JPH0372769B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a hydraulic circuit for a track-type construction machine, such as a hydraulic excavator.

Conventional Technology Taking a track type hydraulic excavator as an example, its actuator is configured to be operated by supplying pressure oil from two or more hydraulic pumps and controlling this with a switching valve. . The actuator usually consists of six pieces: a boom cylinder, an arm cylinder, a bucket cylinder, a swing motor, and left and right travel motors, but these can be operated singly or by a complex operation in which multiple units are operated at the same time. Ru. 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 a separate hydraulic pump to each group of switching valves. It is connected to In such a hydraulic circuit, even if actuators in separate groups 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 above conventional method, when actuators in different groups are operated simultaneously, each actuator receives pressure oil from a separate hydraulic pump without being affected by the operation of other actuators. can be supplied and operated as an independent actuator. However, if actuators in the same switching valve group are activated at the same time,
Pressure oil flows only to actuators with low operating pressure,
Pressure oil does not flow to the actuator with high operating pressure,
An undesirable phenomenon occurs in which the device 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 sent 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.

It is an object of the present invention to solve the above-mentioned problems and to provide a hydraulic system for a hydraulic excavator that does not meander when traveling, especially when actuators other than the travel motor are activated.

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.

(b) Of the switching valves that operate these actuators, a switching valve for operating the travel motor is provided on the most upstream side of each group, and downstream thereof, other switching valve groups for actuators arranged in a parallel circuit are connected in tandem. What I did.

(c) A pilot switching valve is installed in the oil path leading from one hydraulic pump to the switching valve for operating the travel motor of one Greep.

(d) A branch oil passage of an oil passage leading from the other hydraulic pump to the travel motor operation switching valve of the other group is connected to the pilot switching valve, and the pilot switching valve is connected to a drive motor other than the travel motor of both switching valve groups. The oil passages were connected to the switching valves for actuator operation.

E The above-mentioned pilot switching valve normally opens the oil passage leading from one hydraulic pump to the switching valve for operating the traveling motors of one group by the biasing force of the spring, and opens the oil passage leading from the other hydraulic pump to the traveling motor operating switching valve of the other group. The branch oil path of the oil path leading to the operation switching valve is closed, but when activated, it forms an oil path leading from one hydraulic pump to the operation switching valve for actuators other than the travel motors of both groups, and the other A branch oil passage of the oil passage leading from the hydraulic pump to the travel motor operation switching valve of the other group is opened so that it also communicates with one of the travel motor operation switching valves.

(f) An on-off valve that operates in conjunction with the switching valve for operating the travel motor in each group and opens the internal passage when not in neutral, and an on-off valve that operates in conjunction with the switching valve for operating actuators other than the traveling motor and closes the internal passage when not in neutral. The on-off valves are connected to the on-off valves in this order in tandem by oil passages, with the ends of the oil passages communicating with the tank, and on the other hand, the inlets of the on-off valves linked to the switching valves for operating the respective travel motors are connected with the specified oil passages. Pressure oil from a hydraulic source whose pressure is regulated to the pressure of

G. The downstream oil passage of the sub-switching valve linked to the travel motor operating switching valve of each group is branched to extract the pressure oil as pilot pressure, and guide it to the pilot switching valve via the shuttle valve. to operate.

It is.

Function When the travel motor and other actuators are operated at the same time, the pressure oil from the regulated hydraulic pressure source passes through the on-off valve that is linked to the travel motor operation switching valve, and is transferred to the on-off valve located downstream. Since the valve is closed and acts as pilot pressure on the pilot switching valve via the shuttle valve, the pilot switching valve is switched, and the travel motors of both groups and the actuators other than the travel motors of both groups are operated by separate hydraulic pumps. Since the vehicle will be supplied with oil from the vehicle, there will be no meandering during travel, ensuring straight-line travel, and other actuators that are operated while traveling are supplied with pressure oil from a dedicated hydraulic pump. , reliable operation is possible regardless of the operating pressure during driving.

Embodiments Hereinafter, embodiments of the present invention will be described in detail based on the drawings, taking a track type hydraulic excavator as an example.

1 is a switching valve for operating the first travel motor 2; 3 is a switching valve for operating the swing motor 4; 5 is a first switching valve for operating the boom cylinder 6; and 7 is a first switching valve for operating the arm cylinder 8. However, these switching valves 1, 3, 5, and 7 form a first switching valve group A, and the first switching valve 1 for operating the travel motor on the most upstream side
An oil passage 10 is connected from the first hydraulic pump 9 to the first hydraulic pump 9.
The travel motor operating switching valve 1 and the other actuator operating switching valves 3, 5, 7 are connected in a tandem manner.
7 are connected in parallel, and oil passages 11, 12, and 13 communicate with each of the switching valves 3, 5, and 7 from the downstream side of the first travel motor operation switching valve 1.

14 is a switching valve for operating the second traveling motor 15, 16 is a switching valve for operating the bucket cylinder 17, and 18 is linked with the first switching valve 5 for operating the boom cylinder, and connects an oil path to the boom cylinder 6. 19
20 is a second switching valve for operating the arm cylinder which is linked with the first switching valve for operating the arm cylinder 7 and has a confluence oil passage 53 formed in the arm cylinder 8. However, these switching valves 14, 16, 18, and 20 form a second switching valve group B, and the switching valve 14 for operating the second traveling motor on the most upstream side has a second hydraulic pump 2.
An oil passage 22 communicates from the second travel motor operating switching valve 14 to the other actuator operating switching valve 1.
6, 18, and 20 are connected in tandem, and the other actuator operation switching valves 16, 18, and 20 are connected in parallel, respectively, and each switching valve 16, 18,2
Oil passages 23, 24, and 25 communicate with 0.

Reference numeral 26 designates a pilot switching valve provided in the oil passage 10 leading from the first hydraulic pump 9 to the first travel motor operating switching valve 1, which is connected to the first and second traveling motor operating switching valves 1 and 14 of both groups A and B. When operating one or more of the other switching valves,
As will be described later, the pilot pressure acts on the pilot oil chamber and switches the second hydraulic pump 21 to the first travel motor operation switching valve 1 and the second travel motor operation switching valve 14 in parallel. 1 hydraulic pump 9
The pilot switching valve 26 is connected to the discharge valve of the second hydraulic pump 21 in parallel to the other switching valves 3, 5, 7, 16, 18, 20 of both switching valve groups A and B. A branch oil passage 27 communicates with the side oil passage 22, and the pilot switching valve 2
6 to the switching valves 3, 5, and 7 of the first switching valve group A other than the first travel motor operation switching valve 1.
8 and 29 are in communication, and the switching valves 1 other than the second travel motor operating switching valve 14 of the second switching valve group B
Oil passages 28 and 30 communicate with 6, 18, and 20.

Reference numeral 31 designates a third hydraulic pump, from which a pilot oil passage 32 and parallel pilot oil passages 33 and 34 communicate.
3 and 34 are a shuttle valve 35 and a pilot oil passage 36
It communicates with the pilot oil chamber of the pilot selector valve 26 through the. Reference numeral 37 denotes an on-off valve provided in the pilot oil passage 33, and the on-off 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. This is for opening the pilot oil passage 33 only when the oil passage 33 is closed. Similarly, 39 is an on-off valve provided in the pilot oil passage 34, and the on-off 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 state other than neutral. A throttle 40 is provided in the pilot oil passage 34 on the upstream side of the on-off valve 39 to open the pilot oil passage 34 only when the valve is closed. 4
Reference numeral 1 denotes a bypass oil passage leading from the pilot oil passage 33 to the tank 42, and the oil passage 41 has three on-off valves 4.
3, 44, and 45 are provided in series. Open/close valve 43
is an on-off valve that is interlocked with the swing motor operation switching valve 3, the on-off valve 44 is an on-off valve that is interlocked with the first boom operation on-off valve 5, and the on-off valve 45 is interlocked with the first arm operation switching valve 7. Only when these switching valves 3, 5, and 7 are in the neutral position,
The on-off valves 43, 44, and 45 are each opened, and closed when switched to any other state. Similarly, 46 is a bypass oil passage leading from the pilot oil passage 34 to the tank 42;
Three on-off valves 47, 48, and 49 are provided in series. The on-off valve 47 is an on-off valve that works with the bucket switching valve 16, the on-off valve 48 is an on-off valve that works with the second switching valve 18 for boom operation, and 49 is an on-off valve that works with the second switching valve 20 for arm operation. 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 50 and 54 are both 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.

During simple running, that is, running motors 2, 15
If the other actuators do not operate at all, operate the first travel motor operation switching valve 1 and the second travel motor operation switching valve 14. The pilot switching valve 26 is equipped with a third hydraulic pump 3.
1, pilot oil passages 32, 33, 34, and 36 communicate with each other, and an on-off valve 37 in one of the pilot oil passages 33 is switched to open in conjunction with the first travel motor operating switching valve 1. , 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 and second
Since the switching valves other than the travel motor operation switching valves 1 and 14 in switching valve groups A and B are not operated at all, the on-off valves 43 and 4 that are linked to these switching valves are
4, 45, 47, 48, and 49 are all open, and bypass oil passages 41, 46 to tank 42
Since the valve is open, no pilot pressure acts on the pilot switching valve 26, and the valve 26 is in the state shown in FIG. Therefore, the pressure oil from the first oil passage pump 9 passes through the pilot switching valve 26, the oil passage 10, and the first travel motor operation switching valve 1 to the travel motor 2.
The return oil returns to the tank 42 via the first travel motor operation switching valve 1 and the return oil path 52. Similarly, the oil pressure from the second hydraulic pump 21 is applied to the oil passage 22,
The return oil reaches the travel motor 15 via the second travel motor operation switching valve 14 and returns to the tank 42 via the second travel motor operation switching valve 14 and return oil path 52. In this way, the traveling motor 2 is connected to the first oil passage pump 9.
The traveling motor 15 is operated by pressure oil from the second hydraulic pump 21, and the vehicle body moves straight.

Next, when operating the travel motor and other actuators at the same time, i.e. in wetlands or
When traveling on a slope, etc., use other booms, arms, etc. to make it easier to proceed, or when traveling by operating the swing motor to make a turn. The case where the robot operates and turns will be explained. As described above, the travel motor operation switching valves 1 and 14 are operated to operate the travel motors 2 and 15, and the swing motor operation switching valve 3 is also operated to switch them. The on-off valve 43 interlocked with the valve 3 is switched, and the tank 4
The bypass oil passage leading to 2 is blocked. Since the bypass oil passage 41 is closed, the pilot oil in the oil passage 33 passes through the shuttle valve 35 and the oil passage 36 and reaches the pilot oil chamber of the pilot switching valve 26.
Switch 6 to the left side. Therefore, the pressure oil of the second hydraulic pump 21 not only flows through the oil passage 22 to the second travel motor operation switching valve 14 but also through the branch oil passage 2.
7, it flows through the pilot switching valve 26 and the oil passage 10 to the first travel motor operating switching valve 1. That is, the two travel motors 2 and 15 both receive pressure oil from the second hydraulic pump 21. On the other hand, the pressure oil of the first hydraulic pump 9 reaches the swing motor 4 through the pilot switching valve 26, the oil passages 28, 29, 11, and the switching valve 3 for operating the swing motor, and the return oil is used for operating the swing motor. The oil returns to the tank 42 through the switching valve 3 and the return oil path 52, and the swing motor 4 is activated.
When the travel motors 2, 15 and other actuators are operated simultaneously in this way, they are operated by separate hydraulic pumps, and the travel motors 2, 15 are operated by separate hydraulic pumps. The traveling motors 2 and 15 always operate normally without being affected by the influence, and no meandering occurs.

The above explanation is for the case where the swing motor 4 is operated while traveling, but in addition to that, the boom cylinder 6, arm cylinder 8, or bucket cylinder 17 in other switching valve group B may be operated while traveling. The same applies to the case where the on-off valves 44, 45, 47 that interlock the switching valves 5, 7, 16 that operate these actuators close either of the bypass circuits 41, 46, and the pilot pressure is not applied to the pilot switching valve 26. It works exactly the same way.

If two or more actuators other than the travel motors 2 and 15 are operated in the same way while traveling, these actuators will all be connected to the first hydraulic pump 9 in parallel. Regardless of whether the actuator is in the first switching valve group A or in both switching valve groups A and B, it operates in the same way as described above, and if there is a difference in the operating pressure, For example, only the actuator on the low pressure side operates.

When performing work in a stopped state, that is, when operating actuators other than the travel motors 2 and 15, the travel motor operation switching valves 1 and 14 are not operated, so the on-off valves 37 and 39 are both closed and the pilot No pilot pressure acts on the switching valve 26, and the valve 26 is in the state shown in FIG.
switching valve 3 for operating the swing motor of switching valve group A;
The first switching valve 5 for boom operation and the first switching valve 7 for arm operation both communicate in parallel with the first hydraulic pump 9, and similarly, the bucket switching valve 16 of the second switching valve group B and the second switching valve for boom operation The valve 18 and the second switching valve 20 for arm operation communicate in parallel with the second hydraulic pump 21, and the actuators of both groups receive pressure oil independently from each separate hydraulic pump.

Effects of the Invention As described above, the present invention divides the actuators of a track-type construction machine such as a hydraulic excavator into two groups, each of which is operated by a separate hydraulic pump, and the most upstream side of each group is operated by a travel motor. The other actuator operating switching valve groups are connected in tandem on the downstream side, and the other actuator operating switching valves are connected in parallel on the downstream side, and the discharge of one hydraulic pump is connected in tandem. A pilot switching valve is provided in the middle of the side oil passage, and the pilot oil chamber of the pilot switching valve is equipped with a pilot switching valve that is operated only when the switching valve for operating the travel motor and the switching valve for operating the other actuator in the group are operated at the same time. Since the pressure is guided, both travel motors are supplied with oil from separate hydraulic pumps when only traveling, so there is no meandering during travel. In addition, when the travel motor and another actuator operate simultaneously to escape from mud, pilot pressure acts on the pilot switching valve and switches, and the pressure oil discharged from one hydraulic pump is used to operate the actuator other than the travel motor. Pressure oil discharged from the other hydraulic pump flows in parallel to the switching valve for operating the travel motor.
Since each flow is dedicated to each, it is possible to exert running power, and actuators other than the running motor can be operated reliably regardless of the load on the running motor.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram of the present invention. DESCRIPTION OF SYMBOLS 1... First switching valve for operating the travel motor, 3... Switching valve for swing motor operation, 5... First switching valve for boom cylinder operation, 7... First switching valve for arm cylinder operation, 9... First switching valve 1 hydraulic pump, 14...second
Travel motor operation switching valve, 16... Bucket cylinder operation switching valve, 18... Boom cylinder operation second switching valve, 20... Arm cylinder operation second switching valve, 21... Second hydraulic pump, 26... Pilot switching valve, 27... Oil passage, 28... Oil passage,
29... Oil passage, 30... Oil passage, 33... Pilot oil passage, 34... Pilot oil passage, 37... On-off valve, 39... On-off valve, 41... Oil passage, 43... On-off valve, 44... Open/close valve, 45... Open/close valve, 46...
...Oil passage, 47...On-off valve, 48...On-off valve, 49
...Opening/closing valve, A...First switching valve group, B...
2nd switching valve group.

Claims (1)

[Claims] 1 Divide the actuator operation switching valves of track-type construction machinery into two groups, and one group includes one travel motor operation switching valve and one or more actuator operation switching valves other than the travel motor, and the other In each group, the other travel motor operation switching valve and one or more other actuator operation switching valves other than the travel motor are arranged, and each group is supplied with pressure oil discharged from a separate hydraulic pump. In this hydraulic operation circuit, a pilot switching valve is provided in the middle of the oil path leading from the hydraulic pump to the operation switching valve group, and when the pilot switching valve is switched, one hydraulic pump is switched to operate the left and right travel motors. In a hydraulic circuit in which the other hydraulic pump forms oil passages for exclusively supplying discharge pressure oil to a switching valve for operating an actuator other than the travel motor, the pilot oil chamber of the pilot switching valve has a The oil source is guided as pilot pressure from two pilot oil passages each having a throttle via a shuttle valve, and a switching valve for operating the travel motor is interlocked with a switching valve in the middle of each pilot oil passage, and the valve is in neutral state. An on-off valve that opens only at other times is provided, and an oil path is provided that branches from the downstream side of the on-off valve and leads to the tank, and the oil path is connected to a switching valve for operating an actuator other than the travel motor belonging to each group. A hydraulic circuit for construction machinery, characterized in that it is provided with tandem on-off valves that are interlocked and open only when the switching valve is in neutral.