JP2013221458A - Hydraulic pressure rotary machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent increase in a load of a driving source which drives a pump, with excellent responsiveness, and to effectively decrease energy consumption, in an oil pressure rotary machine.SOLUTION: A pump unit includes: a hydraulic pump 74 (82); a servo mechanism 92 (96) controlling a swash plate angle of a movable swash plate 90 of the hydraulic pump 74 (82); and a piston movement regulating mechanism 248 regulating increase of the swash plate angle of the movable swash plate 90. The piston movement regulating mechanism 248 includes: an outside cylinder 258; a control piston 252 which is slidably provided in an axial direction inside the outside cylinder 258 and whose one end faces an axial end face of a servo piston 100; and a pressure introducing path 256 which introduces operating oil pressure to the other end side of the control piston 252 such that the control piston 252 approaches the servo piston 100 against biasing force of a control spring 254.

Description

  The present invention relates to a hydraulic rotary machine used as, for example, a hydraulic pump unit or a hydraulic continuously variable transmission.

  2. Description of the Related Art Conventionally, in an excavation work machine called a backhoe, which is a ground working vehicle, for example, an excavation unit including an arm, a boom, a bucket, a fork, and the like is provided in an upper structure as a turning unit, and the excavation unit is a hydraulic actuator such as a hydraulic cylinder. The excavation work is enabled by operating. For example, Patent Document 1 describes a backhoe including a hydraulic operation device.

  In the case of the excavation work machine of Patent Document 1, a boom cylinder provided between the boom and the swivel, an arm cylinder provided between the arm and another boom, a bucket cylinder provided between the arm and the bucket, and Each motor is provided in a crawler type traveling device. Each cylinder and motor correspond to an actuator. For example, the boom can be turned up and down by expansion and contraction of the boom cylinder. A hydraulic pump unit including first to fourth hydraulic pumps is provided, and is connected to the engine output shaft so that the first to fourth hydraulic pumps can be driven in parallel. A motor is connected to the discharge side of the first hydraulic pump and the second hydraulic pump. An actuator switching valve such as a boom switching valve is connected to the discharge side of the first hydraulic pump. An actuator switching valve such as an arm switching valve is connected to the discharge side of the third hydraulic pump. Each switching valve is a pilot type, and each operation portion is connected to the pilot valve via a pilot oil passage. The pilot valve is switched by turning the operation lever so that the hydraulic cylinder can be operated. As prior art documents related to the present invention, there are Patent Documents 2 to 7 in addition to Patent Document 1.

Japanese Patent Laid-Open No. 2000-220666 JP 2007-92803 A JP 2000-319942 A Japanese Patent No. 3752326 Japanese Patent Publication No. 4-9922 Japanese Patent Laid-Open No. 6-10828 Japanese Patent Application Laid-Open No. 2007-1000031

  In Patent Document 1, the variable displacement pump is a movable swash plate type, and as shown in FIG. It is described that a swash plate operation unit is provided.

  However, in the hydraulic pump unit corresponding to the hydraulic rotary machine described in Patent Document 1, the variable displacement pump is driven by a drive source that is an engine or an electric motor, but an increase in the load of the drive source is prevented with good responsiveness. In addition, there is room for improvement in terms of effectively reducing the energy consumption of the drive source. For example, it can not be said that there is no possibility that inconvenience may occur in the use of the drive source, such as when the hydraulic pressure is supplied by a pump and the load of the actuator to be driven is excessively high, the engine will stall. For this reason, there is room for improvement in terms of preventing load increase with good responsiveness and effectively reducing energy consumption.

  In the above description, the inconvenience in the case where the hydraulic rotating machine is a variable displacement type hydraulic pump unit including a movable swash plate has been described. As a hydraulic rotating machine, as in Patent Document 2, a hydraulic pump and a hydraulic motor are installed in a case. In some cases, a variable displacement hydraulic continuously variable transmission having at least a hydraulic pump having a movable swash plate is used. In the case of such a hydraulic continuously variable transmission, the hydraulic pump is driven by the engine. However, there is room for improvement in terms of reducing engine energy consumption and preventing increase in engine load with good responsiveness. There is. For example, the configuration of Patent Document 2 includes a hydraulic pump and a hydraulic motor, at least one of which is a variable displacement movable swash plate, and a hydraulic servo mechanism is provided for each of them. Further, the hydraulic pump and the hydraulic motor are connected by a closed main oil passage. Each hydraulic servo mechanism includes a piston and a servo spool that is slidably fitted inside the piston, and an end of a speed change drive pin that is a speed change drive member is fitted in a groove provided on the outer periphery of the servo spool. Has been. A piston is slidably accommodated in a servo cylinder provided in the case, and a pin shaft protruding from a movable swash plate is fitted to the side surface of the piston, and a speed change drive member is linked to the movable swash plate. Has been. In addition, a shift operation lever is linked to the shift drive pin. Furthermore, a load control mechanism is provided for each of the hydraulic pump and the hydraulic motor. Each load control mechanism includes a control cylinder that sucks and discharges hydraulic oil in the main oil passage, and a control spool that is slidably inserted into the control cylinder and engages with a corresponding speed change drive pin. The main oil passage is communicated with one side of the control spool in the control cylinder, and when controlling the load, the control pin is pressed by the pressure oil force from the main oil passage, and the control spool facing the control pin is pressed, The swash plate angle of the movable swash plate is controlled by moving the speed change drive pin.

  However, even in the case of the configuration described in Patent Document 2 in which the load control mechanism is provided in this way, the servo cylinder is moved via the control spool of the load control mechanism, so that the load increases when the engine load is high. There is room for improvement in terms of preventing responsiveness. If the increase in the load cannot be prevented with good responsiveness, the fuel consumption may not be effectively reduced.

  No means for solving such a problem is disclosed in any of Patent Documents 1 to 7. As described above, the techniques described in Patent Documents 1 to 7 have room for improvement in terms of preventing an increase in load with high responsiveness and effectively reducing energy consumption.

  An object of the hydraulic rotating machine according to the present invention is to prevent an increase in the load of a driving source that drives a pump with high responsiveness and to effectively reduce energy consumption.

  A first hydraulic rotary machine according to the present invention is a variable displacement hydraulic rotary machine including a movable swash plate, and is a hydraulic servo mechanism that is provided inside a case and controls the swash plate angle of the movable swash plate. A servo cylinder provided in the case, and a servo piston provided in the servo cylinder so as to be slidable in the axial direction and interlocking with the movable swash plate, and by moving the servo piston in the axial direction. A hydraulic servo mechanism for changing a capacity of the hydraulic rotary machine; and a piston movement restricting mechanism for restricting an increase in a swash plate angle of the movable swash plate, the case being disposed inside the case or a fixed member fixed to the case. A regulating cylinder provided therein, a control piston provided in the regulating cylinder so as to be slidable in the axial direction, and having one end opposed to the axial end surface of the servo piston, and the case Is provided between the fixed member and the control piston, and biases the control piston in a direction in which one end of the control piston separates from the servo piston, and the control piston biases the bias. And a piston movement restricting mechanism including a restricting pressure introducing path for introducing hydraulic oil pressure to the other end side of the control piston so as to approach the servo piston against the biasing force of the member. It is a hydraulic rotating machine.

  According to the first hydraulic rotating machine of the present invention, the control piston that opposes the servo piston interlocked with the movable swash plate, and the control piston is operated so as to approach the servo piston against the biasing force of the biasing member. A regulating pressure introduction path for introducing the oil pressure to the other end of the control piston opposite to the servo piston. For this reason, the range of the tilt angle of the movable swash plate can be reduced by introducing a hydraulic pressure that increases as the load of the hydraulic rotary machine increases according to the increase in the load of the hydraulic rotary machine to the other end of the servo piston through the regulating pressure introduction path. Can be regulated. Therefore, it is possible to prevent an increase in the load of the drive source that drives the pump with good responsiveness and to effectively reduce energy consumption.

  A second hydraulic rotary machine according to the present invention is a hydraulic rotary machine including a variable displacement type variable displacement pump including a movable swash plate, and is provided inside a case, and the swash plate angle of the movable swash plate And includes a servo cylinder provided in the case, and a servo piston provided in the servo cylinder so as to be slidable in the axial direction and interlocking with the movable swash plate. When the hydraulic oil is selectively introduced into either the first oil chamber or the second oil chamber of the servo cylinder formed on one end side and the other end side of the servo piston, the servo piston moves in the axial direction and the hydraulic pressure The hydraulic servomechanism that changes the capacity of the rotating machine, a fixed displacement pump that supplies hydraulic oil to the servo cylinder, and a piston movement restriction mechanism that restricts an increase in the swashplate angle of the movable swashplate A connection path that allows the first oil chamber that moves the servo piston in a small capacity direction by introduction of the hydraulic oil to pass through a discharge side of the fixed capacity pump; and a pilot pressure that is provided in the connection path. The piston movement restricting mechanism including a pilot-type switching valve that connects the connection path at a pressure higher than the pressure and shuts off the connection path when the pilot pressure is less than a predetermined pressure, and the variable as the pilot pressure of the pilot-type switching valve The hydraulic rotary machine is characterized in that hydraulic oil pressure after discharge from the capacity pump is introduced.

  According to the second hydraulic rotary machine of the present invention, when the hydraulic oil pressure after discharge from the variable displacement pump increases due to an increase in load, the pilot-type switching valve connects the connection path, and the fixed displacement pump The hydraulic oil pressure after discharge is introduced into the first oil chamber. The first oil chamber moves the servo piston interlocked with the movable swash plate in the direction of small capacity when the hydraulic oil pressure is introduced. For this reason, the servo piston interlocked with the movable swash plate moves in the direction of small capacity, and an increase in the load of the driving source for driving the pump can be prevented with good responsiveness, and energy consumption can be effectively reduced.

  According to the hydraulic rotating machine according to the present invention, it is possible to prevent an increase in the load of the drive source that drives the pump with high responsiveness and to effectively reduce energy consumption.

1 is a schematic diagram of an excavating work machine that is a work vehicle including a pump unit that is a hydraulic rotating machine according to a first embodiment of the present invention. It is a top view which abbreviate | omits one part and shows several apparatuses provided in the apparatus accommodating part which comprises the excavation work machine of FIG. FIG. 2 is an overall view of a hydraulic circuit of the excavating work machine in FIG. 1. It is a figure which shows the basic composition of the pump unit of 1st Embodiment. It is a cross-sectional view of the basic configuration of the pump unit. It is AA sectional drawing of FIG. It is the figure which took out the port block from FIG. 6, and was seen from the left side of FIG. It is BB sectional drawing of FIG. It is CC sectional drawing of FIG. 6 which abbreviate | omits and shows a part. It is the figure seen from the left side of FIG. 6 to the right side. It is the figure seen from the upper side of FIG. 6 to the lower side. It is DD sectional drawing of FIG. It is EE sectional drawing of FIG. It is a figure which shows the state which abbreviate | omitted the rotation angle sensor and the sensor support member from FIG. 11, which shows the attachment state of the lever for rotation angle detection. FIG. 6 is a diagram for explaining the operation of a servo mechanism and a balance piston mechanism in the basic configuration of the pump unit of FIG. 5. FIG. 16 is a diagram corresponding to FIG. 15 in the specific configuration of the pump unit of the first embodiment. It is a figure which shows the hydraulic circuit of a continuously variable transmission including the servo mechanism which comprises the continuously variable transmission which is the hydraulic rotary machine of 2nd Embodiment which concerns on this invention. It is a figure corresponding to Drawing 15 showing the pump unit of a 3rd embodiment concerning the present invention. It is a figure which shows the hydraulic circuit of a continuously variable transmission including the servo mechanism which comprises the continuously variable transmission which is the hydraulic rotary machine of 4th Embodiment which concerns on this invention.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 to 16 are views showing a first embodiment according to the present invention. As shown in FIG. 1, an excavation work machine 10, which is a work vehicle including a pump unit that is a hydraulic rotary machine of the present embodiment, includes a traveling device 12 including a pair of left and right crawler belts, and a central portion of the traveling device 12. 2, a turning motor 16 provided at the center of the rotating table 14, and a rotating table 14 on the upper side of the traveling device 12 to turn around a turning axis O (FIG. 2) in the vertical direction. And an upper structure 18 that is a pivoting portion that can be attached. Note that the hydraulic rotating machine of the present invention is not limited to the configuration used by being mounted on the excavating work machine 10, but is a device including various actuators such as a motor driven by a working fluid such as hydraulic oil. Can be used. For example, the hydraulic rotating machine according to the present invention can be mounted on a work vehicle such as an agricultural tractor in which left and right wheels are independently driven by two hydraulic motors and an excavating work machine is mounted on the rear part of the machine body. In the following, the case where the pump unit includes two hydraulic pumps will be described. However, the present invention is not limited to this, and the present invention is applied to a pump unit including one or more hydraulic pumps. You can also

  As shown in FIG. 1, the upper structure 18 includes a device accommodating portion 20 that is provided on the upper side and closes the opening with a lid. Inside the device accommodating portion 20, an engine 22, which is a drive source, a pump unit 24, a plurality of directional control valves 26a and 26b, and a plurality of switching pilot valves 28a and 28b are provided. A driver's seat 30 is provided outside the upper part of the device accommodating portion 20. An operator 32 such as an operation lever or a pedal linked to the switching pilot valve is provided on the front side and one or both sides of the driver seat 30.

  The upper structure 18 can be rotated about the turning axis O (FIG. 2) in the vertical direction with respect to the traveling device 12 by the turning motor 16. Further, the left and right crawler belts 240 and 242 provided in the traveling device 12 can be rotated forward or backward by the two traveling motors 34a and 34b (FIG. 2) corresponding thereto. That is, the left and right crawler belts are driven independently from each other by the left and right traveling motors 34a and 34b, which are actuators. Further, a blade 36, which is a soil discharge plate, is attached to the rear side of the traveling device 12 (right side in FIG. 1). Supported by the device 12.

  The excavation part 40 is attached to the front part (left part of FIG. 1) of the upper structure 18. The lower end portion of the excavation part 40 is supported by the swing support part 42. As shown in FIG. 2, the swing support portion 42 can be rotated around the shaft 44 in the vertical direction (the front and back direction in FIG. 2) at the front portion of the upper structure 18. A swing cylinder 46 is provided between the swing support portion 42 and the upper structure 18. As shown in FIG. 1, the boom 48 of the excavation unit 40 is supported by the swing support unit 42 so as to be swingable about a horizontal axis 50.

  The excavation unit 40 includes a boom 48, an arm 52 that is supported at the tip of the boom 48 so as to be rotatable up and down, and a bucket 54 that is supported at the tip of the arm 52 so as to be rotatable up and down. A boom cylinder 56 is attached between the middle part of the boom 48 and the swing support part 42, and the boom 48 can be turned up and down by expansion and contraction of the boom cylinder 56.

  An arm cylinder 58 is attached between an intermediate portion of the boom 48 and an end portion of the arm 52, and the arm 52 can be rotated with respect to the boom 48 by expansion and contraction of the arm cylinder 58. A bucket cylinder 60 is attached between the end of the arm 52 and a link connected to the bucket 54, and the bucket 54 can be rotated with respect to the arm 52 by expansion and contraction of the bucket cylinder 60. As shown in FIG. 2, the entire excavation part 40 (FIG. 1) can swing left and right by expansion and contraction of the swing cylinder 46. Each of the boom cylinder 56, the arm cylinder 58, and the bucket cylinder 60 is a lifting cylinder of the excavation unit 40.

  A plurality of engine housings 20, an engine cooling radiator 64, a pump unit 24 coupled to the engine 22, and a plurality of hydraulic fluids that can be supplied from the pump unit 24 as working fluid (in this example, The valve unit 66 including the direction control valve of 8), an oil tank 68, and a fuel tank (not shown) for the engine are arranged. The pump unit 24 includes a gear case 70 coupled to the flywheel side of the engine 22 and a gear pump 72 that is a pilot pump for supplying hydraulic oil to the switching pilot valves 28a and 28b (FIG. 1). The upper structure 18 is not limited to the above-described configuration. For example, a driver's seat is provided on one side in the left-right direction of the upper structure, and an oil tank, an engine, a pump unit, and the like are arranged on the other side in the left-right direction. It is also possible to provide a device accommodating portion and cover the whole with a bonnet.

  FIG. 3 is an overall view of the hydraulic circuit of the excavation work machine 10 (FIG. 1), which includes an actuator, an actuator switching valve, and a pump unit. As shown in FIG. 3, a first hydraulic pump 74 constituting the pump unit 24 and a gear pump 72 are connected to the output shaft of the engine 22 so that the pumps 74 and 72 can be driven by the engine 22. . The power of the engine 22 is increased by a speed increasing mechanism 80 constituted by a large diameter gear 76 and a small diameter gear 78 and can be transmitted to a second hydraulic pump 82 constituting the pump unit 24. Can be driven by the engine 22.

  A bucket cylinder 60, a boom cylinder 56, a swing cylinder 46, and a left traveling motor, which are actuators, are respectively connected to the first hydraulic pump 74 via directional control valves 26a which are closed center type actuator switching valves corresponding to the first hydraulic pumps 74, respectively. 34a is connected in parallel. In addition, the second hydraulic pump 82 is connected to the arm cylinder 58, the blade cylinder 38, the swing motor 16, and the right-side traveling through the directional control valve 26b, which is a closed center type actuator switching valve corresponding to the second hydraulic pump 82, respectively. Motor 34b is connected in parallel.

  Output ports of switching pilot valves 28a and 28b are connected to switching oil chambers provided at the left and right ends of the directional control valves 26a and 26b, respectively. The switching pilot valves 28 a and 28 b are also of a closed center type, and each input port is connected in parallel to the discharge port of the gear pump 72. The suction port of the gear pump 72 is connected to the oil tank 68. Each switching pilot valve 28a, 28b can be mechanically switched by an operating element 32 provided corresponding to the periphery of the driver's seat 30 (FIG. 1). When the corresponding directional control valves 26a, 26b are hydraulically switched from the neutral position to the operating position by switching the switching pilot valves 28a, 28b, the corresponding cylinders 60, 56, 46, 58, 38 are expanded / contracted. In addition, the rotation directions of the traveling motors 34a and 34b and the turning motor 16 are switched. Further, the rotation direction of the swing motor 16 is switched by switching the direction control valve 26 b corresponding to the swing motor 16. For example, when the discharge port of the second hydraulic pump 82 is connected to the turning motor 16 via the direction control valve 26b, the upper structure 18 (FIG. 1) can be turned left and right in a desired direction. The operation element 32 can be operated to swing the lever in the cross direction, and the operation amount in each direction can correspond to the instruction of the operation amount of two different actuators. A variable throttle valve for gradually increasing the discharge flow rate to the actuator is provided at the operation position of the direction control valves 26a and 26b. Therefore, the opening degree of the direction control valves 26a, 26b is arbitrarily adjusted according to the operation amount of each switching pilot valve 28a, 28b.

  In order to simultaneously change the tilt angle of the movable swash plates of the left and right traveling motors 34a and 34b with respect to the motor shaft, one speed increasing switching valve 84 is provided, and the speed increasing switching valve 84 is connected to the gear pump. 72 discharge ports are connected. The speed increase switching valve 84 can change the tilt angle of the movable swash plate of each traveling motor 34a, 34b in two steps. For example, the speed increasing switching valve 84 is switched so that the gear pump 72 is simultaneously supplied to and discharged from each of the volume changing actuators 86 connected to the movable swash plates of the traveling motors 34a and 34b, whereby the traveling motors 34a and 34b. The volume of increases. On the other hand, by switching so that the oil in the volume changing actuator 86 is discharged to the oil tank 68, the volumes of the traveling motors 34a and 34b are reduced. For this reason, it is possible to change the speed of each of the traveling motors 34a and 34b. The speed increasing switching valve 84 is provided in common for each of the traveling motors 34a and 34b. The speed increasing switching valve 84 can be switched by the operating element 32 which is a second speed switching lever among the operating elements 32 provided in the periphery of the driver's seat 30 (FIG. 1).

  Each traveling motor 34a, 34b is connected to a discharge port of a corresponding hydraulic pump 74, 82 via a direction control valve 26a, 26b. Each of the switching pilot valves 28a and 28b for hydraulically switching the direction control valves 26a and 26b is supported by the operating element 32 as a shift lever among the operating elements 32 provided in the periphery of the driver's seat 30 (FIG. 1). It is possible to switch which of the two ports of the traveling motors 34a and 34b is connected to the discharge ports of the hydraulic pumps 74 and 82, and to change the amount of oil supplied to the traveling motors 34a and 34b. For this reason, by operating the corresponding operation element 32, the forward rotation and the reverse rotation of the traveling motors 34a and 34b corresponding to the forward movement and the reverse movement can be changed, and the speed can be adjusted.

  By making the oil supply amount and the oil supply direction the same by the switching pilot valves 28a and 28b corresponding to the left and right traveling motors 34a and 34b, the work vehicle travels straight. Further, by operating the operating element 32 independently to vary the amount of oil supply and the direction of oil supply, the outputs of the traveling motors 34a and 34b are different, and the excavation work machine 10 (FIG. 1) can be turned.

  In the present embodiment, hydraulic oil can be supplied from the first hydraulic pump 74 to the bucket cylinder 60, the boom cylinder 56, the swing cylinder 46, and the left traveling motor 34a, and the arm cylinder 58, the blade cylinder 38, and the swing motor 16 are supplied. The hydraulic oil can be supplied from the second hydraulic pump 82 to the right traveling motor 34b. The reason for configuring in this way is to avoid the fact that actuators that are frequently used at the same time are driven by the same hydraulic pump, thus causing pressure interference when different actuators are driven by the same hydraulic pump. This is to reduce things. That is, the bucket cylinder 60, the boom cylinder 56, the swing cylinder 46, and the left traveling motor 34a are used less frequently. In addition, the arm cylinder 58, the blade cylinder 38, and the right traveling motor 34b are used less frequently. On the other hand, the swing motor 16 is frequently used simultaneously with other actuators such as the arm cylinder 58. In this case, it is necessary to reduce the pressure interference and operate the actuator and the swing motor 16 at a high speed. It is necessary to prevent the smooth operation from being impaired. For this purpose, the speed increasing mechanism 80 is used as described above so that the discharge amount of the second hydraulic pump 82 is larger than the discharge amount of the first hydraulic pump 74. Further, with this configuration, it is not necessary to provide another pump for driving only the turning motor 16 exclusively.

  FIG. 4 is a diagram showing a basic configuration of the pump unit according to the present embodiment. The pump unit 24 includes a first hydraulic pump 74 that is a first variable displacement pump, a movable swash plate 90 for changing the capacity of the first hydraulic pump 74, and a first swash plate operating unit that is a first servo piston unit. A first servo mechanism 92 and a first balance piston mechanism 94 connected to the first servo mechanism 92 so that power can be transmitted.

  The pump unit 24 includes a second hydraulic pump 82 that is a second variable displacement pump, a movable swash plate 90 for changing the capacity of the second hydraulic pump 82, a second swash plate operation unit, and a second servo. It includes a second servo mechanism 96 that is a piston unit, and a second balance piston mechanism 98 that is connected to the second servo mechanism 96 so that power can be transmitted.

  Each of the servo mechanisms 92 and 96 includes a servo piston 100 that is slidable in the axial direction inside a cylinder formed on an inner wall of a main body of a pump case 108 (see FIGS. 5, 6, and 8), which will be described later, and a servo piston. 100 and a spool 102 that constitutes a direction switching valve that is slidably provided in the axial direction inside 100. Between the spool 102 and the servo piston 100, a spring 104, which is a biasing member that biases the spool 102 in one axial direction, is provided. An operation pin 106 coupled to the movable swash plate 90 is engaged with the servo piston 100, and the tilt angle of the movable swash plate 90 can be changed by the movement of the servo piston 100.

When the spool 102 is moved in one direction, together with the hydraulic oil from the servo piston 100 on one side of the pressure receiving chamber is discharged to the oil reservoir 110 in the pump case 108 (FIG. 5) is discharged at a pressure P _PL from the gear pump 72, the pressure Pch Is adjusted to the pressure receiving chamber on the other side of the servo piston 100. For this reason, the servo piston 100 is pressed by the pressure in the pressure receiving chamber on the other side, and moves in one direction following the spool 102. On the contrary, when the spool 102 moves in the other direction, the hydraulic oil is discharged from the pressure receiving chamber on the other side of the servo piston 100 to the oil reservoir 110, and the hydraulic oil adjusted by the pressure Pch from the gear pump 72 is supplied to one side of the servo piston 100. It is introduced into the pressure receiving chamber. For this reason, the servo piston 100 moves in the other direction following the spool 102.

Each balance piston mechanism 94, 98 includes a piston body 112 provided in a piston case 180 (see FIGS. 6 and 8), which will be described later, so as to be slidable in the axial direction. Moreover, the primary side before passage of each directional control valve 26a, 26b (FIG. 3) which is the discharge pressure of the corresponding hydraulic pumps 74, 82 at a portion facing the small diameter portion on one axial end side of each piston main body 112. Pressures P _P1 (= P1) and P _P2 (= P2) are introduced. Further, the portion of each piston body 112 facing the large diameter portion on one end side in the axial direction is connected to the discharge side of the gear pump 72, and is adjusted from the variable pressure reducing valve 114 that can adjust the pressure reducing amount by inputting an electric signal. Pressures P _CON1 and P _CON2 can be introduced.

Further, the secondary side pressure after passing through each direction control valve 26a, 26b (FIG. 3), that is, the load side pressure (load pressure) is applied to the portion of each piston body 112 facing the small diameter portion on the other axial end side. Of these, maximum load pressures P _L1 and P _L2 are introduced. For example, the maximum load pressure can be introduced into each balance piston mechanism 94 and 98 by a circuit unit including a plurality of shuttle valves. Further, in a portion opposed to the large diameter portion of the axial end of the piston body 112 is discharged by the pressure P _PL from the gear pump 72 introduces a pressure [Delta] P _LS adjusted to a desired pressure in the fixed pressure reducing valve 116 . The fixed pressure reducing valve 116 is maintained constant, that is, fixed in a state where the amount of pressure reduction is set in advance.

Then, by each balance piston mechanism 94, 98, a load sensing difference, which is a differential pressure between the primary pressures P _P1 , P _P2 and the maximum load pressures P _L1 , P _L2 before passing through the corresponding directional control valves 26a, 26b. The tilt angle, which is the tilt of the corresponding hydraulic pumps 74 and 82 with respect to the pump shaft of the movable swash plate 90, is controlled so that the pressure (LS differential pressure) becomes a preset desired pressure. That is, according to the change of the load sensing differential pressure, the servo mechanisms 92 and 96 are operated by the corresponding balance piston mechanisms 94 and 98 to change the tilt angle of the movable swash plate 90 of the corresponding hydraulic pumps 74 and 82. Yes. This will be described in detail below.

  Returning to FIG. 3, the hydraulic pumps 74 and 82 are maintained in a state where the movable swash plate 90 (FIG. 4) is slightly inclined (for example, about 2 degrees) with respect to a plane orthogonal to the pump axis at the initial position. So that you are on standby. For this reason, when the engine 22 is driven, actuators such as all the corresponding cylinders are not operated, and even when the corresponding directional control valves 26a and 26b and the travel switching valve 88 are in the closed position (closed) in the neutral position, Hydraulic fluid is discharged from the hydraulic pumps 74 and 82. Along with this, when the unload valve 118 is provided in the oil passage on the discharge side of the hydraulic pumps 74 and 82, and all the corresponding directional control valves 26a (or 26b) and the travel switching valves 88 are in the neutral position, The unload valve 118 is opened so that the hydraulic oil is discharged to the oil tank 68. The unload valve 118 is configured to introduce the output hydraulic pressure to the closing side as a switching signal when the direction control valves 26a and 26b are set to the operating position, and stop the discharge of the hydraulic oil to the oil tank 68. ing.

  Next, the basic configuration of the pump unit 24 will be described with reference to FIGS. The pump unit 24 has the circuit configuration shown in FIG. In the following description, the same elements as those shown in FIGS. 1 to 4 are denoted by the same reference numerals.

  FIG. 5 is a cross-sectional view of the pump unit 24. 6 is a cross-sectional view taken along the line AA in FIG. 5, and FIG. 7 is a view of the port block taken out from FIG. 6 and viewed from the left side to the right side in FIG. 8 is a cross-sectional view taken along the line BB in FIG. 6, and FIG. 9 is a cross-sectional view taken along the line CC in FIG. 10 is a diagram viewed from the left side to the right side of FIG. 6, and FIG. 11 is a diagram viewed from the upper side to the lower side of FIG. 12 is a DD cross-sectional view of FIG. 6, and FIG. 13 is a EE cross-sectional view of FIG. FIG. 14 is a diagram illustrating a state where the rotation angle detection lever is attached, and illustrating a state where the rotation angle sensor and the sensor support member are omitted from FIG. 11.

  As shown in FIG. 5, the pump unit 24 has two axial piston type variable displacement pumps, and includes a pump case 108 and a first hydraulic pump 74 and a variable displacement pump housed in the pump case 108, respectively. A second hydraulic pump 82, a first pump shaft 120 and a second pump shaft 122, and two movable swash plates 90 are provided. Further, as shown in FIG. 8, the pump unit 24 includes a first servo mechanism 92 and a second servo mechanism 96, a first balance piston mechanism 94 and a second balance piston mechanism 98, and a gear pump 72 (FIG. 5). Prepare.

  As shown in FIG. 5, the pump case 108 has a case main body 124 having an opening at one end (the right end in FIG. 5), the opening of the case main body 124 and the first hydraulic pump 74 and the second hydraulic pump 82. A gear case 128 including a port block 126, which is a block that forms a port for supplying and discharging oil, and a wrapper-shaped flywheel housing that is coupled to the opposite side of the case main body 124 of the port block 126 and encloses the flywheel. And a piston case 180 (FIG. 6, FIG. 8, etc.). As shown in FIGS. 6 and 7, a plurality of ports T1, T2, T3, and T4 communicating with a kidney port, which will be described later, are opened on the upper and lower surfaces of the port block 126. Further, as shown in FIG. 5, both ends of the first pump shaft 120 and the second pump shaft 122 are rotatably supported by the case main body 124 and the port block 126 by bearings. As shown in FIG. 10, in the flywheel housing of the gear case 128, holes 130 are formed at a plurality of locations in the circumferential direction of the outer end of the engine side end, and bolts (not shown) inserted through the holes 130. Thus, it can be coupled to the mounting flange of the engine 22 (FIG. 2). The gear case 128 and the flywheel housing are integrally formed in the present embodiment, but may be a member in which both members are detachably coupled.

  Further, as shown in FIG. 5, an input shaft 132 that can be connected to the output shaft of the engine 22 is rotatably supported by a bearing on the gear case 128 and is positioned approximately in the center in the radial direction of the flywheel housing. The first pump shaft 120 and the input shaft 132 are arranged on the same axis, and are spline-engaged inside the central cylindrical shaft of the large-diameter gear 76 constituting the speed increasing mechanism 80. For this reason, the first pump shaft 120 and the input shaft 132 are coupled via the large-diameter gear 76 so as to be able to rotate in synchronization with each other.

  Further, the second pump shaft 122 is spline-engaged inside the central cylindrical shaft of the small diameter gear 78 constituting the speed increasing mechanism 80 and the large diameter gear 76 and the small diameter gear 78 are engaged. For this reason, the second hydraulic pump 82 is accelerated by the gear ratio of the speed increasing mechanism 80 with respect to the first hydraulic pump 74. Both ends of the central cylinder shaft of each gear 76 and 78 are rotatably supported by the port block 126 and the gear case 128 by bearings, respectively. As described above, in the pump unit 24 that drives the two or more pumps 74 and 82 at the same time, the plurality of gears 76 and 78 such as the speed increasing mechanism 80 are both supported by the pump case 108 and each pump shaft 120 is supported. , 122 can be supported on both sides of the pump case 108, and the corresponding pump shafts 120, 122 and gears 76, 78 can be connected to each other. For this reason, the strength and durability of the pump shafts 120 and 122 and the gears 76 and 78 can be improved, and the maintenance work of the hydraulic pumps 74 and 82 is facilitated.

  An oil sump 110 that is a pump side space is provided inside the pump case 108, and a gear side space 134 is provided inside the gear case 128 in which the speed increasing mechanism 80 is disposed, so that the oil sump 110 and the gear side space 134 are independent from each other. . In this way, in the pump unit 24 that drives the two or more pumps 74 and 82 simultaneously, the gear side space 134 that is a room for housing the gears 76 and 78 interlocked with the pumps 74 and 82, and the pumps 74 and 82. The structure which makes the pump side space which is the chamber to accommodate mutually independent so that oil cannot flow can be employed. For this reason, the loss of power for driving the pumps 74 and 82 can be reduced. While the oil sump 110 is filled with oil, the amount of oil enclosed in the gear side space 134 is reduced. For example, the oil sealed in the gear-side space 134 in FIG. 5 is set so that the lower ends of the gears 76 and 78 are immersed.

  As shown in FIGS. 6 and 9, an oil hole 136 is formed in the support wall facing the gear-side space 134 of the gear case 128 so as to penetrate the bearing support recess 128a up and down. In each oil hole 136, the upper and lower ends that open to the outer surface of the gear case 128 are closed by a detachable plug 138. Each oil hole 136 is communicated with the gear side space 134 through a lateral hole 136a formed so as to face the peripheral portion of the top and bottom positions of the gears 76 and 78. Therefore, oil can be supplied to and discharged from the gear-side space 134 through the oil holes 136 and the lateral holes 136a with the upper plug 138 removed.

  As shown in FIG. 5, the input shaft 132 for connection to the engine 22 (FIG. 2) has an axial hole 140 that opens to one end surface (the right end surface in FIG. 5) side of the first pump shaft 120, and the axial direction. Radially formed radial holes 142 communicating with the holes 140 are provided. The outer end portion of the radial hole 142 is opened to the bearing support recess 128a. For this reason, as shown in FIG. 9, the oil in the gear side space 134 reaches the bearing support recess 128 a from the lateral hole 136 a through the oil hole 136 by the action of the gear pump when the gears 76 and 78 rotate, and the input shaft 132. Through these holes 140 and 142, it is possible to supply the spline portion between the outer peripheral surface of one end of the first pump shaft 120 and the inner peripheral surface of the large-diameter gear 76 shown in FIG. For this reason, durability of a spline part can be improved more effectively. In addition, since the one end surface (the right end surface in FIG. 5) of the second pump shaft 122 on the small-diameter gear 78 side is also open in the bearing support recess 128a, it passes through the lateral hole 136a and the oil hole 136 into the bearing support recess 128a. The discharged oil can sufficiently lubricate the spline portion between the outer peripheral surface of the one end portion of the second pump shaft 122 and the inner peripheral surface of the small diameter gear 78.

  Next, the hydraulic pumps 74 and 82 will be described. The hydraulic pumps 74 and 82 are accommodated in a cylinder block 154 that can rotate integrally with the pump shafts 120 and 122 by spline engagement with the pump shafts 120 and 122, and can be reciprocated in the cylinder of the cylinder block 154. A plurality of pistons 156 and a spring provided between the inner peripheral surface of the cylinder block 154 and the outer peripheral surfaces of the pump shafts 120 and 122. The spring has a function of pressing a shoe supported on one end of each piston 156 to the movable swash plate 90 side by a washer having a spherical outer peripheral surface via a pin.

  Each of the hydraulic pumps 74 and 82 includes a valve plate 144 that is supported on one side (the left side in FIG. 5) of the port block 126 so as to prevent displacement in the surface direction. The valve plate 144 has a substantially arc-shaped intake port and a discharge port, respectively, penetrating in parallel with the pump shafts 120 and 122 on both sides in the vertical direction. The suction port is connected to suction oil passages U1, U2 formed on the lower side of the port block 126 in the vehicle mounted state shown in FIG. 7, and the discharge port is a discharge oil passage formed on the upper side of the port block 126 shown in FIG. It leads to U3 and U4. One end of each oil passage U1, U2, U3, U4 is provided with a kidney port that opens on one side of the port block 126 (the surface in FIG. 7), and communicates with a suction port or a discharge port of the valve plate 144, respectively. ing. Inlet ports T1 and T2 for the first hydraulic pump 74 (FIG. 5) or the second hydraulic pump 82 (FIG. 5) on both sides of the lower surface and the upper surface width direction (left and right direction in FIG. 7) of the port block 126, respectively. And outlet ports T3 and T4 are opened. In such a configuration, the hydraulic oil is sucked into the pump unit 24 (FIG. 6) from the lower side, and the hydraulic oil is discharged from the upper side. In this way, in the pump unit 24 that drives the two or more pumps 74 and 82 at the same time, the outlet ports T3 and T4 are mounted on the work vehicle so as to be arranged upward, so that the valve piping is attached to the pump unit 24. Work can be done easily.

  Further, in order to supply oil to each of the inlet ports T1, T2, a supply pipe 146 can be connected to the pump unit 24 as shown in FIG. The end of the supply pipe 146 opposite to the pump unit 24 connection side is connected to an external oil tank 68 (FIG. 2). Further, the supply pipe 146 is branched on the connection side of the pump unit 24 into a main body portion 148 and a small diameter portion 150 that is smaller than the diameter of the main body portion 148. The main body 148 is provided in a substantially linear shape at least on the connection side of the pump unit 24. The upper end portion of the small diameter portion 150 is connected to the inlet port T1 on the first hydraulic pump 74 side, and the upper end portion of the main body portion 148 is connected to the inlet port T2 on the second hydraulic pump 82 side. The piping having such a large diameter is connected to the second hydraulic pump 82 side, and the piping having the small diameter is connected to the first hydraulic pump 74 side by the speed increasing mechanism 80 (FIG. 5). The rotation of the pump 82 is increased as compared with the first hydraulic pump 74, and the second hydraulic pump 82 has a larger discharge capacity per unit time than the first hydraulic pump 74, so as to correspond to the required amount of sucked oil. Because. As the supply pipes, two supply pipes having different inner diameter dimensions can be connected to the respective inlet ports T1 and T2 without using such a branched configuration.

  As described above, in the pump unit 24 that simultaneously drives two or more pumps 74 and 82 having different discharge capacities, the main body 148 that is a supply pipe of the hydraulic pump 82 having a large discharge capacity is provided in a substantially straight line. Therefore, it is possible to adopt a configuration in which the small-diameter portion 150 that is a supply pipe of the hydraulic pump 74 having a small discharge capacity is branched. Therefore, it is possible to effectively prevent cavitation from occurring in the supply pipe 146 even though the suction flow rate in the hydraulic pump 82 having a large discharge capacity is larger than that of the hydraulic pump 74 having a small discharge capacity.

  Further, as shown in FIGS. 6 and 7, the valve block 144 is disengaged below the valve plate 144 at an intermediate portion of a kidney port which is an arcuate opening opening on the valve plate 144 side of the port block 126 of the suction oil passages U1 and U2. An extension 152 extending to the position is provided. The lower end portion of the extension portion 152 is communicated with the oil sump 110 through one end opening of the case main body 124. For this reason, even if oil leaks from the elements in the case main body 124 such as the hydraulic pumps 74 and 82 and accumulates in the oil sump 110, the oil is sucked from the suction port of the valve plate 144 through the extension 152. . In this way, in the pump unit 24 that drives the two or more pumps 74 and 82 simultaneously, the suction ports of the hydraulic pumps 74 and 82 communicate with each other in the pump case 108 in which the oil leaked from the plurality of pumps 74 and 82 accumulates. The configuration can be adopted. For this reason, it is not necessary to return the surplus oil in the pump case 108 to the reservoir tank via piping or the like, piping can be omitted or reduced, and cost can be reduced by reducing the number of parts.

  A case 158 of an external gear pump 72 that is a fixed capacity pump is fixed to the outer surface of the case body 124, and a gear pump shaft of the gear pump 72 is coupled and fixed to the first pump shaft 120 inside the pump case 108. A drive gear (or inner rotor) is fixed to the gear pump shaft. The gear pump 72 can be a trochoid pump or the like that meshes the driven gear with the drive gear or rotates the outer rotor while being eccentric with respect to the inner rotor. In addition, although illustration is abbreviate | omitted, a gear pump axis | shaft may protrude from the outer surface of case 158 of the gear pump 72, and the power transmission part for connecting with another apparatus can also be provided in the protruded part. For example, the power transmission part can be configured by forming a male spline part or a female spline part at the end of the gear pump shaft. For example, a rotating shaft of a cooling fan (not shown) can be splined to the power transmission unit.

  5, 6, and 8, each movable swash plate 90 is a swash plate operation unit, and is a hydraulic servo mechanism, and is tilted at a swash plate angle by corresponding servo mechanisms 92 and 96. The angle is changed, i.e. controlled. Each movable swash plate 90 has a convex surface portion 160 having a circular arc cross section, which is a side surface opposite to each piston 156, and an upper surface portion 162 facing upward. The case main body 124 is provided with a concave surface portion having an arc-shaped cross section that matches the convex surface portion 160 as a fixed member, and the convex surface portion 160 can be slid along the concave surface portion. As shown in FIG. 8, the operation pin 106 is coupled to the upper surface portion 162 in the vertical direction, and the operation pin 106 is engaged with the servo piston 100 constituting the servo mechanisms 92 and 96.

  Each of the servo mechanisms 92 and 96 includes a cylinder 164 that is a servo cylinder provided on the case main body 124 in parallel to a direction orthogonal to the pump shafts 120 and 122, and is slidable in the axial direction within the cylinder 164. A hollow servo piston 100 provided, a direction switching valve provided inside the servo piston 100 so as to be slidable in the axial direction, and one direction in the axial direction of the spool 102 with respect to the servo piston 100 And a spring 104 that is a biasing member that biases the spring. Each servo piston 100 includes a locking groove 166 that is a locking portion that engages with the operation pin 106 coupled to the corresponding movable swash plate 90 and a plurality of internal oil passages on the outer surface thereof. The locking groove 166 is provided in a direction orthogonal to the axial direction of the cylinder 164. For this reason, each servo piston 100 is interlocked with the corresponding movable swash plate 90.

  FIG. 15 is a view for explaining the operation of the balance piston mechanism 94 (98) and the servo mechanism 92 (96) for driving the servo mechanism 92 (96) in the pump unit 24. As shown in FIG. 15, the servo piston 100 is provided with a first oil passage 168, a second oil passage 170, and a third oil passage 172. In the cylinder 164, a first oil chamber 244 and a second oil chamber 246 are formed on one end side (left end side in FIG. 15) and the other end side (right end side in FIG. 15) of the servo piston 100, respectively. ing. The first oil passage 168 is connected to an oil passage connected to the discharge port of the gear pump 72 and has a function of introducing a predetermined adjustment pressure from the piston 100 outer peripheral surface side to the piston 100 inner peripheral surface side. That is, the gear pump 72 supplies hydraulic oil into the cylinder 164. Further, the second oil passage 170 has one end on the inner circumferential surface of the piston 100 at a position shifted to one side in the axial direction of the piston 100 (left side in FIG. 15) with respect to the opening end of the first oil passage 168 on the piston 100 side. The other end is opened on the other axial end surface (right end surface in FIG. 15) of the piston 100. For this reason, the other end of the second oil passage 170 is connected to the second oil chamber 246. The third oil passage 172 has one end on the inner peripheral surface of the piston 100 at a position shifted from the piston 100 side opening end of the first oil passage 168 to the other axial side of the piston (right side in FIG. 15). The other end is opened on one axial end surface (left end surface in FIG. 15) of the piston 100. For this reason, the other end of the third oil passage 172 is connected to the first oil chamber 244.

  The spool 102 is provided on the outer peripheral surface, and is formed in an annular shape that can simultaneously face the opening end on the inner peripheral surface side of the piston 100 of the first oil passage 168 and the one end opening of the second oil passage 170 or the third oil passage 172. A groove 174 is included. The groove 174 has a function of switching between a state in which the first oil passage 168 and the second oil passage 170 are communicated and a state in which the first oil passage 168 and the third oil passage 172 are in communication. The servo mechanisms 92 and 96 are provided between the piston main body 112 and the spool 102 constituting the corresponding balance piston mechanisms 94 and 98, and move the spool 102 in synchronization with the axial movement of the piston main body 112. An arm member 176 that is an intermediate locking member is provided.

  Further, the spool 102 is provided with an oil passage 238 on the inner side, and the oil passage 238 is always in communication with the oil sump 110 in the case main body 124 of FIG. The oil passage 238 communicates with the third oil passage 172 in a state where the first oil passage 168 and the second oil passage 170 communicate with each other via the groove portion 174, and the first oil passage 168 and the third oil passage 172 communicate with the groove portion 174. In communication with the second oil passage 170, the second oil passage 170 is communicated. Such servo mechanisms 92 and 96 are configured to selectively introduce hydraulic oil into either the first oil chamber 244 or the second oil chamber 246 by moving the spool 102 in the axial direction relative to the servo piston 100. The piston 100 moves in the axial direction to change the capacity of the corresponding hydraulic pump 74 (or 82).

  As shown in FIG. 8, each servo mechanism 92, 96 is housed in an internal space above the case body 124, and an opening 178 for projecting the upper end of the arm member 176 into the upper portion of each internal space. Is provided. Further, a piston case 180 is coupled and fixed to the upper side of the case main body 124 with a bolt as a fastening member. The piston case 180 accommodates a first balance piston mechanism 94 and a second balance piston mechanism 98 that face the servo mechanisms 92 and 96, respectively. The balance piston mechanisms 94 and 98 are connected to the spools 102 of the corresponding servo mechanisms 92 and 96 so as to be able to move synchronously, and can be slid in the axial direction within the cylinder 182 which is a balance cylinder. And a provided piston body 112. Arm members 176 are provided between the spools 102 of the servo mechanisms 92 and 96 and the corresponding piston main bodies 112.

  As shown in FIG. 6, the arm member 176 has an upper shaft 184 and a lower shaft 186 provided on the same axis in the vertical direction, a flange 188 coupled between both shafts 184 and 186, and an upper surface of the tip of the flange 188. And a support shaft 190 erected in the vertical direction. As shown in FIG. 8, the upper shaft 184 is engaged with a locking groove 192 provided on the entire circumference of the intermediate portion of the piston main body 112, and the lower shaft 186 is engaged with a locking groove provided on the entire periphery of the intermediate portion of the spool 102. 194 is engaged. With this configuration, the spools 102 of the servo mechanisms 92 and 96 can move in synchronization with the movement of the corresponding balance piston mechanisms 94 and 98 in the axial direction of the piston main body 112.

Further, each balance piston mechanism 94, 98 includes a first pressure receiving chamber 196 and a fourth pressure receiving chamber 198 provided on one axial end side of the cylinder 182, and a second pressure receiving pressure provided on the other axial end side of the cylinder 182. A chamber 200 and a third pressure receiving chamber 202. In the first pressure receiving chamber 196, the discharge pressures of the first and second hydraulic pumps 74 and 82, which are variable displacement pumps, and before passing through the direction control valves 26a, 26b (FIG. 3) which are actuator switching valves. The primary hydraulic oil pressure P _P is introduced, and the maximum load pressure P _L (hereinafter simply referred to as “load pressure P _L ”) after passing through the direction control valves 26a and 26b is introduced into the second pressure receiving chamber 200. Is done. A set load sensing pressure ΔP _LS is introduced into the third pressure receiving chamber 202. The set load sensing pressure ΔP _LS corresponds to a working fluid differential pressure generated before and after passing through the direction control valves 26a and 26b in a steady state at the operation position of the direction control valves 26a and 26b, and is a preset set pressure. . As shown in FIG. 15, a pressure Pch obtained by adjusting the discharge pressure P _PL of the gear pump 72 and vacuum to the desired value by a fixed pressure reducing valve 116, so that set load sensing pressure [Delta] P _LS is obtained.

Further, as shown in FIG. 8, the valve case 204 is fixed on the upper surface of the piston case 180 at a position facing the upper side of the intermediate portion in the width direction between the two balance piston mechanisms 94 and 98. As shown in FIG. 12, the valve case 204 is provided with a fixed pressure reducing valve 116 common to the balance piston mechanisms 94 and 98 (FIG. 8). The fixed pressure reducing valve 116 includes a cylinder, a valve body 206 that is slidable with respect to the cylinder, a cap 208 that is fixed to the valve case 204, a screw shaft 210 that is screwed to the cap 208, and a screw shaft 210. A spacer 212 to be pressed and a spring 214 provided between the valve body 206 and the spacer 212 are provided. The spring 214 biases the valve body 206 in one direction. Pressure Pch from the gear pump 72 (FIG. 15) is introduced into a space where the valve body 206 is disposed through an oil passage (not shown) of the valve case 204. The pressure Pch is reduced according to the urging force of the spring 214, and the set load sensing pressure ΔP _LS is introduced into each third pressure receiving chamber 202 (FIG. 8) through the oil passage. As shown in FIG. 12, the amount of pressure reduction by the fixed pressure reducing valve 116 can be adjusted by changing the urging force of the spring 214 by adjusting the amount of screw shaft 210 entering the cap 208 inside.

As shown in FIG. 13, the fourth pressure receiving chamber 198 can introduce a variable pressure after the discharge pressure of the gear pump 72 (FIG. 15) is reduced by the corresponding proportional control type variable pressure reducing valve 114. That is, the fourth pressure receiving chamber 198 is introduced with a variable pressure that can be arbitrarily set. Normally, the hydraulic oil introduced from the gear pump 72 into the fourth pressure receiving chamber 198 can be shut off. Each variable pressure reducing valve 114 has a proportional solenoid 216 and a pressure reducing valve body 218 whose amount of pressure reduction is controlled by the proportional solenoid 216. The proportional solenoid 216 receives, for example, a signal indicating a load of the engine 22 (FIG. 2). Entered. When the engine load is high, the proportional solenoid 216 reduces the decrease amount of the pressure P _CON on the secondary side to the pressure reducing valve body 218 so that the pressure close to the pressure Pch is introduced into the fourth pressure receiving chamber 198. Regulate the amount. The proportional solenoid 216 is fixed so as to protrude from the side surface of the piston case 180 facing in the horizontal direction. Further, a cable 220 for inputting a command signal is connected to the proportional solenoid 216.

  Thus, in the pump unit 24 that simultaneously drives two or more variable displacement pumps, the servo mechanisms 92 and 96 that are interlocked with the movable swash plate 90 when mounted on a work vehicle are provided on the upper portion of the case main body 124. The piston case 180 that is a member that accommodates the balance piston mechanisms 94 and 98 is provided above the servo mechanisms 92 and 96. For this reason, maintenance work can be easily performed by opening the bonnet normally provided in the apparatus accommodating part 20 (FIG. 1).

  Further, as shown in FIG. 8, in order to detect the tilt angle of each movable swash plate 90, a rotation angle sensor 222, which is two potentiometers corresponding to each movable swash plate 90, is provided. For this purpose, the sensor support member 224 is coupled and fixed at two positions facing the upper side of the balance piston mechanisms 94 and 98 on the upper side of the piston case 180 with bolts as fastening members. Each sensor support member 224 is fixed to the upper side of the piston case 180 and the valve case 204, respectively. The rotation angle sensor 222 is fixed to the upper side of each sensor support member 224, and the sensor shaft 226 is directed in the vertical direction. The lower end portion of the sensor shaft 226 protrudes downward from the lower surface of the sensor support member 224.

  On the other hand, as described above, the arm member 176 engaged between the servo mechanisms 92 and 96 and the corresponding balance piston mechanisms 94 and 98 has the support shaft 190 (FIG. 6). The support shaft 190 protrudes to the upper side of the piston case 180 through a hole penetrating the piston case 180 in the vertical direction, and an intermediate portion of the first lever 228 that is a rotation angle detection lever is coupled to the protruded portion. ing. In addition, one end of a second lever 230 that is a rotation angle detection lever is swingably supported by a pin at the tip of the first lever 228. The other end of the second lever 230 is coupled and fixed to the lower end of the sensor shaft 226. For this reason, when the tilt angle of the movable swash plate 90 changes and the spool 102 moves following the servo piston 100, the upper shaft 184 and the lower shaft 186 of the arm member 176 move in the reverse direction of FIG. Along with this, the support shaft 190 rotates about the center of the hole of the piston case 180, and the first and second levers 228 and 230 swing, so that the sensor shaft 226 of the rotation angle sensor 222 rotates. Therefore, the rotation angle sensor 222 can detect the rotation angle corresponding to the tilt angle of the movable swash plate 90. The levers 228 and 230 connected by pins and the rotation angle sensor 222 constitute a rotation angle detection unit. As described above, the pump unit 24 that simultaneously drives two or more variable displacement pumps includes the pump case 108 or two or more support shafts 190 rotatably supported by members fixed to the pump case 108. Can be connected to the corresponding rotation angle sensor 222 and can detect the rotation interlocking with the movement of the corresponding movable swash plate 90.

  Also, as shown in FIGS. 12 and 14, the initial position is set in the horizontal direction at the end (left end in FIG. 12) of each first lever 228 opposite to the coupling side of the second lever 230 (FIG. 6). The end of the screw shaft 232 is abutted. Each screw shaft 232 functions as a stopper, and is inserted into a plate portion 234 erected on a fixed member on the upper surface of the piston case 180, and a nut is tightened from both sides, thereby adjusting the protruding amount of the screw shaft 232 with respect to the plate portion 234. It is possible. For this reason, the initial tilt angle, which is the initial position of the movable swash plate 90 (FIG. 5), can be arbitrarily set, and the operation element 32 (FIG. 3) such as an operation lever or a pedal is in the neutral position and the actuator such as a motor. Even when 236 (see FIG. 15) is not in operation, the hydraulic pumps 74 and 82 are on standby so that the hydraulic oil is slightly discharged.

  The detection value of the rotation angle sensor 222 shown in FIG. 11 is input to a controller (not shown). If the controller determines that the tilt angle of the movable swash plate 90 (FIG. 5) has become larger than a preset threshold value, the controller instructs the proportional solenoid 216 to reduce the amount of pressure reduction by the pressure reducing valve body 218. Output a signal. Thereby, a large pressure is introduced into the fourth pressure receiving chamber 198 (FIG. 13), and the tilt angle of the movable swash plate 90 is regulated to be maintained within a desired range.

  In addition, when the engine speed is input to the controller from the engine 22 (FIG. 2) and it is determined that the load of the engine 22 is higher than a preset threshold value, the pressure reduction amount by the pressure reducing valve body 218 is supplied to the proportional solenoid 216. A command signal for controlling to be small is output. In this case, the tilt angle of the movable swash plate 90 is regulated so that the tilt angle of the movable swash plate 90 is reduced and the load on the engine 22 is reduced.

  Next, the effect obtained by the present embodiment will be described with reference to FIG. FIG. 15 schematically shows a connection relationship of the servo mechanism 92 (or 96), the balance piston mechanism 94 (or 98), and the actuator with respect to the pumps 72 and 74. Also, one actuator 236 such as a motor is shown for convenience of explanation. Actually, however, the servo pump 92 (or 96) and the balance piston mechanism 94 are provided from the gear pump 72 as shown in FIG. The hydraulic oil is supplied to a plurality of actuators connected in parallel such as a cylinder such as the bucket cylinder 60 corresponding to (or 98) and a motor such as the traveling motor 34a. In the following description, the case of controlling the tilt angle of the movable swash plate 90 of the first hydraulic pump 74 will be described as a representative, but the same applies to the case of the second hydraulic pump 82. As shown in FIG. 15, the tilt angle of the movable swash plate 90 is controlled by a servo mechanism 92, a balance piston mechanism 94, a variable pressure reducing valve 114, and a fixed pressure reducing valve 116.

Discharge pressure P regulated pressure Pch from _PL of the gear pump 72 is introduced into the first oil passage 168 of the servo piston 100. The primary hydraulic pressure P _P before passing through the direction control valve 26 a is introduced into the first pressure receiving chamber 196 of the balance piston mechanism 94. Further, the secondary pressure pressure P _L after passing through each directional control valve 26 a is introduced into the second pressure receiving chamber 200. Further, a set load sensing pressure ΔP _LS obtained by reducing the pressure Pch by the fixed pressure reducing valve 116 is introduced into the third pressure receiving chamber 202. The pressure applied to both sides of the piston body 112 is balanced under the following conditions.
(Primary pressure P _P ) = (Set load sensing pressure ΔP _LS ) + (Load pressure P _L )

When the pumps 72 and 74 are driven when the pressure P _CON by the variable pressure reducing valve 114 is zero and the closed center type directional control valve 26a is in the neutral position when the engine is started, as shown in FIG. The primary pressure P _P (unload pressure) acts on the first pressure receiving chamber 196, and the set load sensing pressure ΔP _LS acts on the third pressure receiving chamber 202. Since the load pressure P _L acting on the second pressure receiving chamber 200 is zero, P _P > ΔP _LS + P _L and the piston main body 112 moves to the illustrated position. When the piston main body 112 is in this position, the stopper by the arm member 176 (FIG. 8), the support shaft 190, and the screw shaft 232 (FIG. 12) prevents further movement to the right in FIG. The servo piston 100 follows the spool 102 of the servo mechanism 92 linked to the main body 112, and the movable swash plate 90 tilts and stands by so as to maintain the amount of oil discharged from the hydraulic pump 74 at a prescribed minimum value.

Next, when the directional control valve 26a is held in the operating position deviated from the neutral position, a load pressure P _L to the second pressure receiving chamber 200 is generated, but there is no change in the differential pressure before and after passing through the directional control valve 26a. Therefore, the relationship of P _P = ΔP _LS + P _L is maintained, the piston main body 112 is maintained at that position, and a certain amount of oil is discharged from the hydraulic pump 74. On the other hand, in the transitional state of switching from the neutral position to the operating position of the directional control valve 26a, the primary pressure P _P becomes low at the moment when the oil that has been blocked until then starts to flow to the actuator 236. The differential pressure before and after passing through the direction control valve 26a changes in a direction approaching the value of the load pressure P _L. Thus, a relationship of _{P P <ΔP LS + P L} . Accordingly, the balance between the thrust in the right direction in FIG. 15 applied to the piston main body 112 and the thrust in the left direction is lost, and the piston main body 112 moves to the left in FIG. To do. Along with this, the spool 102 and the servo piston 100 of the servo mechanism 92 move to the left in FIG. Then, the tilt angle of the movable swash plate 90 increases, and the amount of oil discharged from the first hydraulic pump 74 increases.

After that, the amount of oil discharged from the first hydraulic pump 74 increases, and when the pressure difference fluctuates before and after passing through the variable throttle valve with time, the relationship P _P = ΔP _LS + P _L is established. The thrust of the piston body 112 in the right direction in FIG. 15 is balanced with the thrust in the left direction, and the movement of the piston body 112 in the left direction stops. In this case, the tilt angle of the movable swash plate 90 is maintained at that position via the servo mechanism 92, the amount of oil discharged from the first hydraulic pump 74 is maintained constant, and a desired actuator hydraulic oil amount is obtained. When the switching pilot valves 28a and 28b are set to the neutral position, the unload valve 118 is opened and the piston body 112 returns to the position shown in FIG. Thus, the servo mechanism 92 (or 98) changes the capacity of the corresponding hydraulic pump 74 (or 82) of the pump unit 24 by the movement of the servo piston 100 in the axial direction.

  As described above, according to the present embodiment, the amount of oil discharged from the hydraulic pumps 74 and 82 can be controlled by load sensing in accordance with the work load pressure of the actuator. , 82 while discharging, the excess flow discharged from the hydraulic pumps 74, 82 can be reduced. For this reason, energy consumption can be reduced. Further, unlike the case of the configuration described in Patent Document 4, the pump discharge capacity can be controlled only by the pressure change of the pressure receiving chambers 196, 198, 200, 202 constituting the balance piston mechanisms 94, 98, and the load. There is no inconvenience that the control pressure of the pump is influenced by the extension amount of the spring provided on the pilot chamber side of the regulator valve corresponding to the sensing valve. For this reason, the actuator can be controlled more stably.

  Furthermore, many parts of a conventional pump unit provided with a servo mechanism, which is a swash plate operation unit, can be shared. For example, in the present embodiment, the pump unit 24 of the present embodiment can be configured using many parts for a pump unit that includes a servo mechanism but does not have a load sensing function. For this reason, it is possible to configure the pump unit 24 as an option by providing a load sensing function to the conventional product, and in this case, no significant changes are made to the components on the hydraulic pumps 74 and 82 side. Easy to reduce costs. As a result, the pump unit 24 has a servo mechanism, but has a structure in which many parts can be used in common with a pump unit that does not have a load sensing function. The discharge amounts 74 and 82 can be controlled more stably.

The balance piston mechanisms 94 and 98 further include a fourth pressure receiving chamber 198 provided adjacent to the first pressure receiving chamber 196 on one end side in the axial direction of the piston main body 112. A variable pressure that is arbitrarily settable by the pressure reducing valve 114 is introduced. As a result, the thrust from the fourth pressure receiving chamber 198 is added to the thrust from the first pressure receiving chamber 196 and the movement of the piston body 112 in the right direction in FIG. This is the resistance to thrust in the left direction of FIG. For this reason, for example, as in the present embodiment, the pump unit 24 is driven when the switching pilot valves 28a, 28b are operated to the operating positions and the hydraulic pumps 74, 82 are discharging a desired amount of oil. When the load of the engine 22 reaches a predetermined value or when the movable swash plate 90 reaches a predetermined tilt angle, there is no need to further increase the pump discharge oil amount, or it is necessary to reduce the oil amount from the current state. When they occur, they are the secondary variable pressures of the variable pressure reducing valve 114 according to the external signals, respectively, and the proportional valve secondary pressure P _CON (0 ≦ Pcon ≦ after passing through the variable pressure reducing valve 114 after discharge from the gear pump 72) Pch) is controlled. For this reason, it can utilize effectively for the maximum discharge amount setting of the hydraulic pumps 74 and 82, and engine 22 load control. Therefore, high performance of the apparatus using the pump unit 24 can be effectively achieved.

  Further, since the servo mechanisms 92 and 96 as described above are provided as the operation portion of the movable swash plate 90, the balance piston mechanisms 94 and 98 drive the servo piston 100. Therefore, the operating force of the movable swash plate 90 can be reduced, and the tilt angle of the movable swash plate 90 can be controlled more stably.

  In the present embodiment, the pump unit 24 is coupled to each other by bolts or the like so that the gear case 128, the port block 126, and the case main body 124 are arranged in this order from the engine 22 side. However, the arrangement order can be freely changed. Further, the gear case 128 can be detachably coupled to an engine 22 coupling flange called an engine mounting flange. In this case, by replacing only the engine coupling flange according to the type of the engine 22, it is possible to attach to various engines 22 without greatly changing the parts.

  The basic configuration of the pump unit 24 of the present embodiment is as described above. However, in the case of the present embodiment, the engine 22 (FIGS. 2 and 3) which is a drive source for driving the hydraulic pumps 74 and 82 is further provided. In order to prevent the increase in load) with high responsiveness and to more effectively reduce energy consumption, a special configuration described later is employed. First, the reason why this special configuration was conceived will be described with reference to the basic configuration shown in FIG. As described above, in the basic configuration, the engine speed is input to the controller, and when the controller determines that the load of the engine 22 has become higher than the threshold value, the controller outputs a command signal to the proportional solenoid of the variable pressure reducing valve 114, etc. Thus, the tilt angle of the movable swash plate 90 is reduced to control the load of the engine 22 to be small.

  However, since the engine speed is detected and the like, there is a possibility that a control response delay occurs when load control is required. That is, there is room for improvement in terms of preventing the increase in the load on the engine 22 with high responsiveness. When the load is high, the energy consumption of the pump unit 24 increases, and the fuel consumption of the engine 22 that drives the pump unit 24 may deteriorate. In contrast, the present inventor intends to solve these problems by providing a piston movement restricting mechanism having a control piston disposed opposite to the servo piston 100 of the servo mechanisms 92 and 96 as described below. Thought.

  FIG. 16 is a diagram corresponding to FIG. 15 in the specific configuration of the pump unit of the present embodiment. In FIG. 16, the vertical positional relationship among the hydraulic pump 74 (or 82), the servo mechanism 92 (or 96), and the balance piston mechanism 94 (or 98) is shown opposite to that in FIG. Note that the position of the variable pressure reducing valve 114 in FIG. 16 does not indicate the actual arrangement position, and the variable pressure reducing valve 114 is disposed at the same position as the balance piston mechanism 94 (or 98) in the vertical direction of FIG. Yes.

  As shown in FIG. 16, in this embodiment, the increase in the swash plate angle of the corresponding movable swash plate 90 is restricted to the left and right sides of the pump case 108 in FIG. Two piston movement restriction mechanisms 248 are attached. In FIG. 16, the same or corresponding elements as those in the basic configuration shown in FIGS. 1 to 15 described above are denoted by the same reference numerals, and redundant illustration and description will be omitted or simplified below. Also, one piston movement restricting mechanism 248 corresponding to one servo mechanism 92 and another piston movement restricting mechanism 248 corresponding to another servo mechanism 96 are the same as shown in FIG. It has a configuration.

  The piston movement restriction mechanism 248 includes an outer cylinder member 250 that is a second fixing member that is fixed to the outer end portion of the cover 108a that is a first fixing member that is coupled and fixed to the pump case 108 by screw coupling, the cover 108a, A control piston 252 disposed inside the outer cylinder member 250, a control spring 254 as a biasing member, and a pressure introduction path 256 as a restriction pressure introduction path are included. A part of the control piston 252 is provided in an outer cylinder 258 that is a restriction cylinder provided inside the outer cylinder member 250 so as to be slidable in the axial direction.

  That is, the outer cylinder 258 is formed in the outer cylinder member 250 so that the inner end (left end in FIG. 16) is open and the outer end (right end in FIG. 16) is closed. The outer cylinder 258 includes a large-diameter portion 260 on the inner end side and a small-diameter portion 262 on the outer end side. The control piston 252 includes a sliding shaft portion 264 that is slidable in the axial direction in the small diameter portion 262, an intermediate shaft portion 266 coupled to the sliding shaft portion 264, and one end side of the intermediate shaft portion 266. A screw shaft 268 provided on a certain inner end side (left end side in FIG. 16), a pressing member 270 externally fitted to the screw shaft 268, and a nut 280 that couples and fixes the pressing member 270 to the screw shaft 268 are included. Further, the control spring 254 is provided between a wall portion 282 provided on the cover 108 a and a flange 284 provided on an intermediate portion in the axial direction of the control piston 252.

  A pressing member 270 provided at one end of the control piston 252 is opposed to the other axial end surface (the right end surface in FIG. 16) of the servo piston 100. The control spring 254 biases the control piston 252 in a direction in which the pressing member 270 is separated from the servo piston 100. The cover 108a and the outer cylinder member 250 are formed by a single member, or a portion corresponding to the cover 108a is formed by a part of the pump case 108, or the cover 108a and the outer cylinder member 250 are formed on the cover 108a and the outer cylinder member 250. A corresponding portion can be formed by a part of the pump case 108.

Further, the pressure introduction path 256 is provided at the outer end portion of the outer cylinder member 250 in the radial direction of the outer cylinder member 250. One end of the pressure introduction path 256 is connected to the outer end portion of the small diameter portion 262 of the outer cylinder 258. The other end of the pressure introduction path 256 is opened on the outer peripheral surface of the outer cylinder member 250. The pressure introduction path 256 may be provided in the axial direction of the outer cylinder member 250, and the end portion of the pressure introduction path 256 may be opened on the outer end surface in the axial direction of the outer cylinder member 250. The other end of the pressure introduction path 256 is connected to the downstream end portion of the external pipe 286 connected to the discharge side of the first hydraulic pump 74 (or the second hydraulic pump 82). Therefore, the control piston 252 is pressed toward the servo piston 100 (the left side in FIG. 16) by the pressure introduced into the outer cylinder 258 from the first hydraulic pump 74 (or the second hydraulic pump 82) through the pressure introduction path 256. . That is, the pressure introduction path 256 switches the actuator after discharging from the first hydraulic pump 74 (or the second hydraulic pump 82) so that the control piston 252 approaches the servo piston 100 against the biasing force of the control spring 254. the hydraulic fluid pressure P _P of the primary side of the front passage of a valve direction control valve 26a (or 26a), which is the other end side of the control piston 252, disposed outside the small diameter portion 262 (the right side in FIG. 16) It has a function of being introduced into the hydraulic chamber 287.

  As shown in FIG. 16, an orifice member 288 having an orifice inside is fixed to the pressure introduction path 256, and the pressure introduced to the outside of the control piston 252 (right side in FIG. 16) through the pressure introduction path 256 is abrupt. Variations can also be suppressed. In the outer cylinder 258, a spring chamber 290 in which the control spring 254 is accommodated is formed by the wall portion 282 of the cover 108 a and the flange 284 of the control piston 252. The spring chamber 290 is a first oil chamber on the other end side of the control piston 252 in the cylinder 164 that is a servo cylinder through a gap formed between the hole formed in the wall portion 282 and the outer peripheral surface of the control piston 252. 244 is communicated. For this reason, it is not necessary to form a discharge path connected to the spring chamber 290 in the outer cylinder member 250 and connected to the oil tank via the external pipe.

According to the pump unit including such a piston movement restriction mechanism 248, it is possible to prevent the increase in the load of the engine 22 (FIGS. 2, 3 and the like) that drives the hydraulic pumps 74 and 82 with good responsiveness and reduce energy consumption. It can be reduced more effectively. That is, in the transitional state of switching from the neutral position to the operating position of the directional control valve 26a (or 26b), the primary pressure P _P becomes low, and the piston main body 112 constituting the balance piston mechanism 94 (or 98) It moves to the right side of FIG. Along with this, the spool 102 constituting the servo mechanism 92 (or 96) also moves in the same direction, and hydraulic oil is introduced from the gear pump 72 into the second oil chamber 246 constituting the servo mechanism 92 (or 96). The hydraulic oil is discharged from the oil chamber 244 to the oil sump 110 in the pump case 108 through the oil passage 238. For this reason, the servo piston 100 moves in the direction of increasing the swash plate angle of the movable swash plate 90 (right side in FIG. 16).

When the hydraulic oil pressure P _P introduced into the pressure introduction path 256 is low, as shown in FIG. 16, the pressing member 270 of the control piston 252 is biased by the servo mechanism 92 (or 96) by the biasing force of the control spring 254. ), Which is a part of the servo piston 100. For this reason, the tilt angle of the movable swash plate 90 of the corresponding hydraulic pump 74 (or 82) can be changed without being restricted by the control piston 252.

On the other hand, when a load is applied to the actuator 236 and the primary hydraulic pressure P _P after discharge from the first hydraulic pump 74 (or the second hydraulic pump 82) becomes higher than a preset threshold value, The hydraulic oil pressure P _P introduced through the introduction path 256 presses the control piston 252 toward the servo piston 100 against the biasing force of the control spring 254. For this reason, the maximum value of the stroke amount, which is the displacement of the servo piston 100, is regulated to be small, and the servo piston 100 is pushed back in some cases, and the movable swash plate 90 of the corresponding hydraulic pump 74 (or 82) is tilted. The angle becomes smaller. That is, the maximum swash plate angle of the movable swash plate 90 is restricted. For this reason, the maximum discharge amount of the hydraulic pump 74 (or 82) is reduced, and an increase in the load on the engine 22 can be prevented promptly, that is, with good response. At the same time, the energy consumption of the hydraulic pumps 74 and 82 can be more effectively reduced, and the fuel consumption of the engine 22 can be more effectively reduced.

  Further, as in the present embodiment, when it is determined that the load of the engine 22 has become higher than a preset threshold value according to detection of the engine speed or the like, the variable pressure reducing valve 114 is controlled by the controller and the piston Even when the stroke amount of the main body 112 is limited, the increase in load can be prevented with high responsiveness by the piston movement restricting mechanism 248 before being limited by the controller. In addition, as long as the excessive increase of the load can be prevented only by the piston movement restriction mechanism 248, the load control based on the load detection such as the rotation speed detection on the engine 22 side may not be performed.

[Second Embodiment]
FIG. 17 is a diagram showing a hydraulic circuit of a continuously variable transmission including a servo mechanism that constitutes a continuously variable transmission that is a hydraulic rotating machine according to a second embodiment of the present invention. In the present embodiment, the present invention is applied to a continuously variable transmission that is a hydraulic rotating machine. The continuously variable transmission 292 shown in FIG. 17 is called an HST (Hydro Static Transmission) which is a hydrostatic power transmission device. It is mounted and used on a work vehicle such as the excavation work machine 10 (see FIG. 1) described in the embodiment. For example, in the traveling device of the excavation work machine 10, it is used for driving a drive unit such as a wheel or a crawler belt by a hydraulic motor. The continuously variable transmission 292 includes a hydraulic pump 296 and a hydraulic motor 298 that are respectively provided in the case 294. The hydraulic motor 298 is supplied with pressure oil, which is hydraulic oil discharged from the hydraulic pump 296, and is driven. . The continuously variable transmission 292 performs hydrostatic transmission by a hydraulic pump 296 and a hydraulic motor 298.

  That is, the hydraulic pump 296 has a pump-side first port P1 and a pump-side second port P2, which are two ports. The hydraulic motor 298 has two ports, a motor-side first port M1 and a motor-side second port M2. The first ports P1 and M1 of the hydraulic pump 296 and the hydraulic motor 298 are connected by a first oil passage S1 that is a forward main oil passage, and the second ports P2 and M2 of the hydraulic pump 296 and the hydraulic motor 298, respectively. Are connected by a second oil passage S2, which is a reverse main oil passage. The first oil passage S1 and the second oil passage S2 constitute a main circuit that is a closed circuit that fluidly couples, that is, connects the hydraulic pump 296 and the hydraulic motor 298.

  The hydraulic pump 296 is a variable capacity pump having a movable swash plate 90 and is driven by a drive source (not shown) such as an engine or an electric motor. The charge pump 300, which is an auxiliary pump and a fixed capacity pump, is also driven by a drive source. For example, the hydraulic pump 296 and the charge pump 300 are driven by a single rotating shaft that is driven by a driving source or different from each other. When the rotating shaft of the hydraulic pump 296 is driven, pressurized hydraulic fluid is discharged from one of the first port P1 and the second port P2, and hydraulic fluid is sucked from the other port. The hydraulic pump 296 includes a movable swash plate 90 that is swingably supported by the case 294, and can change the tilt angle of the movable swash plate 90 with respect to the drive shaft, that is, the tilt angle.

  The movable swash plate 90 can change the direction and angle of the movable swash plate 90 by rotating an operation pin that is a swash plate operation shaft provided in the case 294. The discharge side and the suction side of the first port P1 and the second port P2 are determined by the direction and angle of the movable swash plate 90, and the discharge capacity is also determined. Further, in response to the operation of the speed change operation lever 302 that is an acceleration instruction portion provided in the periphery of the driver's seat of the vehicle, the lever 304 coupled to the speed change operation lever 302 swings, and a servo mechanism 306 described below. The swash plate operating pin rotates via the, and the capacity of the hydraulic pump 296 changes.

  That is, the servo mechanism 306 is provided in the case 294. The basic configuration of the servo mechanism 306 is the same as that of the servo mechanisms 92 and 96 provided in the pump unit shown in FIG. For this reason, in FIG. 17, the same or corresponding elements as those shown in FIG. 15 are denoted by the same reference numerals, and redundant description is omitted or simplified. Further, unlike the case of the configuration shown in FIG. 15, the continuously variable transmission 292 is not provided with balance piston mechanisms 94 and 98. A speed change drive pin 308 that is a speed change drive member is engaged with the outer peripheral surface of the spool 102 constituting the servo mechanism 306. The shift drive pin 308 is interlocked with the lever 304. The lever 304 swings around the swing center by operating the shift operation lever 302 to the F side (the side instructing the vehicle to advance) or the R side (the side instructing the vehicle to move backward) in FIG. To do. In this case, since the spool 102 moves in either direction of arrows α and β, the servo piston 100 also moves in the same direction as the spool 102. For this reason, the tilt angle of the movable swash plate 90 is inclined in a direction corresponding to the forward side or the reverse side from the neutral position, and the hydraulic pump 296 corresponds to the forward side or the reverse side of the vehicle and the first port of the hydraulic motor 298. As the hydraulic oil is driven to be supplied to M1 or the second port M2 and the operation amount of the speed change operation lever 302 is increased, the discharge capacity from the hydraulic pump 296 is changed. That is, the servo mechanism 306 includes a cylinder 164 that is a servo cylinder provided in the case 294, and a servo piston 100 that is provided in the cylinder 164 so as to be slidable in the axial direction and interlocks with the movable swash plate 90. The displacement of the hydraulic pump 296 is changed by the movement of the piston 100 in the axial direction.

  The hydraulic motor 298 is a constant-capacity motor having a fixed swash plate, and is a rotatable motor drive shaft (coupled to a drive unit such as a vehicle wheel or the like so that power can be transmitted directly or via a power transmission unit or the like ( (Not shown). When high-pressure hydraulic oil is drawn from one of the first port M1 and the second port M2, the piston provided in the cylinder bore of the hydraulic motor 298 reciprocates, and the motor drive shaft rotates. In this case, hydraulic fluid is discharged from the other port of the first port M1 and the second port M2. The hydraulic motor 298 supports a fixed swash plate on the case 294 so that the inclination angle with respect to the motor drive shaft cannot be changed. In the first port M1 and the second port M2, the rotation direction of the motor drive shaft is switched depending on whether the discharge side or the suction side is selected. For example, when the shift operation lever 302 is moved forward, the first port M1 is on the suction side and the second port M2 is on the discharge side. In this case, a drive unit such as a wheel rotates forward, and the vehicle travels forward. Further, during reverse operation of the speed change operation lever 302, the second port M2 is on the suction side and the first port M1 is on the discharge side. In this case, the vehicle travels backward. Further, as the discharge flow rate of the hydraulic pump 296 changes, the rotational speed of the hydraulic motor 298 changes. That is, when the discharge flow rate of the hydraulic pump 296 increases, the rotation speed of the hydraulic motor 298 increases, and when the discharge flow rate of the hydraulic pump 296 decreases, the rotation speed of the hydraulic motor 298 decreases.

  In the continuously variable transmission 292, the discharge port of the charge pump 300 is provided with relief valves 310 and 2 that respectively constitute the charge circuit SC via external piping and an internal oil passage formed inside the case 294. The two charge check valves 312 and 314 are connected to each other. The relief valve 310 has a function of regulating the hydraulic pressure in the charge circuit SC to a hydraulic pressure equal to or lower than a set value. The oil relief side of the relief valve 310 is connected to an oil sump (not shown) that is the space inside the case 294. The charge check valves 312 and 314 are configured such that when the first oil passage S1 or the second oil passage S2 on the low pressure side is lower than the charge pressure that is the pressure of the charge circuit SC, the secondary side is the low pressure side. The charge check valve 312 (or 314) is opened, and the charge circuit SC communicates with the first oil passage S1 or the second oil passage S2.

  The charge check valves 312 and 314 have a high-pressure relief valve function so that the first oil passage S1 or the second oil passage S2 on the high-pressure side becomes a high pressure that is higher than the set pressure, so that the high-pressure relief valve has a high-pressure relief valve. Oil path S1 (or S2) and the charge check valves 312 and 314 are connected to each other, the charge check valve 314 (or 312) whose secondary side is the low pressure side is opened, and the second oil which is the low pressure side An excessive pressure can be applied to the path S2 or the first oil path S1.

  In such a continuously variable transmission 292, only the hydraulic pump 296 of the hydraulic pump 296 and the hydraulic motor 298 is a variable displacement type having the movable swash plate 90. It is also possible to adopt a configuration in which only the motor 298 or both are of a variable capacity type having a movable swash plate. The servo mechanism 306 controls the tilt angle of at least one of the movable swash plate 90 of the hydraulic pump 296 and the hydraulic motor 298, and operates the shift drive pin 308 linked to the movable swash plate 90 by operating the shift operation lever 302. It is configured to move.

  The continuously variable transmission 292 includes a piston movement restricting mechanism 248 that restricts an increase in the swash plate angle of the movable swash plate 90. The piston movement restriction mechanism 248 is provided in an outer cylinder 258 that is a restriction cylinder provided inside an outer cylinder member 250 that is a fixed member fixed to the case 294, and is slidable in the axial direction in the outer cylinder 258. And a control piston 252 having one end opposed to the axial end surface of the servo piston 100, a control spring 254 as a biasing member, and a pressure introduction path 256 as a restriction pressure introduction path. The control spring 254 is provided between a cover 316 that is a fixing member fixed to the case 294 and the control piston 252, and the control piston 252 has one end portion (the left end portion in FIG. 17) at the servo piston 100. Energize in the direction away from.

  The pressure introduction path 256 is formed in the outer cylinder member 250, and one end of the pressure introduction path 256 is connected to the hydraulic chamber 287 facing the outer end surface of the sliding shaft portion 264 in the outer cylinder 258. The other end opens on the outer peripheral surface of the outer cylinder member 250. The open end of the pressure introduction path 256 is connected to an end of an external pipe that constitutes a branch path 318 that is connected to branch from the first oil path S1 that is on the high pressure side when the vehicle is moving forward. For this reason, the pressure introduction path 256 has the other end side (the right side in FIG. 16) of the sliding shaft portion 264 of the control piston 252 so that the control piston 252 approaches the servo piston 100 against the biasing force of the control spring 254. The hydraulic oil pressure is introduced into the hydraulic chamber 287. That is, of the first oil passage S1 and the second oil passage S2, the pressure piston 252 becomes a high-pressure side when moving forward so that the control piston 252 approaches the servo piston 100 against the biasing force of the control spring 254 through the pressure introduction passage 256. The hydraulic oil pressure from the first oil passage S <b> 1 is introduced into the hydraulic chamber 287.

  In such a configuration, hydraulic oil is introduced from the charge pump 300 to the second oil chamber 246 by operating the speed change operation lever 302 from the neutral position (N position in FIG. 17) to the forward side (F side in FIG. 17). Then, the hydraulic oil is discharged from the first oil chamber 244 to the oil sump in the case 294 through the oil passage 238, whereby the servo piston 100 moves in the direction of increasing the swash plate angle (right side in FIG. 17).

  On the other hand, the control piston 252 of the piston movement restriction mechanism 248 is against the biasing force of the control spring 254 by the pressure from the first oil passage S1 that becomes high pressure when moving forward (on the left side in FIG. 17). By moving to, the maximum swash plate angle of the movable swash plate 90 is restricted. For this reason, the control spring 254 is introduced by introducing the pressure from the first oil passage S1 that becomes high pressure as the hydraulic oil pressure increases as the loads of the hydraulic pump 296 and the hydraulic motor 298 increase into the hydraulic chamber 287 through the pressure introduction passage 256. The range of the tilt angle of the movable swash plate 90 can be regulated by pressing the control piston 252 against the servo piston 100 against the urging force. Therefore, the maximum discharge amount of the hydraulic pump 296 is reduced, and the increase in the load of the engine 22 can be prevented quickly, that is, with good responsiveness. At the same time, the energy consumption of the hydraulic pump 296 can be reduced more effectively.

  In the above description, of the first oil passage S1 and the second oil passage S2, the hydraulic oil pressure from the first oil passage S1 that becomes the high pressure side when moving forward is introduced into the hydraulic chamber 287 that is the other end side of the control piston 252. To be. However, similarly to the configuration described in Patent Document 2 above, the first branch path branched from the first oil path S1 and the second branch path branched from the second oil path S2 are connected at the collecting portion, The hydraulic chamber 287 and the collecting portion are connected, and check valves are provided in each of the first branch path and the second branch path, and load control is performed by the piston movement restriction mechanism 248 in both cases of forward and reverse travel. Can also be configured.

  Although the case where the hydraulic motor 298 is a fixed displacement motor has been described above, the present embodiment can be applied even when the hydraulic motor 298 is a variable displacement type having a movable swash plate. In this case, a servo mechanism having a servo piston interlocked with the movable swash plate of the hydraulic motor 298 is provided, and a servo cylinder of the servo mechanism is configured, and in the oil chamber in which the servo piston is moved in the large capacity direction by introducing hydraulic oil, The pressing member of the control piston is opposed to the servo piston. Further, as described above, an assembly portion connecting the first branch path branched from the first oil path S1 and the second branch path branched from the second oil path S2 is connected via the pressure introduction path in the case. Connect to the hydraulic chamber on the opposite side of the control piston from the servo piston. According to such a configuration, the movable swash plate of the hydraulic motor 298 can be tilted in the large capacity direction by the pressure of the first oil passage or the second oil passage that becomes high when the vehicle is moving forward or backward. 298 can be decelerated to prevent an increase in the load of a driving source such as an engine.

[Third Embodiment]
FIG. 18 is a view corresponding to FIG. 15, showing a pump unit according to a third embodiment of the present invention. In this embodiment, in the first embodiment shown in FIGS. 1 to 16, the piston movement restriction that restricts the increase in the swash plate angle of the movable swash plate 90 of the first hydraulic pump 74 (or the second hydraulic pump 82). The mechanism 320 does not use a configuration having a means for bringing the control piston closer to the servo piston 100 side. Instead, when the load on the actuator 236 increases, the discharge pressure of the gear pump 72, which is a fixed displacement pump, is reduced by the servo cylinder. A configuration introduced into a certain cylinder 164 is employed.

  That is, in the pump unit of the present embodiment, the outer cylinder member 250, the control piston 252 and the control spring 254 (see FIG. 16) are omitted and the cover 108a fixed to the pump case 108 is omitted in the first embodiment. A pressure introduction path 322 is formed in the bottom plate portion to penetrate both the inner and outer surfaces. By fixing the cover 108 a to the pump case 108, a first oil chamber 244 is formed in the cylinder 164. The first oil chamber 244 moves the servo piston 100 interlocked with the movable swash plate 90 in the small capacity direction (left direction in FIG. 18) by introducing hydraulic oil. The piston movement restriction mechanism 320 constitutes a corresponding servo mechanism 92 (or 96), and includes a connection path 324 that allows the first oil chamber 244 to pass through the discharge side of the gear pump 72, and a pilot-type switching valve 326. The connection path 324 includes an internal oil path provided in the pump case 108, the pressure introduction path 322, and an external end having an upstream end connected to the internal oil path and a downstream end connected to the pressure introduction path 256. Formed by piping.

The pilot-type switching valve 326 is provided in the connection path 324, and the connection path 324 is connected via the pilot-type switching valve 326 when the pilot pressure is equal to or higher than a predetermined pressure, and the pilot pressure is less than the predetermined pressure. The path 324 is configured to be blocked. Further, in the pilot type switching valve 326, the hydraulic oil pressure P _P discharged from the corresponding hydraulic pump 74 (or 82) is introduced as the pilot pressure. That is, the primary hydraulic oil pressure P _P after the discharge from the corresponding hydraulic pump 74 (or 82) and before passing through the directional control valve 26a (or 26b) which is the actuator switching valve is the pilot pressure of the pilot type switching valve 326. Has been introduced. In addition, with the pilot-type switching valve 326 connecting the discharge side of the corresponding hydraulic pump 74 (or 82) and the first oil chamber 244, the discharge side of the gear pump 72 is connected via the pilot-type switching valve 326. Connected to the oil tank 68.

  According to such an embodiment, when the hydraulic oil pressure after discharge from the corresponding hydraulic pump 74 (or 82) increases due to an increase in the load of the actuator 236, the pilot-type switching valve 326 causes the connection path 324 to pass through. The hydraulic oil pressure after discharging from the gear pump 72 is connected to the first oil chamber 244. For this reason, the servo piston 100 interlocked with the movable swash plate 90 moves in the small capacity direction (the left direction in FIG. 18), and the engine 22 (FIGS. 2, 3, etc.) that is the drive source for driving the hydraulic pumps 74, 82 Load) can be prevented with good responsiveness, energy consumption can be effectively reduced, and fuel efficiency of the engine 22 can be more effectively reduced. Other configurations and operations are the same as those of the first embodiment shown in FIGS.

[Fourth Embodiment]
FIG. 19 is a diagram showing a hydraulic circuit of a continuously variable transmission including a servo mechanism 306 that constitutes a continuously variable transmission that is a hydraulic rotating machine according to a fourth embodiment of the present invention. In this embodiment, the piston movement restricting mechanism 320 used in the third embodiment shown in FIG. 18 is combined with the continuously variable transmission 292 of the second embodiment shown in FIG.

  That is, the continuously variable transmission 292 of the present embodiment omits the outer cylinder member 250, the control piston 252 and the control spring 254 in the second embodiment, and penetrates both the inner and outer surfaces through the bottom plate portion constituting the cover 316. A pressure introduction path 322 is formed. Further, by fixing the cover 316 to the case 294, the first oil chamber 244 is formed in the cylinder 164 which is a servo cylinder. The first oil chamber 244 moves the servo piston 100 interlocked with the movable swash plate 90 in the small capacity direction (left direction in FIG. 19) by introducing hydraulic oil. Piston movement restricting mechanism 320 constitutes servo mechanism 306, and includes a connection path 324 that allows first oil chamber 244 to pass through the discharge side of charge pump 300, and pilot-type switching valve 326. The connection path 324 includes an internal oil path provided in the case 294, the pressure introduction path 256, and an external pipe having an upstream end connected to the internal oil path and a downstream end connected to the pressure introduction path 256. And is formed by.

  The pilot-type switching valve 326 is provided in the connection path 324, connects the connection path 324 via the pilot-type switching valve 326 when the pilot pressure is equal to or higher than a predetermined pressure, and shuts off the connection path 324 when the pilot pressure is less than the predetermined pressure. It is configured as follows. Further, in the pilot type switching valve 326, the hydraulic oil pressure discharged from the hydraulic pump 296 is introduced as the pilot pressure. That is, the hydraulic oil pressure discharged from the hydraulic pump 296 is the hydraulic oil pressure supplied via the first oil passage S1 that is on the high-pressure side during forward movement of the first oil passage S1 and the second oil passage S2. Is introduced as a pilot pressure of the pilot type switching valve 326.

  According to such an embodiment, the pilot-type switching valve 326 connects the connection path 324 with the pressure from the first oil path S1 that becomes a high pressure during forward movement, and the hydraulic oil pressure discharged from the charge pump 300 is the first oil. Introduced into chamber 244. For this reason, the servo piston 100 interlocked with the movable swash plate 90 moves in the small capacity direction (left direction in FIG. 19), and it is possible to prevent an increase in the load of a driving source such as an engine driving the hydraulic pump 296 with high responsiveness. , Energy consumption can be effectively reduced. Other configurations and operations are the same as those of the first embodiment shown in FIG. 17 or the second embodiment shown in FIG.

  Note that, in the above, the first oil chamber 244 in which the hydraulic oil pressure from the first oil passage S1 that is the high pressure side during forward movement is the other end side of the servo piston 100 among the first oil passage S1 and the second oil passage S2. To be introduced. However, similarly to the configuration described in Patent Document 2 above, the first branch path branched from the first oil path S1 and the second branch path branched from the second oil path S2 are connected at the collecting portion, In addition to connecting the first oil chamber 244 and the collecting portion, a check valve is provided in each of the first branch path and the second branch path, and the piston movement restriction mechanism 320 is used in both cases of forward and reverse travel. It can also be configured to perform load control.

  Although the case where the hydraulic motor 298 is a fixed displacement motor has been described above, the present embodiment can be applied even when the hydraulic motor 298 is a variable displacement type having a movable swash plate. In this case, a servo mechanism having a servo piston interlocked with the movable swash plate of the hydraulic motor 298 is provided, and a servo cylinder of the servo mechanism is configured to move the servo piston in a large capacity direction by introducing hydraulic oil. Forming a pressure introduction path connected to the. And, as described above, the connecting portion that connects the first branch path branched from the first oil path S1 and the second branch path branched from the second oil path S2, the above-described pressure introduction path, the above described Connect to the oil chamber on one side of the motor. With such a configuration, the movable swash plate of the hydraulic motor 298 can be tilted in the large capacity direction by the pressure of the first oil passage S1 or the second oil passage S2 that is high during forward or reverse travel. 298 can be decelerated to prevent an increase in the load of a driving source such as an engine.

  DESCRIPTION OF SYMBOLS 10 Excavation work machine, 12 traveling apparatus, 14 turntable, 16 turning motor, 18 superstructure, 20 equipment accommodating part, 22 engine, 24 pump unit, 26a, 26b direction control valve, 28a, 28b switching pilot valve, 30 operation Seat, 32 Operator, 34a, 34b Traveling motor, 36 blade, 38 blade cylinder, 40 excavation part, 42 swing support part, 44 axis, 46 swing cylinder, 48 boom, 50 axis, 52 arm, 54 bucket, 56 Boom cylinder, 58 arm cylinder, 60 bucket cylinder, 64 radiator, 66 valve unit, 68 oil tank, 70 gear case, 72 gear pump, 74 first hydraulic pump, 76 large diameter gear, 78 small diameter gear, 80 speed increasing mechanism, 82 2 hydraulic pumps, 84 speed increasing switching valve, 6 Volume change actuator, 88 Travel switching valve, 90 Movable swash plate, 92 First servo mechanism, 94 First balance piston mechanism, 96 Second servo mechanism, 98 Second balance piston mechanism, 100 Servo piston, 102 Spool, 104 Spring , 106 Operation pin, 108 Pump case, 108a Cover, 110 Oil reservoir, 112 Piston body, 114 Variable pressure reducing valve, 116 Fixed pressure reducing valve, 118 Unload valve, 120 First pump shaft, 122 Second pump shaft, 124 Case body , 126 port block, 128 gear case, 128a bearing support recess, 130 hole, 132 input shaft, 134 gear side space, 136 oil hole, 136a side hole, 138 plug, 140 axial hole, 142 radial hole, 144 valve plate, 146 Supply piping, 148 Body part, 150 Small diameter part, 152 Extension part, 154 Cylinder block, 156 Piston, 158 Case, 160 Convex surface part, 162 Upper surface part, 164 Cylinder, 166 Locking groove, 168 1st oil path, 170 2nd oil path, 172 Third oil passage, 174 groove, 176 arm member, 178 opening, 180 piston case, 182 cylinder, 184 upper shaft, 186 lower shaft, 188 flange, 190 support shaft, 192, 194 locking groove, 196 first pressure receiving pressure Chamber, 198 fourth pressure receiving chamber, 200 second pressure receiving chamber, 202 third pressure receiving chamber, 204 valve case, 206 valve body, 208 cap, 210 screw shaft, 212 spacer, 214 spring, 216 proportional solenoid, 218 pressure reducing valve body 220 cable 222 rotation angle sensor 224 sensor support member 226 Sensor shaft, 228 first lever, 230 second lever, 232 screw shaft, 234 plate portion, 236 actuator, 238 oil passage, 240, 242 crawler belt, 244 first oil chamber, 246 second oil chamber, 248 piston movement restriction Mechanism, 250 outer cylinder member, 252 control piston, 254 control spring, 256 pressure introduction path, 258 outer cylinder, 284 flange, 287 hydraulic chamber, 288 orifice member, 290 spring chamber, 292 continuously variable transmission, 294 case, 296 hydraulic Pump, 298 Hydraulic motor, 300 Charge pump, 302 Shifting operation lever, 304 lever, 306 Servo mechanism, 308 Shifting drive pin, 310 Relief valve, 312, 314 Check valve, 316 Cover, 318 Branch path, 320 Piston movement restriction mechanism 322 Pressure introduction path, 324 connection path, 326 Pilot type switching valve.

Claims (6)

A variable displacement hydraulic rotating machine having a movable swash plate,
A hydraulic servo mechanism that is provided inside the case and controls a swash plate angle of the movable swash plate, the servo cylinder provided in the case, and provided in the servo cylinder so as to be slidable in an axial direction; A servo piston that interlocks with the movable swash plate, and the hydraulic servo mechanism that changes the capacity of the hydraulic rotating machine by moving the servo piston in the axial direction;
A piston movement restricting mechanism for restricting an increase in the swash plate angle of the movable swash plate, the restricting cylinder provided inside the case or a fixed member fixed to the case, and an axial direction in the restricting cylinder A control piston provided slidably and having one end opposed to the axial end surface of the servo piston, and provided between the case or the fixing member and the control piston, and the control piston is connected to the control piston. An urging member that urges one end of the control piston in a direction away from the servo piston, and the hydraulic pressure of the control piston is adjusted so that the control piston approaches the servo piston against the urging force of the urging member. A hydraulic rotary machine comprising: a piston movement restricting mechanism including a restricting pressure introducing path introduced to the other end side. The hydraulic rotary machine according to claim 1,
A variable displacement pump provided in the case and a balance piston mechanism are used as a hydraulic pump unit constituting a hydraulic circuit including an actuator and a closed center type actuator switching valve,
The variable displacement pump includes the movable swash plate, and is used to supply a working fluid to the actuator via the actuator switching valve.
The balance piston mechanism is connected to the servo piston of the hydraulic servo mechanism and is provided so as to be slidable in the axial direction within the balance cylinder; and a first provided on one end side in the axial direction of the balance cylinder. A pressure receiving chamber, and a second pressure receiving chamber and a third pressure receiving chamber provided on the other axial end of the balance cylinder,
The first pressure receiving chamber is introduced with a primary hydraulic pressure (P _P ) after discharge from the variable displacement pump and before passing through the actuator switching valve,
The second pressure receiving chamber is introduced with the hydraulic oil pressure (P _L ) on the secondary side after passing through the actuator switching valve,
The third pressure receiving chamber is in a steady state at the operating position of the actuator switching valve, corresponds to a hydraulic oil pressure difference generated before and after passing through the actuator switching valve, and is supplied with a preset set pressure (ΔP _LS ). ,
The primary side after the discharge from the variable displacement pump and before the passage of the actuator switching valve so that the control piston approaches the servo piston against the biasing force of the biasing member through the regulation pressure introduction path Hydraulic pressure (P _P ) is introduced into the other end of the control piston. The hydraulic rotary machine according to claim 1,
A hydraulic pump and a hydraulic motor provided in the case, wherein at least one of the hydraulic pump and the hydraulic motor is used as a variable capacity type hydraulic continuously variable transmission having the movable swash plate;
The hydraulic servo mechanism controls an inclination angle of the movable swash plate of at least one of the hydraulic pump and the hydraulic motor, and moves a speed change drive member linked to the movable swash plate by operating a speed change operation lever. Composed of
A closed circuit for connecting the hydraulic pump and the hydraulic motor, comprising a forward main oil passage that is a high-pressure side during forward travel and a reverse main oil passage that is a high-pressure side during backward travel;
Through the regulation pressure introduction path, the control piston moves closer to the servo piston against the biasing force of the biasing member, and the high pressure side of the forward main oil path and the reverse main oil path A hydraulic rotary machine, wherein hydraulic oil pressure from a main oil passage is introduced to the other end of the control piston. A hydraulic rotary machine including a variable displacement type variable displacement pump including a movable swash plate,
A hydraulic servo mechanism that is provided inside the case and controls a swash plate angle of the movable swash plate, the servo cylinder provided in the case, and provided in the servo cylinder so as to be slidable in an axial direction; Including the servo piston interlocked with the movable swash plate, the hydraulic oil is selectively introduced into either the first oil chamber or the second oil chamber of the servo cylinder formed on one end side and the other end side of the servo piston. The hydraulic servo mechanism in which the servo piston moves in the axial direction to change the capacity of the hydraulic rotary machine;
A fixed displacement pump for supplying hydraulic fluid to the servo cylinder;
Furthermore, the piston movement restricting mechanism for restricting an increase in the swash plate angle of the movable swash plate, the fixed displacement pump with respect to the first oil chamber that moves the servo piston in a small capacity direction by introducing the hydraulic oil. A connection path that passes through the discharge side, and a pilot-type switching valve that is provided in the connection path, connects the connection path when the pilot pressure is greater than or equal to a predetermined pressure, and shuts off the connection path when the pilot pressure is less than the predetermined pressure. Including the piston movement restricting mechanism,
The hydraulic rotary machine according to claim 1, wherein a hydraulic oil pressure discharged from the variable displacement pump is introduced as a pilot pressure of the pilot type switching valve. The hydraulic rotating machine according to claim 4,
A variable displacement pump provided in the case and a balance piston mechanism are used as a hydraulic pump unit constituting a hydraulic circuit including an actuator and a closed center type actuator switching valve,
The variable displacement pump includes the movable swash plate, and is used to supply a working fluid to the actuator via the actuator switching valve.
The fixed displacement pump is operatively coupled to the variable displacement pump;
The balance piston mechanism is connected to the hydraulic servo mechanism that is an operation part of a movable swash plate that changes the capacity of the variable displacement pump, and is provided so as to be axially slidable in the balance cylinder; A first pressure receiving chamber provided on one end side in the axial direction of the balance cylinder; a second pressure receiving chamber and a third pressure receiving chamber provided on the other end side in the axial direction of the balance cylinder;
The first pressure receiving chamber is introduced with a primary working fluid pressure (P _P ) after discharge from the variable displacement pump and before passing through the actuator switching valve,
The second pressure receiving chamber is introduced with the working fluid pressure (P _L ) on the secondary side after passing through the actuator switching valve,
The third pressure receiving chamber corresponds to a working fluid differential pressure generated before and after passing through the actuator switching valve in a steady state at the operating position of the actuator switching valve, and is supplied with a preset set pressure (ΔP _LS ). ,
A hydraulic rotary machine characterized in that a primary hydraulic pressure (P _P ) after discharge from the variable displacement pump and before passing through the actuator switching valve is introduced as a pilot pressure of the pilot switching valve. The hydraulic rotating machine according to claim 4,
A hydraulic pump and a hydraulic motor provided in the case, wherein the hydraulic pump is used as a hydraulic continuously variable transmission which is the variable displacement pump having the movable swash plate;
The hydraulic servo mechanism is configured to control an inclination angle of the movable swash plate of the variable displacement pump, and to move a shift drive member linked to the movable swash plate by operating a shift operation lever;
A closed circuit for connecting the variable displacement pump and the hydraulic motor, the closed circuit including a forward main oil passage that becomes a high pressure side during forward travel and a reverse main oil passage that becomes a high pressure side during backward travel ,
The hydraulic oil pressure after discharge from the variable displacement pump, wherein the hydraulic oil pressure supplied through the main oil passage on the high pressure side of the forward main oil passage and the reverse main oil passage is the pilot. A hydraulic rotary machine, which is introduced as a pilot pressure of a type switching valve.

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