JPH0424491B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in the hydraulic circuit of a hydraulic loading shovel.

FIG. 1 shows the appearance of an example of a conventional hydraulic loading shovel. When performing excavation operations with a hydraulic loading shovel, the arm operating lever is normally left in and out, and the bucket operating lever is operated as necessary. That is, while the arm cylinder 1 is constantly operated in the rod extension direction and the arm 2 is rotated forward, the bucket cylinder 3 is operated in the rod extension direction as necessary, and the bucket belt 4 is rotated.
Rotate in the scooping direction (tilt direction) and put the load into the bucket 4. In FIG. 1, 5 is a boom cylinder, 6 is a boom, 7 is a rotating body, and 8 is a traveling body. FIG. 2 shows an example of the hydraulic circuit of a conventional hydraulic loading shovel. A first directional valve group 10 of a monoblock type four-way type is provided for the first main hydraulic pump 9, and a second directional valve group 10 of a monoblock type four-way type is provided for the second main hydraulic pump 11. A valve group 12 is provided.

First and second swirl pumps 13, 14 are separately provided. In the first directional valve group 10,
A bucket directional switching valve 15, a first arm directional switching valve 16, a first boom directional switching valve 17, and a right travel directional switching valve 18 are connected in parallel. The second directional valve group 12 includes a bucket opening/closing directional valve 19 and a second arm directional valve 2.
0, the second boom direction switching valve 21 and the left travel direction switching valve 22 are connected in parallel. As actuators, only the arm cylinder 23 and bucket cylinder 24, which are directly necessary for the digging operation, are shown.
The boom cylinder, bucket opening/closing cylinder, right travel motor, and left travel motor are omitted. Also,
A directional switching valve for turning and a turning motor are also omitted.

25 and 26 are relief valves, 27 and 28 are filters, 29 is an oil cooler, and 30 is a tank.

As shown in FIG.
Regarding this, it has a two-stage arm circuit where the pressure oil from the two main hydraulic pumps 9 and 11 can merge.
On the other hand, the bucket cylinder 24 has a one-stage bucket circuit to which only pressure oil from one main hydraulic pump 9 is supplied. In such a hydraulic circuit, normally the arm operation lever is turned on and off, and the arm cylinder 23 is moved in the rod extension direction to perform digging, and the load applied to the arm cylinder 23 becomes too large, causing the relief valves 25 and 26 to close. When the relief operation is performed, the arm cylinder 23
Since it is no longer possible to dig with a chisel, the bucket cylinder 24 is operated in the rod extension direction by operating the bucket control lever, and the bucket 4 is rotated in the scooping direction. As a result, the pressure oil discharged from the first main hydraulic pump 9 is supplied to the bucket cylinder 24 by the bucket directional control valve 15 and works effectively, but on the other hand, the pressure oil discharged from the first main hydraulic pump 9 Pressure oil discharged from the relief valve 26
Due to the relief operation, the energy is wasted into the tank 30, resulting in a loss of energy. In addition, when the bucket cylinder 24 operates independently, only the pressure oil from the first main hydraulic pump 9 is used, and the pressure oil from the second main hydraulic pump 11 is not used, so 1/2 of the motor output is used. This means that it is only being used effectively, and Bucket's operation speed is also slow.

In order to eliminate the above-mentioned drawbacks, as shown in FIG. 3, a carry-over port 31 is provided in the second directional control valve group 12, and a single bucket speed increasing directional control valve is installed in the carry-over port 31. 32
It is conceivable to connect the pump port of The center bypass port of the bucket speed increasing directional switching valve 32 is connected to the tank circuit 34 by a pipe 33, and the work port is connected to the bottom side oil chamber of the bucket cylinder 24 by a pipe 35. As a result, when the bucket cylinder 24 operates independently in the rod extension direction, pressure oil from the two main hydraulic pumps 9 and 11 is supplied to the bottom side oil chamber of the bucket cylinder 24. The operating speed of the bucket in the scooping direction is twice that of the case shown in FIG.

However, in FIG. 3, the bucket speed increasing directional switching valve 32 is connected in tandem to the second directional switching valve group 12, so if the arm operating lever is left in the open position, the second directional switching valve 32 is connected to the second directional switching valve group 12 in tandem. The center bypass 36 of the valve group 12 is blocked, pressure oil does not flow to the bucket speed increasing directional control valve 32, and even if the bucket tilt pilot valve 37 is operated, the first main hydraulic pump does not flow to the bucket cylinder 24. Only pressure oil from 9 is supplied. Therefore, when the load on the arm cylinder 23 becomes too large and the relief valve 26 performs a relief operation, all the pressure oil in the second main hydraulic pump 11 is wasted and discharged into the tank 30, and no effective work is done. I will not do it.

An object of the present invention is to solve the above-mentioned problems, and to be able to achieve an increase in the speed of the bucket when operating the bucket alone at low cost, and to avoid cases where the load on the arm cylinder is too large during combined operation of the arm and bucket. An object of the present invention is to provide a hydraulic circuit for a hydraulic loading shovel that can prevent relief loss and increase the speed of the bucket.

In order to achieve this object, the present invention provides a bucket speed increasing directional control valve outside the first and second directional valve groups, and connects the pump port of the bucket speed increasing directional control valve to the second directional control valve group. connected in parallel to the common pump port of the directional valve group, and the most downstream part of the center bypass of the second directional valve group, normally communicating the most downstream part with the tank;
A logic valve is provided that closes the most downstream part when the bucket is operated, so that the first and second
The pressurized oil from the hydraulic pump is used in the bucket cylinder via the bucket directional control valve and the bucket speed increasing directional control valve, respectively.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 4 shows an embodiment of the present invention. Components similar to those in FIG. 3 are designated by the same reference numerals. A single bucket speed increasing directional valve 32 is provided outside the first and second directional valve groups 10, 12, and its pump port P is connected to the common pump port 38 of the second directional valve group 12. It is connected to the pump circuit 39 via piping 40 so as to be parallel to the pump circuit 39 . The input side of the logic valve 41 is connected to the most downstream portion of the center bypass 36 of the second directional valve group 12, that is, the carryover port 31, and the output side thereof is connected to the tank circuit 34. The pressure chamber 42 of the logic valve 41 is connected to the tank circuit 34 via a switching valve 43. The logic valve 41 includes a valve body 45 having a communication hole 44 and a return spring 46. The switching valve 43 receives a pilot pressure signal from the bucket tilt pilot valve 37 as a switching pressure.

In the case of single bucket operation, when the bucket tilt pilot valve 37 is operated, a pilot pressure signal is input to the switching valve 43, which is switched to the closed position. As a result, the pressure chamber 4 of the logic valve 41
2 is disconnected from the tank 30 and the logic valve 41
becomes closed. Therefore, the pressure oil of the second main hydraulic pump 11 is transferred to the bucket speed increasing directional control valve 3.
2 to the bottom side oil chamber of the bucket cylinder 24, and joins the pressure oil from the first main hydraulic pump 9. Therefore, the operating speed of the bucket in the scooping direction is equivalent to the speed of two pumps, and the digging speed can be increased.

When the bucket to-tilt pilot valve 37 is not operated, the switching valve 43 is in the closed position, so the pressure chamber 42 of the logic valve 41 is closed to the tank 30.
and if none of the directional control valves 19 to 22 are operating, a pressure difference is applied to the valve body 45,
The logic valve 41 becomes open. Therefore,
The center bypass 36 communicates with the tank 30 and the second
The directional control valve group 12 operates normally.

During combined operation of the arm and bucket, the switching valve 43 is switched to the closed position by operating the bucket tilt/tilt pilot valve 37, and the logic valve 41 is placed in the closed state. and the second main hydraulic pump 1
The pressure oil of No. 1 is divided into the second arm directional switching valve 20 and the bucket speed increasing directional switching valve 32. Therefore, if the load on the arm cylinder 23 becomes too large, the bucket cylinder 2 with lower load pressure
Most of the pressure oil from the second main hydraulic pump 11 is supplied to the pump 4, and the relief valve 26 can prevent relief loss during its operation.

As described above, according to the present invention, the pump port of the bucket speed increasing directional control valve is connected in parallel to the common pump port of the second directional control valve group including the second arm directional control valve. Therefore, during combined operation of the arm and bucket, if the load on the arm cylinder becomes too large, pressure oil from the second hydraulic pump can be supplied to the bucket cylinder via the bucket speed increasing directional control valve. , it is possible to prevent relief loss and increase the speed of the bucket. In addition, since the bucket speed increasing directional control valve is provided outside the first and second directional control valve groups, there is no need to change the type of directional control valve group to one with one more valve group, which reduces costs. It can be done. Furthermore, a logic valve is provided at the most downstream part of the center bypass of the second directional switching valve group, which normally communicates the most downstream part with the tank and closes the most downstream part when the bucket is operated.
When the bucket is operated alone, the pressure oil of the second hydraulic pump can be supplied to the directional switching valve for increasing the speed of the bucket, and the independent operating speed of the bucket can be increased to the speed of two pumps.

Even if the oil pressure of the center bypass becomes high, the logic valve closes the valve without leakage, so that the pressure oil of the second hydraulic pump can be effectively used for increasing the bucket speed.

[Brief explanation of drawings]

Figure 1 is a side view of an example of a conventional hydraulic loading shovel, Figure 2 is a hydraulic circuit diagram of an example of a conventional hydraulic loading shovel, and Figure 3 is a hypothetical hydraulic loader that can be considered based on the conventional technology level. FIG. 4 is a hydraulic circuit diagram of an example of a digging shovel. FIG. 4 is a hydraulic circuit diagram of an embodiment of the present invention. 9...First main hydraulic pump, 10...First directional valve group, 11...Second main hydraulic pump, 12...Second directional valve group, 15...
... Directional switching valve for bucket, 16... Directional switching valve for first arm, 20... Directional switching valve for second arm, 23... Arm cylinder, 24... Bucket cylinder, 25, 26... Relief Ben, 30...
Tank, 31...Carryover port, 32...
Bucket speed increasing directional switching valve, 36...Center bypass, 38...Common pump port, 41...Logic valve, 43...Switching valve, P...Pump port.

Claims (1)

[Claims] 1 In the first directional valve group for the first hydraulic pump, the first arm directional valve and bucket directional valve are connected in parallel, and the second directional valve group for the second hydraulic pump is connected in parallel. In the hydraulic circuit of the hydraulic loading shovel equipped with the second arm directional switching valve, a bucket speed increasing directional switching valve is provided outside the first and second directional switching valve groups, and the bucket speed increasing directional switching valve is provided outside the first and second directional switching valve groups. The pump ports of the directional valves are connected in parallel to the common pump port of the second directional valve group, and the most downstream part is normally connected to the most downstream part of the center bypass of the second directional valve group. 1. A hydraulic circuit for a hydraulic loading shovel, characterized in that a logic valve is provided which communicates with the flowchart and closes the most downstream portion during bucket operation.