JP2000185537A - Cylinder device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a vehicle height to be lowered as necessary in a self-leveling type hydraulic shock absorber. SOLUTION: A piston 6, to which a piston rod 7 is connected, is fitted together with a cylinder 2 to achieve an intended configuration. A pump rod 14, secured on the cylinder 2 side, is fitted into a pump tube 11 secured to the piston rod 7 end to form a pump chamber 15. As the piston rod 7 extends or contracts, the pump chamber 15 is enlarged or reduced. This results in a hydraulic fluid being supplied from a main oil tank 4 to the cylinder 2. The hydraulic fluid is also returned from the cylinder 2 back to the main oil tank 4 through an orifice passageway 20, thereby keeping the extended length of the piston rod 7 (vehicle height) at a constant level. A selector valve 22 is selected to shut down a reservoir 3 from the cylinder 2, allowing the hydraulic fluid to be discharged from the cylinder 2 to a low-pressure tank 5, thereby decreasing the vehicle height. The hydraulic fluid is supplied from the low- pressure oil tank 5 to the pump chamber 15 by means of a pilot type open/close valve 28 until a pressure in the low-pressure oil tank 5 becomes lower than a predetermined level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder device such as a hydraulic shock absorber having a vehicle height adjusting function mounted on a suspension device of a vehicle such as an automobile.

[0002]

2. Description of the Related Art Generally, in a vehicle such as an automobile, a hydraulic shock absorber (cylinder device) is provided between a sprung portion and a unsprung portion of a suspension device.
Is mounted to attenuate sprung and unsprung vibrations to improve ride comfort and steering stability.

[0003] Meanwhile, in a vehicle having a relatively large loading weight such as a van or a wagon, a change in the loading load caused by the occupant getting on and off, loading and unloading of the luggage causes a great change in the vehicle height, and the riding comfort and steering stability. Performance may be reduced. Therefore, there is a demand for a suspension device that can automatically maintain a constant vehicle height regardless of the magnitude of the loaded load.

Therefore, conventionally, for example, Japanese Patent Application Laid-Open No. 60-261
No. 713, an oil tank and a reservoir filled with a high-pressure gas, a pump means for supplying the oil liquid in the oil tank into the cylinder by expansion and contraction of a piston rod, and an expansion and contraction position of the piston rod. Pump means and return means for returning pressurized oil from the cylinder to the oil tank. The pump means and return means are operated by utilizing the vibration of the suspension device during running to appropriately adjust the pressure in the cylinder to thereby adjust the piston rod. There has been proposed a so-called self-leveling type hydraulic shock absorber in which a constant vehicle height is automatically maintained by adjusting the extension length of the self-leveling.

[0005]

The so-called R
Vehicles with relatively high vehicle heights such as V (recreational vehicles) have inconveniences that they may not be able to get into and out of places with height restrictions, such as tower parking, in addition to poor ingress and egress. There is a requirement to be able to lower. However, in the above-described conventional self-leveling type hydraulic shock absorber, the adjusted vehicle height cannot be reduced as necessary.

[0006] The present invention has been made in view of the above points, and has as its object to provide a self-leveling type cylinder device capable of appropriately reducing the vehicle height.

[0007]

In order to solve the above-mentioned problems, the invention according to claim 1 comprises a cylinder filled with an oil liquid, a piston slidably fitted in the cylinder,
A piston rod having one end connected to the piston and the other end extending to the outside of the cylinder, a main oil tank for storing an oil liquid, and an oil liquid from the main oil tank to the cylinder due to expansion and contraction of the piston rod. Pump means for supplying, and return means for returning the oil liquid from the cylinder to the main oil tank according to the extension length of the piston rod, between the cylinder and the main oil tank by expansion and contraction of the piston rod. A cylinder device configured to supply and discharge an oil liquid so as to adjust the extension length of the piston rod to be constant, wherein a low-pressure oil tank that stores an oil liquid having a pressure lower than that of the main oil tank; and First valve means for selectively communicating with and shutting off the cylinder;
When the pressure of the low-pressure oil tank is less than a predetermined pressure, supply an oil liquid from the main oil tank to the pump means,
When the pressure of the low-pressure oil tank is equal to or higher than a predetermined pressure, a second valve means for supplying an oil liquid from the low-pressure oil tank to the pump means is provided.

[0008] With this configuration, the pump means is operated by expansion and contraction of the piston rod due to periodic vibration during running of the vehicle to supply oil liquid from the main oil tank to the cylinder, thereby extending the piston rod. Further, the extension length of the piston rod is adjusted to be constant by returning the oil liquid from the cylinder to the main oil tank by the return means to shorten the piston rod. The piston rod is shortened by connecting the cylinder to the low-pressure tank by the first valve means and introducing the oil liquid of the cylinder to the low-pressure tank. When the oil liquid is introduced from the cylinder and the pressure in the low-pressure oil tank is equal to or higher than a predetermined pressure, the oil liquid is supplied from the low-pressure oil tank to the cylinder via the second valve means by the operation of the pump means, and the low-pressure oil tank Is less than the predetermined pressure, the pumping means supplies the oil liquid from the main oil tank to the cylinder via the second valve means.

According to a second aspect of the present invention, in the configuration of the first aspect, the first valve means shuts off the cylinder and the reservoir when the low-pressure oil tank communicates with the cylinder. When the low-pressure oil tank and the cylinder are shut off, the cylinder and the reservoir are communicated with each other.

[0010] With this configuration, when the oil is discharged from the cylinder to the low-pressure oil tank, the cylinder is shut off from the reservoir, so that the oil can be quickly discharged from the cylinder.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings. As shown in FIG. 1, the hydraulic shock absorber 1 (cylinder device) includes a cylinder 2 and a cylinder 2
And a main oil tank 4 disposed below the cylinder 2.
A low-pressure oil tank 5 is provided separately from these components. The cylinder 4 is filled with an oil liquid, and the reservoir 3 and the main oil tank 4 are filled with an oil liquid and a high-pressure gas (usually 20 to 30).
kgf / cm ² or so) it is sealed, and the low pressure oil tank, hydraulic fluid and a low pressure gas (usually about 1 kgf / cm ²⁾
Is enclosed.

A piston 6 is slidably fitted in the cylinder 2.
The inside is defined as two chambers, a cylinder upper chamber 2a and a cylinder lower chamber 2b. One end of a hollow piston rod 7 is connected to the piston 6, and the other end of the piston rod 7 is inserted through an oil seal 8 attached to the upper end of the cylinder 2 and extends outside the cylinder 2. ing. The piston 6 has an oil passage 9 for communicating between the cylinder upper and lower chambers 2a and 2b, and a damping force generating mechanism 10 including an orifice and a disk valve for controlling the flow of the oil flowing through the oil passage 9 to generate a damping force. Is provided.

A small diameter portion 11a is provided inside the piston rod 7.
A stepped pump tube 11 having a large diameter portion 11b and an annular oil passage 12 is formed around the pump tube 11. The annular oil passage 12 communicates with the cylinder upper chamber 2a by an oil passage 13 provided on a side wall of the piston rod 7.

A tubular pump rod 14 is provided in the cylinder 2 along the center axis thereof. Pump rod 14
Has its base end connected to the bottom of the cylinder 2,
The distal end portion penetrates the piston 6 and is inserted into the large-diameter portion 11b of the pump tube 11 inside the piston rod 7 to form a small-diameter portion.
It is slidably fitted in 11a. A pump chamber 15 (pump means) is formed in the small diameter portion 11a by the tip of the pump rod 14.

The pump chamber 15 is connected to an oil passage 17 in the pump rod 14 through a check valve 16 provided at the tip of the pump rod 14.
The check valve 16 is connected to the pump chamber from the oil passage 17 side.
Only the flow of the oil liquid to the 15 side is allowed. Further, the pump chamber 15 is communicated with the annular oil passage 12 via a check valve 18 provided at the distal end of the small diameter portion 11a of the pump tube 11,
The check valve 18 allows only the flow of the oil liquid from the pump chamber 15 side to the annular oil passage 12 side.

A groove 19 is formed in the side surface of the pump rod 14 so as to extend from the tip to a predetermined portion along the axial direction. An orifice passage 20 (return means) is provided on a side wall of the pump rod 14. Orifice passage
The reference numeral 20 is disposed at a position on the distal end side of the pump rod 14 with respect to the end of the groove 19 (the lower end in the figure). When the extension length of the piston rod 7 reaches a predetermined standard range,
When the groove 19 communicates with the large diameter portion 11b of the pump tube 11, and exceeds a predetermined standard range, the orifice passage 20 communicates with the large diameter portion 11b.

The cylinder lower chamber 2b is connected to a switching valve by an oil passage 21.
Port 1 of 22 (3 port 2 position switching valve; 1st valve means)
The other two ports of the switching valve 22 are connected to the reservoir 3 and the low-pressure oil tank 5 via oil passages 23 and 24, respectively. Orifice in oilway 23
23A is provided. The switching valve 22 includes an oil passage 21 and an oil passage 23,
An electromagnetic switching valve for selectively switching the connection with the oil passage 24, wherein the oil passage 21 and the oil passage 23 are connected when not energized, and the oil passage 21 is connected to the oil passage 24 when energized. In addition,
The switching valve 22 can be energized by, for example, a switch provided in a vehicle interior or the like or a switch linked to opening and closing of a back door of a luggage compartment.

The oil passage 17 of the pump rod 14 is connected to the low-pressure oil tank 5 via a check valve 26 by an oil passage 25. The check valve 26 allows only the flow of the oil liquid from the low pressure oil tank 5 side of the oil passage 25 to the oil passage 17 side. The oil passage 17 is provided with an on-off valve 28 (second valve means) by an oil passage 27.
Is connected to the main oil tank 4. On-off valve 28
Is a pilot-type opening / closing valve that uses the pressure of the low-pressure oil tank 5 as a pilot pressure. When the pressure of the low-pressure oil tank 5 is lower than a predetermined pressure, the valve is opened to connect the oil passage 27 and the pressure of the low-pressure oil tank 5 is reduced. When the pressure is equal to or higher than a predetermined pressure, the oil passage 27 is shut off.

Next, the operation of the embodiment constructed as described above will be described. The hydraulic shock absorber 1 is mounted between a sprung portion and a unsprung portion of a vehicle suspension system, similarly to a normal hydraulic shock absorber. Normally, as shown in FIG.
Is in a non-energized state, and makes the oil passage 21 and the oil passage 23 communicate with each other. The pressure of the low-pressure oil tank 5 is 1 kgf / cm
^{About 2} and the closing pressure of the on-off valve 28 (pilot pressure)
Therefore, the on-off valve communicates the oil passage 27.

The hydraulic shock absorber 1 moves the piston 6 in accordance with the expansion and contraction of the piston rod 7 to move the cylinder upper and lower chambers.
The oil liquid flows through the oil passage 9 between 2b and 2b, and the damping force generating mechanism 10 generates a damping force. At this time, the piston rod 7
When the volume of the cylinder upper and lower chambers 2b and 2b changes due to intrusion and retraction of the cylinder 2 due to the expansion and contraction of the cylinder,
An oil passage 21, a switching valve 22, and an oil passage between the reservoir 2b and the reservoir 3;
The oil is supplied and received by the orifice 23A through the orifice 23A, and the gas in the reservoir 3 is compensated by being compressed and expanded.

Next, the automatic height adjustment function of the hydraulic shock absorber 1 will be described. When the vehicle is empty, the extension length of the piston rod 7 is within a predetermined standard range.
The groove 19 of the pump rod 14 is the large diameter portion 11b of the pump tube 11.
The pump chamber 15 communicates with the lower cylinder chamber 2b via the groove 19 and the large diameter portion 11b, so that the pumping operation is not performed even if the piston rod 7 expands and contracts.

When the vehicle height decreases due to an increase in the loading load or the like and the extension length of the piston rod 7 becomes shorter than the standard range, the groove 19 of the pump rod 14 is formed by the small diameter portion 11a of the pump tube 11 into the large diameter portion 11b. Be cut off from. In this state, when the piston rod 7 expands and contracts due to the periodic vibration of the suspension during traveling, during the extension stroke, the inside of the pump chamber 15 is depressurized by the retraction of the pump rod 14, and the check valve
16 is opened, the oil in the main oil tank 4 is filled with oil passage 27,
It is introduced into the pump chamber 15 through 28 and the oil passage 17. During the contraction stroke, the inside of the pump chamber 15 is pressurized by the advance of the pump rod 14, the check valve 18 opens, and the pump chamber
The oil liquid in 15 is supplied to the cylinder upper chamber 2a through the annular oil passage 12 and the oil passage 13. At this time, since the pressure of the low-pressure oil tank 5 is sufficiently lower than the pressure of the main oil tank 4,
The oil liquid is not supplied from the low-pressure oil tank 5 to the pump chamber 15.

In this manner, the pumping operation is repeated by the expansion and contraction of the piston rod 7 during traveling, and the oil liquid is supplied from the main oil tank 4 to the cylinder upper and lower chambers 2b, 2b, thereby extending the piston rod 7. Raise the vehicle height. When the extension length of the piston rod 7 reaches the standard range, the groove 19 of the pump rod 14 is
Even if the piston rod 7 expands and contracts by communicating with the large diameter portion 11b, the pump chamber 15 and the cylinder upper and lower chambers 2b, 2b have substantially the same pressure, and the pumping operation is released. Thereby, the extension length of the piston rod 7 can be adjusted within the standard range, and the vehicle height can be adjusted to a constant value.

On the other hand, when the vehicle height rises due to the decrease in the load and the extension length of the piston rod 7 exceeds the standard range, the orifice passage 20 of the pump rod 14 communicates with the large diameter portion 11b of the pump tube 11. Therefore, the oil liquid in the cylinder lower chamber 2b flows into the large diameter portion 11b, the orifice passage 20, the oil passage 17, the oil passage
It is returned to the main oil tank 4 through 27 and the on-off valve 28,
The piston rod 7 is shortened and the vehicle height is reduced. When the piston rod 7 is shortened to the standard range, the orifice passage 20
Is closed by the small diameter portion 11a of the pump tube 11, and the returning operation of the oil liquid from the cylinder lower chamber 2b to the main oil tank 4 is released. Thereby, the extension length of the piston rod 7 can be adjusted within the standard range, and the vehicle height can be adjusted to a constant value. At this time, the check valve 26 closes and the oil passage 25
Is closed, the oil liquid does not return from the cylinder 2 to the low-pressure oil tank 5.

In this manner, the pumping operation and the returning operation are repeated by using the periodic vibration of the suspension during traveling, so that the extension length of the piston rod 7 can be adjusted to the standard range, and The vehicle height can be constantly adjusted regardless of the load.

Next, a description will be given of a case where the vehicle height is reduced while the vehicle is stopped as required. Electricity is supplied by a switch provided in a vehicle interior or the like or a switch linked to opening and closing of a back door of a luggage compartment, and as shown in FIG. Connect to 24. As a result, the cylinder 2 is shut off from the reservoir 3, and the oil liquid in the cylinder 2 flows to the low-pressure oil tank 5 through the oil passage 21, the switching valve 22, and the oil passage 24, and the piston rod 7 is shortened to increase the vehicle height. Go down. At this time, the cylinder 2 is
Therefore, the oil liquid in the cylinder 2 can be directly discharged to the low-pressure oil tank 5 without expanding the gas in the reservoir 3, and the vehicle height can be rapidly reduced.

As described above, by lowering the vehicle height, it is possible to improve the getting on and off of the vehicle, and it is easy to enter a place having a height restriction such as a tower parking lot. Performance can be improved.

In this case, for example, the normal pressure in the cylinder 2 is 20 kgf / cm ² , the sectional area of the piston rod 7 is 3.8 cm ² ,
The spring constant of the suspension spring is 1.8 kgf / mm, and the cylinder 2 is connected to the low-pressure oil tank 5 to reduce the pressure to 20 kgf / cm.
^{When the} pressure is reduced from ² to 2 kgf / cm ² , the piston rod 7
Is reduced by (20-2) × 3.8 = 68.4 (kgf), and the compression of the suspension spring, that is, the decrease in vehicle height is 68.4 ÷ 1.8 = 38 (mm) ). The gas capacity of the low-pressure oil tank 5 may be about twice as large as the product of the decrease in vehicle height and the cross-sectional area of the piston rod.

To release the function of lowering the vehicle height, the switching valve
The power supply to the oil passage 22 is stopped, and the oil passage 21 is cut off from the oil passage 24 to communicate with the oil passage 23. At this time, the low-pressure oil tank 5
The oil liquid in the cylinder 2 is introduced, and the pressure is adjusted by the on-off valve 28.
, The on-off valve 28 is closed and the oil passage 27 is shut off. When the vehicle travels in this state, the hydraulic fluid in the low-pressure oil tank 5 is first supplied to the cylinder 2 through the oil passage 25 by opening the check valve 26 by the pumping action due to the periodic expansion and contraction of the piston rod 7. Then, the oil liquid is transferred from the low pressure oil tank 5 to the cylinder 2
When the pressure of the low-pressure oil tank 5 is sufficiently reduced, the on-off valve 28 is opened. Thereafter, the oil liquid is supplied from the main oil tank 4 to the cylinder 2 as described above. In this way, the pressure in the low-pressure oil tank 5 can be kept low at all times, and the vehicle height can be quickly reduced as needed.

In the above-described embodiment, the switching valve 22 is a switching valve for switching the connection between the oil passage 21 and the oil passages 23 and 24. An on-off valve that communicates with and shuts off the passage 24 can also be used. Also, the case where the present invention is applied to a hydraulic shock absorber having a damping force adjusting mechanism has been described, but the present invention is not limited to this, and the damping force adjusting mechanism is omitted and used together with a normal hydraulic shock absorber. It can also be a vehicle height adjustment unit.

[0031]

As described above in detail, according to the first aspect of the present invention, a low pressure oil tank and first and second valve means are provided in a cylinder device having a self-leveling mechanism, so that a piston rod during traveling can be provided. The extension length of the piston rod can be adjusted by the expansion and contraction of the piston rod. By connecting the cylinder to the low-pressure tank by the first valve means, the piston rod can be shortened and the vehicle height can be appropriately reduced.

Further, according to a second aspect of the present invention, in addition to the configuration of the first aspect, when the first valve means communicates the low-pressure oil tank with the cylinder, the first valve means shuts off the cylinder and the reservoir, and the low-pressure oil When the tank and the cylinder are shut off, the cylinder and the reservoir communicate with each other, so that when the oil is discharged from the cylinder to the low-pressure oil tank, the cylinder is shut off from the reservoir. Can be discharged.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a normal state of a cylinder device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a state in which the vehicle height is reduced in the device of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydraulic shock absorber (cylinder device) 2 Cylinder 4 Main oil tank 5 Low-pressure oil tank 6 Piston 7 Piston rod 15 Pump chamber (Pump means) 20 Orifice passage (Return means) 22 Switching valve (First valve means) 28 On-off valve ( Second valve means)

Claims (2)

[Claims] 1. A cylinder filled with oil, a piston slidably fitted in the cylinder, and a piston rod having one end connected to the piston and the other end extending out of the cylinder. And a main oil tank for storing oil liquid,
Pump means for supplying an oil liquid from the main oil tank to the cylinder by expansion and contraction of the piston rod, and return means for returning the oil liquid from the cylinder to the main oil tank according to the extension length of the piston rod, A cylinder device configured to supply and discharge an oil liquid between the cylinder and the main oil tank by expansion and contraction of the piston rod to adjust the extension length of the piston rod to be constant. A low-pressure oil tank for storing a low-pressure oil liquid; first valve means for selectively communicating and shutting off the low-pressure oil tank with the cylinder; and a main oil when the pressure of the low-pressure oil tank is lower than a predetermined pressure. An oil liquid is supplied from the tank to the pump means, and when the pressure in the low-pressure oil tank is equal to or higher than a predetermined pressure, the low-pressure oil tank A second valve means for supplying oil to the pump means. 2. The first valve means shuts off the cylinder and the reservoir when the low-pressure oil tank communicates with the cylinder, and shuts off the low-pressure oil tank and the cylinder when the low-pressure oil tank communicates with the cylinder. The cylinder device according to claim 1, wherein the cylinder and the reservoir are communicated with each other.