JPH10141212A - Variable displacement piston pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power loss by balancing pressure balance of a cylinder block as well as to achieve reduction in the shape dimension of a multi-flow pump, improvement of machine efficiency and prevention of overload of a motor. SOLUTION: Two first and second cylinder banks 4a, 4b in which pistons 41, 42 are so housed as to be reciprocated and slid, and a variable swash plate 5 for adjusting the reciprocating stroke of the pistons are provided in a cylinder block 2 of a variable displacement piston pump. Two first and second port groups to be communicated with the first cylinder bank 4a on the inner peripheral side are formed in the coaxial circumferential position of the port side end surface 2a of the cylinder block, and a third port group to be communicated with the second cylinder bank 4b on the outer peripheral side is arranged on the inner peripheral side. A suction side through hole capable of being simultaneously communicated with approximately half of port groups is formed in the suction side range of a valve plate 3 joined to the port side end surface, and three discharge side through holes 32, 33, 34 capable of being simultaneously communicated with approximately half of port groups are formed on the discharge side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic piston pump for supplying hydraulic fluid to various actuators to operate these actuators, and more particularly to a variable displacement type pump used as a power source for construction machines such as shovels. It relates to a piston pump.

[0002]

2. Description of the Related Art Conventionally, in construction machines such as shovels,
As shown in FIG. 9, three independent hydraulic systems are configured, a first pump (101) for supplying pressure oil to the right traveling system (100), and a pressure oil for the left traveling system (110). Three hydraulic sources are required: a second pump (111) to supply and a third pump (121) to supply pressure oil to the swirling system (120). Here, the right traveling system (100) and the left traveling system (110) are made independent from each other because even when the loads applied to the left and right traveling systems (100, 110) are different from each other, the traveling straightness can be improved. And the left and right traveling systems (100, 110) and the turning system (120).
Are independent of each other because the operation feeling of the turning system (120) is kept good even during traveling, and the turning system (12)
This is to maintain the straight traveling property even during the operation of 0).

For this reason, as a hydraulic source for construction machines such as shovels, a multi-flow pump (200) as shown in FIG. 10 capable of supplying three discharge flows is generally employed.
In this device, an input shaft (221) is connected to the two-way piston pump (210), while a two-way piston pump (210) that independently supplies two equal discharge flows from one cylinder block (211). ) Can be supplied with three discharge flows by adding a gear pump (220) rotated by a pump shaft (212). And as this type of two-way type piston pump, for example,
Japanese Patent Application Laid-Open No. 6-307330 is known. In this apparatus, a port group is formed on a port side end surface of a cylinder block at concentric circumferential positions having two different diameters about a pump shaft, and formed in a line in a circumferential direction inside the cylinder block. The ports of the above-mentioned inner peripheral side port group and the respective ports of the above-mentioned outer peripheral side port group communicate with each other alternately one by one with respect to the even-numbered cylinder chambers. Also, two arc-shaped discharge side through holes in the inner and outer peripheral directions are provided on the discharge side of the valve plate that is in sliding contact with the port side end surface so that the inner peripheral side port group and the outer peripheral side port group can be individually communicated. Are formed so as to independently supply two equal-flow discharge flows from one cylinder block by discharging the pressurized oil independently through the two discharge-side through holes. I have. Thereby, in the multi-flow type pump (200), the left and right traveling systems (10
0, 110), and the pressure oil can be independently supplied from the gear pump (220) to the turning system (120).

[0004]

However, when the conventional multi-flow type pump (200) is driven by a prime mover,
Generally, in order to connect the output shaft of the prime mover and the pump shaft (212) in series, the prime mover is connected to the multi-flow pump (200).
However, the multi-flow pump (200) has a configuration in which the gear pump (220) is disposed on one end face of the two-flow piston pump (210) in the pump axial direction. Inevitably, the length of the power source must be increased in the axial direction of the pump, so that the entire power source including the multi-flow pump (200) and the prime mover becomes large in size. In particular, in the case of a small excavator such as a so-called mini excavator having a body weight of 6 tons or less, there is a strong demand for downsizing of the vehicle body, so that an increase in the size of a power source is extremely inconvenient.

The amount of oil discharged from the gear pump (220) to the hydraulic system of the turning system (120) is determined by the rotation speed of the prime mover regardless of the hydraulic pressure of the turning system (120). As the hydraulic pressure of the system (120) rises, the load on the prime mover from the gear pump (220) increases, so that the prime mover tends to be overloaded, and the hydraulic pressure of the turning system (120) must be released from the relief valve. In some cases, the power loss cannot be obtained, and there is a disadvantage that the power loss is large. In addition, the gear pump generally has a higher noise during operation than the piston pump, and has a lower maximum discharge pressure and poor sliding characteristics. Therefore, the addition of this gear pump makes the multi-flow pump (200) quiet and quiet as a whole. There is also a disadvantage that the operation efficiency is reduced.

In order to solve these inconveniences, a second cylinder line is newly provided on the inner peripheral side or outer peripheral side of the conventional first cylinder line with respect to the cylinder block of the two-flow type piston pump. Thus, it is conceivable to supply three independent discharge flows from one cylinder block. In this case, generally, in the case of a shovel or the like, it is necessary to make the above three discharge flow rates approximately equal in view of the operability. However, when the second cylinder row is disposed on the inner peripheral side of the first cylinder row,
The pistons accommodated in the first cylinder row are in sliding contact with the inner peripheral side of the swash plate, and the strokes of these pistons are considerably smaller than the strokes of the pistons accommodated in the first cylinder row. In order to sufficiently increase the discharge flow rate from the second cylinder row,
This second cylinder row must be made up of a considerably large number of cylinder chambers, or the cross-sectional area of each cylinder chamber must be set considerably large. It is extremely difficult to realize the above-described configuration in a limited space between the first cylinder row and the pump shaft.

On the other hand, when the second cylinder row is disposed on the outer peripheral side of the first cylinder row, the second cylinder row is disposed on the outermost peripheral side of the cylinder block. A port group arranged on the port side end face of the cylinder block so as to communicate with the second cylinder row is also arranged on the outermost peripheral side of this port side end face. For this reason, a discharge side through hole formed in the valve plate so as to be able to communicate with the port group must be arranged on the outermost peripheral side of the valve plate, and is formed in an arc shape over substantially half the circumference of the valve plate. The circumferential length of the discharge-side through hole becomes large, and the cross-sectional area of the opening becomes excessive. If the opening cross-sectional area of the discharge-side through-hole is excessive, there is a disadvantage that the pressure balance of the cylinder block cannot be balanced. To explain this in detail, generally, a cylinder block has
Due to the discharge pressure of the pump acting on the port side end face through the discharge side through hole of the valve plate, a pressing force on the swash plate side proportional to the area of the discharge side through hole and the pressure receiving area of the seal portion (cylinder block) Of the cylinder plate on the discharge side while the pressing force on the valve plate side is proportional to the sum of the cross-sectional areas of these cylinders due to the hydraulic pressure in each cylinder chamber on the discharge side. A pressing force (pressing force against the plate side) is applied, and the joint state between the cylinder block and the valve plate is maintained by the balance between these opposing pressing forces (pressure balance). If the area of the discharge side through hole is too large, the pressing force on the swash plate side due to the discharge pressure acting through the discharge side through hole is too large. It cannot be balanced with the pressing force on the side, and the pressure balance of the cylinder block will be lost. As a result, the amount of pressure oil leaking from the gap between the cylinder block and the valve plate increases, power loss increases, and the discharge pressure decreases.

The present invention has been made in view of such circumstances, and an object of the present invention is to reduce the external dimensions of a multi-flow pump used for construction machines such as shovels and to improve mechanical efficiency.・ Multiple rows of cylinders are arranged in the cylinder block of the piston pump to prevent overloading of the prime mover, etc.Furthermore, by reducing the pressure balance of the cylinder block, power loss is reduced and discharge pressure is maintained. It is to plan.

[0009]

In order to achieve the above object, an invention according to claim 1 comprises a pump shaft (1) and a cylinder block (2) which rotates integrally with the pump shaft (1).
, And pistons (41, 41,...) Are reciprocally slid in the direction of the pump shaft (1) in the cylinder block (2) at respective positions on the circumference around the pump shaft (1). A plurality of cylinder chambers (24, 24, ...) accommodated as possible
The pistons (42, 42, 42, 42, 42) are disposed at respective positions on a concentric circle on the outer peripheral side with respect to the first cylinder row (4a) in the cylinder block (2). ..) Are accommodated in the plurality of cylinder chambers (25, 25,...) So as to be reciprocally slidable in the direction of the pump shaft (1).
And a second cylinder row (4b) constituted by the first and second cylinder rows (4a) and (4b).
A variable swash plate (5) for increasing or decreasing the reciprocating stroke of a reciprocating motion of the cylinder block (2, 42,...) And a valve plate slidably joined to the port side end surface (2a) of the cylinder block (2). (3). First and second two rows of ports arranged on the port side end surface (2a) in the inner and outer peripheral directions so as to communicate with the respective cylinder chambers (24) of the first cylinder row (4a). Group (21,2
2) and a circumferentially arranged at an inner peripheral side of the first port group (21) and the second port group (22), and
A third port group (23) communicating with each cylinder chamber (25) of the second cylinder row (4b) is formed, and the valve plate (3) is formed around the pump shaft (1). A suction-side through-hole (31) disposed in a suction-side area occupying substantially half of the circumferential direction and formed to be able to communicate with substantially half of the three port groups (21, 22, 23).
And the pump shaft (1) disposed in the discharge side range occupying another approximately half of the circumferential direction and individually communicating with approximately half of the three port groups (21, 22, 23). 3 formed at concentric circumferential positions of different diameters with respect to the center
And two arc-shaped discharge side through holes (32, 33, 34).

In the case of the above construction, the three discharge side through-holes (32, 33, 33) formed in the valve plate (3) by the reciprocating movement of the pistons (41, 42) accompanying the rotation of the cylinder block (2). 34), the pressure liquid is discharged independently. For this reason, it becomes possible to supply the pressurized liquid from one cylinder block (2) of one variable displacement type piston pump as three independent discharge flows. The gear pump can be omitted. By omitting the gear pump, it is possible to reduce the size of the pump in the pump axial direction, and to reduce the mechanical loss, increase the discharge pressure, and reduce the operation noise. The pistons (4) of the first cylinder row (4a) and the second cylinder row (4b)
, 41,..., 42, 42,...) Is increased or decreased or adjusted by one variable swash plate (5). For all of the discharge flows of the book, the discharge amount can be increased or decreased and adjusted according to the change in the discharge pressure.
The load on the prime mover that rotationally drives the cylinder block (2) can be suppressed to a predetermined value or less to prevent the overload operation. In addition, it is possible to perform comprehensive total horsepower control based on the sum of the loads with respect to the flow rates and pressures of the three discharge flows.
Further effective use of the output of the prime mover is achieved.

Further, a second cylinder row (4b) is disposed on the outermost peripheral side of the cylinder block (2).
Third port group (23) communicating with the cylinder row (4b)
Is the port side end surface (2) of the cylinder block (2).
A third discharge side through-hole (34), which is disposed on the inner peripheral side in (a) and communicates with the third port group (23), is formed on the inner peripheral side of the valve plate (3). Therefore, the circumferential length of the third discharge side through hole (34) is relatively small. For this reason, since the opening cross-sectional area of the third discharge side through hole (34) is relatively small, the port side end surface (2a) of the cylinder block (2) is formed through the third discharge side through hole (34). The separation pressure for separating the cylinder block (2) from the valve plate (3) becomes relatively small due to the discharge pressure acting on the cylinder chamber (42) of the second cylinder row (4b). , 42,...) Does not become excessive with respect to the pressing force for pressing the cylinder block (2) toward the valve plate (3). Therefore, the pressure balance of the cylinder block (2) can be balanced so that the cylinder block (2) and the valve plate (3) can be maintained in a predetermined joint state. This makes it possible to reduce the power loss and maintain the discharge pressure.

According to a second aspect of the present invention, in the first aspect of the present invention, the distal end side (1a) of the pump shaft (1) is set in a non-penetrating state from the swash plate side (2b) with respect to the cylinder block (2). In the cylinder block (2), the tip surface (1a) of the pump shaft (1) is located at a position on the inner peripheral side of each port (23a) of the third port group (23).
And a plurality of balance cylinder chambers (71, 7) that are individually opened to communicate with the ports (23a).
1, ...) are arranged. The base end is housed in these balance cylinder chambers (71, 71,...) So as to be liquid-tight and relatively slidable with respect to each of the balance cylinder chambers (71), while the tip end is located on the pump shaft (1). ) Is in contact with the front end surface (1a) of the balance cylinder chamber (71,
, 71), the balance pistons (72, 72,...) Pressing the tip surface (1a) of the pump shaft (1) in response to the hydraulic pressure in the pump shaft (1).
…)).

In the above configuration, in addition to the operation according to the first aspect of the present invention, it is possible to balance the moment balance of the cylinder block (2) due to the hydraulic pressure. That is, in the first aspect of the present invention, the second cylinder row (2b) is disposed on the outermost peripheral side of the cylinder block (2), while the third discharge communicating with the second cylinder row (4b). Side plate (34) is the valve plate (3)
Is arranged on the inner peripheral side of the cylinder block, the pressing force and the separating force act on the cylinder block (2) at a position radially different from each other as a couple. The moment balance of (2) may be lost. On the other hand, according to the second aspect of the present invention, the third port group (2) in the cylinder block (2) is provided.
The balance cylinder chambers (71, 71,...) Are disposed on the inner peripheral side with respect to 3), that is, on the innermost peripheral side with respect to the third discharge side through hole (34) of the valve plate (3). The balance pistons (72, 72,...) Housed in the balance cylinder chambers (71, 71,...) Move the third port group (23) with respect to the balance cylinder chambers (71, 71,. The innermost side of the cylinder block (2) is pressed against the valve plate (3) by the reaction force because the tip surface (1a) of the pump shaft (1) is pressed by receiving the discharge pressure guided from the pump shaft (1). Will be done. Therefore,
By generating a moment in the cylinder block (2) in the opposite direction to the moment due to the couple, it is possible to balance the moment balance of the cylinder block (2). The rotation operation is stabilized.

According to a third aspect of the present invention, in the first or second aspect, the cylinder block (2) is formed in a cylindrical shape, and the outer peripheral surface of the cylinder block (2) and the casing (9) are formed. ), A bearing (8) for rotatably supporting the cylinder block (2) with respect to the casing (9) is provided.

In the case of the above configuration, claim 1 or claim 2
In addition to the operation according to the described invention, a bearing (8) is provided between the outer peripheral surface of the cylinder block (2) and the inner peripheral surface of the casing (9), and the bearing (8) allows the cylinder block (2) to be disposed. ) Is rotatably supported, so that a bearing for supporting the pump shaft (1) can be omitted. As a result, the pump shaft (1) can be shortened by the length required for mounting the bearing, and the entire variable displacement piston pump can be made compact accordingly.
Further, the pump shaft (1) according to the second aspect of the present invention.
Even when the cylinder block (2) is not penetrated into the cylinder block (2), the cylinder block (2) can be reliably rotationally supported from the outer peripheral side.

According to a fourth aspect of the present invention, the bearing (8) according to the third aspect of the present invention is constituted by a slide bearing that supports the outer peripheral surface of the cylinder block (2) all around.

In the above configuration, in addition to the operation according to the third aspect of the present invention, the bearing portion (8) is constituted by a slide bearing that supports the outer peripheral surface of the cylinder block (2) all around. The liquid film formed on the bearing portion (8) makes it possible to support the cylinder block (2) against a radial load applied to the cylinder block (2), thereby achieving quietness. Improvement can be achieved.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> FIG. 1 shows a variable displacement piston pump (hereinafter simply referred to as a pump) according to a first embodiment of the present invention, and 1 denotes a pump shaft which is driven to rotate by a motor (not shown). Numeral 2 denotes a cylindrical cylinder block which rotates integrally with the pump shaft (1). Numeral 3 denotes an oil-tightly slidable joint with the port side end surface (2a) of the cylinder block (2). This is a valve plate for distributing the pressure oil discharged from the block (2). Further, reference numeral 4a denotes a first cylinder row disposed on the inner peripheral side of the cylinder block (2), 4b denotes a second cylinder row disposed on the outer peripheral side thereof, and 5 denotes these cylinder rows (4a, 4).
The variable swash plate for increasing and decreasing the stroke of the reciprocating motion of the pistons (41, 41,..., 42, 42,...) accommodated in the respective cylinder chambers constituting the b). This is a spring mechanism that biases the inclination angle to increase. Further, reference numeral 7 denotes a balance piston mechanism that receives the discharge pressure from the second cylinder row (4b) and presses the distal end surface (1a) of the pump shaft (1). Reference numeral 8 denotes an outer peripheral surface of the cylinder block (2). A journal bearing 9 constituted by slide bearings arranged over the entire circumference, 9 is a casing main body for accommodating the cylinder block (2) and the like, and 10 is an end cap for closing an open end of the casing main body (9). The inside of the pump casing constituted by the casing body (9) and the end cap (10) is in a state of being filled with oil.

The pump shaft (1) is rotatably supported around a central axis (X) by an angular bearing (1b) at a base end side (right side in the figure), and a distal end side (left side in the figure).
Is inserted into the center of the cylinder block (2) from the swash plate side (right side in the figure) to a part of the cylinder block (2) and is in a non-penetrating state.
c) and are configured to rotate integrally with each other while being relatively displaceable in the central axis (X) direction.

In the cylinder block (2),
As shown in FIG. 2, the pistons (41, 41,...) Are formed in a row in the circumferential direction around the pump shaft (1) so that the pistons (41, 41,...) Can reciprocate in the longitudinal direction of the pump shaft (1). The ten cylinder chambers (24, 24,...) To be accommodated constitute the first cylinder row (4a), and pistons (42, 42) are provided on the outer peripheral side of the first cylinder row (4a). ,
) Are formed at equal intervals in the circumferential direction to accommodate five cylinder chambers (25, 25,...) Which reciprocally slide in the longitudinal direction of the pump shaft (1). 4a)
Is composed.

On the port side end surface (2a) of the cylinder block (2) (see FIG. 3), a port group (21, 22, 22) is provided at three concentric circumferential positions around the pump shaft (1).
23) are formed, and five ports (21a) constituting the first port group (21) are formed at equal intervals at a first circumferential position near the outer periphery. Each of the ports (21a) is provided with five cylinder chambers (2) of a first group arranged alternately in the first cylinder row (4a).
4a, 24a,...) Are individually communicated with each other by communication passages extending in the direction of the pump shaft (1) from substantially the center positions of the respective cylinder chambers (24a) (see FIG. 4). In addition, five ports (22a) constituting the second port group (22) are arranged at equal intervals and alternately with respect to each port (21a) of the first port group at a second circumferential position on the inner side. Is formed. Each port (22a) of the second port group is connected to five cylinder chambers (24b, 24b,...) Of the second group other than the first group in the first cylinder row (4a). On the other hand, these cylinder chambers (24b) are individually communicated by communication passages extending in the direction of the pump shaft (1) from positions near the pump shaft (1). Further, at a third circumferential position closest to the inner periphery, five ports (2) constituting the third port group (23) are arranged.
3a, 23a,...) Are formed at equal intervals, and each of the ports (23a) extends from the inner peripheral side to the outer peripheral side in the radial direction of the cylinder block (2). , 26), each cylinder chamber (2) of the third group constituting the second cylinder row (4b).
5) is individually communicated. The port side end surface (2a) has a circular recess (2c) on the inner peripheral side of the third port group (23) around the pump shaft (X), and the third port group (23) and the second An annular first annular groove (2d) is provided concentrically with the port group (22), and an annular second annular groove (2e) is provided concentrically on the outer peripheral side of the first port group (21). Is formed. The circular recess (2c) and the first annular groove (2d) are communicated with the casing main body (9) through communication passages (not shown) to form drain passages, and the second annular groove (2e). Have five concave grooves (2) extending radially outward from the outer peripheral edge thereof.
e, 2e,...) communicate with the inside of the casing body (9) to form a drain passage. Further, between the circular recess (2c) and the first annular groove (2d) and the first
Between the annular groove (2d) and the second annular groove (2e),
The first, second, or third port groups (21, 21,
2, 23) is provided with a seal portion.

The swash plate-side end surface (2b) of the cylinder block (2) (see FIG. 1) has a cylinder chamber (24, 2) constituting the first cylinder row (4a) on the inner peripheral side.
4,...) Are opened, and the cylinder chambers (25, 25,...) Constituting the second cylinder row (4b) on the outer peripheral side.
Are open and their respective pistons (41, 4
2) the base end side of each cylinder chamber (24, 25)
While the front end thereof protrudes from the opening toward the variable swash plate (5) and slides on the variable swash plate (5) via slippers (43, 44) disposed at the front end. Movably abutting. Then, each piston (41,
42) is obtained by rotating the cylinder block (2).
It is configured to revolve around the pump shaft (1) and reciprocate in the longitudinal direction of the pump shaft (1) according to the inclination angle of the variable swash plate (5). In FIG. 1, reference numeral 45 denotes a holding plate for connecting the pistons (41, 42) and the slippers (43, 44), and reference numeral 46 denotes a rotation of the holding plate (45) with respect to the pump shaft (1). It is a holding plate guide to be connected as much as possible.

The above-mentioned valve plate (3) (see FIG. 5)
Is connected to the inner surface of the end cap (10), while the port-side end surface (2) of the cylinder block (2) is
a), which is slidably joined to the pump shaft (1) and occupies substantially a half in the circumferential direction around the pump shaft (1). The suction-side through-holes (31) having a shape are formed in the ports (21a,..., 22a,..., 23a,...) Of the three port groups (21, 22, 23) arranged on the port-side end surface (2a). Almost half of them are installed so that they can communicate simultaneously. The suction-side through hole (31) connects the later-described suction-side passage (10a) formed on the inner surface of the end cap (10) with the ports (21a,..., 22a,..., 23a,. The cylinder chamber (24, 24,
, 25, 25,...). Further, the pump shaft (1) is located in a discharge side range (upper range in FIG. 5) occupying substantially half of the valve plate (3) in the circumferential direction around the pump shaft (1).
The three discharge-side through-holes (32, 33, 34) having a substantially arc shape are formed at concentric circumferential positions around the center, and the first discharge-side through-hole (32) on the outermost peripheral side is a first port group ( ..), Which are arranged so as to be able to communicate simultaneously with substantially half of the ports (21a, 21a,...), And the second discharge formed on the inner peripheral side of the first discharge side through-hole (32). Side through hole (3
3) Ports (22) constituting the second port group (22)
a, 22a,...), and the third discharge-side through-hole (34) on the inner peripheral side constitutes a third port group (23). 23
a,...) are provided so as to be able to communicate simultaneously with approximately half of them. Here, the third discharge-side through-hole (34) is formed on the inner peripheral side of the three discharge-side through-holes (32, 33, 34), and has a smaller circumferential length (FIG. In the example, about half of the first discharge-side through-hole (32)) is set, so that the opening cross-sectional area of the third discharge-side through-hole (34) is relatively small. The reciprocating motion of the pistons (41, 41,..., 42, 42,...) Causes the cylinder chambers (24a,.
b,..., 25,.
, 22,..., 23,...), And independently pass through the respective discharge side through holes (32, 33, 34) to form a first discharge side described later formed in the end cap (10). The air is distributed to the passage (10b), the second discharge side passage (10c), or the third discharge side passage (10d).

The variable swash plate (5) has a donut-shaped main body (51) having a sliding surface (51a) on its upper surface (the left side surface in FIG. 1), and is located at the center of the main body (51). Rotation center position (A) offset to spring mechanism (6) side
A rotating shaft (52) formed so as to protrude outward from an outer peripheral surface of the main body (51) so as to pass through the main body (51);
The protruding portion (53) protrudes outward from the outer peripheral surface at one end (upper end in FIG. 1) in the direction orthogonal to the rotation axis (52). The variable swash plate (5) is provided with pistons (41, 41,..., 42,
42,...), A self-returning moment in the direction in which the inclination angle decreases (counterclockwise in FIG. 1) is generated. Further, the variable swash plate (5) is tilted in a state where the protruding portion (53) is in contact with the bottom wall (the right side wall in FIG. 1) of the casing body (9) and further rotation is prevented. While the angle becomes the maximum (for example, 17 degrees) maximum tilt state, the main body (51) abuts against the bottom wall of the casing main body (9) by rotating in the opposite direction, and further rotation is prevented. It is configured such that the tilt angle is in a neutral state of zero degree in the state of being tilted. The rotation of the variable swash plate (5) causes the slipper (4) to slide on the sliding surface (51a).
, 44, 44,...), The reciprocating strokes of the pistons (41, 41,..., 44, 44,.

The spring mechanism (6) includes two coil springs (61, 62) arranged coaxially with each other.
It is housed in a tubular portion (91) projecting obliquely outward (upper left in FIG. 1) from the peripheral surface of the casing body (9). The urging force of the two coil springs (61, 62) is applied between the variable swash plate (5) and the projecting portion (53) to push the variable swash plate (5) substantially in proportion to its inclination angle. It is configured such that it is biased by pressure to the maximum inclined side (clockwise in FIG. 1).

The balance piston mechanism (7) (FIG. 1,
2 and 6) are arranged at equal intervals in the circumferential direction on the innermost side centered on the center axis (X) of the pump shaft (1) on the port side in the cylinder block (2). Each of the five balance cylinder chambers (7) having a circular cross section formed to extend in the direction of the central axis (X) while opening opposite to the tip end surface (1a) of the pump shaft (1).
, 71,...) And each of these balance cylinder chambers (7
1), the base end side is connected to each of these balance cylinder chambers (7
A substantially cylindrical balance piston (7) which is housed so as to be liquid-tight and relatively slidable with respect to (1), while being disposed so that the distal end thereof is in contact with the distal end surface (1a) of the pump shaft (1).
2, 72,...). Each of the balance cylinder chambers (71) is provided with a second communication passage (27, 2).
,...) Are individually communicated with the first communication passages (26, 26,...) So that the discharge pressure is guided from the second cylinder row (4b). The pressing force (72, 72,...) Against the valve plate (3) is applied to the cylinder block (2) by the reaction force pressing the tip end surface (1a) of the pump shaft (1).

The journal bearing (8) has a bearing surface (2f) formed on the swash plate side of the outer peripheral surface of the cylinder block (2) with a predetermined width over the entire circumference, and the bearing surface (2f).
It is disposed between an annular projection (92) formed over the entire circumference so as to protrude from the inner peripheral surface of the casing body (9) toward the cylinder block (2) so as to face f). The bearing surface (2f) and the bearing surface (2f).
An oil film is formed between the oil film and the opposing surface (92a) opposing to (f), and the oil film supports the cylinder block (2) in the radial direction.

In the end cap (10), a suction side passage (10a) (see FIG. 6) and first, second, and third discharge side passages (10b, 10c, 10d) are formed. , 41b,..., 42, through the respective discharge side through holes (32, 33, 34) and the suction side through hole (321) formed in the valve plate (3).
…). The first discharge-side passage (10b) is connected to the left traveling system of the shovel (not shown), the second discharge-side passage (10c) is connected to the right traveling system of the shovel, and the third discharge-side passage (10d) is connected to the shovel. The swing system of the shovel is independently connected to each other by hydraulic piping, and the suction side passageway (10a) is connected to an oil tank (not shown) provided in the shovel by hydraulic piping. Further, the suction side passageway (10a) is communicated with the inside of the casing body (9) by a drain passageway (10e), and the port side end face (2a) and the valve plate (3) on the discharge side of the cylinder block (2). ), The pressure oil leaking into the casing body (9) from the casing body (9) returns to the suction side passage from inside the casing body (9).

In FIG. 1, reference numeral 11 denotes a trochoid pump which is driven to rotate by a pump shaft (1).
The trochoid pump (11) sucks oil in the casing body (9) through a passage (11a) formed in the bottom wall of the casing body (9), and is formed in the casing body (9). Pressure oil is supplied to a pilot operation circuit (not shown) of the shovel via the passage (11b).

Next, the operation of the pump according to the first embodiment and the operation and effect thereof will be described.

First, when the pump shaft (1) is rotated by the operation of a prime mover (not shown), the pistons (41, 41, 41, 41) are rotated.
.., 42, 42,.
The maximum amount of oil is sucked in and the maximum amount of pressure oil is discharged by reciprocating the maximum reciprocating stroke along. At this time, the first
The pressure oil in the cylinder chambers (24a, 24a,...) Of the group passes through the first port group (21) and the first discharge side through hole (32), and flows into the first discharge side passage (10b). The pressure oil in the cylinder chambers (24b, 24b,...) Of the group passes through the second port group (22) and the second discharge side through hole (33) to the second discharge side passage (10c), and The pressure oil in the cylinder chambers (25, 25,...) Of the third group passes through the third port group (23) and the third discharge side through hole (34), and enters the third discharge side passage (10d). It circulates independently and is supplied independently to each hydraulic system of the shovel via hydraulic piping. Here, the first group of cylinder chambers (24a,
24a,...) And the second discharge flow discharged from the second group of cylinder chambers (24b, 24b,...) Constitute the first cylinder row (4a). This is an equal amount of discharge flow discharged from the cylinder chamber (24) having the same volume. By supplying both discharge flows independently to the left and right traveling systems of the shovel, the traveling straightness of the shovel can be improved. Things.
Further, the cylinder chambers (25, 25,
…) Is supplied to the turning system of the shovel, so that the turning system can be operated without being affected by the operation of the left and right traveling systems, and the operability is good. It can be. In other words, the pressure oil can be independently supplied from the single cylinder block (2) to the three hydraulic systems of the shovel, and the conventionally required gear pump is omitted. The length of the power source can be reduced in the axial direction, so that the power source can be made more compact. The mechanical pump and the operating noise can be reduced by omitting the gear pump, and the second cylinder row (4b) can be used instead of the gear pump.
, The pressure of the third discharge flow is increased.

Further, the variable swash plate (5) receives the discharge pressure of the pump acting via the discharge-side pistons (24, 24,..., 25, 25,...) And presses the spring mechanism (6). The variable swash plate (5) is configured such that the hydraulic pressure on the discharge side and the urging force of the spring mechanism (6) are balanced with each other, since the variable swash plate (5) is rotated in a direction in which the inclination angle decreases against the force. The angle will be maintained in the state. As a result, each of the first discharge flow, the second discharge flow, and the third discharge flow can be reduced with an increase in their discharge pressures. Load operation can be prevented, and the frequency of opening the relief valve can be reduced to reduce power loss.
In other words, by performing overall total horsepower control based on the total load as the flow rate / pressure control of the pump, further effective use of the output of the prime mover is achieved.

Further, in the above pump, although the second cylinder row (4b) is disposed on the outer peripheral side of the first cylinder row (4a), the third cylinder row (4b) communicates with the second cylinder row (4b). Since the port group (23) is disposed on the inner peripheral side of the port side end surface (2a) of the cylinder block (2), the third discharge side through-hole (34) communicating with the third port group (23). ) Are formed on the inner peripheral side of the valve plate (3), the opening cross-sectional area thereof is set relatively small, and the port side end surface (2a) is arranged so as to surround the third port group (23). The area of the provided seal portion is also set relatively small. For this reason, the port side end face (2) is inserted through the third discharge side through hole (34).
Due to the discharge pressure acting on a), the separation force for separating the cylinder block (2) from the valve plate (3) becomes relatively small, and the second cylinder row (4)
The pressure in the cylinder block (2) is pressed against the valve plate (3) by hydraulic pressure in the cylinder chambers (42, 42,...). That is, since the pressure balance of the cylinder block (2) is balanced, the cylinder block (2) and the valve plate (3) can be maintained in a predetermined joint state. ) And the valve plate (3), the amount of pressure oil leaking from the gap can be reduced to reduce power loss and maintain discharge pressure.

In addition, in the above-mentioned pump, the moment balance by the hydraulic pressure is balanced on the discharge side of the cylinder block (2). This will be described with reference to FIG. 6. In the cylinder block (2), the second cylinder row (4b) has the cylinder block (2).
Of the second cylinder row (4
Since the third discharge-side through-hole (34) communicating with b) is disposed on the inner peripheral side of the valve plate (3), on the discharge side (upper side in the figure) of the cylinder block (2),
The pressing force (F1) acting on the outermost side and the separating force (F2) acting on the inner side act as a couple at positions different in the radial direction. A moment in a direction (counterclockwise in the drawing) in which the cylinder block (2) is separated from the valve plate (3) is generated with the tip position (B) on the discharge side on the port side end surface (2a) of (2) as a fulcrum. I do. On the other hand, the third port group (23) is disposed on the inner peripheral side, that is, on the inner peripheral side of the third discharge side through hole (34) of the valve plate (3). On the discharge side of the cylinder block (2), a balance force (F3) for pressing the innermost peripheral side of the cylinder block (2) toward the valve plate (3) by the balance piston mechanism (7).
) Works. And, by the balance force (F3), the above-mentioned moment can be canceled and the moment balance of the cylinder block (2) can be balanced.
Thereby, the rotation operation of the cylinder block (2) can be stabilized. Moreover, since the balance force (F3) presses the cylinder block (2) toward the valve plate (3), the separation force (F2) can be set to be larger by the balance force (F3). become able to. Accordingly, the opening cross-sectional area of the third discharge-side through hole (34) can be set to be relatively large, and the third port group (23) is adjusted accordingly.
By setting the opening cross-sectional area of each port (23a) large, the self-priming of the cylinder block (2) can be improved.

In addition, in the above pump, the bearing surface (2f) formed on the entire outer peripheral surface of the cylinder block (2) and the annular projecting portion (92) on the casing body (9) side. A journal bearing (8) is provided therebetween, and a radial load applied to the cylinder block (2) is supported by an oil film. For this reason, generation of meshing noise between the cylinder block (2) and the pump shaft (1) at the spline (1c) due to the radial load applied to the cylinder block (2) is eliminated, thereby improving quietness. Is achieved. In the above pump, oil is supplied to the trochoid pump (11) from within the casing body (9), and a drain passage (10e) is formed in the end cap (10) to form a cylinder block (2) and a valve. The pressure oil leaking from between the plate (3) and the plate (3) is recirculated from the casing body (9) to the suction-side passage (10a), thereby simplifying the hydraulic piping for the pump.

<Second Embodiment> FIG. 7 shows a variable displacement piston pump according to a second embodiment of the present invention. In this device, a pump shaft (12) penetrates a cylinder block (2) (see FIG. 8), and the distal end side thereof is an end cap (1).
0) having a circular cross-section formed therein and having a circular cross section, and a sliding bearing (13a) formed on the inner surface of the hole (13) and an angular bearing (11) on the proximal end side. Are rotatably supported by the casings (9 and 10). The pump according to the first embodiment has a configuration in which the balance piston mechanism (7) and the journal bearing (8) are omitted, and the other configuration is the same as that of the pump according to the first embodiment. The same reference numerals are given to the members, and the description is omitted.

In the case of the second embodiment, as in the case of the first embodiment, since three discharge flows can be independently supplied from one cylinder block, a gear pump can be omitted. As a result, it is possible to reduce the size of the pump, reduce mechanical loss and operation noise, increase the pressure of the third discharge flow, etc., and to use the power of the prime mover effectively by comprehensive total horsepower control. Can be planned. Further, similarly to the first embodiment, the pressure balance of the cylinder block (2) can be balanced so that the cylinder block (2) and the valve plate (3) can be maintained in a predetermined joint state. The leakage amount of the pressure oil from the gap between the cylinder block (2) and the valve plate (3) is reduced, so that the power loss is reduced and the discharge pressure is maintained. In addition, balance piston mechanism (7)
By omitting the above, the structure can be simplified, and the above-described functions and effects can be realized at a relatively low cost.

<Other Embodiments> The present invention relates to the first embodiment.
The present invention is not limited to the second embodiment, and includes various other embodiments. That is, in the first and second embodiments, the variable displacement piston pump is applied to the hydraulic piston pump, but is not limited thereto, and may be applied to a hydraulic pump using a liquid other than oil.

In the first and second embodiments, the center of rotation of the variable swash plate (5) is offset toward the spring mechanism (6). However, the present invention is not limited to this, and various arrangements are possible. It is.

In the first and second embodiments, the first cylinder row (4a) is composed of ten cylinder chambers, and the second cylinder row (4b) is composed of five cylinder chambers. However, the present invention is not limited to this, and the first cylinder row may be configured with cylinder chambers other than 10 cylinders, and the second cylinder row may be configured with cylinder chambers other than 5 cylinder chambers.

In the first embodiment, the journal bearing is provided on the outer peripheral surface of the cylinder block (2). However, the present invention is not limited to this. For example, another bearing such as a roller bearing may be provided. It is possible.

[0043]

As described above, according to the variable displacement piston pump according to the first aspect of the present invention, the size of the conventional multi-flow type pump is shortened by omitting the gear pump in the conventional pump. As well as reducing the mechanical loss, increasing the discharge pressure, and reducing the operating noise. Further, the load on the prime mover that rotationally drives the cylinder block (2) can be suppressed to a predetermined value or less to prevent the overload operation, and the output of the prime mover can be effectively used.

Further, the second cylinder row (4b) disposed on the outermost peripheral side of the cylinder block (2) is disposed on the inner peripheral side of the port side end surface (2a) of the cylinder block (2). By communicating with the third port group (23), the pressure balance of the cylinder block (2) can be balanced and the cylinder block (2) and the valve plate (3) can be maintained in a predetermined joint state. Thus, it is possible to reduce the power loss and maintain the discharge pressure by reducing the leakage amount of the pressurized liquid.

According to the second aspect of the present invention, in addition to the effect of the first aspect of the present invention, in addition to the effect of the first aspect of the present invention, the balance plate (72, 72,...) By generating a pressing force on the side of 3), the moment balance of the cylinder block (2) can be balanced.
The rotation operation of the cylinder block (2) can be stabilized.

According to the third aspect of the present invention, in addition to the effects of the first or second aspect, a bearing for supporting the pump shaft (1) is omitted, and the pump shaft is accordingly reduced. (1) The length can be reduced, whereby the entire variable displacement piston pump can be made compact. Further, even when the pump shaft (1) is not penetrated with respect to the cylinder block (2), the cylinder block (2) can be reliably rotated and supported from the outer peripheral side.

According to the fourth aspect of the invention, in addition to the effect of the third aspect of the invention, it is possible to improve the quietness during the rotation operation of the cylinder block (2).

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a variable displacement piston pump according to a first embodiment of the present invention.

FIG. 2 is a transverse sectional view taken along line YY of FIG.

FIG. 3 is a plan view showing a port-side end surface of a cylinder block.

FIG. 4 is a schematic diagram showing a communication state between first and second cylinder rows and a port group.

FIG. 5 is a plan view showing a configuration of a valve plate.

FIG. 6 is a partial sectional view taken along line ZZ of FIG. 2;

FIG. 7 is a diagram corresponding to FIG. 1 according to a second embodiment of the present invention.

FIG. 8 is a diagram corresponding to FIG. 2 according to a second embodiment.

FIG. 9 is a schematic diagram illustrating an example of a hydraulic system of a construction machine such as a shovel.

FIG. 10 is a partially cutaway view showing an example of a multi-flow type pump conventionally used as a hydraulic pressure source for construction machines such as shovels.

[Explanation of symbols]

 Reference Signs List 1 pump shaft 2 cylinder block 2a port side end face of cylinder block 3 valve plate 4a first cylinder row 4b second cylinder row 5 variable swash plate 6 spring mechanism 8 journal bearing (bearing part) 9 casing body (casing) 21 first port Group 22 Second port group 23 Third port group 24 Cylinder chambers constituting the first cylinder row 25 Cylinder chambers constituting the second cylinder row 31 Suction side through holes 32, 33, 34 Discharge side through holes 41 First cylinder row Piston 42 accommodated in the second cylinder row 71 balance cylinder 72 balance piston

Claims (4)

[Claims] 1. A pump shaft (1), a cylinder block (2) rotating integrally with the pump shaft (1), and a circumference around the pump shaft (1) in the cylinder block (2). The pistons (41, 41,
41,...) Are reciprocally slidable in the direction of the pump shaft (1), a first cylinder row (4a) constituted by a plurality of cylinder chambers (24, 24,...), And the cylinder block (2). Are arranged at respective positions on a concentric circle on the outer peripheral side with respect to the first cylinder row (4a),
A plurality of cylinder chambers (25, 2) accommodating pistons (42, 42,...) Reciprocally slidable in the direction of the pump shaft (1).
5,...), The first cylinder row (4a) and the second cylinder row (4).
b) pistons (41, 41,..., 42, 4)
A variable swash plate (5) for increasing / decreasing / changing the reciprocating stroke of a reciprocating motion of a valve plate (3) relatively slidably connected to a port side end surface (2a) of the cylinder block (2). )
The first and second ports arranged on the port-side end face (2a) in the inner and outer peripheral directions so as to be communicated with the respective cylinder chambers (24) of the first cylinder row (4a). And two rows of port groups (21, 22), which are arranged in a circumferential direction at an inner peripheral side of the first port group (21) and the second port group (22), and the second cylinder row A third port group (23) communicated with each cylinder chamber (25) of (4b) is formed, and the valve plate (3) is substantially half in a circumferential direction about the pump shaft (1). A suction-side through-hole (31) arranged in the suction-side area occupied so as to be able to communicate with approximately half of the three port groups (21, 22, 23).
And the pump shaft (1) disposed in the discharge side range occupying another approximately half of the circumferential direction and individually communicating with approximately half of the three port groups (21, 22, 23). First, second and third arc-shaped discharge side through holes (3) formed at concentric circumferential positions having different diameters with respect to the center.
2, 33, 34). 2. The pump shaft (1) according to claim 1, wherein a distal end (1a) of the pump shaft (1) is fitted inside the cylinder block (2) in a non-penetrating state from a swash plate side (2b). In block (2), a third port group (2
3) The pump shaft (1) is open at a position on the inner peripheral side of each port (23a) so as to face the distal end surface (1a) of the pump shaft (1).
A plurality of balance cylinder chambers (71, 71,...) That are individually communicated with the respective ports (23a) are provided, and a base end side of each of the balance cylinder chambers (71, 71,. While being housed in a liquid-tight and relatively slidable manner with respect to the chamber (71), the front end side is in contact with the front end surface (1a) of the pump shaft (1), and the balance cylinder chamber (71, 71,...) A variable displacement piston pump is provided with balance pistons (72, 72,...) Which press the tip end surface (1a) of the pump shaft (1) by receiving the above hydraulic pressure. 3. The cylinder block (2) according to claim 1, wherein the cylinder block (2) is formed in a cylindrical shape, and the cylinder block (2) is provided between the outer peripheral surface of the cylinder block (2) and the inner peripheral surface of the casing (9). A variable displacement piston pump, comprising a bearing (8) for rotatably supporting the cylinder block (2) with respect to the casing (9). 4. The variable displacement piston pump according to claim 3, wherein the bearing (8) is constituted by a sliding bearing that supports the outer peripheral surface of the cylinder block (2) all around.