JP2000110737A - Plunger pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure durability of a plunger pump by preventing a seal member from jamming into a narrow space between the outside peripheral surface of a plunger and the inside peripheral surface of a cylinder hole of a pump housing even when the plunger is in the process of discharging. SOLUTION: In this plunger pump a ring-shaped entrance room 19 connected with a pump room 20 via an intake valve 27 is formed on the outside periphery of a plunger 11 with a front-end surface facing the pump room 20 and a ring- shaped seal groove 40 for mounting an elastic seal member 44 is formed on the outside peripheral surface of the plunger 11 between the entrance room 19 and the pump room 20. In this plunger pump, a tapered surface 41 whose bus-line intersects with a back-wall surface 40a of the seal groove 40 at an obtuse angle θ is formed on the outside peripheral surface of the plunger 11 between the entrance room 19 and the seal groove 40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plunger pump mainly applied to a hydraulic pump, and more particularly, to a pump housing having a cylinder hole and a pump which is slidably fitted in the cylinder hole and is provided in the cylinder hole. A plunger having a front end face facing the chamber, and a suction valve for allowing a unidirectional flow of fluid from the annular inlet chamber formed between the outer peripheral surface of the plunger and the inner peripheral surface of the cylinder bore to the pump chamber,
The present invention relates to an improvement in which an annular seal groove formed on an outer peripheral surface of a plunger between an inlet chamber and a pump chamber is provided with an elastic seal member closely contacting an inner peripheral surface of a cylinder hole.

[0002]

2. Description of the Related Art Such a plunger pump is already known, for example, as disclosed in Japanese Patent Application Laid-Open No. 6-129348.

[0003]

As shown in FIG. 3, in the conventional plunger pump, the outer peripheral surface of the plunger 011 is formed as a straight cylindrical surface on both sides of the seal groove 040 in which the seal member 044 is mounted. Therefore, before and after the seal groove 040, the plunger 01
A narrow sliding gap 043 formed between the outer peripheral surface 1 and the inner peripheral surface of the cylinder hole 04 of the pump housing 02 is adjacent.
In such a case, the plunger 011 is connected to the pump chamber 020
During the discharge stroke of sliding in the direction to reduce the volume of the gas, the large pressure difference generated between the high pressure pump chamber 020 and the low pressure inlet chamber 019 causes the seal member 044 in the seal groove 040 to move into the inlet chamber 019. Side, the rear end of the outer periphery protrudes from the seal groove 040 to the inlet chamber 019 side, penetrates into the narrow sliding gap 043, and may be damaged by concentrated stress. The damage of
This causes pressure leakage from the pump chamber to the inlet chamber side, which causes a reduction in pump efficiency.

[0004] The present invention has been made in view of such circumstances, and the seal member does not bite into the narrow gap between the outer peripheral surface of the plunger and the inner peripheral surface of the cylinder hole of the pump housing even during the discharge stroke of the plunger. Thus, an object of the present invention is to provide the plunger pump capable of securing its durability and maintaining high pump efficiency for a long period of time.

[0005]

To achieve the above object, the present invention provides a pump housing having a cylinder bore,
A plunger which is slidably fitted in the cylinder hole and has a front end face facing the pump chamber of the cylinder hole, and a pump chamber formed from an annular inlet chamber formed between the outer peripheral surface of the plunger and the inner peripheral surface of the cylinder hole. A suction valve that allows fluid to flow in one direction, and an elastic seal member that is in close contact with the inner peripheral surface of the cylinder bore is mounted in an annular seal groove formed on the outer peripheral surface of the plunger between the inlet chamber and the pump chamber. The plunger pump is characterized in that a tapered surface is formed on the outer peripheral surface of the plunger between the inlet chamber and the seal groove, where the bus bar forms an obtuse angle with the rear wall surface of the seal groove.

According to this feature, between the tapered surface and the inner peripheral surface of the cylinder bore, there is formed an annular space having a triangular cross section with an interval extending toward the rear wall surface of the seal groove. When the sealing member is strongly pressed rearward due to a high pressure difference between the high-pressure pump chamber and the low-pressure inlet chamber, the outer peripheral rear end enters the annular space. Due to the shape, the stress at the rear end of the outer periphery gradually increases toward the rear, so that the stress concentration is small. In addition, since the stress has already sufficiently increased at the front end of the outer peripheral rear end that has entered the narrow rear end of the annular space, the stress has not sufficiently penetrated the narrow sliding gap between the plunger and the cylinder hole. Therefore it is not damaged.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on embodiments of the present invention shown in the accompanying drawings.

FIG. 1 is a longitudinal sectional view of a plunger pump according to a first embodiment of the present invention, and FIG. 2 is a sectional view similar to FIG. 1 showing a second embodiment of the present invention.

First, a description will be given of the first embodiment of the present invention. In FIG. 1, a pump housing 2 of a plunger pump 1 has a cam chamber 3 opened on one side thereof and a pair of cylinder holes 4 arranged coaxially with the cam chamber 3 interposed therebetween. Shown). The cylinder hole 4 includes a small-diameter hole 4a having one end opened to the cam chamber 3, and a large-diameter hole 4b connected to the other end. The pump housing is further provided with a mounting hole 5 and a screw hole 6 having a larger diameter connected to the large diameter hole 4b.

An electric motor 7 is mounted on one side surface of the pump housing 2, and an eccentric cam shaft 9 fitted on the outer periphery of an end of an output shaft 8 thereof, and a ball mounted on the outer periphery of the eccentric cam shaft 9. The bearing 10 is housed in the cam chamber 3.

A plunger 11 is slidably fitted in the cylinder hole 4, and a cylindrical pump chamber body 12 and an outlet chamber body 13 are sequentially fitted in the mounting hole 5 from the inner end side. . At that time, the pump chamber 12 and the outlet chamber 13
Are temporarily connected to each other by press-fitting a connecting cylinder 14 made of a synthetic resin to the outer periphery of both, and a sealing member 15 is interposed between the outer peripheral surface of the outlet chamber 13 and the inner peripheral surface of the mounting hole 5. You.

A screw plug 16 for pressing the outlet chamber 13 inward is screwed into the screw hole 6, whereby the pump chamber 12 is
And the outlet chamber 13 are held in contact with each other,
At the same time, the pump chamber 12 is held in a state of contacting the step between the mounting hole 5 and the large-diameter hole 4b.

The plunger 11 has a large-diameter piston portion 11b fitted into the large-diameter hole 4b of the cylinder hole 4, and a cylinder hole 4b.
And a small-diameter piston portion 11a fitted into the small-diameter hole 4a. The small-diameter piston portion 11a is disposed so as to abut the outer peripheral surface of the ball bearing 10.

An annular inlet chamber 19 is formed on the outer peripheral surface of the plunger 11 between the small-diameter and large-diameter piston portions 11a and 11b, and communicates with a suction port 21 formed in the pump housing 2.

The pump chamber body 12 has a large-diameter piston portion 11b.
A pump chamber 20 is defined between the pump chamber 20 and a front end face of the valve chamber.
2 and a plurality of radially arranged through holes 23 communicating the inlet chamber 19 with the valve seat hole 22, and a filter 24 is interposed between the inlet chamber 19 and the through hole 23.

In the pump chamber 20, in addition to a return spring 25 for urging the plunger 11 toward the eccentric cam shaft 9, a spherical suction which can be seated on a valve seat 26 formed at the open end of the valve seat hole 22. A valve 27 and a valve spring 28 for urging the suction valve 27 toward the valve seat 26 are housed therein.

The pump chamber 12 defines an outlet chamber 29 between the pump chamber 12 and the outlet chamber 13. A valve seat hole 30 communicating the outlet chamber 29 with the pump chamber 20 is provided in the pump chamber 12. . A spherical discharge valve 32 which can be seated on a valve seat 31 formed at the opening end of the valve seat hole 30 to the outlet chamber 29 and a valve spring 36 for urging the valve toward the valve seat 31 are provided in the outlet chamber 29. Will be accommodated.

The outlet chamber 29 is connected to a discharge port 35 formed in the pump housing 2 through a communication groove 33 at the inner end of the outlet chamber body 13 and a plurality of through holes 34 provided in the connecting cylinder 14. Communicate.

A portion of the plunger 11 sandwiched between the inlet chamber 19 and the pump chamber 20, ie, the outer peripheral surface of the large-diameter piston portion 11b, has an annular seal groove 40 having a U-shaped cross section, and a rear wall surface of the seal groove 40. A tapered surface 41 is formed in which 40a intersects the generating line at an obtuse angle θ. Thus, between the tapered surface 41 and the inner peripheral surface of the large-diameter hole 4b of the cylinder hole 4, an annular space 42 having a triangular cross section with a space extending toward the seal groove 40 is formed. ,
It continues to the normal sliding gap 43 between the large-diameter piston portion 11b and the large-diameter hole 4b.

A seal member 44 is mounted in the seal groove 40. The seal member 44 is made of an elastic material such as rubber, and has an annular lip 44a slidably in contact with the inner peripheral surface of the large-diameter hole 4b.

An annular seal groove 45 is also formed on the outer periphery of the small-diameter piston portion 11a, and a seal member 46 slidably in close contact with the inner peripheral surface of the small-diameter hole 4a is mounted thereon.

Next, the operation of the first embodiment will be described.

When the electric motor 7 is operated to rotate the eccentric cam shaft 9, the plunger 11 is moved by the eccentric movement of the ball bearing 10 and the repulsive force of the return spring 25.
With a stroke that is twice the eccentric amount e of the eccentric cam shaft 9,
The suction stroke that slides in the direction to increase the volume of the pump chamber 20 and the discharge stroke that slides in the direction to reduce the volume of the pump chamber 20 are repeated.

In the suction stroke of the plunger 11,
The pressure in the pump chamber 20 causes the discharge valve 32 to close and the suction valve 27 to open.
4 through the through hole 23 and the valve seat hole 22,
Inhaled to zero. At that time, the inlet chamber 19 is pressurized due to the reduction of the volume, so that the flow of the fluid from the inlet chamber 19 to the pump chamber 20 is promoted.

Next, when the plunger 11 moves to the discharge stroke, the pressure in the pump chamber 20 causes the suction valve 27 to close and the discharge valve 32 to open, so that the fluid in the pump chamber 20 flows from the valve seat hole 30 to the outlet chamber. 29 and further through the communication groove 33 to the discharge port 35. At this time, since the pressure in the inlet chamber 19 is reduced by expanding the volume, the suction port 2
The fluid is suctioned from 1 to prepare for the next suction stroke.

During the operation of the plunger 11, the seal member 44 mounted in the seal groove 40 of the large-diameter piston portion 11b comes into close contact with the inner peripheral surface of the large-diameter hole 4b, and the pump chamber 20 and the inlet chamber are formed. In particular, during the discharge stroke of the plunger 11, a large pressure difference is generated between the high-pressure pump chamber 20 and the low-pressure inlet chamber 19. Due to the difference, the sealing member 4
4 is strongly pressed backward, that is, toward the entrance chamber 19 side.

On the outer peripheral surface of the large-diameter piston portion 11b, there is formed a tapered surface 41 at which the generating line intersects the rear wall surface 40a of the seal groove 40 at an obtuse angle θ.
Since an annular space 42 having a triangular cross section is formed between the inner peripheral surface of the cylinder hole 4 and the large-diameter hole 4b, the outer periphery of the seal member 44 is strongly pressed rearward. The rear end portion 44b (shown by a dashed line in FIG. 1) enters the annular space 42.
Since the stress at the outer peripheral rear end portion 44b gradually increases toward the rear due to the triangular cross-section, the stress concentration is small. In addition, since the stress has already sufficiently increased at the distal end of the outer peripheral rear end portion 44b that has entered the narrow rear end portion of the annular space 42, the narrow sliding gap between the large-diameter piston portion 11b and the large-diameter hole 4b is obtained. It is not enough to cut into 43. In this manner, the seal member 44 can be prevented from being damaged and can maintain durability, so that pressure leakage between the pump chamber 20 and the inlet chamber 19 can be prevented for a long time, and pump efficiency can be increased.

Next, a second embodiment of the present invention will be described with reference to FIG.

In the second embodiment, the pump housing 2
A cylinder sleeve 50 having high wear resistance is fitted therein, and a plunger 11 is fitted in the cylinder hole 4 formed therein.
The inlet chamber 19 communicates with the suction port 21 of the pump housing 2 through a through hole 51 formed in the cylinder sleeve 50. Since other configurations are substantially the same as those of the previous embodiment, the same reference numerals in the drawing denote parts corresponding to those of the previous embodiment, and a description thereof will be omitted.

The present invention is not limited to the above embodiment, and various design changes can be made without departing from the gist of the present invention. For example, there is no difference in diameter between the front and rear ends of the plunger 11 so that the inlet chamber 19 does not change in volume even when the plunger 11 reciprocates.

[0031]

As described above, according to the present invention, in the plunger pump, a tapered surface where the bus bar forms an obtuse angle with the rear wall surface of the seal groove is formed on the outer peripheral surface of the plunger between the inlet chamber and the seal groove. As a result, an annular space having a triangular cross-section is formed between the tapered surface and the inner peripheral surface of the cylinder bore, the interval of which increases toward the rear wall surface of the seal groove. Even if the sealing member is strongly pushed backward due to the high pressure difference between the chamber and the low-pressure inlet chamber, stress concentration when the outer peripheral rear end enters the annular space is small.
And the rear end of the outer periphery does not extend from the annular space into the narrow sliding gap between the plunger and the cylinder hole, thereby avoiding damage to the seal member and ensuring its durability. Therefore, high pump efficiency can be maintained for a long time.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a plunger pump according to a first embodiment of the present invention.

FIG. 2 is a sectional view similar to FIG. 1, showing a second embodiment of the present invention;

FIG. 3 is an enlarged sectional view of a main part of a conventional plunger pump.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Plunger pump 2 ... Pump housing 4 ... Cylinder hole 11 ... Plunger 19 ... Inlet chamber 20 ... Pump chamber 27 ... Suction valve 40 ... Seal groove 41: tapered surface 43: sliding gap 44: sealing member θ: obtuse angle

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3H070 AA01 BB02 BB07 CC07 CC22 CC29 DD28 DD35 DD66 3H071 AA03 BB01 CC13 CC26 CC28 DD01 DD03 DD12 DD13 DD53

Claims (1)

[Claims] 1. A pump housing (2) having a cylinder hole (4), which is slidably fitted in the cylinder hole (4), and has a front end face in a pump chamber (20) in the cylinder hole (4). Plunger (11) facing the
A suction valve (27) for allowing fluid to flow in one direction from an annular inlet chamber (19) formed between the outer peripheral surface of 1) and the inner peripheral surface of the cylinder hole (4) to the pump chamber (20); The plunger (1) between the inlet chamber (19) and the pump chamber (20).
1) An annular seal groove (40) formed on the outer peripheral surface is fitted with an elastic seal member (4
In the plunger pump equipped with 4), the plunger (11) between the inlet chamber (19) and the seal groove (40).
On the outer peripheral surface, the generating line is the rear wall surface (40a) of the seal groove (40).
A plunger pump characterized by forming a tapered surface (41) intersecting at an obtuse angle (θ) with the plunger.