JP2006077708A - Variable displacement swash plate type hydraulic pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure positions of feedback links provided in a plurality of variable displacement swash plate type hydraulic pumps respectively, without providing position sensors in the respective variable displacement swash plate type hydraulic pumps. <P>SOLUTION: Swash plates 28A, 28B, tilting actuators 33A, 33B driving the swash plates 28A, 28B and the feedback links 41A, 41B for transmitting tilting angles of the swash plates 28A, 28B to a regulator are provided. Measurement ports 42A, 42B into which the position sensors 50A, 50B measuring the positions of the feedback links 41A, 41B, respectively can be inserted are formed in a casing main body 2. Plugs 43A, 43B for closing the measurement ports 42A, 42B when the respective position sensors 50A, 50B are not inserted into the corresponding measurement ports 42A, 42B are provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a variable displacement swash plate hydraulic pump suitable as a hydraulic source for construction machines such as hydraulic excavators or industrial machines.

  There exists a thing shown by patent document 1 as this type of prior art. This prior art includes a casing, a cylinder block that is rotatably provided in the casing and has a plurality of cylinders drilled along the circumferential direction, a drive shaft that rotates the cylinder block, that is, a rotation shaft, and a cylinder block. A plurality of pistons accommodated in the cylinders in a reciprocating manner, and a swash plate provided with a sliding surface on which shoes attached to the end portions of these pistons slide and which can be tilted in the casing And an operation piston for tilting the swash plate, that is, a tilt actuator.

  In addition, a feedback mechanism is provided that transmits the tilt angle of the swash plate or the amount of movement of the tilt actuator to a regulator that controls the displacement of the pump, and this feedback mechanism is provided in the casing in the direction of movement of the tilt actuator. A displacement detector that extends along the line and outputs an electrical signal is included.

  In addition, unlike the above-described prior art, a casing, a rotating shaft, a cylinder block having a cylinder, a piston, a swash plate, a tilting actuator, etc. are provided, but another feedback link having a feedback link that engages the swash plate as a feedback mechanism. A conventional technology, that is, a tandem swash plate type hydraulic pump is disclosed in Patent Document 2.

In this other conventional technique, a value corresponding to the tilt angle of the swash plate is transmitted to the servo piston of the regulator via a feedback link.
Japanese Patent Publication No. 6-86873 Japanese Patent Laid-Open No. 9-42148

  During maintenance and inspection of the hydraulic pump, the flow rate between the theoretical discharge flow rate determined by the tilt angle of the swash plate, that is, the displacement of the pump, and the discharge flow rate actually discharged from the pump at the tilt angle of the corresponding swash plate Work is being done to check if the error is within an acceptable range.

  The same applies to a hydraulic pump provided with a feedback link as shown in the other prior art of Patent Document 2 described above, and the position of the feedback link corresponding to the tilt angle of the swash plate is measured during maintenance inspection of this hydraulic pump. Then, the tilt angle of the swash plate is obtained from the measured value, and the theoretical discharge flow rate is obtained.

  When measuring the position of such a feedback link, as disclosed in Patent Document 1, it is conceivable to dispose a displacement detector that outputs an electrical signal in the casing as a position measuring device that measures the position of the feedback link. . However, with such a configuration, since a displacement detector is provided for each pump, there is a problem that the cost for manufacturing the hydraulic pump increases and the cost for measuring the position of the feedback link increases.

  Also, depending on the arrangement of the displacement detector, for example, as shown in Patent Document 1, when the displacement detector is arranged along the extending direction of the tilt actuator, it corresponds to the moving direction of the tilt actuator. There is a problem that the size of the casing in the direction becomes large, and the miniaturization of the overall shape cannot be realized.

  In the tandem swash plate type hydraulic pump as shown in Patent Document 2, when the displacement detector is arranged based on the above-described concept, the dimension of the casing in the direction along the axial direction of the rotating shaft is considerably increased. End up. Therefore, in such a tandem swash plate hydraulic pump, it is practically difficult to provide a displacement detector as disclosed in Patent Document 1.

  The present invention has been made in accordance with the above-described prior art, and an object of the present invention is to provide a feedback mechanism including a feedback link that feeds back a tilt angle of a swash plate to a regulator. An object of the present invention is to provide a variable displacement swash plate type hydraulic pump that can measure the position of a feedback link provided in each hydraulic pump without being provided in each pump.

  In order to achieve the above object, the present invention provides a casing, a cylinder block that is rotatably provided in the casing, and in which a plurality of cylinders are formed along the circumferential direction, and a rotating shaft that rotates the cylinder block. A plurality of pistons housed in each cylinder of the cylinder block so as to be reciprocally movable, and a sliding surface on which a shoe attached to the end of these pistons slides, and can be tilted in the casing A swash plate provided on the swash plate, a tilt actuator that drives the swash plate to tilt, and a feedback mechanism that transmits a value corresponding to the tilt angle of the swash plate to the regulator. In a variable displacement swash plate hydraulic pump including an engaging feedback link, position measurement for measuring the position of the feedback link on the casing To form a possible measurement port insertion location, when the position measuring device is not inserted in the measuring port, and comprising the closing means for closing said measuring port.

  The present invention configured as described above detects the tilt angle of a swash plate related to one hydraulic pump, for example, when measuring the position of a feedback link provided in each of a plurality of variable displacement swash plate hydraulic pumps. Therefore, when detecting the position of the feedback link, the closing means for closing the measuring port formed in the one hydraulic pump is removed, and the position measuring device is inserted into the measuring port of the one hydraulic pump, The position of the feedback link corresponding to the tilt angle of the swash plate may be measured by this position measuring device.

  Further, when measuring the position of the feedback link in order to detect the tilt angle of the swash plate related to another hydraulic pump, the closing means for closing the measurement port formed in the casing of the other hydraulic pump is removed. For example, if the position measuring device described above is inserted into the measurement port of the other hydraulic pump, and the position of the feedback link corresponding to the tilt angle of the swash plate of the other hydraulic pump is measured by this position measuring device. Good.

  Further, when the position of the feedback link is measured in order to detect the tilt angle of a swash plate related to another hydraulic pump, it can be measured using the same position measuring device, for example.

  As described above, according to the present invention, the position of the feedback link provided in each hydraulic pump can be measured by the same position measuring device without providing the position measuring device in each of the plurality of variable displacement swash plate hydraulic pumps. it can. Further, since the measurement port may be formed so as to penetrate the wall portion of the casing, the position of the feedback link can be measured without increasing the outer shape of the casing.

  Further, the present invention is characterized in that, in the above invention, the extending direction of the measurement port is set to a direction intersecting with the moving direction of the tilt actuator in a plan view.

  Further, the present invention is characterized in that in the above invention, the extending direction of the measurement port is set to a direction along the moving direction of the feedback link.

  In order to achieve the above object, the present invention provides a casing, a cylinder block that is rotatably provided in the casing, and in which a plurality of cylinders are formed along the circumferential direction, and a rotation that rotates the cylinder block. A shaft, a plurality of pistons housed in each cylinder of the cylinder block so as to be reciprocable, and a sliding surface on which a shoe mounted on the end of these pistons slides and tilts in the casing A swash plate that can be provided; a tilt actuator that tilts the swash plate; and a feedback mechanism that transmits a value corresponding to the tilt angle of the swash plate to the regulator. In the variable displacement swash plate type hydraulic pump including a feedback link engaged with the casing, the feedback link is connected to the measurement port formed in the casing. Position causes insertion of the position measuring device for measuring a, it is characterized by comprising a sealing means for preventing leakage of oil in the casing from the position measuring device part.

  In the present invention configured as described above, the position of the feedback link provided in the hydraulic pump can be measured by the position measuring device, and the casing from the position measuring device portion is sealed by the sealing means during the measuring operation. It is possible to prevent leakage of oil in the interior, and it is possible to prevent loss due to outflow of oil to the outside of the casing during measurement work and contamination with oil.

  When the measurement of the position of the feedback link of the hydraulic pump is completed, the position measuring device may be removed from the measurement port and the measurement port may be closed by the closing means. The extracted position measuring device can be used for measuring the position of the feedback link of another hydraulic pump.

  As described above, according to the present invention, the position of the feedback link provided in each hydraulic pump can be measured by the same position measuring device without providing the position measuring device in each of the plurality of variable displacement swash plate hydraulic pumps. it can. In addition, since the measurement port into which the position measuring device is inserted may be formed so as to penetrate the wall portion of the casing, the position of the feedback link can be measured without increasing the outer shape of the casing.

  Further, the present invention is characterized in that, in the above invention, the casing is provided with a first pump and a second pump driven by the rotating shaft, and is formed into a tandem swash plate type hydraulic pump.

  The present invention can measure the position of the feedback link of the corresponding hydraulic pump by inserting the same position measuring device into the measurement port formed in the casing of each of the variable displacement swash plate hydraulic pumps. In other words, the position of the feedback link of each hydraulic pump can be measured without providing a position measuring device in each of the plurality of variable displacement swash plate hydraulic pumps. The increase in the production cost of the hydraulic pump can be suppressed, and the cost for measuring the position of the feedback link can be reduced.

  Further, since the position of the feedback link can be measured without increasing the outer shape of the casing, the overall shape including the casing can be reduced in size.

  The best mode for carrying out the variable displacement swash plate hydraulic pump according to the present invention will be described below with reference to the drawings.

  FIG. 1 is a sectional view showing an embodiment of a variable displacement swash plate hydraulic pump according to the present invention. The present embodiment is provided, for example, in a hydraulic excavator and includes a tandem swash plate type hydraulic pump including a first pump 16A and a second pump 16B in a casing 1 as shown in FIG. The casing 1 includes a casing body 2, a front casing 3, and a rear casing 4.

  The first pump 16A includes a first cylinder block 20A in which a plurality of cylinders, that is, a first cylinder 21A are formed along a circumferential direction, and a first cylinder block 20A that is in sliding contact with the first cylinder block 20A and has a suction port and a discharge port. One valve plate 17A, a first piston 23A accommodated in each first cylinder 21A so as to be able to reciprocate, and a sliding surface on which a first shoe 24A attached to the end of the first piston 23A slides. The first swash plate 28A is provided in the casing body 2 so as to be tiltable, and a first tilt actuator 33A that tilts and drives the first swash plate 28A.

  Similarly, the second pump 16B includes a plurality of cylinders along the circumferential direction, that is, a second cylinder block 20B in which the second cylinder 21B is drilled, and the second cylinder block 20B in sliding contact, and a suction port and a discharge port. A second valve plate 17B having a second piston plate 23B accommodated in each second cylinder 21B so as to be able to reciprocate, and a slide on which a second shoe 24B attached to the end of the second piston 23B slides. A second swash plate 28B that has a moving surface and is provided in the casing body 2 so as to be tiltable, and a second tilting actuator 33B that tilts and drives the second swash plate 28B.

  Further, in the casing 1, a rotating shaft 10 common to the first pump 16A and the second pump 16B, that is, a rotating shaft 10 for rotating the first cylinder block 20A and the second cylinder block 20B is disposed.

  Further, the first pump 16A is provided with a feedback mechanism that transmits a value corresponding to the tilt angle of the first swash plate 28A to a regulator (not shown). The feedback mechanism engages with the first swash plate 28A and moves in the direction indicated by the arrow 60A in FIG. 1, that is, the direction orthogonal to the rotary shaft 10 as the first swash plate 28A is driven to tilt. A first feedback link 41A is included.

  Similarly, the second pump 16B is also provided with a feedback mechanism that transmits a value corresponding to the tilt angle of the second swash plate 28B to another regulator (not shown). This other feedback mechanism is engaged with the second swash plate 28B, and in the direction indicated by the arrow 60B in FIG. The moving second feedback link 41B is included.

  In the present embodiment, in particular, a first measurement port 42A into which a later-described first position measurement device 50A for measuring the position of the first feedback link 41A can be inserted into the casing body 2, and the first measurement port 42A. Closing means for closing the first measurement port 42A when the first position measuring device 50A is not inserted, for example, a first plug plug having a screw portion screwed into a screw portion formed in the first measurement port 42A. 43A.

  Similarly, a second measurement port 42B into which a later-described second position measurement device 50B for measuring the position of the second feedback link 41B can be inserted into the casing body 2, and a second position is connected to the second measurement port 42B. A closing means for closing the second measurement port 42B when the measurement device 50B is not inserted, for example, a second plug plug 43B having a screw portion screwed into a screw portion formed in the second measurement port 42B. It has a configuration provided.

  The extending direction of the first measurement port 42A and the second measurement side port 42B described above intersects with the respective moving directions of the first tilt actuator 33A and the second tilt actuator 33B in a plan view, for example, an arrow 60A. Are set in the direction along the moving direction of the first feedback link 41A indicated by, and in the direction along the moving direction of the second feedback link 41B indicated by the arrow 60B.

  2 is a cross-sectional view showing a state in which the position measurement device is mounted on the embodiment shown in FIG. 1, and FIG. 3 is an enlarged cross-sectional view showing the configuration of the position measurement device shown in FIG.

  At the time of measuring the position of the first feedback link 41A and the second feedback link 41B, as shown in FIG. 2, the first position measurement for measuring the position of the first feedback link 41A in the first measurement port 42A formed in the casing body 2 is performed. The device 50A is inserted, and the second position measuring device 50B for measuring the position of the second feedback link 41B is inserted into the second metering side port 42B.

  For example, as shown in FIG. 3, the first position measuring device 50 </ b> A has a case 51 having a screw portion that is screwed into a screw portion of the first measurement port 42 </ b> A formed in the casing body 2, and is movable to the case 51. For example, a measuring rod 52 formed with a scale 53 corresponding to the tilt angle of the first swash plate 28A, and housed in the case 51, one end of which is engaged with a spring receiver 54 provided on the measuring rod 52. The other end is attached to the wall surface of the case 51, the spring 55 is capable of biasing the measuring rod 52, the first seal 56 that seals the gap formed between the case 51 and the measuring rod 52, and the case 51 and a second seal 57 that seals a gap formed between the casing body 2.

  The first seal 56 and the second seal 57 described above constitute seal means for preventing oil leakage in the casing 1 from the first position measuring device 50A portion inserted into the first measurement port 42A.

  Although the description is omitted, the second position measuring device 50B has the same configuration as the first position measuring device 50A shown in FIG. 3 described above.

  In the present embodiment configured as described above, the first pump 16A and the second pump 16B are used for the first measurement as shown in FIG. The first plug plug 43A and the second plug plug 43B are kept screwed into the port 42A and the second measurement port 42B, respectively. Therefore, the first measurement port 42A and the second measurement port 42B are sealed, and leakage of oil in the casing 1 from the first measurement port 42A and the second measurement port 42B is prevented.

  Further, by driving the rotary shaft 10, the first cylinder block 20A of the first pump 16A and the second cylinder block 20B of the second pump 16B rotate, and accordingly, the first shoe 24A of each first piston 23A, Each of the second shoes 24B of the second piston 23B slides on the first swash plate 28A and the second swash plate 28B, whereby the first cylinder 21A of the first cylinder block 20A and the second cylinder block 20B of the second cylinder block 20B. The low pressure oil is sucked into the two cylinders 21B from the suction ports of the first valve plate 17A and the second valve plate 17B, and the pressure oil that has become high pressure by the sliding of the first piston 23A and the second piston 23B The air is discharged from the discharge ports of the first valve plate 17A and the second valve plate 17B. The pressure oil discharged from the first pump 16A and the second pump 16B is supplied for driving each actuator such as a boom cylinder and an arm cylinder (not shown).

  Further, at the time of maintenance and inspection of the first pump 16A and the second pump 16B, for example, the first plug plug 43A and the second plug plug 43B shown in FIG. 1 are removed, and the first measurement port 42A as shown in FIG. The first position measuring device 50A is inserted, and the measuring rod 52 is held so that the end of the measuring rod 52 contacts the first feedback link 41A. Similarly, the second position measuring device is inserted into the second measuring port 42B. 50B is inserted, and the measuring rod is held so that the end of the measuring rod hits the second feedback link 41B.

  In such a state, the pressure of the pressure oil discharged from the first pump 16A and the second pump 16B, that is, not shown, individually provided in relation to each of the first pump 16A and the second pump 16B. The first pump 16A and the second pump 16B are driven until the respective pressure values of the pressure sensors become the first predetermined pressure.

  When the first predetermined pressure is reached, a value corresponding to the tilt angle of the first swash plate 28A of the first pump 16A is read by the scale 53 of the measuring rod 52 of the first position measuring device 50A. Similarly, a value corresponding to the tilt angle of the second swash plate 28B of the second pump 16B is read by the scale of the measuring rod of the second position measuring device 50B. The theory of the first pump 16A and the second pump 16B is based on the values read by the scale 53 of the measuring rod 52 of the first position measuring device 50A and the scale of the measuring rod of the second position measuring device 50B. The upper discharge flow rate is required.

  On the other hand, the first pump 16A set in advance from the pressure value of the pressure sensor provided in relation to the first pump 16A and the pressure value of the pressure sensor provided in relation to the second pump 16B. The flow rate actually discharged from the first pump 16A and the second pump 16B is obtained based on the pressure-flow rate characteristic specific to each of the second pumps 16B.

  If the theoretical discharge flow rate is compared with the actual discharge flow rate and the comparison result is within a predetermined flow rate error range, the first pump 16A and the second pump 16B are determined to be normal, and the predetermined flow rate error is determined. When the range is exceeded, it is determined that an abnormality has occurred in the corresponding one of the first pump 16A and the second pump 16B.

  In such a state, for example, in the state where the first pump 16A and the second pump 16B are driven so that each pressure value of the pressure sensor (not shown) is a second predetermined pressure higher than the first predetermined pressure. Is also performed.

  By the way, when manufacturing a tandem swash plate type hydraulic pump, normally, a large number of tandem swash plate type hydraulic pumps having the same configuration having the first measurement port 42A, the second measurement port 42B and the like shown in this embodiment are manufactured. Is done. Therefore, when measuring the position of the feedback link in order to detect the tilt angle of the swash plate related to another tandem swash plate type hydraulic pump having the same configuration, for example, the first position measuring device used in this embodiment. Both 50A and the second position measuring device 50B can be used for position measurement of the feedback link related to the other tandem swash plate hydraulic pump.

  As described above, according to the present embodiment, for example, a set of first position measurement is performed without providing a position measurement device for detecting the position of the feedback link in each of a plurality of tandem swash plate hydraulic pumps having the same configuration. By simply preparing the device 50A and the second position measuring device 50B, the positions of the respective feedback links 41A and second feedback links 41B provided in the tandem swash plate type hydraulic pump of the same configuration are measured. Can do. As a result, an increase in the manufacturing cost of each tandem swash plate hydraulic pump can be suppressed, and the cost for measuring the positions of the first feedback link 41A and the second feedback link 41B can be reduced.

  Further, since the first measurement port 42A and the second measurement port 42B may be formed so as to penetrate the wall portion of the casing main body 2, the first feedback link 41A and the first feedback link 41A can be formed without increasing the outer shape of the casing 1. 2 The position of the hood back link 41B can be measured, and the overall shape including the casing 1 can be reduced in size.

  In addition, as illustrated in FIG. 3, the present embodiment is configured such that the first position measurement device 50 </ b> A and the second position measurement device 50 </ b> B measure the position of the first feedback link 41 </ b> A and the second feedback link 41 </ b> B during the first operation. The sealing means such as the first seal 56 and the second seal 57 can prevent leakage of oil in the casing 1 from the first position measuring device 50A and the second position measuring device 50B, and the casing 1 during position measurement work. Loss due to oil spill to the outside and contamination by oil can be prevented.

  In the above-described embodiment, the position of the first feedback link 41A on the first pump 16A side, the second position measurement device 50A, the second position measurement device 50B, that is, the two position measurement devices are used. Although the position of the second feedback link 41B on the pump 16B side is measured simultaneously, the first feedback link 41A on the first pump 16A side is simply used by using only one position measuring device, for example, the first position measuring device 50A. And the position of the second feedback link 41B on the second pump 16B side can also be detected.

  In addition, even between variable displacement swash plate hydraulic pumps having different internal configurations, for example, measurement ports having the same diameter are formed in each casing at least between hydraulic pumps having feedback links. Thus, the position measuring device inserted into these measuring ports can also be used.

  That is, in the above embodiment, the tandem swash plate hydraulic pump having the two pumps of the first pump 16A and the second pump 16B in the casing 1 has been described. However, the present invention is such a tandem swash plate type. Not limited to hydraulic pumps. For example, the present invention can also be applied to a configuration including only one variable displacement swash plate hydraulic pump.

  Moreover, in the above, as illustrated in FIG. 3, the scale 53 such as the measuring rod 52 of the first position measuring device 50A or the like has a value corresponding to the tilt angle of the first swash plate 28A or the like. However, instead of the tilt angle, a value indicating the displacement determined from the tilt angle may be set in the scale 53 or the like.

  Further, in the above, as shown in FIG. 3, the first position measuring device 50 </ b> A or the like is configured to have a measuring rod 52 or the like on which a scale 53 or the like that can be visually checked by an operator is formed. The measurement device is not limited to such a configuration. Instead of the first position measuring device 50A and the like illustrated in FIG. 3, the contact type is used in contact with the first feedback link 41A or the second feedback link 41B, and these first feedback links are used. 41A, a position measuring device capable of outputting an electrical signal corresponding to the position of the second feedback link 41B, that is, a stroke sensor, is inserted into each of the first measuring port 42A and the second measuring port 42B formed in the casing body 2. You may make it make it. In addition, a position measuring device that is a non-contact type and can output an electrical signal corresponding to the position of the first feedback link 41A and the second feedback link 41B is represented by a first measurement port 42A and a second measurement port. You may make it insert in each of 42B.

  Further, in the above description, as means for closing the first measurement port 42A and the second measurement port 42B, the screw portions that are screwed into the screw portions formed in the first measurement port 42A and the second measurement port 42B, respectively. Although the first plug plug 43A and the second plug plug 43B are provided, the closing means is not limited to the first plug plug 43A and the second plug plug 43B. For example, the closing means may be constituted by a closing tool having a flange portion that is fastened to the casing body 2 with a bolt and thereby closes the first measurement port 42A and the second measurement port 42B.

1 is a cross-sectional view showing an embodiment of a variable displacement swash plate hydraulic pump according to the present invention. It is sectional drawing which shows the state which mounted | wore the position measuring apparatus with one Embodiment shown in FIG. It is an expanded sectional view which shows the structure of the position measuring apparatus shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Casing 2 Casing main body 10 Rotating shaft 16A 1st pump 16B 2nd pump 20A 1st cylinder block 20B 2nd cylinder block 21A 1st cylinder 21B 2nd cylinder 23A 1st piston 23B 2nd piston 24A 1st shoe 24B 2nd shoe 28A First swash plate 28B Second swash plate 33A First tilt actuator 33B Second tilt actuator 41A First feedback link 41B Second feedback link 42A First measurement port 42B Second meter side port 43A First plug plug (Blocking means)
43B Second plug (blocking means)
50A First position measuring device 50B Second position measuring device 51 Case 52 Measuring rod 53 Scale 54 Spring receiver 55 Spring 56 First seal (sealing means)
57 Second seal (sealing means)

Claims (5)

A casing, a cylinder block that is rotatably provided in the casing and has a plurality of cylinders drilled along the circumferential direction, a rotary shaft that rotates the cylinder block, and a reciprocating motion to each cylinder of the cylinder block A plurality of pistons housed in the housing, a swash plate having a sliding surface on which a shoe attached to the end of these pistons slides, and provided in a tiltable manner in the casing; A variable capacity swash plate type including a tilt actuator that drives to tilt, and a feedback mechanism that transmits a value corresponding to the tilt angle of the swash plate to a regulator, the feedback mechanism including a feedback link that engages the swash plate In the hydraulic pump,
In the casing, forming a measurement port capable of inserting a position measuring device for measuring the position of the feedback link,
A variable displacement swash plate type hydraulic pump comprising a closing means for closing the measurement port when the position measuring device is not inserted into the measurement port. In the invention of claim 1,
A variable displacement swash plate hydraulic pump characterized in that the extending direction of the measuring port is set to a direction intersecting with the moving direction of the tilting actuator in a plan view. In the invention of claim 2,
A variable displacement swash plate hydraulic pump characterized in that an extending direction of the measurement port is set in a direction along a moving direction of the feedback link. A casing, a cylinder block that is rotatably provided in the casing and has a plurality of cylinders drilled along the circumferential direction, a rotary shaft that rotates the cylinder block, and a reciprocating motion to each cylinder of the cylinder block A plurality of pistons housed in the housing, a swash plate having a sliding surface on which a shoe attached to the end of these pistons slides, and provided in a tiltable manner in the casing; A variable capacity swash plate type including a tilt actuator that drives to tilt, and a feedback mechanism that transmits a value corresponding to the tilt angle of the swash plate to a regulator, the feedback mechanism including a feedback link that engages the swash plate In the hydraulic pump,
A position measuring device for measuring the position of the feedback link is inserted into a measuring port formed in the casing, and seal means for preventing leakage of oil in the casing from the position measuring device portion is provided. Variable displacement swash plate hydraulic pump. In the invention according to any one of claims 1 to 4,
A variable displacement swash plate type hydraulic pump comprising a tandem swash plate type hydraulic pump having a first pump and a second pump driven by the rotating shaft in the casing.

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