JP7051475B2 - Hydraulic pump - Google Patents

Description

The present invention relates to a hydraulic pump used for a construction vehicle or the like, and more particularly to a variable displacement hydraulic pump.

Variable capacity hydraulic pumps are used in a wide range of fields such as construction vehicles. Variable displacement hydraulic pumps generally have a cylinder block with multiple cylinder holes that rotate around the axis of rotation and extend along the axis of rotation, and a piston that is slidably held in each cylinder hole. And, in order to change the tilt angle (tilt angle) of the swash plate for sliding each piston in each cylinder hole and the swash plate with respect to the rotation axis of the cylinder block by rotating the cylinder block around the rotation axis. It has a mechanism of.

For example, Patent Document 1 discloses a variable capacity type swash plate hydraulic pump in which the discharge capacity is adjusted by changing the tilt angle of the swash plate. The hydraulic pump disclosed in Patent Document 1 includes a cylinder block that rotates around a swash plate, a piston that is slidably held in each cylinder hole formed in the cylinder block, and a tilt angle that can be changed. The swash plate, the first urging means for urging the swash plate in the direction in which the tilt angle of the swash plate is large, and the second urging means for urging the swash plate in the direction in which the tilt angle of the swash plate is small. The second urging means has a means, and the second urging means has an urging rod and a plurality of urging pins, and each urging pin is urged according to the signal pressure corresponding to each urging pin. The swash plate is urged through the rod. Such a hydraulic pump has an advantage that the tilt angle of the swash plate can be adjusted by a simple mechanism.

Japanese Unexamined Patent Publication No. 2018-3609

In the technique disclosed in Patent Document 1, the signal pressure generated by the control valve in response to the lever operation of the operator is input to the second pressure chamber formed in the urging pin unit. The urging piston is urged by the signal pressure input to the second pressure chamber, and the fourth urging pin is urged toward the urging rod by the urging piston. As a result of diligent studies by the present inventors on such a mechanism, a hydraulic pump having such a mechanism has a cross-sectional area larger than the cross-sectional area of the urging pin and has a relatively large component size. It was found that it is difficult to miniaturize the urging pin unit because a piston is required, and there is a limit to the miniaturization and weight reduction of the entire hydraulic pump.

Further, in the technique disclosed in Patent Document 1, the signal pressure generated by the control valve in response to the lever operation of the operator is radially from the center of the rear end surface of the urging rod via the fourth urging pin. It acts on the displaced position. Due to this, the urging rod urged by the signal pressure may generate a moment of rotation about an axis orthogonal to the longitudinal direction of the urging rod. Due to this moment, the urging rod is pressed against the first guide portion, and a relatively large friction is generated between the urging rod and the first guide portion. As a result, the urging rod and the first guide portion may be worn, and the operation of the urging rod may become unstable. Further, due to friction between the urging rod and the first guide portion, even though the same signal pressure is input to the second pressure chamber, the movement toward the swash plate side and the swash plate There is a possibility that so-called hysteresis occurs, in which the position of the urging rod differs between when moving toward the opposite side. This may also cause the operation of the urging rod to become unstable.

The present invention has been made in consideration of such a point, and an object of the present invention is to provide a hydraulic pump capable of stable operation while suppressing an increase in size.

The hydraulic pump according to the present invention
A cylinder block that rotates around the axis of rotation and has a plurality of cylinder holes formed therein.
A piston that is slidably held in each cylinder hole,
A swash plate for sliding each piston in each cylinder hole by rotating the cylinder block around the rotation axis, and a swash plate configured so that the tilt angle can be changed.
A first urging means for urging the swash plate in a direction in which the tilt angle of the swash plate increases,
It has a second urging means for urging the swash plate in a direction in which the tilt angle of the swash plate becomes smaller.
The second urging means has an urging rod for urging the swash plate.
At least one of the flow rate control signal pressure and the horsepower shift signal pressure acts on the end surface of the urging rod opposite to the swash plate.

In the hydraulic pump of the present invention
The flow rate control signal pressure may act on the end face.

In the hydraulic pump of the present invention
The flow control signal pressure may be a negative flow control signal pressure.

In the hydraulic pump of the present invention
The flow control signal pressure or the horsepower shift signal pressure may act on the end face via an orifice.

In the hydraulic pump of the present invention
The flow control signal pressure or the horsepower shift signal pressure may act on the end face via a slow return mechanism.

In the hydraulic pump of the present invention
The flow rate control signal pressure or the horsepower shift signal pressure may be a signal pressure in which an electric signal is converted into hydraulic pressure by an electromagnetic proportional valve.

In the hydraulic pump of the present invention
A signal pressure having a relatively high pressure among the flow rate control signal pressure and the horsepower shift signal pressure may act on the end face.

In the hydraulic pump of the present invention
Further having a guide portion for guiding the side surface of the urging rod,
Pressure oil from another pump may be supplied between the side surface and the guide portion.

In the hydraulic pump of the present invention
The guide portion is provided with a supply hole for supplying pressure oil from the other pump between the side surface and the guide portion.
An oil holding groove for holding the pressure oil supplied from the supply hole is provided on the side surface.
The oil holding groove may face the supply hole at any position during the advancing / retreating operation along the guide portion of the urging rod.

In the hydraulic pump of the present invention
The second urging means further comprises an urging pin.
The urging pin may urge the swash plate via the urging rod according to the signal pressure corresponding to the urging pin.

According to the present invention, it is possible to provide a hydraulic pump capable of stable operation while suppressing an increase in size.

FIG. 1 is a diagram for explaining one embodiment according to the present invention, and is a diagram showing a cross section of a hydraulic pump. FIG. 2 is a diagram showing a cross section of the urging pin unit of the hydraulic pump, and is a diagram showing a cross section corresponding to the line II-II of FIG. FIG. 3 is a diagram showing a modified example of the hydraulic pump. FIG. 4 is a diagram showing another modification of the hydraulic pump. FIG. 5 is a diagram showing still another modification of the hydraulic pump. FIG. 6 is a diagram showing still another modification of the hydraulic pump. FIG. 7 is a diagram showing still another modification of the hydraulic pump. FIG. 8 is a diagram showing still another modification of the hydraulic pump. FIG. 9 is a diagram showing still another modification of the hydraulic pump, showing the positional relationship between the urging rod and the lubricating oil supply hole when the urging rod is located on the side opposite to the swash plate. It is a figure. FIG. 10 is a diagram showing the positional relationship between the urging rod and the supply hole when the urging rod of FIG. 9 is located closest to the swash plate side. FIG. 11 is a cross-sectional view showing still another modification of the hydraulic pump. FIG. 12 is a cross-sectional view showing still another modification of the hydraulic pump.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings attached to the present specification, the scale and the aspect ratios are appropriately changed and exaggerated from those of the actual product for the convenience of illustration and comprehension.

In addition, the terms such as "parallel", "orthogonal", and "identical" and the values of length and angle, etc., which specify the shape and geometric conditions and their degrees as used in the present specification, are strictly referred to. Without being bound by the meaning, we will interpret it including the range where similar functions can be expected.

1 to 11 are diagrams for explaining one embodiment according to the present invention. Of these, FIG. 1 is a diagram showing a cross section of the hydraulic pump.

The hydraulic pump 10 of the present embodiment is a so-called swash plate type variable displacement hydraulic pump. The hydraulic pump 10 outputs a driving force based on the discharge of the hydraulic oil from the cylinder hole 32 (and the supply of the hydraulic oil to the cylinder hole 32), which will be described later. More specifically, by rotating the rotary shaft 25 by the power from a power source such as an engine, the cylinder block 30 coupled to the rotary shaft 25 by spline coupling or the like is rotated, and the piston is rotated by the rotation of the cylinder block 30. 38 is reciprocated. In response to the reciprocating operation of the piston 38, hydraulic oil is discharged from some of the cylinder holes 32 and hydraulic oil is sucked into the other cylinder holes 32 to realize a hydraulic pump.

The hydraulic pump 10 shown in FIG. 1 has a housing 20, a rotary shaft 25, a cylinder block 30, a swash plate 40, a first urging means 50, and a second urging means 60. Further, the hydraulic pump 10 shown in FIG. 1 is equipped with a gear pump 14 as an example of another pump described later.

The housing 20 has a first housing block 21 and a second housing block 22 connected to the first housing block 21 by a fastening means (not shown) or the like. The housing 20 houses a part of the rotating shaft 25, a cylinder block 30, a swash plate 40, and a first urging means 50. In the example shown in FIG. 1, inside the first housing block 21, one end of a rotating shaft 25 and a supply port and a discharge port (not shown) communicating with a plurality of cylinder holes 32 via a suction / discharge plate 35. A first guide portion (guide portion) 23 for guiding the urging rod 61, which will be described later, is arranged. Further, the supply port is provided so as to penetrate the first housing block 21 and communicates with a hydraulic source (tank) provided outside the hydraulic pump 10.

A rotation shaft hole 24a into which the rotation shaft 25 is inserted is formed in the first housing block 21, and the rotation shaft 25 is rotatably supported around the rotation axis A by a bearing 28a in the rotation shaft hole 24a. .. The rotation axis A extends along the longitudinal direction of the rotation shaft 25. One end of the rotary shaft 25 is located in the rotary shaft hole 24a and is connected to the rotary shaft 16 of the gear pump 14 via a spline coupling portion 26a formed at the one end.

The second housing block 22 is formed with a rotation shaft hole 24b through which the rotation shaft 25 penetrates, and the rotation shaft 25 extends from one end to the other end through the cylinder block 30 and the swash plate 40. There is. The rotary shaft 25 is rotatably supported around the rotary axis A by a bearing 28b arranged in the rotary shaft hole 24b at the other end. In the illustrated example, the other end of the rotary shaft 25 projects outward from the rotary shaft hole 24b and is connected to a power source such as an engine via a spline coupling portion 26b formed at the other end. To.

In the example shown in FIG. 1, the rotary shaft 25 is spline-coupled to the cylinder block 30 at a spline coupling portion 26c provided in a portion penetrating the cylinder block 30. The rotary shaft 25 can move independently of the cylinder block 30 in the direction of the rotary axis A due to the spline coupling with the cylinder block 30, but rotates integrally with the cylinder block 30 in the rotary direction around the rotary axis A. do. Further, the rotary shaft 25 is rotatably supported by the bearing 28a in the first housing block 21 and rotatably supported in the second housing block 22 via the bearing 28b so as not to come into contact with the swash plate 40. ing. Therefore, the rotary shaft 25 is provided so as to be rotatable in the rotational direction around the rotary axis A together with the cylinder block 30 without being hindered by members other than the cylinder block 30.

A gear pump (another pump) 14 is attached to the hydraulic pump 10 of the present embodiment. The gear pump 14 is coupled to the first housing block 21 of the hydraulic pump 10 on the opposite side of the second housing block 22 along the rotation axis A by a fastening means (not shown) or the like. In the example shown in FIG. 1, the gear pump 14 has a rotary shaft 16. The rotation shaft 16 is rotatably arranged around the rotation axis A. That is, the rotation axis 25 and the rotation axis 16 share the rotation axis A. As described above, one end of the rotary shaft 25 is connected to the rotary shaft 16 of the gear pump 14 via a spline coupling portion 26a formed at the one end. Specifically, one end of the rotary shaft 25 and the sleeve 18 are connected via a spline coupling portion 26a, and the rotary shaft 16 and the sleeve 18 are connected via a spline coupling portion 17a formed on the rotary shaft 16. It is connected.

When the rotary shaft 25 connected to the power source of the engine or the like rotates by the driving force from the power source, the rotary shaft 25 and the rotary shaft 16 rotate integrally around the rotary axis A. As a result, pressure oil is supplied from the gear pump 14 to each part of the hydraulic pump 10 and the work machine or the like in which the gear pump 14 is incorporated at a constant pressure. In particular, in the present embodiment, as will be described later, a part of the pressure oil discharged from the gear pump 14 is supplied between the side surface 61c of the urging rod 61 and the first guide portion 23 that guides the side surface 61c. It is supplied via the line L. Since the gear pump 14 can be configured in the same manner as a known gear pump, the description of its specific configuration will be omitted.

The cylinder block 30 rotates about the rotation axis A together with the rotation axis 25, and has a plurality of cylinder holes 32 formed around the rotation axis A. In particular, in the example shown in FIG. 1, each cylinder hole 32 is provided so as to extend in a direction parallel to the rotation axis A. Not limited to this, the cylinder hole 32 may be provided so as to extend along a direction inclined with respect to the rotation axis A. The number of the plurality of cylinder holes 32 formed in the cylinder block 30 is not particularly limited, but these cylinder holes 32 are equally spaced (equally spaced) on the same circumference when viewed from the direction along the rotation axis A. It is preferable to arrange at.

An opening 32a communicating with each of the plurality of cylinder holes 32 is formed at the end of the cylinder block 30 on the side opposite to the side on which the swash plate 40 is provided. Further, a suction / exhaust plate 35 having a plurality of through holes (not shown) is arranged facing the end of the cylinder block 30 on the side opposite to the side on which the swash plate 40 is provided. The plurality of cylinder holes 32 communicate with supply ports and discharge ports (not shown) provided in the first housing block 21 through these openings 32a and through holes, and operate through these supply ports and discharge ports. Oil is supplied and discharged. Further, in the example shown in FIG. 1, the spring 44 and the retainers 45a and 45b described later are accommodated around the rotation shaft 25 at the end of the cylinder block 30 opposite to the side on which the swash plate 40 is provided. A recess 30a is formed.

The suction / exhaust plate 35 shown in FIG. 1 is fixed to the first housing block 21, and even when the cylinder block 30 rotates together with the rotating shaft 25, the suction / exhaust plate 35 is relative to the housing 20 (first housing block 21). It is stationary. Therefore, the cylinder hole 32 communicating with each of the supply port and the discharge port is switched via the suction / exhaust plate 35 according to the rotation state of the cylinder block 30, and operates in the state where the hydraulic oil is supplied from the supply port and in the discharge port. The state of discharging oil repeatedly comes.

The pistons 38 are slidably arranged with respect to the corresponding cylinder holes 32. In other words, the piston 38 is slidably held in the corresponding cylinder hole 32. In particular, each piston 38 is provided so as to be reciprocating along a direction parallel to the rotation axis A with respect to the corresponding cylinder hole 32. The inside of the piston 38 is hollow and is filled with the hydraulic oil in the cylinder hole 32. Therefore, the reciprocating movement of the piston 38 is linked to the supply and discharge of the hydraulic oil to the cylinder hole 32, and when the piston 38 is pulled out from the cylinder hole 32, the hydraulic oil is supplied into the cylinder hole 32 from the supply port and the piston. When the 38 enters the cylinder hole 32, the hydraulic oil is discharged from the inside of the cylinder hole 32 to the discharge port.

In the present embodiment, the shoe 43 is attached to the end of each piston 38 on the swash plate 40 side (the end on the side protruding from the cylinder hole 32). Further, a spring 44, retainers 45a and 45b, a connecting member 46, a pressing member 47 and a shoe holding member 48 are provided around the rotating shaft 25. The spring 44 and the retainers 45a and 45b are housed in a recess 30a formed around a rotating shaft 25 at an end of the cylinder block 30 opposite to the side on which the swash plate 40 is provided. In the example shown in FIG. 1, the spring 44 is a coil spring and is arranged in the recess 30a in a compressed state between the retainer 45a and the retainer 45b. Therefore, the spring 44 generates an urging force in the direction in which the spring 44 extends due to its elastic force. The urging force of the spring 44 is transmitted to the pressing member 47 via the retainer 45b and the connecting member 46. Each shoe 43 is held by the shoe holding member 48, and the pressing member 47 receives the urging force of the spring 44 and presses each shoe 43 toward the swash plate 40 via the shoe holding member 48.

In the example shown in FIG. 1, the swash plate 40 can be tilted at various angles, but due to the urging force of the spring 44, each shoe 43 with respect to the swash plate 40 regardless of the tilt angle of the swash plate 40. It is properly followed and pressed. As a result, when the piston 38 rotates together with the cylinder block 30, each shoe 43 slides on the swash plate 40 in a circular orbit. In the illustrated example, the end portion of the piston 38 on the swash plate 40 side forms a spherical convex portion, and the convex portion of the piston 38 is fitted into the spherical concave portion formed in the shoe 43, and the concave portion of the shoe 43. It is crimped to form a spherical bearing structure with a piston 38 and a shoe 43. Due to this spherical bearing structure, even if the tilt angle of the swash plate 40 changes, each shoe 43 can appropriately slide and rotate on the swash plate 40 following the tilt of the swash plate 40.

The swash plate 40 is for sliding each piston 38 in each cylinder hole 32 by rotating the cylinder block 30 around the rotation axis A. The swash plate 40 has a flat sliding surface 41 on the side facing the cylinder block 30, and a shoe 43 connected to the end of the piston 38 on the swash plate 40 side is pressed against the sliding surface 41. There is. Further, the swash plate 40 is provided so as to be tiltable, and the reciprocating stroke of the piston 38 changes according to the tilt angle of the swash plate 40 (sliding surface 41). That is, the larger the tilt angle of the swash plate 40 (sliding surface 41), the larger the supply amount and the discharge amount of the hydraulic oil to the cylinder hole 32 due to the reciprocating movement of each piston 38, and the swash plate 40 (sliding surface 41). ), The smaller the tilt angle, the smaller the supply amount and discharge amount of hydraulic oil to the cylinder hole 32 due to the reciprocating movement of each piston 38. Here, the tilt angle of the swash plate 40 (sliding surface 41) means an angle formed by the plate surface (sliding surface 41) of the swash plate 40 with respect to a virtual plane orthogonal to the rotation axis A. There is. When the tilt angle is 0 degrees, each piston 38 does not reciprocate even if the cylinder block 30 rotates around the rotation axis A, and the amount of hydraulic oil discharged from each cylinder hole 32 becomes zero. In the example shown in FIG. 1, the swash plate 40 comes into contact with the stopper 27 provided on the second housing block 22 as the tilt angle thereof is reduced. The stopper 27 is configured to be able to advance and retreat with respect to the swash plate 40. Thereby, the minimum tilt angle of the swash plate 40 can be appropriately adjusted by advancing and retreating the stopper 27 with respect to the swash plate 40. Further, the swash plate 40 has an abutting surface 42 on the outside of the sliding surface 41 to which the urging rod 61 described later abuts and receives the urging force from the urging rod 61. In the illustrated example, the contact surface 42 is provided so as to be parallel to the sliding surface 41.

The first urging means 50 urges the swash plate 40 in a direction in which the tilt angle of the swash plate 40 increases. In the example shown in FIG. 1, the first urging means 50 has a first retainer 51 arranged on the side opposite to the swash plate 40 (first housing block 21 side) and a swash plate 40 side (second housing block). It has a second retainer 52 arranged on the 22 side) and springs 54 and 55 arranged between the first retainer 51 and the second retainer 52. The first spring 54 is arranged in a compressed state between the first retainer 51 and the second retainer 52. Therefore, the elastic force of the first spring 54 generates an urging force in the direction in which the first spring 54 extends. The second spring 55 is arranged inside the first spring 54. Therefore, the winding diameter of the second spring 55 is formed to be smaller than the winding diameter of the first spring 54.

In the example shown in FIG. 1, the second spring 55 is fixed to the second retainer 52 and is separated from the first retainer 51 in a state where the tilt angle of the swash plate 40 is large (see FIG. 1). As a result, while the tilt angle of the swash plate 40 is large, only the urging force of the first spring 54 acts on the swash plate 40. As the tilt angle of the swash plate 40 becomes smaller, the second spring 55 comes into contact with the first retainer 51 at a certain tilt angle. Further, when the tilt angle of the swash plate 40 becomes smaller, the second spring 55 is also compressed between the first retainer 51 and the second retainer 52, whereby the swash plate 40 has the first spring 54 and the second spring. Both of the 55 urging forces act. Therefore, according to the illustrated first urging means 50, the urging force can be changed stepwise according to the tilt angle of the swash plate 40. The second spring 55 is not limited to the one fixed to the second retainer 52, but may be fixed to the first retainer 51, or may be fixed to either the first retainer 51 or the second retainer 52. Instead, it may be movable between the first retainer 51 and the second retainer 52. In the illustrated example, the separation distance of the first retainer 51 with respect to the second retainer 52 is made adjustable by advancing and retreating the adjuster 57 toward the first retainer 51. Thereby, the initial urging force of the first urging means 50, particularly the initial urging force of the first urging means 50 by the first spring 54 can be appropriately adjusted.

The second urging means 60 causes the swash plate 40 to exert an urging force in the direction opposite to the urging force of the first urging means 50 on the swash plate 40. In particular, the second urging means 60 is inclined in a direction in which the tilt angle of the swash plate 40 becomes smaller against the urging force of the first urging means 50 in the direction in which the tilt angle of the swash plate 40 becomes larger. Encourage the plate 40. In the example shown in FIG. 1, the second urging means 60 has an urging rod 61 and an urging pin unit 70. The urging rod 61 is urged toward the swash plate 40 by the signal pressure P input (introduced) to the first pressure chamber 81 formed between the urging rod 61 and the urging pin unit 70. The swash plate 40 is tilted around its tilt axis. The urging pin unit 70 has a unit case 76 and a plurality of first urging pins 71. Each first urging pin 71 urges the urging rod 61 toward the swash plate 40 according to the signal pressure corresponding to each first urging pin 71. In other words, each first urging pin 71 urges the swash plate 40 via the urging rod 61 according to the signal pressure corresponding to each first urging pin 71.

In the example shown in FIG. 1, the urging rod 61 has a substantially columnar shape as a whole, and is attached to the contact surface 42 of the swash plate 40 so that its axis is parallel to the rotation axis A. It is arranged between each first urging pin 71 of the swash pin unit 70. The urging rod 61 is not limited to the one whose axis is arranged so as to be parallel to the rotation axis A, and the urging rod 61 may be arranged so that its axis is inclined with respect to the rotation axis A. The urging rod 61 includes a front end surface 61a facing the swash plate 40 (contact surface 42), a rear end surface (end surface) 61b formed on the opposite side of the front end surface 61a along the axis of the urging rod 61, and a front end surface. It has a side surface 61c that connects the 61a and the rear end surface 61b. In the illustrated example, the tip surface 61a has a spherical shape. As a result, even if the angle formed by the swash plate 40 (contact surface 42) and the urging rod 61 changes due to the change in the tilt angle of the swash plate 40, the urging force against the swash plate 40 is applied to the tip surface 61a. Can be appropriately transmitted to the contact surface 42. Further, the rear end surface 61b of the urging rod 61 has a flat surface orthogonal to the axis of the urging rod 61. The rear end surface 61b may have a shape that can function as an action surface on which the signal pressure P acts, and the specific shape thereof is not particularly limited. The rear end surface 61b may have a flat surface inclined with respect to the axis of the urging rod 61, or may include a curved surface. For example, the rear end surface 61b has a spherical shape protruding from the urging rod 61, a spherical shape recessed toward the urging rod 61, a wavy shape, a shape combining a plurality of flat surfaces, a shape combining a plurality of curved surfaces, and a flat surface. The shape may be a combination of a curved surface and a curved surface, a shape including a step portion, or the like.

The first housing block 21 (housing 20) is provided with a first guide portion (guide portion) 23 for guiding the side surface 61c of the urging rod 61, and the urging rod 61 is provided with the first guide portion 23. It is slidably arranged with respect to. Therefore, a part of the urging rod 61 is slidably held in the first guide portion 23. The first guide portion 23 is composed of a through hole provided in the first housing block 21 and has a cross-sectional shape complementary to the cross-sectional shape of the urging rod 61. That is, the first guide portion 23 is composed of a cylindrical through hole having a circular cross section. In the example shown in FIG. 1, the first guide portion 23 is provided integrally with the first housing block 21 (housing 20). When the first guide portion 23 is provided integrally with the first housing block 21, the first guide portion 23 can be formed by drilling the first housing block 21, and the first guide portion can be formed by simple processing. It becomes possible to form 23. Further, since no additional member is required to provide the first guide portion 23, it contributes to the reduction of the number of parts of the hydraulic pump 10 and the cost reduction. The configuration of the first guide unit 23 is not limited to this. As an example, a first guide portion 23 formed by using a member, which is different from the first housing block 21, for example, a cylindrical shape, may be attached to the housing 20.

The first housing block 21 (housing 20) is formed with a concave portion 29 communicating with the first guide portion 23, and the convex portion 78 of the urging pin unit 70 is fitted into the concave portion 29.

When the swash plate 40 is urged by the urging rod 61, the reaction force from the swash plate 40 may act on the urging rod 61 in a direction inclined with respect to the axial direction of the urging rod 61. .. Since the hydraulic pump 10 of the present embodiment has the above-mentioned first guide portion 23, a force in a direction inclined with respect to the axial direction of the urging rod 61 acts on the urging rod 61. However, since the first guide portion 23 can appropriately hold the urging rod 61, the urging rod 61 can be operated stably.

In the example shown in FIG. 1, pressure oil from another pump is supplied between the side surface 61c of the urging rod 61 and the first guide portion 23. In the illustrated example, the gear pump 14 attached to the hydraulic pump 10 is used as another pump. The pressure oil is supplied from the gear pump 14 into the first guide portion 23 through the supply line L. As an example, the supply line L can be a passage that passes through the inside of the gear pump 14 and the housing 20 (first housing block 21) and opens to the first guide portion 23. The other pump may be a hydraulic pump arranged independently of the hydraulic pump 10, or may be a hydraulic pump other than the gear pump.

The pressure oil supplied from the other pump functions as a lubricating oil that reduces the frictional resistance between the side surface 61c and the first guide portion 23. In the technique disclosed in Patent Document 1, oil held in the housing or in the recess of the first housing block is supplied to the side surface of the urging rod, whereby the side surface of the urging rod and the first guide portion are connected to each other. Lubrication was done between them. In the present embodiment, the pressure oil discharged from another pump is forcibly supplied between the side surface 61c and the first guide portion 23 at a predetermined pressure, so that the side surface 61c and the first guide are more effectively supplied. Lubrication with the portion 23 can be performed. In particular, in the technique disclosed in Patent Document 1, when the urging rod starts to move, the urging rod does not move even if the urging force by the urging pin starts to be generated, and the urging force by the urging pin becomes large. The urging rod suddenly started to move. As a result, the tilt angle of the swash plate changes abruptly, and there is a risk that the pressure oil cannot be stably discharged by the hydraulic pump. On the other hand, in the present embodiment, the pressure oil discharged from another pump is forcibly supplied between the side surface 61c and the first guide portion 23 at a predetermined pressure, so that the urging rod 61 Can be smoothly moved, and the pressure oil can be stably discharged by the hydraulic pump 10.

Further, in the technique disclosed in Patent Document 1, the urging force by each urging pin acts at a position radially deviated from the center on the rear end surface of the urging rod. Due to this, the urging rod urged by the urging force may generate a moment of rotation about an axis orthogonal to the longitudinal direction of the urging rod. Due to this moment, the urging rod is pressed against the first guide portion, and a relatively large friction is generated between the urging rod and the first guide portion. As a result, even though the same signal pressure is input to the first pressure chamber and the second pressure chamber, the urging rod is moving toward the swash plate side and moving toward the opposite side of the swash plate. There is a possibility that so-called hysteresis, which is in a different position, may occur. On the other hand, in the present embodiment, the pressure oil discharged from another pump is forcibly supplied between the side surface 61c and the first guide portion 23 at a predetermined pressure, whereby the urging rod 61 It is possible to reduce the friction that may occur between the side surface 61c of the above and the first guide portion 23, and to suppress the occurrence of hysteresis with respect to the position of the urging rod 61.

An oil holding groove 65 for holding pressure oil supplied from another pump is provided on the side surface 61c of the urging rod 61. In the example shown in FIG. 1, the oil holding groove 65 has a predetermined width in the longitudinal direction (axial direction) of the urging rod 61, a predetermined depth in the radial direction, and is along the side surface 61c. It is formed over the entire circumference in the circumferential direction. In other words, the urging rod 61 has a small diameter portion whose diameter is relatively narrow, and a diameter larger than the diameter of the small diameter portion adjacent to the tip side (tip surface 61a side) of the small diameter portion along the longitudinal direction. It has a first large diameter portion having a second large diameter portion adjacent to the rear end side (rear end surface 61b side) of the small diameter portion along the longitudinal direction and having a diameter larger than the diameter of the small diameter portion. There is. In the illustrated example, the diameter of the first large diameter portion and the diameter of the second large diameter portion are the same. The depth of the oil holding groove 65 along the radial direction can be 0.5 mm or more and 1.5 mm or less as an example. Since the urging rod 61 has such an oil holding groove 65, a cylindrical gap is formed between the urging rod 61 and the first guide portion 23, and a cylindrical gap is formed in this gap from another pump. It becomes possible to hold the supplied pressure oil. As a result, the lubricating oil is stably and uniformly supplied from the oil holding groove 65 between the first large diameter portion and the first guide portion 23 and between the second large diameter portion and the first guide portion 23. Can be supplied. Therefore, the urging rod 61 can be operated stably and smoothly. The specific shape of the oil holding groove 65 is not limited to the shape shown in FIG.

The surface of the urging rod 61 may be surface-treated in order to suppress wear of the urging rod 61 and the like. When the tip surface 61a of the urging rod 61 is surface-treated, the frictional resistance between the tip surface 61a and the contact surface 42 of the swash plate 40 is reduced, and the tip surface 61a and the contact surface 42 are worn away. It can be suppressed. When the side surface 61c of the urging rod 61 is surface-treated, the frictional resistance between the side surface 61c and the first guide portion 23 can be reduced, and the wear of the side surface 61c and the first guide portion 23 can be suppressed. .. Further, when the rear end surface 61b of the urging rod 61 is surface-treated, it is possible to suppress the wear of the rear end surface 61b and the first urging pin 71 and the adjusting pin 73 that come into contact with the rear end surface 61b. Such surface treatment can be performed, for example, by forming an amorphous carbon film on the surface of the urging rod 61.

A first pressure chamber 81 is formed between the urging rod 61 and the urging pin unit 70. More specifically, the space located between the rear end surface 61b of the urging rod 61 and the urging pin unit 70 is the first pressure chamber 81. A signal pressure P, which is at least one of a flow rate control signal pressure and a horsepower shift signal pressure, is input to the first pressure chamber 81. As a result, the signal pressure P acts on the rear end surface 61b of the urging rod 61. In particular, the signal pressure P acts directly on the rear end surface 61b of the urging rod 61. Here, "acting directly" means that the signal pressure P acts on the rear end surface 61b of the urging rod 61 without interposing another member such as an urging pin.

The flow rate control signal pressure is a signal pressure generated in response to a lever operation by an operator who operates a work machine or the like in which the hydraulic pump 10 is incorporated. More specifically, the flow rate control signal pressure is a signal pressure generated in response to the operation of the control valve in response to the lever operation by the operator. For example, in the negative flow rate control (negative control) mechanism, an orifice is provided between the control valve and the tank in the center bypass line from the variable displacement hydraulic pump to the tank via the control valve. Then, the leakage flow rate of the pressure oil passing through the orifice is detected as the back pressure of the orifice, and the detected back pressure is fed back to the variable displacement hydraulic pump as a negative flow rate control signal pressure. As an example, this negative flow rate control signal pressure can be input to the first pressure chamber 81 as the flow rate control signal pressure.

It is also possible to use the load sensing (LS) flow rate control signal pressure as the flow rate control signal pressure. When the flow rate reduction signal pressure from the load sensing flow rate control mechanism is input into the first pressure chamber 81, the urging rod 61 is urged toward the swash plate 40, and the tilt angle of the swash plate 40 becomes smaller. .. As a result, the amount of pressure oil discharged from the hydraulic pump 10 is reduced.

The horsepower shift signal pressure is a signal pressure for reducing (shifting) the maximum discharge flow rate of the pressure oil from the hydraulic pump 10. For example, when a work machine or the like in which a hydraulic pump 10 is incorporated is used at a high altitude, the amount of oxygen contained in the atmosphere is small, so that the driving force output from a power source such as an engine is reduced. If the tilt angle of the swash plate 40 is maximized so that the pressure oil is discharged from the hydraulic pump 10 at the maximum discharge flow rate in this state, a high load is applied to the power source and the power source may stall. In order to prevent this, in a place with a high altitude, a horsepower shift signal pressure is input to the first pressure chamber 81 to shift the maximum tilt angle of the swash plate 40 to a small size, and the maximum discharge of pressure oil from the hydraulic pump 10 is performed. The flow rate can be reduced.

Only one of the flow control signal pressure and the horsepower shift signal pressure may be input to the first pressure chamber 81, or both the flow control signal pressure and the horsepower shift signal pressure are input to the first pressure chamber 81. May be good.

As described above, by allowing at least one of the flow rate control signal pressure and the horsepower shift signal pressure to act on the rear end surface 61b of the urging rod 61, the component size is relatively large in the technique disclosed in Patent Document 1. It is possible to omit the urging piston, which can effectively suppress the increase in size of the hydraulic pump 10.

Further, as described above, in the technique disclosed in Patent Document 1, the signal pressure generated by the control valve in response to the lever operation of the operator is transmitted to the rear end surface of the urging rod via the fourth urging pin. It acts at a position that is radially offset from the center. Due to this, the urging rod urged by the signal pressure may generate a moment of rotation about an axis orthogonal to the longitudinal direction of the urging rod. Due to this moment, the urging rod is pressed against the first guide portion, and a relatively large friction is generated between the urging rod and the first guide portion. As a result, the urging rod and the first guide portion may be worn, and the operation of the urging rod may become unstable. Further, due to friction between the urging rod and the first guide portion, even though the same signal pressure is input to the second pressure chamber, the movement toward the swash plate side and the swash plate There is a possibility that so-called hysteresis occurs, in which the position of the urging rod differs between when moving toward the opposite side. This may also cause the operation of the urging rod to become unstable. On the other hand, in the present embodiment, at least one of the flow rate control signal pressure and the horsepower shift signal pressure acts on the entire rear end surface 61b of the urging rod 61, which is orthogonal to the longitudinal direction of the urging rod. It is possible to effectively suppress the generation of a moment that rotates around the axis. Therefore, it is possible to suppress the wear of the urging rod 61 and the first guide portion 23 and the occurrence of hysteresis regarding the position of the urging rod 61. That is, it becomes possible to impart stability to the operation of the hydraulic pump 10.

Since the area of the rear end surface 61b of the urging rod 61 is sufficiently larger than the cross-sectional area of the first urging pin 71, even when a relatively small signal pressure is input to the first pressure chamber 81. The urging rod 61 can exert a sufficient urging force to change the tilt angle of the swash plate 40 without using the urging piston.

Next, a specific configuration of the urging pin unit 70 will be described with reference to FIGS. 1 and 2. FIG. 2 shows a cross section corresponding to the line II-II of FIG. In the illustrated example, the urging pin unit 70 has a plurality of first urging pins 71, an adjusting pin 73, an adjuster 77, and a unit case 76. Each first urging pin 71 urges the swash plate 40 via the urging rod 61 according to the signal pressure corresponding to each first urging pin 71.

In the example shown in FIGS. 1 and 2, the first urging pin 71 has a substantially columnar shape as a whole, and the axis thereof is parallel to the axis of the urging rod 61. It is arranged on the opposite side of the swash plate 40 of the rod 61. In particular, in the illustrated example, the first urging pin 71 is arranged so that its axis is parallel to the rotation axis A. The tip surface of the first urging pin 71 facing the urging rod 61 has a flat surface. Not limited to this, the tip surface of the first urging pin 71 may have a shape other than a flat surface such as a spherical surface.

The unit case 76 is provided with a plurality of second guide portions 75 for guiding the side surface of the first urging pin 71, and each first urging pin 71 is provided with respect to each second guide portion 75. It is slidably arranged. Therefore, each first urging pin 71 is slidably held in a second guide portion 75 to which at least a part thereof corresponds. Each of the second guide portions 75 is composed of holes provided in the unit case 76, and has a cross-sectional shape complementary to the cross-sectional shape of the first urging pin 71. That is, each second guide portion 75 is composed of a cylindrical hole having a circular cross section. A second pressure chamber 82 that receives the signal pressure for the first urging pin 71 is formed on the side of the second guide portion 75 opposite to the urging rod 61 of the first urging pin 71.

In the example shown in FIGS. 1 and 2, the second guide portion 75 is provided integrally with the unit case 76. When the second guide portion 75 is provided integrally with the unit case 76, each second guide portion 75 can be formed by drilling in the unit case 76, and the second guide portion 75 is formed by simple processing. Will be possible. Further, since no additional member is required to provide the second guide portion 75, it contributes to the reduction of the number of parts of the hydraulic pump 10 and the cost reduction. The configuration of the second guide unit 75 is not limited to this. As an example, a second guide portion 75 formed by using a member, which is different from the unit case 76, for example, a cylindrical shape, may be attached to the unit case 76.

The adjusting pin 73 is a member for adjusting the position of the urging rod 61 when the urging rod 61 is pushed most to the side opposite to the swash plate 40. Therefore, the position of the adjusting pin 73 can be adjusted in the longitudinal direction by the adjuster 77. In the example shown in FIG. 1, the adjuster 77 is composed of a set screw and a nut. The unit case 76 has a through hole connecting the surface of the unit case 76 opposite to the urging rod 61 and the rear chamber 89 in which the end of the adjusting pin 73 opposite to the urging rod 61 is accommodated. It is formed and the set screw of the adjuster 77 is screwed into this through hole. Therefore, the position of the adjusting pin 73 in the longitudinal direction can be adjusted by rotating the set screw to change the position of the set screw with respect to the through hole.

The housing 20 side (the urging rod 61 side) of the unit case 76 has a convex portion 78 formed so as to surround the first urging pin 71. The convex portion 78 is fitted into the concave portion 29 provided in the first housing block 21 (housing 20). As shown in FIG. 2, the convex portion 78 has a circular cross section. Further, the concave portion 29 of the first housing block 21 also has a circular cross-sectional shape corresponding to the cross-sectional shape of the convex portion 78.

If the first urging pin 71 is configured so that the urging rod 61 can be urged toward the swash plate 40 according to the signal pressure corresponding to each first urging pin 71, its specific shape and its specific shape and The arrangement is not particularly limited, but as an example, each first urging pin 71 may have a shape and arrangement as described below mainly with reference to FIG.

In the example shown in FIG. 2, each first urging pin 71 and adjustment pin 73 is viewed from the axial direction of each first urging pin 71 and adjustment pin 73, that is, from the axial direction of the urging rod 61. All have a circular cross section having the same diameter. According to the first urging pin 71 and the adjusting pin 73 having such a shape, for example, the first urging pin 71 and the adjusting pin 73 are manufactured by cutting one long bar. Can be done. Further, it can be formed by drilling a plurality of second guide portions 75 with the same diameter. This makes it possible to simplify the manufacturing process of each of the first urging pin 71, the adjusting pin 73, and each of the second guide portions 75.

Further, in the illustrated example, each first urging pin 71 is arranged so that its center (axis) is located on one circumference C when viewed from the axial direction of each first urging pin 71. ing. In particular, the first urging pins 71 are arranged at equal intervals along one circumference C. In other words, the central angles at the center of the circumference C by the two adjacent first urging pins 71 on the circumference C are all equal. In the illustrated example, the central angles at the center of the circumference C by the two adjacent first urging pins 71 on the circumference C are all 90 °. Further, in the illustrated example, the center (axis) of each first urging pin 71 is arranged in a region overlapping with the urging rod 61 when viewed from the axial direction of each first urging pin 71. Further, in the illustrated example, the entire first urging pin 71 is arranged in the region overlapping with the urging rod 61 when viewed from the axial direction of each first urging pin 71. By arranging the first urging pin 71 in this way, the urging pin unit 70 can be effectively miniaturized.

In the example shown in FIGS. 1 and 2, the urging rod 61, each first urging pin 71, and the adjusting pin 73 are formed of a solid member. When the urging rod 61 and the pins 71 and 73 are formed of a solid member, the urging rod 61 and the pins 71 and 73 can be manufactured in a relatively simple process, and the urging rod 61 and the pin 71 can be manufactured. , 73 can be imparted with sufficient mechanical strength. Therefore, it is possible to effectively prevent the deformation of the urging rod 61 and the pins 71 and 73 while reducing the size of the urging rod 61 and the pins 71 and 73, thereby extremely tilting the swash plate 40. It can be done stably.

The side surface of the adjusting pin 73 may be provided with a groove or a notch through which oil can flow from one end to the other end. As an example, the notch may have a part of the side surface chamfered so that the cross section orthogonal to the longitudinal direction of the adjusting pin 73 is substantially D-shaped. For example, if oil flows from the first pressure chamber 81 into the rear chamber 89 through the gap between the adjusting pin 73 and the unit case 76, the position of the adjusting pin 73 may shift to the urging rod 61 side due to the presence of this oil. There is. On the other hand, if a groove or notch is provided on the side surface of the adjusting pin 73, the oil flowing into the rear chamber 89 when the adjusting pin 73 is pressed by the urging rod 61 is taken into this groove or notch. It can be quickly returned to the first pressure chamber 81 via. Therefore, it is possible to improve the position accuracy of the urging rod 61 when the urging rod 61 is pushed to the side opposite to the swash plate 40 most.

In each second pressure chamber 82 corresponding to each first urging pin 71, for example, a signal pressure from hydraulic oil discharged from the hydraulic pump 10 or a signal from another hydraulic pump driven by the same drive source. The pressure and the signal pressure corresponding to the operation of an external device such as an air conditioner driven by the same drive source are input. When the hydraulic pump 10 is a hydraulic pump having a so-called split flow structure in which one pump has the functions of two pumps, the signal pressures of the two hydraulic oils discharged from the hydraulic pump 10 are separately attached to the first. It can be input to the hydraulic pump 71.

Therefore, each first urging pin 71 is driven by the signal pressure from the hydraulic oil discharged from the hydraulic pump 10, the signal pressure from another hydraulic pump driven by the same drive source, or the same drive source. It is driven by a signal pressure or the like corresponding to the operation of an external device such as an air conditioner. As a result, each of the first urging pins 71 urges the urging rod 61 toward the swash plate 40.

Next, the tilting operation of the swash plate 40 will be described. The rotary shaft 25 of the hydraulic pump 10 is driven by a drive source such as a diesel engine. When a load larger than the driving force of the driving source is applied to this driving source, the driving source stalls. Therefore, it is necessary to control the operation of the hydraulic pump 10 so that the load on the drive source is equal to or less than the drive force of the drive source. Further, in hydraulic equipment, one drive source may drive a plurality of hydraulic pumps. In this case, it is preferable to control the operation of the hydraulic pump 10 so that the total driving force of the plurality of hydraulic pumps driven by one drive source is equal to or less than the driving force of the drive source. Further, when an external device such as an air conditioner is driven by the same drive source, it is preferable to control the operation of the hydraulic pump 10 in consideration of the load on the drive source by the external device.

Further, when the operator who operates the hydraulic equipment does not operate the operating lever, the hydraulic actuator driven by the hydraulic oil discharged from the hydraulic pump does not operate. Further, when the operator operates the operating lever at a shallow angle (fine operation), the hydraulic actuator operates slowly (fine operation). In these cases, the hydraulic actuator requires only a small amount of hydraulic oil from the hydraulic pump, and the hydraulic oil not used for driving the hydraulic actuator has been conventionally discharged to a recovery tank or the like. However, in this case, most of the driving force of the hydraulic pump is wasted, and the fuel consumed by the drive source such as the diesel engine that drives the hydraulic pump is also wasted. Conventionally, some so-called high-grade hydraulic equipment has a function of reducing the amount of hydraulic oil discharged from the hydraulic pump when the hydraulic actuator is not operating or when the hydraulic actuator is finely operated. However, inexpensive hydraulic equipment having such a function has not been realized. Therefore, it is desired to realize a function of reducing the discharge amount of hydraulic oil of the hydraulic pump when the hydraulic actuator is not operating and when the hydraulic actuator is finely operated by a simple mechanism.

Here, a negative flow control signal pressure is input to the first pressure chamber 81, and the signal pressure due to the hydraulic oil discharged from the hydraulic pump 10 is the same in the second pressure chamber 82 corresponding to each first urging pin 71. An example in which a signal pressure from another hydraulic pump driven by the drive source of the above and a signal pressure corresponding to the operation of an air conditioner driven by the same drive source are input will be described.

The first urging pin 71 corresponding to the second pressure chamber 82 to which the signal pressure is not input can be a spare urging pin. If such a spare urging pin is provided, the hydraulic pump 10 is to be controlled in consideration of the operation of the hydraulic pump or the external device by adding another hydraulic pump or an external device. By inputting the signal pressure from the or external device into the second pressure chamber 82 corresponding to the spare urging pin, this spare urging pin can be used as the urging pin corresponding to the hydraulic pump or the external device. can do. Therefore, it is possible to flexibly cope with the addition of other hydraulic pumps and external devices, and it is possible to effectively improve the versatility of the hydraulic pump 10.

The swash plate 40 is urged by the first urging means 50 in a direction in which the tilt angle of the swash plate 40 increases, and by the second urging means 60 in a direction in which the tilt angle of the swash plate 40 decreases. Be swashplate. The swash plate 40 has the magnitude of the moment around the tilt axis of the swash plate 40 due to the urging force of the first urging means 50 (counterclockwise moment in FIG. 1) and the swash plate 40 by the second urging means 60. It tilts to a position where the magnitude of the moment around the tilt axis (clockwise moment in FIG. 1) becomes equal and stops.

In the example described here, the flow rate control signal pressure is input to the first pressure chamber 81. Specifically, the back pressure of the orifice in the center bypass line of the negative flow rate control mechanism is detected, and the detected back pressure is input to the first pressure chamber 81 as the negative flow rate control signal pressure. The flow rate control signal pressure input to the first pressure chamber 81 acts on the rear end surface 61b of the urging rod 61. In particular, the flow rate control signal pressure input to the first pressure chamber 81 presses the rear end surface 61b of the urging rod 61.

By operating the control valve in the negative flow control mechanism in order to make the hydraulic actuator inoperable or finely operated, the flow rate of the pressure oil toward the hydraulic actuator via the control valve is reduced, and the control valve from the hydraulic pump 10 The flow of hydraulic pressure returned to the tank via the, ie, through the center bypass line, increases. An orifice is provided between the control valve and the tank in the center bypass line, and when the flow rate of the pressure oil passing through the center bypass line increases, the pressure of the pressure oil (back pressure) in front of the orifice of the center bypass line increases. Increase. By inputting this back pressure as a negative flow rate control signal pressure into the first pressure chamber 81, this signal pressure acts on the rear end surface 61b of the urging rod 61, and the urging rod 61 acts on the swash plate 40 (contact surface 42). ) Is urged.

The signal pressure of the hydraulic oil discharged from the hydraulic pump 10 is input to the second pressure chamber 82 corresponding to the first urging pin 71 of one of the plurality of first urging pins 71. For example, the flow path of the hydraulic oil discharged from the hydraulic pump 10 is branched and connected to the second pressure chamber 82, so that the signal pressure due to the hydraulic oil discharged from the hydraulic pump 10 is sent to the first urging pin 71. It is input to the corresponding second pressure chamber 82. When the load of the hydraulic actuator driven by the hydraulic oil discharged from the hydraulic pump 10 becomes large, the pressure of the hydraulic oil discharged from the hydraulic pump 10 becomes large. That is, the signal pressure due to the hydraulic oil discharged from the hydraulic pump 10 increases. Then, the first urging pin 71 is urged toward the urging rod 61 by this signal pressure. Therefore, the first urging pin 71 urges the swash plate 40 (contact surface 42) via the urging rod 61.

The signal pressure from another hydraulic pump driven by the same drive source is input to the second pressure chamber 82 corresponding to the other first urging pin 71. For example, the flow path of the hydraulic oil discharged from another hydraulic pump is branched and connected to the second pressure chamber 82, so that the signal pressure due to the hydraulic oil discharged from the hydraulic pump is applied to the first urging pin 71. Is input to the second pressure chamber 82 corresponding to. When the load of the hydraulic actuator driven by the hydraulic oil discharged from another hydraulic pump becomes large, the pressure of the hydraulic oil discharged from the hydraulic pump becomes large. That is, the signal pressure due to the hydraulic oil discharged from other hydraulic pumps increases. Then, the first urging pin 71 is urged toward the urging rod 61 by this signal pressure. Therefore, the first urging pin 71 urges the swash plate 40 (contact surface 42) via the urging rod 61.

Further, a signal pressure corresponding to the operation of the air conditioner driven by the same drive source is input to the second pressure chamber 82 corresponding to the other first urging pin 71. For example, another hydraulic circuit is branched and connected to the second pressure chamber 82 corresponding to the first urging pin 71. Further, a valve such as a solenoid valve (solenoid valve) is provided in the flow path of the hydraulic oil between the portion branched from the hydraulic circuit and the second pressure chamber 82. Then, while the air conditioner is not operating, the flow path of the hydraulic oil is closed by the valve, and when the air conditioner is operated, the valve operates to open the flow path of the hydraulic oil in response to the signal (electric signal). As a result, the signal pressure is not input to the second pressure chamber 82 corresponding to the first urging pin 71 while the air conditioner is not operating, and when the air conditioner is operated, another hydraulic circuit is supplied to the second pressure chamber 82. The signal pressure is input from. Then, the first urging pin 71 is urged toward the urging rod 61 by this signal pressure. Therefore, the first urging pin 71 urges the swash plate 40 (contact surface 42) via the urging rod 61.

The urging force for urging the swash plate 40 (contact surface 42) of the urging rod 61, that is, the urging force for the swash plate 40 by the second urging means 60 is applied to the urging rod 61 of the first urging pin 71. It becomes the sum of the swash plate. The moment around the tilt axis of the swash plate 40 due to the urging force of the second urging means 60 (clockwise moment in FIG. 1) is around the tilt axis of the swash plate 40 due to the urging force of the first urging means 50. When it becomes larger than the moment (counterclockwise moment in FIG. 1), the swash plate 40 is tilted so that its tilt angle becomes smaller, and the swash plate 40 is tilted by the urging force of the second urging means 60. When the moment around the axis and the moment around the tilting axis of the swash plate 40 due to the urging force of the first urging means 50 are balanced, the swash plate 40 stops tilting. As a result, the flow rate of the hydraulic oil discharged from the hydraulic pump 10 is reduced.

In the hydraulic pump 10 of the present embodiment, the operator does not operate or finely operates the operation lever, the load of the hydraulic actuator driven by the hydraulic oil discharged from the hydraulic pump 10 increases, and the same drive The second urging means 60 is attached when at least one of the cases where the load of another hydraulic pump driven by the source increases and the external device such as an air conditioner driven by the same drive source operates. As the force increases, the swash plate 40 tilts so that its tilt angle becomes smaller, and the flow rate of hydraulic oil discharged from the hydraulic pump 10 decreases. This makes it possible to effectively prevent the occurrence of stall of a drive source such as a diesel engine that drives the hydraulic pump 10. Further, it is possible to reduce the waste of fuel consumed by the drive source and effectively improve the energy saving of the hydraulic equipment provided with the hydraulic pump 10.

The hydraulic pump 10 of the present embodiment is a cylinder block 30 that rotates around the rotation axis A, and is a cylinder block 30 in which a plurality of cylinder holes 32 extending along the rotation axis A direction are formed, and each cylinder hole 32. A swash plate 40 for sliding each piston 38 in each cylinder hole 32 by rotating the piston 38 slidably held inside and the cylinder block 30 around the rotation axis A. The swash plate 40 is configured so that the tilt angle can be changed, the first urging means 50 that urges the swash plate 40 in the direction in which the tilt angle of the swash plate 40 increases, and the tilt angle of the swash plate 40. The second urging means 60 has a second urging means 60 for urging the swash plate 40 in a smaller direction, and the second urging means 60 has an urging rod 61 for urging the swash plate 40. At least one of the flow control signal pressure and the horsepower shift signal pressure acts on the rear end surface 61b on the opposite side of the swash plate 40.

According to such a hydraulic pump 10, by allowing at least one of the flow rate control signal pressure and the horsepower shift signal pressure to act on the rear end surface 61b of the urging rod 61, the urging that the component size becomes relatively large. The piston can be omitted, and the increase in size of the hydraulic pump 10 can be effectively suppressed.

Further, according to such a hydraulic pump 10, the flow rate control signal pressure and / or the horsepower shift signal pressure acts on the entire rear end surface 61b of the urging rod 61, and the longitudinal direction of the urging rod 61 is increased. It is possible to effectively suppress the generation of a moment that rotates around orthogonal axes. Therefore, it is possible to suppress the wear of the urging rod 61 and the first guide portion 23 and the occurrence of hysteresis regarding the position of the urging rod 61. That is, the hydraulic pump 10 can be operated stably.

In the hydraulic pump 10 of the present embodiment, the flow rate control signal pressure acts on the rear end surface 61b.

Further, in the hydraulic pump 10 of the present embodiment, the flow rate control signal pressure is a negative flow rate control signal pressure.

According to such a hydraulic pump 10, the urging force of the second urging means 60 increases when the hydraulic actuator is not operating and when the hydraulic actuator is slightly operated, and the swash plate 40 is tilted so that its tilt angle becomes smaller. Then, the flow rate of the hydraulic oil discharged from the hydraulic pump 10 is reduced. This makes it possible to effectively prevent the occurrence of stall of a drive source such as a diesel engine that drives the hydraulic pump 10. Further, it is possible to reduce the waste of fuel consumed by the drive source and effectively improve the energy saving of the hydraulic equipment provided with the hydraulic pump 10. The flow rate control signal pressure may be a load sensing flow rate control signal pressure.

The hydraulic pump 10 of the present embodiment further has a guide portion 23 for guiding the side surface 61c of the urging rod 61, and pressure oil from another pump is supplied between the side surface 61c and the guide portion 23. ..

According to such a hydraulic pump 10, the pressure oil discharged from another pump is forcibly supplied between the side surface 61c and the first guide portion 23 at a predetermined pressure to provide the urging rod 61. It becomes possible to move smoothly, the pressure oil can be stably discharged by the hydraulic pump 10, and the friction that may occur between the side surface 61c of the urging rod 61 and the first guide portion 23 is reduced. It is possible to suppress the occurrence of hysteresis with respect to the position of the urging rod 61.

In the hydraulic pump 10 of the present embodiment, the second urging means 60 further has an urging pin 71, and the urging pin 71 has an urging rod 61 according to the signal pressure corresponding to the urging pin 71. The swash plate 40 is urged through the swash plate 40.

According to such a hydraulic pump 10, in addition to the flow control signal pressure and / or the horsepower shift signal pressure acting on the rear end surface 61b of the urging rod 61, the signal pressure due to the hydraulic oil discharged from the hydraulic pump 10 is the same. The urging rod 61 is also attached to the swash plate 40 by other signal pressures such as a signal pressure from another hydraulic pump driven by the same drive source and a signal pressure corresponding to the operation of an air conditioner driven by the same drive source. Can be urged towards. That is, the flow rate of the pressure oil discharged from the hydraulic pump 10 can be controlled based on the flow rate control signal pressure and / or the signal pressure other than the horsepower shift signal pressure. Therefore, the flow rate of the pressure oil discharged from the hydraulic pump 10 can be controlled with a higher degree of freedom.

It is possible to make various changes to the above-described embodiment. Hereinafter, modification examples will be described with reference to the drawings as appropriate. In the following description and the drawings used in the following description, the same reference numerals as those used for the corresponding portions in the above-described embodiment will be used for the portions that can be configured in the same manner as in the above-described embodiment. Duplicate explanations will be omitted.

FIG. 3 is a diagram showing a modification of the hydraulic pump 10, and is a diagram for explaining a signal pressure P input to the first pressure chamber 81 of the hydraulic pump 10. In the example shown in FIG. 3, the signal pressure P, which is at least one of the flow rate control signal pressure and the horsepower shift signal pressure, is input to the first pressure chamber 81 via the orifice 91. That is, the signal pressure P acts on the rear end surface 61b of the urging rod 61 via the orifice 91.

When a hydraulic circuit (closed circuit) in which the hydraulic pump, the control valve and each actuator are closed is configured, the pressure oil is input to the first pressure chamber via these hydraulic pumps, the control valve and each actuator. The signal pressure P may oscillate. When the signal pressure P oscillates, the operation of the urging rod becomes unstable, and as a result, the flow rate of the pressure oil discharged from the hydraulic pump becomes unstable. On the other hand, in the hydraulic pump 10 of this modification, the amplitude can be reduced by the orifice 91 and the signal pressure P can be input to the first pressure chamber. Therefore, the operation of the urging rod and the flow rate of the pressure oil discharged from the hydraulic pump can be stabilized.

FIG. 4 is a diagram showing another modification of the hydraulic pump 10, and is a diagram for explaining a signal pressure P input to the first pressure chamber 81 of the hydraulic pump 10. In the example shown in FIG. 4, the signal pressure P, which is at least one of the flow rate control signal pressure and the horsepower shift signal pressure, is input to the first pressure chamber 81 via the slow return mechanism 93. That is, the signal pressure P acts on the rear end surface 61b of the urging rod 61 via the slow return mechanism 93.

The slow return mechanism 93 has an orifice 94 and a check valve 95 connected in parallel with each other. The check valve 95 of this modification is configured so that the pressure oil flowing out of the first pressure chamber 81 can pass through, but the pressure oil flowing into the first pressure chamber 81 cannot pass through. Not limited to this, the check valve 95 is configured so that the pressure oil flowing into the first pressure chamber 81 can pass through, but the pressure oil flowing out from the first pressure chamber 81 cannot pass through. You may.

According to this modification, a slow return function can be added to the hydraulic pump 10. In particular, in the illustrated example, the tilt angle of the swash plate 40 is increased by the flow rate increase signal from the control valve to increase the flow rate of the pressure oil discharged from the hydraulic pump 10, that is, the urging rod 61 is swash plate. When moving to the opposite side of 40, the pressure oil in the first pressure chamber 81 passes through the check valve 95 of the slow return mechanism 93 and quickly flows out, and the flow reduction signal from the control valve causes the swash plate 40 to flow out. When the tilt angle is reduced to reduce the flow rate of the pressure oil discharged from the hydraulic pump 10, that is, when the urging rod 61 is moved to the swash plate 40 side, the pressure oil is the orifice 94 of the slow return mechanism 93. Slowly flows into the first pressure chamber 81.

FIG. 5 is a diagram showing still another modification of the hydraulic pump 10, and is a diagram for explaining a signal pressure P input to the first pressure chamber 81 of the hydraulic pump 10. In the example shown in FIG. 5, the signal pressure P, which is at least one of the flow rate control signal pressure and the horsepower shift signal pressure, is generated by converting the electric signal into hydraulic pressure by the electromagnetic proportional valve 97.

In the illustrated example, the pressure oil from the oil supply source S passes through the electromagnetic proportional valve 97 and is input to the first pressure chamber 81 as the signal pressure P. The electromagnetic proportional valve 97 receives a signal for flow rate control and / or horsepower shift as an electric signal, and adjusts the opening degree of the flow path of the pressure oil from the oil supply source S according to the electric signal.

According to this modification, since the signals for flow rate control and / or horsepower shift can be treated as electric signals, the number of hydraulic pipes can be reduced, and the hydraulic pump 10 can be further miniaturized.

FIG. 6 is a diagram showing still another modification of the hydraulic pump 10, and is a diagram for explaining a signal pressure P input to the first pressure chamber 81 of the hydraulic pump 10. In the example shown in FIG. 6, the flow rate control signal pressure P1 and the horsepower shift signal pressure P2 are both input to the first pressure chamber 81 through the shuttle valve 99. In the shuttle valve 99, only the signal pressure having a relatively high pressure among the two input signal pressures P1 and P2 can pass, and the relatively low pressure among the two input signal pressures P1 and P2 can pass. The signal pressure with is impassable. Then, only one of the signal pressures P1 and P2 that has passed through the shuttle valve 99 is input to the first pressure chamber 81 as the signal pressure P. That is, the signal pressure P is a signal pressure having a relatively high pressure among the flow rate control signal pressure and the horsepower shift signal pressure.

According to this modification, the signal pressure having a relatively high pressure among the flow rate control signal pressure P1 and the horsepower shift signal pressure P2 can be selectively input to the first pressure chamber 81.

As yet another modification, as shown in FIG. 7, the signal pressure P that has passed through the shuttle valve 99 may be further passed through the orifice 91 and input to the first pressure chamber 81. Further, as shown in FIG. 8, the signal pressure P that has passed through the shuttle valve 99 may further pass through the slow return mechanism 93 and be input to the first pressure chamber 81.

9 and 10 are views showing still another modification of the hydraulic pump 10, and are views showing the positional relationship between the urging rod 61 and the lubricating oil supply hole 68. In particular, FIG. 9 is a diagram showing the positional relationship between the urging rod 61 and the lubricating oil supply hole 68 when the urging rod 61 is located on the side opposite to the swash plate 40, and FIG. 10 is a diagram showing the positional relationship between the urging rod 61 and the lubricating oil supply hole 68. It is a figure which shows the positional relationship between the urging rod 61 and the supply hole 68 when the rod 61 is located most on the swash plate 40 side.

In the example shown in FIGS. 9 and 10, the guide portion 23 is provided with a supply hole 68 for supplying pressure oil from another pump between the side surface 61c of the urging rod 61 and the guide portion 23. ing. As shown in FIG. 9, the supply hole 68 faces the oil holding groove 65 of the urging rod 61 when the urging rod 61 is located on the side opposite to the swash plate 40. Further, as shown in FIG. 10, the supply hole 68 faces the oil holding groove 65 of the urging rod 61 even when the urging rod 61 is located closest to the swash plate 40. That is, the supply hole 68 faces the oil holding groove 65 at any position during the advancing / retreating operation along the guide portion 23 of the urging rod 61. In other words, the oil holding groove 65 faces the supply hole 68 at any position during the advancing / retreating operation along the guide portion 23 of the urging rod 61.

According to such a hydraulic pump 10, the supply hole 68 and the oil holding groove 65 can communicate with each other regardless of the position of the urging rod 61 during the advancing / retreating operation. That is, the pressure oil from another pump can always be supplied into the oil holding groove 65. Therefore, lubrication between the side surface 61c of the urging rod 61 and the guide portion 23 can be stably performed.

FIG. 11 is a cross-sectional view showing still another modification of the hydraulic pump 10. The hydraulic pump 10 of this modification is a hydraulic pump having a so-called split flow structure, in which one pump has the functions of two pumps, and two signal pressures Pa and Pb due to the hydraulic oil discharged from the hydraulic pump 10 are output. Will be done.

In the illustrated example, the urging pin unit 70 has a second urging pin 72, an adjuster 77 and a unit case 76. The second urging pin 72 has a large diameter portion having a relatively large diameter and a small diameter portion adjacent to the urging rod 61 on the opposite side to the large diameter portion and having a relatively small diameter. There is. Both the large-diameter portion and the small-diameter portion are formed in a columnar shape and have a circular cross section when viewed along the longitudinal direction of the second urging pin 72. The central axis of the cylinder forming the large diameter portion and the central axis of the cylinder forming the small diameter portion coincide with each other. Further, the large diameter portion and the small diameter portion are integrally formed.

A third pressure chamber 83 and a fourth pressure chamber 84 are formed in the unit case 76, and from the small diameter portion of the surface of the large diameter portion of the second urging pin 72 facing the opposite side to the urging rod 61. The exposed portion is located in the third pressure chamber 83, and the surface of the small diameter portion of the second urging pin 72 facing the opposite side to the urging rod 61 is located in the fourth pressure chamber 84. In the illustrated example, the area of the portion of the surface of the large-diameter portion facing the opposite side of the urging rod 61 exposed from the small-diameter portion and the area of the surface of the small-diameter portion facing the opposite side of the urging rod 61 are defined as Are equal.

The two signal pressures Pa and Pb due to the hydraulic oil discharged from the hydraulic pump 10 are input to the pressure chambers 83 and 84, respectively. That is, the signal pressure Pa is input to the third pressure chamber 83 and acts on the portion of the surface facing the opposite side of the large diameter portion of the urging rod 61 that is exposed from the small diameter portion to attach the second urging pin 72. Bounce toward the force rod 61. Further, the signal pressure Pb is input to the fourth pressure chamber 84 and acts on the surface of the small diameter portion facing the opposite side of the urging rod 61 to urge the second urging pin 72 toward the urging rod 61. .. At this time, the urging force for urging the second urging pin 72 toward the urging rod 61 is the sum of the urging force due to the signal pressure Pa and the urging force due to the signal pressure Pb.

In a hydraulic pump 10 having a split flow structure, when an attempt is made to urge the urging rod 61 via an urging pin with two signal pressures Pa and Pb due to hydraulic oil discharged from the hydraulic pump 10, two urging rods are urged. You will need a pin. On the other hand, the urging rod 61 is directed toward the swash plate 40 by using one second urging pin 72 according to the total of the two signal pressures Pa and Pb due to the hydraulic oil discharged from the hydraulic pump 10. Can be urged. Therefore, the number of parts of the urging pin unit 70 can be reduced.

Further, the second urging pin 72 of this modification also has the function of the adjusting pin 73 in the hydraulic pump 10 shown in FIG. That is, the position of the second urging pin 72 in the longitudinal direction can be adjusted by the adjuster 77. In this case, one second urging pin 72 functions as three pins, two urging pins and one adjusting pin, and the number of parts of the urging pin unit 70 is further increased. Can be reduced.

FIG. 12 is a cross-sectional view showing still another modification of the hydraulic pump 10. The hydraulic pump 10 of this modification is a so-called split flow hydraulic pump having the functions of two pumps with one pump, similar to the modification described with reference to FIG. 11, and is discharged from the hydraulic pump 10. Two signal pressures due to the hydraulic pressure applied are output.

In the illustrated example, the urging pin unit 70 has a second urging pin 72, an adjuster 77 and a unit case 76. The second urging pin 72 is formed in a columnar shape and has a circular cross section when viewed along the longitudinal direction of the second urging pin 72. A fifth pressure chamber 85 is formed in the unit case 76, and a surface of the second urging pin 72 facing the opposite side of the urging rod 61 is located in the fifth pressure chamber 85.

An intermediate pressure Pc of two signal pressures due to the hydraulic oil discharged from the hydraulic pump 10 is input to the fifth pressure chamber 85. The intermediate pressure Pc is a signal pressure having a pressure intermediate between the two signal pressures, and assuming that the two signal pressures are Pa and Pb,
Pc = (Pa + Pb) / 2 ... (1)
Will be. As the intermediate pressure Pc, for example, the "intermediate pressure P'" generated in the "pressure communication passage 54" by the pressure oil flowing out from the "opening hole 53" in JP-A-6-307330 can be used.

According to this modification, the same effect as that of the modification described with reference to FIG. 11 can be exhibited. Further, according to this modification, the second urging pin 72 can have a simple cylindrical shape, and one fifth pressure chamber is provided in the unit case 76 corresponding to the second urging pin 72. It can be a pressure chamber 85. Therefore, the structure of the urging pin unit 70 can be simplified.

In the modified example described with reference to FIGS. 11 and 12, one or more first urging pins 71 may be provided in addition to the second urging pin 72.

As yet another modification, in the embodiment described with reference to FIGS. 1 and 2, the hydraulic pump 10 has four first urging pins 71, but is not limited thereto. The hydraulic pump 10 may have two, three, or five or more first urging pins 71.

Although some modifications to the above-described embodiments have been described above, it is naturally possible to apply a plurality of modifications in combination as appropriate.

10 Hydraulic pump 14 Gear pump 16 Rotating shaft 20 Housing 21 1st housing block 23 1st guide part 29 Recess 22 2nd housing block 25 Rotating shaft 30 Cylinder block 32 Cylinder hole 35 Suction / exhaust plate 38 Piston 39 Cylinder chamber 40 Slan plate 41 Sliding Surface 42 Contact surface 43 Shoe 50 1st urging means 51 1st retainer 52 2nd retainer 54 1st spring 55 2nd spring 60 2nd urging means 61 urging rod 61a Tip surface 61b Rear end surface (end surface)
61c Side 65 Oil holding groove 68 Supply hole 70 Biasing pin unit 71 1st urging pin 72 2nd urging pin 73 Adjustment pin 75 2nd guide part 76 Unit case 77 Adjuster 78 Convex part 81 1st pressure chamber 82 2nd Pressure chamber 83 3rd pressure chamber 84 4th pressure chamber 85 5th pressure chamber 91 Orifice 93 Slow return mechanism 94 Orifice 95 Check valve 97 Electromagnetic proportional valve 99 Shuttle valve A Rotating axis L Supply line P Signal pressure S Oil supply source

Claims (9)

A cylinder block that rotates around the axis of rotation and has a plurality of cylinder holes formed therein.
A piston that is slidably held in each cylinder hole,
A swash plate for sliding each piston in each cylinder hole by rotating the cylinder block around the rotation axis, and a swash plate configured so that the tilt angle can be changed.
A first urging means for urging the swash plate in a direction in which the tilt angle of the swash plate increases,
A second urging means having an urging rod for urging the swash plate and urging the swash plate in a direction in which the tilt angle of the swash plate becomes smaller.
A hydraulic pump having a guide portion for guiding the side surface of the urging rod.
At least one of the flow rate control signal pressure and the horsepower shift signal pressure for reducing the maximum discharge flow rate of the pressure oil from the hydraulic pump acts on the end face of the urging rod opposite to the swash plate.
A hydraulic pump to which pressure oil from another pump is supplied between the side surface of the urging rod and the guide portion . A cylinder block that rotates around the axis of rotation and has a plurality of cylinder holes formed therein.
A piston that is slidably held in each cylinder hole,
A swash plate for sliding each piston in each cylinder hole by rotating the cylinder block around the rotation axis, and a swash plate configured so that the tilt angle can be changed.
A first urging means for urging the swash plate in a direction in which the tilt angle of the swash plate increases,
A hydraulic pump having a second urging means for urging the swash plate in a direction in which the tilt angle of the swash plate becomes smaller.
The second urging means has an urging rod for urging the swash plate and an urging pin.
At least one of the flow rate control signal pressure and the horsepower shift signal pressure for reducing the maximum discharge flow rate of the pressure oil from the hydraulic pump acts on the end surface of the urging rod opposite to the swash plate.
The urging pin is a hydraulic pump that urges the swash plate via the urging rod according to a signal pressure corresponding to the urging pin. The hydraulic pump according to claim 1 or 2 , wherein the flow rate control signal pressure acts on the end face. The hydraulic pump according to claim 3 , wherein the flow rate control signal pressure is a negative flow rate control signal pressure. The hydraulic pump according to any one of claims 1 to 4 , wherein the flow rate control signal pressure or the horsepower shift signal pressure acts on the end face via an orifice. The hydraulic pump according to any one of claims 1 to 4 , wherein the flow control signal pressure or the horsepower shift signal pressure acts on the end face via a slow return mechanism having an orifice and a check valve connected in parallel with each other. .. The hydraulic pump according to any one of claims 1 to 6 , wherein the flow rate control signal pressure or the horsepower shift signal pressure is a signal pressure in which an electric signal is converted into hydraulic pressure by an electromagnetic proportional valve. The hydraulic pump according to any one of claims 1 to 7 , wherein a signal pressure having a relatively high pressure among the flow rate control signal pressure and the horsepower shift signal pressure acts on the end face. The guide portion is provided with a supply hole for supplying pressure oil from the other pump between the side surface and the guide portion.
An oil holding groove for holding the pressure oil supplied from the supply hole is provided on the side surface.
The hydraulic pump according to claim 1 , wherein the oil holding groove faces the supply hole at any position during the advancing / retreating operation along the guide portion of the urging rod.

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