JP2009275776A - Fluid pressure actuator control circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid pressure actuator control circuit providing the stability of a pump rotational speed and highly efficient operation of a prime mover for pump driving when working fluid is supplied from a pump and an accumulator into the fluid pressure actuator. <P>SOLUTION: The head side of a cylinder Cy is connected to the accumulator Acc through an accumulator control valve 1, and connected to the rod side through a regeneration control valve 2. The discharge side of a variable displacement pump Pp is connected to a pump flow control valve 3, and connected to the cylinder Cy through a shut-off control valve 4. A control device 5 provides a function of controlling pump flow discharged from the pump Pp or the pump power to a substantially constant level when the accumulator Acc is in an accumulation state, and supplying an insufficient flow rate from the accumulator Acc by controlling the accumulator control valve 1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fluid pressure actuator control circuit including an accumulator for recovering potential energy.

In a hydraulic excavator that moves a work machine up and down by a boom cylinder, the head side of the boom cylinder is connected to an accumulator via an accumulator operation valve, and connected to a tank via a variable relief valve. Depending on the position of the machine, the accumulator operation valve and variable relief valve are controlled to generate hydraulic pressure in the accumulator that balances the weight of the work equipment, and when raising the boom, pumps and accumulators are installed in multiple boom cylinders. There is a device for recovering and utilizing the potential energy of a hydraulic excavator in which hydraulic oil is supplied from (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 01-199001 (page 2-3, FIG. 1)

  In this conventional potential energy recovery and utilization device, when hydraulic oil is supplied from the accumulator to the boom cylinder, only a small amount of hydraulic oil is supplied from the pump to the boom cylinder, and the load on the prime mover driving the pump is reduced. The On the other hand, since the load fluctuation of the prime mover is large, the rotational speed and output of the prime mover are likely to fluctuate, the stability of the pump rotational speed is lacking, and the stability of the entire system is affected, and the rotational speed and output of the prime mover There is an energy loss due to the fluctuation of the engine, and the prime mover cannot be operated with high efficiency.

  The present invention has been made in view of these points, and ensures the stability of the pump rotation speed and the high-efficiency operation of the prime mover for driving the pump when the working fluid is supplied from the pump and the accumulator to the fluid pressure actuator. An object of the present invention is to provide a fluid pressure actuator control circuit that can be used.

  The invention described in claim 1 is raised by a fluid pressure actuator and a pump flow rate control valve that controls the direction and flow rate of the working fluid supplied from the variable displacement pump driven by the prime mover to the fluid pressure actuator. An accumulator capable of accumulating potential energy of the load body as accumulated pressure when descending, and an accumulator control valve provided in a passage between the fluid pressure actuator and the accumulator to control the flow of the working fluid from the accumulator to the fluid pressure actuator And a control device having a function of controlling the accumulator control valve to supply a deficient flow rate from the accumulator while controlling the pump flow rate or pump power discharged from the pump substantially constant when the accumulator is in a pressure accumulation state. Fluid pressure actuator control circuit equipped with It is.

  According to a second aspect of the present invention, the load body in the fluid pressure actuator control circuit according to the first aspect is a working device of a hydraulic excavator, and the fluid pressure actuator is a hydraulic cylinder that rotates the working device in the vertical direction. Is.

  According to the first aspect of the present invention, when the working fluid is supplied from the pump and the accumulator to the fluid pressure actuator, when the accumulator is in the pressure accumulation state, the pump flow rate or the pump discharged from the pump by the control device The power is controlled almost constant, and the accumulator control valve is controlled to supply the insufficient flow rate from the accumulator, so fluctuations in the rotational speed and output of the prime mover driving the pump are suppressed, and the stability of the pump rotational speed is improved. As a result, the entire system can be stabilized, energy loss associated with fluctuations in the rotational speed and output of the prime mover can be reduced, and the prime mover for driving the pump can be operated with high efficiency.

  According to the second aspect of the present invention, in the hybridization of the fluid pressure supply source that supplies the working fluid to the hydraulic cylinder that moves up and down the working device of the hydraulic excavator, the pump rotation when the pump and the accumulator are operated in common Speed stability and high efficiency operation of the prime mover for driving the pump can be ensured.

  Hereinafter, the present invention will be described in detail with reference to one embodiment shown in FIGS.

  As shown in FIG. 8, the excavator 10 as a work machine is provided with a work device 12 as a load body movably with respect to the machine body 11, and the work device 12 is connected to the machine body 11 and the machine body 11. A base end of a boom cylinder 14 as a hydraulic cylinder and a tip end of a rod are rotatably connected to a boom 13 pivotally supported so as to be rotatable in the vertical direction. Further, the boom 13 and the tip of the boom 13 are also connected. The base end portion of the arm cylinder 16 and the tip end portion of the rod are rotatably connected to the arm 15 pivotally supported by the arm 15, and the arm 15 and the tip end portion of the arm 15 are rotatable. A base end portion of the bucket cylinder 18 and a linkage 19 at the tip end portion of the rod are rotatably connected to the pivotally supported bucket 17.

  The boom cylinder 14 is a fluid pressure actuator that can receive a load W of the work device 12 and perform a reduction operation. Hereinafter, this type of fluid pressure actuator is referred to as a cylinder Cy.

  As shown in FIG. 1, the head side of the cylinder Cy is provided so as to be able to communicate with the accumulator Acc through a passage passing through an accumulation control valve 1a for energy accumulation control which is a part of the accumulator control valve 1, and through the accumulator Acc. On the opposite side, a release control valve 1b for energy release control, which is a part of the accumulator control valve 1, is provided.

  Further, a regeneration control valve 2 is provided in a passage that allows communication between the head side and the rod side of the cylinder Cy.

  Further, the discharge side passage of the variable displacement pump Pp driven by the engine E as the prime mover is connected to the supply port of the pump flow control valve 3, and one output port of the pump flow control valve 3 is connected to the passage M. The other port is connected to the rod side of the cylinder Cy via the closing control valve 4.

  The accumulation control valve 1a is an energy accumulation control valve that controls the direction and flow rate of the flow from the head side of the cylinder Cy to the accumulator Acc or the tank T. To switch between the accumulator Acc and the tank T, another valve is used. It may be used.

  The release control valve 1b is a valve for discharging the storage energy that controls the flow from the accumulator Acc to the head side of the cylinder Cy, and can be shared by the control valve 1 as one.

  With this release control valve 1b, the injection destination when reusing the energy stored in the accumulator Acc can be a circuit other than the cylinder Cy (boom cylinder 14) as the potential energy recovery destination. .

  Moreover, although the connection destination is set downstream of the pump flow rate control valve 3 by the release control valve 1b, the connection destination can be changed to the upstream side of the pump flow rate control valve 3. In this case, the pump power when using the accumulator Acc increases, which is not desirable in terms of energy saving, but is advantageous in terms of flexibility of the connection destination.

  The regeneration control valve 2 is a valve that controls the regeneration flow rate from the head side of the cylinder Cy to the rod side, and selects a valve having a large opening area when fully opened.

  The pump flow rate control valve 3 controls the direction of the pump flow rate injected into each load body drive device (boom cylinder 14, arm cylinder 16, bucket cylinder 18, etc.) and the return flow rate returned from each load body drive device to the tank T. It is a control valve that controls the flow rate and may be a spool valve in which the relationship between the injection flow rate and the return flow rate is fixed, but it is desirable that the relationship between the injection flow rate and the return flow rate can be controlled separately by a plurality of logic valves. .

  The closing control valve 4 is an auxiliary valve that closes the flow path to the tank T side when the pump flow control valve 3 cannot close the flow path to the tank T side during regeneration from the head side to the rod side of the cylinder Cy. .

  In FIG. 1, only one set of the cylinder Cy (boom cylinder 14 or the like) constituting the fluid pump and one load body driving device is shown, but a plurality of sets may be provided.

  An operating lever (electric joystick) L for operating the cylinder Cy, etc., a pressure sensor Sph for detecting the head pressure Ph of the cylinder Cy, a pressure sensor Spr for detecting the rod pressure Pr of the cylinder Cy, the pressure stored in the accumulator Acc, that is, the accumulator pressure The pressure sensor Sac for detecting Pa, the pressure sensor Spp for detecting the pump discharge pressure Ppp, the angle sensor San for detecting the angle of the load body such as the boom 13, and the rotation speed sensor R for detecting the rotation speed of the engine E are controlled. It is connected to the input unit of the device 5.

  The control device 5 incorporates an arithmetic processing device, a storage device, and the like, and an output unit of the control device 5 includes a movable control unit (solenoid or the like) of each control valve 1, 1a, 2, 3, 4 and an engine. It is connected to an engine control unit (such as an electronic governor G) that controls the rotational speed of E (= pump speed) and a pump capacity control unit (such as a swash plate regulator) that controls the capacity of the pump Pp. Control. A one-dot chain line in FIG. 1 represents a control signal line, and a solid line represents a hydraulic line.

  The control device 5 controls the rotational speed of the engine E and the capacity of the pump Pp, and when the accumulator Acc is in a pressure accumulation state, controls the pump flow rate or pump power discharged from the pump Pp to be substantially constant, for example, the pump Pp Has a function of supplying a constant base flow rate to the cylinder Cy from the accumulator Acc by controlling the accumulator control valve 1.

  Here, the pump power is determined by the pump discharge pressure Ppp detected by the pressure sensor Spp, the pump rotational speed and the pump capacity detected by the rotational speed sensor R (swash plate tilt angle controllable by the control device 5). Since the calculation can be performed by the product with the pump flow rate, the control device 5 can control the pump power almost constant by variably controlling the pump rotation speed or the pump capacity.

  Next, the energy release control by the control device 5 shown in FIG. 1 will be described with reference to the flowchart shown in FIG. Note that the circled numbers in the flowchart indicate step numbers. In the accumulator Acc, it is assumed that the working fluid flowing out from the head side of the cylinder Cy due to the lowering operation of the boom 13 or the like is accumulated to the maximum extent.

(Step 1)
It is determined by the pressure sensor Sac whether or not a sufficient accumulator pressure Pa is accumulated in the accumulator Acc.

(Step 2)
When there is a sufficient accumulator pressure Pa, it is determined whether or not the required flow rate calculated from the operation amount of the operation lever (electric joystick) L is larger than the base flow rate Qpc from the pump Pp.

(Step 3)
When a sufficient accumulator pressure Pa is accumulated in the accumulator Acc and the required flow rate is higher than the base flow rate Qpc from the pump Pp, the discharge flow rate from the pump Pp is suppressed to the base flow rate Qpc, and from the pump Pp In addition to the base flow rate Qpc, the shortage is compensated by the flow rate Qa from the accumulator Acc, and the required flow rate is supplied to the cylinder Cy head, and the boom 13 is pushed at the boom up speed commanded by the lever operation amount. increase.

(Step 4)
As shown in FIG. 3, since there is a certain relationship between the accumulator pressure Pa and the accumulator accumulation amount, it is determined that the release from the accumulator Acc is completed when the accumulator pressure Pa becomes less than the minimum set value Pmin. Since the discharge completion time t1 of the accumulator Acc is known, the discharge completion time t1 is always checked to determine whether or not it has elapsed. If it is before the discharge completion time t1 (NO), steps 1 to 4 are repeated.

(Step 5)
When the accumulated amount is completely discharged from the accumulator Acc (YES in step 4), or when the accumulator pressure Pa is not accumulated in the accumulator Acc in step 1 (NO), and the required flow rate is pump Pp in step 2. When the flow rate is not larger than the base flow rate Qpc from (NO), the variable flow means such as the pump swash plate is controlled and the pump flow rate control valve 3 is controlled so that the required flow rate Qp is supplied from the pump Pp to the cylinder Cy head. The boom 13 is pushed up at the boom up speed commanded by the lever operation amount.

  Next, based on the graph shown in FIG. 4, the operation of the control device at the time of energy release control will be described.

  It is assumed that the accumulator Acc can be supplied at a constant base flow rate Qao throughout one cycle. That is, the capacity of the accumulator Acc is Qao · tc. tc is the time required for one cycle.

  If the required flow rate calculated from the operation amount of the control lever L is higher than the base flow rate Qpc from the pump Pp, the shortage should be compensated by the flow rate Qa from the accumulator Acc in addition to the base flow rate Qpc from the pump Pp. Then, the required flow rate is supplied to the head side of the cylinder Cy.

  On the other hand, when the required flow rate is smaller than the base flow rate Qpc from the pump Pp, the necessary flow rate Qp is supplied only from the pump Pp to the head side of the cylinder Cy.

  Further, even after the discharge completion time t1 when the accumulated amount in the accumulator Acc has been discharged, the necessary flow rate Qp is supplied from the pump Pp only to the head side of the cylinder Cy.

  Next, FIG. 5 shows another operation example of the energy release control shown above in contrast to the energy release control shown in FIG. 4. Until the accumulated total amount is completely discharged from the accumulator Acc, the pump Pp It is necessary for the cylinder Cy by controlling the capacity to control the pump discharge flow rate to the minimum flow rate Qmin and controlling the opening degree of the release control valve 1b according to the required flow rate calculated from the operation amount of the operation lever L. Supply the flow rate.

  On the other hand, at the discharge completion time t1 of the accumulated amount from the accumulator Acc, the capacity of the pump Pp and the pump flow rate control valve 3 are controlled to supply the necessary flow rate to the cylinder Cy only from the pump Pp.

  The energy release control method shown in FIG. 5 uses the capacity of the accumulator Acc, so that there is an advantage that the required energy of the pump consumed by the pump Pp can be minimized, and the change in the pump rotation speed is large. The rotational speed and output of the engine E driven with the pump Pp as a load are also likely to fluctuate.

  On the other hand, in the energy release control method shown in FIG. 4, when the working fluid is supplied from the pump Pp and the accumulator Acc to the cylinder Cy, when the accumulator Acc is in the pressure accumulation state by the control device 5, By controlling the rotational speed of the engine E and the capacity of the pump Pp, the pump flow rate or pump power discharged from the pump Pp is controlled to be substantially constant (the pump flow rate is controlled to a constant base flow rate Qpc), and the accumulator control valve 1 is controlled to supply the insufficient flow rate Qa from the accumulator Acc, so that fluctuations in the rotational speed and output of the engine E that drives the pump Pp can be suppressed to ensure the stability of the pump rotational speed and the stability of the entire system. And can reduce energy loss caused by fluctuations in the rotational speed and output of the engine E. The can be operated at high efficiency.

  When this control method is applied to the boom cylinder 14 that moves the working device 12 of the excavator 10 shown in FIG. 8 up and down, the fluid pressure supply source that supplies the working fluid to the boom cylinder 14 is hybridized. In addition, the stability of the pump rotation speed when the pump Pp and the accumulator Acc are operated in common and the high-efficiency operation of the prime mover for driving the pump can be ensured.

  Next, the points to be noted when controlling the rotation speed of the engine E and the capacity of the pump Pp and the points to be noted when determining the base flow rate will be described from the viewpoints of stability of the pump rotation speed, engine fuel efficiency, and the like.

(1) There are the following two methods to keep in mind when setting the pump base flow rate Qpc.

  (i) The base flow rate is obtained by multiplying the pump maximum flow rate Qpmax by a coefficient A (0 <A ≦ 1). The coefficient A is a constant value.

    The pump maximum flow rate Qpmax is generally a variable of the pump discharge pressure Ppp.

    ・ If the flow rate is constant without considering the pump torque limit, the pump power fluctuates due to pressure fluctuation.

    FIG. 6 shows the relationship between the pump discharge pressure Ppp and the pump maximum flow rate Qpmax when the rotational speed is constant. The maximum pump flow rate Qpmax when the rotation speed fluctuates can be set by the following two methods.

    a. The value at the target rotational speed ωo is the pump maximum flow rate Qpmax.

    b. Further, when the pump rotational speed ω varies from the target rotational speed ωo, the pump maximum flow rate Qpmax may be varied according to the variation rate. When inversely proportional to the rotational speed fluctuation rate (multiplying by ωo / ω), the pump power approaches a constant value, and the load fluctuation can be reduced.

    In general, the pump discharge pressure is often kept at a substantially constant value according to the load (except for a short time during the pressure rise). At this time, the maximum pump flow rate Qpmax is almost constant. Kept.

  (ii) The pump base flow rate Qpc is variable according to the accumulated amount of accumulator Acc.

    The aim is to use up the accumulated amount of accumulator Acc.

a.Pump base flow rate Qpc1 = Required flow rate-Accumulator accumulated amount / 1 cycle required time tc
However, Qpc ≧ lower limit value is set so that it can be used even when the required flow rate is small.

Accumulator average flow rate = Accumulator accumulation / 1 cycle required time tc
b. Furthermore, in order to reduce the load fluctuation, the coefficient B shown in FIG.
Qpc2 ＝ Qpcl ・ factor B
It is good. Thus, consideration should be given so that a constant load can be obtained even at high pressure.

(Points to remember)
(i) Points to be noted in Method 1
a. Target rotational speed aims at high engine efficiency, high torque point, and high output point (point where necessary power can be output).

    b. The method of determining the coefficient A is arbitrary, but in general, it is obtained from the ratio of the average flow rate of various operations to the maximum pump flow rate.

(ii) Points to be noted in method 2 Set so that the coefficient B = 1 at the average pressure point of various operations.

(2) Points to keep in mind when controlling the engine speed The target engine speed aims at high engine efficiency, high torque, and high output (a point that can provide the required power).

(3) Points to note when controlling pump capacity
(i) Calculation formula Pump required power = Pump discharge pressure Ppp, Pump capacity V, Pump rotation speed ω / Pump efficiency V · ω = Pump flow rate

(ii) Points to note when controlling pump capacity
a. The pump flow rate is obtained by a method that suppresses flow rate fluctuation (and / or power fluctuation) (see (1) above).

    b. The pump capacity is divided by the rotation speed signal to determine the control command.

  The present invention can also be applied to fluid pressure actuators other than cylinders, such as a hydraulic motor for turning a hydraulic excavator.

  The present invention can be used not only for a hydraulic excavator but also for a working machine such as a crane truck.

It is a circuit diagram showing one embodiment of a fluid pressure actuator control circuit concerning the present invention. It is a flowchart which shows the control procedure of a control circuit same as the above. It is a characteristic view which shows the relationship between the accumulator pressure and the accumulator accumulation amount. It is a characteristic view which shows the flow control operation | movement at the time of energy release control of a control circuit same as the above. It is a characteristic view which shows the flow control operation | movement at the time of energy release control to contrast. It is a characteristic view which shows the relationship between a pump discharge pressure and a pump flow rate. It is a characteristic view which shows the relationship between a pump discharge pressure and the coefficient B. It is a side view of a hydraulic excavator provided with the control circuit same as the above.

Explanation of symbols

E Engine as prime mover
Pp pump
Cy fluid pressure actuator (this is called a cylinder)
Acc Accumulator 1 Accumulator control valve 3 Pump flow control valve 5 Control device
10 Excavator
12 Working device as a load
14 Boom cylinder as a hydraulic cylinder

Claims (2)

A pump flow rate control valve for controlling the direction and flow rate of the working fluid supplied to the fluid pressure actuator from a variable displacement pump driven by a prime mover;
An accumulator capable of accumulating potential energy of the load body raised by the fluid pressure actuator as accumulated pressure when descending;
An accumulator control valve provided in a passage between the fluid pressure actuator and the accumulator to control the flow of the working fluid from the accumulator to the fluid pressure actuator;
A control device having a function of controlling the pump flow rate or pump power discharged from the pump to be almost constant when the accumulator is in a pressure accumulation state, and supplying an insufficient flow rate from the accumulator by controlling the accumulator control valve. A fluid pressure actuator control circuit. The load body is an excavator working device,
The fluid pressure actuator control circuit according to claim 1, wherein the fluid pressure actuator is a hydraulic cylinder that rotates the working device in a vertical direction.

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