JP2006336730A - Load sensing control circuit in work machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To adjust a damping for transmitting a load pressure signal to a pressure compensating valve in a load sensing control circuit formed by disposing a control valve and the pressure compensating valve in a pressure oil supply passage starting at a hydraulic pump to a hydraulic actuator. <P>SOLUTION: In this load sensing control circuit in a work machine, a damping adjusting means 34 formed by using an orifice 38 and a solenoid selector valve 39 switchable between an OFF position N for bypassing the orifice 38 and an ON position X for passing the orifice 38 is installed in a load pressure signal circuit 26 for introducing load pressure signals to compensator valves 13 to 18. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention belongs to the technical field of load sensing control circuits in work machines such as hydraulic excavators.

In general, a working machine such as a hydraulic excavator includes various hydraulic actuators such as a hydraulic motor for running and turning and a hydraulic cylinder for operating a working unit, and a hydraulic pressure serving as a hydraulic supply source of these hydraulic actuators. Some pump flow control is performed by so-called load sensing control in which the flow rate is increased or decreased according to the load pressure. In such load sensing control, the pressure oil supply oil passage from the hydraulic pump to each hydraulic actuator switches the direction of pressure oil supply to each hydraulic actuator based on the operation of the operation tool, and has a meter-in restrictor. And a pressure compensation valve that receives the load pressure signal and operates so as to keep the differential pressure across the control valve constant.
By the way, in the load sensing control circuit, as described above, the pressure compensation valve receives the load pressure signal and operates to keep the differential pressure across the control valve constant. In this case, the hydraulic actuator If the load fluctuation is frequent (fluctuates in a short cycle), hunting occurs in the load pressure signal, which may impair the stability. In view of this, a technique is disclosed in which an orifice capable of imparting damping is provided in a load pressure signal circuit that transmits a load pressure signal to each pressure compensation valve (see, for example, Patent Document 1).
JP 2004-205019 A

  By the way, there are various hydraulic actuators provided in the work machine, and different damping may be required depending on the type of the hydraulic actuator. In other words, for example, a hydraulic actuator for a traveling system is subject to frequent load fluctuations, is likely to cause hunting, and requires strong damping. On the other hand, a hydraulic actuator such as a boom cylinder or a stick cylinder that operates a front working portion of a hydraulic excavator Is relatively stable and requires only weak damping. However, in the above-mentioned patent document 1, since any hydraulic actuator is operated and damped equally, the hydraulic actuator that requires strong damping is used as a reference for other hydraulic actuators. On the other hand, when hydraulic actuators that require only weak damping are used as a reference, hydraulic actuators with frequent load fluctuations cause insufficient hunting and hunting. There are problems, and here are the problems that the present invention seeks to solve.

The present invention has been created in order to solve these problems in view of the above-described circumstances, and the invention of claim 1 provides a hydraulic oil supply path from a hydraulic pump to a hydraulic actuator. A pressure control valve that switches the pressure oil supply / discharge direction to the actuator and operates to maintain a constant differential pressure across the control valve in response to a load pressure signal introduced from the load pressure signal circuit. In a load sensing control circuit for a work machine including a compensation valve, the load pressure signal circuit is provided with a damping adjustment means for adjusting damping given to transmission of the load pressure signal to the pressure compensation valve. It is characterized by this.
In this way, damping suitable for each hydraulic actuator can be imparted to the transmission of the load pressure signal, and excessive damping is imparted to the hydraulic actuator that requires weak damping, resulting in responsiveness. It is possible to prevent a problem that hunting occurs due to insufficient damping for a hydraulic actuator that is deteriorated or requires strong damping.
The invention of claim 2 is characterized in that, in claim 1, the damping adjusting means is constituted by using a damping throttle and a valve means capable of bypassing the damping throttle.
And by doing in this way, the damping given to transmission of a load pressure signal can be adjusted.
According to a third aspect of the present invention, in the first aspect, the damping adjusting means is configured by using a plurality of damping throttles having different throttle amounts and a valve means capable of selecting one of the damping throttles. It is characterized by.
And by doing in this way, the damping given to transmission of a load pressure signal can be adjusted.
The invention of claim 4 is characterized in that, in claim 1, the damping adjusting means is configured using a damping diaphragm capable of varying a diaphragm amount.
And by doing in this way, the damping given to transmission of a load pressure signal can be adjusted.
According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the load sensing control circuit of the work machine controls a flow rate of the hydraulic pump in response to a load pressure signal introduced from the load pressure signal circuit. The pump displacement variable means is provided, and the introduction of the load pressure signal to the pump displacement variable means is performed via the damping adjustment means.
And by doing in this way, damping suitable for each hydraulic actuator can be given also about transmission of a load pressure signal to a pump capacity variable means.
According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the load sensing control circuit of the work machine receives the load pressure signal introduced from the load pressure signal circuit, A differential pressure relief valve for limiting the pressure is provided, and the introduction of the load pressure signal to the differential pressure relief valve is performed via a damping adjusting means.
And by doing in this way, damping suitable for each hydraulic actuator can be given also about transmission of a load pressure signal to a differential pressure relief valve.

Next, a first embodiment of the present invention will be described based on the drawings.
FIG. 1 shows a load sensing control circuit of a hydraulic excavator as an example of a work machine. In FIG. 1, P is a variable displacement hydraulic pump, T is an oil tank, and 1 to 6 are provided in the hydraulic excavator. 1 and 2 are left and right traveling motors, 3 is a turning motor, 4 is a stick cylinder, 5 is a boom cylinder, and 6 is a bucket cylinder.

  Control pressure valves 7 to 12 and compensator valves (pressure compensation valves) 13 to 18 to be described later are arranged in the pressure oil supply oil passages from the hydraulic pump P to the hydraulic actuators 1 to 6, respectively.

  The control valves 7 to 12 are three-position switching valves having pilot ports 7a, 7b to 12a and 12b, and are hydraulic actuators when no pilot pressure is input to the pilot ports 7a, 7b to 12a and 12b. 1 to 6 is located at a neutral position N where no pressure oil is supplied, but when pilot pressure is input to the pilot ports 7a, 7b to 12a, 12b, the pressure oil of the hydraulic pump P is passed through the meter-in restrictor. The operation position X is switched to the operation position X or the operation position Y, which is supplied to the hydraulic actuators 1 to 6 and flows the oil discharged from the hydraulic actuators 1 to 6 to the oil tank T.

  On the other hand, 19a, 19b to 24a, 24b are electromagnetic proportional pressure reducing valves, and these electromagnetic proportional pressure reducing valves 19a, 19b to 24a, 24b are controlled according to the operation of each hydraulic actuator operation tool (not shown). Pilot pressure is output to the pilot ports 7a, 7b-12a, 12b of the valves 7-12. In the present embodiment, each of the hydraulic actuator operating tools is constituted by an electric lever, and the operation direction and operation amount thereof are input to a controller (not shown), and the electromagnetic proportional pressure reducing valves 19a, 19b to 24a are supplied from the controller. 24b, a pilot pressure output signal is output, but the pilot pressure output from the electromagnetic proportional pressure reducing valves 19a, 19b to 24a, 24b increases or decreases in accordance with the operation amount of the operating tool. In addition, the opening amount of the meter-in throttle of the control valves 7 to 12 at the operating position X or Y is configured to increase or decrease in accordance with the input pilot pressure, and thus corresponds to the operation tool operation amount. The meter-in control is performed. In the figure, 25 is a pilot hydraulic pressure source.

  The compensator valves 13 to 18 receive a load pressure signal input to pilot ports 13a to 18a from a load pressure signal circuit 26, which will be described later, and keep the differential pressure across the control valves 7 to 12 constant. Although the pressure compensating valve is operated, the compensator valves 13 to 18 are arranged on the downstream side of the pressure oil supply of the meter-in throttle of the control valves 7 to 12, and thus, an after orifice type load sensing control circuit. Is formed.

  On the other hand, reference numerals 27 to 32 denote load pressure detection circuits into which the load pressures of the respective hydraulic actuators 1 to 6 are introduced. The load pressures introduced into these load pressure detection circuits 27 to 32 are increased by a plurality of shuttle valves 33. The highest load pressure that has passed through the final shuttle valve 33a is guided to the load pressure signal circuit 26 as a load pressure signal. Then, the load pressure signal guided to the load pressure signal circuit 26 passes through a damping adjusting means 34 described later, and the load sensing regulator 35 of the hydraulic pump P and the pilot ports 13a to 18a of the compensator valves 13 to 18 are supplied. , And the differential pressure relief valve 36.

  The load sensing regulator 35 is a regulator provided in the hydraulic pump P to control the flow rate of the hydraulic pump P based on the load pressure signal input from the load pressure signal circuit 26, and the variable pump capacity according to the present invention. Although this corresponds to the means, this hydraulic pressure is such that the discharge pressure of the hydraulic pump P is higher than the highest load pressure by a predetermined differential pressure (discharge pressure = load pressure + predetermined differential pressure). The flow rate of the pump P is controlled. In FIG. 1, reference numeral 52 denotes a constant horsepower control regulator provided in the hydraulic pump P.

  A load pressure signal is input to the pilot ports 13 a to 18 a of the compensator valves 13 to 18 via a branch load pressure signal circuit 26 a that is branched from the load pressure signal circuit 26. Each of the compensator valves 13 to 18 operates to receive the load pressure signal inputted from the branch load pressure signal circuit 26a and keep the differential pressure across the control valves 7 to 12 constant. Since the highest load pressure is simultaneously input to all the compensator valves 13 to 18 as a load pressure signal, saturation can be prevented during the interlocking operation of two or more hydraulic actuators 1 to 6 (anti Saturation function).

  Here, an orifice 26b is provided in the branch load pressure signal circuit 26a reaching the pilot ports 13a to 18a of the compensator valves 13 to 18. The orifice 26b is for stabilizing the transmission of the load pressure signal to each of the compensator valves 13 to 18 by damping, but the orifice 26b provided in the branch load pressure signal circuit 26a is stable. The throttle amount is suitable for a hydraulic actuator (for example, stick cylinder 4, boom cylinder 5, etc.) that requires good and weak damping.

  Further, the differential pressure relief valve 36 is used when the differential pressure between the pressure of the discharge circuit 37 of the hydraulic pump P and the load pressure input from the load pressure signal circuit 26 is higher than a preset differential pressure. This is a valve for discharging the pressure oil of the discharge circuit 37 to the oil tank T, whereby the maximum pressure of the discharge circuit 37 of the hydraulic pump P can be limited.

  On the other hand, the damping adjusting means 34 is arranged in the load pressure signal circuit 26 as described above, and the load pressure signal that has passed through the final shuttle valve 33a passes through the damping adjusting means 34 and then is supplied to the hydraulic pump P. The load sensing regulator 35, the pilot ports 13 a to 18 a of the compensator valves 13 to 18, and the differential pressure relief valve 36 are input, and this damping adjustment means 34 imparts damping to the transmission of the load pressure signal. And an electromagnetic switching valve 39 that switches between an OFF position N that bypasses the orifice 38 and an ON position X that passes through the orifice 38 based on a command from the controller, as will be described later, the orifice 38 and the electromagnetic Check to allow reverse flow without passing through switching valve 39 It is constituted by a 40.

  As described above, the controller inputs an operation signal from each hydraulic actuator operation tool, and outputs a pilot pressure output signal to the electromagnetic proportional pressure reducing valves 19a, 19b to 24a, 24b based on the input signal. Further, a command is output to the electromagnetic switching valve 39 in accordance with the hydraulic actuators 1 to 6 operated by the operation tool.

  That is, the controller is positioned at the OFF position N with respect to the electromagnetic switching valve 39 when a hydraulic actuator that requires stable and weak damping such as the stick cylinder 4 and the boom cylinder 5 is operated. Outputs a command. As a result, the load pressure signal of the load pressure signal circuit 26 does not pass through the orifice 38 of the damping adjustment means 34, the load sensing regulator 35 of the hydraulic pump P, the pilot ports 13 a to 18 a of the compensator valves 13 to 18, and the difference The pressure is input to the pressure relief valve 36, so that the flow rate control of the hydraulic pump P, the pressure compensation operation of the compensator valves 13 to 18, and the circuit pressure limitation by the differential pressure relief valve 36 can be performed with good responsiveness. It has become. Even in this case, the input of the load pressure signal to the pilot ports 13a to 18a of the compensator valves 13 to 18 is weakly damped by the orifice 26b provided in the branch load pressure signal circuit 26a as described above. It has come to be.

  On the other hand, the controller is positioned at the ON position X with respect to the electromagnetic switching valve 39 when a hydraulic actuator such as the traveling motors 1 and 2 that is frequently subjected to load fluctuations and requires strong damping is operated. Outputs a command. As a result, the load pressure signal of the load pressure signal circuit 26 passes through the orifice 38 of the damping adjusting means 34, the load sensing regulator 35 of the hydraulic pump P, the pilot ports 13a to 18a of the compensator valves 13 to 18, and the differential pressure. It is input to the relief valve 36. Therefore, the flow control of the hydraulic pump P, the pressure compensation operation of the compensator valves 13 to 18, and the circuit pressure limitation by the differential pressure relief valve 36 are stable with damping. Can be done.

Further, when a hydraulic actuator that requires strong damping such as the traveling motors 1 and 2 and a hydraulic actuator that requires weak damping such as the stick cylinder 4 and the boom cylinder 5 are operated simultaneously, In the embodiment, the hydraulic actuator that requires strong damping is given priority, that is, the controller is configured to output a command located at the ON position X passing through the orifice 38 to the electromagnetic switching valve 39. Yes.
The priority when a plurality of hydraulic actuators are operated simultaneously is not limited to the above-described embodiment. For example, when good response is important, a hydraulic actuator that requires weak damping is selected. It is also possible to adopt a configuration in which a command is output from the controller so as to be positioned at the OFF position N that bypasses the orifice 38 with respect to the electromagnetic switching valve 39.

  Furthermore, in the present embodiment, a communication oil path 41 that connects the pressure oil supply oil paths from the hydraulic pump P to the left and right traveling motors 1 and 2 on the downstream side of the compensator valves 13 and 14, and the communication oil An opening / closing valve 42 for opening and closing the path 41 based on a command from the controller is provided. Then, the controller outputs a command to open the communication oil passage 41 to the on-off valve 42 during straight traveling. As a result, pressure oil is supplied at the same flow rate to the left and right traveling hydraulic motors 1 and 2 during straight traveling, thereby ensuring good straightness.

  In the present embodiment configured as described, the compensator valves 13 to 18 operate so as to keep the differential pressure across the control valves 7 to 12 constant based on the load pressure signal introduced from the load pressure signal circuit 26. However, the load pressure signal circuit 26 can be switched between an orifice 38 for damping the transmission of the load pressure signal, an OFF position N that bypasses the orifice 38, and an ON position X that passes through the orifice 38. A damping adjusting means 34 including a solenoid switching valve 39 is provided.

  As a result, when the electromagnetic switching valve 39 is switched in correspondence with the hydraulic actuators 1 to 6 in operation, that is, when a hydraulic actuator such as a traveling motor that requires frequent damping and strong damping is operated. When the electromagnetic switching valve 39 is set to the ON position X to provide damping by the orifice 38, when a hydraulic actuator such as the stick cylinder 4 or the boom cylinder 5 that requires stable and weak damping is operated, the electromagnetic switching is performed. By setting the valve 39 to the OFF position N and bypassing the orifice 38, it is possible to apply damping suitable for each hydraulic actuator, and thus excessive damping is applied to the hydraulic actuator that requires weak damping. Responsiveness deteriorates or strong damping is required. A problem such as hunting damping is insufficient occurs can be prevented against pressure actuator.

  Moreover, in the present embodiment, the damping adjustment by the damping adjusting means is also performed on the load pressure signal input to the load sensing regulator 35 and the differential pressure relief valve 36 of the hydraulic pump P. Therefore, the flow control of the hydraulic pump P by the load sensing regulator 35 and the transmission of the load pressure signal for limiting the circuit pressure by the differential pressure relief valve 36 are also given damping suitable for the operated hydraulic actuator. be able to.

Of course, the present invention is not limited to the first embodiment, and as the damping adjusting means, the second to fourth shown in FIGS. 2 (A), (B), (C) are used. It can also be configured as follows.
That is, the damping adjustment means 43 of the second embodiment shown in FIG. 2A is configured using the electromagnetic switching valve 44 that switches between the OFF position N and the ON position X based on a command from the controller. A damping orifice 45 is formed at the ON position X of the electromagnetic switching valve 44.
In addition, the damping adjusting means 46 of the third embodiment shown in FIG. 2B provides first and second orifices 47 and 48 (the first orifice 47 that gives weak damping and strong damping) that have different throttle amounts. The second orifice 48) and an electromagnetic switching valve 49 that switches between the OFF position N and the ON position X based on a command from the controller to select one of the orifices 47 or 48.
Furthermore, the damping adjusting means 50 of the fourth embodiment shown in FIG. 2C is configured using a variable throttle valve 51 whose throttle amount is variable based on a command from the controller.
Also in these second to fourth embodiments, each hydraulic actuator is switched by switching the electromagnetic switching valves 44 and 49 or changing the throttle amount of the variable throttle valve 51 corresponding to the hydraulic actuator to be operated. Can be applied to the transmission of the load pressure signal.
In the third embodiment, even when the electromagnetic switching valve 49 is in the OFF position N, weak damping is applied by the first orifice 47, and the fourth embodiment In the embodiment, damping can always be imparted by the variable throttle valve 51. Therefore, in the third and fourth embodiments, the orifice (provided in the branch load pressure signal circuit leading to each compensator valve) ( The orifice 26b) of the first embodiment can be omitted. Incidentally, even if the damping adjusting means 34, 43 of the first and second embodiments are adopted, if there is a case where damping is not necessary for transmission of the load pressure signal, it is arranged in the branch load pressure signal circuit. The orifice may be omitted. Furthermore, the damping adjusting means of the first to fourth embodiments is provided with a check valve 40 that allows the flow in the reverse direction without passing through the damping restrictor. Although the return can be performed quickly, it goes without saying that the present invention can be implemented even if the check valve 40 is not provided.

It is a load sensing control circuit diagram of a hydraulic excavator. (A), (B), (C) is a figure which shows the damping adjustment means of 2nd, 3rd, 4th embodiment.

Explanation of symbols

1-6 Hydraulic actuator 7-12 Control valve 13-18 Pressure compensation valve (compensator valve)
26 Load pressure signal circuit 34 Damping adjustment means 35 Pump capacity variable means (regulator for load sensing)
36 Differential pressure relief valve 38 Damping throttle (orifice)
39 Valve means (electromagnetic switching valve)
43 Damping adjustment means 44 Valve means (electromagnetic switching valve)
45 Restriction for damping (orifice)
46 Damping adjustment means 47, 48 Damping restriction (first and second orifices)
49 Valve means (electromagnetic switching valve)
50 Damping adjustment means 51 Variable throttle valve P Hydraulic pump

Claims (6)

  Controls the pressure oil supply passage from the hydraulic pump to the hydraulic actuator by switching the pressure oil supply / discharge direction to the hydraulic actuator and receiving a load pressure signal introduced from the load pressure signal circuit and a control valve with a meter-in throttle In a load sensing control circuit of a work machine that is provided with a pressure compensation valve that operates so as to maintain a constant pressure difference across the valve, the load pressure signal circuit is configured to transmit the load pressure signal to the pressure compensation valve. A load sensing control circuit in a work machine, characterized in that a damping adjusting means for adjusting applied damping is provided.   2. The load sensing control circuit according to claim 1, wherein the damping adjusting means is configured using a damping throttle and a valve means capable of bypassing the damping throttle.   In a working machine according to claim 1, wherein the damping adjusting means is configured using a plurality of damping throttles having different throttle amounts and valve means capable of selecting any one of the damping throttles. Load sensing control circuit.   2. The load sensing control circuit in a work machine according to claim 1, wherein the damping adjustment means is configured by using a damping diaphragm capable of varying a diaphragm amount.   5. The load sensing control circuit for a work machine according to claim 1, further comprising: a pump capacity varying unit that controls a flow rate of the hydraulic pump in response to a load pressure signal introduced from the load pressure signal circuit. The load sensing control circuit in the work machine is characterized in that the introduction of the load pressure signal to the pump displacement variable means is performed via a damping adjustment means.   6. The differential pressure relief according to claim 1, wherein the load sensing control circuit of the work machine receives the load pressure signal introduced from the load pressure signal circuit and limits the pressure of the discharge circuit of the hydraulic pump. A load sensing control circuit in a work machine, comprising a valve and introducing a load pressure signal to the differential pressure relief valve via a damping adjustment means.

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