JPH0228001B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention provides, for example, a power shovel,
The present invention relates to a hydraulic circuit having multiple circuit systems.

(Conventional Hydraulic Circuit) The conventional hydraulic circuit shown in FIG. 1 includes two circuit systems a and b, and a first pump 1 and a second pump that supply pressure oil to each circuit system a and b.
It is equipped with pump 2.

The circuit systems a and b are provided with a plurality of control valves 3 to 5 and 6 to 8, and each of these control valves is normally open center.

Each of the control valves, which are normally open centers as described above, is connected via tandem passages 9 and 10, and parallel passages 11 and 12.
It is also connected in parallel via.

Each of the control valves connected in this way creates a tandem passage 9, 1 for the downstream control valve when the upstream control valve is switched.
0 is closed. At this time, the control valve on the downstream side communicates with each pump 1, 2 via parallel passages 11, 12.

For example, in a hydraulic circuit of a power shovel, when operating an arm cylinder, the oil discharged from pumps 1 and 2 of both circuit systems a and b are combined to increase the operating speed of the arm cylinder.

In order to merge the oil discharged from both pumps 1 and 2 as described above, this conventional hydraulic circuit is configured as follows.

That is, the detection valve 14 is provided in the relay flow path 13 connected further downstream of the most downstream control valve 5 of one circuit system a, and the relay flow path 1 between the control valve 5 and the detection valve 14 is provided.
3 is connected to a carryover passage 15.

The detection valve 14 is provided with a poppet 16, which normally blocks communication between the relay flow path 13 and the tank flow path 17.
An orifice 18 is formed in the poppet 16, and a pilot passage 19 connected to the downstream side of the orifice 18 is connected to the sub-valve 20.

The sub-valve 20 is arranged to operate in conjunction with the most downstream control valve 8 of the other circuit system b. That is, this sub-valve 20 is in a relationship such that when the control valve 8 is at the neutral position shown, the sub-valve 20 is also held at the neutral position.

When the sub-valve 20 is in the neutral position, the pilot passage 19 is communicated with the tank 21, and when the control valve 8 is switched to either the left or right side, the sub-valve 20 is also switched, and the pilot passage 19 and the tank 21 are communicated with each other. I am trying to cut off communication between the two.

Further, the carryover passage 15 is connected to an import 22 of the control valve 8 which communicates with the parallel passage 12.

Note that reference numerals 23 and 24 in the figure are check valves for preventing backflow from the control valve 8.

Therefore, if each control valve of one circuit system a is held at the neutral position, and the most downstream control valve 8 of the other circuit system b is also held at the neutral position, the oil from the first pump 1 will flow in tandem. The detection valve 14 is reached through the passage 9 and the relay flow path 13.

At this time, since the sub-valve 20 is also held at the neutral position as described above, the pilot flow path 19 is in communication with the tank 21. Therefore, a flow of oil is generated in the orifice 18, and the orifice 1
A differential pressure occurs around 8. Due to this difference, the poppet 16 of the detection valve 14 opens, and the entire amount of oil discharged from the first pump 1 passes through the tank flow path 17 to the tank 25.
Return to In other words, as long as the most downstream control valve 8 in the other circuit system b is held at the neutral position, the oil in the first pump 1 will not be carried over to the other circuit system b.

On the other hand, when the most downstream control valve 8 of the other circuit system b is switched from the illustrated neutral position to either the left or right side, the sub-valve 20 is also switched, and communication between the pilot flow path 19 and the tank 21 is cut off.

For this purpose, the poppet 16 of the detection valve 14 remains closed. Since the poppet 16 is closed, the oil of the first pump 1 that has reached the relay passage 13 passes through the carryover passage 15 and reaches the import 22 of the other circuit system b, and the oil of the first pump 1 that has reached the relay passage 13 reaches the import 22 of the other circuit system b.
It merges with the discharged oil.

The conventional hydraulic circuit as described above has the disadvantage that the sub-valve 20 must be provided.
In other words, this sub-valve complicates the piping, etc., which not only increases the pressure loss within the circuit but also increases the size of the device.

(Objective of the present invention) The present invention does not require sub-valves like the conventional hydraulic circuit, and aims to simplify the circuit and device.

(Embodiment of the invention) In the first embodiment shown in FIG. 2, the import 2 of the most downstream control valve 8 of the other circuit system b
The carryover passage 15 is directly connected to the pilot passage 1 to omit the sub-valve, and the pilot passage 1
9 is a tandem passage 10 between control valves 7 and 8.
The other points are the same as those of the prior art.

With the control valves of both circuit systems a and b held in the neutral position as shown, the tandem passage 10 of the other circuit system b communicates with the tank 27 through the tank passage 26.

Therefore, since the pilot flow path 19 also communicates with the tank 27, the oil from the first pump 1 passes through the orifice 18 of the detection valve 14 and reaches the tank 27, generating a pressure difference across the orifice 18. .

As mentioned above, when a pressure difference occurs before and after the orifice 18, the poppet 16 opens and the first pump 1
The entire amount of oil discharged from tank 2 is transferred from tank passage 17 to tank 2.
Return to 5.

Furthermore, if each control valve of one circuit system a is held in the neutral position and only the most downstream control valve 8 of the other circuit system b is switched to the left or right, the tandem passage 10 of the other circuit system and the tank Communication with 27 is cut off.

In this state, no flow is generated before or after the orifice, and therefore the poppet 16 of the detection valve 14 does not open. If poppet 16 does not open,
The total amount of oil discharged from the first pump 1 is the carryover passage 1
5 into the import 22. That is, the oil discharged from the first pump 1 joins the oil discharged from the second pump 2 and flows into the control valve 8.

The second embodiment shown in FIG. 3 is basically the same as the first embodiment, but negative control mechanisms 28 and 29 are provided at the most upstream positions of tank passages 17 and 25 connected to the detection valve 14. This is different from the first embodiment in that it is provided.

That is, the negative control mechanisms 28, 29
are the detection orifices 30, 31 and the relief valve 3.
2 and 33, and further upstream of the detection orifices 30 and 31 is a pump control command pressure passage 3.
4 and 35 are connected to each other, and their command pressure passages 34 and 35 are connected to the first and second pumps 1 and 2.

Therefore, when all the control valves are in the neutral position shown in the figure and the entire amount of oil discharged from the pump is returning from the tank passages 17 and 26 to the tanks 25 and 27, a pressure difference is generated before and after the detection orifices 30 and 31. , the pressure is pump control command pressure passage 3
It acts on both pumps 1 and 2 through ports 4 and 35, adjusts the tilt angle of the pumps, and reduces the discharge amount.

In other words, in this second embodiment, when the actuator connected to each control valve is under no load, the discharge amount of both pumps is reduced to minimize energy loss.

In each of the above embodiments, the carryover passage 15 is connected to the import 22 of the most upstream control valve 8 of the other circuit system b, but this carryover passage 15 is connected to the import 22 of the control valve 8 of the other circuit system b. may be connected to. In other words, the other circuit system b that controls the actuator that needs to merge the discharge oil of the first pump 1
The above carryover passage can be connected to the import of the control valve.

(Structure of the present invention) The present invention includes one circuit system connected to a first pump and the other circuit system connected to a second pump, and each circuit system has a normally open circuit system that controls a predetermined actuator. A plurality of control valves are provided, and each control valve in each circuit system is connected in tandem through a tandem passage when they are in a neutral position,
When the upstream control valve is switched from the normal position, the control valve located downstream of the switched control valve is configured to communicate with the pump via a parallel passage, while the one circuit system A relay flow path is connected further downstream of the most downstream control valve, a detection valve is provided between the relay flow path and the tank flow path, and the relay flow path between the detection valve and the most downstream control valve is connected to the relay flow path. The carry-over passage is connected to the input of the required control valve of the other circuit system, and the poppet of this detection valve is activated only when oil flow occurs in the orifice provided in the detection valve. In a hydraulic circuit configured such that when the poppet is opened, oil from the first pump is returned to the tank, and when the poppet is closed, oil from the first pump flows into the carry-over passage, the other circuit system is connected to the carry-over passage. A pilot passage leading to the orifice of the detection valve is connected to the tandem passage of the connected required control valve.

Therefore, there is no need for a conventional sub-valve.

Since no sub-valve is required, the circuit is simplified, pressure loss is reduced accordingly, and the device can be made more compact.

In addition, since the pilot flow path of the detection valve provided in one circuit system was connected to the tandem passage connected to the required control valve of the other circuit system, a pilot flow path was specially provided for this required control valve. There's no need. Since no special pilot flow path is required in this way, pressure loss is further reduced and the control valve does not need to be specially designed. Since the control valve does not have to be specially designed, costs can be reduced accordingly.

[Brief explanation of drawings]

FIG. 1 is a conventional circuit diagram, and FIGS. 2 and 3 are circuit diagrams of first and second embodiments of the present invention. 1...First pump, 2...Second pump, 3-8
...Control, 9,10...Tandem passage,
11, 12... Parallel passage, 13... Relay flow path, 14... Detection valve, 15... Carry over passage, 16... Poppet, 17, 26... Tank passage, 18... Orifice, 19... Pilot flow Road.

Claims (1)

[Claims] 1 One circuit system connected to the first pump and the other circuit system connected to the second pump, each circuit system is provided with a plurality of normally open control valves that control a predetermined actuator, and each Each control valve in the circuit is connected in tandem through tandem passages when they are in the neutral position, and when the upstream control valve is switched from the normal position, the downstream control valve is While the control valve located on the side communicates with the pump via a parallel passage, a relay passage is connected to the further downstream side of the most downstream control valve of one of the circuit systems, and this relay passage and the tank are connected. A detection valve is provided between the flow paths, a carryover path is connected to the relay flow path between the detection valve and the most downstream control valve, and the carryover path is connected to the import of the required control valve of the other circuit system. At the same time, the poppet of this detection valve opens only when oil flow occurs in the orifice provided in the detection valve.
In a hydraulic circuit configured to return oil from a pump to a tank, and in a state where the poppet is closed, oil from the first pump flows into the carry-over passage,
A hydraulic circuit comprising a plurality of circuit systems in which a pilot flow path leading to the orifice of a detection valve is connected to a tandem passage of a desired control valve which is the other circuit system and is connected to the carryover passage.