JP2009275769A - Fluid pressure cylinder control circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid pressure cylinder control circuit efficiently recovering potential energy. <P>SOLUTION: The 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. The 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 accelerating the cylinder Cy subjected to a load by opening the reproduction control valve 2 in the contracting direction, and supplying and accumulating a flow rate from the head side into the accumulator Acc by opening the accumulator control valve 1 at a predetermined speed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a hydraulic cylinder 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. According to the position of the machine, there is a position energy recovery and utilization device for a hydraulic excavator that controls the accumulator operation valve and the variable relief valve to generate hydraulic pressure in the accumulator that balances the weight of the work machine (for example, Patent Document 1).
Japanese Patent Laid-Open No. 01-199001 (page 2-3, FIG. 1)

  In this conventional one, a part of the return oil flowing out from the head side of the boom cylinder is stored in the pressure accumulator through the pressure accumulator operation valve, but the amount of oil discharged to the tank via the variable relief valve is large, and the potential energy Recovery efficiency is not good.

  The present invention has been made in view of such a point, and an object thereof is to provide a fluid pressure cylinder control circuit capable of efficiently recovering potential energy.

  According to the first aspect of the present invention, there is provided a pump flow rate control valve for controlling a pump flow rate supplied from a variable displacement type pump to a single rod type fluid pressure cylinder for moving up and down the load body, and there is no rod of the fluid pressure cylinder. An accumulator for pressure accumulation that can communicate with the head side, and an accumulator control valve that is provided in a passage between the head side of the fluid pressure cylinder and the accumulator and controls the flow of fluid from at least the head side of the fluid pressure cylinder to the accumulator And a regeneration control valve that controls the regeneration flow rate of the working fluid from the head side to the rod side of the fluid pressure cylinder, and the fluid pressure cylinder that receives the load by opening the regeneration control valve is accelerated in a contraction direction, and a predetermined cylinder Control with the function of supplying the flow from the head side to the accumulator and accumulating pressure by opening the accumulator control valve at speed A hydraulic cylinder control circuit; and a location.

  According to a second aspect of the present invention, the control device in the fluid pressure cylinder control circuit according to the first aspect opens the regeneration control valve and regenerates the fluid flowing out from the head side of the fluid pressure cylinder to the rod side. The control is performed in the priority mode, and when the cylinder speed reaches the target speed, the regeneration control valve is throttled to switch to the pressure increase priority mode for increasing the pressure on the head side of the fluid pressure cylinder.

  According to a third aspect of the present invention, in the control device in the fluid pressure cylinder control circuit according to the first or second aspect, when the pressure on the head side of the fluid pressure cylinder becomes equal to or higher than the pressure accumulated in the accumulator, A control function is provided for controlling the opening degree of the accumulator control valve according to the speed command value, the differential pressure across the accumulator control valve, the opening degree of the regeneration control valve, and the differential pressure across the regeneration control valve.

  According to a fourth aspect of the present invention, in the fluid pressure cylinder control circuit according to any one of the first to third aspects, the pressure on the head side of the fluid pressure cylinder increases as the accumulator pressure increases. And a function to open the regeneration control valve.

  A fifth aspect of the present invention is the fluid pressure cylinder control circuit according to any one of the first to fourth aspects, further comprising a closing control valve provided on the outlet side of the pump flow rate control valve.

  According to a sixth aspect of the present invention, the load body in the fluid pressure cylinder control circuit according to any one of the first to fifth aspects is a working device for a hydraulic excavator, a single rod type fluid pressure cylinder is moved up and down the working device. The hydraulic cylinder rotates in the direction.

  According to the first aspect of the present invention, the control device controls the regeneration control valve from the head side of the fluid pressure cylinder when the one-rod type fluid pressure cylinder contracts in response to the load of the load body. By controlling the regenerative flow rate for regenerating the fluid that flows out to the rod side, the potential energy accumulated on the head side of the fluid pressure cylinder can be effectively regenerated on the rod side without being wasted, and the fluid on the rod side can be regenerated. The load body can be quickly accelerated to a predetermined lowering speed by pressure, and the speed and responsiveness at the time of lowering can be secured, and the potential energy of the load body is converted into kinetic energy, so that the rod side of the fluid pressure cylinder Further, the pressure on the head side can be increased, and in this state, by controlling and opening the accumulator control valve, the potential energy can be efficiently collected in the accumulator.

  According to the second aspect of the present invention, the control device opens the regeneration control valve and performs control in the acceleration priority mode, and when the descending speed of the load body reaches the target speed, the control device throttles the regeneration control valve to prioritize the pressure increase. Since the mode is switched, the pressure accumulated in the accumulator can be increased more than the initial head pressure, and the potential energy can be efficiently collected in the accumulator.

  According to the third aspect of the invention, when the pressure on the head side of the fluid pressure cylinder becomes equal to or higher than the pressure accumulated in the accumulator, the speed command value of the fluid pressure cylinder, the differential pressure across the accumulator control valve, the regeneration control valve Since the opening of the accumulator control valve is controlled according to the opening of the valve and the differential pressure across the regeneration control valve, the accumulator control valve can be opened under certain conditions to ensure the flow rate to the accumulator and the speed command value A predetermined cylinder lowering speed can be achieved and maintained. That is, the decrease in the total volume in the cylinder due to the downward movement of the single rod type fluid pressure cylinder is balanced by the increase in pressure on the head side, the flow rate to the accumulator, and the regeneration flow rate to the rod side, By controlling the opening degree of the accumulator control valve, it is possible to realize the cylinder lowering speed according to the speed command value while ensuring the accumulator flow rate.

  According to the fourth aspect of the present invention, when the head pressure increases in accordance with the increase in the accumulator pressure, the control device opens the regeneration control valve, so that the load body descending speed is maintained while maintaining the head pressure at a high pressure. Can be kept constant.

  According to the fifth aspect of the present invention, even when the passage to the tank side cannot be closed by the pump flow rate control valve at the time of regeneration from the head side to the rod side of the fluid pressure cylinder, the closing control valve is set. By closing, it is possible to prevent the regeneration flow rate from being discharged into the tank and to prevent the regeneration efficiency from being lowered.

  According to the sixth aspect of the present invention, when the working device of the excavator is lowered from the raised position, the potential energy of the working device at the raised position can be efficiently collected in the accumulator.

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

  As shown in FIG. 3, a hydraulic excavator 10 as a work machine is provided with a work device 12 as a load body movably provided to a 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 cylinder capable of performing a reduction operation in response to the entire load W of the work device 12. Hereinafter, this kind of fluid pressure cylinder is simply 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.

  The discharge side passage of the pump Pp is connected to the supply port of the pump flow rate control valve 3, and one output port of the pump flow rate control valve 3 is connected to the head side of the cylinder Cy via the passage M, and 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 discharge control valve 1b is a valve for discharging accumulation energy that controls the flow from the accumulator Acc to the head side of the cylinder Cy, and can be shared by the accumulator 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 output when the accumulator Acc is used is increased, 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 cylinders (boom cylinder 14 and the like) constituting the fluid pump and one load body driving device is shown, but a plurality of sets may be provided.

  In such a potential energy recovery / reuse system, the pressure on the head side from the piston of the cylinder Cy detected by the pressure sensor Sph is the head pressure Ph, the head side area of the piston is the header area Ah, and the pressure sensor Spr The rod-side pressure from the piston of the cylinder Cy detected by the above is the rod pressure Pr, the rod-side area of the piston is the rod area Ar, the load body mass is m, the second-order differential of the cylinder position X, that is, the acceleration is α. Then, the force balance equation is as follows.

  m ・ α ＝ W + （Pr ・ Ar−Ph ・ Ah） …… (1)

  In an equilibrium state where the cylinder speed is constant, both sides of equation (1) are zero.

  The pressure accumulated in the accumulator Acc, that is, the accumulator pressure is Pa, and the initial pressure of the accumulator Acc (slightly higher than the enclosed gas pressure) is PaO.

  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 An angle sensor San that detects the angle of the load body such as the boom 13 is connected to an input unit of the control device 5, and the control device 5 includes an arithmetic processing device, a storage device, and the like. Are connected to the movable control units of the control valves 1, 1a, 2, 3 and 4 and the capacity variable control unit (swash plate regulator, etc.) of the pump Pp, and these are controlled by electric signals. 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 opens the regeneration control valve 2 to accelerate the cylinder Cy that receives the load in the contracting direction, and opens the accumulator control valve 1 at a predetermined cylinder speed, thereby supplying the flow rate from the head side to the accumulator Acc. It has a function of supplying and accumulating pressure.

  Furthermore, the control device 5 initially controls the regeneration control valve 2 in the acceleration priority mode in which the regeneration control valve 2 is fully opened to regenerate the fluid flowing out from the head side of the cylinder Cy to the rod side, and regeneration control is performed when the cylinder speed reaches the target speed. The valve 2 is throttled to have a function of switching to a boosting priority mode for increasing the head pressure Ph of the fluid pressure cylinder Cy.

  Further, when the head pressure Ph of the cylinder Cy becomes equal to or higher than the accumulator pressure Pa, the control device 5 determines the speed command value of the cylinder Cy by the operation lever L, the opening degree of the regeneration control valve 2, the accumulator control valve 1 and the regeneration control valve 2. A control function is provided for controlling the opening degree of the accumulator control valve 1 in accordance with the front-rear differential pressure.

  That is, when the head pressure Ph becomes equal to or higher than the accumulator pressure Pa, the control device 5 opens the accumulator control valve 1 to establish a flow path to the accumulator Acc, and the rod of the one-rod cylinder Cy moves to the head side (down) The decrease in the total volume in the cylinder due to operation) is balanced by the increase in the head pressure Ph, the flow rate to the accumulator Acc, and the regenerative flow rate to the rod side of the cylinder Cy. At this time, the accumulator control valve 1 is speeded. A function for controlling the accumulator flow rate according to the command value is provided.

  Further, the control device 5 has a function of opening the regeneration control valve 2 in accordance with an increase in the accumulator pressure Pa.

  Next, the control operation of 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.

(Step 1)
In an equilibrium state (m · α = 0) before operation, the initial pressure PaO of the accumulator Acc is set based on the accumulator set pressure Pset, the rod pressure Pr is almost 0, and the head pressure Ph is the above (1). It is a positive value with the right side of the expression being 0. That is, the value in parentheses on the right side of the equation (1) is −W.

(Step 2)
When the operation lever L is lowered, the control device 5 controls the regeneration control valve 2 to be fully opened and regenerates the working fluid from the head side of the cylinder Cy to the rod side, thereby causing the working device 12 to descend by its own weight. (Acceleration priority control).

  At this time, the closing control valve 4 or the pump flow rate control valve 3 reliably closes the flow path through which the regeneration flow from the head side of the cylinder Cy to the rod side is discharged to the tank T. If the flow path to the tank T side cannot be closed by the pump flow rate control valve 3 during this regeneration, the flow path to the tank side is reliably closed by the closing control valve 4.

(Step 3)
The head pressure Ph decreases due to the outflow of the cylinder Cy from the head side, and the rod pressure Pr becomes Pr = Ph−c. c is a constant value (differential pressure) determined by the opening degree of the regeneration control valve 2.

(Step 4)
Since the value on the right side of the above equation (1) is a positive value, the cylinder Cy is accelerated and descends.

(Step 5)
Since the one-rod type piston of the cylinder Cy satisfies the header area Ah> the rod area Ar, the total volume in the cylinder Cy decreases and the head pressure Ph and the rod pressure Pr increase due to the lowering of the piston. However, while the above equation (1) is positive (m · α> 0), the descending speed increases. In addition, the head pressure Ph and the rod pressure Pr continue to increase because the decrease continues at a constant speed even when the speed equilibrium state is reached.

(Step 6)
It is determined whether or not the head pressure Ph> the accumulator initial pressure PaO. When PaO ≧ Ph (NO), there is no flow to the accumulator Acc side.

(Step 7)
When head pressure Ph> accumulator initial pressure PaO, this speed is set so that the flow rate corresponding to the speed command value Vc from the operating lever L can flow through the opening of the accumulation control valve 1a of the accumulator control valve 1, that is, the opening area A1. Depending on the command value Vc or in addition to the speed command value Vc, the front-rear differential pressure ΔPh-a of the accumulator control valve 1, the opening A2 of the regeneration control valve 2 and the front-rear differential pressure ΔPh-r (ie, to the rod side) Control according to the regeneration flow rate Qr).

That is, the header area is Ah, the opening area of the accumulator control valve 1 is A1 (control target), the opening area of the regeneration control valve 2 is A2 (controlled amount), and the differential pressure ΔPh-a = Ph− across the accumulator control valve 1 Assuming Pa and the differential pressure ΔPh−r = Ph−Pr across the regeneration control valve 2, the flow balance equation is
Ah ・ Vc ＝ Cd1 ・ A1 ・ √ΔPh-a + Qr
Qr ＝ Cd2 ・ A2 ・ √ΔPh-r
(However, Cd1 and Cd2 are constants.) In this flow rate balance type, the opening area A1 of the accumulator control valve 1 is controlled.

(Step 8)
Thereby, a recovery flow rate to the accumulator Acc is generated, and the accumulator Acc is accumulated.

(Step 9)
Due to the collected flow rate to the accumulator Acc, the rising speed of the head pressure Ph is slowed, and the boom lowering speed is accelerated accordingly.

  At this time, if the opening degree of the regeneration control valve 2 is reduced by the amount of the recovery flow rate to the accumulator Acc, the change in the head pressure Ph is not affected by the recovery flow rate to the accumulator Acc. continue. As the head pressure Ph increases, the flow rate to the accumulator Acc increases, and the accumulation speed in the accumulator Acc is accelerated.

(Step 10)
The boom lowering speed is detected, it is determined whether the boom lowering speed has reached the target (command) speed, and the boom lowering speed is accelerated until the target speed is reached. The boom lowering speed detecting means can obtain the boom lowering speed by differentiating the boom angle detected by the angle sensor San, but the lowering speed may be detected by a speed detector, or an alternative means. As an alternative, the speed may be determined from the elapsed time or from the differential pressure in a prior simulation.

(Step 11)
When the load body descending speed reaches the command speed (target speed), the opening of the regeneration control valve 2 is controlled to reduce the regeneration flow rate, increase the head pressure Ph, and increase the amount accumulated in the accumulator Acc. (Step-up priority control).

(Step 12)
The accumulator pressure Pa detected by the pressure sensor Sac gradually increases due to the accumulation in the accumulator Acc, so the head pressure Ph also gradually increases. This head pressure Ph becomes a resistance, and the load lowering speed slightly decreases. However, as the accumulator pressure Pa increases, the lowering speed can be kept constant by variably controlling the regeneration control valve 2 to be slightly opened and controlling the opening degree of the accumulation control valve 1a. That is, the equilibrium state of the descending speed can be maintained (speed equilibrium state maintaining mode).

  In this way, first, the regeneration control valve 2 is fully opened to regenerate the oil flowing out from the head side of the boom cylinder 14 to the rod side (acceleration priority control), and when the descending speed reaches the target (command) speed, the regeneration control valve 2 is variably controlled (pressure-boosting priority control), and energy is recovered in the accumulator Acc while maintaining the descending speed at the command speed by controlling the opening degree of the accumulation control valve 1a.

  Next, characteristics of the potential energy recovery method controlled by the control device 5 will be described.

(1) General When the cylinder Cy that has lifted the work device 12 is lowered from the equilibrium state where the work device 12 is stopped at a fixed position, the work device 12 can be lowered to prevent the work efficiency from being lowered. Further, except for unavoidable losses such as pressure loss or leak, that is, the discharge to the tank T can be minimized, and the total potential energy of the ascending load can be efficiently collected and accumulated in the accumulator Acc. Furthermore, the accumulated pressure in the accumulator Acc can be increased, that is, it can be increased beyond the initial head pressure. In order to secure these effects in a balanced manner, the following measures are taken.

(2) Increasing accumulated pressure To ensure that the accumulator set pressure (Pset) is higher than the specified accumulator pressure, set the gas pressure in the accumulator Acc to an appropriate pressure (PaO ≒ Pset). By controlling, it becomes possible to pressurize the accumulator pressure Pa beyond the initial head pressure in the cylinder Cy.

(3) Acceleration priority control The regeneration control valve 2 for energy regeneration from the head side to the rod side of the cylinder Cy is provided. In order to secure and maintain the descending speed, the regeneration control valve 2 is controlled to control the rod pressure Pr. Is controlled to a high value according to the increase in the head pressure Ph.

  That is, when the regeneration control valve 2 is opened and the head side fluid is regenerated to the rod side, the regenerated amount is not accumulated in the accumulator Acc, but the pump output can be made almost zero, so that the same effect can be achieved in terms of efficiency. .

  As the regeneration control valve 2, a valve having an appropriate maximum opening area is selected so that the differential pressure between the head pressure Ph and the rod pressure Pr can be substantially zero at the maximum opening.

  Then, in order to ensure the boom lowering speed, acceleration priority control for increasing the opening of the regeneration control valve 2 so as to increase the rod pressure Pr according to the head pressure Ph (increase α in the equation (1)) This is advantageous in terms of responsiveness.

  Since the one-rod-side piston has a header area Ah> rod area Ar, a decrease in the head-side volume due to the lowering of the piston is partly used to increase the head pressure Ph and a part is regenerated to the rod side. .

  While the descending speed is smaller than the target speed command value (operation speed command value), the load body descending speed is controlled by acceleration priority control that increases the opening of the regeneration control valve 2 so that the head pressure Ph≈rod pressure Pr. Enlarge.

(4) Boosting priority control When the descending speed reaches the target speed, switching to boosting priority control is performed to reduce the opening of the regeneration control valve 2 from the acceleration priority control.

(5) Energy Accumulation When the head pressure Ph ≧ accumulator initial pressure PaO, the accumulation control valve 1a of the accumulator control valve 1 is opened to the accumulator Acc side, and pressure accumulation in the accumulator Acc, that is, energy recovery / accumulation is performed.

  At this time, if the load lowering speed has reached the target speed, the opening amount to the regeneration control valve 2 is narrowed to increase the collection amount to the accumulator Acc as much as possible. If there is a check function between the accumulation control valve 1a and the accumulator Acc, the accumulation control valve 1a may be opened earlier.

  On the other hand, when it is determined that the target speed need not be achieved, the opening degree of the regeneration control valve 2 is narrowed down and priority is given to accumulation in the accumulator Acc.

(6) Lowering speed equilibrium state maintenance mode In addition to the operating speed command value Vc determined by the operating amount of the operating lever L, the regeneration flow rate Qr to the rod side, the differential pressure ΔPh-a across the accumulator control valve 1, the regeneration control valve 2 By controlling the opening degree (opening area A1) of the accumulation control valve 1a of the accumulator control valve 1 according to the front-rear differential pressure ΔPh-r, a predetermined lowering speed is achieved and maintained.

  At the same time, the energy accumulation in the accumulator Acc is made equal to or higher than the set pressure Pset, and the potential energy is collected and accumulated in the accumulator Acc with a minimum loss, and a part is regenerated to the rod side. At this time, the decrease in the head-side volume of the cylinder Cy due to the lowering of the load body means that the accumulated flow rate in the accumulator Acc and the head pressure Ph increase (however, the head pressure Ph does not change in the speed equilibrium state), the regeneration to the rod side Balanced by flow rate.

(7) Energy saving To save energy when descending, the pump output (pressure / flow rate) is controlled to the minimum so that the minimum flow rate is bypassed to the tank T except during speed priority operation.

(8) Speed priority operation If the speed command value is too large before the target speed is reached and the head pressure Ph reaches the speed equilibrium value or if a quick response is desired, control the accumulation control valve 1a. It is also possible to perform a speed priority operation in which the pressure is extracted from the head side of the cylinder Cy to the tank T or the pump flow rate control valve 3 is controlled to forcibly inject the pump flow rate to the rod side. However, if this speed priority operation is performed, an energy loss is generated correspondingly, so the operation is stopped in the minimum time.

  Next, effects of the above embodiment will be described.

  The control device 5 controls the regeneration control valve 2 to regenerate the fluid flowing out from the head side of the cylinder Cy to the rod side when the single rod type cylinder Cy is contracted by receiving the load of the working device 12. By controlling this, the potential energy accumulated on the head side of the cylinder Cy is effectively recycled to the rod side without wasting it, and the work device 12 is quickly accelerated to a predetermined lowering speed by the rod pressure Pr. It is possible to secure the speed and responsiveness when descending, convert the potential energy of the working device 12 into kinetic energy, and increase the rod side of the cylinder Cy and the head pressure Ph. By controlling and opening the accumulator control valve 1, the potential energy can be efficiently collected in the accumulator Acc.

  Since the control device 5 opens the regeneration control valve 2 and performs control in the acceleration priority mode, when the descending speed of the working device 12 reaches the target speed, the regeneration control valve 2 is throttled to switch to the boost priority mode. It is also possible to increase the accumulated pressure to be higher than the initial head pressure, and the potential energy can be efficiently collected in the accumulator Acc.

  When the head pressure Ph of the cylinder Cy exceeds the accumulator pressure Pa accumulated in the accumulator Acc, the speed command value Vc of the cylinder Cy, the differential pressure ΔPh-a of the accumulator control valve 1, the opening degree of the regeneration control valve 2, and the regeneration control Since the opening area A1 of the accumulator control valve 1 is controlled in accordance with the differential pressure ΔPh-r across the valve 2, the accumulator control valve 1 can be opened under certain conditions to ensure the flow rate to the accumulator Acc and the speed command A predetermined cylinder lowering speed according to the value Vc can be achieved and maintained. That is, the decrease in the total volume in the cylinder due to the one-rod cylinder Cy operating on the descending side is balanced by the increase in the head pressure Ph, the flow rate to the accumulator Acc, and the regeneration flow rate Qr to the rod side, By controlling the opening area A1 of the accumulator control valve 1, it is possible to realize the cylinder lowering speed according to the speed command value Vc while ensuring the accumulator flow rate.

  When the head pressure Ph increases according to the increase of the accumulator pressure Pa, the control device 5 opens the regeneration control valve 2 to maintain the lowering speed of the working device 12 constant while maintaining the head pressure Ph at a high pressure. Can do.

  Even when the pump flow control valve 3 cannot close the passage to the tank side during regeneration from the head side to the rod side of the cylinder Cy, the regeneration flow rate is discharged to the tank T by closing the closing control valve 4. Can be prevented, and a decrease in reproduction efficiency can be prevented.

  When the working device 12 of the excavator 10 is lowered from the raised position, the potential energy of the raised working device 12 can be efficiently collected in the accumulator Acc.

  As described above, in the system that uses the accumulator Acc when recovering the potential energy, according to the system configuration described above, the regeneration control valve 2 is provided separately from the pump flow rate control valve 3 so that the regeneration control valve 2 is Since the control signal can be controlled independently of the operation signal of the control valve 3, it is possible to secure a descending speed, increase the accumulator Acc pressure and achieve a high recovery efficiency, and provide a control system that can realize the following effects simultaneously or in a balanced manner. .

(1) The boom lowering speed and responsiveness when the boom is lowered when recovering the potential energy to the accumulator Acc can be secured.

  That is, since the regeneration control valve 2 is provided to appropriately control the differential pressure between the head side and the rod side of the cylinder Cy when descending, the descending speed of the working device 12 can be increased and the responsiveness can be improved. it can.

  Furthermore, by controlling the accumulator control valve 1 and the regeneration control valve 2 in conjunction with each other, it is possible to ensure a descending speed according to the operation command. In particular, the head pressure Ph of the cylinder Cy can be increased, and a predetermined lowering speed can be maintained even when the head pressure is high.

(2) The potential energy accumulated on the head side of the cylinder Cy at the ascending position of the working device 12 is accumulated in the accumulator Acc without wastefully discarding it into the tank T, that is, reducing the discharge amount to the tank T to almost zero. it can. That is, when recovering potential energy using the accumulator Acc, potential energy can be efficiently recovered.

  In addition, since the flow rate on the cylinder Cy head side is regenerated to the rod side, the existing pump Pp and the pump flow rate control valve 3 are operated so that the pump output ≈ 0 to save energy. Even if the injection amount to the side is zero, the speed and responsiveness when descending can be ensured, so that the energy for driving the pump can be saved.

(3) Since the accumulator pressure Pa can be increased to a necessary high pressure, the effectiveness at the time of reusing the accumulator can be enhanced. In order to make the accumulator pressure Pa as high as desired, the system configuration and the accumulator initial pressure PaO need only be set slightly higher.

(4) A simple system configuration can be achieved by the plurality of control valves 1 to 4 and the control device 5.

  Note that the present invention is not limited to the boom cylinder 14, and for example, the piston of the arm cylinder 16 can also be moved by receiving a load such as earth and sand in the bucket 17, so that the present invention can be applied. Furthermore, the present invention is not limited to a hydraulic excavator, and can also be applied to a hydraulic cylinder such as a crane truck.

  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 flowchart which shows the control procedure 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 cylinder (simply called cylinder)
Acc Accumulator 1 Accumulator control valve 2 Regeneration control valve 3 Pump flow control valve 4 Closing control valve 5 Control device
10 Excavator
12 Working device as a load
14 Boom cylinder as a hydraulic cylinder

Claims (6)

A pump flow rate control valve for controlling a pump flow rate supplied from a variable displacement pump to a single rod type fluid pressure cylinder for vertically moving the load body;
An accumulator for pressure accumulation that can communicate with the head side without a rod of the fluid pressure cylinder;
An accumulator control valve provided in a passage between the head side of the fluid pressure cylinder and the accumulator to control a flow of fluid from at least the head side of the fluid pressure cylinder to the accumulator;
A regeneration control valve for controlling the regeneration flow rate of the working fluid from the head side to the rod side of the fluid pressure cylinder;
It has a function to accelerate the fluid pressure cylinder that receives the load by opening the regeneration control valve in the shrinking direction, and to open the accumulator control valve at a predetermined cylinder speed and supply the accumulator with the flow rate from the head side to accumulate pressure A fluid pressure cylinder control circuit. The control device
At first, the regeneration control valve is opened to control in the acceleration priority mode in which the fluid flowing out from the head side of the fluid pressure cylinder is regenerated to the rod side. When the cylinder speed reaches the target speed, the regeneration control valve is throttled and the fluid pressure cylinder head is The fluid pressure cylinder control circuit according to claim 1, further comprising a function of switching to a boosting priority mode for increasing the pressure on the side. The control device
If the pressure on the head side of the fluid pressure cylinder exceeds the pressure accumulated in the accumulator, the speed command value of the fluid pressure cylinder, the differential pressure across the accumulator control valve, the opening of the regeneration control valve, and the differential pressure across the regeneration control valve The fluid pressure cylinder control circuit according to claim 1, further comprising a control function for controlling an opening degree of the accumulator control valve. The control device
The fluid pressure cylinder control circuit according to any one of claims 1 to 3, further comprising a function of opening the regeneration control valve when the pressure on the head side of the fluid pressure cylinder increases in accordance with an increase in accumulator pressure. . The fluid pressure cylinder control circuit according to any one of claims 1 to 4, further comprising a closing control valve provided on an outlet side of the pump flow control valve. The load body is an excavator working device,
The fluid pressure cylinder control circuit according to any one of claims 1 to 5, wherein the single rod type fluid pressure cylinder is a hydraulic cylinder that rotates the working device in a vertical direction.

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