JPS6145248Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a hydraulic circuit for a hydraulic shovel in a construction vehicle or the like.

In general, the hydraulic circuit of a hydraulic excavator consists of a compound control valve that includes a first switching valve group that controls actuators such as right travel, bucket, boom, etc., and a second switching valve that controls actuators such as left travel, swing, and arm. The control valve is divided into a group of compound control valves and is controlled by being connected to the first and second hydraulic pumps.

However, since the cylinder of the boom requires a large amount of flow when the boom is raised or raised, a boom switching valve for merging is provided in the second switching valve group to compensate for the lack of flow when the boom is raised or raised.

However, the above-mentioned composite control valve of the second switching valve group, which includes travel, swing, arm, and boom switching valves, causes the following problems during complex operations.

A: During rotation pressing and arm excavation, the arm load is small, so the rotation pressing force decreases to the arm load pressure and the rotation pressing cannot be maintained.

B: When operating the swing and boom (lowering), the boom does not require pressure due to its own weight when lowering, so oil flows to the boom cylinder, making it impossible to swing.

C When operating the arm (retraction) and boom (lowering),
Retracting the arm requires pressure due to a reduction in the pressure-receiving area on the cylinder rod side and its own weight, but lowering the boom requires almost no pressure, so there are problems such as the arm becoming unable to operate.

To solve this problem, the boom cuts off the passage connecting to its cylinder rod side, and
By supplying oil only from the boom switching valve in the switching valve group, we compensate for the inability to swing when swinging and lowering the boom.Also, a throttle is installed on the head side of the boom cylinder, and the back pressure of the throttle balances the load. The method compensates for the inability to arm (shrink) and boom (lower). Furthermore, the arm is equipped with a restriction in the passage on the cylinder rod side, and by using the back pressure of the restriction to balance the load, it compensates for the inability to rotate during pressing and arm excavation, as well as the inability to turn the arm during arm (extension) and boom (lifting). are doing.

However, in either method, during independent operation, the effective pressure of the oil supplied to the actuator decreases due to pressure loss caused by unnecessary throttling, resulting in problems such as a decrease in actual excavation force and heat generation due to the loss, which is undesirable.

The present invention was developed in view of the above-mentioned problems, and its purpose is to develop a hydraulic excavator that effectively utilizes the hydraulic pump discharge oil and improves the operability of the actuator even during single or combined operations. Located in providing hydraulic circuit.

The drawings showing one embodiment of the present invention will be described below. In the drawings, reference numeral 1 denotes a composite control valve, 2 denotes a valve body of the composite control valve 1, one end of a center bypass passage 3 provided in the valve body 2 is connected to a hydraulic pump 5 via a pump port 4 and the other end is connected to a tank 7 via a tank port 6, and a switching valve A having two parallel supply passages 8a, 8b is provided on the left side of the center bypass passage 3 located upstream of the center bypass passage 3. A switching valve B having only an extension 8C of the supply passage 8b is provided adjacent to the switching valve A.

The switching valve A has a traveling switching valve 13 that controls a traveling motor (not shown) and a swinging switching valve 14 that controls a swinging motor 10. The switching valve B has one arm switching valve 15 for controlling the arm cylinder 11 and a boom switching valve 16 for controlling the boom cylinder 12, and the switching valve 15 has a neutral position and a second switching position. and a second switching position, and when switched to the above position, the supply passage 8c is connected to the head side 11a of the cylinder 11 via the throttle 17 and the cylinder passage 18 provided therein. At the same time, the center bypass passage 3 is also connected to the head side 11a of the cylinder 11, and the center bypass passage 3 is connected to the head side 11a of the cylinder 11.
1b is adapted to be connected to the tank 7 via the cylinder passage 19 on the opposite side. When switched to the position, the supply passage 8c is connected to the rod side 11b of the cylinder 11 via the cylinder passage 19, and the head side 11a is connected to the tank 7 via the cylinder passage 18.
Connect to. The switching valve 16 has a neutral position, a position, and a neutral position, and when it is switched to the neutral position, the supply passage 8c is connected to the rod side 12b of the cylinder 12 via the throttle 20 provided therein and the cylinder passage 21.
At the same time, the center bypass passage 3 is also connected to the rod side 12b of the cylinder 12.
The head side 12a of 2 is the cylinder passage 22 on the opposite side.
Connect to tank 7 via. When switched to the position, the supply passage 8c is connected to the head side of the cylinder 12 via the cylinder passage 22, and the supply passage 8c is connected to the head side of the cylinder 12 through the cylinder passage 22.
b is connected to the tank 7 via the cylinder passage 21.

Next, the operation of the present invention will be explained. Switching valve 1
3, 14, 15 and 16 are in the neutral position shown, the pressure oil of the hydraulic pump 5 is pumped to the pump port 4,
It is discharged to the tank 7 via the center bypass passage 3 and the tank port 6.

Now, when the switching valve 15 of the arm is switched from the neutral position shown in the figure to the position, the flow rate of the pressure oil of the hydraulic pump 5 through the supply passage 8c, the throttle 17, and the flow rate through the center bypass passage 3 are changed to the cylinder passage 1.
8, and this combined pressure oil flows into cylinder 1.
1, and is supplied to the head side 11a of rod side 1.
The oil in 1b is returned to the return passage 2 via the cylinder passage 19.
3 and the cylinder 11 is extended. Furthermore, when the switching valve 15 of the arm is switched to the position, the center bypass passage 3 is cut off, so the oil in the supply passage 8c is supplied to the rod side 11b of the cylinder 11 via the cylinder passage 19, and the oil is supplied to the rod side 11b of the cylinder 11 through the cylinder passage 19. The oil is returned to the return passage 23 via the cylinder passage 18, and the cylinder 11 is compressed. In this manner, when the cylinder 11 is extended and retracted, the pressure oil of the hydraulic pump is supplied to the cylinder 11 without causing pressure loss.

Furthermore, when the switching valve 15 of the arm is switched to the position and the switching valve 14 of the swing motor 10 is switched to either direction, the center bypass passage 3 on the downstream side of the switching valve 14 is immediately cut off, so that the center bypass passage 3 is cut off via the throttle 17. Only the pressure oil in the supply passage 8c is supplied to the cylinder 1.
1 to the head side 11a, and the rod side 11b.
The oil returns to the return passage 23 along the same route as the expansion operation.
will be returned to. Also, when the switching valve 15 of the arm is switched to the position and the switching valve 16 of the boom is switched to the position, the pressure oil of the center bypass passage 3 is supplied to the cylinder head side 11a of the arm, and the supply passage 8c is supplied to the cylinder head side of the boom. pressure oil is supplied, but
Pressure oil from the pump 5 flows only into the cylinder head in the arm extension direction where the load is significantly smaller than in the boom raising direction. However, the boom cylinder is operated at the same time as the boom switching valve 16, and can be extended using the oil discharged from the other hydraulic pump by using another boom switching valve (not shown) belonging to the first switching valve group.

Further, when the switching valve 15 of the arm is switched to the position and the switching valve 14 of the swing motor 10 is switched to either direction, the pressure oil in the supply passage 8c and the oil on the head side 11a of the cylinder 11 are transferred to the cylinder 11.
It flows in and out through the same path as the contraction operation. Since the load pressure on the arm is extremely low when the cylinder 11 of the arm is extended, a pressure difference is created by the throttle 17 to balance the load with the swing motor 10 and enable compound operations. Furthermore, when the cylinder 11 of the arm is contracted, load pressure is applied due to the arm's own weight, so the switching valve 14 is different from the supply passage 8.
b and 8c are connected in parallel to enable combined operation of the cylinder 11 and the swing motor 10 without resistance.

Further, when the switching valve 16 of the boom is switched from the neutral position shown in the drawing to the position, the pressure oil in the supply passage 8c is supplied to the head side 1 of the cylinder 12 via the cylinder passage 22.
2a and the oil on the rod side 12b is returned to the return passage 23 via the cylinder passage 21, so that the cylinder 12 is extended. Furthermore, when the switching valve 16 is switched to the position, the flow rate through the supply passage 8c and the throttle 20 and the flow rate through the center bypass passage 3 are merged, and this merged amount flows through the cylinder passage 21 to the rod side 12b of the cylinder 12. The supplied oil on the head side 12a is returned to the return passage 23 via the cylinder passage 22, so that the cylinder 12 is compressed.
In this manner, when the cylinder 12 is extended and retracted independently, the pressure oil of the hydraulic pump is supplied to the cylinder 12 without causing pressure loss.

Further, when the switching valve 16 of the boom is switched from the neutral position to the neutral position and the switching valve 14 of the swing motor 10 is switched in either direction, the pressure oil in the supply passage 8c and the oil on the rod side 12b of the cylinder 12 are transferred to the cylinder 12. flows in and out through the same path as the stretching action of. When the switching valve 16 is switched to the position and the switching valve 14 of the swing motor 10 is switched to either direction, the pressure oil in the supply passage 8c is controlled by the throttle 20,
Oil is supplied to the rod side 12b of the cylinder 12 through the cylinder passage 21, and the oil on the head side 12a is returned following the same path as the cylinder 12 is compressed. Furthermore, when the boom switching valve 16 is switched to the position 16 and the arm switching valve 15 is switched to the 1st position, the restricted oil flows into the cylinder rod side 12b of the boom via the throttle 20, and the oil is restricted to the arm cylinder rod side 11b. Since the oil from the supply passage 8c flows into the pump, it is possible to balance the retraction operations of the boom and the arm, and therefore it is possible to eliminate the inoperability of the arm. In this way, when the cylinder 12 of the boom is retracted, the load pressure on the cylinder 12 is extremely low, so a pressure difference is created by the throttle 20, and the load is balanced with the switching valve 14 of the swing motor 10. enable operation.
Also, when cylinder 12 of the boom is extended, cylinder 1
Since there is a load pressure on the boom cylinder 12 and the swing motor 10, the switching valve 14 of the swing motor 10 and the supply passages 8b and 8c are connected in parallel, so that the combined operation of the cylinder 12 of the boom and the swing motor 10 can be operated without any resistance. Can be done.

As described above, according to the present invention, the connection between the supply passage and the actuator is skillfully configured in a circuit through the switching valve, so that the pressure oil of the hydraulic pump causes a pressure loss even when the switching valve is operated alone or in combination. Since it can be used effectively and balanced compound operations can be performed without any effort, it has the effect of improving the digging power of the actual machine.

[Brief explanation of the drawing]

The figure is a system diagram of a hydraulic circuit showing an embodiment of the present invention. 1... Composite control valve, 2... Valve body, 3... Center bypass passage, 8a, 8b, 8c... Supply passage,
11...Arm cylinder, 12...Boom cylinder, 14...Swivel switching valve, 15...Arm switching valve, 16...Boom switching valve, 17, 20...
Aperture.

Claims (1)

[Scope of utility model registration request] Among the plurality of switching valves that have a center bypass passage and are ordered upstream and downstream by the passage, the upstream includes a swing switching valve that controls a swing motor, and the supply passages are mutually connected in parallel to a hydraulic power source. In a hydraulic circuit in which one or more switching valves are arranged downstream, a plurality of switching valves including at least an arm switching valve that controls an arm cylinder and a boom switching valve that controls a boom cylinder, the arm switching valve and Each boom switching valve has a parallel supply passage connected to a hydraulic power source adjacent to one side of the center bypass passage, and in the first switching position, pressure oil from the center bypass passage is connected to the parallel supply passage through an internal restriction. In the case of the arm cylinder, the pressure oil from A hydraulic circuit for a hydraulic excavator characterized in that oil is supplied to the rod side for an arm cylinder and to the head side for a boom cylinder, and the other side is connected to a tank.