JPH03187422A - Hydraulic circuit - Google Patents

Abstract

PURPOSE:To make straight forward travelling possible when a boom is operated by short-circuiting both discharge passages of first and second pumps with first and second junction valves and a short-circuit passage, providing a left travelling valve and a boom valve respectively to the discharge passages of both pumps, and providing a right travelling valve on the side of the short- circuit passage. CONSTITUTION:When the first junction valve 24 is situated at the communicating position A and the second junction valve 34 at the cutoff position B, the discharge passage 20a of the first pump 20 is connected to a short-circuit passage 25, and discharge pressure oil is supplied respectively to left and right travel valves 22, 33. Also, the discharge pressure oil of the second pump 30 is supplied to a boom valve 31, thereby making the pressure of left and right travel motors equal and straight forward travelling possible when the boom is operated while travelling.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydraulic circuit that uses two pumps to supply pressure oil to a plurality of actuators.

[Conventional technology]

A hydraulic circuit disclosed in Japanese Unexamined Patent Publication No. 62-206125 is known.

That is, as shown in FIG. 2, a swing valve 3, an arm valve 4, and a left running valve 5 are provided in the discharge path 2 of the first pump 1, and an on-off valve 6 is provided between the swing valve 3 and the arm valve 4. , a right travel valve 9, a boom valve 10, and a bucket valve 11 are provided in the discharge passage 8 of the second pump 7, and the discharge passage 2 of the first pump 1 and the second
This is a hydraulic circuit in which a discharge path 8 of a pump 7 can be communicated with and shut off by a merging valve 12.

With such a hydraulic circuit, the discharge pressure oil of the first pump 1 can be supplied to the swivel valve 3, the arm valve 4, and the left travel valve 5 by setting the merging valve 12 to the cutoff position (2), and the discharge pressure of the second pump 7 can be Oil can be supplied to the right travel valve 9, boom valve 10, and bucket valve 11, so even if the loads are different when simultaneously operating the boom and arm, left travel and right travel, swing and boom, and swing and arm, each can be operated independently. It can be operated by

[Problem to be solved by the invention]

With such a hydraulic circuit, when traveling while raising the boom, the pressure oil discharged from the second pump 7 is supplied to the right travel valve 9 and the boom valve 10, and the pressure oil discharged from the first pump 1 is supplied to the left travel valve 5.
Therefore, the pressure of the pressure oil supplied to the left and right travel motors from the left and right travel valves 5 and 9 may be different, and the vehicle may not be able to travel straight.

Therefore, an object of the present invention is to provide a hydraulic circuit that can solve the above-mentioned problems.

[Means and effects for solving the problem] The discharge path of the first pump and the discharge path of the second pump are short-circuited by the first and second merging valves and a short circuit, and a left travel valve is connected to the discharge path of the first pump. established, second
A boom valve is provided in the discharge path of the pump, and a right travel valve is provided on the short circuit side, and by switching between the first and second merging valves, the discharge pressure oil of the first pump is supplied to the left and right travel valves, and the second pump This is a hydraulic circuit that supplies the discharge pressure oil to the boom so that it can travel straight when operating the boom while traveling.

〔Example〕

As shown in FIG. 1, the discharge passage 20a of the first pump 20 is provided with a swivel valve 21, a left travel valve 22, and an arm valve 23, and a first merging valve is provided between the left travel valve 22 and the arm valve 23. 24
A boom valve 31, a bucket valve 32, and a right traveling valve 33 are provided in the discharge passage 30a of the second pump 30, and a second merging valve 34 is provided between the bucket valve 32 and the right traveling valve 33. The inlet side of the arm valve 23 in the discharge path 20a of the first pump 2o and the inlet side of the right traveling valve 33 in the discharge path 30a of the second pump 30 communicate with each other through a short-circuit path 25.

The first and second merging valves 24 and 34 are moved to communication position A by spring force.
and is held by the solenoid 24a.

When 34a is energized, it becomes the cutoff position B.

In FIG. 1, 26 is a swing motor, 27 is a left travel motor, 28 is an arm cylinder, 35 is a boom cylinder, 3
6 is a bucket cylinder, and 37 is a right travel motor.

Therefore, the first merging valve 24 is placed in the communication position A, and the second merging valve 3
4 is the cutoff position B, the pressure oil discharged from the first pump 20 is transferred to the arm valve 23, and the pressure oil discharged from the second pump 30 is transferred to the boom valve 3.
1, the discharge pressure oil of the first pump 20 can be supplied to the swivel valve 21, and the discharge pressure oil of the second pump 30 can be supplied to the boom valve 31, respectively.

Moreover, if the first merging valve 24 is set to the blocking position B and the second merging valve 34 is set to the communicating position A, the discharge pressure oil of the first and second pumps 20 and 30 can be supplied to the left and right traveling valves 22 and 23, respectively. , the discharge pressure oil of the first pump 20 can be supplied to the swivel valve 21, and the discharge pressure oil of the second pump 30 can be supplied to the arm valve 23.

Further, as described above, the first merging valve 24 is set to the communication position A,
If the second merging valve 34 is set to the cutoff position B, the first pump 20
Since the discharge pressure oil of the second pump 30 can be supplied to the left and right travel valves 22.33 and the discharge pressure oil of the second pump 30 can be supplied to the boom valve 31, the pressure of the left and right travel motors 27.37 can be reduced when raising the boom while traveling. You can run straight ahead by keeping it equal.

〔Effect of the invention〕

By switching the first and second merging valves 24 and 34, the discharge path 20a of the first pump 20 can be connected to the short circuit path 25 to supply pressure oil to the right travel valve 33, and the discharge path 3 of the second pump 30 can be connected to the short circuit path 25.
Pressure oil can be supplied to the boom valve 31 by blocking off the 0a with the second merging valve 34.

Therefore, the discharge pressure oil of the first pump 20 can be supplied to the left and right travel valves 22 and 23, and the discharge pressure oil of the second pump 30 can be supplied to the boom valve 31, so that when operating the boom while traveling, the left and right travel motor It is possible to travel in a straight line by equalizing the pressure.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention, and FIG. 2 is a conventional hydraulic circuit diagram. 20 is a first pump, 20a is a discharge path, 21 is a swirl valve, 2
2 is a left travel valve, 23 is an arm valve, 24 is a first merging valve, 2
5 is a short circuit path, 30 is a second pump, 30a is a discharge path, 31
is the boom valve, 32 is the bucket valve, 33 is the right travel valve, 34
is the second merging valve.

Claims (1)

[Claims] A swivel valve 21, a left travel valve 22, and an arm valve 23 are provided in the discharge passage 20a of the first pump 20, and a first merging valve 24 is provided between the left travel valve 22 and the arm valve 23. A boom valve 31, a bucket valve 32, and a right running valve 33 are provided in the discharge path 30a of the second pump 30, and the bucket valve 3
A second merging valve 34 is provided between the arm valve 23 and the right travel valve 33, and the inlet side of the arm valve 23 and the inlet side of the right travel valve 33 are connected through a short circuit 25.