JP2009275774A - Fluid pressure control circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid pressure control circuit securely providing a reuse flow rate from an accumulator when needed. <P>SOLUTION: The head side of a potential energy recovery cylinder Cy1 is provided in communication with the accumulator Acc through one recovery control valve 1. A discharge passage of a main pump Pp1 is provided in communication with an accumulator Acc through the other recovery control valve 2. A suction port of a dedicated pump Pp2 is provided in communication with the accumulator Acc. The discharge port of the dedicated pump Pp2 is provided in communication with a reuse passage between the head and rod through one regeneration control valve 3, and provided in communication with the discharge passage of the main pump Pp1 through the other reuse control valve 4. A control device 8 provides a function of setting a necessary reuse desired value and a recovery desired value according to an operation command L of a main circuit 9, calculating a final calculated value by a reuse correction value and regeneration correction value set according to an accumulator charge ratio, and also calculating a control command from the final calculated value. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fluid pressure 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 system, a part of the return oil flowing out from the head side of the boom cylinder is stored in the accumulator through the accumulator operation valve. The working fluid is accumulated in the accumulator and the working fluid is accumulated from the accumulator. Since the state of being reused cannot be controlled in a balanced manner, the reuse flow rate from the accumulator may not be obtained even when necessary.

  The present invention has been made in view of these points, and an object of the present invention is to provide a fluid pressure control circuit that can reliably obtain a reuse flow rate from an accumulator when necessary.

  According to the first aspect of the present invention, there is provided a main circuit for supplying a working fluid discharged from a main pump to a fluid pressure actuator according to an operation command, an accumulator for accumulating the working fluid discharged from the fluid pressure actuator, and an accumulator. Control valve for controlling the flow of the working fluid accumulated in the control circuit, a reuse control valve for controlling the flow when the working fluid recovered through the recovery control valve is reused in the main circuit, and an operation command for the main circuit The required reuse value and collection request value are set according to the final value, and the reuse request value and collection request value are corrected by the reuse correction value and collection correction value set according to the accumulator accumulation state. A fluid pressure control circuit including a control device that calculates a value and calculates a control command for controlling a recovery control valve and a reuse control valve from a final calculated value

  According to a second aspect of the present invention, in the fluid pressure control circuit according to the first aspect of the present invention, the fluid pressure control circuit includes a variable capacity type dedicated pump that sucks the working fluid discharged from the accumulator and supplies the working fluid to the main circuit. In accordance with the command, the flow rate of the variable capacity type exclusive pump is controlled.

  In a third aspect of the present invention, the control device in the fluid pressure control circuit according to the first or second aspect sets an upper limit for the final calculated value.

  According to a fourth aspect of the present invention, the fluid pressure actuator in the fluid pressure control circuit according to any one of the first to third aspects is a boom cylinder that rotates the working device of the hydraulic excavator in the vertical direction.

  According to the first aspect of the present invention, the required reuse request value and the recovery request value are set according to the operation command of the main circuit, and the reuse correction value and the recovery set according to the accumulation state of the accumulator are set. The flow rate of the main circuit is controlled by a control unit that corrects the reuse request value and the collection request value with the correction value, sets the final calculation value, and calculates a control command for controlling the collection control valve and the reuse control valve from the final calculation value. The optimum reuse amount or recovery amount that satisfies both the state and the accumulation state of the accumulator can be determined, and the reuse flow rate from the accumulator can be reliably obtained when necessary.

  According to the second aspect of the present invention, since the accumulator pressure can be reduced by the dedicated pump, it is possible to increase the opportunity for the power assist of the accumulator, so that the reuse flow rate from the accumulator when necessary. Is more reliably obtained.

  According to the third aspect of the present invention, by setting an upper limit to the final calculated value, the maximum flow rate can be limited and leveling can be achieved, so that the recycle flow rate from the accumulator is ensured when necessary. Is obtained.

  According to the fourth aspect of the present invention, when the working device of the excavator is moved up and down by the boom cylinder, a recycle flow rate from the accumulator can be reliably obtained when necessary.

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

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

  The boom cylinder 14 is a fluid pressure actuator that rotates the working device 12 in the vertical direction. The boom cylinder 14 is a potential energy recovery cylinder that can perform a reduction operation in response to the entire load W of the working device 12. It is called cylinder Cy1. Further, other fluid pressure actuators (hydraulic cylinder or hydraulic motor) other than the potential energy recovery cylinder Cy1 are referred to as other circuit cylinder Cy2.

  FIG. 1 shows a specific system configuration example. The head side of the potential energy recovery cylinder Cy1 is provided so as to be able to communicate with an accumulator Acc via one recovery control valve 1, and is also a variable capacity driven by an engine E. The discharge passage of the main pump Pp1 is provided so as to be able to communicate with the accumulator Acc via the other recovery control valve 2. A part of the fluid discharged from the head side of the potential energy recovery cylinder Cy1 or the fluid discharged from the main pump Pp1 is accumulated in the accumulator Acc.

  The accumulator Acc is connected to a suction port of a variable capacity type dedicated pump Pp2 driven by the engine E together with the main pump Pp1. The discharge port of the dedicated pump Pp2 is connected to one of the recycle control valves 3 to recover potential energy. The cylinder Cy1 is provided so as to be able to communicate with the head-rod regeneration passage, and is provided so as to be able to communicate with the discharge passage of the main pump Pp1 via the other reuse control valve 4.

  In addition, a regeneration control valve 5 is provided in a regeneration passage that allows the head side of the potential energy recovery cylinder Cy1 to communicate with the rod side. Between the regeneration passage and the main pump Pp1, a closing control valve 6 and a pump flow rate are provided. A control valve 7 is provided. The discharge passage of the main pump Pp1 is connected to the supply port of the pump flow rate control valve 7.

  The recovery control valve 1 is for positional energy recovery control for controlling the flow rate when recovering the working fluid discharged from the head side of the potential energy recovery cylinder Cy1 to the accumulator Acc.

  The recovery control valve 2 controls the flow of recovering the excess flow rate from the main pump Pp1 to the accumulator Acc.

  The reuse control valve 3 controls the regeneration flow rate when the working fluid on the head side of the potential energy recovery cylinder Cy1 discharged from the dedicated pump Pp2 is reused on the rod side of the potential energy recovery cylinder Cy1.

  The reuse control valve 4 controls the flow of reusing the accumulated energy of the accumulator Acc via the dedicated pump Pp2, and is connected to the discharge line of the main pump Pp1.

  The regeneration control valve 5 controls when the fluid is directly regenerated from the head side to the rod side of the potential energy recovery cylinder Cy1, but is not essential and may be deleted together with the regeneration passage.

  The closing control valve 6 is necessary and essential when the pump flow rate control valve 7 cannot close the flow path to the tank T side during regeneration from the head side to the rod side of the potential energy recovery cylinder Cy1. is not.

  The pump flow rate control valve 7 controls the direction of the pump injection 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. The control valve for controlling the flow rate may be a spool valve in which the relationship between the injection flow rate and the return flow rate is fixed, but the relationship between the injection flow rate and the return flow rate can be controlled separately by a plurality of logic valves. desirable.

  One output port of the pump flow control valve 7 is connected to the head side of the potential energy recovery cylinder Cy1 via the passage M, and the other port is connected to the rod side of the potential energy recovery cylinder Cy1 via the closing control valve 6. Has been. The connection control object of this pump flow rate control valve 7 includes not only the position energy recovery cylinder Cy1 such as a boom cylinder for recovering potential energy but also other circuit cylinders Cy2 such as a bucket cylinder, and each of the plural circuits has flow control and direction control. To do.

  In FIG. 1, the reuse control valve 4 is connected to the upstream side of the pump flow control valve 7, but when limiting the subsystem (circuit such as a boom cylinder) to be reused, It may be connected downstream. At this time, when the flow of the recovery control valve 1 is set in both directions and the recovery control valve 1 is also used for injection to the head side, the reuse control valve 4 is not necessary.

  The dedicated pump Pp2 sucks the working fluid released from the accumulator Acc when flowing high-pressure fluid when reusing the accumulated energy of the accumulator Acc (in the reuse mode), and the head side of the potential energy recovery cylinder Cy1 or the main Further, the fluid is supplied to the discharge passage of the pump Pp1, and the fluid on the head side of the potential energy recovery cylinder Cy1 is supplied as a regeneration flow rate to the rod side of the potential energy recovery cylinder Cy1 via the reuse control valve 3 in the potential energy recovery mode. It has a function and has a flow rate adjustment function by means of variable capacity such as a swash plate.

  In FIG. 1, only one set of the fluid pump and the cylinders (boom cylinders, etc.) constituting each circuit is illustrated, but a plurality of sets may be installed.

  An operation lever (electric joystick) that inputs the operation direction and operation command speed of the potential energy recovery cylinder Cy1, etc. as an operation command L, and pressure sensors Sph, Spr that detect the head pressure Ph and rod pressure Pr of the potential energy recovery cylinder Cy1, respectively. Pressure sensor Sac for detecting accumulator pressure Pa stored in accumulator Acc, angle sensor San for detecting angle θ of load body such as boom 13, pressure sensor Spp for detecting discharge pressure Ppo of main pump Pp1, dedicated pump Pp2 Pressure sensor Spp2 for detecting the discharge pressure Ppp2, pressure sensor Snfc for detecting the negative flow control pressure Pnfc generated in the center bypass line of the pump flow control valve 7, and the gas temperature enclosed in the accumulator Acc (hereinafter referred to as accumulator temperature) Ta A temperature sensor Sta for detecting is connected to the input unit of the control device 8.

  This control device 8 incorporates an arithmetic processing device, a storage device, etc., and the output unit of this control device 8 is a movable control unit (such as a solenoid) of each control valve 1-7 and variable capacity control of the main pump Pp1. Connected to the control unit (swash plate regulator, etc.) and the capacity variable control unit (swash plate regulator, etc.) of the dedicated pump Pp2, 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.

  A fluid pressure circuit that controls the working fluid discharged from the main pump Pp1 according to the operation command L and supplies the working fluid to the potential energy recovery cylinder Cy1 or the other circuit cylinder Cy2 is referred to as a main circuit 9 for the accumulator circuit. Although only one operation command L is shown, it is input to the control device 8 for each cylinder, and the displacement amount of the spool (or stem) in the pump flow rate control valve 7 and the target value in the displacement direction for each cylinder. Become.

  The control device 8 grasps the accumulation state (accumulator filling rate) of the accumulator Acc by calculating the accumulator pressure Pa detected by the pressure sensor Sac and the enclosed gas temperature Ta of the accumulator Acc detected by the temperature sensor Sta. Therefore, the control valves 1 to 7, the main pump Pp1 and the dedicated pump Pp2 are controlled based on the accumulation state and the flow rate request state based on the operation command L input from the operation lever.

  Further, the control device 8 sets the required reuse request value and the collection request value according to the operation command L of the main circuit 9 as shown in FIG. 2, and the accumulation state of the accumulator Acc as shown in FIG. Based on the reuse correction value and the collection correction value set according to (filling rate), the reuse request value and the collection request value are corrected as shown in FIG. 4 to calculate the final calculation value. A function of calculating a control command for controlling the recovery control valve and the reuse control valve is provided. Further, as shown in FIG. 4, a function for setting an upper limit to the final calculated value is provided.

  In such a potential energy recovery / reuse system, if the frictional force is ignored, the force balance equation is as follows.

  The pressure on the head side from the piston of the potential energy recovery cylinder Cy1 detected by the pressure sensor Sph is the head pressure Ph, the area on the head side of the piston is the header area Ah, and the potential energy recovery cylinder Cy1 detected by the pressure sensor Spr If the pressure on the rod side of the piston is the rod pressure Pr, the area on the rod side of the piston is the rod area Ar, the load body mass is m, the second derivative of the cylinder position X, that is, the acceleration is α, and the friction force is ignored 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 accumulator pressure stored in the accumulator Acc is Pa, and the initial pressure of the accumulator Acc (slightly higher than the enclosed gas pressure) is PaO.

  An arrow N shown in FIG. 1 is a flow path from the existing system to the rod side of the potential energy recovery cylinder Cy1, and is used in a mode other than the potential energy recovery mode.

  In the potential energy recovery mode, the flow rate discharged from the main pump Pp1 is set to 0 in principle, and the working fluid discharged from the potential energy recovery cylinder Cy1 is lowered while the potential energy recovery cylinder Cy1 is lowered by the load W of the working device 12. This is a control mode that accumulates in the accumulator Acc. The recovery control valve 2, the reuse control valve 4 and the pump flow rate control valve 7 are closed, the recovery control valve 1, the reuse control valve 3 and the regeneration control valve 5 are opened, and the dedicated pump Pp2 To control the flow rate.

  If necessary, the control device 8 allows a part of the head side fluid of the potential energy recovery cylinder Cy1 to flow to the rod side of the potential energy recovery cylinder Cy1 via the dedicated pump Pp2 and the reuse control valve 3. The pressure Pr can be increased, the right side of the equation (1) can be increased, and the downward acceleration α can be increased.

At this time, the accumulated flow rate Q1 to the accumulator Acc and the flow rate Q2 to the rod side are:
Q1 = Cd · A · √ (Ph-Pa), where Cd is a constant Q2 = volume of the dedicated pump Pp2 × number of revolutions, A can be freely controlled by the opening of the recovery control valve 1, the volume of the dedicated pump Pp2 Can be freely controlled by the swash plate, the ratio of these flow rates Q1 and Q2 can also be set freely.

  As an example of the potential energy recovery mode, the control device 8 first opens the regeneration control valve 5 so that the fluid flowing out from the head side of the potential energy recovery cylinder Cy1 is regenerated to the rod side. The potential energy recovery cylinder Cy1 that receives the load W generates acceleration in the downward direction, the head speed Ph and the rod pressure Pr increase as the cylinder speed increases, and the head pressure Ph becomes the accumulator initial pressure. When PaO is exceeded, the regeneration control valve 5 is throttled and the collection control valve 1 is opened to supply and accumulate the flow rate from the head side to the accumulator Acc.

  In short, both the system state and the accumulation state (filling rate) of the accumulator Acc are required to realize a system that can reliably supply the re-use flow from the accumulator Acc when necessary, not by over-extending the equipment, but by contriving the configuration and control. Therefore, the following method is adopted to automatically determine collection and reuse.

  As shown in FIG. 2, one required reuse value or collection request value is set according to the operation command L.

  As shown in FIG. 3, a correction amount for correcting the reuse request value and the collection request value is obtained according to the accumulation state of the accumulator Acc, and the final calculated value after correction is set as shown in FIG. A and B are examples of correction values, and one correction value is determined according to the filling rate of the accumulator Acc.

  As shown in FIG. 4, the reuse calculation value or the recovery calculation value after correction is corrected by A or B, respectively. In the reuse prohibited area shown in FIG. 3, the reuse calculation value is zero. The recovery calculation value is 0 in the recovery prohibited area. The correction coefficient outside these prohibited areas is 1, and this correction coefficient is multiplied by each calculated value. The final calculated value is obtained by cutting the calculated value at each upper limit value shown in FIG. In the potential energy recovery mode, no correction value is added.

  The control command is calculated from the final calculated value.

  At the same time, an accumulator system control mode is obtained from the value of the final calculation value, and control such as collection / reuse is performed according to the mode.

  In addition, the maximum flow rate is limited for leveling, and it is devised to realize reliable reuse when necessary.

  Next, FIG. 5 is a flowchart showing functions of the control device 8. The circled numbers in this figure indicate step numbers.

(Step 1)
In accordance with the operation command L of the main circuit 9 input from the operation lever (electric joystick), the required reuse request value and the collection request value are set from the characteristic table in FIG. ).

(Step 2)
The accumulation state (accumulator filling rate) of the accumulator Acc obtained from the accumulator pressure Pa detected by the pressure sensor Sac and the accumulator gas temperature Ta detected by the temperature sensor Sta, and the characteristic table of FIG. 3 in the storage device Thus, the reuse correction value and the recovery correction value corresponding to the accumulator filling rate are set (correction value setting).

(Step 3)
The reuse request value and the collection request value obtained in step 1 are corrected by the reuse correction value and the collection correction value obtained in step 2, the characteristic table of FIG. 4 is set, and the final calculation value is calculated (final calculation value) Calculated value calculation).

(Step 4)
A control command for controlling the collection control valves 1 and 2 and the reuse control valves 3 and 4 is calculated from the final calculated value (control command calculation).

(Step 5)
The accumulator system control mode is obtained from the final calculated value, and control such as collection or reuse is performed according to each mode (mode-corresponding control).

  Next, details of the schematic flow shown in FIG. 5 will be described with reference to the flowcharts shown in FIGS. Although the concept is the same, there may be many small variations, but the following is described as a typical example.

  First, referring to the flowchart shown in FIG. 6, the flow relating to the required value setting in step 1 will be described. In this flow, the degree of recovery to the accumulator Acc or reuse from the accumulator Acc can be set according to the operation command L of each circuit.

(Step 11)
It is determined whether the accumulator collection area or the accumulator reuse area is selected from the three areas of the accumulator collection area, the accumulator reuse area, and the accumulator 0 utilization area according to the operation command L shown in FIG. To do.

(Step 12)
In the accumulator collection area or the accumulator reuse area, the collection request value or the reuse request value is determined so as to be increased or decreased according to the operation command L as shown in FIG. Value or reuse request value is set. In the case of a complex operation in which a plurality of fluid pressure actuators are operated simultaneously, a circuit having the maximum required value is selected.

(Step 13)
In the accumulator 0 usage area, the collection request value and the reuse request value are set to 0 as shown in FIG.

  The above settings can be individually set for each operation circuit (and operation direction). Depending on the operation mode (such as excavation mode), only one or two of the three areas may be required, so that it can be accommodated.

(Step 14)
It is determined whether or not the descent operation command of the potential energy recovery cylinder Cy1 (boom cylinder or the like) exceeds a certain set value.

(Step 15)
When the descending operation command exceeds a certain set value, the potential energy recovery mode is set regardless of the presence or absence of an operation command for another circuit.

  Next, the flow relating to the correction value setting in step 2 will be described with reference to the flowchart shown in FIG.

  In this flow, a reuse prohibited area and a collection prohibited area are provided according to the accumulation state of the accumulator Acc, and outside of these prohibited areas, the degree of reuse / recovery can be increased or decreased according to the accumulation state of the accumulator Acc. It is a thing.

  As the accumulation state of the accumulator Acc, an accumulator filling rate indicating the degree of empty or full of the accumulator Acc is used.

  The area other than the prohibited area is divided into a zero correction area and a correction area. In the 0 correction area, there is no request from the accumulator Acc, and the operation required value remains unchanged. In the correction area, the degree of reuse / recovery (this is referred to as a reuse correction value or a collection correction value) according to the filling rate. )

(Step 21)
The accumulator pressure Pa is detected by the pressure sensor Sac, and the sealed gas temperature Ta of the accumulator Acc is detected by the temperature sensor Sta.

(Step 22)
The accumulator filling rate is obtained from the accumulator pressure Pa and the enclosed gas temperature Ta. When the accumulation amount of the accumulator Acc increases, the accumulator pressure Pa increases. When the temperature rises, the pressure increases even with the same accumulation amount. Therefore, the accumulator filling rate is calculated from the accumulator pressure Pa and the enclosed gas temperature Ta. Specifically, the calculation is based on the “Van der Waals equation” indicating the relationship between the pressure, temperature, and volume of the sealed gas.

(Step 23)
The reuse correction value A or the recovery correction value B is obtained from the characteristics shown in FIG. 3 according to the accumulator filling rate.

  Next, the flow relating to the final calculation value calculation in step 3 will be described with reference to the flowchart shown in FIG. This is to correct the request on the operation command with the request from the accumulation state of the accumulator Acc in order to match the request on the operation command and the request from the accumulation state of the accumulator Acc.

(Step 30)
It is determined whether the operation command L is a collection area-0 use area or a reuse area-0 use area.

(Step 31)
In the collection area-0 use area, the collection correction value B is added to the collection request value.

(Step 32)
It is determined whether or not the accumulator Acc side is in the collection prohibited area.

(Step 33)
The collection request value is set to 0 in the collection prohibited area.

(Step 34)
It is determined whether or not the potential energy recovery mode in step 15 is set.

(Step 35)
When the potential energy recovery mode is set, no recovery correction value is added in the recovery correction area-recovery 0 correction area.

(Step 36)
Even if the potential energy recovery mode is set, the recovery request value becomes 0 in the recovery prohibition area. At this time, the potential energy recovery mode is reset.

(Step 37)
If it is determined in step 30 that the operation command L is the reuse area-0 use area, the reuse correction value A is added to the reuse request value.

(Step 38)
It is determined whether or not the accumulator Acc side is in a reuse prohibited area.

(Step 39)
The reuse request value is set to 0 in the reuse prohibited area. FIG. 4 shows a specific relationship of correction.

(Step 40)
As illustrated by dotted lines in the upper and lower parts of FIG. 4, the reuse upper limit value and the recovery upper limit value are individually set for the reuse calculation value and the recovery calculation value after correction so that the accumulator Acc can be used throughout the cycle. .

  The upper limit at the time of reuse is important to ensure that the accumulator Acc can be assisted when necessary. This is especially important when downsizing. However, no upper limit is set in the potential energy recovery mode.

  A final calculated value K is obtained from the solid line portion of FIG. 4 cut by the upper limit value.

  Next, the flow relating to the control command calculation in step 4 will be described with reference to the flowchart shown in FIG. In this flow, the control mode of the accumulator system is determined based on the final calculated value K. However, the potential energy recovery mode is shown in FIG.

  In a case other than the potential energy recovery mode, it is determined whether or not the final calculated value K is a positive value (step 41). When the final calculated value K is positive, the recycle mode is set (step 42). It is determined whether or not the value is negative (step 43). When the final calculated value K is negative, the recovery mode is set (step 44), and when the final calculated value K is 0, the separation mode is set (step 45). .

In the reuse mode, the final calculated value K is compared with the reuse flow rate restriction value Qa2 · C2 (constant coefficient) (step 46). After confirming that the final calculated value K is less than the value of Qa2 · C2, The final calculated value K is set as a flow control value (step 47). If the final calculated value K exceeds the value of Qa2 · C2, the final calculated value K is changed to Qa2 · C2 to obtain a flow control value (step 48).

In recovery mode, compare the final calculated value K (absolute value) with the flow rate restriction value Qa1 · C1 (constant coefficient) during recovery (step 49) and confirm that the final calculated value K is less than or equal to Qa1 · C1. The final calculated value K is set as a flow control value (step 47). If the final calculated value K exceeds the value of Qa1 · C1, the final calculated value K is changed to Qa1 · C1 to be a flow control value (step 50).

  The constant coefficients C1 and C2 are positive numbers of 1 or less, and values are set individually from the viewpoint of ensuring leveling operation, thereby ensuring that the flow rate is less than or equal to the reusable flow when necessary.

  Next, the flow relating to the mode-corresponding control in step 5 will be described with reference to the flowchart shown in FIG. In this flow, each control valve and pump are controlled according to the accumulator system control mode.

(Step 51)
It is determined whether or not the potential energy recovery mode is set.

(Step 52)
In the potential energy recovery mode, the control value of the recovery control valve 1 is determined according to the final calculated value K, the reuse control valve 3 and the regeneration control valve 5 are opened, and the recovery control valve 2 and the reuse control valve are opened. 4 is closed. The dedicated pump Pp2 determines the flow control value according to the final calculated value K. The flow rate discharged from the main pump Pp1 is set to 0 in principle, the closing control valve 6 is in a bypass state, and the pump flow rate control valve 7 is closed. However, if the regeneration flow rate is insufficient due to the restriction on the maximum flow rate of the dedicated pump Pp2, it is necessary to compensate from the main pump Pp1.

(Step 53)
It is determined whether or not it is a reuse mode.

(Step 54)
In the case of the reuse mode, the control command value for the dedicated pump Pp2 is determined according to the flow rate control value in step 47 or 48. The reuse control valve 4 is opened, and the flow rate assist of the corresponding circuit to the cylinders Cy1 and Cy2 is performed via the pump flow rate control valve 7. The flow rate from the main pump Pp1 is reduced by the flow rate assist. The control valves 1 to 3 and the regeneration control valve 5 are closed, and the closing control valve 6 is opened only when supplied to the potential energy recovery cylinder Cy1, and is closed otherwise.

(Step 55)
It is determined whether or not the collection mode is set.

(Step 56)
In the recovery mode, the control command is determined by calculating the opening area of the recovery control valve 2 in accordance with the flow control value in step 47 or 50. The dedicated pump Pp2 is stopped or brought to zero volume, and the control valves 1, 3 to 5 are closed. The flow rate from the main pump Pp1 is increased by the recovered flow rate. The control of the pump flow rate control valve 7 is controlled according to the control command of the corresponding circuit and is not changed. The closing control valve 6 is opened only when supplied to the potential energy recovery cylinder Cy1, and is closed otherwise.

  Here, when the accumulator pressure Pa ≧ the main pump discharge pressure Ppo cannot be recovered, the recovery control valve 2 is left open if there is no fear of backflow. Further, when the recovery control valve 2 has a maximum opening area and the recovered flow rate cannot be flowed due to a decrease in the differential pressure, the main pump flow rate is increased by the flow rate value at the maximum opening area (0 value when the value is negative). .

(Step 57)
When none of the potential energy recovery mode, the reuse mode and the recovery mode is selected, the control valves 1 to 5 are closed as the disconnect mode, and the dedicated pump Pp2 is set to zero output. Since there is no collection / reuse, the flow rate output from the main pump Pp1 does not increase or decrease.

  Next, the function and effect of this embodiment will be described.

  The control device 8 sets the required reuse request value and the collection request value according to the operation command of the main circuit 9, and reuses the reuse correction value and the collection correction value set according to the accumulation state of the accumulator Acc. The final calculation value is set by correcting the request value and the recovery request value, and the control command for controlling the recovery control valve and the reuse control valve is calculated from the final calculation value. Therefore, the flow state of the main circuit 9 and the accumulation of the accumulator Acc are calculated. The optimum reuse amount or recovery amount that satisfies both conditions can be determined, and the reuse flow rate from the accumulator Acc can be reliably obtained when necessary.

  Since the accumulator pressure Pa can be reduced by the dedicated pump Pp2, the opportunity for power assist of the accumulator Acc can be increased, so that the reuse flow rate from the accumulator Acc can be obtained more reliably when necessary.

  The optimal amount of reuse (recovery) that satisfies both the system state and the accumulator Acc accumulation state can be determined, and the maximum flow rate is limited and leveled by multiplying the coefficient or setting an upper limit on the final calculated value Therefore, the reuse flow rate from the accumulator Acc can be reliably obtained when necessary.

  When the working device 12 of the excavator 10 is moved up and down by the boom cylinder 14, a recycle flow rate from the accumulator Acc can be reliably obtained when necessary.

  In this way, in order to realize a system that can reliably supply the recycle flow from the accumulator Acc when necessary, it is possible to realize the system state and accumulator Acc accumulation state (filling rate) by means of system configuration and control rather than excessive equipment. ) From both of the above, the system automatically determines collection and reuse.

  That is, when the accumulator Acc is nearly empty, priority is given to collection and storage, and when the accumulator Acc is almost full, priority is given to reuse, so that a request on the operation command (if you want to use the assist of the accumulator Acc or the accumulator Acc And the request based on the accumulation state of the accumulator Acc (when you want to use the assist of the accumulator Acc or when you want to collect to the accumulator Acc), you can assist when necessary.

  A system that can be used continuously when it is necessary to reuse the accumulator Acc can be realized without increasing the capacity of the accumulator Acc, thereby contributing to the realization of downsizing of the device.

  The present invention is applicable to work machines such as hydraulic excavators and loaders.

It is a circuit diagram showing one embodiment of a fluid pressure control circuit according to the present invention. It is a characteristic view which shows the operation command-request value relationship of a circuit same as the above. It is a characteristic view which shows the relationship of the accumulator filling factor-correction value of a circuit same as the above. It is a characteristic view which shows the relationship between the operation command-final calculation value of a circuit same as the above. It is a flowchart explaining the function which the control apparatus of a circuit same as the above has. It is a flowchart which shows the request value setting flow of a control apparatus same as the above. It is a flowchart which shows the correction value setting flow of a control apparatus same as the above. It is a flowchart which shows the last calculation value calculation flow of a control apparatus same as the above. It is a flowchart which shows the control command calculation flow of a control apparatus same as the above. It is a flowchart which shows the mode corresponding | compatible control of a control apparatus same as the above. It is a side view which shows the working machine provided with the circuit same as the above.

Explanation of symbols

Pp1 main pump
Pp2 dedicated pump
Cy1, Cy2 Fluid pressure actuator
Acc Accumulator 1, 2 Recovery control valve 3, 4 Reuse control valve 8 Controller 9 Main circuit
10 Excavator
12 Working equipment
14 Boom cylinder as a fluid pressure actuator

Claims (4)

A main circuit for supplying the working fluid discharged from the main pump to the fluid pressure actuator according to the operation command;
An accumulator for accumulating the working fluid discharged from the fluid pressure actuator;
A recovery control valve for controlling the flow of the working fluid accumulated in the accumulator;
A reuse control valve for controlling the flow when the working fluid recovered through the recovery control valve is reused in the main circuit;
The required reuse request value and recovery request value are set according to the operation command of the main circuit, and the reuse request value and recovery request value are set by the reuse correction value and recovery correction value set according to the accumulation state of the accumulator. A fluid pressure control circuit comprising: a control device that calculates a final calculated value after correction, and calculates a control command for controlling the recovery control valve and the reuse control valve from the final calculated value. It is equipped with a variable capacity dedicated pump that sucks the working fluid released from the accumulator and supplies it to the main circuit,
The fluid pressure control circuit according to claim 1, wherein the control device controls the flow rate of the variable capacity type dedicated pump in accordance with a control command. The fluid pressure control circuit according to claim 1, wherein the control device sets an upper limit for the final calculated value. The fluid pressure control circuit according to any one of claims 1 to 3, wherein the fluid pressure actuator is a boom cylinder that rotates a working device of the excavator in a vertical direction.

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