JP5978176B2 - Work machine - Google Patents

Description

  The present invention relates to a work machine capable of regenerating energy of hydraulic oil discharged from a hydraulic actuator and driving the hydraulic actuator with the regenerated energy.

  Conventionally, a system for driving a hydraulic actuator of this type of work machine has a high driving efficiency, and therefore a configuration in which one hydraulic pump for driving each hydraulic actuator is attached to each hydraulic actuator is known. It has been. However, this configuration requires the number of hydraulic pumps corresponding to the number of hydraulic actuators to be used, and each of these hydraulic pumps must be directly connected to the engine that is the prime mover. Tends to be used for so-called large hydraulic excavators.

  On the other hand, a configuration having a hydraulic pump driven by hydraulic oil discharged from a predetermined hydraulic actuator and energy storage means is known. In this configuration, it is not necessary to connect the hydraulic pump directly to the engine. Therefore, it is relatively easy to secure the installation space for the hydraulic pump, and it is not easy to secure the installation space for a plurality of hydraulic pumps. Can be used.

  And the prior art which has this kind of hydraulic pump is disclosed by patent document 1, for example. The prior art disclosed in Patent Document 1 is configured such that a pressure accumulator is connected to a hydraulic pump directly connected to a prime mover, and energy by hydraulic oil discharged from a hydraulic actuator, that is, regenerative energy is stored in the pressure accumulator. Yes. Furthermore, a variable displacement hydraulic pump motor is connected to the accumulator, and the variable displacement hydraulic pump motor includes two units that rotate in synchronization with the variable displacement hydraulic pump motor. A fixed displacement hydraulic pump motor is installed.

Japanese Patent Laid-Open No. 11-117907

  In the prior art disclosed in Patent Document 1 described above, when the hydraulic actuator is stopped, one of the fixed displacement type hydraulic pump motors is rotationally driven by the hydraulic oil discharged from the hydraulic actuator, and this fixed displacement type Hydraulic oil pumped by driving the variable displacement hydraulic pump motor in synchronization with the hydraulic pump motor is stored in the accumulator. When the hydraulic actuator is driven, the variable displacement hydraulic pump motor is driven to rotate by the hydraulic oil stored in the pressure accumulator, and either one of the fixed displacements is synchronized with the variable displacement hydraulic pump motor. The hydraulic actuator can be driven by hydraulic fluid that is pumped by driving the hydraulic pump motor of the mold.

  However, in order to drive one hydraulic actuator, in addition to one variable displacement type hydraulic pump motor, two fixed displacement type hydraulic pump motors are required, and a total of three hydraulic pump motors are required. is necessary. For this reason, the space for installing these three hydraulic pump motors must be secured, and the mountability is not excellent.

  The present invention has been made from the above-described actual state of the prior art, and an object thereof is to provide a work machine having excellent mountability.

In order to achieve this object, the present invention includes a machine body, a work machine provided in the machine body, and a hydraulic actuator having a first connection part and a second connection part to drive the work machine. 1st hydraulic pump which is connected to the 1st connection part and 2nd connection part of the said hydraulic actuator, and has a pump function which pumps hydraulic fluid, and a motor function driven by the supplied hydraulic fluid A motor and a motor function that rotates in synchronization with the rotation of the first hydraulic pump motor and is connected to the first connection portion of the hydraulic actuator to pump hydraulic oil and to be driven by the supplied hydraulic oil A variable displacement type second hydraulic pump motor having a hydraulic pressure, and an energy which is attached to the second hydraulic pump motor and which is supplied from the second hydraulic pump motor. Wherein a蓄energy unit, and a control unit for controlling the drive of the second hydraulic pump motor, between the second connecting portion and the first hydraulic pump motor of the hydraulic actuator, and a first connecting portion of the hydraulic actuator A flow rate adjusting unit attached between the first hydraulic pump motor and the second hydraulic pump motor , wherein the control device detects an operation state of the hydraulic actuator; and the hydraulic actuator A state quantity detection unit that detects a state quantity of the hydraulic actuator and a pressure detection unit that detects a pressure on the first connection part side of the hydraulic actuator, and the operation state detection unit, the state quantity detection unit, and the pressure detection unit Based on each detected information detected, the capacity | capacitance of the said 2nd hydraulic pump motor and the flow volume of the said flow volume adjustment part are controlled, It is characterized by the above-mentioned.

  According to the present invention configured as described above, since the regenerative energy obtained through the second hydraulic pump motor can be stored in the energy storage unit, the first or second hydraulic pump motor rotates in accordance with the drive of the hydraulic actuator. Thus, the hydraulic oil is supplied to one of the first and second connection portions of the hydraulic actuator, and the hydraulic oil is discharged from the other of the first and second connection portions. Therefore, by using these two first and second hydraulic pump motors, hydraulic oil can be supplied and discharged in accordance with the drive of the hydraulic actuator, so the number of hydraulic pump motors can be reduced, and the mountability is improved. be able to.

Further , even when the hydraulic oil flow rate is insufficient on either the first or second connection side of the hydraulic actuator, the flow rate adjustment unit is used to connect the second connection unit of the hydraulic actuator and the first hydraulic pump motor. The hydraulic actuator can be appropriately driven by adjusting the flow rate of the hydraulic fluid between the first connection portion of the hydraulic actuator and the first hydraulic pump motor and the second hydraulic pump motor. Therefore, even if the number of installed hydraulic pump motors is reduced, the hydraulic actuator can be appropriately driven.

The operation state of the hydraulic actuator detected by the operation state detection unit, the state amount of the hydraulic actuator detected by the state amount detection unit, and the first connection portion side of the hydraulic actuator detected by the pressure detection unit The hydraulic actuator can be driven more appropriately by controlling the capacity of the second hydraulic pump motor and the flow rate of the flow rate adjusting unit with the control device based on the detection information about the pressure.

  According to the present invention, since the regenerative energy obtained through the second hydraulic pump motor can be stored in the energy storage unit, the first or second hydraulic pump motor rotates according to the driving of the hydraulic actuator, so that the hydraulic actuator The hydraulic oil is supplied to one of the first and second connection portions, and the hydraulic oil is discharged from the other of the first and second connection portions. With this configuration, the present invention uses the regenerative energy stored in the energy storage unit to drive these two first and second hydraulic pump motors, thereby supplying and discharging hydraulic oil according to the drive of the hydraulic actuator. Therefore, not only the conventional energy saving performance can be obtained, but also the number of installed hydraulic pump motors can be reduced and the mountability can be improved. Problems, configurations, and effects other than those described above will be made clear from the following description of embodiments.

1 is a schematic side view showing a hydraulic excavator that is an example of a work machine according to a first embodiment of the present invention. It is the schematic which shows the drive device for driving the said hydraulic shovel. It is the schematic which shows the principal part structure of the control apparatus of the said drive device. It is a flowchart which shows the control procedure of the said control apparatus. It is a schematic side view which shows the state at the time of jack-up operation | movement of the said hydraulic shovel. It is the schematic which shows the drive device for driving the hydraulic shovel which is an example of the working machine which concerns on 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a schematic side view showing a hydraulic excavator that is an example of a work machine according to a first embodiment of the present invention. FIG. 2 is a schematic diagram showing a drive device for driving the hydraulic excavator. FIG. 3 is a schematic diagram illustrating a configuration of a main part of the control device of the driving device.

<Overall configuration>
As shown in FIG. 1, a hydraulic excavator 1 as a work machine according to a first embodiment of the present invention includes a lower traveling body having a pair of left and right traveling devices 2c and 2d driven by a pair of traveling motors 2a and 2b. 2 and an upper swing body 4 as a machine body attached to the lower traveling body 2 via a swing device 3 so as to be pivotable. The upper swing body 4 is attached on the lower traveling body 2 via a swing motor 3 a constituting the swing device 3.

  A driver's cab 4 b is provided on the front side of the upper swing body 4, and an engine room 4 c is provided at an intermediate portion of the upper swing body 4. A counterweight 4d is attached to the rear side of the engine chamber 4c, and a front work machine 5 capable of excavation work or the like is attached to the front side of the upper swing body 4 so as to be rotatable in the vertical direction. The front work machine 5 includes a boom 5a, one end of which is pivotally connected to the upper swing body 4 so as to be able to suppress wrinkles, and an arm 5b, which is pivotally connected to the tip of the boom 5a. The bucket 5d is rotatably connected to the tip of the arm 5b through a four-bar linkage mechanism 5c.

  Further, the front work machine 5 includes a pair of boom cylinders 6 that are hydraulic actuators for supporting and driving the boom 5a up and down, and an arm cylinder 7 for supporting and operating the arms 5b up and down. And a bucket cylinder 8 for supporting and operating the bucket 5d so as to be movable up and down. The boom cylinder 6 has a cylinder tube 6a side end, which is a first connection portion on the base end side, fixed to the front upper surface of the upper swing body 4 so as to be rotatable, and a cylinder rod 6b which is a second connection portion on the front end side. The side end is fixed to the side surface of the base end of the boom 5a so as to be rotatable. The end of the cylinder tube 7a on the base end side of the arm cylinder 7 is fixed to the upper surface of the middle part of the boom 5a so that the arm cylinder 7 is pivotable. It is fixed to the part so that rotation is possible. Further, the bucket cylinder 8 has an end on the cylinder tube 8a side on the base end side fixed to the upper surface of the arm 5b so as to be rotatable, and an end on the cylinder rod 8b side on the distal end side rotated on the four-bar linkage mechanism 5c. It is attached as possible.

<Drive device>
Next, the excavator 1 is driven by the driving device 11 shown in FIG. The drive device 11 is a drive system that regenerates the energy of the return hydraulic oil from the boom cylinder 6 and can drive the boom cylinder 6 by reusing the regenerated energy. Specifically, the drive device 11 includes an engine 12 that is a prime mover, a main pump 13 that is a hydraulic pump driven by the engine 12, and a control valve device 14 that controls the flow of hydraulic oil discharged from the main pump 13. And.

  The control valve device 14 controls an arm control valve 14a for controlling the drive of the arm cylinder 7, a bucket control valve 14b for controlling the drive of the bucket cylinder 8, and a drive of the swing motor 3a. And a turning control valve 14c. These arm, bucket and swivel control valves 14a, 14b and 14c are attached to a discharge oil passage 11a which is a hydraulic circuit on the discharge side of the main pump 13, and these arm, bucket and swivel control valves 14a, A discharge oil passage 11 b which is a hydraulic circuit on the discharge side of 14 b and 14 c is connected to the hydraulic oil tank 10.

Further, the drive device 11 includes a fixed displacement type first hydraulic pump motor 20 connected to the head side which is the cylinder tube 6a side of the boom cylinder 6 and the rod side which is the cylinder rod 6b side. The first hydraulic pump motor 20 is configured to have a pump function for pumping hydraulic oil and to have a motor function that is rotationally driven by the supplied hydraulic oil. Further, a variable displacement type second hydraulic pump motor 21 that rotates in synchronization with the first hydraulic pump motor 20 is attached to the first hydraulic pump motor 20. The second hydraulic pump motor 21 also has a pump function for pumping hydraulic oil and a motor function that is rotationally driven by the supplied hydraulic oil. The second hydraulic pump motor 21 is connected to the head side of the boom cylinder 6. The second hydraulic pump motor 21 is provided with a pressure accumulator 19 that is an accumulator as an energy storage unit that stores the pressure of the hydraulic oil supplied from the second hydraulic pump motor 21, that is, energy.

The pressure accumulator 19 is connected to the discharge oil passage 11 a of the main pump 13. A flow rate adjusting valve 24 that is an on / off valve for supplying hydraulic oil discharged from the main pump 13 to the pressure accumulator 19 is attached to the discharge oil passage 11 a between the pressure accumulator 19 and the main pump 13. Further, a pressure sensor 25 for detecting the pressure in the pressure accumulator 19 is attached between the flow rate adjusting valve 24 and the second hydraulic pump motor 21. The flow rate adjusting valve 24 and the pressure sensor 25 are connected to a vehicle body controller 30 as a control device, and when the pressure in the pressure accumulator 19 detected by the pressure sensor 25 falls below a predetermined threshold value, The flow control valve 24 is opened by the controller 30, and hydraulic oil discharged from the main pump 13 is supplied to the pressure accumulator 19 through the flow control valve 24.

  Further, an oil passage 11c, which is a hydraulic circuit between the rod side of the boom cylinder 6 and the first hydraulic pump motor 20, serves as a flow rate adjusting unit that is an on / off switching valve having an open position 26a and a closed position 26b. A first flow rate adjustment valve 26 is attached. Further, an oil passage 11d that is a hydraulic circuit between the head side of the boom cylinder 6 and the first and second hydraulic pump motors 20 and 21 is also an on / off type switching valve having an open position 27a and a closed position 27b. A second flow rate adjustment valve 27 as a certain flow rate adjustment unit is attached. Here, the boom cylinder 6 is a closed circuit that does not use a so-called throttle by oil passages 11 c and 11 d through the first hydraulic pump motor 20.

  Further, a pilot check valve 23 is attached to the oil passage 11d. The pilot check valve 23 is connected to the vehicle body controller 30 and is controlled to open and close by an operation signal output from the vehicle body controller 30. That is, the pilot check valve 23 prevents and prevents the boom 5a from being lowered by the hydraulic oil discharged from the head side of the boom cylinder 6 due to the weight of the boom 5a or the like while the drive of the boom cylinder 6 is stopped. To do. A first pressure sensor 31a for detecting the operating oil pressure in the oil passage 11e is attached to the oil passage 11e that is a hydraulic circuit between the pilot check valve 23 and the head side of the boom cylinder 6. . The first pressure sensor 31 a detects the hydraulic pressure on the head side of the boom cylinder 6.

On the other hand, the cab 4b of the hydraulic excavator 1, the boom cylinder 6, arm cylinder 7, an operation device for operating the bucket cylinder 8 and the turning motor 3a, boom operation lever 6c, arm control lever 7c, bucket An operation lever 8c and a turning operation lever 3c are attached. Each of these operating levers 6c, 7c, 8c, 3c is connected to a pilot pump 15 that generates a pilot pressure in response to the operation of these operating levers 6c, 7c, 8c, 3c. The arm control valve 14a is controlled to be switched by operating the arm control lever 7c, the bucket control valve 14b is controlled to be switched by operating the bucket operating lever 8c, and the swing control valve is controlled by operating the swing operating lever 3c. 14c is controlled to be switched.

  Here, the boom operation lever 6c is an operation state detection unit capable of detecting the operation state of the boom cylinder 6, and is a second for detecting the pilot pressure output in response to the operation of the boom operation lever 6c. A pressure sensor 31b and a third pressure sensor 31c are attached. The second and third pressure sensors 31b and 31c are connected to the vehicle body controller 30, and a lever output signal corresponding to the pilot pressure detected by the second and third pressure sensors 31b and 31c is output to the vehicle body controller 30. Sent.

  Next, the second hydraulic pump motor 21 includes a regulator 22 for adjusting the tilt angle (tilt position) of the swash plate 21a of the second hydraulic pump motor 21, that is, the tilt capacity. A displacement sensor 28 for detecting the amount of displacement of the swash plate 21 a by the regulator 22 is attached to the regulator 22. The displacement sensor 28 is a regulator position detection unit for detecting the position of the regulator 22, is connected to the vehicle body controller 30, and the displacement amount detected by the displacement sensor 28 is sent to the vehicle body controller 30. Further, between the first and second hydraulic pump motors 20, 21, a rotation sensor 32, which is a rotation speed detection unit for detecting the rotation speeds of the first and second hydraulic pump motors 20, 21, is attached. ing. The rotation sensor 32 is connected to the vehicle body controller 30, and the rotation amount detected by the rotation sensor 32 is sent to the vehicle body controller 30. Here, the displacement sensor 28 and the rotation sensor 32 are state quantity detection units for detecting the state quantity of the boom cylinder 6.

  The vehicle body controller 30 calculates the control amount of the regulator 22 based on detection signals sent from the displacement sensor 28, the second or third pressure sensors 31b and 31c, and the rotation sensor 32, and this calculation is performed. An output signal based on the controlled variable is sent to the regulator 22, and the tilt angle of the swash plate 21a by the regulator 22 is controlled. As a result, the tilt capacity of the second hydraulic pump motor 21 is controlled, and the first hydraulic pump motor 20 is driven and the boom cylinder 6 is driven in accordance with the control of the tilt capacity of the second hydraulic pump motor 21.

  Further, the vehicle body controller 30 controls the switching of the first and second flow rate adjusting valves 26 and 27 based on detection signals sent from the first pressure sensor 31a and the second or third pressure sensors 31b and 31c. And an output signal based on the calculated control is sent to the first and second flow rate adjusting valves 26, 27, and the driving of the first and second flow rate adjusting valves 26, 27 is controlled. As a result, the opening and closing drive of the first and second flow rate adjusting valves 26 and 27 is controlled, and the excess and deficiency of the hydraulic fluid flow rate on the head side and the rod side of the boom cylinder 6 are adjusted.

  Specifically, as shown in FIG. 3, the vehicle body controller 30 includes a target speed calculator 40a for calculating the target speed of the boom 5a, an actual speed calculator 40b for calculating the actual speed of the boom 5a, A tilt position calculator 40c for calculating the tilt position of the swash plate 21a of the second hydraulic pump motor 21 is provided. The vehicle body controller 30 detects the pilot pressure based on the operation of the boom operation lever 6c by the second or third pressure sensors 31b and 31c, and outputs a lever output signal corresponding to the detected pilot pressure to the target speed calculation unit. Input to 40a. The target speed calculation unit 40a calculates and outputs a target speed for driving the boom 5a based on the input lever output signal.

Further, the vehicle body controller 30 detects the tilting position, which is the displacement of the regulator 22 of the second hydraulic pump motor 21 by the displacement sensor 28, the rotational speed of the first hydraulic pump motor 20 in time Utatese capacitors 32 And an output signal corresponding to the detected tilt position and rotation speed is input to the actual speed calculation unit 40b. The actual speed calculation unit 40b calculates and outputs an actual speed, which is the actual driving speed of the boom 5a, based on each input output signal.

  Further, the vehicle body controller 30 compares the target speed output from the target speed calculation unit 40a with the actual speed output from the actual speed calculation unit 40b, and inputs the compared value to the tilt position calculation unit 40c. . The tilt position calculation unit 40c calculates the tilt position of the swash plate 21a of the second hydraulic pump motor 21 based on the input comparison value, and the tilt input signal of the regulator 22 corresponding to the calculated tilt position. Is output to the regulator 22.

<Operation>
Next, the operation of the vehicle body controller 30 of the excavator 1 according to the first embodiment will be described with reference to FIG. FIG. 4 is a flowchart showing a control procedure of the vehicle body controller 30.

  First, the pilot pressure of the boom operation lever 6c is detected by the second or third pressure sensor 31b, 31c to determine the operation state of the boom 5a. In this case, based on the pilot pressure detected by the second and third pressure sensors 31b and 31c, the vehicle body controller 30 determines whether the boom operation lever 6c is in the neutral position (S1). If it is determined in S1 that the boom operation lever 6c is in the neutral position (Yes), a control signal for switching the first and second flow rate adjusting valves 26, 27 to the closed positions 26b, 27b, respectively. These are output to the first and second flow rate adjusting valves 26 and 27 to be switched (S5).

  On the other hand, if it is determined in S1 that the boom operation lever 6c is not in the neutral position (No), the vehicle body controller is based on the pilot pressure detected by the second and third pressure sensors 31b and 31c. At 30, it is determined whether the boom operation lever 6c is operated in a so-called boom raising direction (boom raising operation) that rotates the tip side of the boom 5a upward (S2). If it is determined in S2 that the boom operation lever 6c is operated to raise the boom (Yes), the operation of the oil passage 11e on the bottom side of the boom cylinder 6 detected by the first pressure sensor 31a is performed. It is determined whether the hydraulic pressure (bottom pressure) is higher than a predetermined value (S3).

If it is determined in S3 that the bottom pressure of the boom cylinder 6 is higher than the predetermined value (Yes), the first flow rate adjustment valve 26 is switched to the open position 26a and the second flow rate adjustment valve 27 is closed. A control signal for switching to the position 27b is output to the first and second flow rate adjusting valves 26 and 27 to perform switching control (S6). On the other hand, if it is determined in S3 that the bottom pressure of the boom cylinder 6 is a low pressure that is not higher than a predetermined value (No), the first flow rate adjustment valve 26 is switched to the closed position 26b and the second flow rate adjustment is performed. A control signal for switching the valve 27 to the open position 27a is output to the first and second flow rate adjusting valves 26 and 27 to perform switching control (S7).

Further, even when it is determined in S2 that the boom operation lever 6c is not operated to raise the boom (No), the first pressure sensor 31a determines whether the bottom pressure of the boom cylinder 6 is higher than a predetermined value. It is judged (S4). If it is determined in S4 that the bottom pressure of the boom cylinder 6 is higher than the predetermined value (Yes), the first flow rate adjustment valve 26 is switched to the open position 26a and the second flow rate adjustment valve 27 is closed. A control signal for switching to the position 27b is output to the first and second flow rate adjusting valves 26 and 27 to perform switching control (S8). On the other hand, when it is determined in S4 that the bottom pressure of the boom cylinder 6 is lower than the predetermined value (No), the first flow rate adjustment valve 26 is switched to the closed position 26b and the second flow rate adjustment valve 27 is switched. A control signal for switching to the open position 27a is output to the first and second flow rate adjusting valves 26 and 27 to perform switching control (S9).

  Next, the operation of the excavator 1 according to the first embodiment will be described as an example of the operation.

<When boom is raised>
For example, when the boom operation lever 6c is operated in a boom raising direction (boom raising position) that rotates the tip side of the boom 5a upward, the pilot pressure is increased by the second pressure sensor 31b on the boom raising side. A lever output signal corresponding to the pilot pressure is detected and output to the target speed calculator 40a. In this case, a positive (+) target speed is input to the vehicle body controller 30, and the drive signal is moved from the vehicle body controller 30 to the large tilt side that increases the tilt capacity of the second hydraulic pump motor 21. Is output to the regulator 22. As a result, the pressure stored in the accumulator 19 is reduced by the second hydraulic pump motor 21 and hydraulic oil is supplied to the head side of the boom cylinder 6, and the second hydraulic pump motor 21 is driven by this hydraulic oil. Torque is supplied to the first hydraulic pump motor 20 by being driven.

  Therefore, the first hydraulic pump motor 20 is driven, the hydraulic oil on the head side of the boom cylinder 6 is set to a high pressure, and is supplied to the head side of the boom cylinder 6. As a result, the cylinder rod 6b of the boom cylinder 6 is extended, and the boom raising operation is performed. At this time, if the area ratio between the head side and the rod side of the boom cylinder 6 does not match the flow rate ratio of hydraulic fluid between the head side and the rod side, the vehicle body controller 30 controls the first flow rate adjustment valve. 26 is switched to the open position 26 a to discharge excess hydraulic oil to the hydraulic oil tank 10 and supply insufficient hydraulic oil from the hydraulic oil tank 10. As a result, it is possible to prevent the phenomenon that the hydraulic pressure on the rod side of the boom cylinder 6 unexpectedly increases or the pressure on the rod side of the boom cylinder 6 unexpectedly becomes negative pressure and decreases. Good operability can be secured during boom raising operation.

<Boom lowering operation>
For example, when the boom operation lever 6c is operated in a boom lowering direction (boom lowering position) that rotates the tip side of the boom 5a downward, the pilot pressure is increased by the third pressure sensor 31c on the boom lowering side. A lever output signal corresponding to the pilot pressure is detected and output to the target speed calculator 40a. In this case, a negative (−) target speed is input to the vehicle body controller 30, and the drive signal is moved from the vehicle body controller 30 to the small tilt side for reducing the tilt capacity of the second hydraulic pump motor 21. Is output to the regulator 22. As a result, the first hydraulic pump motor 20 is driven as the second hydraulic pump motor 21 is driven, the hydraulic oil is sucked from the head side of the boom cylinder 6, and the first hydraulic pump motor 20 is driven to reduce the hydraulic oil. Is supplied to the rod side of the boom cylinder 6, and torque is supplied to the second hydraulic pump motor 21 as the first hydraulic pump motor 20 is driven.

  Therefore, the second hydraulic pump motor 21 is driven, and the hydraulic oil sucked from the head side of the boom cylinder 6 is supplied to the pressure accumulator 19 via the second hydraulic pump motor 21 and accumulated. As a result, the cylinder rod 6b of the boom cylinder 6 is retracted, and the boom lowering operation is performed. At this time, for example, when the bucket 5d is not in contact with the ground, since the hydraulic pressure on the head side of the boom cylinder 6 is high, the vehicle body controller 30 performs the first operation similarly to the boom raising operation described above. By switching the flow regulating valve 26 to the open position 26a, excess hydraulic oil is discharged to the hydraulic oil tank 10, and insufficient hydraulic oil is supplied from the hydraulic oil tank 10, so that it is good even during the boom lowering operation. Secure operability.

<When jacking up by lowering the boom>
FIG. 5 is a schematic side view showing a state of the excavator 1 during jack-up operation. For example, as shown in FIG. 5, in a state where the bucket 5d of the front working machine 5 of the excavator 1 is grounded to the ground, high pressure hydraulic oil is supplied to the rod side of the boom cylinder 6 to perform a boom lowering operation, so-called jack. In order to perform the up operation, the boom operation lever 6c is operated to the boom lowered position. In this case, as in the boom lowering operation described above, the pilot pressure is detected by the third pressure sensor 31c, and a lever output signal corresponding to the pilot pressure is output to the target speed calculation unit 40a. Then, a negative target speed is input to the vehicle body controller 30, and a drive signal for moving the tilt capacity of the second hydraulic pump motor 21 to the small tilt side is output from the vehicle body controller 30 to the regulator 22.

  In this case, since the bucket 5d is in contact with the ground, the cylinder rod 6b of the boom cylinder 6 does not retract, and the hydraulic pressure on the head side of the boom cylinder 6 becomes low. Therefore, when the vehicle body controller 30 determines that the boom lowering operation has not been performed by comparing the output value of the rotation sensor 32 and the tilting capacity of the second hydraulic pump motor 21, the second hydraulic pump motor 21. A drive signal for moving the tilt capacity to the large tilt side that increases the tilt capacity in the direction opposite to the boom lowering operation described above is output to the regulator 22. Then, torque is supplied to the first hydraulic pump motor 20 by driving the second hydraulic pump motor 21.

  Accordingly, the first hydraulic pump motor 20 is driven, high-pressure hydraulic oil is supplied to the rod side of the boom cylinder 6, the cylinder rod 6b of the boom cylinder 6 is retracted, and the jack-up operation is performed by lowering the boom. At this time, hydraulic oil is supplied to the oil passage 11d between the head side of the boom cylinder 6 and the first and second hydraulic pump motors 20, 21 from the head side of the second hydraulic pump motor 21 and the boom cylinder 6. The

  Furthermore, a large amount of hydraulic oil is supplied to the oil passage 11d between the head side of the boom cylinder 6 and the first and second hydraulic pump motors 20 and 21, and the area ratio between the head side and the rod side of the boom cylinder 6 is As a result, the flow ratios of the hydraulic oils on the head side and the rod side do not match, and the hydraulic pressure on the head side of the boom cylinder 6 becomes unexpectedly high. Therefore, by switching the second flow rate adjustment valve 27 to the open position 27a by the vehicle body controller 30 and discharging the excess hydraulic oil to the hydraulic oil tank 10, good operability can be achieved even during the jack-up operation by lowering the boom. Can be secured.

<When boom is raised with jack up>
For example, in the state where the jack-up operation described above is performed and the front side of the lower traveling body 2 of the hydraulic excavator 1 is jacked up, the hydraulic oil is discharged from the rod side of the boom cylinder 6 to perform the boom raising operation, and the front side of the hydraulic excavator 1 Is operated to the boom raising position. In this case, as in the boom raising operation described above, the pilot pressure is detected by the second pressure sensor 31b, and a lever output signal corresponding to the pilot pressure is output to the target speed calculation unit 40a. At this time, since the bucket 5d is in a state of being grounded to the ground and during the boom raising operation in the jack-up state described above, a positive target speed is input to the vehicle body controller 30. A drive signal for moving the tilt capacity of the second hydraulic pump motor 21 to the small tilt side is output to the regulator 22.

  As a result, the first hydraulic pump motor 20 is driven as the second hydraulic pump motor 21 is driven, the hydraulic oil is sucked in from the rod side of the boom cylinder 6, and the first hydraulic pump motor 20 is driven to reduce the hydraulic oil. Is supplied to the head side of the boom cylinder 6, and torque is supplied to the second hydraulic pump motor 21 as the first hydraulic pump motor 20 is driven. Therefore, the second hydraulic pump motor 21 is driven, and the hydraulic oil sucked from the rod side of the boom cylinder 6 is supplied to the pressure accumulator 19 through the second hydraulic pump motor 21 and accumulated. As a result, the cylinder rod 6b of the boom cylinder 6 is extended, and the boom raising operation is performed.

  At this time, the bucket 5d is in a state of being grounded to the ground, similarly to the jack-up operation by the boom lowering described above. When the boom raising operation is performed from this state, hydraulic oil is supplied from the oil passage 11d to the second hydraulic pump motor 21 and the boom cylinder 6 head side, contrary to the jack-up operation by lowering the boom. As a result, the hydraulic oil in the oil passage 11d becomes insufficient, and the area ratio between the head side and the rod side of the boom cylinder 6 does not match the flow ratio of the hydraulic oil between the head side and the rod side. The hydraulic pressure on the head side of the cylinder 6 is unexpectedly lowered and becomes negative. In this case, the vehicle body controller 30 switches the second flow rate adjustment valve 27 to the open position 27a and supplies the insufficient hydraulic oil from the hydraulic oil tank 10, so that the boom raising operation in the jack-up state can be performed. Good operability can be secured.

<Effect>
Thus, the head side of the boom cylinder 6, both connecting the first and second hydraulic pump motors 20, 21, connects the first hydraulic pump motor 20 to the rod side of the boom cylinder 6. Further, a first flow rate adjusting valve 26 is provided in the oil passage 11c between the rod side of the boom cylinder 6 and the first hydraulic pump motor 20, and the head side of the boom cylinder 6 and the first and second hydraulic pump motors 20, The second flow rate adjusting valve 27 is provided in the oil passage 11d between the first and second oil passages 21.

As a result, by controlling the regulator 22 by the vehicle body controller 30 according to the operation position of the boom operation lever 6c, the drive speed of the boom cylinder 6 can be controlled, and the operation position of the boom operation lever 6c and the boom cylinder 6 can be controlled. The boom cylinder 6 can be driven smoothly by switching and controlling the first and second flow rate adjusting valves 26 and 27 by the vehicle body controller 30 based on the operating hydraulic pressure on the head side.

  Therefore, not only the energy saving performance similar to that of Patent Document 1 described above can be obtained, but the number of installed hydraulic pump motors can be reduced. That is, the energy of the hydraulic oil discharged from the boom cylinder 6 is regenerated, and the drive device 11 for driving the boom cylinder 6 by reusing the regenerated energy can be reduced in size. Can be improved. Furthermore, the operability of each operation can be secured by this configuration.

[Second Embodiment]
FIG. 6 is a schematic view showing a drive device 11A for driving the hydraulic excavator 1 which is an example of the work machine according to the second embodiment of the present invention. The second embodiment is different from the first embodiment described above in that the first embodiment is configured in the drive device 11 using the first flow rate adjustment valve and the second flow rate adjustment valve, whereas the second embodiment is different from the first embodiment. The drive device 11A uses the low-pressure selection valve 35. In the second embodiment, the same or corresponding parts as those in the first embodiment are denoted by the same reference numerals.

<Configuration>
Specifically, in the second embodiment, as illustrated in FIG. 6, the drive device 11 </ b> A includes a low-pressure selection valve 35 that is a flow rate adjusting unit. The low pressure selection valve 35 includes an oil passage 11c between the rod side of the boom cylinder 6 and the first hydraulic pump motor 20, and between the head side of the boom cylinder 6 and the first and second hydraulic pump motors 20 and 21. It is attached between the oil passage 11d. The low pressure selection valve 35 has a first position 35 a that connects the rod side of the boom cylinder 6 to the hydraulic oil tank 10, and a second position 35 b that connects the head side of the boom cylinder 6 to the hydraulic oil tank 10. . The low pressure selection valve 35 includes a first pressure receiving surface 35c that receives the hydraulic pressure of the oil passage 11d on the head side of the boom cylinder 6 and a second pressure receiving surface 35d that receives the hydraulic pressure of the oil passage 11c on the rod side of the boom cylinder 6. Of these oil passages 11 d and 11 c, the oil passages 11 d and 11 c on the side where the hydraulic pressure is lower are connected to the hydraulic oil tank 10.

  Next, the operation of the excavator 1 according to the second embodiment will be described as an example of the specific work.

<When boom is raised>
When the boom operating lever 6c is operated at the boom raising position, the pilot pressure is detected by the second pressure sensor 31b, and a drive signal for increasing the tilting capacity of the second hydraulic pump motor 21 is received from the vehicle body controller 30. Output to the regulator 22. At this time, when the area ratio between the head side and the rod side of the boom cylinder 6 and the flow rate ratio of the hydraulic oil between the head side and the rod side do not match, generally, the hydraulic pressure on the head side of the boom cylinder 6 is Since the hydraulic pressure on the rod side is higher than that, the low pressure selection valve 35 is switched to the first position 35a. As a result, the rod side oil passage 11c of the boom cylinder 6 is connected to the hydraulic oil tank 10, and excess hydraulic oil in the oil passage 11c is discharged to the hydraulic oil tank 10, and the insufficient hydraulic oil is discharged to the hydraulic oil tank. 10 is supplied.

<Boom lowering operation>
When the boom operating lever 6c is operated at the boom lowered position, the pilot pressure is detected by the third pressure sensor 31c, and a drive signal for reducing the tilting capacity of the second hydraulic pump motor 21 is received from the vehicle body controller 30. It is output to the regulator 22. At this time, as in the boom raising operation described above, generally, during the boom lowering operation, the hydraulic pressure on the head side of the boom cylinder 6 is higher than the hydraulic pressure on the rod side. The operation is switched to the position 35 a, and the oil passage 11 c on the rod side of the boom cylinder 35 is connected to the hydraulic oil tank 10.

<When jacking up by lowering the boom>
When the boom control lever 6c is operated to the boom lowering position with the bucket 5d in contact with the ground, the pilot pressure is detected by the third pressure sensor 31c as in the boom lowering operation described above, and the vehicle body A drive signal for increasing the tilting capacity of the second hydraulic pump motor 21 in the direction opposite to the boom lowering operation described above is output from the controller 30 to the regulator 22. At this time, generally, during boom lowering operation such as during jack-up operation, the hydraulic pressure on the rod side of the boom cylinder 6 is higher than the hydraulic pressure on the head side, so the low pressure selection valve 35 is switched to the second position 35b. Then, the oil passage 11 d on the head side of the boom cylinder 6 is connected to the hydraulic oil tank 10, and excess hydraulic oil in the oil passage 11 d is discharged to the hydraulic oil tank 10.

<When boom is raised with jack up>
When the boom operating lever 6c is operated at the boom raising position in the jack-up state, the pilot pressure is detected by the second pressure sensor 31b, and the second controller 31 detects that the second pressure sensor 31b A drive signal for reducing the tilt capacity of the hydraulic pump motor 21 is output to the regulator 22. At this time, generally, during the boom raising operation in the jack-up state, the hydraulic pressure on the rod side of the boom cylinder 6 is higher than the hydraulic pressure on the head side, so the low pressure selection valve 35 is switched to the second position 35b. The As a result, the oil path 11 d on the head side of the boom cylinder 6 is connected to the hydraulic oil tank 10, and insufficient hydraulic oil is supplied from the hydraulic oil tank 10 to the oil path 11 d.

<Effect>
Thus, the oil passage 11c between the rod side of the boom cylinder 6 and the first hydraulic pump motor 20 and the oil passage 11d between the head side of the boom cylinder 6 and the first and second hydraulic pump motors 20 and 21 are obtained. Even in the configuration in which the low pressure selection valve 35 is attached between the two, as well as the first embodiment, not only can energy saving be obtained, but also the number of installed hydraulic pump motors can be reduced. Therefore, the energy of the hydraulic oil discharged from the boom cylinder 6 is regenerated, and the drive device 11A for driving the boom cylinder 6 by reusing the regenerated energy can be reduced in size. It can be improved.

Further, since the low pressure selection valve 35 is appropriately switched to the first or second position 35a, 35b based on the change in the hydraulic pressure between the rod side and the head side of the boom cylinder 6, the low pressure selection valve 35 There is no need to electrically control the switching operation, for example, by the vehicle body controller 30 or the like. Therefore, the drive device 11A for driving the boom cylinder 6 can be further simplified.

[Others]
In addition, this invention is not limited to embodiment mentioned above, Various deformation | transformation aspects are included. For example, the above-described embodiments have been described in order to explain the present invention in an easy-to-understand manner, and the present invention is not necessarily limited to those having all the configurations described.

In the first embodiment, the first and second flow rate adjusting valves 26 and 27 are on / off type switching valves. However, the first and second flow rate adjusting valves 26 and 27 are on / off type. For example, a proportional valve (throttle valve) capable of adjusting the flow rate may be used. Further, when the first and second flow rate adjusting valves 26 and 27 are proportional valves, it is possible to more appropriately perform control when connecting the rod side or the head side of the boom cylinder 6 to the hydraulic oil tank 10. It becomes.

  Furthermore, in each of the above-described embodiments, the case where the driving devices 11 and 11A are mounted on the hydraulic excavator 1 has been described as an example. However, the present invention is not limited thereto, and driving such as a hydraulic crane or a wheel loader is possible. Any work machine other than the hydraulic excavator 1 can be used as long as it is a working machine including a hydraulic actuator that can be driven by the devices 11 and 11A.

  Moreover, in each said embodiment, although it was set as the structure which regenerates and reuses the energy which the hydraulic fluid discharged | emitted from the boom cylinder 6 has, if it is a hydraulic actuator which can regenerate the energy which the hydraulic fluid discharged | emitted etc. have Even hydraulic actuators other than the boom cylinder 6 can be applied. In particular, a hydraulic actuator having an area difference in pressure receiving area is more preferable because energy can be reliably regenerated and reused.

  Furthermore, although the displacement sensor 28 and the rotation sensor 32 are used as means for detecting the state quantity of the boom cylinder 6, the displacement amount of the cylinder rod 6b of the boom cylinder 6, that is, the displacement sensor for detecting the displacement, The state quantity of the boom cylinder 6 can also be detected using an angle sensor that detects the angle, a speed sensor that detects the speed when the boom cylinder 6 is driven to advance and retract, and the like.

  Further, by attaching a pressure sensor to the rod side of the boom cylinder 6, the hydraulic pressure that can be detected by this pressure sensor and the hydraulic pressure that can be detected by the first pressure sensor 31 a attached to the head side of the boom cylinder 6. Based on the above, the thrust of the boom cylinder 6 can be calculated. Therefore, it can be configured to recognize whether or not it is in a jack-up state when the boom cylinder 6 is driven.

1 Excavator (work machine)
DESCRIPTION OF SYMBOLS 2 Lower traveling body 2a, 2b Traveling motor 2c, 2d Traveling apparatus 3 Turning apparatus 3a Turning motor 3c Turning operation lever 4 Upper turning body (machine main body)
4b cab 4c engine room 4d counterweight 5 front work machine (work machine)
5a Boom 5b Arm 5c Four-bar linkage mechanism 5d Bucket 6 Boom cylinder (hydraulic actuator)
6a Cylinder tube (first connection part)
6b Cylinder rod (second connection part)
6c Boom operation lever (operation state detector)
7 Arm cylinder 7a Cylinder tube 7b Cylinder rod 7c Arm operation lever 8 Bucket cylinder 8a Cylinder tube 8b Cylinder rod 8c Bucket operation lever 10 Hydraulic oil tank 11 Drive unit 11a Discharge oil path 11b Discharge oil path 11c Oil path 11d Oil path 11e Oil path 12 Engine 13 Main pump 14 Control valve device 14a Arm control valve 14b Bucket control valve 14c Turning control valve 15 Pilot pump 19 Accumulator (energy storage part)
DESCRIPTION OF SYMBOLS 20 1st hydraulic pump motor 21 2nd hydraulic pump motor 21a Swash plate 22 Regulator 23 Pilot check valve 24 Flow control valve 25 Pressure sensor 26 1st flow control valve (flow control part)
26a Open position 26b Closed position 27 Second flow rate adjustment valve (flow rate adjustment unit)
27a Open position 27b Closed position 28 Displacement sensor (state quantity detector)
30 Body controller (control device)
31a 1st pressure sensor (pressure detection part)
31b 2nd pressure sensor 31c 3rd pressure sensor 32 Rotation sensor (state quantity detection part)
35 Low pressure selection valve (flow rate adjustment part)
35a 1st position 35b 2nd position 35c 1st pressure receiving surface 35d 2nd pressure receiving surface 40a Target speed calculating part 40b Actual speed calculating part 40c Tilt position calculating part

Claims (1)

A work machine comprising a machine body, a work machine provided in the machine body, and a hydraulic actuator that has a first connection part and a second connection part and drives the work machine,
A first hydraulic pump motor connected to the first connection portion and the second connection portion of the hydraulic actuator and having a pump function for pumping hydraulic oil and a motor function driven by the supplied hydraulic oil;
A variable having a pump function that rotates in synchronization with the rotation of the first hydraulic pump motor , is connected to the first connection portion of the hydraulic actuator, and that pumps hydraulic oil and is driven by the supplied hydraulic oil. A capacity-type second hydraulic pump motor;
An energy storage unit that is attached to the second hydraulic pump motor and stores energy of hydraulic oil supplied from the second hydraulic pump motor;
A control device for controlling driving of the second hydraulic pump motor;
A flow rate attached between the second connection portion of the hydraulic actuator and the first hydraulic pump motor and between the first connection portion of the hydraulic actuator, the first hydraulic pump motor and the second hydraulic pump motor. An adjustment unit ,
The control device includes an operation state detection unit that detects an operation state of the hydraulic actuator, a state amount detection unit that detects a state amount of the hydraulic actuator, and a pressure that detects a pressure on a first connection portion side of the hydraulic actuator. And detecting the capacity of the second hydraulic pump motor and the flow rate of the flow rate adjustment unit based on each detection information detected by the operation state detection unit, the state quantity detection unit, and the pressure detection unit. A working machine characterized by