JP5357073B2 - Pump controller for construction machinery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize energy saving by making difference in absorption torque (pump flow rate) of a hydraulic pump between a shrinkage side and an elongation side of the hydraulic cylinder to reduce loss. <P>SOLUTION: In a return piping 17 through which return oil from an actuator to a tank passes, pressure becomes higher as return flow rate increases, and a condition of operation in the elongation side and the shrinkage side of the hydraulic cylinder can be comprehensively determined by the pressure of the return piping, so that the pressure of the return piping is detected by a return piping pressure sensor 26, and a necessary absorption torque is determined from the pressure of the return piping in a controller 23, and thus the pump flow rate based on the necessary absorption torque is commanded to pump regulators 21 and 22. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a pump control device that controls the absorption torque of a hydraulic pump in a construction machine such as a hydraulic excavator.

  Conventionally, instead of the so-called constant horsepower control, in which the absorption torque of the hydraulic pump is fixed and the pump flow rate is controlled so that the pump output does not exceed the fixed absorption torque, the absorption torque of the hydraulic pump is changed to the discharge pressure (pump A technique for controlling the pressure according to the pressure is known. (See Patent Document 1).

  With this technology, it is recognized that if the pump pressure is high, the load is large and a high absorption torque is required, and the work efficiency is improved by increasing the absorption torque on the high pressure side (increasing the pump flow rate). Yes.

JP 2002-138965 A

  However, in an actual hydraulic circuit in a construction machine such as a hydraulic excavator, the pump pressure is detected as a value including pressure loss due to a throttle in a meter-in and meter-out opening of a control valve or a pipe line. Therefore, determining the absorption torque of the hydraulic pump is not necessarily the optimum horsepower setting.

  A hydraulic excavator will be specifically described as an example.

  As shown in FIG. 10, the excavator is configured such that an upper swing body 2 is rotatably mounted on a crawler-type lower traveling body 1, and a work attachment 3 is mounted on the upper swing body 2.

  The work attachment 3 includes an up and down boom 4, an arm 5 attached to the tip of the boom 4, a bucket 6 attached to the tip of the arm 5, and a boom, an arm, and a bucket cylinder for operating them ( The hydraulic actuators (7) to (9), and a hydraulic actuator (not shown) including a turning motor and a traveling motor are driven by one or more hydraulic pumps.

  Of these, the boom, arm, and bucket cylinders 7 to 9 require a large force because the expansion side is the side that moves the load, whereas the contraction side does not require a large force because the load is boosted. .

  For the boom and arm cylinders 7 and 8, the extension side (boom raising, arm pulling) requires a large force to lift the attachment weight and bucket soil weight, while the contraction side (boom lowering, arm pushing) ) Requires less power because it is on the side where the work is done by gravity.

  A typical operation is an arm pushing / boom lowering operation for returning to an excavation posture after excavation and dumping.

  In this operation, although the horsepower required to actually move both the boom and arm cylinders 7 and 8 may be small, if a large flow rate is flowed without making this distinction, the pressure loss on the meter-out side increases. Pump pressure will increase.

  In addition, in this case, the pressure loss on the meter-out side of both cylinders 7 and 8 acts as a force that opposes the force that moves both cylinders 7 and 8, and the loss is originally large.

  Therefore, in the above-described known technique in which the absorption torque of the hydraulic pump is determined based only on the pump pressure, the horsepower is increased during the arm pushing / boom lowering operation, which originally has a large loss, and control is performed in a direction that further increases the loss. For this reason, the effect of improving energy efficiency is low, which is disadvantageous in terms of fuel consumption.

  Accordingly, the present invention provides a pump control device for a construction machine that can achieve energy saving by making a difference in absorption torque (pump flow rate) of a hydraulic pump between a contraction side and an extension side of a hydraulic cylinder, and reducing loss. Is.

  The invention of claim 1 is driven by a variable displacement hydraulic pump driven by an engine, a pump regulator that adjusts a pump flow rate that is an amount of oil discharged from the hydraulic pump, and pressure oil from the hydraulic pump. A hydraulic cylinder, a control valve which is operated by the operating means to control the operation of the hydraulic cylinder, a pump control means which controls the discharge flow rate of the hydraulic pump through the pump regulator, and a return pipe pressure which detects the pressure of the return pipe Detecting means, and the pump control means sets the required absorption torque in accordance with the return pipe pressure detected by the return pipe pressure detection means so as to be lower on the high pressure side of the return pipe pressure, and the hydraulic pump The flow rate is commanded to the pump regulator so that the actual absorption torque is less than this required absorption torque. Those configured to.

  According to a second aspect of the present invention, in the configuration of the first aspect, the pump control means reduces the required absorption torque on the high pressure side of the return pipe pressure based on a preset relationship between the return pipe pressure and the required absorption torque. It is configured.

  According to a third aspect of the present invention, in the configuration of the first aspect, the pump control means estimates the return flow rate flowing through the return pipe from the return pipe pressure detected by the return pipe pressure detection means, and the estimated return flow rate. Accordingly, the required absorption torque is reduced on the side where the estimated return flow rate is large.

  According to a fourth aspect of the present invention, in the configuration of the first aspect, the pump control means estimates the return flow rate flowing through the return pipe from the return pipe pressure detected by the return pipe pressure detection means, and this estimated return According to the ratio between the flow rate and the pump flow rate, the required absorption torque is lowered on the side where the flow rate ratio is high.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the apparatus includes a plurality of hydraulic actuators including a hydraulic cylinder, and pump pressure detecting means for detecting a pump pressure that is a discharge pressure of the hydraulic pump. The pump control means is
(i) obtaining a horsepower limit flow rate by horsepower control from the necessary absorption torque obtained based on the return pipe pressure detected by the return pipe pressure detection means and the pump pressure detected by the pump pressure detection means;
(ii) obtaining the positive control flow rate from the operation amount of the operation means for each hydraulic actuator;
(iii) Select the lower horsepower limit flow rate and positive control flow rate,
(iv) It is configured to command the flow rate selected at the lower level to the pump regulator.

  In the hydraulic circuit, the return pipe that passes the return oil from the actuator to the tank increases in pressure as the return flow rate increases, so the return flow pressure is detected to detect the magnitude of the return flow rate, that is, on the cylinder extension side. It is possible to indirectly detect the difference between the contraction side and the contraction side operation amount.

  In addition, there are many combinations of the expansion side and contraction side of each cylinder and the size of the operation amount during combined operation, but by detecting the pressure of the return pipe, the expansion side and the contraction side are comprehensively detected. The status of the operation can be determined.

  On the other hand, by detecting the operation of the operating means and the magnitude of the operation amount, it is possible to determine the operation status of the expansion side and the contraction side, but the actual operating speed of the actuator varies depending on the external load of the actuator to be written. However, the magnitude of the operation amount may not always match.

  Therefore, in the present invention, the pressure of the return pipe is detected, the required absorption torque of the hydraulic pump is obtained based on this return pipe pressure, and the pump flow rate is controlled so that the actual absorption torque of the hydraulic pump is less than or equal to this required absorption torque. It was set as the structure to do.

  With this configuration, it is possible to improve the energy efficiency and improve the fuel efficiency by suppressing the pump flow rate at the time of the contraction side operation, which originally has a lot of loss and does not require a large flow rate.

  In addition, by using the return pipe pressure as a base, it is possible to more accurately determine the operation status of each actuator during the combined operation, and to appropriately control the absorption torque (pump flow rate).

  In this case, the relationship between the return pipe pressure and the required absorption torque may be determined in advance as in the second aspect of the invention, and the required absorption torque may be obtained directly according to the return pipe pressure. As in the invention, the return flow rate may be estimated from the return pipe pressure, and the necessary absorption torque may be obtained from the estimated return flow rate.

  Further, as in the invention of claim 4, the necessary absorption torque may be obtained according to the ratio of the return flow rate estimated from the return pipe pressure and the pump flow rate.

  According to this configuration, it is advantageous in that it is possible to more accurately determine the operation state of the expansion side and the contraction side and to perform torque control in accordance with the actual situation during the combined operation of a plurality of hydraulic cylinders having different capacities (cylinder cross-sectional areas). .

  According to the invention of claim 5, the horsepower limit flow rate by the horsepower control (PQ calculation) is obtained from the necessary absorption torque obtained based on the return pipe pressure and the detected pump pressure, and this horsepower limit flow rate and the operation amount Since the low-order selection with the positive control flow rate by the positive control that changes the pump flow rate in response to the control flow is performed and the low-order selected flow rate is commanded to the pump regulator, the operator's intention can be reflected in the control.

1 is a hydraulic circuit diagram according to a first embodiment of the present invention. It is a block block diagram of the control system of the same embodiment. It is a figure which shows the characteristic of the pump output by the constant horsepower control at the time of the actual work of a hydraulic excavator, and an actuator output. It is a figure which shows the change condition of return piping pressure same as the above. It is a figure which shows the change condition of a return flow rate similarly. It is a figure which shows the change condition of the pump absorption torque by 1st Embodiment of this invention. FIG. 4 is a view corresponding to FIG. It is a partial control block diagram which shows 2nd Embodiment of this invention. It is a partial control block diagram which shows 3rd Embodiment of this invention. 1 is a schematic side view of a hydraulic excavator to which the present invention is applied.

  An embodiment of the present invention will be described with reference to FIGS.

  In the embodiment, a hydraulic excavator is applied.

1st Embodiment (refer FIGS. 1-7)
FIG. 1 shows a hydraulic circuit.

  Here, the first and second variable displacement hydraulic pumps 11 and 12 are provided, the first hydraulic pump 11 is used for boom and bucket cylinders 7 and 9, and the second hydraulic pump 12 is used for the arm cylinder 8 and the swing motor. The case where 10 is driven is taken as an example. In addition, the traveling motor is excluded.

  The hydraulic actuators 7 to 10 are controlled by hydraulic pilot control valves 13 to 16, respectively. The control valves 13 to 16 are operated by remote control valves as operating means (not shown).

  Reference numeral 17 denotes a return pipe through which oil returns from the actuators 7 to 10 to the tank T via the control valve. The return pipe 17 is provided with a boost check valve 18, an oil cooler 19, and a bypass check valve 20.

  21 and 22 are pump regulators that adjust the discharge flow rate (pump flow rate) by changing the tilt of the hydraulic pumps 11 and 12, and are controlled by a controller 23 as pump control means.

  On the other hand, as detection means, pump pressure sensors (pump pressure detection means) 24 and 25 for detecting the discharge pressure (pump pressure) of both hydraulic pumps 11 and 12 and return pipe pressure sensor (return for detecting the pressure of the return pipe 17). (Pipe pressure detecting means) 26 is provided, and signals from these sensors 24 to 26 are input to the controller 23.

  The controller 23 is necessary based on the input pump pressure, return pipe pressure, and operation signals from the remote control valve (operation amounts for raising the boom, lowering the boom, pulling the arm, pushing the arm, excavating the bucket, and discharging the bucket). The pump flow rate is obtained and commanded to the pump regulators 21 and 22.

  The configuration of the controller 23 and the contents of the control will be described in detail with reference to FIG.

  The controller 23 includes a required absorption torque calculation unit 27 to which the return pipe pressure is input, a horsepower limit flow rate calculation unit 28 to which the pump pressures of the first and second hydraulic pumps 11 and 12 are input, and operation of each operation unit. A positive control flow rate calculation unit 29 for inputting the quantity, and two low order selection units 30 and 31 are provided.

  The required absorption torque calculation unit 27 obtains the required absorption torque from the return pipe pressure / required absorption torque map that is set and stored in advance, and sends this to the horsepower limit flow rate calculation unit 28.

  The horsepower limiting flow rate calculation unit 29 obtains a pump flow rate (restricted pump flow rate) that should be limited by the horsepower control from a pump pressure / absorption torque map that is set and stored in advance, and sends this to the low level selection units 30 and 31. .

  The positive control flow rate calculation unit 29 obtains a pump flow rate (positive control flow rate) corresponding to the operation amount from a preset / stored operation amount / pump flow rate map, and sends this to the low order selection units 30 and 31.

  The lower selection units 30 and 31 select the lower one of the sent limit pump flow rate and positive control flow rate, and send the selected pump flow rate to the pump regulators 21 and 22 as command flow rates for both the hydraulic pumps 11 and 12.

  Thereby, both hydraulic pumps 11 and 12 discharge the commanded flow rate.

  In this way, the return pipe pressure is detected, the required absorption torque of the hydraulic pumps 11 and 12 is obtained based on the return pipe pressure, and basically the actual absorption torque of the hydraulic pumps 11 and 12 is less than or equal to this required absorption torque. Since the pump flow rate is controlled so as to be, it is possible to suppress the pump flow rate and improve the energy efficiency and improve the fuel efficiency at the time of the contraction side operation, which originally has a lot of loss and does not require a large flow rate.

  In this case, the return pipe pressure is detected as the operation amount on the contraction side, and when the return pipe pressure is high, it is judged that there is a lot of operation on the contraction side (the return flow is large and the loss is large, so the energy efficiency is poor). Therefore, it is possible to more accurately determine the operation status of the actuators 7 to 10 during the combined operation, and to appropriately control the absorption torque (pump flow rate).

  Further, a horsepower limit flow rate by horsepower control is obtained from the necessary absorption torque obtained based on the detected return pipe pressure and the detected pump pressure, and a low-order selection between the horsepower limit flow rate and the positive control flow rate by positive control is performed. Since the configuration is such that the lower selected flow rate is commanded to the pump regulators 21 and 22, the operator's intention can be reflected in the control.

  The effect of this embodiment will be described with reference to FIGS. 3 to 7 in comparison with the case where the absorption torque of the hydraulic pumps 11 and 12 is constant.

  3 to 6 show changes in power (pump output and actuator output) when excavation work is performed with constant torque control.

  As shown in FIG. 3, the first half of the operation area is the arm pulling / boom raising / bucket excavation (each cylinder extension side) operation for excavation, and the second half is the arm pushing for dumping / boom lowering / bucket discharging (each cylinder) (Shrink side) operation is performed.

  As shown in the figure, the ratio of the actuator output to the pump output is high in the first half and the system loss is small. However, in the second half, the pump output is large and the hydraulic system loss is large even though the actuator output is small.

  At this time, the return pipe pressure and the return pipe flow rate increase in the latter half of the operation area as shown in FIGS. That is, arm pushing / boom lowering / bucket discharging is a contraction-side operation of the cylinders 7 to 9, and the return flow rate increases with respect to the pump flow rate due to the cylinder cross-sectional area ratio, and the loss increases.

  On the other hand, according to the embodiment, as shown in FIG. 6, control is performed in which the absorption torque decreases in the latter half of the loss.

  As a result, as shown in FIG. 7, the pump absorption torque can be reduced in the latter half of the operation range (arm pushing / boom lowering / bucket dumping dump operation range) than in the case of constant horsepower control (shown by a broken line). it can. For this reason, it becomes energy saving and can improve a fuel consumption.

Other Embodiments In the first embodiment, as shown in FIG. 2, the required absorption torque calculation unit 27 has a configuration for obtaining the required absorption torque directly from the detected return pipe pressure. However, as the second embodiment, As shown in FIG. 8, in the required absorption torque calculation unit 27, first, the return flow rate is estimated from the return pipe pressure using a function that takes into account the pressure loss of the flow path, and the map of the return flow rate / absorption torque set and stored in advance. On the basis of this, the necessary absorption torque may be calculated from the estimated value of the return flow rate.

  As a third embodiment, as shown in FIG. 9, after estimating the return flow rate from the return pipe pressure, from the estimated value of this return flow rate and the ratio of the pump flow rate (flow rate ratio) detected by the flow rate sensor or the like The necessary absorption torque may be determined.

  This is advantageous in that, during combined operation of a plurality of hydraulic cylinders having different capacities (cylinder cross-sectional areas), it is possible to more accurately determine the operation state on the expansion side and the contraction side and perform torque control in accordance with the actual situation.

  The present invention is not limited to a hydraulic excavator, and may be applied to other construction machines configured with a hydraulic excavator as a base, and the construction flow machine requires a smaller flow rate when operating on the cylinder contraction side than when operating on the expansion side. it can.

7 Boom cylinder 8 Arm cylinder 10 Rotating motor 11, 12 Hydraulic pump 13 Control valve 17 Return pipe T Tank 21 Pump regulator 23 Controller (pump control means)
24, 25 Pump pressure sensor 26 Return pipe pressure sensor 27 Necessary absorption torque calculation unit 28 of controller 28, horsepower limit flow rate calculation unit 29

Claims (5)

  A variable displacement hydraulic pump driven by an engine, a pump regulator for adjusting a pump flow rate that is an amount of oil discharged from the hydraulic pump, a hydraulic cylinder driven by pressure oil from the hydraulic pump, and an operation means A control valve which is operated to control the operation of the hydraulic cylinder, a pump control means for controlling the discharge flow rate of the hydraulic pump through the pump regulator, and a return pipe pressure detection means for detecting the pressure of the return pipe, The pump control means sets the required absorption torque to be lower on the high pressure side of the return pipe pressure in accordance with the return pipe pressure detected by the return pipe pressure detection means, and the actual absorption torque of the hydraulic pump is It was configured to command the flow rate to the pump regulator so that it was below the required absorption torque. Preparative pump control system for a construction machine according to claim.   2. The construction according to claim 1, wherein the pump control means is configured to reduce the required absorption torque on the high pressure side of the return pipe pressure based on a preset relationship between the return pipe pressure and the required absorption torque. Mechanical pump control device.   The pump control means estimates the return flow rate flowing through the return pipe from the return pipe pressure detected by the return pipe pressure detection means, and the necessary absorption torque on the side where the estimated return flow rate is large according to the estimated return flow rate. The construction machine pump control device according to claim 1, wherein the pump control device is configured to lower the pressure.   The pump control means estimates the return flow rate flowing through the return pipe from the return pipe pressure detected by the return pipe pressure detection means, and the flow rate ratio is determined according to the ratio between the estimated return flow rate and the pump flow rate. 2. The construction machine pump control device according to claim 1, wherein the required absorption torque is lowered on the higher side. The pump control unit includes a plurality of hydraulic actuators including a hydraulic cylinder, and includes a pump pressure detection unit that detects a pump pressure that is a discharge pressure of the hydraulic pump.
(i) obtaining a horsepower limit flow rate by horsepower control from the necessary absorption torque obtained based on the return pipe pressure detected by the return pipe pressure detection means and the pump pressure detected by the pump pressure detection means;
(ii) obtaining the positive control flow rate from the operation amount of the operation means for each hydraulic actuator;
(iii) Select the lower horsepower limit flow rate and positive control flow rate,
(iv) The pump control device for a construction machine according to any one of claims 1 to 4, wherein the pump controller is configured to command a flow rate selected at a lower level to the pump regulator.

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