JPH02562B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic cylinder control device for a working machine that uses the kinetic energy of a cylinder piston to strike a wave-impacted object, such as a hydraulic breaker, a pile driver, and 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, so there is a drawback that it takes time to discharge the hydraulic oil. Moreover, 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 its configuration is such that a liquid chamber with a small pressure-receiving area of a double-rod type double-acting cylinder whose rods have different diameters is connected to a pump, and a liquid chamber with a large pressure-receiving area is connected to the pump. Either the chambers can be connected alternately to the pump and the tank using a pilot-operated 3-port 2-position switching valve, or both fluid chambers of a double-rod double-acting cylinder can be connected alternately to the pump and tank using a pilot-operated 4-port 2-position switching valve. The piston of the double-rod type double-acting cylinder switches from the working stroke to the return stroke when the pump hydraulic pressure is introduced into the pilot chamber of the two-position switching valve, and returns when the pilot chamber is communicated with the tank. In a cylinder control device configured to switch from a stroke to a work stroke, the above-mentioned 2.
In the passage connecting the pilot chamber and the tank of the position switching valve, there is a sequence valve that opens when the hydraulic pressure on the pump side exceeds a predetermined pressure, and downstream of the sequence valve, there is a position at or near the position where the piston is switched from the return stroke to the working stroke. A first 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 connected to the pump via 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. It is characterized by

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.
In addition, 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, and this annular groove is formed between the piston 15 from the upper limit (the right stroke end, the end of the return stroke in the figure) and the vicinity of the upper limit. The chambers 20 and 21 formed at appropriate intervals in the piston rod insertion hole 19 of the casing 13 are communicated with each other only when the piston rod is located at It communicates with a tank 23 via a pipe line 9. The annular groove 18 of the piston rod 17 and the chambers 20, 21 constitute a first valve mechanism.

The 3-port 2-position switching valve 8 has pilot chambers 24 and 25 with different pressure-receiving areas.
4 and the sequence valve 26
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. This 3
The 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. Sequence valve 26
The pilot chamber 30 is connected to the conduit 3 through a passage 31, and is constantly supplied with hydraulic pressure from the pump 5.

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.

Furthermore, instead of the 3-port 2-position switching valve 8, a pilot-operated 4-port 2-position switching valve is used to alternately operate the liquid chambers 2 and 6 of the double-rod type double-acting cylinder (in this embodiment, the double-rod type differential cylinder 1). The pump 5 and the tank 23 may be connected to each other.
In this case, the other end of the pump pressure supply path for supplying to the pilot chamber with a small pressure receiving area of the 4-port 2-position switching valve and the pilot chamber of the sequence valve 26 is connected to the chamber 1 in the hole 14 into which the piston rod 11 is inserted.
6 and an opening opened at an appropriate interval. Thereby, the second valve mechanism is constituted by the opening, the chamber 16, and the annular groove of the piston rod 11 that communicates the opening and the chamber 16 only when the piston 15 is located between the lower limit and the vicinity of the lower limit. It turns out.

Next, the operation of the present invention will be explained. 3 ports 2
When the position switching valve 8 is in position A due to the hydraulic pressure acting on the pilot chamber 24, the liquid chamber 6 of the differential cylinder 1 is communicated with the tank 23, and the piston 15 is moved to the right in the figure by the pump working liquid in the liquid chamber 2. During the return stroke, the hydraulic pressure in the pump side line 3 is lower than the set pressure of the sequence valve 26, and the sequence valve 26 blocks the passage 27. When the piston 15 reaches or near the upper limit, the chamber 20 communicates with the chamber 21 through the annular groove 18 and into the tank 23, but since the pilot chamber 24 is disconnected from the chamber 20, the 3-port 2-position switching is performed. Valve 8 is still in position A. Then, when the piston 15 stops at the upper limit, the pump hydraulic pressure increases, and when this hydraulic pressure exceeds the set pressure of the sequence valve 26, the sequence valve 26
is switched from position A to position B, and the pilot chamber 24
is communicated with the tank 23. Therefore, the two-position switching valve 8 is pushed by the hydraulic pressure in the pilot chamber 25 to discharge the hydraulic fluid in the pilot chamber 24, and when switched to position B, communicates the liquid chamber 6 with the pump 5. As a result, the piston 15 receives high pressure fluid (the set pressure of the sequence valve 26) on both sides thereof, and moves to the left from the upper limit to the lower limit based on the difference in the pressure receiving areas on both sides (working stroke).
That is, as a result of the piston 15 receiving high-pressure pump working fluid at the upper limit, it has a large kinetic energy during the working stroke, and as it approaches the lower limit, the hit object 1
collides with 0. In this work process, the communication between the chambers 20 and 21 of the first valve mechanism is cut off when the annular groove 18 leaves the chamber 21, so the pilot chamber 24 of the two-position switching valve 8 also loses communication with the tank 23. Cut off. When the piston rod 11 collides with the object 10 to be hit, the chamber 16 of the second valve mechanism communicates with the pump side pipe line 3 via the annular groove 12 and the liquid chamber 2, and the pump enters the pilot chamber 24 of the two-position switching valve 8. Directs hydraulic pressure. As a result, the switching valve 8 is switched from position B to position A, and in order to communicate the liquid chamber 6 with the tank 23, the piston 15 is turned back from the lower limit by the pump working liquid in the liquid chamber 2 and moves to the right in the figure ( (return stroke), and the above-mentioned operations are then repeated.

Although the pump hydraulic pressure during the piston return stroke is lower than the hydraulic pressure at the beginning of the piston working stroke, it still maintains a considerably high pressure.On the other hand, the sequence valve 26 It has returned to position A.

As explained above, according to the present invention, the pilot chamber of the two-position switching valve is a sequence valve that opens when the hydraulic pressure on the pump side exceeds a predetermined pressure, and a position at or near the position where the piston is switched from the return stroke to the working stroke. The sequence valve is connected to the tank via a first valve mechanism that opens the valve when the piston is switched from the working stroke to the return stroke. Since the piston is connected to the piston, high-pressure hydraulic fluid can be applied to the piston from the beginning of the working stroke, thereby imparting large kinetic energy to the piston. Further, since the piston reciprocates in a set operating range without being affected by the viscosity of the hydraulic oil, the piston stroke is always constant.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram of an embodiment of the present invention. 1...Differential cylinder, 5...Pump, 8...3
Port 2 position switching valve, 10... hit object, 12,
18...Annular groove, 15...Piston, 16,2
0, 21...room, 24...pilot room, 26...
...Sequence 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 sequence valve that opens when the hydraulic pressure on the pump side exceeds a predetermined pressure is provided in the passage connecting the pilot chamber and the tank;
A first valve mechanism is disposed downstream of the sequence valve and opens at or near the position where the piston is switched from the return stroke to the working stroke, and upstream of the sequence valve is located at or near the position where the piston is switched from the working stroke to the return stroke. A cylinder control device characterized in that the cylinder control device is connected to a pump via a second valve mechanism that opens the valve at .