JPH0526901B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a regeneration circuit for the cylinder return flow rate of a hydraulic excavator, and its purpose is 1) to regenerate the entire flow rate of the cylinder return side to the cylinder supply side when the cylinder drops under its own weight due to an external force. 2) When the pressure on the cylinder supply side increases to a certain pressure due to excavation resistance, etc., the cylinder return flow rate is transferred to the tank side. put it back,
The objective is to make effective use of cylinder driving force.

Figure 1 is a circuit diagram of a conventional hydraulic excavator, where 1 is a pump, 2 is a control valve, and the valve 2
is composed of a relief valve 3, a traveling spool valve 4, a turning spool valve 5, and an arm spool valve 6. 7 is a hydraulic oil tank, 8 is an arm cylinder, 9 is a conduit connected to the rod side of the arm cylinder 8, and 10 is a conduit connected to the bottom side of the arm cylinder 8. Reference numeral 11 denotes a flow rate limiting check valve provided in the pipe line 9 connected to the rod side of the arm cylinder.

In this manner, by restricting the cylinder return line 9 using the flow rate limiting check valve 11, the cylinder speed is regulated to match the flow rate of the pump entering the cylinder supply side. This conventional method does not generate negative pressure on the cylinder supply side. However, since the cylinder speed cannot be increased due to the presence of the throttle, work efficiency inevitably deteriorates.

In the case of FIG. 2, since a flow rate limiting check valve as shown in FIG. 1 is not provided, an arm spool valve 6', which will be described next, is used. That is, the circuit is such that the flow rate on the cylinder return side is regenerated to the cylinder supply side by switching the regeneration poppet 12, thereby increasing the cylinder speed. However, with this structure, at the beginning of switching the spool valve, the regeneration poppet 1
2 is not moving towards the playback side. Therefore, after a certain amount of time has elapsed, the regeneration poppet 12 moves to the regeneration side and the cylinder speed increases. This means that the cylinder speed fluctuates during operation, and smooth operation cannot be expected.

FIG. 3 shows a circuit according to the invention. The difference between FIG. 3 and FIG. 1 is that an arm spool valve 6'' is installed in place of the flow rate limiting check valve 11.

FIG. 4 shows the internal circuit of the arm spool valve when the spool valve 6'' is switched to the "A position". 6a is a regeneration poppet, 6b is a spring that tries to maintain the regeneration poppet 6a in the "A position" at all times, and 6c is a spring that tries to maintain the regeneration poppet 6'' in the "A position".
This is a passageway that connects to a conduit 9 connected to the rod side of the arm cylinder 8 when the arm cylinder 8 is opened. 6d is a passage connected to the conduit 10 connected to the bottom side of the arm cylinder 8 when the arm spool valve 6'' is set to the "A position", and 6e is a passage that is connected to the conduit 10 connected to the bottom side of the arm cylinder 8, and the regeneration poppet 6a is moved to the "A position" by the pressure generated in the passage 6d. 6f is an orifice provided in the passage 6e, and 6g is a passage connecting the passage 6c and the passage 6d when the regeneration poppet 6a is in the "A" position.
6h is an orifice provided in the passage 6d, and 6i is an orifice provided in the passage 6c when the regenerating poppet 6a is in the "ro" position.
6j is an orifice provided in the passage 6i, 6k is a passage connecting the chamber on the spring 6b side of the regeneration poppet 6a and the tank passage, 6
1 is a damping orifice provided in the passage 6k.

Next, the operation will be explained.

A) When the arm spool 6'' is switched to the "A position" with the bucket (not shown) off the ground, the arm cylinder 8 receives a force in the direction of extension due to the weight of the bucket arm, causing the arm cylinder 8 to fall under its own weight. In this case, the conduit 9 connected to the arm cylinder 8 becomes the return side, and the conduit 10 becomes the supply side.

In this state, for example, when the pressure in the conduit 10 is low, that is, when the dead weight of the arm cylinder 8 is falling quickly, the regeneration poppet 6a is held in the "A position" by the force of the spring 6b, so that the return side conduit 9
is connected to the conduit 10 via the passages 6g and 6d, so the flow rate returned to the rod side of the arm cylinder 8 is regenerated to the bottom side of the arm cylinder 8. In other words, the flow rate supplied to the bottom side of the arm cylinder 8 is the sum of the pump discharge amount and the return flow rate on the rod side of the arm cylinder 8.

In order to prevent the arm cylinder 8 from moving faster than the total flow rate, an orifice 6h is provided in the passage 6g to regulate the return flow rate on the rod side of the arm cylinder 8. It is desirable that the orifice 6h has a diameter that allows a certain amount of pressure to be generated on the bottom side of the arm cylinder 8.

In this case, a similar pressure is generated in the passage 6e, which attempts to move the regeneration poppet 6a to the "A" position, but attempts to maintain it in the "A" position by the force of the spring 6b. Therefore, by setting the setting force of the spring 6b to an appropriate value, the regeneration poppet 6a can be placed in the optimum position "A" or "B". In addition, in order to regulate the return flow rate of the arm cylinder 8 to the rod side even when the arm cylinder 8 is suddenly switched to the "A" or "B" position, an orifice 6j is provided in the passage 6i to regulate the flow rate and prevent the arm cylinder 8 from reaching extreme speeds. I try not to change.

B) When the arm spool 6'' is switched to the "A position" in the digging state, a considerable amount of pressure is required on the bottom side of the arm cylinder 8 in the normal digging state. For this reason, the regeneration poppet 6a overcomes the spring 6b and becomes the "ro" position, and the return flow rate on the rod side of the arm cylinder 8 flows to the tank passage through the pipe 9, passages 6c and 6i, and becomes the same as the conventional circuit. .

When the arm spool valve 6'' is switched to the A position to extend the arm cylinder 8 as described above,
When the bucket is off the ground, the regeneration spool 6a is at the "A" position until the pressure on the bottom side of the arm cylinder 8 reaches a certain pressure, so the return flow rate on the rod side of the arm cylinder 8 is lower than the bottom side of the arm cylinder 8. is regenerated, allowing for faster operation.

Also, during excavation, the regeneration poppet 6a is in the ``ro'' position, and the circuit is the same as the conventional one.

In the above description, the spool valve for an arm was explained, but the same effect can be obtained even if it is used for a spool valve for a bucket.

Recycle poppet 6a and orifices 6h, 6j as 1
The cylinder regeneration circuit has been made more compact because it is configured as a spool valve for the arm.

Furthermore, since the entire return flow rate of the arm cylinder is regenerated to the cylinder supply side, negative pressure is less likely to be generated on the cylinder supply side, and the potential energy possessed by the arm cylinder can be effectively utilized.

[Brief explanation of drawings]

Figure 1 shows an example of a cylinder regeneration circuit for a conventional hydraulic excavator. Figure 2 is also the second example. FIG. 3 is a cylinder regeneration circuit for a hydraulic excavator according to the present invention. FIG. 4 is a detailed diagram of the internal circuit when the arm spool valve is switched to the "A position". In the figure: 1...pump, 2...control valve, 3...relief valve, 4...travel spool valve, 5...swivel spool valve, 6, 6',
6″... Arm spool valve, 7... Hydraulic oil tank, 8... Arm cylinder, 9... (rod side of arm cylinder) pipe line, 10... (bottom side of arm cylinder) pipe line, 11... ...Flow rate limiting type check valve, 6a...Regeneration poppet, 6b...Spring, 6c
...(Pressure oil) passage, 6d, 6e, 6g, 6i,
6k...oil passage, 6j, 6h...orifice, 6
f, 6l... (for damping) Orifice.

Claims (1)

[Claims] 1 When the arm cylinder 8 of the hydraulic excavator receives a force in the direction of extension due to the weight of the arm and falls under its own weight, the arm spool valve has a circuit that regenerates the entire return flow rate of the arm cylinder to the supply side. The arm spool valve has a regeneration poppet 6a that maintains a regeneration circuit at all times with a spring 6b, and the regeneration poppet 6a constantly allows the cylinder return flow to flow into the cylinder supply side passage via the orifice 6h, thereby reducing the cylinder supply pressure. A cylinder regeneration circuit for a hydraulic excavator, characterized in that when the pressure exceeds a predetermined pressure, a regeneration poppet 6a is switched to allow the flow to flow into a tank passage via an orifice 6j.