JPH021343Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a hydraulic circuit for a hoist that raises or lowers a heavy object.

(Prior art) Fig. 2 shows a hydraulic circuit of a conventional hoist, in which a variable displacement pump p and an electromagnetic switching valve v communicate with each other via a supply passage 1 and a return passage 2, and the electromagnetic switching valve v and hydraulic pressure It communicates with the motor m via a high pressure passage 3 and a low pressure passage 4.

When the electromagnetic switching valve v is in the illustrated neutral position, it blocks communication between the supply passage 1 and the return passage 2, and the high pressure passage 3 and the low pressure passage 4. Then, when the electromagnetic switching valve v is switched to the left position in the drawing,
The supply passage 1 and the high pressure passage 3 communicate with each other, and
The return passage 2 and the low pressure passage 4 are communicated with each other. Also,
When the electromagnetic switching valve v is switched to the right side position in the figure, the supply passage 1 and the low pressure passage 4 communicate with each other, and the return passage 2 and the high pressure passage 4 communicate with each other.

And between the supply passage 1 and the return passage 2,
This flushing valve f has pilot chambers 5 and 6 on both sides thereof, and one pilot chamber 5 is connected to the supply passage 1, and the other pilot chamber 6 is connected to the return passage 2. is connected to.

Therefore, when the supply passage 1 is at high pressure, pilot pressure acts on the pilot chamber 5, and the flushing valve f is switched to the left position in the drawing, and when the return passage 2 is at high pressure, no pilot pressure is applied to the pilot chamber 6. acts, and the flushing valve f is switched to the right position in the drawing. and flushing valve f
When is in the left position, a part of the return oil on the return passage 2 side is communicated with the tank T via passage 7 → flushing valve f → passage 8 → relief valve 9. Moreover, when it is in the right-hand position, a part of the supply oil on the supply passage 1 side is communicated with the tank T via the same path as above.

The circuit configured as described above is further provided with a boost pump b, which is connected to the check valve 11 or 12 from the supply passage 10.
Hydraulic oil is supplied to the supply passage 1 or the return passage 2 via. The discharge pressure of this boost pump b is controlled by the relief valve 13.
The set pressure of this relief valve 13 is higher than the set pressure of the relief valve 9.

When the hydraulic oil is discharged from the variable displacement pump p and the electromagnetic switching valve v is switched to the left position in the figure, the hydraulic pressure is transferred to the hydraulic motor m via the supply passage 1 → electromagnetic switching valve v → high pressure passage 3. is supplied to lift the heavy load w. The return oil at this time returns to the variable displacement pump p via the low pressure passage 4 → electromagnetic switching valve f → return passage 2, and forms a closed circuit between the variable displacement pump p and the hydraulic motor m. do.

When the heavy load W is being raised in this manner, the high pressure oil on the supply passage 1 side acts on one pilot chamber 5 of the flushing valve f, so the flushing valve f is switched to the left side position in the drawing.

Therefore, some of the return oil on the return passage 2 side is
While returning to the tank T through the above-described route, the oil discharged from the boost pump b is supplied to the return passage 2 via the supply passage 10 and the check valve 12. In other words, a portion of the return oil is replaced with the boost oil to perform flushing.

Also, when pressure oil is discharged from the variable displacement pump p and the electromagnetic switching valve v is switched to the right position in the drawing,
The oil discharged from the pump p is supplied to the hydraulic motor m through the low pressure passage 4, and lowers the heavy object W. At this time, the hydraulic motor m receives a load and performs a pumping action, so that the high pressure passage 3 and the return passage 2, which are the return sides, have a higher pressure than the supply passage 1 and the low pressure passage 7, which are the supply sides.

Note that since the variable displacement pump p maintains the rotational speed constant by the action of an electric motor (not shown), a braking force acts on the motor m.

If the pressure on the return passage 2 side becomes high as described above, the other pilot chamber 6 of the flushing valve f
Since the pilot pressure acts on the flushing valve f, the flushing valve f is switched to the right position in the drawing.

When the flushing valve f is switched to the above-mentioned right position, a part of the supplied oil on the supply passage 1 side is transferred to the above-mentioned tank T.
On the other hand, the oil discharged from the boost pump b is replaced by the supply passage 10 and the check valve 11.
Since the supply oil is supplied to the supply passage 1 side via the supply oil, a part of the supplied oil and the boost oil are replaced and flushing is performed.

(Problems to be solved by the present invention) In the conventional hydraulic circuit as described above, for example,
When the electromagnetic switching valve v is switched to the left position in the figure and the heavy object W is being raised, this switching valve v
When attempting to lower the heavy object by switching the valve f to the right position, a delay in response occurs in the flushing valve f. If the switching of the flushing valve f is momentarily delayed in this way, the return passage 2 side becomes high pressure while the flushing valve f maintains the left position, so this high pressure oil passes through the flushing valve f that maintains the left position. There was a risk that the hoist would run away and return to Tank T.

The object of this invention is to provide a hydraulic circuit for a hoist that does not cause a response delay in a flushing valve even if the switching valve is switched to lower the heavy object while the heavy object is being raised.

(Means for solving the problem) In order to achieve the above object, this invention connects the supply passage to the discharge side of the variable displacement pump, connects the return passage to the return side, and connects the supply passage to the return side of the variable displacement pump. hand,
A variable displacement pump is connected to a switching valve, and this switching valve and a hydraulic motor are connected through a high pressure passage and a low pressure passage, so that when the switching valve is switched, a closed circuit is created between the variable displacement pump and the hydraulic motor. In the hydraulic circuit of the hoisting machine, which is configured with a flushing valve and a boost pump for flushing, a flushing valve is provided between the switching valve and the hydraulic motor, and the pilot chamber of this flushing valve is connected to the pilot chamber of the flushing machine. It is connected to the high pressure passage, and when pressure acts on this pilot chamber, the flushing valve is switched to the switching position, thereby communicating the low pressure passage side with the tank.

(Operation of the present invention) With the above structure, when the hydraulic motor is being driven, the flushing valve is always held at the switching position and guides oil from the low pressure passage side to the tank. Then, the oil discharged from the boost pump is supplied to the circuit, so that flushing is performed.

In addition, when the hydraulic motor is being driven as described above, the flushing valve always maintains the switching position, so the switching valve must be switched from the state in which the heavy object is being raised to lowering it. Moreover, there is no delay in the response of the flushing valve, and there is no possibility that the fluid will flow into the pressure oil tank on the high pressure side.

(Effects of the present invention) Therefore, there is no danger that the hoist will run away the moment the switching valve is switched.

(Embodiment of the present invention) The embodiment shown in FIG. 1 is similar to the conventional case in that an electromagnetic switching valve V is connected between the variable displacement pump P and the hydraulic motor M. That is, the variable displacement pump P has the supply passage 14 connected to its discharge side, the return passage 15 connected to its return side, and the variable displacement pump P connected to the electromagnetic switching valve V via both passages 14 and 15. are doing. Further, the electromagnetic switching valve V and the hydraulic motor M are connected via a high pressure passage 16 and a low pressure passage 17.

The operation of the electromagnetic switching valve V is exactly the same as in the conventional case.

Between the high pressure passage 16 and the low pressure passage 17,
A flushing valve F is connected, and this flushing valve F has pilot chambers 18 and 19 on both sides, one pilot chamber 18 is connected to the high pressure passage 16, and the other pilot chamber 19 is connected to the low pressure passage 17.
is connected to. The first port 20 of the flushing valve F thus constructed is connected to the low pressure passage 17 via a passage 21, while the second port 22 is communicated with the tank T via a relief valve 23.

When no pilot pressure is acting on both the pilot chambers 18 and 19, the flushing valve F maintains the normal position shown. When the flushing valve F is in the normal position, communication between the ports 20 and 22 is cut off. Further, when pressure oil flows into the high pressure passage 16 side, the pressure acts on one of the pilot chambers 18, and the flushing valve F is switched to the switching position on the left side of the drawing.
Both ports 20 and 22 are brought into communication.

This hydraulic circuit is equipped with a boost pump B as in the conventional case, but this boost pump B has a supply passage 24 and a check valve 25.
or 26, the high pressure passage 16 or the low pressure passage 1
It is connected to 7. The discharge pressure of the boost pump B is controlled by a relief valve 27, and the set pressure of the relief valve 27 is higher than the set pressure of the relief valve 23.

Reference numerals 28 and 29 in the figure are check valves, and in order to compensate for the amount of leakage in the circuit, the oil discharged from the boost pump B is transferred to the supply passage 16 or the return passage 17 via these check valves 28 and 29. We are trying to supply it to

Now, when pressure oil is discharged from the variable displacement pump P and the electromagnetic switching valve V is switched to the switching position, this discharged oil flows from the supply passage 14 to the electromagnetic switching valve V.
→The oil is supplied to the hydraulic motor M via the high pressure passage 16, while the return oil of the hydraulic motor M is returned to the variable displacement pump P via the low pressure passage 17→electromagnetic switching valve V→return passage 15. The hydraulic motor M
is driven to raise the heavy object W. In this case, a closed circuit is formed between the variable displacement pump P and the hydraulic motor M, as in the conventional case.

At this time, the pressure on the high pressure passage 16 side becomes high, so
This pressure acts as pilot pressure on one pilot chamber 18 of the flushing valve F, and
switch to the switching position. When the flushing valve F is switched in this way, a part of the return oil on the low pressure passage 17 side is transferred to the tank T via the passage 21 → the first port 20 of the flushing valve F → the second port 22 → the relief valve 23. communicate. At the same time, the oil discharged from the boost pump B is supplied to the low pressure passage 17 via the supply passage 24 and the check valve 26. In other words, some of the return oil on the low pressure passage 17 side is in the tank T.
Instead of returning to , the oil discharged from the boost pump B is replenished into the low pressure passage 17 and flushing is performed.

Further, when pressure oil is discharged from the variable displacement pump P and the electromagnetic switching valve V is switched to the right position in the figure, the pressure oil in the supply passage 14 flows into the hydraulic motor M via the low pressure passage 17, and this oil pressure The return oil of the motor M is transferred from the high pressure passage 16 to the return passage 1.
5 and returns to the variable displacement pump P, so the heavy object W is lowered.

At this time, the hydraulic motor M receives a load and performs a pumping action, so the high pressure passage 1 on the return side
6 and the return passage 15 side have a higher pressure than the supply passage 14 and low pressure passage 17 sides, which are the supply sides.

Therefore, since the pressure on the high pressure passage 16 side acts on the one pilot chamber 18, a part of the supplied oil on the low pressure passage 17 side returns to the tank T, and the discharge of the boost pump B is reduced, as described above. Oil passes through the check valve 26 to the low pressure passage 17 on the supply side.
is replenished and flushing is performed.

Note that since the variable displacement pump P maintains the rotational speed constant by the action of an electric motor (not shown), a braking force acts on the motor M.

Then, even if the electromagnetic switching valve V is switched to the left position to raise the heavy object as described above, even when the electromagnetic switching valve V is switched to the right position to lower the heavy object, the high pressure passage Since the pressure on the 16 side is maintained at high pressure, the flushing valve F remains in the switching position. In other words, no matter which way the electromagnetic switching valve V is switched, the flushing valve F is maintained at the switched position, so there is no delay in the responsiveness of the flushing valve F. At the same time, the pressure oil on the high pressure passage 16 side will no longer flow from the flushing valve F to the tank T.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing an embodiment of this invention, Figure 2 is a circuit diagram showing an embodiment of this invention.
The figure is a conventional circuit diagram. P...variable displacement pump, 14...supply passage, 1
5...Return passage, V...Solenoid switching valve, 18...Pilot chamber, 16...High pressure passage, 17...Low pressure passage, M...Hydraulic motor, F...Flushing valve,
B...boost pump, T...tank.

Claims (1)

[Scope of utility model registration request] Connect the supply passage to the discharge side of the variable displacement pump,
A return passage is connected to the return side, and a variable displacement pump is connected to the switching valve via both passages, while this switching valve and a hydraulic motor are connected via a high pressure passage and a low pressure passage, and the switching valve is connected to the switching valve. In the hydraulic circuit of a hoist, which forms a closed circuit between the variable displacement pump and the hydraulic motor when the switching valve is switched, and is equipped with a flushing valve and a boost pump to perform flushing, the switching valve and the hydraulic motor are connected to each other. A flushing valve is provided in between, and the pilot chamber of this flushing valve is connected to the high pressure passage, and when pressure acts on this pilot chamber, the flushing valve is switched to the switching position, and the low pressure passage side is communicated with the tank. The hydraulic circuit of the hoist is configured to