JP2950173B2 - Single acting hydraulic cylinder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic cylinder for one-way drive used for a lifter or the like for a vehicle, and more particularly to a hydraulic cylinder for reducing a shock at a stroke end.

[0002]

2. Description of the Related Art A so-called single-acting hydraulic cylinder is used as a drive device for a lifter of a vehicle used for getting on / off of a handicapped person or loading / unloading luggage, which requires a large power only when the lifter is raised. Is used. When the hydraulic cylinder is suddenly stopped or suddenly started at the stroke end, an impact is applied to the load on the lifter. Therefore, it is desirable to provide a buffer mechanism that prevents sudden stop or sudden start at the stroke end.

A double-acting (bidirectional driving type) hydraulic cylinder 9 provided with such a buffering mechanism has, for example, a projection 911 having tapered surfaces 913 and 914 on both sides of a piston 91 as shown in FIG. , 912 are provided. Then, the protrusions 911 and 912 are gradually inserted into the oil passages 921 and 922, and the oil passages 921 and 922 are gradually narrowed to suppress the sudden stop of the piston 91. Also in the case of starting in the opposite direction, the oil passages 921 and 922 are gradually opened in the same manner to suppress sudden starting.

In FIG. 3 , reference numerals 923 and 924 denote an inflow / outflow port of hydraulic oil, reference numeral 93 denotes a rod, and reference numeral 991 denotes a cylinder fixing shaft. Examples of other hydraulic cylinder with a buffer mechanism, as shown in FIG. 4, large diameter main oil road 925 on the end block 94 of the hydraulic cylinder 90
In addition, there is one provided with a small-diameter buffer oil passage 926.

At the end of the piston 910, the above-mentioned
A protruding shaft 915 fitted to the oil passage 925 is provided.4
As shown in FIG.
After the shaft 915 is inserted into the main oil passage 925, the hydraulic oil
The hydraulic oil flows through the small-diameter buffer oil passage 926 of FIG.
As a result, the piston 910 gradually decelerates to reduce the impact.
I can do it.

When starting in the opposite direction,
As shown in FIG. 4 (b), through the buffer oil road 926 starts the flow of hydraulic fluid, then since the main oil road 925 is opened, it is possible to smooth abrupt start. In FIG. 4 , reference numeral 951 denotes a cushion valve for adjusting the restriction of the buffer oil passage 926, and reference numeral 952 denotes a check valve.

[0007] The check valve 952 is to open the Aburado 927 slightly increases the startup speed when moving the piston 910 backward as shown in Figure 4 (b). By providing the buffer mechanism also at the end block on the other end side, the buffer function can be exerted at the stroke ends at both ends. The above two buffer mechanisms shown in FIGS. 3 and 4 can be used in combination.

[0008]

However, the hydraulic cylinder having the shock absorbing mechanism has the following problems. The hydraulic cylinders are all pistons 91, 9
That is , hydraulic oil is required in the cylinder rooms on both front and rear sides of the cylinder 10, and a so-called double-acting hydraulic cylinder for driving the piston in both directions must be used.

As described above, a single-acting hydraulic cylinder is used in a vehicle lifter. In a single-acting hydraulic cylinder, hydraulic oil is introduced into a room on one side of a piston. Air occupies the space. Therefore, such a buffer mechanism cannot be used for the single-acting hydraulic cylinder. The present invention has been made in view of such conventional problems, and has as its object to provide a single-acting hydraulic cylinder having a buffer function at the time of stopping and starting.

[0010]

SUMMARY OF THE INVENTION The present invention is a single-acting hydraulic cylinder in which only the forward path is hydraulically driven and the return path is in a state in which the hydraulic pressure is released. The hydraulic cylinder includes a cylinder, a rod connected to a load, A main piston connected to the tip of the rod and first and second cylinders for closing both ends of the cylinder;
An end block, a shock-absorbing piston that slides between a rear surface of the first end block on the distal end side and a stopper provided near the front of the cylinder, and an inlet and an outlet for hydraulic oil. A first surface formed by a rear surface of the block, a front surface of the cushioning piston, and an inner wall surface of the cylinder;
An oil chamber, and an inlet for hydraulic oil at a base end side.
A second oil chamber defined by a front surface of the end block, a rear surface of the main piston, and an inner wall surface of the cylinder; an air port having an air port near the stopper; a rear surface of the cushioning piston; a front surface of the main piston; has an air chamber formed by the inner wall surface of the cylinder, the outlet of the hydraulic oil of the first oil chamber communicates with the inlet of the hydraulic oil in the second oil chamber, also, the buffer piston Is
A cylindrical portion that slides on the inner wall of the cylinder and a front portion of the cylindrical portion;
Together they have a tapered projection of the conical side shape gradually decreasing outer diameter towards the front in the plane, between the side surfaces of the front and the cylindrical portion of the tapered projections and bored small oil road Ah
And the cushioning piston is in the up position in the retracted position.
The oil path from the inlet to the outlet of the first oil chamber is
Open and gradually narrow the oil passage while moving forward.
In the forward position, the tapered protrusion or the cylindrical portion
The oil path is blocked by the small diameter oil path
A single-acting hydraulic cylinder configured to communicate with an oil path .

[0011] The first of the most remarkable points in the present invention is
Point is the provision of a cushioning piston on the distal end side of the cylinder in addition to the main piston. Then, a first oil chamber is formed by the first end block and the buffer piston,
This is to communicate with the second oil chamber formed by the second end block and the main piston. Further, an air chamber provided with an air port is provided between the buffer piston and the main piston.

The most notable point is that a tapered projection having a conical side surface that gradually reduces the outer diameter toward the front is provided on the front surface of the cushioning piston, and the front surface of the tapered projection and the side surface of the cylindrical portion are connected. A small-diameter oil passage was drilled between them. And
When the buffer piston is retracted,
1 Open the oil path from the inlet to the outlet of the oil chamber
On the other hand, when it is advanced,
The oil passage is blocked by the cylinder and
Through the oil path above, and
That is, the oil passage is configured to be gradually narrowed .

[0013]

Operation and Effect The hydraulic cylinder according to the present invention operates as follows. First, when hydraulic oil flows in from the inlet of the first oil chamber, the buffer piston whose rear surface is the air chamber retreats toward the stopper, and the first oil chamber expands. Then, the buffer piston comes into contact with the stopper and stops. In the retracted state of the buffer piston, the flow
The oil path from the inlet to the outlet is open.

Further, when the hydraulic oil flows in, the hydraulic oil
It flows out from the outlet of the oil chamber and flows into the second oil chamber from the inlet of the second oil chamber. Then, the main piston is pushed forward, and the main piston (and the rod) moves forward.

When hydraulic oil further flows in and the main piston moves forward, the front surface of the main piston comes into contact with the rear surface of the cushioning piston, and the two pistons move together in this state .

Then, when the main piston and the buffer piston move further forward, the taper of the buffer piston
The oil in the first oil chamber is formed by the protrusion or the column.
The road is gradually blocked. Then, the front surface of the buffer piston comes into contact with the rear surface of the first end block, whereby both pistons stop .

During the forward movement of the buffer piston,
The oil passage is gradually narrowed by the tapered protrusion or the cylindrical portion . Therefore, the shock-absorbing piston (and the main piston) does not suddenly stop, but gradually decelerates and stops. As a result, the impact on the load is suppressed (shockless stopping action). In addition, the advance of this buffer piston is completed
In the state, the oil passage in the first oil chamber is blocked.
In addition, the oil path is connected only by the small diameter oil path.
Kept in shape.

Next, when the buffer piston (main piston) retreats, the first oil chamber and the second oil chamber communicate with each other only through the small-diameter oil passage, so that the flow rate of the hydraulic oil is extremely small. Suppressed low, both pistons start slowly. Then, the front surface of the buffer piston slowly separates from the rear surface of the first end block (slow start action).

While the buffer piston is being retracted, the oil passage is gradually opened from the above-mentioned blocked state. As a result, the flow rate of hydraulic oil increases slowly, and the piston gradually increases its speed (slow acceleration action) .

According to the present invention as above SL can be buffered stop and the buffer start-up to provide a single-acting hydraulic cylinder capable.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A hydraulic cylinder according to an embodiment of the present invention will be described with reference to FIGS. This example is a single-acting hydraulic cylinder that hydraulically drives only the forward path and releases the hydraulic pressure on the return path, and drives a lifter for a vehicle. As shown in FIG. 1, a hydraulic cylinder 10 of the present embodiment is configured to close both ends of a cylinder 11, a rod 12 connected to a load, a main piston 13 connected to a tip of the rod 12, and the cylinder 11. And a shock-absorbing piston 20 that slides between a rear surface of the first end block 14 on the distal end side and a stopper 16 provided near the front of the cylinder 11 . . Ma
The hydraulic cylinder 10 has an inlet 31 and an outlet 32 for hydraulic oil, and has a first oil chamber 30 formed by a rear surface of the first end block 14, a front surface of the buffer piston 20, and an inner wall surface of the cylinder 11. A second oil chamber 35 having a hydraulic oil inlet 36 at the base end side and formed by the front surface of the second end block 15, the rear surface of the main piston 13, and the inner wall surface of the cylinder 11; An air chamber 171 having an air port 171 in the vicinity is formed by a rear surface of the buffer piston 20, a front surface of the main piston 13, and an inner wall surface of the cylinder 11.

The outlet 32 of the working oil in the first oil chamber 30 communicates with the inlet 36 of the second oil chamber 35 by a pipe or the like. On the front surface of the cushioning piston 20, a tapered projection 22 having a conical side surface that gradually reduces the outer diameter toward the front is formed, and between the front surface of the tapered projection 22 and the side surface of the cylindrical portion 21. A small diameter oil passage 25 is formed.

The cushioning piston 20 is shown in FIG.
In the retracted position, the inlet of the first oil chamber 30
Open oilway 200 from 31 to outlet 32, on the way forward
In, the oilway 200 is gradually narrowed, and
In the case of the oil passage,
The oil passage 200 is blocked by the small-diameter oil passage 25.
Are connected to each other.

A communication passage 141 is formed in the first end block 14 and opens frontward to the atmosphere and is parallel to the cylinder axis 111. The communication passage 141 is provided in front of the cushioning piston 20. A cylindrical protruding shaft 24 that fits and slides is formed . In FIG. 1, reference numeral 41 denotes a shaft for fixing the hydraulic cylinder 10.

The hydraulic cylinder 10 is used for the vehicle lifter 1 shown in FIG. That is, the hydraulic cylinder 10
Is driven by a hydraulic pump (not shown) to operate the lifter 1 when the runner 41 is pulled in the directions of (a) to (c) in FIG.

On the other hand, as shown in FIG. 2D, a step of further pushing the entire platform 40, and FIG.
The step of pulling out and lowering the lifter in the directions of (a) to (a) is driven by manual operation and the urging force of a spring, and the hydraulic cylinder 10 does not operate. In FIG. 2, reference numeral 45 denotes a lifter guide rail, and reference numeral 46 denotes an arm connected to the rod 12.

Next, the operation of the hydraulic cylinder 10 will be described. As shown by the broken line in FIG. 1, the hydraulic cylinder 10 starts the hydraulic operation from the state where the main piston 13 is on the base end side. When hydraulic oil flows in from the inlet 31 of the first oil chamber 30, the no-load buffer piston 20 moves backward and hits the stopper 16 and stops.

Then, the outflow port 32 is fully opened, hydraulic fluid flows in from the inflow port 36 of the second oil chamber 35, and drives the main piston 13 forward. When the main piston 13 moves further forward, it comes into contact with the rear surface of the buffer piston 20, and moves forward while the buffer piston 20 and the main piston 13 are in contact with each other.

When the main piston 13 and the buffer piston 20 further advance, the oil passage 200 between the buffer piston 20 and the first end block 14 is gradually narrowed by the tapered projection 22 of the buffer piston 20. When the tapered projection 22 comes into contact with the rear surface of the first end block 14, only the small-diameter oil passage 25 allows the communication between the first oil chamber 30 and the outlet 32.

That is, as the buffer piston 20 approaches the first end block 14, the oil passage 200 is gradually narrowed by the tapered projection 22 whose diameter gradually increases rearward. As a result, the flow rate of the hydraulic oil flowing between the first oil chamber and the second oil chamber decreases, and accordingly, the speed of the pistons 13 and 20 decreases.

Immediately before the buffer piston 20 stops, the flow rate of the hydraulic oil becomes a small flow rate through the small-diameter oil passage 25, and the stroke movement becomes extremely slow. As described above, the hydraulic cylinder 10 of this embodiment has a so-called shockless stopping action without suddenly stopping the piston.

Next, the operation for retracting the main piston 13 will be described. The operation of retracting the main piston 13 is performed by applying a tensile force to the rod 12 from the load side of the rod 12 (the hydraulic pump is not operated). When the rod 12 is pulled, the hydraulic oil is reduced
25, flows from the second oil chamber 35 toward the first oil chamber 30, and flows into the main piston 13 and the buffer piston 2.
Retreats from 0.

At this time, the pistons 13 and 20 are almost in contact with each other and move in parallel (however, the buffer piston 20 is
6). And in this starting process,
The flow rate Q of the hydraulic oil between the first oil chamber 30 and the second oil chamber 35 gradually increases.

This is because at the time of starting, the small-diameter oil passage 2
Since the hydraulic oil flows only through 5, the hydraulic oil flow rate Q is extremely small, and the strokes of the pistons 13 and 20 change slowly (slow start function). Then, as the buffer piston 20 moves away from the first end block 14, the hydraulic oil flow rate Q gradually increases (slow acceleration action). This is because, by the action of the tapered projections 22 gradually increasing the diameter, the oil path 200 of the working oil is because it is gradually spread apart.

As described above, the hydraulic cylinder 10 of this embodiment
When the main piston 13 is moved backward, it gradually accelerates after a slow start. And the buffer piston 20
Until the hydraulic cylinder 10 contacts the stopper 16, the hydraulic cylinder 10 operates without returning the hydraulic oil to the external hydraulic system, and thereafter operates while returning the hydraulic oil to the external hydraulic system.

As described above, according to this embodiment, it is possible to provide a single-acting hydraulic cylinder having a buffer function at the time of stopping and starting. When the hydraulic cylinder 10 is applied to a lifter, the impact at the time of stopping when the runner is raised and retracted is reduced, and when the runner is extended and lowered, the runner extracting operation is suddenly started. Nothing.

[Brief description of the drawings]

FIG. 1 is a sectional view of a hydraulic cylinder according to an embodiment.

FIG. 2 is a perspective view of a lifter according to the embodiment.

FIG. 3 is a sectional view of a conventional hydraulic cylinder.

FIG. 4 is a schematic sectional view of a main part of another conventional hydraulic cylinder.

[Explanation of symbols]

 10. . . 12. hydraulic cylinder, . . Main piston, 14. . . 14. first end block, . . Second end block, 20. . . Buffer piston, 22. . . 25. taper projection, . . Small diameter oilway, 30. . . First oil chamber, 32. . . Outlet, 35. . . The second oil chamber,

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F15B 15/00-15/28

Claims (2)

(57) [Claims] 1. A single-acting hydraulic cylinder for hydraulically driving only the forward path and releasing the hydraulic pressure on the return path, comprising a cylinder, a rod connected to a load, and a tip of the rod. With the connected main piston,
A first and a second end block for closing both ends of the cylinder, a shock-absorbing piston sliding between a rear surface of the first end block on the front end side and a stopper provided near the front of the cylinder; A first oil chamber having an oil inlet and an oil outlet formed by a rear surface of the first end block, a front surface of the buffer piston, and an inner wall surface of the cylinder; A second oil chamber having an inlet formed by a front surface of the second end block, a rear surface of the main piston, and an inner wall surface of the cylinder; a rear surface of the cushioning piston having an air port near the stopper; An air chamber formed by a front surface of the main piston and an inner wall surface of the cylinder; an outlet of the hydraulic oil in the first oil chamber is connected to an inlet of the hydraulic oil in the second oil chamber; And, also, the buffer piston, the inner wall of the cylinder and sliding
A cylindrical portion which, has a tapered projection of the conical side shape gradually decreasing outer diameter towards the front in front of the circular column portion
At the same time, a small-diameter oil passage is formed between the front surface of the tapered projection and the side surface of the cylindrical portion , and the shock-absorbing piston is in the retracted position.
1 Open the oil path from the inlet to the outlet of the oil chamber
In the course of forward movement, the above oil path is gradually narrowed.
In the advanced position, the tapered projection or the cylindrical
The oil path is blocked by the oil path
Single-acting type, characterized in that it is configured to communicate
Hydraulic cylinder. 2. The first end block according to claim 1, wherein a communication passage parallel to the cylinder axis is formed in the first end block, and the communication passage is opened forward to the atmosphere. , single-acting hydraulic cylinder, characterized in that projecting shaft to slide fitted to said communication passage is formed.