JPH08247202A - Hydraulic shock absorber - Google Patents

Abstract

(57) [Summary] (Correction) [Purpose] Even with a short overall length, it is possible to obtain a sufficient expansion / contraction stroke and sufficient bottoming energy. [Structure] The piston 12 is provided with an expansion port communicating with two oil chambers and a pressure port 18, an expansion side leaf valve 19 is openably and closably provided at the outlet end of the expansion port, and a pressure side leaf is provided at the outlet end of the pressure port 18. In the hydraulic shock absorber in which the valve 20 is openable and closable, a pressing member P facing the pressure side leaf valve 20 is movably provided in the hollow housing 21 above the pressure side leaf valve 20, and the piston rod 13 is further provided.
A hollow portion 27 is provided in the lower part of the
Is communicated with the oil chamber 14 opposite to the rod side and the oil chamber 25 in the housing 21, and a poppet type valve 29 urged downward is inserted into the internal passage 28 of the hollow portion 27 so as to be vertically movable. The valve includes a valve body 31 that comes into contact with a valve seat in the middle of the internal passage 28 so as to open and close, and a rod 32 that extends downward.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic shock absorber which is mounted on a vehicle such as a snowmobile or a motorcycle and which damps vibrations on snow and road surfaces.

[0002]

2. Description of the Related Art Generally, in a snowmobile, a hydraulic shock absorber, which also functions as a suspension and a shock absorber, is interposed between a vehicle body and a slide plate to suspend the vehicle body and to dampen an input such as vibration from snow. ing.

Since this hydraulic shock absorber is installed in a short mounting space between the vehicle body and the sliding plate, it is necessary to secure sufficient absorbed energy with a small stroke. Therefore, the hydraulic shock absorber is required to have a high compression side damping force and a high spring force. As a result, it is difficult to obtain a soft riding comfort while securing the bottomed absorbed energy.

The pressure side damping force characteristics required for a hydraulic shock absorber as a countermeasure for this are: (a) low damping force in order to obtain a soft ride comfort from the initial stage to the middle of the compression stroke, and (b) near the end of the stroke. Then, in order to absorb the bottomed energy, it is necessary to have a high damping force, that is, a compression side damping force characteristic having a stroke dependency.

In order to obtain this characteristic, for example, an oil lock structure in a hydraulic shock absorber having a structure shown in FIG. 4 is known.

This hydraulic shock absorber comprises a cylinder 1, a piston rod 3 movably inserted into the cylinder 1 via a piston 2 having a damping force generating mechanism, and a rod partitioned into the cylinder 1 by the piston 2. A side oil chamber 5 and an anti-rod side oil chamber 4, an oil lock piece 6 provided at the lower end of the piston rod 3, and an oil lock groove 7 formed at the bottom of the cylinder 1 and facing the oil lock piece 6. The anti-rod side oil chamber 4 communicates with another tank via a hose 8.

In this hydraulic shock absorber, the damping force mechanism on the expansion side and the compression side provided on the piston 2 generates a damping force during a normal expansion / contraction stroke, and when the compression side stroke reaches near the end, the oil lock piece 4 moves into the oil lock groove. 7 is gradually fitted, a high damping force is generated by the oil lock pressure, and the bottoming energy is absorbed.

[0008]

However, in the hydraulic shock absorber as shown in FIG. 4, since the oil lock piece 6 is long, the stroke is reduced by the length in the axial direction. This is because, for example, the installation length between the snowmobile body and the sliding plate is fixed, and since the space is small, when installing a hydraulic shock absorber of a short length regulated by this installation length, a long oil Lock piece 6
This is because the normal expansion / contraction stroke is limited by that amount.

SUMMARY OF THE INVENTION An object of the present invention is to provide a hydraulic shock absorber which can have a sufficient expansion / contraction stroke and a sufficient bottoming energy even if its total length is short.

[0010]

In order to achieve the above object, the structure of the present invention is such that a piston rod is movably inserted into a cylinder via a piston, and the piston is opposed to the rod side oil chamber in the cylinder. It divides the rod side oil chamber, the piston is provided with an extension port and a pressure port that connect the two oil chambers, an extension side leaf valve is provided at the outlet end of the extension port to be openable and closable, and an outlet end of the pressure port is provided. In a hydraulic shock absorber in which a pressure side leaf valve is openable and closable, a hollow housing is provided above the pressure side leaf valve, a pressing member facing the pressure side leaf valve is movably provided in the housing, and a piston rod A hollow portion is provided in the lower portion of the hollow portion, the internal passage of the hollow portion communicates with the anti-rod side chamber and the oil chamber in the housing, and the poppet-type valve urged downward in the internal passage of the hollow portion. Vertically movably is inserted, the poppet valve is characterized in that it comprises a rod extending abutting the valve body and the lower openably to said internal passage way of the valve seat.

In this case, the oil chamber in the housing communicates with the rod-side oil chamber via the orifice provided in the housing,
The poppet type valve is preferably urged downward by a spring interposed between the valve body and the upper wall of the internal passage. Further, it is preferable that the pressing member is composed of a washer that comes into contact with the pressure side leaf valve and a plunger that comes into contact with the washer and is vertically inserted into a guide hole of the housing.

[0012]

In the normal expansion and contraction stroke, the expansion side leaf valve and the compression side leaf valve provided on the piston generate a damping force. When the compression stroke reaches near the end, the rod hits the bottom of the cylinder and retracts against the spring into the internal passage of the hollow. Therefore, the pressure oil on the side opposite to the rod acts on the pressing member via the internal passage, and the pressing member presses the pressure side leaf valve in the closing direction. Therefore, the rigidity of the pressure side leaf valve becomes high, the pressure side leaf valve is bent from the non-rod side oil chamber to throttle the oil flowing to the rod side oil chamber, and the pressure side damping force is increased accordingly and absorbs the bottomed energy.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to FIGS.

The hydraulic shock absorber comprises a cylinder 11, a piston rod 13 movably inserted into the cylinder 11 via a piston 12, a rod side oil chamber 15 defined by the piston 12 in the cylinder 11, and an opposite rod side. It is composed of an oil chamber 14 and a tank 17 that communicates with the oil chamber 14 on the side opposite to the rod via a hose 16.

The piston 12 is formed with an expansion port and a pressure port 18 for communicating the two oil chambers 14 and 15, and an expansion side leaf valve 19 is provided at the outlet end of the expansion port so as to be openable and closable. A pressure side leaf valve 20 is openably and closably provided at the outlet end.

A hollow housing 21 connected to the piston rod 13 is disposed above the pressure side leaf valve 20, and a vertical guide hole 22 is provided in the housing 21.
A plunger 23 is inserted through the so as to be vertically movable. The lower end of the plunger 23 may directly contact the upper surface of the pressure side leaf valve 20, or may contact the upper surface of the pressure side leaf valve 20 through the washer 24. The plunger 23 and the washer 24 form a pressing member P.

An oil chamber 25 defined by the outer wall of the housing 21 and the pressing member P is provided in the housing 21, and the oil chamber 25 communicates with the rod-side oil chamber 15 through the orifice 26 or the outer peripheral gap of the plunger 23. I am letting you.

A hollow portion 27 is provided in the lower portion of the piston rod 13, and a through hole 33 at the lower end, a central internal passage 28, and an upper through hole 34 are formed in the hollow portion 27.
Reference numeral 8 communicates with the oil chamber 14 opposite to the rod side through the through hole 33, and communicates with the oil chamber 25 inside the housing 21 through the through hole 34. A poppet type valve 29 biased downward is inserted in the internal passage 28 so as to be vertically movable.

The poppet type valve 29 includes a poppet type valve body 31 that comes into contact with a valve seat in the middle thereof, for example, a valve seat formed at the upper end of the through hole 33 so as to be openable and closable, and a rod 32 extending below the through hole 33. It is composed of.

A spring 30 is interposed between the valve body 31 and the upper wall of the internal passage 28. Normally, the spring 30 is provided.
Presses the valve element 31 against the valve seat to close the through hole 33. When the rod 32 is pushed upward as described later, the valve body 31 opens the through hole 33 against the spring 30. In a normal expansion / contraction operation, the poppet type valve 29 is pushed by the spring 30 and closed. At this time, for example, at the time of extension, the oil in the rod side oil chamber 15 opens the extension side leaf valve 19 through the extension port and flows out to the opposite rod side oil chamber 14, and the extension side leaf valve 19 generates an extension side damping force. . At the time of compression, the oil in the non-rod side oil chamber 14 flows out to the rod side oil chamber 15 via the pressure port 18 and the pressure side leaf valve 20, and a pressure side damping force is generated via the pressure side leaf valve 20.
(FIG. 2) On the other hand, as shown in FIG. 3, when the compression stroke is made up to the most compression, that is, near the bottom, the rod 32 comes into contact with the bottom of the cylinder 11, for example, the upper surface of the projection 35 standing at the center of the bottom, and the poppet. The mold valve 29 rises against the spring 30, and at this time, the valve body 31 opens the through hole 33, and the oil in the non-rod side oil chamber 14 passes through the hole 33-internal passage 28-through hole 34.
Is led to the oil chamber 25 in the housing 21 via the, and further flows to the rod side oil chamber 15 via the orifice 26. At this time, a differential pressure of the pressure oil flowing through the orifice 26 is generated, and the pressure oil acts on the plunger 23. Therefore, the plunger 23
The washer 24 descends and presses the pressure-side leaf valve 20 in the closing direction, so that the rigidity of the pressure-side leaf valve 20 increases, and as a result, flows from the non-rod side oil chamber 14 to the rod side oil chamber 15 via the pressure port 18. The amount of oil is reduced, the damping force on the compression side is increased, and the bottoming energy is absorbed. That is, a cushion that prevents bottoming is applied. At this time, the compression side damping force is the outer diameter of the washer 24, the number of plungers 23,
The size of the orifice 26 can be adjusted. The compression stroke can be adjusted by the length of the rod 32.

[0021]

The present invention has the following effects.

Since the pressing member facing the pressure side leaf valve, the passage for introducing the pressure oil to the pressing member, and the poppet type valve which opens and closes the passage and opens near the bottom are provided, the extension provided on the piston in the normal expansion and contraction operation. The expansion side damping force is generated by the side leaf valve, and the compression side damping force is generated by the compression side leaf valve.However, when the compression stroke reaches the point of maximum compression, the rod hits the bottom of the cylinder and opens the poppet valve, so The pressure acts on the pressing member, and this pressing member urges the pressing side leaf valve in the closing direction, and as a result, a high damping force is generated by the pressing side leaf valve, and it is possible to absorb the bottomed energy and make the cushion work. .

Since the rod retreats upward near the time of maximum compression, a large compression stroke can be obtained, and as a result, a sufficient stroke can be taken even if the basic length is short.

[Brief description of drawings]

FIG. 1 is a partially cutaway vertical front view of a hydraulic shock absorber according to an embodiment of the present invention.

FIG. 2 is a partially enlarged sectional view of FIG. 1 showing an operating state of a valve at a normal stroke.

FIG. 3 is a partially enlarged sectional view of FIG. 1 showing an operating state of the valve near the time of maximum compression.

FIG. 4 is a sectional view of a conventional hydraulic shock absorber.

[Explanation of symbols]

 11 Cylinder 12 Piston 13 Piston Rod 14 Anti-Rod Side Oil Chamber 15 Rod Side Oil Chamber 18 Pressure Port 19 Expansion Side Leaf Valve 20 Pressure Side Leaf Valve 21 Housing 22 Guide Hole 23 Plunger 24 Washer 25 Oil Chamber in Housing 26 Orifice 27 Hollow Part 28 internal passage 29 poppet type valve 30 spring 31 valve body 32 rod P pressing member

Claims (3)

[Claims] 1. A piston rod is movably inserted into a cylinder via a piston, the piston defines a rod-side oil chamber and a non-rod-side oil chamber in the cylinder, and two oil chambers communicate with the piston. The expansion port and the pressure port are provided, and the expansion side leaf valve is provided at the outlet end of the expansion port so that it can be opened and closed.
In the hydraulic shock absorber in which the pressure side leaf valve is openable and closable at the outlet end of the pressure port, a hollow housing is provided above the pressure side leaf valve, and a pressing member facing the pressure side leaf valve is moved inside the housing. The piston rod is provided with a hollow portion under the hollow portion, the inner passage of the hollow portion communicates with the anti-rod side chamber and the oil chamber in the housing, and is urged downward in the inner passage of the hollow portion. A hydraulic shock absorber, wherein a poppet-type valve is vertically movably inserted, and the poppet-type valve includes a valve body that opens and closes a valve seat in the middle of the internal passage and a rod that extends downward. . 2. The oil chamber in the housing communicates with the rod-side oil chamber via an orifice provided in the housing, and the poppet-type valve is a spring interposed between the valve body and the upper wall of the internal passage. 2. The hydraulic shock absorber according to claim 1, wherein the hydraulic shock absorber is urged to. 3. The hydraulic shock absorber according to claim 1, wherein the pressing member includes a washer that abuts against the pressure side leaf valve, and a plunger that abuts against the washer and is vertically movable into a guide hole of the housing.