JP2009275771A - Fluid pressure actuator control circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid pressure actuator control circuit sharing control of pump required energy to the minimum when working fluid is supplied from a pump and an accumulator into a fluid pressure actuator. <P>SOLUTION: A head side of a cylinder Cy is connected to an accumulator Acc through an accumulator control valve 1, and connected to a rod side through a reproduction control valve 2. A discharge side passage 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 reducing pump power and supply working fluid from the accumulator Acc into the cylinder Cy to make the accumulator Acc run out of accumulating force by opening the accumulator control valve 1 when a pressure accumulating force remains in the accumulator Acc, and supplying the working fluid from the pump Pp into the cylinder Cy by controlling pump power. <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, hydraulic oil is supplied to a plurality of cylinders from a pump and an accumulator. However, when the pump and the accumulator are operated in common, the pump needs to be consumed by the pump. No control system has been established that can minimize energy.

  The present invention has been made in view of the above points, and provides a fluid pressure actuator control circuit that can control the required energy of a pump to a minimum when supplying a working fluid from a pump and an accumulator to the fluid pressure actuator. With the goal.

  According to the first aspect of the present invention, there is provided a pump flow rate control valve for controlling the direction and flow rate of a working fluid supplied from a variable displacement pump to a fluid pressure actuator, and a position of a load body raised by the fluid pressure actuator. An accumulator capable of accumulating energy as a stored 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, and an accumulator While the pressure is on, the pump power is reduced and the accumulator control valve is opened to supply the working fluid from the accumulator to the fluid pressure actuator. With the accumulated pressure in the accumulator running out, the pump power is controlled to move the pump to the actuator. Function to supply working fluid A hydraulic actuator control circuit comprising a example was controller.

  According to a second aspect of the present invention, the connection destination of the accumulator control valve in the fluid pressure actuator control circuit according to the first aspect is the downstream side of the pump flow rate control valve.

  According to a third aspect of the present invention, there is provided a storage control for energy storage control in which the accumulator control valve in the fluid pressure actuator control circuit according to the first or second aspect is provided in a passage between the fluid pressure actuator and the accumulator. And a release control valve for controlling energy release provided between the valve and an accumulator and a downstream side of the pump flow control valve.

  According to a fourth aspect of the present invention, the load body in the fluid pressure actuator control circuit according to any one of the first to third aspects is a working device for a hydraulic excavator, and the fluid pressure actuator is rotated in the vertical direction. This is a hydraulic cylinder.

  According to the first aspect of the present invention, the variable capacity type pump and the accumulator control valve are controlled by the control device, and while the accumulator has accumulated pressure, the pump power is reduced and the accumulator control valve is opened. When the accumulator supplies the working fluid to the fluid pressure actuator and the accumulator is depleted, the working fluid is supplied from the pump to the actuator. The required energy can be minimized.

  According to the invention described in claim 2, since the connection destination of the accumulator control valve is located downstream of the pump flow rate control valve, energy consumption due to an unnecessary increase in pump discharge pressure when using the accumulator can be prevented, When a plurality of pumps are used, an imbalance between a pump connected to the accumulator and a pump not connected to the accumulator can be prevented.

  According to the invention described in claim 3, the accumulator control valve is provided with the accumulation control valve and the discharge control valve separately, so that the injection destination when the energy accumulated in the accumulator is reused is the potential energy recovery source. It is possible to use other fluid pressure actuators other than the fluid pressure actuator.

  According to the invention described in claim 4, 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 requirement for the shared operation of the pump and the accumulator is required. Energy can be minimized.

  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 passes through the passage M. Then, 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., pressure sensors Sph, Spr for detecting the head pressure Ph and rod pressure Pr of the cylinder Cy, a pressure sensor Sac for detecting the pressure accumulated in the accumulator Acc, that is, the accumulator pressure 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 rotational speed sensor R for detecting the rotational speed (= pump rotational speed) of the engine E are the control device. 5 is connected to the input unit.

  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 controller (such as an electronic governor G) that controls the rotational speed of E (= pump speed) and a pump capacity controller (such as a swash plate regulator) that controls the capacity of the pump Pp. Control. The solid line in FIG. 1 represents a hydraulic line, and the alternate long and short dash line represents a control signal line.

  Then, the control device 5 controls the variable displacement pump Pp and the pump flow rate control valve 3 when the single rod type cylinder Cy is reduced by receiving the load of the load body, and the rod side of the cylinder Cy from the pump Pp. The flow rate of the pump supplied to the cylinder is controlled to almost zero, the opening of the regeneration control valve 2 accelerates the cylinder Cy that receives the load in the reduction direction, and the accumulator control valve 1 opens to the accumulator Acc from the head side. Accumulate pressure by supplying flow rate.

  At that time, first, the regeneration control valve 2 is opened to control in the acceleration priority mode in which the fluid flowing out from the head side of the cylinder Cy is regenerated to the rod side, and when the cylinder speed reaches the target speed, the regeneration control valve 2 is throttled to the cylinder. Switch to the boost priority mode that increases the pressure on the cylinder head side, that is, the cylinder head pressure.

  Next, when the energy accumulated in the accumulator Acc is released as described above, the position energy accumulated in the accumulator Acc is reused in combination with the pump flow rate to perform operations such as boom-up. However, simply adding the accumulator flow rate to the pump flow rate can be expected to improve the workability by improving the speed of the fluid pressure actuator, but the energy required for the pump cannot be reduced, and the fuel consumption of the pump drive engine will not be reduced. Therefore, a control method that can contribute to the most fuel consumption reduction while maintaining workability will be described below.

(a) The energy stored in the accumulator Acc is used in a way that can contribute the most to fuel efficiency.

  i. While pressure is accumulated in the accumulator Acc, the target drive system (for example, a boom, etc., but may be a drive system (for example, an arm, etc.) different from the energy recovery drive system) is supplied with working fluid only from the accumulator Acc. Supply.

  The accumulator control valve 1 (accumulation control valve 1a or discharge control valve 1b) is controlled from 0 to fully open according to the speed command value to secure the head flow rate supplied to the head side of the cylinder Cy and drive the cylinder Cy. .

  At this time, the regeneration control valve 2 is closed, the closing control valve 4 is opened, and the working fluid on the rod side of the cylinder Cy is discharged from the pump flow control valve 3 to the tank. As a result, the pump flow rate can be saved by the accumulator flow rate.

  ii. The accumulator control valve 1 (accumulation control valve 1a or discharge control valve 1b) is connected to the downstream side of the pump flow rate control valve 3 to prevent an unnecessary increase in the pump discharge pressure Ppp when the accumulator Acc is used.

  At this time, in order to save energy, control is performed so that the pump power of the corresponding drive system is minimized (the degree of bypassing the minimum flow rate to the tank).

  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 of the pump flow rate, the control device 5 can control the pump power by variably controlling the pump rotation speed or the pump capacity.

  If there are a plurality of corresponding pumps Pp, all the pumps Pp are operated to the minimum flow rate. Only the flow path from the pump flow rate control valve 3 to the tank T is used (the pressure is minimized), and the capacity of the pump Pp (swash plate tilt angle, etc.) is also controlled to a minimum.

  Further, the pump discharge pressure Ppp is also set to almost zero when the accumulator is reused, thereby saving the power consumed by the pump Pp.

  iii. The above control minimizes the pump input (power / equipment efficiency) during the operation cycle.

  iv. If the accumulator Acc is connected to the upstream side of the pump flow rate control valve 3, if multiple pumps are used, only one of the pumps will be assisted by the accumulator Acc. When pump control is performed, it is not preferable due to the influence of high pressure on one side, but this problem can be solved by connecting the accumulator Acc to the downstream side of the pump flow control valve 3.

(b) When the accumulator Acc becomes empty, the accumulator Acc is supplied from the pump Pp to the head side of the injection destination cylinder Cy through the pump flow rate control valve 3.

(c) This method is generally applicable regardless of the energy storage method in the accumulator Acc.

  Next, FIG. 2 is a schematic diagram showing a configuration for explaining the fuel efficiency improvement operation at the time of reusing accumulator stored energy. Based on FIG. 2, fluid is supplied from both the pump Pp and the accumulator Acc. In some cases, a sharing scheme that can minimize pump energy is verified.

(System configuration)
FIG. 2 shows an energy discharge system that supplies fluids to a plurality of circuits in a shared manner from both the pump Pp and the accumulator Acc, and is a configuration example for a case where the capacity of the accumulator Acc is limited.

  Qp is the pump flow rate, Qa is the accumulator flow rate, Qm is the required flow rate in the first circuit, Qo is the required flow rate in the second circuit, and Qb is the bypass flow rate returned to the tank. As each opening degree of the first circuit and the second circuit increases, the opening degree of the bypass circuit decreases. In FIG. 2, a solid line represents a fluid pressure (hydraulic pressure) circuit, and a one-dot chain line represents a control signal (control command or the like) circuit.

  In FIG. 2, the pump flow control valve 3 may have other configurations and configurations, but here, the pump flow control valve 3 has two circuits and is illustrated as an open center configuration. Yes.

  Conventionally, the pump Pp supplies a flow having a margin with respect to the required flow of the circuit and is adjusted to a predetermined flow rate by the pump flow rate control valve 3, but the verification here is for both the pump Pp and the accumulator Acc. The case where the flow rate can be supplied from each and each has a flow rate control function is targeted.

  Further, the pressure of the accumulator Acc is sufficiently high (you may have a dedicated pump Pp if necessary) and can be supplied to each circuit. In addition, the capacity (accumulated fluid volume) of accumulator Acc is limited, so consider the case where it is not possible to supply all the flow rate required for one-cycle operation (boom-up, etc.) (when supply from pump Pp is also required) To do.

(Examination, consideration)
(1) Flow balance type
Qp + Qa = Qm + Qo + Qb

(2) Assumptions There are many combinations of Qp and Qa that satisfy the required flow rates Q1 and Q2, but consider a sharing method that can minimize the pump energy for one-cycle operation.

  It is assumed that the accumulator Acc can be supplied at a constant flow rate (Qa0) throughout one cycle. That is, the capacity of the accumulator Acc is Qa0 · tc. tc is the time of one cycle.

(3) Operation method and pump energy requirement
(a) Base operation (Fig. 3)
Control with accumulator flow rate Qa = Qa0 (constant).

  Here, when the operation command from the operation lever L is small and Qa0 <Qm + Qo, Qa = Qm + Qa0. At this time, the fluid accumulated in the accumulator Acc during one cycle cannot be used up. Conversely, if the operation cycle is longer than expected, the accumulator Acc becomes empty during the cycle. In this case, Qa = 0.

  Control with pump flow rate Qp = Qm + Qo + Qb-Qa.

  However, although the pump flow rate Qp varies with time, FIG. 3 schematically illustrates the average flow rate Qpa. Therefore, the total flow rate is also shown as a constant average flow rate. Thereafter, for the sake of simplification, the investigation is illustrated with the average flow rate within the usage time (actually, it varies according to the operation command).

  Furthermore, in the following examination, the operation command is sufficiently large, and the case where the fluid accumulated in the accumulator Acc is used up in one cycle will be examined.

  FIG. 3 shows a flow rate sharing schematic diagram of the accumulator Acc and the pump Pp.

  In FIG. 3, when the required pump energy is calculated, the required pump energy EO in one cycle can be approximated by the following equation. Strictly speaking, it is treated as a time function, and energy is also calculated by integration. However, since the purpose is to grasp a tendency, hereinafter, the average value is assumed to be constant.

EO ＝ ∫ (Qp ・ P ・ CO) dt ≒ Qpa ・ P ・ CO ・ tc

  Here, Qp (time function) is approximated as a constant value Qpa and the study proceeds. CO is the reciprocal of the pump efficiency, and this efficiency is also taken as an average value during one cycle, and the study proceeds as a constant value. Furthermore, P is a pump pressure, which actually varies somewhat, but can be approximated with a substantially constant value according to the load body, and is set to a constant value P for simplification.

(b) Operation to increase accumulator flow Qa in a short time (Fig. 4)
Consider increasing the Qa within t1 (<tc) and using up the fluid accumulated in the accumulator Acc.

  When 0 <t <t1, Qa = Qa0 + Qa1> Qa0, and when t1 <t <tc, Qa = 0

  As in the base operation, the pump flow rate Qp is controlled by Qp = Qm + Qo + Qb−Qa.

  A flow rate distribution diagram at this time is as shown in FIG. Actually, the pump flow rate Qp and the total flow rate change with time, but the average value is displayed as constant.

Here, the following equation A holds.
Qa1 ・ t1 ＝ Qa0 ・ t2 (A)

  The required pump energy E1 at this time is approximated by the following equation.

E1 ≒ (Qpa-Qa1) ・ P ・ C1 ・ t1 ＋ (Qpa + Qa0) P ・ C2 ・ t2
= (Qpa-Qa1) · P · C1 · t1 + Qpa · P · C2 · t2 + Qa0 · P · C2 · t2

  However, since the total flow rate is the same as that in the base operation, the pump pressure P is the same. C1 and C2 are reciprocals of the pump efficiency at times t1 and t2, and the pump efficiency generally deteriorates as the pressure increases and the flow rate decreases, so that C1> CO> C2.

When the energy EO required for one cycle of the base operation is transformed,
Since tc = t1 + t2,
EO = (Qpa-Qa1) · P · CO · t1 + Qa1 · P · CO · t1 + Qpa · P · CO · t2
From equation A:
EO = (Qpa-Qa1) · P · CO · t1 + Qa0 · P · CO · t2 + Qpa · P · CO · t2
Comparing the required energy EO and E1 of the pump,
EO-E1
＝ (Qpa−Qa1) ・ P ・ t1 ・ (CO−C1) + Qpa ・ P ・ t2 ・ (CO−C2) + Qa0 ・ P ・ t2 ・ (CO−C2)
＝ (Qpa−Qa1) ・ P ・ t1 ・ (CO−C1) + (Qpa + Qa0) ・ P ・ t2 ・ (CO−C2)… （B）

  From the general characteristic of pump efficiency (C1> CO> C2), the first term of the formula (B) is negative and the second term is positive.

  The sign of equation (B) cannot be determined if Qa1 is small. However, if Qa1 is increased and brought closer to Qpa, that is, if the entire amount is injected from the accumulator Acc, the influence of the first term is reduced and the second term is reduced. It becomes the main element, and as it becomes positive, the positive range increases.

  Since EO−E1> 0, EO> E1, and the required pump energy E1 during operation of increasing the accumulator flow rate Qa in a short time is less than the required pump energy EO during base operation.

  In short, to minimize the energy required for the pump, it is better to use up the accumulator Acc first.

(c) Efficient sharing method (conclusion)
From the above, it has been found that the following sharing method is good in terms of energy used by the pump.

  (i) Before the accumulator Acc becomes empty, the accumulator Acc is used alone.

(When accumulator Acc is connected upstream of pump flow control valve 3 (pump side))
Ensure minimum pump flow rate Qmin. The pump flow rate control valve 3 includes a first control valve 3a for the first circuit and a second control valve 3b for the second circuit, and the flow rate ratio between the first circuit required flow rate Qm and the second circuit required flow rate Qo is The opening balance between the first control valve 3a and the second control valve 3b is controlled so as to be secured.

(When accumulator Acc is connected downstream of pump flow control valve 3)
The pump Pp shares the second circuit required flow rate Qo. When Qo≈0, the energy used can be further reduced by greatly opening the bypass line to lower the pump pressure P.

Qp = Qo + Qb ≧ Qmin

  The first control valve 3a is fully closed (that is, the bypass line is fully opened), and the second control valve 3b is slightly opened.

When Qo> Qmin, Qp = Qo.

  Since the pump flow rate control valve 3 only needs to target the second circuit required flow rate Qo, the control can be easily performed.

  When the first control valve 3a is fully closed (bypass line is fully open), the second control valve 3b is in a fully open state as shown in FIG. However, the second control valve 3b opens the bypass line greatly only when a minute flow rate of Qb <Qm is required.

  Since the passage flow rate of the pump flow rate control valve 3 is only the second circuit required flow rate Qo, the pressure loss at the pump flow rate control valve 3 is reduced. That is, the pump pressure P is slightly reduced. Therefore, it is advantageous for efficiency improvement.

  (ii) After the accumulator Acc becomes empty, the working fluid is supplied only from the pump Pp.

  At this time, there is no difference depending on the connection destination of the accumulator Acc.

  Qp = Qm + Qo + Qb

  Aiming for Qb = 0, but in order to secure the minimum flow rate Qmin, if Qm + Qo <Qmin, open the bypass line.

  The pump flow rate control valve 3 balances the opening between the first control valve 3a and the second control valve 3b so that a flow rate ratio between the first circuit required flow rate Qm and the second circuit required flow rate Qo can be secured.

  That is, when the first circuit required flow rate Qm> the second circuit required flow rate Qo, the first control valve 3a is controlled to be fully opened, and the second control valve 3b is throttled according to the required flow rate ratio.

  Further, when the first circuit required flow rate Qm <the second circuit required flow rate Qo, the first control valve 3a is throttled according to the required flow rate ratio, and the second control valve 3b is controlled to be fully opened.

  Next, the outline of the energy release control will be described with reference to the flowchart shown in FIG.

(Step 1)
It is determined whether or not the accumulator Acc has an energy accumulation, that is, a pressure accumulation state.

(Step 2)
If there is energy accumulation in step 1 (YES), in short, the pump Pp is controlled to the lowest possible flow rate Qmin, and the necessary flow rate Qa is supplied only from the accumulator Acc.

  That is, the control device 5 controls the existing system pump Pp to the minimum power operation. For example, the capacity of the pump Pp is controlled to approximately 0, the discharge amount of the pump Pp is controlled to approximately 0, and the pump discharge pressure Ppp is controlled to approximately 0. When there are a plurality of pumps Pp, the same control is performed for all the pumps. In order to enable this, the connection destination of the accumulation control valve 1a or the discharge control valve 1b is set downstream of the pump flow rate control valve 3.

  At the same time, the control device 5 controls the opening degree of the dedicated accumulation control valve 1a or the discharge control valve 1b from 0 to fully open according to the speed command, and ensures the load body ascending speed according to the command.

(Step 3)
As shown in FIG. 7, 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 the minimum set value Pmin or less. 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 3 are repeated.

(Step 4)
If the discharge completion time t1 of the accumulator Acc has elapsed or if no energy is accumulated in step 1 (NO), the entire amount required is supplied from the pump Pp.

  In short, when the control device 5 senses that the accumulator Acc is empty from the accumulator pressure Pa detected by the pressure sensor Sac, the control device 5 supplies the working fluid from the existing system pump Pp to the actuator.

  Next, effects of the illustrated embodiment will be described.

  The control device 5 controls the variable displacement pump Pp and the accumulator control valve 1 to reduce the pump power and open the accumulator control valve 1 from the accumulator Acc to the cylinder Cy while the accumulator Acc has accumulated pressure. When the working fluid is supplied and the accumulated pressure of the accumulator Acc disappears, the pump Pp consumes the pump Pp when the pump Pp and the accumulator Acc are operated in common by supplying the working fluid from the pump Pp to the cylinder Cy. Energy can be minimized.

  When the accumulator control valve 1 is connected to the downstream side of the pump flow control valve 3, energy consumption due to an unnecessary increase in the pump discharge pressure Ppp when using the accumulator can be prevented, and a plurality of pumps are used. Can prevent imbalance between the pump connected to the accumulator Acc and the pump not connected.

  The accumulator control valve 1 is provided with a storage control valve 1a and a discharge control valve 1b separately, so that the injection destination when the energy stored in the accumulator Acc is reused is the cylinder Cy (boom cylinder 14) that is the source of potential energy recovery. Other fluid pressure actuators (for example, arm cylinder 16 etc.) can be used.

  In the hybrid of the hydraulic supply source that supplies hydraulic oil to the boom cylinder 14 that moves up and down the working device 12 of the excavator 10, the energy required for the pump when the pump Pp and the accumulator Acc are shared can be minimized. .

  As described above, the accumulator Acc is connected to the downstream side of the existing control valve (pump flow rate control valve 3), and the control device 5 directly controls the accumulator control valve 1, that is, the accumulation control valve 1a or the discharge control valve 1b. When the accumulator Acc can be used by the method, supplying the working fluid to the actuator only from the accumulator Acc is an efficient control method when the energy stored in the accumulator Acc is released and reused.

  In the accumulator control valve 1 of the present invention, the accumulation control valve 1a and the discharge control valve 1b may be configured integrally or separately. When configured separately, the stored energy can be released to other circuits. 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 cylinder control circuit concerning the present invention. It is a schematic diagram which shows the structure at the time of the accumulator stored energy reuse of a control circuit same as the above. It is the characteristic view which illustrated the pump flow rate typically by the average flow rate. It is a characteristic view which shows the flow volume distribution state which concerns on the accumulator storage energy reuse of a control circuit same as the above. It is a characteristic view which shows the opening characteristic of the 2nd control valve provided in the pump flow control valve of a control circuit same as the above. 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 accumulator accumulation amount of a control circuit same as the above. It is a side view of a hydraulic excavator provided with the control circuit same as the above.

Explanation of symbols

Pp pump
Cy fluid pressure actuator (this is called a cylinder)
Acc Accumulator 1 Accumulator control valve
1a Accumulation control valve
1b Release 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 (4)

A pump flow control valve that controls the direction and flow of the working fluid supplied from the variable displacement pump to the fluid pressure actuator;
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;
While the accumulator is accumulating, the pump power is reduced and the accumulator control valve is opened to supply the working fluid from the accumulator to the fluid pressure actuator. And a control device having a function of supplying a working fluid from the actuator to the actuator. The fluid pressure actuator control circuit according to claim 1, wherein the connection destination of the accumulator control valve is on the downstream side of the pump flow rate control valve. The accumulator control valve
A storage control valve for controlling energy storage provided in a passage between the fluid pressure actuator and the accumulator;
The fluid pressure actuator control circuit according to claim 1, further comprising: a release control valve for controlling energy release provided between the accumulator and a downstream side of the pump flow control valve. The load body is an excavator working device,
The fluid pressure actuator control circuit according to any one of claims 1 to 3, wherein the fluid pressure actuator is a hydraulic cylinder that rotates the working device in a vertical direction.

Images