JPH0352275Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a hydraulic circuit for a fully hydraulic construction machine such as a crawler type hydraulic excavator.

Conventional technology For example, various actuators of a crawler type hydraulic excavator are 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. In a typical hydraulic circuit, the switching valves that operate each actuator are divided into two groups, and a separate hydraulic pump is connected to each group of switching valves. It is connected in parallel. In such a hydraulic circuit, actuators belonging to separate switching valve groups can be operated simultaneously with actuators belonging to other switching valve groups without being affected by the actuators belonging to other groups. However, when the actuators in the same switching valve group are operated simultaneously, an undesirable phenomenon occurs in that the pressure oil flows only to the actuator with a low operating pressure, and the pressure oil does not flow to the actuator with a high operating pressure, so that the actuator does not operate. For example, if the left and right travel motors are activated at the same time while the vehicle is moving, and another actuator with a lower operating pressure is activated, the amount of oil sent to the travel motors in the same group as that actuator will be reduced. 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 the travel becomes meandering. In order to prevent this, in the conventional hydraulic circuit, as shown in FIG. 26, when the first and second traveling motors 2, 15 and other actuators are operated simultaneously, for example, when traveling in a wetland or on a slope, the vehicle may be moved using a boom, arm, etc. while traveling. There is no problem. For example, the case where the boom cylinder 6 is operated while the vehicle is traveling will be explained with reference to FIG. First and second travel motor operation switching valve 1;
14 is operated, the first travel motor 2 and the second travel motor 15 are operating, and the switching valve 5 for operating the boom cylinder 6 is further operated to switch them. In this state, the on-off valves 37, 44, and 39 that operate in conjunction with the switching valves 1, 5, and 14 operate, the on-off valve 37 opens the oil passage 33, the on-off valve 44 shuts off the oil passage 41, and the on-off valve 39 opens the oil passage 33. Route 34 is now open. Therefore, since the bypass oil passage 41 is closed, the discharge pressure oil of the third hydraulic pump 31 passes through the throttle 38, oil passage 33, on-off valve 37, and then passes through the shuttle valve 35 and oil passage 36 as pilot pressure oil. Pilot switching valve 2
6, and the pilot switching valve 26 is switched to the A position. Therefore, the pressure oil of the second hydraulic pump 21 not only flows through the oil passage 22 to the second travel motor operating switching valve 14, but also flows through the branch oil passage 27, the internal passage at the pilot switching valve 26 position, and the oil passage. It also flows through 10 to the switching valve 1 for operating the first travel motor. On the other hand, the pressure oil from the first hydraulic pump 9 passes through the internal passage at the pilot switching valve 26a position, and flows to the switching valve 5 for operating the boom cylinder 6 located downstream of the switching valve 1 for operating the first travel motor. It flows in from the upstream side.
Therefore, the two travel motors 2 and 15 simultaneously receive only pressure oil from the second hydraulic pump 21 independently of actuators other than the travel motors, so that the boom cylinder 6 cannot be extended or contracted while traveling. However, it does not meander. Furthermore, when operating the first and second travel motor operation switching valves 1 and 14, or when simultaneously operating one or more switching valves other than the above-mentioned boom cylinder 6 operation switching valve, Similarly to the above, the pilot switching valve 26
Since the position is switched to the "yes" position, the pressure oil discharged from the second hydraulic pump 21 is exclusively supplied to the first and second travel motors 2 and 15, so that the aircraft can move in a specified manner without meandering during travel. This is done at a speed of

Problems to be Solved by the Invention In the conventional hydraulic circuit described above, when both the first and second travel motors and other actuators are operated simultaneously, the pilot switching valve switches, and the pressure oil discharged from the first hydraulic pump changes. The discharge pressure oil of the second hydraulic pump is exclusively supplied to actuators other than the travel motor, such as a predetermined amount, to both the first and second travel motors. Therefore, the ratio between the moving speed of the aircraft and the speed of the boom or arm remains constant. However, taking a crawler type hydraulic excavator as an example, if the hydraulic excavator escapes from a wetland,
Or when climbing up a steep slope,
In addition to the movement force provided by the travel motor, it is often necessary to move using the force of the boom or arm. In such a case, in the conventional hydraulic circuit, as described above, since the moving speed of the aircraft and the operating speed of the boom or arm remain constant, it is impossible to fully exert the respective forces.

In view of this point, this invention was developed when the travel motor and the switching valve for operating the actuator other than the travel motor arranged downstream of the travel motor are simultaneously switched, and when the pilot switching valve is switched, the discharge pressure oil of the first hydraulic pump is switched. By allowing a portion of the oil to flow into the discharge oil path of the second hydraulic pump or vice versa, and by adjusting the amount of inflow as necessary, the moving speed of the aircraft, boom, arm, etc. The aim is to make it possible to change the ratio between the actuator's operating speed and the actuator's operating speed.

Means for Solving the Problems The means of this invention taken to solve the above problems are as follows: (1) Dividing the switching valves for operating multiple actuators into two groups and supplying pressure oil from a separate hydraulic pump to each group. , a hydraulic circuit in which a switching valve for operating a travel motor is provided on the most upstream side of each group of switching valves, and a switching valve for operating an actuator other than the traveling motor is arranged downstream of the switching valve in parallel, and (b) one hydraulic pump. , between the oil passages leading to the travel motor operation switching valves belonging to one of the switching valve groups;
The branch oil path of the oil path from the other hydraulic pump that leads to the other travel motor operation switching valve is closed, but when it is switched by the pilot signal, the discharge oil path of one hydraulic pump is connected to the two switching valves. From the downstream side of the group's travel motor operation switching valve,
Equipped with a pilot switching valve that connects to the oil line that supplies pressure oil to the switching valve for operating an actuator other than the travel motor, and allows the discharge oil passage of the other hydraulic pump to communicate with both switching valves for operating the travel motor at the same time. (d) The pilot switching valve is provided with a signal from a means for generating a pilot signal when a switching valve for operating a travel motor is operated and a switching valve for operating an actuator other than a traveling motor belonging to the switching valve group is operated at the same time. In addition, when the pilot switching valve is switched, an oil passage is provided to communicate the discharge oil passages of the two hydraulic pumps, and A variable aperture means capable of adjusting the aperture is provided.

Operation When the travel motor and other actuators are operated at the same time, the pilot switching valve is switched and both are supplied with pressure oil from separate hydraulic pumps, and both the first and second hydraulic pumps are supplied with pressure oil. The discharge port is communicated with the operator's cab by a variable throttle means whose throttle can be easily adjusted. Therefore, since the operating pressure on the drive motor side is normally high, the second
A portion of the pressure oil from the hydraulic pump is sent to other actuators through the variable throttle section. Therefore, the operating speed of the actuator on the other actuator side increases, but this speed can be adjusted by the driver's operation.

Embodiments Hereinafter, embodiments of this invention will be described in detail based on the drawings. FIG. 1 is a circuit diagram showing an embodiment in which this invention is applied to the hydraulic circuit of a crawler type hydraulic excavator. 4 is a switching valve for operating, 5 is a switching valve for operating boom cylinder 6, and 7 is a switching valve for operating arm cylinder 8. These switching valves 1, 3, 5, 7
form a switching valve group A, and an oil passage 10 from the first hydraulic pump 9 communicates with the first switching valve 1 for operating the travel motor on the most upstream side, and the switching valve 1 for operating the first traveling motor and the other switching valves are connected to each other. 3, 5, and 7 are connected in tandem, and oil passages 11, 12, and 13 for forming parallel circuits communicate from the downstream side of the first travel motor operation switching valve 1 to each switching valve 3, 5, and 7. .

14 is a switching valve for operating the second travel motor 15, 16 is a switching valve for operating the bucket cylinder 17, and 18 is a switching valve for operating the boom cylinder 5.
20 is a switching valve that operates in conjunction with the switching valve 7 for arm cylinder operation and forms a merging oil passage 53 in the arm cylinder 8. , these switching valves 14, 16, 18, 20 form a switching valve group B, and an oil passage 22 from a second hydraulic pump 21 communicates with the switching valve 14 for operating the second traveling motor on the most upstream side. The switching valve 14 for operating the second traveling motor and the other switching valves 16, 18, 20 are connected in tandem, and the other switching valves 16, 18, 20 are connected in parallel, respectively. Oil passage 2 from the downstream side to each switching valve 16, 18, 20
3, 24, and 25 are connected.

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. and when operating one or more of the other switching valves,
The second hydraulic pump 21 is connected in parallel to the first travel motor operating switching valve 1 and the second traveling motor operating switching valve 14, and the first hydraulic pump 9 is connected to the switching valve groups A and B for switching other than the above. Valve 3, 5, 7, 16, 1
8 and 20 in parallel, and a branch oil passage 27 from the discharge side oil passage 22 of the second hydraulic pump 21 communicates with the pilot switching valve 26. In addition, oil passages 28 and 29 are provided from the pilot switching valve 26 to the switching valves 3, 5, and 7 other than the switching valve 1 for operating the first traveling motor of switching valve group A, for operating the second traveling motor of switching valve group B. Oil passages 28, 30 communicate with switching valves 16, 18, 20 other than switching valve 14 via check valves 50, 50, respectively.

Reference numeral 31 designates a third hydraulic pump, and the pressure oil discharged from the hydraulic pump 31 branches through a pilot oil passage 32 to form parallel pilot oil passages 33 and 34, and the pilot oil passages 33 and 34 are connected to the shuttle valve 3.
5. It communicates with the pilot switching valve 26 via the pilot oil passage 36. 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 valve is closed, and a throttle 38 is provided in the oil passage 33 on the upstream side of the on-off valve 37. Similarly, 39 is an on-off valve provided in the pilot oil passage 34, and this on-off valve 39 is a second on-off valve.
It is linked to the travel motor operation switching valve 14 and opens the pilot oil passage 34 only when the second travel motor operation switching valve 14 is switched to a position other than neutral. A throttle 40 is provided in the pilot oil passage 34 on the side.
Reference numeral 41 denotes a bypass oil passage leading from the pilot oil passage 33 to the tank 42, and the bypass oil passage 41 is provided with three on-off valves 43, 44, and 45 in series.
The on-off valve 43 is an on-off valve that works with the swing motor operation switching valve 3, the on-off valve 44 is an on-off valve that works with the boom operation switching valve 5, and the on-off valve 45 works with the arm operation switching valve 7. It is an on-off valve, and only when these switching valves 3, 5, and 7 are in the neutral position,
It opens the on-off valves 43, 44, and 45, respectively, and closes them when they are switched to other conditions. Similarly, 46 is a bypass oil passage leading from the pilot oil passage 34 to the oil tank 43, and the bypass 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 interlocks with the switching valve 16 for bucket operation, and the on-off valve 48
49 is an on-off valve that is interlocked with the merging operation switching valve 18 of the boom cylinder, and 49 is an on-off valve that is interlocked with the merging operation switching valve 20 of the arm cylinder. 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. In the present invention, an oil passage 55 is provided between the first hydraulic pump 9 and the oil passage 10 on the upstream side of the first travel motor operation switching valve 1, and a variable throttle 56 is provided in the middle of the oil passage 55. , is additionally set in parallel with the oil passage 10 passing through the pilot switching valve 26. The aperture adjustment of the variable aperture 56 is performed by the driver using an operating tool 57 in the driver's cab 58. In FIG. 1, 54 is a check valve, 51 is a relief valve, and 52 is a return oil path.

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

In the cited crawler type hydraulic excavator, the first
The operating function of this hydraulic circuit when operating the second travel motor and other actuators at the same time is also when operating the swing motor 4 while traveling, or in addition, when operating the boom cylinder 6 and arm cylinder 8 while traveling. The same applies to the operation of the bucket cylinder 17, so the following explanation will be based on the assumption that the hydraulic excavator uses a boom to facilitate climbing while traveling in a wetland or on a slope. As mentioned above, the travel motor operation switching valves 1, 1
4 is operated, the first and second traveling motors 2, 15
is in operation, and the switching valve 5 for operating the boom cylinder 6 is further operated to switch it. The on-off valve 44 interlocked with the switching valve 5 is switched, and the oil tank 42
Bypass oil passage 41 leading to is shut off. Since the bypass oil passage 41 is closed, the pilot oil in the oil passage 33 flows through the on-off valve 37, the shuttle valve 35, and the oil passage 3.
6 to reach the pilot switching valve 26, and switch the pilot switching valve 26 to the A position. Therefore, the pressure oil of the second hydraulic pump 21 not only flows through the oil passage 22 to the switching valve 14 for operating the second travel motor 15, but also flows through the branch oil passage 27 and the internal oil passage at position A of the pilot switching valve 26. , flows through the oil passage 10 to the switching valve 1 for operating the first travel motor 2. That is, both the two travel motors 2 and 15 are connected to the second hydraulic pump 21.
Receives pressure oil supply from. On the other hand, the pressure oil of the first hydraulic pump 9 is supplied to the internal passage at position A of the pilot switching valve 26, the oil passage 28, the check valve 50, the oil passage 29,
The oil reaches the boom cylinder 6 through the oil passage 12, the check valve 54, and the switching valve 5 for operating the boom cylinder 6, and the return oil returns to the oil tank 42 through the switching valve 5 and the oil passage 52, is activated. In this way, when the travel motors 2 and 15 and other actuators are operated simultaneously, they are operated by separate hydraulic pumps, and the travel motors 2 and 15 are affected by the influence of the other actuators. This ensures that the hydraulic excavator travels in a straight line. Then, in the present invention, the pilot switching valve 26 is connected from the first hydraulic pump 9.
In parallel with the oil passage 10 passing through the oil passage 10, an oil passage 55 having a variable throttle 56 is communicated with the oil passage 10. This allows the discharge port sides of the first hydraulic pump 9 and the second hydraulic pump 21 to communicate through the variable throttle 56 when the pilot switching valve 26 is switched to the A position. For this purpose, the second hydraulic pump 21 is either on the side of the travel motor that supplies the discharge oil or on the side of the first hydraulic pump.
Pressure oil flows through the variable throttle 56 from the other actuator side to which the hydraulic pump 9 supplies discharge oil, or from the side with higher oil pressure to the side with lower oil pressure. In this embodiment, since the operating pressure on the normal travel motor side is high, the pressure oil from the second hydraulic pump 21 is transferred to the oil path 2.
7. Pilot switching valve 26, right oil passage at position A;
Variable throttle 56, oil passage 55, pilot switching valve 2
6. Left side oil passage at position A, oil passage 28, check valve 5
The oil is sent to the boom cylinder 6 through the oil passage 29, oil passage 12, check valve 54, and switching valve 5. Therefore, the operating speed of the boom cylinder 6 increases. The operating speed in this case can be adjusted by the driver operating the operating tool 57 in the driver's cab 58 to adjust the throttling effect of the variable throttle 56.

Note that although the diagram shown in FIG. 2 is another embodiment of the present invention, the oil passage 55 and the variable throttle 56 in FIG.
Instead, the operator's cab 58 is located inside the pilot switching valve 26'.
A variable diaphragm 56' that can be adjusted by an operating tool 57 inside is provided.

Effects of the invention As mentioned above, the present invention has two actuators for fully hydraulic construction machinery similar to crawler hydraulic excavators.
The first hydraulic pump is divided into two groups, each operated by a separate hydraulic pump, and the first hydraulic A communicating oil passage having a variable throttle that can be adjusted from the outside is provided between the pump and the discharge port of the second hydraulic pump.
In conventional hydraulic circuits, when the travel motor and other actuators are operated at the same time, the discharge pressure oil of the first and second hydraulic pumps flows exclusively into each of them, and the operating speed of both is controlled. Since the ratio was constant, it was inappropriate except under certain working conditions, and it was difficult to achieve highly efficient work by combining the operating forces of multiple actuators. For example, in the case of a hydraulic excavator equipped with the hydraulic circuit of the present invention with an additional restriction, when moving forward in a swamp, even when it is difficult to move forward with self-propelled power alone, if the boom and arm are operated simultaneously, A portion of the high-pressure oil on the travel motor side passes through a variable throttle and flows into low-pressure actuators such as the boom and arm. Therefore, it became possible to increase the operating speed of the boom, arm, etc. At the same time, depending on the situation on the ground,
When it becomes necessary to slow down or speed up the operation speed of the boom, arm, etc., the driver adjusts the aperture using a variable aperture operating tool. By doing so, the operating speed of the boom, arm, etc. can be adjusted as necessary, improving the work efficiency of not only crawler hydraulic excavators but also similar fully hydraulic construction machinery while the work attachment is running. Now I can do it.

[Brief explanation of the drawing]

FIG. 1 is a hydraulic circuit diagram of the present invention, FIG. 2 is another embodiment of FIG. 1, and FIG. 3 is a hydraulic circuit diagram of the prior art. 1...Switching valve, 2...First travel motor, 4...
Swing motor, 6...Boom cylinder, 8...Arm cylinder, 9...First hydraulic pump, 10...Oil passage, 21...Second hydraulic pump, 26, 26'...
Pilot switching valve, 31...Third hydraulic pump, 3
2...Pilot oil path, 35...Shuttle valve, 3
7... Opening/closing valve, 38... Throttle, 39... Opening/closing valve,
55... Oil path, 56, 56'... Variable throttle, 57
...Operation tool, 58...Driver's cab.

Claims (1)

[Scope of utility model registration request] A plurality of switching valves for actuator operation are divided into two switching valve groups, each of which is supplied with pressure oil from a separate hydraulic pump, and a switching valve for driving motor operation is provided at the most upstream side of each switching valve group. Switching valves for operating actuators other than the travel motor are arranged in parallel on the downstream side, and are provided in the middle of the oil passage leading from one hydraulic pump to the switching valve for operating the travel motor of one switching valve group. The oil path leading from the hydraulic pump to one of the travel motor operation switching valves is opened, and the branch oil path from the other hydraulic pump leading to the other travel motor operation switching valve is closed. When switched by a signal, the oil passage from one hydraulic pump is simultaneously connected to the switching valve for actuator operation other than the traveling motor from the downstream side of the switching valve for operating the travel motor in the two switching valve groups, and the other In a hydraulic circuit equipped with a pilot switching valve that allows an oil passage from a hydraulic pump to communicate with one of the driving motor operating switching valves at the same time as the other driving motor operating switching valve, a driving motor operating switching valve is used. When any one or more of the actuator operation switching valves other than the travel motor belonging to the switching valve group are operated simultaneously, means for issuing a signal to the pilot switching valve, and the pilot switching valve switching in response to the signal. The oil passage includes an oil passage that communicates the discharge oil passages of the two hydraulic pumps through a variable throttle means that can be adjusted from the outside only when the oil is broken, and an operating tool that can adjust the throttle of the variable throttle means. Hydraulic circuit for construction machinery.