JP2009197709A - Swash plate type variable displacement hydraulic pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact swash plate type variable displacement hydraulic pump having excellent installation space efficiency, a small number of components, a simple structure, and an excellent assembly property while any secular degradation of the detection accuracy caused by the wear or the like of a slidably contact part hardly occurs. <P>SOLUTION: The swash plate type variable displacement hydraulic pump (1) comprises a cylinder barrel (6) rotated around the axis of rotation, a plurality of axial cylinders (60) formed at equal intervals in the circumferential direction of the cylinder barrel, a piston (61) which is inserted in each axial cylinder so as to be reciprocated, a swash plate (7) which is slidably brought into contact with an end of each piston to provide axial displacement to each piston, and a controller (3) for controlling the angle of the inclination of the swash plate. The controller includes a control cylinder (4) having a control piston (41) connected to the swash plate, and a non-contact linear displacement sensor (5) for directly detecting the displacement of the control piston. The controller performs the feedback of the displacement detected by the linear displacement sensor to control the feed of pressurized oil to the control cylinder. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a swash plate type variable displacement hydraulic pump capable of changing the discharge amount of pressure oil.

  A swash plate type variable displacement hydraulic pump, that is, a variable displacement swash plate type axial piston pump, controls the discharge amount of pressure oil by controlling the tilt angle (referred to as the tilt angle) of the swash plate that gives axial displacement to each piston. It can be changed continuously. The swash plate is controlled by a controller including an actuator (hydraulic cylinder) for tilting the swash plate and a detecting means for detecting a tilt angle of the swash plate or a displacement amount of the actuator. Such a controller is integrated with the pump. It is equipped with.

  As a means for detecting the tilt angle of the swash plate, there is known a device in which a rotation shaft of a lever that swings with the swash plate is passed through the pump casing and the rotation angle is detected by a potentiometer provided on the side of the pump casing. (For example, see Patent Document 1). However, with this method, it is necessary to secure an installation space for the swing lever inside the pump casing, and the detection mechanism including the potentiometer protrudes outside the casing, which deteriorates the space efficiency when installing the pump. There is.

  On the other hand, as a means for detecting the displacement amount of the actuator, a swing lever is connected to the piston of the actuator through a long hole, and the linear displacement of the piston is converted into the rotation angle of the swing lever and detected by a potentiometer. Etc. are known (see, for example, Patent Document 2). However, this method requires a mechanical conversion mechanism that converts the linear displacement of the piston into the rotation angle of the swing lever, which complicates the structure, and such a mechanical conversion mechanism provides sliding contact between members. As a result, there is a risk of variations in detection accuracy due to the finished accuracy of each member.

  Further, in any detection means, it is necessary to assemble and adjust the detection mechanism in parallel with the assembly and adjustment of the swash plate type axial piston pump itself, and the detection accuracy due to wear or the like at the sliding contact portion of the detection mechanism. There is a concern that the necessary control accuracy cannot be maintained due to the fact that the deterioration of the aging is not denied.

JP-A-11-37042 JP-A-2005-320912

  The present invention has been made in view of such a state of the prior art, and the object thereof is compact, has a good installation space efficiency, has a small number of parts, is simple in structure, has good assemblability, and has good sliding contact. It is an object of the present invention to provide a swash plate type variable displacement hydraulic pump that does not cause deterioration in detection accuracy due to wear of a part.

In order to solve the above problems, a swash plate type variable displacement hydraulic pump (1) according to the present invention includes:
A cylinder barrel (6) that is driven to rotate about a rotation shaft, a plurality of axial cylinders (60) that are perforated at equal intervals in the circumferential direction of the cylinder barrel, and a reciprocating motion to each axial cylinder The inserted piston (61), the swash plate (7) that slides on the end of each piston and applies axial displacement to each piston, and the controller (3) that controls the tilt angle of the swash plate ) And
The controller includes a control cylinder (4) having a control piston (41) coupled to the swash plate, and a non-contact linear displacement sensor (5) for directly detecting a displacement amount of the control piston, The displacement amount detected by the displacement sensor is fed back to control the supply of pressure oil to the control cylinder.

Since the swash plate type variable displacement hydraulic pump according to the present invention is configured as described above, it has the following effects.
First, there is no need for a mechanical conversion mechanism or detection mechanism for detecting the tilt angle of the swash plate or the displacement amount of the control piston, and the number of parts can be reduced, the structure can be simplified, and the assembly can be improved. Installation space for the mechanical conversion mechanism and stroke detection mechanism is almost unnecessary, and it is compact and has excellent space efficiency for installation.
Second, since the displacement amount of the control piston is directly detected without contact, it is possible to eliminate aged deterioration in detection accuracy due to variations in detection accuracy due to the finishing accuracy of the mechanical contact portion and wear of the sliding contact portion. Detection accuracy can be maintained over a period, and durability and maintainability are improved.

  In the present invention, the linear displacement sensor (5) comprises a magnetostrictive linear displacement composed of a magnet (52) disposed in the control piston and a magnetostrictive wire probe (51) disposed in the control cylinder. A sensor is preferred. In this aspect, no wiring for sensing is required on the control piston side, which is a movable part, and the signal line of the magnetostrictive probe is drawn from the detection unit (53) located outside the control cylinder. Since the part and the detection part are completely independent, there is an advantage that the apparatus can be easily assembled and adjusted.

  The control piston (41) has an axial hole (50) extending along the central axis from one pressure receiving surface, and the magnet (52) is an annular magnet disposed in the axial hole. In the aspect in which the magnetostrictive wire probe (51) extends from the end surface of the control cylinder facing the pressure receiving surface to the inside of the axial hole through the inside of the magnet, Since the gap with the axial hole is filled with hydraulic oil and a fixed oil film is always interposed, the probe is held at the center of the magnet, and stable detection can be performed.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a front view showing a swash plate type variable displacement hydraulic pump 1 according to an embodiment of the present invention, and FIG. In the figure, a swash plate type variable displacement hydraulic pump 1 includes a pump body 2 and a controller 3. The pump body 2 is composed of a cylinder barrel 6, a swash plate 7, a valve plate 8, an auxiliary pump 9 fixed to the outside of the casing 10, and the like disposed inside the casing 10. (Actuator), linear displacement sensor 5, controller 31, servo valve 32, and the like.

  The cylinder barrel 6 is supported through a spline on a rotating shaft 21 that is rotatably supported in a bearing hole penetrating the casing 10 via bearings 22 and 23, and is connected to an end of the rotating shaft 21. It is driven and rotated together with the rotating shaft 21 by an electric motor or an internal combustion engine (not shown). A plurality of axial cylinders 60 are bored in the cylinder barrel 6 at equal intervals in the circumferential direction, and pistons 61 are fitted into the respective axial cylinders 60 so as to be able to reciprocate.

  The base end portion of each piston 61 is connected to a shoe 63 through a ball joint 62. Each shoe 63 is held in sliding contact with the swash plate 7 (bearing plate) by a ball retainer 64 and a retainer 65 which are externally fitted to the cylinder barrel 6 and urged by a spring 66. An axial displacement corresponding to the inclination angle of the plate 7 and the rotation angle phase of the cylinder barrel 6 is given to each piston 61.

  In the swash plate 7, the arcuate guided surfaces 74 formed on both sides of the rotating shaft 21 are engaged with the inner arcuate guiding surface 24 formed in the casing 10 with the rotating shaft 21 passing through the center. It is supported so as to be slidable, and can be tilted about the tilting shaft 67. A connecting portion 71 extends from the end of the swash plate 7 on the control portion 3 side, and one end of a link 72 is rotatably connected to the connecting portion 71 by a pin 73. The other end is rotatably connected by a pin 43 to a connecting portion 42 of a control piston 41 described later.

  On the other hand, the end surface of the cylinder barrel 6 opposite to the swash plate 7 is pressed against the valve plate 8 by the bias of the spring 66. As shown by a broken line in FIG. 1, the valve plate 8 is provided with two arc-shaped ports 81 and 82, one port 81 communicates with the suction port 11, and the other port 82 is a discharge port. 12 communicates.

  In addition, each axial cylinder 60 of the cylinder barrel 6 communicates with the end face pressed against the valve plate 8 via an individual passage, and the cylinder barrel 6 rotates according to the angular position according to the angular position. The ports 81 and 82 are sequentially communicated, and in the middle of the ports 81 and 82, the ports are switched after being completely closed once.

  The auxiliary pump 9 is constituted by a fixed displacement pump such as a gear pump, and the rotating shaft 91 is connected to the rotating shaft 21 of the pump main body 2 via the coupling 25, whereby the cylinder barrel 6 (that is, the main pump). The hydraulic oil is driven and rotated by a common drive source, and hydraulic oil sucked from an unillustrated oil tank or the like through the suction port 13 is discharged from the discharge port 14 at a constant pressure, and a pilot pressure is supplied to the control unit 3.

  That is, the discharge port 14 of the auxiliary pump 9 is connected to the servo valve 32 through a passage (14) (not shown) formed in the casing 10 and the wall of the control cylinder 4, and is operated to the control cylinder 4 through the oil feed pipe 16 or 17. While supplying oil and supplying pilot pressure, the servo valve 32 is in the closed position, and when the discharge port 14 reaches a predetermined high pressure, the relief valve 18 is opened and the hydraulic oil is released into the casing 10 (low pressure drain).

  The control cylinder 4 is a double-acting cylinder capable of supplying hydraulic pressure to both sides of the control piston 41, but the central portion 40 communicates with the inside of the casing 10 (low pressure drain) of the pump body 2 through the opening 30. A connecting portion 42 is provided in the central portion of the control piston 41 located in the central portion 40.

  The connecting portion 42 is formed in a radial direction (in FIG. 2) from a ring-shaped fitting portion that is fitted to one of the left and right pistons 41 a, 41 b of the control piston 41 (the right side 41 a in FIG. 2) and the shaft portion 41 c. The other end (left side in FIG. 2) is fitted to the shaft portion 41c, and the shaft portion is sandwiched between the left and right pistons 41a and 41b. It is fixed to the control piston 41 by screwing and fastening a nut to the end portion (screw portion) of 41c.

  In the state where the control cylinder 4 is assembled to the casing 10 of the pump main body 2, the connecting portion 42 penetrates the control cylinder 4 and the opening 30 of the casing 10 and reaches the inside of the casing 10. The other end of the link 72 described above is rotatably connected by a pin 43. In the actual assembling procedure, the link 72 is rotated upward, pulled out from the opening 30 and connected to the connecting portion 42, and then the control cylinder 4 is attached to the pump body 2 (casing 10). .

  An axial hole 50 that allows the probe 51 of the linear displacement sensor 5 to be inserted in a non-contact manner is formed in the pressure receiving surface of the one piston 41a of the left and right pistons 41a and 41b constituting the control piston 41. ing. The axial hole 50 extends along the central axis from the pressure receiving surface of the piston 41a, and the innermost part reaches the central part of the shaft part 41c. An annular magnet 52 (permanent magnet) is attached to the large diameter portion 50a.

  The linear displacement sensor 5 is a magnetostrictive linear displacement sensor using the Weedmann effect, and is a probe 51 (magnetostrictive line) extending from one end face 4a of the control cylinder 4 through the inside of the magnet 52 into the axial hole 50. And a detection unit 53 at one end thereof, and the detection unit 53 is fixed to the end surface 4a. The linear displacement sensor 5 applies a current pulse to the probe 51 to generate a circumferential magnetic field, and detects torsional distortion (vibration) generated by the axial magnetic field of the magnet 52 by converting it into an electrical signal. The distance from the propagation speed and the arrival time to the magnet 52 is calculated, so that the position of the control piston 41 can be detected without contact.

  Next, the operation based on the above embodiment will be described.

  The displacement of the control piston 41 detected by the linear displacement sensor 5 is compared with a set value in the controller 31, and the port of the servo valve 32 is switched based on the calculation result to the port 46 or 47 of the control cylinder 4. Feedback control is performed to supply hydraulic pressure and bring the displacement of the control piston 41 close to the set value.

  The controller 31 is connected to a control device (not shown) of a hydraulic system including the swash plate type variable displacement hydraulic pump 1, and is given the set value by the control device. The tilt angle of the plate 7 is controlled, and the discharge amount of the swash plate type variable displacement hydraulic pump 1 can be controlled. In the swash plate type variable displacement hydraulic pump 1 of the embodiment, the tilt angle of the swash plate 7 is changed from the neutral position indicated by the solid line in FIG. 2 within the range indicated by the two-dot chain lines 7 ′ and 7 ″ in both positive and negative directions. Therefore, not only the discharge amount but also the discharge direction can be controlled.

  For example, in FIG. 2, the servo valve 32 is controlled by the controller 31, the pilot pressure is supplied to the port 46 on the right side of the control cylinder 4 through the oil feeding pipe 16, and the control piston 41 moves to the left side in the drawing, When the plate 7 is tilted 7 'from the neutral position where the tilt angle is zero (the tilt angle is in the positive range), the shoe 63 of each piston 61 is guided by the swash plate 7' as the cylinder barrel 6 rotates. Then, each piston 61 reciprocates in the axial cylinder 60 according to the tilt angle, and hydraulic oil is sequentially sucked into each axial cylinder 60 through the suction port 11 and the port 81 in the angle range of the port 81 of the valve plate 8. In the angle range of the port 82, the sucked hydraulic oil is sequentially discharged through the port 82 and the discharge port 12.

  On the contrary, the pilot pressure is supplied to the port 47 on the left side of the control cylinder 4 through the oil feeding pipe 17, the control piston 41 moves to the right side of the diagram, and the swash plate 7 is moved from the neutral position to the 7 ″ side (the tilt angle is In the angular range of the port 82 of the valve plate 8, the hydraulic oil is sucked into each axial cylinder 60 through the discharge port 12 and the port 82, and the port 81 and the suction port in the angular range of the port 81. 11 is discharged.

  In the control of the discharge amount and the discharge direction as described above, it is important to detect the neutral position where the tilt angle of the swash plate 7 becomes zero. However, the swash plate 7 and the control piston 41 which are movable parts are arranged in the casing 10. In addition, since the linear displacement sensor 5 is housed in the control cylinder 4 and detects the position of the control piston 41 in a non-contact manner, the neutral position cannot be determined mechanically.

  Therefore, prior to the operation of the swash plate type variable displacement hydraulic pump 1, the swash plate 7 is set to a neutral position with a zero tilt angle through a work hole or a jig, and the detection value of the linear displacement sensor 5 in that state is set. It is necessary to perform the calibration for the neutral position.

  In this regard, adjustments after assembly are indispensable because there is a limit to the mechanical characteristics for converting the operation and the assembly accuracy in the conventional position detection mechanism. Since the position of the control piston 41 can be directly detected in a non-contact manner without using a mechanism for converting the linear displacement of the control piston into an angular displacement, the assembly is performed by performing the calibration as described above. Regardless of accuracy, the position of the control piston 41 can be detected stably, and it is possible to eliminate aged deterioration in detection accuracy due to variations in detection accuracy due to the finishing accuracy of the mechanical contact portion, wear of the sliding contact portion, etc. Thus, the detection accuracy can be maintained well, and durability and maintainability are improved.

  Further, since a mechanical conversion mechanism and a detection mechanism are not required, the number of parts can be reduced, the structure can be simplified, and the assemblability can be improved, and the probe 51 and the magnet 52 of the linear displacement sensor 5 are provided inside the control cylinder 4. Since it is disposed, almost no installation space is required. In addition, since the gap between the probe 51 and the axial hole 50 and the magnet 52 is always filled with hydraulic oil and a certain oil film is interposed, the probe 51 is held at the center of the magnet 52 and stable detection can be performed.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment, Based on the technical idea of this invention, a various deformation | transformation and change are possible.

  For example, although the case where a magnetostrictive linear displacement sensor is used as the non-contact linear displacement sensor has been described in the above embodiment, a differential transformer type non-contact linear displacement sensor can also be used. In that case, the core of the differential transformer is disposed at the position of the probe 51, the primary coil and the secondary coil are disposed in the axial hole 50, and the signal line is drawn out from the central portion 40 or the like to the controller. Just connect.

  The type and control method of the servo valve are not particularly limited, and a known servo valve such as a proportional solenoid valve or a hydraulic servo valve can be used.

1 is a front view showing a swash plate type variable displacement hydraulic pump according to an embodiment of the present invention. It is AA sectional drawing of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Swash plate type variable displacement hydraulic pump 2 Pump main-body part 3 Control part 4 Control cylinder 5 Linear displacement sensor 6 Cylinder barrel 7 Swash plate 8 Valve plate 9 Auxiliary pump 10 Casing 11, 13 Suction port 12, 14 Discharge port 21 Rotating shaft 30 Opening 31 Controller 32 Servo valve 40 Central part 41 Control piston 42 Connection part 50 Axial hole 51 Probe 52 Magnet 53 Detection part 60 Axial cylinder 61 Piston

Claims (3)

A cylinder barrel driven and rotated about a rotation axis; a plurality of axial cylinders drilled at equal intervals in the circumferential direction of the cylinder barrel; and a piston fitted and removably inserted into each axial cylinder. A swash plate that slidably contacts the end of each piston to impart axial displacement to each piston, and a controller that controls the tilt angle of the swash plate,
The controller includes a control cylinder having a control piston coupled to the swash plate, and a non-contact linear displacement sensor that directly detects a displacement amount of the control piston, and a displacement amount detected by the linear displacement sensor. A swash plate variable displacement hydraulic pump configured to feed back and control the supply of pressure oil to the control cylinder.   2. The swash plate type variable sensor according to claim 1, wherein the linear displacement sensor is a magnetostrictive linear displacement sensor including a magnet disposed in the control piston and a magnetostrictive wire probe disposed in the control cylinder. Capacity type hydraulic pump.   The control piston has an axial hole extending from one pressure receiving surface along the central axis, the magnet is an annular magnet disposed in the axial hole, and the magnetostrictive wire probe is the pressure receiving 3. The swash plate type variable displacement hydraulic pump according to claim 2, wherein the swash plate type variable displacement hydraulic pump extends from the end face of the control cylinder facing the face to the inside of the axial hole through the inside of the magnet.

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