JPH11291737A - Suspension device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a suspension device having a large difference in damping force between the cases when a hydraulic cylinder is placed in its extension/ contraction with an in-phase and with an anti-phase. SOLUTION: A pressure side sub-damping value 100U, main damping valve 100V, and an extension side sub-damping valve 100W are layered and connected successively in a lower end side faucet part of a piston rod, in the other hand, a switching spool opened/closed in response to a pressure difference between lower part chambers of a pair of right/left hydraulic cylinders is slidably fitted between the pressure side sub-damping valve and a lower part chamber 100B and between the extension side sub-damping valve and an upper part chamber 100A in a spool hole of the faucet part, the main damping valve of high valve opening pressure and the extension/pressure side sub-damping valves of low opening pressure are all opened by the switching spool held in a neutral condition in the case of operating a pair of the hydraulic cylinders in an in-phase, and low damping force is generated. In reverse, high damping force is switched to by cutting off the extension/pressure side sub-damping valves in the case of operating a pair of the hydraulic cylinders in an anti-phase or only one cylinder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a suspension device, and more particularly to an improvement in a suspension device set to enable suppression of vehicle body vibration in a running vehicle.

[0002]

2. Description of the Related Art In recent years, suspension systems are often set not only to support a vehicle body while performing damping operation, but also to suppress vehicle body vibration in a running vehicle. There is one disclosed in Japanese Patent No. 72127.

In a suspension device shown in FIG. 5 corresponding to FIG. 1 of this publication, the inside of a hydraulic cylinder 2 is defined by a piston 6 having a throttle 9 added thereto into an upper chamber 7 and a lower chamber 8, and the hydraulic cylinder 2 is connected to a wheel side. One of the vehicle body side is connected to the body of the cylinder 2, the other is connected to the hydraulic cylinder 2 interposed between the wheel side and the vehicle body side connected to the piston 6, and to one of the upper and lower chambers of the hydraulic cylinder 2 The oil chamber 14 communicates with the oil chamber 14, and the oil chamber 14 and the high-pressure gas chamber 13 include the pressure adjusting device 3 including the pressure adjusting cylinder 11 a defined by the free piston 12.

A hydraulic cylinder 2 is mounted on at least two of the four wheels,
Is provided with a pressure adjusting cylinder 11a for each of the hydraulic lines 16 and 17 of the respective hydraulic cylinders, and the free pistons 12 and 12 of the respective pressure adjusting cylinders 11a are integrally configured to interlock with each other. , 17 with each other
Are communicated through When the pair of left and right hydraulic cylinders 2 and 2 expand and contract in the same direction,
The amount of hydraulic oil passing through the throttle 1a is small, and the operation of the hydraulic cylinder 2 is attenuated by the hydraulic oil passing through the throttles 9 added to the pistons 6 of the respective hydraulic cylinders 2 and 2.

When the pair of left and right hydraulic cylinders 2 expands and contracts in opposite directions, a large amount of hydraulic oil flows to the throttle member 4 on the pressure adjusting cylinder 11a side. The operation of the hydraulic cylinder 2 is attenuated by the passage of the hydraulic oil through the added throttle 9 and the throttle member 4 on the pressure adjusting cylinder 11a side. For this reason, when a difference occurs in the operation direction of the pair of left and right hydraulic cylinders 2, the throttle member 4 on the pressure regulating cylinder 11a side exerts a damping effect.

[0006] Therefore, vertical movements such as pitching and bouncing occur in the vehicle body, and a pair of left and right hydraulic cylinders 2 are formed.
Expand and contract in the same direction (in-phase), a low damping effect is obtained. On the other hand, left and right swing such as rolling occurs,
When the pair of left and right hydraulic cylinders 2 expands and contracts in the opposite direction (reverse phase), a high damping effect is obtained, and vibration of the vehicle body can be effectively suppressed.

[0007]

The damping force generated during the reverse phase is caused by the hydraulic cylinders 2 and 2 and the pressure regulating device 3 side.
The throttle 4 is provided between the respective hydraulic oil chambers 14 connected to the two free pistons 12. The resistance of the hydraulic oil generated in the throttle 4, that is, the pressure difference before and after the throttle (hereinafter, abbreviated as "differential pressure") does not generate a differential pressure higher than the gas pressure, so the gas pressure in the high-pressure gas chamber becomes the upper limit. When the gas pressure is increased, the differential pressure before and after the throttle 4 can be increased, but the change in reaction force (cross-sectional area of the piston rod x change in gas pressure = gas spring constant) when the hydraulic cylinder 2 expands and contracts in phase. It becomes bigger and the ride is worse. Therefore, if the cross-sectional area of the piston rod 10 of the cylinder 2 is increased, the damping force can be increased even with the same differential pressure. However, in this case, similarly, the change in the reaction force when the hydraulic cylinder 2 expands and contracts in the same phase is large. And the ride quality deteriorates. As described above, the damping force to be added at the time of the opposite phase is restricted by the riding comfort, and there is a problem that the difference between the damping force at the time of the in-phase and the damping force at the time of the opposite phase cannot be sufficiently increased.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a suspension having a large difference in damping force between when the expansion and contraction of a hydraulic cylinder is in and out of phase. It is to provide a device.

[0009]

According to the present invention, there is provided a fuel cell system comprising: an upper end of one of a piston rod and an outer cylinder connected to a vehicle body; and a lower end connected to an axle. A pair of left and right hydraulic cylinders and a free piston are slidably housed therein, and a piston supported by a hollow rod and provided with a throttle is slidably fitted in the hollow portion of the free piston to form an upper chamber and a lower part. And a suspension device in which an upper chamber and a lower chamber of the differential valve are connected to respective oil chambers of the pair of left and right hydraulic cylinders via a hydraulic pipeline. is there.

A first means adopted by the present invention to solve the above-mentioned problem is that a compression sub-attenuation valve, a main damping valve, and an extension-side sub-damping valve are sequentially laminated on the lower end side lower part of the piston rod. On the other hand, a spool hole formed in the spigot portion is provided between the compression side sub damping valve and the lower chamber and the expansion side sub damping valve and the upper chamber to form a lower chamber of the pair of hydraulic cylinders. A switching spool that opens and closes in response to the pressure difference between the two is slidably fitted, and when the pair of left and right hydraulic cylinders operate in phase, the switching spool held in a neutral state reduces the valve opening pressure. The main damping valve set to a high value and the extension side and compression side sub damping valves set to a low valve opening pressure are all opened to have a low damping force, and conversely, the pair of left and right hydraulic cylinders are in opposite phases or one of a pair. When operating is high to switch the damping force "blocked the extension side and the compression side sub damping valve.

The second means is that the upper surface of the switching spool which is vertically movably fitted into a spool hole formed in a lower end side spigot portion of one of the pair of left and right hydraulic cylinders is provided. The pressure in the lower chamber of the other hydraulic cylinder is applied, and is urged downward by an upper spring housed in the upper portion of the spool hole, while the lower surface of the switching spool fitted in the spool hole has While the pressure of the lower chamber of each hydraulic cylinder is added, the lower chambers of the pair of left and right hydraulic cylinders communicate with each other through the throttle of the differential valve, and communicate with the lower spring chamber formed larger than the spool hole. The lower surface of the switching spool abuts on a spacer movably accommodated and urged upward by a lower spring, and the step of the lower spring chamber is stepped. By the spacer comes into contact with the parts, it is possible "to hold the neutral state. The pressure of the gas chamber of the differential valve may be applied to the upper surface of the switching spool fitted into the spool hole of the piston rod, or a gas corresponding to the pressure of the gas chamber of the differential valve may be filled. . Also, if the set load of the spring that urges the switching spool downward fitted into the spool hole of the piston rod is set appropriately, the upper surface of the switching spool may be released to the atmosphere or may correspond to the atmospheric pressure. A low-pressure gas may be sealed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a suspension device according to the present invention will be described with reference to a first embodiment shown in FIG. The most significant feature of the present invention is that a variable damping force mechanism that operates by a differential pressure is provided in a piston portion of a hydraulic cylinder. In this embodiment, a free piston 301 fitted with a seal 301A on the outer peripheral side is fitted inside the differential valve 300 so as to be vertically movable, and a high-pressure gas chamber 300G, an upper chamber 300A and a lower chamber filled with hydraulic oil are filled. 300B. The free piston 301 is formed in a cap shape, and a restrictor 30 is
2A is provided.

The lower chamber 100 of one hydraulic cylinder 100
B is connected to the lower chamber 300B of the differential valve 300 by a hydraulic line 100R. Similarly, the lower chamber 200B of the other hydraulic cylinder 200 is provided with a hollow rod 30 supported on the bottom cover of the differential valve 300 by a hydraulic line 200R.
It is connected to the upper chamber 300A through three hollow holes.
The upper chamber 300A and the lower chamber 300B are
02 is communicated via a diaphragm 302A added to the reference numeral 02.

The outer diameter of the free piston 301 and the diameter of the hollow portion forming the upper chamber 300A are set so that the pressure receiving areas of the upper chamber 300A and the lower chamber 300B of the differential valve 300 are the same. Further, the volume of the gas chamber 300G of the differential valve 300 is sufficiently large,
The gas pressure is set not to largely fluctuate due to the expansion and contraction of the piston rods 101 and 201 of 0 and 200.

As shown in a detailed view of the piston portion in FIG. 2, a pressure-side sub damping valve 106 having a small rigidity is bent on the upper surface of the pressure-side disk 105, as shown in a detailed view of the piston portion of the hydraulic cylinders 100 and 200. The lower pressure-side sub damping valve 100U having a low valve opening pressure, and the upper and lower surfaces of the piston 102 are opposed to the compression-side damping valve 103 and the expansion-side damping valve 104 having high flexural rigidity.
A main damping valve 100V having a high valve opening pressure that communicates with the lower chamber 100B and an expansion sub-attenuation valve 108 having a low valve opening pressure and a lower sub-attenuation valve 108 having a low flexural rigidity facing the lower surface of the expansion disk 107. 100W are sequentially mounted in a stacked state.

The main damping valve 100V having a high valve opening pressure is:
The upper chamber 100A and the lower chamber 100B are directly connected to each other through damping valves 103 and 104 having high flexural rigidity. The sub damping valves 100U and 100W having a low valve opening pressure are connected to the upper chamber 1A.
00A and the lower chamber 100B are provided in parallel, bypassing the main damping valve 100V, via a switching spool 109 slidably fitted in a spool hole 101B formed in the lower end spigot portion of the piston rod. ing.

The lower end surface 109C of the switching spool abuts on a spacer 112 which is urged upward by the lower spring 111 into the lower spring chamber 101C and slidably fits therein, and the upper end surface 109D is accommodated above the spool hole 101B. The upper spring 110 is urged downward. The lower spring chamber 101C has a spool hole 101.
B is formed larger than B. For this reason, the upward movement of the spacer 112 urged upward by the lower spring 111 is restricted by the upper end step of the lower spring chamber 101C, so that the switching spool 109 is in the normal state as shown in FIG. The sub damping valve 100 is held between the upper chamber 100A and the lower chamber 100B as shown in FIG.
U, and communicates via 100V.

The pressure of the lower chamber 100B acts on the lower end surface 109C of the switching spool 109 of one hydraulic cylinder 100 via the through hole 101D. Lower chamber 100B of hydraulic cylinder 100 and lower chamber 300B of differential valve
The pilot hydraulic pipeline 200P branched from the middle of the hydraulic pipeline 100R connecting the lower hydraulic chamber 100R and the lower hydraulic chamber 100 of the other hydraulic cylinder 200 A pressure of 100B is applied.

Similarly, a pilot hydraulic line 100P that branches off from the middle of a hydraulic line 200R that connects the lower chamber 200B of the other hydraulic cylinder 200 and the upper chamber 300A of the differential valve forms an internal passage of the piston rod 101. Through the switching spool 10 of one hydraulic cylinder 100
9, a lower chamber 200B of another hydraulic cylinder 200
Pressure is acting.

Next, in the second embodiment shown in FIG. 3, the pressure of the lower chamber of the other hydraulic cylinder is applied as a pilot pressure above the switching spool 109 built in the pair of left and right hydraulic cylinders 100 and 200. Instead, the pressure of the gas chamber 300G of the differential valve is directly led.

In the third embodiment shown in FIG. 4, the pilot hydraulic line 10 in the first embodiment is used.
0P and 200P are omitted. Since the pressure of the lower chamber 150B acts on the lower spring chamber 101C of the switching spool 109 of the hydraulic cylinder 150, the upper spring chamber partitioned above the spool hole 101B has:
A high-pressure gas corresponding to the pressure of the gas chamber 300G of the differential valve 300 is sealed therein and sealed by a sealing means such as a plug 151A. The switching spool 109 is normally held at the neutral position shown in the detailed view of FIG. 2A by the pressure applied to the upper and lower spring chambers 101B and 101C and the balance between the pair of upper and lower springs 110 and 111.

In the third embodiment, the upper spring chamber 101B is opened to the atmosphere or filled with a low-pressure gas of about atmospheric pressure, and is switched to the pressure applied from the lower spring chamber 101C to the force multiplied by the pressure receiving area of the spool 109. It is also possible to balance with the spring force of the corresponding upper spring chamber 101B. Although the main damping valve and the sub damping valve are disposed in the piston portion, the sub damping valve is omitted, and the through holes 101F, 101G and the through holes 101H, 10H provided in the pilot portion of the piston rod are omitted.
1J may be opened and closed directly by the switching spool 109.

Next, the operation will be described. In the first embodiment shown in FIG.
When 00 and 200 move up and down, hydraulic oil corresponding to the volume in which the respective piston rods 101 and 201 enter and exit the oil chamber enters and exits the differential valve 300 via the hydraulic pipeline.

In the first embodiment shown in FIG. 1, when the pair of left and right hydraulic cylinders 100 and 200 move in the same phase, the amount of oil entering and leaving the lower chamber 300B of the differential valve from one hydraulic cylinder 100 is determined. The amount of oil entering and leaving the upper chamber 300A from the other hydraulic cylinder 200 is the same. At this time, the left and right hydraulic cylinders 100, 2
With the pressure oil from 00, the free piston 301 moves up and down against the pressure of the gas chamber 300G, so that no hydraulic oil flows in the throttle 302A. Therefore, the upper and lower spring chambers 101B, 101B of the switching spool 109 inserted in the piston rods of the hydraulic cylinders 100, 200
There is no difference in the pressure applied to C.
(A) Maintain the neutral position.

When the switching spool 109 is in the neutral state shown in FIG. 2A in a so-called extension stroke in which the piston rod extends, the hydraulic oil in the upper chamber 100A causes the extension port 102A of the piston, the lower opening window 102C, Through hole 1
02E, the through hole 101H of the piston rod, the groove 109A of the switching spool, the through hole 101 of the piston rod.
J, flows into the lower opening window 107A from the through hole 107B of the extension disk and pushes open the extension sub damping valve 108 provided opposite to the lower opening window 107A to open the lower chamber 1
Flow out to 00B. Since the extension side sub damping valve 108 is set to have a smaller bending rigidity than the extension side damping valve 104 of the main damping valve 100V, a low extension side damping force is generated by the passage resistance at this time.

Similarly, in the so-called compression stroke in which the piston rod contracts, the switching spool 109 is moved to the position shown in FIG.
When the operating oil is in the neutral state as shown in FIG.
D, through the through hole 102F, through the through hole 101 of the piston rod.
G, through the groove 109B of the switching spool and the through hole 101F of the piston rod, flows into the upper opening window 105A from the through hole 105B of the pressure side disk, and the upper opening window 105A.
Pushes the pressure side sub damping valve 106 provided opposite to the upper side to flow out to the upper chamber 100A. Since the compression side sub damping valve 106 is set to have a smaller bending rigidity than the compression side damping valve 103 of the main damping valve 100V, a low pressure side damping force is generated by the passage resistance at this time.

Thus, at the neutral position of the switching spool, the passages of both the main damping valve 100V having a high valve opening pressure and the sub damping valves 100U and 100W having a low valve opening pressure are open. The hydraulic oil flows through the sub damping valves 100U and 100W having a smaller passage resistance than the main damping valve 100V having a high valve opening pressure.

When the hydraulic cylinders 100 and 200 move in opposite phases to each other, or when only one of the hydraulic cylinders moves alone, there is a difference in the amount of oil flowing into and out of the upper and lower chambers 300A and 300B of the differential valve 300. For example, when the left and right hydraulic cylinders 100 and 200 move in completely opposite phases, the upper chamber 3
00A and the lower chamber 300B have the same pressure receiving area, so that hydraulic oil flows into the lower chamber 300B of the differential valve from one hydraulic cylinder 100, and from the upper chamber 300A to the other hydraulic cylinder 200. A quantity of hydraulic oil spills. At this time, while the pressure in the lower chamber 300B increases, the upper chamber 3
00A is decompressed. That is, the force that pushes up the free piston 301 upward by increasing the pressure of the lower chamber 300B and the upper chamber 3
The free piston 301 does not move because the force for pulling the free piston 301 downward at the reduced pressure of 00A becomes the same.

The upper and lower chambers 300A, 3 of the above-described differential valve
Due to the pressure difference between 00B and 00B, the hydraulic oil in lower chamber 300B flows into upper chamber 300A through throttle 302A and generates a damping force. At this time, the pressure in the lower chamber 300 </ b> B of the differential valve is changed to the switching spool 1 on one hydraulic cylinder 100 side.
09 in the lower spring chamber 101C below the upper chamber 3
The pressure of 00A is switched via the pilot hydraulic line 100P.
Join the room. Due to the pressure difference between the upper and lower spring chambers,
For example, the switching spool of the hydraulic cylinder 100 on the contraction side moves upward in the figure as shown in FIG. 2 (B), shuts off the sub damping valves 100U and 100W, and the switching spool of the hydraulic cylinder 200 on the extension side 2 (C), the sub damping valve 200
U, 200W is cut off.

As described above, when the switching spool 109 shuts off the sub damping valves 200U and 200W of the hydraulic cylinder 200 on the extension side as shown in FIG. The hydraulic oil of 200A flows into the lower opening window 102C of the main damping valve 100V through the extension port 102A of the piston, and the lower opening window 102C
Extension-side damping valve 10 having a large flexural rigidity provided opposite to
4 is pushed open and flows out into the lower chamber 200B, and a high extension side damping force is generated by the passage resistance at this time.

Similarly, the switching spool 109 is provided as shown in FIG.
As shown in FIG. 2B or FIG. 2C, when the sub damping valve 100U or 100W of the hydraulic cylinder 100 on the contraction side is shut off, the hydraulic oil in the upper chamber 100A passes through the pressure side port 102B of the piston. It flows into the upper opening window 102D of the main damping valve 100V, and the upper opening window 102D
Pressure-side damping valve 10 having a large flexural rigidity provided opposite to
3 is pushed open to return to the upper chamber 100A, and a high pressure side damping force is generated by the passage resistance at this time.

In the second embodiment shown in FIG. 3, the pressure of the gas chamber 300G of the differential valve is added above the switching spool 109 instead of adding the pressure of the lower chamber of another hydraulic cylinder as the pilot pressure. Except for the first in FIG.
The operation and effect are the same as those of the embodiment.

In this embodiment, the pressure in the gas chamber 300G of the differential valve is directly above the switching spool 109 and below the free piston 30 of the differential valve.
1 indirectly via 1. Therefore, unless a differential pressure is generated in the throttle 302A of the differential valve, the differential pressure applied to the upper and lower sides of the switching spool does not change even when the gas pressure fluctuates due to a temperature change or a stroke position of the piston rod. Therefore, in this embodiment, the design is such that the gas pressure change of the differential valve does not become large (for example,
It is not necessary to increase the volume of the gas chamber or to add a radiation fin.

The operation and effects of the third embodiment shown in FIG. 4 are the same as those of the first embodiment shown in FIG. 1 except that no pilot pressure acts on the switching spool 109. The switching operation of the switching spool 109 is performed only by the pressure in the lower chambers of the hydraulic cylinders 150 and 250 applied below the switching spool 109. Differential valve 3
Since the volume of the gas chamber 310G of 00 is set to be sufficiently large, a change in gas pressure due to the expansion and contraction of the piston rod is slight.

When the pair of left and right hydraulic cylinders 150 and 250 contract, for example, in phase, the pressure of one of the increased hydraulic cylinders 150 is applied to the lower chamber 300B of the differential valve, and the pressure of the other hydraulic cylinder 250 is similarly reduced. Joins the upper chamber 300A of the differential valve and pushes up the free piston 301 of the differential valve. Therefore, the hydraulic cylinder 15
The pressure changes in the lower chambers 150B, 250B of 0, 250 are small, and no force is generated enough to move the switching spool built in each hydraulic cylinder up and down. Conversely, when moving in the opposite phase, as described in the first embodiment, a pressure difference occurs before and after the throttle 302A, so that, for example, the lower chamber 150B of the contraction-side hydraulic cylinder 150 increases while the extension-side hydraulic cylinder 250 The pressure in the lower chamber 250B is reduced.

When the pressure below the switching spool 109 communicating with the lower chamber of the hydraulic cylinder changes, the balance holding the neutral position is lost, and the switching spool 109 moves downward or upward depending on the expansion and contraction of the hydraulic cylinders 150 and 250, respectively. In motion, shut off the sub damping valve as shown in FIG. 2 (B) or FIG. 2 (C). Therefore, the hydraulic oil flows only through the main damping valves 150V and 250V, and generates a high damping force.

[0037]

As described above in detail, according to the present invention, a variable damping force mechanism is provided in the piston portion of the hydraulic cylinder, and the differential pressure generated before and after the throttle of the free piston built in the differential valve is utilized. The switching of the damping force generated in the piston portion is performed. When the pair of right and left hydraulic cylinders operate in opposite phases, the throttle of the differential valve generates damping force also in this part, and the generated differential pressure is used as the bi-rot pressure to increase the damping force of the piston part and switch the vehicle body. Rolling is attenuated quickly. In addition, since the damping force is generated by using the flow of hydraulic oil between the piston upper and lower chambers (the cross-sectional area is larger than the piston rod), a large damping force is generated when the hydraulic cylinder moves in the opposite phase compared to when it moves in the same phase. can get. Further, even if the damping force at the same phase is set low for the purpose of improving the riding comfort, the driving stability can be improved because the damping force can be switched to a high damping force at the opposite phase.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a suspension device according to a first embodiment of the present invention.

FIG. 2A is a cross-sectional view showing a neutral state of a switching spool built in a hydraulic cylinder of the present invention. (B) It is sectional drawing which shows the interruption | blocking state accompanying the upward movement of a switching spool. (C) It is sectional drawing which shows the interruption | blocking state accompanying the upward movement of a switching spool.

FIG. 3 is a configuration diagram of a suspension device according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram of a suspension device according to a third embodiment of the present invention.

FIG. 5 is a configuration diagram of a suspension device according to the related art.

[Explanation of symbols]

100, 200, 150, 250 Hydraulic cylinder 100A, 200A, 150A, 250A Upper chamber (of hydraulic cylinder) 100B, 200B, 150B, 250B Lower chamber (of hydraulic cylinder) 100P, 200P (Pilot) hydraulic line 100R, 200R Hydraulic Pipe 100U, 200U Compression side sub damping valve 100V, 200V Main damping valve 100W, 200W Extension side sub damping valve 101, 201 Piston rod 101B Spool hole 101C Lower spring chamber 109 Switching spool 110 Upper spring 111 Lower spring 112 Spacer 300 Differential valve 301 Free piston 302 Piston 302A Restrictor 303 Hollow rod

Claims (5)

[Claims] 1. A pair of left and right hydraulic cylinders which are disposed on the left and right sides of a vehicle and one of a piston rod and an outer cylinder is connected to a vehicle body and the lower end is connected to an axle side. The free piston is housed slidably,
A differential valve defining an upper chamber and a lower chamber in which a piston supported by a hollow rod and having a throttle is slidably fitted into a hollow portion of the free piston to define an upper chamber and a lower chamber; In a suspension device in which a lower chamber is connected to respective oil chambers of the pair of left and right hydraulic cylinders via a hydraulic pipe, a lower pressure side sub-damping valve, a main damping valve, and an expansion side sub-damping are provided at a lower end side lower portion of the piston rod. While the valves are stacked and connected in order, a spool hole formed in the spigot portion is provided between the compression side sub damping valve and the lower chamber and between the expansion side sub damping valve and the upper chamber, and the pair of hydraulic pressures. A switching spool that opens and closes in response to the pressure difference between the lower chambers of the cylinders is slidably fitted, and when the pair of left and right hydraulic cylinders operate in phase, the switching is maintained in a neutral state. By the spool, the main damping valve for which the valve opening pressure is set high and the expansion side and compression side sub damping valves for which the valve opening pressure is set low are all opened to have a low damping force. When only one of the phases is operated, the expansion side and compression side sub damping valves are shut off to switch to a high damping force. 2. A pair of left and right hydraulic cylinders, which are disposed on the left and right sides of the vehicle and one of a piston rod and an outer cylinder is connected to the vehicle body and the lower end is connected to the axle side. The free piston is housed slidably,
A differential valve defining an upper chamber and a lower chamber in which a piston supported by a hollow rod and having a throttle is slidably fitted into a hollow portion of the free piston to define an upper chamber and a lower chamber; In a suspension device in which a lower chamber is connected to respective oil chambers of the pair of left and right hydraulic cylinders via a hydraulic pipeline, a spool formed in a lower end side lower part of one of the piston rods of the pair of left and right hydraulic cylinders. On the upper surface of the switching spool that fits vertically into the hole,
While the pressure of the lower chamber of the other hydraulic cylinder is applied and urged downward by an upper spring housed in the upper part of the spool hole, the lower surface of the switching spool fitted in the spool hole has The pressure in the lower chamber of the hydraulic cylinder is applied, and the lower chambers of the pair of left and right hydraulic cylinders communicate with each other through the throttle of the differential valve, and move to the lower spring chamber formed larger than the spool hole. The neutral state is maintained by the lower surface of the switching spool abutting on the spacer freely housed and urged upward by the lower spring, and the spacer abutting on the stepped portion of the lower spring chamber. The hydraulic cylinder of the suspension device. 3. The pressure of the gas chamber of the differential valve is applied to an upper surface of the switching spool fitted into a spool hole inside the spigot portion. Hydraulic cylinder for suspension device. 4. A high pressure gas corresponding to a pressure of a gas chamber of the differential valve is sealed in an upper surface of the switching spool fitted in a spool hole inside the spigot portion. Or the hydraulic cylinder of the suspension device according to 2. 5. The switching spool according to claim 1, wherein an upper surface of the switching spool fitted in a spool hole inside the spigot portion is filled with a low-pressure gas corresponding to the atmosphere or the atmospheric pressure. Hydraulic cylinder for suspension device.