered to the toe-out side and the turning inner wheel is steered to the toe-in side.
After that, when the damper unit 70 starts a stroke and a lateral force starts to act on the front lateral link 30 and the rear lateral link 40, the influence of the lateral force compliance steer and the bump steer becomes stronger, the turning outer wheel is on the toe-in side, and the turning inner ring is on Cut back to toe side.
As described above, when the rear wheels are steered in the opposite direction between the initial turning and the steady turning, there is a case where a bad influence is exerted on the steering stability of the vehicle.
Therefore, in the first embodiment, toe correction control is performed to generate a toe change in a direction that reduces or cancels the vertical force compliance steer at the beginning of turning.
This point will be described below.

The suspension device of the first embodiment changes (increases or decreases) the spring constant among the bushes provided at the ends of the front lateral link 30, the rear lateral link 40, the upper link 50, and the trailing link 60. A part of bushes (toe-in side specific bushes) capable of rotating the housing 20 to the toe-in side and a part of bushes (toe-out side specific bushes) that can be rotated to the toe-out side are variable rigidity bushes, By changing the spring constant, the influence of vertical force compliance steer is reduced.
Such a change in the spring constant of the bush can be realized, for example, by using a liquid seal bush or the like in which an MR fluid whose viscoelastic characteristics are changed by applying a magnetic field.

FIG. 8 is a block diagram illustrating a configuration of a control system for the suspension device according to the first embodiment.
The suspension control system 100 includes an electric power steering (EPS) control unit 110, a behavior control unit 120, a bush stiffness control unit 130, a toe correction control unit 140, and the like.
These can communicate with each other via a CAN communication system 150 which is a kind of in-vehicle LAN, for example.

The EPS control unit 110 controls an electric power steering device that generates a steering assist torque in accordance with an input torque from a driver.
A steering angle sensor 111 and a torque sensor 112 are connected to the EPS control unit 110.
The rudder angle sensor 111 detects the current steering angle (steering wheel angle) of the steering system.
The torque sensor 112 detects input torque input from the driver to the steering system.

The behavior control unit 120 generates a moment in a direction to suppress the behavior by generating a braking force difference between the left and right wheels when a behavior such as oversteer or understeer occurs in the vehicle.
The behavior control unit 120 controls a hydraulic control unit (HCU) 123 that can individually control the brake hydraulic pressure supplied to the LH brake 121 and the RH brake 122.
The behavior control unit 120 is connected to a vehicle speed sensor 124 that outputs a pulse signal corresponding to the rotational speed of the wheel, and can acquire the vehicle speed.

  The bush rigidity control unit 130 controls the spring constants of the toe-in specific bush and the toe-out specific bush described above.

The toe correction control unit 140 performs toe correction control that temporarily generates a toe change in a direction that suppresses or cancels the above-described vertical force compliance steer when the turning start is detected based on information from the EPS control unit 110 or the like. Is what you do.
A stroke sensor 141 and a top mount load sensor 142 are connected to the toe correction control unit 140.
The stroke sensor 141 detects the strokes of the dampers of the left and right damper units 70, respectively.
The top mount load sensor 142 detects the vertical load acting on the top mounts provided at the upper ends of the left and right damper units 70, respectively.

FIG. 9 is a flowchart illustrating toe angle correction control of the suspension device according to the first embodiment.
Hereinafter, the steps will be described step by step.

<Step S01: Handle angle θs acquisition>
The toe correction control unit 140 acquires the handle angle θs from the EPS control unit 110.
Thereafter, the process proceeds to step S02.

<Step S02: Steering speed θs'calculation>
The toe correction control unit 140 calculates the steering speed θs ′ by differentiating the steering wheel angle θs acquired in step S01 with respect to time.
Thereafter, the process proceeds to step S03.

<Step S03: Vehicle speed determination>
The toe correction control unit 140 acquires the vehicle speed V from the behavior control unit 120.
If the current vehicle speed V is equal to or lower than the preset upper limit vehicle speed Vmax and equal to or higher than the lower limit speed Vmin, it is determined that the toe correction control is to be executed, and the process proceeds to step S04.
In other cases, it is determined that the toe correction control should not be executed, and the series of processing ends (returns).

<Step S04: Steering start judgment flag judgment>
If the flag value of the steering start determination flag is 0, the toe correction control unit 140 proceeds to step S05 in order to determine whether or not steering has started.
If the value of the steering start determination flag is 1, it is assumed that steering has already started, and the process proceeds to step S09.

<Step S05: Disturbance judgment>
When the product of the steering wheel angle θs acquired in step S01 and the driver input torque Ts acquired from the EPS control unit 110 is equal to or greater than a predetermined threshold, the toe correction control unit 140 performs an intentional steering operation by the driver. As a result, the process proceeds to step S06.
In other cases, even if there is a change in the steering wheel angle θs or the like, it is determined that it is due to a disturbance, and a series of processing ends (returns).

<Step S06: Steering Speed Absolute Value Determination>
The toe correction control unit 140 compares the absolute value of the steering speed θs ′ calculated in step S02 with a preset threshold value.
When the absolute value of the steering speed θs ′ is greater than or equal to the threshold value, the process proceeds to step S07, and in other cases, a series of processing ends (returns).

<Step S07: Judgment of increase / return of cut>
When the product of the steering wheel angle θs acquired in step S01 and the steering speed θs ′ calculated in step S02 is positive (greater than 0), the toe correction control unit 140 increases the steering angle by driver operation. It is determined that the number is being rounded up, and the process proceeds to step S08.
On the other hand, in other cases, it is determined that the steering angle is being reduced, and the series of processing ends.

<Step S08: Set steering start flag>
The toe correction control unit 140 changes the flag value of the steering start determination flag from 0 to 1, and sets the flag.
Thereafter, the process proceeds to step S09.

<Step S09: Bush rigidity correction control>
The toe correction control unit 140 issues a command to the bush rigidity control unit 130 to perform bush rigidity correction control.
The bush stiffness correction control changes the spring constant of the toe-in specific bush on the turning outer ring side and the toe-out specific bush on the turning inner ring side, and rotates the outer ring side housing 20 to the toe-in side and the inner ring side housing 20 to the toe-out side. It is something to move.
Then, it progresses to step S10.

<Step S10: Stroke Change Detection>
The toe correction control unit 140 detects the stroke of the left and right damper units 70 using the stroke sensor 141.
Then, it progresses to step S11.

<Step S11: Outer ring side stroke determination>
The toe correction control unit 140, when the stroke change amount from the straight traveling of the damper unit 70 on the turning outer wheel side is equal to or greater than a preset threshold value, is toe-in on the outer ring and on the inner ring depending on the lateral force compliance steer characteristic and bump steer characteristic. It is determined that the toe-to-toe change has sufficiently occurred, and the process proceeds to step S12.
In other cases, it is determined that it is necessary to continue toe correction control, and a series of processing ends (returns).

<Step S12: Steering start determination flag clear>
The toe correction control unit 140 clears the steering start determination flag as 0, and proceeds to step S13.

<Step S13: End of bush stiffness correction>
The toe correction control unit 140 ends the bush rigidity correction and ends a series of processes.

FIG. 10 is a graph schematically showing an example of the transition of the rear wheel toe angle in the suspension device of the first embodiment.
The vertical axis indicates the toe angle of the turning outer wheel, and the upper side indicates the toe-in side.
The horizontal axis indicates the time from the start of steering.
Further, the history when the bush stiffness correction control is not performed is indicated by a broken line, and the history when the bush stiffness correction control is performed is indicated by a solid line.
In addition, although the toe-in and toe-out are reversed on the turning inner wheel side, a substantially similar history is shown.

When bush stiffness correction control is not performed, the rear wheel toe angle first changes in the toe-out direction due to the vertical force compliance steer characteristic, and then when the suspension stroke changes or lateral force occurs, the bump steer characteristic and lateral force compliance steer characteristic Changes to the toe-in side.
In contrast, in the first embodiment, the housing 20 is rotated to the toe-in side on the turning outer wheel side and the toe-out side on the turning inner wheel side by the rigidity control of the link bush, thereby suppressing the influence of the vertical force compliance steer and controlling the steering. Can be improved.

(Modification)
The present invention is not limited to the embodiments described above, and various modifications and changes are possible, and these are also within the technical scope of the present invention.
(1) The configuration of the suspension device is not limited to the above-described embodiment, and can be changed as appropriate. For example, the type of the suspension device is not limited to the double wishbone type as in the embodiment, but may be other types such as a strut type, a multi-link type, and a trailing arm type. Further, the configuration of the control system is not particularly limited.
Further, the bush for changing the rigidity (spring constant) can be appropriately set according to the type and geometry of the suspension.
(2) In the embodiment, the toe correction control is ended based on the damper stroke, but the present invention is not limited to this, and the toe correction control may be ended by another method. For example, the control may be terminated when the top mount load of the damper changes by a predetermined value or more. Moreover, you may make it complete | finish control by predetermined time after the start of turning. Further, the method for gradually changing the control amount is not particularly limited.

DESCRIPTION OF SYMBOLS 1 Suspension apparatus 10 Sub frame 11 Front member 12 Rear member 13 Side member 20 Housing 30 Front lateral link 40 Rear lateral link 50 Upper link 60 Trailing link 70 Damper unit 80 Stabilizer apparatus 100 Suspension control system 110 Electric power steering (EPS) control unit 111 Steering angle sensor 112 Torque sensor 120 Behavior control unit 121 LH brake 122 RH brake 123 Hydraulic control unit 124 Vehicle speed sensor 130 Bush rigidity control unit 140 Toe correction control unit 141 Stroke sensor 142 Top mount load sensor 150 CAN communication system

Claims (1)

A hub bearing housing that rotatably supports the rear wheel of the vehicle around the axle;
Suspension links for supporting both ends of the hub bearing housing with respect to the vehicle body so that the both ends can be slidably mounted on the vehicle body and the hub bearing.
A suspension spring that generates a reaction force according to the amount of relative displacement in the vertical direction of the hub bearing housing with respect to the vehicle body;
A suspension device comprising: a damper that generates a damping force according to a vertical speed relative to the vehicle body of the hub bearing housing;
Having a vertical force compliance steer characteristic that steers the rear wheel on the toe-in side or toe-out side by increasing the vertical force acting on the tread of the rear wheel;
A toe change generating means for generating a toe change in a direction that cancels or suppresses the toe change caused by the vertical force compliance steer characteristic temporarily in an initial turning of the vehicle;
The toe change generating means is provided in a part of the suspension link, and a spring constant of a variable rigid bush capable of rotating the hub bearing housing in a toe-in direction or a toe-out direction by changing a spring constant. Change temporarily at the beginning of the turn ,
The toe change generating means ends the generation of the toe change in response to a stroke of the suspension spring and the damper becoming a predetermined value or more .

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