JP2019007586A - Hydraulic drive system - Google Patents

Abstract

To provide a hydraulic drive system capable of regenerating kinetic energy during a speed reduction operation to a hydraulic motor at any timing.SOLUTION: A hydraulic drive system 1A comprises: a hydraulic motor 16; a bidirectional pump 23 which is connected with the hydraulic motor so as to form a first closed loop 4, and driven by an engine 21 and supplies a working oil to the hydraulic motor; a first regulator 24 which adjusts a tilt angle of the bidirectional pump; a bidirectional motor 26 which is connected with the hydraulic motor so as to form a second closed loop 5 and driven by a working oil discharged from the hydraulic motor during a speed reduction operation to the hydraulic motor; a fly wheel 54 which is rotated by the bidirectional motor; a second regulator 27 which adjusts a tilt angle of the bidirectional motor; and a control device 9 which controls the first regulator and the second regulator based on operation to the hydraulic motor.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hydraulic drive system.

  In a construction machine such as a hydraulic excavator or a hydraulic crane or an industrial vehicle such as a wheel loader, each part is driven by a hydraulic drive system. As such a hydraulic drive system, there is a conventional system using a hydraulic continuously variable transmission (HST) in a traveling circuit or a turning circuit.

  For example, Patent Literature 1 discloses a hydraulic drive system configured to regenerate kinetic energy during a turning deceleration operation. In this hydraulic drive system, a bidirectional pump (also referred to as an over-center pump) driven by an engine is connected to a turning motor so as to form a closed loop by a pair of supply / discharge lines. The engine also drives a supply pump that supplies hydraulic oil to hydraulic actuators other than the turning motor.

  In the hydraulic drive system disclosed in Patent Document 1, the bidirectional pump is driven by the hydraulic oil discharged from the turning motor during the turning deceleration operation. As a result, the bidirectional pump functions as a motor, and the drive of the supply pump by the engine is assisted by the kinetic energy during the turning deceleration operation.

Japanese Patent Laid-Open No. 2006-80009

  However, in the hydraulic drive system disclosed in Patent Document 1, kinetic energy during the turning deceleration operation is regenerated only when the supply pump supplies hydraulic oil to any of the hydraulic actuators.

  Therefore, an object of the present invention is to provide a hydraulic drive system capable of regenerating kinetic energy at the time of deceleration operation on a hydraulic motor at an arbitrary timing.

  In order to solve the above-mentioned problem, a hydraulic drive system according to one aspect of the present invention includes a hydraulic motor and an engine driven by an engine connected to the hydraulic motor so as to form a first closed loop. A hydraulic pump for supplying hydraulic oil; a first regulator for adjusting a tilt angle of the bidirectional pump; and the hydraulic motor connected to the hydraulic motor to form a second closed loop during the deceleration operation of the hydraulic motor. Based on an operation on the hydraulic motor, a bidirectional motor driven by hydraulic oil discharged from the vehicle, a flywheel rotated by the bidirectional motor, a second regulator for adjusting a tilt angle of the bidirectional motor, and the hydraulic motor. And a control device that controls the first regulator and the second regulator.

  According to said structure, the kinetic energy at the time of deceleration operation with respect to a hydraulic motor can be accumulate | stored in a flywheel. Therefore, the kinetic energy at the time of the deceleration operation on the hydraulic motor can be regenerated at an arbitrary timing. For example, during acceleration or constant speed operation of a hydraulic motor, if the bidirectional motor is driven by a flywheel and the bidirectional motor functions as a pump with a tilt angle of the bidirectional motor other than zero, the energy accumulated in the flywheel A hydraulic motor can be driven. Alternatively, when the engine also drives a supply pump that supplies hydraulic oil to hydraulic actuators other than the hydraulic motor, the output shaft of the hydraulic motor can be locked by a lock mechanism even when the hydraulic motor is not accelerated or operated at a constant speed. If the bidirectional motor is driven by the flywheel and the bidirectional motor is caused to function as a pump with the tilt angle of the bidirectional motor being other than zero after being locked, the bidirectional pump functions as a motor. Therefore, the drive of the supply pump by the engine can be assisted by the energy accumulated in the flywheel.

  The hydraulic drive system includes a first switching valve that is controlled by the control device and permits or prohibits the circulation of hydraulic oil through the first closed loop, and the second closed loop that is controlled by the control device. A second switching valve that permits or prohibits the circulation of the hydraulic oil. According to this configuration, it is possible to instantaneously switch between permission and prohibition of circulation through the first closed loop and permission and prohibition of circulation through the second closed loop. Further, if the first switching valve and the second switching valve are configured to function as check valves in the circulation-inhibited state, the backflow of hydraulic oil in the bidirectional pump and the bidirectional motor can be prevented.

  The first switching valve has a neutral state that prohibits the circulation of hydraulic oil through the first closed loop, a first state that permits the circulation of hydraulic oil through the first closed loop in the first direction, and the first The second switching valve can be switched to a second state that allows the hydraulic oil to circulate through the first closed loop in a second direction opposite to the direction, and the second switching valve circulates the hydraulic oil through the second closed loop. A neutral state prohibiting the hydraulic oil, a first state allowing the hydraulic oil to circulate through the second closed loop in a third direction in which the hydraulic oil passes through the hydraulic motor in the same direction as the first direction, It may be possible to switch to a second state that permits the circulation of hydraulic oil through the second closed loop in a fourth direction opposite to the third direction. According to this configuration, when hydraulic fluid is supplied to the hydraulic motor from both the bidirectional pump and the bidirectional motor (when both the first switching valve and the second switching valve are switched to the first state or the second state), The backflow of the working oil in the first closed loop or the second closed loop can be prevented.

  For example, the hydraulic drive system further includes a speed detector that detects a speed of an object driven by the hydraulic motor, and the control device sets the second switching valve to the second switching valve during a deceleration operation on the hydraulic motor. The second switching valve may be switched to the neutral state when the speed of the object detected by the speed detector becomes zero after the deceleration operation.

  The hydraulic drive system further includes a speed detector that detects a rotational speed of the flywheel, and the control device is detected by the second detector during acceleration operation and constant speed operation on the hydraulic motor. If the rotational speed of the flywheel is greater than the predetermined value, the second switching valve is switched to the first state or the second state, the first switching valve is switched to the neutral state, and the speed detector If the rotational speed of the flywheel detected at step S is smaller than a predetermined value, both the first switching valve and the second switching valve may be switched to the first state or the second state. According to this configuration, the energy accumulated in the flywheel is preferentially used for driving the hydraulic motor over the engine, and the energy accumulated in the flywheel is insufficient for driving the hydraulic motor in both directions. Hydraulic oil can be supplied from both the pump and the bidirectional motor.

  The hydraulic drive system includes a boom cylinder, a supply pump that supplies hydraulic oil to the boom cylinder via a control valve, driven by the engine, and hydraulic oil that is discharged from the boom cylinder during a boom lowering operation. And a regenerative motor that is driven to rotate the flywheel. According to this configuration, since the potential energy of the boom can be stored in the flywheel, the potential energy of the boom can also be used for driving the hydraulic motor.

  Further, a hydraulic drive system according to another aspect of the present invention includes a hydraulic motor and hydraulic fluid connected to the hydraulic motor so as to form a closed loop and discharged from the hydraulic motor during a deceleration operation on the hydraulic motor. A bidirectional motor that is rotated, a flywheel that is rotated by the bidirectional motor, a regulator that adjusts a tilt angle of the bidirectional motor, a control device that controls the regulator based on an operation on the hydraulic motor, and a boom cylinder A supply pump driven by an engine for supplying hydraulic oil to the boom cylinder via a control valve, and a regenerative drive driven by the hydraulic oil discharged from the boom cylinder during a boom lowering operation to rotate the flywheel. And a motor.

  According to said structure, the kinetic energy at the time of deceleration operation with respect to a hydraulic motor can be accumulate | stored in a flywheel. Therefore, similarly to the hydraulic drive system according to one aspect of the present invention, the kinetic energy at the time of the deceleration operation on the hydraulic motor can be regenerated at an arbitrary timing. Further, in the above configuration, since the potential energy of the boom can be stored in the flywheel, the potential energy of the boom can also be used for driving the hydraulic motor.

  According to the present invention, it is possible to regenerate kinetic energy at the time of deceleration operation on the hydraulic motor at an arbitrary timing.

1 is a schematic configuration diagram around an engine and a turning motor of a hydraulic drive system according to a first embodiment of the present invention. It is a schematic block diagram around the boom cylinder of the hydraulic drive system shown in FIG. It is a side view of the hydraulic excavator which is an example of a construction machine. It is a schematic block diagram around an engine and a turning motor of a hydraulic drive system according to a second embodiment of the present invention.

(First embodiment)
1 and 2 show a hydraulic drive system 1A according to the first embodiment of the present invention, and FIG. 3 shows a construction machine 10 on which the hydraulic drive system 1A is mounted. Although the construction machine 10 shown in FIG. 3 is a hydraulic excavator, the present invention is also applicable to other construction machines such as a hydraulic crane. Alternatively, the present invention is not limited to construction machines, and can be applied to industrial vehicles such as wheel loaders.

  In this embodiment, HST is used for the turning circuit, and HST is not used for the traveling circuit. That is, in the present embodiment, the swing motor 16 described later corresponds to the hydraulic motor of the present invention. However, HST may be used for the running circuit without using HST for the turning circuit. In this case, each of the left traveling motor and the right traveling motor, which will be described later, corresponds to the hydraulic motor of the present invention. Alternatively, HST may be used for both the turning circuit and the traveling circuit.

  The construction machine 10 shown in FIG. 3 is self-propelled, and includes a traveling body 11 and a revolving body 12 that is supported by the traveling body 11 so as to be able to swivel. The traveling body 11 is driven by a left traveling motor and a right traveling motor which will be described later, and the revolving body 12 is driven by a turning motor 16 which will be described later. The revolving body 12 is provided with a cabin for accommodating the operator, and a boom is connected thereto. An arm is connected to the tip of the boom, and a bucket is connected to the tip of the arm. However, the construction machine 10 may not be self-propelled.

  The hydraulic drive system 1A includes, as hydraulic actuators, a boom cylinder 13, an arm cylinder 14 and a bucket cylinder 15 shown in FIG. 3, and also includes a turning motor 16 shown in FIG. 1, a left travel motor and a right travel motor (not shown). The hydraulic drive system 1A includes a bidirectional pump 23 dedicated to the swing motor 16 and a supply pump 22 that supplies hydraulic oil to a hydraulic actuator other than the swing motor 16 via a control valve. The bidirectional pump 23 and the supply pump 22 are driven by the engine 21.

  In FIGS. 1 and 2, hydraulic actuators other than the swing motor 16 and the boom cylinder 13 are omitted for simplification of the drawings. In the illustrated example, only one supply pump 22 is provided, but a plurality of supply pumps 22 may be provided.

  The bidirectional pump 23 is a variable displacement pump whose tilt angle can be changed. The tilt angle of the bidirectional pump 23 is adjusted by a regulator 24 (corresponding to the first regulator of the present invention). In this embodiment, the bidirectional pump 23 is a swash plate pump in which the swash plate can be tilted to both sides from the center (a direction orthogonal to the axial direction of the bidirectional pump 23). That is, the angle of the swash plate with respect to the center is the tilt angle. However, the bidirectional pump 23 may be an oblique pump in which the oblique shaft can tilt from the center (the axial direction of the bidirectional pump 23) to both sides.

  The bi-directional pump 23 is connected to the turning motor 16 so as to form a first closed loop 4 by a pair of supply / discharge lines 4a and 4b. That is, the hydraulic oil is supplied from the bidirectional pump 23 to the swing motor 16 through one of the supply / discharge lines 4a and 4b, and the hydraulic oil is discharged from the swing motor 16 to the bidirectional pump 23 through the other of the supply / discharge lines 4a and 4b.

  While the swing motor 16 is stopped, the output shaft of the swing motor 16 is locked by a lock mechanism (not shown). The lock mechanism includes, for example, a hydraulic cylinder that operates to grip the output shaft of the turning motor 16.

  The supply / discharge lines 4 a and 4 b are connected by a first bridge 41, a second bridge 43, and a third bridge 45. In the present embodiment, the first bridge road 41, the second bridge road 43, and the third bridge road 45 are arranged in this order from the bidirectional pump 23 toward the turning motor 16. However, the positions of the second bridge 43 and the third bridge 45 may be interchanged.

  The engine 21 described above also drives the charge pump 25. A circulation line 31 extends from the charge pump 25 to the tank, and a relief valve 32 is provided in the circulation line 31. In the present embodiment, the downstream portion of the relief valve 32 in the circulation line 31 also serves as the drain line of the bidirectional pump 23.

  The first bridge 41 is provided with a pair of check valves 42 in opposite directions. The portion between the check valves 42 in the first bridge 41 is connected to the upstream portion of the relief valve 32 in the circulation line 31 by the supply line 33. The second bridge 43 is provided with a pair of relief valves 44 in opposite directions, and the third bridge 45 is provided with a pair of check valves 46 in opposite directions. A portion between the relief valves 44 in the second bridge 43 is connected to a portion between the check valves 46 in the third bridge 45 by a relay line 47.

  The supply / discharge lines 4a and 4b are connected to the switching valve 37 by relief lines 48 and 49, respectively. A discharge line 38 extends from the switching valve 37 to the tank, and a relief valve 39 is provided in the discharge line 38. In the present embodiment, the downstream portion of the relief valve 39 in the discharge line 38 also serves as the drain line of the swing motor 16.

  The switching valve 37 is configured to communicate the other line, which has a lower pressure, with the discharge line 38 when the pressure of one of the supply / discharge lines 4a, 4b is high. That is, one of the relief valves 44 provided in the second bridge 43 prevents the pressure on the supply side to the swing motor 16 from becoming higher than the set value, and the relief valve 39 provided in the discharge line 38 This prevents the pressure on the discharge side from the swing motor 16 from becoming higher than the set value.

  The regulator 24 described above is operated by an electrical signal. For example, the regulator 24 may electrically change the hydraulic pressure acting on the servo piston connected to the swash plate of the bidirectional pump 23, or may be an electric actuator connected to the swash plate of the bidirectional pump 23. May be.

  The regulator 24 is controlled by the control device 9. However, in FIG. 1, only a part of the signal lines is drawn for simplification of the drawing. A turning operation signal output from the turning operation device 67 is input to the control device 9. The turning operation device 67 is an electric joystick that outputs an electric signal as a turning operation signal.

  The turning operation device 67 includes an operation lever that receives a turning operation (operation on the turning motor 16), and outputs a turning operation signal (a left turning operation signal or a right turning operation signal) corresponding to the tilt angle of the operation lever. That is, the turning operation signal output from the turning operation device 67 increases as the tilt angle (operation amount) of the operation lever increases.

  The control device 9 controls the regulator 24 based on the turning operation signal output from the turning operation device 67. For example, the control device 9 has a memory such as a ROM and a RAM and a CPU, and a program stored in the ROM is executed by the CPU. The control of the regulator 24 will be described in detail later.

  Furthermore, in this embodiment, the bidirectional motor 26 is connected to the turning motor 16 so as to form the second closed loop 5 by a pair of supply / discharge lines 5a and 5b. That is, the end of the supply / discharge line 5a on the swing motor 16 side has a common flow path with the end of the supply / discharge line 4a on the swing motor 16 side, and the end of the supply / discharge line 5b on the swing motor 16 side. The portion is a flow path common to the end portion of the supply / discharge line 4b on the side of the turning motor 16 described above.

  The bi-directional motor 26 is driven by the hydraulic oil discharged from the turning motor 16 at the time of turning deceleration (when the turning operation signal output from the turning operation device 67 decreases). That is, at the time of turning deceleration, the working oil is supplied from the turning motor 16 to the bidirectional motor 26 through one of the supply / discharge lines 5a, 5b, and the working oil is discharged from the bidirectional motor 26 to the turning motor 16 through the other of the supply / discharge lines 5a, 5b. Is done.

  The supply / discharge lines 5 a and 5 b are connected by a bridge 51. The bridge 51 is provided with a pair of check valves 52 in opposite directions. A portion between the check valve 52 in the bridge 51 is connected to an upstream portion of the relief valve 32 in the circulation line 31 by a supply line 34.

  The bi-directional motor 26 is a variable capacity motor whose tilt angle can be changed. The tilt angle of the bidirectional motor 26 is adjusted by a regulator 27 (corresponding to the second regulator of the present invention). In this embodiment, the bi-directional motor 26 is a swash plate motor in which the swash plate can be tilted to both sides from the center (a direction orthogonal to the axial direction of the bi-directional motor 26). That is, the angle of the swash plate with respect to the center is the tilt angle. However, the bi-directional motor 26 may be an oblique motor whose tilt axis can tilt from the center (axial direction of the bi-directional motor 26) to both sides.

  The regulator 27 is operated by an electric signal. For example, the regulator 27 may electrically change the hydraulic pressure acting on the servo piston connected to the swash plate of the bidirectional motor 26 or may be an electric actuator connected to the swash plate of the bidirectional motor 26. May be.

  The regulator 27 is controlled by the control device 9. The control device 9 controls the regulator 27 based on the turning operation signal output from the turning operation device 67. The control of the regulator 27 will be described in detail later.

  The bidirectional motor 26 is for rotating the flywheel 54. In the present embodiment, the bidirectional motor 26 is connected to the flywheel 54 via a speed increaser 53 that is a gear train. However, the bidirectional motor 26 may be directly connected to the flywheel 54. In this embodiment, no clutch is provided between the bidirectional motor 26 and the speed increaser 53. However, whether or not torque transmission is permitted between the bidirectional motor 26 and the speed increaser 53 is determined. A clutch for switching may be provided.

  Further, in the present embodiment, the flywheel 54 is connected to the regenerative motor 28 via the speed increaser 53 and the one-way clutch 55. The one-way clutch 55 allows only torque transmission from the regenerative motor 28 to the speed increaser 53.

  A first switching valve 61 and a second switching valve 64 are incorporated in the turning circuit. The first switching valve 61 and the second switching valve 64 are controlled by the control device 9. The first switching valve 61 permits or prohibits the circulation of hydraulic oil through the first closed loop 4 described above, and the second switching valve 64 permits or prohibits the circulation of hydraulic oil through the second closed loop 5 described above.

  In this embodiment, the 1st switching valve 61 is comprised by the switching valve 62 provided in the supply / discharge line 4a, and the switching valve 63 provided in the supply / discharge line 4b. Moreover, the 2nd switching valve 64 is comprised by the switching valve 65 provided in the supply / discharge line 5a, and the switching valve 66 provided in the supply / discharge line 4b.

  In the neutral position, the switching valve 62 functions as a check valve that allows the flow from the bidirectional pump 23 to the swing motor 16 through the supply / discharge line 4a but prohibits the reverse flow. When a command current is supplied from the control device 9 to the switching valve 62 and the switching valve 62 is switched to the operating position, the switching valve 62 allows a bidirectional flow. Similarly, in the neutral position, the switching valve 63 functions as a check valve that allows the flow from the bidirectional pump 23 to the swing motor 16 through the supply / discharge line 4b but prohibits the reverse flow. When a command current is supplied from the control device 9 to the switching valve 63 and the switching valve 63 is switched to the operating position, the switching valve 63 allows a bidirectional flow.

  That is, the first switching valve 61 includes a neutral state in which the switching valve 62 and the switching valve 63 are positioned at the neutral position, a first state in which the switching valve 62 is in the neutral position and the switching valve 63 is positioned in the operating position, and the switching valve 62. Can be switched between a second state in which the switching valve 63 is in the neutral position and a third state in which the switching valve 62 and the switching valve 63 are in the operating position. The neutral first switching valve 61 prohibits the circulation of hydraulic oil through the first closed loop 4. The first switching valve 61 in the first state allows the hydraulic oil to circulate through the first closed loop 4 in the first direction, while operating through the first closed loop 4 in the second direction opposite to the first direction. Prohibit oil circulation. The first switching valve 61 in the second state permits the circulation of the hydraulic oil through the first closed loop 4 in the second direction, while prohibiting the circulation of the hydraulic oil through the first closed loop 4 in the first direction. The first switching valve 61 in the third state allows the hydraulic oil to circulate through the first closed loop 4 in the first direction and the second direction.

  In the neutral position, the switching valve 65 functions as a check valve that allows the flow from the bidirectional motor 26 to the turning motor 16 through the supply / discharge line 5a but prohibits the reverse flow. When a command current is supplied from the control device 9 to the switching valve 65 and the switching valve 65 is switched to the operating position, the switching valve 65 allows a bidirectional flow. Similarly, in the neutral position, the switching valve 66 functions as a check valve that allows the flow from the bidirectional motor 26 to the turning motor 16 through the supply / discharge line 4b but prohibits the reverse flow. When a command current is supplied from the control device 9 to the switching valve 66 and the switching valve 66 is switched to the operating position, the switching valve 66 allows bidirectional flow.

  That is, the second switching valve 64 includes a neutral state in which the switching valve 65 and the switching valve 66 are positioned at the neutral position, a first state in which the switching valve 65 is in the neutral position and the switching valve 66 is positioned in the operating position, and the switching valve 65. Can be switched between a second state in which the switching valve 66 is in the neutral position and a third state in which the switching valve 65 and the switching valve 66 are in the operating position. The neutral second switching valve 64 prohibits the circulation of hydraulic oil through the second closed loop 5. The second switching valve 64 in the first state allows the hydraulic oil to circulate through the second closed loop 5 in the third direction in which the hydraulic oil passes through the turning motor 16 in the same direction as the first direction. The circulation of hydraulic oil through the first closed loop 4 in the fourth direction opposite to the three directions is prohibited. The second switching valve 64 in the second state permits the circulation of the hydraulic oil through the second closed loop 5 in the fourth direction, while prohibiting the circulation of the hydraulic oil through the first closed loop 4 in the third direction. The second switching valve 64 in the third state allows the hydraulic oil to circulate through the second closed loop 5 in the third direction and the fourth direction.

  The first bridge 41 and the supply line 33 described above serve to prevent cavitation on the suction side of the two-way pump 23 when the first switching valve 61 prohibits the circulation of hydraulic oil through the first closed loop 4. Fulfill. Similarly, the bridge 51 and the supply line 34 serve to prevent cavitation on the suction side of the bidirectional motor 26 when the second switching valve 64 prohibits the circulation of hydraulic oil through the second closed loop 5. .

  The supply pump 22 described above is a variable displacement pump (swash plate pump or oblique shaft pump) whose tilt angle can be changed. The tilt angle of the supply pump 22 is adjusted by a regulator (not shown). The discharge flow rate of the supply pump 22 may be controlled by any of a hydraulic negative control method, an electric positive control method, and a load sensing method.

  The supply pump 22 is connected to a plurality of control valves including a boom control valve 73 (other than the boom control valve 73 is not shown) through a supply line 71. The boom control valve 73 is connected to the boom cylinder 13 by a boom raising supply line 75 and a boom lowering supply line 74. In this embodiment, a bleed line 72 is branched from the supply line 71, and this bleed line 72 is a center bleed line that passes through a plurality of control valves. However, the bleed line 72 may not be passed through the plurality of control valves, and the bleed line 72 may be provided with an unload valve. The boom control valve 73 is connected to the tank by a tank line 76.

  The boom control valve 73 is switched from the neutral position to the boom raising operation position (left side position in FIG. 1) or the boom lowering operation position (right side position in FIG. 1) by operating the boom operation device 68. In the boom raising operation position, the boom control valve 73 communicates the boom raising supply line 75 with the supply line 71 and the boom lowering supply line 74 with the tank line 76. On the other hand, in the boom lowering operation position, the boom control valve 73 communicates the boom lowering supply line 74 with the supply line 71 and communicates the boom raising supply line 75 with the tank line 76.

  In the present embodiment, the boom control valve 73 is a hydraulic pilot type and has a pair of pilot ports. However, the boom control valve 73 may be an electromagnetic pilot type.

  The boom operation device 68 includes an operation lever that receives a boom operation (operation on the boom cylinder 13), and outputs a boom operation signal (a boom raising operation signal or a boom lowering operation signal) according to the tilt angle of the operation lever. That is, the boom operation signal output from the boom operation device 68 increases as the tilt angle (operation amount) of the operation lever increases.

  In the present embodiment, the boom operation device 68 is an electric joystick that outputs an electric signal as a boom operation signal. A boom operation signal output from the boom operation device 68 is input to the control device 9.

  The control device 9 controls the boom control valve 73 via a pair of electromagnetic proportional valves (not shown) so that the boom control valve 73 has an opening area corresponding to the boom operation signal. However, the boom operation device 68 may be a pilot operation valve that outputs a pilot pressure as a boom operation signal. In this case, the pilot port of the boom control valve 73 is connected to the boom operation device 68 that is a pilot operation valve through the pilot line. When the boom operation device 68 is a pilot operation valve, the pilot pressure output from the boom operation device 68 is detected by the pressure sensor and input to the control device 9.

  The regenerative motor 28 described above is driven by the hydraulic oil discharged from the boom cylinder 13 during the boom lowering operation (when the boom lowering operation signal is output from the boom operation device 68), and rotates the flywheel 54. As a configuration for this purpose, the tank line 76 is provided with a regenerative valve 81. The regenerative valve 81 is connected to the regenerative motor 28 via a regenerative line 82. However, the regenerative valve 81 may be provided in the boom raising supply line 75.

  The regenerative motor 28 is a variable capacity motor (swash plate motor or oblique shaft motor) whose tilt angle can be changed. The tilt angle of the regenerative motor 28 is adjusted by a regulator (not shown). For example, the regulator for the regenerative motor 28 is controlled by the control device 9 based on the boom operation signal. However, the regenerative motor 28 may be a fixed capacity motor.

  The regenerative valve 81 is provided in the tank line 76 so as to divide the tank line 76 into an upstream flow path on the boom control valve 73 side and a downstream flow path on the tank side. The regenerative valve 81 communicates the upstream flow path of the tank line 76 with the downstream flow path in the neutral position. The regenerative valve 81 is controlled by the control device 9. The regenerative valve 81 is switched to the operating position during the boom lowering operation, and communicates the upstream flow path of the tank line 76 with the regenerative line 82.

  A check valve 83 is provided in the regeneration line 82. The downstream portion of the check valve 83 in the regenerative line 82 is connected to the upstream portion of the relief valve 32 in the circulation line 31 by a replenishment line 35 provided with the check valve 36. The replenishment line 35 plays a role of preventing cavitation on the suction side of the regenerative motor 28 when the regenerative valve 81 is located at the neutral position.

  Furthermore, a relief line 84 branches off from the downstream side of the check valve 83 in the regenerative line 82, and a relief valve 85 is provided in the relief line 84. Further, the downstream side portion of the check valve 83 in the regenerative line 82 is connected to the tank by a replenishment line 86 provided with a check valve 87.

  Next, the control of the regulators 24 and 27 and the first switching valve 61 and the second switching valve 64 performed by the control device 9 will be described. The control device 9 is electrically connected not only to the turning operation device 67 and the boom operation device 68 but also to the first speed detector 91 and the second speed detector 92. The first speed detector 91 detects the speed of the revolving structure 12, and the second speed detector 92 detects the rotational speed of the flywheel 54.

  First, the control from the state where energy is not accumulated in the flywheel 54 when the construction machine 10 is started, that is, the state where the rotational speed of the flywheel 54 detected by the second speed detector 92 is zero will be described. . In this initial state, the first switching valve 61 and the second switching valve 64 are maintained in a neutral state.

  When the turning operation is started by tilting the operation lever of the turning operation device 67, the control device 9 sets the first switching valve 61 according to the type of the turning operation signal (left turning or right turning). Switch to the first state or the second state. In addition, the control device 9 determines that the turning operation signal output from the turning operation device 67 is other than zero at the time of turning acceleration operation (when the turning operation signal output from the turning operation device 67 increases) and at the turning constant speed operation. The regulator 24 is controlled so that the discharge flow rate of the bidirectional pump 23 in the direction corresponding to the type of the turning operation signal (left turning or right turning) increases as the turning operation signal increases.

  Further, during the turning acceleration operation and the turning constant speed operation, in order to drive the bidirectional motor 26 immediately after the start of the turning deceleration operation, the control device 9 determines that the tilt angle of the bidirectional motor 26 is the type and magnitude of the turning operation signal. The regulator 27 is controlled to have an angle according to the angle.

  During the turning deceleration operation in which the operation lever of the turning operation device 67 is returned toward the neutral position, the control device 9 changes the second switching valve 64 according to the type of turning operation signal (left turning or right turning). While switching to the 1 state or the 2nd state, the 1st switching valve 61 is switched to a neutral state. At the same time, the control device 9 controls the regulator 24 so that the tilt angle of the bidirectional pump 23 becomes zero.

  For example, if the first switching valve 61 is in the first state during the turning acceleration operation, the second switching valve 64 is switched to the first state during the turning deceleration operation, and the circulation of the hydraulic oil in the first direction is activated in the third direction. Shift to oil circulation. Thereby, the bidirectional motor 26 is driven by the hydraulic oil discharged from the turning motor 16, and the kinetic energy during the turning deceleration operation is accumulated in the flywheel 54. However, during the turning deceleration operation, the second switching valve 64 may be switched to the third state instead of switching to the first state or the second state.

  After the turning deceleration operation, when the speed of the turning body 12 detected by the first speed detector 91 becomes zero, the control device 9 switches the second switching valve 64 to the neutral state. At the same time, the control device 9 controls the regulator 27 so that the tilt angle of the bidirectional motor 26 becomes zero.

  When the turning operation is started in a state where energy is accumulated in the flywheel 54, that is, in a state where the rotational speed of the flywheel 54 detected by the second speed detector 92 is not zero, the control device 9 outputs a turning operation signal. Depending on the type, the second switching valve 64 is switched to the first state or the second state. The control device 9 also discharges the bidirectional motor 26 in the direction corresponding to the type of the turning operation signal (left turning or right turning) as the turning operation signal increases during turning acceleration operation and turning constant speed operation. The regulator 27 is controlled so as to increase.

  Further, when supplying hydraulic oil from the bi-directional motor 26 to the swing motor 16, whether or not to supply hydraulic oil from the bi-directional pump 23 to the swing motor 16 is switched based on the amount of energy accumulated in the flywheel 54. It is done.

  Specifically, if the rotational speed Vf of the flywheel 54 detected by the second speed detector 92 is greater than a predetermined value Vs (Vf> Vs), the control device 9 maintains the first switching valve 61 in a neutral state. To do. On the other hand, if the rotational speed Vf of the flywheel 54 is smaller than the predetermined value Vs (Vf <Vs), the control device 9 sets the first switching valve 61 in the first state or the second state depending on the type of the turning operation signal. Switch to. Further, the control device 9 controls the regulator 24 for the bidirectional pump 23 based on the magnitude of the turning operation signal.

  For example, if the second switching valve 64 is in the first state, the first switching valve 61 is also switched to the first state to enable the circulation of hydraulic oil in the first direction and the hydraulic oil in the third direction. . As a result, hydraulic oil is supplied to the turning motor 16 from both the bidirectional motor 26 and the bidirectional pump 23.

  At the time of turning deceleration operation when the rotational speed of the flywheel 54 is not zero, the control device 9 performs the same control as when the rotational speed of the flywheel 54 described above is zero.

  Thus, in the present embodiment, during the turning acceleration operation or the turning constant speed operation, the bidirectional motor 26 is driven by the flywheel 54, and the bidirectional motor 26 is caused to function as a pump with the tilt angle of the bidirectional motor 26 being other than zero. Then, the turning motor 16 can be driven by the energy accumulated in the flywheel 54.

  On the other hand, when energy is stored in the flywheel 54, it is possible to use the energy stored in the flywheel 54 even if the turning operation is not performed. For example, when an operation other than the turning operation is performed and the supply pump 22 supplies hydraulic oil to at least one hydraulic actuator, the control device 9 sets the output shaft of the turning motor 16 to the above-described lock mechanism (not shown). If the bi-directional motor 26 is driven by the flywheel 54 and the bi-directional motor 26 is caused to function as a pump with the tilt angle of the bi-directional motor 26 set to a value other than zero, the bi-directional pump 23 functions as a motor. . Therefore, driving of the supply pump 22 by the engine 21 can be assisted by the energy accumulated in the flywheel 54.

  As described above, in the hydraulic drive system 1 </ b> A of the present embodiment, the kinetic energy during the turning deceleration operation can be accumulated in the flywheel 54. Therefore, the kinetic energy during the turning deceleration operation can be regenerated at an arbitrary timing.

  Further, in the present embodiment, since each of the first switching valve 61 and the second switching valve 64 permits circulation in only one direction in the first state or the second state, the bidirectional pump 23 and the bidirectional motor 26 are provided to the swing motor 16. When the hydraulic oil is supplied from both sides (when both the first switching valve 61 and the second switching valve 64 are switched to the first state or the second state), the work in the first closed loop 4 or the second closed loop 5 is performed. Oil backflow can be prevented.

  Furthermore, in the present embodiment, when the rotational speed of the flywheel 54 is high, only the second switching valve 64 is switched to the first state or the second state, and when the rotational speed of the flywheel 54 is low, the first switching valve 61 is switched. Both the second switching valve 64 and the second switching valve 64 are switched to the first state or the second state. Therefore, when the energy stored in the flywheel 54 is preferentially used for driving the swing motor 16 over the engine 21, and the energy stored in the flywheel 54 is insufficient for driving the swing motor 16, the swing motor 16 is used. The hydraulic oil can be supplied from both the bidirectional pump 23 and the bidirectional motor 26.

  In the present embodiment, since the regenerative motor 28 is provided and the potential energy of the boom can be stored in the flywheel 54, the potential energy of the boom can also be used to drive the turning motor 16.

(Second Embodiment)
FIG. 4 shows a hydraulic drive system 1B according to the second embodiment of the present invention. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and a duplicate description is omitted. In FIG. 4, the speed increaser 53, the flywheel 54, the one-way clutch 55, and the regenerative motor 28 shown in FIG.

  In this embodiment, the 1st switching valve 61 is a single 3 position valve which combined the switching valves 62 and 63 of 1st Embodiment. That is, the neutral position of the first switching valve 61 is the neutral state described in the first embodiment, and one operating position (the upper position in FIG. 4) of the first switching valve 61 is the first position described in the first embodiment. The second operation state (the lower position in FIG. 4) of the first switching valve 61 is the second state described in the first embodiment.

  Similarly, the 2nd switching valve 64 is a single 3 position valve which combined the switching valves 65 and 66 of 1st Embodiment. That is, the neutral position of the second switching valve 64 is the neutral state described in the first embodiment, and one operating position (the upper position in FIG. 4) of the second switching valve 64 is the first position described in the first embodiment. The second operation position (the lower position in FIG. 4) of the second switching valve 64 is the second state described in the first embodiment.

  Also in this embodiment, the same effect as the first embodiment can be obtained.

(Other embodiments)
The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

  For example, when the present invention is applied to a construction machine, in the hydraulic drive system (1A or 1B), since the potential energy of the boom is very large, the bidirectional pump 23 and the first switching valve 61 are omitted, and the flywheel It is possible to drive the turning motor only with the energy stored in 54. In this case, the second switching valve 64 may also be omitted.

  Alternatively, when the present invention is applied to an industrial vehicle in which HST is used in the traveling circuit, the boom cylinder 13 and the regenerative motor 28 may be omitted.

  In the first and second embodiments, the first switching valve 61 and the second switching valve 64 are omitted, and the hydraulic fluid is circulated through the first closed loop 4 and / or the second switching valve 64 is controlled only by the regulators 24 and 27. 2. Circulation of hydraulic oil through the closed loop 5 can be permitted or prohibited. However, if the first switching valve 61 and the second switching valve 64 are provided as in the first and second embodiments, the circulation is permitted and prohibited through the first closed loop 4 and the circulation through the second closed loop 5. It is possible to switch between permission and prohibition instantly. Further, if the first switching valve 61 and the second switching valve 64 are configured to function as check valves in the circulation prohibited state, it is possible to prevent backflow of hydraulic oil in the bidirectional pump 23 and the bidirectional motor 26. it can.

1A, 1B Hydraulic drive system 13 Boom cylinder 16 Rotating motor (hydraulic motor)
21 Engine 22 Supply pump 23 Two-way pump 24 Regulator (first regulator)
26 Bi-directional motor 27 Regulator (second regulator)
28 regenerative motor 4 first closed loop 5 second closed loop 54 flywheel 61 first switching valve 64 second switching valve 73 boom control valve 9 control device 91 first speed detector 92 second speed detector

Claims (7)

A hydraulic motor;
A bidirectional pump connected to the hydraulic motor to form a first closed loop and driven by an engine to supply hydraulic oil to the hydraulic motor;
A first regulator for adjusting a tilt angle of the bidirectional pump;
A bidirectional motor connected to the hydraulic motor to form a second closed loop and driven by hydraulic oil discharged from the hydraulic motor during a deceleration operation on the hydraulic motor;
A flywheel rotated by the bidirectional motor;
A second regulator for adjusting a tilt angle of the bidirectional motor;
A control device for controlling the first regulator and the second regulator based on an operation on the hydraulic motor;
A hydraulic drive system comprising: A first switching valve that is controlled by the control device and permits or prohibits the circulation of hydraulic oil through the first closed loop;
2. The hydraulic drive system according to claim 1, further comprising: a second switching valve that is controlled by the control device and permits or prohibits the circulation of hydraulic oil through the second closed loop. The first switching valve has a neutral state that prohibits the circulation of hydraulic oil through the first closed loop, a first state that permits the circulation of hydraulic oil through the first closed loop in the first direction, and the first Switchable to a second state allowing hydraulic fluid to circulate through the first closed loop in a second direction opposite to the direction;
The second switching valve has a neutral state in which the circulation of hydraulic oil through the second closed loop is prohibited, and the third direction in the third direction in which the hydraulic oil passes through the hydraulic motor in the same direction as the first direction. 2 is switchable between a first state that permits the circulation of hydraulic oil through the closed loop and a second state that permits the circulation of hydraulic oil through the second closed loop in a fourth direction opposite to the third direction. The hydraulic drive system according to claim 2, wherein A speed detector for detecting the speed of an object driven by the hydraulic motor;
The controller switches the second switching valve to the first state or the second state during a deceleration operation on the hydraulic motor, and the speed of the object detected by the speed detector becomes zero after the deceleration operation. The hydraulic drive system according to claim 3, wherein the second switching valve is switched to a neutral state at a time. A speed detector for detecting the rotational speed of the flywheel;
When the rotational speed of the flywheel detected by the second detector is greater than the predetermined value during acceleration operation and constant speed operation with respect to the hydraulic motor, the control device moves the second switching valve to the second switching valve. When the first switching valve is switched to the neutral state and the rotational speed of the flywheel detected by the speed detector is smaller than a predetermined value, the first switching valve is switched to the first state or the second state. The hydraulic drive system according to claim 3 or 4, wherein both the second switching valve and the second switching valve are switched to the first state or the second state. A boom cylinder;
A supply pump driven by the engine for supplying hydraulic oil to the boom cylinder via a control valve;
A regenerative motor that is driven by hydraulic oil discharged from the boom cylinder during a boom lowering operation and rotates the flywheel;
The hydraulic drive system according to any one of claims 1 to 5, further comprising: A hydraulic motor;
A bidirectional motor connected to the hydraulic motor to form a closed loop and rotated by hydraulic fluid discharged from the hydraulic motor during a deceleration operation on the hydraulic motor;
A flywheel rotated by the bidirectional motor;
A regulator for adjusting the tilt angle of the bidirectional motor;
A control device for controlling the regulator based on an operation on the hydraulic motor;
A boom cylinder;
A supply pump driven by an engine for supplying hydraulic oil to the boom cylinder via a control valve;
A regenerative motor that is driven by hydraulic oil discharged from the boom cylinder during a boom lowering operation and rotates the flywheel;
A hydraulic drive system comprising:

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