JP2013249900A - Hydraulic drive circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic drive circuit in which for flow rates of a supply side to and a discharge side from an actuator are individually controlled, the hydraulic drive circuit not generating useless pressure loss even when a load direction changes during work, and achieving an actuator speed according to an operation amount.SOLUTION: An operation lever 10 outputs an operation signal based on an operation amount to a computing device 11. The computing device 11 determines a target speed v of an arm cylinder according to the operation amount, and calculates target flow rates Qb and Qr to a bottom side hydraulic chamber and a rod side hydraulic chamber based on the target speed v, and a bottom side hydraulic chamber sectional area Ab and a rod side hydraulic chamber sectional area Ar of the arm cylinder. Then, on the basis of the target flow rates Qb and Qr, pressure Pp from a pressure sensor 7, pressures Pb and Pr from pressure sensors 8 and 9, a flow rate coefficient C of hydraulic fluid, and a viscosity coefficient ρ of the hydraulic fluid, the computing device 11 calculates a target opening area Aof a direction control valve 3 and a target opening area Aof a direction control valve 4. Then, the direction control valves 3 and 4 are independently controlled to achieve the target opening areas Aand A.

Description

  The present invention relates to a hydraulic drive circuit for a work machine such as a hydraulic excavator.

  In a hydraulic drive circuit that controls the pressure oil supplied from the hydraulic pump to the hydraulic actuator, a meter-in spool valve that controls the flow rate of the pressure oil supplied to the hydraulic actuator, and a meter-out that controls the pressure on the supply side of the hydraulic actuator A spool valve, a multiplier for multiplying the pressure on the supply side of the hydraulic actuator controlled by the meter-out spool valve by a pressure gain β, a subtractor for subtracting the operation value of the multiplier from the command flow rate Qc, and an operation value of the subtractor There is an opening control means having an electromagnetic actuator that operates a meter-in spool valve in accordance with the control and controls an opening area (see Patent Document 1).

    JP-A-6-193605

  Generally, in a hydraulic actuator drive circuit, pressure oil discharged by a hydraulic pump is guided to a hydraulic actuator via a direction control valve, and at the same time, pressure oil discharged from the hydraulic actuator is hydraulically transmitted via a direction control valve. The circuit configuration leads to the tank.

In such a hydraulic drive circuit, the direction control valve normally controls the flow rate of the pressure oil guided to the hydraulic actuator by switching the direction in which the pressure oil is guided and simultaneously adjusting the opening area.
However, since the opening areas on the supply side and the discharge side of the hydraulic actuator are controlled by a single directional control valve, the combination of the opening areas of both paths is uniquely set at the time of design.

  A general method for determining the opening area of the directional control valve is as follows. When a load is applied to the hydraulic actuator in a direction that follows the operation direction, the opening area on the discharge side of the hydraulic actuator is set to be reduced in order to prevent the operation from escaping. Further, when a load in a direction opposite to the operation direction is generated in the hydraulic actuator, the opening area on the supply side is set to be reduced. As a result, the actuator speed is controlled without causing unnecessary pressure on the discharge side path.

However, there are many hydraulic actuators for work machines whose load direction changes during work depending on the work state.
For example, an arm cylinder of a work machine such as a hydraulic excavator is moved forward by its own weight until the arm trajectory reaches bottom dead center or until the bucket toe reaches the ground and excavation starts. A load is generated. After the bottom dead center of the arm trajectory or after excavation starts, a load in the opposite direction is generated in the operation due to the weight of the arm and excavation resistance.

When controlling the speed of the hydraulic actuator in which the load direction changes, it is usually set so that the discharge-side opening area is reduced in order to prevent the escape of the operation in consideration of safety.
However, in a circuit that controls the opening area on the supply side and the discharge side of these hydraulic actuators with a single directional control valve, the pressure loss that occurs at the meter-out opening after the actuator load is in the opposite direction to the operation. There is no use and there is a problem in terms of energy saving.

Further, in a hydraulic drive apparatus such as Patent Document 1 that individually controls the opening area on the supply side and the discharge area on the hydraulic actuator, the opening area of the meter-in spool valve is determined according to the pressure controlled by the meter-out spool valve. Therefore, when the actuator is under a forward load, the operating amount of the operating lever does not correspond to the speed of the hydraulic actuator, and the operating amount of the operating lever corresponds to the force of the hydraulic actuator. turn into.
For this reason, as in the case of the hydraulic drive circuit that controls the opening area of the supply side and the discharge side of the hydraulic actuator with a single directional control valve, a scene of force control of the hydraulic actuator occurs, and the hydraulic pressure according to the operation amount of the operator There is a problem that the actuator speed cannot be obtained.

  Thus, in the operation of the hydraulic actuator in which speed controllability is important, the operability does not match the operator's sense of operation, and the operability may be deteriorated.

  In the hydraulic drive circuit that individually controls the flow rate of pressure oil on the supply side to the hydraulic actuator and on the discharge side of the hydraulic actuator, the present invention does not cause useless pressure loss even when the load direction changes during work. And a hydraulic drive circuit capable of realizing the speed of the hydraulic actuator in accordance with the operation amount of the operator.

  In order to achieve the above object, the first invention provides a hydraulic pump, a hydraulic actuator driven by pressure oil discharged from the hydraulic pump, and a flow rate of pressure oil supplied from the hydraulic pump to the hydraulic actuator. A first flow rate control unit for controlling the pressure, a second flow rate control unit for controlling the flow rate of the pressure oil discharged from the hydraulic actuator to the tank, and a flow rate of the pressure oil discharged from the hydraulic actuator to the hydraulic actuator. And control means for controlling the first flow rate control unit and the second flow rate control unit so as to be larger than the flow rate of the pressure oil.

  According to a second aspect of the present invention, in the first aspect, the control means detects the hydraulic actuator from a differential pressure detecting means for detecting a differential pressure across the first and second flow rate control units and an operation amount of an operating lever. A signal obtained from a target flow rate calculation means for calculating a target flow rate to be supplied to and discharged from the system is fetched, and the opening area of the first flow rate control unit is controlled based on the differential pressure across the first flow rate control unit and the target flow rate. And outputting a command for controlling the opening area of the second flow rate control unit to the first flow rate control unit and the second flow rate control unit based on the differential pressure across the second flow rate control unit and the target flow rate, respectively. It is characterized by.

Further, according to a third aspect, in the second aspect, the control means calculates a target speed calculation unit that calculates a target speed of the hydraulic actuator from an operation amount signal of an operation lever, and the target speed calculation unit calculates the target speed. A target flow rate calculation unit that calculates a target flow rate of pressure oil to the hydraulic actuator for driving the hydraulic actuator at a target speed, the target flow rate of pressure oil calculated by the target flow rate calculation unit, and the differential pressure detection A target opening area calculation unit for calculating a target opening area of the first and second flow rate control units based on the differential pressure across the first and second flow rate control units detected by the means; and the target opening And a command calculation unit that calculates command signals for driving the first and second flow rate control units so as to be the target opening area calculated by the area calculation unit.

  According to a fourth aspect of the invention, in the second or third aspect of the invention, the first flow rate control unit is disposed between the hydraulic pump and one oil chamber of the hydraulic actuator, and the second flow rate control unit Is arranged between the hydraulic pump and the other oil chamber of the hydraulic actuator, and the control means takes in signals obtained from the differential pressure detection means and the target flow rate detection means, and the first flow rate control unit And adjusting the opening area of the second flow rate control unit so that the flow rate of the pressure oil discharged from the hydraulic actuator is controlled to be larger than the flow rate of the pressure oil supplied to the hydraulic actuator.

  According to a fifth invention, in any one of the first to third inventions, a makeup is provided between the first flow rate control unit and the hydraulic actuator and between the second flow rate control unit and the hydraulic actuator. An up check valve is further provided.

  According to a sixth aspect, in any one of the first to third aspects, the hydraulic actuator is an arm cylinder that drives an arm of a work machine.

  According to the present invention, even when the load direction changes during work of the work machine, the speed of the hydraulic actuator according to the operation amount of the operator can be realized without causing unnecessary pressure loss. The operability of the hydraulic actuator where controllability is important can be improved. As a result, productivity of the work machine and mental fatigue of the operator can be reduced.

It is a side view of a hydraulic excavator provided with a hydraulic drive circuit of the present invention. It is a lineblock diagram showing the outline of a 1st embodiment of the hydraulic drive circuit of the present invention. It is a block diagram which shows the control logic of the direction control valve in 1st Embodiment of the hydraulic drive circuit of this invention. It is a block diagram which shows the control logic of the tilt angle of the hydraulic pump in 1st Embodiment of the hydraulic drive circuit of this invention. It is explanatory drawing which shows the operation | movement of the excavation operation | work of a hydraulic shovel provided with 1st Embodiment of the hydraulic drive circuit of this invention. It is a block diagram which shows the outline of 2nd Embodiment of the hydraulic drive circuit of this invention. It is a figure which shows the outline of the other form of the hydraulic drive circuit of this invention.

  Embodiments of a hydraulic drive circuit according to the present invention will be described below with reference to the drawings.

<First Embodiment>
A first embodiment of a hydraulic drive circuit according to the present invention will be described with reference to FIGS. FIG. 1 is a side view of a hydraulic excavator provided with the hydraulic drive circuit of the present invention, FIG. 2 is a configuration diagram showing an outline of the first embodiment of the hydraulic drive circuit of the present invention, and FIG. 3 is a diagram of the hydraulic drive circuit of the present invention. 4 is a block diagram showing the control logic of the directional control valve in the first embodiment, FIG. 4 is a block diagram showing the control logic of the tilt angle of the hydraulic pump in the first embodiment of the hydraulic drive circuit of the present invention, and FIG. It is explanatory drawing which shows the operation | movement of the excavation operation | work of a hydraulic shovel provided with 1st Embodiment of the hydraulic drive circuit of this invention.
1 to 5, a case where the present invention is applied to a hydraulic excavator as a work machine having a hydraulic drive circuit and an arm cylinder of the hydraulic excavator as a hydraulic actuator will be described as an example.

  In FIG. 1, the excavator includes a traveling body 100, a revolving body 101, and a front work machine 102.

  The traveling body 100 has left and right crawler traveling devices 103a and 103b, and is driven by left and right traveling motors 104a and 104b. The turning body 101 is mounted on the traveling body 100 so as to be able to turn, and is driven to turn by a turning motor (not shown). The front work machine 102 is attached to the front portion of the swing body 101 so as to be able to be raised and lowered. The revolving body 101 is provided with an engine room 106 and a cabin (operating room) 107. In the engine room 106, hydraulic devices such as an engine, a hydraulic pump 1 and a sub pump, which will be described later, are disposed. Has been placed.

  The front work machine 102 has an articulated structure having a boom 111, an arm 112, and a bucket 113. The boom 111 rotates in the vertical direction by the expansion and contraction of the boom cylinder 114, and the arm 112 moves in the vertical and longitudinal directions by the expansion and contraction of the arm cylinder 2. , And the bucket 113 is rotated up and down and back and forth by the expansion and contraction of the bucket cylinder 116.

Next, a first embodiment of the hydraulic drive circuit of the present invention will be described with reference to FIG.
FIG. 2 is a block diagram showing an outline of the hydraulic drive circuit for driving the arm cylinder 2 provided in the arm 112 of the hydraulic excavator in the first embodiment of the hydraulic drive circuit of the present invention. In addition, the same code | symbol is attached | subjected to the same part as the previous figure, and description is abbreviate | omitted (the following figure is also the same).

  In FIG. 2, the hydraulic drive circuit is provided in a hydraulic excavator as shown in FIG. 1, and includes a hydraulic pump 1 that discharges pressure oil, and an arm cylinder 2 (hydraulic actuator) that is driven by receiving the pressure oil. Have

In addition, a direction in which pressure oil from the hydraulic pump 1 is guided to the arm cylinder 2 to the pipe lines X1 and X2 connected to the hydraulic pump 1 and the bottom side oil chamber 2a and the piston rod side oil chamber 2b of the arm cylinder 2. The direction control valves 3 and 4 for switching are respectively arranged.
These directional control valves 3 and 4 are, in this example, a 2-port 3-position type, which switches the supply / discharge direction of pressure oil supplied / discharged to / from the arm cylinder 2 and at the same time functions as a throttle. And the flow rate of the pressure oil can be controlled by arbitrarily adjusting the opening area of the valve. Further, pipes X1 and X2 between the direction control valves 3 and 4 and the arm cylinder 2 are respectively provided with pipes X3 and X4 connected to the tank 6 via a make-up check valve 5.

  A pressure sensor 8 (first pressure gauge) is provided in the pipe line X <b> 1 between the direction control valve 3 and the arm cylinder 2. A pressure sensor 9 (second pressure gauge) is provided in the pipe line X <b> 2 between the direction control valve 4 and the arm cylinder 2. These pressure sensors 8 and 9 respectively detect the pressure oil pressure between the arm cylinder 2 and the direction control valves 3 and 4 and output the pressure oil to an arithmetic unit 11 (control means) described later.

  Further, a pressure sensor 7 (third pressure gauge) is provided in the pipe line X5 between the hydraulic pump 1 and the direction control valves 3 and 4. The pressure sensor 7 detects the pressure oil pressure between the hydraulic pump 1 and the direction control valves 3 and 4 and outputs the pressure oil to the arithmetic unit 11 described later. The first pressure gauge, the second pressure gauge, and the third pressure gauge are configured as differential pressure detecting means for detecting the differential pressure across the first and second flow rate control units.

  An operating lever 10 for operating the operating direction of the arm cylinder 2 is provided in the cabin 107 of the excavator. The operation lever 10 includes an operation amount detector 10 a that detects an operation amount of the operator, and outputs an operation signal detected by the operation amount detector 10 a to the arithmetic device 11.

  The arithmetic unit 11 determines the opening area of the direction control valves 3 and 4 and the command value of the tilt angle of the hydraulic pump 1 according to the detection values detected by the operation amount detector 10 a of the operation lever 10 and the pressure sensors 7, 8 and 9. And the direction control valves 3 and 4 are controlled so that the flow rate of the pressure oil discharged from the hydraulic actuator is larger than the flow rate of the pressure oil supplied to the hydraulic actuator based on the calculation result.

  Further, the directional control valves 3 and 4 are respectively provided with pilot solenoid valves 12, 13, 14, and 15 for supplying pilot pressure oil to the operation portions. The swash plate adjuster 1 </ b> A of the hydraulic pump 1 is provided with a pilot solenoid valve 16 that supplies pressure oil for adjusting the inclination angle of the swash plate.

Next, the detailed configuration of the arithmetic unit 11 will be described with reference to FIGS.
3 and 4, reference numerals shown in FIGS. 1 and 2 are the same parts, and thus detailed description thereof is omitted.
The arithmetic unit 11 takes in the arm cloud operation signal from the operation amount detector 10a of the operation lever 10, and determines the target speed v of the arm cylinder 2 according to the “lever operation amount / cylinder speed” characteristic map stored in the storage unit in advance. The product of the target speed calculation unit 11a, the target speed v determined by the target speed calculation unit 11a, the cross-sectional area Ab of the bottom side oil chamber 2a of the arm cylinder 2 and the cross-sectional area Ar of the rod side oil chamber 2b is obtained. A target flow rate calculation unit 11b that calculates a target flow rate Qb of pressure oil to the bottom side oil chamber 2a and a target flow rate Qr of pressure oil to the rod side oil chamber 2b, and a target flow rate calculated by the target flow rate calculation unit 11b qb, a target opening area calculating section 11c for calculating a target opening area a ₄ of the target opening area a ₃ and the directional control valve 4 of the directional control valve 3 from Qr, the target opening area a computed , So as to drive the directional control valve 3, 4 according to _{A 4,} the pilot solenoid valves 12, 13, 14, 15, stored in advance in the storage unit each "target area / solenoid valve command value" characteristic map 11d _{1 to} 11d ₄ and a solenoid valve command current value calculation unit 11d that outputs a current value signal. The target flow rate calculation unit 11b and the target speed calculation unit 11a are configured as target flow rate calculation means.
Among these, the target opening area calculation unit 11c, more specifically, when the sign of the target flow rate calculated by the target flow rate calculation unit 11b is +, the calculated target flow rate Qb, Qr, the direction control input from the pressure sensor 7 Based on the pressure Pp before the valves 3 and 4, the pressures Pb and Pr after the direction control valves 3 and 4 input from the pressure sensors 8 and 9, the flow coefficient C and the viscosity coefficient ρ of the hydraulic oil being used, According to (1) and (2), the target opening area A ₃ of the directional control valve ₃ and the target opening area A ₄ of the directional control valve ₄ are respectively calculated. Pp-Pb and Pp-Pr are the differential pressures ΔP across the directional control valves 3 and 4, respectively.

A ₃ = Qb / C (ρ / 2 (Pp−Pb)) ^1/2 (1)
A ₄ = Qr / C (ρ / 2 (Pp−Pr)) ^1/2 (2)

When the sign of the target flow rate is-, the pressure before the direction control valves 3 and 4 is Pb, Pr, the pressure after the direction control valves 3 and 4 is 0 (tank pressure), and the coefficient K is added to the target flow rate. According to (3) and (4), the target opening areas A ₃ and A ₄ of the direction control valves 3 and ₄ are calculated, respectively.

A ₃ = (Qb + K) / C (ρ / 2Pb) ^1/2 (3)
A ₄ = (Qr + K) / C (ρ / 2Pr) ^1/2 (4)

The target speed v has a sign of + − depending on the driving direction of the arm cylinder 2, and the arm cloud direction is set to +.

  The arithmetic unit 11 selects a pressure on the supply side to each hydraulic actuator such as the arm cylinder 2 (the pressure is zero when no operation is performed), and each actuator selected by the condition arithmetic unit 11e. A maximum value calculator 11f that selects the supply-side maximum pressure when a plurality of actuators are operated simultaneously from the supply-side pressure, and a certain coefficient L to the supply-side maximum pressure Pmax selected by the maximum value calculator 11f. The condition calculator 11g that calculates the sum as the pump discharge target pressure P0, the discharge target pressure P0 calculated by the condition calculator 11g, and the pump discharge pressure (pressure before the direction control valves 3 and 4) detected by the pressure sensor 7 ) A calculator 11h that calculates the difference from Pp, and a swash plate adjustment that drives the tilt of the swash plate of the hydraulic pump 1 to fill the difference calculated by the calculator 11h. And an output unit 11i for outputting the output current value to the solenoid valve 16 supplies pressure oil to 1A.

  Next, the operation of the above-described first embodiment of the hydraulic drive circuit of the present invention will be described with reference to FIGS.

  Assume that an operator performs an arm cloud operation on the operation lever 10 in a hydraulic excavator provided with a hydraulic drive circuit as shown in FIG. The operation lever 10 that has received this arm cloud operation outputs an arm cloud operation signal corresponding to the operation amount to the arithmetic unit 11 as shown in FIG.

Receiving this arm cloud operation signal, the arithmetic unit 11 determines the target speed v of the arm cylinder 2 in the target speed calculator 11a as shown in FIG.
Thereafter, in the target flow rate calculation unit 11b, the target flow rate Qb (= Ab · v) of the pressure oil from the previously determined target speed v to the bottom side oil chamber 2a of the arm cylinder 2 and the pressure oil to the rod side oil chamber 2b. The target flow rate Qr = (− Ar · v) is calculated (here, the area of the rod side oil chamber 2b is given a minus sign, and the target flow rate Qr to the rod side oil chamber 2b is −).
Then, the target opening area calculating section 11c, the target opening area A ₃ of the directional control valve 3 for supplying pressure oil to the bottom side oil chamber 2a formula (1), the pressure oil from the rod side oil chamber 2b emissions a target opening area a ₄ of the directional control valve 4 for calculating respectively on the basis of equation (4).
Next, the solenoid valve command current value computing section 11d, based on the characteristic map 11d ₁ of the top with respect to the direction control valve 3 to the target opening area A ₃ has a positive sign, the target opening area A ₄ is - for directional control valve 4 to be code based on the characteristic map 11d ₄ bottom calculates the current value signal to the pilot solenoid valves 13 and 15, and outputs.
The pilot solenoid valves 13 and 15 that have received this current value signal supply pilot pressures to the operation portions of the direction control valves 3 and 4 in order to drive the spool so that the pressure oil flows according to the target flow rate.
Therefore, the direction control valve 3 functions as a first flow rate control unit that controls the flow rate of the pressure oil supplied to the arm cylinder 2, and the direction control valve 4 controls the flow rate of the pressure oil discharged from the arm cylinder 2. Functions as a flow control unit.

More specifically, in the cloud operation of the arm 112, until the arm trajectory reaches bottom dead center (range A in FIG. 5A), or until the tip of the bucket 113 reaches the ground and excavation starts ( In the range of A in FIG. 5B, a forward load is generated in the operation due to the weight of the arm 112, so the speed of the arm cylinder 2 is determined according to the flow rate on the discharge side of the arm cylinder 2.
At this time, when the opening area control in the direction control valve 3 on the supply side and the direction control valve 4 on the discharge side is accurately performed, or when the control variation occurs, the opening area of the direction control valve 4 is the target. It is larger than the opening area a ₄ consider the case where the exhaust flow rate than the target flow rate Qr is increased. In these cases, the arm cylinder 2 operates at a speed corresponding to the flow rate on the discharge side, that is, a speed approximately corresponding to the operation amount of the operation lever 10, and the pressure in the supply line X1 tends to be negative. Since an insufficient flow rate is sucked from the hydraulic tank 6 through the check valve 5, negative pressure in the pipe line X <b> 1 is suppressed. Further, even if the variation in the control opening area of the directional control valve 3 occurs becomes larger supply flow rate than a target opening area A ₃ from becoming larger target flow rate Qb, originally target opening area A ₄ are coefficients of discharge side Since it is increased by K, the arm cylinder 2 operates at a speed corresponding to the flow rate on the discharge side (speed corresponding to the operation amount of the operation lever 10), and in the same manner within the flow rate range corresponding to the coefficient K. Oil is sucked from the tank 6 so as to compensate for the insufficient flow rate from the tank 6 in the pipe X1. For this reason, the pressure loss generated on the supply side can be utilized without wasting as much as the coefficient K.

Further, after the bottom dead center of the arm trajectory (range B in FIG. 5 (A)) or after excavation starts (range B in FIG. 5 (B)), the arm 112 is operated by its own weight and excavation resistance. A reverse load is generated. In this case, the speed of the arm cylinder 2 is determined according to the flow rate on the supply side of the arm cylinder 2.
At this time, when the opening area control on the supply side and the discharge side is accurately performed, or when the discharge flow rate becomes larger than the target flow rate due to control variations, the direction control valve 4 opens as desired. However, since the discharge pressure is insufficient due to the relationship with the opening area on the direction control valve 3 side, the flow rate of the discharged pressure oil is limited, but the arm cylinder 2 has a speed corresponding to the flow rate on the supply side, that is, an operation lever. It operates at a speed corresponding to the operation amount of 10. Speed The supply flow rate by the variation of the control even if has become larger than the target value, in order originally target opening area A ₄ of the discharge side is large by a factor K min, the arm cylinder 2 in response to the flow rate of the supply-side It operates at a speed approximately corresponding to the amount of operation of the control lever 10 and the discharge flow rate is similarly limited within the flow rate range of the coefficient K, but the pressure loss generated on the supply side is wasted by the factor K. You can use it without doing it.

  According to the first embodiment of the present invention described above, the operation lever can be operated even when a load is applied to the arm cylinder 2 in a direction following the operation direction or a load against the operation direction. The amount can correspond to the speed of the arm cylinder 2 without limit. For this reason, even when the load direction changes during work, the speed of the arm cylinder 2 corresponding to the operation amount of the operation lever 10 by the operator can be obtained, and the operability can be improved. At the same time, it is possible to suppress generation of useless pushing pressure on the supply side of the arm cylinder 2 and to prevent generation of useless pressure loss. Therefore, it is possible to improve the operability of the hydraulic actuator in which speed controllability is important, and as a result, the productivity of the work machine and the mental fatigue of the operator can be reduced.

<Second Embodiment>
A second embodiment of the hydraulic drive circuit of the present invention will be described with reference to FIG. FIG. 6 is a block diagram showing an outline of the second embodiment of the hydraulic drive circuit of the present invention.
The second embodiment of the hydraulic drive circuit is mounted on a hydraulic excavator, and is substantially the same as the first embodiment of the hydraulic drive circuit in that the arm cylinder 2 is driven. Description is omitted.

As shown in FIG. 6, in the second embodiment of the hydraulic drive circuit of the present invention, the pressure oil from the hydraulic pump 1 is switched and supplied to the bottom side oil chamber 2a and the rod side oil chamber 2b of the arm cylinder 2. Flow rate adjusting valves 23 and 24 for controlling the flow rate of the pressure oil are arranged in the pipe lines X6 and X7, respectively.
These flow rate adjusting valves 23 and 24 can arbitrarily adjust the opening area of the valve based on a control command from the arithmetic unit 21 to be described later, thereby controlling the flow rate of the pressure oil flowing through these valves. It is configured to be able to. Further, pipes X6 and X7 between the flow rate adjusting valves 23 and 24 and the arm cylinder 2 are respectively provided with pipes X8 and X9 connected to the tank 6 through the make-up check valve 5.

  In addition, pressure oil supplied to and discharged from the arm cylinder 2 is connected to the pipe X10 between the hydraulic pump 1 and the flow rate adjusting valves 23 and 24 and to the pipe X11 between the tank 6 and the flow rate adjusting valves 23 and 24. A direction control valve 22 for switching the supply / discharge direction is provided.

  Further, a pressure sensor 7 is provided in the pipe line X 10 between the hydraulic pump 1 and the direction control valve 22. Further, a pressure sensor 8 is provided in a pipe line X6 between the flow rate adjusting valve 23 and the arm cylinder 2, and a pressure sensor 9 is provided in a pipe line X7 between the flow rate adjusting valve 24 and the arm cylinder 2. These pressure sensors 7, 8, 9 detect the pressure oil pressure in the respective pipelines X 10, X 6, X 7 and output them to the arithmetic unit 21.

  The arithmetic unit 21 determines the operation direction of the direction control valve 22, the opening area of the flow rate adjusting valves 23 and 24, and the tilt angle of the hydraulic pump 1 according to the detection values detected by the operation lever 10 and the pressure sensors 7, 8, and 9. The flow rate adjusting valves 23 and 24 and the direction control valve are calculated so that the flow rate of the pressure oil discharged from the arm cylinder 2 is larger than the flow rate of the pressure oil supplied to the arm cylinder 2 based on the calculation result. 22 is controlled.

  Further, the flow rate adjusting valves 23 and 24 are respectively provided with pilot electromagnetic valves 25 and 26 for supplying pilot pressure oil. The directional control valve 22 is provided with pilot solenoid valves 27 and 28 for supplying pilot pressure oil to the operation portion.

The arithmetic device 21 in the second embodiment of such a hydraulic drive circuit, like the arithmetic device 11 of the hydraulic drive circuit in the first embodiment, when the operator performs an arm cloud operation on the operation lever 10, The target speed v of the arm cylinder 2 is determined in accordance with the “lever operation amount / cylinder speed” characteristic map stored in advance in the storage unit. Thereafter, the target flow rate Qb, Qr is calculated by taking the product of the previously determined target speed v and the cross-sectional areas Ab, -Ar of the bottom side oil chamber 2a and the rod side oil chamber 2b of the arm cylinder 2, and this target flow rate Qb , Qr, the pressure Pp before the flow rate adjusting valves 23, 24 input from the pressure sensor 7, the pressures Pb, Pr after the flow rate adjusting valves 23, 24 input from the pressure sensors 8, 9, the flow coefficient C of the hydraulic oil, and Based on the viscosity coefficient ρ, the target opening areas A ₂₃ and A ₂₄ are calculated in accordance with the above-described equations (1)-(4) (note that the front-rear differential pressure ΔP of the flow rate adjusting valves 23, 24 has a flow rate sign of + (Pp-Pr or Pp-Pr on the supply side, and Pb or Pr on the discharge side where the flow rate sign is-). Then, in order to drive the flow rate adjusting valves ₂₃ , ₂₄ according to the target opening areas A ₂₃ , A ₂₄ , the “target area / solenoid valve command” previously stored in the storage unit is stored for each pilot electromagnetic valve 23, 24. A current value signal is output according to the “value” characteristic map.

  Also in the second embodiment of the hydraulic drive circuit of the present invention, substantially the same effect as that of the first embodiment of the hydraulic drive circuit described above, that is, a load is applied to the arm cylinder 2 in the direction following the operation direction. Even when a load is applied in the direction opposite to the operation direction, the operation amount of the operation lever can be made to correspond to the speed of the arm cylinder 2 as much as possible, and even when the load direction changes during the operation, the operation lever of the operator The speed of the arm cylinder 2 corresponding to the operation amount of 10 can be obtained and the operability can be improved, and at the same time, the generation of useless pushing pressure on the supply side of the arm cylinder 2 can be suppressed. Generation of excessive pressure loss can be prevented. Therefore, it is possible to improve the operability of the hydraulic actuator in which speed controllability is important, and as a result, the effect of reducing the productivity of the work machine and the mental fatigue of the operator can be obtained.

<Others>
In addition, this invention is not restricted to said embodiment, A various deformation | transformation and application are possible.

For example, the flow rate on the discharge side is controlled to be larger than the flow rate on the supply side by an amount corresponding to the factor K, but the flow rate on the supply side is set to an amount corresponding to the factor K rather than the flow rate on the discharge side. It is also possible to control to reduce the number.
In this case, taking the same configuration as that of the first embodiment as an example, the arithmetic unit calculates A ₃ and A ₄ when the target flow rate value is + when calculating the target opening areas A ₃ and A _4. = (Q−K) / C (ρ / 2ΔP) ^1/2 , and when the sign of the target flow rate value is −, according to the formula of A ₃ , A ₄ = (Q) / C (ρ / 2ΔP) ^1/2 , In accordance with the target opening areas A ₃ and A ₄ , current value signals are output to the pilot solenoid valves 12, 13, 14 and 15.
Even with this configuration, the supply-side opening area and the discharge-side opening area can be controlled so that the flow rate on the discharge side is larger than the supply side in accordance with the input / output flow rate ratio calculated from the specifications of the hydraulic actuator. The same effect can be obtained.
Further, when the target flow rates Qb and Qr are calculated, the sign of the area of the rod side oil chamber 2b is given, but the same is true even if the sign of the area of the bottom side oil chamber 2a of the arm cylinder 2 is given. An effect is obtained.

  Further, the coefficient K in the above formulas (3) and (4) is desirably adjusted as appropriate so that the increase in the supply flow rate inevitably generated due to control variations does not fall outside the range of the coefficient K. This prevents the shortage from being replenished from the tank or the discharge flow rate not being restricted, thereby preventing deterioration of controllability in operation and occurrence of unnecessary pushing pressure on the actuator. be able to.

  In addition, an example has been shown in which the arm cylinder 2 is attached so that the cylinder extends during the arm cloud operation and contracts during the arm dump operation. Conversely, the cylinder contracts during the arm cloud operation and extends during the arm dump operation. Even if attached, the present invention is applied.

Although the case where the hydraulic drive circuit of the present invention is applied to the arm cylinder 2 as a hydraulic actuator has been described, other hydraulic actuators such as a boom cylinder 114 and a bucket cylinder 116, left and right traveling motors 104a and 104b, a swing The hydraulic drive circuit of the present invention can also be applied to a hydraulic drive circuit intended for a motor.
Furthermore, as shown in FIG. 7, the present invention can be applied even if a circuit similar to a hydraulic drive circuit for driving the arm cylinder 2 is connected in parallel to the tip of the hydraulic pump 1. For example, as shown in FIG. 7, the present invention can also be applied when a hydraulic drive circuit for driving the boom cylinder 114 and the bucket cylinder 116 and a hydraulic circuit for driving the left and right traveling motors 104a and 104b are connected simultaneously. It is.

  Further, the present invention is applied to the arm cylinder 2 of the backhoe shovel as shown in FIG. 1, but the present invention can also be applied to a hydraulic drive circuit of any hydraulic actuator of the loading shovel.

  Furthermore, although the hydraulic excavator is taken as an example of the work machine, the work machine is not limited to this, and for example, the present invention can be applied to other work machines such as a crane truck.

1 ... Hydraulic pump,
1A ... Swash plate adjuster,
2 ... arm cylinder,
2a ... Bottom side oil chamber,
2b ... Rod side oil chamber,
3, 4 ... Directional control valve,
5 ... Check valve,
6 ... Hydraulic tank,
7, 8, 9 ... pressure sensor,
10 ... Control lever,
10a ... manipulated variable detector,
11, 21 ... arithmetic device,
11a ... target speed calculation unit,
11b ... target flow rate calculation unit,
11c ... Target opening area calculation unit,
11d ... Solenoid valve command current value calculation unit,
11e ... Conditional calculator,
11f: Maximum value calculator,
11g ... Conditional calculator,
11h: arithmetic unit,
11i ... output machine,
12, 13, 14, 15, 16, 25, 26, 27, 28 ... pilot solenoid valve,
22 ... Directional control valve,
23, 24 ... Flow control valve,
100 ... traveling body,
101 ... revolving body,
102 ... Front working machine,
103a ... traveling device,
104a ... travel motor,
106 ... Engine room,
107 ... cab (cabin),
111 ... Boom,
112 ... arm,
113 ... bucket,
114 ... Boom cylinder,
116 ... bucket cylinder,
X1, X2, X3, X4, X5, X6, X7, X8, X9, X10, X11.

Claims (6)

A hydraulic pump;
A hydraulic actuator driven by the pressure oil discharged by the hydraulic pump;
A first flow rate controller that controls the flow rate of pressure oil supplied from the hydraulic pump to the hydraulic actuator;
A second flow rate controller for controlling the flow rate of the pressure oil discharged from the hydraulic actuator;
Control means for controlling the first flow rate control unit and the second flow rate control unit so that the flow rate of the pressure oil discharged from the hydraulic actuator is larger than the flow rate of the pressure oil supplied to the hydraulic actuator. A hydraulic drive circuit characterized by that. The hydraulic drive circuit according to claim 1, wherein
The control means includes
Signals obtained from a differential pressure detecting means for detecting the differential pressure across the first and second flow rate control units and a target flow rate calculating means for calculating a target flow rate to be supplied to and discharged from the hydraulic actuator from an operation amount of the operating lever, respectively. Taking in, controlling the opening area of the first flow rate control unit based on the differential pressure across the first flow rate control unit and the target flow rate, and based on the differential pressure across the second flow rate control unit and the target flow rate A hydraulic drive circuit, wherein a command for controlling an opening area of the second flow rate control unit is output to each of the first flow rate control unit and the second flow rate control unit. In the hydraulic drive circuit according to claim 2,
The control means includes
A target speed calculator for calculating a target speed of the hydraulic actuator from an operation amount signal of an operation lever;
A target flow rate calculation unit for calculating a target flow rate of pressure oil to the hydraulic actuator for driving the hydraulic actuator at the target speed calculated by the target speed calculation unit;
Based on the target flow rate of the pressure oil calculated by the target flow rate calculation unit and the differential pressure before and after the first and second flow rate control units detected by the differential pressure detection means, the first and second A target opening area calculation unit for calculating a target opening area of the flow rate control unit;
A hydraulic drive circuit comprising: a command calculation unit that calculates a command signal for driving the first and second flow rate control units so as to be the target opening area calculated by the target opening area calculation unit . In the hydraulic drive circuit according to claim 2 or 3,
The first flow rate control unit is disposed between the hydraulic pump and one oil chamber of the hydraulic actuator, and the second flow rate control unit is disposed between the hydraulic pump and the other oil chamber of the hydraulic actuator. Placed in
The control means takes in signals obtained from the differential pressure detection means and the target flow rate detection means, adjusts opening areas of the first flow rate control unit and the second flow rate control unit, and discharges them from the hydraulic actuator. A hydraulic drive circuit characterized by controlling a flow rate of pressure oil to be larger than a flow rate of pressure oil supplied to the hydraulic actuator. The hydraulic drive circuit according to any one of claims 1 to 3,
A hydraulic drive circuit further comprising a make-up check valve between the first flow control unit and the hydraulic actuator and between the second flow control unit and the hydraulic actuator. The hydraulic drive circuit according to any one of claims 1 to 3,
The hydraulic drive circuit, wherein the hydraulic actuator is an arm cylinder that drives an arm of a work machine.

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