JPH07253136A - Hydro-pneumatic cylinder - Google Patents

Abstract

PURPOSE:To provide a hydro-pneumatic cylinder which pressure-feeds working fluid on a low pressure side toward a high pressure side through the rebound action of a wheel for adjusting a car height. CONSTITUTION:A hydro-pneumatic cylinder 1 is composed of a cylinder body 2, an inner cylinder 3, a piston 4, a hollow piston rod 5, a hollow pump rod 6, a pump section 7 and a communication mechanism 8. In the case where the piston 4 moves in the direction of its extension, the pump section 7 discharges working fluid drawn into a pump chamber 7a from a low pressure chamber 22 to a high pressure working fluid chamber 14. A free piston 41 is slidably provided in the low pressure chamber 22, and pressurizes the working fluid in the low pressure chamber 22 by the pressing force of a coil spring 45 provided in an atmospheric pressure chamber 42. When the pressure in the low pressure chamber 22 lowers suddenly, the free piston 41 abuts on a spool 48 to move it upward to communicate the pump chamber 7a with the communicating path 23 of the hollow pump rod 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydro-pneumatic cylinder, and more particularly to a hydro-pneumatic cylinder configured to maintain a constant vehicle height regardless of variations in the vehicle load.

[0002]

2. Description of the Related Art For example, in an automobile, each wheel is supported by a suspension, and a shock absorber of the suspension expands and contracts according to the load applied to each wheel to absorb the shock. Therefore, when traveling on an uneven road surface, the shock absorber expands and contracts and a damping force is generated by using the resistance of the working fluid filled in the cylinder, so that the impact due to the road surface unevenness is alleviated.

However, because the shock absorber expands and contracts and the vehicle height fluctuates depending on the number of passengers in the vehicle or the weight of the load, when the weight applied to each wheel increases and the shock absorber is compressed, the road surface is reduced. The impact of unevenness on the vehicle may not be absorbed well, and the steering stability may also be affected.Therefore, even if the number of passengers in the vehicle or the weight of the load fluctuates, a hydro train that keeps the vehicle height constant Matic cylinders are being developed.

An example of this type of hydro-pneumatic cylinder is SAE (Society of Autom).
Otive Enginieers, INC.) 780052 is known.

This hydropneumatic cylinder is
A high-pressure working fluid chamber and a low-pressure working fluid chamber, in which high-pressure gas is filled, are provided in the cylinder body, and when the vehicle height decreases due to the number of passengers in the vehicle or the weight of the load, when the hydropneumatic cylinder expands or contracts. The working fluid in the low-pressure working fluid chamber is pumped to the high-pressure working fluid chamber by the pumping action of the sliding movement of the piston, and the vehicle height is kept constant by increasing the pressure in the high-pressure working fluid chamber. Further, when the number of passengers in the vehicle or the weight of the load decreases, the piston lowers and the working fluid in the high pressure working fluid chamber is returned to the low pressure working fluid chamber to keep the vehicle height constant.

[0006]

However, in the above hydropneumatic cylinder, since the high-pressure gas is enclosed in the high-pressure chamber created by the diaphragm,
The high-pressure gas and the working fluid in the high-pressure working fluid chamber are sealed from each other by a cylindrically shaped diaphragm. Both ends of this diaphragm are fitted in a groove formed between the high pressure working fluid chamber and the inner wall of the cylinder, but if the diaphragm is damaged due to aging or assembly process,
The working fluid in the high pressure working fluid chamber or the high pressure gas in the high pressure chamber may leak to the outside.

As described above, in the hydropneumatic cylinder, since the working fluid in the high-pressure working fluid chamber is pressurized by the high-pressure gas to support the vehicle weight, when the working fluid in the high-pressure working fluid chamber or the high-pressure gas leaks. As a result, the vehicle weight is supported and the pressure becomes insufficient, resulting in a decrease in vehicle height.
Then, if the pressure in the high-pressure working fluid chamber is drastically reduced during traveling, the vehicle height is drastically reduced, which gives the driver and the passenger anxiety.

Therefore, in view of the above problems, an object of the present invention is to provide a hydro-pneumatic cylinder in which the vehicle height decreasing speed when the pressure in the high-pressure working fluid chamber is decreased is alleviated.

[0009]

The invention according to claim 1 is
A cylinder having a working fluid chamber filled with working fluid;
A high-pressure working fluid chamber communicating with the working fluid chamber, a first piston slidably provided in the working fluid chamber in the cylinder, and the first piston provided at one end, and the working fluid is stored inside. A hollow piston rod having a filled low pressure chamber, a low pressure working fluid chamber communicating with the low pressure chamber, one end inserted into the hollow piston rod, the other end fixed to the cylinder, and the low pressure chamber inside. A hollow pump rod having a communication passage that communicates with the low-pressure working fluid chamber, and a second pump provided at one end of the hollow pump rod that defines the interior of the hollow pump rod into the low-pressure chamber and the pump chamber.
And an opening valve for sucking the working fluid in the low pressure working fluid chamber into the pump chamber via the communication passage of the hollow pump rod and the low pressure chamber of the hollow piston rod in the process of the piston moving in the compression direction. An inlet valve, and an outlet valve that opens so as to discharge the working fluid sucked into the pump chamber to the high-pressure working fluid chamber in the process in which the piston moves in the extension direction,
And a free piston provided so as to slide in the low pressure chamber according to a change in pressure of the low pressure chamber.

Further, in the invention of claim 2, when a pressure drop occurs in the high pressure working fluid chamber in the communication passage of the hollow pump rod, the free piston is brought into contact with the communication passage and the pump chamber. It is characterized in that a valve member that is displaced to a communicating position is provided.

According to a third aspect of the invention, a cylinder having a working fluid chamber filled with working fluid, a high pressure working fluid chamber communicating with the working fluid chamber, and a working fluid chamber in the cylinder are slidable. , A hollow piston rod having a low pressure chamber in which the working fluid is filled, a low pressure working fluid chamber communicating with the low pressure chamber, and the hollow piston rod having one end. A hollow pump rod that is inserted into the cylinder, has the other end fixed to the cylinder, and internally has a communication passage that communicates the low pressure chamber and the low pressure working fluid chamber; and the hollow piston rod and the hollow pump rod that are opposite to each other. Means for discharging the working fluid in the low-pressure working fluid chamber to the high-pressure working fluid chamber in accordance with a dynamic expansion and contraction operation, and the high-pressure working fluid chamber in response to a decrease in pressure in the high-pressure working fluid chamber. And valve means for reducing or interrupting the flow area between the working fluid chamber, characterized by comprising more.

Further, according to a fourth aspect of the invention, a pair of seal members for sealing between the hollow piston rod and the sliding portion of the cylinder are provided at a sliding portion of the cylinder on which the hollow piston rod slides. A recirculation passage is provided between the pair of sealing members so that the recirculation passage for recirculating the working fluid leaked from the working fluid chamber to the low pressure chamber is opened between the pair of sealing members.

[0013]

According to the first aspect of the present invention, the free piston, which slides in the low pressure chamber in response to the pressure change in the low pressure chamber, slides in the direction in which the low pressure chamber is contracted when a pressure drop occurs in the high pressure working fluid chamber. As a result, it is possible to prevent the driver's vehicle and passengers from feeling uneasy by reducing the vehicle height lowering speed.

According to a second aspect of the present invention, a valve member is provided in the communication passage of the hollow pump rod, and when an extreme pressure drop occurs in the high pressure working fluid chamber, the valve member abuts the free piston and the communication passage. By displacing the pump chamber with the pump chamber, the pump operation is stopped and the pressure in the high-pressure working fluid chamber is prevented from rising excessively.

According to the third aspect of the present invention, the piston and the hollow piston rod are reduced by reducing or blocking the flow passage area between the high pressure working fluid chamber and the working fluid chamber in accordance with the pressure drop of the high pressure working fluid chamber. It becomes difficult for the vehicle to slide, and the speed of lowering the vehicle height is reduced to prevent the driver's vehicle and passengers from feeling uneasy.

According to a fourth aspect of the present invention, a return passage for returning the working fluid leaking from the working fluid chamber to the low pressure chamber between the pair of sealing members for sealing between the hollow piston rod and the sliding portion of the cylinder. With the opening of the seal member, even if the working fluid leaks from the working fluid chamber due to wear of the seal member or the like, the working fluid can be collected in the low pressure chamber. .

[0017]

1 to 3 show a first embodiment of a hydropneumatic cylinder according to the present invention.

In each of the drawings, the hydropneumatic cylinder 1 is incorporated as a shock absorber of a suspension that supports the rear wheels of an automobile, for example.

The hydropneumatic cylinder 1 comprises a cylinder body 2, an internal cylinder 3, a piston 4, a hollow piston rod 5, a hollow pump rod 6, a pump section (pump means) 7, and a communication mechanism 8. Become. The cylinder body 2 functions as an outer cylinder of the hydropneumatic cylinder 1, has a connecting portion 9 connected to a vehicle body (not shown) at the upper end, and a hollow piston rod 5 is slidably guided at the lower end opening. The bearing member 10 is fitted.

The pump portion 7 has a pump chamber 7a in which the working fluid in the low pressure chamber 22 is sucked in the process of moving the piston 4 in the compression direction, as will be described later, and the process of moving the piston 4 in the extending direction. The working fluid sucked into the pump chamber 7a is discharged to the high-pressure working fluid chamber 14 as a high-pressure chamber.

Further, at the lower end opening of the cylinder body 2,
An annular fixing member 11 is fitted to fix the bearing member 10 so as not to fall off. A pair of O-ring grooves 10 are formed on the inner peripheral surface of the bearing member 10 through which the hollow piston rod 5 penetrates.
a and 10b are provided at a predetermined distance. The hollow piston rod 5 is provided in the O-ring grooves 10a and 10b.
O-rings 52a and 52b for inserting a seal between the outer circumferences of the O-rings and the outer periphery of the Therefore, even if the hollow piston rod 5 slides on the bearing member 10 as the piston 4 reciprocates, the double leakage of the O-rings 52a and 52b prevents the working fluid from leaking.

Further, the inside of the cylinder body 2 is divided into a low pressure working fluid chamber 13 and a high pressure working fluid chamber 14 by a cylindrical inner tube 12, and inside the low pressure working fluid chamber 13 and the high pressure working fluid chamber 14. Is filled with a working fluid that generates a resistance force. Moreover, a gap is formed on the entire circumference between the inner tube 12 and the inner cylinder 3, and this gap functions as a passage 40 that connects the high pressure working fluid chamber 14 and the inner cylinder 3 to each other.

As the working fluid, "working oil having viscosity" is generally used, and by selecting working oils having different viscosities, the damping characteristic (the resistance force to the stroke of the piston) is set.

A cylindrical diaphragm 15 is inserted between the inner wall of the cylinder body 2 and the high-pressure working fluid chamber 14, and the diaphragm 15 has upper and lower ends at the inner tube 12 and the bearing member 10. It is locked by.
A high pressure gas chamber 17 is formed between the diaphragm 15 and the inner wall of the cylinder body 2. This high pressure gas chamber 17
Is a high pressure gas such as nitrogen gas (in FIGS. 1 and 2,
(Indicated by pear pattern) is enclosed.

Therefore, the working fluid filled in the high-pressure working fluid chamber 14 is pressurized by the gas pressure in the high-pressure gas chamber 17 via the diaphragm 15. Further, the low-pressure working fluid chamber 13 is not provided with a diaphragm because of the low pressure, but a low-pressure gas chamber 16 filled with a low-pressure gas (shown as a pear pattern in FIGS. 1 and 2) is formed in the upper portion. , The lower part is filled with working fluid.

The inside of the inner cylinder 3 inserted into the cylinder body 2 is a working fluid chamber, and the working fluid chamber is divided into an upper chamber 18 and a lower chamber 19 by a piston 4 slidably fitted therein. Well defined. This upper chamber 18 and lower chamber 1
9 is filled with the working fluid pressurized by the gas pressure of the high-pressure gas chamber 17.

The piston 4 has a lower chamber 1 when it moves downward.
A small hole 4a for guiding the working fluid of No. 9 to the upper chamber 18 and a small hole 4b for guiding the working fluid of the upper chamber 18 to the lower chamber 19 when moving upward are provided. Therefore, when the piston 4 slides in the internal cylinder 3 by the vibration input from the wheel (not shown), the working fluid passes through the small hole 4a or the small hole 4b as the damping force generating portion to generate a resistance force. Let

The piston 4 is provided with a leaf valve 4c on the lower surface side for opening / closing the small hole 4b and a leaf valve 4d on the upper surface side for opening / closing the small hole 4a. Therefore, when the piston 4 slides in the compression direction, the leaf valve 4c on the lower surface side opens, and when the piston 4 slides in the extension direction, the leaf valve 4d on the upper surface side opens.

The hollow piston rod 5 is provided with the piston 4 at the upper end, and the shaft 21a of the connecting portion 21 connected to the supporting arm (not shown) for supporting the wheel is fitted at the lower end opening. Inside the hollow piston rod 5, there is a low pressure chamber 22 penetrating in the axial direction. The low pressure chamber 22 is closed by the shaft 21a of the connecting portion 21,
2 is filled with the working fluid urged by the low pressure gas.

The hollow pump rod 6 has one end inserted into the hollow piston rod 5 and the other end fixed to the inner surface of the upper portion of the cylinder body 2, and the communication passage 2 penetrating therethrough in the axial direction.
Have three. An upper end of the communication passage 23 is connected to a pipe 24 inserted into the low pressure working fluid chamber 13, and a lower end thereof is inserted into the low pressure chamber 22 of the hollow piston rod 5. Therefore, the working fluid in the low pressure working fluid chamber 13 is supplied to the low pressure chamber 22 through the pipe 24 and the communication passage 23.

The pump portion 7 is provided in a pump chamber 7a formed between the hollow pump rod 6 and the hollow piston rod 5. The pump portion 7 includes a pump piston 25 provided at the lower end of the hollow pump rod 6, a suction passage 26 that is formed in the pump piston 25 and connects the low pressure chamber 22 and the pump chamber 7 a, and the operation of the low pressure chamber 22. An inlet valve 27 that opens the suction passage 26 when sucking fluid into the pump chamber 7a, and a discharge passage 29 that is bored in the upper end portion 28 of the hollow piston rod 5 and that connects the pump chamber 7a and the upper chamber 18 of the internal cylinder 3 to each other. And the discharge passage 29 when the working fluid in the pump chamber 7a is discharged to the upper chamber 18 of the internal cylinder 3.
And an outlet valve 30 that opens.

The inlet valve 27 and the outlet valve 30 are adapted to open or close the suction passage 26 and the discharge passage 29 due to the pressure difference generated as the piston 4 reciprocates. Therefore, in the suction stroke in which the piston 4 moves upward (compression direction) and the pump chamber 7a is expanded,
In the discharge stroke in which the inlet valve 27 opens to suck the working fluid in the low pressure chamber 22 into the pump chamber 7a, and the piston 4 moves downward (in the extending direction) to reduce the pump chamber 7a, the outlet valve 30 opens. The working fluid in the pump chamber 7a is discharged to the upper chamber 18 of the internal cylinder 3.

Further, the inlet valve 27 is biased in the valve closing direction by the spring force of the coil spring 33 interposed between the inlet valve 27 and the lower end of the spring receiving member 32 fixed to the hollow pump rod 6. The spring receiving member 32 has a fitting portion 32a that is fitted and fixed in the concave portion of the hollow pump rod 6, and its axial position is regulated.

As shown in FIG. 3, the communication mechanism 8 includes a communication passage 23 of the hollow pump rod 6 and an upper chamber 18 of the internal cylinder 3.
And an opening / closing valve 31 that slides along the hollow pump rod 6 by the expansion operation of the hollow piston rod 5 to open and close the communication hole 6a.

A communication hole 6 formed in the hollow pump rod 6.
As will be described later, a is opened when the piston 4 is displaced in the extending direction (downward) and reaches a predetermined lower limit position so that the communication passage 23 of the hollow pump rod 6 and the upper chamber 18 of the internal cylinder 3 communicate with each other. It is drilled at the position where

That is, when the opening / closing valve 31 moves below the communication hole 6a, the communication hole 6a is fully opened. In this way, by sliding the open / close valve 31 downward, the communication passage 23 of the hollow pump rod 6 and the upper chamber 18 of the internal cylinder 3 are communicated with each other, and the working fluid in the upper chamber 18 of the internal cylinder 3 operates at a low pressure. It is returned to the fluid chamber 13.

Therefore, the communication mechanism 8 has a simple structure including the communication hole 6a and the opening / closing valve 31, and when the load on the wheel is reduced, the communication passage 23 and the upper chamber 18 are connected through the communication hole 6a. And are switched to the communication state, and the vehicle height is adjusted automatically.

The on-off valve 31 is a cylindrical sliding portion 31a which is fitted to the hollow pump rod 6 to open and close the communication hole 6a.
And the collar portion 3 protruding in the radial direction from the lower end of the sliding portion 31a.
It consists of 1b. As will be described later, as the piston 4 moves downward, the upper end portion 28 of the hollow piston rod 5 contacts the upper end of the sliding portion 31a and presses the open / close valve 31 downward.

Normally, the opening / closing valve 31 is held at a position where the communication hole 6a of the hollow pump rod 6 is closed by a coil spring 34 interposed between the opening / closing valve 31 and the upper end of the spring receiving member 32.

The flange 31b and the spring receiving member 32 of the opening / closing valve 31 are provided with a plurality of notches or small holes (not shown). Therefore, the working fluid that has flowed into the pump chamber 7a due to the opening of the inlet valve 27 is
After passing through a notch or a small hole formed in the flange portion 31b and the spring receiving member 32, the outlet valve 30 opens the valve to discharge it to the upper chamber 18 of the inner cylinder 3.

A free piston 41 is slidably inserted in the hollow piston rod 5. That is,
The interior of the hollow piston rod 5 is divided into a low pressure chamber 22 and an atmospheric pressure chamber 42 by a free piston 41.

Air is supplied to the atmospheric pressure chamber 42 through an air introduction hole 43 formed in the lower portion of the hollow piston rod 5. An O-ring 44 that seals between the low pressure chamber 22 and the atmospheric pressure chamber 42 is provided in the groove 41 a formed on the outer circumference of the free piston 41.
The second working fluid is prevented from leaking to the atmospheric pressure chamber 42.

A coil spring 45 for urging the free piston 41 upward (toward the low pressure chamber 22) is interposed in the atmospheric pressure chamber 42. Therefore, the free piston 41 is
The pressure of 2 and the spring force of the coil spring 45 are held in a balanced position. Therefore, as will be described later, when the pressure in the low-pressure chamber 22 decreases, the free piston 41 moves to the coil spring 4
The spring force of 5 moves upward to pressurize the low-pressure chamber 22 so that the pressure does not decrease, and the pressure of the low-pressure chamber 22 operates so as to have a constant value.

Further, at the lower end of the communication passage 23 of the hollow pump rod 6, a valve mechanism 46 that comes into contact with the free piston 41 and switches from the valve closed state to the valve opened state is provided. The valve mechanism 46 is provided in the hollow pump rod 6 and is connected to the communication passage 2
3 communicating with the pump chamber 7a and the communication passage 23
Of a cylindrical spool (valve member) 48 slidably inserted into the lower end opening 23a of the disk, a small hole 49 bored in the spool 47, and the spool 48 and the step portion of the lower end opening 23a. Coil spring 50 for urging the spool 48 downward
And consists.

The upper end of the coil spring 50 is press-fitted into the lower end opening 23a of the communication passage 23, and the lower end thereof is in the spool 48.
Is engaged with the inner circumference of the upper end of the. Therefore, the spool 48 is biased downward by the coil spring 50, and
The communication passage 23 is prevented from falling off the lower end opening 23a.

The spool 48 is a hollow pipe having a passage 48a for communicating the communication passage 23 and the low pressure chamber 22 therein, and is normally slid downward by a coil spring 50 to block the small hole 46. Then, as will be described later, when the pressure in the low-pressure chamber 22 suddenly drops and the free piston 41 abruptly moves upward, the free piston 41 contacts the lower end of the spool 48 and pushes the spool 48 upward.

Therefore, the small hole 49 of the spool 48 is the small hole 4
7 is slid to a position communicating with the communication passage 23 and the pump chamber 7a.
And are switched to the communication state. As a result, it is possible to prevent an excessive increase in the pressure of the high-pressure working fluid chamber 14 due to the stop of the pump operation due to the bouncing / rebound of the running wheel.

The operation of the hydropneumatic cylinder 1 having the above structure will be described below.

For example, when the wheel moves up and down while passing through the unevenness of the road surface, the vibration is transmitted to the hollow piston rod 5 through the connecting portion 21. The piston 4 provided at the upper end of the hollow piston rod 5 reciprocates in the internal cylinder 3 as the wheel moves up and down.

Thus, when the piston 4 moves upward, the working fluid in the upper chamber 18 passes through the small hole 4b of the piston 4 and flows into the lower chamber 19, and when the piston 4 moves downward, the working fluid in the lower chamber 19 moves. Passes through the small holes 4a and flows into the upper chamber 18. At that time, viscous resistance is generated in the small holes 4a and 4b, and this becomes a resistance force that damps the vertical movement of the wheel.

The operation of the piston 4 in accordance with the vertical movement of the wheel depends on the gas pressure of the high pressure gas chamber 17 because the gas pressure of the high pressure gas chamber 17 defined by the diaphragm 15 acts the same as the air spring. Be absorbed.

Next, the vehicle height adjusting operation for keeping the vehicle height constant will be described.

When the piston 4 moves upward (compression direction) as the wheel moves up and down, the pump piston 2 is relatively moved.
5 will move downward in the hollow piston rod 5. The upper chamber 18 and the lower chamber 19 in the internal cylinder 3 are filled with the working fluid pressurized by the gas pressure of the high pressure gas chamber 17, and the low pressure chamber 22 of the hollow piston rod 5 is filled.
Is filled with a working fluid urged by a low pressure gas.

Further, when the piston 4 moves upward and the pump piston 25 relatively moves downward, the volume of the pump chamber 7a is expanded and the volume of the low pressure chamber 22 is reduced. Therefore, the volume of the low pressure chamber 22 decreases, the inlet valve 27 opens, and the working fluid in the low pressure chamber 22 passes through the suction passage 26 of the pump piston 25 and flows into the pump chamber 7a.

Next, when the piston 4 moves downward (extension direction) and the pump piston 25 relatively moves upward, the volume of the pump chamber 7a is reduced and the volume of the low pressure chamber 22 is expanded. Therefore, the volume of the pump chamber 7a decreases, and the outlet valve 30 opens and the inlet valve 27 closes. Therefore, the working fluid in the pump chamber 7a passes through the discharge passage 29 as the volume of the pump chamber 7a decreases, and the working fluid in the upper chamber 18 of the internal cylinder 3
Is discharged.

Since the upper chamber 18 communicates with the high pressure working fluid chamber 14 through the passage 40, when the working fluid in the low pressure chamber 22 is supplied into the internal cylinder 3 by the operation of the pump portion 7, the upper chamber 18 is The working fluid in the high-pressure working fluid chamber 14 increases, and the gas pressure in the high-pressure gas chamber 17 rises. The gas pressure in the high-pressure gas chamber 17 absorbs the shock transmitted from the wheels.

By the way, in the conventional hydropneumatic cylinder described above, when the working fluid bound in the cylinder bounces when the wheel passes through the unevenness of the road surface (the piston moves in the compression direction), it becomes a low pressure due to the pump action. Since the working fluid in the working fluid chamber is pressure-fed to the high-pressure working fluid chamber, the resistance force of the piston sliding operation at the time of bouncing becomes large. Therefore, there is a problem that an upward impact that acts on the wheels from the road surface is transmitted to the vehicle body and the riding comfort deteriorates.

On the other hand, in the above embodiment, as described above, the working fluid in the pump chamber 7a is discharged to the upper chamber 18 in the process of the extension operation in which the piston 4 moves downward.
For example, even when the wheel bounces when the wheel passes through the unevenness of the road surface (the piston moves in the compression direction), the working fluid in the low-pressure working fluid chamber 13 is not pumped to the high-pressure working fluid chamber 14 by the pump action, so the piston at the time of bounding The sliding force does not increase the resistance.

Therefore, since the working fluid in the pump chamber 7a is not discharged to the high-pressure working fluid chamber 14 in the process in which the piston 4 moves in the compression direction as described above, the upward impact that acts on the wheels from the road surface and the load on the vehicle. It is possible to satisfactorily absorb the downward impact exerted on the wheels by the vehicle and improve the riding comfort.

When the number of passengers or the weight of the load increases, the load acting on the connecting portion 9 at the upper end causes the piston 4 to move upward and the pump piston 25 to move relatively downward. Therefore, when the pump operation is repeated, the working fluid in the low pressure chamber 22 is gradually supplied to the upper chamber 18 of the internal cylinder 3, so that the gas pressure in the high pressure gas chamber 17 eventually rises and the vehicle height rises.

When the gas pressure in the high-pressure gas chamber 17 rises or the number of passengers or the weight of the load decreases due to the pump operation, the piston 4 moves downward due to the difference in pressure receiving area between the upper chamber 18 and the lower chamber 19. . Further, when the piston 4 moves downward, as shown in FIG. 4, the upper end portion 28 of the hollow piston rod 5 contacts the on-off valve 31 and slides it downward. Therefore, the on-off valve 31 moves downward along the hollow pump rod 6 to open the communication hole 6a.

Further, when the piston 4 moves downward, the communication hole 6a is located above the piston 4 and opens into the upper chamber 18. Therefore, the working fluid in the upper chamber 18 flows into the communication passage 23 in the hollow pump rod 6 through the communication hole 6a, and the upper chamber 1
The pressure of 8 is reduced.

As described above, the working fluid supplied to the high-pressure working fluid chamber 14 is returned to the low-pressure working fluid chamber 13, the gas pressure in the high-pressure gas chamber 17 decreases, and the vehicle height becomes constant. Therefore, since the vehicle height is adjusted to be constant, it is possible to favorably absorb the upward impact that acts on the wheels from the road surface and the downward impact that the load of the vehicle acts on the wheels, and improve the riding comfort. be able to.

Next, in the hydropneumatic cylinder 1 having the above structure, since the high pressure gas is enclosed in the high pressure chamber 17 created by the diaphragm 15, the high pressure gas and the working fluid in the high pressure working fluid chamber 14 are The diaphragms 15 formed in a shape are sealed so as not to leak from each other. Both ends of the diaphragm 15 are fitted in a groove formed between the high pressure working fluid chamber 14 and the inner wall of the cylinder body 2. However, when the diaphragm 15 is damaged due to aging or an assembly process, the high pressure The working fluid in the working fluid chamber 14 or the high-pressure gas in the high-pressure chamber 17 may leak to the outside.

In that case, a large amount of the working fluid in the low pressure working fluid chamber 13 and the low pressure working fluid chamber 22 is supplied to the high pressure working fluid chamber 14 by the pump operation. For this reason, the pressure in the low pressure chamber 22 is extremely reduced, and the vehicle height is rapidly reduced.

In such a case, as shown in FIG. 5, since the pressure in the low pressure chamber 22 is reduced by the pump operation, the free piston 41 is pushed by the spring 45 and moves upward in accordance with the pressure reduction in the low pressure chamber 22. To do. As a result, the volume of the low pressure chamber 22 is reduced, and the pressure in the low pressure chamber 22 is pressurized by the free piston 41 and maintained at a predetermined pressure determined by the biasing force of the coil spring 45. Therefore, the upward movement of the free piston 41 gradually reduces the pressure in the low-pressure chamber 22, so that it is possible to mitigate the sudden decrease in vehicle height.

When the working fluid is sucked from the low pressure chamber 22 into the pump chamber 7a, the cavitation is likely to occur because the working fluid passes through the suction passage 26 having a small flow passage area and flows into the pump chamber 7a having a large flow passage area. Can be prevented by the pressurizing operation of the free piston 41.

Further, when the pressure in the low pressure chamber 22 decreases,
As shown in FIG. 6, the free piston 41 is attached to the spool 48.
Abut the lower end of. Accordingly, the passage 4 of the spool 48
8a is closed by the free piston 41 and the communication passage 2
3 and the low pressure chamber 22 are shut off. Therefore, since the flow of the working fluid is blocked, the working fluid on the low pressure side is not sent to the high pressure side, and the piston 4 is locked.

Therefore, even if the pressure in the low-pressure chamber 22 is reduced due to the leakage of the high-pressure working fluid chamber 14, the vehicle height is maintained at a predetermined height, and the reduction in vehicle height can be prevented. Further, since the working fluid is prevented from being sucked into the pump chamber 7a by the pump operation, it is possible to prevent the occurrence of cavitation, which is likely to occur when the working fluid is sucked into the pump chamber 7a.

Further, in the state shown in FIG.
And the free piston 41 contact portion, or the spool 48
As shown in FIG. 7, due to the leakage of the working fluid from the contact part between the hollow pump rod 6 and the hollow piston rod 6,
It contacts the lower end of the spool 48 and pushes the spool 48 upward. As a result, the spool 48 slides to a position where the small hole 49 communicates with the small hole 47, and the communication passage 23 and the pump chamber 7
a is switched to a communication state.

Therefore, the piston 4 becomes slidable by communicating with the communication passage 23 and the pump chamber 7a, and the working fluid passes through the small holes 47, 49 having a small opening area, so that the piston 4 slides. The speed is quite slow. Therefore, the piston 4 gradually moves in the compression direction, and the vehicle height lowering speed becomes slower. Therefore, the vehicle height lowering speed is moderated, so that it is possible to prevent the driver and the occupant from feeling uneasy.

Further, the working fluid in the pump chamber 7a is filled with the small holes 4
Since it flows through 7, 49 to the low pressure side, it is possible to prevent the pump operation due to the bouncing / rebound of the running wheel from stopping and the pressure in the high pressure working fluid chamber 14 from rising excessively.

In the first embodiment, the spring 45 for pressing the free piston 41 upward is provided in the atmospheric pressure chamber 42, but the spring 45 is not always necessary. That is, if the atmosphere is introduced into the atmospheric pressure chamber 42, the free piston 4
1 moves to a position where the pressure in the low pressure chamber 22 and the pressure in the atmospheric pressure chamber 42 are balanced.

8 and 9 show a second embodiment of the present invention.

In both figures, in the hydropneumatic cylinder 51, the bearing member 1 through which the hollow piston rod 5 penetrates.
A pair of O-ring grooves 10a, 10 provided on the inner peripheral surface of 0
b. In the O-ring grooves 10a and 10b, the O-ring 5 that seals with the outer circumference of the hollow piston rod 5 is provided.
2a and 52b are inserted. In the present embodiment, the upper O-ring 52a is set to have a small compression allowance so as to withstand a low pressure, and the lower O-ring 5a.
2b has a large compression margin so that it can withstand high pressure.

Therefore, the resistance of the upper O-ring 52a with respect to the hollow piston rod 5 is smaller than usual.
The sliding resistance of the hollow piston rod 5 is reduced accordingly. Also, when the load increases due to an increase in the number of passengers or the load, the pressure of the working fluid applied to the upper O-ring 52a increases, but the pressing force of the O-ring 52a against the hollow piston rod 5 is alleviated by the leakage of the working fluid. The resistance is reduced. Therefore, it is possible to prevent deterioration of riding comfort when the load increases.

An end 53a of a recovery passage 53 for recovering the working fluid leaking from the O-ring 52a is opened between the pair of O-ring grooves 10a and 10b. The recovery passage 53 is formed in an L shape, and the other end 53b is open to the lower surface of the bearing member 10.

Reference numeral 54 denotes a recovery tube, a joint 54a provided at one end is connected to the other end 53b of the recovery passage 53, and a joint 54b provided at the other end is a connection bored on the lower outer circumference of the hollow piston rod 5. It is connected to the mouth 55.

Since the hollow piston rod 5 slides along with the piston 4 in the axial direction, the recovery tube 54 is spirally wound around the outer circumference of the hollow piston rod 5 so as not to hinder the reciprocating motion.

Therefore, when the working fluid leaks from the upper O-ring 52a, the working fluid passes through the recovery passage 53 and the recovery tube 54 and is recovered in the low pressure chamber 22 and is prevented from flowing out.

10 and 11 show a third embodiment of the present invention.

In both figures, the hydropneumatic cylinder 61 is the upper O-ring 52a as in the second embodiment.
Is set to have a small compression margin so that it can withstand a low pressure, and the lower O-ring 52b is set to have a large compression margin so as to withstand a high pressure.

Therefore, the resistance of the upper O-ring 52a with respect to the hollow piston rod 5 is smaller than usual.
The sliding resistance of the hollow piston rod 5 is reduced accordingly. Also, when the load increases due to an increase in the number of passengers or the load, the pressure of the working fluid applied to the upper O-ring 52a increases, but the pressing force of the O-ring 52a against the hollow piston rod 5 is alleviated by the leakage of the working fluid. The resistance is reduced. Therefore, it is possible to prevent deterioration of riding comfort when the load increases.

This hydro-pneumatic cylinder 61
Then, a joint 62a provided at one end of the recovery tube 62
Is connected to the other end 53b of the recovery passage 53, and a joint 62b provided at the other end is connected to a connection port 63 formed on the outer periphery of the upper portion of the cylinder body 2.

Therefore, the recovery tube 62 extends upward along the cylinder body 2 and communicates with the low pressure working fluid chamber 13. When the working fluid leaks in the upper O-ring 52a, the working fluid is prevented from passing through the recovery passage 53 and the recovery tube 62 to be recovered by the low pressure working fluid chamber 13 and flowing out.

12 and 13 show a fourth embodiment of the present invention.

In the figure, in the hydropneumatic cylinder 81, an opening / closing mechanism (valve) is provided in the middle of a passage 82 bent in an inverted U shape from the upper end of the passage 40 formed between the inner tube 12 and the inner cylinder 3. Means) 83 is provided. The relief valve 83 includes a pilot chamber 84 that intersects the passage 82, a spool 85 slidably inserted in the pilot chamber 84, and a coil spring 86 that urges the spool 85 to a valve closed position. A throttle 82a is provided in the middle of the passage 82 for holding the pilot pressure in the pilot chamber 84.

The spool 85 has a large diameter portion 85a that closes the passage 82, a small diameter portion 85b that opens the passage 82, and a pressure receiving portion 85 that receives the pilot pressure introduced from the passage 40.
and c. The pilot chamber 84 communicates with the passage 40 through the small hole 84a, and the high pressure working fluid chamber 14 is always connected.
Is acting on the spool 85.

As shown in FIG. 12, normally, the spool 85
Is the pilot pressure supplied to the pilot chamber 84,
The open valve position, which is slid to the left, is maintained. That is, the spool 85 is in a position where the small diameter portion 85 b opens the passage 82, and the high pressure working fluid chamber 14 is provided via the passage 40 and the passage 82.
And the upper chamber 18 are kept in communication with each other.

As a result, when the above-described pumping operation associated with the reciprocating movement of the piston 4 is performed, the working fluid on the low pressure side passes through the opening / closing mechanism 83 and is supplied to the high pressure working fluid chamber 14.

However, when the diaphragm 15 is damaged and the pressure in the high pressure working fluid chamber 14 is drastically reduced, the pilot pressure is also drastically reduced, so that the spool 85 slides to the right as shown in FIG. . Therefore, the high pressure working fluid chamber 1
When the pressure of No. 4 decreases, the spool 85 causes the coil spring 86 to
It is pushed by and gradually slides to the right, and eventually the large diameter portion 85a
Blocks the passage 82. As a result, the upper chamber 18 and the high-pressure working fluid chamber 14 are disconnected from each other, so that the piston 4 is locked in a non-sliding state.

When the spool 85 slides to the right, the same action and effect can be obtained by configuring the spool 85 so as to reduce the communication area of the passage 82 instead of blocking the passage 82. To be Therefore, the piston 4 and the hollow piston rod 5 are less likely to slide, a sudden decrease in vehicle height can be prevented, and the vehicle height decrease speed can be moderated to prevent the driver's vehicle and passengers from feeling uneasy. .

In the above embodiment, an automobile is taken as an example, but it goes without saying that it can be applied to other vehicles.

[0094]

As described above, according to the first aspect, when the free piston sliding in the low pressure chamber in response to the pressure change in the low pressure chamber causes a pressure drop in the high pressure working fluid chamber, the low pressure chamber is reduced. Since it slides in the direction in which the vehicle height decreases, it is possible to mitigate the vehicle height decrease speed and prevent the driver's vehicle and passengers from feeling uneasy. Further, since the working fluid is prevented from being sucked into the pump chamber by the pump operation, it is possible to prevent the occurrence of cavitation, which is likely to occur when the working fluid is sucked into the pump chamber.

According to the second aspect of the present invention, a valve member is provided in the communication passage of the hollow pump rod, and when an extreme pressure drop occurs in the high pressure working fluid chamber, the valve member abuts the free piston and the communication passage. And the pump chamber are communicated with each other, so that the pump operation can be stopped and the pressure in the high-pressure working fluid chamber can be prevented from rising excessively.

According to the third aspect of the present invention, the piston and the hollow piston rod are provided to reduce or block the flow passage area between the high pressure working fluid chamber and the working fluid chamber according to the pressure drop of the high pressure working fluid chamber. It becomes difficult to slide, and it is possible to mitigate the vehicle height lowering speed and prevent the driver's vehicle and passengers from feeling uneasy.

According to the fourth aspect of the present invention, a return passage for returning the working fluid leaking from the working fluid chamber to the low pressure chamber is provided between the pair of sealing members for sealing between the hollow piston rod and the sliding portion of the cylinder. By opening the valve, even if the working fluid leaks from the working fluid chamber due to wear of the sealing member or the like, the working fluid can be collected in the low pressure chamber. You can

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a first embodiment of a hydropneumatic cylinder according to the present invention.

FIG. 2 is an enlarged vertical sectional view of the inside of the cylinder body.

FIG. 3 is a vertical cross-sectional view showing an enlarged communication mechanism.

FIG. 4 is a vertical cross-sectional view for explaining a sliding operation of a piston.

FIG. 5 is a vertical sectional view for explaining the operation of the free piston.

FIG. 6 is a vertical cross-sectional view for explaining a state where a free piston is in contact with a spool.

FIG. 7 is a vertical cross-sectional view for explaining a state in which a free piston presses a spool to move it upward.

FIG. 8 is a vertical sectional view of a second embodiment of the present invention.

FIG. 9 is an enlarged vertical sectional view showing a main part of the second embodiment.

FIG. 10 is a vertical sectional view of a third embodiment of the present invention.

FIG. 11 is a vertical cross-sectional view showing an enlarged main part of the third embodiment of the present invention.

FIG. 12 is a vertical sectional view of a fourth embodiment of the present invention.

FIG. 13 is a vertical sectional view for explaining the operation of the fourth embodiment.

[Explanation of symbols]

1,51,61,81 Hydropneumatic cylinder 2 Cylinder body 3 Internal cylinder 4 Piston 5 Hollow piston rod 6 Hollow pump rod 7 Pump part 8 Communication mechanism 12 Inner tube 13 Low pressure working fluid chamber 14 High pressure working fluid chamber 15 Diaphragm 16 Low pressure Gas chamber 17 High-pressure gas chamber 18 Upper chamber 19 Lower chamber 22 Low-pressure chamber 23 Communication passage 25 Pump piston 27 Inlet valve 30 Outlet valve 31 Open / close valve 41 Free piston 42 Atmospheric pressure chamber 46 Valve mechanism 48 Spool 53 Recovery passage 54, 62 Recovery tube 83 Opening / closing mechanism 84 Pilot chamber 85 Spool

Claims (4)

[Claims] 1. A cylinder having a working fluid chamber filled with working fluid, a high-pressure working fluid chamber communicating with the working fluid chamber, and a first slidably provided in the working fluid chamber in the cylinder. A hollow piston rod having a low pressure chamber in which a working fluid is filled, a low pressure working fluid chamber communicating with the low pressure chamber, and a hollow piston rod having one end in the hollow piston rod. A hollow pump rod having the other end fixed to the cylinder and having a communication passage therein, which communicates the low pressure chamber and the low pressure working fluid chamber, and the inside of the hollow pump rod with the low pressure chamber and the pump chamber. And a second piston provided at one end of the hollow pump rod and a working fluid in the low pressure working fluid chamber in the process of the piston moving in the compression direction. An inlet valve that opens so as to be sucked into the pump chamber via the communication passage of the hollow piston and the low pressure chamber of the hollow piston rod, and the working fluid sucked into the pump chamber during the movement of the piston in the extending direction. An outlet valve that opens so as to discharge to the high-pressure working fluid chamber, and a free piston that is provided so as to slide in the low-pressure chamber according to a pressure change in the low-pressure chamber. Matic cylinder. 2. When a pressure drop occurs in the high-pressure working fluid chamber, the hollow pump rod is brought into contact with the free piston and displaced to a position where the communication passage communicates with the pump chamber when a pressure drop occurs. 2. The hydropneumatic cylinder according to claim 1, further comprising a valve member. 3. A cylinder having a working fluid chamber filled with working fluid, a high-pressure working fluid chamber communicating with the working fluid chamber, and a piston slidably provided in the working fluid chamber in the cylinder. A hollow piston rod having a low pressure chamber in which the piston is provided at one end and filled with a working fluid, a low pressure working fluid chamber communicating with the low pressure chamber, one end inserted into the hollow piston rod, and the other end Is fixed to the cylinder and has a hollow pump rod internally having a communication passage that communicates the low pressure chamber and the low pressure working fluid chamber, and with the relative expansion and contraction operation of the hollow piston rod and the hollow pump rod. Pump means for discharging the working fluid of the low pressure working fluid chamber to the high pressure working fluid chamber; and the high pressure working fluid chamber and the working fluid chamber in response to a decrease in the pressure of the high pressure working fluid chamber. And valve means for reducing or blocking the passage area between, hydropneumatic cylinder, characterized by comprising more. 4. A pair of seal members, which seal between the hollow piston rod and the sliding portion of the cylinder, are provided at predetermined intervals in a sliding portion of the cylinder along which the hollow piston rod slides. The recirculation passage for recirculating the working fluid leaking from the working fluid chamber to the low pressure chamber is provided between the pair of seal members so as to open.
Hydro-pneumatic cylinder.