JPH0118305Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to a hydraulic circuit for a hydraulic breaker used by being attached to a hydraulic excavator.

Conventional technology Hydraulic excavators currently have actuators divided into two groups in order to increase operating efficiency.
A system in which each hydraulic pump is driven separately is often adopted. When installing a hydraulic breaker on such a hydraulic excavator, one group of distribution valves should have switching valves for boom, travel, bucket, and breaker, and the other group should have switching valves for arm, travel, boom, and swing. The breaker and arm are supplied with pressure oil from separate hydraulic pumps, so that the arm can be used freely even when the breaker is in use. This means that, for example, even if the arm is actuated during breaker work, both actuators are supplied with pressure oil from completely separate hydraulic pumps, so they will be able to maximize their performance regardless of the operating status of the other actuator. can.

Problems to be solved by the invention The above method is very convenient because it can operate the breaker and arm at the same time, but it is possible for one to operate ignoring the ability of the other. This creates an unreasonable condition for the aircraft. That is, for example, while performing a striking action with the breaker, the arm can be actuated to tilt the breaker and cause the chisel to become stiff. In this case, since the arm can be operated with a strong force regardless of the operation of the breaker, an unreasonable force is applied to the chisel, which may cause breakage or breakage due to seizing of the shank. This breakage of the chisel is caused by the bending moment that is applied to the chisel during operation.

The purpose of this invention is to solve the above-mentioned problems and to provide a device that does not cause problems such as breakage of the chisel or seizure of the shank even if forced operation is performed.

Means for Solving the Problem The means of this invention taken to solve the above problem are as follows: (a) The actuator of the hydraulic excavator is divided into two groups, each of which is operated by a separate hydraulic pump.

(b) The arm cylinder and breaker should be placed in separate groups and operated by separate hydraulic pumps.

C. A branch circuit is provided from the oil passage leading to the head side oil chamber of the arm cylinder to the tank, and a pilot switching valve is installed in this circuit, and an overload relief valve set at a pressure lower than the normal arm cylinder operating pressure is installed downstream of the pilot switching valve. What I did.

(2) A pilot circuit is provided from the breaker operating circuit to the pilot switching valve, and a throttle valve and a check valve are provided in the circuit.

(e) A branch circuit is provided from the pilot circuit to the third hydraulic pump circuit, and a check valve is provided in the circuit.

It is.

Operation During striking work with the breaker, the breaker operating pressure oil acts as pilot pressure on the pilot switching valve, and the oil passage leading to the head side oil chamber of the arm cylinder is communicated with the tank via the overload relief valve. Since a large force is not generated even when the arm cylinder is operated, lubrication is maintained between the shank and the bush, preventing seizure from occurring in this area. Furthermore, since compressive stress due to impact and bending stress due to the arm cylinder are not applied at the same time, there is no disadvantage in terms of strength. In addition, unless the engine is stopped, the check valve provided in the branch circuit from the pilot circuit to the third hydraulic pump circuit will not open, so the pilot switching valve will maintain the above state and operate the arm cylinder after the impact is completed. Even if a breaker is used instead of a ripper, the force of the arm cylinder is weak, so the chisel may break or
The degree of wear of the chisel bushing due to being hit is small, and there is no problem of reducing the strength of the chisel.

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

Reference numeral 1 designates a first hydraulic pump; an oil passage 3 communicates from the hydraulic pump 1 to a first distribution valve 2; and a return oil passage 4 communicates from the distribution valve 2 to a tank 5. 6 is the second
In the hydraulic pump, an oil passage 8 communicates with the second distribution valve 7, and an oil passage 9 returns from the distribution valve 7 to the tank 5. Reference numeral 10 denotes an arm cylinder of a hydraulic excavator, in which an oil passage 12 runs from the arm cylinder switching valve 11 of the first distribution valve 2 to a head side oil chamber 13, and an oil passage 14 connects to a rod side oil chamber. Each leads to 15. Reference numeral 16 denotes a hydraulic breaker, to which an oil passage 18 communicates from the breaker switching valve 17 of the second distribution valve 7, and an oil passage 19 which returns from the breaker 16 to the tank 5. 20 is a pilot switching valve, and 21 is an overload relief valve. These valves 20 and 21 are provided in an oil passage 22 that branches from the oil passage 12 and leads to the tank 5. Pilot switching valve 2
0 is for opening the oil passage 22 only when the breaker is activated, and a pilot oil passage 23 is connected from the oil passage 18, and a pilot oil passage 23 is connected to the valve 20 so that the pulsation when the breaker is activated does not affect the valve 20. A throttle valve 24 to prevent backflow and a check valve 25 to prevent backflow are provided. The overload relief valve 21 is used to limit the operating pressure of the arm cylinder 10 to 50 to 60% of the normal pressure when the breaker is activated.
It is installed on the downstream side of the Reference numeral 26 denotes a hydraulic pump for operating the breaker 16, and 27 is an oil passage on its discharge side.A branch oil passage 28 is connected to the oil passage from the pilot oil passage 23, and a check valve 2 is connected to the oil passage 28.
9 is provided, and even if the breaker operation is stopped while the engine is rotating, that is, while the hydraulic pumps 1 and 6 are operating, the pilot pressure will be released through the check valve 29 and the pilot switching valve 20 will switch. I'm trying not to get angry. Note that 30 is a relief valve.

The present invention is constructed as described above, but to explain the case in which it actually operates, the hydraulic breaker 1
6, operate the switching valve 17 to send pressure oil from the second hydraulic pump 6 to the breaker 16 through the oil passages 8 and 18 to perform the striking work, and also operate the switching valve 11 for arm operation. Operate breaker 16
However, when pressure oil flows into the oil passage 18 and the breaker 16 is activated, it passes through the throttle valve 24, the check valve 25, and the oil passage 23 to the pilot switching valve 2.
Since pilot pressure acts on the valve 20 and the valve 20 is switched to the right side, the oil passage 22 is opened, and the oil passage 12 passes through the oil passage 22 to close the overload relief valve 21.
It communicates with the head side oil chamber 13 of the arm cylinder 10.
The hydraulic pressure is limited by the set pressure of the overload relief valve 21. The set pressure of the valve 21 is set in advance to the normal working pressure of the arm cylinder 10.
Since the oil pressure is set to 50 to 60%, when operating the arm cylinder 10, the operating force is 50 to 60% of the operating force when not operating the breaker 16, that is, when performing normal excavation work. This means that only the power will come out. Therefore, for example, even if an attempt is made to knead the object to be struck with the chisel at the tip of the breaker 16 while performing a striking operation, the chisel will not break because the force is weak, and the chisel will not break. Even if the arm cylinder 10 is forcibly pressed against the object to be struck, the force applied to the shank portion of the chisel is weak, and no oil runs out or seizure occurs.

During breaker work, the breaker switching valve 17
Even if the operation of the breaker 16 is temporarily stopped by operating the breaker 16, as long as the engine is operating and the oil pressure in the oil passage 28 leading to the hydraulic pump 26 is maintained above a certain value, the pilot pressure in the pilot oil passage 23 will remain the same. Since the pilot switching valve 20 maintains the state in which it is switched to the right without lowering the pressure, the arm cylinder 10 can perform 100% of its capacity by simply stopping the operation of the breaker 16 in a series of breaker operations. There isn't. This means that during breaker work, by limiting the capacity of the arm cylinder 10 regardless of the operation of the breaker 16, it limits ripping work with a chisel accompanying breaker work, and This will help prevent damage caused by excessive force.

When used as a hydraulic excavator, the operating pressure of the breaker is not applied, so the switching valve does not switch, and the arm cylinder 10 can exert 100% of its capacity without any restrictions.

Effects of the invention As mentioned above, this invention provides a pilot switching valve and an overload relief valve in the branch oil passage leading from the oil passage leading to the head side oil chamber of the arm cylinder of the hydraulic excavator to the tank, and The pilot oil path is guided from the breaker operating oil path so that when the breaker is activated, the arm cylinder is limited to the set pressure of the overload relief valve, so even if the arm cylinder is operated while the breaker is activated, the arm cylinder will not be affected. Since no large force is exerted, lubrication between the shank and the bushing is maintained.
Seizing will not occur in this area. Further, since the compressive stress caused by the impact and the excessive bending stress caused by the arm cylinder are not applied at the same time, there is no disadvantage in terms of strength. In addition, even if the arm cylinder is activated after the striking is completed and the breaker is used as a ripper, the force of the arm cylinder is weak, so there is less chance of the chisel breaking or the chisel bushings being hit and worn out, which increases the strength of the chisel. No problems will occur that will damage the product.

[Brief explanation of drawings]

FIG. 1 is a hydraulic circuit diagram of an embodiment of the present invention, and FIG. 2 is a conventional hydraulic circuit diagram. 1...First hydraulic pump, 2...First distribution valve, 5
... Tank, 6 ... Second hydraulic pump, 7 ... Second
Distribution valve, 10... Arm cylinder, 12... Oil passage, 13... Head side oil chamber, 20... Pilot switching valve, 21... Overload relief valve, 2
2...Oil passage, 23...Pilot oil passage, 24...
Throttle valve, 25...Check valve.

Claims (1)

[Scope of utility model registration request] In an actuating device in which the actuators of a hydraulic excavator are divided into two groups, each operated by pressure oil from a separate hydraulic pump, and the hydraulic breakers are arranged in one group and the arm cylinders in the other group, the arm A branch oil passage is provided from the oil passage leading to the head side oil chamber of the cylinder to the tank, and a pilot switching valve that opens the internal oil passage when pilot pressure acts on the branch oil passage, and an overload relief valve on the downstream side of the pilot switching valve. In addition to providing
A pilot oil passage is connected from the breaker operating oil passage to the pilot switching valve via a throttle valve and a check valve, and a third valve serving as an operating hydraulic pressure source is connected to the intermediate point of the pilot oil passage between the pilot valve and the check valve.
A device for preventing breakage of a chisel of a breaker, comprising a branch circuit that communicates with a discharge circuit of a pump, and a check valve that allows flow only from a pilot switching valve to a discharge circuit of a third pump.