JPS6333002B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a cushion device for preventing a piston sliding in a cylinder from colliding with a cylinder cover at the end of the cylinder's stroke.

Conventionally, as this type of cushion device, those shown in FIGS. 1 and 2 are known. That is, in the drawing, a head cover 1 is provided on the end surface of the cylinder 1.
A and a rod cover 1B are provided with a cylinder cover, and the head cover 1A is formed with a cushion hole 2 into which a cushion ring (to be described later) is fitted, and a supply/discharge port 3. Similarly, the rod cover 1B also has a cushion hole 4, a supply/discharge port 3. 5 is formed.
A rod 6 is guided to the rod cover 1B,
A piston 7, which defines oil chambers A and B within the cylinder 1, is fixed to the rod 6. In the rod 6, cushion members 8, 9, such as tapered cushion rings or plungers, which fit into the cushion holes 2, 4 with a small gap are provided in front and behind the piston 7.

In such a conventional cylinder cushioning device, when pressure oil is supplied to chamber B from the supply/discharge port 5, for example, the piston 7 enters a contraction stroke and is displaced to the right in the figure at high speed, and enters a cushioning stroke. The cushion ring 8 is fitted into the cushion hole 2. At this time, since the cushion ring 8 has a tapered shape, as it is inserted into the cushion hole 2, the pressure inside the chamber A becomes high, which creates resistance against the piston 7, and also creates resistance between the cushion hole 2 and the cushion ring 8. The area of the flow path formed by the gap between the two is narrowed, and the flow resistance of the oil flowing through this flow path generates a damping force, which provides a cushioning effect to the piston 7. In addition, when pressure oil is supplied from the supply/discharge port 3 to the chamber A, the piston 7 undergoes an extension stroke and is displaced to the left in the figure, and the cushion ring 9 is fitted into the cushion hole 4, the same procedure as described above is performed. gives a cushioning effect.

However, prior art cushioning devices constructed in this manner have a number of drawbacks.

That is, firstly, since the annular gap formed by the cushion hole 2 and the cushion ring 8 is very small, the cushion performance and the concentricity of the gap vary due to manufacturing errors and assembly errors. If the cushion ring 8 is provided eccentrically with respect to 2, there is a drawback that galling and seizure phenomena occur. Second, the cushioning action is affected by the viscosity of the oil, and as the oil temperature rises, the viscosity of the oil decreases and flow resistance decreases, making it impossible to obtain sufficient cushioning performance. Third
In order to avoid the second drawback, the annular gap can be made even smaller, but making the annular gap extremely small requires high-precision machining and assembly work. The drawback was that it was not practical. Fourth, when the piston 7 moves in the direction away from the cylinder cover, even if pressure oil is supplied from the supply/discharge port 3, the flow path area is restricted by the annular gap, so the pressure oil does not flow into the chamber A. Not only does this restrict the inflow of pressure to the entire piston 7, but also the piston 7 is forced into the cushion hole 2.
There was a drawback that pressure oil suddenly flowed into the chamber A when it was released from the chamber A, causing abnormal noise.

The present invention was made in view of the problems of the prior art, and provides a hydraulic cylinder that provides reliable cushioning action at the end of the stroke without being affected by changes in oil temperature, manufacturing errors, assembly errors, etc. The purpose of the present invention is to provide a cushioning device for the invention.

To achieve this object, the present invention includes a hydraulic cylinder having a cylinder cover, and a rod slidably attached to the hydraulic cylinder so as to define two chambers A and B within the hydraulic cylinder. In the cushioning device for a hydraulic cylinder, the cushioning device includes a piston, a cushioning member provided on at least one side of the piston, and a cushioning hole drilled in the cylinder cover in the axial direction and into which the cushioning member is fitted at a stroke end. A plate chamber is formed in the radial direction of the cylinder cover so as to open facing the cushion hole, and a plate chamber is slidably provided in the plate chamber, and the cushion A plate that changes the flow path area of the hole, a piston chamber formed in the radial direction of the cylinder cover corresponding to the plate chamber, and a piston chamber inside the piston chamber so as to define two chambers C and D. a plate driving piston that is slidably provided and connected to the plate; an oil passage that communicates with one chamber C defined by the plate driving piston and one chamber A defined by the piston; and a spring member provided in another chamber D defined by the plate driving piston, which normally biases the plate into a state slightly protruding into the cushion hole.

With this configuration, when the piston approaches the stroke end and the cushion member is fitted into the cushion hole, the space between the plate and the cushion member becomes a gap through which oil flows, and the oil flowing through the gap is Provides cushioning action with resistance. At this time, depending on the high or low pressure in chamber A,
In addition to changing the amount of movement of the plate driving piston, even if the oil temperature changes, the pressure in chamber A changes due to viscosity. Provides appropriate cushioning action depending on the temperature.

Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 3 to 5. In this embodiment, the same components as in FIGS. 1 and 2 are given the same reference numerals.

In the figure, reference numeral 10 denotes a through hole bored in the head cover 1A of the cylinder 1 in a radial direction relative to the cushion hole 2;
slides from a position close to the cushion hole 2 a plate chamber 12 housing a plate 11 that can move forward and backward with respect to the cushion hole 2, a reduced diameter portion 14 into which a stop bolt 13 is screwed, and a plate driving piston 15. Piston chamber 16 that can be inserted and adjustment bolt 1
7 is screwed into the small diameter portion 18. The inside of the piston chamber 16 is divided into chambers C and D by the plate driving piston 15. One end side of a shaft 19 provided in the axial direction of the through hole 10 is screwed onto the plate 11, and the shaft 19 passes through the center of the stop bolt 13 and protrudes into the piston chamber 16, and the other end side is screwed into the plate 11. The plate 11 and the plate driving piston 15 are screwed onto the plate driving piston 15.
are connected. The locking bolt 13 is provided with a seal member 13A for sealing the shaft 19, the plate driving piston 15 is provided with a seal member 15A for sealing the piston chamber 16, and the chamber C is provided with a seal member 13A for sealing the shaft 19, and a seal member 15A for sealing the piston chamber 16. A spring 20 is tensioned in the chamber C to bias the plate driving piston 15 toward the small diameter portion 18.

Further, an oil passage 21 is formed in the head cover 1A, and one end of the oil passage 21 opens into the chamber C, and the other end communicates with the chamber A within the cylinder 1.

Further, a spring 22 having a larger spring force than the spring 20 is tensioned in the other chamber D of the piston chamber 16. One end of the spring 22 contacts the plate driving piston 15, and the other end is attached to the spring receiver 23. It is in contact with the tip of the adjustment bolt 17 via the. and,
Screw the adjustment bolt 17 and attach the spring receiver 23.
By expanding and contracting the spring 22 via the spring constant, the spring constant can be changed.

In the cylinder cushion device constructed in this way, the spring force of the spring 22 is applied in a direction to push down the plate driving piston 15 against the spring force of the spring 20 opposing it, and the plate 11 connected thereto is moved into the cushion hole. 2 and is held in a slightly protruding state.

However, when pressure oil is supplied into the chamber B of the cylinder 1, the piston 7 moves at high speed to the right in FIG. Entering the clothing process. At this time, the pressure in the chamber A increases to absorb the inertial force of the piston 7, and the pressure oil flows into the chamber C through the oil passage 21.
Acting on the plate driving piston 15, the spring 22
Push upward against the spring force. When the plate driving piston 15 is pushed up, the plate 11 connected to the plate driving piston 15 is drawn into the plate chamber 12 by the shaft 19, so the flow path area of the cushion hole 2 increases,
By reducing the flow resistance of the oil, the stroke of the piston 7 can be stably controlled.

On the other hand, even when entering the cushion stroke, the pressure in chamber A does not increase much, and when the desired resistance force against the inertial force of piston 7 is not obtained, the pressure in chamber C does not increase. Therefore, the plate 11 cannot be drawn into the plate chamber 12, and therefore the flow path area of the cushion hole 2 remains restricted, and the pressure oil flowing out from the chamber A creates a large flow resistance. This increases the cushioning action on the piston 7.

On the other hand, if the piston 7 is driven when the temperature of the pressure oil in the cylinder 1 is low and its viscosity has increased significantly, when the cushion stroke begins, the pressure in the chamber A will become extremely high and the piston 7 will suddenly This will add some resistance. Therefore, in the cushioning device according to the prior art described above, the pressure waveform becomes as shown in curve A in FIG. 6, and a significantly large peak pressure is generated during the cushioning stroke. When the pressure increases, the plate 11 is pulled into the plate chamber 12 to expand the flow path area in the cushion hole 2, making it easier for the oil to flow. Prevents peak pressure from occurring,
Demonstrates smoother cushioning action.

In addition, when the oil temperature in the cylinder 1 increases, the viscosity of the oil decreases, so even if the cushion stroke begins, the flow resistance when the oil flows out cannot be increased, and the pressure in the chamber A decreases. may not rise to the expected level. In such cases,
Since the pressure within the chamber C does not rise to the extent that it can resist the spring 22, the plate 11 is not retracted, and therefore the flow resistance of the oil passing through the annular gap increases, making it possible to increase the cushion performance. .

Furthermore, if the axis of the cushion member 9 is eccentric with respect to the axis of the cushion hole 2, the flow resistance passing through the annular gap changes, and the desired cushioning action may not be obtained. However, even in such a case, the plate 1 changes depending on the pressure inside the chamber A.
1 moves forward and backward with respect to the plate chamber 12, the flow path area automatically changes, and the cushion performance can be adjusted.

Therefore, if the adjustment bolt 17 is screwed in advance to set the protruding position of the plate 11 due to the spring load of the spring 22 according to manufacturing errors and assembly errors, it will be possible to prevent the device from being accurately aligned. Stable cushion performance can be obtained even when oil temperature changes.

Furthermore, when the piston 7 is actuated to the left in the figure by supplying pressure oil from the supply/discharge port 3 while the piston 7 is at the stroke end, the pressure oil acts on the end surface of the cushion member 9 and the cushion member 9 It flows into the chamber A through an annular gap formed on the outer periphery of the chamber. At this time, the pressure oil also acts on the plate 11 and pushes up the plate 11, thereby shortening the throttle section, so the pressure oil quickly flows into the chamber A, and the interior of the chamber A becomes negative as in the prior art. There is no risk of pressure building up and causing abnormal noise.

In this embodiment, only one plate 11 is provided, but two or more plates 11 may be provided. Also, attach the plate 11 to the head cover 1A.
Rod cover 1B, not limited to those provided only on the side
Similar plates can also be provided on the sides. Furthermore, a stopper (not shown) for restricting the downward position of the plate driving piston 15 may be provided to protrude from the inner wall of the piston chamber 16. Therefore,
The stopper moves the plate 11 into the cushion hole 2.
If the spring 20 is held in a slightly protruding state, the spring 20 can be omitted and only the spring 22 is provided.

The hydraulic cylinder cushioning device of the present invention is as described in detail above, and has the following effects.

Since the flow path area of the annular gap is adjusted by the plate 11 which moves forward and backward depending on the internal pressure of the chamber A of the cylinder 1, the stroke of the piston 7 can be stably controlled.

Even if the resistance force against the piston 7 changes due to a change in the viscosity of the pressure oil supplied into the chamber A of the cylinder 1 due to a change in oil temperature, the pressure inside the chamber A will change accordingly. 15, the advancing and retreating position of the plate 11 connected to the plate driving piston 15 with respect to the cushion hole 2 changes, and the flow path area can be increased or decreased, so that changes in the cushion action can be reliably caused by changes in oil temperature. It can be prevented.

In particular, when the viscosity of the oil is high and the pressure in the chamber A inside the cylinder 1 becomes extremely high during the cushion stroke, the pressure oil acts on the plate driving piston 15 and quickly draws the plate 11 into the plate chamber 12. , can reduce peak pressure and improve cushioning performance.

Even if the axis of the cushion member 8 is eccentric with respect to the axis of the cushion hole 2, a reduction in cushion performance can be prevented by changing the protruding position of the plate 11 according to the amount of eccentricity.

Since eccentricity can be corrected by the above-mentioned method, there is no need to improve the machining accuracy of the cylinder cover, cushion member, etc., and the number of machining steps can be reduced.

When the piston 7 at the stroke end is started in the opposite direction, the oil passing through the annular gap formed on the outer periphery of the cushion member 8 acts on the plate 11 and pushes the plate 11 up, so that the flow path expands. Since the pressure oil can be quickly applied to the entire piston 7, the pressure in the chamber A increases rapidly, and no abnormal noise is generated when the cushion member 8 comes out of the cushion hole 2.

[Brief explanation of the drawing]

1 and 2 show a conventional hydraulic cylinder cushioning device, FIG. 1 is a vertical sectional view showing its overall structure, FIG. 2 is a partially enlarged view of FIG. 1, and FIGS. The figures show a cushion device for a hydraulic cylinder according to an embodiment of the present invention, FIG. 3 is a partial vertical sectional view thereof, FIG. 4 is an enlarged view of the main part of FIG. 3,
FIG. 5 is a sectional view taken along the line V-V in FIG. 3, and FIG. 6 is a diagram showing pressure-stroke characteristics. 1...Cylinder, 1A...Head cover, 2...
...Cushion hole, 7...Piston, 8...Cushion member, 11...Plate, 12...Plate chamber, 15...Plate driving piston, 16...
Piston chamber, 21...oil passage, 22...spring, A,
B, C, D...room.

Claims (1)

[Claims] 1 A hydraulic cylinder having a cylinder cover, a piston having a rod slidably provided in the hydraulic cylinder so as to define the interior of the hydraulic cylinder into two chambers A and B, and a rod provided on at least one side of the piston. A cushioning device for a hydraulic cylinder comprising a cushioning member having a cylindrical shape and a cushioning hole formed in the cylinder cover in the axial direction and into which the cushioning member is fitted at a stroke end, the cushioning device having an opening facing the cushioning hole; a plate chamber formed in the radial direction of the cylinder cover;
a plate slidably provided in the plate chamber and changing the flow path area of the cushion hole by moving forward and backward with respect to the cushion hole; and a plate formed in the radial direction of the cylinder cover corresponding to the plate chamber. a piston chamber slidably provided in the piston chamber so as to define the piston chamber into two chambers C and D, and a plate driving piston connected to the plate; An oil passage communicating with one chamber C defined by the piston and one chamber A defined by the piston, and another chamber D defined by the plate driving piston, and is normally connected to the plate. A cushion device for a hydraulic cylinder, characterized in that the cushion device comprises a spring member that urges the cushion to slightly protrude into the cushion hole.