JP2831423B2 - Hydraulic circuit for civil engineering and construction machinery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention forms a load sensing system which is provided in a civil engineering or construction machine such as a hydraulic shovel and includes a closed center type directional control valve for controlling the drive of an actuator. The present invention relates to a hydraulic circuit of a civil engineering / construction machine suitable for a case where an additional directional control valve needs to be provided for a special specification.

[Conventional technology]

Hydraulic circuits for civil engineering and construction machinery include a hydraulic circuit with a closed center type directional control valve that is center-blocked in a neutral state and a hydraulic circuit with an open center type directional valve that is in a conductive state in a neutral state. There is. Hydraulic circuits with open-center directional valves have been known for quite some time, and directional valves have become very common. Recently, a closed center type directional control valve has been provided from the viewpoint of energy saving and improvement of operability. However, compared to an open center type directional control valve, it is not generally used at present.

FIG. 4 is a circuit diagram showing a main configuration of a hydraulic circuit of a conventional civil engineering / construction machine, for example, a hydraulic shovel provided with the above-mentioned closed center type directional control valve.

The prior art shown in FIG. 4 includes a prime mover 1 and a hydraulic source 2 having a load sensing regulator driven by the prime mover 1. The hydraulic source 2 includes a hydraulic pump driven by the prime mover 1, for example, a variable displacement hydraulic pump 3, a control actuator 5 for controlling the displacement of the hydraulic pump 3, and a flow rate for controlling the drive of the control actuator 5. And a load sensing regulator including a regulating valve 6. Then, actuators 7 and 8 driven by pressure oil supplied from the hydraulic source 2, that is, pressure oil discharged from the hydraulic pump 3.
And a closed center type directional control valve 9, 10 for controlling the flow of pressure oil supplied to these actuators 7, 8.
And pressure control valves 11 and 12 for controlling the differential pressure between the upstream pressure and the downstream pressure of these directional control valves 9 and 10, that is, the differential pressure between the upstream and downstream, and the maximum load pressure among the load pressures of the actuators 7 and 8. The pipelines 13 and 14 and the shuttle valves 15 and 1 that constitute transmission means for transmitting the control pressure for controlling the supply flow rate to the hydraulic pressure source 2, that is, the spring chamber side forming one drive unit of the flow rate adjustment valve 6.
6 and conduits 17 and 18. A pump pressure is applied to the other drive unit of the flow control valve 6 via a pipe 19.

In the prior art thus configured, in the neutral holding state of the directional control valves 9 and 10, these directional control valves 9 and
As the block 10 is center-blocked, the discharge oil from the hydraulic pump 3 is not supplied to the actuators 7 and 8, and the actuators 7 and 8 are stopped and held. Further, by appropriately switching the direction switching valves 9 and 10, a differential pressure between upstream and downstream of the direction switching valves 9 and 10 is generated, and the differential pressure between the upstream and downstream of the direction switching valves 9 and 10 is controlled by the pressure control valves 11 and 12. And the differential pressure is maintained so as to balance the force of the springs of the pressure control valves 11 and 12, so that the flow rate flowing through the directional control valves 9 and 10 is kept constant. A flow rate corresponding to the opening areas of the directional control valves 9 and 10 can be supplied to the actuators 7 and 8 irrespective of the load fluctuations of the other actuators, and a good combined drive of these actuators 7 and 8 can be realized. be able to. The load pressure of each of the actuators 7 and 8 is extracted from the pipes 13 and 14, and the maximum load pressure of the actuators 7 and 8 is transmitted through the shuttle valves 15 and 16 and the pipes 17 and 18 to drive one of the flow rate adjusting valves 6 constituting the regulator. And the other driving portion of the flow control valve 6 is supplied with a pump pressure via a pipe line 19, whereby the flow control valve 6 is subjected to a force generated by a differential pressure between the pump pressure and the maximum load pressure. , And a part of the discharge flow rate of the pump 3 is given to the bottom side of the control actuator 5 in response to this.
The piston moves against the force of the spring and the hydraulic pump 3
, The flow rate of the hydraulic pump 3 is controlled so that the pump pressure becomes larger than the maximum load pressure of the actuators 7 and 8 by the amount corresponding to the spring force of the flow regulating valve 6. Is performed.

[Problems to be solved by the invention]

By the way, in the case of civil engineering and construction machines such as hydraulic shovels, there are cases where it is desired to perform special work in addition to the original work. For example, a hydraulic shovel is usually intended for excavation work, etc., but sometimes it is necessary to perform rock crushing work or gripping work, and in such a case, a work implement for performing the corresponding work is required. It is required that an actuator for driving the work implement and a directional control valve for controlling the drive of the actuator be provided as a special specification. In response to such demands, there is a demand on the design and manufacturer side to provide a more general and easily available open center type directional control valve as described above. Cannot implement a load sensing system. Therefore, even in such a case, it is necessary to provide a closed center directional control valve which is not common and relatively difficult to obtain. There was a problem that it was difficult to improve productivity in the specification.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances in the prior art, and has as its object to provide a circuit including a closed center type directional control valve and capable of implementing a load sensing system. An object of the present invention is to provide a hydraulic circuit of a civil engineering / construction machine that can be mounted on a vehicle.

[Means for solving the problem]

In order to achieve this object, the present invention provides a prime mover, a hydraulic source having a load sensing regulator driven by the prime mover, and a plurality of hydraulic sources driven by hydraulic oil supplied from the hydraulic source. A closed center type directional control valve provided between the actuator, the hydraulic pressure source and the actuator for controlling the flow of pressure oil supplied to the actuator, and supplying the maximum load pressure of the load pressure of the actuator to the hydraulic source. In a hydraulic circuit of a civil engineering / construction machine having a transmission means for transmitting a control pressure to a hydraulic source as a control pressure for controlling a flow rate, the hydraulic circuit is connected to a supply pipe of a hydraulic source, and cuts off or cuts off pressure oil from the supply pipe. It has a variable throttle valve capable of adjusting the maximum opening amount, and a pressure control valve for controlling a differential pressure between upstream and downstream of the variable throttle valve, that is, a differential pressure between the upstream and downstream, to a predetermined value or less. Provided with a composite valve,
A detecting means connected to the transmitting means for detecting the outlet pressure of the variable throttle valve, which is the outlet pressure of the composite valve, is provided.

[Action]

Since the present invention has the above-described configuration, the pressure difference between the front and rear of the variable throttle valve is kept constant by the pressure control valve forming the composite type valve, so that the flow rate depending on the opening area of the variable throttle valve can be varied. The outlet pressure of the variable throttle valve can be supplied from the outlet port of the throttle valve, that is, the outlet port of the composite valve. Thus, the regulator that forms the hydraulic power source can be driven, that is, the function equivalent to that of the closed center directional control valve that forms the load sensing system can be ensured by the composite valve. This makes it possible to form a load sensing system by connecting an open center type directional control valve to the outlet port of the composite valve, that is, the outlet port of the variable throttle valve. The connection with the directional control valve is easy, so that the closed center type directional control valve can be easily mounted.

〔Example〕

Hereinafter, an embodiment of a hydraulic circuit of a civil engineering / construction machine according to the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing a configuration of a main part of the present invention. The first embodiment shows, for example, a hydraulic circuit of a hydraulic shovel, and a motor 1 similar to that shown in FIG.
A regulator comprising a flow regulating valve 6 and a control actuator 5, a hydraulic source 2 comprising a variable displacement hydraulic pump 3 driven by a prime mover 1, and an actuator 7 driven by hydraulic oil supplied from the hydraulic pump 3. , 8 and
Closed center type directional control valves 9 and 10 for controlling the driving of these actuators 7 and 8, pressure control valves 11 and 12 for controlling the differential pressure between these directional control valves 9 and 10, and actuators 7 and 8 Pipelines 13 and 1 for transmitting the maximum load pressure of the load pressure as a control pressure to one drive unit of the flow control valve 6.
4. Shuttle valves 15 and 16; pipes 17 and 18; and pipe 19 for transmitting pump pressure to the other drive unit of flow control valve 6.

A composite valve 20 is provided so as to be connected to the supply line 2a of the hydraulic power source 2, that is, the discharge line of the hydraulic pump 3.
The composite valve 20 is a variable throttle valve 21 that can cut off or inflow of pressure oil from the supply pipe 2a, and a differential pressure between the upstream pressure and the downstream pressure of the variable throttle variable 21, that is, a differential pressure before and after the variable throttle valve 21. Spring 21a
And a pressure control valve 22 that keeps the pressure at or below a certain value according to the force of the pressure. As shown in FIG. 1, the above-described variable throttle valve 21 is in a neutral state, maintains its upper position in the figure by the force of a spring 21a, and communicates with the tank via a tank line 2b. And
As the variable throttle valve 21 moves upward, its opening area increases, and the amount of movement that determines the opening area, that is, the stroke, can be adjusted by the stroke adjusting device 23. The stroke adjusting device 23 includes a screw rod 23a and a locking nut 23b for fixing the screw rod 23a, and the screw rod 23a can be moved by loosening the locking nut 23b, whereby the stroke of the variable throttle valve 21 can be adjusted. ing. Further, a pipeline 24, a shuttle valve 25, and a pipeline which are connected to the above-described transmission means to detect the outlet pressure of the variable throttle valve 21
26 detecting means are provided.

The outlet port of the composite valve 20, that is, the outlet port 21c of the variable throttle valve 21 is closed by a blind plate, and the end 28 of the pilot pipe 27 connected to the drive unit 21b of the variable throttle valve 21 is also blind. It is closed by a plate, and the end 29 of the tank line 2b is also closed by a blind plate.

In the first embodiment configured as described above, the composite valve
Since the block 20 is kept in a non-operating state, if there is no need to provide a separate directional control valve for special specifications, the circuit configuration is the same as the circuit configuration shown in FIG. By switching the valves 9 and 10, combined driving of the actuators 7 and 8 can be performed.

If it is necessary to separately provide a directional control valve for special specifications, the differential pressure before and after the variable throttle valve 21 forming the composite valve 20 is controlled by the pressure control valve 22. As in the closed center type directional control valve, a constant flow rate can be supplied from the outlet port 21c as in the closed center type directional control valve. It can control the actuator that drives the work implement of the specification. By appropriately adjusting the stroke adjusting device 23, the opening area of the variable throttle valve 21 is limited, whereby the flow supplied to the actuator for the special specification is reduced to a minimum necessary flow according to the actuator. It can be. In addition, the load pressure of the corresponding actuator can be detected as the outlet pressure of the variable throttle valve 21, and the outlet pressure is selectively guided as control pressure to the transmission means via the pipeline 24 and the shuttle valve 25, and the flow rate It contributes to driving of the regulating valve 6 and forms a load sensing system.
When a special open center type directional control valve is provided, the end 28 of the pilot line 27 is connected to driving means for guiding the pilot pressure for driving the variable throttle valve 21, and the end of the tank line 2b. The part 29 is connected to a center bypass and a tank port of the open center type directional control valve, respectively. In the first embodiment configured as described above, an open center type directional control valve can be connected as a directional control valve for a special specification. In this case, the blind plate of the outlet port 21c of the composite valve 20 is excluded. Connected to the drive means except for the blind plate at the end 28 of the pilot line 27, and connected to the drive means except for the blind plate at the tank line 2b. Since it is only connected to the center bypass and the tank port, this open center type directional control valve can be easily mounted. Since such an open center type directional control valve is general and easily available, Productivity can be improved with special equipment.

FIG. 2 is a circuit diagram showing a main configuration of a second embodiment of the present invention. In the second embodiment, in addition to the configuration of the first embodiment shown in FIG. 1, actuators 30 and 31 for driving work tools (not shown) of special specifications, and open center type directional switching valves 32 and 33 are provided. The open center type directional control valves 32 and 33 are connected to the outlet port of the composite valve 20, that is, the outlet port 21c of the variable throttle valve 21. The center bypasses of the direction switching valves 32 and 33 and the tank port are connected to the end portion 29 of the tank pipe 2b via the pipe. Further, pilot pressure for driving the directional control valves 32, 33 is taken out by shuttle valves 35, 36 and a shuttle valve 37, and the shuttle valve 37 is connected to a pilot line 27 connected to the drive unit 21b of the variable throttle valve 21. Connected. The above-mentioned shuttle valves 35, 36, 37 constitute driving means for opening the variable throttle valve 21 of the composite valve 20 in response to driving of the open center type directional switching valve.

In the second embodiment constructed as described above, when the open center type directional valves 32 and 33 are not operated and the closed center type directional valves 9 and 10 are operated, the composite type valve 20 is not operated. The supply line 2a of the pump 3 as shown in FIG.
4 is maintained in a state in which the flow of pressure oil from and into the fluid is interrupted, that is, a state in which it does not operate, and forms a circuit equivalent to the circuit shown in FIG. 4 described above. The combined driving of the actuators 7 and 8 can be performed.

Further, when the directional control valves 32, 33 are operated with the intention of driving the actuators 30, 31 for special specifications, the pilot pressure used for the operation is extracted via the shuttle valve 35 or the shuttle valve 36. And the shuttle valve 3
7. It is led through the pilot line 27 and is given to the drive unit 21b of the variable throttle valve 21. Thereby, the variable throttle valve 21 operates upward in FIG. 2 until it is regulated by the stroke adjusting device 23 against the force of the spring 21a. Then, the pressure difference between the front and rear of the variable throttle valve 21 is given to the driving portion of the pressure control valve 22, and the pressure difference between the front and rear is controlled by the pressure control valve 22 so as to balance the force of the spring 22a. Accordingly, the variable throttle valve 21 is supplied from the hydraulic pump 3 via the supply line 2a and the pressure control valve 22.
Is a constant flow rate corresponding to the opening area of the variable throttle valve 21 limited by the stroke adjusting device 23. This flow rate is guided to the open center type directional control valves 32 and 33 through the outlet port 21c, and further to the actuator 3
0, 31 and can drive a working tool (not shown) of a desired special specification. And actuator 30,
The load pressure of 31 is detected as an outlet pressure of the variable throttle valve 21 by the pipeline 24 and the shuttle valve 25, and is used as a control pressure together with the load pressure of the actuators 7, 8, and is applied to these actuators 30, 31, 7, 8. The maximum load pressure of the load pressure is line 18
To the drive unit of the flow control valve 6 via the control unit, thereby realizing a load sensing system.

In the second embodiment configured as described above, the first embodiment described above is used.
In addition to having the same operation and effect as the embodiment, the shuttle valve 35,
The variable throttle valve 21 can be driven in conjunction with the operation of the direction switching valves 32, 33 via 36, 37, and the operation of the variable throttle valve 21 can be performed simply and reliably.

FIG. 3 is a circuit diagram showing a configuration of a main part of a third embodiment of the present invention.

The third embodiment differs from the first embodiment only in the configuration of the variable throttle valve 41 of the composite valve 20. The variable throttle valve 21 in the first embodiment described above is
The branch point of the pipeline for taking out the downstream pressure of the actuator and the load pressure of the actuator for the special specification led through the outlet port 21c is provided in the variable throttle valve 21. The third branch shown in FIG. In the embodiment, the branch point is provided outside the variable throttle valve 41. In the third embodiment configured as described above, the first embodiment
In addition to the same operation and effect as those of the embodiment, the structure of the variable throttle valve 41 is simple and easy to manufacture.

〔The invention's effect〕

Since the hydraulic circuit of the civil engineering and construction machine of the present invention is configured as described above, the hydraulic circuit including the closed center type directional control valve and capable of implementing the load sensing system is described below.
The open center type directional control valve can be easily installed. This open center type directional control valve is well known in the past, is common and easily available, and therefore requires additional special-purpose working tools and actuators. In some cases, an open center type directional control valve can be adopted, and the productivity for this special specification or the like can be increased.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a hydraulic circuit for a civil engineering / construction machine according to a first embodiment of the present invention, FIG. 2 is a circuit diagram showing a main configuration of a second embodiment of the present invention, FIG. 3 shows the third embodiment of the present invention.
FIG. 4 is a circuit diagram showing a configuration of a main part of a hydraulic circuit of a conventional civil engineering / construction machine. DESCRIPTION OF SYMBOLS 1 ... Motor, 2 ... Hydraulic source, 3 ... Variable displacement hydraulic pump, 5 ... Control actuator, 6 ... Flow regulating valve,
7, 8 Actuator, 9, 10 Closed center type directional control valve, 17, 18 Pipe line, 19 Pipe line, 20
Compound type valve, 21 …… Variable throttle valve, 22 …… Pressure control valve,
23 Stroke adjusting device, 24 Pipe line, 25 Shuttle valve, 26 Pipe line, 27 Pilot pipe line, 30, 31
Actuator, 32, 33 ... Open-center type directional control valve, 34 ... Pipe line, 35, 36, 37 ... Shuttle valve, 41 ... Variable throttle valve.

──────────────────────────────────────────────────の Continued on the front page (72) Inventor Genroku Sugiyama 650, Kandate-cho, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. (56) References JP-A-59-85040 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) E02F 9/22

Claims (2)

(57) [Claims] 1. A motor, a hydraulic source having a load sensing regulator driven by the motor,
A plurality of actuators driven by pressure oil supplied from the hydraulic source, and a closed center type direction provided between the hydraulic source and the actuator and controlling the flow of the pressure oil supplied to the actuator. In a hydraulic circuit for a civil engineering / construction machine, comprising: a switching valve; and a transmission unit configured to transmit a maximum load pressure of the load pressure of the actuator to the hydraulic source as a control pressure for controlling a supply flow rate of the hydraulic source. A variable throttle valve which is connected to a supply line of a hydraulic power source, is capable of blocking or inflow of pressurized oil from the supply line, and capable of adjusting a maximum opening amount; an upstream pressure of the variable throttle valve; A composite valve having a pressure control valve for controlling a pressure difference between the pressures to be equal to or less than a predetermined value, and a variable valve which is connected to the transmission means and is an outlet pressure of the composite valve. Civil engineering and construction machine hydraulic circuit, characterized in that a detecting means for detecting the outlet pressure of Ri valve. 2. An open center type directional control valve is connected to an outlet port of the composite type valve, and drive means for opening a variable throttle valve in response to driving of the open center type directional control valve is provided. The hydraulic circuit for civil engineering and construction machinery according to claim 1.