JPH04146336A - Hydraulic circuit for hydraulic shovel - Google Patents

Abstract

PURPOSE:To permit a running equipment to take the most preference by composing first and second control valve groups including a running switching valve, and a third control valve group including a discharge plate switching valve, to be communicated with the first and second control valve groups, according to switching the running switching valve. CONSTITUTION:In a first control valve group 10 including a oneside running switching valve 16, and a second control valve group 20 including an other-side running switching valve 26, the running switching valves 16, 26 are arranged at first preferential positions. After that, they are respectively tandem jointed to a boom switching valve 18 and the others, and an arm switching valve 28 and other downstream switching valves. Besides, both the control valve groups 10, 20 are communicated with a combined valve 50 and a passage 54. Then, by opening or closing the combined valve 50, discharge oil is fed to the first and second control valve groups 10, 20. As a result, a running equipment can be set independently from any other work equipments and can be preferentially driven.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a hydraulic circuit for a hydraulic excavator, and more specifically, in this type of hydraulic circuit equipped with a discharge plate, a traveling system actuator is connected to another actuator. The present invention relates to a hydraulic circuit configured to give top priority to

[Conventional technology]

Generally, driving performance is important in hydraulic excavators equipped with earth removal plates. For this reason, in this type of hydraulic circuit, the control valve group usually includes a first (in this case, the right side) travel switching valve 16, boom switching valve 18, and the like, as shown in FIG. Control valve group 1
0, the other (left side) second control valve group 20 that includes a travel switching valve 26, arm switching valve 28, and others, and a third control valve group 30 that includes an earth removal plate switching valve 36, and others. The first and second control valve groups 10.20 are connected by a communication valve 40.

Note that the first, second, and third control valve groups 10, 2
0.30 is for the first, second, and third pumps 12, 2, respectively.
2.32 and the discharge oil of these pumps is respectively discharged into the tank via a central bypass passage 14.2-4.34.

Therefore, according to such a hydraulic circuit, since the travel system is independent from the earth removal plate system, it is possible to smoothly perform ground leveling work etc. by performing combined operation of the travel system and the earth removal plate system. Further, since the oil discharged from the first and second pumps can be combined, the boom or arm system can be driven at high speed by the combined oil discharged from the first and second pumps as required.

[Problem to be solved by the invention]

However, in the conventional hydraulic circuit as described above, there are still problems that should be improved as described below.

In other words, in the conventional hydraulic circuit, the traveling system is driven independently when the earth removal plate system and the traveling system are operated in combination, but the traveling system is driven independently when the other working system (boom or arm) and the traveling system are operated in a combined manner. When performing a combined operation, the first and second control valve groups are connected via the communication valve as described above.
One of the first and second pumps drives the work system, and the other pump drives both the left and right travel systems.

However, when the left and right demarcation systems are driven simultaneously by one pump, first of all, when the left and right running loads are approximately equal, such as on flat ground, straightness cannot be maintained. However, if the left and right running loads are different, such as on a slope, the straightness is lost. Next, the travel speed is reduced to approximately half the speed during solo travel operation where both the left and right travel systems are driven by their respective pumps.

As described above, the hydraulic circuit of the conventional hydraulic excavator has the disadvantage that the running performance is hindered and the running speed is reduced during a combined operation of the working system other than the earth removal system and the running system.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a hydraulic circuit for a hydraulic excavator that can always operate the traveling system as a top priority independently of all working systems during combined operation of the traveling system and the working system. be.

[Means to solve the problem]

In order to achieve the above object, a hydraulic circuit for a hydraulic excavator according to the present invention includes a first control valve group that includes multiple switching valves including one traveling switching valve and is connected to a first pump; A second control valve group includes a multiple switching valve including the other traveling switching valve and is connected to the second pump; and a second control valve group includes a multiple switching valve including the discharge plate switching valve and is connected to the third pump. the first and second control valve groups are connected in tandem to the downstream switching valve with their respective traveling switching valves located at the first priority position; , each of the center bypass passages is provided with a merging valve that closes the center bypass passage in response to switching of the traveling switching valve of the other control valve group, and furthermore, the upstream center of each of the merging valves is A passage connecting the inlet passage to the center bypass passage on the downstream side of the travel switching valve of the other control valve group via a check valve is provided, while the third control valve group has the above-mentioned passage in its center bypass passage. A merging valve is provided that closes the center bypass passage in response to switching of one of the travel switching valves, and a center bypass passage on the upstream side of the merging valve is connected to a center bypass passage on the downstream side of at least one of the travel switching valves. It is characterized by providing a passage connected to the bypass passage via a check valve.

In this case, the switching signal of each merging valve of the first and second control valve groups is the secondary of the pressure reducing valve provided in the pressure oil supply line to each travel switching valve of the second and first control valve groups, respectively. The pressure can further consist of an output obtained when passing through a respective selector valve connected to each of the travel switching valves. Alternatively, the switching signal of each of the merging valves may be such that the first control valve group includes a boom switching valve in addition to one traveling switching valve, and the second control valve group includes a boom switching valve in addition to the other traveling switching valve. When arm switching valves are included, the maximum operation signals for the traveling and arm switching valves and the traveling and boom switching valves of the second and first control valve groups may be used.

Further, in the hydraulic circuit, a fourth control valve group including a multiple switching valve is connected to the pressure oil supply line of the third pump, and the fourth control valve group is connected to the first and/or second control valve group. When simultaneously switching the running switching valve of the control valve group and the non-running switching valve of the first control valve group, the pressure oil supply line of the third pump is switched to the running switching valve of the first control valve group. connected to the center bypass passage on the downstream side of the valve, and on the other hand, when simultaneously switching the travel switching valve of the first and/or second control valve group and the non-travel switching valve of the second control valve group, It is also possible to configure the pressure oil supply line of the pump No. 3 to be connected to the center bypass passage on the downstream side of the traveling switching valve of the second control valve group.

[Effect]

In the hydraulic circuit of the present invention, the first
, the second control valve group is configured such that the travel switching valve is installed at a first priority position and a predetermined communication is established between the two control valve groups in response to switching of the other travel switching valve. On the other hand, the third control valve group including the soil removal plate switching valve is configured to be able to communicate with the first and second control valve groups in accordance with the switching of the travel switching valve. has been done.

As a result, in the hydraulic circuit of the present invention, the first, second,
During combined operation of the third control valve group, if both travel systems of the first and second control valve groups and the earth removal plate system of the third control valve group are driven simultaneously, both travel systems It goes without saying that the oil discharged from the first and second pumps is supplied independently and with the highest priority, but in the same way, during the combined operation, for example, both the first and second control valve groups are supplied Even when the system and the working system are operated at the same time, the oil discharged from the eleventh and second pumps is supplied to both traveling systems with the highest priority, as in the case described above. In this case, the working system is supplied with oil discharged from the third pump.

In addition, in the hydraulic circuit of the present invention, it is possible to further connect a fourth control valve group to the third pump, but in this case, the fourth control valve group is connected to the first control valve group. and/or the discharge oil of the third pump can be configured to be supplied to the first or second control valve group respectively in response to switching of the switching valve of the second control valve group; However, the operation of the hydraulic circuit remains basically unchanged from the operation of the hydraulic circuit described above.

In this way, in the hydraulic circuit of the present invention, the traveling system can always be driven with the highest priority independently from all the working systems during a combined operation of the traveling system and the working system.

〔Example〕

Next, an embodiment of the hydraulic circuit for a hydraulic excavator according to the present invention will be described in detail with reference to attached screens. For convenience of explanation, the same reference numerals are given to the same components as in the conventional structure shown in FIG. 3, and detailed explanation will be omitted.

First of all, the basic configuration of the hydraulic circuit of the hydraulic excavator of the present invention is the same as the conventional configuration shown in FIG. That is, in FIG. 1, the hydraulic circuit includes a first control valve group 10 that includes a traveling switching valve 16, a boom switching valve 18, and the like on one side (on the right side in this case) and is connected to a first pump 12; (Left side) A second control valve group 20 that includes a travel switching valve 26, an arm switching valve 28, and others and is connected to the second pump 22, and a soil removal plate switching valve 36.
and the like and connected to the third pump 32.
control valve group 30, and the oil discharged from each pump 12, 22.32 is configured to flow into a tank via a center bypass passage 14, 24.34, respectively.

However, in the hydraulic circuit of the present invention, the first and second control valve groups 10.20 are connected to the traveling switching valves 16.20.
26 are arranged in the first priority position and connected in tandem to the boom switching valve 18 and the arm switching valve 28 and other downstream switching valves, and a merging valve is connected between both control valve groups 10 and 20. and are configured to communicate in a predetermined manner via a passage. That is, the first control valve group 10 is provided with a merging valve 50 in the most downstream center bypass passage 14', and the upstream center bypass passage 14' of this merging valve 50 is connected to the travel switching valve of the other control valve group 20. 26 is connected to the downstream center bypass passage 24 via a check valve 52 and a passage 54, and the secondary pressure of a pressure reducing valve 56 provided in the pressure oil supply line passes through a selector valve 58 connected to the travel switching valve 14. The output obtained when doing so is connected to a merging valve 62 of the other control valve group 2° (described later) (and a merging valve 74 of the third control valve group 30, described later) via a pilot line 6°.

Further, the second control valve group 2° includes a merging valve 62 provided in the center bypass passage 24' at the most downstream side.
The upstream center bypass passage 24' of the second control valve group 10 is connected to the downstream center bypass passage 14 of the traveling switching valve 16 of the other control valve group 10 via a check valve 64 and a passage 66, and a pressure oil supply line is provided. The output obtained when the secondary pressure of the pressure reducing valve 68 passes through the selector valve 70 connected to the travel switching valve 24 is connected to each of the merging valves 50, 62, and 74 via a pilot line 72. On the other hand, the third control valve group 30 is provided with the above-mentioned merging valve 74 in its center bypass passage 34 and connected to the above-mentioned pilot line 60. It is configured to be connected to the downstream side center bypass passage 14 of the traveling switching valve 16 of the first control valve group 10 via a check valve 76 and a passage 78. In this case, either one of the pilot lines 60, 72 may be connected to the merging valve 74, and the one passage 78 may be configured to be simultaneously connected to the downstream center bypass passage 24 of the second control valve group 20. can.

Next, the operation of the hydraulic circuit of the present invention having such a configuration will be explained, but first, the dual speed switching valve 16.
26 and the soil removal plate switching valve 36 at the same time, each switching valve 1
It is clear that the discharge oil from the first, second, and third pumps 12, 22, and 32 is supplied independently to 6, 26, and 36, respectively. Each case in which only the working system is driven in groups 10 and 20, or when the traveling system and the working system are driven simultaneously will be explained.

First, when only one work system is to be driven, that is, when only the boom switching valve 18 of the first control valve group 10 is operated, the switching valve 18 is connected to the first pump 12.
Discharge oil is supplied from. In this case, if necessary, the switching valve 1 may be connected to the merging valve 62 of the second control valve group 20.
By applying operation signals P and M of 8 to close the merging valve 62, the oil discharged from the second pump 22 is transferred to the passage 6.
6 to the discharge oil of the first pump 12. Similarly, when only the arm switching valve 28 of the second control valve group 20 is operated, the switching valve 28 is supplied with oil discharged from the second pump 22. The switching valve 2 is connected to the merging valve 50 of the control valve group 10.
By applying the operation signal PAM 8 and closing the merging valve 50, the oil discharged from the first pump 12 is transferred to the passage 5.
4 can be discarded and combined with the discharge oil of the second pump 22.

Next, when operating one traveling system, for example, the right travel switching valve 16, and one working system, for example, the boom switching valve 18,
The entire amount of oil discharged from the first pump 12 is preferentially supplied to the right travel selector valve 16, but at this time, the pressure reducing valve 56, selector valve 58 and pilot line 60 are operated by operating the right travel selector valve 16. Since both the merging valves 62 and 74 are closed by the switching signal applied through the
The discharge oil from the pumps 22 and 32 can be supplied to the boom switching valve 18 via the passages 66 and 78, respectively. In addition, the left travel switching valve 26 and the arm switching valve 2
8, the entire amount of oil discharged from the second pump 22 is preferentially supplied to the left travel switching valve 26.
On the other hand, at this time, both the merging valves 50 and 74 are closed by the switching signal applied through the pressure reducing valve 68, the selector valve 70, and the selector valve 72 by operating the left travel switching valve 26, so that the first and second merging valves 50 and 74 are closed. The oil discharged from the three pumps 12 and 32 is passed through passages 54 and 78 to the arm switching valve 28.
It becomes possible to supply

Next, the switching valve 16.26 for both speeding and the switching valve 18 for both working.
．． 28, the entire amount of oil discharged from the first and second pumps 12, 22 is preferentially supplied to the dual-speed switching valves 16 and 26, respectively.

On the other hand, at this time, the switching signal is applied to the merging valve 74 in the same direction via the pilot lines 60 and 72, and the merging valve 50 closes. is applied in the opposite direction via the pilot lines 60, 72 to maintain the open condition, so that the discharge oil from the third pump 32 is directed to the passage 7.
8 to the center bypass passage 14.14' of the first control valve group 10 and further via the passage 54 to the center bypass passage 24.
24' and drains into a tank. That is,
The switching valve 18° 28 for both operations can receive the supply of oil discharged from the third pump 32.

In addition, several cases different from the above-mentioned case can be assumed, but in any case, when the dual travel switching valve is operated, the first and second switching valves are connected to the dual travel switching valve. It is easily understood that the oil discharged from each pump is supplied in its entirety and preferentially. That is, according to the hydraulic circuit of the present invention, even if the traveling system is operated in combination with any work system, the traveling system can be driven independently from all the working systems and with the highest priority. That is, a hydraulic circuit for a hydraulic excavator with excellent running performance and stable performance is provided.

In the above embodiment, the switching signals of the respective merging valves of the first and second control valve groups are set to the second and first control valve groups, respectively.
The same operation can be obtained by configuring the control valve group with the maximum operation signals of the travel and arm switching valves and the travel and boom switching valves, but this can be easily understood from the above embodiment. Since it is analogous, the explanation will be omitted.

FIG. 2 shows another embodiment of a hydraulic circuit for a hydraulic excavator according to the present invention. In this embodiment, a fourth control valve group is further connected to the third pump in the embodiment shown in FIG.

That is, in FIG. 2, the fourth control valve group 80
is connected to the third pump 32 via a pressure oil supply line 82. This fourth control valve group 80 has three switching valves 84, 86, 88, which connect the center bypass passage 90 through passages 92, 94, respectively.
A passage 66 communicating with the downstream center bypass passage 14 of the traveling switching valve 16 of the first control valve group, and a passage 54 communicating with the downstream center bypass passage 24 of the traveling switching valve 26 of the second control valve group 20. It is connected to the.

The pilot lines 96.98° 100 of the three switching valves 84° 86.88 are connected to the operating signals for the running switching valves 16° 26 of the first and second control valve groups 10.20, respectively. 1 control valve group 10 working switching valve 18. ... - operation signal, second control valve group 20
0 work switching valve 28. . . . are configured to apply operation signals.

In such a configuration, when all the switching valves of the first and second control valve groups 10.20 are not operated, the discharge oil of the third pump 32 is transferred to the third and fourth control valve groups 30. .80 switching valves in parallel. However, at this time, for example, the first control valve group 10
When the running switching valve 16, the working switching valve 18, and the running switching valve 26 of the second control valve group 20 are operated, the switching valves 84 and 86 are connected to the pilot line 96° and 98°, respectively.
The discharge oil of the third pump 32 is further supplied to the center bypass passage 14 of the first control valve group 10 via the passage 92.66. . Therefore, in this case, the discharge oil of the first and second pumps 12.22 is supplied to both traveling direction switching valves 16.26, respectively, and the working direction switching valve 18.
The discharge oil of the third pump 32 is supplied to the switching valves of the third and fourth control valve groups in parallel.

That is, in the hydraulic circuit of this embodiment as well, the above-mentioned first
Essentially the same operation is achieved as in the hydraulic circuit of the embodiment shown in the figures.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments, and many design changes can be made without departing from the spirit thereof.

〔Effect of the invention〕

As explained above, the hydraulic circuit of the hydraulic excavator according to the present invention includes the first and second control valve groups including the travel switching valve and the work switching valve, and the third control valve group including the soil removal plate switching valve.
In a hydraulic circuit consisting of a control valve group, the first and second control valve groups switch the traveling switching valve to the first control valve group.
The control valve group is arranged at a priority position, and the two control valve groups are configured to be interlocked in a predetermined manner according to the switching of the traveling switching valve. Since the structure is configured such that the drive system is connected to the first and second control valve groups, even if the drive system is operated in combination with all work systems including the earth removal system at the same time, the drive system remains independent from any work system. Therefore, each pump can always be driven with the highest priority. In other words, it is possible to reliably eliminate the instability of the traveling system and the decrease in traveling speed that occurred in the conventional hydraulic circuit of this type when the working system and the traveling system were combined at a distance of 4 degrees beyond the earth removal system. .

In addition, in the hydraulic circuit of the present invention, it is possible to further connect a fourth control valve group to the third pump, but in this case, the fourth control valve group is connected to the first control valve group. and/or the discharge oil of the third pump can be configured to be supplied to the first or second control valve group respectively in response to switching of the switching valve of the second control valve group; However, the operation of the hydraulic circuit remains basically unchanged from the operation of the hydraulic circuit described above.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram illustrating one embodiment of the hydraulic circuit for a hydraulic excavator according to the present invention, and FIG. 2 is a hydraulic circuit diagram illustrating another embodiment of the hydraulic circuit for a hydraulic excavator according to the present invention.
FIG. 3 is a hydraulic circuit diagram illustrating a hydraulic circuit of a conventional hydraulic excavator. 10...First control valve group 12...First pump 14.14'...Center bypass passage 16...Right travel switching valve 18...Boom switching valve 20...No. 2 control valve group 22...Second pump 24, 24'...Center bypass passage 26...Left travel switching valve 28...Arm switching valve 30...Third control valve group 32... Third pump 34... Center bypass passage 36... Soil discharge plate switching valve 50... Merging valve 52... Check valve 54...
... Passage 56 ... Pressure reducing valve 58 ... Selector valve 60 ... Pilot line 62 ... Merging valve 64 ... Check valve 66 ...
- Passage 68...Reducing valve 70...Selector valve 72...Pilot line 74...Merge valve 76...Check valve 78
...Passage 80...Third control valve group 82...Pressure oil supply line 84.86.88...Switching valve 90...Center bypass passage 92.94...Passage

Claims (4)

[Claims] (1) The first valve is equipped with multiple switching valves including one running switching valve.
a first control valve group connected to the pump, a second control valve group including a multiple switching valve including the other travel switching valve and connected to the second pump, and a soil removal plate switching valve. and a third control valve group connected to the third pump, the first and second control valve groups having their respective travel switching valves in the first priority position. and are connected in tandem to the downstream switching valve, and each center bypass passage is provided with a merging valve that closes the center bypass passage in response to switching of the travel switching valve of the other control valve group. Further, a passage is provided which connects the upstream center bypass passage of each of the merging valves to the downstream center bypass passage of the traveling switching valve of the other control valve group via a check valve, while the third control valve The group is provided with a merging valve in the center bypass passage that closes the center bypass passage in response to switching of at least one of the traveling switching valves, and a merging valve that closes the center bypass passage on the upstream side of the merging valve. A hydraulic circuit for a hydraulic excavator, comprising a passage connected to a center bypass passage on the downstream side of a travel switching valve via a check valve. (2) A fourth control valve group including multiple switching valves is connected to the pressure oil supply line of the third pump;
In the control valve group, when the traveling switching valve of the first and/or second control valve group and the switching valve other than the traveling switching valve of the first control valve group are simultaneously switched, the pressure oil of the third pump is The supply line is connected to the central bypass passage downstream of the running switching valves of the first control valve group, while the running switching valves of the first and/or second control valve group and the running switching valves of the second control valve group 2. The pressure oil supply line of the third pump is configured to be connected to the center bypass passage on the downstream side of the traveling switching valve of the second control valve group when switching simultaneously with a switching valve other than the operating switching valve. Hydraulic excavator hydraulic circuit. (3) The switching signal of each merging valve of the first and second control valve groups is the secondary of the pressure reducing valve provided in the pressure oil supply line to each travel switching valve of the second and first control valve groups, respectively. 3. The hydraulic circuit for a hydraulic excavator according to claim 1, wherein the output is an output obtained when pressure is further passed through each selector valve connected to each travel switching valve. (4) The first control valve group includes a boom switching valve in addition to one traveling switching valve, the second control valve group includes an arm switching valve in addition to the other traveling switching valve, and the second control valve group includes an arm switching valve in addition to the other traveling switching valve. 2. The switching signal of each merging valve of the first and second control valve groups is the maximum operation signal of each of the travel and arm switching valves and travel and boom switching valves of the second and first control valve groups, respectively. The hydraulic circuit of the hydraulic excavator according to 1 or 2.