JPH0621462B2 - Hydraulic circuit of civil construction machinery - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a hydraulic circuit provided in a civil construction machine such as a hydraulic shovel.

<Prior Art> As a hydraulic circuit provided in a civil engineering construction machine, for example, a hydraulic shovel, a hydraulic pump and an actuator such as a boom cylinder, an arm cylinder, and a bucket cylinder have been conventionally used.
A directional control valve that controls the flow of pressure oil supplied from the hydraulic pump to the actuator, a main relief valve that regulates the discharge pressure of the hydraulic pump, and a pressure in the pipeline that connects the directional control valve and the actuator. , An overload relief valve that is set to a pressure higher than the main relief pressure of the main relief valve.

<Problems to be Solved by the Invention> However, in the conventional hydraulic circuit, the main relief pressure defined by the main relief valve is uniquely set, that is, once set, the main relief pressure of each actuator is set. The set value cannot be changed during the work performed via the drive, and the same applies to the overload relief pressure set by the overload relief valve. Depending on the type of work, such as insufficient pressure, the main relief pressure and overload relief pressure were not always optimal.

The present invention has been made in view of the above-mentioned conventional circumstances, and an object thereof is to determine the pressure supplied to the actuator even when the actuator is being driven and the type of work. An object of the present invention is to provide a hydraulic circuit for a civil engineering and construction machine that can change the pressure to an optimum pressure according to.

<Means for Solving Problems> In order to achieve this object, the present invention relates to a hydraulic pump connected to a tank, a main relief valve provided between a discharge line of the hydraulic pump and the tank, Installed in the actuator that operates by the pressure oil discharged from the hydraulic pump, the direction switching valve that controls the flow of pressure oil supplied from the hydraulic pump to the actuator, and the conduit that connects this direction switching valve and the actuator. A main relief valve is provided in parallel between the hydraulic pump and the tank, the set pressure of these main relief valves is made different, and one of these main relief valves is provided. And a first selecting means, which is, for example, a first directional switching valve, for selectively operating the valve, and the set pressure of the overload relief valve is selectively changed. And a second selection means including a second directional control valve.

<Operation> Since the present invention is configured as described above, different set pressures of the plurality of main relief valves and a plurality of set pressures of the overload relief valve are set in advance as work that does not require high pressure. The value can be set to an appropriate value depending on the work requiring a special high pressure, and in such a set state, through the first selecting means or the first selecting means and the second The maximum value of the pressure supplied from the hydraulic pump to the actuator via the directional control valve can be changed to an optimum value according to the type of work through the cooperation with the selecting means. .

<Example> Hereinafter, the hydraulic circuit of the civil construction machine of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing a main part configuration of an embodiment of the present invention.
For example, the hydraulic circuit of the hydraulic shovel is shown. In this figure, 19 is a tank, 1 is a hydraulic pump connected to this tank 19, for example, a variable displacement hydraulic pump, 12, 1.
Reference numerals 3 and 14 are actuators driven by pressure oil supplied from the variable displacement hydraulic pump 1, for example, a boom cylinder, an arm cylinder, and a bucket cylinder, respectively.
3, 4, 5 are arranged between the boom cylinder 12, the arm cylinder 13, the bucket cylinder 14 and the variable displacement hydraulic pump 1, and the variable displacement hydraulic pump 1 to the boom cylinder 12, the arm cylinder 13, the bucket. A boom directional control valve, an arm directional control valve, and a bucket directional control valve that control the flow of pressure oil supplied to the cylinder 14. Further, 6 and 7 are overload relief valves that regulate the pressure in the two conduits that connect the boom direction switching valve 3 and the boom cylinder 12, respectively, and 8 and 9 are the arm direction switching valve 4 and the arm cylinder, respectively. The overload relief valves 10 and 11 for defining the pressures in the two conduits communicating with 13 define the pressures in the two conduits communicating with the bucket directional control valve 5 and the bucket cylinder 14, respectively. It is an overload relief valve. The set pressure of these overload relief valves 6, 7, 8, 9, 10, 11 is set to, for example, 300 kg / cm ² . In addition, these overload relief valves 6, 7, 8, 9, 10,
3 out of 11 overload relief valves 6, 8, 10
The set pressure can be changed.

Further, 16 and 17 are the variable displacement hydraulic pump 1 and the tank 19.
And a plurality of, for example, two main relief valves provided in parallel with each other, of which the set pressure of the main relief valve 16 is set to, for example, 285 kg / cm ² , and the set pressure of the main relief valve 17 is set to, for example, 325 kg / cm ² . I am doing it. Reference numeral 15 denotes a first directional control valve arranged between the main relief valves 16 and 17 and the variable displacement hydraulic pump 1, which is the first directional control valve.
The direction switching valve 15 constitutes a first selecting means for selectively operating one of the main relief valves 16 and 17.

Reference numeral 20 is a pilot line connected to the drive units of the overload relief valves 6, 8 and 10, 21 is a pilot pump for supplying a pilot pressure of 40 kg / cm ² to this pilot line 20, and 18 is a pilot line. The second directional control valve provided in 20 is a relief valve 22 which regulates the pressure oil discharged from the pilot pump 21 to 40 kg / cm ² . The pilot pump 21, the pilot conduit 20, the second directional control valve 18, and the relief valve 22 constitute second setting means for selectively changing the set pressure of the overload relief valves 6, 8, 10. is doing.

In this embodiment, the variable displacement hydraulic pump 1 is driven, and the boom directional switching valve 3, the arm directional switching valve 4, and the bucket directional switching valve 5 are appropriately switched, so that the boom cylinder 12, the arm cylinder 13, the bucket cylinder. 14, the boom, arm, and bucket (not shown) are driven to perform desired excavation work and the like. In this case, when the switching position of the first directional control valve 15 is in the state shown in the figure, the variable displacement hydraulic pump 1 and the main relief valve 16 are in communication, while the variable displacement hydraulic pump 1
The main relief valve 17 is disconnected from the main relief valve 17, whereby the pressure of the hydraulic oil flowing in the main circuit is regulated to 285 kg / cm ² which is the set pressure of the main relief valve 16.
The boom cylinder 12, the arm cylinder 13, and the bucket cylinder 14 are driven by the pressure of g / cm ² , and normal work that does not require high pressure can be performed.

Then, for example, when the first direction switching valve 15 is switched to the upper position in the drawing during such work, the variable displacement hydraulic pump 1 and the main relief valve 17 are connected to each other, while the variable displacement hydraulic pump 1 and the main relief valve 17 are connected. Since the communication with the relief valve 17 is cut off, the pressure of the pressure oil flowing through the main circuit is regulated to 300 kg / cm ² which is the set pressure of the overload relief valves 6, 7, 8, 9, 10, 11. , Boom cylinder 1
2, the arm cylinder 13 and the bucket cylinder 14 can be driven at a higher pressure than in the above case.

Further, while the first direction switching valve 15 is switched to the upper position in the drawing, the pilot pump 21
When the second directional control valve 18 is switched to the left position in the drawing, the pilot pump 21 and the respective drive parts of the overload relief valves 6, 8 and 10 are connected, and the pilot pressure of the pilot pump 21 is connected. Is guided to the drive units of the overload relief valves 6, 8, 10 and the set pressure of these overload relief valves 6, 8, 10 is 3
It is changed to 00 + 40 = 340 (kg / cm ² ). In this state, the pressure in the main circuit is regulated to the set pressure of the main relief valve 17 of 325 kg / cm ² , and this 325 kg / cm ²
Boom cylinder 12 and arm cylinder 1
3. The bucket cylinder 14 is driven, and it is possible to perform work requiring a special high pressure.

In the embodiment configured in this way, the boom cylinder is appropriately operated even by the proper switching of the first direction switching valve 15 and the second direction switching valve 18 together. 12, the pressure of the hydraulic oil supplied to the arm cylinder 13 and the bucket cylinder 14 is 285 kg / cm ² , 300 kg / c
It is possible to specify three different maximum values of m ² and 325 kg / cm ² , and it is possible to change to the optimum pressure according to the type of work.

In the above embodiment, two main relief valves 16 and 17 are provided, but this main relief valve can be replaced by 3 if necessary.
One or more may be provided.

Further, in the above, the set pressure of the overload relief valves 6, 8 and 10 is configured to be changeable, but only one of them may be configured to be changeable, and the other overload relief valve 7 , 9, 11 may also be configured to be changeable together.

Further, in the above, as shown in the drawing, the first directional control valve 1
5, the second directional control valve 18 is configured to be a manual switching type, but may be configured to be switched according to an electric signal.

Further, in the above, as an example of the actuator, the boom cylinder 12, the arm cylinder 13, the bucket cylinder 1
However, the actuator is not limited to this, and may be a swing motor, a left-right direction motor, or the like.

Further, although the hydraulic circuit of the hydraulic shovel has been described above as an example, the present invention can be applied to other civil engineering construction machines such as crane working machines.

<Effects of the Invention> Since the hydraulic circuit of the civil construction machine of the present invention is configured as described above, the first selecting means, the first selecting means and the first selecting means can be used even when work is performed by driving the actuator. The pressure supplied to the actuator via the two selection means can be changed to the optimum pressure according to the type of work, and therefore the work efficiency can be improved as compared with the conventional one.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a main part configuration of an embodiment of a hydraulic circuit of a civil engineering construction machine of the present invention. 1 ... Variable displacement hydraulic pump, 3 ... Boom direction switching valve, 4 ... Arm direction switching valve, 5 ... Bucket direction switching valve, 6, 7, 8, 9, 10, 11 ... Overload Relief valve, 12 ... Boom cylinder, 13 ... Arm cylinder, 14 ... Bucket cylinder, 15 ... First direction switching valve (first selection means), 16, 17 ... Main relief valve, 18 ... ... second directional control valve (second selection means), 19 ... tank, 20 ... pilot line (second)
Selection means), 21 ... Pilot pump (second selection means), 22 ... Relief valve (second selection means).

Claims (1)

[Claims] 1. A hydraulic pump connected to a tank, a main relief valve provided between a discharge line of the hydraulic pump and the tank, and an actuator operated by pressure oil discharged from the hydraulic pump, A directional control valve that controls the flow of pressure oil supplied from the hydraulic pump to the actuator,
In a hydraulic circuit of a civil engineering construction machine provided with an overload relief valve provided in a conduit that connects the directional control valve and the actuator, a plurality of main relief valves are provided in parallel between the hydraulic pump and the tank. Of the main relief valve and the second selector for selectively changing the set pressure of the overload relief valve, and the first selection means for selectively operating any one of these main relief valves. A hydraulic circuit for a civil construction machine, comprising: a selecting means.