JP2009058097A - Fluid control circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid control circuit capable of preventing generation of shock due to drop of travel speed when a tool is operated during straight travel. <P>SOLUTION: The fluid control circuit is provided with; a pair of travel control valves 16-1, 16-2 controlling working fluid supplied to travel actuators 1m-1, 1m-2 from a first variable displacement pump 11-1 and a second variable displacement pump 11-2 respectively; a tool bypass control valve 17 controlling working fluid supplied to a tool actuator 9a from the second variable displacement pump 11-2; a straight travel valve 14 supplying same quantity of working fluid to the pair of travel control valves 16-1, 16-2 from the first variable displacement pump 11-1 and the second variable displacement pump 11-2 by change-over to a straight travel position; and a control means 33 slowly operating the tool bypass control valve 17 when the tool is operated during operation of the straight travel valve 14. The control means 33 controls change speed when pilot pressure is turned on/off. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fluid control circuit including a travel actuator and a tool actuator.

  In hydraulic construction machinery vehicles, the remaining part that is circulated from the hydraulic pump to the travel control valve during straight travel to prevent travel deceleration and the accompanying shock that occur when other actuators are operated simultaneously with the travel actuator A variable throttle valve is used as a valve to throttle the flow rate of pressure oil, and a variable throttle valve is arranged in the flow path of some pressure oil to flow to other actuator control valves to adjust the flow rate of pressure oil. (For example, refer to Patent Document 1).

  Also, when interlocking operation of the travel actuator and tool actuator, in order to ensure travel straightness, the travel straight valve is driven, the travel actuator is driven by the drive pump, and the tool actuator is driven by the idle pump. I have to.

The straight travel valve has a structure in which oil flows from the idle pump to the travel system through the orifice when the operating pressure of the tool actuator is sufficiently higher than the operating pressure of the travel actuator. However, since the path of the center bypass line that determines the negative control pressure is the same regardless of whether the travel straight valve is driven or stopped, the amount of oil discharged by the idle pump during the interlock operation of the tool actuator and travel actuator is , The sum of the tool operation amount and the left travel operation amount.
Japanese Patent Laid-Open No. 5-187041 (first page, FIG. 1)

  If the operating pressure of the tool actuator is not sufficiently higher than the operating pressure of the travel actuator when the tool actuator is operated during travel, the amount of oil that flows from the idle pump side to the travel actuator via the travel straight valve orifice Less.

  When traveling alone, the amount of oil for two pumps flowed into the traveling actuator, but the moment the tool lever was operated, the flow rate flowing from the idle pump to the traveling actuator suddenly decreased, resulting in a large shock. .

  The present invention has been made in view of these points, and an object of the present invention is to provide a fluid control circuit capable of preventing the occurrence of shock due to a decrease in traveling speed when a tool is operated during straight traveling.

  The invention described in claim 1 includes a pair of travel control valves for controlling the working fluid respectively supplied from the first pump and the second pump to the pair of travel actuators, and the second pump. A tool control valve for controlling the working fluid supplied to the tool actuator, and an equal flow rate of working fluid from the first pump and the second pump to the pair of traveling control valves by switching to the straight traveling position. It is a fluid control circuit including a traveling straight valve to be supplied and a control unit that operates a tool control valve at a slow speed when a tool is operated during operation of the traveling straight valve.

  According to a second aspect of the present invention, the control means in the fluid control circuit according to the first aspect includes a speed limiter that limits a rate of change when the pilot pressure acting on the tool control valve is turned on and off. Is.

  According to the first aspect of the present invention, when the tool is operated during the operation of the travel straight valve, the tool control valve is operated at a slow speed by the control means. Therefore, the travel control is performed from the first pump and the second pump. The rapid change of the flow rate supplied to the valve to the tool control valve can be prevented, thereby preventing the occurrence of shock due to a decrease in traveling speed when the tool is operated during straight traveling.

  According to the second aspect of the present invention, when the tool is operated during straight traveling and the tool operation is stopped by the speed limiter that limits the change speed when the pilot pressure acting on the tool control valve is turned on and off. It is possible to reliably prevent the occurrence of a shock due to a change in traveling speed at the time.

  Hereinafter, the present invention will be described in detail with reference to one embodiment shown in FIGS.

  FIG. 4 shows a work machine A according to the present invention. An upper swing body 3 that can be swung by a swing actuator 3m via a swing bearing portion 2 with respect to a lower travel body 1 having a travel actuator 1m on the left and right sides. Is provided, and the power unit 4 and the cab 5 are mounted on the upper swing body 3 to constitute the body B.

  The working device 6 is mounted on the machine body B. In the working device 6, the base end of the boom 7 is pivotally supported on the upper swing body 3 so as to be rotatable in the vertical direction, and an arm 8 is pivotally supported on the distal end of the boom 7. The tool 9 is pivotally supported in place of the bucket, the boom 7 is rotated in the vertical direction by the boom actuator 7a, that is, moved up and down, the arm 8 is rotated by the arm actuator 8a, and the tool 9 is It is actuated by the tool actuator 9a and rotated by the bucket actuator 9b.

  FIG. 1 shows a fluid control circuit 10 which is mounted on a work machine A and has a feature in a traveling / tool interlocking circuit. In the fluid control circuit 10, the working fluid is oil using hydraulic fluid, and the fluid pressure is hydraulic.

  The hydraulic circuit is roughly divided into a first working fluid supply circuit 10-1 shown on the right side in FIG. 1 and a second working fluid supply circuit 10-2 shown on the left side.

  The first working fluid supply circuit 10-1 includes a first center bypass in a discharge line 12-1 of a first variable displacement pump (drive pump directly connected to the engine) 11-1 as a first pump. The line 13-1, the straight travel valve 14 and the first hydraulic oil supply line 15-1 are connected to the first center bypass line 13-1 and the first hydraulic oil supply line 15-1, A travel control valve 16-1 and the like are connected.

  The second working fluid supply circuit 10-2 is connected to a discharge line 12-2 of a second variable displacement pump (idle pump connected to the engine via a drive pump) 11-2 as a second pump. The traveling straight valve 14, the second center bypass line 13-2, and the second hydraulic oil supply line 15-2 are connected, and the second center bypass line 13-2 and the second hydraulic oil supply line 15 are connected. The left travel control valve 16-2 and the tool bypass control valve 17 as a tool control valve are connected to -2.

  The straight travel valve 14 mainly uses the lower work switching position during normal work, but is switched to the upper travel position shown in FIG. 1 by excitation of the solenoid during straight travel. The straight traveling valve 14 includes an internal passage 14a having an orifice and a check valve. The internal passage 14a allows the discharge line 12-1 of the first variable displacement pump 11-1 and the second variable displacement pump 11 to be connected. -2 discharge line 12-2 is in communication.

  The traveling straight valve 14 supplies the discharge flow rate from the first variable displacement pump 11-1 only to the first working fluid supply circuit 10-1 at the lower work switching position, The discharge flow rate from the variable displacement pump 11-2 is supplied only to the second working fluid supply circuit 10-2, but at the upper switching position used during straight traveling shown in FIG. When the discharge pressure of the mold pump 11-2 is higher than the discharge pressure of the first variable displacement pump 11-1, the discharge flow rate from the first variable displacement pump 11-1 is set to the right travel control valve 16-1. In addition to supplying to the left travel control valve 16-2, the discharge flow rate from the second variable displacement pump 11-2 also passes through the internal passage 14a of the travel straight valve 14 to the right travel control valve 16-1 and left travel. Supply to control valve 16-2.

  That is, the traveling straight valve 14 switches to the traveling straight position shown in FIG. 1, and the discharge pressure of the second variable displacement pump 11-2 is greater than the discharge pressure of the first variable displacement pump 11-1. If it is high, the work switching position from the first variable displacement pump 11-1 and the second variable displacement pump 11-2 to the right travel control valve 16-1 and the left travel control valve 16-2. The flow rate almost twice that in the case can be supplied equally.

  The right traveling control valve 16-1 provided in the first working fluid supply circuit 10-1 and the left traveling control valve 16-2 provided in the second working fluid supply circuit 10-2 are respectively A bypass passage 16b for bypassing the hydraulic oil from the upstream side to the downstream side in the neutral position is provided therein, and the hydraulic oil discharged from the first and second variable displacement pumps 11-1 and 11-2 in the non-neutral position Is supplied to the left and right travel actuators 1m-1 and 1m-2 according to the travel lever operation amount.

  The tool bypass control valve 17 provided in the second working fluid supply circuit 10-2 includes therein a bypass passage 17b for bypassing hydraulic oil from the upstream side to the downstream side in the neutral position, and in the switching position, the output line. 18 is a spool valve that supplies hydraulic oil to the tool control valve 19 via 18, and the tool control valve 19 supplies hydraulic oil that has been direction-controlled and flow-controlled to the tool actuator 9a.

  Downstream portions of the center bypass lines 13-1 and 13-2 are connected to a hydraulic oil storage tank 25 via pressure setting valves, that is, relief valves 23-1, 23-2 and throttles 24-1, 24-2. The negative control lines 26-1, 26-2 are branched immediately before the relief valves 23-1, 23-2 and the throttles 24-1, 24-2, and are variable via the check valves 27-1, 27-2. The swash plates 28-1 and 28-2 of the displacement pumps 11-1 and 11-2 are connected to regulators 29-1 and 29-2.

  The variable displacement pumps 11-1 and 11-2 are mounted together with an engine (not shown) on the upper swing body 3 of the machine body B and driven by the engine. It is mounted near the upper pump and supplies hydraulic oil to the pump suction port.

  The negative control pressures of the negative control lines 26-1, 26-2 acting on the regulators 29-1, 29-2 are the spools of the left and right traveling control valves 16-1, 16-2 and the tool bypass control valve 17. It varies according to the stroke amount.

  That is, the larger the spool stroke amount of the travel control valves 16-1, 16-2 and the tool bypass control valve 17, the smaller the negative control pressure generated through the bypass passages 16b, 17b in these valves, As the negative control pressure is smaller, the regulators 29-1 and 29-2 control the pump capacity to be larger.

  Conversely, the spool strokes of the left and right traveling control valves 16-1 and 16-2 and the tool bypass control valve 17 are smaller, and the closer to the neutral position, the more they pass through the bypass passages 16b and 17b in these valves. The generated negative control pressure increases, and the higher the negative control pressure, the smaller the regulators 29-1 and 29-2 control the pump displacement.

  As described above, the first working fluid supply circuit 10-1 includes the first center bypass line 13-1 provided in the first variable displacement pump 11-1 together with the first working fluid supply line 15-1. Further, the negative control pressure is fed back through the negative control line 26-1, and the second working fluid supply circuit 10-2 supplies the second working fluid supply line 15- to the second variable displacement pump 11-2. The negative control pressure is fed back from the second center bypass line 13-2 provided together with 2 through the negative control line 26-2.

  A travel pedal 31 for operating the travel actuators 1m-1 and 1m-2, a tool lever 32 for operating the tool actuator 9a, and the like are connected to an input section of the control means 33, and an output section of the control means 33 includes A straight traveling valve 14, left and right traveling control valves 16-1, 16-2, a tool bypass control valve 17, a tool control valve 19, and the like are connected. FIG. 1 shows only the arrangement for the tool bypass control valve 17.

  The control means 33 has a function of causing the tool bypass control valve 17 to operate at a slow speed when the tool lever is operated while the travel straight valve 14 is in operation.

  That is, as shown in FIG. 2, the control means 33 includes a speed limiter 36 that limits the rate of change when the pilot pressure acting on the tool bypass control valve 17 is turned on and off. On the other hand, a status discriminator 37 for judging whether the straight traveling valve 14 is on / off, a pilot pressure setting unit 38 for setting a target pilot pressure for tool operation from the lever operation amount of the tool lever 32, and a tool bypass control valve A ramp value setting unit 39 for setting various conditions (a ramp gradient, a ramp gradient, a ramp gradient start pressure, a ramp gradient start pressure) relating to the gradient (ramp) of the pilot pressure change characteristic acting on 17 is connected.

  Next, the function and effect of the illustrated embodiment will be described.

  As shown in FIG. 3, the speed limiter 36 of the control means 33 limits the change speed of the pilot pressure when the pilot pressure is turned on or off in the tool bypass control valve 17 during straight running, Control is performed so that the ON signal is gradually increased and the OFF signal is gradually decreased.

  Therefore, when the tool lever 32 is operated during the straight traveling by the traveling straight valve 14, the speed limiter 36 of the control means 33 opens the tool bypass control valve 17 slowly. Further, when the tool lever 32 is operated to return while traveling straight ahead, the speed limiter 36 of the control means 33 slowly closes the tool bypass control valve 17.

  Since the amount of oil discharged by the second variable displacement pump 11-2 is the sum of the spool drive amount of the left travel control valve 16-2 and the spool drive amount of the tool bypass control valve 17, the travel straight valve If the opening area of the tool bypass control valve 17 is small while the 14 is driven, the discharge pressure of the second variable displacement pump 11-2 increases. When the discharge pressure of the second variable displacement pump 11-2 increases, the hydraulic fluid discharged from the second variable displacement pump 11-2 passes through the internal passage 14a such as an orifice in the traveling straight valve 14 or the like. As a result, the traveling speed does not decrease so much because it flows into the left and right traveling actuators 1m-1 and 1m-2.

  At this time, since the tool bypass control valve 17 is slowly opened as described above, the discharge pressure of the second variable displacement pump 11-2 is also slowly lowered and the traveling speed is also slowly lowered. For this reason, even if the tool actuator 9a is operated during independent traveling, the traveling speed does not change suddenly, so that there is no shock of circuit switching and the operation can be performed smoothly.

  If the opening of the tool bypass control valve 17 is set to be smaller than usual, the traveling speed at the time of interlocking can be adjusted.

  Thus, when interlocking operation of the travel actuators 1m-1, 1m-2 and the tool actuator 9a, in order to ensure the straight travel performance, the solenoid of the travel straight valve 14 is excited, and the travel actuator 1m-1, When 1m-2 is driven by the first variable displacement pump 11-1 and the tool actuator 9a is driven by the second variable displacement pump 11-2, the discharge pressure of the second variable displacement pump 11-2 Is higher than the discharge pressure of the first variable displacement pump 11-1, the discharged oil of the second variable displacement pump 11-2 passes through the internal passage 14a of the travel straight valve 14 and travel actuator 1m-1, It flows into 1m-2.

  On the other hand, if the tool operating pressure supplied from the second variable displacement pump 11-2 is not sufficiently higher than the traveling operating pressure supplied from the first variable displacement pump 11-1, the traveling actuator 1m- 1,1m-2 will be operated only by the first variable displacement pump 11-1, and if the tool 9 is operated while the travel pedal 31 is fully operated, the travel speed will be reduced to about half at a stretch. A big shock occurs. Therefore, when the tool 9 is operated during traveling, the discharge pressure of the second variable displacement pump 11-2 is kept high by slowly opening the tool bypass control valve 17 by the speed limiter 36 of the control means 33. In this manner, the hydraulic oil of the second variable displacement pump 11-2 flows into the travel actuators 1m-1 and 1m-2 via the internal passage 14a of the travel straight valve 14, and the tool lever 32 is The shock is reduced by preventing the running speed from suddenly dropping at the moment of turning on.

  As described above, when the tool is operated during the operation of the straight travel valve 14, the speed limiter 36 of the control means 33 operates the tool bypass control valve 17 at a slow speed, so that the first variable displacement pump 11-1 and the first variable displacement pump 11-1 This prevents sudden changes in the flow rate supplied to the control valve 16-1 and 16-2 for traveling from the variable displacement pump 11-2 of No. 2 to the tool bypass control valve 17. It is possible to prevent the occurrence of a shock due to a decrease in the traveling speed at the time.

  In other words, the speed limiter 36 that limits the speed at which the pilot pressure acting on the tool bypass control valve 17 is turned on and off, changes the running speed when the tool is operated during straight running and when the tool is stopped. It is possible to reliably prevent the occurrence of shock due to. Furthermore, since it is possible to prevent the occurrence of a shock due to the tool operation during the traveling of the machine body, the riding comfort of the work machine A can be improved, and the tool 9 can be operated without any trouble during traveling, so that the work efficiency can be improved by simultaneous operation.

  INDUSTRIAL APPLICABILITY The present invention can be used for a work machine having a straight traveling function by a traveling straight valve.

It is a circuit diagram showing one embodiment of a fluid control circuit concerning the present invention. It is a block diagram which shows the structure of the control means of a fluid control circuit same as the above. It is explanatory drawing explaining the function of the speed limiter of a fluid control circuit same as the above. It is a side view of the working machine provided with the fluid control circuit same as the above.

Explanation of symbols

1m-1, 1m-2 Traveling actuator
9a Tool actuator
11-1 First variable displacement pump as the first pump
11-2 Second variable displacement pump as second pump
14 Travel straight valve
16-1, 16-2 Driving control valve
17 Bypass control valve for tools as a control valve for tools
33 Control means
36 Speed limiter

Claims (2)

A pair of travel control valves for controlling the working fluid respectively supplied from the first pump and the second pump to the pair of travel actuators;
A tool control valve for controlling the working fluid supplied from the second pump to the tool actuator;
A traveling straight valve for supplying an equal flow of working fluid from the first pump and the second pump to the pair of traveling control valves by switching to the traveling linear position;
A fluid control circuit comprising: control means for causing the tool control valve to operate at a slow speed when a tool is operated during operation of the straight traveling valve. The control means
The fluid control circuit according to claim 1, further comprising a speed limiter that limits a change speed when the pilot pressure acting on the tool control valve is turned on and off.

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