JP4581880B2 - Suspension device - Google Patents

Description

  The present invention relates to each of four fluid cylinders provided corresponding to front, rear, left, and right wheels of a vehicle, among a plurality of accumulators belonging to an accumulator group composed of a plurality of accumulators connected in parallel to each fluid cylinder. The present invention relates to a suspension device provided with a spring constant changing device that changes the spring constant of the accumulator group by changing the one in communication with the fluid cylinder.

Patent Document 1 describes an example of a suspension device including the above-described spring constant changing device. In this suspension device, the spring constant is increased when the vehicle is in a braking state or a driving state and is not traveling on a rough road.
JP-A-6-127249

  An object of the present invention is to alleviate inconveniences when a spring constant changing device is abnormal in a suspension device provided with a spring constant changing device.

Means and effects for solving the problem

  The suspension device according to claim 1 includes: (a) four fluid cylinders provided between a wheel holding device for holding a wheel and a vehicle body corresponding to each of the front, rear, left, and right wheels of the vehicle; b) a driving state detection device for detecting the driving state of the vehicle; (c) a steering state detection device for detecting an operation state of a steering member of the vehicle; and (d) each of the four fluid cylinders. A spring constant changing device that changes a spring constant of the accumulator group by changing one that is in communication with the fluid cylinder among a plurality of accumulators that belong to the accumulator group that includes a plurality of accumulators connected in parallel to the cylinder. And (e) a left side that switches between a state in which the fluid cylinder on the left wheel and the fluid cylinder on the right wheel are in communication with and a state in which the fluid cylinder on the right wheel is disconnected on each of the front wheel side and the rear wheel side of the vehicle. When the travel condition detecting device detects that the vehicle is in a braking state or a driving state, the spring constant changing device includes at least a front wheel side and a rear wheel side of the vehicle. Including a spring constant increasing portion for increasing a spring constant of each of the accumulator groups connected to each of the fluid cylinders of the left wheel and the right wheel belonging to the side on which the load increases due to the traveling state of the vehicle, The left and right communication device is detected by the traveling state detection device that the vehicle is in a braking state or a driving state, and the steering member is in a steering state representing straight traveling by the steering state detection device. Is detected, the fluid in the left wheel on at least one of the front wheel side and the rear wheel side whose spring constant has been increased by the spring constant changing device. It is intended to include Linda and linear braking and driving at the right and left communicating portion for communicating a fluid cylinder of the right wheel.

In the braking state of the vehicle, the load on the rear wheel decreases and the load on the front wheel increases. Therefore, if the spring constant of the wheel is increased on the front wheel side, it is possible to suppress the posture change caused by braking. In the braking state, if the spring constants of the wheels are increased on both the front wheel side and the rear wheel side, it is possible to more effectively suppress the posture change.
In the driving state of the vehicle, the load on the front wheels decreases and the load on the rear wheels increases. Therefore, if the spring constant of the wheel is increased on the rear wheel side, it is possible to suppress the posture change caused by driving. If the spring constant of the wheel is increased on both the rear wheel side and the front wheel side, the effect of suppressing the posture change is increased.
Further, when the operation state of the steering member is a steering state representing straight traveling (hereinafter abbreviated as a straight steering state), the vehicle travels straight, and the hydraulic pressure of the fluid cylinders of the left and right wheels is equal to the load If they are the same, they should be the same height. In this case, even if the fluid cylinder of the left wheel and the fluid cylinder of the right wheel are communicated, the hydraulic fluid does not flow between the left and right fluid cylinders, and the spring constant is large in each of the left wheel and the right wheel. State is maintained.
On the other hand, if any one of the part for changing the spring constant of the left wheel of the spring constant changing device and the part for changing the spring constant of the right wheel is abnormal, either the left wheel or the right wheel In some cases, the spring constant of is increased and the other spring constant is not increased (it remains small). As a result, the spring constant of the right wheel and the spring constant of the left wheel are different, and the vehicle height of the left wheel and the vehicle height of the right wheel are different. Also, the amount of change in vehicle height, the rate of change, and the like differ between the left and right wheels.
In the suspension device, the suspension arm and the tie rod are moved along with the change in the relative position of the wheel with respect to the vehicle body (change in the vehicle height), but due to the change in the relative positional relationship between the suspension arm and the tie rod accompanying the change in the vehicle height, Wheel toe angle changes. This is referred to as roll steer. In a normal suspension device, the wheel tilts to the toe-out side when the distance between the wheel holding device and the vehicle body is small, and tilts to the toe-in side when the distance is large. When the vehicle height is the same between the left wheel and the right wheel, the toe angle is also the same, so the vehicle goes straight when it is in the straight-ahead steering state. On the other hand, if the vehicle height differs between the left wheel and the right wheel, the toe angle differs between the left wheel and the right wheel, and the vehicle is deflected even in a straight steering state. Therefore, if the fluid cylinder of the left wheel and the fluid cylinder of the right wheel are connected, the left and right spring constants are the same, and the hydraulic pressures are the same. As a result, the vehicle height difference is reduced, and the deflection of the vehicle can be suppressed.
In principle, the left wheel and the right wheel have the same spring constant. However, when the spring constant is increased by the spring constant changing device, if there is an abnormality, the left wheel and the right wheel The spring constant may not increase in either one. When the spring constant changing device is abnormal, a difference in spring constant occurs between the left and right wheels, resulting in a difference in vehicle height. Therefore, in the suspension device described in this section, the left and right fluid cylinders are communicated with each other on the side of the front wheel side and the rear wheel side on which the spring constant is increased by the spring constant changing device.
From the above, in the braking state and the straight steering state, the spring constants for the left wheel and the right wheel are increased on the front wheel side, and the fluid cylinder of the left wheel and the fluid cylinder of the right wheel on the front wheel side are increased. The spring constants for the left and right wheels on both the front wheel side and the rear wheel side (that is, for all the front, rear, left and right wheels) are increased, and both the front wheel side and the rear wheel side are connected. In some cases, the fluid cylinder of the left wheel and the fluid cylinder of the right wheel may be communicated with each other. Similarly, in the driving state, the spring constants of the left and right wheels are increased on the rear wheel side and the left and right fluid cylinders are communicated with each other, and all the wheels on both the rear wheel side and the front wheel side are connected. In some cases, the spring constant is increased, and the left and right fluid cylinders are communicated with each other on the rear wheel side and the front wheel side.

Patentable invention

  In the following, the invention that is claimed to be claimable in the present application (hereinafter referred to as “claimable invention”. The claimable invention is at least the “present invention” to the invention described in the claims. Some aspects of the present invention, including subordinate concept inventions of the present invention, superordinate concepts of the present invention, or inventions of different concepts) will be illustrated and described. As with the claims, each aspect is divided into sections, each section is numbered, and is described in a form that cites the numbers of other sections as necessary. This is merely for the purpose of facilitating understanding of the claimable invention, and is not intended to limit the set of components constituting the claimable invention to those described in the following sections. In other words, the claimable invention should be construed in consideration of the description accompanying each section, the description of the embodiments, etc., and as long as the interpretation is followed, another aspect is added to the form of each section. Moreover, the aspect which deleted the component from the aspect of each term can also be one aspect of the claimable invention.

(1) Four fluid cylinders provided between a vehicle body and a wheel holding device for holding wheels, corresponding to the front, rear, left and right wheels of the vehicle,
A traveling state detection device for detecting a traveling state of the vehicle;
A steering state detection device for detecting an operation state of the steering member of the vehicle;
For each of the four fluid cylinders, by changing one of the plurality of accumulators belonging to the accumulator group consisting of a plurality of accumulators connected in parallel to each fluid cylinder, the one in communication with the fluid cylinder A spring constant changing device for changing the spring constant of the group;
A left and right communication device that switches between a state in which a fluid cylinder on the left wheel and a fluid cylinder on the right wheel are in communication with each other and a state in which the fluid cylinder is disconnected on each of the front wheel side and the rear wheel side of the vehicle;
When the spring constant changing device detects that the vehicle is in a braking state or a driving state by the traveling state detection device, at least the vehicle of the front wheel side and the rear wheel side of the vehicle The left and right wheels belonging to the side on which the load increases due to the running state includes a spring constant increasing portion that increases the spring constant of each accumulator group connected to each of the fluid cylinders of the right wheel; When the traveling state detection device detects that the vehicle is in a braking state or a driving state, and the steering state detection device detects that the steering member is in a steering state representing straight traveling The flow rate of the fluid cylinder and the flow of the right wheel on the left wheel on at least one of the front wheel side and the rear wheel side whose spring constant has been increased by the spring constant changing device. Suspension device which comprises a linear braking and driving at the right and left communicating portion for communicating the cylinder (claim 1).
It is desirable that the traveling state detection device includes a braking / driving state detection unit that detects whether the vehicle is in a braking state or a driving state. The traveling state detection device can include a longitudinal acceleration sensor or can include at least one of a brake switch and an accelerator switch. The traveling state detection device may include a pitch posture detection unit that detects the pitch posture. In this case, the vehicle state detection device detects a tilt angle in the front-rear direction of the vehicle body, and detects the vehicle height on the front wheel side and the rear wheel side. The difference from the vehicle height can be detected.
The steering state detection device detects an operation state of the steering member, and may include, for example, a steering angle detection unit that detects a steering angle of a steering wheel as a steering member. When the absolute value of the steering angle is equal to or less than the set value (straight-ahead steering state), it can be considered that the steering state represents straight-ahead travel.
(2) The suspension device according to (1), wherein the suspension device includes an abnormality detection device that detects an abnormality of the spring constant changing device.
(3) The left and right communicating portions during straight braking / driving are connected to at least an accumulator group whose spring constant cannot be increased by the spring constant increasing portion when an abnormality of the spring constant changing device is detected by the abnormality detecting device. (2) The suspension device according to (2), further including an abnormal left and right communicating portion that communicates the fluid cylinder of the wheel and the fluid cylinder of the wheel on the opposite side to the left and right wheels.
In the suspension device described in this section, when the abnormality detection device identifies whether the abnormal portion of the spring constant changing device is a portion that changes the spring constant of the wheel at the front, rear, left, or right position At least, the fluid cylinder of the wheel to which the specified abnormal portion is connected is communicated with the fluid cylinder of the wheel on the opposite side to the wheel. Further, even if the position of the abnormal part is not specified by the abnormality detection device, it is a part for changing the spring constant of either the left or right front wheel or a part for changing the spring constant of either the left or right rear wheel. Is detected separately, the fluid cylinders of the left and right wheels are communicated at least on the side where the abnormal portion is detected.
On the other hand, when the abnormality is detected by the abnormality detection device but the abnormal part is not specified, the spring constant of the left and right wheels is increased on either the front wheel side or the rear wheel side. In the case (when the spring constant changing device is normal, the spring constant is actually increased, but when abnormal, the spring constant remains small), at least on one side thereof, The left and right fluid cylinders are communicated. This is because the vehicle is deflected because the spring constant is not increased although the spring constant is increased by the spring constant changing device. In addition, when the spring constants of all the wheels on the front wheel side and the rear wheel side are increased, if an abnormality is detected without identifying the abnormal part, both the front wheel side and the rear wheel side The fluid cylinders of the left and right wheels can be made to communicate with each other.
As described above, when the abnormality detecting device detects an abnormality of the spring constant changing device and the position of the abnormal portion is specified by the abnormality detecting device, at least the The fluid cylinder of the wheel to which the abnormal part is connected communicates with the fluid cylinder of the wheel on the opposite side, but even if the position of the abnormal part is not specified, the side that is determined according to the situation of the spring constant changing device in that case The left and right fluid cylinders communicate with each other.
(4) The spring constant changing device includes: (a) each of the fluid cylinders provided corresponding to the front, rear, left and right wheels, and between each fluid cylinder and one or more of the plurality of accumulators. And (b) switching the accumulator communication control valves to at least the open state and the closed state by controlling the current supplied to the solenoid, thereby bringing the accumulator communication control valves into communication with the fluid cylinder. The suspension apparatus according to any one of (1) to (3), further including a current control unit that changes a certain accumulator to change a spring constant.
In the suspension device described in this section, for one fluid cylinder, when the number of accumulator communication control valves in the closed state is large, the spring constant is larger than when the number is small. In this case, if one or more of the accumulator communication control valves is in the closed state but remains open, the spring constant for that wheel will not be increased. .
For example, when two accumulators are connected to one fluid cylinder and an accumulator communication control valve is provided between one of the accumulators and the fluid cylinder, 2 in the fluid cylinder when the accumulator communication control valve is open. Since two accumulators are connected, the spring constant is in a small state, and when the accumulator communication control valve is in a closed state, one accumulator is connected to the fluid cylinder, so that the spring constant is large. In this case, if the accumulator communication control valve does not switch to the closed state even though the supply current to the solenoid is controlled so that the accumulator communication control valve switches from the open state to the closed state, the accumulator communication control valve Even when a command for switching to a closed state is output, the spring constant for the wheel remains small, for example, when the current supplied to the solenoid is not controlled accordingly. These can be collectively referred to as an open fixing abnormality, but in this specification, an abnormality of the spring constant changing device means that the spring constant does not increase even though the spring constant is increased (spring The suspension device described in this section is an open fixing abnormality in a broad sense (in other words, an abnormality that cannot be closed).
(5) The spring constant changing device includes: (a) each of the fluid cylinders provided corresponding to the front, rear, left and right wheels, and between each fluid cylinder and a plurality of accumulators having different spring constants. An accumulator communication control valve provided; and (b) an accumulator in communication with the fluid cylinder by switching the accumulator communication control valve to at least an open state and a closed state by controlling a supply current to the solenoid. The suspension device according to any one of (1) to (4), further including a current control unit that changes the spring constant by changing the spring constant.
When a plurality of accumulators having different spring constants (different capacities) are connected to the fluid cylinder, the spring constant is changed by changing the accumulator communicated with the fluid cylinder. In this case, by controlling one or more accumulator communication control valves, the accumulator communicated with the fluid cylinder is changed, and the spring constant is changed. In the suspension device described in this section, there is an abnormality in which the accumulator communication control valve does not switch as commanded.
(6) The abnormality detection device (a) is provided corresponding to each of the front, rear, left, and right wheels, and detects a vehicle height that is a relative position between the wheel and a corresponding portion of the vehicle body. The vehicle height sensor and (b) the steering state detection device detects that the steering member is in a steering state representing straight traveling, and the spring constant increasing portion increases the spring constant. A vehicle height detected by the vehicle height sensor corresponding to the left wheel belonging to at least one of the front wheel side and the rear wheel side, and a vehicle height detected by the vehicle height sensor corresponding to the right wheel. When the absolute value of the difference is greater than or equal to a set value, it is detected that the part related to increasing the spring constant of either the left wheel or the right wheel of the spring constant changing device is abnormal. Left-right difference To (2) not including the output portion (5) Suspension apparatus according to any one of claims (claim 3).
If the absolute value of the difference in vehicle height between the left and right wheels is large when the vehicle is in a straight-ahead steering state, it can be considered that the spring constant is different between the left and right. A portion related to increasing the spring constant of either the left wheel or the right wheel can be considered abnormal. For example, in the suspension device described in (4) or (5), the part may be an accumulator communication control valve provided corresponding to the fluid cylinder of the wheel, or the accumulator communication control valve. In addition, it can be considered that the part of the current control unit that controls the current supplied to the solenoid of the accumulator communication control valve is applicable.
In addition, since the change amount and change speed of the vehicle height are different for the left and right wheels, the abnormality of the spring constant changing device can be detected based on the change amount and change speed of the vehicle height.
(7) The traveling state detection device includes a turning state detection unit that detects a turning state of the vehicle, and the abnormality detection device is in a steering state in which the steering member represents straight traveling by the steering state detection device. (2) to (2) or (2) or (2) includes a turning abnormality detection unit that detects that the spring constant changing device is abnormal when the traveling state detection device detects that the vehicle is in a turning state. The suspension device according to any one of items 6) (claim 4).
If the vehicle is in a straight-ahead steering state, the vehicle should go straight. On the other hand, it is considered that the vehicle turns due to the roll steer of the suspension device and the vehicle height differs between the left and right wheels. Therefore, when the vehicle is in a straight-ahead steering state and the vehicle is deflected, the spring constant changing device can be considered abnormal.
In this case, if the spring constant of the left and right wheels on either the front wheel side or the rear wheel side is increased by the spring constant changing device, either one of the spring constant changing devices is used. It can be assumed that the part related to increasing the spring constant of the left and right wheels on the left side is abnormal. On the other hand, when the spring constants of the left and right wheels are increased on both the front wheel side and the rear wheel side (that is, when the spring constants of all the wheels are increased), the front wheels It cannot be specified whether an abnormality has occurred in the portion where the spring constant on either the side or the rear wheel side is increased.
Therefore, when the abnormality is detected by the turning abnormality detection unit when the spring constant of the left and right wheels on either the front wheel side or the rear wheel side is increased by the spring constant changing device It can be considered that there is an abnormality in the part related to increasing the spring constant of either one of the left and right wheels on that side, and at least the left and right fluid cylinders are communicated with each other. When the spring constants for all wheels are increased by the changing device and the abnormality is detected by the turning abnormality detection unit, the left and right fluid cylinders are communicated on both the front wheel side and the rear wheel side. It can also be made.
According to both the turning abnormality detection unit and the left-right speed difference abnormality detection unit, even in the latter case, the abnormal part of the spring constant changing device is a part related to changing the spring constant on the front wheel side. It is possible to specify whether it is a part related to changing the spring constant on the rear wheel side.
(8) The suspension device includes a center cylinder that is connected to the four fluid cylinders and operates according to a hydraulic pressure relationship between the four fluid cylinders. Suspension device.
(9) The left and right communication devices connect (a) a fluid cylinder of a left wheel and a fluid cylinder of a right wheel on each of the front wheel side and the rear wheel side, bypassing the center cylinder, respectively. (B) a left and right communication valve provided in each of the liquid passages and switchable between a closed state and an open state by controlling a supply current to the solenoid; and (c) the steering state detection device. When the steering member is detected to be in a steering state representing a straight traveling, and the traveling state detection device detects that the vehicle is in a braking state or a driving state, the spring constant increasing portion causes a spring. The communication control valve is switched from the closed state to the open state by controlling the supply current to the solenoid of the left and right communication valves provided on at least one of the front wheel side and the rear wheel side where the constant is increased. And a current control unit (8) Suspension device according to claim (Claim 5).
In the closed state of the left and right communication valves, the center cylinder is operated by the hydraulic pressure of each fluid cylinder. In the open state of the left and right communication valves, the left and right fluid cylinders communicate with each other by bypassing the center cylinder, so that the center cylinder is not operated by the hydraulic pressure of the fluid cylinders communicated with each other by the left and right communication valves. As described above, the center cylinder is operated by the hydraulic pressure of the left and right fluid cylinders (hereinafter referred to as an effective state) by the open / close control of the left and right communication valves, or is not operated by the hydraulic pressure (hereinafter referred to as the effective state). , Referred to as an invalid state).
When the operation of the center cylinder is effective, a hydraulic pressure difference occurs between the left and right fluid cylinders due to the difference in spring constant between the left wheel and the right wheel on either the front wheel side or the rear wheel side. However, these differences are reduced by the operation of the center cylinder. However, the effect of the operation of the center cylinder affects the fluid cylinder on the other side of the front wheel side and the rear wheel side, and the vehicle height may change on the other side. On the other hand, if a difference in spring constant occurs, if the left and right communication valves are opened, the center cylinder is invalidated, and it is possible to avoid affecting the other side. it can.
(10) Four fluid cylinders provided between the vehicle wheel holding device and the vehicle body corresponding to the front, rear, left, and right wheels of the vehicle,
For each of the four fluid cylinders, by changing one of the plurality of accumulators belonging to the accumulator group consisting of a plurality of accumulators connected in parallel to each fluid cylinder, the one in communication with the fluid cylinder A spring constant changing device for changing the spring constant of the group;
An abnormality detecting device for detecting an abnormality of the spring constant changing device;
When the abnormality of the spring constant changing device is detected by the abnormality detecting device, the left and right fluid cylinders communicate with each other on at least one of the front wheel side and the rear wheel side of the vehicle. A suspension device including a communication device.
When the spring constant is increased on either the front wheel side or the rear wheel side, if an abnormality is detected in the spring constant changing device, at least the left and right fluid cylinders on that side are connected. It is done.
When the spring constant is increased on both the front wheel side and the rear wheel side, an abnormality of the spring constant changing device is detected, and when the abnormal part is specified, the abnormality part is related. When the left and right fluid cylinders are communicated with each other on the side, the left and right fluid cylinders may be communicated on both the opposite side and the side related to the abnormal portion.
The technical features described in any one of the items (1) to (9) can be employed in the suspension device described in this item.

A suspension device according to an embodiment of the present invention will be described below with reference to the drawings.
In this suspension apparatus, as shown in FIG. 1, suspensions as fluid cylinders are provided between the wheel holding devices 6FL, FR, RL, RR for holding the front, rear, left and right wheels 4FL, FR, RL, RR and the vehicle body 8, respectively. Cylinders 10FL, FR, RL, and RR are provided together with a suspension spring (not shown). The suspension cylinders 10FL, FR, RL, and RR are operated by hydraulic fluid as fluid. Hereinafter, when it is necessary to distinguish the suspension cylinder 10 or the like, it is used with symbols FL, FR, RL, and RR representing wheel positions, and when there is no need to distinguish between them, they are used without a symbol.
The suspension cylinders 10FL, FR, RL, and RR have the same structure, and each includes a housing 11, a piston 12 fitted inside the housing 11 so as to be relatively movable, and a piston rod 14. The rod 14 is connected to the wheel holding device 6 and the housing 11 is connected to the vehicle body 8 so as not to move relative to each other in the vertical direction. The piston 12 is provided with a communication path 20 that communicates the two liquid chambers 16 and 18 partitioned by the piston 12, and the communication path 20 is provided with a throttle. The throttle generates a damping force corresponding to the relative moving speed of the piston 12 with respect to the housing 11 (the flow rate of the working fluid flowing through the throttle). The suspension cylinder 10 functions as a shock absorber.
The housing 11 can be connected to the wheel holding device 6 and the piston rod 14 can be connected to the vehicle body.

Individual passages 22FL, FR, RL, and RR are connected to the liquid chambers 16 of the suspension cylinders 10FL, FR, RL, and RR, respectively.
In each of the individual passages 22FL, FR, RL, RR, the accumulators 24FL, FR, RL, RR and the accumulators 26FL, FR, RL, RR and the accumulators 26FL, FR, RL, RR are connected in parallel to each other corresponding to each of the suspension cylinders 10FL, FR, RL, RR. And are connected. Further, spring constant switching valves 28FL, FR, RL, and RR are provided between the suspension cylinders 10FL, FR, RL, and RR and the accumulators 26FL, FR, RL, and RR, respectively.

Each of these accumulators 24 and 26 has a function as a spring, and includes, for example, a housing and a partition member for partitioning the inside of the housing, and the individual passage 22 communicates with one volume change chamber of the partition member. And the other volume change chamber is provided with an elastic body, and the volume of the other volume change chamber decreases due to the increase in the volume of one volume change chamber, thereby generating an elastic force. Can be. The accumulators 24 and 26 may be bellows type, bladder type, piston type, or the like.
In this embodiment, the accumulator 24 has a larger spring constant than the accumulator 26. Hereinafter, the accumulator 24 is referred to as a high-pressure accumulator, and the accumulator 26 is referred to as a low-pressure accumulator. The spring constant switching valve 28 is a normally open electromagnetic on-off valve.

  The individual passages 22FL, FR, RL, and RR are provided with variable throttles 30FL, FR, RL, and RR, respectively. As described above, the hydraulic fluid flows in and out in the liquid chamber 16 by the vertical movement of the wheel holding device 6 relative to the vehicle body 8. In this case, the flow area of the individual passage 22 is controlled by the variable throttle 30. As a result, the damping force generated in the suspension cylinder 10 is controlled. In the present embodiment, a damping force adjusting mechanism is configured by the variable diaphragm 30 and the like.

  Each of the suspension cylinders 10FL, FR, RL, RR is connected to the center cylinder 48 via individual passages 22FL, FR, RL, RR. The center cylinder 48 includes a piston assembly 50 formed by connecting three pistons, and a cylinder housing 51 that accommodates the piston assembly 50 in a liquid-tight and slidable manner. The piston assembly 50 includes, in order from the right side in FIG. 1, a first piston 52, a second piston 53, and a third piston 54. The first piston 52 and the second piston 53, and the second piston 53 and the third piston 54. Are connected in series by connecting rods 56 and 58, respectively.

The cylinder housing 51 includes a stepped cylinder bore having a large-diameter portion and a small-diameter portion, and four liquid chambers are formed in the housing 51 by fitting the piston assembly 50 into the cylinder bore. . A second piston 53 is fitted to the large diameter portion of the cylinder bore, and a first piston 52 and a third piston 54 are fitted to the small diameter portion, respectively. Therefore, the diameters of the first piston 52 and the third piston 54 are smaller than the diameter of the second piston 53. The diameters of the first piston 52 and the third piston 54 are the same.
The opposite side of the first piston 52 from the second piston 53 is the first liquid chamber 60, the first piston 52 and the second piston 53 are between the second liquid chamber 61, and the second piston 53 and the third piston 54. Is the third liquid chamber 62, and the third piston 54 is the fourth liquid chamber 63 on the opposite side of the second piston 53. In the first piston 52, the first liquid chamber 60 side is an outer pressure receiving surface 65, and the second liquid chamber 61 side is an inner pressure receiving surface 66. In the second piston 53, the second liquid chamber 61 side is an inner pressure receiving surface 67, the third liquid chamber 62 side is an inner pressure receiving surface 68, and in the third piston 54, the third liquid chamber 62 side is an inner pressure receiving surface. A surface 69 is formed, and the fourth liquid chamber 63 side is an outer pressure receiving surface 70.

The fluid chamber 16 of the suspension cylinder 10FR of the right front wheel 4FR and the fluid chamber 16 of the suspension cylinder 10FL of the left front wheel 4FL are connected to the first fluid chamber 60 and the fourth fluid chamber 63 via individual passages 22FR and FL, respectively. The As a result, the outer pressure receiving surface 65 of the piston assembly 50 receives the fluid pressure in the fluid chamber 16 of the suspension cylinder 10FR of the right front wheel 4FR (hereinafter referred to as the fluid pressure of the suspension cylinder), and the outer pressure receiving surface 70 is the left front wheel 4FL. The hydraulic pressure of the suspension cylinder 10FL is received. In the present embodiment, the diameters of the first piston 52 and the third piston 54 are equal, and the pressure receiving areas of the outer pressure receiving surface 65 and the outer pressure receiving surface 70 are also equal.
A suspension cylinder 10RL of the left rear wheel 4RL is connected to the second liquid chamber 61 between the first piston 52 and the second piston 53 adjacent to each other by an individual passage 22RL, and the second piston 53 and the third piston A suspension cylinder 10RR for the right rear wheel 4RR is connected to the third fluid chamber 62 between the right rear wheel 4RR and the third fluid chamber 62.
On the other hand, the inner pressure receiving surface 66 of the first piston 52 and the inner pressure receiving surface 67 of the second piston 53, which are opposite to each other on both sides of the second liquid chamber 61, are hydraulic pressures of the suspension cylinder 10RL of the left rear wheel 4RL. Receive. However, the force applied to the first piston 52 having the smaller diameter of the two pistons is applied to the portion of the inner pressure receiving surface 67 of the second piston 53 having the larger diameter that has the same pressure receiving area as the inner pressure receiving surface 66 of the first piston 52. Offset by force. Therefore, the effective pressure receiving area with respect to the fluid pressure of the second fluid chamber 61 of the piston assembly 50 is a size obtained by subtracting the pressure receiving area of the inner pressure receiving surface 66 of the first piston 52 from the pressure receiving area of the inner pressure receiving surface 67 of the second piston 53. It becomes. Similarly, the effective pressure receiving area with respect to the hydraulic pressure of the third liquid chamber 62 of the piston assembly 50 is obtained by subtracting the pressure receiving area of the inner pressure receiving surface 69 of the third piston 54 from the pressure receiving area of the inner pressure receiving surface 68 of the second piston 53. It becomes size. That is, the force expressed by the product of the hydraulic pressure of the second liquid chamber 61 and the third liquid chamber 62 and the above-described effective pressure receiving area acts on the piston assembly 50, respectively.

As described above, since the diameter of the first piston 52 and the diameter of the third piston 54 are equal, the effective pressure receiving area for the second liquid chamber 61 and the effective pressure receiving area for the third liquid chamber 62 of the piston assembly 50 are also equal. . Furthermore, in this embodiment, the effective pressure receiving area for the second liquid chamber 61 and the third liquid chamber 62 of the piston assembly 50 is equal to the pressure receiving area for the first liquid chamber 60 and the fourth liquid chamber 63. The diameter of the second piston 53 is determined.
Therefore, in the piston assembly 50, the two pressure receiving surfaces 65 and 67 on the same side receive forces FFR and FRL corresponding to the hydraulic pressures of the suspension cylinders 10FR and 10RL of the right front wheel 4FR and the left rear wheel 4RL, respectively. The two pressure receiving surfaces 70 and 68 on the opposite side to the two pressure receiving surfaces 65 and 67 receive forces corresponding to the hydraulic pressures of the suspension cylinders 10FL and 10RR of the left front wheel 4FL and the right rear wheel 4RR, respectively.
In the center cylinder 48. Return springs 71 and 72 are provided between the outer pressure receiving surface 65 of the piston assembly 50 and the end surface of the housing 51, and between the outer pressure receiving surface 70 and the end surface of the housing 51, respectively.

The suspension device is provided with a vehicle height adjusting device 74. The vehicle height adjusting device 74 includes a high pressure source 76, a reservoir as the low pressure source 78, an individual control valve device 80, and the like.
The high-pressure source 76 includes a pump device 84 having a pump 81 and a pump motor 82, a pressure accumulator 86, and the like. The pump device 84, the pressure accumulator 86, and the like are provided in the control passage 88. The hydraulic fluid in the reservoir 78 is pumped up and discharged by the pump 81, and is stored in a pressurized state in the pressure accumulator 86. The accumulator 86 for pressure accumulation is connected to the control passage 88 via a pressure accumulation control valve 90 which is a normally closed electromagnetic on-off valve. A fluid pressure sensor 92 is provided in the control passage 88. According to the fluid pressure sensor 92, the discharge pressure and the accumulator pressure of the pump 81 can be detected.
A check valve 94 and a silencing accumulator 96 are provided on the discharge side of the pump 81 in the control passage 88. An outflow passage 104 that connects the high pressure side and the low pressure side of the pump 81 is provided, and an outflow control valve 106 is provided in the outflow passage 104.
The outflow control valve 106 is a mechanical on-off valve that uses the discharge pressure of the pump 81 as a pilot pressure. When the pump 81 is not in operation, it is in a communication state, but when the discharge pressure becomes high due to the operation of the pump 81, the communication state is cut off. The pump 81 is a gear pump.

The individual control valve device 80 includes individual control valves 110FL, FR, RL, RR provided in the individual control passages 108FL, FR, RL, RR. The individual control paths 108FL, FR, RL, and RR are paths that connect the control path 88 and the individual paths 22FL, FR, RL, and RR, respectively. The left and right communication valves 112 are provided in the front wheel side left and right communication passages 111 connecting the individual control passages 108FL and FR, and the left and right communication valves 114 are provided in the rear wheel side left and right communication passages 113 connecting the individual control passages 108RL and RR. . The suspension cylinder 10 and the control pressure passage 88 are connected to each other by the individual control passage 108 and the individual passage 22.
These individual control valves 110FL, FR, RL, RR, and left and right communication valves 112, 114 are normally closed electromagnetic on-off valves, and the individual control valves 110FL, FR, RL, RR are operated when the left and right communication valves 112, 114 are shut off. By individually controlling each wheel 4FL, FR, RL, RR, the wheel holding device 6FL, FR, RL, RR and the corresponding body part 8 (corresponding to the suspension cylinders 10FL, FR, RL, RR) The vehicle height, which is the distance between the vehicle and the vehicle, can be controlled independently.

  This suspension apparatus is controlled by a suspension ECU 200 mainly including a computer. The suspension ECU 200 includes an execution unit 204, a storage unit 206, an input / output unit 208, and the like. The input / output unit 208 includes a spring constant switching valve 28, a coil of the variable throttle 30, a vehicle height adjusting device 74 (a pressure accumulation control valve 90). , Individual control valve 110, coils of left and right communication valves 112, 114, pump motor 82, etc.) are connected via a drive circuit (not shown), fluid pressure sensor 92, provided for each of the front, rear, left and right wheels. Vehicle height sensor 220 for detecting vehicle travel state, travel state detection device 222 for detecting the travel state of the vehicle, vehicle height adjustment mode selection switch 224, vehicle height adjustment instruction switch 226, and steering angle of the steering wheel as a steering state detection device are detected. A steering angle sensor 227 and the like are connected to each other.

The traveling state detection device 222 detects the traveling state of the vehicle, and includes a brake switch 228 and a yaw rate sensor 230 that detect that the vehicle is in a braking state. A longitudinal acceleration sensor may be used instead of the brake switch 228, and a lateral acceleration sensor may be used instead of the yaw rate sensor. An accelerator switch can also be included.
The vehicle height adjustment mode selection switch 224 is operated by the driver, and the operation of the switch 224 selects either the automatic mode or the manual mode. When the automatic mode is selected, the vehicle height is changed accordingly when a predetermined condition is satisfied. When the manual mode is selected, the vehicle height adjustment instruction switch 226 is instructed. It can be changed accordingly.
The vehicle height adjustment instruction switch 226 is a switch that is operated when the vehicle height is increased, when the vehicle height is decreased, and the like, and is switched by a driver's manual operation.
The storage unit 206 stores a spring constant change program and the like represented by the flowchart of FIG.

The operation of the suspension device configured as described above will be described.
In the center cylinder 48, the piston assembly 50 has a force corresponding to the fluid pressure of the suspension cylinder 10 provided on each wheel (the force represented by the product of the fluid pressure and the corresponding pressure-receiving area of the pressure-receiving surface). ), And in principle, they are balanced in a stationary state.
When the vehicle body is pitched, for example, when the distance between the wheel holding device 6 and the vehicle body 8 decreases on the front side of the vehicle and increases on the rear side (for example, when braking), the left and right front wheels 4FL, 4FR suspension cylinders 10FL , 10FR is increased, and the hydraulic pressures of the suspension cylinders 10RL, 10RR of the left and right rear wheels 4RL, 4RR are decreased. Therefore, the hydraulic pressure acting on the outer pressure receiving surfaces 65 and 70 of the first piston 52 and the third piston 54 is increased, and the hydraulic pressure acting on the inner pressure receiving surfaces 67 and 68 of the second piston 52 is decreased. In this case, since the balance of the forces acting on the piston assembly 50 does not change, the movement of the piston assembly 50 is suppressed, and the suspension cylinders 10 are equal to being independent of each other. Force is generated and the pitching of the vehicle is effectively suppressed.
When rolling on the vehicle body, for example, when the distance between the wheel holding device 6 and the vehicle body 8 increases on the left side of the vehicle and decreases on the right side (for example, when turning left), the left front wheel 4FL, the left rear wheel 4RL The hydraulic pressures of the suspension cylinders 10FL and 10RL are reduced, and the hydraulic pressures of the suspension cylinders 10FR and 10RR of the right front wheel 4FR and the right rear wheel 4RR are increased. Accordingly, the hydraulic pressure acting on the outer pressure receiving surface 70 of the third piston 54 and the inner pressure receiving surface 67 of the second piston 53 is reduced, and the outer pressure receiving surface 65 of the first piston 52 and the inner pressure receiving surface 68 of the second piston 53 are reduced. The fluid pressure acting on the fluid increases. If the balance of the forces acting on the piston assembly 50 does not change even during rolling, the suspension cylinders 10 are almost independent from each other (extremely speaking, the state in which the center cylinder 48 is not present) Thus, a large damping force is generated in each of the suspension cylinders 10 with the movement of the piston 20, and the rolling is effectively suppressed.

  When an input is applied to one of the front, rear, left, and right wheels from the road surface, for example, a force is applied to reduce the distance between the wheel holding device 6 and the vehicle body 8 to the suspension cylinder 10FL provided on the left front wheel 4FL. (For example, when the left front wheel FL rides on the road bump) or a force that moves the wheels in the same position to the wheels on the diagonal position of the vehicle body 8, for example, the suspension cylinders 10FL, 10RR to the wheel holding device 6 and the vehicle body 8 When a force for reducing the interval is applied, the hydraulic pressures of the suspension cylinders 10FL and 10RR are increased, and the hydraulic pressures of the suspension cylinders 10FR and 10RL are decreased. Accordingly, the hydraulic pressure acting on the outer pressure receiving surface 70 of the third piston 54 and the inner pressure receiving surface 68 of the second piston 52 increases, and the inner pressure receiving surface 67 of the second piston 52 and the outer pressure receiving surface of the first piston 52 are increased. The hydraulic pressure acting on 65 is lowered. Thereby, the piston assembly 50 moves to the right in FIG. As a result, the volumes of the fourth liquid chamber 63 and the third liquid chamber 62 are increased, and the volumes of the second liquid chamber 61 and the first liquid chamber 60 are decreased. Accordingly, the hydraulic fluid flows out from the suspension cylinders 10FL and 10RR and flows into the suspension cylinders 10FR and 10RL, as if the two suspension cylinders 10FL and 10RR and the two suspension cylinders 10FR and 10RL communicate with each other via the center cylinder 48. Thus, the hydraulic fluid is exchanged between them.

The vehicle height corresponding to the four wheels 4FL, FR, RL, RR is controlled by the vehicle height adjusting device 74.
The left and right communication valves 112 and 114 and the individual control valve 110 are normally in the illustrated original positions. For example, for the left front wheel 4FL, when the vehicle height, which is the distance between the wheel holding device 6FL and the portion corresponding to the left front wheel 4FL of the vehicle body 8, is increased, the individual control valve 110FL is brought into a communication state and the pump 81 is activated. Since the outflow control valve 106 is shut off by the operation of the pump 81, the hydraulic fluid discharged from the pump 81 is supplied to the suspension cylinder 10FL, and the vehicle height increases. When the actual vehicle height reaches the target value, the individual control valve 110FL is shut off and the operation of the pump 81 is stopped.
When lowering the vehicle height, the individual control valve 110FL is in communication. Since the pump 81 is in a stopped state, the outflow control valve 106 is in a communication state. The working fluid is caused to flow from the suspension cylinder 10FL to the reservoir 78. When the actual vehicle height reaches the target value, the individual control valve 110FL is turned off.
Further, the left and right communication valves 112 and 114 are switched to a communication state during traveling on a rough road, for example. Accordingly, the flow of hydraulic fluid between the left and right suspension cylinders on each of the front wheel side and the rear wheel side is allowed, and vibration of the vehicle body caused by input from the road surface can be suppressed.

In each of the suspension cylinders 10, the damping characteristic is controlled by controlling the variable throttle 30.
When the flow area of the individual passage 22 is reduced by the variable throttle 30, the suspension hardness is hard (a state in which the damping force increases when the relative movement speed in the vertical direction between the wheel and the vehicle body is the same), When the flow path area is increased, it becomes soft (a state where the damping force is reduced when the relative movement speed is the same). The hardness of the suspension is switched in accordance with an operation by a driver of a mode selection switch (not shown), but may be controlled based on the running state of the vehicle.

Further, the spring constant is switched by the control of the spring constant switching valve 28.
When the spring constant switching valve 28 is in communication, the two accumulators 24 and 26 are communicated with the liquid chamber 16 so that the spring constant is small, and the spring constant switching valve 28 is shut off. In this case, since the low pressure accumulator 26 is shut off from the liquid chamber 16 and the high pressure accumulator 24 is communicated, the spring constant is increased.

In this embodiment, when the vehicle is in a braking state, the spring constants of the left and right front wheels 4FL, FR are increased by controlling the spring constant switching valves 28FL, FR to switch from the communication state to the cutoff state. In addition, when the absolute value of the detected value θ detected by the steering angle sensor 227 is equal to or less than the set value θ0, the left and right communication valves 112 are switched from the shut-off state to the communication state, whereby the left and right front wheels 4FL, FR suspension cylinders 10FL, FR communicates.
In the braking state, the load on the front wheel side increases and the load on the rear wheel side decreases, so that the posture change can be suppressed by increasing the spring constant on the front wheel side. In this case, if the spring constant on the rear wheel side is also increased, the change in pitch posture can be more effectively suppressed.

Even if a current is supplied to the solenoid so that the spring constant switching valves 28FL and FR are switched from the communication state to the cutoff state, any one of the spring constant switching valves does not switch to the cutoff state accordingly. Even if the suspension ECU 200 outputs a command to switch to the shut-off state, if no current is supplied to the solenoid of one of the spring constant switching valves, one of the spring constant switching valves 28 remains in a communicating state. The spring constant remains small. This abnormality is referred to as an open fixing abnormality in a broad sense, and is hereinafter referred to as an open fixing abnormality of the spring constant switching valve.
If an open sticking abnormality occurs in either one of the spring constant switching valves 28FL, FR, the spring constants are different between the left front wheel 4FL and the right front wheel 4FR. A difference in vehicle height occurs between the left front wheel 4FL and the right front wheel 4FR, and the vehicle is deflected even when the steering wheel is in the neutral position.
In the suspension device, the toe angle of the wheel 4 changes as the distance between the wheel holding device 6 and the vehicle body 8 changes due to roll steer. This is because the trajectory of the suspension arm and the trajectory of the tie rod differ according to the change in the vehicle height, so that the relative positional relationship between these changes. In this case, when the vehicle height is the same between the left wheel 4FL and the right wheel 4FR, the toe angle is also the same, so the vehicle will not be deflected, but if the vehicle height is different, the toe angle will be different. It deflects.
On the other hand, if the left and right communication valves 112 are in the communication state, the left and right spring constants can be made the same, and the difference in vehicle height between the left and right can be reduced. If the left and right communication valves 112 are in communication, the accumulator 26 corresponding to the spring constant switching valve 28 (abnormal spring constant switching valve) that remains in communication is made common to the left and right suspension cylinders 10FL and FR. The As a result, the spring constants for the left and right suspension cylinders 10FL, FR have the same magnitude, which is an intermediate magnitude between the large and small cases.
In the case where the spring constant switching valve 28 is abnormally stuck firmly, it is conceivable that both the spring constants of the left and right wheels are made the same by reducing them. On the other hand, as in the present embodiment, the left and right communication valves 112 are switched to the communication state, and are set to the same size when the spring constant is large and when the spring constant is small. Therefore, the spring constant can be increased as compared with the case where both spring constants are reduced, and the posture change can be more effectively suppressed.
It should be noted that the difference in the vehicle height caused by the difference in spring constant between the left wheel 4FL and the right wheel 4FR is reduced by the operation of the center cylinder 48, but it is not made the same. Therefore, even if the center cylinder 48 is provided, the toe angle between the left wheel 4FL and the right wheel 4FR is not the same, and the vehicle is deflected. The degree of vehicle deflection is suppressed by the center cylinder 48, but it is not eliminated.

In step 1 (hereinafter abbreviated as S1; the same applies to other steps) of the flowchart of the spring constant changing program, it is detected whether or not the brake switch 228 is in the ON state. That is, when the vehicle is in a braking state, a command for switching the left and right spring constant switching valves 28FL, FR on the front wheel side to the shut-off state is output in S2. In S3, it is determined whether or not the absolute value of the detected value θ by the steering angle sensor 227 is equal to or smaller than the set value θ0, that is, whether or not the driver intends to go straight ahead. When the absolute value of the steering angle θ is equal to or smaller than the set value θ0, a command for switching the left and right communication valves 112 to the communication state is output in S4. The set value θ0 is a steering angle when the driver is steering the steering wheel in order to move the vehicle straight, and is a value that can be considered that the steering wheel is substantially in the neutral position.
When the spring constant switching valves 28FL, FR, etc. are normal, the spring constant switching valves 28FL, FR are both switched to the cutoff state, and the spring constants for the left front wheel 4FL and the right front wheel 4FR are increased. In this case, the left and right suspension cylinders 10FL, FR are brought into communication with the left and right communication valves 112 being in a communicating state. However, as a general rule, during straight running, the hydraulic pressure of the left and right suspension cylinders 10FL, FR is Since it is the same, hydraulic fluid does not flow between the left and right suspension cylinders 10FL, FR. A large spring constant is maintained in both the left wheel 4FL and the right wheel 4FR.
Temporarily, either one of the spring constant switching valves 28FL, FR is in an open fixing abnormality, the spring constant is large on one side of the left front wheel 4FL or the right front wheel 4FR, and the spring constant is small on the other side. It may become. However, since the left and right suspension cylinders 10FL, FR are brought into communication with each other by the left and right communication valves 112, the difference between these spring constants is reduced and the difference in vehicle height is reduced. The difference in toe angle between the left front wheel 4FL and the right front wheel 4FR is reduced, and the vehicle can be prevented from turning.

  On the other hand, if the absolute value of the steering angle θ is larger than the set value θ0 in the braking state, the left and right communication valves 112 are kept in the shut-off state in S5. When the spring constant switching valves 28FL, FR, etc. are normal, the left and right front wheels 4FL, FR have a large spring constant, whereby the pitch posture associated with braking can be suppressed, and the roll accompanying the turning The posture can be suppressed. When braking is not being performed, the spring constant switching valves 28FL and FR are kept in communication and the left and right communication valves 112 are also kept in communication.

Thus, in the present embodiment, when the absolute value of the steering angle θ of the steering wheel is equal to or smaller than the set value θ0 and in a braking state, the spring constants of the left and right front wheels 4FL, FR are increased and the left and right The suspension cylinders 10FL and FR are communicated. Accordingly, the pitch posture associated with braking can be suppressed, and even if any one of the spring constant switching valves 28FL and FR is in an open fixing abnormality, the vehicle can be prevented from being deflected.
Further, as described above, the hydraulic pressure difference between the left and right suspension cylinders 10FL and FR is reduced by the operation of the center cylinder 48, and the vehicle height difference is reduced without the left and right communication valves 112 being in the communication state. The operation of the center cylinder 48 caused by the difference in spring constant between the wheels 4FL and FR causes an influence on the rear wheel side. For example, when the spring constant of the right front wheel 4FR is large and the spring constant of the left front wheel 4FL is small, the vehicle height of the left front wheel 4FL is lower than that of the right front wheel 4FR, but the load is the same. The amount of deformation of the suspension spring is larger than that of the right front wheel 4FR, and the hydraulic pressure of the suspension cylinder 10FL is lowered. Thereby, in the center cylinder 48, the hydraulic pressure in the hydraulic pressure chamber 63 becomes lower than the hydraulic pressure in the hydraulic pressure chamber 60, and the piston assembly 50 moves to the left in FIG. Thereby, the hydraulic fluid is supplied to the suspension cylinder 10RR of the right rear wheel 4RR, the vehicle height increases in the right rear wheel 4RR, and the hydraulic fluid flows out from the suspension cylinder 10RL of the left rear wheel 4RL. Vehicle height decreases. The vehicle body 8 is inclined with respect to the longitudinal axis so that the left side is downward. On the other hand, if the left and right communication valves 112 are in communication with each other on the front wheel side, the center cylinder 48 can be prevented from operating due to the difference in spring constant between the left and right front wheels 4FL and FR. The influence on the vehicle can be reduced, and the inclination of the vehicle body can be suppressed.
Further, according to the operation of the center cylinder 48, the difference between the hydraulic pressure of the suspension cylinder 10FL of the left front wheel 4FL and the hydraulic pressure of the suspension cylinder 10FR of the right front wheel 4FR can be reduced. Can not. On the other hand, if the left and right communication valves 112 are in communication, the hydraulic pressures of the suspension cylinders 10FL and FR of the left and right front wheels 4FL and FR can be made the same.

  As described above, in this embodiment, the spring constant changing valve 28 and the part for controlling the spring constant changing valve 28 of the suspension ECU 200 constitute the spring constant changing device, and the left and right communication valves 112 and the left and right communication valves of the suspension ECU 200 are configured. The left and right communication device is configured by the part that controls 112. Of the spring constant changing device, the spring constant switching valve 28 and the portion that stores S1 and S2 of the suspension ECU 200, the portion that executes the spring constant increasing portion, and the like, and the spring constant increasing portion is configured. A portion for storing S3 and 4 of the ECU, a portion for executing the ECU, and the like constitute a left-right communication portion during straight braking and driving. The part that stores S3 and S4 of the suspension ECU and the part that executes the suspension ECU are also current control units.

In the above embodiment, the spring constants of the left and right front wheels 4FL, FR are increased and the left and right suspension cylinders 10FL, FR are communicated with each other on the front wheel side when the vehicle is in a braking state and is in a straight-ahead steering state. However, in the braking state, the spring constants of all the wheels 4FL, FR, RL, RR are increased on both the front wheel side and the rear wheel side, and the left and right communication valves 112, 114 are By bringing both into communication, the left and right suspension cylinders 10FL, FR, 10RL, and RR can be communicated with each other on both the front wheel side and the rear wheel side.
If a longitudinal acceleration sensor is provided instead of the brake switch 228, it is possible to detect whether the vehicle is in a braking state or a driving state. In the driving state, the spring constants of the left and right rear wheels 4RL and RR are increased, and in the straight-ahead steering state, the left and right communication valves 114 are in the communication state, and in the driving state, The spring constants of all the wheels 4FL, FR, RL, and RR can be increased, and both the left and right communication valves 112 and 114 on the front wheel side and the rear wheel side can be brought into a communication state when the vehicle is in a straight-ahead steering state.

Furthermore, in the above-described embodiment, the left and right communication valves 112 are brought into the communication state without detecting whether one of the spring constant switching valves 28FL, FR is in an open fixing abnormality. When it is detected that one of the spring constant switching valves 28FL, FR is in an open fixing abnormality, the left and right communication valves 112 can be brought into a communication state. One example will be described with reference to the flowchart of FIG. In the present embodiment, it is assumed that the damping force control device including the variable diaphragm 30 and the like is known in advance.
In S21, it is determined whether or not the abnormality flag is set. When the abnormality flag is in the set state, the control of the spring constant switching valves 28FL and FR and the control of the left and right communication valves 112 are not performed (S22).
If the abnormality flag is in the reset state, it is determined in S23 whether or not the brake switch 228 is in the ON state. If it is in the ON state, the front wheel side spring constant switching valves 28FL, FR are determined in S24. A command for switching to the shut-off state is output, and in S25, it is determined whether or not the absolute value of the steering angle θ is equal to or less than the set value θ0. When the absolute value of the steering angle θ is equal to or smaller than the set value θ0, abnormality detection is performed in S26. In S27, it is determined whether or not the abnormality flag is in the set state. If the abnormality flag is abnormal, the left and right communication valves 112 are in communication in S28, and if not abnormal, the left and right communication are in S29. The valve 112 remains in the shut-off state. Even when the absolute value of the steering angle θ is larger than the set value θ0, the left and right communication valves 112 remain in the shut-off state.

In the present embodiment, the absolute value of the difference between the vehicle heights HFL and HFR between the left wheel 4FL and the right wheel 4FR although the command for switching the spring constant switching valves 28FL and FR to the shut-off state is output. When HFL-HFR | is larger than the set value H0, it is determined that the spring constant differs between the left and right wheels 4FL, FR, and an abnormality flag is set. The set value H0 is such that the spring constant is different, the toe angle is different between the left wheel 4FL and the right wheel 4FR, and the vehicle is considered to be deflected.
In S61 of the flowchart of FIG. 4, the vehicle heights HFL, FR are detected for each of the left and right front wheels 4FL, FR. In S62, whether or not the absolute value of the difference between these vehicle heights HFL, HFR is less than or equal to the set value H0. Determined. If the absolute value of the difference in vehicle height is less than or equal to the set value, it is normal, so the abnormality flag is reset in S63, and if it is greater than the set value, it is abnormal, so the abnormality flag is set in S64. Set.
Thus, the vehicle height difference between the left and right wheels 4FL, FR is detected on the side where the spring constant is increased. As described above, this is because the abnormality in this embodiment is an open fixing abnormality in a broad sense.
If it is abnormal, the determination in S21 is YES and S23 and the subsequent steps are not executed, and the control of the spring constant switching valve 28 and the left and right communication valves 112 is not performed.

  In this embodiment, the vehicle height sensor 220, the part that stores S26 of the suspension ECU 200, the part that executes S26, and the like execute the abnormality detecting device. The part is composed. The abnormality detection device is also a left-right difference dependency abnormality detection unit.

  In the above embodiment, an abnormality is detected based on the difference in vehicle height between the left and right wheels 4FL, FR. However, the change speeds dHFL / dt, dHFR / dt, the change amount ΔHFL, It is also possible to detect based on ΔHFR. If the absolute value | dHFL / dt−dHFR / dt | of the difference in vehicle height change speed is larger than the set value d0, the right and left wheels The spring constant is assumed to be different between 4FL and FR, and an abnormal flag is set.

Further, S21 and 22 of the spring constant changing program are not indispensable. Regardless of whether the abnormality flag is set, S23 and subsequent steps can be executed.
Furthermore, when the absolute value of the yaw rate γ is larger than the set value γ0, it can be determined that one of the spring constant switching valves 28FL and FR is in an open fixing abnormality. When the spring constant on the front wheel side is increased and the spring constant on the rear wheel side is not increased as in the present embodiment, it is considered that the abnormality in the spring constant changing device has occurred on the front wheel side. Because it can.
In S71 of FIG. 5, the detection value by the yaw rate sensor 230 is acquired, and in S72, it is determined whether or not the absolute value of the detection value by the yaw rate sensor 230 is larger than the set value. If the absolute value of the yaw rate γ is larger than the set value γ0, it is considered that the difference is caused by a large vehicle height difference between the left and right front wheels 4FL, FR. Therefore, the spring constant switching valves 28FL, FR of the left and right front wheels 4FL, FR One of these is considered abnormal.
In the present embodiment, a turning abnormality detecting unit is configured by a part that stores S71 and 72, a part that executes S71, 72, and the like.

Further, when the absolute value of the difference between the vehicle heights HFL, HFR of the left and right front wheels 4FL, FR is larger than the set value H0 and the absolute value of the yaw rate γ is larger than the set value γ0, the spring constant switching valves 28FL, FR It can also be assumed that one of them has an open fixing abnormality.
In S76 of FIG. 6, the vehicle heights HFL and HFR of the left and right front wheels 4FL and FR are acquired. In S77, the detection value γ by the yaw rate sensor 230 is detected. In S78, the absolute value of the vehicle height difference between the left and right wheels is set. It is determined whether or not the absolute value of the yaw rate γ is larger than the set value. If the determination is YES, an abnormality flag is set in S79, and if the determination is NO, the abnormality flag is reset in S80.
As described above, if the absolute value of the yaw rate γ is larger than the set value and the absolute value of the difference between the left and right vehicle heights is larger than the set value, the determination accuracy as abnormal is determined. Can be improved.

Furthermore, when the vehicle is in a braking state, if the spring constants of the left and right front wheels 4FL, FR and the left and right rear wheels 4RL, RR are increased, the open fixing is maintained even if the absolute value of the yaw rate γ is greater than the set value γ0. It cannot be specified whether the abnormal spring constant switching valve 28 belongs to the front wheel side or the rear wheel side. On the other hand, it is not always necessary to specify whether the abnormal spring constant switching valve 28 belongs to the front wheel side or the rear wheel side, and the absolute value of the steering angle θ is less than the set value θ0. In addition, when the absolute value of the yaw rate γ is larger than the set value γ0, both the left and right communication valves 112 and 114 on the front wheel side and the rear wheel side can be brought into a communication state. This is because in the straight-ahead steering state, the left and right suspension cylinders may communicate with each other. An example in that case is shown in FIG.
If it is detected in S82 that the brake switch 228 is in the ON state, a command to turn off the spring constant switching valves 28FL, FR, RL, RR is output for all wheels in S83. In S84, it is determined whether or not the absolute value of the steering angle θ is equal to or smaller than the set value θ0. If the absolute value of the yaw rate γ is equal to or smaller than the set value in S85 and 86, the absolute value of the yaw rate γ is equal to or smaller than the set value. It is determined whether or not there is a normal value, and if it is equal to or less than the set value, the left and right communication valves 112 and 114 on the front wheel side and the rear wheel side are kept in the shut-off state in S87. When the absolute value of the yaw rate γ is larger than the set value γ0, it is determined that the spring constant is different on the left and right on at least one of the front wheel side and the rear wheel side. In S88, the left and right communication valves 112 and 114 are in communication. State.

In addition, the vehicle height H of each of the front, rear, left and right wheels 4FL, FR, RL, RR is detected, and whether or not the absolute value of the difference between the left and right wheel heights is larger than the set value on each of the front wheel side and the rear wheel side. Can also be determined. In this way, it is possible to acquire whether there is an abnormality on either the front wheel side or the rear wheel side. An example is shown in FIG.
In S83, after a command to shut off all spring constant switching valves 28FL, FR, RL, RR is output, in S91, vehicle heights HFL, FR, RL are set for all wheels 4FL, FR, RL, RR. , RR are detected, and it is determined in S92 whether the absolute value of the difference in vehicle height between the left and right wheels 4FL, FR is equal to or less than a set value (| HFL−HFR | ≦ H0) on the front wheel side. In 94, it is determined whether or not the absolute value of the vehicle height difference between the left and right wheels 4RL and RR on the rear wheel side is equal to or less than a set value (| HRL−HRR | ≦ H0). Whether the front wheel side and the rear wheel side are abnormally stuck or not is determined.
If both the front wheel side and the rear wheel side are normal, in S95, the left and right communication valves 112 and 114 are both kept in a shut-off state. In contrast, if it is determined that the front wheel side is normal but one of the spring constant switching valves 28RL and 28RR is abnormally open and stuck on the rear wheel side, the left and right communication on the front wheel side is determined in S96. The valve 112 remains in the shut-off state, and the left and right communication valves 114 on the rear wheel side are in the communication state. Also, if the front wheel side is abnormally open and stuck, but the rear wheel side is normal, in S97, the left and right communication valves 112 are in a communication state and the left and right communication valves 114 remain in a shut-off state. Is done. Further, when there is an open sticking abnormality both on the front wheel side and on the rear wheel side, both the left and right communication valves 112 and 114 are in communication. If the abnormality flag is in the set state and the determination in S81 is YES, the brake switch 228 is OFF, and if the determination in S82 is YES, the absolute value of the steering angle is greater than the set value, and the determination in S84 is If YES, in S99, the spring constant switching valve 28 is kept in communication, and the left and right communication valves 112, 114 on the front wheel side and rear wheel side are kept in a shut-off state.
In this way, since the position of the open fixing abnormality of the spring constant switching valve is specified, the left and right communication valves can be controlled accordingly.

Furthermore, the center cylinder 48 is not essential. Even when the center cylinder 48 is not provided, the same effect can be obtained. Further, when the center cylinder 48 is not provided, the difference in vehicle height due to the difference in spring constant between the left and right wheels when the left and right communication valves are shut off becomes large. In other words, the effect of switching the left and right communication valves to the communication state is significant.
Furthermore, the left and right communication valves on the side where the open adhering abnormality is detected can be kept in a shut-off state, and the left and right communication valves on the non-abnormal side can be set in a communication state. The difference between the left and right sides is reduced by the operation of the center cylinder on the side where the open fixing is abnormal, and the influence on the operation of the center cylinder can be suppressed by setting the left and right communication valves to the communication state on the non-abnormal side.

  As described above, various aspects have been described. In addition, the present invention can be implemented in variously modified and improved aspects based on the knowledge of those skilled in the art.

1 is a diagram illustrating an entire suspension device according to an embodiment of the present invention. It is a flowchart showing the program etc. of a spring constant change memorize | stored in the memory | storage part of suspension ECU of the said suspension apparatus. It is a flowchart showing another program, such as another spring constant change memorize | stored in the memory | storage part of the said suspension ECU. It is a flowchart showing a part (abnormality detection) of programs, such as the said spring constant change. It is a flowchart showing another aspect of a part of the vehicle height adjustment program. It is a flowchart showing another aspect of a part of the vehicle height adjustment program. It is a flowchart showing another program, such as another spring constant change memorize | stored in the said memory | storage part. It is a flowchart showing another program, such as another spring constant change memorize | stored in the said memory | storage part.

Explanation of symbols

  10: suspension cylinders 24, 26: accumulator 28: spring constant switching valve 48: center cylinder 50: piston assembly 112, 114: left and right communication valve 200: suspension ECU

Claims (5)

Four fluid cylinders provided between the vehicle wheel holding device and the vehicle body corresponding to the front, rear, left and right wheels of the vehicle,
A traveling state detection device for detecting a traveling state of the vehicle;
A steering state detection device for detecting an operation state of the steering member of the vehicle;
For each of the four fluid cylinders, by changing one of the plurality of accumulators belonging to the accumulator group consisting of a plurality of accumulators connected in parallel to each fluid cylinder, the one in communication with the fluid cylinder A spring constant changing device for changing the spring constant of the group;
A left and right communication device that switches between a state in which a fluid cylinder on the left wheel and a fluid cylinder on the right wheel are in communication with each other and a state in which the fluid cylinder is disconnected on each of the front wheel side and the rear wheel side of the vehicle;
When the spring constant changing device detects that the vehicle is in a braking state or a driving state by the traveling state detection device, at least the vehicle of the front wheel side and the rear wheel side of the vehicle The left and right wheels belonging to the side on which the load increases due to the running state includes a spring constant increasing portion that increases the spring constant of each accumulator group connected to each of the fluid cylinders of the right wheel; When the traveling state detection device detects that the vehicle is in a braking state or a driving state, and the steering state detection device detects that the steering member is in a steering state representing straight traveling The flow rate of the fluid cylinder and the flow of the right wheel on the left wheel on at least one of the front wheel side and the rear wheel side whose spring constant has been increased by the spring constant changing device. Suspension device which comprises a linear braking and driving at the right and left communicating portion for communicating the cylinder.   The suspension device includes an abnormality detection device that detects an abnormality of the spring constant changing device, and when the straight braking / driving left and right communication portion detects an abnormality of the spring constant changing device by the abnormality detecting device, At least an abnormal-time left and right communication portion that connects a fluid cylinder of a wheel connected to an accumulator group that cannot increase a spring constant by the spring constant increasing portion and a fluid cylinder of a wheel on the opposite side to the left and right wheels. 2. The suspension device according to 1.   The abnormality detection device is (a) provided for each of the front, rear, left, and right wheels, and detects a vehicle height that is a relative position between the wheel and a corresponding portion of the vehicle body. And (b) the front wheel side where the steering state detecting device detects that the steering member is in a steering state representing straight traveling, and the spring constant is increased by the spring constant increasing portion; Absolute difference between the vehicle height detected by the vehicle height sensor corresponding to the left wheel belonging to at least one of the rear wheel side and the vehicle height detected by the vehicle height sensor corresponding to the right wheel When the value is equal to or greater than a set value, the left-right difference for detecting that the part related to increasing the spring constant of either the left wheel or the right wheel of the spring constant changing device is abnormal. Reliance abnormality detection The suspension system of claim 2 comprising and.   The traveling state detection device includes a turning state detection unit that detects a turning state of the vehicle, and the abnormality detection device detects that the steering member is in a steering state representing straight traveling by the steering state detection device. And a turning abnormality detecting unit that detects that the spring constant changing device is abnormal when the running state detecting device detects that the vehicle is in a turning state. Suspension device. The suspension device includes a center cylinder that is connected to the four fluid cylinders and operates according to a hydraulic pressure relationship between the four fluid cylinders, and the left and right communication devices are: (a) the front wheel side and the rear wheel side And a fluid passage connecting the fluid cylinder of the left wheel and the fluid cylinder of the right wheel, bypassing the center cylinder, respectively, and (b) provided in each of the fluid passages to the solenoid. A left and right communication valve that can be switched at least between a closed state and an open state by controlling the supply current; and (c) the steering state detection device detects that the steering member is in a steering state representing a straight traveling, and The spring constant is increased by the spring constant increasing portion when the running state detecting device detects that the vehicle is in a braking state or a driving state. A current control unit that switches the left and right communication valves from a closed state to an open state by controlling a supply current to a solenoid of the left and right communication valves provided on at least one of the front wheel side and the rear wheel side The suspension device according to claim 1, comprising:

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