JP4715380B2 - Suspension device - Google Patents

Description

  The present invention relates to a suspension apparatus including a fluid cylinder and an accumulator group including a plurality of accumulators connected to the fluid cylinder.

Patent Documents 1 to 3 describe switching of opening and closing of an electromagnetic on-off valve provided between a fluid cylinder and one accumulator. Among them, in the suspension device described in Patent Document 1, when the electromagnetic on-off valve is switched from the closed state to the open state, when the vehicle height becomes the same as the vehicle height when the electromagnetic on-off valve is in the closed state, Switch to open state.
JP-A 63-78806 JP-A-63-130419 JP 63-49512 A

  An object of the present invention is to suppress an unexpected vehicle height change accompanying a change in an accumulator in communication with a fluid cylinder.

The above-mentioned problem is that the suspension device according to claim 1 is (1) four fluid cylinders provided between a wheel holding device for holding wheels and a vehicle body corresponding to each of the front, rear, left and right wheels of the vehicle. And (2) in each of the four fluid cylinders, a low-pressure accumulator connected in parallel to each other and a high-pressure accumulator having a spring constant larger than that of the low-pressure accumulator,
In each of the four fluid cylinders, a spring constant switching valve provided between the low pressure accumulator and (3) controlling each of the spring constant switching valves and closing the spring constant switching valves. And an accumulator communication control device that shuts off each of the fluid cylinders from the low-pressure accumulator and communicates with the high-pressure accumulator, and (4) supplies or discharges fluid in each of the four fluid cylinders. A vehicle height adjustment device that adjusts the vehicle height corresponding to each of the wheels, and (5) a mass change acquisition device that acquires a mass change or a mass change possibility of the vehicle body and the load, when the accumulator connection control device, in the stop state of the (i) the vehicle, the vehicle height adjustment is performed by the vehicle height adjusting device, the field Means for closing the constant switching valve, and (ii) when the mass change acquisition device has acquired a mass change or a possibility of mass change in the stop state of the vehicle, (a) the vehicle height adjustment is Means for switching to an open state even if the spring constant switching valve is closed, and (b) prohibiting the switching of the spring constant switching valve to a closed state even when the vehicle height adjustment request is made. This is solved by including a mass change communication section provided with at least one of the means for performing the above.

In the suspension device, when a suspension spring is provided together with the fluid cylinder between the wheel holding device and the vehicle body, the mass of the vehicle body and the load is received by the four fluid cylinders and the suspension spring. The pressure of is determined by the accumulator in communication therewith. Therefore, when the mass of the vehicle body and the load changes and the load applied to the wheels changes, the pressure of the fluid cylinder and the elastic force of the suspension spring change. Although the mass of the vehicle body rarely changes, the mass of the load often changes. For example, a person or a baggage corresponds to the load.
When the mass of the load changes in a state where at least one accumulator belonging to the accumulator group is shut off from the fluid cylinder, a pressure difference is generated between the accumulator and the fluid cylinder in the at least one shut off state. Thereafter, when a predetermined condition is satisfied and the accumulator in the shut-off state is brought into communication, the vehicle height changes accordingly. This change in vehicle height is often unpredictable.

Therefore, in the suspension device described in this section, when the mass change or the possibility of mass change (hereinafter abbreviated as mass change) of the vehicle body and the load is acquired, the fluid cylinder and all the accumulators are The communication state is assumed.
For example, in the case where the fluid cylinder and at least one accumulator are in the shut-off state, the accumulator in the shut-off state is brought into the communication state when a mass change or the like is acquired. Although the vehicle height changes when the accumulator is brought into communication, it is predictable that the vehicle height changes due to a mass change or the like.
Further, when a change in mass or the like is acquired when the fluid cylinder is in communication with all the accumulators, at least one of the plurality of accumulators is prohibited from being shut off from the fluid cylinder. For example, the vehicle height adjustment may be performed in a state where one or more accumulators belonging to the accumulator group are shut off from the fluid cylinder. This is because when the sum of the capacities of the accumulators in communication with the fluid cylinder is small, the time required for vehicle height adjustment is shorter than when the sum is large. On the other hand, in the suspension device described in this section, when a mass change or the like is acquired, the fluid cylinder and all the accumulators are maintained in communication. Even if it is necessary to shut off the accumulator (for example, even if it is necessary to adjust the vehicle height in the above-described suspension device), the accumulator is not cut off from the fluid cylinder. In addition, a change in the vehicle height that occurs when the accumulator is switched from the shut-off state to the communication state can be avoided.
It should be noted that blocking of the accumulator from the fluid cylinder may be prohibited while a change in mass of the vehicle body and the load is acquired. This is because the accumulator may be disconnected from the fluid cylinder in a state where the mass is kept constant after the mass change is completed.
Furthermore, the mass change acquisition device can acquire a mass change or the like only when the vehicle is stopped. This is because there is almost no mass change or the like during traveling.
The accumulator communication control device (a) relates to each of the fluid cylinders provided corresponding to the front, rear, left and right wheels, and is provided between each fluid cylinder and one or more of the plurality of accumulators. The accumulator communication control valve, and (b) a current control unit that switches the accumulator communication control valve at least between an open state and a closed state by controlling a supply current to the solenoid.

3. The suspension device according to claim 2, wherein the mass change acquisition device is based on a relationship between a pressure of the fluid cylinder and a vehicle height which is a distance between the wheel holding device and the vehicle body. It is assumed that a pressure / vehicle height related mass change acquisition unit for acquiring the mass change of the vehicle is included.
During vehicle height adjustment, fluid is exchanged between a fluid cylinder (and accumulator) corresponding to the vehicle height adjustment target wheel and an external device (for example, a fluid supply / discharge device). And the relationship between the pressure of the accumulator) and the vehicle height changes. When the vehicle height is not being adjusted and the load applied to the wheel changes due to changes in the mass of the vehicle body or the load, fluid is exchanged between the fluid cylinder corresponding to the wheel and the external device. Therefore, the relationship between the pressure of the fluid cylinder and the vehicle height changes.
From these circumstances, the relationship between the pressure of the fluid cylinder and the vehicle height at the wheel where the load changes due to the mass change of the vehicle body and the load, and the relationship between the pressure of the fluid cylinder and the vehicle height at the vehicle height adjustment target wheel. It is normal to be different. By utilizing this fact, it is possible to acquire the presence / absence of a change in mass of the vehicle body and the load based on the relationship between the pressure of the fluid cylinder and the vehicle height.
The relationship between the pressure of the fluid cylinder and the vehicle height will be described in detail in the following [Example].
Furthermore, in the suspension device according to claim 3, the pressure / vehicle height relationship-dependent mass change acquisition unit is configured to increase the mass when the pressure of the fluid cylinder increases and the vehicle height decreases. The suspension device according to claim 4, further comprising means for acquiring that the mass has decreased when the pressure of the fluid cylinder decreases and the vehicle height increases. When the vehicle height adjustment is performed by the vehicle height adjustment device, the vehicle height-related mass change acquisition unit does not acquire the change in the mass for each of the four wheels.

A suspension device according to an embodiment of the present invention will be described below with reference to the drawings.
In the present suspension device, as shown in FIG. 1, suspensions as suspension 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.

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 that partitions the inside of the housing, and the individual passage 22 communicates with one volume change chamber of the partition member. 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 the 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, and the first piston 52 and the second piston 53, 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.
Accordingly, 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, the communication state is established. 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. When the left and right communication valves 112, 114 are shut off, the individual control valves 110FL, FR, RL, RR are operated. 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), and fluid pressure sensor 92 is provided for each of the front, rear, left and right wheels. A vehicle height sensor 220 for detecting the hydraulic pressure of the suspension cylinder 10, a hydraulic pressure sensor 221 for detecting the hydraulic pressure of the suspension cylinder 10 (the hydraulic pressure of the suspension cylinder 10 and the accumulator in communication with the suspension cylinder 10) A driving state detection device 222 for detecting the driving state of the vehicle, a vehicle height adjustment mode selection switch 224, a vehicle height adjustment instruction switch 226, and a boarding / alight prediction device 228 Stacking such prediction apparatus 230, alighting intended detection device 232, the start intention detection device 234 and the like are connected. The load applied to each wheel 4 is supported by the cylinder rod 14 of each suspension cylinder 10, and the fluid pressure in the fluid chamber 16 and the accumulators 24 and 26 has a magnitude corresponding to the load.

The traveling state detection device 222 detects the traveling state of the vehicle, and includes a vehicle speed sensor 236 that detects the traveling speed of the vehicle. The vehicle speed sensor 236 can detect whether or not the vehicle is stopped.
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 boarding / alighting prediction device 228 is a device that detects that a person may get on or off the vehicle, and includes a door courtesy lamp switch 240 that detects the open / closed state of the door 242 shown in FIG. The door courtesy lamp switch 240 is a switch whose state changes as each of the plurality of doors 242 is opened and closed. When the door 242 is opened, a courtesy lamp (not shown) is lit and turned on. When opening / closing of the door 242 is detected, a person may get on and off.
The loading prediction device 230 detects the possibility of loading or unloading a load on the vehicle, and attaches the load to the roof carrier 248 and the switch 246 that detects the open / closed state of the luggage compartment door (outer panel) 244. Or at least one of the switch 250 that detects that it has been removed. The switch 250 can detect, for example, the operating state of a fixture for fixing a load provided on the roof carrier 248. If the opening or closing of the luggage compartment door 244 is detected, it may be possible to load or unload the luggage into the trunk room, and the switch 250 detects that the fixture is in operation. In such a case, there is a possibility that the luggage may be fixed to or removed from the roof carrier 248.
Alighting intention detection device 232 detects the presence or absence of a passenger's intention to get off, and includes a shift position sensor 252, a parking brake switch 254, and the like. When the vehicle in the running state stops and then the shift position is switched from the drive position to the parking position, or when the parking brake is activated, it can be estimated that the passenger gets off.
The start intention detection device 234 detects a driver's start intention, and includes the above-described shift position sensor 252, the ignition switch 256, and the like. If the shift position is switched from the parking position to the drive position after a person gets on the vehicle in the stop state, or if the ignition switch 256 is switched from OFF to ON, it may be estimated that the vehicle has an intention to start. it can.
In addition, a portable device 262 is connected to the suspension ECU 200 via the communication device 260. Wireless communication is performed between the communication device 260 and the portable device 262.
The storage unit 206 stores a spring constant switching valve control 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 ridge) or the force that moves them in-phase with the wheels at the diagonal positions of the vehicle body 8, for example, the suspension cylinders 10FL and 10RR are moved 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 are communicated 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 in the illustrated positions when the vehicle height is not adjusted. 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.
In order to reduce the vehicle height, the individual control valve 110FL is in a communication state. 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.

The vehicle height adjustment is performed at a high speed (when the change speed of the vehicle height is large, which is referred to as a high speed vehicle height adjustment) and when it is performed at a low speed (when the change speed of the vehicle height is small) The vehicle height adjustment is performed at a high speed when a predetermined high-speed vehicle height adjustment request is satisfied in a state where the traveling speed of the vehicle is equal to or lower than a set speed that can be regarded as a stopped state. In this embodiment, (a) when the vehicle height adjustment instruction switch 230 is operated in the manual mode, (b) when a predetermined condition is satisfied in the automatic mode, (c) information from the portable device 262 It is assumed that the high-speed vehicle height adjustment request is satisfied, for example.
In the OFF state of the ignition switch, the vehicle height is normally set to the standard vehicle height in order to improve the appearance. On the other hand, since it is difficult for people to ride at the standard vehicle height, the vehicle height is lowered at high speed when the “information indicating an instruction to reduce the vehicle height” transmitted from the portable device 262 is received. The vehicle height may be lowered when the portable device 262 enters a predetermined communication area.
Further, in the automatic mode, when the intention to get off is detected, the vehicle height is reduced at high speed. While the vehicle is running, it is at a standard height, so it is reduced to a height that makes it easy for people to get off. Note that the vehicle height is reduced at a high speed even when a predetermined set time elapses after the traveling vehicle stops, even when the above-described conditions are not satisfied.
Furthermore, when the intention to start is detected, it is enlarged at high speed. The vehicle height, which is reduced when boarding, is increased to the standard height before traveling. Even when the vehicle height is reduced for boarding and the opening / closing of the door 254 is detected, the vehicle height is automatically increased even when the start intention is not detected before the set time elapses.
On the other hand, the vehicle height adjustment is performed at a low speed during traveling. This is because it is not desirable to adjust the vehicle height at high speed during traveling.

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.
The spring constant switching valve 28 is also cut off when high speed vehicle height adjustment is performed. This is because the hydraulic fluid is prevented from being exchanged with the accumulator 26, and accordingly, the time required to reach the target vehicle height can be shortened. The spring constant switching valve 28 may be in a shut-off state both when the vehicle height is reduced and increased at a high speed, or may be shut off when the vehicle height is reduced, and may remain in a communication state when the vehicle height is increased. .

In this embodiment, when it is detected that the mass of the load changes or the mass of the load may change in the shut-off state of the spring constant switching valve 28 (hereinafter, The spring constant switching valve 28 is switched to the communication state when the mass change or the like of the load is detected. When the mass of the load changes in the shut-off state of the spring constant switching valve 28, a hydraulic pressure difference is generated before and after the spring constant switching valve 28. Therefore, the spring constant switching valve 28 is in communication with a predetermined condition. When switched to a state, an unexpected change in vehicle height occurs. On the other hand, if a change in the mass of the load is detected, if the spring constant switching valve 28 is switched to the communication state, it is possible to avoid a hydraulic pressure difference before and after the spring constant switching valve 28.
Further, when a change in the mass of the load is detected in the communication state of the spring constant switching valve 28, the switching of the spring constant switching valve 28 to the cutoff state is prohibited. As a result, it is possible to avoid in advance that a hydraulic pressure difference occurs before and after the spring constant switching valve 28.

When it is detected that there is a possibility that a person gets on and off by the boarding / prediction prediction device 228 while the vehicle is stopped, or when it is detected that there is a possibility that the loading / unloading may be performed by the prediction device 230 such as loading Is collectively referred to as a case where there is a possibility of a change in the mass of the load, which includes persons, luggage, etc.) and the suspension cylinders 10FL, FR, RL, RR of all wheels 4 For each of these, the spring constant switching valve 28 is in communication. When the spring constant switching valve 28 is in the shut-off state, it is switched to the communication state, and when it is in the communication state, it is not switched to the shut-off state.
In the flowchart of FIG. 3, in step 1 (hereinafter abbreviated as S <b> 1. The same applies to other steps), it is determined whether or not the vehicle is in a stopped state based on the detected value by the vehicle speed sensor 236. .
In S2, as described above, it is determined whether or not there is a possibility of a change in the mass of the load.
If the determinations in steps S1 and S2 are both YES, it is determined in S3 whether or not the spring constant switching valve 28 is in the shut-off state. In many cases, the spring constant switching valve 28 is in the communication state in the stopped state, but as described above, the spring constant switching valve 28 is cut off when the vehicle height adjustment is performed at high speed, and a predetermined condition is satisfied. In the case of failure, the communication state is restored. Therefore, the spring constant switching valve 28 is in the shut-off state during the high-speed vehicle height adjustment until a predetermined condition is satisfied.
In the shut-off state of the spring constant switching valve 28, the spring constant switching valve 28 is switched to the communication state in S4. When the spring constant switching valve 28 is switched from the shut-off state to the communication state, the vehicle height changes. This vehicle height change is caused by a mass change and is a predicted change.
When the spring constant switching valve 28 is in the communication state, the determination in S3 is NO, and a switching prohibition flag is set in S5. If there is no possibility of a change in the mass of the load, the switch prohibition flag is reset in S6.
As described above, in this embodiment, the switching prohibition flag is kept in the set state while it is detected that there is a possibility of a change in the mass of the load, specifically, while the door 242 is open. Be drunk. In other words, when there is no possibility that the mass of the load changes (for example, after the mass change is completed), the accumulator 26 may be switched from the suspension cylinder 10 to the shut-off state. The prohibit flag is reset.

On the other hand, in the vehicle height adjustment program shown in the flowchart of FIG. 4, it is determined in S31 whether or not the high-speed vehicle height adjustment requirement is satisfied, and in S32, it is determined whether or not the switching prohibition flag is set. Is done. When the switching prohibition flag is in the reset state, the high-speed vehicle height adjustment is performed in S33 and 34. The vehicle height control such as the spring constant switching valve 28 is switched to the shut-off state and the individual control valve 110 is opened is performed so that the actual vehicle height approaches the target vehicle height. On the other hand, when the switching prohibition flag is in the set state, the vehicle height adjustment is performed in S35 and 36 without the spring constant switching valve 28 being switched to the cutoff state. As a result, the vehicle height adjustment is performed at the same speed as the low-speed vehicle height adjustment.
In the present embodiment, the mass change communication unit is configured by the storage ECU 200 that stores S4 of the flowchart of FIG. 3 and S35 of the flowchart of FIG. The apparatus 230 or the like constitutes a mass change acquisition device.

  In the above embodiment, (a) when the possibility of a change in the mass of the load is detected in the shut-off state of the spring constant switching valve 28, the spring constant switching valve 28 is switched to the communication state; (b) In the communication state of the spring constant switching valve 28, while there is a possibility of a change in the mass of the load, both the switching of the spring constant switching valve 28 to the cutoff state is prohibited. However, either one may be executed and the other may not be executed.

In the above embodiment, the possibility of the mass change of the load is detected. However, the mass of the load actually changes based on the relationship between the hydraulic pressure of the suspension cylinder 10 and the vehicle height. It is also possible to detect whether or not (whether or not it is changing).
In principle, the relationship between the hydraulic pressure of the suspension cylinder 10 and the vehicle height differs between when the mass of the load changes and when the vehicle height adjustment is performed. When the mass of the load changes, the relationship shown in FIG. 5 (hereinafter referred to as a relationship during mass change) is established, and when vehicle height adjustment is performed, the relationship shown in FIG. 6 (relation during vehicle height adjustment). Is established.
In principle, when the hydraulic fluid is not exchanged in the closed space, that is, between the suspension cylinder 10 and the outside (vehicle height adjusting device 74), the mass of the load increases and the load on the wheel 4 is increased. As the wheel 4 increases, the vehicle height decreases and the hydraulic pressure of the suspension cylinder 10 (hereinafter sometimes simply referred to as hydraulic pressure) increases, the mass of the load decreases, and the load on the wheel 4 increases. When it becomes smaller, the hydraulic pressure decreases and the vehicle height increases.
During the vehicle height adjustment, the hydraulic fluid is exchanged between the suspension cylinder 10 and the vehicle height adjustment device 74 for the vehicle height adjustment target wheel. Therefore, if the load applied to the wheels 4 is the same, when hydraulic fluid is supplied from the vehicle height adjusting device 74 to the suspension cylinder 10, the vehicle height increases and the fluid pressure in the suspension cylinder 10 increases, and the suspension cylinder 10. If hydraulic fluid is allowed to flow out of the vehicle, the vehicle height decreases and the hydraulic pressure decreases.
Further, as shown in FIG. 5, when the mass changes, the vehicle height and the system pressure (the hydraulic pressure detected by the hydraulic pressure sensor 221) change according to the nonlinear characteristic. This is because the spring constants in the accumulators 24 and 26 have nonlinear characteristics. As shown in FIG. 6, when the vehicle height adjustment is performed, the vehicle height and the system pressure change according to the linear characteristic. As described above, since the system pressure is determined by the relationship with the mass, it changes linearly as the vehicle height changes.
In the case where there is the center cylinder 48, since the hydraulic fluid is exchanged between the suspension cylinders 10, the situation is not always the same.

A case where the mass of the load changes will be described.
First, a case where there is no center cylinder 48 will be described.
For example, as shown in FIG. 7 (1), when the load applied to all four wheels increases due to an increase in the mass of the load, the vehicle height decreases for all four wheels, and the liquid in the suspension cylinder 10 is reduced. The pressure increases, and the vehicle height and the hydraulic pressure change according to the mass change relationship.
As shown in Fig. 7 (2), when the load applied to the front wheel (rear wheel) wheel increases due to the increase in the mass of the load, the vehicle height of the front wheel (rear wheel) wheel However, the vehicle height is increased and the hydraulic pressure is lowered for the rear wheel (front wheel side) wheel, and all the four wheels change according to the mass change relationship.
As shown in FIG. 7 (3), for example, when the load applied to the left front wheel 4FL increases due to an increase in the mass of the load, the vehicle height decreases and the hydraulic pressure increases for the left front wheel 4FL. It changes according to the relationship when the mass changes. Further, since the vehicle body 8 is a rigid body, the vehicle body 8 has (a) an inclination in which the left front wheel around the diagonal connecting the right front wheel and the left rear wheel is downward, and (b) the left side around the longitudinal axis is downward. (C) a posture determined by a combination of one or more of inclinations in a direction in which the front wheel side around the horizontal axis is downward.

In the case of (a), for the right rear wheel 4RR, the vehicle height increases and the hydraulic pressure decreases. For the right front wheel 4FR and the left rear wheel 4RL, the vehicle height decreases and the hydraulic pressure increases. Accordingly, the hydraulic pressure and the vehicle height change according to the mass change relationship for all four wheels.
In the case of (b), for the left rear wheel 4RL, the vehicle height decreases and the fluid pressure increases, and for the right front wheel 4FR and the right rear wheel 4RR, the vehicle height increases and the fluid pressure decreases. Any wheel 4 changes according to the mass change relationship.
In the case of (c), for the right front wheel 4FR, the vehicle height is reduced and the hydraulic pressure is increased, and for the left and right rear wheels 4RL and RR, the vehicle height is increased and the hydraulic pressure is reduced. 4 also changes according to the mass change relationship.
Similarly, when the posture is a combination of two or more of (a) to (c), the posture also changes according to the mass change relationship.

Next, a case where there is a center cylinder 48 will be described. As shown in Figs. 7 (1) and (2), when the load applied to all four wheels increases due to the increase in the mass of the load, the center load increases when the load on the front wheel side or rear wheel side increases. The situation is the same even with the cylinder 48. In the center cylinder 48, when the balance state does not change, the center cylinder 48 is not operated.
As shown in FIG. 7 (3), when the load applied to the left front wheel 4FL increases, the hydraulic pressure of the suspension cylinder 10FL of the left front wheel 4FL increases. Accordingly, when the balance in the piston assembly 50 is not satisfied, the piston assembly 50 moves to the right in FIG. 7 (3). The hydraulic fluid flows out from the suspension cylinder 10RR of the right rear wheel 4RR, and the hydraulic fluid flows into the suspension cylinders 10RL and FR of the left rear wheel 4RL and the right front wheel 4FR. However, since the vehicle body 8 is a rigid body, as in the case described above, one or more combinations of (a) tilt around a diagonal line, (b) tilt around a longitudinal axis, and (c) tilt around a lateral axis. The posture is determined by. However, the change in the posture of the vehicle body 8 is suppressed by the operation of the center cylinder 48.

In any of the cases (a) to (c), the vehicle height of the right rear wheel 4RR is increased, the hydraulic pressure is decreased, and changes according to the mass change relationship.
In the case of (a), for the right front wheel 4FR and the left rear wheel 4RL, hydraulic fluid is supplied to the suspension cylinders 10FR, RL, but when the vehicle height decreases, the hydraulic pressure increases and the mass changes. It changes according to the time relationship.
In the case of (b), for the left rear wheel 4RL, the vehicle height decreases and the hydraulic pressure increases. For the right front wheel 4FR, hydraulic fluid is supplied to the suspension cylinder 10FR, but the vehicle height increases. The hydraulic pressure is determined by the balance in the center cylinder 48. In this case, it is considered that the hydraulic pressure becomes low and changes according to the mass change relationship.
In the case of (c), the hydraulic pressure of the right front wheel 4FR increases because the vehicle height decreases. For the left rear wheel 4RL, hydraulic fluid is supplied to the suspension cylinder 10RL, but the vehicle height increases. From the balance in the center cylinder 48, it is considered that the hydraulic pressure becomes low and changes in accordance with the mass change relationship.
As described above, when the mass increases, regardless of the presence or absence of the center cylinder 48, the hydraulic pressure and the vehicle height at the front, rear, left, and right wheels 4FL, FR, RL, and RR are the same when the mass changes. It is thought to change according to the relationship. The same applies when the mass is reduced.

Next, a case where vehicle height adjustment is performed will be described.
When the vehicle height is increased by simultaneously supplying hydraulic fluid to the front, rear, left and right four wheels 4FL, FR, RL, and RR (when there are four wheels to be controlled), as shown in FIG. In addition, for all four wheels, the vehicle height increases and the hydraulic pressure increases. For all wheels, the hydraulic pressure and vehicle height change according to the relationship during vehicle height adjustment. The situation is the same even with the center cylinder 48.
As shown in FIG. 8 (2), when the vehicle height is increased by supplying hydraulic fluid to the left and right front wheels 4FL, FR (when the wheel to be controlled is the left and right front wheels), the left and right front wheels 4FL, FR Since the hydraulic pressure increases and the vehicle height increases, it changes according to the vehicle height adjustment relationship. As for the left and right rear wheels 4RL and RR, the vehicle height decreases and the hydraulic pressure increases due to an increase in the load caused by the movement of the center of gravity, and changes according to the relationship when the mass changes. The situation is the same even with the center cylinder 48. If the balance does not change, the piston assembly 50 is not moved.

  As shown in FIG. 8 (3), when the vehicle height is increased by supplying hydraulic fluid to the left front wheel 4FL, for example (when the wheel to be controlled is the left front wheel), As the hydraulic pressure increases, the vehicle height increases and changes according to the vehicle height adjustment relationship. Although the vehicle height of the left front wheel 4FL is increased, since the vehicle body 8 is a rigid body, (d) the inclination is such that the left front wheel 4FL around the diagonal line connecting the right front wheel 4FR and the left rear wheel 4RL is upward. e) An attitude determined by one or more combinations of an inclination in which the left side around the longitudinal axis is upward and (f) an inclination in which the front wheel side around the lateral axis is upward.

When there is no center cylinder 48,
In any of the cases (d) to (f), the right rear wheel 4RR has a lower vehicle height and a higher hydraulic pressure, and changes according to the mass change relationship.
In the case of (d), for the right front wheel 4FR and the left rear wheel 4RL, the vehicle height increases and the hydraulic pressure decreases, and changes according to the relationship when the mass changes.
In the case of (e), for the right front wheel 4FR, the vehicle height is reduced and the hydraulic pressure is increased, and for the left rear wheel 4RL, the vehicle height is increased and the hydraulic pressure is reduced. It changes according to the relationship.
In the case of (f), for the right front wheel 4FR, the vehicle height increases and the hydraulic pressure decreases, and for the left rear wheel 4RL, the vehicle height decreases and the hydraulic pressure increases, and changes according to the relationship with the mass change. To do.
As described above, when there is no center cylinder 48, the hydraulic pressure and the vehicle height change according to the vehicle height adjustment relationship for the vehicle height adjustment target wheel, and the mass change for the wheel that is not the vehicle height adjustment target wheel. It changes according to the time relationship.

Similarly, when the center cylinder 48 is provided, the vehicle body 8 has a posture determined by a combination of one or more of (d) to (f).
With respect to the left front wheel 4FL, the vehicle height increases and the fluid pressure increases, but the operation fluid is exchanged also in the suspension cylinder 10 of the wheel that is not the vehicle height adjustment target wheel by the operation of the center cylinder 48. The hydraulic fluid is allowed to flow out from the suspension cylinder 10RR of the right rear wheel 4RR, and the hydraulic fluid is supplied to the suspension cylinders 10FR, RL of the right front wheel 4FR and the left rear wheel 4RL.
In any of the cases (d) to (f), the vehicle height of the right rear wheel 4RR is small, but the hydraulic fluid is allowed to flow out from the suspension cylinder 10RR, so the hydraulic pressure is low, and the hydraulic pressure and the vehicle High is considered to change according to the vehicle height adjustment relationship.
In the case of (d), regarding the right front wheel 4FR and the left rear wheel 4RL, the hydraulic fluid is supplied to the suspension cylinders 10FR, RL, so that the vehicle height is considered to increase. However, the hydraulic pressure in the piston assembly 50 Determined by the balance. If the hydraulic pressure increases, it changes according to the vehicle height adjustment relationship, and if it becomes lower or the same, it changes according to the mass change relationship.
In the case of (e), the vehicle height of the right front wheel 4FR is reduced and the hydraulic pressure is increased, so that it changes according to the change in mass, and the hydraulic fluid is supplied to the suspension cylinder 10RL for the left rear wheel 4RL. However, the vehicle height increases. From the balance in the piston assembly 50, it is considered that the hydraulic pressure becomes lower and changes according to the mass change relationship.
In the case of (f), the vehicle height of the left rear wheel 4RL becomes small, so that the hydraulic pressure becomes high and changes according to the mass change relationship. Regarding the right front wheel 4FR, although the vehicle height is increased, the hydraulic fluid is supplied to the suspension cylinder 10FR, so whether or not the hydraulic pressure increases is determined by the balance in the piston assembly 50. When the hydraulic pressure becomes smaller, it changes according to the mass change relationship.

As described above, it can be seen that when the mass of the load changes, the vehicle height and the hydraulic pressure change according to the mass change relationship for any wheel. Therefore, when the vehicle height adjustment is not performed, if there is a wheel in which the relationship between the hydraulic pressure and the vehicle height changes according to the mass change relationship, it can be determined that the mass of the load has changed.
In addition, when vehicle height adjustment is performed, for all wheels, there are some wheels in which the vehicle height and the hydraulic pressure do not change according to the vehicle height adjustment relationship but change according to the mass change relationship. Therefore, it cannot be determined that the mass of the load has changed for any one wheel because the hydraulic pressure and the vehicle height have changed according to the relationship at the time of mass change. On the other hand, if at least one wheel changes according to the vehicle height adjustment relationship, it can be determined that the vehicle height is being adjusted. Therefore, if it is not clear whether the vehicle height is being adjusted, the relationship between the change in hydraulic pressure and the change in vehicle height is obtained for each of the four wheels, and the vehicle height adjustment is based on these relationships. It is determined whether or not there is a change in mass. Thus, based on the relationship for each of the four wheels, it is possible to avoid erroneously detecting a change in the mass of the load when the vehicle height is being adjusted.
Furthermore, in the above embodiment, whether the vehicle height adjustment relationship or the mass change relationship is distinguished by the direction of the inclination of the straight line representing the change between the vehicle height and the system pressure, A distinction can also be made between whether the vehicle height and the system pressure change according to a linear characteristic or according to a non-linear characteristic.

In the present embodiment, the vehicle height adjustment is performed at the same time for all four wheels, separately for the left and right front wheels, the left and right rear wheels, or by rotation of four wheels. Rotation is not a vehicle height adjustment for each wheel until it reaches the target vehicle height, but the vehicle height is gradually changed in order, and the vehicle height of each wheel reaches the target vehicle height in multiple cycles. It is the control performed to reach.
In addition, although the change in hydraulic pressure and the change in vehicle height are omitted in the flowchart, the hydraulic pressure detected at the time of execution this time, the vehicle height and the previous time, or the hydraulic pressure detected at the time of execution several times before, the vehicle height It is detected as a difference. When these differences are almost 0, it is considered that neither the vehicle height adjustment nor the mass change is caused.

In the spring constant switching valve control program represented by the flowchart of FIG. 9, it is determined in S41 whether or not the vehicle is stopped, and in S42 it is determined whether or not the vehicle height is being adjusted. If the vehicle is in a stopped state and the vehicle height is not being adjusted, a change in the hydraulic pressure of the suspension cylinder 10 and a change in the vehicle height are acquired for each wheel in S43. It is determined whether there is something to do. If there is something that changes in accordance with the mass change relationship, it is determined that the mass of the load has changed, and in S45, switching the spring constant switching valve 28 to the shut-off state is prohibited. On the other hand, if there is no wheel that changes according to the mass change relationship, the switch prohibition flag is reset in S46.
When the switching prohibition flag is in the set state, as shown in the flowchart of FIG. 4, even if the high speed vehicle height adjustment requirement is satisfied, the spring constant switching valve 28 is not switched to the cutoff state, and the vehicle height Adjustments are made.
In the present embodiment, the pressure / vehicle height-related mass change acquisition unit is configured by the part that stores S43 and S44 of the suspension ECU 200, the part that executes S43, and the like.

In the spring constant switching valve control program represented by the flowchart of FIG. 10, it is determined in S51 whether or not the vehicle is stopped. The relationship between the change of the vehicle and the change of the vehicle height is acquired. In S53, if at least one of the four wheels changes according to the vehicle height adjustment relationship, it is determined that the vehicle height is being adjusted. In this case, the vehicle height adjustment is continuously performed, and the spring constant switching valve 28 is not switched.
On the other hand, when all four wheels change in accordance with the relationship at the time of mass change, it is assumed that the mass of the load is changed. If it is a change in the mass of the load, the determination in S54 is YES, and a switching prohibition flag is set in S55. If not, the switching prohibition flag is reset in S56. For example, the case where the vehicle height adjustment is not performed and the mass does not change is applicable.
Thus, based on the relationship between the vehicle height and the hydraulic pressure of the suspension cylinder 10, it can be determined whether the vehicle height is being adjusted or the mass of the load has changed.

  As described above, although several embodiments have been described, the center cylinder 48 is not essential. Further, the suspension cylinder 10 may be operated by gas, and the structure of the vehicle height adjusting device and the suspension device is not limited. The present invention can be practiced in various modifications and improvements based on the knowledge of those skilled in the art, in addition to the aspects described above.

1 is a diagram illustrating an entire suspension device according to an embodiment of the present invention. It is a figure which shows the vehicle carrying the said suspension apparatus. It is a flowchart showing the spring constant switching valve control program memorize | stored in suspension ECU of the said suspension apparatus. It is a flowchart showing the vehicle height adjustment program memorize | stored in the said suspension ECU. In the suspension device, it is a diagram showing the relationship between the vehicle height and the hydraulic pressure of the suspension cylinder when the mass of the load changes (the diagram shows the relationship when the mass changes). FIG. 3 is a diagram showing a relationship between a vehicle height and a hydraulic pressure of a suspension cylinder when vehicle height adjustment is performed in the suspension device (a diagram showing a relationship during vehicle height adjustment). In the suspension device, it is a diagram showing the relationship between the vehicle height and the hydraulic pressure in each wheel when the mass of the load changes. FIG. 5 is a diagram illustrating a relationship between vehicle height and hydraulic pressure in each wheel when vehicle height adjustment is performed in the suspension device. 7 is a flowchart showing another spring constant switching valve control program stored in the suspension ECU. It is a flowchart showing the another spring constant switching valve control program memorize | stored in the said suspension ECU.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10: Suspension cylinder 24,26: Accumulator 28: Spring constant switching valve 48: Center cylinder 74: Vehicle height adjustment apparatus 200: Suspension ECU 220: Vehicle height sensor 221: Fluid pressure sensor 228: Boarding / alighting prediction apparatus 230: Loading state detection apparatus

Claims (4)

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,
In each of the four fluid cylinders, a low-pressure accumulator connected in parallel with each other and a high-pressure accumulator having a larger spring constant than the low-pressure accumulator,
A spring constant switching valve provided between each of the four fluid cylinders and the low-pressure accumulator;
An accumulator communication control device that controls each of the spring constant switching valves and closes the spring constant switching valves so that each of the fluid cylinders is disconnected from the low pressure accumulator and communicates with the high pressure accumulator ; ,
In each of the four fluid cylinders, a vehicle height adjusting device that adjusts a vehicle height corresponding to each of the wheels by supplying or discharging a fluid;
A mass change acquisition device for acquiring a mass change or a mass change possibility of the vehicle body and the load,
The accumulator communication control device,
(i) means for closing the spring constant switching valve when vehicle height adjustment is performed by the vehicle height adjustment device in a stopped state of the vehicle;
(ii) In the stop state of the vehicle, when the mass change acquisition device acquires a mass change or a possibility of mass change, (a) the spring constant switching valve is set by adjusting the vehicle height. Mass provided with at least one of means for switching to the open state even in the closed state, and (b) means for prohibiting switching of the spring constant switching valve to the closed state even when the vehicle height adjustment request is made A suspension device comprising: a communicating portion at the time of change.   The pressure / vehicle in which the mass change acquisition device acquires a change in mass of the vehicle body and the load based on a relationship between a pressure of the fluid cylinder and a vehicle height that is a distance between the wheel holding device and the vehicle body. The suspension device according to claim 1, further comprising a high relationship-based mass change acquisition unit. The pressure / vehicle height relation-dependent mass change acquisition unit acquires that the mass has increased when the pressure of the fluid cylinder increases and the vehicle height decreases, and the pressure of the fluid cylinder decreases to The suspension device according to claim 2, further comprising means for acquiring that the mass has decreased when the vehicle height has increased. 3. The pressure / vehicle height related mass change acquisition unit does not acquire the change in mass for each of the four wheels when vehicle height adjustment is performed by the vehicle height adjustment device. Or the suspension apparatus of 3.

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