JP2012255375A - Variable displacement swash plate hydraulic pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable displacement swash plate hydraulic pump capable of controlling tilt control of a swash plate without individually providing a capacity control valve outside the pump.SOLUTION: This variable displacement swash plate hydraulic pump 1 comprises: a swash plate 14 tiltable between the maximum tilt and the minimum tilt; tilt actuators 24A, 24B arranged so as to hold a rotary shaft 15 in between and tilting and driving the swash plate 14; and a feedback control means for feeding back the tilt angle of the swash plate 14 tilted by the driving of the tilt actuators 24A, 24B to the driving control of the tilt actuator 24A, wherein each of the tilt actuators 24A, 24B includes a tilt control piston 17, 16 abutting against the swash plate 14 and slidably provided. The hydraulic pump comprises a control pressure supply/discharge means for supplying and discharging a control pressure for sliding the tilt control piston 16 of the tilt actuator 24B, from the tilt actuator 24A for the tilt actuator 24B.

Description

  The present invention relates to a variable displacement swash plate hydraulic pump provided in a construction machine such as a hydraulic excavator.

  2. Description of the Related Art A variable displacement swash plate hydraulic pump that varies the discharge capacity of a hydraulic pump such as a hydraulic pump by tilting a swash plate with a tilt actuator is well known. A conventional variable displacement swash plate type hydraulic pump of this type is shown in Japanese Patent Application Laid-Open No. H10-228707. A conventional variable displacement swash plate hydraulic pump disclosed in Patent Document 1 will be described with reference to FIGS.

  In FIG. 10, reference numeral 31 denotes a casing. The casing 31 includes a stepped cylindrical casing body 32 having a closed end 32A on one end side and an open end 32B on the other end side, and an open end 32B side of the casing body 32. It is composed of a closed front casing, that is, a lid 33. A housing hole 32 </ b> C for housing the cylinder block 35 is formed in the middle portion of the casing body 32 in the longitudinal direction. Cylinders 44A and 45A of the tilt actuators 44 and 45 are formed on the radially outer side of the accommodation hole 32C.

  Reference numeral 34 denotes a rotating shaft that is rotatably provided in the casing 31 via a bearing or the like. The rotating shaft 34 is rotatably attached at one end side to the closed end 32A side of the casing body 32, and the other end side is a lid 33. Protrudes from the outside. A prime mover such as a diesel engine is connected to the projecting end 34A side of the rotating shaft 34 via a power transmission mechanism (both not shown), whereby the rotating shaft 34 is rotationally driven from the outside.

  The above-described cylinder block 35 is provided in the accommodation hole 32 </ b> C of the casing body 32 via the rotation shaft 34. The cylinder block 35 is splined to the outer peripheral side of the rotary shaft 34 in the casing 31 and is driven to rotate integrally with the rotary shaft 34. In addition, a plurality of cylinders 36 (only one is shown) extending in the axial direction are formed in the cylinder block 35 around the rotating shaft 34, and one end side of these cylinders 36 slides on a switching valve plate 37 described later. Touch.

  The switching valve plate 37 is fixed to the closed end 32 </ b> A side of the casing body 32 so as to be in sliding contact with the cylinder block 35. The switching valve plate 37 is formed with a pair of supply / exhaust ports 37A, 37B having an eyebrow shape, and a shaft insertion hole 37C of the rotary shaft 34 is formed between the supply / exhaust ports 37A, 37B on the center side of the switching valve plate 37. Is drilled. Reference numerals 38A and 38B denote a pair of supply / discharge passages formed on the closed end 32A side of the casing body 32. These supply / discharge passages 38A, 38B communicate with supply / discharge ports 37A, 37B of the switching valve plate 37, and hydraulic oil in a tank 47 (see FIG. 11), which will be described later, is supplied into each cylinder 36 as the cylinder block 35 rotates. The pressure oil pressurized in each cylinder 36 is discharged to the outside.

  The pistons 39 are slidably fitted into the cylinders 36 of the cylinder block 35. The pistons 39 reciprocate in the cylinders 36 as the cylinder block 35 rotates, and from the switching valve plate 37 side. The hydraulic oil is sucked into each cylinder 36 and pressurized to high pressure oil in each cylinder 36. Further, shoes 40 are swingably mounted on the end portions of the pistons 39 protruding from the cylinders 36, and these shoes 40 are pressed toward the swash plate 42 by an annular shoe presser 41 or the like. . Here, as shown in FIG. 10, each piston 39 that reciprocates in each cylinder 36 becomes a bottom dead center position at a position above the rotation shaft 34, and when it is located below, it becomes a top dead center position. During each rotation of the cylinder block 35, each piston 39 slides in each cylinder 36 from the top dead center to the bottom dead center and slides from the bottom dead center to the top dead center. The discharge stroke that is dynamically displaced is repeated.

  That is, in the suction stroke of the piston 39 corresponding to the half rotation of the cylinder block 35, each of the supply / discharge passages 38A and 38B is supplied from the supply / discharge passage 38A side, which is the suction side, through the supply / discharge port 37A of the switching valve plate 37. Hydraulic oil is sucked into the cylinder 36. Further, in the discharge stroke of the piston 39 corresponding to the remaining half rotation of the cylinder block 35, each piston 39 is pushed into each cylinder 36, and the hydraulic oil sucked into each cylinder 36 in the suction stroke is discharged. Pressurize. The hydraulic oil pressurized in each cylinder 36 becomes high pressure hydraulic oil, and is discharged to the outside through the supply / discharge passage 38B from the supply / discharge port 37B side of the switching valve plate 37, for example.

  The above-described swash plate 42 is tiltably provided on the lid 33 side of the casing 31, and one side (surface side) serves as a smooth surface 42 </ b> A that slidably guides each shoe 40. A shaft insertion hole 42B for the rotation shaft 34 is formed. The swash plate 42 is formed with a pair of leg portions 42C (only one is shown) on both the left and right sides of the shaft insertion hole 42B, and the surface side of these leg portions 42C constitutes a part of the smooth surface 42A. Yes. Further, the back surface side of each leg portion 42C becomes a convex curved surface 42D that protrudes toward the tilt support member 43 described later, and these convex curved surfaces 42D are formed with a constant radius of curvature.

  The tilt support member 43 described above is provided on the lid 33 of the casing 31 so as to be positioned on the back side of the swash plate 42, and is formed of a material with high wear resistance. Has a shaft insertion hole 43A. Further, the tilt support member 43 is provided with a pair of concave curved surface portions 43B (only one is shown) on both the left and right sides of the shaft insertion hole 43A, and these concave curved surface portions 43B are convex curved surfaces 42D of the swash plate 42. Are formed as circular arc surfaces having a constant radius of curvature. Here, each leg portion 42C of the swash plate 42 is slidably fitted into each concave curved surface portion 43B of the tilting support member 43 via the convex curved surface 42D. It is tilted in the direction of arrows A and B.

  When the swash plate 42 is driven to tilt in the direction indicated by the arrow A, the tilt angle increases, thereby increasing the stroke amount of each piston 39 with respect to each cylinder 36, and pump capacity (pressure oil discharge amount). Increase. Further, when the swash plate 42 is tilted in the direction indicated by the arrow B in order to reduce the tilt angle, the stroke amount of each piston 39 relative to each cylinder 36 is shortened, thereby reducing the pump capacity.

  Reference numerals 44 and 45 denote tilting actuators for tilting the swash plate 42. These tilting actuators 44 and 45 are positioned so as to sandwich the cylinder block 35 from the radially outer side in the tilting direction of the swash plate 42. . These tilting actuators 44 and 45 are slidably fitted into cylinders 44A and 45A formed in the casing main body 32 and these cylinders 44A and 45A, and end portions protruding from the cylinders 44A and 45A are spherical. The tilt control pistons 44B and 45B having a shape are roughly configured. Further, as shown in FIG. 10, the tilt actuators 44 and 45 are provided with control pressure chambers 44C and 45C between the cylinders 44A and 45A and the tilt control pistons 44B and 45B, respectively. When the control pressure is supplied to and discharged from these control pressure chambers 44C and 45C through the capacity control valve 51 shown in FIG. 11, the tilt control pistons 44B and 45B advance and retreat from the cylinders 44A and 45A toward the swash plate 42 side. To do.

  In this case, the tilt control piston 45B (cylinder 45A) is formed to have a larger diameter than the tilt control piston 44B (cylinder 44A), and the tilt control piston 45B is more than the tilt control piston 44B by the pressure receiving area difference. It has a configuration that generates a large tilt driving force. Further, the tilt control pistons 44B and 45B are arranged on the surface side of the swash plate 42 so as to sandwich the cylinder block 35 from the outside in the radial direction, and the spherical end portions are always in contact with the swash plate 42. Then, the tilt control pistons 44B and 45B drive the swash plate 42 in the directions indicated by arrows A and B in FIG. 10 according to the control pressure supplied and discharged into the control pressure chambers 44C and 45C.

  A pilot pump 46 shown in FIG. 11 is a pilot pressure generating source. The pilot pump 46 sucks the hydraulic oil in the tank 47 and supplies the control pressure into the control line 48. A branch pipe 49 is provided in the middle of the control pipe 48, and this branch pipe 49 connects the control pressure chamber 44 </ b> C of the tilt actuator 44 to the pilot pump 46 through the control pipe 48. 11, reference numeral 50 denotes another control pipe connected to the control pressure chamber 45C of the tilting actuator 45, and 51 denotes the capacity control valve provided between the control pipes 48 and 50. 51 is composed of, for example, a three-port, three-position hydraulic pilot type servo valve or the like, and switches from the neutral position (A) to the switching position (B) according to the pilot pressure for tilt control supplied to the hydraulic pilot part 51A ( C) is controlled to switch. Further, 52 is provided between the control sleeve 51C of the capacity control valve 51 and the swash plate 42, and the tilt angle of the swash plate 42 tilted by the drive of the tilt actuators 44 and 45 is adjusted by the tilt actuators 44 and 45. Feedback means for feeding back to the drive control, that is, a feedback link. The feedback link 52 slides and displaces the control sleeve 51C following the tilting operation of the swash plate 42, and performs feedback control of the capacity control valve 51.

Japanese Patent Laid-Open No. 2000-220568

  In the above-described prior art, it is necessary to provide the capacity control valve 51 in order to operate the tilt actuators 44 and 45, and it is necessary to provide the feedback link 52 that feeds back the tilt angle to the capacity control valve 51. Since the capacity control valve 51 is often provided outside the pump as a separate body, the size of the entire pump tends to increase.

  In addition, in the prior art mentioned above, since the feedback link 52 is needed, there exists a tendency for a number of parts to increase. The feedback link 52 not only transmits the tilt angle of the swash plate 42 with high accuracy, but also needs to be excellent in durability, so high reliability is required.

  The present invention has been made from the above-described prior art, and its purpose is to provide a variable displacement swash plate hydraulic pressure capable of controlling the tilt of the swash plate without separately providing a displacement control valve outside the pump. To provide a pump.

  In order to achieve this object, the present invention provides a casing, a rotating shaft rotatably supported by the casing, and a plurality of cylinders provided in the casing so as to rotate integrally with the rotating shaft. A plurality of pistons fitted into and reciprocatingly inserted into each cylinder of the cylinder block; and a reciprocating motion of each piston is converted into a rotational motion of the cylinder block, and a bottom portion of the casing; A swash plate that is provided facing and is a smooth surface on which the piston slides and can tilt between a maximum tilt position and a minimum tilt position; and a tilt actuator that tilts and drives the swash plate; A valve plate provided with a pair of supply / discharge ports intermittently communicating with the cylinders when the casing and the cylinder block rotate while sliding; and the tilting actuator Feedback means for feeding back the tilt angle of the swash plate tilted by the drive of the motor to the drive control of the tilt actuator, and the tilt actuators are arranged so as to sandwich the rotating shaft therebetween. Each of the tilt actuators, and each of these tilt actuators has a variable displacement swash plate type liquid having a tilt control piston whose end is in contact with the swash plate and is slidable. The pressure pump includes control pressure supply / discharge means for supplying and discharging a control pressure for sliding the tilt control piston of the other tilt actuator from the one tilt actuator to the other tilt actuator. It is characterized by that.

  In the present invention configured as described above, when one tilt actuator is driven, the control pressure is supplied / discharged from one tilt actuator to the other tilt actuator via the control pressure supply / discharge means. The tilt control piston of the other tilt actuator is slid by the supply and discharge of this control pressure, and the swash plate is made to respond to the drive of one tilt actuator by the cooperation of one tilt actuator and the other tilt actuator. The tilt angle can be maintained. Thus, according to the present invention, one tilting actuator disposed inside the casing can also function as a conventional capacity control valve. That is, according to the present invention, tilt control of the swash plate can be performed without separately providing a capacity control valve outside the pump.

  In the present invention, the one tilt actuator is formed in the casing, the cylinder in which the tilt control piston is accommodated, and the cylinder is accommodated in the cylinder and fixed to the casing. A stopper that slidably holds the tilt control piston of the tilt actuator, and is accommodated in the cylinder formed in the casing, and is disposed so as to be farther from the swash plate than the stopper. The tilt control piston of the rolling actuator is slidably held, and has a sleeve slidable with respect to the cylinder formed in the casing, and the control pressure supply / discharge means includes the one tilt actuator. A first oil passage formed on the tilt control piston for guiding the control pressure, and the one of the tilt actuators. A second oil passage that is formed in a groove and selectively communicates with the first oil passage, and is formed in the casing and is connected to the tilt control piston of the second oil passage and the other tilt actuator. And a third oil passage communicating with the control pressure chamber.

  According to the present invention, in the above invention, the feedback means comprises the swash plate. In the present invention configured as described above, feedback means for performing feedback control with respect to one tilting actuator can also serve as a swash plate, and a conventional feedback link is not required.

  In the invention, the one tilting actuator is formed between the stopper and the sleeve and is connected to a drain chamber formed between the stopper and the sleeve, and is disposed in the drain chamber, and one end is locked to the stopper. And the other end is formed between the spring locked to the sleeve, the bottom of the cylinder formed in the casing and the end surface of the sleeve facing the bottom of the cylinder formed in the casing, And a control pressure chamber to which a command pressure for sliding the sleeve is applied.

  Also, in the present invention according to the invention, the one tilting actuator is formed between a bottom portion of the cylinder formed in the casing and an end surface of the sleeve facing the bottom portion of the cylinder formed in the casing. A drain chamber communicating with the tank, a spring disposed in the drain chamber, one end locked to the end surface of the sleeve and the other end locked to the bottom of the cylinder formed in the casing, and the stopper And a control pressure chamber formed between the sleeve and the sleeve, to which a command pressure for sliding the sleeve is applied.

  According to the present invention, one tilt actuator can also function as a conventional capacity control valve, and tilt control of the swash plate can be performed without providing a capacity control valve separately outside the pump. Thereby, a pump can be made smaller than before. In addition, since there is no need for a separately provided capacity control valve, the number of parts can be reduced as compared with the prior art.

It is principal part sectional drawing which shows one Embodiment of the variable displacement swash plate type hydraulic pump which concerns on this invention. It is a figure which shows the principal part structure of this embodiment. It is a figure which shows operation | movement of this embodiment, and is a figure which shows operation | movement at the time of enlarging a tilt angle from the state shown in FIG. It is a figure which shows the state settled to the designated inclination angle, for example, the maximum inclination angle, from the state shown in FIG. It is principal part sectional drawing which shows this embodiment of the state maintained at the maximum inclination angle corresponding to FIG. It is a figure which shows operation | movement of this embodiment, and is a figure which shows operation | movement at the time of making a tilt angle small from the state shown to FIG. It is principal part sectional drawing which shows this embodiment of the state maintained at the minimum inclination angle. It is a figure which shows the characteristic acquired by this embodiment. It is a figure which shows the characteristic acquired by another embodiment. It is principal part sectional drawing which shows the conventional variable displacement type swash plate type hydraulic pump. It is a figure which shows the tilt control mechanism with which the variable displacement swash plate type hydraulic pump shown in FIG. 10 is equipped.

  Embodiments of a variable displacement swash plate hydraulic pump according to the present invention will be described below with reference to the drawings.

[Configuration of this embodiment]
FIG. 1 is a cross-sectional view showing a main part of an embodiment of a variable displacement swash plate type hydraulic pump according to the present invention, and FIG.

  The variable displacement swash plate hydraulic pump according to the present invention comprises, for example, a variable displacement swash plate hydraulic pump 1 shown in FIG. The hydraulic pump 1 includes a casing 2 that forms an outer shell. The casing 2 has a stepped cylindrical casing body 2A in which one end side is a closed end and the other end side is an open end, and the casing body. It is comprised from the front casing which closed the opening end side of 2A, ie, the cover body 2B. In FIG. 1, reference numeral 5 denotes a rotating shaft that is rotatably provided in the casing 2 via a bearing or the like. The rotating shaft 5 is provided at one end side in the bearing 3 and the lid 2B provided in the casing body 2A. The bearing 4 is rotatably supported.

  Reference numeral 6 denotes a cylinder block provided in the casing body 2 via the rotating shaft 5, and one end side of each cylinder of the cylinder block 6 is in sliding contact with the switching valve plate 8. The switching valve plate 8 is fixed to the closed end 2 </ b> A side of the casing body 2 so as to be in sliding contact with the cylinder block 6, and has a pair of supply / discharge ports 8 </ b> A and 8 </ b> B having an eyebrow shape. Reference numerals 9A and 9B denote a pair of supply / discharge passages formed on the closed end 2A side of the casing body 2. These supply / discharge passages 9A, 9B communicate with the supply / discharge ports 8A, 8B of the switching valve plate 8, and as the cylinder block 6 rotates, hydraulic oil in the tank 10 described later is sucked into each cylinder of the cylinder block 6. In addition, the pressurized oil pressurized in each cylinder is discharged to the outside. A bushing 11 is disposed between the cylinder block 6 and the rotating shaft 5.

  7 are pistons slidably inserted into the cylinders of the cylinder block 6, and these pistons 7 reciprocate in the cylinders as the cylinder block 6 rotates, and the cylinder block from the switching valve plate 8 side. The hydraulic oil is sucked into each cylinder 6 and pressurized with high pressure oil in each cylinder of the cylinder block 6. A shoe 12 is swingably mounted on the end of each piston 7 protruding from each cylinder of the cylinder block 6, and each shoe 12 is pressed toward the swash plate 14 side by an annular shoe presser 13 or the like. Has been.

  The swash plate 14 is provided so as to be tiltable toward the lid 2B side of the casing 2, and one side (surface side) is a smooth surface for guiding each shoe 12 so as to be slidable, and the tilt provided on the lid 2B. It is supported by the rolling support member 15 so as to be tiltable.

  Reference numerals 24A and 24B denote tilt actuators that drive the swash plate 14 to tilt between a maximum tilt position and a minimum tilt position. Each of these tilt actuators 24A and 24B has an end on the swash plate 14. Tilt control pistons 16 and 17 are provided so as to be in contact with and slidable. The tilt control piston 16 is formed to have a larger diameter than the tilt control piston 17 and generates a tilt driving force that is larger than the tilt control piston 17 by the pressure receiving area difference. The swash plate 14 described above constitutes feedback means that feeds back the tilt angle of the swash plate 14 tilted by the drive of the tilt actuator 24A to the drive control of the tilt actuator 24A.

  Each of the tilt control pistons 24A and 24B includes cylinders 18 and 19 formed so as to sandwich the cylinder block 6 from the radially outer side in the casing body 2A. The tilt control piston 16 of the tilt actuator 24B is slidably inserted into the cylinder 18, and the end of the tilt control piston 16 protruding from the cylinder 18 contacts the swash plate 14. . The tilt actuator 24 </ b> B includes a control pressure chamber 20 formed between the cylinder 18 and the tilt control piston 16. The control pressure chamber 20 is supplied and discharged with a control pressure for controlling the tilt control piston 16 as will be described later.

  As shown in FIG. 2, the tilt actuator 24 </ b> A is formed in the casing body 2 </ b> A in addition to the tilt control piston 17 described above, and a cylinder 19 in which the tilt control piston 17 is accommodated, and the cylinder 19. And a stopper 23 that slidably holds the tilt control piston 17 of the tilt actuator 24A and a cylinder 19 formed in the casing body 2A. Further, the sleeve 22 is disposed so as to be further away from the swash plate 14, holds the tilt control piston 17 so as to be slidable, and includes a sleeve 22 slidable with respect to the cylinder 19 formed in the casing body 2 </ b> A. The tilt actuator 24A is formed between the stopper 23 and the sleeve 22 and is disposed in the drain chamber 26 communicating with the tank 10, and one end of the tilt actuator 24A is locked to the stopper 23 and the other end. Is formed between the bottom of the cylinder 19 and the end face of the sleeve 22 facing the bottom, and is provided with a control pressure chamber 21 to which a command pressure Pi for sliding the sleeve 22 is applied. It has. When the command pressure Pi is guided to the control pressure chamber 21 through the oil passage 29 formed in the casing body 2A, the sleeve 22 slides so as to contract the spring 25.

  In addition, a cylinder 27 having a diameter smaller than the diameter of the cylinder 19 is formed in communication with the bottom of the cylinder 19, and the tilt control piston 17 is slidably attached to each of the cylinder 27, the sleeve 22, and the stopper 23. Has been inserted. A control pressure chamber 28 is formed between the bottom of the cylinder 27 and the tilt control piston 17, and the servo pressure Ps, that is, the control pressure is always introduced into the control pressure chamber 28.

  The present embodiment is provided with control pressure supply / discharge means for supplying and discharging a control pressure for sliding the tilt control piston 16 of the tilt actuator 24B from the tilt actuator 24A to the tilt actuator 24B.

  This control pressure supply / discharge means is formed, for example, in the tilt control piston 17 of the tilt actuator 24A, and is formed in the first oil passage 17A for guiding the control pressure Ps and the sleeve 22 of the tilt actuator 24A. A second oil passage 22A that selectively communicates with 17A and a third oil passage 30 that is formed in the casing body 2A and communicates with the second oil passage 22A and the control pressure chamber 20 of the tilting actuator 24B are included. .

[Operation of this embodiment]
FIG. 3 is a diagram showing the operation of the present embodiment. FIG. 4 is a diagram showing the operation when the tilt angle is increased from the state shown in FIG. 2, and FIG. 4 is a specified tilt angle such as the maximum tilt from the state shown in FIG. FIG. 5 is a diagram showing a state settled at the corner, FIG. 5 is a cross-sectional view of the main part showing the present embodiment in a state maintained at the maximum tilt angle corresponding to FIG. 4, and FIG. 6 is a diagram showing the operation of the present embodiment. FIGS. 7A and 7B are views showing the operation when the tilt angle is reduced from the state shown in FIGS. 4 and 5, and FIGS. 7A and 7B are cross-sectional views showing the main part of the embodiment in a state where the minimum tilt angle is maintained.

  In the state shown in FIG. 2, the first oil passage 17A and the second oil passage 22A are shut off, and the second oil passage 22A and the drain chamber 26 are also shut off. From this state, when an external command pressure Pi that generates an acting force larger than the force of the spring 25 on the end face of the sleeve 22 is guided to the control pressure chamber 21 of the tilt actuator 24A through the oil passage 29, as shown in FIG. Then, the sleeve 22 moves in the direction in which the spring 25 is contracted, stops at a position where the acting force on the sleeve 22 and the force of the spring 25 are balanced, and the second oil passage 22A and the drain chamber 26 communicate with each other. The pressure in the control pressure chamber 20 of the tilting actuator 24B always connected to the second oil passage 22A via 30 is reduced.

  Since the servo pressure Ps is always guided to the control pressure chamber 28, the acting force of the tilting control piston 17 of the tilting actuator 24A is larger than the acting force of the tilting control piston 16 of the tilting actuator 24B. The swash plate 14 is tilted and driven to the large tilt side by the tilt control piston 17 of the rolling actuator 24A. When the tilt control piston 17 moves to a certain position, as shown in FIG. 4, the second oil passage 22 </ b> A and the drain chamber 26 are shut off, and the tilt control piston 16 of the tilt actuator 24 </ b> B transmitted via the swash plate 14. When the acting force of the tilt control piston 17 of the tilt actuator 24A becomes equal, it stops. FIG. 5 shows a state in which, for example, the maximum tilt angle is maintained in this way.

  4 and 5, the first oil passage 17A and the second oil passage 22A are shut off, and the second oil passage 22A and the drain chamber 26 are also shut off. From this state, the external command pressure Pi When the pressure is reduced, the acting force on the sleeve 22 is lower than the force of the spring 25, and the sleeve 22 is slid by the spring 25. As a result, the first oil passage 17A and the second oil passage 22A communicate with each other as shown in FIG. 6, and the control pressure of the tilting actuator 24B passes through the first oil passage 17A, the second oil passage 22A, and the third oil passage 30. Servo pressure Ps is introduced into the chamber 20.

  Due to the pressure receiving area difference between the control pressure chamber 20 of the tilt actuator 24B and the control pressure chamber 21 of the tilt actuator 24A, the acting force on the tilt control piston 16 of the tilt actuator 24B is changed to the tilt control piston 17 of the tilt actuator 24A. The swash plate 14 is tilted and driven to the small tilt side. At the same time, when the tilt control piston 17 of the tilt actuator 24B is pushed down to a certain position, the first oil passage 17A and the second oil passage 22A are blocked, and the tilt actuator 24B transmitted via the swash plate 14 is tilted. When the acting force of the tilt control piston 17 of the control piston 16 and the tilt actuator 24A becomes equal, the control piston 16 stops. FIG. 7 shows a state in which, for example, the minimum tilt angle is maintained in this way.

  In the variable displacement swash plate hydraulic pump 1 according to the present embodiment, as shown in FIG. 8, when the external command pressure Pi is taken on the horizontal axis and the volume of the variable displacement pump 1 is taken on the vertical axis, the external command pressure Pi A characteristic is obtained in which the pump volume gradually increases with the increase.

  In the present embodiment configured as described above, when the tilting actuator 24A is driven by increasing / decreasing the command pressure Pi, the first oil passage 17A and the second oil passage 22A included in the control pressure supply / discharge means. The control pressure is supplied to and discharged from the tilt actuator 24A to the tilt actuator 24B via the third oil passage 30. The tilt actuator 24B is slid by the supply / discharge of the control pressure, and the swash plate 14 is tilted according to the driving of the tilt actuator 24A based on the command pressure Pi by the cooperation of the tilt actuator 24A and the tilt actuator 24B. It can be kept at the turning angle. As described above, in this embodiment, the tilt actuator 24A disposed inside the casing body 24A can also function as a conventional capacity control valve. That is, in this embodiment, the tilt control of the swash plate 14 can be performed without separately providing a capacity control valve outside the pump. Thereby, size reduction of the variable displacement swash plate hydraulic pump 1 can be realized. Moreover, since the capacity control valve is not required individually, the number of parts can be reduced.

  In the above-described embodiment, the tilt actuator 24A has the drain chamber 26 provided between the stopper 23 and the sleeve 22, and the spring 25 is provided in the drain chamber 26. Is not limited to such a configuration. That is, the tilt actuator 24A is formed between the bottom of the cylinder 19 formed in the casing body 2A and the end surface of the sleeve 22 facing the bottom, and is disposed in the drain chamber communicating with the tank 10, A control which is formed between a spring whose one end is locked to the end face of the sleeve 22 and whose other end is locked to the bottom of the cylinder 19, and the stopper 23 and the sleeve 22, and which gives a command pressure Pi for sliding the sleeve 22. You may make it the structure which has a pressure chamber.

  In the configuration as described above, the command pressure Pi-pump volume characteristic becomes a characteristic that the pump volume gradually increases as the external command pressure Pi decreases as shown in FIG. 9, but the first embodiment described above. The same effect can be obtained.

DESCRIPTION OF SYMBOLS 1 Variable displacement type swash plate type hydraulic pump 2 Casing 2A Casing main body 2B Cover body 10 Tank 14 Swash plate (feedback means)
16 Tilt Control Piston 17 Tilt Control Piston 17A First Oil Pass 17B Cylinder 18 Cylinder 19 Cylinder 20 Control Pressure Chamber 21 Oil Chamber 22 Sleeve 22A Second Oil Pass 23 Stopper 24A Tilt Actuator 24B Tilt Actuator 25 Spring 26 Drain Chamber 27 Cylinder 28 Control pressure chamber 29 Oil passage 30 Third oil passage

Claims (5)

A casing,
A rotating shaft rotatably supported by the casing;
A cylinder block provided in the casing so as to rotate integrally with the rotating shaft, and having a plurality of cylinders formed therein;
A plurality of pistons fitted in each cylinder of the cylinder block so as to be reciprocally movable;
The reciprocating motion of each piston is converted into the rotational motion of the cylinder block, and is provided so as to face the bottom portion of the casing, and the surface side becomes a smooth surface on which the piston slides between the maximum tilt position and the minimum tilt position. A swash plate that can be tilted at
A tilt actuator that tilts and drives the swash plate;
A valve plate having a pair of supply / exhaust ports that are intermittently communicated with each cylinder when the casing and the cylinder block rotate while sliding;
Feedback means for feeding back the tilt angle of the swash plate tilted by driving the tilt actuator to drive control of the tilt actuator;
The tilt actuator is composed of one tilt actuator and the other tilt actuator which are arranged so as to sandwich the rotation shaft, and each of these tilt actuators has an end abutting against the swash plate and sliding. In a variable displacement swash plate hydraulic pump having a tilt control piston provided movably,
Control pressure supply / discharge means for supplying and discharging control pressure for sliding the tilt control piston of the other tilt actuator from the one tilt actuator to the other tilt actuator is provided. Variable displacement swash plate hydraulic pump. The variable displacement swash plate hydraulic pump according to claim 1,
The one tilt actuator is formed in the casing, the cylinder in which the tilt control piston is accommodated, and the tilt control of the one tilt actuator, which is accommodated in the cylinder and fixed to the casing. A stopper that slidably holds a piston, and is accommodated in the cylinder formed in the casing and is arranged so as to be farther from the swash plate than the stopper, and the tilt control piston of the one tilt actuator is A sleeve that is slidably held and slidable relative to the cylinder formed in the casing;
The control pressure supply / discharge means is formed in the tilt control piston of the one tilt actuator, formed in the first oil passage for guiding the control pressure, and in the sleeve of the one tilt actuator, A second oil passage selectively communicating with one oil passage, and a control pressure chamber formed in the casing and connected to the tilt control piston of the other tilt actuator are communicated with each other. A variable displacement swash plate hydraulic pump comprising a third oil passage. The variable displacement swash plate hydraulic pump according to claim 1 or 2,
2. The variable displacement swash plate type hydraulic pump, wherein the feedback means comprises the swash plate. The variable displacement swash plate hydraulic pump according to claim 3,
The one tilting actuator is formed between the stopper and the sleeve and is connected to the drain chamber, and is disposed in the drain chamber. One end is locked to the stopper and the other end is locked to the sleeve. Formed between the spring formed on the casing and the bottom surface of the sleeve facing the bottom of the cylinder formed on the casing, and gives a command pressure for sliding the sleeve. And a variable pressure swash plate hydraulic pump. The variable displacement swash plate hydraulic pump according to claim 3,
The one tilting actuator is formed between a bottom portion of the cylinder formed in the casing and an end surface of the sleeve facing the bottom portion of the cylinder formed in the casing, and is connected to a tank. And a spring disposed at the drain chamber and having one end locked to the end surface of the sleeve and the other end locked to the bottom of the cylinder formed on the casing, and formed between the stopper and the sleeve. And a control pressure chamber to which a command pressure for sliding the sleeve is applied, and a variable displacement swash plate hydraulic pump.

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