JP2013104244A - Hydraulic shovel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the energy consumption of a pump driving source without causing problems of an increase of a manufacturing cost and the impairment of operation responsiveness.SOLUTION: Between a first discharge port 10a of a hydraulic pump 10 and a first suction port 20a of a revolving hydraulic motor 20 and between a second discharge port 10b and a second suction port 20b, oil supply passages 70A, 70B are provided which have oil supply check valves 71A, 71B for making a connection between the hydraulic pump 10 and the revolving hydraulic motor 20 independently of the position of a neutral holding valve 60 and preventing the passage of oil from the revolving hydraulic motor 20 to the hydraulic pump 10. When arranged at a first position, the neutral holding valve 60 permits the passage of the oil from the second suction port 20b to the second discharge port 10b and prevents the passage of the oil from the first suction port 20a to the first discharge port 10a, and when arranged at a second position, it permits the passage of the oil from the first suction port 20a to the first discharge port 10a and prevents the passage of the oil from the second suction port 20b to the second discharge port 10b.

Description

  The present invention relates to a hydraulic excavator provided with a turning hydraulic circuit that rotates a turning hydraulic motor in a first rotation direction and a second rotation direction by controlling supply of oil from a variable displacement hydraulic pump. More specifically, the present invention relates to an improvement of a turning hydraulic circuit having a neutral holding function of a turning hydraulic motor.

  For a hydraulic excavator in which a swivel body is swung by a swivel hydraulic motor, a variable displacement pump is applied as a hydraulic pump, and a pair of main oil passages are provided between the hydraulic pump and the swivel hydraulic motor. Provides a turning hydraulic circuit that constitutes a closed circuit. In this turning hydraulic circuit, by changing the tilt angle of the hydraulic pump, the torque and rotation speed required for the turning hydraulic motor can be obtained continuously, and the rotation direction of the turning hydraulic motor is reversed. It is also possible to do.

  In this type of turning hydraulic circuit, when the tilt angle of the hydraulic pump is zero, that is, when the operation lever is in the non-operating state, the hydraulic pump is stopped, so that oil is supplied to the turning hydraulic motor. There is no. However, even when the operating lever is not operated, for example, when an external force is applied to turn the turning body, such as when the excavator is stopped on a slope, the turning hydraulic motor is stopped. It is difficult to set up, and there is a possibility that the work machine provided on the revolving structure may turn downward on the slope. For this reason, this type of turning hydraulic circuit is often provided with a neutral holding function.

  For example, in Patent Document 1, when a neutral holding unit having a check valve is interposed in each of two main oil passages connecting between a hydraulic pump and a turning hydraulic motor, and the operation lever is in an unoperated state, The oil is prevented from passing from the hydraulic motor to the hydraulic pump. Similarly, in Patent Document 2, a neutral holding valve having a built-in check valve function is interposed in two main oil passages that connect between a hydraulic pump and a turning hydraulic motor, and the operation lever is in an unoperated state. The function of the check valve prevents oil from passing from the turning hydraulic motor to the hydraulic pump.

  According to these prior arts, when the operating lever is in the non-operating state, the check valve prevents the passage of oil from the turning hydraulic motor to the hydraulic pump, so an external force is applied to turn the turning body. In this case, the turning hydraulic motor can be continuously maintained in the stopped state.

  Here, in the initial stage of operating the operation lever from the neutral state and supplying oil from the hydraulic pump to the turning hydraulic motor, the pressure closer to the turning hydraulic motor than the check valve in the main oil passage is A state may occur where the pressure is higher than the pressure on the side closer to the hydraulic pump than the check valve. In such a case, since the oil in the main oil passage once flows toward the hydraulic pump, there arises a problem that the revolving body revolves in the direction opposite to the operation direction of the operation lever. Specifically, even when the operation lever is operated so as to turn the turning body upward on the slope, the turning body once turns downward on the slope, and then the oil supplied from the hydraulic pump When the pressure in the main oil passage rises, a situation in which the swivel body turns in a desired direction can occur.

  On the other hand, in Patent Document 3, a neutral holding valve having a built-in check valve function is interposed in each of two main oil passages, and when the operation lever is in a non-operating state and when the hydraulic pump supplies oil to the turning hydraulic motor. When the oil is supplied, the flow of oil from the turning hydraulic motor to the hydraulic pump is blocked by the function of the check valve. According to Patent Document 3, when the operation lever is operated from the neutral state and oil is supplied from the hydraulic pump to the turning hydraulic motor, the pressure closer to the turning hydraulic motor than the check valve in the main oil passage. Even if the flow rate is high, the flow of oil toward the hydraulic pump is blocked by the check valve, so that there is no possibility of causing a situation where the swinging body turns in the direction opposite to the operation direction of the operation lever.

JP-A-56-134663 JP-A-57-81536 JP 2011-33177 A

  However, in Patent Document 3, it is difficult to ensure a large opening cross-sectional area of the portion having the function of the check valve provided in the neutral holding valve. Also, the pressure loss when flowing is large. For this reason, the energy consumption of the pump drive source for driving the hydraulic pump, for example, the fuel consumption of the engine inevitably increases, which is not necessarily preferable from the viewpoint of energy saving.

  Such a problem can be solved by increasing the size of the neutral holding valve. That is, if the diameter of the spool of the neutral holding valve is increased, it is possible to secure a large opening area of the check valve function part and reduce pressure loss. However, in the case of an enlarged neutral holding valve, not only the manufacturing cost increases, but also the response to the operation of the operation lever may be impaired. For this reason, the pilot pressure must be increased in order to ensure the operation responsiveness. Consequently, the fuel consumption of the pump drive source cannot be denied.

  An object of the present invention is to provide a hydraulic excavator that can reduce the energy consumption of a pump drive source without incurring problems that the manufacturing cost increases and operation responsiveness is impaired. And

  In order to achieve the above object, a hydraulic excavator according to the present invention includes a first main oil passage that connects a first discharge port of a variable displacement hydraulic pump and a first suction port of a turning hydraulic motor, and the hydraulic pump. A second discharge port and a second suction port of the turning hydraulic motor, and a second main circuit that forms a closed circuit between the hydraulic pump and the turning hydraulic motor by the first main oil passage. An oil passage; and a neutral holding valve that is interposed in the first main oil passage and the second main oil passage and controls passage of oil between the hydraulic pump and the turning hydraulic motor, the neutral holding valve For turning to prevent the turning of the turning body by blocking the passage of oil from the turning hydraulic motor to the hydraulic pump and stopping the rotation of the turning hydraulic motor Hydraulic excavator with hydraulic circuit The turning hydraulic circuit includes a first discharge port of the hydraulic pump and a first suction port of the turning hydraulic motor, and a second discharge port of the hydraulic pump and the turning hydraulic motor. Between the second suction port, the hydraulic pump and the turning hydraulic motor are connected regardless of the position of the neutral holding valve, and the passage of oil from the turning hydraulic motor to the hydraulic pump is prevented. A separate oil supply passage having an oil supply check valve to be blocked is provided, and the neutral holding valve is interposed over both the first main oil passage and the second main oil passage, and from the neutral position to the first position or When switching to the second position and being arranged at the first position, the passage of oil from the second suction port of the turning hydraulic motor to the second discharge port of the hydraulic pump is allowed. And the first suction of the turning hydraulic motor. When oil is prevented from passing from the opening toward the first discharge port of the hydraulic pump and is disposed at the second position, the first discharge port of the hydraulic pump is discharged from the first suction port of the turning hydraulic motor. The passage of oil toward the outlet is allowed, and the passage of oil from the second suction port of the turning hydraulic motor toward the second discharge port of the hydraulic pump is prevented.

  In the above-described hydraulic excavator, the oil supply passage may be provided between the first discharge port of the hydraulic pump and the first suction port of the turning hydraulic motor so as to bypass the neutral holding valve. The second discharge port of the hydraulic pump is connected to the second suction port of the turning hydraulic motor.

  Further, according to the present invention, in the above-described hydraulic excavator, the oil supply passage passes between the neutral holding valve and passes between the first discharge port of the hydraulic pump and the first suction port of the turning hydraulic motor and the hydraulic pressure. A second discharge port of the pump and a second suction port of the turning hydraulic motor are connected to each other, and the oil supply check valve is provided outside the neutral holding valve.

  According to the present invention, the first discharge port of the hydraulic pump and the first suction port of the turning hydraulic motor are connected, and the second discharge port of the hydraulic pump and the second suction port of the turning hydraulic motor are connected. When the oil supply check valve is arranged in the oil supply passage and the neutral holding valve is arranged at the neutral position, the oil supply check valve of the oil supply passage is made to function to prevent the oil from passing from the turning hydraulic motor to the hydraulic pump, Even when oil is supplied from the hydraulic pump to the turning hydraulic motor through one of the oil supply passages, the oil check valve interposed in the oil supply passage functions to prevent the oil from passing from the turning hydraulic motor to the hydraulic pump. I am doing so. Therefore, it is possible to provide the function of the oil supply check valve outside the neutral holding valve, and it is possible to sufficiently secure the oil passage opening cross-sectional area and reduce the pressure loss without increasing the size of the neutral holding valve. . As a result, the energy consumption of the pump drive source can be reduced without incurring problems that the manufacturing cost increases and problems that impair operation responsiveness.

FIG. 1 is a turning hydraulic circuit diagram applied to the hydraulic excavator according to the first embodiment of the present invention. FIG. 2 is an external side view of a hydraulic excavator to which the turning hydraulic circuit shown in FIG. 1 is applied. FIG. 3 is a plan view of the excavator shown in FIG. FIG. 4 is a turning hydraulic circuit diagram applied to the hydraulic excavator according to the second embodiment of the present invention.

  Exemplary embodiments of a hydraulic excavator according to the present invention will be described below in detail with reference to the accompanying drawings.

(Embodiment 1)
FIG. 1 is a turning hydraulic circuit diagram applied to the hydraulic excavator according to the first embodiment of the present invention. The hydraulic excavator exemplified here is applied to a hydraulic excavator provided with an upper swing body 1 and a lower traveling body 2 as shown in FIGS. 2 and 3, and the upper swing body 1 is moved vertically with respect to the lower traveling body 2. The hydraulic pump 10 driven by the engine 3, the hydraulic motor 20 for rotation driven by the oil supplied from the hydraulic pump 10, the hydraulic pump 10 and A pair of main oil passages 30 </ b> A and 30 </ b> B constituting a closed circuit is provided between the turning hydraulic motor 20.

  The hydraulic pump 10 is a variable displacement type in which the displacement volume and the oil discharge direction are changed by changing the tilt angle of the swash plate 11, and is attached to the engine 3 disposed in the upper swing body 1. It is provided. As shown in FIG. 1, the hydraulic pump 10 is provided with a capacity control unit 12 for operating the swash plate 11. The capacity control unit 12 includes a capacity control cylinder 121 that operates the swash plate 11 of the hydraulic pump 10 and a capacity control valve 122 that controls supply of oil to the two pressure chambers of the capacity control cylinder 121. is there.

  The displacement control cylinder 121 is connected to the swash plate 11 of the hydraulic pump 10 via the piston rod 121a, and the swash plate 11 of the hydraulic pump 10 can be tilted when the piston rod 121a moves back and forth. is there. The capacity control cylinder 121 is provided with a built-in spring 121b that biases the piston rod 121a so that the tilt angle of the swash plate 11 becomes zero in a normal state.

  The capacity control valve 122 operates by the pilot pressure given through the two capacity control electromagnetic proportional valves 41 </ b> A and 41 </ b> B when a control signal is output from the controller 40 described later, and the two pressures of the capacity control cylinder 121. The position of the piston rod 121a is changed by appropriately supplying / discharging oil to / from the chamber. The oil supplied to the capacity control cylinder 121 via the oil supply port 122a of the capacity control valve 122 is discharged from the discharge port of the charge pump 51 described later.

  The turning hydraulic motor 20 is provided in a hydraulic excavator so that the upper turning body 1 provided with the work machine 1a can be turned with respect to the lower traveling body 2 when driven. In the first embodiment, as shown in FIGS. 2 and 3, the turning hydraulic motor 20 is disposed on the upper turning body 1 with the output shaft 21 facing vertically downward, and the output shaft 21 is connected to the output shaft 21. The output gear 4 a of the connected turning speed reducer 4 is meshed with the turning ring 5 of the lower traveling body 2. When the turning hydraulic motor 20 rotates, the output gear 4a rotates about the axis of the output shaft 21 and revolves around the turning axis C along the turning ring 5 of the lower traveling body 2 to lower the traveling body 2 On the other hand, the upper-part turning body 1 turns around the turning axis C. The rotation direction of the turning hydraulic motor 20 can be changed according to the oil supply direction from the hydraulic pump 10, and the upper turning body 1 can be turned clockwise or counterclockwise as viewed from above. it can.

  The pair of main oil passages 30 </ b> A and 30 </ b> B are connected to a first discharge port 10 a located above the hydraulic pump 10 and a first suction port 20 a located above the turning hydraulic motor 20 in FIG. 1. The second main oil passage 30B connecting the main oil passage 30A and the second discharge port 10b located below the hydraulic pump 10 and the second suction port 20b located below the turning hydraulic motor 20 in FIG. It has. The first main oil passage 30A and the second main oil passage 30B are provided with a neutral holding valve 60 and two oil supply passages 70A and 70B between the hydraulic pump 10 and the turning hydraulic motor 20.

  The neutral holding valve 60 is operated by a pilot pressure applied via two neutral holding electromagnetic proportional valves 42A and 42B when a control signal is output from the controller 40 described later, and the first discharge port of the hydraulic pump 10 is operated. A first pump port 60a connected to 10a and a second pump port 60b connected to the second discharge port 10b, a first motor port 60c connected to the first suction port 20a of the turning hydraulic motor 20, and a second pump port 60b. Oil passage control is performed with the second motor port 60d connected to the suction port 20b. As shown in FIGS. 2 and 3, in the first embodiment, the neutral holding valve is disposed so as to be attached to the turning hydraulic motor 20.

  As shown in FIG. 1, the neutral holding valve 60 is switched to a neutral position, a first position, and a second position. The neutral position of the neutral holding valve 60 is to maintain a state in which the space between the first pump port 60a and the first motor port 60c and the space between the second pump port 60b and the second motor port 60d are blocked. . When the neutral holding valve 60 is switched to the first position, the first pump port 60a and the first motor port 60c remain disconnected from the second motor port 60d to the second pump port 60b. Directed oil is allowed to pass. On the other hand, when the neutral holding valve 60 is switched to the second position, the first motor port 60c to the first motor port 60c remains in a state where the second pump port 60b and the second motor port 60d are blocked. The passage of oil toward the pump port 60a is allowed.

  The oil supply passages 70A and 70B are provided between the first discharge port 10a of the hydraulic pump 10 and the first suction port 20a of the turning hydraulic motor 20 and the second discharge port 10b of the hydraulic pump 10 so as to bypass the neutral holding valve 60. And the second suction port 20b of the turning hydraulic motor 20, each having oil supply check valves 71A and 71B. The oil supply check valves 71A and 71B allow only passage of oil from the hydraulic pump 10 to the turning hydraulic motor 20. In the following, for convenience, the connection between the first discharge port 10a of the hydraulic pump 10 and the first suction port 20a of the turning hydraulic motor 20 will be referred to as a first oil supply passage 70A, and the second of the hydraulic pump 10 will be described. The connection between the discharge port 10b and the second suction port 20b of the turning hydraulic motor 20 will be referred to as a second oil supply passage 70B.

  On the other hand, the hydraulic circuit for turning the excavator includes a charge unit 50 and a regulator unit 80, and a controller 40.

  The charge unit 50 is for replenishing oil when the pressure in one of the main oil passages 30A and 30B becomes lower than a set value, and includes a charge pump 51 driven by the engine 3 and one end portion. Is connected to the discharge port of the charge pump 51 and the other end is connected to the first main oil passage 30A and the second main oil passage 30B via the low pressure selection valve 52, and the charge passage 53 branches off. The charge oil supply passage 54 connected to the oil supply port 122a of the capacity control valve 122 and the charge relief valve 55 connected to the charge passage 53 are provided. In the charge unit 50, when the engine 3 is driven, the charge pump 51 is always driven. For example, the first main oil passage 30A and the second oil passage 30A are caused by internal leakage of the hydraulic pump 10 and the turning hydraulic motor 20. When the pressure of any one of the main oil passages 30B becomes lower than the set pressure of the charge relief valve 55, the oil is replenished from the charge pump 51 to the main oil passages 30A, 30B on the low pressure side. If the pressures in the first main oil passage 30A and the second main oil passage 30B are both equal to or higher than the set pressure of the charge relief valve 55, the oil discharged from the charge pump 51 passes through the charge relief valve 55. Returned to tank T.

  The regulator unit 80 is for releasing oil to the other main oil passages 30A, 30B when the pressure in one of the main oil passages 30A, 30B exceeds a set value, and the first main oil passage A pressure adjustment check valve 82 is interposed in the suction oil passage 81 connecting between 30A and the second main oil passage 30B so as to be opposite to each other, and a pressure control valve 83 is provided in parallel with each pressure adjustment check valve 82. Connected and configured. In the regulator unit 80, when the oil pressure of one of the main oil passages 30A, 30B, for example, the first main oil passage 30A rises due to the influence of an external force or the like and exceeds the set pressure of the pressure control valve 83, the suction oil passage 81 becomes a communication state, and the oil in the first main oil passage 30A flows into the second main oil passage 30B on the low pressure side.

  When the controller 40 detects that the operation lever 43 has been operated, the control signal corresponding to the operation amount and operation direction of the operation lever 43 is sent to the capacity control electromagnetic proportional valves 41A and 41B and the neutral holding electromagnetic proportional valve 42A. , 42B.

  In the hydraulic circuit for turning the excavator configured as described above, when the operation lever 43 is disposed at the neutral position, both ends of the capacity control valve 122 are connected to the tank pressure via the capacity control electromagnetic proportional valves 41A and 41B. At the same time, both ends of the neutral holding valve 60 become the tank pressure via the neutral holding electromagnetic proportional valves 42A and 42B, and the capacity control valve 122 and the neutral holding valve 60 are respectively disposed at the neutral positions. When the displacement control valve 122 is disposed at the neutral position, the swash plate tilt angle of the hydraulic pump 10 becomes zero. Therefore, even if the engine 3 is started from this state and the hydraulic pump 10 is driven, the hydraulic pump 10 The amount of oil discharged becomes zero, and the turning hydraulic motor 20 does not rotate.

  Moreover, in this state, the neutral holding valve 60 is also disposed at the neutral position, and the flow of oil from the turning hydraulic motor 20 toward the hydraulic pump 10 is blocked. In the first oil supply passage 70A and the second oil supply passage 70B provided so as to bypass the neutral holding valve 60, oil supply check valves 71A, 71B for preventing the flow of oil from the turning hydraulic motor 20 toward the hydraulic pump 10, respectively. Is provided. Thus, even when an external force is applied to the upper swing body 1 such as stopping the hydraulic excavator on a slope, the swing hydraulic motor 20 can be maintained in a stopped state. There is no possibility of incurring a situation where the revolving unit 1 turns carelessly.

  When the driver operates the operation lever 43 to turn the upper swing body 1 from the state described above, a control signal corresponding to the operation amount and operation direction of the operation lever 43 is sent from the controller 40 to the proportional solenoid valves 41A, 41B for capacity control. Output to the neutral holding electromagnetic proportional valves 42A and 42B, the swash plate tilt angle of the hydraulic pump 10 is changed, and the neutral holding valve 60 is switched.

  As a result, for example, when oil is discharged from the first discharge port 10a of the hydraulic pump 10 and the neutral holding valve 60 is switched to the first position, the first main oil passage is formed from the first discharge port 10a of the hydraulic pump 10. The oil discharged to 30A is supplied to the first suction port 20a of the turning hydraulic motor 20 via the first oil supply passage 70A. The oil supplied to the turning hydraulic motor 20 is discharged from the second suction port 20b to the second main oil passage 30B, and then is supplied to the second hydraulic pump 10 via the neutral holding valve 60 disposed at the first position. It reaches the discharge port 10b. That is, oil is circulated and supplied clockwise from the hydraulic pump 10 to the turning hydraulic motor 20 in FIG. 1, for example, the upper turning body 1 turns clockwise with respect to the lower traveling body 2.

  On the contrary, when the operation lever 43 is operated and, for example, oil is discharged from the second discharge port 10b of the hydraulic pump 10 and the neutral holding valve 60 is switched to the second position, the first of the hydraulic pump 10 is changed. The oil discharged from the second discharge port 10b to the second main oil passage 30B is supplied to the second suction port 20b of the turning hydraulic motor 20 through the second oil supply passage 70B. The oil supplied to the turning hydraulic motor 20 is discharged from the first suction port 20a to the first main oil passage 30A and then the first of the hydraulic pump 10 through the neutral holding valve 60 disposed at the second position. It reaches the discharge port 10a. That is, oil is circulated and supplied counterclockwise in FIG. 1 from the hydraulic pump 10 to the turning hydraulic motor 20, and the upper turning body 1 turns counterclockwise with respect to the lower traveling body 2, for example.

  During these operations, according to the hydraulic excavator, oil is always supplied from the hydraulic pump 10 to the turning hydraulic motor 20 via the oil supply check valves 71A and 71B of the oil supply passages 70A and 70B. The oil flow from the hydraulic motor 20 toward the hydraulic pump 10 is blocked. Therefore, even when the pressure of the main oil passages 30A and 30B is low at the initial stage when the operation lever 43 is operated from the neutral state, the situation where the upper swing body 1 turns in the opposite direction against the operator's will. Without being invited, the turn starts in the direction corresponding to the operation direction of the operation lever 43 from the stopped state.

  Moreover, since the oil supply check valves 71A and 71B are provided outside the neutral holding valve 60, a sufficient oil passage area can be secured and the pressure loss can be reduced without increasing the size of the neutral holding valve 60. Can do. As a result, it is possible to reduce the fuel consumption of the engine 3 and contribute to energy saving without incurring problems that the manufacturing cost increases or the operation responsiveness is impaired.

(Embodiment 2)
In the hydraulic excavator according to the first embodiment described above, the oil supply passages 70A and 70B are provided to bypass the neutral holding valve 60, but the present invention is not limited to this. For example, in the hydraulic excavator of the second embodiment shown in FIG. 4, the neutral discharge valve 160 passes through the first discharge port 10 a of the hydraulic pump 10 and the first suction port 20 a of the turning hydraulic motor 20. At the same time, an oil supply passage is provided so as to connect the second discharge port 10b of the hydraulic pump 10 and the second suction port 20b of the turning hydraulic motor 20.

  That is, the neutral holding valve 160 of the second embodiment has the first pump port 160a connected to the first discharge port 10a and the second pump port 160b connected to the second discharge port 10b on the hydraulic pump 10 side. On the other hand, the first motor port 160c connected to the first suction port 20a on the side of the turning hydraulic motor 20, the first oil supply port 160e connected to the first suction port 20a via the oil supply check valve 171A, the second suction port A second motor port 160d connected to the port 20b, and a second oil supply port 160f connected to the second suction port 20b via an oil supply check valve 171B, and the two ports 160a on the side of the hydraulic pump 10 Oil passage control between 160b and the four ports 160c, 160e, 160d, 160f on the side of the turning hydraulic motor 20 is performed. The two fuel check valves 171A and 171B are both provided outside the neutral holding valve 160.

  This neutral holding valve 160 switches to the three positions of the neutral position, the first position, and the second position, similarly to the neutral holding valve 60 of the first embodiment. The neutral position of the neutral holding valve 160 is between the first pump port 160a and the first oil supply port 160e and between the second pump port 160b and the second oil supply port with the first motor port 160c and the second motor port 160d shut off. It is maintained in a state of communication with each other. When the neutral holding valve 160 is switched to the first position, the first motor port 160c is shut off and the second motor is kept in communication with the first pump port 160a and the first oiling port 160e. The passage of oil from the port 160d to the second pump port 160b is allowed. On the other hand, when the neutral holding valve 160 is switched to the second position, the second motor port 160d is shut off and the second pump port 160b and the second oil supply port 160f remain in communication with each other. The passage of oil from the first motor port 160c toward the first pump port 160a is allowed. When the control signal is output from the controller 40, the neutral holding valve 160 is operated by the pilot pressure given through the two neutral holding electromagnetic proportional valves 42A and 42B, as in the first embodiment.

  In addition, in the hydraulic circuit for turning of the excavator shown in the second embodiment, the configuration other than the above and the arrangement mode on the upper rotating body 1 and the lower traveling body 2 are the same as those in the first embodiment. The same reference numerals are attached and detailed descriptions of each are omitted.

  In the swing hydraulic circuit of the hydraulic excavator configured as described above, the oil passage connected from the first pump port 160a of the neutral holding valve 160 to the first main oil passage 30A via the first oil supply port 160e and the oil supply check valve 171A. Constitutes one oil supply passage (hereinafter referred to as the first oil supply passage 170A) and is connected from the second pump port 160b of the neutral holding valve 160 to the second main oil passage 30B through the second oil supply port 160f and the oil supply check valve 171B. This oil passage constitutes another oil supply passage (hereinafter referred to as second oil supply passage 170B).

  When the operation lever 43 is disposed at the neutral position, both ends of the capacity control valve 122 become the tank pressure via the capacity control electromagnetic proportional valves 41A and 41B, and the neutral holding electromagnetic proportional valves 42A and 42B are Thus, both ends of the neutral holding valve 160 become the tank pressure, and the capacity control valve 122 and the neutral holding valve 160 are respectively disposed at the neutral positions. When the displacement control valve 122 is disposed at the neutral position, the swash plate tilt angle of the hydraulic pump 10 becomes zero. Therefore, even if the engine 3 is started from this state, the oil discharge amount from the hydraulic pump 10 becomes zero. The turning hydraulic motor 20 does not rotate.

  In addition, in this state, the neutral holding valve 160 is also arranged at the neutral position, and the first motor port 160c and the second motor port 160d are shut off, so that the oil flow from the turning hydraulic motor 20 toward the hydraulic pump 10 Is in a blocked state. In the first oil supply passage 170A and the second oil supply passage 170B provided so as to pass through the neutral holding valve 160, oil supply check valves 171A and 171B for preventing the flow of oil from the turning hydraulic motor 20 toward the hydraulic pump 10, respectively. Is provided. Thus, even when an external force is applied to the upper swing body 1 such as stopping the hydraulic excavator on a slope, the swing hydraulic motor 20 can be maintained in a stopped state. There is no possibility of incurring a situation where the revolving unit 1 turns carelessly.

  When the driver operates the operation lever 43 to turn the upper swing body 1 from the state described above, a control signal corresponding to the operation amount and operation direction of the operation lever 43 is sent from the controller 40 to the proportional solenoid valves 41A, 41B for capacity control. Output to the neutral holding electromagnetic proportional valves 42A, 42B, the swash plate tilt angle of the hydraulic pump 10 is changed, and the neutral holding valve 160 is switched.

  As a result, for example, when oil is discharged from the first discharge port 10a of the hydraulic pump 10 and the neutral holding valve 160 is switched to the first position, the first main oil passage is formed from the first discharge port 10a of the hydraulic pump 10. The oil discharged to 30A is supplied to the first suction port 20a of the turning hydraulic motor 20 via the first oil supply passage 170A. The oil supplied to the turning hydraulic motor 20 is discharged from the second suction port 20b to the second main oil passage 30B, and then the second motor port 160d and the second motor port 160d of the neutral holding valve 160 disposed at the first position. It reaches the second discharge port 10b of the hydraulic pump 10 through the pump port 160b. That is, oil is circulated and supplied clockwise from the hydraulic pump 10 to the turning hydraulic motor 20 in FIG. 1, for example, the upper turning body 1 turns clockwise with respect to the lower traveling body 2.

  On the contrary, when the operation lever 43 is operated and, for example, oil is discharged from the second discharge port 10b of the hydraulic pump 10 and the neutral holding valve 160 is switched to the second position, the first of the hydraulic pump 10 is changed. The oil discharged from the second discharge port 10b to the second main oil passage 30B is supplied to the second suction port 20b of the turning hydraulic motor 20 via the second oil supply passage 170B. The oil supplied to the turning hydraulic motor 20 is discharged from the first suction port 20a to the first main oil passage 30A, and then the first motor port 160c and the first motor port 160c of the neutral holding valve 160 disposed at the second position. It reaches the first discharge port 10a of the hydraulic pump 10 through the pump port 160a. That is, oil is circulated and supplied counterclockwise in FIG. 1 from the hydraulic pump 10 to the turning hydraulic motor 20, and the upper turning body 1 turns counterclockwise with respect to the lower traveling body 2, for example.

  During these operations, according to the hydraulic excavator, oil is always supplied from the hydraulic pump 10 to the turning hydraulic motor 20 via the oil supply check valves 171A and 171B of the oil supply passages 170A and 170B. The oil flow from the hydraulic motor 20 toward the hydraulic pump 10 is blocked. Therefore, even when the pressure of the main oil passages 30A and 30B is low at the initial stage when the operation lever 43 is operated from the neutral state, the situation where the upper swing body 1 turns in the opposite direction against the operator's will. Without being invited, the turn starts in the direction corresponding to the operation direction of the operation lever 43 from the stopped state.

  Moreover, since the oil supply check valves 171A and 171B are provided outside the neutral holding valve 160, a sufficient oil passage area can be secured and the pressure loss can be reduced without increasing the size of the neutral holding valve 160. Can do. As a result, it is possible to reduce the fuel consumption of the engine 3 and contribute to energy saving without incurring problems that the manufacturing cost increases or the operation responsiveness is impaired.

DESCRIPTION OF SYMBOLS 1 Upper revolving body 10 Hydraulic pump 10a 1st discharge port 10b 2nd discharge port 20 Hydraulic motor for rotation 20a 1st suction port 20b 2nd suction port 21 Output shaft 30A, 30B Main oil path 60 Neutral holding valve 70A, 70B Oil supply path 71A, 71B Oil supply check valve 160 Neutral holding valve 170A, 170B Oil supply passage 171A, 171B Oil supply check valve C Rotating shaft center

Claims (3)

A first main oil passage connecting the first discharge port of the variable displacement hydraulic pump and the first suction port of the turning hydraulic motor;
The second discharge port of the hydraulic pump and the second suction port of the turning hydraulic motor are connected, and a closed circuit is formed between the hydraulic pump and the turning hydraulic motor by the first main oil passage. A second main oil passage;
A neutral holding valve that is interposed in the first main oil passage and the second main oil passage and that controls passage of oil between the hydraulic pump and the turning hydraulic motor, and the neutral holding valve is in a neutral position. A turning hydraulic circuit that prevents oil from passing from the turning hydraulic motor to the hydraulic pump when switching, and prevents turning of the turning body by stopping rotation of the turning hydraulic motor; A hydraulic excavator,
In the turning hydraulic circuit,
The neutral holding is performed between the first discharge port of the hydraulic pump and the first suction port of the turning hydraulic motor and between the second discharge port of the hydraulic pump and the second suction port of the turning hydraulic motor. An individual oil supply passage having an oil supply check valve that connects between the hydraulic pump and the swing hydraulic motor regardless of the position of the valve and prevents passage of oil from the swing hydraulic motor to the hydraulic pump. Provided,
The neutral holding valve is interposed over both the first main oil passage and the second main oil passage, and switches from the neutral position to the first position or the second position.
When arranged at the first position, the oil is allowed to pass from the second suction port of the turning hydraulic motor toward the second discharge port of the hydraulic pump, and the first of the turning hydraulic motor is allowed to pass. Blocking the passage of oil from the suction port toward the first discharge port of the hydraulic pump;
When arranged at the second position, the oil is allowed to pass from the first suction port of the turning hydraulic motor to the first discharge port of the hydraulic pump, and the second of the turning hydraulic motor is allowed to pass. A hydraulic excavator characterized in that it prevents passage of oil from a suction port toward a second discharge port of the hydraulic pump.   The oil supply passage is between the first discharge port of the hydraulic pump and the first suction port of the turning hydraulic motor and bypasses the neutral holding valve and the second discharge port of the hydraulic pump and the turning hydraulic pressure. The hydraulic excavator according to claim 1, wherein a connection is made between the second suction port of the motor.   The oil supply passage passes between the neutral holding valve and between the first discharge port of the hydraulic pump and the first suction port of the turning hydraulic motor, and the second discharge port of the hydraulic pump and the turning hydraulic motor. 2. The hydraulic excavator according to claim 1, wherein the oil supply check valve is connected to the second suction port and the fuel check valve is provided outside the neutral holding valve.

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