JPS61165429A - Hydraulic circuit for construction machine - Google Patents

Abstract

PURPOSE:To secure the straightforward traveling of a construction machine by a method in which each hydraulic pump is connected to each valve group, and when operating the uppermost traveling switch valve for each valve group, the hydraulic oil of one pump is supplied to the valves other than the traveling switch valves for both groups and that of the other pump is supplied to the traveling switch valves for both groups. CONSTITUTION:Valve groups A and B are connected to the uppermost traveling switch valves 1 and 14 and receive pressure oil from hydraulic pumps 9 and 21. Each valve group is connected to the valves 1 and 14 in tandem, having switch valves 3-7 and 16-20 which are connected in parallel. When the valves 1 and 14 are operated, the pressure oil of the first hydraulic pump 9 is supplied through a pilot switch valve 26 to the other switch valves for both groups, and that of the second hydraulic pump 21 is supplied to the traveling switch valves 1 and 14 for both groups. On the one hand, when operating the traveling switch valves 1 and 14, a switch valve 26 receives pilot pressure through valves 37 and 39 in operation. The straightforward traveling of a construction machine is secured.

Description

[Detailed description of the invention] Industrial use bone The present invention relates to a hydraulic circuit for a hydraulic excavator.

Conventional technology hydraulic excavators have two actuators or
Pressure oil is supplied from a larger number of hydraulic pumps, and the system is configured to operate by controlling this with a switching valve.

The actuator usually consists of six actuators: a boom cylinder, an arm cylinder, a packet cylinder, a swing motor, and left and right travel motors, and these are actuated either singly or by a complex operation in which a plurality of actuators are actuated simultaneously.

Conventionally, the most common hydraulic circuit divides each actuator into two groups of switching valves, connects a separate hydraulic pump to each group of switching valves, and connects the switching valves in parallel within each group. It is connected to In such a hydraulic circuit, even if the actuators in each separate group are operated simultaneously with actuators in other groups, they can operate independently without being influenced by the actuators in other groups.

Problems to be Solved by the Invention In the conventional method described above, when actuators in different groups are operated simultaneously, each actuator is not affected by the operation of other actuators, and each actuator is operated from a separate hydraulic pump. It can be supplied with pressure oil and operate as an independent actuator. However, if actuators in the same switching valve group are activated at the same time, pressure oil will flow only to the actuator with lower operating pressure.
Pressure oil does not flow to the actuator, which has a high operating pressure, resulting in an undesirable phenomenon in which the actuator does not operate.

For this reason, for example, if the left and right travel motors are activated at the same time and another actuator is activated, the amount of oil sent to the travel motor in the same group as that actuator will be transferred to the other actuator. As a result, the amount of oil supplied to the left and right travel motors is different, and the rotational speeds of the travel motors are different, resulting in an undesirable situation in which travel becomes meandering.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide a hydraulic system for a hydraulic excavator that does not meander even when actuators other than the travel motor are activated during travel.

Means for Solving the Problems The means of the present invention taken to solve the above problems are as follows: (a) The actuators of the hydraulic excavator are divided into two groups, each of which is driven by a separate hydraulic pump.

Of the switching valves that operate these actuators, a switching valve for operating the travel motor is provided in the front row of each group, and this and switching valves for other actuators are connected in tandem.
In addition, the tandem passage of the travel motor operation switching valve is passed from the middle of the center bypass passage of the other actuators to the parallel passage via a check valve, and the other actuator switching valves are connected in parallel.

C. A pilot switching valve is provided in the oil path leading from one hydraulic pump to the switching valve for operating the travel motor of that group.

(vii) An oil passage is made to pass from the other hydraulic pump to the pilot switching valve, and an oil passage is made to pass from the pilot switching valve to each of the actuator operation switching valves other than the travel motor of both switching valve groups.

E. Pilot oil passages are provided in parallel to the pilot switching valves, and each pilot oil passage is provided with an on-off valve that is linked to the travel motor operation switching valve and opens only when the valve is in a position other than neutral.

In each pilot oil passage, a bypass oil passage leading to the tank is provided between the on-off valve and the pilot switching valve, and the oil passage is linked with a switching valve for operating the actuator other than the switching valve for operating the travel motor, and the switching valve is connected to the switching valve for operating the actuator. Each valve is equipped with an on-off valve that opens only when the valve is in neutral.

It is.

Even if the driving motor and other actuators are operated at the same time, oil is supplied to both from separate hydraulic pumps, so there is no meandering while driving, and straightness is maintained when driving on flat ground. Secured. In addition, other actuators that are operated during traveling are supplied with pressure oil from a single hydraulic pump, so they can be operated reliably regardless of the operating pressure during traveling.

Embodiments Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

1 is a switching valve for operating the first travel motor 2, 3 is a switching valve for operating the swing motor 4, and 5 is a switching valve for operating the boom cylinder 6.
7 is a first switching valve for operating the arm cylinder 8; these switching valves 1.3.5.
7 forms a first switching valve group A, and an oil passage 10 from the first hydraulic pump 9 communicates with the first switching valve l for operating the travel motor on the most upstream side, and the switching valve l for operating the first traveling motor and others The switching valve 3.5.7 is connected in tandem with the other switching valve 3.5.7.
5.7 are connected in parallel, and an oil path 11 is connected from the downstream side of the first travel motor operation switching valve 1 to each switching valve 3.5.7.
．． 12.13 is working.

14 is a switching valve for operating the second travel motor 15; 16 is a switching valve for operating the cylinder 17; 18 is a switching valve for operating the first boom cylinder; 20 is a switching valve for operating the second boom cylinder that forms a passage 19, and 20 is interlocked with the switching valve 7 for operating the first arm cylinder, and a confluent oil passage 5 is formed in the arm cylinder 8.
These switching valves 14, 16, 18, and 20 form a second switching valve group B, and the switching valves for operating the second travel motor on the most upstream side 14, an oil passage 22 from the second hydraulic pump 21 communicates with the second travel motor operation switching valve 14 and other switching valves 16.
．． 18.20 is connected in tandem with the other switching valve 16.
．． 18, 20 are connected in parallel, and each switching valve 16, 18.
20 is connected to oil lines 23, 24, 25.

26 is a pyro installed in the oil passage 10 leading from the first hydraulic pump 9 to the first travel motor operating switching valve 1;

1.14 of the first and second travel motor operation switching valves of both groups A and B, and any one of the other switching valves.
When the two hydraulic pumps are operated, the second hydraulic pump 21 is switched between the first travel motor operation switching valve 1 and the second travel motor operation switching valve 14.
are connected in parallel to each other, and the first hydraulic pump 9 is connected to the other switching valves 3.5.7.16.18. of both switching valve groups A and B.
A branch oil passage 27 communicates with the pilot switching valve 26 from the discharge side oil passage 22 of the second hydraulic pump 21, and a branch oil passage 27 communicates with the pilot switching valve 26 in parallel with the first switching valve 20. The oil passages 28, 29 communicate with switching valves 3.5.7 other than the first travel motor operation switching valve 1 of valve group A, and the oil passages 28, 29 communicate with switching valves 3.5.7 other than the first travel motor operation switching valve 1 of valve group A, and the oil passages 28. Oil passage 28 to the switching valve 16, 18, 20
．． 30 is working.

31 is a third hydraulic pump, and a pilot oil passage 32 is connected to the hydraulic pump 31, and a pilot oil passage 33.
34 communicates, and the pilot oil passages 33 and 34 pass through the check valve 35 and the pilot oil passage 36 to the pilot switching valve z6.
is familiar with Reference numeral 37 denotes an on-off valve provided in the pilot oil passage 33. This valve 37 is interlocked with the first travel motor operation switching valve 1, and when the first travel motor operation switching valve 1 is switched to a position other than neutral. A throttle 38 is provided in the oil passage 33 on the upstream side of the on-off valve 37 to open the pilot oil passage 33 . Similarly, 39 is an on-off valve provided in the pilot oil passage 34, and this valve 39 is interlocked with the second travel motor operation switching valve 14, and the second travel motor operation switching valve 14 is switched to a position other than neutral. A throttle 40 is provided in the pyro oil passage 34 on the upstream side of the on-off valve 39 to open the pilot oil passage 34 only when the opening/closing valve 39 is closed. 41 is from the pilot oil path 33 to the tank 4z
The oil passage 42 is a bypass oil passage leading to the oil passage 42, and three on-off valves 43, 44, and 45 are provided in series in the oil passage 42. The on-off valve 43 is an on-off valve that works with the switching valve 3 for operating the swing motor, the on-off valve 44 is an on-off valve that works with the switching valve 5 for operating the first boom, and the on-off valve 45 is a switching valve for operating the first arm. The on-off valves 43, 44, and 45 are opened only when these switching valves 3, 5, and 7 are in the neutral position, and are closed when they are switched in any other way. It is something. Similarly, 46 is a bypass oil passage leading from the pilot oil passage 34 to the tank 42, and the oil passage 46 is provided with three on-off valves 47, 48, and 49 in series. The on-off valve 47 is an on-off valve that works with the packet switching valve 16, the on-off valve 48 is an on-off valve that works with the second boom operation switching valve 18, and 49 is an on-off valve that works with the second arm operation switching valve 20. These opening/closing valves 47, 48, 49 are opened only when the switching valves 16, 18, 20 are in the neutral position, and are closed when the switching valves 16, 18, 20 are in the neutral position.

Note that all k are check valves, 51 is a relief valve, and 52 is a return oil path.

Although the present invention is configured as described above, a case in which it actually operates will be explained.

When traveling simply, that is, when only the traveling motor 2.15 operates and no other actuators operate, the first
The travel motor operation switching valve 1 and the second travel motor operation switching valve 14 are operated.

Pilot oil passages 32, 33, 34, and 36 from the third hydraulic pump 31 communicate with the switching valve 26, and an on-off valve 37 in one of the pilot oil passages 33 is used as a switching valve for operating the first travel motor. Switches and opens in conjunction with valve 1,
Further, the on-off valve 39 in the pilot oil passage 34 opens in conjunction with the second travel motor operation switching valve 14, but the first
Since the switching valves other than the travel motor operating switching valves 1.14 in the second switching valve groups A and B are not operated at all, the on-off valves 43, 44, 45, and 47 that are linked to these switching valves are
．． 48 and 49 are in the open state, and the bypass oil passage 41% 46 to the tank 42 is open, so no pilot pressure acts on the pilot changeover valve 26, and the valve 26
is in the state shown in FIG. Therefore, the pressure oil from the first hydraulic pump 9 reaches the travel motor 2 via the pilot switching valve 26, the oil passage 101 and the first travel motor operation switching valve 1, and the return oil reaches the first travel motor operation switching valve 1, Return oil path 5
2 and return to tank 42. Similarly, the second hydraulic pump 21
The pressure oil from the oil reaches the travel motor 15 via the oil passage 22 and the second travel motor operation switching valve 14, and the return oil passes through the second travel motor operation switching valve 14 and the return oil passage 52 and reaches the tank 42.
Return to In this way, the travel motor 2 is operated by pressure oil from the first hydraulic pump 9, and the travel motor 15 is operated by the second hydraulic pump 2.
Operated by pressure oil from 1, the vehicle moves straight.

Next, when operating the travel motor and other actuators at the same time, for example, when traveling in a wet area or on a slope, etc., when traveling while using other booms, arms, etc., In the case of turning by operating the turning motor while traveling, for example, the case of operating the turning motor 4 and turning while traveling will be explained. As described above, the traveling motor operating switching valve 1.14 is operated, and the traveling motor 2.15 is operating, and the swing motor operating switching valve 3 is further operated to switch it. The on-off valve 43 interlocked with the valve 3 is switched, and the bypass oil path leading to the tank 42 is shut off. Since the bypass oil passage 41 is closed, the pilot oil in the oil passage 38 is supplied to the double check valve 35.
, reaches the pilot switching valve 26 through the oil passage 36, and switches the valve 26 to the left side. Therefore, the second hydraulic pump 2
In addition to flowing through the oil passage 22 to the second travel motor operation switching valve 14, the pressure oil No. 1 flows through the branch oil passage 27, the pilot switching valve 26, and the oil passage 10 to the first travel motor operation switching valve 1. flows to That is, both of the two travel motors 2.15 are supplied with pressure oil from the second hydraulic pump 21. on the other hand,
The pressure oil of the first hydraulic pump 9 is supplied to a pilot switching valve 26, oil passages 28, 29, 11, and a switching valve 3 for operating the swing motor.
The return oil passes through the swing motor operation switching valve 3 and the return oil passage 52 and returns to the tank 42.
The swing motor 4 is activated. In this way, the traveling motor 2.
15 and other actuators at the same time, they will be operated by separate hydraulic pumps, and the travel motor z115 will not be affected by the other actuators. 2.1
5 always operates normally and no meandering occurs.

The above explanation is for the case where the swing motor 4 is activated while traveling, but it is also possible to operate the boom cylinder 6, arm cylinder 8, or packet cylinder 17 in another switching valve group B while traveling. It is exactly the same when it works,
5.7.16 Switching valves operating these actuators
The on-off valves 44, 45, and 47 that operate in conjunction with the bypass circuit 41
．． 46 is closed and pilot pressure acts on the pilot switching valve 26, so it operates in exactly the same way.

If two or more actuators other than the travel motor 2.15 are to be operated at the same time while driving, all of these actuators will be connected to the first hydraulic pump 9 in parallel. Regardless of whether the actuators are in the first switching valve group A or, rather, in both switching valve groups A and B,
It operates in the same manner as above, and if there is a difference in operating pressure, only the actuator on the low pressure side will operate.

When working in a stopped state, in other words, if the traveling motor 2
．． When actuating an actuator other than 15, since the travel motor operation switching valve 1.14 is not operated, the on-off valves 37.39 are all closed, and the pilot switching valve 2 is closed.
6, the valve 26 is in the state shown in FIG. are all connected in parallel to the first hydraulic pump 9, and similarly, the packet switching valve 16, the second boom switching valve 18, and the second arm switching valve 20 of the second switching valve group B are connected in parallel to the second hydraulic pump 21. , both groups of actuators are supplied with pressure oil independently from separate hydraulic pumps.

Effects of the Invention As described above, the present invention divides the actuators of a hydraulic excavator into two groups, each of which is operated by a separate hydraulic pump, and provides a switching valve for operating the travel motor in tandem on the most upstream side of each group. The switching valves of other actuators are connected in parallel on the downstream side, and a high-lot switching valve is provided in the discharge side oil passage of one hydraulic pump, and a pilot oil passage is connected in parallel to this, and each pilot oil An on-off valve that is interlocked with a switching valve for operating the travel motor is provided in the passageway, a bypass oil passage is provided downstream of the pilot oil passage leading to the tank, and the on-off oil passage is provided with an on-off valve that is interlocked with an actuator switching valve other than the travel motor. The pilot pressure is activated only when the travel motor operation switching valve is operated, and an oil passage is made to flow from the other hydraulic pump to the pilot switching valve, and the travel motor operation is controlled from the pilot switching valve. Since the oil passages are connected in parallel to the switching valves other than the switching valves for the drive, the drive motor and other actuators receive oil from separate hydraulic pumps when the drive is running. Even if it is activated, it will not be affected by it at all, and therefore will not meander.

Further, when the travel motor and other actuators are activated to escape from the mud, the other actuators receive pressure oil from a single hydraulic pump, so their operation is reliable.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram of the present invention. 1-----1 First travel motor operating switching valve 3--1 Swing motor operating switching valve 5--+-1st boom cylinder operating switching valve 7--1--1st arm cylinder Operation switching valve 9--1 1st
Hydraulic pump 14---r-Second travel motor operation switching valve 16---
---Packet cylinder operation switching valve 18---Second boom cylinder operation switching valve 20--M-Second arm cylinder operation switching valve 21--Second hydraulic pump 26- ----- Pilot switching valve 27 ----- Oil path 28 ----- # 29 --- 7F 30 ----- tt 33 ----- Pilot oil path 34 ----- -p 37----Opening/closing valve 39-111-〃 41----One night passage 43-2------Opening/closing valve 44---# 45----# 46---- ---Oil passage 47----1 Opening/closing valve 48----- #49 ------- #A-----1st switching valve group B-----1 2nd switching valve group and above

Claims (1)

[Claims] (1) In a hydraulic excavator in which the actuators of the hydraulic excavator are divided into two groups and each group is driven by a separate hydraulic pump, a switching valve for operating the travel motor is provided in the front row of each group, and this and other actuator operations are The switching valves for actuator operation are connected in tandem, and the other switching valves for actuator operation are connected in parallel, and a pilot switching valve is provided in the oil path leading from one hydraulic pump to the switching valve for operating the travel motor of that group. An oil passage is passed from the other hydraulic pump to the switching valve, and an oil passage is passed from the pilot switching valve to each switching valve other than the switching valve for operating the travel motor in both switching valve groups, so that the pilot switching valve When switched, one hydraulic pump is connected to the travel motor operating switching valve of both switching valve groups, and the other hydraulic pump is connected to the other switching valves, and a pilot oil passage is provided in parallel to the pilot switching valve. , each pilot oil passage is provided with an on-off valve that is linked to the travel motor operating switching valve and opens only when the valve is in a position other than neutral; A hydraulic circuit for construction machinery, characterized in that a bypass oil passage is provided, and each of the oil passages is provided with an on-off valve that operates in conjunction with a switching valve other than a travel motor operating switching valve, and opens only when the switching valve is in neutral. .