JPH02563B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a hydraulic cylinder of a working machine that uses the kinetic energy of a cylinder piston to strike an object, such as a hydraulic breaker, a pile driver, or a punching press.

The kinetic energy of the piston of a fluid pressure cylinder is given by the product of the piston working stroke, the effective pressure receiving area of the piston, and the fluid pressure acting on the piston.
The working stroke and effective pressure receiving area of the piston are determined by the size of the cylinder, but the fluid pressure is generated by the load on the piston. By the way, in the conventional hydraulic cylinder of this type of work machine, for example, the hydraulic cylinder of a hydraulic breaker, when the piston collides with the object to be hit via the chisel near the bottom dead center, that is, just before the working stroke ends. Only a large fluid pressure is generated. Therefore, there is a drawback that the kinetic energy of the piston during the forward stroke of the piston, which is the working stroke, is small. In addition, a sequence valve is installed in the inlet passage of the pilot chamber of the two-position switching valve.
A throttle valve is installed in the outlet side passage, and when the sequence valve is opened, the 2-position switching valve switches and switches the piston from the forward stroke to the return stroke, and the switching from the return stroke to the forward stroke is set by the opening of the throttle valve. (For example, Japanese Patent Application Laid-open Nos. 17788-1988 and 4976-1983) have been proposed. Therefore, in the return stroke, the hydraulic oil in the pilot chamber of the two-position switching valve is discharged into the tank via the throttle valve, which has the disadvantage that it takes time to discharge the hydraulic oil. Furthermore, since the amount of oil passing through the throttle valve is affected by the viscosity of the hydraulic oil, the switching point from the return stroke to the forward stroke changes depending on the outside air temperature.
For this reason, there is a problem that, for example, the number of hits per unit time is different in winter and summer.

The present invention aims to eliminate the above-mentioned drawbacks and to improve the switching characteristics of a two-position switching valve.The present invention has a structure in which a double-rod type double-acting cylinder in which both rods have different diameters has a small pressure-receiving area. Either the liquid chamber is connected to the pump and the liquid chamber with a large pressure-receiving area is connected alternately to the pump and tank using a pilot-operated three-port two-position switching valve, or both liquid chambers of a double-rod double-acting cylinder are pilot-operated. The piston of the double-rod type double-acting cylinder is alternately connected to the pump and tank by a two-position switching valve at the port, and when the pump hydraulic pressure is introduced into the pilot chamber of the two-position switching valve, the piston changes from the working stroke to the return stroke. In this cylinder control device, the piston is switched from the return stroke to the working stroke when the pilot chamber is switched to the tank, and the piston is switched from the return stroke to the working stroke. A first valve mechanism is provided that opens the valve at or near the position where the piston is switched from the working stroke to the return stroke, and a second valve mechanism that opens the valve at or near the position where the piston is switched from the working stroke to the return stroke is provided. A sequence valve that opens when the pump hydraulic pressure exceeds a predetermined pressure is interposed in the passage connecting the second valve mechanism and the pilot chamber.

Embodiments of the present invention will be described below with reference to the drawings.
In FIG. 1, 1 connects one liquid chamber 2 to pipes 3 and 4.
The other liquid chamber 6 is connected to the pump 5 via a conduit 7 and a 3-port 2-position switching valve 8 to a conduit 4 and a return conduit 9.
This is a differential cylinder that is selectively connected to the piston rod 11 and has an annular groove 12 formed at the base end of the piston rod 11 located on the side of the object 10 to be hit, and the piston 15 is located at the lower limit ( A chamber 16 that communicates with the pump-side pipe line 3 via the annular groove 12 and the liquid chamber 2 only when located between the left stroke end (in the figure, the working stroke end) and the vicinity of the lower limit.
This chamber 16 and the piston rod 11
The annular groove 12 constitutes a second valve mechanism.
Further, an annular groove 18 is formed at the tip of the other piston rod 17, which has a smaller diameter than the piston rod 11. This annular groove is formed in a chamber 20 formed at an appropriate interval in the piston rod insertion hole 19 of the casing 13 only when the piston 15 is located between the upper limit (the right stroke end, the return stroke end in the figure) and the vicinity of the upper limit. This communication allows the chamber 20 to communicate with the tank 23 via the passage 22 and the return pipe 9, which is a tank side pipe. The annular groove 18 and chambers 20, 21 of the piston rod 17
and constitute a first valve mechanism.

The 3-port 2-position switching valve 8 includes pilot chambers 24 and 25 with different pressure-receiving areas, and the pilot chamber 24, which has a large pressure-receiving area, is connected to the chamber 20 through a passage 27.
In addition, the chamber 16 is connected to the chamber 16 by a passage 28 branching from the passage 27.
A sequence valve 26 is interposed in this passage 28, and its pilot chamber 30 is connected to the pump-side conduit 3 through a passage 31, and the hydraulic pressure from the pump 5 is constantly introduced thereto. On the other hand, the pilot chamber 25, which has a small pressure receiving area, is connected to the pipe line 3 through a passage 29.
The hydraulic pressure from the pump 5 is constantly introduced. The 3-port 2-position switching valve 8 is set to take position B when no hydraulic pressure is applied to the pilot chamber 24, and to take position A when hydraulic pressure is applied.

Note that the pilot chamber 25 of the 3-port 2-position switching valve 8 can be replaced with a spring. Further, the piston rod 1 may be connected to the first valve mechanism using, for example, a detection rod.
A switching valve with a detection rod that switches from closed to open when the 7th end is detected may be used.

Next, the operation of the embodiment shown in FIG. 1 will be explained. The 3-port 2-position switching valve 8 is connected to the pilot chamber 24.
In the illustrated state in which the cylinder 1 assumes position A due to the hydraulic pressure acting on it, the liquid chamber 6 of the cylinder 1 communicates with the tank 23, and the piston 15 moves to the right in the figure due to the pump working liquid in the liquid chamber 2 (return stroke). When the piston 15 reaches the upper limit or its vicinity, the pilot chamber 24 communicates with the tank 23 through communication between the chambers 20 and 21 through the annular groove 18, and the two-position switching valve 8 switches from position A to position B to pump the liquid chamber 6. In order to communicate with 5,
The piston 15 receives pump working fluid on both sides, and moves to the left in the figure based on the difference in pressure receiving areas on both sides (working stroke). That is, the piston 15 is quickly turned back at the starting point of the working stroke without substantially any pressure fluctuation. During the working process, the hydraulic pressure from the pump 5 is lower than the set pressure of the sequence valve 26, so
Even if the chamber 16 communicates with the liquid chamber 2 through the annular groove 12 near the lower limit of the piston when the piston rod 11 collides with the object 10 to be hit, the sequence valve 26 is in position A and blocks the passage 28. For this reason, 2
The position switching valve 8 is still in position B. piston 15
When the pump reaches its lower limit and stops, the hydraulic pressure in the pipes 3, 4, 7 and the points connected thereto rises, and when this hydraulic pressure exceeds the set pressure of the sequence valve 26, the sequence valve 26 assumes position B and pumps the pump fluid. Pressure in pilot chamber 2
Lead to 4. This causes the two-position switching valve 8 to move to position A.
As a result, the piston 15 moves to the right in the figure (return stroke) due to the high pressure hydraulic fluid in the liquid chamber 2, and the above-described operation is repeated thereafter.

That is, in the one shown in Fig. 1, the piston receives high pump hydraulic pressure (sequence valve set pressure) from the beginning of the rightward stroke (return stroke), then reaches the upper limit, turns around, and moves leftward. Although the pressure decreases slightly during this period, it is still under quite high pressure, so the piston is filled with quite high-pressure hydraulic fluid from the beginning of the rightward stroke until it collides with the object near the end of the leftward stroke. As a result, a large amount of kinetic energy is generated, and in actual use, a more stable operation is obtained compared to a system in which high-pressure hydraulic fluid is applied to the piston from the beginning of the leftward stroke.

What is shown in FIG. 2 is another embodiment of the invention. This one replaces the 3-port 2-position switching valve 8 shown in FIG. 1 with a 4-port 2-position switching valve 32,
Both liquid chambers 2 and 6 of cylinder 1 are connected to pump 5 and tank 2.
3, and accordingly, one pilot chamber 25 and the pilot chamber 30 of the sequence valve 26 are connected to a passage 33 branched from the pump side pipe line 4, and the piston 15 is connected to the other end of this passage 33.
A chamber 35 is provided which communicates only with the chamber 16 via an annular groove 34 formed at the base of the piston rod 11 only when the piston rod is at or near the lower limit. and constitute a second valve mechanism, and the other mechanisms are the same as those shown in FIG.

In the embodiment shown in FIG. 2, when the two-position switching valve 32 is at position A and the piston 15 moves to the right in the figure, when the upper limit or its vicinity is reached, as in the case of FIG. The annular groove 18 communicates the pilot chamber 24 with the tank 23, the two-position switching valve 32 assumes position B, and the piston 15 moves to the left in the figure. Since the pump hydraulic pressure during this working stroke is lower than the set pressure of the sequence valve 26, even if the piston 15 approaches the lower limit and only the chambers 16 and 35 are in communication through the annular groove 34, the sequence valve 26
is in position A, and the two-position switching valve 32 is in position B.
When the piston 15 reaches the lower limit and stops, the pipe line 4,
7. When the hydraulic pressure in the passage 33 and the parts connected thereto increases and this hydraulic pressure exceeds the set pressure of the sequence valve 26, the sequence valve 26 assumes position B and the pump hydraulic pressure is applied to the pipe 4, the passage 33, and the chamber. 35, annular groove 34,
It acts on the pilot chamber 24 via the chamber 16, the passage 28, and the sequence valve 26, and the two-position switching valve 32 is in position B.
It switches from to position A. As a result, the piston 15
moves to the right in the drawing (return stroke) by the hydraulic fluid in the fluid chamber 2 and repeats the above-mentioned operation, and has the same effect as the embodiment shown in FIG.

As explained above, according to the present invention, the pilot chamber of the two-position switching valve is connected to the tank via the first valve mechanism that opens at or near the position where the piston is switched from the return stroke to the working stroke. Also, the piston is connected to the pump via a second valve mechanism that opens at or near a position where the piston is switched from the working stroke to the return stroke, and the pump is connected to a passage connecting the second valve mechanism and the pilot chamber. Since a sequence valve is installed that opens when the hydraulic pressure exceeds a predetermined pressure, the piston reciprocates through the set operating range without being affected by the viscosity of the hydraulic oil, and the piston stroke is always constant. Furthermore, since high-pressure (sequence valve set pressure) hydraulic oil is applied to the piston from the beginning (lower limit) of the return stroke, it is possible to impart large kinetic energy to the piston. In addition, since a two-position switching valve switches the spool to the other end using a spring or hydraulic pressure guided to a small pilot chamber when pilot pressure is not introduced to the pilot chamber, the spool pressing force is comparatively low. The target is small. Therefore, when high-pressure hydraulic fluid is introduced into the pilot chamber of the two-position switching valve via the sequence valve, the two-position switching valve is quickly switched. On the other hand, when a sequence valve is interposed between the two-position switching valve and the first valve mechanism and the two-position switching valve is switched in order to apply high-pressure hydraulic fluid to the piston at the upper limit, a spring or the like is used. Since the hydraulic oil in the pilot chamber is discharged to the tank side by overcoming the resistance of the sequence valve and the tank side passage with a relatively small spool pressing force, it takes time to discharge the hydraulic oil, and the switching time is longer than in the present invention. . Therefore,
When high-pressure hydraulic fluid is applied to the piston at the lower limit as in the present invention, the number of strikes per unit time increases.

[Brief explanation of drawings]

1 and 2 are hydraulic circuit diagrams of embodiments of the present invention, respectively. 1...Differential cylinder, 5...Pump, 8...3
Port 2 position switching valve, 10... hit object, 12,
18, 34...Annular groove, 15...Piston, 1
6, 20, 21, 35...chamber, 24...pilot chamber, 26...sequence valve, 32...4 port 2 position switching valve.

Claims (1)

[Claims] 1. Connect the liquid chamber with a small pressure-receiving area to the pump in a double-rod double-acting cylinder with two rods of different diameters, and connect the liquid chamber with a large pressure-receiving area to the pump and tank alternately using a pilot-operated 3-port two-position switching valve. Alternatively, both liquid chambers of a double-rod double-acting cylinder are alternately connected to the pump and tank by pilot-operated four-port two-position switching valves, and the piston of the double-rod double-acting cylinder is connected to the two positions. In a cylinder control device that switches from the working stroke to the return stroke when pump hydraulic pressure is introduced into the pilot chamber of the switching valve, and switches from the return stroke to the working stroke when the pilot chamber is communicated with the tank, A first valve mechanism that opens at or near the position where the piston is switched from the return stroke to the working stroke is provided in the passage connecting the pilot chamber and the tank, and the pilot chamber and the pump switch the piston from the working stroke to the return stroke. A sequence valve that is connected via a second valve mechanism that opens at or near the switching position, and that opens when the pump hydraulic pressure exceeds a predetermined pressure in a passage that connects the second valve mechanism and the pilot chamber. A cylinder control device characterized by being equipped with.