JP2016183535A - Shovel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shovel capable of efficiently using regeneratable energy.SOLUTION: A shovel includes an undercarriage, a revolving super structure mounted on the undercarriage in a revolvable manner, a revolving hydraulic motor 21 for driving the revolving super structure in a revolvable manner, a regenerating hydraulic motor 14A for regenerating energy of working fluid flowing out of a hydraulic actuator such as the revolving hydraulic motor 21 and a boom cylinder 7 so as to assist an engine 11, and a first accumulator 85L disposed in the downstream side of the regenerating hydraulic motor 14A.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an excavator provided with a regenerative hydraulic motor.

  Supply hydraulic oil to prevent cavitation on the suction side of the regenerative hydraulic motor that rotates with hydraulic oil (return oil) that flows out from the discharge side of the hydraulic motor for turning during return and assists the engine. An excavator provided with an accumulator is known (see Patent Document 1).

  In this excavator, when the hydraulic oil pressure in the accumulator falls below the set value and the accumulator cannot release the hydraulic oil, the regenerative hydraulic motor functions as a hydraulic pump to supply the hydraulic oil from the hydraulic oil tank to the accumulator. accumulate. Alternatively, the hydraulic oil flowing out from the discharge side of the turning hydraulic motor via the relief valve is directly accumulated in the accumulator without going through the regeneration hydraulic motor.

JP 2011-220390 A

  However, when the pressure of the hydraulic oil in the accumulator falls below the set value, the above-described excavator causes the hydraulic oil for regeneration to function as a hydraulic pump and accumulates hydraulic oil from the hydraulic oil tank in the accumulator. Consume. And when the load of the shovel is high, if this engine output is consumed, the operation performance of the shovel is temporarily lowered. Alternatively, high-pressure return oil that flows out from the discharge side of the turning hydraulic motor via the relief valve is directly accumulated in the accumulator, so that the return oil is discharged from the accumulator to prevent cavitation during turning deceleration without being used for regeneration. Resulting in. Therefore, the energy which can be regenerated cannot be used effectively.

  Therefore, it is desired to provide an excavator that makes more effective use of regenerative energy.

  An excavator according to an embodiment of the present invention includes a regenerative hydraulic motor that regenerates energy of hydraulic oil flowing out from a hydraulic actuator to assist the engine, a first accumulator disposed downstream of the regenerative hydraulic motor, Is provided.

  By the above-described means, it is possible to provide an excavator that makes more effective use of energy that can be regenerated.

It is a side view of the shovel which concerns on the Example of this invention. It is the schematic which shows the structural example of the hydraulic circuit mounted in the shovel of FIG. It is a figure which shows the state of the hydraulic circuit of FIG. 2 at the time of turning acceleration. It is a figure which shows the state of the hydraulic circuit of FIG. 2 at the time of turning deceleration. It is the schematic which shows another structural example of the hydraulic circuit mounted in the shovel of FIG. It is a figure which shows the state of the hydraulic circuit of FIG. 5 at the time of boom lowering operation.

  FIG. 1 is a side view showing an excavator as a construction machine to which the present invention is applied. An upper swing body 3 is mounted on the lower traveling body 1 of the excavator via a swing mechanism 2. A boom 4 is attached to the upper swing body 3. An arm 5 is attached to the tip of the boom 4, and a bucket 6 is attached to the tip of the arm 5. The boom 4, the arm 5, and the bucket 6 as work elements constitute a drilling attachment that is an example of an attachment, and are hydraulically driven by the boom cylinder 7, the arm cylinder 8, and the bucket cylinder 9, respectively. The upper swing body 3 is provided with a cabin 10 and is mounted with a power source such as the engine 11 and a controller 30.

  The controller 30 is a control device as a main control unit that performs drive control of the shovel. In the present embodiment, the controller 30 is configured by an arithmetic processing unit including a CPU and an internal memory, and realizes various functions by causing the CPU to execute a drive control program stored in the internal memory.

  FIG. 2 is a schematic diagram illustrating a configuration example of a hydraulic circuit mounted on the shovel of FIG. In the present embodiment, the hydraulic circuit mainly includes a first pump 14L, a second pump 14R, a regeneration hydraulic motor 14A, a control valve 17, a first accumulator 85L, a second accumulator 85H, and a hydraulic actuator. The hydraulic actuator mainly includes a boom cylinder 7, an arm cylinder 8, a bucket cylinder 9, and a turning hydraulic motor 21. The hydraulic actuator may include a left-side traveling hydraulic motor (not shown) and a right-side traveling hydraulic motor (not shown).

  The boom cylinder 7 is a hydraulic cylinder that raises and lowers the boom 4. A regeneration valve 7 a is connected between the bottom side oil chamber and the rod side oil chamber, and a holding valve 7 b is installed on the bottom side oil chamber side. . The arm cylinder 8 is a hydraulic cylinder that opens and closes the arm 5. A regeneration valve 8a is connected between the bottom side oil chamber and the rod side oil chamber, and a holding valve 8b is installed on the rod side oil chamber side. Is done. The bucket cylinder 9 is a hydraulic cylinder that opens and closes the bucket 6, and a regeneration valve 9a is connected between the bottom side oil chamber and the rod side oil chamber. The regeneration valves 7a, 8a, and 9a are all installed outside the control valve 17, and are installed adjacent to the associated hydraulic cylinder, for example.

  The turning hydraulic motor 21 is a hydraulic motor for turning the upper turning body 3, and the ports 21L and 21R are connected to the hydraulic oil tank T through relief valves 22L and 22R, respectively, and the switching valve 22G through the shuttle valve 22S. And is connected to the hydraulic oil tank T via check valves 23L and 23R.

  The relief valve 22L opens when the pressure on the port 21L side reaches a predetermined relief pressure, and discharges the hydraulic oil on the port 21L side to the hydraulic oil tank T. The relief valve 22R opens when the pressure on the port 21R side reaches a predetermined relief pressure, and discharges the hydraulic oil on the port 21R side to the hydraulic oil tank T.

  The shuttle valve 22S supplies hydraulic oil having a higher pressure on the port 21L side and the port 21R side to the switching valve 22G.

  The switching valve 22G is a valve that operates in response to a command from the controller 30, and is a 2-port 2-position switchable switch between communication and blocking between the turning hydraulic motor 21 (shuttle valve 22S) and the second accumulator 85H. It is a solenoid valve. Specifically, the switching valve 22G communicates between the turning hydraulic motor 21 and the second accumulator 85H when in the first position, and blocks the communication when in the second position.

  The check valve 23L opens when the pressure on the port 21L side becomes lower than the pressure on the opposite side, and supplies hydraulic oil from the hydraulic oil tank T or the first accumulator 85L to the port 21L side. The check valve 23R opens when the pressure on the port 21R side becomes lower than the pressure on the opposite side, and supplies hydraulic oil to the port 21R side from the hydraulic oil tank T or the first accumulator 85L. In this manner, the check valves 23L and 23R constitute a supply mechanism that supplies hydraulic oil to the suction side port when the hydraulic hydraulic motor 21 is braked.

  The first pump 14L is a hydraulic pump that sucks and discharges hydraulic oil from the hydraulic oil tank T. In the present embodiment, the first pump 14L is a swash plate type variable displacement hydraulic pump. The first pump 14L is connected to a regulator (not shown). The regulator changes the swash plate tilt angle of the first pump 14L in accordance with a command from the controller 30, and controls the displacement volume (discharge amount per rotation) of the first pump 14L. The same applies to the second pump 14R.

  The regeneration hydraulic motor 14A is a hydraulic motor that assists the engine by regenerating the energy of the hydraulic oil that flows out from the hydraulic actuator, and is a swash plate type variable displacement hydraulic motor in this embodiment. The regenerative hydraulic motor 14A can also function as a hydraulic pump (third pump).

  The regenerative hydraulic motor 14A is connected to a regulator in the same manner as the first pump 14L and the second pump 14R. The regulator changes the swash plate tilt angle of the regenerative hydraulic motor 14A in accordance with a command from the controller 30 to control the displacement of the regenerative hydraulic motor 14A. Further, the regulator may be able to set the displacement volume (swash plate tilt angle) of the regenerative hydraulic motor 14A to zero. This is because the hydraulic oil can be rotated without being consumed (sucked and discharged), and the flow of the hydraulic oil passing through the regeneration hydraulic motor 14A can be blocked.

  A first accumulator 85L, a switching valve 86, and a relief valve 90 are arranged downstream of the regeneration hydraulic motor 14A (discharge side) via a check valve 88.

  The first accumulator 85L is a hydraulic device that accumulates hydraulic fluid discharged by the regenerative hydraulic motor 14A. In the present embodiment, the first accumulator 85L is controlled by the switching valve 86 to release the hydraulic oil. Moreover, the operating pressure of the first accumulator 85L is higher than the pressure of the hydraulic oil in the hydraulic oil tank T, and is, for example, in the range of 0.2 to 5 MPa. This is because it is possible to prevent the occurrence of cavitation by reliably supplying hydraulic oil to the suction side port of the turning hydraulic motor 21 at the time of turning deceleration.

  The switching valve 86 is a valve that operates in response to a command from the controller 30. In this embodiment, the switching valve 86 is a 2-port 2-position electromagnetic valve that can switch communication / blocking between the first accumulator 85 </ b> L and the turning hydraulic motor 21. Specifically, the switching valve 86 communicates between the first accumulator 85L and the turning hydraulic motor 21 when in the first position, and shuts off the communication when in the second position.

  The check valve 88 blocks the flow of hydraulic oil flowing into the discharge side port of the regeneration hydraulic motor 14A. In the present embodiment, the check valve 88 blocks the flow of hydraulic oil from the first accumulator 85L to the regeneration hydraulic motor 14A.

  The relief valve 90 opens when the pressure on the discharge side of the regenerative hydraulic motor 14A (the pressure of the hydraulic oil in the first accumulator 85L) reaches a predetermined relief pressure, and discharges the hydraulic oil on the discharge side to the hydraulic oil tank. To do.

  A second accumulator 85H is arranged via a switching valve 87 upstream (suction side) of the regeneration hydraulic motor 14A. The upstream side (suction side) of the regenerative hydraulic motor 14 </ b> A is also connected to the hydraulic oil tank T via the check valve 89.

  The second accumulator 85 </ b> H is a hydraulic device that accumulates hydraulic fluid that flows out of the turning hydraulic motor 21. In the present embodiment, in the second accumulator 85H, hydraulic oil accumulation is controlled by the switching valve 22G, and hydraulic oil release is controlled by the switching valve 87. In addition, the working pressure of the second accumulator 85H is higher than the working pressure of the first accumulator 85L, and is, for example, in the range of 15 to 30 MPa. This is because the assisting force by the regenerative hydraulic motor 14A can be increased as the pressure difference between the operating pressure of the first accumulator 85L and the operating pressure of the second accumulator 85H increases. However, the working pressure of the second accumulator 85H is lower than the relief pressure of the relief valves 22L and 22R.

  The switching valve 87 is a valve that operates in response to a command from the controller 30. In this embodiment, the switching valve 87 is a 2-port 2-position electromagnetic valve that can switch communication / blocking between the second accumulator 85H and the regenerative hydraulic motor 14A. Specifically, the switching valve 87 communicates between the second accumulator 85H and the regenerative hydraulic motor 14A when in the first position, and shuts off the communication when in the second position.

  The check valve 89 blocks the flow of the hydraulic oil flowing out to the hydraulic oil tank T. In the present embodiment, the check valve 89 prevents a part of the hydraulic oil flowing from the second accumulator 85H to the regeneration hydraulic motor 14A from flowing out to the hydraulic oil tank T. Note that the check valve 89 does not block the flow of hydraulic oil from the hydraulic oil tank T to the third pump when the regenerative hydraulic motor 14A functions as the third pump.

  With the above configuration, the discharge-side port of the turning hydraulic motor 21, the shuttle valve 22S, the switching valve 22G, the second accumulator 85H, the switching valve 87, the regeneration hydraulic motor 14A, the check valve 88, the first accumulator 85L, and the switching valve 86. The turning regeneration circuit connecting the check valves 23L and 23R and the suction side port of the turning hydraulic motor 21 forms a closed loop of one-way flow.

  In the present embodiment, the drive shafts of the first pump 14L, the second pump 14R, and the regenerative hydraulic motor 14A are mechanically coupled. Specifically, each drive shaft is connected to the output shaft of the engine 11 through the transmission 13 at a predetermined speed ratio. Therefore, if the engine speed is constant, each speed is also constant. However, the first pump 14L, the second pump 14R, and the regenerative hydraulic motor 14A are connected to the engine 11 via a continuously variable transmission or the like so that the rotation speed can be changed even if the engine rotation speed is constant. Also good.

  The control valve 17 is a hydraulic control device that controls a hydraulic drive system in the excavator. The control valve 17 mainly includes variable load check valves 51 to 53, a merging valve 55, unified bleed-off valves 56L and 56R, and flow control valves 170 to 173.

  The flow control valves 170 to 173 are valves that control the direction and flow rate of hydraulic oil flowing into and out of the hydraulic actuator. In the present embodiment, each of the flow control valves 170 to 173 is a 4-port 3 position that operates by receiving pilot pressure generated by an operating device (not shown) such as a corresponding operating lever at either the left or right pilot port. This is a spool valve. The operating device causes the pilot pressure generated according to the operation amount (operation angle) to act on the pilot port on the side corresponding to the operation direction.

  Specifically, the flow control valve 170 is a spool valve that controls the direction and flow rate of the hydraulic oil flowing into and out of the turning hydraulic motor 21, and the flow control valve 171 is the hydraulic oil flowing into and out of the arm cylinder 8. A spool valve that controls the direction and flow rate.

  The flow control valve 172 is a spool valve that controls the direction and flow rate of the hydraulic oil flowing into and out of the boom cylinder 7, and the flow control valve 173 controls the direction and flow rate of the hydraulic oil flowing into and out of the bucket cylinder 9. This is a spool valve.

  The variable load check valves 51 to 53 are valves that operate in response to a command from the controller 30. In this embodiment, the variable load check valves 51 to 53 are two ports that can switch communication / blocking between each of the flow control valves 171 to 173 and at least one of the first pump 14L and the second pump 14R. This is a two-position solenoid valve. Note that the variable load check valves 51 to 53 have a check valve that blocks the flow of hydraulic oil returning to the pump side at the first position. Specifically, when the variable load check valve 51 is in the first position, the flow control valve 171 communicates with at least one of the first pump 14L and the second pump 14R and is in the second position. In that case, the communication is cut off. The same applies to the variable load check valve 52 and the variable load check valve 53.

  The junction valve 55 is an example of a junction switching unit, and is a valve that operates in response to a command from the controller 30. In the present embodiment, the merging valve 55 is a hydraulic oil discharged from the first pump 14L (hereinafter referred to as “first hydraulic oil”) and a hydraulic oil discharged from the second pump 14R (hereinafter referred to as “second hydraulic oil”). ").” Is a 2-port 2-position solenoid valve capable of switching whether or not to join. Specifically, the merging valve 55 merges the first hydraulic oil and the second hydraulic oil when in the first position, and merges the first hydraulic oil and the second hydraulic oil when in the second position. Do not let it.

  The unified bleed-off valves 56 </ b> L and 56 </ b> R are valves that operate in response to a command from the controller 30. In this embodiment, the unified bleed-off valve 56L is a 2-port 2-position electromagnetic valve capable of controlling the discharge amount of the first hydraulic oil to the hydraulic oil tank T. The same applies to the unified bleed-off valve 56R. With this configuration, the unified bleed-off valves 56 </ b> L and 56 </ b> R can realize the combined opening of the associated flow control valves among the flow control valves 170 to 173. Specifically, when the merging valve 55 is in the second position, the unified bleed-off valve 56L can realize a combined opening of the flow control valve 170 and the flow control valve 171, and the unified bleed-off valve 56R A synthetic opening of the flow control valve 173 can be realized. The unified bleed-off valve 56L functions as a variable throttle that adjusts the opening area of the synthetic opening in accordance with a command from the controller 30 when in the first position, and opens the synthetic opening when in the second position. Cut off. The same applies to the unified bleed-off valve 56R.

  Note that each of the variable load check valves 51 to 53, the merging valve 55, and the unified bleed-off valves 56L and 56R may be a pilot pressure driven spool valve.

  Next, referring to FIG. 3, the state of the hydraulic circuit in FIG. 2 during turning acceleration will be described. The thick solid lines in FIG. 3 indicate the flow of hydraulic oil that flows into the suction sides of the regenerative hydraulic motor 14A and the turning hydraulic motor 21, respectively. A thick dotted line indicates the flow of hydraulic oil flowing out from the discharge side of each of the regeneration hydraulic motor 14A and the turning hydraulic motor 21.

  The controller 30 determines the operation content of the operator on the shovel based on the output of an operation detection unit such as an operation pressure sensor (not shown) that detects the pilot pressure generated by the operation device.

  When the controller 30 determines that the turning operation has been performed, the controller 30 supplies the first hydraulic oil to the flow control valve 170 according to the operation amount of the turning operation lever. The flow control valve 170 receives the pilot pressure corresponding to the operation amount of the turning operation lever, moves to the right position, and causes the first hydraulic oil to flow into the suction side port 21 </ b> R of the turning hydraulic motor 21. Further, the hydraulic oil flowing out from the discharge side port 21L of the turning hydraulic motor 21 is discharged to the hydraulic oil tank T.

  Further, the controller 30 determines a discharge amount command value of the first pump 14L corresponding to the operation amount of the turning operation lever based on pump discharge amount control such as negative control control, positive control control, load sensing control, horsepower control and the like. . Then, the controller 30 controls the corresponding regulator so that the discharge amount of the first pump 14L becomes the command value.

  Moreover, the controller 30 outputs a command to the switching valve 87 and switches the switching valve 87 to the first position. Further, a command is output to the regenerative hydraulic motor 14A, and the swash plate tilt angle of the regenerative hydraulic motor 14A is adjusted so that the revolving hydraulic motor 14A has a rotational speed suitable for assisting the engine 11. To do. When the switching valve 87 is switched to the first position, the second accumulator 85H releases the hydraulic oil toward the regeneration hydraulic motor 14A. The regenerative hydraulic motor 14A rotates in response to the hydraulic oil released from the second accumulator 85H, and causes the hydraulic oil to flow out from the discharge side port toward the first accumulator 85L. The first accumulator 85L accumulates hydraulic fluid that flows out from the regeneration hydraulic motor 14A. Thus, the controller 30 can assist the engine 11 by using the hydraulic oil accumulated in the second accumulator 85H as the rotational power of the regenerative hydraulic motor 14A, and can reduce the engine load.

  Note that, when the hydraulic oil is not sufficiently accumulated in the second accumulator 85H, the controller 30 may cause the regeneration hydraulic motor 14A to function as the third pump while maintaining the switching valve 87 in the second position. In this case, the regenerative hydraulic motor 14A as the third pump is rotationally driven by the engine 11 and discharges the hydraulic oil sucked from the hydraulic oil tank T toward the first accumulator 85L. The first accumulator 85L accumulates hydraulic oil discharged from the regenerative hydraulic motor 14A. Note that the first accumulator 85L may accumulate hydraulic fluid that flows out from the relief valves 22L and 22R at the time of turning acceleration. In this case, the first accumulator 85L is connected downstream of the relief valves 22L and 22R via a not-shown pipeline and a switching valve.

  Further, the controller 30 assists the engine 11 by rotating the regenerative hydraulic motor 14 </ b> A by switching the switching valve 87 to the first position not only at the time of turning acceleration with a heavy engine load but also at any timing other than at the time of turning acceleration. May be.

  Next, with reference to FIG. 4, the state of the hydraulic circuit in FIG. 2 during turning deceleration will be described. Note that the thick solid line in FIG. 4 indicates the flow of hydraulic oil flowing into the suction side of the turning hydraulic motor 21. A thick dotted line indicates the flow of hydraulic oil flowing out from the discharge side of the turning hydraulic motor 21.

  When the controller 30 determines that the turning operation has been stopped, the controller 30 returns the flow control valve 170 to the neutral position. The flow control valve 170 that has returned to the neutral position blocks communication between the turning hydraulic motor 21 and the first pump 14L. Therefore, the hydraulic oil pressure at the discharge side port 21L of the turning hydraulic motor 21 increases. The rotation of the turning hydraulic motor 21 (discharge of hydraulic oil from the discharge side port 21L) is continued by the inertia of the upper swing body 3 and the outflow to the hydraulic oil tank T is blocked, and the hydraulic oil in the discharge side port 21L is compressed. It is to be done.

  At this time, the controller 30 outputs a command to the switching valve 22G and switches the switching valve 22G to the first position. When the switching valve 22G is switched to the first position, the hydraulic oil in the discharge side port 21L flows out toward the second accumulator 85H. The second accumulator 85 </ b> H accumulates hydraulic fluid that flows out from the turning hydraulic motor 21.

  On the other hand, the pressure of the hydraulic oil in the suction side port 21R of the turning hydraulic motor 21 decreases. The rotation of the swing hydraulic motor 21 (suction of hydraulic oil into the suction side port 21L) is continued by the inertia of the upper swing body 3 and the inflow from the first pump 14L is blocked, so that the hydraulic oil in the suction side port 21R is insufficient. It is to do.

  At this time, the controller 30 outputs a command to the switching valve 86 and switches the switching valve 86 to the first position. When the switching valve 86 is switched to the first position, the first accumulator 85L discharges the hydraulic oil toward the suction side port 21R of the turning hydraulic motor 21. Therefore, the first accumulator 85L can prevent cavitation from occurring at the suction side port 21R. Note that the hydraulic oil from the hydraulic oil tank T may be additionally supplied when a larger flow rate than that released by the first accumulator 85L is required at the suction side port 21R. In this case, the hydraulic oil from the hydraulic oil tank T flows through the check valve 91 into the suction side port 21R. Further, the check valve 91 blocks the flow of hydraulic oil from the first accumulator 85L to the hydraulic oil tank T.

  In the above-described embodiment, the second accumulator 85H may be omitted. In this case, the controller 30 outputs a command to the switching valve 22G, the switching valve 87, and the regenerative hydraulic motor 14A at the time of turning deceleration. Then, the switching valve 22G and the switching valve 87 are switched to the first position, and the swash plate is tilted so that the rotation speed of the regeneration hydraulic motor 14A becomes a rotation speed suitable for assisting the engine 11. Adjust the corners. When the switching valve 22G and the switching valve 87 are switched to the first position, the hydraulic oil flowing out from the discharge side port of the turning hydraulic motor 21 passes through the shuttle valve 22S, the switching valve 22G, and the switching valve 87, and the regenerative hydraulic pressure. It flows into the suction side of the motor 14A. The regenerative hydraulic motor 14 </ b> A assists the engine 11 by receiving and rotating the hydraulic oil flowing out from the discharge side of the turning hydraulic motor 21. Then, the hydraulic oil flows out from the discharge side toward the first accumulator 85L, and the hydraulic oil is accumulated in the first accumulator 85L. In this way, even when the second accumulator 85H is omitted, the controller 30 regenerates the hydraulic energy of the hydraulic oil flowing out from the turning hydraulic motor 21 during turning deceleration as the engine assist torque. The hydraulic oil can be accumulated in the first accumulator 85L.

  With the above configuration, the hydraulic circuit in FIG. 2 accumulates the hydraulic oil flowing out from the turning hydraulic motor 21 during turning deceleration in the second accumulator 85H, and then regenerates the accumulated hydraulic oil at an arbitrary timing 14A. Can be released toward Therefore, the regenerative hydraulic motor 14A can assist the engine 11 by reusing regenerative energy at an arbitrary timing, such as when the engine load is large, and can improve the excavator's motion performance.

  Further, since the first accumulator 85L is disposed downstream of the regenerative hydraulic motor 14A in the hydraulic circuit of FIG. 2, the first accumulator 85L is used with hydraulic oil when the regenerative energy is reused in the regenerative hydraulic motor 14A. Can be filled. In addition, since the swivel regeneration circuit forms a closed loop with a one-way flow, the swivel regeneration circuit can be made to function simply by supplementing the hydraulic oil that has exited the closed loop due to leakage, etc., and uses little engine output. The swivel regeneration circuit can be made to function continuously. Therefore, it is not necessary to temporarily reduce the outputs of the first pump 14L and the second pump 14R for allocation to other engine outputs, and it is also necessary to provide functional elements for realizing the temporary reduction. Absent.

  Further, since the first accumulator 85L is disposed downstream of the regeneration hydraulic motor 14A in the hydraulic circuit of FIG. 2, the regeneration hydraulic motor 14A can function as an on-off valve of the first accumulator 85L.

  Next, another configuration example of the hydraulic circuit mounted on the shovel of FIG. 1 will be described with reference to FIG. The hydraulic circuit in FIG. 5 mainly flows in and out of the bottom side oil chamber of the boom cylinder 7 in that the direction and flow rate of the hydraulic oil flowing into and out of the arm cylinder 8 are controlled by the two flow control valves 171A and 171B. The point where the flow rate of the hydraulic oil is controlled by the two flow rate control valves 172A and 172B, and the point where the merging switching unit is constituted by a variable load check valve instead of the merging valve (the merging valve is omitted), It is different from the hydraulic circuit but is common in other points. Therefore, the difference will be described in detail while omitting the description of the common points.

  The flow control valves 171A and 171B are valves that control the direction and flow rate of hydraulic oil flowing into and out of the arm cylinder 8, and correspond to the flow control valve 171 in FIG. Specifically, the flow control valve 171 </ b> A supplies the first hydraulic oil to the arm cylinder 8, and the flow control valve 171 </ b> B supplies the second hydraulic oil to the arm cylinder 8. Therefore, the first hydraulic oil and the second hydraulic oil can flow into the arm cylinder 8 at the same time.

  The flow control valve 172A is a valve that controls the direction and flow rate of hydraulic oil flowing into and out of the boom cylinder 7, and corresponds to the flow control valve 172 in FIG.

  The flow control valve 172B is a valve that allows the first hydraulic oil to flow into the bottom side oil chamber of the boom cylinder 7 when the boom raising operation is performed. When the boom lowering operation is performed, the boom cylinder 7 The hydraulic oil flowing out from the bottom side oil chamber can be merged with the first hydraulic oil.

  The flow control valve 173 is a valve that controls the direction and flow rate of the hydraulic oil flowing into and out of the bucket cylinder 9 and corresponds to the flow control valve 173 in FIG.

  The variable load check valves 50, 51A, 51B, 52A, 52B, 53 are respectively flow rate control valves 170, 171A, 171B, 172A, 172B, 173 and at least one of the first pump 14L and the second pump 14R. It is a 2-port 2-position valve that can be switched between communication and blocking. These six variable load check valves operate in conjunction with each other, thereby functioning as a merging switching unit and realizing the function of the merging valve 55 of FIG. Therefore, the junction valve 55 of FIG. 2 is omitted from the hydraulic circuit of FIG.

  The unified bleed-off valves 56L and 56R are 2-port 2-position valves capable of controlling the discharge amount of the first hydraulic oil to the hydraulic oil tank T, and correspond to the unified bleed-off valves 56L and 56R in FIG.

  The six flow control valves in FIG. 5 are all 6-port 3-position spool valves, and have a center bypass port, unlike the flow control valve in FIG. Therefore, the unified bleed-off valve 56L in FIG. 5 is arranged downstream of the flow control valve 171A, and the unified bleed-off valve 56R is arranged downstream of the flow control valve 171B.

  The switching valve 62A is a three-port three-position valve that can switch whether or not to let the hydraulic oil discharged from the boom cylinder 7 flow into the suction side of the regenerative hydraulic motor 14A. Specifically, the switching valve 62A communicates between the bottom oil chamber of the boom cylinder 7 and the suction side of the regenerative hydraulic motor 14A when in the first position (left position), and the second position (right When in the third position (neutral position), the communication between the rod side oil chamber of the boom cylinder 7 and the suction side of the regenerative hydraulic motor 14A is cut off.

  The switching valve 62 </ b> B is a 2-port 2-position variable relief valve capable of switching whether to discharge the hydraulic oil discharged from the rod side oil chamber of the boom cylinder 7 to the hydraulic oil tank T. Specifically, the switching valve 62B communicates between the rod-side oil chamber of the boom cylinder 7 and the hydraulic oil tank T when in the first position, and blocks communication when in the second position. The switching valve 62B has a check valve that blocks the flow of hydraulic oil from the hydraulic oil tank T in the first position.

  The switching valve 62C is a 2-port 2-position variable relief valve capable of switching whether or not to discharge the hydraulic oil discharged from the bottom side oil chamber of the boom cylinder 7 to the hydraulic oil tank T. Specifically, the switching valve 62C communicates between the bottom side oil chamber of the boom cylinder 7 and the hydraulic oil tank T when in the first position, and shuts off the communication when in the second position. Note that the switching valve 62C has a check valve that blocks the flow of hydraulic oil from the hydraulic oil tank T at the first position.

  Next, the state of the hydraulic circuit in FIG. 5 during the boom lowering operation will be described with reference to FIG. The thick solid line in FIG. 6 indicates the flow of hydraulic oil flowing into the rod side oil chamber of the boom cylinder 7. The thick dotted line indicates the flow of hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder 7.

  For example, when the controller 30 determines that the boom lowering operation has been performed, the controller 30 switches the variable load check valve 52A and the switching valve 62A to the first position. The flow control valve 172A receives a pilot pressure corresponding to the operation amount of the boom operation lever, moves to the right position, and causes the second hydraulic oil to flow into the rod side oil chamber of the boom cylinder 7. Further, the hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder 7 is caused to flow into the suction side of the regenerative hydraulic motor 14A via the switching valve 62A. The hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder 7 may be regenerated into the rod side oil chamber via the regeneration valve 7a.

  Further, the hydraulic circuit of FIG. 5 may be configured such that hydraulic oil flowing out from other hydraulic actuators other than the boom cylinder 7 such as the arm cylinder 8 and the bucket cylinder 9 flows into the suction side of the regenerative hydraulic motor 14A. .

  As described above, the hydraulic circuit of FIG. 5 can supply the hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder 7 to the suction side of the regenerative hydraulic motor 14A in addition to the effect of the hydraulic circuit of FIG. It has the additional effect of.

  Further, in the hydraulic circuit of FIG. 5, since the first accumulator 85L is arranged downstream of the regenerative hydraulic motor 14A, similarly to the hydraulic circuit of FIG. 2, when the regenerative energy is reused by the regenerative hydraulic motor 14A, The first accumulator 85L can be filled with hydraulic oil. In addition, since the swivel regeneration circuit forms a closed loop with a one-way flow, the swirl regeneration circuit can be made to function only by supplementing the hydraulic oil from the closed loop with hydraulic fluid from the boom cylinder 7 due to leakage or the like. The turning regeneration circuit can be continuously functioned without using the engine output. Therefore, it is not necessary to temporarily reduce the outputs of the first pump 14L and the second pump 14R for allocation to other engine outputs, and it is also necessary to provide functional elements for realizing the temporary reduction. Absent.

  Further, in the hydraulic circuit of FIG. 5, since the first accumulator 85L is arranged downstream of the regenerative hydraulic motor 14A, similarly to the hydraulic circuit of FIG. 2, the regenerative hydraulic motor 14A is used as an opening / closing valve of the first accumulator 85L. Can function.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.

  DESCRIPTION OF SYMBOLS 1 ... Lower traveling body 2 ... Turning mechanism 3 ... Upper turning body 4 ... Boom 5 ... Arm 6 ... Bucket 7 ... Boom cylinder 8 ... Arm cylinder 9 ... Bucket cylinders 7a, 8a, 9a ... regeneration valves 7b, 8b ... holding valves 10 ... cabin 11 ... engine 13 ... transmission 14L ... first pump 14R ... second Pump 14A ... Regenerative hydraulic motor 17 ... Control valve 21 ... Turning hydraulic motor 21L, 21R ... Port 22G ... Switching valve 22L, 22R ... Relief valve 22S ... Shuttle valve 23L, 23R ... Check valve 30 ... Controller 50, 51, 51A, 51B, 52, 52A, 52B, 53 ... Variable load check valve 55 ... Flow valve 56L, 56R ... Unified bleed-off valve 62A, 62B, 62C ... Switching valve 85L ... First accumulator 85H ... Second accumulator 86, 87 ... Switching valve 88, 89 ... Check valve 90 ... Relief valve 91 ... Check valve 170, 171, 171A, 171B, 172, 172A, 172B, 173 ... Flow control valve T ... Hydraulic oil tank

Claims (5)

A regenerative hydraulic motor that regenerates energy of hydraulic oil flowing out from the hydraulic actuator and assists the engine;
A first accumulator disposed downstream of the regenerative hydraulic motor;
Excavator equipped with. A lower traveling body,
An upper swivel body that is turnably mounted on the lower traveling body;
A turning hydraulic motor that drives the upper turning body to turn,
The first accumulator supplies hydraulic oil to the suction side of the turning hydraulic motor during turning deceleration.
The excavator according to claim 1. A second accumulator disposed upstream of the regenerative hydraulic motor;
The shovel according to claim 1 or 2. The working pressure of the second accumulator is higher than the working pressure of the first accumulator,
The excavator according to claim 3. The hydraulic oil discharged from the second accumulator is supplied to the first accumulator via the regeneration hydraulic motor.
The excavator according to claim 4.

Images