JPH10184532A - Variable displacement piston pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an outer measurement of a variable displacement piston pump by discharging three independent discharge streams with the same flow rate from one cylinder block. SOLUTION: A leading end of a shaft 1 is internally fitted to a cylinder block 2 at its end on the port side. A first cylinder line 4a reciprocatingly and sliding movably housing pistons 41 is arranged on an outer peripheral side inside the cylinder block. On its inner peripheral side, a second cylinder line 4b is arranged between a leading end surface 1a of the shaft and a swash plate side end surface 2b of the cylinder block. A variable swash plate 4b is arranged for adjusting stroke of reciprocation of the pistons. First and second port groups communicating with the first cylinder line, and a third port group communicating with the second cylinder line are arranged on a port side and surface 2a of the cylinder block. A suctioning side through-hole communicatable with substantially half of the port groups are formed within a certain range of the sectioning side of a valve port 3. Three discharging side through-holes communicatable with the other half of the port groups are formed on a range of the discharging 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 and operating these actuators, and more particularly to a variable displacement pump used as a power source for construction machines such as hydraulic excavators. It relates to a type piston pump.

[0002]

2. Description of the Related Art Conventionally, a construction machine such as a hydraulic excavator has three independent hydraulic systems as shown in FIG. 7, and a first hydraulic system for supplying hydraulic oil to a right traveling system (100). Three hydraulic sources, a pump (101), a second pump (111) for supplying pressure oil to the left traveling system (110), and a third pump (121) for supplying pressure oil to the turning system (120) is required. Here, the right traveling system (100) and the left traveling system (110) are independent of each other because the traveling straightness can be improved even when the loads on the left and right traveling systems (100, 110) are different from each other. In order to maintain, the left and right traveling systems (100, 110) and the turning system (1)
20) is independent to maintain a good operational feeling of the turning system (120) even during traveling, and to maintain straight traveling performance even during operation of the turning system (120). It is. Furthermore, in the case of a hydraulic excavator, from the viewpoints of improving the operability of each system and effectively using a power source, the above-mentioned 3rd aspect is adopted.
It is desirable that the flow rates of the pressure oil supplied from the plurality of hydraulic sources be approximately the same.

[0003] Conventionally, a multi-flow pump (200) as shown in FIG. 8 capable of supplying three discharge flows has been generally employed as a hydraulic source for construction machines such as hydraulic excavators. In this case, one cylinder block (21
The input shaft (221) is provided for the two-flow type piston pump (210) that supplies two equal discharge flows independently from 1).
Is the shaft (2) of the two-way piston pump (210).
By adding a gear pump (220) rotated by 12), three discharge flows can be supplied. And as this type of two-way piston pump,
For example, one described in JP-A-6-307330 is known. In this configuration, two rows of port groups are formed in the inner and outer peripheral directions around the rotation axis of the cylinder block on the port side end face of the cylinder block, and an even number of ports formed in a row in the circumferential direction inside the cylinder block are formed. Each port of the above-mentioned inner peripheral side port group and each of the above-mentioned outer peripheral side port group are alternately communicated one by one with the individual 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, and the pressure oil is discharged independently through both of these discharge-side through holes, so that two equal-flow discharge flows are independently supplied from one cylinder block. ing. 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, the shaft (21) of the multi-flow pump (200)
2) to connect the output shaft of the prime mover in series with
When it is necessary to dispose the prime mover in the pump axial direction of the multi-flow pump (200),
No. 0) has a configuration in which the gear pump (220) is disposed on one end face in the pump axial direction of the two-way piston pump (210), so that it must be enlarged in the pump axial direction. There is a disadvantage that the entire power source including the flow pump (200) and the prime mover becomes large.
In particular, in the case of a small shovel such as a so-called mini shovel having a body weight of 6 tons or less, there is a strong demand for downsizing the vehicle body.

Further, 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). The load on the prime mover from the gear pump (220) increases with the increase in the hydraulic pressure in (120), so that the prime mover is likely to be overloaded. In addition, the hydraulic pressure of the turning system (120) must be released from the relief valve. In some cases, there is an inconvenience that the power loss tends to increase. 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 outer peripheral side or inner 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. However, when the second cylinder row is disposed on the outer peripheral side of the first cylinder row,
Are arranged on the outermost peripheral side of the cylinder block. Therefore, the port group arranged on the port side end face of the cylinder block so as to communicate with the second cylinder row also has the port side end face. It will be arranged on the outermost side. 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. As a result, there is a disadvantage that the pressure balance of the cylinder block cannot be balanced.

On the other hand, when the second cylinder row is disposed on the inner peripheral side of the first cylinder row, the piston accommodated in the second cylinder row comes into sliding contact with the inner peripheral side of the swash plate. The strokes of these pistons are smaller than the strokes of the pistons accommodated in the first cylinder row, and the inner peripheral side of the first cylinder block penetrates the center of the cylinder block. Since the shaft is provided and the space between the shaft and the first cylinder row is narrow, the cross-sectional area of each cylinder constituting the second cylinder row cannot be set sufficiently large. For this reason, the volume of each cylinder in the second cylinder row must be reduced. Therefore, the third discharge flow rate discharged from the second cylinder row is set to a sufficient discharge flow rate substantially equal to the first and second two discharge flow rates discharged from the first cylinder row. There is an inconvenience that you cannot do it.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a multi-flow type piston pump used for construction machines such as a hydraulic shovel.
It is configured to be able to discharge three independent discharge flows of the same flow rate from each cylinder block, thereby shortening the external dimensions of the multi-flow type piston pump, improving the mechanical efficiency, and improving the performance of the motor. The purpose is to prevent overloading.

[0009]

In order to achieve the above object, an invention according to claim 1 comprises a cylinder block (2) rotatably supported in a casing (9), and the cylinder block (2). A plurality of cylinder chambers (24, 24,...) Accommodating the piston (41) at each position on the circumference around the rotation axis (X) so as to be reciprocally slidable in the direction of the rotation axis (X). The first and second cylinder rows (4a) are arranged so as to communicate with the respective cylinder chambers (24) of the first cylinder row (4a) on the port side end surface (2a) of the cylinder block (2). The first and second two rows of port groups (21, 21)
2) and the piston (4) of the first cylinder row (4a).
And a variable swash plate (5) for increasing / decreasing / changing the reciprocating stroke of (1, 41,...), And through the port groups (21 or 22) with the rotation of the cylinder block (2). A variable displacement piston pump configured to discharge hydraulic oil independently of each other is assumed. In this one,
A shaft (1) extending along the rotation axis (X) and connected to a port-side end of the cylinder block (2);
And a piston (4) at each position on the inner peripheral side of the first cylinder row (4a) in the cylinder block (2) and on a concentric circle with the first cylinder row (4a).
A second cylinder row (4b) composed of a plurality of cylinder chambers (25, 25,...) Accommodating 2) reciprocally slidable in the direction of the rotation axis (X), and the port-side end surface (2a).
In order to communicate with each cylinder chamber (25) of the second cylinder row (4b), the port groups (21,
22) and is formed in the circumferential direction at a position on the inner peripheral side with respect to the second cylinder row (4b) with the rotation of the cylinder block (2).
Third port group (2) that supplies and discharges hydraulic oil independently of 3)
3).

In the above configuration, the shaft (1) for rotating and driving the cylinder block (2) is connected to the port-side end of the cylinder block (2) so as not to penetrate the cylinder block (2). In this state, a sufficiently wide space can be secured on the inner peripheral side in the cylinder block (2). The first cylinder row (4a) is disposed on the outer peripheral side in the cylinder block (2), while the second cylinder row (4b) is disposed in a sufficiently wide space on the inner peripheral side. The cross-sectional area of each cylinder chamber (25) constituting the two-cylinder row (4b) is set to be sufficiently large. Then, with the rotation of the cylinder block (2), each of the pistons (41, 4) accommodated in the first and second cylinder rows (4a, 4b), respectively.
Due to the reciprocating motion of 2), the first, second and third port groups (21, 22, 23) formed on the port side end surface (2a) of the cylinder block (2) are independently formed. The pressurized liquid is discharged and supplied as first, second and third discharge flows. At this time, since the cross-sectional area of each cylinder chamber (25) constituting the second cylinder row (4b) is set to be sufficiently large, the third discharge flow discharged from the second cylinder row (4b) is set. The discharge flow rate can be made sufficiently large.
It is possible to make the second and third discharge flow rates approximately equal to each other. Accordingly, it is possible to supply three independent and equal flow rates of the pressure fluid from one cylinder block (2) of one variable displacement piston pump. It becomes possible to omit the gear pump in the shape pump. 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 (41, 41,..., 42,...) Of the first cylinder row (4a) and the second cylinder row (4b)
,..) Is adjusted by one variable swash plate (5).
a, 4b), it becomes possible to adjust the discharge amount of all three discharge flows to be increased or decreased according to the change of the discharge pressure, thereby rotating the cylinder block (2). It is possible to prevent the overload operation of the prime mover by suppressing the load on the prime mover below a predetermined set value. In addition, it is possible to perform comprehensive total horsepower control based on the total of the loads on the flow rates and pressures of the three discharge flows, thereby further utilizing the output of the prime mover.

According to a second aspect of the present invention, in the first aspect, 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 bearing (7) rotatably supported with respect to (9) is provided.

In the above configuration, in addition to the operation according to the first aspect of the present invention, the cylinder block (2) is reliably rotated and supported by the bearing (7) disposed on the outer peripheral surface thereof. That is, the shaft (1) is internally fitted to the cylinder block (2) in a non-penetrating state, and the bearing for supporting the shaft (1) is connected to the cylinder block (2).
The cylinder block (2) can be reliably rotated and supported by the bearing portion (7) disposed on the outer peripheral surface of the cylinder block (2), although the cylinder block (2) is disposed only on one side. Accordingly, the cylinder block (2) can be smoothly rotated.

According to a third aspect of the present invention, the bearing (7) according to the second 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 second aspect of the present invention, since the bearing portion (7) 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 (7) makes it possible to rotationally support the cylinder block (2) against a radial load applied to the cylinder block (2), thereby achieving quietness. Can be improved.

[0016]

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

FIG. 1 shows a variable displacement piston pump (hereinafter simply referred to as a pump) according to an embodiment of the present invention.
1 is a shaft that is driven to rotate by a prime mover not shown,
2 is a cylindrical cylinder block that rotates integrally with the shaft (1), and 3 is joined to the port side end surface (2a) of the cylinder block (2) so as to be slidable in an oil-tight manner. This is a valve plate that supplies and discharges hydraulic oil to and from 2). Reference numeral 4a denotes a first cylinder row arranged on the outer peripheral side of the cylinder block (2).
b is a second cylinder row arranged on the inner peripheral side thereof, and 5 is a piston (41, 41,..., 42, 4) housed in each cylinder chamber constituting these cylinder rows (4a, 4b).
2, ...) a variable swash plate that adjusts the stroke of reciprocation
Reference numeral 6 denotes a spring mechanism for urging the variable swash plate (5) in a direction to increase its inclination angle. Further, reference numeral 7 denotes a journal bearing constituted by a sliding bearing disposed on the entire outer peripheral surface of the cylinder block (2), 8 denotes a trochoid pump driven by the shaft (1), and 9 denotes a cylinder block (2). ), Etc., housing the housing
Reference numeral 0 denotes an end cap for closing the open end of the casing body (9). And the casing body (9)
And the inside of the pump casing constituted by the end cap (10) is in a state filled with oil.

The shaft (1) is rotatably supported around a central axis by a bearing (not shown) with respect to an end cap (10) at a base end side (left side in the drawing), while a distal end ( The right side in the figure is fitted inside the port-side end (left side in the figure) of the cylinder block (2), and is connected to the cylinder block (2) via a spline (1b). It is configured to rotate integrally.

Inside the cylinder block (2),
As shown in FIG. 2, the pistons (41, 41,...) Are formed in a row in the circumferential direction around the rotation axis (X) and accommodate the pistons (41, 41,. The ten cylinder chambers (24, 24,...) Are in the first cylinder row (4
a). Also, the first cylinder row (4
On the inner peripheral side of a), five cylinder chambers (25, 25,...) for accommodating the pistons (42, 42,. Are formed at equal intervals to form a second cylinder row (4a). Here, the shaft (1) is connected to the cylinder block (2).
, The swash plate side end face (2b) of the cylinder block (2) and the tip end face (1a) of the shaft (1) on the inner peripheral side of the cylinder block (2). A sufficiently large space is secured between the cylinders, and each of the cylinder chambers (25) of the second cylinder row disposed in this space has a sufficiently large cross-sectional area.

As shown in FIG. 3, the port group (21, 2) is provided at three concentric circumferential positions about the rotation axis (X) on the port side end surface (2a) of the cylinder block (2).
2, 23) are formed, and each port (21) constituting the first port group (21) is located at a first circumferential position near the outer periphery.
a) are formed at equal intervals. Each of the ports (21a) is connected to each of the five cylinder chambers (24a, 24a,...) Of the first group arranged alternately in the first cylinder row (4a). The individual cylinder chambers (24a) are individually communicated with each other by a communication passage extending in the direction of the rotation axis (X) from a substantially central position (see FIG. 4). The 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 (21) at a second circumferential position on the inner side. Are formed. Each port (22a) of the second port group (22) is provided with five cylinder chambers (24b, 24b, 24b, 24b, 24b) of a second group other than the first group in the first cylinder row (4a). …)When,
These cylinder chambers (24a) are individually communicated with the cylinder chambers (24a) by communication paths extending in the direction of the rotation axis (X) from positions offset on the inner peripheral side of the cylinder block (2). Further, at the third circumferential position closest to the inner circumference, five ports (23a, 23a) constituting the third port group (23) are provided.
a) are formed at equal intervals, and their ports (23a) are connected to the third cylinder row (4b) constituting the second cylinder row (4b).
Each of the five cylinder chambers (25, 25,...) Of the group is individually communicated with a communication path extending from a substantially central position of each of the cylinder chambers (25) in the direction of the rotation axis (X).

The port-side end surface (2a) has a third port group (23) and a second port group (23) centered on the rotation axis (X).
An annular first annular groove (2c) is located at an intermediate position with respect to the port group (22), and an annular second annular groove (2d) is located at a concentric position on the outer peripheral side of the first port group (21). The first annular groove (2c) is communicated with the casing body (9) by a communication passage (not shown) to form a drain passage, and the second annular groove (2d) extends from the outer peripheral edge thereof. Five concave grooves (2e, 2) extending radially outward
e,...) communicate with the inside of the casing body (9) to form a drain passage. The inner peripheral side of the first annular groove (2c) and the first annular groove (2c)
Seal portions are provided between the annular groove portions (2d) so as to surround the first, second, or third port groups (21, 22, 23), respectively.

A cylinder chamber (24, 24,...) Of the first cylinder row (4a) is opened on the outer peripheral side of the swash plate side end surface (2b) (see FIG. 1) of the cylinder block (2). The cylinder chambers (25, 25,...) Of the second cylinder row (4b) are open on the inner peripheral side, and the pistons (41, 42) housed in the respective cylinder chambers (24, 25) are , The base end side of each cylinder chamber (2
4, 25), while the distal end projects from the opening toward the variable swash plate (5) and passes through the variable swash plate (5) via slippers (43, 44) disposed at the distal end thereof. )
Slidably in contact with Each of the pistons (41, 42) revolves around the rotation axis (X) by the rotation of the cylinder block (2) and tilts the variable swash plate (5) in the direction of the rotation axis (X). It is configured to reciprocate according to the angle.

The valve plate (3) (see FIG. 5)
Is bonded to the inner surface of the end cap (10),
A suction side range (lower side in the figure) which is slidably joined to the port side end surface (2a) of the cylinder block (2) and occupies substantially half of the circumference around the rotation axis (X). Range) includes a wide, substantially arc-shaped suction-side through hole (3).
1) are ports (21a,...) Of three port groups (21, 22, 23) arranged on the port side end surface (2a).
, 22a,..., 23a,. The suction side through hole (31) is formed between the suction side passage (10a) (see FIG. 6) formed on the inner surface of the end cap (10) and the ports (21a,..., 22a,. ,...) And the cylinder chambers (24, 2)
4,..., 25, 25,...). Further, the discharge side range (upper range in FIG. 5) occupying substantially half of the circumference of the valve plate (3) around the rotation axis (X), the rotation axis (X) being the center. Three substantially arc-shaped discharge side through-holes (32, 33, 34) are formed at concentric circumferential positions, and the outermost first side is formed.
The discharge-side through-hole (32) is provided so as to be able to communicate with substantially half of the ports (21a, 21a,...) Constituting the first port group (21) at the same time. The second discharge side through hole (3) formed on the inner peripheral side of (32)
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. The pistons (41, 41,..., 42,
42,...), The pressure oil in the cylinder chambers (24a,..., 24b,..., 25,. From the discharge side through-holes (32, 33,
34), a first discharge side passage (10b) (see FIG. 6), which will be described later, formed in the end cap (10).
The air is distributed to the discharge side passage (10c) or the three discharge side passages (10d).

The variable swash plate (5) has one end face (FIG. 1).
A left side surface of the main body (51) having a sliding surface (51a) and a rotation center position (A) offset toward the spring mechanism (6) with respect to the center position of the main body (51). A rotation shaft (52) formed so as to protrude outwardly (perpendicular to the plane of FIG. 1) from the outer peripheral surface of the main body (51) so as to pass therethrough; A projection (53) projecting from the outer peripheral surface at one end (upper end in FIG. 1) in a direction orthogonal to 52). The variable swash plate (5) receives the reaction force of the piston (41, 41,..., 42, 42,. A self-returning moment in a decreasing direction (counterclockwise in FIG. 1) is generated. Further, the variable swash plate (5) has a protrusion (53).
Abuts against the bottom wall (the right side wall in FIG. 1) of the casing body (9) to prevent further rotation, and the inclination angle becomes the maximum (for example, 17 degrees) while the maximum inclination state is reached. It is configured to rotate to the opposite side so that the main body portion (51) abuts against the bottom wall portion of the casing main body (9) and further rotation is prevented, and the tilt angle becomes a neutral state of zero degree. I have. By the rotation of the variable swash plate (5), slippers (43, 43,...)
44, 44,...).
, 41,..., 44, 44,.

The spring mechanism (6) accommodates a coil spring (61) in a cylindrical portion (91) projecting obliquely outward (upper left in FIG. 1) from the peripheral surface of the casing body (9). The coil spring (61) applies a urging force between the distal end wall portion of the tubular portion (91) and the protruding portion (53) of the variable swash plate (5), thereby causing the variable swash plate ( 5) is urged toward the maximum inclination side (clockwise in FIG. 1) with a pressing force substantially proportional to the inclination angle.

The journal bearing (7) includes 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 a 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).
The cylinder block (2) is configured to be rotatably supported in the radial direction by an oil film formed between the cylinder block (2) and the facing surface (92a) facing f). Further, the trochoid pump (8) is disposed in the end cap (10), and is driven to rotate by the shaft (1) to form a suction side passage (described later) formed in the end cap (10). 10a) The oil supplied from the communication passage (81) from the communication passage (81) is discharged from a later-described fourth discharge passage (10e) formed in the end cap (10). ing.

As shown in FIG. 6, the end cap (10) is formed in a thick disk shape and constitutes a pump casing integrally with the casing body (9), and penetrates the center. A suction-side passage communicating with a suction-side through hole (31) of the valve plate (3) is provided in a suction-side range (a lower range in the figure) occupying substantially half of the circumferential direction around the shaft (1). (10a) is formed, and three discharge side through holes (32, 33) of the valve plate (3) are provided in the discharge side range (upper range in the figure) occupying substantially half of the opposite side in the circumferential direction. , 34), the first, second and third three discharge side passages (10b, 10).
c, 10d) are formed. Further, a communication passage (81) for supplying oil from the suction side passage (10a) to the trochoid pump (8) is formed, and a fourth discharge side for flowing the pressure oil discharged from the trochoid pump (8). The passage (10e) is connected to the first, second, and third discharge-side passages (1).
0b, 10c, 10d). In addition, the end cap (10) has a suction-side passage (1).
0a) and the inside of the casing body (9) are formed with a drain passage (10f), and a clearance between the port side end surface (2a) and the valve plate (3) on the discharge side of the cylinder block (2). The pressurized oil leaking into the casing body (9) returns from the casing body (9) to the suction side passage (10a).

The first discharge-side passage (10b) is connected to the left traveling system of a hydraulic shovel (not shown), and the second discharge-side passage (10c) is connected to the right traveling system of the hydraulic shovel. The passage (10d) is independently connected to the turning system of the excavator by a hydraulic pipe, and the fourth discharge side passage (10e) is connected to a pilot operation circuit of the excavator. The side passage (10a) is connected to an oil tank (not shown) of the excavator by a hydraulic pipe.

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

First, when the shaft (1) is rotated by the operation of the prime mover (not shown), the pistons (41, 41, 41, 41) are rotated.
, 42, 42, ...) reciprocate along the variable swash plate (5) to suck oil from the suction side and discharge it to the discharge side. At this time, the cylinder chambers (24a, 24a) of the first group
a) pass through the first port group (21) and the first discharge side through hole (32) and pass through the first discharge side passage (10b).
The second group of cylinder chambers (24b, 24b,...)
Similarly, the pressure oil in the second discharge side passageway (10c) and the pressure oil in the third group of cylinder chambers (25, 25,...) Are similarly independent of the third discharge side passageway (10d). And is independently supplied to each hydraulic system of the shovel via hydraulic piping.

The first discharge flow discharged from the first group of cylinder chambers (24a, 24a,...) And the second discharge flow discharged from the second group of cylinder chambers (24b, 24b,...) Each of the flows is an equal amount of discharge flow discharged from an equal volume cylinder chamber (24) constituting the first cylinder row (4a), and the two discharge flows are respectively transmitted to the left and right traveling systems of the shovel. By independently supplying the shovel, the traveling straightness of the shovel can be improved. In addition, each cylinder chamber (2
Since the cross-sectional area of 5) is set to be sufficiently large, the flow rate of the third discharge flow discharged from the cylinder chambers (25, 25,...) Of the third group is equal to the first and second equal flow rates. And a sufficient discharge flow rate comparable to the above discharge flow. Therefore, by independently supplying the third discharge flow to the turning system of the shovel, it is possible to improve the operability of the turning system while effectively utilizing the output of the prime mover. That is, since the hydraulic oil having the flow rate of the identification degree can be independently supplied from the single cylinder block (2) to the three hydraulic systems of the shovel, the gear pump conventionally required is omitted. By omitting the gear pump, the size of the pump can be shortened especially in the axial direction of the pump, and the power source can be made compact.
In addition to reducing mechanical loss and operation noise, the third group of cylinder chambers (2
5, 25,...), It is possible to discharge a higher pressure oil than before.

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) balances the oil pressure on the discharge side and the urging force of the spring mechanism (6) because the variable swash plate (5) is configured to rotate in a direction in which the inclination angle decreases against the force. In this state, the angles are maintained, so that the flow rates of the first discharge flow, the second discharge flow, and the third discharge flow can be reduced as the discharge pressures thereof increase. Accordingly, it is possible to prevent the prime mover from being overloaded due to an increase in the hydraulic pressure of the turning system, and to reduce the frequency of opening the relief valve to reduce the power loss. That is, comprehensive total horsepower control based on the sum of the loads is performed as the flow rate / pressure control of the pump, thereby further utilizing the output of the prime mover.

Further, in the above-mentioned pump, between the bearing surface (2f) formed over the entire outer peripheral surface of the cylinder block (2) and the annular projecting portion (92) on the casing body (9) side. Since the journal bearing (7) is provided on the cylinder block (2), the bearing for rotatably supporting the shaft (1) is provided only in the end cap (10) on one side of the cylinder block (2). Regardless, the cylinder block (2) is formed by the journal bearing (7).
Can be reliably supported for rotation. In addition, in the journal bearing (7), the radial load applied to the cylinder block (2) is supported by an oil film, so that the radial load applied to the cylinder block (2) and the shaft ( 1) can be prevented from being applied to the spline portion (1b) connecting the cylinder block (2) and the shaft (1) at the spline (1b) portion, and the generation of the meshing noise can be eliminated. As a result, silence is improved.

In addition, in the above pump, the first, second and third groups of cylinder chambers (24a, 24b,
25) and the trochoid pump (8) are supplied with oil from the same suction side passage (10a), while the first, second and third groups of cylinder chambers (24a, 2a) are supplied with oil.
4b, 25).
And the third three discharge-side passages (10b, 10c, 10
d) and a fourth discharge side passageway (10e) through which the pressure oil discharged from the trochoid pump (8) flows, and the cylinder block (2) and the valve plate (3) The pressurized oil leaking from the space is returned to the suction side passage (10a) by a drain passage (10f) formed in the end cap (10). For this reason, the hydraulic piping on the suction side connecting the pump and the oil tank is all common, and the drain piping is not required.Moreover, the piping on the discharge side can be collectively arranged on the same surface of the pump, This simplifies and facilitates the hydraulic piping between the pump and the hydraulic shovel.

<Other Embodiments> The present invention is not limited to the above-described embodiments, but includes various other embodiments. That is, in the above embodiment,
Although the present invention is applied to a hydraulic piston pump as a variable displacement piston pump, the invention is not limited to this, and it is also possible to apply it to a hydraulic pump using a liquid other than oil.

In the above embodiment, the center of rotation of the variable swash plate (5) is offset from the spring mechanism (6), but the present invention is not limited to this, and various arrangements are possible.

In the above embodiment, the first cylinder row (4
a) 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 is other than ten cylinder chambers. The second cylinder row may be composed of cylinder chambers other than five cylinder chambers.

In the above 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. is there.

[0039]

As described above, according to the variable displacement piston pump according to the first aspect of the invention, the shaft (1) is connected to the port-side end of the cylinder block (2). By setting the non-penetrating state to (2), the discharge flow rate from the second cylinder row (4b) can be made sufficiently large.
Three cylinders of the same flow rate can be supplied independently from each other from the cylinder blocks (2). For this reason,
It is possible to omit the gear pump in the conventional multi-flow type pump and reduce the dimension in the pump axial direction by that amount, and to reduce mechanical loss, increase discharge pressure and reduce operation noise. it can. Further, the load applied to 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 load and flow of the three discharge flows can be reduced. , A total total horsepower control based on the sum of the powers can be performed, thereby further utilizing the output of the prime mover.

According to the second aspect of the invention, in addition to the effect of the first aspect, the cylinder block (2) is rotatably supported by the bearing portion (7) disposed on the outer peripheral surface thereof. In addition, the cylinder block (2) can be reliably rotated and smoothly rotated.

According to the third aspect of the invention, in addition to the effect of the second 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 an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the cylinder block 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 each 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 schematic diagram illustrating an example of a hydraulic system in a construction machine such as a hydraulic shovel.

FIG. 8 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 a hydraulic shovel.

[Explanation of symbols]

 Reference Signs List 1 shaft 2 cylinder block 2a port side end surface of cylinder block 2b swash plate side end surface of cylinder block 4a first cylinder row 4b second cylinder row 5 variable swash plate 7 journal bearing (bearing part) 9 casing body (casing) 21 first Port group 22 Second port group 23 Third port group 24 Cylinder chamber forming first cylinder row 25 Cylinder chamber forming second cylinder row 41 Piston housed in first cylinder row 42 Piston housed in second cylinder row Piston X Rotation axis of cylinder block

Claims (3)

[Claims] 1. A cylinder block (2) rotatably supported in a casing (9), and a piston (2) in each position on a circumference around a rotation axis (X) in the cylinder block (2). 41) in which a plurality of cylinder chambers (24, 24, 24,
..) And the respective cylinder chambers (24) of the first cylinder row (4a) on the port side end surface (2a) of the cylinder block (2).
The first is formed in the inner and outer peripheral directions so as to communicate with the
And the second two rows of port groups (21, 22) and the first
A variable swash plate (5) for increasing or decreasing the stroke of reciprocation of the pistons (41, 41,...) Of the cylinder row (4a), and each of the port groups as the cylinder block (2) rotates. A variable displacement piston pump configured to discharge hydraulic oil independently from each other via (21 or 22), wherein the distal end extends along the rotation axis (X) and has a tip on the port side of the cylinder block (2). A shaft (1) connected to the end of the first cylinder row (4a) in the cylinder block (2);
At each position on the circumference of the circle concentric with a), a second cylinder chamber (25, 25,...) accommodating a piston (42) slidably in the direction of the rotation axis (X). The cylinder row (4b) and the port side end surface (2a) are located inside the two rows of port groups (21, 22) so as to communicate with the cylinder chambers (25) of the second cylinder row (4b). Hydraulic oil is formed at a circumferential position in the circumferential direction, and is independent of the first or second port group (22 or 23) with respect to the second cylinder row (4b) as the cylinder block (2) rotates. And a third port group (23) for supplying and discharging air. 2. The cylinder block (2) according to claim 1, wherein the cylinder block (2) is rotatable with respect to the casing (9) between an outer peripheral surface of the cylinder block (2) and an inner peripheral surface of the casing (9). A variable displacement type piston pump characterized in that a bearing part (7) for supporting is provided. 3. The variable displacement piston pump according to claim 2, wherein the bearing (7) is constituted by a sliding bearing that supports the outer peripheral surface of the cylinder block (2) all around.