JP2011069432A - Regenerative control device of working machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently recover, regenerate and utilize the energy of a hydraulic cylinder while suppressing increase in costs with a simple constitution. <P>SOLUTION: A pair of conduits for drive is connected between the hydraulic pump 2 and hydraulic cylinder 3 of a working machine like a closed circuit. In addition, a pressure increasing means 10A for increasing the pressure of the hydraulic oil discharged from the hydraulic cylinder 3 when the hydraulic cylinder 3 is extended or withdrawn in the actuation direction of a load on the hydraulic cylinder 3, and a pressure accumulating means 30A for accumulating the hydraulic oil having a pressure increased by the pressure increasing means 10A are provided. Furthermore, a regeneration means 30B for supplying the hydraulic oil accumulated in the pressure accumulating means 30A to the hydraulic pump 2 for regeneration when the hydraulic cylinder 3 is extended or withdrawn in a reverse direction to the actuation direction of a load on the hydraulic cylinder 3, and a return flow rate control means 30C for controlling the flow rate of the hydraulic oil returned from the hydraulic cylinder 3 to the hydraulic pump 2 depending on the pressure of the hydraulic oil regenerated by the regeneration means 30B are provided. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hydraulic oil regeneration control device in a hydraulic circuit of a work machine.

Conventionally, in revolving control machines such as hydraulic excavators, a regenerative control device has been developed that stores hydraulic oil energy discharged from the hydraulic cylinder during hydraulic cylinder expansion and contraction and uses that energy to drive the hydraulic cylinder. Has been.
For example, Patent Document 1 discloses a boom drive circuit for a hydraulic excavator that includes a regenerative hydraulic motor that is rotationally driven by return oil from a boom cylinder. In this circuit, the flow path of the return oil at the time of the boom cylinder reduction operation is branched, and the regenerative hydraulic motor is rotationally driven by one branch flow to generate power and charge the battery. Further, when the boom cylinder is extended, the regenerative hydraulic motor is operated as an electric motor so that electric energy is reused to assist the supply of hydraulic oil. With these configurations, it is said that an increase in the regeneration amount and an improvement in operability can be achieved at a high level without causing a sudden change in operability.

JP 2006-136392 A

However, the technique described in Patent Document 1 requires a regenerative hydraulic motor for generating electric power and various electric devices such as a battery device, an inverter device, and a controller for storing energy, which complicates the system. Therefore, there are problems that it is difficult to reduce costs and that it is difficult to increase the reliability of the entire system.
In particular, in the case of a large-sized hydraulic excavator, a large-capacity motor generator, a capacitor, an inverter device, and the like are required, which further increases the cost, and the installation space is also required, resulting in a more difficult layout. .

  The present invention has been made in view of such a problem, and can reduce costs with a simple configuration, and can efficiently recover and reuse the energy of the hydraulic cylinder. An object of the present invention is to provide a regeneration control device for a machine.

  In order to achieve the above object, a regenerative control device for a working machine according to a first aspect of the present invention is a hydraulic circuit in which a pair of drive pipes are connected in a closed circuit between a hydraulic pump and a hydraulic cylinder of the working machine. A hydraulic oil regeneration control device according to claim 1, wherein the hydraulic oil discharged from the hydraulic cylinder is increased when the hydraulic cylinder expands or contracts in a direction of a load applied to the hydraulic cylinder; Pressure accumulating means for accumulating hydraulic oil increased by the pressure increasing means, and hydraulic oil accumulated in the pressure accumulating means when the hydraulic cylinder expands or contracts in a direction opposite to the direction of the load applied to the hydraulic cylinder. Is supplied to the hydraulic pump and regenerated, and a recirculation amount control means for controlling the flow rate of the working oil that is recirculated from the hydraulic cylinder to the hydraulic pump in accordance with the pressure of the hydraulic oil regenerated by the regenerating unit. It is characterized by having a and.

  According to a second aspect of the present invention, there is provided the regenerative control device for a work machine according to the first aspect, wherein the recirculation amount control means is operated by the regeneration means when the hydraulic cylinder is driven by the hydraulic pump. When the hydraulic oil to be regenerated is equal to or higher than a predetermined pressure, the flow rate of the hydraulic oil that is recirculated from the hydraulic cylinder to the hydraulic pump is decreased, and when the hydraulic oil regenerated by the regeneration means is less than the predetermined pressure, It is characterized in that the flow rate of the hydraulic oil that returns from the hydraulic cylinder to the hydraulic pump is increased.

According to a third aspect of the present invention, there is provided the regenerative control device for a work machine according to the first or second aspect, wherein the pressure increasing means includes a regenerative pipe connecting the pair of drive pipes. A regenerative valve that is interposed on the regenerative pipe and regenerates hydraulic oil discharged from one hydraulic oil chamber located in the direction of action of the load in the hydraulic cylinder to the other hydraulic oil chamber. It is characterized by.
According to a fourth aspect of the present invention, there is provided a regenerative control device for a working machine according to the third aspect, wherein the pressure accumulating means sets a supply direction of the hydraulic oil from the hydraulic pump in response to an operation input. An operating lever and a first drive pipe connected to the one hydraulic oil chamber of the pair of drive pipes, and supplying hydraulic oil to the other hydraulic oil chamber When the operation lever is operated, the first drive pipe is opened, and when the operation lever is operated in a direction to supply hydraulic oil to the one hydraulic oil chamber, the first drive pipe is opened. A switching valve that closes the drive line, and a second drive line connected to the other hydraulic oil chamber of the pair of drive lines, and the hydraulic pump from the hydraulic cylinder side Bypass switching valve for blocking the flow of hydraulic fluid to the side, and the bypass switching on the second drive pipe A pressure accumulating line formed by branching from the hydraulic pump side, and an accumulator that is interposed on the pressure accumulating line and accumulates hydraulic oil discharged from the one hydraulic oil chamber. It is said.

  According to a fifth aspect of the present invention, there is provided the regenerative control device for a working machine according to the fourth aspect, in addition to the configuration according to the fourth aspect, wherein the pressure accumulating means is closer to the hydraulic pump than the switching valve on the first drive conduit. Pressure accumulation pilot pipe formed by branching from the pressure accumulation pilot pipe and the pressure accumulation pilot when the operation lever is operated in a direction to supply hydraulic oil to the other hydraulic oil chamber. A pilot switching valve for closing the pressure accumulating pilot line when the operating lever is operated in a direction to open the line and supplying the working oil to the one hydraulic oil chamber; And when the hydraulic pressure of the pressure accumulating pilot line is greater than or equal to a second predetermined pressure, the pressure accumulating line is opened, and when the hydraulic pressure of the pressure accumulating pilot line is less than the second predetermined pressure, An accumulator switching valve for closing the accumulator pipeline; and the second When the operating hydraulic pressure of the pressure accumulating pilot line is greater than or equal to the second predetermined pressure, the second driving valve is interposed between the bypass switching valve on the dynamic line and the branch point of the pressure accumulating line. Operation from the hydraulic pump side to the other hydraulic oil chamber side in the second drive pipeline when the pipeline is closed and the hydraulic pressure of the pressure accumulating pilot pipeline is less than the second predetermined pressure And a pilot check valve that allows oil to flow.

  According to a sixth aspect of the present invention, there is provided a regeneration control device for a work machine according to the fifth aspect of the present invention, wherein the regeneration means is connected in parallel to the pressure accumulation switching valve on the pressure accumulation conduit. A regeneration valve that is disposed on the regeneration conduit and opens the regeneration conduit when the operation lever is operated in a direction to supply the hydraulic fluid to the one hydraulic fluid chamber, and the regeneration A regeneration check valve interposed on the pipeline and allowing the flow of hydraulic oil from the accumulator side to the second drive pipeline side, and the reflux control means has one end at the bypass switching valve. A bypass line connected to the hydraulic oil tank at the other end, and the bypass line connected to the bypass line when the hydraulic pressure of the regeneration line is equal to or higher than the predetermined pressure. The bypass line is opened when the operating oil pressure of the regeneration line is less than the predetermined pressure. A bypass valve, and the bypass switching valve is discharged from the other hydraulic oil chamber when the operating lever is operated in a direction to supply the hydraulic oil to the one hydraulic oil chamber. The hydraulic oil is introduced into the bypass pipe.

  According to a seventh aspect of the present invention, there is provided a regenerative control device for a working machine according to the present invention, wherein the recirculation amount control means is provided between the bypass switching valve and the bypass valve on the bypass pipe. A bypass reflux line formed by branching from the second drive line, and interposed on the bypass return line, from the bypass line side to the second drive line side And a bypass check valve that allows the hydraulic oil to flow.

  The regenerative control device for a work machine according to an eighth aspect of the present invention is the drive on the side of the pair of drive pipes from which hydraulic oil is discharged from the hydraulic cylinder, in addition to the configuration of the seventh aspect It is further characterized by further comprising a charge pump connected to the service pipe and replenishing hydraulic oil.

  According to the regenerative control device for a working machine according to the present invention (claim 1), hydraulic oil can be efficiently accumulated by increasing the hydraulic pressure discharged from the hydraulic cylinder. Further, by providing the recirculation amount control means in the closed circuit type hydraulic circuit, there is no excess or deficiency in the amount of hydraulic fluid flowing into the hydraulic pump when the accumulated hydraulic fluid is recycled. Thereby, the fluctuation | variation of the hydraulic fluid flow rate of the whole closed circuit before and behind reproduction | regeneration can be suppressed, and operation | movement of a hydraulic pump and a hydraulic cylinder can be stabilized.

Further, according to the regenerative control device for a working machine of the present invention (Claim 2), the flow rate of the hydraulic fluid recirculated from the hydraulic cylinder to the hydraulic pump is controlled in accordance with the pressure of the regenerated hydraulic fluid, so that the closed circuit The fluctuation | variation of the whole hydraulic fluid flow rate can be suppressed.
Further, according to the regenerative control device for a working machine of the present invention (Claim 3), the hydraulic oil discharged from the hydraulic cylinder can be increased in pressure while being regeneratively supplied, and the energy regeneration efficiency of the hydraulic oil is increased. be able to.

Further, according to the regenerative control device for a working machine of the present invention (Claim 4), the hydraulic oil can be stored in the accumulator while the hydraulic cylinder is regeneratively operated with a simple configuration.
Further, according to the regenerative control device for a working machine of the present invention (Claim 5), the hydraulic oil is stored in the accumulator at a pressure equal to or higher than the second predetermined pressure by the control according to the hydraulic pressure introduced from the pressure accumulating pilot pipeline. be able to. Further, for example, when the load on the hydraulic cylinder is reduced and the pressure of the hydraulic oil to be accumulated is lowered, the high-pressure hydraulic oil can be held in the accumulator by closing the pressure accumulation pipeline.

  According to the regenerative control device for a working machine of the present invention (Claim 6), the hydraulic oil is discharged to the hydraulic oil tank by introducing the return oil from the hydraulic cylinder into the bypass line when the hydraulic oil is regenerated. be able to. That is, the hydraulic fluid can be regenerated without greatly changing the hydraulic fluid flow rate in the closed circuit. In addition, implementation by pilot control not using an electronic control device is easy, and the circuit configuration can be simplified.

  According to the regenerative control device for a working machine of the present invention (Claim 7), when the regeneration pressure is reduced during the regeneration of the hydraulic oil, the bypass conduit is connected to the second drive conduit side with a simple configuration. And hydraulic oil can be distributed. That is, when the hydraulic oil stored in the accumulator decreases and regeneration is completed, the hydraulic oil discharged from the hydraulic cylinder can be supplied to the hydraulic pump.

  Further, according to the regeneration control device for a working machine of the present invention (claim 8), the hydraulic oil can be supplemented to the closed circuit, and the circuit operation can be further stabilized.

It is a typical perspective view showing a hydraulic excavator provided with a regeneration control device concerning one embodiment of the present invention. It is a circuit diagram which shows the hydraulic circuit to which this regeneration control apparatus was applied. FIG. 3 is a schematic circuit diagram showing a distribution state of hydraulic oil during a boom raising operation and hydraulic pressure regeneration in the hydraulic circuit of FIG. 2. FIG. 3 is a schematic circuit diagram illustrating a flow state of hydraulic oil during a boom raising operation and non-regeneration of hydraulic pressure in the hydraulic circuit of FIG. 2. FIG. 3 is a schematic circuit diagram showing a distribution state of hydraulic oil during boom lowering operation and pressure accumulation in the hydraulic circuit of FIG. 2. FIG. 3 is a schematic circuit diagram illustrating a flow state of hydraulic oil during a boom lowering operation and a non-accumulated pressure in the hydraulic circuit of FIG. 2.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[1. Hydraulic excavator configuration]
The present invention is applied to a hydraulic excavator 50 shown in FIG. The hydraulic excavator 50 includes a lower traveling body 51 equipped with a crawler traveling device, and an upper swing body 52 mounted on the lower traveling body 51. The upper turning body 52 is installed on the lower traveling body 51 via a turning device so as to be turnable.

A cab 54 on which an operator (operator) rides is provided on the vehicle front side of the upper turning body 52, and a front work device 55 provided adjacent to the cab 54 so as to extend forward of the vehicle. A counterweight 56 is provided at the rearmost end of the upper swing body 52 to maintain the weight balance of the aircraft.
An engine room and a pump room are formed immediately before the counterweight 56. An engine 1 that is a drive source of the hydraulic excavator 50 is installed in the engine room, and a hydraulic pump 2 that is a hydraulic oil supply source such as a turning device and a front work device 55 is installed in the pump room. A hydraulic oil tank 9 is installed in front of the pump room.

  The front work device 55 includes three members, which are a boom 3A, a stick 4A, and a bucket 5A, each of which operates independently. Between the boom 3A and the upper swing body 52, a pair of hydraulically driven boom cylinders 3 for swinging the boom 3A in the vertical direction is interposed. The boom 3 </ b> A is provided so as to be freely raised and lowered with respect to the upper swing body 52 according to the expansion and contraction of the boom cylinder 3. Similarly, the stick cylinder 4 and the bucket cylinder 5 shown in FIG. 1 are hydraulic cylinders for driving the stick 4A and the bucket 5A, respectively.

The boom cylinder 3 of the hydraulic excavator 50 is an actuator that expands and contracts when supplied with hydraulic oil from the hydraulic pump 2. Between the hydraulic pump 2 and the boom cylinder 3, a pair of driving pipes are connected in a closed circuit shape. The expansion / contraction direction of the boom cylinder 3 depends on the flow direction of the hydraulic oil in the closed circuit, that is, the supply direction of the hydraulic oil from the hydraulic pump 2.
That is, the hydraulic circuit related to the driving of the boom cylinder 3 is not an open hydraulic circuit whose expansion and contraction direction is controlled via a control valve as described in Patent Document 1, but to the input / output port of the hydraulic pump 2. Thus, the boom cylinder 3 is formed as a closed circuit in which the input / output ports of the boom cylinder 3 are connected one-to-one.

  In the cab 54, a boom operation lever 21 (operation lever) for inputting a telescopic operation direction of the boom cylinder 3 (that is, a swinging direction of the boom 3A) is disposed. The flow direction of the hydraulic oil discharged from the hydraulic pump 2 is selected according to the operation input of the boom operation lever 21, and the boom cylinder 3 is expanded or contracted. When the bucket 5A is not grounded, a load due to the weight of the front working device 55 acts on the boom cylinder 3. The acting direction of the load is the direction in which the boom cylinder 3 is reduced.

  An accumulator 7 is disposed in the pump room. The accumulator 7 is a pressure accumulator having a liquid chamber that stores high-pressure hydraulic oil and a gas chamber that expands and contracts in accordance with the internal pressure of the liquid chamber. In the present embodiment, high-pressure hydraulic oil discharged when the boom cylinder 3 is operated in the contracting direction is temporarily stored in the accumulator 7, and is discharged when the boom cylinder 3 is operated in the extending direction. By supplying to, hydraulic energy is regenerated. The type of accumulator 7 may be a piston type accumulator or a bladder type accumulator.

[2. Hydraulic circuit configuration]
FIG. 2 shows a hydraulic circuit for driving the boom cylinder 3. Here, only one of the pair of boom cylinders 3 is illustrated. For convenience, the hydraulic circuits are classified according to their functions and are described in order.
The hydraulic circuit includes a cylinder drive closing circuit 10, a pressure increasing circuit 10A (pressure increasing means), a pilot pressure generating circuit 20, a pressure accumulating circuit 30A (pressure accumulating means), a regeneration circuit 30B (regenerating means), and a recirculation amount control circuit 30C (return). A flow rate control means). In FIG. 2, a portion corresponding to the pressure accumulation circuit 30 </ b> A is surrounded by a two-dot chain line, and a portion corresponding to the pressure increasing circuit 10 </ b> A, the regeneration circuit 30 </ b> B and the reflux amount control circuit 30 </ b> C is surrounded by a one-dot chain line.

[2-1. Pilot pressure generation circuit 20]
The pilot pressure generation circuit 20 is a circuit for outputting a pilot pressure corresponding to an input operation to the boom operation lever 21. As shown in FIG. 2, a remote control valve 22 is fixed to the lower end portion of the boom operation lever 21. The remote control valve 22 is a control valve that generates a pilot pressure having a magnitude corresponding to the operation amount and the operation direction input to the boom operation lever 21. A pilot pump 25 and a hydraulic oil tank 9 are connected to the remote control valve 22.

  A pair of pressure reducing valves 23U, 23D and a pilot shuttle valve 24 are built in the remote control valve 22, and the upper ends of the pair of pressure reducing valves 23U, 23D are connected to the lower end of the boom operation lever 21. One of the pair of pressure reducing valves 23U and 23D corresponding to the tilting direction of the boom operating lever 21 is opened according to the tilting angle, and a pilot pressure corresponding to the opening is generated. The pilot shuttle valve 24 is a high pressure selection valve that selects one of the high pressures from the downstream pressures of the pair of pressure reducing valves 23U and 23D.

  The symbol U in FIG. 2 indicates the pilot pressure generated during operation in the direction in which the boom cylinder 3 is extended (extension direction, boom raising direction), and the symbol D is the direction in which the boom cylinder 3 is reduced (contraction direction, boom lowering direction). It shows the pilot pressure that occurs during operation. Symbol C is a pilot pressure that does not depend on the operation direction, that is, a pilot pressure that is generated when some operation input is made. These pilot pressures U, D, and C are transmitted to a cylinder drive closing circuit 10, a pressure increasing circuit 10A, a pressure accumulating circuit 30A, a regeneration circuit 30B, and a recirculation amount control circuit 30C, which will be described below. Is used for the control of the present invention as a pilot pressure at the same symbol.

[2-2. Cylinder drive closed circuit 10]
The cylinder drive closed circuit 10 is a closed circuit related to the driving of the boom cylinder 3. The cylinder drive closed circuit 10 is provided with a hydraulic pump 2 and a charge pump 6 driven by the engine 1, and a boom cylinder 3 driven by hydraulic oil discharged from these hydraulic pumps 2 and 6. Yes.

  The hydraulic pump 2 has a tilting swash plate mechanism having a pair of input / output ports. The hydraulic pump 2 discharges hydraulic oil from one of the two ports and sucks hydraulic oil from the other port. Is configured to do. Hereinafter, the two ports of the hydraulic pump 2 are referred to as an ascending port 2U and a descending port 2D, respectively. The port formed in the rod chamber 3a (second hydraulic oil chamber) of the boom cylinder 3 is referred to as a descending port 3D, and the port formed in the head chamber 3b (first hydraulic oil chamber) is referred to as an ascending port 3U. Call.

The ascending port 2U of the hydraulic pump 2 is connected to the ascending port 3U of the boom cylinder 3 via lines U1 and U2 (first driving lines) as drive lines. Similarly, the lowering port 2D of the hydraulic pump 2 is connected to the lowering port 3D of the boom cylinder 3 via pipes D1 and D2 (second driving pipes).
The boom cylinder 3 expands by pushing up the piston when hydraulic oil flows into the ascending port 3U, and discharges hydraulic oil from the descending port 3D. Further, when the hydraulic oil flows into the descending port 3D, the piston is pushed down to perform a reduction operation, and the hydraulic oil is discharged from the ascending port 3U.

  The hydraulic pump 2 is provided with a swash plate control mechanism 2a (regulator) that controls the discharge flow rate, the discharge pressure, and the discharge direction by adjusting the inclination angle of both tilting swash plates. A shuttle valve 16 is provided for selecting one of the hydraulic pressures of the pipelines U1 and D1 (that is, the discharge pressure of the hydraulic pump 2). The pilot pressures U and D generated by the pilot pressure generation circuit 20 and the discharge pressure of the hydraulic pump 2 are input to the swash plate control mechanism 2a.

A switching valve 17 is interposed on the pipe lines U1 and U2. The hydraulic oil flow path closer to the hydraulic pump 2 than the switching valve 17 is the pipe line U1, and the hydraulic oil flow path closer to the boom cylinder 3 than the switching valve 17 is the pipe line U2.
The switching valve 17 is a two-position switching valve, and a pilot circuit for introducing a pilot pressure D is connected to one end of the spool. The switching valve 17 holds the spool in the D position when the pilot pressure D is introduced, and directly communicates the pipeline U1 side and the pipeline U2 side. On the other hand, when the pilot pressure D is not introduced, the spool is held at the X position, and functions as a check valve that allows only hydraulic oil to flow from the pipe line U1 side to the pipe line U2 side. That is, the hydraulic oil flows from the pipe line U2 side to the pipe line U1 side only when the boom operation lever 21 is operated in the contracting direction.

When the boom operation lever 21 is operated in the extending direction, the spool of the switching valve 17 is set to the X position, but the flow of hydraulic oil from the pipe line U1 side to the pipe line U2 side is allowed. Hydraulic oil is supplied from the hydraulic pump 2 to the boom cylinder 3.
A bypass switching valve 18 is interposed on the pipelines D1 and D2, and the pipeline D1 and the pipeline D2 are divided by the bypass switching valve 18 as a boundary. The bypass switching valve 18 is a three-position switching valve that drives the spool by introducing two types of pilot pressures U and D to both ends of the spool. In addition to the pipe lines D1 and D2, a bypass pipe line D6 connected to the hydraulic oil tank 9 is connected to this valve.

  When neither of the two types of pilot pressures U and D is introduced, the spool of the bypass switching valve 18 is set to the X position, blocks the bypass pipeline D6, and from the pipeline D2 side to the pipeline D1 side. It functions as a check valve that blocks the flow of hydraulic oil. Further, when the pilot pressure D is introduced, the spool is set at the D position, and the pipeline D1 and the bypass pipeline D6 are communicated with each other, and the hydraulic oil flow from the pipeline D2 side to the pipeline D1 side is blocked. . On the other hand, when the pilot pressure U is introduced, the spool is set at the U position, and the bypass line D6 and the line D2 are communicated.

  As described above, the bypass switching valve 18 has a function of switching the connection between the pipelines D1 and D2 and the bypass pipeline D6. That is, a function of introducing hydraulic oil (return oil) to be returned to the hydraulic pump 2 when the boom cylinder 3 is extended to the bypass pipeline D6 side, and a pipeline from the pipeline D2 side when the boom cylinder 3 is contracted and stopped. And a function of preventing backflow of hydraulic oil to the D1 side.

  Between the pipe lines U2 and D2, three passages A1, A2 and A3 connected in parallel to the boom cylinder 3 are formed. An overload relief valve 11a for setting an upper limit value of the hydraulic pressure on the pipe line U2 is interposed on the first path A1, and an upper limit of the hydraulic pressure on the pipe line D2 side is set on the second path A2. An overload relief valve 11b for setting a value is interposed. These overload relief valves 11a and 11b function to release the hydraulic fluid to the other pipeline when the hydraulic fluid in one pipeline becomes excessively high due to the load acting on the boom cylinder 3. .

A regenerative valve 13 is interposed on the third passage A3 (regenerative pipeline). The regenerative valve 13 is a two-position switching valve, and a pilot circuit for introducing a pilot pressure D is connected to one end of the spool. When the pilot pressure D is not introduced, the regenerative valve 13 holds the spool at the X position and blocks the third passage A3.
On the other hand, when the pilot pressure D is introduced, the spool is held at the D position, and functions as a check valve that allows hydraulic oil to flow from the pipe line U2 side to the pipe line D2 side. As a result, when the boom cylinder 3 operates in the contracting direction, the hydraulic oil discharged from the ascending port 3U of the head chamber 3b passes through the third passage A3 and is introduced into the pipeline D2 via the regenerative valve 13, and the descending port It is supplied from 3D to the rod chamber 3a for regenerative use.

As described above, the third passage A3 and the regenerative valve 13 are configured so that the hydraulic oil discharged from the head chamber 3b flows into the rod chamber 3a side when the boom cylinder 3 is operated in the contracting direction. , And functions as a pressure-increasing circuit (pressure-increasing means) that increases the operating oil pressure in the pipe line U2.
A fourth passage A4 is connected between the pipeline U1 and the bypass pipeline D6, and a charge valve 12 is interposed on the passage A4. The charge valve 12 is a pilot control valve for connecting the flow path connected to the variable capacity type charge pump 6 to the pipe lines U1 and D1, and switching the spool position to the three positions to change the flow rate and flow direction of the hydraulic oil. Is variably controlled.

The pilot pressure U described above is introduced into one end of the spool of the charge valve 12, and the hydraulic pressure of the pipeline D <b> 1 is introduced as the pilot pressure Z into the other end. A pilot circuit for introducing the pilot pressure Z is connected between the bypass switching valve 18 and the pilot check valve 37 on the pipe line D1.
When neither of the two types of pilot pressures U and Z is introduced, the spool of the charge valve 12 is held at the X position, and the passage A4 is closed inside the spool of the charge valve 12. That is, the hydraulic oil discharged from the charge pump 6 is discharged as it is to the hydraulic oil tank 9 and is not supplied to the cylinder drive closed circuit 10 side.

When the pilot pressure U is introduced, the spool of the charge valve 12 is moved and set to the U position, and the charge pump 6 is connected to the bypass line D6 side. On the other hand, when the pilot pressure Z is introduced, the spool of the charge valve 12 moves and is set to the Z position, and the charge pump 6 is connected to the pipe line U1 side.
The pilot pressure Z is a high pressure when the boom cylinder 3 is not compressed when the boom cylinder 3 is contracted, and drives the spool of the charge valve 12 to the Z position. For example, when the boom cylinder 3 is extended, the bypass switching valve 18 introduces hydraulic oil in the pipe D2 to the bypass pipe D6, so that the pilot pressure Z is not so large as to drive the spool of the charge valve 12. Further, even when the boom cylinder 3 is contracted, in the state where the accumulator 7 is accumulating, the pilot check valve 37 closes the pipe line D1, so that no pilot pressure Z is generated. The pilot check valve 37 will be described later as a configuration of the pressure accumulating circuit 30A.

  A check valve 15 is interposed between the charge valve 12 and the charge pump 6. The charge pump 6 and the charge valve 12 function to replenish hydraulic oil in the cylinder drive closing circuit 10 that is reduced by relief from a recirculation amount control circuit 30C described later. The charge pump 6 is provided with a swash plate control mechanism 6 a (regulator) similar to the hydraulic pump 2. The swash plate control mechanism 6 a changes the swash plate inclination angle of the charge pump 6 according to the pilot pressure C generated by the pilot pressure generation circuit 20 and controls the amount of hydraulic oil discharged from the charge pump 6.

[2-3. Accumulation circuit 30A, regeneration circuit 30B]
The pressure accumulating circuit 30A and the regeneration circuit 30B are circuits for accumulating high-pressure hydraulic oil generated when the boom cylinder 3 is operated in the contracting direction in the accumulator 7 and regenerating it when the boom cylinder 3 is operated in the extending direction. .
As shown in FIG. 2, an accumulator 7 is connected to the tip of a pressure accumulation regeneration pipeline D3 that is branched from the pipeline D1. Further, the accumulator regeneration pipe D3 is branched into the accumulator duct D4 and the regeneration duct D5 in the middle of the accumulator 7, and further merges in the vicinity of the accumulator 7. The accumulator line D4 is a flow path when the hydraulic oil flows into the accumulator 7 side, and the regeneration pipe D5 is a flow path when the hydraulic oil flows out from the accumulator 7.

A pressure accumulation switching valve 31 is interposed on the pressure accumulation line D4. The pressure accumulation switching valve 31 is a two-position switching valve that switches the spool position in accordance with the pilot pressure P introduced from the pressure accumulation regeneration pilot line B3. When the pilot pressure P is less than a predetermined first pilot pressure P ₁ (first predetermined pressure), the pressure accumulation switching valve 31 holds the spool at the X position and shuts off the pressure accumulation line D4. On the other hand, when the pilot pressure P is equal to or higher than the first pilot pressure P ₁ , the spool is held at the Y position, and functions as a check valve that allows hydraulic oil to flow in the direction of inflow into the accumulator 7. The accumulator regeneration pilot line B3 will be described later.

  In addition, a pilot check valve 37 is interposed on the bypass switching valve 18 side from the branch point with the pressure accumulation regeneration pipeline D3 on the pipeline D1. The pilot check valve 37 is a check valve having a function of fixing the poppet by pilot control and blocking the working oil flow. The pilot check valve 37 is introduced with a pilot pressure P introduced from a pressure accumulation regeneration pilot line B3.

When the pilot pressure P is less than a predetermined second pilot pressure P ₂ (second predetermined pressure), the pilot pressure P functions as a general one-way valve that allows hydraulic fluid to flow from the hydraulic pump 2 side to the bypass switching valve 18 side. . On the other hand, to block the conduit D1 to fix the poppet in the closed state of the pipe line D1 when the pilot pressure P is the second pilot pressure P ₂ or more. Note that the second pilot pressure P ₂ in this embodiment is set to a magnitude equal to or higher than the first pilot pressure P ₁ , and at least when the pilot check valve 37 closes the pipe D 1, the pressure accumulation pipe D 4 It is considered as a characteristic that is not closed.

  A regeneration valve 32 and a regeneration check valve 33 are interposed in series on the regeneration conduit D5. The regeneration valve 32 is a two-position switching valve that switches the spool position by pilot control, and a pilot circuit that introduces a pilot pressure U is connected to one end of the spool. The regeneration valve 32 holds the spool in the U position when the pilot pressure U is introduced, and opens the regeneration conduit D5. On the other hand, when the pilot pressure U is not introduced (that is, when nothing is operated, or when the boom operation lever 21 is operated in the contracting direction), the spool is held at the X position, and the regeneration pipe line Block D5.

The regeneration check valve 33 is a one-way valve interposed on the regeneration pipeline D5 on the branching point side with respect to the pressure accumulation regeneration pipeline D3 rather than the regeneration valve 32, and operates from the pipeline D1 side to the regeneration valve 32 side. It prevents oil backflow.
The cylinder drive closed circuit 10 is provided with a pressure accumulation pilot line B1 branched from the line U1. The pressure accumulation pilot line B1 is a line for transmitting the hydraulic pressure during pressure accumulation as the pilot pressure of each control valve.

  In addition, a regeneration pilot line B2 is branched from the pressure accumulation regeneration line D3 side (downstream side when hydraulic oil flows out of the accumulator 7) from the regeneration check valve 33 in the regeneration line D5. The regeneration pilot line B2 is a line that transmits the hydraulic pressure when the pressure oil is supplied from the accumulator 7, that is, the hydraulic pressure to be regenerated, as the pilot pressure of each control valve.

  Either one of the hydraulic pressures of the pressure accumulation pilot line B1 and the regeneration pilot line B2 is selected by the pilot switching valve 34 and introduced into the pressure accumulation regeneration pilot line B3. The pilot switching valve 34 is a pilot control valve that variably controls the flow direction of hydraulic oil by switching the spool position to three positions. The pilot pressures U and D described above are introduced at both ends of the spool of the pilot switching valve 34.

  When neither of the two types of pilot pressures U and D is introduced, the pilot switching valve 34 holds the spool in the X position, and the pressure accumulation pilot line B1, the regeneration pilot line B2, and the pressure accumulation regeneration pilot line B3 Block everything. On the other hand, when the pilot pressure U is introduced, the spool is moved to the U position, and the regeneration pilot line B2 and the pressure accumulation regeneration pilot line B3 are connected. When the pilot pressure D is introduced, the spool is moved to the D position, and the pressure accumulation pilot line B1 and the pressure accumulation regeneration pilot line B3 are connected.

Therefore, the magnitude of the pilot pressure P in the accumulated pressure regeneration pilot line B3 is the hydraulic pressure that is accumulated when accumulating, and the outlet pressure of the accumulator 7 during regeneration.
As described above, in the present embodiment, high-pressure hydraulic oil generated when the boom cylinder 3 is operated in the contracting direction is hydraulically supplied from the pipe line U2 and the pipe line U1 by the functions of the boom operation lever 21, the switching valve 17, and the bypass switching valve 18. It is introduced into the pipe line D1 through the pump 2. Further, the high pressure hydraulic oil is guided to the accumulator 7 and accumulated by the action of the pressure accumulation regeneration line D3, the pressure accumulation line D4, the pressure accumulation pilot line B1, the pilot switching valve 34, and the pressure accumulation switching valve 31. Further, due to the action of the regeneration pipe D5, the regeneration valve 32 and the regeneration check valve 33, the hydraulic oil is regenerated when the boom cylinder 3 is operated in the extending direction.

[2-4. Reflux amount control circuit 30C]
The recirculation amount control circuit 30C balances the flow rate of the pressure oil regenerated and supplied from the accumulator 7 into the cylinder drive closing circuit 10 and the flow rate of the hydraulic oil to be recirculated from the boom cylinder 3 side to the hydraulic pump 2 side. It is a circuit which performs control for stabilizing the total flow rate of hydraulic oil in the circuit.

  The bypass line D6 is a reflux discharge line that connects between the bypass switching valve 18 and the hydraulic oil tank 9. A bypass valve 35 is interposed on the bypass line D6. The bypass valve 35 is a two-position switching valve that switches the spool position by pilot control, and a pilot circuit that introduces a pilot pressure C is connected to one end of the spool. The other end of the spool is connected to a pressure accumulation regeneration pilot line B3 for introducing the pilot pressure P.

When the pilot pressure C is introduced and the pilot pressure P is less than the predetermined third pilot pressure P ₃ (third predetermined pressure), the bypass valve 35 moves the spool to the C position to bypass the bypass line D6. Configured to close. On the other hand, when the pilot pressure C is not introduced (that is, when the boom operation lever 21 is not operated) or when the pilot pressure P is equal to or higher than the third pilot pressure P ₃ , the spool is moved to the Y position. Then, the bypass line D6 is opened to the hydraulic oil tank 9.

Note that the third pilot pressure P ₃ in this embodiment is smaller than the first pilot pressure P ₁ and the second pilot pressure P ₂ . Therefore, when the hydraulic oil starts to be introduced into the pipe line D1 through the regeneration pipe D5, the spool position of the bypass valve 35 is the Y position. After that, when the hydraulic oil is regenerated and supplied to a certain extent and the hydraulic pressure regenerated and supplied from the accumulator 7 decreases, the spool position of the bypass valve 35 becomes the C position, and the discharge of the reflux to the hydraulic oil tank 9 is stopped.

Further, when the hydraulic oil is accumulated in the accumulator 7 via the pressure accumulation line D4, the spool position of the bypass valve 35 becomes the Y position. On the other hand, for example, when the hydraulic pressure introduced into the accumulator 7 during pressure accumulation decreases due to the grounding of the bucket 5A or the like, the spool position of the bypass valve 35 becomes the C position.
The bypass conduit D6 is provided with a bypass reflux conduit D7 that connects the conduit D1. The end of the bypass reflux line D7 on the bypass line D6 side is connected between the bypass switching valve 18 and the bypass valve 35. Further, the end of the bypass reflux pipe D7 on the pipe D1 side is connected to the hydraulic pump 2 side with respect to the pilot check valve 37 on the pipe D1.

  A bypass check valve 36 is interposed on the bypass recirculation pipe D7, and only the flow of hydraulic oil from the bypass pipe D6 side to the pipe D1 side is allowed. Thus, for example, in a state where the spool of the bypass switching valve 18 is set to the U position and the spool of the bypass valve 35 is set to the C position, the reflux from the boom cylinder 3 introduced into the bypass pipe D6 is prevented. As it is, it is supplied to the pipe D1 side and sucked into the descending port 2D of the hydraulic pump 2.

As described above, in the present embodiment, the operation in the closed circuit at the time of regeneration of the hydraulic oil in the accumulator 7 is performed by the bypass switching valve 18, the bypass conduit D 6, the bypass reflux conduit D 7, the bypass valve 35 and the bypass check valve 36. The total amount of oil is controlled.
The operating state of the boom operation lever 21 and the pilot pressure P of the pressure accumulation regeneration pilot line B3 in this embodiment, the regenerative valve 13, the switching valve 17, the bypass switching valve 18, the pressure accumulation switching valve 31, the regeneration valve 32, and the bypass valve 35 The relationship with the control state is shown below.

[3. Action]
The flow state of the hydraulic oil in the hydraulic circuit will be described with reference to FIGS. In FIG. 3 to FIG. 6, some symbols, symbols, components, and the like are omitted for convenience. Moreover, the direction shown by the arrow in FIGS. 3-6 means the distribution direction of hydraulic fluid. In addition, the arrow displayed with a broken line is a low pressure hydraulic fluid rather than the arrow displayed with the continuous line.

[3-1. During boom raising operation and pressure oil supply]
When the boom operating lever 21 is operated in the extending direction (boom raising direction), the pilot pressure U is generated downstream of the pressure reducing valve 23U in the pilot pressure generating circuit 20, and the cylinder drive closed circuit 10, the pressure accumulating circuit 30A, and the regeneration circuit 30B. To each circuit. The pilot shuttle valve 24 transmits a pilot pressure C equal to the pilot pressure U to the cylinder drive closing circuit 10 and the recirculation amount control circuit 30C.

In response to these pilot pressures U and C, in the cylinder drive closed circuit 10, the swash plate control mechanisms 2 a and 6 a control the swash plates of the hydraulic pump 2 and the charge pump 6. The charge pump 6 discharges hydraulic oil at a flow rate corresponding to the pilot pressure C.
As shown in FIG. 3, the spool position of the charge valve 12 is set to the U position, and the hydraulic oil discharged from the charge pump 6 is supplied to the bypass line D6 side. The hydraulic pump 2 discharges hydraulic oil from the ascending port 2U to the pipe line U1 and sucks the hydraulic oil from the descending port 2D on the pipe line D1 side.

At this time, the spool of the switching valve 17 is held in the X position, and the spool of the bypass switching valve 18 is set in the U position. In addition, the spool of the regenerative valve 13 is in the X position, and the regenerative pipe A3 is closed. Therefore, the hydraulic oil flowing through the pipe line U1 is supplied to the head chamber 3b of the boom cylinder 3 through the pipe line U2.
On the other hand, the spool of the regeneration valve 32 is set to the U position, and the regeneration conduit D5 is opened. As a result, the high-pressure hydraulic oil accumulated in the accumulator 7 is introduced into the hydraulic pump 2 through the pipeline D1 via the regeneration pipeline D5 and the pressure accumulation regeneration pipeline D3. That is, the hydraulic oil stored in the accumulator 7 is recycled by the hydraulic pump 2. This hydraulic oil is further supplied to the head chamber 3b of the boom cylinder 3 through the pipe line U1 and the pipe line U2.

The high-pressure hydraulic oil supplied from the accumulator 7 is also introduced into the regeneration pilot line B2 branched from the regeneration line D5. Since the spool of the pilot switching valve 34 is set at the U position, the regeneration pressure (that is, the outlet pressure of the accumulator 7) is introduced into the pressure accumulation regeneration pilot line B3.
The hydraulic oil in the rod chamber 3a of the boom cylinder 3 is introduced from the pipeline D2 to the bypass pipeline D6 via the bypass switching valve 18. The bypass valve 35 interposed on the bypass line D6 receives the pilot pressure P (the outlet pressure of the accumulator 7) of the pressure accumulation regeneration pilot line B3, and the spool position is controlled to the Y position. Therefore, when the pilot pressure P is equal to or higher than the third pilot pressure P ₃ , the hydraulic oil in the bypass pipe D6 is discharged to the hydraulic oil tank 9. That is, when the cylinder drive closed circuit 10 receives the regeneration supply of the hydraulic oil from the accumulator 7 side, the return oil from the boom cylinder 3 to the hydraulic pump 2 is discharged to the hydraulic oil tank 9. At this time, the hydraulic oil supplied from the charge pump 6 is also discharged to the hydraulic oil tank 9 together.

[3-2. When boom is raised and pressure oil is not supplied]
Further, FIG. 4 shows a state of the hydraulic circuit when the boom raising operation is continued and the pressure oil is supplied to some extent. When the hydraulic oil supplied from the accumulator 7 to the hydraulic pump 2 decreases, the pilot pressure P in the pressure accumulation regeneration pilot pipeline B3 decreases. Thereafter, when the pilot pressure P becomes less than the third pilot pressure P ₃ , the spool of the bypass valve 35 is set to the C position, and the bypass line D6 is closed. The hydraulic oil in the bypass pipe D6 is supplied to the pipe D1 side through the bypass reflux pipe D7 and the bypass check valve 36, and is sucked into the descending port 2D of the hydraulic pump 2. That is, when the regeneration is completed, the return oil from the boom cylinder 3 to the hydraulic pump 2 is again introduced into the cylinder drive closed circuit 10. The hydraulic oil supplied from the charge pump 6 to the bypass line D6 also flows from the bypass recirculation line D7 to the line D1 and is sucked into the hydraulic pump 2.

  By these actions, the hydraulic fluid flow sucked from the pipe D1 to the lowering port 2D of the hydraulic pump 2 does not become excessive or insufficient, and fluctuations in the hydraulic fluid flow in the cylinder drive closed circuit 10 are prevented. Note that the actual discharge flow rate and discharge pressure (output horsepower) from the hydraulic pump 2 are appropriately adjusted according to the pilot pressures D and U and the hydraulic pressures of the pipelines D1 and U1 by the swash plate control mechanism 2a. Assuming that the discharge flow rate from the hydraulic pump 2 is constant, in this cylinder drive closed circuit 10, the return from the boom cylinder 3 is returned to the hydraulic pump 2 side by the amount that the regeneration amount from the regeneration pipeline D5 side is reduced. The hydraulic oil from the charge pump 6 is replenished so as to make up for the shortage.

[3-3. During boom lowering operation and pressure accumulation]
When the boom control lever 21 is operated in the contracting direction (boom lowering direction), a pilot pressure D is generated downstream of the pressure reducing valve 23D in the pilot pressure generating circuit 20, and is transmitted to the cylinder drive closed circuit 10 and the pressure accumulating circuit 30A. The A pilot pressure C, which is the same as the pilot pressure D, is transmitted from the pilot shuttle valve 24 to the cylinder drive closing circuit 10 and the recirculation amount control circuit 30C.

In response to these pilot pressures D and C, in the cylinder drive closed circuit 10, the swash plate control mechanisms 2 a and 6 a control the swash plates of the hydraulic pump 2 and the charge pump 6. The hydraulic pump 2 discharges hydraulic oil from the descending port 2D to the pipe line D1, and sucks the hydraulic oil from the ascending port 2U on the pipe line U1 side.
Here, when the bucket 5 </ b> A of the excavator 50 is not in contact with the ground, a load due to the weight of the front work device 55 acts on the head chamber 3 b of the boom cylinder 3. Thereby, the hydraulic pressure discharged from the head chamber 3b is higher than the hydraulic pressure on the rod chamber 3a side.

  Each spool of the regenerative valve 13, the switching valve 17, the bypass switching valve 18 and the pilot switching valve 34 receives the pilot pressure D and is set to the D position as shown in FIG. Therefore, the hydraulic oil discharged from the head chamber 3b of the boom cylinder 3 is split into two at the branch point between the pipe line U2 and the third passage A3. One of the divided flow flows through the regenerative valve 13 on the regenerative pipe A3 to the pipe D2 side and is regenerated in the rod chamber 3a of the boom cylinder 3. The hydraulic pressure in the head chamber 3b is increased by such regenerative use of the hydraulic oil, and the hydraulic pressure discharged from the head chamber 3b is further increased.

Further, the other of the divided flows flows through the switching valve 17 to the pipe line U1 and is sucked into the rising port 2U of the hydraulic pump 2. The hydraulic pressure of the pipe line U1 is increased by the regenerative action described above. The high-pressure hydraulic oil is introduced into the pressure accumulation pilot line B1, and is introduced into the pressure accumulation regeneration pilot line B3 via the pilot switching valve 34.
The pilot pressure P in the pressure accumulation regeneration pilot line B3 acts on each of the pressure accumulation switching valve 31, the bypass valve 35, and the pilot check valve 37. The spool position of the pressure accumulation switching valve 31 is set to the Y position when the pilot pressure P is equal to or higher than the first pilot pressure P ₁ . Further, the pilot check valve 37, conduit D1 is closed when the pilot pressure P is the second pilot pressure P ₂ or more.

Therefore, the return oil from the boom cylinder 3 flows through the pipeline D 1, the pressure accumulation regeneration pipeline D 3 and the pressure accumulation pipeline D 4 via the hydraulic pump 2, and is accumulated in the accumulator 7 through the pressure accumulation switching valve 31. At this time, the accumulator 7 stores hydraulic oil having a pressure equal to or higher than the first pilot pressure P ₁ . The stored hydraulic oil is reused when the boom cylinder 3 operates in the extending direction.

  Further, since the pilot check valve 37 closes the pipe line D1, the spool of the charge valve 12 is held in the X position, and the hydraulic oil discharged from the charge pump 6 is discharged to the hydraulic oil tank 9 as it is. .

[3-4. During boom lowering operation and non-accumulated pressure]
On the other hand, when the bucket 5A of the excavator 50 is grounded during the boom lowering operation, the load due to the weight of the front work device 55 is distributed to the grounded portion, so that the hydraulic pressure discharged from the head chamber 3b of the boom cylinder 3 is reduced. descend. As a result, the hydraulic pressure in the pipes U2 and U1 decreases, and the pilot pressure P in the pressure accumulation pilot line B1 and the pressure accumulation regeneration pilot line B3 also decreases.

In pilot check valve 37, the pilot pressure P drops to below the second pilot pressure P ₂ is fixed release poppet, hydraulic oil flows from the hydraulic pump 2 side to the bypass switching valve 18 side is permitted. Further, in the pressure accumulation switching valve 31, as shown in FIG. 6, when the pilot pressure P drops to a less than a pilot pressure P ₁ spool is moved to the X position, the accumulator line D4 is blocked. At this time, the pressure accumulation in the accumulator 7 is completed, and the hydraulic oil in the pipe D1 flows to the bypass switching valve 18 side.

  As a result, a pilot pressure Z that drives the spool of the charge valve 12 to the Z position is generated, and both the hydraulic oil passage on the charge pump 6 side and the pipe line U1 are communicated with the hydraulic oil tank 9. Accordingly, the hydraulic oil of the charge pump 6 is appropriately supplemented into the cylinder drive closed circuit 10 according to the hydraulic pressure on the pipe line U1 side, and is discharged to the hydraulic oil tank 9 when the hydraulic oil flow rate is excessive.

Also, the bypass valve 35, the pilot pressure P drops to less than a third pilot pressure P ₃ spool is moved to position C, the bypass conduit D6 is closed. Accordingly, the hydraulic oil in the pipe D1 flows through the pipe D2 via the bypass switching valve 18, is supplied to the rod chamber 3a of the boom cylinder 3, and is used for pressurization on the rod chamber 3a side.

[4. effect]
Thus, according to the present regeneration control device, the hydraulic oil discharged from the head chamber 3b during the reduction operation of the boom cylinder 3 can be regenerated and increased in pressure only by the hydraulic circuit. In addition, by controlling the pilot check valve 37 and the pressure accumulation switching valve 31 according to the pressure of the accumulated hydraulic oil, the increased hydraulic oil energy can be stored in the accumulator 7, and the utilization efficiency of the hydraulic oil energy Can be increased.

Further, since the pressurized hydraulic fluid is stored, the capacity of the accumulator 7 can be reduced. Further, by controlling the regeneration valve 32 on the regeneration line D5 formed in parallel with the pressure accumulation line D4, the stored energy can be reused when the boom cylinder 3 is extended.
That is, the configuration is simple as compared with the conventional technology using electric devices such as an electric motor and a capacitor, and the cost of the entire system can be greatly reduced. In addition, since there is no need for precision electronic devices such as sensors and controllers, there are advantages of high reliability and easy maintenance and inspection. Further, by using a conventional hydraulic device, it can be applied to a large machine relatively easily.

  In the present embodiment, the recirculation amount control circuit 30C that controls the recirculation amount from the boom cylinder 3 to the hydraulic pump 2 at the time of regeneration of the hydraulic oil is formed. Therefore, the cylinder before and after the regeneration of the hydraulic fluid by the accumulator 7 is formed. Variations in the hydraulic fluid flow rate of the entire drive closed circuit 10 can be suppressed. For example, even when the regeneration is started immediately after the boom cylinder 3 starts to operate in the contracting direction, or even when the operation hydraulic pressure in the regeneration conduit D5 is lowered, the amount of hydraulic oil flowing into the hydraulic pump 2 is exceeded. There is no shortage. Therefore, the operations of the hydraulic pump 2 and the boom cylinder 3 can be stabilized.

In particular, the bypass valve 35 in the recirculation amount control circuit 30C has a structure in which the outlet pressure of the accumulator 7 is introduced to the spool as the control pilot pressure P, and the recirculation amount can be reduced reliably and easily with a simple configuration. Can be made.
In the cylinder drive closed circuit 10, the hydraulic oil discharged from the charge pump 6 through the charge valve 12 is supplied to either the pipe line D1 or U1, and is thus discharged from the bypass pipe line D6. The hydraulic oil can be appropriately supplemented, and the total amount of hydraulic oil in the closed circuit can be made substantially constant. Thereby, the circuit operation can be further stabilized.

  Further, since the regeneration pilot line B2 is formed by branching from the downstream side of the regeneration check valve 33 in the regeneration line D5, the influence of the pressure (residual pressure) remaining in the accumulator 7 after regeneration is eliminated. The pilot pressure P at the time of regeneration can be generated accurately. That is, it is possible to reliably detect that the pressure oil in the accumulator 7 has disappeared, and to improve the control accuracy of the bypass valve 35 and the pilot check valve 37 when pressure oil is supplied.

[5. Others]
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above-described embodiment, the bypass valve 35 controls the connection of the bypass line D6 according to the pilot pressure P of the pressure accumulation regeneration pilot line B3. It is also conceivable that the opening degree of the bypass line D6 is controlled accordingly.

For example, the discharge amount to the hydraulic oil tank 9 is increased as the pilot pressure P of the pressure accumulation regeneration pilot line B3 is higher, and the discharge amount is decreased as the pressure is reduced. In this case, the amount of hydraulic oil sucked into the hydraulic pump 2 can be controlled more accurately.
In the above-described embodiment, the threshold values of the pilot pressure P related to the control of the spool positions of the pressure accumulation switching valve 31, the pilot check valve 37, and the bypass valve 35 are the first pilot pressure P ₁ and the second pilot pressure, respectively. Although the pressure P ₂ and the third pilot pressure P ₃ are set, the magnitude relationship between these threshold values can be set as appropriate, and may be the same value, for example.

  Further, in the above-described embodiment, the example in which the present invention is applied to the drive circuit of the boom cylinder 3 related to the turning operation of the hydraulic excavator 50 is illustrated, but the application target of the present invention is not limited to this, and other hydraulic cylinders The present invention can also be applied to the driving circuit. In the present invention, since the pressure is accumulated by using the load due to the weight of the front working device 55 acting on the head chamber 3b side of the boom cylinder 3, the hydraulic circuit is configured in consideration of the acting direction of such a load. It is preferable.

  The present invention can be applied to all working machines such as a hydraulic excavator and a hydraulic crane having a closed circuit-like hydraulic circuit between a hydraulic pump and a hydraulic cylinder.

1 Engine 2 Hydraulic pump 2U Ascending port 2D Lowering port 2a Swash plate control mechanism (regulator)
3 Boom cylinder (hydraulic cylinder)
3U ascending port 3D descending port 3a Rod chamber (second hydraulic oil chamber)
3b Head chamber (first hydraulic oil chamber)
3A Boom 4 Stick cylinder 4A Stick 5 Bucket cylinder 5A Bucket 6 Charge pump 6a Swash plate control mechanism (regulator)
7 Accumulator 9 Hydraulic oil tank 10 Cylinder drive closed circuit (hydraulic circuit)
10A pressure booster (pressure booster)
11a, 11b Overload relief valve 12 Charge valve 13 Regenerative valve 15 Check valve 16 Shuttle valve 17 Switching valve 18 Bypass switching valve 20 Pilot pressure generation circuit 21 Boom operation lever (operation lever)
22 Remote control valve 23U, 23D Pressure reducing valve 24 Pilot shuttle valve 25 Pilot pump 30A Pressure accumulation circuit (pressure accumulation means)
30B Reproduction circuit (reproduction means)
30C Reflux control circuit (Reflux control means)
31 Accumulation Switching Valve 32 Regeneration Valve 33 Regeneration Check Valve 34 Pilot Switching Valve 35 Bypass Valve 36 Bypass Check Valve 37 Pilot Check Valve 50 Hydraulic Excavator 51 Lower Traveling Body 52 Upper Revolving Body 54 Cab 55 Front Working Device 56 Counter Weight U1, U2 Pipe Road (first drive line)
D1, D2 pipeline (second drive pipeline)
D3 pressure accumulation regeneration line D4 pressure accumulation line D5 regeneration line D6 bypass line D7 bypass return line A1 first path A2 second path A3 third path (regeneration line)
A4 Fourth passage B1 Accumulated pilot line B2 Regenerative pilot line B3 Accumulated regenerative pilot line

Claims (8)

A hydraulic oil regenerative control device in a hydraulic circuit formed by connecting a pair of drive pipes in a closed circuit between a hydraulic pump and a hydraulic cylinder of a work machine,
Pressure increasing means for increasing the pressure of the hydraulic oil discharged from the hydraulic cylinder when the hydraulic cylinder expands or contracts in the direction of the load applied to the hydraulic cylinder;
Pressure accumulating means for accumulating the hydraulic oil increased in pressure by the pressure increasing means;
Regenerating means for supplying hydraulic oil accumulated in the pressure accumulating means to the hydraulic pump for regeneration when the hydraulic cylinder expands or contracts in a direction opposite to the direction of the load acting on the hydraulic cylinder;
A recirculation amount control means for controlling the flow rate of the working oil that recirculates from the hydraulic cylinder to the hydraulic pump in accordance with the pressure of the hydraulic oil regenerated by the regenerating means;
A regenerative control device for a work machine, comprising: When the hydraulic oil regenerated by the regenerating means is equal to or higher than a predetermined pressure when the hydraulic cylinder is driven by the hydraulic pump, the recirculation amount control means recirculates the hydraulic oil from the hydraulic cylinder to the hydraulic pump. 2. The hydraulic fluid flow returning from the hydraulic cylinder to the hydraulic pump is increased when the hydraulic fluid regenerated by the regeneration means is less than the predetermined pressure. Regenerative control device for work equipment. The pressure increasing means is
A regenerative pipe connecting the pair of drive pipes;
A regenerative valve that is interposed on the regenerative pipe and regenerates hydraulic oil discharged from one hydraulic oil chamber located in the direction of action of the load in the hydraulic cylinder to the other hydraulic oil chamber. The regenerative control device for a work machine according to claim 1 or 2, characterized in that The pressure accumulating means is
An operation lever for setting a supply direction of the hydraulic oil from the hydraulic pump in response to an operation input;
The operating lever is operated in a direction to supply hydraulic oil to the other hydraulic oil chamber that is interposed on the first hydraulic oil line connected to the one hydraulic oil chamber of the pair of drive pipelines. The first drive pipe is opened when the operation lever is operated in a direction to supply the hydraulic oil to the one hydraulic oil chamber. A switching valve to be closed;
A bypass that is interposed on a second drive conduit connected to the other hydraulic fluid chamber of the pair of drive conduits and blocks the flow of hydraulic fluid from the hydraulic cylinder side to the hydraulic pump side A switching valve;
A pressure accumulating line formed by branching from the hydraulic pump side with respect to the bypass switching valve on the second driving line;
The regenerative control device for a working machine according to claim 3, further comprising an accumulator that is interposed on the pressure accumulation pipe and accumulates hydraulic oil discharged from the one hydraulic oil chamber. The pressure accumulating means is
A pressure accumulating pilot line formed by branching from the hydraulic pump side with respect to the switching valve on the first drive line;
The pressure accumulation pilot line is opened when the operation lever is operated in the direction of supplying hydraulic oil to the other hydraulic oil chamber, which is interposed on the pressure accumulation pilot line, and to the one hydraulic oil chamber. A pilot switching valve that closes the accumulator pilot line when the operating lever is operated in a direction to supply hydraulic oil;
When the operating oil pressure of the pressure accumulating pilot line is greater than or equal to a second predetermined pressure, the pressure accumulating line is opened and the operating oil pressure of the pressure accumulating pilot line is the second predetermined pressure. An accumulator switching valve that closes the accumulator line when less than
When it is interposed between the bypass switching valve and the branch point of the accumulator line on the second drive line, and the operating hydraulic pressure of the accumulator pilot line is equal to or higher than the second predetermined pressure, When the second drive pipe is closed and the hydraulic pressure of the pressure accumulating pilot pipe is less than the second predetermined pressure, the other hydraulic oil from the hydraulic pump side in the second drive pipe The regenerative control device for a working machine according to claim 4, further comprising a pilot check valve that allows the hydraulic oil to flow to the chamber side. The reproducing means is
A regeneration line connected in parallel to the pressure accumulation switching valve on the pressure accumulation line;
A regeneration valve that is interposed on the regeneration conduit and opens the regeneration conduit when the operation lever is operated in a direction to supply the hydraulic fluid to the one hydraulic fluid chamber;
A regeneration check valve interposed on the regeneration pipeline and allowing the flow of hydraulic oil from the accumulator side to the second drive pipeline side,
The reflux amount control means is
A bypass line having one end connected to the bypass switching valve and the other end connected to a hydraulic oil tank;
When the working oil pressure of the regeneration pipe is less than the predetermined pressure when the working oil pressure of the regeneration pipe is opened when the working oil pressure of the regeneration pipe is greater than or equal to the predetermined pressure. A bypass valve for closing the bypass line,
When the operation lever is operated in a direction in which the bypass switching valve supplies the hydraulic oil to the one hydraulic oil chamber, the hydraulic oil discharged from the other hydraulic oil chamber is transferred to the bypass pipeline. The regenerative control device for a working machine according to claim 5, wherein the regenerative control device is introduced. The reflux amount control means is
A bypass reflux line formed by branching from between the bypass switching valve and the bypass valve on the bypass line and connected to the second drive line;
The bypass check valve, which is interposed on the bypass recirculation pipe line and allows the flow of hydraulic oil from the bypass pipe side to the second drive pipe side, Regenerative control device for work equipment. 8. A charge pump for replenishing the hydraulic oil connected to the drive pipe on the side from which the hydraulic oil is discharged from the hydraulic cylinder of the pair of drive pipes is further provided. The regenerative control device for the working machine described.

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