JP2010071376A - Hydraulic control device of construction machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic control device of a construction machine for arranging a switching valve operating by a load sensing signal in a control valve. <P>SOLUTION: A multiple control valve 100 is provided with the switching valve 104 operating by the action of load sensing pressure. The switching valve has a passage for communicating with a tank by passing through the switching valve via an orifice 106 from a first external port PT1, and has a second external port PT2 for a pressure detection port on the upstream side of the switching valve. The switching valve is constituted so as to be switchable to a closing position from an opening position by the action of the load sensing pressure. A fixed capacity pump FP is connected to the first external port, and a partial hydraulic fluid of the fixed capacity pump is fed to a tank port TP. When an operator operates the construction machine, the load sensing pressure increases, and the switching valve is switched to the closing position, and since a flow of the hydraulic fluid stops, pressure Px of the second external port can be increased. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention relates to a multiple-type hydraulic control valve used for a hydraulically operated construction machine, and more particularly to a load sensing type hydraulic control valve.

  In a hydraulically operated construction machine, there is a case where a signal circuit is configured in the hydraulic control valve in order to detect a state in which the work machine is not operated such as traveling work or excavation work (hereinafter, neutral state). For example, it is used to detect neutral and working conditions, detect auto-idle and running work that controls the engine speed of construction machinery, and raise the alarm lamp, alarm sound, and even the maximum pressure of the system.

  The advantage of the load sensing type hydraulic control device is that the flow rate is supplied in proportion to the operation amount of the switching valve even when the load pressure of the hydraulic actuator, that is, the actuator driving pressure changes, or when a new switching valve and hydraulic actuator are added But it is easy to distribute the flow. In that case, the switching valve group having the load sensing function and the switching valve group not having the load sensing function are connected to a common variable displacement pump, and the actuator connected to the switching valve of each of these switching valve groups has inertia, load There is disclosed a hydraulic control device that can obtain very smooth start-up characteristics and operability in accordance with the characteristics of each actuator in a very simple manner even when the pressures are different and when they are driven simultaneously. (Patent Document 1)

A typical hydraulic circuit configuration of a conventional load sensing type hydraulic control device including an unload valve is shown in FIG. 2 (corresponding to FIG. 2 of Patent Document 2).
In FIG. 2, reference numeral 10 denotes a variable displacement pump driven by a prime mover 12, 10A denotes a swash plate of the pump 10, and reference numeral 14 denotes a hydraulic cylinder for adjusting an inclination angle of the swash plate 10A. Reference numerals 20 and 30 are closed center type switching valves connected to the pressure oil supply line L1 from the variable displacement pump 10, and hydraulic actuators ACT1 and ACT2 each consisting of a hydraulic cylinder are connected to these switching valves 20 and 30, respectively. Has been.

  Compensation valves 22 and 32 are provided between the switching valves 20 and 30 and the hydraulic actuators ACT1 and ACT2. Load pressure detection lines SL1 and SL2 are provided between the compensation valves 22 and 32 and the switching valves 20 and 30, and each load pressure is taken out. The taken load pressure is supplied to the compensation valves 22 and 32. On the other hand, the pressures of the load pressure detection line SL1 or SL2 selected by the high pressure selection means 40 are taken out to the signal line SL5, that is, the load sensing line LS simultaneously with the springs 26 and 36 acting in the opening direction. These act on the compensating valves 26 and 36 in the throttle direction. At the same time, the pressure of the signal line SL5 acts on the capacity adjusting device 16 of the variable capacity pump 10 as a line SL7.

  Here, the unload valve 18 is connected to the pressure oil supply line L1 of the variable displacement pump 10, and the unload valve 18 is connected to the pressure of the signal line SL6 and the pressure oil supply line L1 of the variable displacement pump 10. When the difference exceeds a predetermined pressure determined by the force of the spring 18A provided in the unload valve 18, the pressure oil supply line L1 is unloaded.

  In the above configuration, for example, assuming that the switching valve 20 is operated to the position 20B in the drawing, the pressure oil from the variable displacement pump 10 passes from the lines L0, L1, L2 through the supply passage 20B1 in the switching valve 20. The passage L4 is reached, and from the passage L4, the compensation valve 26, the check valve 24, the line L5, the return to the switching valve 20 and the return through the line LA1 to the hydraulic actuator ACT1, and the return side line LB1 to the switching valve 20 And then returned to the tank T via the tank line L8.

  In this case, the driving pressure of the hydraulic actuator ACT1, that is, the pressure in the passage L4 corresponding to the load pressure is detected via the signal line SL1, and further detected as the pressure on the signal line SL5 via the high pressure selection means 40. Acts on the unload valve 18 as the signal line SL6 together with the force of the spring 18A, and cuts off the conduction between the pressure oil supply line L1 of the variable displacement pump 10 and the tank line L11 leading to the tank T. Reference numeral 13 denotes a fixed displacement pump that supplies an operation pressure oil signal to each switching valve, for example, a gear pump.

  The same relationship applies to the case where the switching valve 30 and the hydraulic actuator ACT2 are driven, but detailed description thereof is omitted.

  By the way, in a hydraulically operated construction machine, in order to detect the state of the machine, that is, a state in which traveling work, excavation work or the like is not operated (hereinafter referred to as a neutral state), a signal referred to as a side bypass to each switching valve A circuit may be formed. For example, it detects auto-idle and running work that detects the neutral state and working state and controls the engine speed of construction machinery, and this signal is used to boost the alarm lamp and sound, as well as the maximum pressure of the system. The

In such a case, conventionally, as shown in FIGS. 3A and 3B, communication passages P1, P2, and P3 are provided at the right ends of the spools spr1 and spr2 of the switching valves VL1 and VL2, respectively. Only when in the neutral position, the pressure oil from the pump FP flows to the tank T, and the downstream detection port Px of the throttle Th becomes almost the tank pressure. On the other hand, when even one of the spools is deviated from the neutral position, the downstream detection port Px of the throttle Th becomes the discharge pressure of the pump FP because the flow described above is interrupted. In such an example, the communication paths P1 to P3 must be provided on one end side of each spool, and there is a problem that the spool becomes long and the structure of the control valve becomes large.
Patent Document 2 proposes a method in which each spool is not lengthened in order to solve such problems.

However, even in a method in which the spool is not lengthened, as shown in FIG. 1 of Patent Document 2, a flow sensing path such as a load sensing signal is provided in a valve body that houses each spool. Fine horizontal hole machining was necessary.
Further, in the multi-type control valve, it is necessary to configure a special hydraulic circuit in order to generate the detection signal, and as described above, the valve body must be enlarged in order to secure a space. It was. Furthermore, the manufacturing cost of the valve body has been increased due to the casting and complicated processing of the valve body.
In the load sensing method, a port for detecting the load sensing pressure is indispensable for each actuator, and further, the load sensing pressure rises to a certain pressure by operating each actuator. However, since the load sensing pressure increases to the maximum pressure of the system, there is a problem that the pressure resistance of the sensor and the manufacturing cost increase.

JP 2002-295405 A JP 2007-321908 A

  As a result of intensive studies in view of the above-described points, the present inventor has found that the above problem can be solved by providing the control valve with one switching valve operated by a load sensing signal.

  Accordingly, an object of the present invention is to provide a hydraulic control device for a construction machine in which one control valve that operates according to a load sensing signal is provided in a control valve without machining each valve body or spool.

In order to achieve the above object, a hydraulic control device for a construction machine according to the present invention is a pilot control provided in the hydraulic control device in a hydraulic control device for a construction machine provided with a load sensing multiple hydraulic control valve. A fixed displacement pump that supplies pressure oil to the valve;
A first external port provided in the multiple hydraulic control valve; a conduit for supplying and connecting a part of supply pressure oil from the fixed displacement pump to the first external port; and the multiple hydraulic control valve A switching valve that is connected to the first external port through an orifice and is operated by the load sensing pressure, and the multiple type to take out the pressure between the pressure oil inlet and the orifice of the switching valve to the outside It is characterized by comprising a second external port provided in the hydraulic control valve and a pipe line connecting the pressure oil outlet of the switching valve to the tank line in the multiple hydraulic control valve.

In this case, an auto idle command signal for controlling the engine speed of the construction machine can be generated using the pressure oil signal from the second external port.
Further, in this case, the working state of the construction machine is detected by using an electric signal obtained by hydroelectric conversion of the pressure oil signal from the second external port, thereby warning and displaying to the operator. Can do.

  According to the present invention, in a hydraulic control device for a construction machine including a load-sensing multiple hydraulic control valve, a fixed displacement pump that supplies pressure oil to a pilot operation valve provided in the hydraulic control device, A first external port provided in the multiple hydraulic control valve, a pipe for supplying and connecting a part of the supply pressure oil from the fixed displacement pump to the first external port, and the multiple hydraulic control valve. A switching valve provided and connected to the first external port via an orifice and operated by the load sensing pressure; and the multiple hydraulic pressure for taking out the pressure between the pressure oil inlet and the orifice of the switching valve to the outside. Since it is composed of a second external port provided in the control valve and a pipe line connecting the pressure oil outlet of the switching valve to the tank line in the multiple hydraulic control valve, the construction machine is operated. is doing When detecting the state and neutral state, a special hydraulic circuit is not configured, the manufacturing cost is not increased, the low-pressure sensor can be used, and the damage to the sensor is reduced. It is possible to provide a hydraulic control valve that does not lead to up.

  Hereinafter, an example based on an embodiment of the present invention will be described in detail with reference to FIG. 1 of the accompanying drawings. 1A and 1B are main parts of a hydraulic control apparatus having a switching valve operated by a load sensing signal according to the present invention, wherein FIG. 1A shows its hydraulic circuit, and FIG. 1B shows the configuration in the vicinity of the switching valve main body. FIG.

  In FIG. 1A, reference numeral 100 is a control valve in the present invention, and a plurality of switching valves 102 are provided corresponding to hydraulic actuators (not shown) of the construction machine. Ports A and B are pressure oil supply / discharge ports of corresponding actuators, and ports a and b are ports for pilot operation pressure signals. Port P is a pressure oil supply port supplied from the main pump, and port TP is a tank port. The control valve 100 is provided with a switching valve 104, which is opened by a spring 112 and closed by the pressure of the load sensing line LS.

  Reference numeral 106 denotes a throttle disposed between the first external port PT1 and the input port of the switching valve 104. The first external port PT1 has a fixed displacement pump for supplying pilot pressure to the pilot operation valve 110. Part of the pressure oil from the FP is supplied. Reference symbol RF is a relief valve. The pressure between the throttle 106 and the input port of the switching valve 104 is guided to the second external port PT2 through a broken line passage. The pressure oil signal Px of the second external port PT2 can be directly used, for example, as an auto idle command signal. Further, as indicated by a chain line, the pressure oil signal Px can be hydroelectrically converted and supplied as an electric signal to the control device 108 of the construction machine. Port PT3 is a drain port.

  In FIG. 1A, when all of the plurality of switching valves are in the neutral state, the signal pressure of the load sensing line LS is low, that is, the tank pressure, and the switching valve 104 receives the pressure oil from the pump FP as shown in FIG. It flows through the throttle 106 to the tank port TP. In this state, the pressure oil signal Px of the second external port PT2 is substantially the tank pressure (low).

  On the other hand, even in one of the plurality of switching valves 102, when an operation pressure signal is given through the port a or b, the pressure of the load sensing line LS rises higher than the set force of the spring 112. Therefore, the switching valve 104 is in the lower position, that is, the closed position, and the flow from the throttle 106 is blocked. In this state, the pressure oil signal Px of the second external port PT2 is the supply pressure (high) of the pump FP.

  Therefore, the pressure oil signal Px of the second external port PT2 becomes a high and low pressure oil signal according to the pressure oil level of the load sensing line LS. The discharge pressure of the fixed displacement pump FP is usually about 4 MPa, which is a very small value compared to the pressure of the load sensing line LS corresponding to the driving pressure of the actuator.

  As shown in FIG. 1B, the switching valve 104 is provided on the upper side in the main body of the control valve 100. Reference numeral 104a denotes a spool, and both sides of the small central diameter portion are large diameter portions provided with a labyrinth. The pressure of the load sensing line LS is given to the large diameter portion on the left side of the figure. In addition, the elastic portion of the spring 112 is given to the large diameter portion on the right side in FIG. The spring force of the spring 112 is set to be relatively weak, and is set to be easily compressed even when the load sensing pressure is small. Reference numerals 120, 122, and 124 are stoppers.

  Reference numeral H is a horizontal hole provided at a predetermined position in a small diameter portion near the large diameter portion on the left side of the spool 104a and communicates with the aperture 106. Reference numerals TL1, TL2, TL3, TL4, and TL5 are respective tank lines connected to the tank port TP. The tank line TL1 communicates with the small diameter portion of the spool 104a and further communicates with TL2. The tank line TL3 is a tank line on one side of a plurality of switching valves (not shown) in the control valve 100, and communicates with TL4 through TL2. TL5 is a return passage of the tank line on the other side of the plurality of switching valves, and TL4 communicates with TL5 and is connected to the tank port TP.

  As shown in FIG. 1B, when the pressure in the load sensing line LS rises, the spool 104a moves to the right and the horizontal hole H is closed at the large diameter on the left side, so the signal pressure Px is in the “high” state. It becomes. On the contrary, when the pressure of the load sensing line LS becomes the tank pressure, the spool 104a moves to the left and the large diameter portion on the left side opens the horizontal hole H, so that the signal pressure Px is in the “low” state.

  Although the preferred embodiments of the present invention have been described with reference to the drawings, those skilled in the art can make various modifications based on these disclosed examples.

BRIEF DESCRIPTION OF THE DRAWINGS It is a principal part of the hydraulic control apparatus provided with the switching valve operated by the load sensing signal by this invention, Comprising: (a) shows the hydraulic circuit, (b) is sectional drawing explaining the structure of the switching valve main body vicinity. is there. It is a typical hydraulic circuit diagram of a conventional load sensing type hydraulic control device. In order to generate a conventional auto idle command signal, a communication path is provided in series at one end of each switching valve spool, wherein (a) shows the hydraulic circuit configuration, and (b) shows the communication path. It is a detailed cross section.

Explanation of symbols

100 control valve 102 switching valve 104 switching valve 104a spool 106 throttle 108 control device 110 pilot operation valve 112 spring 114 hydroelectric conversion unit 120, 122, 124 plug FP fixed capacity pump H side hole PT1 first external port PT2 second external port Px Pressure signal TL1, TL2, TL3, TL4, TL5 Tank line TP Tank port

Claims (3)

In the hydraulic control system for construction machinery equipped with load-sensing multiple hydraulic control valves,
A fixed displacement pump for supplying pressure oil to a pilot operation valve provided in the hydraulic control device;
A first external port provided in the multiple hydraulic control valve;
A conduit for supplying and connecting a part of the supply pressure oil from the fixed displacement pump to the first external port;
A switching valve provided in the multiple hydraulic control valve and connected to the first port via an orifice and operated by the load sensing pressure;
A second external port provided in the multiple hydraulic control valve for taking out the pressure between the pressure oil inlet and the orifice of the switching valve to the outside;
A conduit for connecting the pressure oil outlet of the switching valve to a tank line in the multiple hydraulic control valve;
Hydraulic control device for construction machinery consisting of   2. The hydraulic control device for a construction machine according to claim 1, wherein an auto idle command signal for controlling the engine speed of the construction machine is generated using a pressure oil signal from the second external port.   The pressure oil signal from the second external port is converted into a hydroelectric signal, and the working state of the construction machine is detected using a multi-electric signal, thereby warning / displaying the operator. Hydraulic control device for construction machinery described in 1.

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