WO2019004156A1

WO2019004156A1 - Hydraulic drive system

Info

Publication number: WO2019004156A1
Application number: PCT/JP2018/024084
Authority: WO
Inventors: 信治西田; 亮介楠本; 武久加藤; 優樹中山
Original assignee: 川崎重工業株式会社
Priority date: 2017-06-27
Filing date: 2018-06-26
Publication date: 2019-01-03
Also published as: JP7037290B2; JP2019007586A

Abstract

This hydraulic drive system is provided with: a hydraulic motor; a bi-directional pump connected to the hydraulic motor so as to form a first closed loop and driven by an engine to supply hydraulic oil to the hydraulic motor; a first regulator for regulating the tilt angle of the bi-directional pump; a bi-directional motor connected to the hydraulic motor so as to form a second closed loop and driven by hydraulic oil discharged from the hydraulic motor when the hydraulic motor is operated to reduce the speed thereof; a flywheel rotated by the bi-directional motor; a second regulator for regulating the tilt angle of the bi-directional motor; and a control device for controlling the first regulator and the second regulator on the basis of operation on the hydraulic motor.

Description

Hydraulic drive system

The present invention relates to a hydraulic drive system.

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

For example, Patent Document 1 discloses a hydraulic drive system configured to be able to regenerate kinetic energy at the time of turning and decelerating operation. In this hydraulic drive system, a bi-directional pump (also referred to as an over-center pump) driven by an engine is connected to a swing motor so as to form a closed loop by a pair of supply and discharge lines. The engine also drives a supply pump that supplies hydraulic fluid to hydraulic actuators other than the swing motor.

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

JP, 2016-80009, A

However, in the hydraulic drive system disclosed in Patent Document 1, kinetic energy at the time of the swing deceleration operation is regenerated only when the supply pump supplies the hydraulic fluid to any hydraulic actuator.

Then, an object of this invention is to provide the hydraulic drive system which can regenerate | regenerate the kinetic energy at the time of deceleration operation with respect to a hydraulic motor at arbitrary timing.

In order to solve the problem, a hydraulic drive system according to one aspect of the present invention is driven by an engine connected to the hydraulic motor and the hydraulic motor to form a first closed loop, to the hydraulic motor. The hydraulic motor connected to the hydraulic motor so as to form a second closed loop, a bidirectional pump supplying hydraulic fluid, a first regulator for adjusting the tilt angle of the bidirectional pump, and the hydraulic motor at the time of deceleration operation to the hydraulic motor A bidirectional motor driven by hydraulic fluid discharged from the pump, a flywheel rotated by the bidirectional motor, a second regulator for adjusting a tilt angle of the bidirectional motor, and the second motor based on the operation to the hydraulic motor And a controller that controls the first regulator and the second regulator.

According to the above configuration, kinetic energy at the time of deceleration operation to the hydraulic motor can be stored in the flywheel. Therefore, kinetic energy at the time of deceleration operation to the hydraulic motor can be regenerated at any timing. For example, at the time of accelerating operation to the hydraulic motor or at the same speed operation, if the bidirectional motor is driven by the flywheel and the two-directional motor is made to function as a pump while the tilting angle of the bidirectional motor is other than zero, energy stored in the flywheel The hydraulic motor can be driven. Alternatively, when the engine also drives a supply pump that supplies hydraulic fluid to hydraulic actuators other than hydraulic motors, the output shaft of the hydraulic motor is locked with a lock mechanism even when acceleration operation or constant speed operation is not performed on the hydraulic motor. When the motor is locked and the bidirectional motor is driven by the flywheel and the tilt angle of the bidirectional motor is other than zero and the bidirectional motor is functioned as a pump, the bidirectional pump functions as a motor. Therefore, the energy stored in the flywheel can assist the drive of the supply pump by the engine.

The above-described hydraulic drive system is controlled by the control device, and includes a first switching valve that permits or prohibits the circulation of hydraulic fluid through the first closed loop, and the second closed loop controlled by the control device. And a second switching valve for permitting or prohibiting the circulation of the hydraulic fluid. According to this configuration, it is possible to instantly switch between permitting and prohibiting circulation through the first closed loop and permitting and prohibiting circulation through the second closed loop. In addition, if the first switching valve and the second switching valve are configured to function as check valves in the circulation inhibition state, it is possible to prevent the backflow of hydraulic oil in the bidirectional pump and the bidirectional motor.

The first switching valve has a neutral state that prohibits the circulation of hydraulic fluid through the first closed loop, a first state that allows the hydraulic fluid to circulate through the first closed loop in a first direction, and the first state. Switchable to a second state permitting circulation of hydraulic fluid through the first closed loop in a second direction opposite to the direction, the second switching valve circulating hydraulic fluid through the second closed loop A neutral state prohibiting the hydraulic oil, a first state permitting circulation of the hydraulic oil 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 switchable to a second state which permits the circulation of hydraulic fluid through the second closed loop in a fourth direction opposite to the third direction. According to this configuration, when the hydraulic motor is supplied with hydraulic fluid 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 above-described hydraulic drive system further includes a speed detector that detects the speed of an object driven by the hydraulic motor, and the control device is configured to reduce the second switching valve when the hydraulic motor is decelerated. 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 decelerating operation.

The above hydraulic drive system further includes a speed detector for detecting the rotational speed of the flywheel, and the control device is detected by the second detector at the time of acceleration operation and constant speed operation on the hydraulic motor. If the rotational speed of the flywheel is larger than the predetermined value, the second switching valve is switched to the first state or the second state, and the first switching valve is switched to the neutral state, and the speed detector Both the first switching valve and the second switching valve may be switched to the first state or the second state as long as the rotational speed of the flywheel detected at step (d) is smaller than a predetermined value. According to this configuration, the energy stored in the flywheel is preferentially used to drive the hydraulic motor rather than the engine, and when the energy stored in the flywheel is insufficient for driving the hydraulic motor, the hydraulic motor is driven in both directions. Hydraulic fluid can be supplied from both the pump and the two-way motor.

The above-described hydraulic drive system includes a boom cylinder, a supply pump driven by the engine that supplies hydraulic fluid to the boom cylinder via a control valve, and hydraulic fluid discharged from the boom cylinder at the time of a boom lowering operation. The motor may further comprise 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 to drive the hydraulic motor.

Further, according to another aspect of the present invention, there is provided a hydraulic drive system comprising: a hydraulic motor; and hydraulic oil discharged from the hydraulic motor at the time of a reduction operation on the hydraulic motor connected to the hydraulic motor to form a closed loop. Two-way motor that is rotated, flywheel that is rotated by the two-way motor, a regulator that adjusts the tilt angle of the two-way motor, a control device that controls the regulator based on the operation on the hydraulic motor, boom cylinder An engine driven feed pump for supplying hydraulic fluid to the boom cylinder via a control valve; and a regenerative brake driven by hydraulic fluid discharged from the boom cylinder at the time of a boom lowering operation to rotate the flywheel And a motor.

According to the above configuration, kinetic energy at the time of deceleration operation to the hydraulic motor can be stored in the flywheel. Therefore, as in the hydraulic drive system according to one aspect of the present invention, kinetic energy at the time of deceleration operation on the hydraulic motor can be regenerated at any timing. Furthermore, 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 to drive the hydraulic motor.

According to the present invention, kinetic energy at the time of deceleration operation to a hydraulic motor can be regenerated at any timing.

FIG. 2 is a schematic configuration view around an engine and a swing motor of the hydraulic drive system according to the first embodiment of the present invention. It is a schematic block diagram of a boom cylinder periphery of a hydraulic drive system shown in FIG. It is a side view of the hydraulic shovel which is an example of construction machinery. It is a schematic block diagram of the engine of the hydraulic drive system concerning a 2nd embodiment of the present invention, and a revolution motor circumference.

First Embodiment
1 and 2 show a hydraulic drive system 1A according to a 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 shovel, the present invention is also applicable to other construction machines such as a hydraulic crane. Alternatively, the present invention is applicable not only to construction machines but also to industrial vehicles such as wheel loaders.

In the present 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 not be used for the turning circuit, and HST may be used for the traveling circuit. In this case, each of a left traveling motor and a right traveling motor 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 a self-propelled type, and includes a traveling body 11 and a swing body 12 rotatably supported by the traveling body 11. The traveling body 11 is driven by a left traveling motor and a right traveling motor described later, and the swing structure 12 is driven by a swing motor 16 described later. The revolving unit 12 is provided with a cabin for accommodating a pilot and a boom is connected. 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 a boom cylinder 13, an arm cylinder 14 and a bucket cylinder 15 shown in FIG. 3 as hydraulic actuators, and also includes a swing motor 16 shown in FIG. 1 and a left travel motor and a right travel motor. The hydraulic drive system 1A also includes a bidirectional pump 23 dedicated to the swing motor 16 and a supply pump 22 that supplies hydraulic fluid to hydraulic actuators other than the swing motor 16 via control valves. The bidirectional pump 23 and the feed 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. Further, although only one supply pump 22 is provided in the illustrated example, a plurality of supply pumps 22 may be provided.

The two-way pump 23 is a variable displacement pump capable of changing the tilt angle. The tilt angle of the bidirectional pump 23 is adjusted by the regulator 24 (corresponding to the first regulator of the present invention). In the present embodiment, the bidirectional pump 23 is a swash plate pump in which the swash plate can be tilted to both sides from the center (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 axis pump in which the oblique axis can be tilted to both sides from the center (the axial direction of the bidirectional pump 23).

The bidirectional pump 23 is connected to the swing motor 16 so as to form a first closed loop 4 by a pair of supply and

discharge lines

4 a and 4 b. That is, the hydraulic fluid is supplied from the bidirectional pump 23 to the swing motor 16 through one of the supply and

discharge lines

4a and 4b, and the hydraulic fluid is discharged from the swing motor 16 to the bidirectional pump 23 through the other of the supply and

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 locking mechanism includes, for example, a hydraulic cylinder that operates to grip the output shaft of the pivot motor 16.

The supply and

discharge lines

4 a and 4 b are connected to each other by a first bridge 41, a second bridge 43 and a third bridge 45. In the present embodiment, the first bridge path 41, the second bridge path 43 and the third bridge path 45 are arranged in this order from the bidirectional pump 23 toward the swing 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 side portion of the relief valve 32 in the circulation line 31 doubles as the drain line of the bidirectional pump 23.

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

The supply and

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 the discharge line 38 is provided with a relief valve 39. 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.

When the pressure of one of the supply and

discharge lines

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

The regulator 24 described above operates 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 is an electric actuator connected to the swash plate of the bidirectional pump 23 May be

The regulator 24 is controlled by the controller 9. However, in FIG. 1, only some signal lines are 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 (left turning operation signal or right turning operation signal) according to the tilt angle of the operation lever. That is, the turning operation signal output from the turning operation device 67 becomes larger as the tilt angle (operation amount) of the operation lever becomes larger.

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 or 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 the present embodiment, the bidirectional motor 26 is connected to the swing motor 16 so as to form the second closed loop 5 by the pair of supply and

discharge lines

5a and 5b. That is, the end of the supply / discharge line 5a on the side of the turning motor 16 is a flow path common to the end of the supply / discharge line 4a described above on the side of the turning motor 16, and the end of the supply / discharge line 5b on the side of the turning motor 16 The part is a common flow path with the end of the feed / discharge line 4b described above on the side of the swing motor 16.

The bidirectional motor 26 is driven by the hydraulic oil discharged from the swing motor 16 at the time of the swing decelerating (when the swing operation signal output from the swing operation device 67 decreases). That is, at the time of swing deceleration, hydraulic fluid is supplied from the swing motor 16 to the bidirectional motor 26 through one of the supply and

discharge lines

5a and 5b, and hydraulic fluid is discharged from the bidirectional motor 26 to the swing motor 16 through the other of the supply and

discharge lines

5a and 5b. Be done.

The supply and

discharge lines

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

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

The regulator 27 operates by an electrical 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 is an electric actuator connected to the swash plate of the bidirectional motor 26. May be

The regulator 27 is controlled by the controller 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 two-way 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 increasing gear 53 composed of a gear train. However, the bidirectional motor 26 may be directly coupled to the flywheel 54. Further, in the present embodiment, no clutch is provided between the bidirectional motor 26 and the speed increasing device 53, but whether torque transmission is permitted between the bidirectional motor 26 and the speed increasing device 53 A switching clutch may be provided.

Furthermore, in the present embodiment, the flywheel 54 is connected to the regenerative motor 28 via the speed increasing gear 53 and the one-way clutch 55. One-way clutch 55 allows only torque transmission from regenerative motor 28 to speed increasing device 53.

The first switching valve 61 and the 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 controller 9. The first switching valve 61 permits or prohibits the circulation of hydraulic fluid through the first closed loop 4 described above, and the second switching valve 64 permits or prohibits the circulation of the hydraulic fluid through the second closed loop 5 described above.

In the present embodiment, the first switching valve 61 is configured by the switching valve 62 provided in the supply / discharge line 4 a and the switching valve 63 provided in the supply / discharge line 4 b. The second switching valve 64 is configured of a switching valve 65 provided in the supply and discharge line 5a and a switching valve 66 provided in the supply and discharge line 4b.

In the neutral position, the switching valve 62 functions as a check valve that allows the flow from the bi-directional pump 23 to the swing motor 16 through the supply and discharge line 4a but prohibits the reverse flow. When a command current is supplied from the controller 9 to the switching valve 62 and the switching valve 62 is switched to the operating position, the switching valve 62 allows 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 via the supply and 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 bidirectional flow.

That is, the first switching valve 61 is in the neutral state in which the switching valve 62 and the switching valve 63 are in the neutral position, the first state in which the switching valve 62 is in the neutral position, and the switching valve 63 is in the operating position, In the operating position, the switch valve 63 is in the neutral position, and the third state in which the switch valve 62 and the switch valve 63 are in the operating position. The first switching valve 61 in the neutral state prohibits the circulation of hydraulic fluid through the first closed loop 4. The first switching valve 61 in the first state permits circulation of hydraulic fluid 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 circulation of hydraulic fluid through the first closed loop 4 in the second direction, while inhibiting circulation of hydraulic fluid 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 and second directions.

In the neutral position, the switching valve 65 functions as a check valve that allows the flow from the two-way motor 26 to the swing motor 16 through the supply and 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 bidirectional flow. Similarly, in the neutral position, the switching valve 66 functions as a check valve that allows the flow from the two-way motor 26 to the turning motor 16 through the supply and discharge line 4b but prohibits the reverse flow. When a command current is supplied from the controller 9 to the switching valve 66 and the switching valve 66 switches to the operating position, the switching valve 66 allows bidirectional flow.

That is, the second switching valve 64 is in the neutral state in which the switching valve 65 and the switching valve 66 are in the neutral position, the first state in which the switching valve 65 is in the neutral position, and the switching valve 66 is in the operating position, Is switchable between a second state in which the switch valve 66 is in the neutral position, and a third state in which the switch valve 65 and the switch valve 66 are in the operating position. The second switching valve 64 in the neutral state prohibits the circulation of hydraulic fluid 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 swing motor 16 in the same direction as the first direction, while The circulation of hydraulic fluid 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 circulation of hydraulic fluid through the second closed loop 5 in the fourth direction, while prohibiting circulation of hydraulic fluid through the first closed loop 4 in the third direction. The second switching valve 64 in the third state allows circulation of hydraulic fluid through the second closed loop 5 in the third and fourth directions.

The first bridge path 41 and the replenishment line 33 described above play a role of preventing cavitation on the suction side of the bidirectional pump 23 when the circulation of hydraulic fluid through the first closed loop 4 is prohibited by the first switching valve 61. Play. Similarly, the bridge path 51 and the supply line 34 play a role in preventing cavitation on the suction side of the bidirectional motor 26 when the circulation of hydraulic fluid through the second closed loop 5 is prohibited by the second switching valve 64. .

The feed 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 feed 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 electrical positive control method, and a load sensing method.

The supply pump 22 is connected by a supply line 71 to a plurality of control valves (not shown except for the boom control valve 73) including the boom control valve 73. 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 the present embodiment, the bleed line 72 is branched from the supply line 71, and this bleed line 72 is a center bleed line passing through a plurality of control valves. However, the bleed line 72 may not pass through a 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 (the left position in FIG. 1) or the boom lowering operation position (the right position in FIG. 1) by operating the boom operating 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 communicates 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 of an electromagnetic pilot type.

Boom operating device 68 includes an operating lever that receives a boom operation (an operation on boom cylinder 13), and outputs a boom operating 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. The 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 solenoid proportional valves (not shown) so that the boom control valve 73 has an opening area corresponding to the boom operation signal. However, the boom control device 68 may be a pilot control valve that outputs a pilot pressure as a boom control signal. In this case, the pilot port of the boom control valve 73 is connected by a pilot line to the boom operating device 68 which is a pilot control valve. When the boom operating device 68 is a pilot operating valve, the pilot pressure output from the boom operating device 68 is detected by the pressure sensor and input to the control device 9.

The above-described regenerative motor 28 is driven by the hydraulic oil discharged from the boom cylinder 13 at the time of 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 that purpose, the tank line 76 is provided with a regenerative valve 81. Further, the regenerative valve 81 is connected to the regenerative motor 28 by 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 displacement motor (swash plate motor or oblique axis 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 displacement motor.

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

The regenerative line 82 is provided with a check valve 83. Further, the downstream side portion of the check valve 83 in the regeneration line 82 is connected to the upstream side portion of the relief valve 32 in the circulation line 31 by the supply 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 at the neutral position.

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

Next, 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 swing 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 rotating body 12, and the second speed detector 92 detects the rotational speed of the flywheel 54.

First, control from a state where energy is not stored in the flywheel 54 at startup of the construction machine 10, that is, a 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 the 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 turning operation signal (whether left turning or right turning). Switch to the first state or the second state. In addition, the control device 9 performs the turning acceleration operation (when the turning operation signal output from the turning operation device 67 increases) and the turning constant speed operation (when the turning operation signal output from the turning operation device 67 is other than zero). At a certain time), the regulator 24 is controlled such that the discharge flow rate of the bidirectional pump 23 in the direction according to the type of the turning operation signal (left turning or right turning) increases as the turning operation signal increases.

Furthermore, at the time of turning acceleration operation and turning constant velocity operation, in order to drive the bidirectional motor 26 immediately after the start of the turning deceleration operation, the controller 9 controls the tilting angle of the bidirectional motor 26 to change the type and magnitude of the turning operation signal. The regulator 27 is controlled to have an angle corresponding to the distance.

At the time of the decelerating 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 the turning operation signal (left turn or right turn). While switching to the 1 state or the second state, the first switching valve 61 is switched to the neutral state. At the same time, the controller 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 at the time of the swing acceleration operation, the second switching valve 64 is switched to the first state at the time of the swing decelerating operation to operate the hydraulic fluid in the first direction in the third direction. Shift to oil circulation. As a result, the bidirectional motor 26 is driven by the hydraulic oil discharged from the swing motor 16, and kinetic energy at the time of the swing reduction operation is accumulated in the flywheel 54. However, when turning and decelerating, the second switching valve 64 may be switched to the third state instead of switching to the first state or the second state.

When the speed of the swing body 12 detected by the first speed detector 91 becomes zero after the turning and decelerating operation, 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 stored in the flywheel 54, that is, when the rotational speed of the flywheel 54 detected by the second speed detector 92 is not zero, the controller 9 generates a turning operation signal The second switching valve 64 is switched to the first state or the second state depending on the type of the valve. Further, at the time of turning acceleration operation and turning constant velocity operation, the controller 9 causes the discharge flow rate of the bidirectional motor 26 in the direction according to the type of turning operation signal (whether left turning or right turning) as the turning operation signal increases. The regulator 27 is controlled so as to become large.

Furthermore, when hydraulic fluid is supplied from the bidirectional motor 26 to the swing motor 16, whether or not hydraulic fluid is also supplied from the bidirectional pump 23 to the swing motor 16 is switched based on the amount of energy stored in the flywheel 54. Be

Specifically, when the rotational speed Vf of the flywheel 54 detected by the second speed detector 92 is larger than the predetermined value Vs (Vf> Vs), the controller 9 maintains the first switching valve 61 in the neutral state. Do. On the other hand, if the rotational speed Vf of the flywheel 54 is smaller than the predetermined value Vs (Vf <Vs), the controller 9 sets the first switching valve 61 in the first state or the second state according to the type of the turning operation signal. Switch to Furthermore, the controller 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 circulation of hydraulic fluid in the first direction and circulation of hydraulic fluid in the third direction. . As a result, hydraulic fluid is supplied to the swing motor 16 from both the bidirectional motor 26 and the bidirectional pump 23.

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

As described above, in the present embodiment, the bi-directional motor 26 is driven by the flywheel 54 and the bi-directional motor 26 functions as a pump with the non-zero tilt angle of the bi-directional motor 26 during the swing acceleration operation or the swing constant velocity operation. Then, the swing motor 16 can be driven by the energy stored 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 swing operation is performed and the supply pump 22 supplies the hydraulic fluid to at least one hydraulic actuator, the control device 9 locks the output shaft of the swing motor 16 as described above. Lock the motor and drive the bidirectional motor 26 with the flywheel 54 and allow the bidirectional motor 26 to function as a pump with a non-zero tilt angle of the bidirectional motor 26, the bidirectional pump 23 will function as a motor. . Therefore, the energy stored in the flywheel 54 can assist the drive of the supply pump 22 by the engine 21.

As described above, in the hydraulic drive system 1A of the present embodiment, kinetic energy at the time of turning and decelerating operation can be stored in the flywheel 54. Therefore, kinetic energy at the time of turning and decelerating operation can be regenerated at any timing.

Further, in the present embodiment, 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. Working in the first closed loop 4 or the second closed loop 5 when the hydraulic fluid is supplied from both (when the first switching valve 61 and the second switching valve 64 are both switched to the first state or the second state) It is possible to prevent the backflow of oil.

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

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

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

In the present embodiment, the first switching valve 61 is a single three-position valve in which the switching

valves

62 and 63 of the first embodiment are combined. That is, the neutral position of the first switching valve 61 is in 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. In the second position, the other operating position (the lower position in FIG. 4) of the first switching valve 61 is the second position described in the first embodiment.

Similarly, the second switching valve 64 is a single three-position valve in which the switching

valves

65 and 66 of the first embodiment are combined. That is, the neutral position of the second switching valve 64 is in the neutral state described in the first embodiment, and one operating position of the second switching valve 64 (the upper position in FIG. 4) is the first embodiment described in the first embodiment. In the second position, the other operating position (the lower position in FIG. 4) of the second switching valve 64 is the second position described in the first embodiment.

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

(Other embodiments)
The present invention is not limited to the embodiments described above, and various modifications can be made without departing from the scope 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 may be omitted to provide a flywheel. It is possible to drive the swing motor with only 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.

Further, in the first and second embodiments, the first switching valve 61 and the second switching valve 64 are omitted, and the circulation of hydraulic oil through the first closed loop 4 and / or the first closed loop 4 only by the control of the

regulators

24 and 27 The circulation of hydraulic fluid 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, permission and prohibition of circulation through the first closed loop 4 and circulation through the second closed loop 5 are provided. It is possible to switch between permission and prohibition instantly. In addition, if the first switching valve 61 and the second switching valve 64 are configured to function as check valves in the circulation inhibition state, the backflow of hydraulic oil in the bidirectional pump 23 and the bidirectional motor 26 can be prevented. it can.

1A, 1B Hydraulic drive system 13 Boom cylinder 16 Swing motor (hydraulic motor)
21 engine 22 supply pump 23 two-way pump 24 regulator (first regulator)
26 2-way 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

Hydraulic motor,
A bi-directional pump driven by an engine and supplying hydraulic fluid to the hydraulic motor, connected with the hydraulic motor to form a first closed loop;
A first regulator for adjusting a tilt angle of the bidirectional pump;
A bidirectional motor connected with the hydraulic motor so as to form a second closed loop, which is driven by hydraulic fluid discharged from the hydraulic motor when the hydraulic motor is decelerated;
A flywheel rotated by the bidirectional motor;
A second regulator for adjusting the tilt angle of the bidirectional motor;
A control device that controls the first regulator and the second regulator based on an operation on the hydraulic motor;
, Hydraulic drive system.
A first switching valve controlled by the control device for permitting or inhibiting the circulation of hydraulic fluid through the first closed loop;
The hydraulic drive system according to claim 1, further comprising: a second switching valve controlled by the control device that permits or prohibits the circulation of hydraulic fluid through the second closed loop.
The first switching valve has a neutral state that prohibits the circulation of hydraulic fluid through the first closed loop, a first state that allows the hydraulic fluid to circulate through the first closed loop in a first direction, and the first state. Switchable to a second state permitting circulation of hydraulic fluid through the first closed loop in a second direction opposite to the direction;
The second switching valve is in a neutral state for inhibiting the circulation of hydraulic fluid through the second closed loop, and in the third direction in which the hydraulic fluid passes through the hydraulic motor in the same direction as the first direction. (2) switchable between a first state permitting circulation of hydraulic fluid through the closed loop and a second state permitting circulation of hydraulic fluid through the second closed loop in a fourth direction opposite to the third direction The hydraulic drive system according to claim 2.
The apparatus further comprises a speed detector for detecting the speed of an object driven by the hydraulic motor,
The control device switches the second switching valve to the first state or the second state when the hydraulic motor is decelerating, and the velocity of the object detected by the speed detector after the decelerating operation becomes zero. The hydraulic drive system according to claim 3, wherein the second switching valve is switched to the neutral state when it is turned off.
It further comprises a speed detector for detecting the rotational speed of the flywheel,
When the rotational speed of the flywheel detected by the second detector is larger than the predetermined value at the time of accelerating operation and equal speed operation to the hydraulic motor, the control device controls the second switching valve to the second switching valve. Switching to the first state or the second state, switching the first switching valve to the neutral state, and if the rotational speed of the flywheel detected by the speed detector is smaller than a predetermined value, the first switching valve The hydraulic drive system according to claim 3 or 4, wherein both of 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, which supplies hydraulic oil to the boom cylinder via a control valve;
A regenerative motor driven by hydraulic fluid discharged from the boom cylinder at the time of a boom lowering operation to rotate the flywheel;
The hydraulic drive system according to any one of claims 1 to 5, further comprising:
Hydraulic motor,
A bidirectional motor connected with the hydraulic motor so as to form a closed loop, which is rotated by hydraulic fluid discharged from the hydraulic motor when the hydraulic motor is decelerated;
A flywheel rotated by the bidirectional motor;
A regulator for adjusting the tilt angle of the bidirectional motor;
A controller that controls the regulator based on an operation on the hydraulic motor;
A boom cylinder,
An engine driven feed pump for feeding hydraulic oil to the boom cylinder through a control valve;
A regenerative motor driven by hydraulic fluid discharged from the boom cylinder at the time of a boom lowering operation to rotate the flywheel;
, Hydraulic drive system.