JP2815863B2 - Hydraulic shock absorber - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic shock absorber, and more particularly to a hydraulic shock absorber whose damping force characteristic changes according to the magnitude of a load applied. Things.

[Prior Art] Generally used for vehicles having a large load change such as buses and trucks, or vehicles having a large load change applied from the outside during running such as off-road vehicles including two-wheeled vehicles and four-wheeled vehicles. Such a hydraulic shock absorber is required to have a characteristic in which the damping force changes according to the magnitude of the load.

In such a damping force characteristic, a progressive characteristic in which the damping force continuously increases gradually as the load increases is ideal, but if this characteristic is provided in the hydraulic shock absorber, the hydraulic shock absorber is Its structure becomes very complicated and costly.

Therefore, in general, the hydraulic shock absorber is often configured so that the damping force changes stepwise.

Conventionally, various types of hydraulic shock absorbers of this type have been considered, and one of them is a hydraulic shock absorber of a variable throttle number as shown in FIG.

As is clear from FIG. 7, this hydraulic shock absorber includes an outer cylinder 01 and an inner cylinder 02 which are arranged concentrically with each other, and a piston 03 slidably received in the inner cylinder 02. Inner cylinder 02
, An appropriate number of orifices 04, 04,... Are formed in the axial direction corresponding to the position of the piston 03 which moves with an increase in load. In such a hydraulic shock absorber, a piston
Since the number of orifices 04, 04,... Decreases with the movement of 03 and the flow path resistance increases, the damping force increases stepwise.

[Problems to be Solved by the Invention] However, in such a structure that generates the damping force of the hydraulic shock absorber, the orifices 04, 04,. Since it is made to flow between the space between the outer cylinder 01 and the inner cylinder 02, the hydraulic shock absorber to which this structure can be applied is a multi-cylinder hydraulic hydraulic system comprising the outer cylinder 01 and the inner cylinder 02. It cannot be applied to anything other than a shock absorber.

In Japanese Patent Publication No. 39-5358, an orifice passage 10 is provided in a piston rod 6, and a switching valve 16 for opening and closing an orifice 11 on the outer periphery of the piston rod and a guide member 20 above the switching valve 16 are slidably movable. When the switching valve 16 is pressed by the guide member 20, the orifice 11 is opened and closed to change the damping force.
Since it changes only in stages, it is not possible to respond finely according to the load, and since the amount of change is large, there is a drawback that the ride feeling and steering stability are deteriorated, and the guide member 20 However, the switching valve 16 also tilts due to the inclination of the guide member 20, causing the switching valve 16 to incline with the piston rod 6, thereby causing a malfunction. Further, the orifice passage 10 is connected to the piston rod 6. In this case, there is a disadvantage that a throttle passage for manually adjusting the damping force cannot be provided.

The present invention solves the above-described problem, and can be applied to a single-cylinder and a double-cylinder hydraulic shock absorber, and can change a damping force minutely and finely according to a load. The purpose is to provide.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention relates to a cylinder 1 filled with oil and a cylinder 1 penetrating through a fixed wall 15 fixed to an upper edge of the cylinder 1. And a first piston 2 fixed to the lower end of the piston rod 5 and slidably accommodated in the cylinder 1 to partition the cylinder 1 into upper and lower oil chambers 3 and 4. A damping valve 26 for generating a damping force in any flow direction of the oil in a passage 25 in the first piston 2 communicating the upper and lower oil chambers 3, 4, and an outer circumference of the piston rod 5 and an inner circumference of the cylinder 1. A movable wall 16 slidably fitted and urged by a spring 18 below the fixed wall 15, a rod member 5a fixed to the outer periphery of the piston rod 5 on the upper surface of the first piston 2, a rod member
An orifice passage 24 formed in 5a and communicating the upper and lower oil chambers 3 and 4 is slidably fitted on the outer periphery of the rod member 5a and is urged upward by a spring 23 so that the orifice A sliding valve 22 for opening the passage 24 and closing the orifice passage 24 when the movable wall 16 is separated; a second piston fixed to the piston rod 5 below the first piston 2 and having a smaller diameter than the first piston 2; A damping valve 29 for generating a damping force in any flow direction of the oil in a passage 28 in a second piston 27 communicating the upper and lower parts of the cylinder, and a slidably disposed lower part in the cylinder 1 and an upper part by a spring 37. And a cylindrical slide ring 36 that allows the second piston 27 to be fitted in a liquid-tight manner so that an oil chamber can be partitioned above and below the second piston 27. Small strike of piston rod 5 near maximum extension In the working area, the movable wall 16 and the sliding valve 22 are brought into contact with each other, and the oil flows through the passage 25 in the first piston 2 and the orifice passage 24 of the rod member 5a in parallel. Passage in the first piston 2
The oil is caused to flow through only the piston 25, and in the large stroke region of the piston rod 5 near the maximum compression of the shock absorber, the second piston 27 is fitted into the slide ring 36 so that the passage 25 in the first piston and the second piston 27 The damping force is made variable depending on the stroke by flowing the oil with the passage 28 in series.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the hydraulic shock absorber includes a cylinder 1. A first piston 2 is provided in the cylinder 1.
Is slidably accommodated, and the first piston 2 vertically partitions the inside of the cylinder 1 into a first oil chamber 3 and a second oil chamber 4. These two oil chambers 3 and 4 are filled with oil. The second oil chamber 4 communicates with a port 1a formed at the lower end of the cylinder 1. Further, a piston rod 5 is slidably disposed with respect to the cylinder 1 inside and outside the cylinder 1, and the first piston 2 is fixed to one end of the piston rod 5 and the other end thereof. A spring receiving seat 6 is provided on the part side. A buffer spring 8 is arranged between the spring receiving seat 6 and a spring receiving seat 7 provided on the outer peripheral portion of the cylinder 1.

On the other hand, a reservoir tank 9 is provided separately from the cylinder 1, and the inside of the reservoir tank 9 is divided into two chambers 11 and 12 by a free piston 10. The upper chamber 11 is filled with gas, and the lower chamber 12
Is filled with oil. The chamber 12 is connected to a port 9a via a valve device 13. The port 9a is connected to the port 1a of the cylinder 1 via the connecting hose 14.

As shown in FIG. 2, a small-diameter portion 1b having a slightly smaller inner diameter than other portions is formed substantially in the center of the cylinder 1, and the first piston 2 is located in the small-diameter portion 1b. It has become.

A fixed wall 15 is fixed to an upper edge of the large diameter portion 1c on the upper side of the cylinder 1, and a lower portion of the fixed wall 15 is a cylindrical portion 15a. An orifice passage 15b is formed in the cylindrical portion 15a. A movable wall 16 is slidably fitted on the outer periphery of the piston rod 5 and the inner periphery of the cylinder 1 on the large diameter portion 1c below the fixed wall 15. Therefore, a third oil chamber 17 is formed above the movable wall 16. The upper portion of the movable wall 16 is formed as a cylindrical portion 16a, which fits into the cylindrical portion 15a of the fixed wall 15 as shown in FIG. 2 when the hydraulic shock absorber is fully extended. It has become.

The movable wall 16 is constantly urged downward by a coil spring 18 so as to come into contact with a rod member 5a fixed to the outer periphery of the piston rod 5 on the upper surface of the first piston 2. Further, the movable wall 16 is formed with two passages 19 and 20 so as to allow the oil flow from the first oil chamber 3 to the third oil chamber 17 but prevent the flow in the opposite direction. A one-way valve 21 that controls opening and closing of the passage 20 is provided. The piston rod 5 slidably passes through the fixed wall 15 and the movable wall 16.

A sliding valve 22 is slidably fitted around the outer periphery of the rod member, and the sliding valve 22 is constantly urged upward by a coil spring 23 and is in contact with the movable wall 16. And sliding valve
The step 22 is separated from the movable wall 16 and when a downward force is not applied, the step 22a is formed in the step 5b formed on the rod member 5a.
, And does not move upward any more.

An orifice passage 24 is formed in the piston rod 5 and the rod member 5a via the first piston 2 to communicate the first oil chamber 3 with the second oil chamber 4. The orifice passage 24 is formed in the hole 22 of the sliding valve 22 when the sliding valve 22 moves downward.
When the sliding valve 22 is in the upper limit position and the sliding valve 22
The opening / closing of the orifice passage 24 is controlled by the sliding valve 22 so as to shut off when the opening of the orifice passage 24 on the rod member 5a side does not match.

A relatively large passage 25 communicating the first oil chamber 3 and the second oil chamber 4 is formed in the first piston 2,
A first damping valve 26 for controlling the flow of oil in the passage 25 is provided. The first damping valve 26 generates a damping force regardless of the direction in which oil flows.

A second piston 27 having a smaller diameter than the first piston is fixed to the piston rod 5 below the first piston 2, and an O-ring 27a is fitted on an outer peripheral edge thereof. This second piston 2
A passage 28 is formed in the upper and lower surfaces of the passage 7, and a second damping valve 29 for controlling the flow of oil in the passage 28 is provided.

A cylindrical nut 30 is screwed to the lower end of the piston rod 5. A passage 31 is formed in the piston rod 5 and the nut 30 to communicate the first oil chamber 3 and the second oil chamber 4. Throttle valve 32 for adjusting the oil flow rate in this passage 31
Is provided on the piston rod 5. Also, nut 30
An orifice passage 33 and a passage 34 are formed, and a one-way valve 35 for opening and closing the passage 34 so as to allow the oil flow from the upper side to the lower side but to prevent the flow in the opposite direction is provided. I have.

As shown in FIG. 3, in the cylinder 1, only the lower end slides on the large-diameter portion 1d, and the other portion is the small-diameter portion 1b.
A slide ring 36 that slides the slide ring is provided. The slide ring 36 is constantly urged upward by a coil spring 37, and its lower end is held at an upper limit position where it abuts a step 1f between the large diameter portion 1d and the small diameter portion 1b. When the piston rod 5 makes a large stroke downward, the second piston 27 fits into the cylinder portion 36a at the upper end of the slide ring 36. The lower surface of the second piston 27 comes into contact with the flange 36b of the slide ring 36.

A fixed wall 38 is fixed to the lower end of the cylinder 1. The fixed wall 38 has a port 1 a (see FIG. 1) and a second oil chamber 4.
, And an orifice passage 41 are formed. The fixed wall 38 has a one-way valve 42 that opens and closes the passage 40 so as to allow the flow of oil from the port 1a toward the second oil chamber 4 but prevent the flow in the opposite direction.
Is provided. Further, a cylindrical oil lock piece 43 is fixed to the fixed wall 38, and the nut 30 fits into the internal space 43 a of the oil lock piece 43 when the piston rod 5 makes a large downward stroke. I have.

Next, the operation of the present embodiment thus configured will be described with reference to FIGS. 4A to 4C and FIGS. 5A to 5C.

First, the compression stroke of the hydraulic shock absorber will be described.
The description will be made assuming that the stroke speed of the piston rod 5 is constant.

In the state where the hydraulic shock absorber is fully extended, as shown by a two-dot chain line in FIG.
Are fitted to the cylindrical portion 15a of the fixed wall 15. In this state, the movable wall 16 does not contact the stepped portion 1e, and the movable wall 16 and the sliding valve 12 are in contact. In this case, since the set load of the coil spring 18 is set to be larger than the set load of the coil spring 23, the slide valve 22 is moved downward, and the orifice passage 24 is opened.

In this state, in a small stroke region in which the piston rod 5 strokes downward, the first piston 2 moves downward as shown by a solid line in FIG. Move down. Therefore, the one-way valve 21 and the first damping valve 26 move upward to open the passages 20, 25. As a result, the oil passes from the second oil chamber 4 to the first oil chamber 3 through the orifice passage 24 and the passage 25 in the first piston 2 as indicated by the arrow, and
It flows from the first oil chamber 3 to the third oil chamber 17 through 19 and 20.
Some oil flows from the second oil chamber 4 to the third oil chamber 17 through the orifice passage 33 and the passage 31. Further, part of the oil in the second oil chamber 4 is removed from the port 1a
And flows into the chamber 12 of the reservoir tank 9. Therefore, the orifice passage 24 and the passage 25 in the first piston 2 are arranged in parallel, so that the overall passage resistance is smaller than the individual passage resistances, and a relatively large amount of oil flows, and the generated damping force Is relatively small. The damping force characteristic at this time is represented by a straight line a in FIG.

As shown in FIG. 4B, the piston rod 5
The movable wall 16 abuts on the step portion 1e in an intermediate stroke region in which the stroke amount is reduced to a predetermined amount. Subsequently, when the piston rod 5 strokes downward, the biasing force of the coil spring 18 is not applied to the slide valve 22, so that the slide valve 22 moves upward. For this reason, the hole 22b of the sliding valve 22 and the opening of the orifice passage 24 on the rod member 5a side are displaced, and the oil flowing in the orifice passage 24 is throttled. As a result, the damping force increases and follows the straight line b in FIG. When the sliding valve 22 reaches the upper limit position, the sliding valve 22 stops flowing in the orifice passage 24,
It flows mainly through the passage 25 in the first piston 2, so that the flow passage resistance becomes larger than when the orifice passage 24 and the passage 25 are arranged in parallel. As a result, the damping force increases, becomes substantially constant, and follows the straight line c. Further, while the one-way valve 21 closes the passage 20, the volume of the third oil chamber 17 does not increase, so that the oil does not flow into the third oil chamber 17.

Further, in the large stroke region where the piston rod 5 strokes downward, as shown in FIG. 4C, the second piston 27 fits into the cylinder portion 36a of the slide ring 36, and the second oil chamber 4 is the upper and lower two oil chambers 4a, 4b
Begins to be partitioned. For this reason, the flow path between the second piston 27 and the slide ring 36 is gradually narrowed, the flow of oil between the oil chambers 4a and 4b is reduced, and the second damping valve 29 moves upward. Thus, the passage 28 is opened to generate a damping force. As a result, the damping force increases and follows the straight line d. The second piston 27 is the cylinder portion 36a
When completely inserted into the passage, the passage 28 is completely opened and the oil flows from the lower oil chamber 4b to the upper oil chamber 4a through only the passage 28,
The passages 25, 28 in the first and second pistons are in series, so that the overall passage is greater than the individual passage resistance.
As a result, the damping force increases, becomes substantially constant, and follows the straight line e. The lower surface of the second piston 27 forms the flange portion 36b of the slide ring 36.

Thereafter, the piston rod 5 moves with the slide ring 36. At this time, since the coil spring 37 is compressed, the spring constant of the hydraulic shock absorber increases as the sum of the spring constants of the two coil springs 8 and 37 increases. That is,
The characteristic is such that the spring constant of the hydraulic shock absorber changes in two stages according to the piston stroke. Further stroke of the piston rod 5 causes the nut 30 to fit into the oil lock piece 43 as shown by a two-dot chain line in FIG. 4C. Since the one-way valve 42 closes the passage 40, the oil in the oil lock piece 43 is discharged from the orifice passage 41.
Therefore, the damping force is further increased to follow the straight line f.

 Next, the extension stroke of the hydraulic shock absorber will be described.

As shown by a two-dot chain line in FIG. 5A, when the nut 30 is fitted into the oil lock piece 43 at the time of maximum compression of the hydraulic shock absorber, the piston strokes in the extension direction shown by the arrow of the piston rod 5. When the nut 30 moves to the position shown by the solid line in FIG.
4b and the one-way valve 42
, The oil flows into the oil lock piece 43 through the passage 40 and the orifice passage 41. Further, since the first and second damping valves 26 and 29 move downward to open the passages 25 and 28, the oil passes through the passage 28 as shown by the arrow and the upper oil chamber.
It flows from the first oil chamber 3 to the upper oil chamber 4a through the passage 25 and from the first oil chamber 3 to the upper oil chamber 4a, and the passages 25 and 28 in the first and second pistons are connected in series. Meanwhile, one-way valve
As 35 opens passage 34, the oil will flow downward through passages 31, 33, 35. Therefore, in a large stroke region near the time of maximum compression, the damping force follows the straight line g in FIG. 6, and becomes a relatively large and substantially constant value. In this case, even when the piston rod 5 moves upward and the nut 30 is detached from the oil lock piece 43, the damping force hardly changes because the one-way valve 42 opens the passage 40.

Further, when the piston rod 5 strokes upward to enter the intermediate stroke region, the second piston 27 comes off the slide ring 36, and the second damping valve 29 gradually closes the passage 28 so that the first piston 2 Passage 25 alone. For this reason, the damping force decreases. When the upper oil chamber 4a and the lower oil chamber 4b are combined into one second oil chamber 4, the damping force is substantially constant. The damping force at this time is substantially constant. The damping force at this time is represented by straight lines h and i.

Further, when the piston rod 5 strokes upward to enter a small stroke region near the maximum extension, the sliding valve 22 comes into contact with the movable wall 16. Therefore, the sliding valve 22 moves downward with respect to the rod member 5a, and the orifice passage 24 is gradually opened. As a result, the oil flows also through the passage 24, and the orifice passage
24, parallel to the passage 25 in the first piston 2. Therefore, the damping force decreases. When the slide valve 22 further moves downward to completely open the passage 24, the damping force becomes constant. The damping force at this time is represented by straight lines j and k.

Thereafter, the movable wall 16 is moved with the movement of the piston rod 5.
When the oil moves upward, the oil in the third oil chamber 17 passes through the passage.
It flows into the first oil chamber 3 through 19. More movable walls
When the 16 moves upward, the cylindrical portion 16a of the fixed wall 15 fits into the cylindrical portion 15a of the fixed wall 15, as shown by a two-dot chain line in FIG. 5C. Therefore, the oil in the third oil chamber 17 is a one-way valve
21 closes the passage 20, so that it flows only through the orifice passage 15b. As a result, increases along the straight line l.

As described above, the hydraulic shock absorber has the piston rod small, medium,
If it is located in each of the large stroke areas, the damping force will have the characteristic of increasing stepwise.

In the above embodiment, a single cylinder type hydraulic shock absorber is used, but the present invention can be applied to a double cylinder type hydraulic shock absorber.

[Effects of the Invention] As is clear from the above description, the hydraulic shock absorber according to the present invention has a passage in the first piston and an orifice passage of the rod member in a small stroke region of the piston rod near the maximum extension of the shock absorber. In parallel to reduce the passage resistance and allow the oil to flow, and in the intermediate stroke region of the piston rod, only the passage in the first piston is used to increase the passage resistance and allow the oil to flow as compared to the parallel operation, and near the maximum compression of the shock absorber. In the large stroke range of the piston rod, the passage in the first piston and the passage in the second piston are connected in series to maximize the passage resistance and flow the oil, thereby making the damping force variable depending on the stroke. Therefore, the damping force changes in three stages according to the increase and decrease of the load.
The damping force is small and soft under light loads such as passengers, and the damping force is large under medium loads such as two-seater, so that the vertical vibration of the vehicle due to the suspension spring is quickly eliminated, and the large gap is passed off-road. For example, when the shock absorber sinks greatly, such as at the time, the damping force can be finely changed so that the damping force is further increased to provide a hard characteristic. Since the damping force changes in three stages, if the difference between the maximum and the minimum of the set damping force is fixed, the change in the damping force in each stroke region is small and does not produce a rough feeling, and the shock absorber of the present invention Can improve the riding comfort and steering stability of the vehicle.

In addition, since the movable wall is slidably fitted on the inner periphery of the cylinder, the sliding valve in contact with the movable wall is not tilted by the movable wall, so that the sliding valve slides on the rod member without being twisted. Since the second piston is fitted in the slide ring in a liquid-tight manner, the second piston is fitted without being twisted in the slide ring, and neither of them causes malfunction.

Further, since the orifice passage is provided in the rod member fixed to the outer periphery of the piston rod, it is possible to provide a throttle passage for manually adjusting the damping force in the piston rod, and together with this, a finer damping force can be provided. Can be adjusted.

Further, since a passage with a restriction is not provided on the wall of the pipe as in the related art, the present invention can be applied to both a single cylinder type and a multiple cylinder type shock absorber.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing an entire embodiment of a hydraulic shock absorber according to the present invention, FIG. 2 is an enlarged sectional view showing an upper half portion inside a cylinder of the embodiment, and FIG. FIGS. 4A to 4C are enlarged cross-sectional views showing the lower half of the inside of the cylinder, and FIGS. 4A to 4C are explanatory views illustrating the operation in the compression stroke of the embodiment, and FIGS.
FIG. 5C is an explanatory diagram illustrating the operation of the embodiment in the extension stroke, FIG. 6 is an explanatory diagram illustrating the damping force characteristics of the embodiment,
FIG. 7 is a sectional view schematically showing a conventional hydraulic shock absorber with a variable number of throttles. 1 ... Cylinder, 2 ... First piston, 3, 4 ... Oil chamber, 5 ... Piston rod, 5a ... Rod member, 15 ...
Fixed wall, 16 movable wall, 18, 37 spring, 22 sliding valve, 24 orifice passage, 25 passage, 26, 29 damping valve, 27 second piston, 36 ...... Slide ring

Claims (1)

(57) [Claims] 1. A cylinder filled with oil, a piston rod provided in the cylinder through a fixed wall fixed to an upper edge of the cylinder, and a cylinder fixed to a lower end of the piston rod. A first piston which is slidably housed in the cylinder and partitions the inside of the cylinder into upper and lower oil chambers, and a damping force in any flow direction of the oil in a passage in the first piston which communicates the upper and lower oil chambers. A damping valve to be generated; a movable wall slidably fitted on the outer periphery of the piston rod and the inner periphery of the cylinder and urged by a spring below a fixed wall; and a piston rod on the first piston upper surface side A rod member fixed to the outer periphery, an orifice passage formed in the rod member and communicating the upper and lower oil chambers, and slidably fitted to the outer periphery of the rod member and urged upward by a spring, A sliding valve that opens the orifice passage when the movable wall abuts and closes the orifice passage when the movable wall separates; a second piston fixed to the piston rod below the first piston and smaller in diameter than the first piston; A damping valve for generating a damping force in any flow direction of the oil in a passage in the second piston communicating with the upper and lower sides of the piston; a damping valve slidably disposed below the cylinder and urged upward by a spring. And a cylindrical slide ring in which the second piston is fitted in a liquid-tight manner so that an oil chamber can be partitioned above and below the second piston. In the small stroke region of the piston rod, the movable wall and the sliding valve are brought into contact with each other to make the passage in the first piston and the orifice passage of the rod member parallel to each other to flow oil. In the intermediate stroke region, the oil flows only through the passage in the first piston, and in the large stroke region of the piston rod near the time of maximum compression of the shock absorber, the second piston is fitted into the slide ring to pass the passage in the first piston. A hydraulic shock absorber characterized in that the damping force is made variable depending on the stroke by flowing oil with the passage in series with the passage in the second piston.