JPH0672437B2 - Hydraulic circuit of hydraulic shovel - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a hydraulic circuit when used at high pressure to increase the working capacity of a hydraulic excavator.

2. Description of the Related Art A hydraulic excavator is usually used for excavation work, but in some cases, it has a strong work capacity, and therefore it is sometimes used as a crane for lifting objects. As a method thereof, for example, a wire rope is hooked on a hook fixed to a bucket, and a crane work for hoisting steel pipes and other structures is performed.At that time, in order to enhance hoisting ability, a boom cylinder related to hoisting work, and A method of increasing the operating pressure of the arm cylinder is used. In other words, during such crane work, the switch provided near the operating lever of the work equipment is operated to operate the solenoid valve, enabling pilot operation provided in the main circuit and the port circuits of the boom cylinder and arm cylinder. The solenoid valve provided in the pilot circuit of such a variable relief valve is operated to change the set pressure of the variable relief valve.

FIG. 7 is a hydraulic circuit diagram showing an outline of what has been done conventionally, 50 is a hydraulic pump, 51 is a main oil passage,
A variable relief valve 52 is provided in the oil passage 51, a pilot oil passage 55 communicates with a pilot portion 53 from a solenoid valve 54, and the solenoid valve 54 is operated by a switch 56 provided in an operating lever 68. . Reference numeral 57 denotes a port oil passage communicating with the head side of the boom silling 58. The oil passage 57 is provided with a variable relief valve 59, and a pilot portion 60 thereof is connected to a pilot oil passage 61 from a solenoid valve 54. Similarly, 62 is a port oil passage communicating with the rod side of the arm cylinder 63, a variable relief valve 64 is provided in the oil passage 62, and a pilot oil passage 66 communicates with a pilot portion 65 thereof. If it is necessary to increase the lifting capacity during crane work, press the switch 56 on the operating lever 68 to switch the solenoid valve 54, and the pilot oil from the pilot pump 67 passes through the solenoid valve 54 and the relief valves 52, 59. , 64 pilot divisions
Since the pressure reaches 53, 60, and 65 and the set pressure of these relief valves is increased, the operating pressure of the boom cylinder 58 and the arm cylinder 63 is increased, and the operating capacity of the crane can be increased.

Problems to be Solved by the Invention The above method is very useful because it increases the operating capacity of some actuators of a hydraulic excavator and improves work efficiency. However, in order to raise the set pressure of the variable relief valve 52 provided in the main oil passage 51, it is only necessary to raise the pressure of some actuators, but the overall system pressure rises. And the structure was adversely affected, and the durability of the product was significantly reduced or damaged. In addition, if this method for increasing the working capacity is used for other purposes, for example, what was originally installed to increase the lifting capacity in crane work is also used for normal excavation work. If such a problem occurs, it will adversely affect the hydraulic equipment and structures for some actuators such as bucket cylinders and traveling motors that are not directly related to this, causing problems such as their durability being reduced or damage being caused. .

The present invention aims to solve the above problems.

Means for Solving the Problems The means of the present invention taken to solve the above problems are a. A hydraulic circuit that connects the variable displacement hydraulic pump to the actuator via the switching valve is formed, and a variable relief valve is provided in the discharge side oil passage of the hydraulic pump and the inflow oil passage of some actuators. A solenoid valve is provided in an oil passage communicating with the relief valve so that the set pressure of the relief valve can be changed by operating the solenoid valve.

B. The pilot oil passage is passed from the solenoid valve to the regulator for controlling the discharge amount of the variable displacement hydraulic pump.

C. A solenoid valve is provided in a pilot oil passage communicating with the regulator for controlling the discharge amount of the variable displacement hydraulic pump, and the solenoid valve is linked with the solenoid valve for operating the variable relief valve.

D. A solenoid valve is provided in a pilot oil passage that operates a switching valve that communicates with an actuator other than the actuator that changes the relief pressure, and the solenoid valve is interlocked with the solenoid valve that operates the variable relief valve.

E. A pilot switching valve is provided in a pilot oil passage for operating the switching valve, and the pilot oil passage of the pilot switching valve is communicated with the pilot oil passage of the variable relief valve.

Is.

The regulator of the variable displacement hydraulic pump is provided with a shuttle valve in the pilot oil passage when the hydraulic pump is in the negative control mode, and the shuttle valve is passed through the pilot oil passage that controls the relief valve. A solenoid valve or pilot switching valve is installed in the oil passage to enable control in conjunction with the control of the relief valve, and on the other hand, in the pilot circuit of the switching valve that controls actuators other than those that increase capacity. Is a pilot switching valve that operates with pilot pressure that controls the relief valve, or a solenoid valve that operates simultaneously with the solenoid valve that opens and closes the pilot oil passage.
Since it was made possible to stop the operation of the actuator other than for the purpose of increasing the capacity, when increasing the set pressure of the relief valve to increase the capacity of the actuator,
Since the discharge rate of the hydraulic pump can be reduced and the operating speed of the actuator can be slowed down, the surge pressure at start and stop will be low, which will have a bad effect on damage to hydraulic equipment and shortened durability. Will not be.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a hydraulic circuit diagram of an embodiment of the present invention, and FIG. 2 is a hydraulic circuit diagram of a main part thereof. In FIG. 1, 1 and 2 are variable displacement hydraulic pumps. 4, 5, 6
Are all switching valves to which pressure oil is supplied from the hydraulic pump 1. The switching valve 5 is a switching valve for operating the boom cylinder 7,
The switching valve 6, which communicates with the oil passages 8 and 9 from the switching valve 5 to the boom cylinder 7, is a switching valve for operating a bucket cylinder.
Oil passages 11 and 12 communicate from the switching valve 6 to the bucket cylinder 10. Reference numerals 13, 14, 15, and 16 are switching valves to which pressure oil is supplied from the hydraulic pump 2. The switching valve 16 is a switching valve for operating the arm cylinder 17, and the valve 16
Oil passages 18 and 19 lead to. 20, 21, 22, and 23 are variable relief valves, the variable relief valve 20 is provided in an oil passage 18 communicating with the rod-side oil chamber of the arm cylinder 17, and the variable relief valve 21 is a head-side oil valve of the boom cylinder 7. The variable relief valve 22 is provided in the main oil passage 24 of the hydraulic pump 1, and the variable relief valve 23 is provided in the main oil passage 25 of the hydraulic pump 2. 26 is a pilot pump and 27 is a solenoid valve.
From the pilot hydraulic pump 26 to each variable relief valve 20, 2
It is for switching pilot oil to be supplied to 1, 22, 23, and is configured to be operated by a switch 29 provided on an operating lever 28. The pilot oil passage 30 extends from the solenoid valve 27 to a variable relief valve 20 In the pilot section 31 of
Pilot oil passage 32 is variable Pilot part 33 of relief valve 21
Further, the pilot oil passage 34 communicates with the pilot portion 35 of the variable relief valve 22, and the pilot oil passage 36 communicates with the pilot portion 37 of the variable relief valve 23. Therefore, when the switch 29 is pressed, the solenoid valve 27 is opened and the pilot oil from the pump 26 is fed to the pilot parts 31, 33, 35,
37, and increase the set pressure of each relief valve 20, 21, 22, 23. Reference numeral 38 is a regulator of the variable displacement hydraulic pump 1, 39 is a regulator of the variable displacement hydraulic pump 2, and a neutral return oil passage 40 from the switching valve 6 communicates with the regulator 38. A shuttle valve 41 is provided in the oil passage 40, and the pilot oil passage 42 from the solenoid valve 27 is passed through the shuttle valve 41 so that the discharge amount of the hydraulic pump 1 can be controlled by operating the solenoid valve 27. ing. Similarly, a neutral return oil passage 43 from the switching valve 16 communicates with the regulator 39, and the shuttle valve 44 is provided in the oil passage 43.
A pilot oil passage 45 is passed from the solenoid valve 27 to the shuttle valve 44, and the discharge amount of the hydraulic pump 2 can be controlled by operating the solenoid valve 27.

A solenoid valve 46 is for operating the switching valve 6 because the switching valve 6 is a pilot switching valve. Pilot oil passages 47 and 48 communicate with the switching valve 6. The solenoid valve
Similarly to the solenoid valve 27, 46 is also operated by the switch 29 of the operating lever 28, and when the switch 29 is ON, both the oil passages 47 and 48 communicate with the tank 49, the switching valve 6 returns to neutral, and the bucket. Cylinder 10 does not operate. Incidentally, 83 is a relief valve of a normal type, and 84 is a throttle.

The present invention is configured as described above, and when performing a normal excavation work as a hydraulic excavator, the switching valves 5, 6, 16 and the like are operated so that the pressure oil of the hydraulic pumps 1, 2 is transferred to the arm cylinder 17,
The boom cylinder 7 and the bucket cylinder 10 are sent to operate these hydraulic cylinders for excavation work. In this case, of course, the switch 29 is not operated, so the switch 29
The solenoid valves 27, 46 communicating with the solenoid valve 27 are both in a neutral state, the pump circuit communicating with the solenoid valve 27 is cut off, and the pilot portions 31, 33, 3 communicating with the solenoid valve 27 are shut off.
Neither 5 or 37 has a supply of pilot oil, so these relief valves 20, 21, 22 and 23 act as normal set pressure relief valves. In addition, the shuttle valves 41, 44
However, since there is no inflow of oil from the oil passages 42 and 45 that communicate with them, these shuttle valves 41 and 44 flow only the oil from the oil passages 40 and 42 from the pumps 1 and 2, and therefore the regulator. 38 and 39 operate under normal conditions, hydraulic pump 1,
In No. 2, the discharge amount is not controlled by others.

Next, when using the hydraulic excavator for other purposes,
For example, when used as a clean object for lifting objects, the switch 29 of the operation lever 28 is turned on. Both solenoid valves 27 and 46 are switched. The solenoid valve 27 opens the pump circuit, and the solenoid valve 46 shuts off the oil passages 47 and 48. The pressure oil of the hydraulic pump 26 passes through the solenoid valve 27 and the oil passage 30 to the pilot portion 31, and also passes through the oil passage 32 to the pilot portion.
33, the pilot portion 35 through the oil passage 34, and the pilot portion through the oil passage 36, respectively, to increase the set pressure of the variable relief valves 20, 21, 22, 23. Therefore, the oil passage 8 provided with these relief valves 20, 21, 22, 23,
The actuators communicating with 18, 24 and 25, for example, the head side of the boom cylinder 7, the rod side of the arm cylinder 17, etc., have increased relief pressures, so that the operating force can be increased. When the hydraulic excavator is used as a crane, its lifting capacity can be increased.

Further, the solenoid valve 46 is switched by the operation of the switch 29, and the control switching valve 16 of the bucket cylinder 10 that communicates with the solenoid valve 46 via the oil passages 47 and 48 returns to neutral and shuts off the circuit. The supply of pressure oil to the cylinder 10 is cut off, and the bucket cylinder 10 cannot operate. This means that the relief valves 20, 21, 22, 23
If the bucket cylinder 10 that is not directly related to its purpose is used when the set pressure of is increased, it will adversely affect hydraulic equipment and structures related to the bucket cylinder, resulting in reduced durability or damage. This is in order to prevent such occurrence. Therefore, actuators other than the boom cylinder 7 and the arm cylinder 17 used as a crane cannot be used not only by providing the bucket cylinder 10 but also by a traveling motor (not shown) or the like, and prevent damage. Others can be prevented. The solenoid valve 46 for operating the switching valve 16 is operated by electric means by operating the switch 29, but it is not limited to this, and the pilot switching valve 70 is used as shown in FIG. , The pilot oil is the same as the oil passage from the solenoid valve 27 to the pilot part of each relief valve.
It is a communication from 71. Relief valves 20, 21, 22,
When the paroitte pressure acts on 23, the pilot pressure acts on the pilot switching valve 70 at the same time, and the circuit leading to the switching valve 16 is cut off, so that the bucket cylinder 10 cannot operate.

Although the above description is for the case where the regulators 38, 39 of the variable displacement hydraulic pumps 1, 2 are of negative control, the configuration is slightly different if this is of positive control. FIG. 4 is a hydraulic circuit diagram of the main part. Oil passage leading to regulators 74 and 75 of variable displacement hydraulic pumps 72 and 73
A solenoid valve 78 is provided on each of 76 and 77, and the solenoid valve 78 is operated by the switch 29. Switch 29 is off
When, the oil passages 76 and 77 are opened, and when ON, the regulator
Both 74 and 75 communicate with the tank 49. Also in this case, the solenoid valve 78 is controlled by an electric method, but it is not necessarily limited to this, and as shown in FIG. 5, a pilot switching valve 80 is used instead of the solenoid valve 78, and The pilot oil passage of the pilot switching valve 80 is passed through a solenoid valve 27 for changing the set pressure of the relief valve. The switch 29 is turned on, the solenoid valve 27 is switched, and the hydraulic pressure of the hydraulic pump 26 is changed to each relief valve 20, 21, 22, 23.
While the flow is flowing to, the pilot oil simultaneously flows into the pilot switching valve 80, so that the valve 80 is switched and the regulators 74 and 75 can pass their circuits to the tank 49, so that the hydraulic pump 72, The discharge rate of 73 decreases.

Since the present invention operates by pressing the switch 29, the driver must keep pressing the switch 29 during work. FIG. 6 is for avoiding this troublesomeness, in which a rotary switch 82 is provided between the switch 29 and the solenoid valve 27. By pressing the switch 29, the rotary switch 82 is turned on and the work can be performed.If the switch 29 is pressed next time, the rotary switch 82 is turned off, so the driver can operate the switch 29 continuously during the work. You don't have to worry about it.

As described above, according to the present invention, a pilot valve provided for controlling a relief valve is provided in the oil passage communicating with the control cylinder of the variable displacement hydraulic pump when the hydraulic pump is a negative control and a shuttle valve is provided. Pass the oil passage from the passage, install a solenoid valve or pilot switching valve for positive control,
A pilot valve that controls the relief valve is provided in the pilot circuit of the switching valve that controls the regulator corresponding to the solenoid valve that controls the pilot pressure of the relief valve. By setting a pilot switching valve that operates with pressure or a solenoid valve that operates simultaneously with the solenoid valve that opens and closes the pilot oil passage, it is possible to stop the operation of actuators other than for the purpose of increasing the capacity. When increasing the capacity of the actuator by increasing it, the discharge amount of the hydraulic pump can be decreased and the operating speed of the actuator can be slowed down, so the surge pressure at start and stop will be low and the hydraulic equipment will be damaged. Or the durability becomes short Bad influence say is eliminated. In addition, since actuators other than those that increase the capacity will not operate, if these actuators are used arbitrarily, unreasonable force above the design strength will act and hydraulic equipment and structures will be damaged, and durability will be reduced. There is no adverse effect such as reduction.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment of the present invention, FIG. 2 is a main part of FIG. 1, and a hydraulic circuit diagram showing an outline of the present invention.
FIG. 4, FIG. 5, FIG. 5 and FIG. 6 are hydraulic circuit diagrams of other embodiments of the present invention, and FIG. 7 is a hydraulic circuit diagram showing the outline of the conventional one. 1,2 …… Variable displacement hydraulic pump 5,6,16 …… Switching valve 7 …… Boom cylinder 10 …… Bucket cylinder 17 …… Arm cylinder 20,21,22,23 …… Variable relief valve 27,46… … Solenoid valve 31,33,35,37 …… Pilot section 38,39 …… Regulator

Claims (4)

[Claims] Claim: What is claimed is: 1. A discharge circuit of a hydraulic pump, comprising a variable displacement hydraulic pump having a discharge amount control regulator for increasing and decreasing a discharge amount in response to a signal acting on a receiving section, forming a hydraulic circuit communicating with an actuator via a switching valve. A variable relief valve having a function of increasing the relief pressure by a predetermined value from the originally set value when pilot pressure oil acts on the pilot portion is provided in the oil passage and the oil passage on the inflow side to the desired actuator. From the pilot valve to the pilot section of the relief valve, a solenoid valve that is switched by an external signal to supply the pressure oil of the pilot pump as pilot pressure oil to the pilot section of the variable relief valve is provided, and through an operating means. In the hydraulic circuit adapted to operate by supplying an external signal to the solenoid valve, the variable displacement hydraulic A means for reducing the discharge amount of the pump to a predetermined value when pilot pressure oil acts on the receiving portion of the regulator for controlling the discharge amount of the pump is provided, and the receiving portion is made to pass through the pilot oil passage through the solenoid valve. Hydraulic circuit of hydraulic excavator characterized by. 2. A discharge according to an external signal when switched to a pilot oil passage communicating with a receiving portion of a regulator for controlling the discharge amount of a variable displacement hydraulic pump that adjusts the discharge amount according to a pilot pressure acting on the receiving portion. The hydraulic circuit of the hydraulic excavator according to claim 1, wherein a solenoid valve for reducing the amount to a predetermined value is provided, and the solenoid valve and the variable relief valve are configured to interlock with each other. 3. The hydraulic circuit of the hydraulic excavator according to claim 1, wherein a pilot for switching a hydraulic pilot type switching valve for an actuator other than a desired actuator provided with a variable relief valve in an inflow oil passage. A solenoid valve is provided in the oil passage to switch when an external signal acts on the receiver, and the solenoid valve having the function of invalidating the switching operation of the hydraulic pilot type switching valve is provided, and a pilot is provided in the receiver of the solenoid valve and the pilot of the variable relief valve. A hydraulic circuit for a hydraulic excavator, characterized in that a signal is simultaneously supplied to a receiving portion of a solenoid valve for supplying pressure oil. 4. A hydraulic pilot type switching, wherein an external signal acts on a receiving portion of a pilot oil passage for switching of a hydraulic pilot type switching valve for an actuator other than a desired actuator provided with a variable relief valve in an inflow side oil passage. The pilot switching valve having the function of invalidating the switching operation of the valve is provided, and the receiving portion of the pilot switching valve and the oil passage communicating with the pilot portion of the variable Lifou valve are connected to each other. Hydraulic circuit of the hydraulic Jobel.