JP2005201300A - Inclining and rolling controller of variable displacement hydraulic pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To switch an ejecting direction of a compressed oil into both directions by inclining and rolling a displacement variable section into forward and rearward directions, to easily perform reducing control of a pump capacity responding to inching operation, to simplify whole structure, and to miniaturize a pump. <P>SOLUTION: In the hydraulic pump 1, a hydraulic inching operation tool 51 displacing a horse power control spool 33 in a direction where a capacity reduces is connected to a hydraulic pilot section 34 of a capacity control valve 31 limiting the capacity within the range of the horse power property of a motor according to inching operation, and a feedback mechanism 36 arranged between the control sleeves 27, 32 of capacity control valves 26, 31 and an inclined plate 21 is constituted of a converting section 37 taking out the inclining and rolling action of the inclined plate 21 by converting the same into an axial directional displacement and a translation bar 39 moving parallel to the axial direction of a rotary shaft 13 by the axial directional displacement taken out by the converting section 37. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a tilt control device for a variable displacement hydraulic pump that is suitably used in a work vehicle such as a wheel loader, a wheel-type hydraulic excavator, a hydraulic crane or a crawler-type hydraulic excavator, and a hydraulic crane.

  In general, in a hydraulic power transmission mechanism (hereinafter referred to as HST) used in a work vehicle such as a construction machine, for example, a variable displacement hydraulic pump serving as a hydraulic source and a hydraulic actuator such as a hydraulic motor are connected by a hydraulic closed circuit. There are a closed circuit type HST configured as described above, and an open circuit type HST configured such that a hydraulic pump and a hydraulic actuator are connected by a hydraulic open circuit.

  The variable displacement hydraulic pump used in the closed circuit type HST is provided with a tilt control device for tilting control of a variable capacity portion such as a swash plate, for example. A regulator mechanism that is assembled so that a tilting actuator and a capacity control valve that tilt-drive the capacity variable portion of the first and second capacity-variable parts form an integral structure is provided (for example, see Patent Document 1).

  The tilt control device in this case is provided with a hydraulic pressure switching valve, an inching operation valve, and the like between the charge pump that generates the tilt control pressure and the capacity control valve of the regulator mechanism. This hydraulic switching valve is constituted by a direction switching valve such as a forward / reverse switching valve for switching the traveling direction of the vehicle, for example, and the direction of the tilt control pressure supplied to and discharged from the tilt actuator of the regulator mechanism is reversed forward and backward. By switching, the displacement part of the hydraulic pump is tilted in both the forward and reverse directions from the neutral position where the tilt angle is zero.

  Further, the inching operation valve increases an opening degree of a variable throttle or the like provided in the middle of the flow path of the tilt control pressure according to an operation amount when an operator performs an inching operation, for example, when the vehicle travels. The displacement (pressure oil discharge amount) of the hydraulic pump is kept low by releasing the tilt control pressure to the low pressure side.

  By using such an inching operation valve, the capacity of the hydraulic pump can be appropriately reduced from a large capacity to a small capacity even when the rotational speed of the prime mover is maintained at a high rotational speed. The braking force (hydraulic brake) corresponding to the inching operation can be applied to the vehicle.

  On the other hand, for construction machines such as hydraulic excavators, the tilt control of variable displacement hydraulic pumps, which is generally used in open circuit hydraulic circuits, etc., is based on the premise that the variable displacement part is tilted in only one direction. Many devices are also used. In this case, the variable displacement hydraulic pump discharges hydraulic oil sucked from the tank in one direction as high-pressure pressure oil when the rotary shaft is driven to rotate in one direction by a prime mover such as a diesel engine. Pressure oil is supplied to each hydraulic actuator such as a working hydraulic cylinder and a traveling or turning hydraulic motor (see, for example, Patent Documents 2 and 3).

  The tilt control apparatus for a variable displacement hydraulic pump according to the prior art includes a tilt actuator that tilts and drives a displacement portion of the hydraulic pump by supplying and discharging a tilt control pressure, and a spool in the control sleeve. And a first displacement control valve that controls the tilt control pressure supplied to and discharged from the tilt actuator according to a command signal from the outside, and for limiting the displacement of the hydraulic pump within a range of horsepower characteristics of the prime mover. A horsepower control spool is provided in the control sleeve, the second capacity control valve for controlling the tilt control pressure in accordance with the discharge pressure of the hydraulic pump, and the control sleeves of the first and second capacity control valves are variable in capacity. And a feedback mechanism that performs feedback control following the tilting operation of the part.

  In this case, when the spool of the first capacity control valve slides and displaces in accordance with an external command signal, the tilt control pressure is switched and the tilt actuator is actuated to tilt and drive the capacity variable portion. For example, the capacity of the hydraulic pump is increased or decreased according to the tilt angle. The second capacity control valve controls the tilt control pressure so as to decrease the pump capacity as the discharge pressure of the hydraulic pump increases, and controls the capacity of the hydraulic pump within the limited horsepower characteristics of the prime mover. (Tilt control) is performed.

  At this time, the feedback mechanism is operated in accordance with the tilting operation of the capacity variable portion, so that, for example, the rotational displacement of the feedback link or the like is transmitted to the control sleeves of the first and second capacity control valves. The regulator is feedback controlled so that the control sleeve is slidably displaced in the same direction as the spool.

JP-A-5-39863 WO95 / 15441 JP 2003-269324 A

  By the way, the tilt control apparatus for a variable displacement hydraulic pump according to the above-described prior art (Patent Document 1) connects a hydraulic actuator such as a hydraulic motor and a hydraulic pump by, for example, a closed hydraulic circuit, and a displacement variable section. It is assumed that the hydraulic oil is tilted in both directions and the discharge direction of pressure oil by the hydraulic pump is switched between the two directions. The tilt actuator that drives the displacement of the displacement of the hydraulic pump and the capacity control valve are integrated. It is comprised by the regulator mechanism assembled so that it may comprise.

  In this case, the regulator mechanism (tilt control device) has a structure in which a main spool and a pressure chamber are provided on both the left and right sides of the regulator piston that serves as a tilt actuator. There is a problem that it is difficult to improve.

  A hydraulic switching valve (forward / reverse switching valve) and an inching operation valve, which are part of the tilt control device, are provided between a charge pump that discharges tilt control pressure and a regulator mechanism such as the capacity control valve. The inching operation valve is configured to increase the opening of a variable throttle or the like provided in the middle of the flow path of the tilt control pressure according to the inching operation of the operator.

  For this reason, it is necessary to attach the inching operation valve to a variable throttle or the like provided outside the regulator mechanism composed of a capacity control valve or the like, which is an obstacle to downsizing the entire tilt control device and making it compact. There's a problem. There is a similar problem with a hydraulic switching valve that is a forward / reverse switching valve.

  On the other hand, the tilt control device for a variable displacement hydraulic pump according to other prior arts (Patent Documents 2 and 3) tilts the variable displacement portion only in one direction so as to be generally adopted in a so-called hydraulic open circuit. For example, a hydraulic actuator such as a hydraulic motor and a hydraulic pump are connected by, for example, a closed hydraulic circuit, and the displacement of the capacity variable unit is tilted in both directions to discharge the pressure oil by the hydraulic pump. When switching between the two directions, the following problems occur.

  That is, the variable displacement hydraulic pump in this case is configured such that the displacement variable portion such as a swash plate is tilted and driven only in one direction (for example, the positive direction) with reference to the neutral position with a tilt angle of zero, for example. It is not designed on the assumption of tilting in both the forward and reverse directions with respect to the neutral position.

  Therefore, when such a variable displacement hydraulic pump is connected to a hydraulic actuator such as a hydraulic motor by using, for example, a hydraulic closed circuit, the variable capacity hydraulic pump in the forward direction and the reverse direction with respect to the neutral position as a reference. Therefore, it is necessary to make a significant design change so as to be tilt-driven.

  In addition, such a tilt control apparatus for the variable displacement hydraulic pump can be used for the first and second displacement control valves, for example, when the capacity variable portion is tilted in the forward direction and when tilted in the reverse direction. There is a problem that the control sleeve is fed back (sliding displacement) in the reverse direction, and feedback control of the control sleeve cannot be performed smoothly.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to change the discharge direction of pressure oil to both directions by tilting the capacity variable portion in the forward direction and the reverse direction, To provide a tilt control device for a variable displacement hydraulic pump that can easily perform pumping reduction control in accordance with inching operation, and that can be downsized by simplifying the overall structure. is there.

  Another object of the present invention is to simplify the circuit configuration by arranging a direction switching valve such as a forward / reverse switching valve for switching the supply / discharge direction of the tilt control pressure between the displacement control valve and the tilt actuator. An object of the present invention is to provide a tilt control device for a variable displacement hydraulic pump that can improve productivity and reduce costs.

  In order to solve the above-described problems, the present invention provides a variable displacement hydraulic pump having a variable displacement portion whose rotational shaft is rotationally driven by a prime mover, and a supply and discharge of a tilt control pressure. A tilt actuator that tilts and drives the capacity variable portion; a first capacity control valve that is provided with a spool in a control sleeve and controls the tilt control pressure supplied to and discharged from the tilt actuator according to a command signal from the outside; A second displacement control valve for controlling the tilt control pressure according to the discharge pressure of the hydraulic pump, wherein a horsepower control spool is provided in the control sleeve to limit the displacement of the hydraulic pump within the range of the horsepower characteristics of the prime mover. And a feedback mechanism that feedback-controls the control sleeves of the first and second displacement control valves following the tilting operation of the displacement variable portion. It applied to the tilting control unit of the flop.

  A feature of the configuration adopted by the invention of claim 1 is that the hydraulic pump is configured to tilt and drive the capacity variable portion from a neutral position with a tilt angle of zero to a forward direction and a reverse direction by the tilt actuator. The second displacement control valve is provided with an inching operation portion for displacing the horsepower control spool in a direction in which the displacement of the hydraulic pump decreases in accordance with an inching operation from the outside.

  According to a second aspect of the present invention, the inching operation section is constituted by a hydraulic inching operation tool that generates an oil pressure corresponding to the inching operation and displaces the horsepower control spool by the oil pressure.

  According to a third aspect of the present invention, the inching operation unit is configured by a mechanical inching operation tool that is mechanically connected to the horsepower control spool and displaces the horsepower control spool by a displacement corresponding to the inching operation. Yes.

  On the other hand, according to the invention of claim 4, between the first and second capacity control valves and the tilt actuator, the capacity variable portion is tilted from the neutral position to the forward direction and the reverse direction. For this purpose, a direction switching valve for switching the supply / discharge direction of the tilt control pressure is provided.

  According to a fifth aspect of the present invention, the feedback mechanism has an initial position on one side in the axial direction along the rotation axis of the hydraulic pump when the displacement variable portion is in the neutral position, and the displacement variable portion is in the normal position. , A conversion unit that converts the displacement operation of the capacity variable unit into an axial displacement so as to be displaced from the initial position toward the other side in the axial direction when tilted in the reverse direction; A displacement transmitting portion provided between the control sleeves of the first and second displacement control valves and transmitting the axial displacement taken out by the converting portion to the control sleeves.

  According to a sixth aspect of the present invention, the displacement transmitting portion of the feedback mechanism is a translation member that translates along the axial direction of the rotating shaft together with the control sleeves when the capacity variable portion tilts. It is constituted by.

  According to a seventh aspect of the present invention, the hydraulic pump includes a cylindrical casing in which the rotating shaft is rotatably provided, and is provided in the casing so as to rotate integrally with the rotating shaft and spaced apart in the circumferential direction. And a cylinder block having a plurality of cylinders extending in the axial direction, a plurality of pistons inserted into the cylinders of the cylinder block so as to be able to reciprocate, and a shoe attached to the end of each piston slide. And a swash plate that can be tilted in the casing as the capacity variable portion, and the tilting actuator is spaced apart in the radial direction of the rotating shaft in the casing. The swash plate is configured by a tilting piston that tilts and drives in a forward and reverse direction from a neutral position, and the first and second capacity control valves are provided in the casing apart from the tilting piston. Previous Each control sleeve is connected to the swash plate via a feedback mechanism, and the displacement transmission part of the feedback mechanism is movable or swingable along the axial direction of the rotating shaft at a midpoint of the control sleeve. It is configured to be mounted on.

  As described above, the invention according to claim 1 is configured such that the displacement variable portion of the hydraulic pump is tilted and driven in the forward and reverse directions from the neutral position where the tilt angle is zero by the tilt actuator. When the variable part is tilted in the forward direction, pressure oil can be supplied and discharged from the hydraulic pump to the hydraulic actuator in one direction, for example through a hydraulic closed circuit, and when the capacity variable part is tilted in the reverse direction Pressure oil can be supplied and discharged from the hydraulic pump to the hydraulic actuator in the other direction (reverse direction). Further, since the inching operation part is provided in the second capacity control valve, for example, when the inching operation part is manually operated from the outside in order to generate a braking force (hydraulic brake) while the work vehicle is traveling, the prime mover The horsepower control spool of the second displacement control valve can be displaced according to the amount of operation at this time even when the number of rotations is kept at a high number of rotations. Therefore, the volume control corresponding to the inching operation can be performed so as to reduce the discharge capacity of the hydraulic pump and reduce the discharge capacity of the hydraulic pump. The feedback mechanism can follow the tilting operation of the capacity variable portion and feedback control the first and second capacity control valves, and slide each control sleeve in the same direction as the horsepower control spool. It can be displaced dynamically.

  Therefore, the pump displacement reduction control can be easily performed according to the inching operation, and there is no need to provide it outside the regulator (capacity control valve) like the inching operation valve described in the prior art. The overall structure of the apparatus can be simplified and the size can be reduced. In addition, even when the hydraulic pump is connected to a hydraulic actuator using, for example, a closed hydraulic circuit, the displacement of the capacity variable portion is tilted from the neutral position to the forward direction and the reverse direction, respectively, to discharge the pressure oil (flow rate) Can be variably controlled in both directions. Since the first and second displacement control valves can be constituted by servo valves having a spool in the control sleeve, the structure of the entire tilt control device can be simplified also by this.

  The invention according to claim 2 can generate an oil pressure corresponding to the inching operation by using the hydraulic inching operation tool, and the tilting angle of the capacity variable portion is reduced by the oil pressure at this time. The horsepower control spool of the second capacity control valve can be displaced.

  According to a third aspect of the present invention, the horsepower control spool has a displacement corresponding to the inching operation by using a mechanical inching operation tool mechanically coupled to the horsepower control spool of the second displacement control valve. Can be displaced, and the tilt angle of the variable capacity portion can be reduced.

  On the other hand, in the invention according to claim 4, the tilt control pressure for the tilt actuator is controlled by switching the direction switching valve provided between the first and second capacity control valves and the tilt actuator. The supply / discharge direction can be switched, and the capacity variable portion can be tilted from the neutral position to the forward direction and the reverse direction according to the tilt control pressure. Further, this makes it possible to simplify the structure of the entire tilt control device including the first and second displacement control valves, thereby improving productivity and reducing costs.

  In the invention according to claim 5, since the feedback mechanism is constituted by the conversion portion and the displacement transmission portion, when the displacement variable portion is in the neutral position, the feedback mechanism is in the axial direction along the rotation axis of the hydraulic pump. When the variable capacity section is driven to tilt in the forward and reverse directions, the conversion section tilts the capacity variable section so that it is displaced from the initial position toward the other side in the axial direction. It can be converted into an axial displacement and taken out. The displacement transmitting unit can transmit such axial displacement to the control sleeves of the first and second displacement control valves, and the first and second displacement sleeves are slid in the same direction as the spool. The second capacity control valve can be feedback-controlled.

  Therefore, even when the hydraulic pump is connected to the hydraulic actuator using, for example, a hydraulic closed circuit, the displacement of the displacement of the capacity variable portion from the neutral position to the forward direction and the reverse direction is performed to reduce the pressure oil discharge amount in both directions. In addition to being able to control, the feedback control of the first and second capacity control valves can be smoothly performed even when the capacity variable portion is tilted in either the forward or reverse direction. Since the first and second displacement control valves can be constituted by servo valves having a spool in the control sleeve, the structure of the entire tilt control device can be simplified. In addition, the hydraulic pump can supply and discharge pressure oil to the hydraulic actuator even when applied to a so-called hydraulic open circuit. Therefore, the hydraulic pump can be applied to both a hydraulic closed circuit and an open circuit, improving versatility and productivity. Improvement, cost reduction, and the like.

  According to a sixth aspect of the invention, the displacement transmitting portion of the feedback mechanism is arranged along the axial direction of the rotating shaft together with the control sleeves of the first and second capacity control valves when the capacity variable section tilts. Therefore, the axial displacement converted and taken out by the converter when the capacity variable portion tilts is regarded as the translational motion of the translation member along the axial direction of the rotary shaft. This can be transmitted to the control sleeves of the first and second displacement control valves, and these control sleeves can be smoothly feedback controlled.

  Further, the invention according to claim 7 uses a swash plate type variable displacement hydraulic pump as a hydraulic pump to be controlled, and the first and second displacement control valves have their control sleeves inclined via a feedback mechanism. The displacement transmission part of the feedback mechanism is configured to be connected to the casing of the hydraulic pump so as to be movable or swingable along the axial direction of the rotary shaft. Even when a displacement type hydraulic pump is connected to a hydraulic actuator using a closed hydraulic circuit, the swash plate can be tilted in both the forward and reverse directions from the neutral position where the tilt angle is zero, and the pressure oil discharge rate can be increased in both directions. And the feedback control of the first and second capacity control valves can be smoothly performed when the swash plate is tilted in either the forward or reverse direction.

  Hereinafter, an example in which the tilt control device for a variable displacement hydraulic pump according to an embodiment of the present invention is applied to a traveling hydraulic circuit in a wheeled work vehicle such as a wheel loader will be described in detail with reference to the accompanying drawings. To do.

  Here, FIG. 1 to FIG. 11 show a first embodiment of the present invention. In the figure, reference numeral 1 denotes a swash plate type variable displacement hydraulic pump as a variable displacement hydraulic pump. The hydraulic pump 1 includes a casing 11, a rotating shaft 13, a cylinder block 14, a valve plate 19, a swash plate 21 and the like which will be described later. It is what is done.

  Further, in the hydraulic pump 1, a rotary shaft 13 is rotationally driven by a prime mover 2 such as a diesel engine, for example, and pressure oil is circulated through a pair of main pipelines 3A and 3B as shown in FIG. The hydraulic pump 1 is connected to a hydraulic motor 5 to be described later via main pipelines 3A and 3B, and constitutes a so-called hydraulic closed circuit 4.

  Reference numeral 5 denotes a traveling hydraulic motor as a hydraulic actuator, and the hydraulic motor 5 is connected to wheels 7 and 7 of a wheeled work vehicle via a reduction gear 6, for example. The hydraulic motor 5 is configured to drive and drive the work vehicle by rotationally driving the wheels 7 when the hydraulic oil from the hydraulic pump 1 is supplied and discharged via the main pipelines 3A and 3B. In addition, a shuttle valve 49 described later is provided between the main pipelines 3A and 3B.

  Reference numeral 11 denotes a casing as an outer shell of the hydraulic pump 1. The casing 11 includes a cylindrical casing main body 11A, a front casing 11B in which both ends of the casing main body 11A are closed, and a rear casing 11A, as shown in FIGS. It is comprised from the casing 11C. The rear casing 11C is provided with a pair of supply / discharge passages 12A and 12B, and the supply / discharge passages 12A and 12B are connected to the main pipelines 3A and 3B shown in FIG.

  Further, as shown in FIG. 3, an opening 11D and a drain passage 11E communicating with the inside of a valve housing 25 of a regulator 24 described later are formed on the outer peripheral side of the casing body 11A. A translation bar 39 (described later) is slidably attached to the opening 11D of the casing body 11A via a guide member 40 and the like. Further, the inside of the casing 11 serves as a drain chamber and is connected to a tank 42 described later.

  Reference numeral 13 denotes a rotating shaft rotatably provided in the casing 11, and the rotating shaft 13 is rotatably supported by a front casing 11B and a rear casing 11C via bearings, and protrudes in the axial direction from the front casing 11B. The projecting end 13 </ b> A side is rotationally driven by the prime mover 2 shown in FIG. 1.

  Reference numeral 14 denotes a cylinder block provided in the casing 11 so as to rotate integrally with the rotary shaft 13. The cylinder block 14 includes a plurality of cylinders 15, 15,. Is provided.

  16, 16,... Are pistons slidably inserted into the respective cylinders 15 of the cylinder block 14. The pistons 16 are arranged when a swash plate 21 described later is tilted in the forward and reverse directions. As the cylinder block 14 rotates, the cylinder 15 is reciprocated to repeat the suction stroke and the discharge stroke.

  Further, as shown in FIGS. 2 to 6, one end side of the piston 16 protrudes from the cylinder 15 of the cylinder block 14 in the axial direction of the rotary shaft 13, and on the protruding end side of the piston 16, shoes 17, 17,. Are attached so as to be swingable.

  Reference numeral 18 denotes an annular shoe presser for holding each shoe 17 against the swash plate 21. The shoe presser 18 pushes the shoe 17 toward a sliding surface 21A of the swash plate 21, which will be described later, as shown in FIGS. Each is pressed to compensate for the sliding displacement of each shoe 17 on the sliding surface 21A of the swash plate 21 so as to draw an annular locus.

  A valve plate 19 is located in the casing 11 and is provided between the rear casing 11C and the cylinder block 14. The valve plate 19 is in sliding contact with the end face of the cylinder block 14, and the cylinder block 14 is connected to the rotary shaft 13. It is supported so that it can rotate together. Further, the valve plate 19 is formed with a pair of supply / discharge ports 19A, 19B having an eyebrow shape as shown in FIG. 3, and these supply / discharge ports 19A, 19B are connected to the supply / discharge passages 12A, 12B of the rear casing 11C. It is something that communicates.

  The supply / discharge ports 19A and 19B of the valve plate 19 are intermittently communicated with the cylinders 15 when the cylinder block 14 rotates, and are sucked into the cylinders 15 from the one supply / discharge passage 12A (or 12B) side. The hydraulic oil is pressurized by the piston 16 and has a function of discharging the pressurized oil in a high pressure state in each cylinder 15 from the other supply / discharge passage 12B (or 12A).

  Reference numeral 20 denotes a swash plate support provided on the front casing 11B around the rotating shaft 13. The swash plate support 20 is located on the back side of the swash plate 21 so that the swash plate 21 can be tilted. It has a tilting support surface 20A for supporting. The tilt support surface 20A has a concave curved surface shape as shown in FIG. 5, and guides the swash plate 21 to be slidable around the tilt center C in the directions indicated by arrows A and B. .

  Reference numeral 21 denotes a swash plate as a capacity variable portion provided in the casing 11 via a swash plate support 20 so as to be tiltable. The swash plate 21 has a sliding surface 21A with respect to each shoe 17 on the front side, and the back side. Is a convex curved tilt guide surface 21B fitted to the tilt support surface 20A of the swash plate support 20.

  Here, the tilt guide surface 21B of the swash plate 21 is formed as an arc surface having a radius R from the tilt center C as shown in FIGS. 5 to 7, and the tilt center C is the axis O− of the rotary shaft 13. It is arranged on O. The swash plate 21 is provided with tilt actuators 22 and 23, which will be described later, in the forward direction (arrow A direction) and the reverse direction (arrow B direction) from the neutral position where the tilt angle is zero as shown in FIGS. The displacement (pressure oil discharge amount Q) of the hydraulic pump 1 is variably controlled according to the tilt angle θ at this time.

  Reference numerals 22 and 23 denote a pair of tilt actuators for tilting and driving the swash plate 21. The tilt actuators 22 and 23 are located on the radially outer side of the cylinder block 14 as shown in FIGS. 11A and a cylinder hole 22A, 23A formed in the cylinder hole 22A, 23A so as to be slidably inserted into the cylinder hole 22A, 23A to define a hydraulic chamber 22B, 23B. The pistons 22C and 23C and springs 22D and 23D which are disposed in the hydraulic chambers 22B and 23B and constantly bias the tilting pistons 22C and 23C toward the swash plate 21 side.

  Here, the tilting actuators 22 and 23 are disposed at positions facing each other in the radial direction of the cylinder block 14 with respect to the casing body 11A, and the tilting pistons 22C and 23C move the swash plate 21 in the directions indicated by arrows A and B. Tilt drive. That is, the hydraulic pressure chambers 22B and 23B of the tilt actuators 22 and 23 are connected to control pipes 45B and 45A, which will be described later, as shown in FIGS. 3 and 7, and the tilt control pressure is supplied and discharged.

  Then, when the tilting piston 23C extends from the cylinder hole 23A as shown in FIG. 6 and the tilting piston 22C contracts into the cylinder hole 22A as shown in FIG. 6, the swash plate 21 is moved by the tilting piston 23C. It is tilted and driven in the direction A (positive direction). In addition, when the tilting piston 22C extends from the cylinder hole 22A and the tilting piston 23C contracts into the cylinder hole 23A, the swash plate 21 tilts in the direction indicated by the arrow B (reverse direction) by the tilting piston 22C. It is driven.

  Reference numeral 24 denotes a regulator for supplying and discharging a tilt control pressure to the tilt actuators 22 and 23. The regulator 24 includes first and second capacity control valves 26 and 31, which will be described later, as shown in FIGS. The capacity control valves 26 and 31 have a common valve housing 25. The valve housing 25 of the regulator 24 is fixed in a liquid-tight manner on the outer surface of the casing 11, and the control sleeves 27 and 32, the spools 28 and 33, and the like are arranged on the rotary shaft 13 (the axis shown in FIGS. 4 and 7). OO) and extend in parallel.

  Further, the valve housing 25 has two sleeve sliding holes 25A and 25B extending in parallel with the axis OO and spaced apart in the radial direction of the rotary shaft 13, and spaced apart in the axial direction of the sleeve sliding holes 25A and 25B. The tilt control pressure supply / discharge ports 25C, 25D and the like are provided. The supply / discharge port 25C of the valve housing 25 is connected to the discharge side of the pilot pump 41 via a control line 43A described later, and the supply / discharge port 25D is connected to a control line 43B described later.

  Reference numeral 26 denotes a first displacement control valve that constitutes a part of the regulator 24. The first displacement control valve 26 varies the tilt control pressure in accordance with an operation (command signal from the outside) of a travel operation valve 47 described later. It comprises an external command-type hydraulic servo valve that is controlled by a control sleeve 27, a spool 28, a hydraulic pilot portion 29, a valve spring 30 and the like which will be described later.

  Reference numeral 27 denotes a cylindrical control sleeve inserted into the sleeve sliding hole 25A of the valve housing 25. The control sleeve 27 has a translation bar 39, which will be described later, provided with a plurality of fixing screws on the outer periphery on one side in the axial direction. Are used as a unit, and follow the movement of the translation bar 39 (translational movement along the axial direction of the rotary shaft 13) in the sleeve sliding hole 25A of the valve housing 25 in the axial direction (indicated by arrows in FIG. 4). D and E directions).

  A spool 28 is slidably inserted into the control sleeve 27. The spool 28 is slidably displaced in the axial direction of the valve housing 25 on the inner peripheral side of the control sleeve 27, thereby supplying and discharging. The port 25D is selectively communicated with or cut off from the supply / discharge port 25C or the drain passage 11E via the second capacity control valve 31.

  A hydraulic pilot portion 29 is provided on the valve housing 25 and is located on one side of the spool 28 in the axial direction. The hydraulic pilot portion 29 drives the spool 28 in the axial direction against a valve spring 30 described later. The command pressure is supplied through a command pressure line 48 described later.

  The plunger 29A of the hydraulic pilot section 29 receives the command pressure from the command pressure line 48 as a pilot pressure, and the spool 28 is slid in the valve housing 25 in the axial direction according to the pilot pressure at this time. Thus, the first capacity control valve 26 shown in FIG. 7 is switched from the neutral position (A) to the switching positions (B) and (C).

  Reference numeral 30 denotes a valve spring disposed between the other axial side of the spool 28 and the valve housing 25. The valve spring 30 constantly urges the spool 28 toward the hydraulic pilot portion 29, for example, FIG. 7 is returned to the neutral position (A).

  Reference numeral 31 denotes a second capacity control valve that constitutes a part of the regulator 24. The second capacity control valve 31 performs so-called constant horsepower control along a characteristic line 53 shown in FIG. It comprises a horsepower control type hydraulic servo valve that variably controls the pressure, and the horsepower control spool 33 is pivoted in a control sleeve 32 (to be described later) so as to reduce the tilt angle θ of the swash plate 21 in accordance with the discharge pressure P of the hydraulic pump 1. It is slid in the direction.

  Reference numeral 32 denotes a cylindrical control sleeve inserted into the sleeve sliding hole 25B of the valve housing 25. The control sleeve 32 is also on the one side in the axial direction like the control sleeve 27 of the first capacity control valve 26. A translation bar 39, which will be described later, is integrally connected to the outer periphery using a plurality of fixing screws or the like, and follows the translational movement of the translation bar 39 in the sleeve sliding hole 25B of the valve housing 25 in the axial direction (in FIG. It slides and displaces in the direction of arrows D and E).

  A horsepower control spool 33 is slidably inserted into the control sleeve 32. The horsepower control spool 33 is slidably displaced in the axial direction of the valve housing 25 on the inner peripheral side of the control sleeve 32. Thus, the supply / discharge port 25D is selectively communicated with or disconnected from the supply / discharge port 25C or the drain passage 11E via the control sleeve 32.

  A hydraulic pilot portion 34 is provided on the valve housing 25 and is located on the other side of the horsepower control spool 33 in the axial direction. The hydraulic pilot portion 34 moves the horsepower control spool 33 in the axial direction against a valve spring 35 described later. A discharge rod P (load pressure) of the hydraulic pump 1 is supplied through a selection pipe 50 which will be described later and inching via a hydraulic pipe 52 which will be described later. Operating pressure is supplied.

  The plunger 34 </ b> A of the hydraulic pilot section 34 receives the discharge pressure P of the hydraulic pump 1 through the selection pipe 50, and thereby the horsepower control spool 33 is axially moved in the valve housing 25 in accordance with the discharge pressure P. The second displacement control valve 31 shown in FIG. 7 is switched from the neutral position (d) to the switching positions (e) and (f). The second displacement control valve 31 is also switched from the neutral position (d) to the switching position (e) and (f) by manual operation of an inching operation tool 51 described later.

  Reference numeral 35 denotes a valve spring disposed between one axial direction of the spool 33 and the valve housing 25. The valve spring 35 constantly urges the spool 33 toward the hydraulic pilot portion 34, for example, FIG. 2 is returned to the neutral position (d).

  Reference numeral 36 denotes a feedback mechanism that feedback-controls the capacity control valves 26 and 31 of the regulator 24 by following the tilting operation of the swash plate 21. The feedback mechanism 36 is a side surface of the swash plate 21 as shown in FIGS. And a conversion bar 37 and a translation bar 39 described later provided between the control sleeves 27 and 32 of the regulator 24.

  Reference numeral 37 denotes a conversion unit for converting the tilting operation of the swash plate 21 into axial displacement along the axis OO of the rotary shaft 13, and the conversion unit 37 is fixed to the swash plate 21. The projection part 38 as an engaging part protruded from the side surface of the swash plate 21 and a slider part 39A as an engaged part provided in a concave shape on a translation bar 39 described later.

  Here, the projecting portion 38 of the converting portion 37 is formed in a cylindrical shape by a bolt or a pin or the like planted on the side surface of the swash plate 21, and the swash plate 21 has a tilt angle of zero as shown in FIGS. It is arranged so as to be positioned on the axis OO of the rotary shaft 13 when the neutral position is reached. Further, the protrusion 38 is disposed at a position separated by a radius Ra from the tilt center C of the swash plate 21 shown in FIG. 8, and this radius Ra is smaller than the radius R of the tilt guide surface 21B (Ra < R).

  The slider portion 39A of the translation bar 39 is slidably engaged with the protrusion 38 on the swash plate 21 side, thereby converting the tilting operation of the swash plate 21 into an axial displacement as will be described later. . The projection 38 on the swash plate 21 side and the slider 39A of the translation bar 39 restrict the translation bar 39 from moving relative to the swash plate 21 (projection 38) in the axial direction of the rotary shaft 13. The swash plate 21 (protrusion 38) and the translation bar 39 are connected to each other so as to be relatively movable so as to allow relative movement between the swash plate 21 (protrusion 38) and the translation bar 39 in the direction orthogonal to the axial direction of the rotary shaft 13.

  Reference numeral 39 denotes a translation bar as a translation member that constitutes a displacement transmission portion of the feedback mechanism 36. The translation bar 39 is slidable into an opening 11D of the casing body 11A via a guide member 40 described later as shown in FIG. And performs a translational motion along the axial direction of the rotary shaft 13 (axis OO shown in FIG. 7). The translation bar 39 extends in the radial direction of the rotary shaft 13 in the casing 11 as shown in FIGS. 3 and 4, and is disposed between the side surface of the swash plate 21 and the control sleeves 32 and 27.

  Here, the translation bar 39 is a concave slider portion 39A having a U-shaped cross section on one side in the length direction, and constitutes the conversion portion 37 together with the projection portion 38 on the swash plate 21 side. The slider portion 39A extends in a direction perpendicular to the axis OO of the rotary shaft 13 as shown in FIG. 7, and a projection 38 on the swash plate 21 side is slidably engaged in the slider portion 39A. Match.

  The slider portion 39A of the translation bar 39 is disposed at the initial position shown in FIG. 8 together with the protrusion 38 of the swash plate 21 when the swash plate 21 is in the neutral position, and is orthogonal to the axis OO of the rotating shaft 13. Located on line FF. At this time, the translation bar 39 is disposed at the position most retracted (retracted in the direction of arrow E in FIG. 7) along the axis OO of the rotation shaft 13.

  Further, when the swash plate 21 is tilted from the neutral position in the direction indicated by the arrow A (positive direction) as shown in FIGS. 6 and 9, the tilt angle θ becomes the angle α (θ = α). The protrusion 38 of the plate 21 is rotated to the position of the angle α with respect to the axis OO. As a result, the slider portion 39A of the translation bar 39 is translated (translated) to the position of the line GG shown in FIG. 9 following the movement of the projection portion 38, and with respect to the line FF at the initial position. It is displaced in the axial direction of the rotary shaft 13 by the dimension a.

  On the other hand, when the swash plate 21 is tilted from the neutral position in the arrow B direction (reverse direction) as shown in FIG. 10 and the tilt angle θ becomes an angle β (θ = β), The protrusion 38 is rotated to the position of the angle β with respect to the axis OO. As a result, the slider portion 39A of the translation bar 39 is translated to the position of the line HH shown in FIG. 10 following the movement of the protrusion 38, and rotated by the dimension b with respect to the line FF at the initial position. The shaft 13 is displaced in the axial direction.

  When the swash plate 21 is tilted in the forward and reverse directions with the same tilt angle θ (for example, angles α and β), the angles α and β corresponding to the tilt angle θ of the swash plate 21 are opposite to each other. The angles have the same direction (α = β), and the dimensions a and b corresponding to the axial displacement at this time are set to the same value (a = b).

  3 and 4, the translation bar 39 has a fixing portion 39B that is elongated in a forked manner so that the other side in the length direction sandwiches the control sleeves 32 and 27 from the outside in the radial direction. 39B is fixed to the outer peripheral side of the control sleeves 32 and 27 by fixing means such as a plurality of fixing screws or rivets. The translation bar 39 is held in a fixed state with respect to the control sleeves 32 and 27 at a constant angle (for example, 90 degrees perpendicular), extends in the radial direction of the control sleeves 27 and 32, and rotates. The control sleeves 27 and 32 are displaced in the directions indicated by arrows D and E in FIG. 4 along 13 axial lines OO.

  As described above, the conversion portion 37 composed of the projection portion 38 on the swash plate 21 side and the slider portion 39A of the translation bar 39 is inclined when the swash plate 21 tilts together with the projection portion 38 in the forward and reverse directions. The tilting operation of the plate 21 is converted into an axial displacement (for example, displacement of dimensions a and b) of the slider portion 39A along the axis OO of the rotary shaft 13 and is taken out. The translation bar 39 serving as a displacement transmitting portion transmits the axial displacement of the slider portion 39A to the control sleeves 27 and 32 as a similar axial displacement by the fixing portion 39B.

  Reference numeral 40 denotes a guide member provided so as to cover the opening 11D of the casing 11 shown in FIGS. 3 and 4. The guide member 40 supports a part of the translation bar 39 so as to be movable (slidable), and translates. It is possible to prevent the bar 39 from swinging upward and downward (for example, the circumferential direction of the cylinder block 14) and the like, and to vibrate due to backlash and the like, so that the translation bar 39 is smooth in the axial direction of the rotary shaft 13. It is intended to compensate for parallel movement (translational movement).

  Thus, when the swash plate 21 is tilted in the directions indicated by arrows A and B in FIG. 2, the translation bar 39 shown in FIGS. 3 and 4 is parallel to the axial direction of the rotary shaft 13 in accordance with the tilting operation of the swash plate 21. To move. The parallel movement of the translation bar 39 is transmitted as it is to the control sleeves 32 and 27 of the regulator 24 on the fixed portion 39B side, whereby feedback control of the regulator 24 (capacity control valves 26 and 31) is performed.

  Reference numeral 41 denotes a pilot pump for generating a tilt control pressure. The pilot pump 41 is driven together with the hydraulic pump 1 by the prime mover 2 shown in FIG. The pressure oil for tilt control is discharged into the control line 43A.

  In this case, the pressure of the pressure oil discharged from the pilot pump 41 is maintained at a pressure sufficiently lower than the discharge pressure P of the hydraulic pump 1 by the low pressure relief valve 44. The control line 43B is provided between a supply / discharge port 25D of the regulator 24 and a forward / reverse switching valve 46 described later.

  45A and 45B are other control lines for supplying and discharging the tilt control pressure to and from the hydraulic chambers 23B and 22B of the tilt actuators 23 and 22, respectively. The control lines 45A and 45B are as shown in FIGS. Are connected to the control lines 43A and 43B through a forward / reverse switching valve 46 described later.

  46 is a forward / reverse switching valve as a direction switching valve provided between the control lines 43A and 43B and the control lines 45A and 45B. The forward / reverse switching valve 46 is, as shown in FIGS. The left and right solenoid portions 46A and 46B are provided. For example, when an operator manually operates a switching lever (not shown) in the driver's cab, the forward position (b) or the reverse position ( c).

  In a state where the forward / reverse switching valve 46 is switched from the stop position (a) to the forward position (b), the tilt control pressure from the pilot pump 41 is controlled in response to the operator depressing a travel pedal 47A described later. The fluid is supplied to the hydraulic chamber 23B of the tilting actuator 23 through the pipelines 43A and 45A.

  At this time, the tilt control pressure is discharged from the hydraulic pressure chamber 22B of the tilt actuator 22 to the tank 42 via the control lines 45B and 43B, the regulator 24, and the like. As a result, the tilting piston 23C of the tilting actuator 23 drives the swash plate 21 to tilt in the direction of arrow A in FIG.

  On the other hand, when the forward / reverse switching valve 46 is switched from the stop position (a) to the reverse position (c), the tilt control pressure from the pilot pump 41 passes through the control lines 43A and 45B according to the depression operation of the travel pedal 47A. The pressure is supplied to the hydraulic chamber 22 </ b> B of the tilt actuator 22. Further, the tilting control pressure is discharged from the hydraulic pressure chamber 23B of the tilting actuator 23 to the tank 42 side through the control lines 45A and 43B, the regulator 24, etc., so that the tilting piston of the tilting actuator 22 is tilted. 22C drives the swash plate 21 in the direction of arrow B in FIG.

  As described above, the forward / reverse switching valve 46 is provided between the regulator 24 and the tilting actuators 22 and 23 and is switched from the stop position (a) of the vehicle to the forward movement position (b) or the reverse movement position (c). Thus, the supply / discharge direction of the tilt control pressure with respect to the tilt actuators 22 and 23 is switched, and the swash plate 21 is tilt-driven from the neutral position to the forward direction and the reverse direction according to the tilt control pressure.

  Reference numeral 47 denotes a travel operation valve as command means provided on the cab side of the wheel type vehicle. The travel operation valve 47 is provided with a travel pedal 47A corresponding to an accelerator pedal of the vehicle. When the vehicle operator depresses the travel pedal 47A, pilot pressure as a command signal is supplied to the hydraulic pilot section 29 of the regulator 24 through the command pressure line 48, and the vehicle travel speed is variably adjusted as will be described later. Is.

  49 is a shuttle valve as a high pressure selection valve, and the shuttle valve 49 is located between the main pipelines 3A and 3B as shown in FIGS. 1, 3, and 7, and the pressure in the main pipeline 3A or 3B on the high pressure side. (The discharge pressure P of the hydraulic pump 1, that is, the load pressure) is selected, and the discharge pressure P at this time is guided into the selection pipe 50. The selection pipe 50 is connected at its distal end to a hydraulic pilot section 34 of the second displacement control valve 31 and supplies a pressure corresponding to the discharge pressure P of the hydraulic pump 1 to the hydraulic pilot section 34 as a pilot pressure. To do.

  Reference numeral 51 denotes a hydraulic inching operation tool as an inching operation unit. The inching operation tool 51 is configured by a manually operated hydraulic cylinder or the like as shown in FIGS. 51A, a piston 51B that is slidably fitted in the tube 51A, an operation lever 51D that slides and displaces the piston 51B via a rod 51C, and a piston 51B that is provided in the tube 51A and always returns. And a return spring 51E and the like.

  Here, the hydraulic inching operation tool 51 slides in the tube 51A by the stroke corresponding to the operation amount of the piston 51B, for example, when the operator of the work vehicle manually performs the inching operation of the operation lever 51D of the inching operation tool 51. By dynamic displacement, an oil pressure corresponding to the inching operation is generated in the tube 51A. The oil pressure at this time is transmitted to the hydraulic pilot section 34 of the capacity control valve 31 via a hydraulic line 52 described later.

  52 is a hydraulic line in which the tube 51A of the inching operation tool 51 is connected to the hydraulic pilot section 34 of the second displacement control valve 31, and the hydraulic line 52 is an oil pressure generated in the tube 51A of the inching operation tool 51. Is supplied to the hydraulic pilot section 34 of the capacity control valve 31.

  Then, the second capacity control valve 31 receives the hydraulic pressure at this time by the plunger 34 </ b> A, thereby slidably displacing the horsepower control spool 33 in the direction indicated by the arrow E in FIG. 4, and the hydraulic inching operation tool 51. The position is switched from the neutral position (d) shown in FIG. 7 to the switching position (e) with a stroke amount corresponding to the manual operation.

  The traveling hydraulic circuit of the wheel type work vehicle provided with the swash plate type variable displacement hydraulic pump 1 according to the present embodiment has the above-described configuration, and the operation thereof will be described next.

  First, in the state where the forward / reverse switching valve 46 shown in FIG. 7 is disposed at the stop position (a), the control lines 45A and 45B are both connected to the control line 43A, and the hydraulic chambers 22B of the tilt actuators 22 and 23 are connected. , 23B are kept at an equal pressure state, so that the swash plate 21 is held at a neutral position with a zero tilt angle.

  For this reason, even if the rotary shaft 13 is driven to rotate by the prime mover 2 and the cylinder block 14 is rotated, each piston 16 does not reciprocate within each cylinder 15 of the cylinder block 14, and the supply / discharge passage of the hydraulic pump 1. 12A and 12B are in the same pressure state, and the supply and discharge of the pressure oil to the hydraulic motor 5 through the main pipelines 3A and 3B remain stopped.

  Next, when the vehicle operator switches the forward / reverse switching valve 46 from the stop position (a) to the forward position (b), the tilt control pressure from the pilot pump 41 in response to the operator depressing the travel pedal 47A. Is supplied to the hydraulic pressure chamber 23B of the tilting actuator 23 through the control lines 43A and 45A.

  At this time, when the travel pedal 47A is depressed, the pilot pressure is supplied from the command pressure line 48 toward the hydraulic pilot portion 29 of the regulator 24 (first displacement control valve 26). In the moving hole 25A, the spool 28 is slid in the axial direction in the control sleeve 27 in accordance with the pilot pressure, and the first capacity control valve 26 is switched from the neutral position (A) to the switching position (B) shown in FIG. Is switched to.

  For this reason, the control line 43B is connected to the tank 42 via the regulator 24, the drain chamber in the casing 11, and the like, and the tilt control pressure is supplied from the inside of the hydraulic pressure chamber 22B of the tilt actuator 22 to the control line. 45B, 43B, the regulator 24, etc. are discharged to the tank 42 side. Thereby, the tilting piston 23C of the tilting actuator 23 drives the swash plate 21 to tilt in the direction indicated by the arrow A in FIG.

  In a state where the swash plate 21 is tilted in the direction indicated by the arrow A, the cylinder block 14 rotates integrally with the rotary shaft 13, whereby each piston 16 has a stroke amount corresponding to the tilt angle θ (displacement volume). Thus, the reciprocating motion is repeated in each cylinder 15 of the cylinder block 14. For this reason, for example, the hydraulic pump 1 discharges pressure oil from the supply / discharge passage 12B side to the main pipeline 3B side while sucking oil into the cylinders 15 from the main pipeline 3A, supply / discharge passage 12A side.

  As a result, in the traveling hydraulic closed circuit 4 shown in FIG. 1, the pressure oil flows along the direction of the arrow A1 in the main pipes 3A and 3B, and the traveling hydraulic motor 5 is supplied and discharged by the pressure oil supply and discharge. It can be rotated. Then, the rotational output of the hydraulic motor 5 is transmitted to the wheels 7 and 7 of the wheel type work vehicle via the speed reducer 6, and the wheels 7 are rotated to drive the work vehicle in the forward direction of the swash plate 21, for example. The vehicle can be driven at a speed corresponding to the tilt angle θ.

  At this time, the discharge pressure P (load pressure) discharged from the hydraulic pump 1 to the main line 3B side is supplied from the shuttle valve 49 to the hydraulic pilot section 34 of the second capacity control valve 31 via the selection line 50. Supplied. The second capacity control valve 31 is configured such that the plunger 34A of the hydraulic pilot section 34 receives the discharge pressure P of the hydraulic pump 1, and the horsepower control spool 33 is pivoted in the valve housing 25 according to the discharge pressure P. The second displacement control valve 31 shown in FIG. 7 is switched from the neutral position (d) to the switching position (e).

  As a result, the control line 43B is also switched and connected to the pilot pump 41 in the same manner as the control line 43A, and the tilt actuators 22 and 23 gradually reduce the pressure difference between the hydraulic chambers 22B and 23B. Tilt in the direction in which the tilt angle θ decreases. When the tilt angle θ of the swash plate 21 is decreased, the capacity (discharge amount Q) of the hydraulic pump 1 is also decreased, whereby the discharge pressure P of the hydraulic pump 1 is gradually decreased.

  Then, as the discharge pressure P decreases, the second displacement control valve 31 is now switched to the neutral position (d) or the switching position (f), whereby the swash plate 21 is tilted by the tilt angle θ. The displacement of the hydraulic pump 1 can be controlled so as to gradually increase, and the pump capacity can be controlled so as to increase or decrease the discharge amount Q of the hydraulic pump 1 in accordance with the discharge pressure P.

  As a result, the relationship between the discharge pressure P of the hydraulic pump 1 and the discharge amount Q of the hydraulic oil is suppressed within the range indicated by the characteristic line 53 in FIG. 11, and the rotary shaft 13 of the hydraulic pump 1 is driven. It is possible to prevent an overload from acting on the prime mover 2 (see FIG. 1) and to prevent the occurrence of engine stall (engine stall) or the like. By providing the second capacity control valve 31 in the regulator 24, the capacity control of the hydraulic pump 1 can be performed within the limited horsepower characteristics of the prime mover 2.

  On the other hand, when the forward / reverse switching valve 46 is switched from the stop position (a) to the reverse position (c), the tilt control pressure from the pilot pump 41 passes through the control lines 43A and 45B according to the depression operation of the travel pedal 47A. The pressure is supplied to the hydraulic chamber 22 </ b> B of the tilt actuator 22. In addition, the tilt control pressure is discharged from the hydraulic chamber 23B of the tilt actuator 23 to the tank 42 side via the control lines 45A and 43B, the regulator 24, and the like, and is tilted by the tilt piston 22C of the tilt actuator 22. The plate 21 can be driven to tilt in the direction of arrow B in FIG.

  In this case, pressure oil can be circulated along the direction indicated by arrow B1 in the traveling hydraulic closed circuit 4 shown in FIG. 1, and the traveling hydraulic motor 5 is driven to rotate in the same direction. The rotation output of the hydraulic motor 5 is transmitted to the wheels 7 and 7 of the wheel type work vehicle via the speed reducer 6, and the work vehicle is driven to travel at a speed corresponding to the tilt angle θ of the swash plate 21, for example, in the reverse direction. it can.

  Also in this case, the displacement of the hydraulic pump 1 is limited by the second displacement control valve 31 provided in the regulator 24 within the limited horsepower characteristic range of the prime mover 2 (within the range of the characteristic line 53 shown in FIG. 11). Control can be performed, and the occurrence of an engine stall or the like can be prevented while suppressing an overload from acting on the prime mover 2 from the hydraulic pump 1.

  By the way, the traveling speed when the vehicle moves forward or backward is determined by the discharge amount Q (flow rate) of the pressure oil from the hydraulic pump 1, and this discharge amount Q is increased or decreased according to the tilt angle θ of the swash plate 21. . Unless the capacity control valves 26 and 31 of the regulator 24 are feedback-controlled according to the tilt angle θ of the swash plate 21, the tilt angle θ of the swash plate 21 (that is, the travel speed of the vehicle) is set to the travel pedal 47A. It is difficult to control stably only by stepping on.

  Therefore, in the present embodiment, a feedback mechanism 36 is provided between the control sleeves 27, 32 of the capacity control valves 26, 31 and the side surface of the swash plate 21, so that the swash plate 21 is positive from the neutral position where the tilt angle is zero. When the drive is tilted in the opposite direction, the displacement control valves 26 and 31 of the regulator 24 are feedback-controlled by the feedback mechanism 36 in accordance with the tilting operation of the swash plate 21.

  The feedback mechanism 36 converts the tilting operation of the swash plate 21 into an axial displacement and takes it out, and the rotating shaft 13 follows the tilting operation by the axial displacement taken out by the converting portion 37. The translation bar 39 is adapted to transmit the axial displacement by the conversion portion 37 to the control sleeves 27 and 32 by the fixing portion 39B on the distal end side.

  In this case, the conversion portion 37 includes a circular protrusion 38 made of a pin or the like fixedly provided on the side surface of the swash plate 21, and the translation bar 39 so as to slidably fit into the protrusion 38. It is constituted by a concave slider portion 39A provided on one side in the length direction and extending in a direction orthogonal to the axis OO of the rotary shaft 13, and the tilting operation of the swash plate 21 is performed along the axis OO. This is converted into a directional displacement and transmitted to the translation bar 39.

  Therefore, when the swash plate 21 is tilted from the neutral position in the arrow A direction (positive direction) as shown in FIG. 9 and the tilt angle θ is an angle α (θ = α), the protrusion of the swash plate 21 The portion 38 is rotated to the position of the angle α with respect to the axis OO, and the slider portion 39A of the translation bar 39 is translated to the position of the line GG shown in FIG. (Translational motion).

  When the protrusion 38 located at the radius Ra from the tilt center C of the swash plate 21 rotates by an angle α, the translation bar 39 rotates from the initial position line FF to the position of the line GG. Since the displacement is in the 13 axial directions, this axial displacement can be obtained as the dimension a by the following equation (1).

  On the other hand, when the swash plate 21 is tilted in the arrow B direction (reverse direction) as shown in FIG. 10 from the neutral position and the tilt angle θ becomes an angle β (θ = β), the projection of the swash plate 21 The portion 38 is rotated to the position of the angle β with respect to the axis OO, and the slider portion 39A of the translation bar 39 is moved to the position of the line HH shown in FIG. can do.

  At this time, the translation bar 39 is displaced in the axial direction of the rotary shaft 13 from the initial position of the line FF to the position of the line H-H, and this axial displacement is also obtained as a dimension b according to the following equation (2). be able to.

  In this way, the tilting operation of the swash plate 21 is changed in the axial direction along the axis OO of the rotary shaft 13 by the conversion portion 37 composed of the projection portion 38 on the swash plate 21 side and the slider portion 39A of the translation bar 39. (For example, displacement of dimensions a and b) can be converted and taken out, and this can be transmitted to the control sleeves 27 and 32 by the translation bar 39 as a similar axial displacement on the fixed portion 39B side.

  The axial displacement at this time is the same in both directions when the swash plate 21 is tilted in the arrow A direction (forward direction) and when it is tilted in the arrow B direction (reverse direction) (see FIG. 4, the control sleeve of the capacity control valves 26 and 31 regardless of whether the swash plate 21 is tilted forward or backward from the neutral position. 27 and 32 can be slid in the same direction as the spool 28 and the like, and the control sleeves 27 and 32 can be smoothly feedback-controlled.

  Further, since the regulator 24 is provided with the first and second capacity control valves 26 and 31, the tilt angle θ of the swash plate 21 is variably controlled in accordance with the operation of the travel operation valve 47 (command signal from the outside). In addition, the capacity of the hydraulic pump 1 can be controlled by the second capacity control valve 31 within the limited horsepower characteristics of the prime mover 2, and the engine stall can be suppressed by preventing an overload from acting on the prime mover 2. Etc. can be prevented.

  Moreover, the second displacement control valve 31 connects a hydraulic inching operation tool 51 that is inched by an operator of the work vehicle to the hydraulic pilot unit 34 via the hydraulic line 52, and a plunger 34 </ b> A of the hydraulic pilot unit 34. Is configured to apply an oil pressure corresponding to the inching operation.

  For this reason, the capacity control valve 31 horsepower control spool 33 can be displaced in the direction of arrow E in FIG. 7 according to the amount of operation at this time, even by manual operation of the hydraulic inching operation tool 51. The control valve 31 is switched from the neutral position (d) to the switching position (e), and the capacity control corresponding to the inching operation is performed so that the tilt angle θ of the swash plate 21 is decreased to reduce the capacity of the hydraulic pump 1. be able to.

  As a result, the operator of the work vehicle can move the second displacement control valve 31 from the neutral position (d) only by manually operating the hydraulic inching operation tool 51 even while maintaining the rotational speed of the prime mover 2 at a high rotational speed. It is possible to switch to the switching position (e), and it is possible to apply a braking force (hydraulic brake) so as to reduce the capacity of the hydraulic pump 1 according to the inching operation and to reduce the traveling speed of the vehicle.

  Such an inching operation tool 51 only needs to be connected to the hydraulic pilot section 34 of the second displacement control valve 31 via the hydraulic line 52, and therefore, like the inching operation valve described in the prior art. This eliminates the need to provide the regulator (capacity control valve) outside, thereby simplifying the configuration of the hydraulic circuit and simplifying the overall structure of the tilt control device for miniaturization.

  Therefore, according to the present embodiment, even when the swash plate variable displacement hydraulic pump 1 is connected to the hydraulic motor 5 using the hydraulic closed circuit 4 illustrated in FIG. 21 can be tilted from the neutral position in the forward direction and in the reverse direction, respectively, so that the discharge amount (flow rate) of the pressure oil can be controlled in both directions. The corresponding speed control can be performed smoothly.

  In addition, since the capacity control valves 26 and 31 of the regulator 24 can be configured by hydraulic servo valves having a simple structure having the spools 28 and 33 in the control sleeves 27 and 32, the tilt actuators 22 and 23, the regulator 24 and The entire structure of the tilt control device including the feedback mechanism 36 can be simplified, the number of parts can be reduced, and workability during assembly can be improved.

  And since it is set as the structure which attaches the inching operation tool 51 to the 2nd capacity | capacitance control valve 31, when decelerating (braking) the vehicle in the middle of driving | running | working, even if keeping the rotation speed of the motor | power_engine 2 at high rotation speed, Pump capacity reduction control can be easily performed only by performing an inching operation, and the configuration of the entire hydraulic circuit can be greatly simplified.

  Further, since the forward / reverse switching valve 46 for switching the traveling direction of the vehicle is provided between the regulator 24 (capacity control valves 26, 31) and the tilt actuators 22, 23, the tilt control including the regulator 24 is performed. The overall structure of the apparatus can be simplified as compared with the prior art, and the productivity can be improved and the cost can be reduced.

  Further, the tilt control device of the hydraulic pump 1 is not limited to the hydraulic closed circuit 4 illustrated in FIG. 1, and can supply and discharge pressure oil to a hydraulic actuator such as a hydraulic motor even when applied to a so-called hydraulic open circuit. Therefore, it can be applied to both a hydraulic closed circuit and an open circuit, and versatility can be improved to improve productivity and reduce costs.

  Next, FIG. 12 shows a second embodiment of the present invention. The feature of the present embodiment is that a second capacity control valve is connected to a mechanical inching operation tool, and the inching operation tool is used for hydraulic pressure. The configuration is such that the capacity of the pump is reduced. In the present embodiment, the same components as those in the first embodiment described above are denoted by the same reference numerals, and the description thereof is omitted.

  In the figure, 61 is the second capacity control valve employed in the present embodiment, and the second capacity control valve 61 is configured in substantially the same manner as the capacity control valve 31 described in the first embodiment, A control sleeve 62, a horsepower control spool 63, a hydraulic pilot part 64, a valve spring 65, and the like are provided.

  The hydraulic pilot section 64 of the capacity control valve 61 has a stepped rod-shaped plunger 64A. The plunger 64A controls the discharge pressure P of the hydraulic pump 1 guided from the shuttle valve 49 through the selection pipe 50. By receiving the pilot pressure, the horsepower control spool 63 is slid in the control sleeve 62 according to the pilot pressure, and the second capacity control valve 61 is changed from the neutral position (d) to the switching position (e), (F).

  However, the capacity control valve 61 in this case is different from the first embodiment in that the plunger 64A is mechanically connected to an inching operation tool 66 described later. The second capacity control valve 61 is switched from, for example, the neutral position (d) to the switching position (e) also by the operator's inching operation.

  Reference numeral 66 denotes a mechanical inching operation tool as an inching operation unit employed in the present embodiment. The inching operation tool 66 has an operation lever 66A that is manually operated by the operator, and is connected to the plunger 64A of the capacity control valve 61. Are connected using a mechanical rigging (not shown) such as a link mechanism or a push-pull wire.

  The mechanical inching operation tool 66 pushes the plunger 64A of the capacity control valve 61 against the valve spring 65 when the operator of the work vehicle manually operates the operation lever 66A of the inching operation tool 66, for example. The horsepower control spool 63 of the capacity control valve 61 is switched from, for example, the neutral position (d) to the switching position (e) by the stroke corresponding to the inching operation.

  Thus, even in the present embodiment configured as described above, for example, when the vehicle during traveling is decelerated (braking), the mechanical inching operation tool 66 is manually operated even if the rotational speed of the prime mover 2 is maintained at a high rotational speed. Only by doing this, it is possible to easily control the pump displacement to be reduced, and it is possible to obtain substantially the same operation and effect as in the first embodiment.

  In the present embodiment, since the plunger 64A of the capacity control valve 61 and the inching operation tool 66 are mechanically connected, the hydraulic pipe line as in the first embodiment. It is not necessary to provide 52 etc., and workability at the time of piping connection etc. can be improved.

  In each of the above embodiments, the traveling operation valve 47 is used as an external command means, and a pilot pressure corresponding to the depression operation amount of the traveling pedal 47A is supplied to the first displacement control valve 26 as a command signal. And explained. However, the present invention is not limited to this. For example, the hydraulic pilot portion 29 of the displacement control valve 26 is configured by an electromagnetic proportional solenoid or the like, and an electric signal corresponding to the depressing operation amount of the travel pedal 47A is output from the external command means as a command signal. It is good also as a structure output as these.

  In each of the above-described embodiments, the displacement transmitting portion that transmits the axial displacement taken out on the conversion portion 37 side of the feedback mechanism 36 to the control sleeves 27 and 32 of the regulator 24 is constituted by the translation bar 39 as a translation member. Explained with an example. However, the present invention is not limited to this. For example, the displacement transmission unit is configured by using a swing link whose middle part is swingably supported (connected) to the casing, and the axial displacement taken out on the conversion unit 37 side is used. It is good also as a structure which transmits to the control sleeves 27 and 32 of the regulator 24 by this rocking | fluctuation link.

  On the other hand, in the above-described embodiments, the case where the tilt control device of the swash plate type variable displacement hydraulic pump 1 is applied to a traveling hydraulic circuit in a wheel work vehicle such as a wheel loader has been described as an example. However, the present invention is not limited to a traveling hydraulic circuit, and can be applied to a hydraulic closed circuit for various purposes such as a turning hydraulic circuit.

  In each of the above embodiments, the tilt control device of the swash plate type variable displacement hydraulic pump 1 has been described as an example. However, the application target of the present invention is not limited to the swash plate type variable displacement hydraulic pump, but may be, for example, a swash plate type variable displacement hydraulic pump. In this case, for example, the valve plate or the like has a displacement variable portion. It constitutes.

  Furthermore, the work vehicle to which the present invention is applied is not limited to a wheel loader. It can also be applied to vehicles and the like.

1 is a circuit diagram showing a hydraulic closed circuit provided with a variable displacement hydraulic pump according to a first embodiment of the present invention. FIG. It is a longitudinal cross-sectional view of the hydraulic pump shown in FIG. It is the longitudinal cross-sectional view which looked at the hydraulic pump from the arrow III-III direction in FIG. It is an expanded sectional view which expands and shows the regulator, the feedback mechanism, etc. in FIG. It is sectional drawing which looked at the state which has a swash plate in a neutral position from the arrow VV direction in FIG. It is sectional drawing in the same position as FIG. 5 which shows the state which the swash plate inclined in the positive direction. It is a circuit block diagram which shows the inclination control apparatus of the swash plate by 1st Embodiment. It is a front view which shows the swash plate in FIG. 7 with a tilting piston. It is a front view which shows the state which inclined the swash plate in FIG. 8 to the positive direction. It is a front view which shows the state which tilted the swash plate in FIG. 8 in the reverse direction. It is a characteristic diagram which shows the horsepower characteristic of a motor | power_engine by the relationship between the discharge pressure and discharge amount of a hydraulic pump. It is a circuit block diagram which shows the tilt control apparatus of the swash plate by 2nd Embodiment.

Explanation of symbols

1 hydraulic pump 2 prime mover 4 hydraulic closed circuit 5 hydraulic motor (hydraulic actuator)
11 Casing 13 Rotating shaft 14 Cylinder block 15 Cylinder 16 Piston 17 Shoe 19 Valve plate 20 Swash plate support 21 Swash plate (capacity variable part)
21A Sliding surface 22, 23 Tilt actuator 22B, 23B Hydraulic chamber 22C, 23C Tilt piston 24 Regulator 25 Valve housing 26 First capacity control valve 27 Control sleeve 28 Spool 29 Hydraulic pilot part 30 Valve spring 31, 61 First 2 capacity control valve 32, 62 control sleeve 33, 63 horsepower control spool 34, 64 hydraulic pilot part 35, 65 valve spring 36 feedback mechanism 37 conversion part 38 projection part (engagement part)
39 Translation bar (displacement transmission part, translation member)
39A Slider (engaged part)
39B Fixed part 40 Guide member 41 Pilot pump 42 Tank 46 Forward / reverse switching valve (direction switching valve)
47 Traveling operation valve (command means)
47A Traveling pedal 48 Command pressure line 49 Shuttle valve (high pressure selection valve)
50 Selection pipeline 51 Hydraulic inching operation tool (Inching operation section)
66 Mechanical Inching Operation Tool (Inching Operation Unit)

Claims (7)

A variable displacement hydraulic pump having a variable displacement portion whose rotational shaft is rotationally driven by a prime mover, and a tilt actuator that tilts and drives the displacement variable portion of the hydraulic pump by supplying and discharging a tilt control pressure; A first displacement control valve that is provided with a spool in the control sleeve and controls the tilt control pressure supplied to and discharged from the tilt actuator according to a command signal from the outside, and the capacity of the hydraulic pump to determine the horsepower characteristics of the prime mover A second capacity control valve for controlling the tilt control pressure according to the discharge pressure of the hydraulic pump, and a first capacity control valve and a second capacity control valve. In a tilt control device for a variable displacement hydraulic pump comprising a feedback mechanism that feedback-controls the control sleeve according to the tilting operation of the displacement variable section,
The hydraulic pump is configured to tilt and drive the capacity variable portion from a neutral position with a tilt angle of zero to a forward direction and a reverse direction by the tilt actuator.
The second displacement control valve is provided with an inching operation portion for displacing the horsepower control spool in a direction in which the displacement of the hydraulic pump decreases in accordance with an inching operation from the outside. Type hydraulic pump tilt control device.   2. The tilting of the variable displacement hydraulic pump according to claim 1, wherein the inching operation unit is configured by a hydraulic inching operation tool that generates an oil pressure corresponding to the inching operation and displaces the horsepower control spool by the oil pressure. Control device.   2. The variable displacement type according to claim 1, wherein the inching operation unit is configured by a mechanical inching operation tool that is mechanically connected to the horsepower control spool and displaces the horsepower control spool by a displacement corresponding to the inching operation. Tilt control device for hydraulic pump.   The tilt control pressure is supplied between the first and second displacement control valves and the tilt actuator in order to drive the displacement of the displacement variable portion from the neutral position in the forward direction and the reverse direction. 4. The tilt control apparatus for a variable displacement hydraulic pump according to claim 1, further comprising a direction switching valve for switching a discharge direction.   The feedback mechanism has an initial position on one axial side along the rotation axis of the hydraulic pump when the displacement variable portion is in a neutral position, and when the displacement variable portion is tilted and driven in the forward and reverse directions. A conversion unit for converting the tilting operation of the capacity variable unit into an axial displacement so as to be displaced from the initial position toward the other side in the axial direction; and the conversion unit and the first and second capacity control valves The variable displacement hydraulic system according to claim 1, 2, 3 or 4, comprising a displacement transmission portion provided between the control sleeve and a displacement transmission portion for transmitting the axial displacement taken out by the conversion portion to each control sleeve. Pump tilt control device.   6. The displacement transmitting portion of the feedback mechanism is configured by a translation member that translates along the axial direction of the rotation shaft together with the control sleeves when the variable capacity portion tilts. Tilt control device for variable displacement hydraulic pump. The hydraulic pump includes a cylindrical casing in which the rotating shaft is rotatably provided, and a plurality of cylinders that are provided in the casing so as to rotate integrally with the rotating shaft and that are separated in the circumferential direction and extend in the axial direction. The variable capacity has a cylinder block having a plurality of pistons inserted into the cylinders of the cylinder block so as to be reciprocally movable, and a sliding surface on which a shoe attached to an end of each piston slides. A swash plate that can be tilted in the casing as a part,
The tilt actuator is constituted by a tilt piston provided in the casing so as to be spaced apart in the radial direction of the rotating shaft and driving the swash plate to tilt forward and backward from a neutral position,
The first and second displacement control valves are provided in the casing so as to be separated from the tilting piston and connect the control sleeves to the swash plate via a feedback mechanism,
The variable displacement hydraulic pump according to claim 5 or 6, wherein the displacement transmission portion of the feedback mechanism is configured such that a midway portion thereof is attached to the casing so as to be movable or swingable along the axial direction of the rotating shaft. Tilt control device.

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