JPH09229018A - Hydraulic cylinder piston structure - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To prevent oil shortage between an outer peripheral surface of a piston and an inner peripheral surface of a cylinder, and to prevent damage due to seizure even if the piston rod moves at high speed or receives a large lateral force. To provide a piston structure of a hydraulic cylinder having excellent durability that does not occur. SOLUTION: In a piston structure of a double-acting hydraulic cylinder in which a front hydraulic chamber 40 and a rear hydraulic chamber 50 are formed in a front-rear pair by a piston 10, an outer peripheral surface 1 of the piston is provided.
A plurality of relatively shallow recesses 13a and 13b provided at equal intervals in the circumferential direction at the front portion including the piston front end and the rear portion including the piston rear end, and the hydraulic pressures of the front hydraulic chamber and the rear hydraulic chamber. Communication oil passages 14a and 14b introduced into the front concave portion and the rear concave portion, respectively, and a flow of the working oil from the oil chamber fitted in the front oil passage and the rear oil passage and supplied with high-pressure working oil to the concave portion. Check valve 1 that allows
5a and 15b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piston structure for a hydraulic cylinder.

[0002]

2. Description of the Related Art For example, as a conventional hydraulic cylinder used in a hydraulic exciter for a vibrating table, as shown in a partial vertical sectional view of FIG. Piston rod 0 with piston 01
It is known that 2 is inserted.

In this type of double-acting hydraulic cylinder, high-pressure hydraulic oil is alternately supplied to the front and rear hydraulic chambers 04 and 05, which are divided by the piston 01 in the cylinder 03, through oil supply holes 06 and 07, respectively. By supplying, the piston rod 02 is reciprocated in the horizontal direction.

Further, the hydraulic oil is sealed between the front hydraulic chamber 04 and the rear hydraulic chamber 05, and the load generated by the lateral force of the piston rod 02 and its own weight is brought into contact with and supported by the cylinder inner peripheral surface 031. In order to prevent running out of oil when running, a plurality of circumferential grooves 01
2 are juxtaposed.

[0005]

However, in the piston structure as described above, when the piston rod 02 moves at high speed or the lateral force acting on it increases, the outer peripheral surface 011 of the piston 01 and the inner peripheral surface of the cylinder 03. Face 03
There is a risk that oil shortage will occur between No. 1 and 1 and damage due to seizure will occur.

The present invention has been proposed to solve such a problem, and prevents oil from running out between the outer peripheral surface of the piston and the inner peripheral surface of the cylinder, so that the piston rod moves at high speed. It is an object of the present invention to provide a piston structure of a hydraulic cylinder having excellent durability that does not cause damage due to seizure even when subjected to a large lateral force.

[0007]

According to the piston structure of the hydraulic cylinder of the present invention, high-pressure hydraulic oil is alternately supplied to the front hydraulic chamber 40 and the rear hydraulic chamber 50 which are formed by the piston 10 in a pair of front and rear. In a piston structure of a double-acting hydraulic cylinder, a plurality of relatively shallow recesses 13a provided at equal intervals in a circumferential direction at a front portion including a piston front end surface and a rear portion including a piston rear end surface of an outer peripheral surface of the piston, respectively.
13b, and communication oil passages 14a and 14b communicating from the front hydraulic chamber and the rear hydraulic chamber to the front concave portion and the rear concave portion, respectively.
And only the flow of the hydraulic oil from the hydraulic chamber fitted in the front and rear communication oil passages and supplied with high-pressure hydraulic oil to the concave portion formed on the outer peripheral surface of the piston is allowed, and the hydraulic pressure from the concave portion is increased. It is characterized by having check valves 15a and 15b for suppressing the flow into the chamber.

[0008]

With the above-mentioned structure, the piston structure of the double-acting hydraulic cylinder according to the present invention operates as follows. Double acting hydraulic cylinder piston forward stroke, but also the return stroke of the type actuated by the action of hydraulic, the pressure of the hydraulic oil flowing into the cylinder P _H, the oil pressure (back pressure) acting on the outlet side P _L Then, the piston alternately receives a thrust force corresponding to the pressure difference, and reciprocates in the cylinder at a speed corresponding to the flow rate of the hydraulic oil.

Regarding the pressure distribution of the working oil in the clearance between the outer peripheral surface of the piston and the inner peripheral surface of the cylinder when the piston slides in the cylinder, the pressure of the working oil flowing into the hydraulic chamber 40 is as shown in FIG. A case will be described where the piston 10 slides in the direction of arrow D at a high pressure P _H and the back pressure on the outflow side of the hydraulic chamber 50 is P _L. Assuming that the piston 10 is stationary, the inflow pressure P _H and the back pressure P _L acting on the piston have a static pressure hydraulic distribution as indicated by a solid line abcd.

When the piston 10 slides in the direction of the arrow D and there is a fluid flow associated with the movement, dynamic pressure is generated. However, even if the recesses 13a and 13b are formed on the outer peripheral surface of the piston, communication is established. Assuming that the oil passages 14a and 14b are not bored and the check valves 15a and 15b are not fitted, the movements in the vicinity of the concave portion 13a which is rearward and in the vicinity of the concave portion 13b which is forward in the traveling direction of the piston are performed. The pressure distribution is as follows.

In the region from the recess 13a to the piston outer peripheral surface 11, the piston outer peripheral surface 11 and the cylinder inner peripheral surface 3
The narrow clearance between the positions 1 and 2 rapidly increases as the piston advances in the recess 13a at the rear of the moving direction, so that the pressure is reduced and the dotted line ef
The negative dynamic pressure distribution has a triangular shape as shown by g.

In the region from the recess 13b to the outer peripheral surface 11 of the piston, the recess 1 located in the forward direction of the piston travels.
Since the clearance is narrower between the piston outer peripheral surface 11 and the cylinder inner peripheral surface 31 which is located behind 3b, the pressure increases,
The triangle-shaped positive dynamic pressure distribution as indicated by the dotted line hij is obtained.

In the case where there is no communication oil passage, and therefore no check valve, as in the structure of the conventional example, a simple superposition of the above two dynamic pressures and static pressure distribution results in a hydraulic pressure distribution indicated by the one-dot chain line amnd, and The level of the hydraulic pressure distribution near the recess 13a on the rear side in the direction decreases, and the bearing capacity by the hydraulic pressure when the piston 10 is pressed in the radial direction decreases.

The drilling of the communication oil passage and the fitting of the check valve according to the present invention are means for suppressing a decrease in the level of the hydraulic pressure distribution in the vicinity of the recessed portion on the outer peripheral surface of the piston located rearward in the traveling direction of the piston. Pressure P of hydraulic oil flowing into the cylinder
Press the check valve open with _H to connect the oil chamber on the high pressure side to the recess. However, in the check valve in the forward direction, that is, on the side where the back pressure P _L acts, the urging force of the valve spring is larger than the force due to the back pressure, so the valve remains closed and the oil from the recess side to the back pressure side is maintained. Dynamic pressure never escapes to the chamber.

As described above, the communicating oil passages 14a and 14b are provided both in the forward stroke and the return stroke of the piston 10.
The check valves 15a and 15b have a function of suppressing a decrease in the level of hydraulic pressure distribution when a negative dynamic pressure is generated, and preventing a problem that the dynamic pressure is released when a positive dynamic pressure is generated. The hydraulic pressure distribution is abnd by the solid line and the chain line
Indicated by

[0016]

1 is a partial vertical sectional view of a piston structure of a double-acting hydraulic cylinder according to an embodiment of the present invention.
The front view is shown in FIG. The structure of the piston will be described with reference to these drawings. In FIGS. 1 and 2, 10 is a piston that performs forward and backward stroke operations in the cylinder 30 by the action of hydraulic pressure, 20 is a piston rod, and 40 and 5
Reference numeral 0 denotes a hydraulic chamber which is formed in front of and behind the piston in the cylinder, and hydraulic fluid of high pressure is alternately supplied via hydraulic fluid passages (not shown), 11 denotes an outer peripheral surface of the piston,
Reference numeral 31 is an inner peripheral surface of the cylinder. 12a and 12b are front and rear end surfaces of the piston 10, 13a and 13b are front portions of the piston outer peripheral surface including the front end surface 12a of the piston,
And a relatively shallow recess formed in the rear portion of the outer peripheral surface of the piston including the rear end surface 12b of the piston in a front-rear pair at equal intervals in the circumferential direction.

The pistons 14a and 14b are axially bored at an intermediate level between the front end face 12a and the rear end face 12b of the piston 10, and are hydraulic chambers 40 and 50 formed in front and rear of the piston 10.
And a recess 1 formed in the front and rear of the outer peripheral surface of the piston
It is an oil passage that communicates with the portions near the ends of 3a and 13b. 15a and 15b are the above-mentioned communication oil passages 14a,
14b, when the high-pressure hydraulic oil is supplied, only the hydraulic oil is allowed to flow from the hydraulic chambers 40, 50 toward the recesses 13a, 13b formed on the outer peripheral surface of the piston. This is a check valve that suppresses the flow from the opposite recess side to the hydraulic chamber side.

With the above-described structure, the piston structure of the double-acting hydraulic cylinder according to the present invention operates as follows. Double acting hydraulic cylinder piston forward stroke, but also the return stroke of the type actuated by the action of hydraulic pressure to P _H of the high pressure hydraulic fluid flowing into the cylinder, the oil pressure (back pressure) acting on the outflow side When P _L is set, the piston alternately receives a thrust force corresponding to the pressure difference, and reciprocates in the cylinder at a speed corresponding to the flow rate of the hydraulic oil.

Regarding the pressure distribution of the hydraulic oil in the clearance between the piston outer peripheral surface 11 and the cylinder inner peripheral surface 31 when the piston 10 slides in the cylinder 30, the operation of flowing into the hydraulic chamber 40 as shown in FIG. The oil pressure is high pressure P _H ,
The back pressure on the hydraulic chamber 50 side, which is the outflow side, is P _L , and the piston 1
A case where 0 slides in the direction of arrow D will be described. Assuming that the piston 10 is stationary, the inflow pressure P _H and the back pressure P _L acting on the piston have a static pressure hydraulic distribution as indicated by a solid line abcd.

When the piston 10 slides in the direction of the arrow D and there is a fluid flow associated with the movement, dynamic pressure is generated, but even if the recesses 13a and 13b are formed on the outer peripheral surface of the piston, the communication is continued. Assuming that the oil passages 14a and 14b are not bored and the check valves 15a and 15b are not fitted, the movement in the vicinity of the recess 13a which is rearward and in the vicinity of the front recess 13b with respect to the traveling direction of the piston is performed. The pressure distribution is as follows.

In the region from the recess 13a to the piston outer peripheral surface 11, the piston outer peripheral surface 11 and the cylinder inner peripheral surface 3
The narrow clearance between the positions 1 and 2 rapidly increases as the piston advances in the recess 13a at the rear of the moving direction, so that the pressure is reduced and the dotted line ef
The negative dynamic pressure distribution has a triangular shape as shown by g.

In the region from the concave portion 13b to the outer peripheral surface 11 of the piston, the concave portion 1 located at the front in the traveling direction of the piston.
Since the clearance is narrower between the piston outer peripheral surface 11 and the cylinder inner peripheral surface 31 which is located behind 3b, the pressure increases,
The triangle-shaped positive dynamic pressure distribution as indicated by the dotted line hij is obtained.

When there is no communication oil passage, and therefore no check valve, as in the structure of the conventional example, a simple superposition of the above two dynamic pressures and static pressure distribution results in a hydraulic pressure distribution indicated by the one-dot chain line amnd, and The level of the hydraulic pressure distribution near the recess 13a on the rear side in the direction decreases, and the bearing capacity by the hydraulic pressure when the piston 10 is pressed in the radial direction decreases.

The drilling of the communication oil passage and the fitting of the check valve according to the present invention are means for suppressing a decrease in the level of the hydraulic pressure distribution in the vicinity of the concave portion of the outer peripheral surface of the piston which is located rearward in the moving direction of the piston. Pressure P of hydraulic oil flowing into the cylinder
Press the check valve open with _H to connect the oil chamber on the high pressure side to the recess. However, in the check valve in the forward direction, that is, on the side where the back pressure P _L acts, the urging force of the valve spring is larger than the force due to the back pressure, so the valve remains closed and the oil from the recess side to the back pressure side is maintained. Dynamic pressure never escapes to the chamber.

As described above, the communicating oil passages 14a and 14b are provided during the forward stroke and the return stroke of the piston 10.
The check valves 15a and 15b have a function of suppressing a decrease in the level of the hydraulic pressure distribution when a negative dynamic pressure is generated, and a function of preventing a problem that the dynamic pressure is released when a positive dynamic pressure is generated. The hydraulic pressure distribution is abnd by the solid line and the chain line
Indicated by

In the operation described above, the flow direction of the working oil flowing into the cylinder 30 on the one hand and pushed away to the outside of the cylinder 30 on the other hand is switched by the direction switching valve (not shown) to the hydraulic chambers 40 and 50. The same applies to the case where the acting hydraulic pressure is alternately reversed, and therefore the direction in which the piston 10 moves is opposite.

[0027]

In summary, according to the present invention, the piston 10
In a piston structure of a double-acting hydraulic cylinder in which a high-pressure hydraulic fluid is alternately supplied to a front hydraulic chamber 40 and a rear hydraulic chamber 50 which are formed in a pair by front and rear, a piston front end surface of the outer peripheral surface of the piston is included. A plurality of relatively shallow recesses 13a and 13b provided at the front part and the rear part including the piston rear end face at equal intervals in the circumferential direction, and the front recess part and the rear recess part from the front hydraulic chamber and the rear hydraulic chamber, respectively. Of the hydraulic oil that is fitted to the front and rear communication oil passages and is supplied with high-pressure hydraulic oil from the hydraulic oil chamber 14a, 14b leading to the Check valve 15 that allows only flow but suppresses flow from the recess to the hydraulic chamber
By including a and 15b, the following effects can be obtained.

Prevents oil shortage between the outer peripheral surface of the piston and the inner peripheral surface of the cylinder, and does not cause damage due to seizure even if the piston rod moves at high speed or receives a large lateral force. It is possible to obtain a piston structure of a hydraulic cylinder having excellent properties.

[Brief description of drawings]

FIG. 1 is a partial vertical cross-sectional view of a piston structure of a hydraulic cylinder according to an embodiment of the present invention.

FIG. 2 is a front view of a piston structure of the hydraulic cylinder shown in FIG.

3A and 3B are a partial vertical sectional view and an oil pressure distribution diagram for explaining the operation of the piston structure of the hydraulic cylinder shown in FIG.

FIG. 4 is a partial vertical sectional view showing a piston structure of a hydraulic cylinder according to a conventional technique.

[Explanation of symbols]

10 ... Piston, 11 ... Piston outer peripheral surface, 12a, 1
2b ... Piston end face, 13a, 13b ... Piston side recess, 14a, 14b ... Communication oil passage, 15a, 15b
... Check valve, 20 ... Piston rod, 30 ... Cylinder, 3
1 ... Inner peripheral surface of cylinder, 40, 50 ... Hydraulic chamber, P _H ... High hydraulic pressure, P _L ... Low hydraulic pressure, D ... Piston movement direction.

Claims (1)

[Claims] 1. A piston structure of a double-acting hydraulic cylinder in which a high-pressure hydraulic fluid is alternately supplied to a front hydraulic chamber (40) and a rear hydraulic chamber (50) formed in a front-rear pair by a piston (10). A plurality of relatively shallow recesses (13a, 13b) provided at equal intervals in a circumferential direction in a front portion including a piston front end surface and a rear portion including a piston rear end surface, respectively, of the outer peripheral surface of the piston; From the hydraulic chamber and the rear hydraulic chamber, communication oil passages (14a, 14b) communicating with the front concave portion and the rear concave portion, respectively, and high pressure hydraulic oil fitted in the front communication oil passage and the rear communication oil passage were supplied. A check valve (15) that allows only the flow of hydraulic oil from the hydraulic chamber to the concave portion formed on the outer peripheral surface of the piston and suppresses the flow from the concave portion to the hydraulic chamber.
a, 15b), and a piston structure for a hydraulic cylinder.