JP5676130B2 - Control method of hydraulic pump and construction machine using the same - Google Patents

Description

  The present invention relates to a control method for a variable displacement hydraulic pump used in a construction machine such as a hydraulic excavator, and more particularly to control of pressure oil supplied from the pump to a hydraulic actuator.

  A construction machine, for example, a hydraulic excavator, usually includes a hydraulic cylinder that drives a boom, an arm, an excavator, and the like, and a swivel base, a caterpillar for traveling, or a hydraulic motor that drives a vehicle. These hydraulic actuators are each supplied with the required pressure oil from the hydraulic pump via the respective hydraulic control valves of the control valve unit mounted on the swivel base.

  By the way, the hydraulic excavator is usually provided with an engine that uses fossil fuel to drive the hydraulic pump. From the viewpoint of global warming and environmental conservation, the hydraulic excavator is required to save energy and improve energy efficiency. ing.

  For example, in the hydraulic circuit shown in FIG. 4 of Patent Document 1, turning independent control is possible by the hydraulic pressure provided via the third hydraulic pump, and the turning hydraulic pump joins the working device flow path and turns. A first travel control valve and a first travel control valve that are sequentially provided from the downstream side of the first hydraulic pump 301 along the first center bypass line 20 in order to maintain the speed of each actuator without a shortage of oil during the combined operation. 302, a first boom control valve 303, and a second traveling control valve 307 and a second boom control valve 308 that are sequentially provided along the second center bypass line 30 from the downstream side of the second hydraulic pump 306. In response to the input valve switching signal, the pressure oil discharged from the third hydraulic pump 401 at the neutral position of the swing control valve 402 that controls the drive of the swing motor 403 is combined. Configuration includes a third center bypass line 40 joins line 36 to be connected to and installed between the supply flow path of the second boom control valve 308 has been disclosed to.

  Further, in the case of the hydraulic circuit described in Patent Document 1, the discharge amount control mechanism of the variable displacement hydraulic pump is not clearly shown in the drawing. However, in Patent Document 2, FIGS. As shown in the figure, in order to control the discharge amount of the variable displacement hydraulic pump 23, pressure switches 34a and 34b are provided in the discharge line, and these detection signals are given to the controller 35, and the feedback signal is the maximum discharge volume. The variable means 31 is provided.

  Other than the above-mentioned Patent Documents 1 and 2, a control method that detects the discharge-side pressure of the variable displacement hydraulic pump, that is, the load-side pressure and uses it as a feedback signal for controlling the discharge amount of the hydraulic pump has been generally used so far. Is used.

  On the other hand, the hydraulic excavator or the like is appropriately provided with a relief valve for avoiding damage to equipment, devices and the like due to a sudden pressure change in the hydraulic circuit. FIG. 5 of the present application is a schematic diagram for explaining general characteristics of the relief valve.

  FIG. 5A is a hydraulic circuit diagram, and HM is a hydraulic motor that drives, for example, a swivel as a load LD via an output shaft X, and switches from a variable displacement pump Pm to a switching valve control valve. Supply of pressure oil of pressure P is received through VL. The relief valve RF is provided in a line L between the pump Pm and the hydraulic motor.

In FIG. 5A, T is the torque generated on the output shaft X of the hydraulic motor HM, Vth is the theoretical discharge amount per rotation of the hydraulic motor HM, and Pa is the input pressure of the hydraulic motor HM. Since the relationship between T, Vth, and Pa is T (Nm) = Pa (MPa) × Vth (cm ³ / rev) / 2π, if the Vth of the hydraulic motor HM is determined, the output torque of the hydraulic motor HM is It is determined by the hydraulic motor inlet pressure Pa. FIG. 5B shows the relationship between the pressure of the input line L of the relief valve RF, that is, the hydraulic motor input pressure Pa and the relief flow rate Q. Qmin is a necessary minimum flow rate at which the relief valve RF functions. For example, in the characteristic C1, when the set pressure CrP is set to 25 MPa, a flow rate equal to or higher than Qmin (10 L / min) is applied to the relief valve RF at the pressure P1 near CrP. It is a necessary condition that it is flowing. In addition, when it is larger than Qmin, the fact that there is no pressure change of the characteristic C1 indicates a state where the relief valve is functioning.

  FIG. 5C shows the state of the rotational speed when the hydraulic motor HM is started. In (c), after the operating pressure signal SG is given to the switching valve control valve VL at time t = 0, the hydraulic motor HM starts to rotate at time t0 after the time T0 has elapsed, and at time t1, a predetermined value is obtained. A state in which the rotational speed Ns is reached is shown.

  In this case, the time T1 is generally determined to be almost constant as a hydraulic excavator in consideration of the operation feeling of the driver. The time T0 is the time until the above-described Qmin is reached.

  FIG. 6 of the present application shows the rotation characteristics of a conventional hydraulic excavator turning motor. In the figure, the hydraulic motor inlet pressure Pa, the hydraulic motor outlet pressure Pb, the pilot operation pressure Pc, the hydraulic motor until the brake is applied and stops immediately after the hydraulic motor reaches a predetermined number of rotations in the activated / accelerated state. Each waveform of the rotational speed Nm is shown.

  Further, FIG. 7 of the present application is a waveform diagram showing constant horsepower control of the hydraulic pump during a single swing operation in the hydraulic excavator. In the same figure, the discharge amount is constant and the torque increases proportionally until the discharge pressure is near 13 MPa, but the discharge amount decreases proportionally when the discharge pressure is 13 MPa or more, and the torque increases as shown in the figure. It is a convex curve.

  FIG. 8 of the present application is a plot waveform diagram showing hydraulic motor rotation characteristics during turning activation and acceleration in the hydraulic excavator. In the figure, the inlet pressure Pa and the rotational speed Nm of the hydraulic motor correspond to the respective waveforms in FIG.

  FIG. 9 of the present application is a plot waveform diagram showing the characteristics at the time of turning start and acceleration of the hydraulic excavator in the case of conventional constant horsepower control.

JP 2010-13927 A JP 62-160333 A

  However, the conventional control methods shown in Patent Document 2 and FIGS. 6 to 9 of the present application have the following problems.

  As shown in FIG. 9, a peak portion is generated in the waveform of the pump discharge amount Qp in the initial state, particularly at the time of turning acceleration, and the rotational speed Nm of the hydraulic motor gradually increases after the peak portion. Yes. For this reason, a large amount of pressurized oil is blown out from the relief valve connected to the hydraulic motor inlet to the tank side at the initial stage of acceleration start, and as a result, heat is generated in the hydraulic circuit system.

  In other words, the conventional hydraulic pump control is called a so-called horsepower control or constant torque control system in which the discharge flow rate is controlled in accordance with the pump discharge pressure within the maximum torque generated by the engine and no engine stall occurs in any case. The mainstream is

  This conventional control method detects the discharge pressure of the hydraulic pump and feeds it back to the hydraulic pump servo section to control the discharge flow rate. In this method, for example, when an upper swing body such as a hydraulic excavator is started by a hydraulic motor, a flow rate corresponding to the pressure is supplied when the hydraulic motor starts to rotate, so that most of the relief valve is installed in the swing motor. Bypassing more, the oil temperature in the hydraulic system is raised, and the engine output torque is consumed more than necessary, and fuel is wasted. Similarly, an excessive flow rate is discharged from the relief valve because an excessive flow rate is supplied even after the turning motor starts rotating. In particular, in the hydraulic excavator, the turning operation is frequently started and stopped, and the surplus flow rate is released through the relief valve at each start-up, so that there is a problem that the proportion of wasted fuel is very high.

  The inventors of the present application have made extensive studies to solve the above-mentioned problems, and as a result, the above-mentioned problems are fundamentally controlled by controlling the amount of oil supplied to the hydraulic motor for turning drive to the minimum required amount. Therefore, instead of the conventional constant torque control method, a discharge flow rate control method that detects the number of rotations of the hydraulic motor and feeds it back to the hydraulic pump servo unit to control the discharge flow rate is used. I found out that it can be realized by adopting it.

  Therefore, the first object of the present invention is to detect the speed of a hydraulic actuator such as a swing motor and feed it back to a hydraulic pump dedicated to the hydraulic actuator so that the optimum minimum flow rate can be supplied to the hydraulic actuator. And a hydraulic device for a construction machine or the like using the method.

  The second object of the present invention is to control the main pump that calculates and calculates the absorption torque of the hydraulic pump according to the control method and controls the absorption torque of the main pump so that this value does not exceed the maximum output torque of the engine. The present invention provides a method and a hydraulic apparatus such as a construction machine using the method.

In order to achieve the above object, a hydraulic pump control method according to the present invention includes a hydraulic actuator, a first variable displacement hydraulic pump that supplies the hydraulic pressure to the hydraulic actuator, a second hydraulic actuator, and the second hydraulic actuator. A second variable displacement hydraulic pump for supplying required hydraulic oil to the hydraulic actuator, a switching valve control valve provided between the first hydraulic pump and the hydraulic actuator, an engine for applying a rotational driving force to the hydraulic pump, and The hydraulic pump is provided with a relief valve provided in a pressure oil supply flow path to the hydraulic actuator, and is discharged from the hydraulic pump in a state where an operation command to the switching valve control valve is given to drive the hydraulic actuator. wherein the hydraulic drive system of the supply of pressure oil comprising means for limiting the hydraulic actuator and the relief valve that first A method for controlling a hydraulic pump, the method includes a first step of providing an operation command to said switching valve control valve to drive the hydraulic actuator, in the first step, the speed of the hydraulic actuator The sum of the second step to be detected and the minimum required flow rate (Qmin), which is the characteristic value of the relief valve, and the pressure oil flow rate to the hydraulic actuator corresponding to the detection speed are calculated during the first step. A third step, a fourth step of giving a calculation result of the third step as a discharge flow rate command value of the hydraulic pump during the first step, and a discharge pressure of the first hydraulic pump during the first step. a fifth step of detecting a difference between the output torque Te of the third calculation result by step as determined from the detected pressure in the fifth step the first hydraulic pump absorption torque Ts and the engine Sixth step of the command to the second hydraulic pump to calculate the instruction absorption torque Tm to et the second hydraulic pump, can be composed of capital.

In order to achieve the above object, a hydraulic pump control method according to the present invention includes: a first hydraulic actuator; a first variable displacement hydraulic pump that supplies required pressure oil to the first hydraulic actuator; A first switching valve control valve provided between a first hydraulic pump and a first hydraulic actuator; a first relief valve provided in a pressure oil supply flow path to the first hydraulic actuator; In a state where an operation command is given to the first switching valve control valve to drive one hydraulic actuator, the supply of pressure oil discharged from the first hydraulic pump is supplied to the first hydraulic actuator and the first hydraulic actuator. Means for limiting to the first relief valve, an engine for giving a rotational driving force to the first hydraulic pump, and a second variable displacement hydraulic pump for giving the rotational driving force by the engine. And a method of controlling the first hydraulic pump in a construction machine having a plurality of hydraulic actuators and a switching valve control valve that receive supply of pressure oil from the second hydraulic pump. A first step of giving an operation command to the first switching valve control valve to drive the hydraulic actuator, a second step of detecting the speed of the first hydraulic actuator during the first step, and the first step The third step of calculating the sum of the minimum required flow rate (Qmin) that is the characteristic value of the first relief valve and the pressure oil flow rate to the first hydraulic actuator corresponding to the detected speed in one step A fourth step of giving a calculation result of the third step as a discharge flow rate command value of the first hydraulic pump during the first step, and a discharge pressure of the first hydraulic pump during the first step. Detect Fifth step and the said from the difference between the absorption torque Ts of the first hydraulic pump determined from the detected pressure and the output torque Te of the engine in the third calculation result by step and the fifth step second hydraulic pump And a sixth step of calculating a command absorption torque Tm to the command to the hydraulic pump.

Furthermore, the hydraulic pump control method according to the present invention for achieving the above object includes a first hydraulic actuator, a first variable displacement hydraulic pump for supplying required pressure oil to the first hydraulic actuator, A first switching valve control valve provided between the first hydraulic pump and a first hydraulic actuator, a first relief valve provided in a pressure oil supply flow path to the first hydraulic actuator, In a state where an operation command is given to the first switching valve control valve to drive the first hydraulic actuator, the supply of pressure oil discharged from the first hydraulic pump is supplied to the first hydraulic actuator and Means limited to the first relief valve, an engine that provides a rotational driving force to the first hydraulic pump, and a second variable displacement hydraulic port that is provided with the rotational driving force by the engine And a method of controlling the first and second hydraulic pumps in a construction machine having a plurality of hydraulic actuators that receive supply of pressure oil from the second hydraulic pump and a switching valve control valve, A first step of giving an operation command to the first switching valve control valve to drive the first hydraulic actuator, and a second step of detecting the speed of the first hydraulic actuator during the first step. And the sum of the minimum required flow rate (Qmin) that is the characteristic value of the first relief valve and the pressure oil flow rate to the first hydraulic actuator corresponding to the detected speed is calculated during the first step. A third step, a fourth step of giving a calculation result of the third step as a discharge flow rate command value of the first hydraulic pump during the first step, and the first hydraulic pump during the first step of A fifth step of detecting a pressure output, wherein the difference between the output torque Te of the third calculation result by step as determined from the detected pressure in the fifth step the first hydraulic pump absorption torque Ts and the engine And a sixth step of calculating a command absorption torque Tm to the second hydraulic pump and using the command absorption torque Tm as a command to the second hydraulic pump.

In addition, a construction machine using a hydraulic pump control method according to the present invention for achieving the above object includes a first hydraulic actuator, a first variable capacity for supplying required pressure oil to the first hydraulic actuator. Type hydraulic pump, second hydraulic actuator, second variable displacement hydraulic pump for supplying the second hydraulic actuator with required pressure oil, and provided between the first hydraulic pump and the first hydraulic actuator The first switching valve control valve, the first relief valve provided in the pressure oil supply passage to the first hydraulic actuator, and the first switching valve control valve to drive the first hydraulic actuator Means for limiting the supply of pressure oil discharged from the first hydraulic pump to the first hydraulic actuator and the first relief valve in a state where an operation command is given to An engine that applies rotational driving force to the first hydraulic pump, a second variable displacement hydraulic pump that receives rotational driving force from the engine, and a plurality of hydraulic actuators that receive pressure oil from the second hydraulic pump, and A construction machine provided with a switching valve control valve, wherein the construction machine provides an operation command means for giving an operation command to the first switching valve control valve to drive the first hydraulic actuator, and the first Speed detecting means for detecting the speed of the hydraulic actuator, a minimum required flow rate (Qmin) which is a characteristic value of the first relief valve, and a pressure oil flow rate to the first hydraulic actuator corresponding to the detected speed A first calculation means for calculating a sum flow rate, and a first discharge flow rate index for giving a calculation result of the first calculation means as a discharge flow rate command value of the first hydraulic pump. Means the absorption of the first and the discharge pressure detecting means for detecting a delivery pressure of the hydraulic pump, the first of said first hydraulic pump calculation results obtained from the detected pressure of the discharge pressure detecting means by the operation means Second calculation means for calculating a command absorption torque Tm to the second hydraulic pump from the difference between the torque Ts and the output torque Te of the engine, and the calculation result of the second calculation means as the second hydraulic pump The second discharge flow rate command means for giving the discharge flow rate command value can be provided.

  In that case, it is preferable that the first hydraulic actuator is a turning hydraulic motor.

  In this case, the first hydraulic actuator is preferably a traveling hydraulic motor.

  Furthermore, it is preferable that the speed detecting means is a rotational speed detecting means for detecting the rotational speed of the output shaft of the hydraulic motor.

  In this case, the speed detecting means may be a flow rate sensor provided in the supply or discharge path near the hydraulic motor.

  According to the first aspect of the present invention, a hydraulic actuator, a variable displacement hydraulic pump that supplies required hydraulic oil to the hydraulic actuator, a switching valve control valve provided between the hydraulic pump and the hydraulic actuator, and the hydraulic actuator Pressure oil discharged from the hydraulic pump in a state in which an operation command is given to the switching valve control valve to drive the hydraulic actuator. Is a method for controlling the hydraulic pump in a hydraulic drive device having means for limiting the supply to the hydraulic actuator and the relief valve, and gives an operation command to the switching valve control valve to drive the hydraulic actuator A first step; a second step of detecting a speed of the hydraulic actuator during the first step; and the first step. A third step of calculating a sum of the minimum required flow rate (Qmin) which is a characteristic value of the relief valve and a pressure oil flow rate to the hydraulic actuator corresponding to the detected speed; and during the first step, Since it comprises the 4th process which gives the calculation result by the 3rd process as a discharge flow rate command value of the above-mentioned hydraulic pump, it becomes possible to reduce energy waste by surplus flow in a relief valve as much as possible. .

According to a second aspect of the present invention, the first hydraulic actuator, the first variable displacement hydraulic pump that supplies required pressure oil to the first hydraulic actuator, the first hydraulic pump, and the first hydraulic pump A first switching valve control valve provided between the hydraulic actuators, a first relief valve provided in a pressure oil supply flow path to the first hydraulic actuator, and the first hydraulic actuator to be driven. In a state where an operation command to the first switching valve control valve is given, supply of pressure oil discharged from the first hydraulic pump is limited to the first hydraulic actuator and the first relief valve. Means, an engine for applying a rotational driving force to the first hydraulic pump, a second variable displacement hydraulic pump to which the rotational driving force is applied by the engine, and pressure oil from the second hydraulic pump. A method for controlling the first hydraulic pump in the construction machine having a plurality of hydraulic actuators and the switching valve control valve for receiving the sheet, the method comprises
A first step of giving an operation command to the first switching valve control valve to drive the first hydraulic actuator; a second step of detecting a speed of the first hydraulic actuator during the first step; During the first step, a flow rate that is the sum of the minimum required flow rate (Qmin) that is a characteristic value of the first relief valve and the pressure oil flow rate to the first hydraulic actuator corresponding to the detected speed is calculated. A construction machine such as a hydraulic excavator includes a third process and a fourth process in which the calculation result of the third process is given as a discharge flow rate command value of the first hydraulic pump during the first process. This makes it possible to save fossil fuel consumption in the engine and reduce environmental pollution. Furthermore, since the excess flow rate of the relief valve can be suppressed to the necessary minimum amount Qmin, the relief valve can be downsized as a result.

  According to a third aspect of the present invention, the first hydraulic actuator, the first variable displacement hydraulic pump that supplies required pressure oil to the first hydraulic actuator, the first hydraulic pump, A first switching valve control valve provided between one hydraulic actuator, a first relief valve provided in a pressure oil supply flow path to the first hydraulic actuator, and the first hydraulic actuator. Therefore, in a state where an operation command is given to the first switching valve control valve, the supply of pressure oil discharged from the first hydraulic pump is limited to the first hydraulic actuator and the first relief valve. Means for applying a rotational driving force to the first hydraulic pump, a second variable displacement hydraulic pump to which the rotational driving force is applied by the engine, and a pressure from the second hydraulic pump. A method for controlling the first and second hydraulic pumps in a construction machine having a plurality of hydraulic actuators and a switching valve control valve, wherein the method drives the first hydraulic actuator to drive the first hydraulic actuator. A first step for giving an operation command to the first switching valve control valve; a second step for detecting the speed of the first hydraulic actuator during the first step; and the first step during the first step. A third step of calculating a sum of a minimum required flow rate (Qmin) that is a characteristic value of the relief valve and a pressure oil flow rate to the first hydraulic actuator corresponding to the detected speed; and during the first step, A fourth step of giving a calculation result of the third step as a discharge flow rate command value of the first hydraulic pump; a fifth step of detecting a discharge pressure of the first hydraulic pump during the first step; Third And a sixth step of calculating a command absorption torque Tm to the second hydraulic pump from the calculated result of the step and the detected pressure in the fifth step and using the command absorption torque Tm to the second hydraulic pump as a command. Therefore, the first hydraulic pump can be controlled with priority over the second hydraulic pump. For example, in a construction machine, the first hydraulic pump is used for a swing motor, and the second hydraulic pump is used for a plurality of other hydraulic pumps. When the hydraulic actuator is used, the turning operation can be prioritized within the output range of the engine.

FIG. 2 is a hydraulic circuit diagram of a hydraulic excavator provided with a dedicated swirling pump and a motor for rotationally driving an upper swivel, illustrating a preferred embodiment of the present invention. It is a detailed control block diagram of the calculating part of FIG. It is a plot figure which shows the characteristic at the time of turning starting and acceleration of the hydraulic shovel to which the control method by this invention is applied. FIG. 10 is a plot diagram comparing the swirl pump discharge amount Q of the control according to the present invention of FIG. 3 with the swirl pump discharge amount Qp of the conventional control of FIG. 9. It is a schematic diagram explaining the general characteristic of a relief valve, Comprising: (a) is a hydraulic circuit diagram, (b) is a figure which shows the relationship between the pressure of the input side line of a relief valve, and a relief flow rate, (c) is hydraulic pressure It is a figure which shows the mode of the rotation speed at the time of starting of a motor. It is a various waveform diagram which shows the rotational characteristic of the conventional hydraulic shovel turning motor. It is a wave form diagram which shows the constant horsepower control of the hydraulic pump at the time of single rotation operation in a hydraulic excavator. It is a plot waveform diagram showing the hydraulic motor rotation characteristics at the time of turning start and acceleration in the hydraulic excavator. It is a plot waveform diagram which shows the characteristic at the time of turning starting and acceleration of the hydraulic shovel in the case of the conventional constant horsepower control.

  Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS.

  FIG. 1 shows a hydraulic circuit of a hydraulic excavator equipped with a dedicated swirling pump and a motor that rotationally drives an upper swivel. In FIG. 1, reference numeral 1 denotes an engine that consumes fossil fuel such as gasoline and generates a rotational driving force on the output shaft Y. The coaxial Y has a variable displacement main pump 2, a rotary pump 4 and Gear pumps 6 and 7 having a constant discharge amount are arranged coaxially. The swing pump 4 and the main pump 2 constitute a first variable displacement hydraulic pump and a second variable displacement hydraulic pump in the present invention, respectively.

  Reference numerals 3 and 5 are a main pump control unit and a swing pump control unit, respectively, and an electromagnetic proportional valve 19 for main pump flow rate control and an electromagnetic proportional control for swing pump flow rate control via a pressure oil signal line indicated by a broken line. A hydraulic control signal is given from the valve 16.

  Reference numeral 8 indicates the supply of pressure oil to a hydraulic actuator of a hydraulic excavator that receives pressure oil supply from the main pump 2 other than the swing motor HM, such as a boom cylinder, an arm cylinder, a bucket cylinder, a traveling hydraulic motor (not shown), and the like. It is a switching control valve unit that controls exhaust.

  Reference numeral 9 is a switching control valve for turning and is supplied with operation pressure signals SG1 and SG2 from the pilot valve 13. The pilot valve 13 is supplied with a pressure oil source from the gear pump 6. The turning switching control valve 9 constitutes the first switching control valve in the present invention, and the boom cylinder, arm cylinder, bucket cylinder, traveling hydraulic motor, etc. are the second in the present invention. A hydraulic actuator is configured.

  Reference numeral 10 denotes a swing motor unit, in which a swing hydraulic motor HM capable of forward and reverse rotation, a pair of relief valves RF, and a check valve CK are arranged. An upper swivel (not shown) is rotatably coupled to the output shaft X of the turning motor HM via a speed reducer 12 and a pinion 12a.

  Reference numeral 11 is a rotation speed detector, which generates an electric signal S1 corresponding to the rotation speed of the turning motor HM and supplies it to the calculation unit 14. In addition, it is also possible to provide the flow rate sensor 10a shown with the broken line instead of the said rotational speed detector 11 in the flow path in the vicinity of the turning motor HM. The turning motor unit 10 constitutes a first hydraulic actuator in the present invention.

  The arithmetic unit 14 is further supplied with an electric signal S2. This signal S2 is the output of the oil / electric converter 17 that detects the pressure P of the discharge side line L of the rotary pump 4. The electromagnetic proportional valves 16 and 19 are supplied with pressure oil from the gear pump 7 as a pressure oil source.

  There are two types of outputs from the calculation unit 14, that is, a flow rate command line 15 to the electromagnetic proportional valve 16 and a torque command line 18 to the electromagnetic proportional valve 19. As shown in FIG. It is given as a command absorption torque Tm to the pump.

  FIG. 2 is a control block diagram illustrating details of the calculation unit 14 of FIG. In FIG. 1, the calculation unit 14 includes a first calculation unit 14a and a second calculation unit 14b. In the calculation unit 14a, the command value Q to the swing pump 4 is calculated from the detected rotational speed Nm of the swing motor HM as shown in the block b1. In this calculation, the product of Qth, that is, the actual rotational speed Nm of the swing motor HM and the unit rotational volume Vth of the swing motor HM (Qth (L / min) = (Vth × Nm) / 1000) and the relief valve RF are necessary. Q (Q = Qth + Qmin) is calculated as the sum of the minimum flow rate Qmin.

  Further, in the block b2, the calculation unit 14b calculates Vact, that is, the discharge volume per unit rotation (Vact (cc / rev) = (1000 × Q) / Nm) required for the rotary pump 4 from the calculated Q. Further, in block b3, the absorption torque Ts (Ts = (P × Vact) / (2π)) of the swing pump 4 is calculated as a product of the detected pressure P on the discharge side of the swing pump 4 and the Vact, In block b4, a difference Tm (Tm = Te−Ts) between the output torques Te and Ts of the engine 1 is calculated, and this difference Tm is given to the electromagnetic proportional valve 19 so as to become a command value of the main pump 2. The relationship between Te, Ts, and Tm may be Te ≧ Tm + Ts. This gives priority to the discharge amount required for the swing pump 4 over the main pump 2 and controls so as not to exceed the maximum output torque of the engine 1.

  Although all the arithmetic processing in the arithmetic unit 14 can be performed by analog processing, it is preferable that the microcomputer system performs arithmetic operations shown in blocks b1 to b4 at predetermined sampling times and outputs Q and Tm. In this case, although not shown, A / D conversion is performed on the signals S1 and S2, and D / A conversion is performed on the signals Q and Tm.

  FIG. 3 is a plot showing characteristics at the time of turning start acceleration of a hydraulic excavator to which the control method of the present invention is applied. As shown in the figure, waveforms of the respective characteristics of the swing pump discharge amount Q, the swing motor theoretical flow rate Qth, the swing motor rotation speed Nm, and the swing motor inlet pressure Pa are shown. Further, as can be seen from the figure, the difference Qmin between the pump discharge amount Q and the motor theoretical flow rate Qth is substantially constant from the start time 3.4 (sec) to the time 8.6 (sec), and the swing pump It is shown that the discharge amount Q satisfactorily follows the turning motor theoretical flow rate Qth.

  FIG. 4 is a plot diagram comparing the swirl pump discharge amount Qp of the conventional control of FIG. 9 and the swirl pump discharge amount Q of the control of the present invention of FIG. As can be seen from FIG. 4, the hatched portion in the figure is a portion related to fuel consumption reduction.

  In the above description, the supply of pressure oil discharged from the first hydraulic pump is performed in a state where an operation command to the first switching valve control valve is given to drive the (first) hydraulic actuator. Although the means limited to the first hydraulic actuator and the first relief valve is not directly described, the limiting means is, for example, in FIG. Therefore, the discharge side flow rate is also supplied and connected only to the swing motor unit 10 via the switching control valve 9, and the limitation is obvious in that sense.

  Although the preferred embodiment of the present invention has been described above, those skilled in the art can make various modifications based on the embodiment of the present invention shown in FIGS.

  For example, instead of the swing pump and the swing motor in FIG. 1, a circuit dedicated to the travel pump and the travel motor can be provided. Further, in addition to the swing pump and the swing motor in FIG. 1, a circuit dedicated to the travel pump and the travel motor can be provided independently.

  A boom cylinder can also be designated as the hydraulic actuator.

  Furthermore, in FIGS. 1 and 2, the first calculation unit 14 a and the second calculation unit 14 b are integrally coupled to the calculation unit 14, but only the first calculation unit may be used.

  Further, in the hydraulic circuit shown in FIG. 1, the swing pump 4 is arranged and configured exclusively for the swing motor unit 10. However, the merging valve is provided only when the merging valve is provided and the slewing switching control valve 9 is in the OFF state. It is also possible to join the pressure oil from the swirl pump to the discharge line of the main pump 2 via In that case, another constant value can be set instead of Qmin.

DESCRIPTION OF SYMBOLS 1 Engine 2 Main pump 3 Main pump control part 4 Swing pump 5 Swing pump control part 6 Gear pump 7 Gear pump 8 Main switching control valve unit 9 Swing switching control valve 10 Swing motor unit 11 Rotational speed detector 12 Decelerator 13 Pilot valve 14 Calculation 15 Flow rate command 16 Proportional solenoid valve for swing pump flow control 17 Oil / electric converter 18 Torque command line 19 Proportional solenoid valve for main pump flow control CK Check valve LD Load HM Hydraulic motor RF Relief valve SG Operation pressure signal SG1 Operation pressure Signal SG2 Operation pressure signal X Hydraulic motor output shaft Y Engine output shaft VL Switching valve Nm Rotating motor rotation speed (rpm)
Te engine output torque (N ・ m)
Ts Rotating pump absorption torque (N · m)
Tm Command absorption torque to the main pump (N · m)
Qth Flow rate per minute to the swing motor (L / min)
Vth Rotation motor unit rotation volume (cc / rev)
Q Command discharge flow rate to the revolving pump (L / min)
Vact Discharge volume per unit rotation required for slewing pump (cc / rev)
P Main pump discharge pressure (MPa)
Qmin Required minimum flow rate of relief valve (L / min)

Claims (8)

The first hydraulic actuator, said supply the required pressure oil to the first hydraulic actuator first variable displacement hydraulic pump, a second hydraulic actuator, first supply the required pressure oil to the second hydraulic actuator 2 variable displacement hydraulic pumps , a switching valve control valve provided between the first hydraulic pump and the hydraulic actuator, an engine for applying a rotational driving force to the first hydraulic pump, and supply of pressure oil to the hydraulic actuator The hydraulic actuator is provided with a relief valve provided in a flow path, and further supplies pressure oil discharged from the hydraulic pump in a state where an operation command is given to the switching valve control valve to drive the hydraulic actuator. And a method of controlling the hydraulic pump in a hydraulic drive device comprising means limited to the relief valve, the method comprising: A first step for giving an operation command to the switching valve control valve to drive the hydraulic actuator; a second step for detecting the speed of the hydraulic actuator during the first step; and the relief valve during the first step. A third step of calculating a sum of a minimum required flow rate (Qmin) that is a characteristic value of the pressure and a pressure oil flow rate to the hydraulic actuator corresponding to the detected speed, and the third step during the first step. A fourth step of giving a calculation result as a discharge flow rate command value of the hydraulic pump; a fifth step of detecting a discharge pressure of the first hydraulic pump during the first step; a calculation result of the third step; Starring command absorption torque Tm to the second hydraulic pump from the difference between the output torque Te of the absorption torque Ts and the engine of the first hydraulic pump determined from the detected pressure in the fifth step The method of the hydraulic pump comprising a sixth step of the commands to the second hydraulic pump.   A first hydraulic actuator, a first variable displacement hydraulic pump that supplies required pressure oil to the first hydraulic actuator, and a first switching provided between the first hydraulic pump and the first hydraulic actuator Operation command to the first switching valve control valve to drive the first relief valve and the first hydraulic actuator provided in the valve control valve and the pressure oil supply flow path to the first hydraulic actuator Means for limiting the supply of pressure oil discharged from the first hydraulic pump to the first hydraulic actuator and the first relief valve, and a rotational driving force to the first hydraulic pump. Engine, a second variable displacement hydraulic pump to which rotational driving force is applied by the engine, and a plurality of hydraulic actuators to which pressure oil is supplied from the second hydraulic pump And a method of controlling the first hydraulic pump in a construction machine having a switching valve control valve, wherein the method operates on the first switching valve control valve to drive the first hydraulic actuator. A first step for giving a command; a second step for detecting the speed of the first hydraulic actuator during the first step; and a minimum required flow rate that is a characteristic value of the first relief valve during the first step. (Qmin) and a third step of calculating the sum of the flow rate of pressure oil to the first hydraulic actuator corresponding to the detected speed, and the calculation result of the third step during the first step is the first step. A fourth step given as a discharge flow rate command value for one hydraulic pump, a fifth step for detecting the discharge pressure of the first hydraulic pump during the first step, a calculation result Q by the third step, and this calculation From result Q The discharge volume per unit rotation required for the engine is calculated, and the first step comprises the sixth step in which the difference between the output torque of the engine and the swing pump is calculated as the product of the pressure of the swing pump and the discharge volume. Hydraulic pump control method.   A first hydraulic actuator, a first variable displacement hydraulic pump that supplies required pressure oil to the first hydraulic actuator, and a first switching provided between the first hydraulic pump and the first hydraulic actuator Operation command to the first switching valve control valve to drive the first relief valve and the first hydraulic actuator provided in the valve control valve and the pressure oil supply flow path to the first hydraulic actuator Means for limiting the supply of pressure oil discharged from the first hydraulic pump to the first hydraulic actuator and the first relief valve, and a rotational driving force to the first hydraulic pump. Engine, a second variable displacement hydraulic pump to which rotational driving force is applied by the engine, and a plurality of hydraulic actuators to which pressure oil is supplied from the second hydraulic pump And a method of controlling the first and second hydraulic pumps in a construction machine having a switching valve control valve, wherein the method is configured to drive the first hydraulic actuator. A first step for giving an operation command to the second step, a second step for detecting the speed of the first hydraulic actuator during the first step, and a characteristic value of the first relief valve during the first step. A third step of calculating a sum of a minimum required flow rate (Qmin) and a pressure oil flow rate to the first hydraulic actuator corresponding to the detected speed; and a calculation result of the third step during the first step As a discharge flow rate command value of the first hydraulic pump, a fifth step of detecting the discharge pressure of the first hydraulic pump during the first step, and a calculation result Q by the third step And this calculation result Q And a sixth step in which a discharge volume per unit rotation required for the swing pump is calculated, and a difference between the engine output torque and the swing pump is calculated as a product of the pressure of the swing pump and the discharge volume. A control method for the first and second hydraulic pumps. A first hydraulic actuator, a first variable displacement hydraulic pump that supplies required pressure oil to the first hydraulic actuator, a second hydraulic actuator, and a second hydraulic actuator that supplies required pressure oil to the second hydraulic actuator. 2 variable displacement hydraulic pumps, a first switching valve control valve provided between the first hydraulic pump and the first hydraulic actuator, and a pressure oil supply flow path to the first hydraulic actuator. Supply of pressure oil discharged from the first hydraulic pump in a state where an operation command is given to the first switching valve control valve to drive the first relief valve and the first hydraulic actuator Means for limiting the first hydraulic actuator and the first relief valve, an engine for applying a rotational driving force to the first hydraulic pump, and a rotational driving force applied by the engine A second variable displacement hydraulic pump and a plurality of hydraulic actuators that receive pressure oil from the second hydraulic pump and a switching valve control valve, the construction machine having the first Operation command means for giving an operation command to the first switching valve control valve to drive the hydraulic actuator, speed detection means for detecting the speed of the first hydraulic actuator, and characteristic values of the first relief valve The first calculation means for calculating the sum of the minimum required flow rate (Qmin) and the pressure oil flow rate to the first hydraulic actuator corresponding to the detected speed, and the calculation result of the first calculation means First discharge flow rate command means for giving a discharge flow rate command value of the first hydraulic pump, discharge pressure detection means for detecting the discharge pressure of the first hydraulic pump,
The difference between the absorption torque Ts of the first hydraulic pump and the output torque Te of the engine, which is obtained from the calculation result by the first calculation means and the detection pressure of the discharge pressure detection means, is applied to the second hydraulic pump. The second calculating means for calculating the command absorption torque Tm, and the second discharge flow rate command means for giving the calculation result of the second calculating means as the discharge flow rate command value of the second hydraulic pump. And construction machinery.   The construction machine according to claim 4, wherein the first hydraulic actuator is a turning hydraulic motor.   The construction machine according to claim 4, wherein the first hydraulic actuator is a traveling hydraulic motor.   The construction machine according to claim 5 or 6, wherein the speed detecting means is a rotational speed detecting means for detecting a rotational speed of an output shaft of the hydraulic motor.   The construction machine according to claim 5 or 6, wherein the speed detecting means is a flow rate sensor provided in a supply or discharge passage in the vicinity of the hydraulic motor.

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