JP2019173949A - Hydraulic circuit of working machine - Google Patents

Abstract

To provide a hydraulic circuit of a working machine which can surely brake a turning motor.SOLUTION: A hydraulic circuit of a working machine comprises: an engine (22); a main pump (23); a pilot pump (27); a turning hydraulic motor (24) driven by a working fluid discharged from the main pump; a direction control valve (41) for controlling a flow direction of the working fluid supplied to the turning hydraulic motor from the main pump; and a flow rate adjustment valve (43) for adjusting a flow rate of the working fluid supplied to the direction control valve from the main pump. The hydraulic circuit also comprises a flow rate adjustment valve control part (70) arranged at a discharge side of the pilot pump, creating command pressure (Pgr') with the discharge pressure of the pilot pump as primary pressure on the basis of an operation of an operation member (37) for braking the turning hydraulic motor, and controlling the flow rate adjustment valve to a direction in which the flow rate adjustment valve is closed by the command pressure.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a hydraulic circuit for a work machine.

  As background art of this technical field, for example, Patent Document 1 discloses that “a motor whose rotation speed is determined based on an operation command, a variable displacement hydraulic pump driven by the prime mover, and a discharge oil from the variable displacement hydraulic pump. A hydraulic circuit of a work machine having a swing motor and a control valve that controls pressure oil supplied from the variable displacement hydraulic pump to the swing motor, and generates a rotation speed signal representing the rotation speed of the prime mover A flow rate control valve that adjusts the flow rate of the pressure oil that is led from the variable displacement hydraulic pump to the control valve, and the flow rate control valve is based on the rotation speed signal that is output by the rotation speed signal generation unit, The differential pressure across the control valve is set to a value corresponding to the rotational speed of the prime mover ”(see summary).

JP 2017-150607 A

  In Patent Document 1, an open center type control valve is used, and when the control valve is in a neutral position, both the primary side port and the secondary side port of the swing motor communicate with each other through the control valve. Therefore, the turning motor continues to rotate due to inertia. In order to brake the turning motor, the turning operation lever is operated in the direction opposite to the turning direction (hereinafter referred to as “reverse lever operation” in this specification). Here, in Patent Document 1, since a difference is provided in the pressure receiving area of the flow control valve, the flow control valve is connected to the tank depending on the pressure balance acting on the control pressure port of the flow control valve when the reverse lever is operated. There may be a case of switching to a position. Then, there is a possibility that the swing motor cannot be braked as intended by the operator.

  An object of the present invention is to provide a hydraulic circuit of a work machine that can reliably brake a swing motor, for example, when a reverse lever is operated.

  In order to achieve the above object, a representative present invention includes an engine, a variable displacement main pump driven by the engine, a fixed displacement pilot pump driven by the engine, and the main pump. A turning hydraulic motor driven by discharged hydraulic oil, a direction control valve that operates by operating an operation member and controls a flow direction of hydraulic oil supplied from the main pump to the turning hydraulic motor, In a hydraulic circuit of a work machine, which is operated by a differential pressure across a directional control valve and adjusts a flow rate of hydraulic oil supplied from the main pump to the directional control valve, a discharge side of the pilot pump The pilot pump discharge pressure is set to a primary pressure based on an operation of the operating member for braking the turning hydraulic motor. It generates a command pressure Te, characterized in that it comprises a flow control valve control unit for controlling the direction to close the flow control valve by the command pressure.

  According to the present invention, for example, when the reverse lever is operated, the swing motor can be reliably braked. Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

It is the schematic of a crane. It is a block diagram of the hydraulic circuit which concerns on 1st Embodiment. It is a block diagram of the hydraulic circuit which concerns on 2nd Embodiment. FIG. 4 is a control block diagram of the controller shown in FIG. 3. It is a block diagram of the hydraulic circuit which concerns on 3rd Embodiment. It is a controller control block diagram shown in FIG.

  Embodiments of the present invention will be described below with reference to the drawings. Each embodiment shown below is an example in which the hydraulic circuit of the working machine according to the present invention is applied to a crane, but the present invention is not limited to this. In addition, about the same structure in each embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

(First embodiment)
With reference to FIGS. 1-2, 1st Embodiment of the hydraulic circuit of the working machine which concerns on this invention is described.

  FIG. 1 is a schematic view of a crane 1. A crane 1 that is an example of a work machine includes a lower traveling body 10 and an upper turning body 20. The lower traveling body 10 includes a pair of crawlers 11, a pair of crawler frames 12, and a pair of traveling hydraulic motors 13 that independently drive and control the crawlers 11. The upper swing body 20 includes a swing frame 21, a cab 6, an engine 22 provided on the swing frame 21, a main pump 23, a pilot pump 27, a swing hydraulic motor 24, and a drive of the swing hydraulic motor 24. A drive mechanism 25 that rotates the upper swing body 20 by force and a control valve unit 26 are provided. In the cab 6, a turning operation lever (operation member) 37 for turning the upper turning body 20 is provided.

  A boom 31 that can be raised and lowered is installed on the upper swing body 20. A sheave (not shown) is provided at the tip of the boom 31, and a suspended load 33 is suspended from a hook (not shown) provided at the tip of a hoisting rope 32 that is hung around the sheave. The upper swing body 20 is driven by a swing hydraulic motor 24 in a desired direction in the forward and reverse directions. The hoisting rope 34 is connected to a pendant rope (not shown). The boom 31 moves up and down by retracting and lifting the hoisting rope 34 with a hoisting winch (not shown). The suspended load 33 is moved up and down by retracting and unwinding the hoisting rope 32 by a unillustrated hoisting winch.

  FIG. 2 is a configuration diagram of the hydraulic circuit 2 according to the first embodiment. The hydraulic circuit 2 includes a main pump 23, a pilot pump 27, a turning hydraulic motor 24 driven by the hydraulic oil discharged from the main pump 23, and a flow direction of the hydraulic oil supplied to the turning hydraulic motor 24. A control valve unit 26 for controlling the flow rate, a pilot relief valve 28 for limiting the upper limit of the discharge pressure of the pilot pump 27, and an engine speed sensing valve unit (referred to as an ESS valve unit) 29 provided on the discharge side of the pilot pump 27 A meter-in pressure selection valve (control pressure selection valve) 46, a reverse rotation determination valve (control pressure switching valve) 47, and a shuttle valve 48 that operate in conjunction with the operation of the turning operation lever 37 (see FIG. 1). .

  In this embodiment, the ESS valve unit 29 (variable throttle 44, pressure control valve 45), meter-in pressure selection valve 46, reverse determination valve 47, and shuttle valve 48 constitute a flow rate control valve control unit 70. As will be described in detail later, the operation of the flow control valve 43 of the control valve unit 26 is controlled by the command pressure Pgr ′ output from the flow control valve controller 70.

  The main pump 23 is driven by the engine 22 and supplies hydraulic oil to the control valve unit 26. The discharge capacity of the main pump 23 is adjusted by a regulator controlled by a controller (not shown). The main pump 23 is a variable displacement hydraulic pump. The pilot pump 27 is driven by the engine 22 and supplies hydraulic oil to the ESS valve unit 29. The pilot pump 27 is a fixed displacement hydraulic pump. Note that the rotational speed of the engine 22 is controlled based on a depression amount of an unillustrated accelerator pedal operated by an operator.

  The control valve unit 26 limits the upper limit of the discharge pressure of the main pump 23 and the direction control valve 41 that controls the flow direction and flow rate of the hydraulic oil (pressure oil) supplied from the main pump 23 to the turning hydraulic motor 24. A relief valve 42 and a flow rate adjustment valve 43 that adjusts the flow rate of hydraulic oil introduced into the direction control valve 41 are provided. The flow rate adjusting valve 43 is installed on an oil passage branched from an oil passage connecting the discharge port of the main pump 23 and the direction control valve 41 and connected to the tank 65.

  The direction control valve 41 has a neutral position 41O in the center shown in the figure, a left position 41A on the left side in the figure, and a right position on the right side in the figure by pilot pressures PiL and PiR generated in response to the operation of the turning operation lever 37 (see FIG. 1). It is switched to an arbitrary position between 41B. When the direction control valve 41 is in the neutral position 41O, the hydraulic oil discharged from the main pump 23 returns to the tank 65 through the bleed-off throttle 41BO. When pilot pressures PiL and PiR are guided to the pilot port of the direction control valve 41, the direction control valve 41 moves toward the left position 41A or the right position 41B, the opening area of the bleed-off throttle 41BO decreases, and the meter-in throttle 41Ia. , 41Ib opening area increases. The hydraulic oil discharged from the main pump 23 is guided to the turning hydraulic motor 24 through the meter-in throttles 41Ia and 41Ib.

  The direction control valve 41 is provided with a port for guiding downstream pressures of the meter-in throttles 41Ia and 41Ib (hereinafter referred to as meter-in throttle downstream pressure) Pc to the flow rate control valve 43. When the direction control valve 41 is in the neutral position 41O, the meter-in throttle downstream pressure Pc is a tank pressure. When the directional control valve 41 is at the left position 41A or the right position 41B, the meter-in throttle downstream pressure Pc is a pressure at which the discharge pressure of the main pump 23 is reduced due to the pressure loss of the meter-in throttles 41Ia and 41Ib.

  The flow rate adjustment valve 43 switches between the closed position 43A and the open position 43B. In the open position 43 </ b> B, a part of the oil discharged from the main pump 23 bypasses the tank 65. In the closed position 43A, the entire amount of oil discharged from the main pump 23 is introduced into the direction control valve 41.

  The switching position of the flow control valve 43 is controlled according to the following three pressures. The first pressure is the discharge pressure Ps of the main pump 23 and is guided to urge the flow rate adjustment valve 43 toward the open position 43B. The second pressure is the meter-in throttle downstream pressure Pc of the direction control valve 41 and is guided so as to urge the flow rate adjustment valve 43 toward the closed position 43A. The third pressure is a command pressure Pgr ′ selected by the shuttle valve 48, and is guided to urge the flow rate adjustment valve 43 toward the closed position 43A.

  The flow rate control valve 43 is configured so that the differential pressure across the meter-in throttles 41Ia and 41Ib of the direction control valve 41, that is, the difference between the discharge pressure Ps of the main pump 23 and the meter-in throttle downstream pressure Pc becomes a value corresponding to the command pressure Pgr ′. It opens and closes and functions as a pressure compensation valve.

  The ESS valve unit 29 has a variable throttle 44 that generates a differential pressure corresponding to the discharge flow rate of the pilot pump 27 and a discharge pressure of the pilot pump 27 as a primary pressure, and the primary pressure according to the differential pressure across the variable throttle 44. And a pressure control valve 45 that generates a regulated first control pressure Pgr. The first control pressure Pgr increases or decreases according to the engine speed.

  The variable throttle 44 switches between the open position 44A and the throttle position 44B based on the discharge pressure Pd of the pilot pump 27 (upstream pressure of the variable throttle 44) Pd and the downstream pressure Pe of the variable throttle 44. Specifically, the discharge pressure Pd of the pilot pump 27 is guided to switch the variable throttle 44 to the open position 44A side, and the downstream pressure Pe of the variable throttle 44 switches the variable throttle 44 to the throttle position 44B side. Led. The spring urges the variable throttle 44 to switch to the throttle position 44B side. The spring has a spring constant such that when the hydraulic oil starts to be discharged from the pilot pump 27, the variable throttle 44 is switched to the open position 44A.

  The variable throttle 44 generates a differential pressure across the pilot pump 27 according to the discharge flow rate, and the open position 44A and the throttle position 44B so that the discharge flow rate of the pilot pump 27 and the differential pressure across the variable throttle 44 are proportional to each other. The opening area at a position between is set. The downstream pressure Pe of the variable throttle 44 is defined by the pilot relief valve 28 so as to be approximately constant.

  The pressure control valve 45 switches between the position 45A and the position 45B based on the upstream pressure Pd and the downstream pressure Pe of the variable throttle 44. When the upstream pressure Pd of the variable throttle 44 is larger than the sum of the downstream pressure Pe of the variable throttle 44 and the first control pressure Pgr, the pressure control valve 45 is switched to the position 45A side, and the upstream pressure Pd of the variable throttle 44 is As a result, the first control pressure Pgr is increased. When the upstream pressure Pd of the variable throttle 44 is smaller than the sum of the downstream pressure Pe of the variable throttle 44 and the first control pressure Pgr, the pressure control valve 45 is switched to the position 45B side and connected to the tank 65. The first control pressure Pgr is decreased. That is, the pressure control valve 45 generates the first control pressure Pgr proportional to the differential pressure across the variable throttle 44 using the downstream pressure Pe of the variable throttle 44 as a primary pressure.

  The meter-in pressure selection valve 46 is switched between the position 46A and the position 46B in conjunction with the operation of the turning operation lever 37. Specifically, when the pilot pressure PiL is input to the pilot port, the meter-in pressure selection valve 46 is switched to the position 46A, and the meter-in oil passage (the turning hydraulic motor 24 and the main pump 23 are connected to the turning hydraulic motor 24). The pressure PL of the connecting oil passage) is output as the second control pressure Pmi. On the other hand, when the pilot pressure PiR is input to the pilot port, the meter-in pressure selection valve 46 switches to the position 46B and outputs the pressure PR of the meter-in oil passage of the turning hydraulic motor 24 as the second control pressure Pmi.

  The reverse rotation determination valve 47 is operated by a differential pressure between the second control pressure Pmi output from the meter-in pressure selection valve 46 and the discharge pressure Ps of the main pump 23. When the second control pressure Pmi is greater than the discharge pressure Ps of the main pump 23 (Pmi> Ps), the reverse rotation determination valve 47 is switched to the position 47A, and the downstream pressure of the variable throttle 44 (downstream pressure of the ESS valve unit 29) Pe is set. Output as the third control pressure Pf. On the other hand, when the second control pressure Pmi is lower than the discharge pressure Ps of the main pump 23 (Pmi <Ps), the reverse rotation determination valve 47 switches to the position 47B and outputs the tank pressure as the third control pressure Pf.

  The shuttle valve 48 selects a control pressure on the high pressure side from the first control pressure Pgr generated by the ESS valve unit 29 and the third control pressure Pf output from the reverse rotation determination valve 47, and the selected high pressure side Is output to the flow rate adjustment valve 43 as a command pressure Pgr ′.

(Hydraulic circuit operation)
Next, the operation of the hydraulic circuit 2 according to the first embodiment will be described.

  When the turning operation lever 37 is normally operated to switch the direction control valve 41 to the left position 41A or the right position 41B, the turning hydraulic motor 24 starts rotating. The meter-in pressure selection valve 46 outputs the pressures PL and PR of the meter-in oil passage of the direction control valve 41 as the second control pressure Pmi according to the pilot pressures PiL and PiR of the direction control valve 41. The reverse determination valve 47 compares the discharge pressure Ps of the main pump 23 with the second control pressure Pmi output from the meter-in pressure selection valve 46. When the swing hydraulic motor 24 is rotating normally, the discharge pressure Ps of the main pump 23 is higher than the second control pressure Pmi (Ps> Pmi), so the reverse rotation determination valve 47 outputs the tank pressure as the third control pressure Pf. .

  When the third control pressure Pf output from the reverse determination valve 47 is the tank pressure, the shuttle valve 48 selects the first control pressure Pgr output from the ESS valve unit 29, and uses the first control pressure Pgr as the command pressure Pgr ′. Output. As a result, the first control pressure Pgr acts on the flow control valve 43, and the flow control valve 43 has a differential pressure across the meter-in throttles 41Ia and 41Ib of the direction control valve 41 equal to or lower than a pressure proportional to the first control pressure Pgr. The upper limit value of the differential pressure across the front and rear is controlled so that The fact that the differential pressure across the meter-in throttles 41Ia and 41Ib is below a predetermined upper limit value means that the direction control valve 41 has a flow rate limit value proportional to the opening area. Therefore, the flow rate adjusting valve 43 has a function of setting the upper limit value of the passing flow rate of the direction control valve 41 to a flow rate proportional to the opening area of the meter-in throttles 41Ia and 41Ib and the rotational speed of the engine 22.

  If the direction control valve 41 is switched (returned) from the left position 41A or the right position 41B to the neutral position 41O while the turning hydraulic motor 24 is rotating, both ports of the turning hydraulic motor 24 communicate with each other via the direction control valve 41. Therefore, the turning hydraulic motor 24 continues to rotate due to inertia. In order to brake the turning hydraulic motor 24 in this state, the turning operation lever 37 is operated in the direction opposite to the rotation direction of the turning hydraulic motor 24 so that the hydraulic oil is discharged from the turning hydraulic motor 24. The direction control valve 41 is temporarily switched (reverse lever operation) so that the port on the other side is in communication with the main pump 23. Then, since the hydraulic oil discharged from the turning hydraulic motor 24 is controlled to a high pressure with the relief set pressure of the relief valve 42 as an upper limit in accordance with the operation amount of the direction control valve 41, the turning hydraulic motor 24 includes Braking torque is generated.

  When the reverse lever operation is performed in this way, the pressure in the meter-in oil passage of the turning hydraulic motor 24 becomes higher than the discharge pressure Ps of the main pump 23, and therefore the second control pressure Pmi output from the meter-in pressure selection valve 46 is also the main. It becomes higher than the discharge pressure Ps of the pump 23. As a result, the second control pressure Pmi of the meter-in pressure selection valve 46 becomes larger than the discharge pressure Ps of the main pump 23 (Pmi> Ps), and the reverse rotation determination valve 47 uses the downstream pressure Pe of the variable throttle 44 as the third control pressure Pf. Output. Since the third control pressure Pf is larger than the first control pressure Pgr, the shuttle valve 48 outputs the third control pressure Pf as the command pressure Pgr ′. Since the third control pressure Pf equal to the downstream pressure Pe of the variable throttle 44 acts on the flow rate adjustment valve 43, the flow rate adjustment valve 43 is held at the closed position 43A.

  As a result, the pressure in the meter-in oil passage of the turning hydraulic motor 24 does not drop when the reverse lever is operated, and the rotating turning hydraulic motor 24 can be reliably braked. More specifically, the discharge pressure Ps of the main pump 23 and the two port pressures PL and PR of the swing hydraulic motor 24 are the opening area of the direction control valve 41, the discharge amount of the main pump 23, and the swing of the upper swing body 20. Since it is determined by the speed and the like, in the case of a configuration in which the downstream pressure Pe of the variable throttle 44 cannot be applied to the flow rate adjustment valve 43 from the reverse rotation determination valve 47 as in the prior art, depending on the operating conditions, the flow rate during reverse lever operation There may be a case where the control valve 43 temporarily switches to the open position 43B. When the flow control valve 43 is switched to the open position 43B, the meter-in oil passage connecting the main pump 23 and the turning hydraulic motor 24 communicates with the tank 65 and the pressure in the meter-in oil passage decreases, so the turning hydraulic motor 24 The braking performance of the is reduced.

  On the other hand, in the present embodiment, the reverse rotation determination valve 47 switches to output the downstream pressure Pe of the variable throttle 44 as the third control pressure Pf by the second control pressure Pmi output from the meter-in pressure selection valve 46. The flow control valve 43 is held at the closed position 43A by the third control pressure Pf, so that the turning hydraulic motor 24 can be reliably braked.

  As described above, in the first embodiment, the upper-part turning body 20 can be driven to turn at a speed corresponding to the engine rotational speed, and even if the pump discharge amount fluctuates due to fluctuations in the engine rotational speed, it is always possible. A wide operating range can be secured. Further, as described above, since the flow rate adjusting valve 43 is reliably held at the closed position 43A during the reverse lever operation, it is possible to suppress the occurrence of a shock during the reverse lever operation.

(Second Embodiment)
Next, a second embodiment of a hydraulic circuit for a work machine according to the present invention will be described with reference to FIGS. FIG. 3 is a configuration diagram of the hydraulic circuit 202 according to the second embodiment. The second embodiment shown in FIG. 3 is different from the first embodiment in the configuration of the flow rate control valve control unit 170 that controls the flow rate control valve 43. Therefore, the difference will be mainly described below.

  As shown in FIG. 3, in the hydraulic circuit 202 according to the second embodiment, the flow control valve control unit 170 is configured by the controller 51, the rotation speed sensor 52, the electromagnetic proportional pressure reducing valve 53, and the pressure sensors 54 to 58. Has been. The electromagnetic proportional pressure reducing valve 53 outputs the command pressure Pgr ′ corresponding to the electric signal from the controller 51 to the flow rate adjusting valve 43 using the discharge pressure Pd of the pilot pump 27 as the primary pressure.

  The controller 51 includes a rotation speed sensor 52 that detects the rotation speed of the engine 22, a pressure sensor 54 that detects a left pilot pressure PiL corresponding to the left turn operation of the turning operation lever 37, and a right turn operation of the turning operation lever 37. Pressure sensor 55 for detecting the right pilot pressure PiR, pressure sensor 56 for detecting the left port pressure of the turning hydraulic motor 24 (pressure on the meter-in side when turning left / hereinafter referred to as the left turning pressure) PL, turning hydraulic motor Each detection from a pressure sensor 57 that detects 24 right port pressure PR (pressure on the meter-in side during right turn / hereinafter referred to as right turn pressure) PR and a pressure sensor 58 that detects the discharge pressure Ps of the main pump 23. A signal is input, and an electric signal for driving the electromagnetic proportional pressure reducing valve 53 is output based on each detection signal.

  Next, details of the control processing of the controller 51 will be described. FIG. 4 is a control block diagram showing the contents of control performed inside the controller. As shown in FIG. 4, the engine speed Neng detected by the speed sensor 52 is referred to by referring to the actual speed-target differential pressure table 101 in which the actual speed of the engine 22 and the target differential pressure PGR are defined. The corresponding target differential pressure PGR is output to the selector 108.

  A difference ΔPi between the left pilot pressure PiL detected by the pressure sensor 54 and the right pilot pressure PiR detected by the pressure sensor 55 is calculated by the adder 102, and the calculated difference ΔPi is output to the switch 103. . The switch 103 outputs the left turning pressure PL detected by the pressure sensor 56 when the difference ΔPi is larger than 0 (ΔPi> 0), and the pressure sensor 57 when the difference ΔPi is 0 or less (ΔPi ≦ 0). The detected right turning pressure PR is output.

  The adder 104 calculates the difference Δ between the selectively output left turning pressure PL or right turning pressure PR and the discharge pressure Ps of the main pump 23 detected by the pressure sensor 58. The difference ΔP is output to the switch 107. The switch 107 receives the constant 0 from the output unit 105 and the constant 5 from the output unit 106. When the difference ΔP input from the adder 104 is larger than 0 (ΔP> 0), the switch 107 is The constant 0 is output to the selector 108. When the difference ΔP is 0 or less (ΔP ≦ 0), the switch 107 outputs the constant 5 to the selector 108. The constant output by the output device 106 is, for example, the set pressure of the pilot relief valve 28.

  The selector 108 selects the maximum value among the target differential pressure PGR and the output (0 or 5) of the switching unit 107 and outputs it to the solenoid output unit 109. The solenoid output unit 109 converts the value output from the selector 108 into a drive signal and outputs it to the electromagnetic proportional pressure reducing valve 53. Thus, in the second embodiment, the output signal generation performed by the system including the ESS valve unit 29, the meter-in pressure selection valve 46, the reverse rotation determination valve 47, and the shuttle valve 48 shown in FIG.

  According to the second embodiment, similarly to the first embodiment, since the flow rate adjustment valve 43 is reliably held at the closed position 43A during the reverse lever operation, it is possible to suppress the occurrence of a shock during the reverse lever operation. In addition, since the control of the flow control valve 43 is electrically realized, the number of parts is reduced compared to the first embodiment, and the configuration of the hydraulic circuit can be simplified.

(Third embodiment)
Next, a third embodiment of the hydraulic circuit for the working machine according to the present invention will be described with reference to FIGS. FIG. 5 is a configuration diagram of a hydraulic circuit 302 according to the third embodiment. The third embodiment shown in FIG. 5 is partially different from the second embodiment in the configuration of the flow rate control valve controller 270 that controls the flow rate control valve 43. Therefore, the following description will focus on the differences.

  As shown in FIG. 5, in the hydraulic circuit 302 according to the third embodiment, the controller 51, the rotation speed sensors 52 and 60, the electromagnetic proportional pressure reducing valve 53, and the pressure sensors 54 and 55 are used. Is configured. The electromagnetic proportional pressure reducing valve 53 outputs a command pressure Pgr ′ corresponding to an electric signal (drive signal) from the controller 51 to the flow rate adjusting valve 43 using the discharge pressure Pd of the pilot pump 27 as a primary pressure.

  The controller 51 includes a rotation speed sensor 52 that detects the rotation speed of the engine 22, a pressure sensor 54 that detects a left pilot pressure PiL corresponding to the left turn operation of the turning operation lever 37, and a right turn operation of the turning operation lever 37. The detection signals from the pressure sensor 55 for detecting the right pilot pressure PiR and the rotation speed sensor 60 for detecting the rotation speed of the upper swing body 20 connected to the turning hydraulic motor 24 and rotating are input. Based on the above, an electric signal for driving the electromagnetic proportional pressure reducing valve 53 is output.

  Next, details of the control processing of the controller 51 will be described. FIG. 6 is a control block diagram showing the contents of control performed inside the controller. As shown in FIG. 6, the engine speed Neng detected by the speed sensor 52 is referred to by referring to the actual speed-target differential pressure table 101 in which the actual speed of the engine 22 and the target differential pressure PGR are defined. The corresponding target differential pressure PGR is output to the selector 108.

  A difference ΔPi between the left pilot pressure PiL detected by the pressure sensor 54 and the right pilot pressure PiR detected by the pressure sensor 55 is calculated by the adder 102, and the calculated difference ΔPi is output to the integrator 110. .

  The switch 111 receives the constant 0 from the output device 105 and the constant 5 from the output device 106. When the product Dir input from the accumulator 110 is smaller than 0 (Dir <0), the switch 111 The constant 0 is output to the selector 108. When the product Dir is 0 or more (Dir ≧ 0), the switch 111 outputs the constant 5 to the selector 108. The point that the constant output by the output device 106 is the set pressure of the pilot relief valve 28 is the same as in the second embodiment.

  The selector 108 selects the maximum value among the target differential pressure PGR and the output (0 or 5) of the switch 111 and outputs it to the solenoid output unit 109. The solenoid output unit 109 converts the value output from the selector 108 into a drive signal and outputs it to the electromagnetic proportional pressure reducing valve 53. As described above, in the third embodiment, as in the second embodiment, the output signal generation performed by the system including the ESS valve unit 29, the meter-in pressure selection valve 46, the reverse rotation determination valve 47, and the shuttle valve 48 shown in FIG. It is realized electrically.

  According to the third embodiment, similarly to the first embodiment, since the flow rate adjustment valve 43 is reliably held at the closed position 43A during the reverse lever operation, it is possible to suppress the occurrence of a shock during the reverse lever operation. In addition, since the control of the flow control valve 43 is electrically realized, the number of parts is reduced compared to the first embodiment, and the configuration of the hydraulic circuit can be simplified.

  In addition, embodiment mentioned above is an illustration for description of this invention, and is not the meaning which limits the scope of the present invention only to those embodiment. Those skilled in the art can implement the present invention in various other modes without departing from the gist of the present invention.

1 Crane (work machine)
2, 202, 302 Hydraulic circuit 22 Engine 23 Main pump 24 Turning hydraulic motor 27 Pilot pump 37 Turning operation lever (operation member)
41 Directional control valve 43 Flow control valve 44 Variable throttle 45 Pressure control valve 46 Meter-in pressure selection valve (control pressure selection valve)
47 Reverse determination valve (control pressure switching valve)
48 Shuttle valve 51 Controller 52 Speed sensor (first speed sensor)
53 Proportional pressure reducing valve 54,55 Pressure sensor (first pressure sensor)
56,57 Pressure sensor (second pressure sensor)
58 Pressure sensor (third pressure sensor)
60 RPM sensor (second RPM sensor)
70, 170, 270 Flow control valve control unit Pgr 'command pressure Pgr first control pressure Pmi second control pressure Pf third control pressure Pe downstream pressure of variable throttle Ps discharge pressure of main pump

Claims (4)

Engine,
A variable displacement main pump driven by the engine;
A fixed displacement pilot pump driven by the engine;
A turning hydraulic motor driven by hydraulic oil discharged from the main pump;
A direction control valve that operates by operating an operation member and controls a flow direction of hydraulic oil supplied from the main pump to the turning hydraulic motor;
In a hydraulic circuit of a work machine, which is operated by a differential pressure across the direction control valve and includes a flow rate adjustment valve that adjusts the flow rate of hydraulic oil supplied from the main pump to the direction control valve.
Based on the operation of the operating member provided on the discharge side of the pilot pump for braking the turning hydraulic motor, a command pressure is generated using a discharge pressure of the pilot pump as a primary pressure, and the command pressure A hydraulic circuit for a working machine, comprising a flow rate control valve control unit that controls the flow rate control valve in a closing direction. In the hydraulic circuit of the work machine according to claim 1,
The flow control valve control unit is
A variable throttle for generating a differential pressure according to the discharge flow rate of the pilot pump;
A pressure control valve that generates a first control pressure according to a differential pressure across the variable throttle;
A control pressure selection valve that operates in conjunction with the operation of the operation member and outputs the pressure on the meter-in side of the turning hydraulic motor as a second control pressure;
When the second control pressure is greater than the discharge pressure of the main pump when the second control pressure is greater than the discharge pressure of the main pump. A control pressure switching valve that outputs a downstream pressure as a third control pressure, and outputs a tank pressure as the third control pressure when the second control pressure is smaller than a discharge pressure of the main pump;
A shuttle valve that outputs, as the command pressure, a control pressure on the high side of the third control pressure output from the control pressure switching valve and the first control pressure generated by the pressure control valve; A hydraulic circuit of a work machine characterized by including. In the hydraulic circuit of the work machine according to claim 1,
The flow control valve control unit is
A first rotational speed sensor for detecting the rotational speed of the engine;
A first pressure sensor for detecting a pilot pressure acting on the directional control valve;
A second pressure sensor for detecting the pressure of the hydraulic oil port of the turning hydraulic motor;
A third pressure sensor for detecting a discharge pressure of the main pump;
An electromagnetic proportional pressure reducing valve for generating the command pressure;
A controller that inputs detection signals of the first rotation speed sensor, the first pressure sensor, the second pressure sensor, and the third pressure sensor, and outputs a drive signal to the electromagnetic proportional pressure reducing valve. A hydraulic circuit of a work machine characterized by the above. In the hydraulic circuit of the work machine according to claim 1,
The flow control valve control unit is
A first rotational speed sensor for detecting the rotational speed of the engine;
A second rotational speed sensor for detecting the rotational speed on the output side of the turning hydraulic motor;
A first pressure sensor for detecting a pilot pressure acting on the directional control valve;
An electromagnetic proportional pressure reducing valve for generating the command pressure;
A controller that inputs detection signals of the first rotation speed sensor, the second rotation speed sensor, and the first pressure sensor and outputs a drive signal to the electromagnetic proportional pressure reducing valve. Hydraulic circuit of work machine.

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