JPH0144851B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic control circuit for a hammer for a pile driver, in which the hammer is driven by reciprocating motion of a hydraulic cylinder. The present invention relates to a hydraulic control circuit for a hammer for a pile driving machine, in which a hydraulic pump for driving a hoisting winch or the like is used to operate the hydraulic cylinder.

As is well known, in some pile driving machines, a hammer is driven by the reciprocating motion of a hydraulic cylinder. The pile driver is also equipped with a hydraulic pump for traveling, rotating the upper revolving structure, and driving the hoisting winch.

Therefore, it is conceivable that the hydraulic cylinders are controlled by these hydraulic pumps. FIG. 1 shows a hydraulic control circuit for such a hammer for a pile driver. In the figure, 1 is an oil tank, 2 is a fixed displacement hydraulic pump that controls the swing hydraulic motor, and 3
and 3' are variable displacement hydraulic pumps that control the left and right traveling drive motors or the hoisting winch drive motors.

A control valve 4 for operating the pile driving machine body is provided on the discharge side of the fixed displacement hydraulic pump 2, and by switching the control valve 4, the swing hydraulic motor can be controlled, and the oil provided on the discharge side can be controlled. The discharge oil is supplied to the suction side of the variable displacement hydraulic pumps 3, 3' via the cooler 5 and the discharge side pipe line 21.

A filter 6 and a back pressure check valve 7 are provided on the suction side of the variable displacement hydraulic pumps 3, 3'. Further, control valves 4A and 4B are provided on the discharge side of the variable displacement hydraulic pumps 3 and 3'.
By switching the control valves 4A and 4B, it is possible to control the traveling drive motor or the hoisting winch drive motor, and also to control the hammer drive hydraulic cylinder 10, which will be described later.

Switching valves 8, 8' are provided downstream of the control valves 4A, 4B, respectively.
By switching 8', control valve 4A,
Hydraulic cylinder 10 for driving the hammer with pressure oil from 4B
(hereinafter abbreviated as a hydraulic cylinder) or a return pipe 11. The switching valves 8, 8' are adapted to supply the combined pressure oil or individual pressure oil of the variable displacement hydraulic pumps 3, 3' to the hydraulic cylinder 10 by switching them simultaneously or separately.

A directional switching valve 9 for controlling the hydraulic cylinder 10 is provided between the switching valves 8, 8' and the hydraulic cylinder 10. A check valve 12 is provided in the drive conduit a connecting the directional switching valve 9 and the rod chamber 10a of the hydraulic cylinder 10 to prevent it from flowing into the rod chamber 10a. A drive line b connecting the switching valve 9 is connected to the rod chamber 10a via a branch line c. The branch pipe c is provided with a check valve 12' for blocking the flow from the drive pipe b into the rod chamber 10a, and the check valve 12' is opened by the hydraulic pressure generated in the drive pipe a. It's starting to become easier.

In this circuit, oil discharged from a fixed displacement hydraulic pump 2 is sent to a return line 11 via a control valve 4, an oil cooler 5, and a discharge side line 21, and then passes through a filter 6 where the required flow rate is variable. The oil is supplied to the displacement hydraulic pumps 3, 3', and the flow rate other than that required by the variable displacement hydraulic pumps 3, 3' is returned to the oil tank 1 by the back pressure check valve 7. The oil discharged from the variable displacement hydraulic pumps 3, 3' is circulated to the return pipe 11 when the switching valves 8, 8' are in the neutral positions A and A' as shown in the figure, and the oil discharged from the switching valves 8, 8' When it is switched to the positions B and B', it is supplied to the directional control valve 9 side. When the directional control valve 9 is in the neutral position C as shown in the figure, the discharged oil is circulated to the return pipe 11. When the directional control valve 9 is now switched to the position D, the head chamber 1 of the hydraulic cylinder 10 is
0b and extends the rod. That is, the hammer is raised.

Further, when the directional control valve 9 is switched to the position E, the discharged oil flows through the drive pipe a. At this time, the discharged oil is blocked by the check valve 12, and the check valve 12' of the branch pipe c is blocked by the oil pressure.
is opened, and the rod chamber 10a and head chamber 10b of the hydraulic cylinder 10 are brought into communication. That is, both chambers of the hydraulic cylinder 10 are in communication with the low pressure side, and the rod is contracted by the weight of the hammer. In other words, the hammer will fall freely.

When this rod reduction is performed, head chamber 1
The oil in the rod 0b is circulated through the drive line b to the return line 11, and a portion of the return oil flows into the rod chamber 10a through the branch line c, thereby preventing negative pressure in the rod chamber. I can escape. Then, as the rod of the hydraulic cylinder 10 repeatedly moves back and forth, it rises.
The descent is continuous. In other words, it becomes possible to drive the pile with a hammer.

By the way, in the hydraulic control circuit for the pile driver hammer shown above, when the hammer is raised, that is, when the rod of the hydraulic cylinder 10 is extended, the rod chamber 1
The amount of oil discharged from the return pipe 11 is smaller than the normal return oil flow rate because the volume difference between the head chamber 10b and the rod chamber 10a causes a flow rate of oil to flow into the return pipe 11. No surge pressure is generated.

However, when the hammer freely descends, that is, when the rod of the hydraulic cylinder 10 is contracted, the head chamber 10b
Since some of the oil in the head chamber 10b is allowed to flow into the rod chamber 10a and the hammer is allowed to fall freely (free fall speed + acceleration), most of the oil in the head chamber 10b is instantly drained into the return pipe 11. Moreover, since the amount of oil returns to the return line 11 and merges with the amount of oil circulating in the return line 11, a surge pressure several times the normal pressure is generated in the return line 11. Therefore, there is a problem that the return pipe 11, the oil cooler 5, and the filter 6 are damaged, and the oil cooler 5 is particularly problematic because its pressure resistance is limited. Furthermore, when surge pressure occurs, there is a problem in that it adversely affects the suction performance of the variable displacement hydraulic pumps 3, 3' connected to the return pipe 11.

Furthermore, when the directional control valve 9 is switched from the position D to the position E, there is a slight time delay until the check valve 12' is opened. Until opening of ', the pressure of the oil discharged from the variable displacement hydraulic pumps 3, 3' increases abnormally. Therefore, the control valves 4A and 4B generally have a built-in main relief valve that sets the discharge pressure of the variable displacement hydraulic pump, and when the above-mentioned abnormal pressure occurs, the main relief valve opens and the variable displacement hydraulic pump 3 and 3' are circulated through the return pipe 11. However, when the main relief valve operates, there is a problem in that the oil temperature in the high pressure side pipe line rises above the appropriate temperature. If the oil temperature exceeds the appropriate temperature, the oil film will break due to a decrease in viscosity, and functionality will decrease due to an increase in the amount of leakage, resulting in the complete operation of the entire machine being impaired. Moreover, the rise in temperature can cause long-term problems such as oil deterioration, sealing material aging, and sludge precipitation.

An object of the present invention is to prevent the oil temperature from rising on the high pressure side during the period from when the directional control valve is switched to the direction in which the rod of the hydraulic cylinder is contracted until the check valve opens, and when the hammer is freely lowered. It is an object of the present invention to provide a hydraulic control circuit for a hammer for a pile driving machine, which can reliably reduce surge pressure in a return pipe and minimize the adverse effects of surge pressure on hydraulic equipment.

In order to achieve the above-mentioned object, the hydraulic control circuit of the hammer for a pile driving machine of the present invention includes at least one variable displacement hydraulic pump and a fixed circuit for supplying pressure oil to the suction side of the variable displacement hydraulic pump. A displacement hydraulic pump, a control valve provided on the discharge side of the variable displacement hydraulic pump, a switching valve for supplying pressure oil from the control valve to a hammer driving hydraulic cylinder or a return pipe, and a control valve provided to the hydraulic cylinder. a directional control valve for switching and controlling the pressure oil of the hydraulic cylinder, an accumulator provided in the return pipe, a communication pipe connecting the drive pipes communicating with the rod chamber and the head chamber of the hydraulic cylinder, respectively, and the communication pipe. a relief valve provided in the rod chamber and arranged to release pressure oil from a drive line communicating with the rod chamber to a drive line communicating with the head chamber, and a check valve for preventing backflow to the relief valve, The relief valve is characterized in that the set pressure is set lower than the set pressure of the main relief valve that sets the pressure on the discharge side of the variable displacement hydraulic pump.

Hereinafter, the present invention will be explained with reference to the drawings. FIG. 2 is a hydraulic control circuit diagram of a hammer for a pile driving machine showing one embodiment of the present invention, and in the figure, the same reference numerals as in FIG. 1 represent the same or equivalent parts.

An accumulator 13 is provided in the return line 11 between the directional control valve 9 and the discharge side line 21 of the fixed displacement hydraulic pump 2 . The accumulator 13 is designed to absorb pressure fluctuations occurring in the return line 11 due to a large amount of oil discharged into the return line 11 when the rod of the hydraulic cylinder 10 is contracted.

Further, a drive pipe a connecting the directional control valve 9 and the rod chamber 10a of the hydraulic cylinder 10,
A communication pipe d is provided which connects the drive pipe b and the head chamber 10b, and the communication pipe d includes:
A relief valve 14 is provided to allow a portion of the pressure oil that has flowed into the drive line a to escape to the drive line b. The relief valve 14 is set at a lower set pressure than the set pressure of a high pressure main relief valve (not shown) built into the control valves 4A, 4B.

A check valve 15 for preventing backflow to the relief valve 14 is provided downstream of the relief valve 14 in the communication pipe d. Further, a stop valve 16 is provided upstream of the relief valve 14. The stop valve 16
is normally open, but for example when performing auger work, the function of the relief valve 14 can be prevented by closing it when controlling an auger drive hydraulic motor (not shown).

Since the hydraulic control circuit of the present invention is configured as described above, when the directional control valve 9 is switched from the D position to the E position to reduce the rod of the hydraulic cylinder 10, the hydraulic control circuit is operated until the check valve 12' is opened. Since there is a time delay, the variable displacement hydraulic pumps 3, 3'
The pressure of the discharged oil increases. When the pressure of the discharged oil exceeds the set pressure of the relief valve 14, the relief valve opens to release a portion of the oil that has flowed into the drive pipe a into the drive pipe b.

Therefore, the oil discharged from the variable displacement hydraulic pumps 3, 3' is circulated, so the check valve 1
Even if there is a time delay before opening 2', the oil temperature will not rise. The oil escaping from the relief valve 14 is returned to the return pipe 11 together with the return oil from the head chamber 10b.

Furthermore, when the rod of the hydraulic cylinder 10 is contracted by opening the check valve 12' (when the hammer is freely lowered), the combined oil in the rod chamber 10a and the head chamber 10b flows instantaneously into the return pipe 11. Therefore, when a pressure fluctuation occurs in the return pipe 11, the pressure fluctuation is absorbed by the accumulator 13, so that return oil at approximately normal pressure flows out into the return pipe 11 downstream from the accumulator 13. do.

That is, since the surge pressure generated in the return pipe line 11 is absorbed by the accumulator 13,
definitely lowered. As a result, the filter 6 provided in the return line 11 is hardly affected by the surge pressure. Furthermore, since almost no surge pressure acts on the discharge side pipe 21 of the fixed displacement hydraulic pump 2 connected to the return pipe 11, the oil cooler 5 provided in this pipe is also affected by the adverse effects of the surge pressure. do not have. Furthermore, fluctuations in the suction pressure of the variable displacement hydraulic pumps 3, 3' are also reduced.

FIG. 3 shows another embodiment of the present invention, which differs from FIG. 2 in that an in-line type accumulator 131 with a partition plate is interposed in the middle of the return pipe 11. The in-line partition plate-equipped accumulator 131 absorbs pressure fluctuations occurring in the return pipe line 11 and is capable of controlling the flow rate of return oil.

This embodiment functions effectively when the oil is used in a cold region, for example, and the viscosity of the oil is high.
That is, when the oil temperature is low, the viscosity of the oil is high, so there is a limit to the reduction in surge pressure. However, in this embodiment, the absolute amount of return oil from the hydraulic cylinder 10 (rod chamber 10a and head chamber 1
If the configuration is configured to limit the flow (merging oil of 0b), a restricted flow rate will pass through the downstream return pipe 11 of the in-line type accumulator with partition plate 131, so even if the viscosity of the oil is high, surge pressure will not occur. definitely lowered.

Although the illustrated embodiment shows an example using two variable displacement hydraulic pumps 3, 3', the present invention is not necessarily limited to this, and at least one variable displacement hydraulic pump 3, 3' is used. A positive displacement hydraulic pump may also be used.

As described above, according to the present invention, a communication pipe is provided to connect the drive pipes that communicate with the rod chamber and the head chamber of the hydraulic cylinder, and a relief valve is provided in the communication pipe, so that the rod chamber and the head chamber are connected to each other. By allowing some of the oil to escape from the communicating drive line to the drive line communicating with the head chamber, it is possible to prevent the oil temperature from rising when the directional control valve is switched so that the rod of the hydraulic cylinder is reduced. It can be prevented. Further, by providing a simple structure in which an accumulator is provided in the return pipe, it is possible to reliably reduce the surge pressure in the return pipe when the hammer is freely lowered. Therefore, it is possible to provide a hydraulic control circuit for a hammer for a pile driving machine that does not adversely affect hydraulic equipment due to surge pressure.

[Brief explanation of drawings]

FIG. 1 is a hydraulic control circuit diagram proposed to be applied to a hammer for a pile driver, and FIG. 2 is a hydraulic control circuit diagram for a hammer for a pile driver showing an embodiment of the present invention.
FIG. 3 is a hydraulic control circuit diagram of a hammer for a pile driver showing another embodiment of the present invention. 1...Oil tank, 2...Fixed capacity hydraulic pump, 3, 3'...Variable capacity hydraulic pump, 4A,
4B...Control valve, 8,8'...Switching valve,
9... Direction switching valve, 10... Hydraulic cylinder for hammer drive, 11... Return pipe, 13... Accumulator, 131... Accumulator with in-line type partition plate, 14... Relief valve, 15... Check valve, a , b... Drive conduit, d... Communication conduit.

Claims (1)

[Claims] 1 at least one variable displacement hydraulic pump;
A fixed displacement hydraulic pump that supplies pressure oil to the suction side of the variable displacement hydraulic pump, a control valve provided on the discharge side of the variable displacement hydraulic pump, and a control valve that supplies pressure oil from the control valve to hydraulic pressure for driving the hammer. A switching valve that supplies the cylinder or the return pipe, a directional switching valve that switches and controls the pressure oil to the hydraulic cylinder, an accumulator provided in the return pipe, and a rod chamber and a head chamber of the hydraulic cylinder, respectively, communicate with each other. a communication pipe connecting the drive pipes; a relief valve provided in the communication pipe and configured to release pressure oil from the drive pipe communicating with the rod chamber to the drive pipe communicating with the head chamber; and a check valve that prevents backflow to the relief valve, and the relief valve is set to a lower set pressure than the set pressure of the main relief valve that sets the pressure on the discharge side of the variable displacement hydraulic pump. Hydraulic control circuit for a hammer for a pile driver.