JP2019094609A - Shovel - Google Patents

Abstract

To provide a shovel capable of preventing cavitation from occurring on a suction side of a revolving hydraulic motor even when regenerating energy of hydraulic oil discharged from the revolving hydraulic motor during rotation deceleration.SOLUTION: A shovel according to an embodiment of this invention comprises: a revolving hydraulic motor 21; a center by-pass duct 40L on which a flow control valve 170 relating to the revolving hydraulic motor 21 is installed; a negative control throttle 18L that is installed on the center by-pass duct 40L; a revolving makeup duct 44 that connects a section between the flow control valve 170 and the negative control throttle 18L with a revolving hydraulic circuit SC including the revolving hydraulic motor 21.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a shovel that regenerates energy of hydraulic fluid discharged by a turning hydraulic motor during turning and decelerating.

  DESCRIPTION OF RELATED ART The shovel which accumulates the hydraulic fluid which the hydraulic motor for revolution discharges at the time of revolution deceleration to an accumulator is known (refer patent document 1).

Patent No. 5412077 gazette

  However, the above-mentioned shovel does not consider the make-up (compensation) of the hydraulic oil shortage on the suction side of the turning hydraulic motor at the time of turning deceleration. Therefore, there is a possibility that cavitation may be generated on the suction side of the turning hydraulic motor at the time of turning deceleration.

  In view of the above-mentioned point, it is desirable to provide a shovel capable of preventing the occurrence of cavitation on the suction side of the turning hydraulic motor even when the energy of the hydraulic fluid discharged by the turning hydraulic motor is regenerated during turning deceleration. Be

  The shovel according to the embodiment of the present invention includes: a turning hydraulic motor; a center bypass pipe line on which a flow control valve related to the turning hydraulic motor is installed; a negative control throttle installed on the center bypass pipe; And a turning make-up line connecting between a flow control valve and the negative control throttle and a turning hydraulic circuit including the turning hydraulic motor.

  According to the above-described means, there is provided a shovel capable of preventing the occurrence of cavitation on the suction side of the turning hydraulic motor even if the energy of the hydraulic fluid discharged by the turning hydraulic motor is regenerated at the time of turning deceleration.

It is a side view of a shovel concerning an example of the present invention. It is a figure which shows the structural example of the hydraulic circuit mounted in the shovel of FIG. It is a figure which shows the state at the time of turning acceleration of a hydraulic circuit when single turning operation is performed. It is a figure which shows the state at the time of turning deceleration of a hydraulic circuit when single turning operation is performed. It is a figure which shows the state at the time of turning acceleration of a hydraulic circuit when composite turning operation is performed. It is a figure which shows the state at the time of turning deceleration of a hydraulic circuit when composite turning operation is performed.

  FIG. 1 is a side view showing a shovel (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 shovel via a turning 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 working elements constitute a digging attachment which 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. A cabin 10 is provided in the upper revolving superstructure 3, and a power source such as an engine 11 and a controller 30 are mounted.

  The controller 30 is a control device as a main control unit that performs drive control of the shovel. In the example of FIG. 1, the controller 30 is configured by an arithmetic processing unit including a CPU and an internal memory, and causes the CPU to execute a program for drive control stored in the internal memory to realize various functions.

  FIG. 2 is a schematic view showing a configuration example of the hydraulic circuit 100 mounted on the shovel of FIG. In the example of FIG. 2, the hydraulic circuit 100 mainly includes a first pump 14L, a second pump 14R, a regenerative hydraulic motor 14A, a control valve 17, an accumulator 85, and a hydraulic actuator. The hydraulic actuator mainly includes a boom cylinder 7, an arm cylinder 8, a bucket cylinder 9, and a hydraulic motor 21 for turning. In addition, the hydraulic actuator may include a left side traveling hydraulic motor (not shown) and a right side traveling hydraulic motor (not shown).

  In the example of FIG. 2, the drive shafts of the first pump 14L, the second pump 14R, and the regenerative hydraulic motor 14A are mechanically connected. Specifically, each drive shaft is connected to the output shaft of the engine 11 at a predetermined gear ratio via a transmission 13 as a pump drive. That is, the transmission 13 is connected to the output shaft of the engine 11 and the output shaft of the regenerative hydraulic motor 14A, and the power of the engine 11 and the power of the regenerative hydraulic motor 14A are used as the first pump 14L and the second pump 14R. introduce. Therefore, when the engine rotational speed is constant, the respective rotational speeds of the first pump 14L, the second pump 14R, and the regeneration hydraulic motor 14A also become 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 rotational speed can be changed even if the engine rotational speed is constant. May be

  The first pump 14L and the second pump 14R circulate the hydraulic oil to the hydraulic oil tank T via the center bypass pipelines 40L, 40R, the parallel pipelines 42L, 42R, the return pipelines 43L, 43R, 43C.

  The center bypass line 40L is a high pressure hydraulic line passing through the flow control valves 170, 172L and 173L disposed in the control valve 17. The center bypass line 40R is a high pressure hydraulic line passing through the flow control valves 171, 172R and 173R disposed in the control valve 17.

  The parallel pipeline 42L is a high pressure hydraulic line parallel to the center bypass pipeline 40L. The parallel pipeline 42L supplies hydraulic fluid to the flow control valve 170L when the flow of hydraulic fluid through the center bypass pipeline 40L is restricted or shut off by the flow control valve 170, 172L, or 173L. Further, the parallel pipeline 42R is a high pressure hydraulic line parallel to the center bypass pipeline 40R. The parallel pipeline 42R supplies hydraulic fluid to the flow control valve when the flow of hydraulic fluid through the center bypass pipeline 40R is restricted or blocked by the flow control valve 171, 172R, or 173R.

  The return line 43L is a low pressure hydraulic line parallel to the center bypass line 40L. The return line 43L distributes the hydraulic oil flowing from the hydraulic actuator through the flow control valves 170, 172L, 173L to the return line 43C. The return line 43R is a low pressure hydraulic line parallel to the center bypass line 40R. The return line 43R distributes the hydraulic oil flowing from the hydraulic actuator through the flow control valves 171, 172R, 173R to the return line 43C.

  The center bypass pipelines 40L, 40R are provided with negative control throttles 18L, 18R and relief valves 19L, 19R between the flow control valves 173L, 173R located most downstream and the return pipeline 43C. The flow of hydraulic fluid discharged by the first pump 14L and the second pump 14R is limited by the negative control throttles 18L and 18R. The negative control throttles 18L and 18R generate control pressure (negative control pressure) for controlling the regulators of the first pump 14L and the second pump 14R. The relief valves 19L and 19R open when the negative control pressure reaches a predetermined relief pressure, and discharge the hydraulic oil of the center bypass pipelines 40L and 40R to the return pipeline 43C.

  A proportional valve 52 is installed at the most downstream side of the return line 43C. In the example of FIG. 2, the proportional valve 52 is an electromagnetic valve that controls the flow rate by adjusting the size of the opening according to the command from the controller 30, and the communication between the return line 43 C and the hydraulic oil tank T It is a 1-port 2-position solenoid proportional valve capable of switching shutoff. Specifically, when the proportional valve 52 is in the first position, the return conduit 43C and the hydraulic fluid tank T can be communicated at the maximum opening, and when in the second position, the communication can be shut off. In the example of FIG. 2, the proportional valve 52 opens and closes in accordance with the operation content of the turning operation lever. Specifically, the proportional valve 52 is in the second position when the turning operation lever is returned to the neutral position during the combined turning operation in which the turning operation lever and the other operation lever are simultaneously operated. Then, when the predetermined time has elapsed or when it is determined that the turning hydraulic motor 21 has stopped, the position returns to the first position. The controller 30 may, for example, determine whether the swing hydraulic motor 21 has stopped based on the output of a pressure sensor that detects the pressure of hydraulic fluid in the swing hydraulic motor 21, a rotation angle sensor that detects the rotation angle of the swing mechanism 2, or the like. Determine if

  The turning hydraulic motor 21 is a hydraulic motor that turns the upper swing body 3. The ports 21L and 21R of the turning hydraulic motor 21 are connected to the turning makeup pipe line 44 via the relief valves 22L and 22R or the check valves 23L and 23R. The ports 21L and 21R are connected to the accumulator 85 and the hydraulic hydraulic motor 14A for regeneration through the check valves 24L and 24R. The swing hydraulic motor 21, the relief valves 22L and 22R, the check valves 23L and 23R, and the check valves 24L and 24R constitute a swing hydraulic circuit SC.

  The turning make-up pipeline 44 is a hydraulic line for making up (compensating) a shortage of hydraulic oil on the suction side of the turning hydraulic motor 21. In the example of FIG. 2, the turning makeup pipeline 44 mainly includes a first makeup pipeline 44A, a second makeup pipeline 44B, and a common makeup pipeline 44C.

  The first makeup pipeline 44A includes a pipeline between the flow control valve 173L located at the most downstream side of the center bypass pipeline 40L and the negative control throttle 18L, and a swing hydraulic circuit SC including the swing hydraulic motor 21. It is a hydraulic line to connect. A check valve 50 is installed in the first makeup pipe line 44A. The check valve 50 allows the flow of hydraulic fluid from the center bypass line 40L to the swing hydraulic circuit SC, and blocks the flow of hydraulic oil from the swing hydraulic circuit SC to the center bypass line 40L.

  The second make-up line 44B is a hydraulic line connecting the upstream side of the proportional valve 52 located on the most downstream side of the return line 43C and the swing hydraulic circuit SC. A check valve 51 is installed in the second makeup pipe line 44B. The check valve 51 allows the flow of hydraulic fluid from the return line 43C to the swing hydraulic circuit SC, and blocks the flow of hydraulic fluid from the swing hydraulic circuit SC to the return line 43C.

  The common make-up line 44C is a hydraulic line connecting the first make-up line 44A and the second make-up line 44B to the swing hydraulic circuit SC.

  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. Further, the relief valve 22R is opened when the pressure on the port 21R side reaches a predetermined relief pressure, and the hydraulic oil on the port 21R side is discharged.

  The check valve 23L is opened when the pressure on the port 21L side becomes lower than the pressure on the opposite side, and the hydraulic fluid is supplied from the swirling make-up pipeline 44 to the port 21L side. The check valve 23R is opened when the pressure on the port 21R side becomes lower than the pressure on the opposite side, and the hydraulic fluid is supplied from the swing makeup pipe 44 to the port 21R side. With this configuration, the check valves 23L and 23R can supply hydraulic oil to the suction side port when the turning hydraulic motor 21 is braked.

  The check valve 24L opens when the pressure on the port 21L side becomes higher than the pressure on the opposite side, and supplies the hydraulic fluid from the port 21L side to at least one of the accumulator 85 and the regeneration hydraulic motor 14A. The check valve 24R opens when the pressure on the port 21R side becomes higher than the pressure on the opposite side, and supplies the hydraulic fluid from the port 21R side to at least one of the accumulator 85 and the regeneration hydraulic motor 14A. With this configuration, the check valves 24L and 24R can supply the hydraulic oil of the discharge side port to at least one of the accumulator 85 and the regeneration hydraulic motor 14A when the turning hydraulic motor 21 is braked.

  The proportional valve 22G is a valve that adjusts the size of the opening in accordance with a command from the controller 30 to control the flow rate. In the example of FIG. 2, the proportional valve 22 </ b> G is a one-port two-position electromagnetic proportional valve capable of switching between communication and disconnection between the swing hydraulic motor 21 and the accumulator 85. Specifically, when the proportional valve 22G is in the first position, the hydraulic motor 21 for turning and the accumulator 85 can be communicated at the maximum opening, and when in the second position, the communication can be shut off.

  The first pump 14L is a hydraulic pump that sucks in and discharges hydraulic oil from the hydraulic oil tank T, and in the example of FIG. 2 is a swash plate type variable displacement hydraulic pump. In addition, 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 response to a command from the controller 30 to control the displacement (discharge amount per one rotation) of the first pump 14L. The same applies to the second pump 14R.

  The regenerative hydraulic motor 14A is a hydraulic motor that regenerates the energy of the hydraulic fluid flowing out of the hydraulic actuator to assist the engine 11, and in the example of FIG. 2 is a swash plate type variable displacement hydraulic motor. The discharge side port of the regenerative hydraulic motor 14A is connected to the return line 43L.

  The regenerative hydraulic motor 14A is connected to the regulator in the same manner as the first pump 14L and the second pump 14R. The regulator changes the swash plate tilting angle of the regenerative hydraulic motor 14A in accordance with a command from the controller 30 to control the displacement volume of the regenerative hydraulic motor 14A. Further, the regulator may be capable of setting the displacement volume (swash plate tilt angle) of the regeneration hydraulic motor 14A to zero. This is to enable rotation without consuming (sucking and discharging) hydraulic oil, and to block the flow of hydraulic oil passing through the regeneration hydraulic motor 14A.

  The upstream side (suction side) of the regenerative hydraulic motor 14 A is connected to the accumulator 85 via the switching valve 87. The accumulator 85 is a hydraulic device that accumulates the hydraulic fluid flowing out from the discharge side port of the turning hydraulic motor 21. In the example of FIG. 2, in the accumulator 85, accumulation of hydraulic fluid is controlled by the proportional valve 22G, and release of hydraulic fluid is controlled by the switching valve 87.

  The switching valve 87 is a valve that operates in response to a command from the controller 30. In the example of FIG. 2, the switching valve 87 is a 1-port 2-position solenoid valve capable of switching between communication and disconnection between the accumulator 85 and the regenerative hydraulic motor 14A. Specifically, the switching valve 87 establishes communication between the accumulator 85 and the regeneration hydraulic motor 14A when in the first position, and cuts off the communication when in the second position.

  The control valve 17 is a hydraulic control device that controls a hydraulic drive system in a shovel. The control valve 17 mainly includes flow control valves 170, 171, 172L, 172R, 173L, and 173R.

  The flow control valves 170, 171, 172L, 172R, 173L, and 173R are valves that control the direction and flow rate of hydraulic fluid flowing into and out of the hydraulic actuator. In the example of FIG. 2, each of the flow control valves 170, 171, 172L, 172R, 173L, and 173R is either a left or right pilot pressure generated by an operating device (not shown) such as a corresponding operating lever. It is a 3 port 3 position spool valve that operates by receiving at a port. The operating device causes the pilot pressure generated according to the amount of operation (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 fluid flowing into and out of the swing hydraulic motor 21, and the flow control valve 171 is a fluid flowing into and out of the bucket cylinder 9. It is a spool valve that controls the direction and flow rate.

  The flow control valves 172L and 172R are spool valves that control the direction and flow rate of hydraulic fluid flowing into and out of the boom cylinder 7, and the flow control valves 173L and 173R direct the hydraulic fluid flowing into and out of the arm cylinder 8. And a spool valve that controls the flow rate.

  The hydraulic circuit 100 configured as described above has a boom lowering regenerative circuit. The boom lowering regeneration circuit mainly includes a pipe 45, a pipe 46, a proportional valve 70, and a switching valve 71.

  The pipe line 45 is a pipe line connecting the bottom side oil chamber of the boom cylinder 7 and the upstream side (suction side) of the regenerative hydraulic motor 14A. The conduit 46 is a conduit branched from the conduit 45 and connecting the conduit 45 and the return conduit 43R.

  The proportional valve 70 is a valve that adjusts the size of the opening in accordance with a command from the controller 30 to control the flow rate, and is provided in the conduit 46. In the example of FIG. 2, the proportional valve 70 is a one-port two-position electromagnetic proportional valve capable of switching communication / shutoff between the bottom side oil chamber of the boom cylinder 7 and the return line 43 </ b> R. Specifically, when the proportional valve 70 is in the first position, the bottom side oil chamber of the boom cylinder 7 and the return conduit 43R are communicated at the maximum opening, and when in the second position, the proportional valve 70 is communicated. It can be shut off.

  The switching valve 71 is a valve that operates in response to a command from the controller 30 and is provided in the conduit 45. In the example of FIG. 2, the switching valve 71 is a one-port two-position solenoid valve capable of switching between communication and disconnection between the bottom side oil chamber of the boom cylinder 7 and the upstream side (suction side) of the regenerative hydraulic motor 14A. It is. Specifically, when the switching valve 71 is in the first position, the bottom oil chamber of the boom cylinder 7 and the upstream side (suction side) of the regenerating hydraulic motor 14A are communicated with each other to be in the second position. In the case of blocking its communication.

  In addition, the controller 30 can adjust the pressure of the hydraulic fluid in the conduit 45 by adjusting the opening degree of the proportional valve 70 when the boom is lowered. That is, it is possible to adjust the back pressure by the working oil directed from the bottom side oil chamber of the boom cylinder 7 to the regeneration hydraulic motor 14A. Therefore, the back pressure which increases due to the response delay of the regenerative hydraulic motor 14A can be adjusted, and the quick response and the fine operability of the boom operation can be secured.

  Further, when the controller 30 does not need to assist the engine 11, the hydraulic oil flowing out from the bottom side oil chamber of the boom cylinder 7 by adjusting the opening degree of the proportional valve 70 to a large value when the boom is lowered. Most of the fluid can be discharged to the hydraulic fluid tank through the return line 43R, the return line 43C, and the proportional valve 52. Therefore, it is possible to prevent over-rotation of the engine due to excessive assistance.

  Next, the state of the hydraulic circuit 100 when the single turning operation is performed will be described with reference to FIGS. 3 and 4. FIG. 3 shows the state at the time of turning acceleration, and FIG. 4 shows the state at the time of turning deceleration. In FIGS. 3 and 4, thick solid lines indicate the flow of hydraulic fluid flowing into the turning hydraulic motor 21, and thick dotted lines indicate the flow of hydraulic fluid flowing out of the turning hydraulic motor 21.

  When the turning operation lever is operated, the flow control valve 170 switches to the right valve position. The hydraulic fluid discharged by the first pump 14L flows into the port 21R of the turning hydraulic motor 21 through the PC port of the flow control valve 170, as shown by the thick solid line in FIG.

  The turning hydraulic motor 21 receives supply of hydraulic fluid from the first pump 14L and rotates, and discharges hydraulic fluid from the port 21L. The hydraulic fluid flowing out of the port 21L reaches the hydraulic fluid tank T through the CT port of the flow control valve 170, the return line 43L, the return line 43C, and the proportional valve 52, as indicated by the thick dotted line in FIG. .

  Thus, the upper swing body 3 is swung by the rotation of the swing hydraulic motor 21.

  Thereafter, when the turning operation lever is returned to the neutral position, the flow control valve 170 switches to the neutral valve position. The hydraulic fluid discharged by the first pump 14L flows through the PT port of the flow control valve 170 toward the negative control throttle 18L downstream of the center bypass pipeline 40L, as shown by the thick solid line in FIG. 4. The flow of hydraulic fluid from the PC port of the flow control valve 170 toward the turning hydraulic motor 21 is shut off.

  At this time, the controller 30 outputs a command to the proportional valve 22G to switch the proportional valve 22G to the first position. This is to regenerate the energy of the hydraulic fluid flowing out of the turning hydraulic motor 21.

  The hydraulic fluid flowing out of the port 21L of the turning hydraulic motor 21 is accumulated in the accumulator 85 through the check valve 24L and the proportional valve 22G as indicated by the thick dotted line in FIG. The hydraulic oil flowing out of the turning hydraulic motor 21 may be supplied to the regenerative hydraulic motor 14A without being accumulated in the accumulator 85.

  The hydraulic oil directed to the negative control throttle 18L through the PT port of the flow control valve 170 is turned for hydraulic pressure through the first make-up line 44A and the common make-up line 44C as shown by the thick solid line in FIG. It flows into the port 21R of the motor 21.

  With this configuration, the hydraulic circuit 100 can prevent the shortage of hydraulic oil on the suction side of the turning hydraulic motor 21 at the time of turning and decelerating even when the turning operation lever is returned to the neutral position during the single turning operation. Therefore, the occurrence of cavitation on the suction side of the turning hydraulic motor can be prevented.

  Next, referring to FIGS. 5 and 6, the state of the hydraulic circuit 100 when the combined swing operation of the boom raising operation and the swing operation is performed will be described. FIG. 5 shows the state at the time of turning acceleration, and FIG. 6 shows the state at the time of turning deceleration. 5 and 6, the thick solid line indicates the flow of hydraulic fluid flowing into the swing hydraulic motor 21, the boom cylinder 7, or the regenerative hydraulic motor 14A, and the thick dotted line indicates the swing hydraulic motor 21, the boom cylinder 7, or The flow of the hydraulic fluid which flows out out of hydraulic motor 14A for regeneration is shown.

  When the turning operation lever is operated, the flow control valve 170 switches to the right valve position. Part of the hydraulic fluid discharged by the first pump 14L flows into the port 21R of the turning hydraulic motor 21 through the PC port of the flow control valve 170, as shown by the thick solid line in FIG.

  When the boom control lever is operated in the upward direction, the flow control valve 172L is switched to the right valve position, and the flow control valve 172R is switched to the right valve position. The remainder of the hydraulic fluid discharged by the first pump 14L flows into the bottom-side oil chamber of the boom cylinder 7 through the PC port of the flow control valve 172L, as shown by the thick solid line in FIG. The hydraulic oil discharged by the second pump 14R joins the hydraulic oil from the flow control valve 172L through the PC port of the flow control valve 172R as shown by the thick solid line in FIG. Flow into the room.

  The turning hydraulic motor 21 receives supply of hydraulic fluid from the first pump 14L and rotates, and discharges hydraulic fluid from the port 21L. The hydraulic fluid flowing out of the port 21L passes through the CT port of the flow control valve 170, the return line 43L, the return line 43C, and the proportional valve 52 to the hydraulic oil tank T, as indicated by the thick dotted line in FIG. .

  The boom cylinder 7 receives the supply of hydraulic oil from the first pump 14L and the second pump 14R, extends it, and discharges hydraulic oil from the rod-side oil chamber. A portion of the hydraulic oil flowing out of the rod side oil chamber operates through the CT port of the flow control valve 172L, the return line 43L, the return line 43C, and the proportional valve 52 as shown by the thick dotted line in FIG. It reaches oil tank T. The remainder of the hydraulic oil flowing out of the rod side oil chamber passes through the CT port of the flow control valve 172R, the return line 43R, the return line 43C, and the proportional valve 52 as shown by the thick dotted line in FIG. It leads to the tank T.

  At this time, the controller 30 may output a command to the switching valve 87 to switch the switching valve 87 to the first position. This is to release the hydraulic oil accumulated in the accumulator 85.

  The hydraulic oil flowing out of the accumulator 85 is supplied to the regeneration hydraulic motor 14A through the switching valve 87, as shown by the thick solid line in FIG. The regeneration hydraulic motor 14A assists the rotation of the engine 11 using the hydraulic oil flowing out of the accumulator 85.

  Thus, the upper structure 3 is turned by the rotation of the turning hydraulic motor 21 and the boom 4 is raised by the extension of the boom cylinder 7.

  Thereafter, when the turning operation lever is returned to the neutral position, the flow control valve 170 switches to the neutral valve position. All of the hydraulic oil discharged by the first pump 14L flows toward the flow control valve 172L as shown by the thick solid line in FIG. The flow of hydraulic fluid from the PC port of the flow control valve 170 toward the turning hydraulic motor 21 is shut off. The hydraulic oil directed to the flow control valve 172L reaches the bottom side oil chamber of the boom cylinder 7 through the PC port of the flow control valve 172L.

  At this time, the controller 30 outputs a command to the proportional valve 22G to switch the proportional valve 22G to the first position. This is to regenerate the energy of the hydraulic fluid flowing out of the turning hydraulic motor 21.

  The hydraulic fluid flowing out of the port 21L of the turning hydraulic motor 21 is accumulated in the accumulator 85 through the check valve 24L and the proportional valve 22G as shown by the thick dotted line in FIG. The hydraulic oil flowing out of the turning hydraulic motor 21 may be supplied to the regenerative hydraulic motor 14A without being accumulated in the accumulator 85.

  The controller 30 also outputs a command to the proportional valve 52 to switch the proportional valve 52 to the second position. This is because the hydraulic fluid flowing through the return conduit 43C is used to make up (compensate) the hydraulic fluid shortage on the suction side of the turning hydraulic motor at the time of the turning deceleration.

  The hydraulic fluid flowing out of the rod-side oil chamber of the boom cylinder 7 is divided into a portion passing through the return line 43L and a portion passing through the return line 43R, and then merges in the return line 43C. Then, it flows into the port 21R of the turning hydraulic motor 21 through the second makeup pipeline 44B and the common makeup pipeline 44C.

  With this configuration, the hydraulic circuit 100 can prevent the shortage of hydraulic oil on the suction side of the turning hydraulic motor 21 at the time of turning and decelerating even when the turning operation lever is returned to the neutral position during the compound turning operation. Therefore, the occurrence of cavitation on the suction side of the turning hydraulic motor can be prevented.

  With the above configuration, the hydraulic circuit 100 can prevent the occurrence of cavitation on the suction side of the turning hydraulic motor even when utilizing energy of the hydraulic fluid flowing out from the discharge side of the turning hydraulic motor at the time of turning deceleration. . Specifically, even when the hydraulic oil flowing out from the discharge side of the swing hydraulic motor during swing decelerating is accumulated in the accumulator 85 or supplied to the regeneration hydraulic motor 14A, the suction side of the swing hydraulic motor Cavitation can be prevented.

  Further, the hydraulic circuit 100 can supply the hydraulic oil having a pressure higher than that of the hydraulic oil tank T to the discharge side of the hydraulic motor for turning at the time of turning and decelerating. Therefore, the configuration for increasing the pressure of the hydraulic fluid in the return line 43C for make-up, such as a spring-loaded check valve on the most downstream side of the return line 43C, can be eliminated. As a result, the pressure loss of the return line 43C can be reduced to improve the energy saving performance.

  Further, the hydraulic circuit 100 can supply the hydraulic oil having a pressure higher than that of the hydraulic oil tank T to the discharge side of the hydraulic motor for turning at the time of turning and decelerating. Therefore, the structure for raising the pressure of the hydraulic fluid of 43 C of return lines, such as a low pressure accumulator which accumulates the hydraulic fluid for makeup, can be excluded. As a result, the problem that the hydraulic circuit configuration becomes complicated can be avoided.

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

  For example, the above-described hydraulic circuit may be mounted on another construction machine such as a lift mug machine equipped with a swing hydraulic motor or a crane.

  1 ... lower traveling body 2 ... turning mechanism 3 ... upper swing body 4 ... boom 5 ... arm 6 ... bucket 7 ... boom cylinder 8 ... arm cylinder 9 .. -Bucket cylinder 10: Cabin 11: Engine 13: Transmission 14L: First pump 14R: Second pump 14A: Hydraulic motor for regeneration 17: Control valve 18L, 18R ... Negative control throttle 19L, 19R ... Relief valve 21 ... Hydraulic motor for turning 21L, 21R ... Port 22G ... Proportional valve 22L, 22R ... Relief valve 23L, 23R, 24L, 24R ... Check valve 30 ... Controller 40L, 40R ... Center bypass pipeline 42L, 42R ... Parallel pipeline 43C, 43L, 43R ... return pipeline 44 ... turning makeup pipeline 44A ... first makeup pipeline 44B ... second makeup pipeline 44C ... common makeup pipeline 50 , 51 ... check valve 52 ... proportional valve 70 ... proportional valve 71 ... switching valve 85 ... accumulator 87 ... switching valve 170, 171, 172, 172L, 172R, 173, 173L, 173R ... Flow control valve SC ... Swirling hydraulic circuit T ... Hydraulic oil tank

Claims (5)

Hydraulic motor for turning,
A center bypass line in which a flow control valve for the swing hydraulic motor is installed;
A negative control throttle installed in the center bypass pipeline;
And a turning make-up pipeline connecting between the flow control valve and the negative control throttle and a turning hydraulic circuit including the turning hydraulic motor.
Excavator. A return line connecting the hydraulic oil tank and the downstream side of the negative control throttle in the center bypass line;
And a proportional valve installed in the return line,
The turning make-up line includes a line connecting the upstream side of the proportional valve and the turning hydraulic circuit.
The shovel according to claim 1. The proportional valve opens and closes in accordance with the operation content of the turning operation lever.
The shovel according to claim 2. And a separate accumulator for accumulating hydraulic oil discharged from the discharge side port of the turning hydraulic motor at the time of turning deceleration.
The shovel according to any one of claims 1 to 3. And a regenerating hydraulic motor driven by hydraulic fluid discharged from a discharge side port of the swing hydraulic motor at the time of rotational deceleration.
The shovel according to any one of claims 1 to 4.

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