Piston type pump

Abstract

To provide a piston type pump in which an efficiency is improved by suppressing a floating of a swing swash plate by a low friction during inhalation.SOLUTION: The piston type pump includes: a swing swash plate which is mounted on a rotational drive body via a bearing with an inclination axis crossing with a center axis as an axial core, and in which a ring surface is provided at a top part; a piston rod which is connected between a joint of a piston and a joint of the swing swash plate, and converts a reciprocating swing of the swing swash plate into a reciprocating motion of the piston; a shaft part which projects from the rotational drive body at an angular position where the piston is pulled down to the vicinity of a bottom dead point; a pressing part which faces the ring surface at a tip end of the shaft part; and a thrust bearing through which the shaft part penetrates at a center thereof and which is arranged between the pressing part and the ring surface.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a piston-type pump that accommodates pistons in a plurality of cylinder bores arranged around a central axis and converts rotational motion into reciprocating linear motion of the pistons to generate pressurized fluid. [Background technology]

[0002] As a pump that converts rotational motion into reciprocating linear motion of a piston to generate pressurized fluid (including reduced pressure), piston-type pumps such as those disclosed in Patent Documents 1 and 2 are known. In such piston-type pumps, the central axis of the oscillating swash plate is supported so as to be inclined with respect to the central axis of the rotary drive body. The oscillating swash plate is attached to the rotary drive body via radial bearings and thrust bearings so as to be rotatable relative to the rotary drive body without receiving any rotational force.

[0003] The cylinder, whose piston reciprocates along the central axis of the rotary driver, has a piston connected to a piston rod connected to a swash plate. The rotational motion is converted into reciprocating oscillation in the axial direction of the swash plate via the rotary driver, and the piston reciprocates due to the piston rod. The reciprocating motion of the piston opens and closes the suction and discharge ports in the cylinder, generating compressed fluid.

[0004] When fluid is drawn into the cylinder from the suction port, the oscillating swash plate receives a force that lifts it up toward the cylinder in the axial direction via the piston rod. In conventional piston-type pumps, a retaining ring is attached to the rotary drive body to prevent the oscillating swash plate from lifting up. Specifically, the retaining ring is attached to the upper side of the radial bearing between the rotary drive body and the oscillating swash plate, at a position where it abuts against the oscillating swash plate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 57-43743 [Patent Document 2] Japanese Patent Application Publication No. 5-231309 Summary of the Invention [Problem to be solved by the invention]

[0006] When the oscillating swash plate tries to rise, the retaining ring comes into contact with it to prevent it from rising, but at that time, the oscillating swash plate and the retaining ring are pressed against each other, causing friction. This generates a large load, significantly reducing the efficiency of the piston pump.

[0007] SUMMARY OF THE PRESENT INVETION An object of the present invention is to provide a piston type pump having improved efficiency by suppressing the lift of the oscillating swash plate during suction with low friction. [Means for solving the problem]

[0008] The piston-type pump of the present invention comprises a piston housed in a plurality of cylinder bores arranged around a central axis; A rotary drive body that rotates around the central axis; a swash plate mounted on the rotary drive body via a bearing having an inclined axis intersecting the central axis as its axis, the swash plate having a ring surface at its top centered on the inclined axis; a piston rod connected between a joint of the piston and a joint of the swash plate to convert the reciprocating motion of the swash plate into the reciprocating motion of the piston in the cylinder bore; a shaft portion protruding from the rotation drive body at an angular position within a plane centered on the inclined axis where the piston is pulled down to near the bottom dead center; a pressing portion at a tip of the shaft portion and facing the ring surface; The shaft portion passes through the center, and a bearing is disposed between the pressing portion and the ring surface. Effect of the Invention

[0009] According to the present invention, it is possible to reduce friction when the oscillating swash plate is supported so as not to rise up from the rotary drive body, thereby providing a piston type pump with improved efficiency. [Brief description of the drawings]

[0010] [Figure 1] 1A and 1B are views showing a piston type pump, in which FIG. 1A is a front view and FIG. 1B is a plan view. [Diagram 2] 2A is a cross-sectional view of a piston type pump taken along line XX, and FIG. 2B is a cross-sectional view of a piston type pump with a motor, and FIG. 2B is a cross-sectional view of a piston type pump without the motor. [Diagram 3] ZZ cross-sectional view. [Figure 4] YY cross-sectional view. [Diagram 5] These are diagrams showing the relationship between the oscillating swash plate and the rotary drive body, where FIG. 5A shows the oscillating swash plate, the rotary drive body, and the associated components disassembled, FIG. 5B shows the oscillating swash plate and the rotary drive body from the direction of the inclination axis c2, and FIG. 5C shows the oscillating swash plate when the rotary drive body rotates. [Figure 6] 6A is a diagram showing the arrangement of the suction passages and the discharge passages in a plan view, FIG. 6B is a diagram showing the suction passages, and FIG. 6C is a diagram showing the discharge passages. [Figure 7] FIG. 2 is a diagram showing a state in which the piston type pump is used as a vacuum pump. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] An example of a piston type compressor as a piston type pump of this embodiment will be described below with reference to the drawings. In Fig. 1A, the piston type compressor includes, from the top, a check valve 8, a top housing 1, a head housing 2, a cylinder housing 3, a crank housing 4, and a motor 7. The top housing 1, the head housing 2, and the cylinder housing 3 are fixed to the crank housing 4 by bolts 12. The motor 7 is fixed to the crank housing 4 by bolts 74. There are four cylinder housings 3, as shown by dotted lines in Fig. 1B.

[0012] 2A shows a cross section taken along the line XX in FIG. 1B. In FIG. 2A, the crank housing 4 has a front housing 4a and a rear housing 4b which are joined and fixed. A fixed shaft 47 is fixed downward to the front housing 4a by a bolt 48 along a central axis c0. The rotary drive body 50 is bored with a cavity 60 centered on the central axis c0. The rotary drive body 50 is supported by the fixed shaft 47 via a radial bearing 52, and is supported in a bore 59 provided in the rear housing 4b via a radial bearing 51 and a thrust bearing 53, and is rotatable about the central axis c0. A key groove 58 is provided at the lower end of the rotary drive body 50.

[0013] The oscillating swash plate 40 is supported by the rotary drive body 50 via a thrust bearing 55 and a radial bearing 57, and the oscillating swash plate 40 is capable of rotating relative to the rotary drive body 50. The thrust bearing 55 and the radial bearing 57 are bearings whose axes are on an inclined axis c2 that intersects with the central axis c0, and are mounted on an inclined disk surface 54 and an inclined cylindrical surface 56 provided on the rotary drive body 50, respectively.

[0014] On the other hand, a connecting shaft 41 protrudes from the outer periphery of the swash plate 40, and a rotor 41a that rolls along the inner periphery of a guide hole 43 provided in the crank housing 4 is provided at the tip of the connecting shaft 41. The guide hole 43 is a hole in the direction of the central axis c0 as seen in FIG. 3, which is a ZZ cross section (see FIG. 1A). The connecting shaft 41 and the guide hole 43 prevent the swash plate 40 from rotating in conjunction with the rotation of the rotary drive body 50. The swash plate 40 is disk-shaped and has an inclined axis c2 as its axis. When the rotary drive body 50 rotates, the inclined axis c2 of the swash plate 40 precesses with respect to the central axis c0 as shown by the arrow a in FIG. 2A. Since the swash plate 40 is not rotated relative to the crank housing 4, the rotational motion of the rotary drive body 50 is converted into a reciprocating swing of the swash plate 40 in the direction of the central axis c0.

[0015] The motor 7 is fixed to the front housing 4a via the rear housing 4b by bolts 74. FIG. 2B shows the motor 7 separated from the rear housing 4b. A rotating top 71 is fixed to the main shaft 70 of the motor 7 by a set screw 73. A key 72 that fits into the key groove 58 is provided on the rotating top 71. When the motor 7 is connected to the rear housing 4b, the main shaft 70 of the motor 7 is loosely inserted into the cavity 60 of the rotation drive body 50. Even if the axis c1 of the main shaft 70 of the motor 7 is slightly deviated from the central axis c0, the key 72 and the key groove 58 cooperate to transmit the rotational motion from the main shaft 70 of the motor 7 to the rotation drive body 50.

[0016] Fig. 4 is a YY cross section of Fig. 1B. A plurality of cylinder bores 30 are formed in the cylinder housing 3 in the direction of the central axis c0, and the cylinder housing 3 is arranged at equal angular intervals around the central axis c0. Pistons 31 are accommodated in the cylinder bores 30. Each piston 31 and the oscillating swash plate 40 are connected by a piston rod 32 via joints 61 and 63. When the rotary driver 50 rotates, the oscillating swash plate 40 oscillates back and forth in the direction of the central axis c0, and the rotation is transmitted to the piston rod 32, causing the pistons 31 to reciprocate within the cylinder bores 30.

[0017] The head housing 2 forms a ceiling surface 21 of the cylinder bore 30. A suction port 22 and a discharge port 23 are provided in the ceiling surface 21. The suction port 22 and the discharge port 23 are formed by check valves that allow fluid to flow in only one direction. When the piston 31 descends, the valve of the suction port 22 opens, and the fluid is taken into the cylinder bore 30. When the piston 31 ascends, the valve of the discharge port 23 opens, and the fluid is discharged from the cylinder bore 30.

[0018] The top housing 1 is provided with an intake passage 13 and an exhaust passage 10. The intake passage 13 is connected to an external opening 25 provided in the head housing 2 via a filter 11. Both ends of the intake passage 13 are blocked by balls 14. FIG. 6A shows the arrangement of the intake passage 13 and the exhaust passage 10 in a plan view with dotted lines. FIG. 6B shows the intake passage 13, and FIG. 6C shows the exhaust passage 10 with light ink. The intake passage 13 is diagonally connected from the central external opening 25 to the intake ports 22 of the multiple cylinder bores 30. On the other hand, the exhaust passage 10 is connected to the check valve 8 by communicating with the exhaust ports 23 of the multiple cylinder bores 30 in a circular manner. The check valve 8 is a one-way valve that exhausts from the exhaust passage 10 to the outside.

[0019] Next, a structure for preventing the oscillating swash plate 40 from floating up will be described with reference to FIG. 5A shows the oscillating swash plate 40, the rotary drive body 50, and the associated members in an exploded state. A screw hole 45 is provided in the top 49 of the rotary drive body 50 along the inclination axis c3 parallel to the inclination axis c2. The position of the screw hole 45 is an angular position in a plane centered on the inclination axis c2, and is an angular position corresponding to when the piston 31 is pulled down to near the bottom dead center by the piston rod 32. However, it is not necessary to be at the angular position of the bottom dead center strictly.

[0020] The top of the swaying swash plate 40 is provided with a ring surface 62 centered on the tilt axis c2. The bearing (thrust bearing 44) has a stepped spacer 42 inserted into its central hole, and the bolt 46 is screwed into the screw hole 45 from above the ring surface 62. The shaft 46a of the bolt 46 passes through the center of the spacer 42, and the head of the bolt 46 is located above the ring surface 62. The spacer 42 is disposed between the head of the bolt 46 and the top 49, and determines the distance between them. In this state, the upper race 44a of the thrust bearing 44 abuts against the head of the bolt 46. The lower race 44b of the thrust bearing 44 abuts against the ring surface 62 that is about to rise. As a result, the head of the bolt 46 functions as a pressing part 46b that receives the swaying swash plate 40 that is about to rise, via the thrust bearing 44. In order to maintain the tightened state of the bolt 46, a locking treatment (not shown) is applied to the bolt 46.

[0021] 5B is a view of the oscillating swash plate 40 and the rotary driver 50 viewed from the direction of the inclined axis c2. As shown in FIG 5B, a portion of the circumference of the thrust bearing 44 overlaps with the ring surface 62. This partial overlap prevents the oscillating swash plate 40 from floating up.

[0022] As already explained, the rotary drive body 50 rotates around the central axis c0, and the oscillating swash plate 40 oscillates back and forth in the direction of the central axis c0 without rotating. On the other hand, since the bolt 46 is fixed to the rotary drive body 50, the inclined axis c3 of the bolt 46 precesses as shown in FIG. 5C. When the bolt 46 rotates once around the central axis c0, the head of the bolt 46 rotates once. During that time, the lower race 44b of the thrust bearing 44 slides on the ring surface 62 independently of the rotation of the head of the bolt 46. In addition, since the race 44b can rotate freely with respect to the head of the bolt 46, the friction with the ring surface 62 is reduced. As a result, the friction caused by the pressing of the bolt 46 is reduced, the load on the motor 7 is reduced, and the efficiency of the piston type pump can be improved.

[0023] In this embodiment, the bolt 46 is used, but a screw shaft may be embedded in the screw hole 45, and a nut may be used instead of the head of the bolt 46 to function as a pressing portion 46b that presses the thrust bearing 44. Also, in this embodiment, one set each of the guide hole 43, connecting shaft 41, and rotor 41a is provided on the left and right, but only the left or right side may be provided.

[0024] The piston type pump of the present invention can also be used as a vacuum pump. In Fig. 7, only the changes from the piston type compressor of the previous embodiment will be explained. The external opening 25 is sealed with a screw 5. The check valve 8 connected to the discharge passage 10 is removed, and the discharge passage 10 is opened to the atmosphere. The screw 6 (see Fig. 4) of the top housing 1 that had been blocking the suction passage 13 from the atmosphere is removed, and a check valve 9 is installed in its place. The check valve 9 is a one-way valve that takes in fluid into the suction passage 13. The check valve 9 functions as a suction hole for the vacuum pump. [Explanation of symbols]

[0025] 1 Top housing 2 Head housing 3 Cylinder housing 4 Crank housing 4a Front housing 4b Rear housing 5, 6 screws 7 Motor 8, 9 Check valve 10 Discharge path 11 Filters 12 Volts 13 Suction passage 14 Ball 21 Ceiling surface 22 Intake port 23 Discharge port 25 External opening 30 Cylinder bore 31 Piston 32 Piston rod 40 Swinging swash plate 41 Articulating shaft 41a Rotating body 42 Spacer 43 Guide hole 44, 55 Thrust bearing 44a, 44b raceway 45 Screw hole 46, 48, 74 volts 46a Shaft 46b Holding part 47 Fixed axis 49 Top of the Head 50 Rotary drive body 51, 52, 57 Radial bearings 54 Inclined disc surface 56 Inclined Cylindrical Surface 58 Keyway 59 Bore 60 hollow 61, 63 Joints 62 Ring Surface 70 Main axis 71 Rotating Top 72 Keys 73 Grub Screw

Claims

1. a piston housed within a plurality of cylinder bores arranged about a central axis; A rotary drive body that rotates around the central axis; a swash plate mounted on the rotary drive body via a bearing having an inclined axis intersecting the central axis as its axis, the swash plate having a ring surface at its top centered on the inclined axis; a piston rod connected between a joint of the piston and a joint of the swash plate to convert the reciprocating motion of the swash plate into the reciprocating motion of the piston in the cylinder bore; a shaft portion protruding from the rotation drive body at an angular position in a plane centered on the inclined axis, the angular position being near an angular position where the piston is pulled down to a bottom dead center; a pressing portion at a tip of the shaft portion and facing the ring surface; A piston-type pump, characterized in that the shaft portion passes through the center, and a bearing is disposed between the pressing portion and the ring surface.

2. The piston type pump according to claim 1, The rotary drive body is rotatably supported in a bore of a crank housing via a bearing, and a key groove is provided at a lower end of the rotary drive body. A piston type pump, characterized in that when a motor having a rotating top with a key protruding therefrom and attached to a main shaft is fixed to said crank housing, said key fits into said key groove.

3. The piston type pump according to claim 1, a piston-type pump, characterized in that the shaft portion and the pressing portion are the shaft portion and the head portion of a bolt, and the bolt is screwed into a screw hole provided in the rotary drive body with respect to an angular position centered on the inclined axis at which the piston is pulled down to near the bottom dead center.

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