JP2010169242A - Hydraulic drive mechanism for construction machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent dropping of engine speed by previously suppressing generation of a rapid drive load of a hydraulic pump. <P>SOLUTION: The hydraulic drive mechanism for construction machine is provided with the hydraulic pump 13 driven by an engine 12, a torque adjusting means 31 for adjusting torque of the hydraulic pump 13, a hydraulic actuator 16 driven by delivered oil from the hydraulic pump 13, an operating device 20 operating the hydraulic actuator 16, an operating condition detector 21 detecting an operating condition of the operating device 20, and a controller 22 controlling the torque adjusting means 31 on the basis of a signal from the operating condition detector 21. The controller 22 is equipped with a first torque control part carrying out control such that the hydraulic pump 13 becomes low torque when the operating device 20 is operated to an operating condition, and a second torque control part carrying out control so as to raise the hydraulic pump 13 from the low torque thereafter to transit to maximum torque. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a hydraulic drive device for a construction machine, and more particularly to a hydraulic drive device for a construction machine that drives a hydraulic pump by an engine and drives a hydraulic actuator by pressure oil from the hydraulic pump.

  Conventionally, in a construction machine such as this type of hydraulic excavator, an upper swing body is mounted on a lower traveling body so as to be able to swing, and a boom is connected to a front portion of the upper swing body so as to be able to move up and down. Also, an arm is pivotally attached to the tip of the boom so as to be vertically rotatable, and a bucket is swingably attached to the tip of the arm. The boom, arm and bucket are driven by hydraulic cylinders as hydraulic actuators.

  An engine is mounted on the upper swing body, and a variable displacement hydraulic pump is connected to the output shaft of the engine. The hydraulic pump is configured to drive the hydraulic cylinder by supplying pressure oil to the hydraulic cylinder via a flow control valve.

Further, in order to stabilize the load of the engine, a negative control throttle is provided on the most downstream side (oil tank side) of the discharge line of the hydraulic pump, the negative control pressure upstream of the negative control throttle is negatively fed back, and the hydraulic pump is negatively fed back. A control method is employed (see Patent Document 1).
JP-A-6-117410

  In the conventional hydraulic drive device, when the hydraulic cylinder reaches the stroke end, a drive load is suddenly generated. At this time, the drive load is detected based on the pressure rise of the hydraulic pump, and the drive load of the hydraulic pump is detected. Is controlled to reduce.

  However, according to the pump load reduction control method, the drive load is detected in a state in which the drive load acts on the hydraulic cylinder rapidly, and thereafter the drive load of the hydraulic pump is reduced afterwards. Accordingly, there has been a problem that the response to the reduction of the pump load is delayed, and as a result, the rotational speed of the engine as the hydraulic pump drive source rapidly decreases.

  If the engine is equipped with a variable capacity turbocharger with adjustable nozzle opening, when the boost pressure of the turbocharger is generated, the driving load of the hydraulic pump is detected based on the increase in the boost pressure. Thus, a control method for reducing the driving load has been proposed. However, even in this control method, the boost pressure is detected in a state where the driving load is applied to the hydraulic cylinder, and then the driving load of the hydraulic pump is reduced afterwards. The response is delayed and the engine speed drops sharply.

  Thus, there is a technical problem to be solved in order to prevent a rapid drive load of the hydraulic pump and prevent a decrease in the engine speed, and the present invention aims to solve this problem. And

  The present invention has been proposed to achieve the above object, and the invention according to claim 1 includes an engine, a hydraulic pump driven by the engine, and torque adjusting means for adjusting the torque of the hydraulic pump. An operation for detecting an operation state of the operation device in a hydraulic drive device for a construction machine, comprising: a hydraulic actuator to which pressure oil discharged from the hydraulic pump is supplied; and an operation device for operating the hydraulic actuator. A state detector, and a controller for controlling the torque adjusting means based on a signal from the operation state detector, wherein the controller is configured to reduce the torque of the hydraulic pump when the operation device is operated. A first torque control unit that controls the low-torque state and the hydraulic pump from low torque to maximum torque after a predetermined time has elapsed in the low-torque state. And a variable capacity turbocharger with an adjustable nozzle opening degree mounted on the engine, and the second torque control unit includes a second torque control unit that controls the transition of the turbocharger. When the nozzle opening speed becomes a predetermined value or more, the torque of the hydraulic pump is controlled so as to increase from a low torque corresponding to the nozzle opening speed and shift to a maximum torque. A hydraulic drive is provided.

  According to this configuration, the hydraulic pump is operated so as to smoothly change from the low torque to the maximum torque by continuously controlling the operation of the torque adjusting means by the first torque control unit and the second torque control unit. That is, first, the first torque control unit is controlled so that the torque of the hydraulic pump becomes a predetermined low torque lower than the maximum torque when the operating device is operated from the non-operating state to the operating state.

Next, after the control in the low torque state is maintained for a predetermined time ΔT (a time during which a sudden drive load can be suppressed), the second torque control unit increases the hydraulic pump torque to the maximum torque according to a predetermined control pattern. Control to ascend. Thus, when the operating device is turned on, the hydraulic pump rises from the low torque and smoothly shifts to the maximum torque.
In the present invention, furthermore, the torque of the hydraulic pump is such that when the nozzle opening speed of the turbocharger is equal to or higher than a predetermined value V _N , that is, higher than the nozzle opening speed at which a required engine output can be secured. Rises from a low torque corresponding to the maximum torque, and shifts to a maximum torque according to a predetermined control pattern.

  According to a second aspect of the present invention, the second torque control unit increases the torque of the hydraulic pump from a low torque corresponding to the nozzle opening speed when the operation speed of the operation device is operated at a predetermined value or more. The hydraulic drive device for a construction machine according to claim 1, wherein control is performed so as to shift to the maximum torque.

According to this configuration, when the operating speed of the operating device (operating lever) becomes equal to or higher than the predetermined value V _L , that is, the operating speed V _{L that} can ensure the required hydraulic driving force, the torque of the hydraulic pump The torque rises from a low torque according to the opening speed, and smoothly shifts to the maximum torque according to a predetermined control pattern.

  A third aspect of the present invention provides the hydraulic drive device for a construction machine according to the first or second aspect, wherein the torque control of the hydraulic pump controls a pump discharge pressure.

  According to this configuration, since the torque control of the hydraulic pump controls the pump discharge pressure, the pressure of the pressure oil is quickly reduced and controlled by connecting the discharge pressure control means to the hydraulic pump.

  According to a fourth aspect of the present invention, there is provided the hydraulic drive device for a construction machine according to the first or second aspect, wherein the torque control of the hydraulic pump controls a pump discharge flow rate.

  According to this configuration, since the torque control of the hydraulic pump controls the pump discharge flow rate, the flow rate of the pressure oil is quickly reduced and controlled by connecting the discharge flow rate control means to the hydraulic pump.

According to the first aspect of the present invention, since the torque of the hydraulic pump smoothly shifts from the low torque to the maximum torque, there is no fear that a sudden drive load acts on the hydraulic pump. not only the rotational speed decrease can be prevented, when the nozzle opening speed of the turbocharger exceeds a predetermined value V _N, the torque of the hydraulic pump, the maximum torque increased from a low torque corresponding to the nozzle opening speed Therefore, even when the nozzle opening speed changes greatly, pump control at the time of maximum torque transition can be performed more smoothly and stably.

According to the second aspect of the present invention, when the operating speed of the operating device becomes equal to or higher than the predetermined value V _L , the hydraulic pump rises from a low torque corresponding to the operating speed and shifts to the maximum torque. In addition to the effects of the described invention, even when the operation speed changes, the control at the time of shifting the maximum torque can be performed smoothly and stably.

  In addition to the effects of the first or second aspect, the invention according to the third aspect can quickly reduce and control the pressure of the pressure oil by connecting the discharge pressure control means to the hydraulic pump, and the torque control can be accurately performed. Can be done well.

  In addition to the effects of the first or second aspect, the invention according to the fourth aspect can reduce the flow rate of the pressure oil quickly by connecting the discharge flow rate control means to the hydraulic pump, and the torque control can be accurately performed. Can be done well.

  SUMMARY OF THE INVENTION In order to achieve the object of preventing a decrease in engine speed by preventing the sudden generation of a driving load of a hydraulic pump, the present invention provides an engine, a hydraulic pump driven by the engine, and the hydraulic pressure In a hydraulic drive device for a construction machine, comprising: a torque adjusting means for adjusting the torque of the pump; a hydraulic actuator to which pressure oil discharged from the hydraulic pump is supplied; and an operating device for operating the hydraulic actuator; An operation state detector for detecting an operation state of the operation device and a controller for controlling the torque adjusting means based on a signal from the operation state detector are provided, and the controller is operated in the operation state. A first torque control unit for controlling the hydraulic pump to have a low torque, and control in the low torque state has elapsed for a predetermined time. And a second torque control unit that controls the hydraulic pump to shift from a low torque to a maximum torque, the engine is equipped with a variable displacement turbocharger with an adjustable nozzle opening, and The second torque control unit causes the torque of the hydraulic pump to increase from a low torque corresponding to the nozzle opening speed and shift to the maximum torque when the nozzle opening speed of the turbocharger exceeds a predetermined value. Realized by controlling to.

  A preferred embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a hydraulic excavator 1 as a construction machine according to the present embodiment. In the figure, an upper swing body 3 is mounted on the lower traveling body 2 so as to be able to swing, and a boom 4 is connected to one front side of the upper swing body 3 so as to be able to move up and down. An arm 5 is pivotally attached to the tip of the boom 4 so as to be pivotable up and down, and a bucket 6 is swingably attached to the tip of the arm 5.

  The boom 4, the arm 5 and the bucket 6 are driven by a boom cylinder 7, an arm cylinder 8 and a bucket cylinder 9, respectively. A cab 10 is mounted on the other front side of the upper swing body 3, and equipment such as an engine 12 is arranged in an engine chamber 11 provided behind the cab 10.

FIG. 2 shows a hydraulic drive circuit diagram of the hydraulic drive apparatus according to the present invention. The present invention can be applied to any hydraulic drive circuit provided with one or more hydraulic cylinders or hydraulic motors such as the boom cylinder 7 as the hydraulic actuator. For convenience of explanation, in the configuration example of FIG. 2, only one hydraulic cylinder is shown, and the other hydraulic actuators are omitted.

  As shown in the figure, a main hydraulic pump 13 and a pilot hydraulic pump 14 are connected to the output shaft of the engine 12, and a swash plate type variable displacement pump is adopted as the main hydraulic pump 13. A driving hydraulic cylinder 16 is connected to the discharge line 15 of the main hydraulic pump 13, and a 6-port 3-position switching flow control valve (direction switching valve) 17 is provided in the middle of the discharge line 15. It has been.

  The flow control valve 17 is supplied from the main hydraulic pump 13 to the bottom side oil chamber or the top side oil chamber of the hydraulic cylinder 16 by switching from the neutral position to the extended position (A) or the contracted position (B). Accordingly, the hydraulic cylinder 16 is configured to expand or contract.

  Further, the flow control valve 17 is actuated via a remote control valve 19 interlocked with the operation lever 18, and the operation lever 18 and the remote control valve 19 constitute the operation device 20 of the present invention. An operation state detector 21 is attached to the operation device 20, and the operation state detector 21 detects an operation state including an operation speed of the operation lever 18 and transmits the signal to a control device 22 as a controller. To do.

  Further, the engine 12 is equipped with a variable capacity turbocharger (hereinafter abbreviated as “VG turbo”) 23 having a built-in turbine, and the VG turbo 23 is installed in a turbine housing (not shown). The supercharging efficiency or output of the engine 12 can be changed by changing the nozzle opening. Furthermore, a speed detector 24 is attached to the VG turbo 23, and the speed detector 24 detects the speed of the nozzle opening and transmits the signal to the control device 22.

  The control device 22 is mainly composed of a microcomputer, and as illustrated in FIG. 3, a signal input unit 22A, a calculation unit 22B, a storage unit 22C, a pump discharge pressure control unit 22D, a pump discharge flow rate control unit 22E, and a first torque control. Section 22F, second torque control section 22G, signal output section 22H and the like, and based on detection signals from the operation state detector 21 and speed detector 24, the discharge pressure, discharge flow rate and torque of the main hydraulic pump 13 Is variably controlled.

  In particular, the first torque control unit 22F has a predetermined torque (hereinafter referred to as “low”) that the torque of the main hydraulic pump 13 is lower than the maximum torque when the operation lever 18 of the operation device 20 is operated from the non-operation state to the operation state. The regulator 31 is controlled so as to be “torque”. Further, the second torque control unit 22G operates for a predetermined time ΔT (a time during which a sudden drive load can be effectively suppressed) in the low torque state, and then the torque of the main hydraulic pump 13 increases from the low torque to the maximum torque. Thus, the operation of the regulator 31 is controlled so that the transition is smoothly performed.

  An oil passage 26 branches off from the discharge line 15 of the main hydraulic pump 13. The oil passage 26 communicates with an oil tank 27, and a relief valve 28 is provided in the middle of the oil passage 26. The relief valve 28 is connected to the pilot hydraulic pump 14 by an oil passage 29, and an electromagnetic switching valve 30 is installed in the middle of the oil passage 29. The solenoid of the electromagnetic switching valve 30 is electrically connected to the output side of the control device 22 and is controlled by a command signal from the control device 22.

  The electromagnetic switching valve 30 controls the discharge pressure P of the main hydraulic pump 13. For example, when the driving load of the hydraulic pump 13 exceeds a set value, the relief valve 28 and the pilot hydraulic pressure are changed when the electromagnetic switching valve 30 is switched from the normal position to the operating position (c) by the discharge pressure lowering signal from the control device 22. Communication with the pump 14 is interrupted. As a result, the set pressure P of the relief valve 28 decreases, and the discharge pressure of the main hydraulic pump 13 decreases (see arrow A in FIG. 4).

  A regulator 31 is electrically connected to the output side of the control device 22, and the operation of the regulator 31 is controlled by a command signal from the control device 22. The regulator 31 can change the setting of the torque value (absorption torque value) or the discharge flow rate value by the control device 22.

  For example, when the driving load of the hydraulic pump 13 is equal to or higher than a predetermined set value, a discharge flow rate lowering signal or a torque lowering signal is output from the control device 22 to the regulator 31, so that the hydraulic cylinder 16 is not stopped. The set value in the regulator 31 is changed to reduce the discharge flow rate value or torque value. As a result, the discharge flow rate Q or the torque T of the main hydraulic pump 13 decreases (see arrow B in FIG. 4 or arrow C in FIG. 5).

  Next, torque control procedures in the hydraulic drive apparatus will be described in detail based on the flowchart of FIG. First, the main hydraulic pump 13 is driven to rotate by starting the engine 12. When the operating lever 18 of the operating device 20 is operated from the non-operating state to the operating state, the pressure oil from the main hydraulic pump 13 is passed through the flow control valve 17 to the bottom side oil chamber or top side of the hydraulic cylinder 16. Supplyed to the oil chamber, the hydraulic cylinder 16 extends or contracts (step S1).

When the operation lever 18 is switched to the operation state, the operation state detector 21 detects this and transmits a detection signal to the control device 22 (step S2). The control device 22 is controlled so that the torque of the main hydraulic pump 13 becomes the maximum value T _M1 by continuously controlling the operation of the regulator 31 by the first torque control unit 22F and the second torque control unit 22G. To do.

That is, first, when the operation lever 18 is operated from the non-operation state to the operation state, the first torque control unit 22F has a predetermined low torque _{TL1 in} which the torque of the main hydraulic pump 13 is lower than the maximum torque _TM1. Thus, the operation of the regulator 31 is controlled (step S3).

Next, after the torque of the main hydraulic pump 13 is held at the low torque T _L1 for a predetermined time ΔT, the second torque control unit 22G increases the torque of the main hydraulic pump 13 to the maximum torque T _M1 according to a predetermined control pattern. Thus, the operation of the regulator 31 is controlled. As described above, when the operation lever 18 is operated, the main hydraulic pump 13 does not immediately increase to the maximum torque T _M1 , but after the pump control in the low torque T _L1 state has elapsed for the predetermined time ΔT, the maximum torque T _M1 Transition smoothly.

In the present embodiment, when the nozzle opening speed of the VG turbo 23 or the operation speed of the operation lever 18 becomes equal to or higher than a predetermined value V _N or V _L , the second torque control unit is operated by the speed detector 24 or the operation state. Based on the signal from the detector 21, the operation of the regulator 31 is performed so that the main hydraulic pump 13 rises from the low torque T _L2 and shifts to the maximum torque T _M2 according to the nozzle opening speed or the lever operation speed. Is controlled (step S4).

Here, the predetermined value V _N or more means a nozzle opening speed or more that can ensure a required engine output, and the predetermined value V _L or more means an operation speed or more that can ensure a required hydraulic driving force.

  As described above, according to the present invention, when the operating lever 18 is operated from the non-operating state to the operating state, the torque of the main hydraulic pump 13 is controlled to be low, and after a predetermined time has elapsed, the main hydraulic pressure is controlled. The torque of the pump 13 smoothly shifts from the low torque to the maximum torque. Thus, since there is no fear that the driving load acts on the main hydraulic pump 13 rapidly, a decrease in the rotational speed of the engine 12 due to the driving load is reliably prevented.

  The torque of the main hydraulic pump 13 rises from a low torque corresponding to the nozzle opening speed when the nozzle opening speed of the VG turbo 23 exceeds a predetermined value, and continues to a maximum torque with a predetermined control pattern. Therefore, even when the nozzle opening speed changes greatly, the control at the time of the maximum torque transition can be executed smoothly and stably.

  Furthermore, the torque of the main hydraulic pump 13 continuously shifts from a low torque corresponding to the nozzle opening speed to a maximum torque when the operation speed of the operation lever 18 exceeds a predetermined value, so that the operation speed is large. Even when it changes, the control at the time of the maximum torque transition can be executed smoothly and stably.

    The torque control of the hydraulic pump according to the present invention can be accurately performed by controlling the pump discharge pressure or the pump discharge flow rate.

  It should be noted that the present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified ones.

1 is a side view of a hydraulic excavator equipped with a hydraulic drive device according to an embodiment of the present invention. 1 is a hydraulic drive circuit diagram of a hydraulic drive device according to the present invention. The block diagram explaining the structural example of the control apparatus which concerns on this invention. The graph of the flow volume-discharge pressure curve explaining the flow volume control / discharge pressure control of the hydraulic pump which concerns on this invention. The graph of the flow volume-discharge pressure curve explaining the torque control of the hydraulic pump which concerns on this invention. The flowchart which shows the control procedure of the pump torque which concerns on this invention.

1 Excavator (construction machine)
3 Upper swing body 4 Boom 5 Arm 6 Bucket 7 Boom cylinder 8 Arm cylinder 9 Bucket cylinder 12 Engine 13 Main hydraulic pump 16 Hydraulic cylinder (hydraulic actuator)
17 Flow control valve 18 Operation lever 19 Remote control valve 20 Operation device 21 Operation state detector 22 Control device (controller)
22F 1st torque control part 22G 2nd torque control part
23 VG turbo 24 speed detector 30 electromagnetic switching valve (discharge pressure control means)
31 Regulator (torque adjustment means)

Claims (4)

An engine, a hydraulic pump driven by the engine, torque adjusting means for adjusting the torque of the hydraulic pump, a hydraulic actuator to which pressure oil discharged from the hydraulic pump is supplied, and for operating the hydraulic actuator In a hydraulic drive device for a construction machine provided with an operation device of
An operation state detector for detecting an operation state of the operation device and a controller for controlling the torque adjusting means based on a signal from the operation state detector are provided, and the controller is operated in the operation state. A first torque control unit that controls the hydraulic pump to have a low torque, and the hydraulic pump shifts from the low torque to the maximum torque after a predetermined time has elapsed in the control in the low torque state. A variable displacement turbocharger having an adjustable nozzle opening, and the second torque control unit includes a nozzle opening speed of the turbocharger. When the pressure exceeds a predetermined value, control is performed so that the torque of the hydraulic pump increases from a low torque corresponding to the nozzle opening speed and shifts to the maximum torque. Hydraulic drive system for a construction machine according to claim.   The second torque control unit is configured to increase the torque of the hydraulic pump from a low torque corresponding to the nozzle opening speed and shift to the maximum torque when the operation speed of the operation device becomes a predetermined value or more. The hydraulic drive device for a construction machine according to claim 1, wherein the hydraulic drive device is controlled.   3. The hydraulic drive device for a construction machine according to claim 1, wherein the torque control of the hydraulic pump controls a pump discharge pressure.   3. The hydraulic drive device for a construction machine according to claim 1, wherein the torque control of the hydraulic pump controls a pump discharge flow rate.

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