JP6612296B2 - Hydraulic control device of excavator - Google Patents

Description

  The present invention relates to a hydraulic control device used for construction machines such as a hydraulic excavator, and more particularly to an improvement of a hydraulic control device for a hydraulic excavator effective for energy saving.

  In the prior art, there is a hydraulic system pump control device described in Patent Document 1. As shown in FIG. 6, the hydraulic control device according to this prior art is discharged from the engine 1, variable displacement type first and second hydraulic pumps 2, 3, and first and second hydraulic pumps 2, 3. A relief valve 4 that determines the maximum pressure of the pressure oil, and an arm cylinder 5, a boom cylinder 6, a swing motor 7, and a bucket cylinder 8 that are driven by the pressure oil discharged from the first and second hydraulic pumps 2 and 3. A plurality of actuators including a plurality of actuators and a control valve for controlling the flow rate and direction of the pressure oil supplied from the first and second hydraulic pumps 2 and 3 to the arm cylinder 5, boom cylinder 6, swing motor 7, and bucket cylinder 8. Open center type switching valves 11 to 14, a pilot pump 15 driven by the engine, and the switching valve based on the oil discharged from the pilot pump 15 And an operating lever device 16 to 19 to generate a control pilot pressure for.

In the figure, arm and boom switching valves 11 and 12 are arranged on a center bypass line connected to the discharge oil passage of the first hydraulic pump 2, and swivel and bucket switching valves 13 and 14 are These are disposed on a center bypass line connected to the discharge oil passage of the second hydraulic pump 3. The first hydraulic pump 2 includes a first regulator 201, and the second hydraulic pump includes a second regulator 301 .

  FIG. 7 is an enlarged view of the first and second regulators 201 and 301 of the hydraulic system shown in FIG. The first regulator 201 includes a tilt control actuator 211 that tilts the swash plate of the first hydraulic pump 2, and a pump flow rate control valve 212 and a pump torque control valve 213 that control the position of the actuator. . These control valves are configured as servo valves.

  The tilt regulator actuator 211 of the first regulator includes a control piston 211a linked to the swash plate and having different pressure receiving areas of pressure receiving portions provided at both ends, and a pressure receiving chamber 211b located on the small area pressure receiving portion side of the control piston. And a pressure receiving chamber 211c located on the large-area pressure receiving portion side, the control piston is operated by the pressure balance of the two pressure receiving chambers, and the tilt angle of the swash plate of the first hydraulic pump is controlled.

  The pump flow rate control valve 212 includes a flow rate control spool 212a, a weak spring 212b for position holding located on one end side of the flow rate control spool, and a pressure receiving chamber 212c located on the other end side of the flow rate control spool. The maximum operating pilot pressure of the operating lever device selected by the shuttle valve is guided as the control signal pressure of the first hydraulic pump 2 through the oil passage.

  The pump torque control valve 213 includes a torque control spool 213a, a spring 213b located on one end side of the torque control spool 213a, a PQ control pressure receiving chamber 213c and a reduced torque control pressure receiving chamber 213d located on the other end side of the torque control spool 213a. And. The PQ control pressure receiving chamber 213c is connected to the discharge line of the first hydraulic pump 2, the discharge pressure of the first hydraulic pump 2 is guided, and the reduced torque control pressure receiving chamber 213d is output from the output port of the first electromagnetic proportional valve 31. Control pressure is introduced.

  Under such a configuration, the pump flow rate control valve 212 changes the pressure in the pressure receiving chamber 211c on the large area side of the tilt control actuator 211 in accordance with the control signal pressure (required flow rate) guided to the pressure receiving chamber 212c, and the first The pump discharge flow rate is controlled by adjusting the tilt angle of the swash plate of the hydraulic pump 2.

  Similarly, the second regulator 301 includes a tilt control actuator 311 that tilts the swash plate of the second hydraulic pump 3, and a pump flow rate control valve 312 and a pump torque control valve 313 that control the drive of the actuator. The configuration is as shown in FIG.

  FIG. 8 is a diagram showing the overall configuration of the pump control apparatus according to the present embodiment provided in the hydraulic system as described above. The pump control device of the present embodiment is connected to the discharge line of the second hydraulic pump 3, and connected to the pressure sensor 35 for detecting the discharge pressure of the second hydraulic pump 3 and the output side of the shuttle valve, and the operation lever device The pressure sensor 36 that detects the control pilot pressure generated by the engine as the turning operation pressure, the engine speed command operation device 37 such as an engine control dial, the controller 38, and the first current described above that is operated by the control current output from the controller. And second electromagnetic proportional valves 31 and 32.

  The controller receives detection signals from the two pressure sensors and a command signal from the engine speed command operating device, performs a predetermined calculation process, and outputs a control current to the first and second electromagnetic proportional valves 31 and 32. Thus, the pump torque control valves 213 and 313 are controlled, and the maximum absorption torque of the first and second hydraulic pumps 2 and 3 is controlled.

  In this prior art, when the control device is applied to a hydraulic excavator, the first pump that supplies pressure oil to the actuator including the boom when setting the torque of the first and second variable displacement pumps driven by the prime mover. On the other hand, the torque setting value is set to the maximum absorption torque, and on the other hand, in the second pump that supplies pressure oil to the actuator including turning, the torque setting is set to the maximum absorption torque and the absorption torque that is lower than the maximum absorption torque is set. The second pump is provided with a pressure sensor. When the pressure of the second pump does not exceed the preset pressure of the relief valve, the maximum absorption torque is set. When the pressure of the relief valve reaches the maximum pressure, the maximum absorption is set. Set the absorption torque below the torque.

  With such a configuration, when operating the hydraulic excavator, the loss due to the relief valve operation at the time of single-turn driving with large inertia is reduced, and at the same time, the pump pressure does not rise to the pressure of the relief valve, the boom, etc. During the combined operation, the pump oil amount can be secured and the speed and operability can be maintained.

JP 2011-157790 A JP-A-6-10841

  The prior art described in Patent Document 1 has an effect of reducing energy loss by reducing the amount of oil discharged from the relief valve at the time of a single swing operation as compared with the case of setting only the maximum absorption torque. .

  However, in this prior art, as shown in FIG. 9, the maximum absorption torque of the variable displacement pump is based on a constant P * Q horsepower curve, for example, a pump control device for a hydraulic excavator having two variable displacement pumps. The absorption torque is reduced only for the pump that supplies the pressure oil for turning in accordance with the operating conditions.

  On the other hand, from the viewpoint of the operation of a practical hydraulic excavator, due to the characteristics of the hydraulic excavator, impact load is frequently applied to the operating hydraulic system, and energy loss still remains when operating actuators other than turning alone or in combination. There are still challenges to occur.

  As another prior art, for example, in the technique described in Patent Document 2, when the pump absorption horsepower is set and the pump load pressure is increased, the pump flow rate is reduced to a predetermined value in the vicinity of the relief setting pressure. Although the so-called “cut-off” function is applied to reduce the flow rate before and after this “cut-off”, the change in flow rate is gradual. May become excessive and may cause energy saving problems.

Therefore, in order to solve these problems, the hydraulic control device according to the present invention has a single or a plurality of variable displacement pumps driven by a prime mover, an arm driven by pressure oil discharged from the pump, a boom, Each cylinder of the bucket, each hydraulic actuator including a turning hydraulic motor driven by the pressure oil discharged from the pump, each switching valve for supplying and discharging the pressure oil to and from each hydraulic actuator, and each switching A hydraulic pilot valve that operates the valve, and adjusts the discharge capacity of the pump corresponding to the load pressure so that the load acting on the pump when operating each switching valve matches the output of the prime mover in the hydraulic control system for a hydraulic excavator constructed as absorption horsepower characteristics of at least one of the pump, against the load pressure acting on the pump A predetermined three reference values provided, wherein when the load pressure of the reference value 1 or less to control the discharge flow rate of the suction horsepower of the pump as a substantially constant, the range wherein the load pressure of the reference value 1 and the reference value 2 Te In some cases, when the absorption horsepower of the pump is less than approximately constant, the discharge flow rate is gradually reduced from the first level according to the load pressure, and when the load pressure is in the range between the reference value 2 and the reference value 3, The pump capacity is adjusted so that the pressure of the supply line is controlled according to the load pressure.

  The load pressure is characterized in that the pump discharge amount is gently changed at the boundary between the reference values even when the load pressure moves high and low with respect to each reference value.

  Furthermore, the number of variable displacement pumps driven by the prime mover may be two, and the absorption horsepower characteristics of each pump may be set to be the same.

  Further, at least the reference value 1 of the three reference values may be adjustable by an external signal.

  When the load pressure is between the reference value 1 and the reference value 2, the change of the discharge flow rate with respect to the change of the load pressure is changed by a predetermined curve, and at the same time, the reference value 1 or less and the reference value 2 or more. The curve may be continuously joined to the curve and the flow rate at each reference value.

  Further, the hydraulic control device of the hydraulic excavator may be configured to shift the levels of the reference values 1 to 3 by an external signal according to the working conditions.

  According to the present invention, the setting of the absorption horsepower for the hydraulic pump of the excavator is set smaller than the P * Q (constant pressure) constant horsepower curve with respect to the motor output when the load pressure is in the high pressure range, When in the middle / low pressure range, change according to the P * Q constant horsepower curve, and control the pressure of the pump near the upper limit of the high pressure to keep the load pressure to a minimum, and further to the work contents Accordingly, since the intersection of the P * Q constant horsepower curve and the smaller horsepower region can be adjusted smoothly and with respect to the load pressure by an external signal, even when each actuator of the hydraulic excavator is operated individually and in combination Significant energy savings can be achieved while maintaining operability and productivity.

1 is a hydraulic circuit diagram of a hydraulic control apparatus according to a first embodiment of the present invention. It is a figure which shows the whole structure of the pump control apparatus in 1st Example of this invention. It is a pump absorption horsepower diagram of the hydraulic control device according to the present invention. It is a hydraulic-circuit figure of the hydraulic-control apparatus which concerns on 2nd Example of this invention. It is a figure which shows the whole structure of the pump control apparatus in 2nd Example of this invention. It is a hydraulic circuit diagram of a conventional hydraulic control device. It is an enlarged view of a regulator in a hydraulic circuit diagram of a conventional hydraulic control device. It is a figure which shows the whole structure of the conventional hydraulic control apparatus. It is a pump absorption horsepower diagram of the conventional hydraulic control apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a hydraulic circuit diagram showing a first embodiment in which the number of hydraulic pumps of the hydraulic control apparatus according to the present invention is one.

  The hydraulic control apparatus according to the first embodiment includes an engine E that is a prime mover, a variable displacement first hydraulic pump 101 that is driven by the engine E, and the maximum pressure oil that is discharged from the first hydraulic pump. A relief valve 103 for determining pressure, a plurality of actuators including an arm cylinder 104, a boom cylinder 105, a bucket cylinder 106, and a swing hydraulic motor 107 driven by the pressure oil discharged from the first hydraulic pump 101; Open center type switching valves 14b, 15b, 16b, 17b for supplying and discharging pressure oil to and from the actuator, a pilot pump 108 driven by the engine E, and each switching valve 14b˜ Hydraulic pilot valves 14pb, 15pb, 16p for operating 17b , And a 17pb.

  Each of the switching valves is a switching valve 14b for the arm, a switching valve 15b for the boom, a switching valve 16b for the bucket cylinder, and a switching valve 17b for the swing hydraulic motor, and these are arranged on the oil passage L11. The upstream side of the path L11 is connected to the discharge oil path 101a of the first hydraulic pump 101, and the downstream side is connected to the tank T. Each of these switching valves is connected in parallel to the discharge oil passage 101 a of the first hydraulic pump 101.

  The first hydraulic pump 101 includes a first regulator 110. The first regulator 110 adjusts the tilt angle of the swash plate 111 of the first hydraulic pump 101 according to the operation amount of each of the hydraulic pilot valves 14pb to 17pb. While controlling the pump discharge flow rate, the tilt angle of the first hydraulic pump 101 is controlled so that the absorption torque of the first hydraulic pump 101 does not exceed the set maximum absorption torque.

  A shuttle valve 112R is connected to the control pilot circuit that guides the control pilot pressure generated by the hydraulic pilot valves 14pb and 15pb to the switching valves 14b and 15b via the shuttle valves 112a and 112b, and the hydraulic pilot valves 16pb and 16pb A shuttle valve 112L is connected to the control pilot circuit that guides the control pilot pressure generated by 17pb to the switching valves 16b and 17b via the shuttle valves 112c and 112d. Further, the shuttle valve 112R and the shuttle valve 112L are connected to the shuttle valve 112.

  The maximum operating pilot pressure generated by the hydraulic pilot valves 14pb to 17pb is selected by the shuttle valves 112R, 112L, 112a, 112b, 112c, and 112d, and is used as a control signal pressure that indicates the required flow rate of the first hydraulic pump 101. It is given to the first regulator 110.

  The first regulator 110 includes a tilt control actuator 113 that tilts the swash plate 111 of the first hydraulic pump 101, and a pump flow rate control valve 114 and a pump torque control valve 115 that control the position of the tilt control actuator 113. have. These control valves 114 and 115 are configured as servo valves.

  The tilt control actuator 113 is linked to the swash plate 111 and has a control piston 113a having different pressure receiving areas at the pressure receiving portions provided at both ends, a pressure receiving chamber 113b located on the small area pressure receiving portion side of the control piston 113a, and a large pressure receiving chamber 113b. The pressure receiving chamber 113c located on the area pressure receiving portion side is provided, and the control piston 113a is operated by the pressure balance between the pressure receiving chambers 113b and 113c to control the tilt angle of the swash plate 111 of the first hydraulic pump 101.

The pressure receiving chamber 113b is connected to the discharge oil passage 108a of the pilot pump 108 via the oil passage L12. The pressure receiving chamber 113c is connected to the pump flow rate control valve 114 and the pump torque control valve 115 via an oil passage L14. The oil passage L14 is connected to the discharge oil passage 108a of the pilot pump 108 via the oil passage L13 and the oil passage L12. It is connected to the. Further, the pump flow rate control valve 114 and the pump torque control valve 115 are connected to the tank T via an oil passage L15.

  The pump flow rate control valve 114 includes a flow rate control spool 114a, a spring S11 located on one end side of the flow rate control spool 114a, and a pressure receiving chamber 114b located on the other end side of the flow rate control spool 114a. In the pressure receiving chamber 114b, a control in which the highest pressure of the operating pilot pressure generated by the hydraulic pilot valves 14pb to 17pb selected by the shuttle valves 112a to 112d indicates the required flow rate of the first hydraulic pump 101 via the oil passage L16. Guided as signal pressure.

  The pump torque control valve 115 includes a torque control spool 115a, a spring S12 positioned at one end of the torque control spool 115a, a PQ control pressure receiving chamber 115b and a reduced torque control pressure receiving chamber 115c positioned at the other end of the torque control spool 115a. And.

  The PQ control pressure receiving chamber 115b is connected to the discharge oil passage 101a of the first hydraulic pump 101 via the oil passage L17, the discharge pressure of the first hydraulic pump 101 is guided, and the reduced torque control pressure receiving chamber 115c is passed through the oil passage L18. Connected to the output port of the first electromagnetic proportional valve 116, and the control pressure output from the first electromagnetic proportional valve 116 is guided.

  The spring S12 and the reduced torque control pressure receiving chamber 115b are opposed to each other, and the right biasing force shown by the spring S12 is set larger than the left biasing force generated by the reduced torque control pressure receiving chamber 115b. The maximum absorption torque of the first hydraulic pump 101 is set by the rightward biasing force in the figure, which is the difference between the biasing force of the torque reducing pressure control pressure receiving chamber 115c. This maximum absorption torque is adjusted by the control pressure from the first electromagnetic proportional valve 116 guided to the reduced torque control pressure receiving chamber 115c.

When the control signal pressure (required flow rate) guided to the pressure receiving chamber 114 b increases, the pump flow rate control valve 114 displaces the flow rate control spool 114 a to the right in the drawing, and the pressure receiving chamber 113 c on the large area side of the tilt control actuator 113 is moved. By communicating with the tank T, the pressure in the pressure receiving chamber 113c is reduced. The tilt control actuator 113 moves the control piston 113a to the left in the figure due to the decrease in the pressure in the pressure receiving chamber 113c , and increases the tilt amount (displacement volume) of the swash plate 111 of the first hydraulic pump 101. The discharge flow rate of the pump 101 is increased.

  On the contrary, when the control signal pressure (required flow rate) decreases, the pump flow control valve 114 displaces the flow control spool 114a to the left in the figure, and the pressure receiving chamber 113c on the large area side of the tilt control actuator 113 is moved to the pilot pump 108. The pressure in the pressure receiving chamber 113c is increased by communicating with the discharge line 108a. The tilt control actuator 113 moves the control piston 113a to the right in the figure as the pressure in the pressure receiving chamber 113c rises, thereby reducing the tilt amount (push volume) of the swash plate 111 of the first hydraulic pump 101, thereby reducing the first hydraulic pressure. The discharge flow rate of the pump 101 is decreased.

  Under such a configuration, the pump flow rate control valve 114 changes the pressure of the pressure receiving chamber 113c on the large area side of the tilt control actuator 113 in accordance with the control signal pressure (required flow rate) guided to the pressure receiving chamber 114b. The pump discharge flow rate is controlled by adjusting the tilt angle of the swash plate 111 of the hydraulic pump 101.

  FIG. 2 is a diagram showing the overall configuration of the pump control apparatus according to the first embodiment of the present invention provided in the hydraulic control apparatus as described above.

  The pump control apparatus of the first embodiment is connected to the discharge oil passage 101a of the first hydraulic pump 101, and is connected to the pressure sensor 130 for detecting the discharge pressure of the first hydraulic pump 101 and the output side of the shuttle valve 112. The pressure sensor 131 detects the control pilot pressure generated by the pilot valves 14pb to 17pb as the turning operation pressure, the engine speed detection device 132 such as an engine control dial, the controller 133, and the control current output from the controller 133 Has a first electromagnetic proportional valve 116 that is actuated by.

  The controller 133 is connected at its input side to the pressure sensors 130 and 131 and the engine speed detecting device 132, and receives a detection signal from the pressure sensors 130 and 131 and a command signal from the engine speed detecting device 132 to input a predetermined signal. Perform arithmetic processing. Then, by outputting a control current to the first electromagnetic proportional valve 116, the pump torque control valve 115 is controlled, and the maximum absorption torque of the first hydraulic pump 101 is controlled.

The controller 133 also has a storage unit 134 and a central operator 135 made of ROM, RAM, etc., and the storage unit 134 variably controls the discharge capacity (discharge flow rate) of the first hydraulic pump 101. The program is stored, and the absorption horsepower characteristic shown in FIG. 3 is stored. Then, next, the absorption horsepower characteristic of the first hydraulic pump by such a pump control device will be described.

  With respect to the load pressure PL acting on the pump, it is set to provide three predetermined reference values, and the reference values 1, 2, and 3 are stored in the storage unit 134 in advance. Next, the pressure sensor 130 detects the load pressure PL and stores it in the storage unit 134.

Then, the central operator 135 starts a processing program from the storage unit 134, and controls the discharge flow rate with the absorption horsepower of the pump being substantially constant when the load pressure PL is equal to or less than the reference value 1 according to the processing program. When the load pressure is in the range between the reference value 1 and the reference value 2, the discharge flow rate is gradually reduced from the first level according to the load pressure PL in a range where the absorption horsepower of the pump is less than the substantially constant, and the load When the pressure is in the range between the reference value 2 and the reference value 3, the pump capacity is adjusted so that the pressure of the supply line is controlled according to the load pressure.

  In FIG. 3, the horizontal axis indicates the pump load pressure of the first hydraulic pump 101 in this embodiment, and the vertical axis indicates the discharge flow rate of this pump. Curve P * Q is a constant absorption horsepower curve of the variable displacement pump.

  The reference value 1, reference value 2, and reference value 3 in the figure respectively indicate the pump load pressure levels in the present invention, and the load pressure levels are as follows: reference value 1 ≦ reference value 2 ≦ reference value 3 To do. Curves a, b, and c show different absorption horsepower curves for the variable displacement pump as the first embodiment. That is, the reference values for the curve a are 1a, 2a, 3, the reference values for the curve b are 1b, 2b, 3, and the reference values for the curve c are 1c, 3, 3.

  Here, in the actual operation of the hydraulic excavator, the high speed of each actuator is required in a state where a load such as earth and sand is loaded on the bucket from the viewpoint of operability and productivity, including various single and complex operations. In this case, the air moving operation is mostly performed, and the pump load pressure in this case is relatively low, and is lower than the pressure of the boom raising operation (usually 120 to 160 bar).

In the case of excavation work, the load pressure is naturally high, but the discharge flow rate is relatively small. Rather, the power, that is, the pump absorption horsepower characteristics, is low flow rate and high pressure. Therefore, the set absorption horsepower for the variable displacement pump at that time is set to an absorption horsepower that is smaller than the constant curve of P * Q, without impairing the speed and operability regardless of the single operation or combined operation of each actuator. A significant energy saving effect can be achieved.

  For example, considering the case of the curve a in FIG. 3, the present invention basically sets the pump absorption torque, and the product of the pump pressure P and the flow rate Q is constant so as to utilize the maximum output of the prime mover as in the prior art. In this range, the maximum absorption torque (constant horsepower) is not set, but the pump absorption torque corresponding to the actual work of the hydraulic excavator is used.

  In this case, the set horsepower is set to a constant horsepower or lower in the high pressure range, and pressure control is performed near the upper limit of the high pressure range, and the flow rate is reduced to a small amount while maintaining the force of the actuator to minimize the relief operation. As a limit, energy loss is reduced. At the same time, after the work object has been moved by this force, it is lifted or removed as a heavy object loaded in the bucket, thereby limiting the horsepower used in the high pressure range, thereby making it possible to In comparison, it is possible to achieve a significant energy saving effect while maintaining work efficiency.

  Further, in the present invention, the change in pump discharge amount is gently changed at the boundary of each reference value. That is, even when the pump load pressure moves up and down with respect to each reference value, the P * Q constant horsepower curve and the flow rate reduction curve before and after the reference value 1 and the reference value 2, and the reference value 2 and the reference value 3 are around. Since the flow rate reduction curve and the pressure at the time of pressure control are connected smoothly, even if the pump load pressure changes before and after these reference values, the rate of change in absorption horsepower is small. The torque load changes smoothly, and excessive fuel consumption can be reduced. Note that the load pressures of the reference value 2 and the reference value 3 may be the same value.

  On the other hand, for example, when performing an operation that requires the pump horsepower to be increased to the level of the P * Q constant horsepower curve in the high pressure range using the maximum output of the prime mover horsepower for arm excavation, the curve a is set to the normal setting. On the other hand, an external signal, for example, a hand switch may be provided and operated to change the curve to the curve b or the curve c. Further, adjustment may be made so that the level of the reference values 1 to 3 is shifted by such an external signal. In this way, by setting the absorption horsepower characteristics in the actual work of the hydraulic excavator to an optimum state, it is possible to make maximum use of the prime mover horsepower.

  Note that the present invention may include a plurality of hydraulic pumps and regulators, such as providing the second hydraulic pump 202 and the second regulator 220 in addition to the first hydraulic pump 201 and the first regulator 210 as a second embodiment. Is possible.

  The hydraulic control apparatus according to the second embodiment includes an engine E as a prime mover, variable displacement type first hydraulic pump 201 and second hydraulic pump 202 driven by the engine E, and these variable displacement pumps. A relief valve 203 that determines the maximum pressure of the pressure oil discharged from the arm, and an arm cylinder 204, a boom cylinder 205, a bucket cylinder 206, and a swing hydraulic motor 207 that are driven by the pressure oil discharged from these variable displacement pumps. , Open center type switching valves 24b, 25b, 26b, and 27b for supplying and discharging pressure oil to and from these hydraulic actuators, a pilot pump 208 driven by the engine E, and a pilot pump 208 Hydraulic pie for operating each switching valve 24b-27b with pressure oil from Ttobarubu 24pb, has 25pb, 26pb, and 27pb.

  Each of the switching valves includes an arm switching valve 24b and a boom switching valve 25b disposed on the oil passage L21, a bucket cylinder switching valve 26b and a swing hydraulic motor disposed on the oil passage L31. This is the switching valve 27b. The upstream side of the oil passage L21 is connected to the discharge oil passage 201a of the first hydraulic pump 201, and the downstream side is connected to the tank T. The upstream side of the oil passage L31 is connected to the discharge oil passage 202a of the second hydraulic pump 202, and the downstream side is connected to the tank T. The switching valve 24b and the switching valve 25b are connected in parallel to the discharge oil passage 201a of the first hydraulic pump 201, and the switching valve 26b and the switching valve 27b are connected in parallel to the discharge oil passage 202a of the second hydraulic pump 202. Yes.

  The first hydraulic pump 201 includes a first regulator 210. The first regulator 210 adjusts the tilt angle of the swash plate 211 of the first hydraulic pump 201 according to the operation amount of the hydraulic pilot valves 24pb and 25pb. While controlling the discharge flow rate, the tilt angle of the first hydraulic pump 201 is controlled so that the absorption torque of the first hydraulic pump 201 does not exceed the set maximum absorption torque.

  The second hydraulic pump 202 includes a second regulator 220 that adjusts the tilt angle of the swash plate 221 of the second hydraulic pump 202 according to the operation amount of the hydraulic pilot valves 26pb and 27pb. While controlling the discharge flow rate, the tilt angle of the second hydraulic pump 202 is controlled so that the absorption torque of the second hydraulic pump 202 does not exceed the set maximum absorption torque.

  The control pilot circuit that guides the control pilot pressure generated by the hydraulic pilot valves 24pb and 25pb to the switching valves 24b and 25b is connected to the shuttle valve 212R via the shuttle valves 212a and 212b, and the hydraulic pilot valves 26pb and 27pb A shuttle valve 212L is connected to the control pilot circuit that guides the generated control pilot pressure to the switching valves 26b and 27b via shuttle valves 212c and 212d.

  The maximum operating pilot pressure generated by the hydraulic pilot valves 24pb and 25pb is selected by the shuttle valves 212R, 212a, and 212b and given to the first regulator 210 as a control signal pressure that indicates the required flow rate of the first hydraulic pump 201. It is done. The maximum operating pilot pressure generated by the hydraulic pilot valves 26pb and 27pb is selected by the shuttle valves 212L, 212c, and 212d, and the second regulator 220 serves as a control signal pressure that indicates the required flow rate of the second hydraulic pump 202. Given to.

  The first regulator 210 includes a tilt control actuator 213 that tilts the swash plate 211 of the first hydraulic pump 201, a pump flow rate control valve 214 that controls the position of the tilt control actuator 213, and a pump torque control valve 215. have. These control valves 214 and 215 are configured as servo valves.

  The tilt control actuator 213 is linked to the swash plate 211 and has a pressure receiving portion provided at both ends of the control piston 213a having different pressure receiving areas, a pressure receiving chamber 213b located on the small area pressure receiving portion side of the control piston 213a, and a large pressure receiving chamber 213b. The pressure receiving chamber 213c located on the area pressure receiving portion side is provided, and the control piston 213a is operated by the pressure balance between the pressure receiving chambers 213b and 213c to control the tilt angle of the swash plate 211 of the first hydraulic pump 201.

The pressure receiving chamber 213b is connected to a discharge oil passage 208a of the pilot pump 208 via an oil passage L22. The pressure receiving chamber 213c is connected to the pump flow rate control valve 214 and the pump torque control valve 215 via an oil path L24, and the oil path L24 is discharged from the pilot pump 208 via the oil path L23 and oil path L22. It is connected to the. Further, the pump flow rate control valve 214 and the pump torque control valve 215 are connected to the tank T via an oil passage L25.

  The pump flow control valve 214 includes a flow control spool 214a, a spring S21 located on one end side of the flow control spool 214a, and a pressure receiving chamber 214b located on the other end side of the flow control spool 214a. In the pressure receiving chamber 214b, the highest pressure of the operating pilot pressure generated by the hydraulic pilot valves 24pb and 25pb selected by the shuttle valves 212R, 212a, 212b indicates the required flow rate of the first hydraulic pump 201 via the oil passage L26. The control signal is guided as pressure.

  The pump torque control valve 215 includes a torque control spool 215a, a spring S22 located on one end side of the torque control spool 215a, a reduced torque (PQ) control pressure receiving chamber 215b located on the other end side of the torque control spool 215a, and a reduced torque. And a control pressure receiving chamber 215c.

  The PQ control pressure receiving chamber 215b is connected to the discharge oil passage 201a of the first hydraulic pump 201 via the oil passage L27, the discharge pressure of the first hydraulic pump 201 is guided, and the reduced torque control pressure reception chamber 215c is connected via the oil passage L28. Connected to the output port of the first electromagnetic proportional valve 216, and the control pressure output from the first electromagnetic proportional valve 216 is guided.

  The spring S22 and the reduced torque control pressure receiving chamber 215b are located opposite to each other, and the right biasing force shown in the figure provided by the spring S22 is set larger than the left biasing force shown in the drawing generated by the reduced torque control pressure receiving chamber 215b. The maximum absorption torque of the first hydraulic pump 201 is set by the rightward biasing force in the drawing, which is the difference between the biasing force and the biasing force of the reduced torque control pressure receiving chamber 215c. This maximum absorption torque is adjusted by the control pressure from the first electromagnetic proportional valve 216 guided to the reduced torque control pressure receiving chamber 215c.

When the control signal pressure (required flow rate) led to the pressure receiving chamber 214b increases, the pump flow rate control valve 214 displaces the flow rate control spool 214a to the right in the drawing, and the pressure receiving chamber 213c on the large area side of the tilt control actuator 213 is moved. By communicating with the tank T, the pressure in the pressure receiving chamber 213c is reduced. The tilt control actuator 213 moves the control piston 213c to the left in the drawing due to the decrease in the pressure in the pressure receiving chamber 213c , and increases the tilt amount (displacement volume) of the swash plate 211 of the first hydraulic pump 201. The discharge flow rate of the pump 201 is increased.

  Conversely, when the control signal pressure (required flow rate) decreases, the pump flow control valve 214 displaces the flow control spool 214a to the left in the figure, and the pressure receiving chamber 213c on the large area side of the tilt control actuator 213 is moved to the pilot pump 208. The pressure in the pressure receiving chamber 213c is raised by communicating with the discharge line 208a. The tilt control actuator 213 moves the control piston 213a to the right in the figure as the pressure in the pressure receiving chamber 213c rises, and decreases the tilt amount (push-up volume) of the swash plate 211 of the first hydraulic pump 201. The discharge flow rate of the pump 201 is decreased.

  Under such a configuration, the pump flow rate control valve 214 changes the pressure of the pressure receiving chamber 213c on the large area side of the tilt control actuator 213 according to the control signal pressure (required flow rate) guided to the pressure receiving chamber 214b, and the first The pump discharge flow rate is controlled by adjusting the tilt angle of the swash plate 211 of the hydraulic pump 201.

  The second regulator 220 includes a tilt control actuator 223 that tilts the swash plate 221 of the second hydraulic pump 202, and a pump flow rate control valve 224 and a pump torque control valve 225 that control driving of the actuator 223. ing. These control valves 224 and 225 are configured as servo valves.

  The tilt control actuator 223, the pump flow control valve 224, and the pump torque control valve 225 are configured in the same manner as the tilt control actuator 213, the pump flow control valve 214, and the pump torque control valve 215 of the first regulator 210.

  The tilt control actuator 223 includes a control piston 223a linked to the swash plate 221 and having different pressure receiving areas of the pressure receiving portions provided at both ends, a pressure receiving chamber 223b positioned on the small area pressure receiving portion side of the control piston 223a, and a large pressure receiving chamber 223b. The pressure receiving chamber 223c located on the area pressure receiving portion side is provided, and the control piston 223a is operated by the pressure balance between the pressure receiving chambers 223b and 223c to control the tilt angle of the swash plate 221 of the second hydraulic pump 202.

The pressure receiving chamber 223b is connected to the discharge oil passage 208a of the pilot pump 208 via an oil passage L22. The pressure receiving chamber 223c is connected to the pump flow rate control valve 224 and the pump torque control valve 225 via an oil passage L34, and the oil passage L34 is discharged from the pilot pump 208 via the oil passage L23 and the oil passage L22. It is connected to the. Furthermore, the pump flow rate control valve 224 and the pump torque control valve 225 are connected to the tank T via an oil passage L25.

  The pump flow rate control valve 224 includes a flow rate control spool 224a, a spring S31 located on one end side of the flow rate control spool 224a, and a pressure receiving chamber 224b located on the other end side of the flow rate control spool 224a. In the pressure receiving chamber 224b, the maximum pressure of the operating pilot pressure generated by the hydraulic pilot valves 26pb and 27pb selected by the shuttle valves 212L, 212c and 212d indicates the required flow rate of the second hydraulic pump 202 via the oil passage L36. The control signal is guided as pressure.

  The pump torque control valve 225 includes a torque control spool 225a, a spring S32 located on one end side of the torque control spool 225a, a PQ control pressure receiving chamber 225b and a reduced torque control pressure receiving chamber 225c located on the other end side of the torque control spool 225a. And.

  The PQ control pressure receiving chamber 225b is connected to the discharge oil passage 202a of the second hydraulic pump 202 via the oil passage L37, the discharge pressure of the second hydraulic pump 202 is guided, and the reduced torque control pressure receiving chamber 225c is passed through the oil passage L38. Connected to the output port of the second electromagnetic proportional valve 226, and the control pressure output from the second electromagnetic proportional valve 226 is guided.

  The spring S32 and the reduced torque control pressure receiving chamber 225b are located opposite to each other, and the right biasing force shown in the figure applied by the spring S32 is set larger than the left biasing force shown in the drawing generated by the reduced torque control pressure receiving chamber 225b. The maximum absorption torque of the second hydraulic pump 202 is set by the rightward biasing force in the figure, which is the difference between the biasing force of the torque reducing pressure control pressure receiving chamber 225c. This maximum absorption torque is adjusted by the control pressure from the second electromagnetic proportional valve 226 guided to the reduced torque control pressure receiving chamber 225c.

When the control signal pressure (required flow rate) guided to the pressure receiving chamber 224b increases, the pump flow rate control valve 224 displaces the flow rate control spool 224a to the right in the figure, and causes the pressure receiving chamber 223c on the large area side of the tilt control actuator 223 to move. By communicating with the tank T, the pressure in the pressure receiving chamber 223c is reduced. The tilt control actuator 223 moves the control piston 223a to the left in the drawing due to the decrease in the pressure in the pressure receiving chamber 223c , and increases the tilt amount (displacement volume) of the swash plate 221 of the second hydraulic pump 202. The discharge flow rate of the pump 202 is increased.

  Conversely, when the control signal pressure (required flow rate) decreases, the pump flow rate control valve 224 displaces the flow rate control spool 224a to the left in the figure, and the pressure receiving chamber 223c on the large area side of the tilt control actuator 223 is moved to the pilot pump 208. By communicating with the discharge line 208a, the pressure in the pressure receiving chamber 223c is increased. The tilt control actuator 223 moves the control piston 223a to the right in the figure as the pressure in the pressure receiving chamber 223c rises, thereby reducing the tilt amount (pushing volume) of the swash plate 221 of the second hydraulic pump 202, and the second hydraulic pressure. The discharge flow rate of the pump 202 is decreased.

  Under such a configuration, the pump flow rate control valve 224 changes the pressure of the pressure receiving chamber 223c on the large area side of the tilt control actuator 223 according to the control signal pressure (required flow rate) guided to the pressure receiving chamber 224b, and the second The pump discharge flow rate is controlled by adjusting the tilt angle of the swash plate 221 of the hydraulic pump 202.

  FIG. 5 is a diagram showing an overall configuration of a pump control apparatus according to the second embodiment of the present invention provided in the hydraulic control apparatus as described above.

  The pump control apparatus of the second embodiment is connected to the discharge oil passage 202a of the second hydraulic pump 202, and connected to the pressure sensor 230 for detecting the discharge pressure of the second hydraulic pump 202 and the output side of the shuttle valve 212L. A pressure sensor 231 that detects a control pilot pressure generated by the pilot valves 26pb and 27pb as a turning operation pressure, an engine speed detection device 232 such as an engine control dial, a controller 233, and a control current output from the controller 233 The first electromagnetic proportional valve 216 and the second electromagnetic proportional valve 226 operated by

  The controller 233 is connected to the pressure sensors 230 and 231 and the engine speed detection device 232 on the input side, and receives a detection signal from the pressure sensors 230 and 231 and a command signal from the engine speed detection device 232 to input a predetermined signal. Perform arithmetic processing. The pump torque control valves 215 and 225 are controlled by outputting a control current to the first electromagnetic proportional valve 216 and the second electromagnetic proportional valve 226, and the maximum absorption torque of the first hydraulic pump 201 and the second hydraulic pump 202. To control.

The controller 233 includes a storage unit 234 including a ROM and a RAM, and a central operator 235. The storage unit 234 includes discharge capacities (discharge flow rates) of the first hydraulic pump 201 and the second hydraulic pump 202. Is stored, and an absorption horsepower characteristic shown in FIG. 3 is stored. The absorption horsepower characteristics of the first hydraulic pump 201 and the second hydraulic pump 202 by such a pump control device are the same as in the first embodiment.

14b-17b, 24b-27b Switching valve 14pb-17pb, 24pb-27pb Hydraulic pilot valve 101, 201 First hydraulic pump 101a, 201a Discharge oil passage 202 Second hydraulic pump 202a Discharge oil passage 103, 203 Relief valve 104, 204 Arm Cylinder 105, 205 Boom cylinder 106, 206 Bucket cylinder 107, 207 Swing hydraulic motor 108, 208 Pilot pump 108a, 208a Discharge oil passage 110, 210 First regulator 111, 211, 221 Swash plate 112, 112R, 112L, 112a-112d Shuttle valves 212R, 212L, 212a to 212d Shuttle valves 113, 213, 223 Tilt control actuators 113a, 213a, 223a Control pistons 113b, 213b, 223b Chamber 113c, 213c, 223c Pressure receiving chamber 114, 214, 224 Pump flow rate control valve 114a, 214a, 224a Flow rate control spool 114b, 214b, 223b Pressure receiving chamber 114c, 214c, 223c Pressure receiving chamber 115, 215, 225 Pump torque control valve 115a, 215a, 225a Torque control spool 115b, 215b, 225b PQ control pressure receiving chamber 115c, 215c, 225c Reduced torque control pressure receiving chamber 116, 216 First electromagnetic proportional valve 220 Second regulator 226 Second electromagnetic proportional valve 130, 230 Pressure sensor 131, 231 Pressure sensor 132, 232 Engine speed detection device 133, 233 Controller 134, 234 Storage unit E Engine T Tank S11, S12 Spring S21, S22, S31, S32 Spring L11-L18, L21 -L28, L31, L34-L38 Oil passage

Claims (9)

Single or multiple variable displacement pumps driven by prime movers;
Hydraulic actuators including arm, boom and bucket cylinders driven by pressure oil discharged from the pump, and swing hydraulic motors driven by pressure oil discharged from the pump;
Each switching valve for supplying and discharging pressure oil to each of these hydraulic actuators,
A hydraulic pilot valve for operating each switching valve;
In the hydraulic control device for a hydraulic excavator configured to adjust the discharge capacity of the pump corresponding to the load pressure so that the load acting on the pump when operating each switching valve matches the output of the prime mover,
The absorption horsepower characteristic of at least one of the pumps is provided with three predetermined reference values for the load pressure acting on the pump,
When the load pressure is less than or equal to the reference value 1, the discharge flow rate is controlled by making the absorption horsepower of the pump substantially constant,
When the load pressure is in the range between the reference value 1 and the reference value 2, the discharge flow rate is gradually reduced from the first level according to the load pressure in a range where the absorption horsepower of the pump is less than the substantially constant,
When the load pressure is in the range of the reference value 2 and the reference value 3, the pressure of the supply line is adjusted according to the load pressure by an adjustment different from that when the load pressure is in the range of the reference value 1 and the reference value 2. The pump capacity is adjusted to control the pressure.
The reference value 1 and the reference value 2 are different values,
The hydraulic control device for a hydraulic excavator, wherein the reference value 2 and the reference value 3 are different values. 2. The hydraulic control device for a hydraulic excavator according to claim 1 , wherein the load pressure gradually changes the pump discharge amount at the boundary between the reference values even when the load pressure moves high and low with respect to the respective reference values. The hydraulic control device for a hydraulic excavator according to claim 1 or 2 , wherein the number of variable displacement pumps driven by the prime mover is two, and the absorption horsepower characteristics of each pump are set to be the same. The number of variable displacement pumps driven by the prime mover is two, and at least one of the variable displacement pumps is set to the absorption horsepower characteristic, and the actuator connected to the variable displacement pump includes turning. The hydraulic control device for a hydraulic excavator according to claim 1 or 2 . The hydraulic control device for a hydraulic excavator according to any one of claims 1 to 4, wherein at least the reference value 1 among the three reference values can be adjusted by an external signal. When the load pressure is between the reference value 1 and the reference value 2, the change of the discharge flow rate with respect to the change of the load pressure is changed by a predetermined curve, and at the same time, the reference value is 1 or less and the reference value is 2 or more. The hydraulic control device for a hydraulic excavator according to any one of claims 1 to 5, wherein the hydraulic pressure excavator is continuously joined to the curve and the flow rate at each reference value. The hydraulic control device for a hydraulic excavator according to any one of claims 1 to 6 , wherein the reference value 2 is changeable. The hydraulic control device for a hydraulic excavator according to any one of claims 1 to 7 , wherein the reference value 1 is changeable. The hydraulic control device for a hydraulic excavator according to any one of claims 1 to 8, wherein the level of the reference values 1 to 3 is shifted by an external signal in accordance with the working conditions.

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