JP2000186678A - Oil pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure sealability between a suction side and a discharge side of an oil pump and prevent seizure abrasion between an inner wall of a housing and a pump gear. SOLUTION: A drive gear 12 and a driven gear 13 stored in a pump chamber composed of a first housing 15 and a second housing 16 form a capacity part 17 for performing pumping operation. In such a mechanism, shot peening is performed on an opposed inner wall 24 of the first housing 15 abutted against gear end faces 18, 20, and an opposed inner wall 34 of the second housing 16 abutted against gear end faces 19, 21. Lubricating films of high abrasion resistance, for instance, are adhered to the gear end faces 18, 19 of the drive gear 12 and the gear end faces 20, 21 of the driven gear 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal gear type oil pump.

[0002]

2. Description of the Related Art An inscribed gear type oil pump is generally composed of a pair of housings which form a pump body by internally connecting a drive gear having an eccentric drive shaft with respect to the rotation center of the driven gear to the driven gear and connecting the drive gear in the axial direction. A drive gear and a driven gear are housed in the pump chamber. Specifically, the pair of housings are generally of a flange-coupling type, for example, in which one is a main housing having a recess for fitting the drive gear and the driven gear, and the other is a lid member for closing the recess.

[0003] The main housing and the cover member have opposed inner walls that abut against respective axial end faces (hereinafter referred to as gear end faces) of the drive gear and the driven gear, and the main housing has an inner peripheral wall that inscribes the outer peripheral face of the driven gear. The pump chamber is defined by the opposed inner wall and the inner peripheral wall. At least one of the opposed inner walls of the pump chamber has a suction port and a discharge port that are open to a suction volume section and a discharge volume section formed by engagement of the accommodated drive gear and driven gear. The suction port and the discharge port are
It communicates with a suction passage and a discharge passage formed in the housing member having the suction port and the discharge port.

[0004] As a material of the oil pump, an iron-based sintered metal is usually used for the drive gear and the driven gear, and aluminum is used for the main housing and the lid member. In such an oil pump, there is a difference between a linear expansion coefficient of the drive gear and the driven gear and a linear expansion coefficient of the main housing and the lid member. At a high temperature, the main housing and the lid member expand significantly, and the pump chamber expands. There has been a problem that the clearance between the surface and the inner peripheral wall of the main housing and the clearance between the gear end surface and the opposed inner wall are increased, and the sealing function between the suction volume section and the discharge volume section is reduced.

[0005] For this reason, Japanese Patent Application Laid-Open No. 62-681 and Japanese Utility Model Publication No. 3-20553 disclose a material in which a linear expansion coefficient of a drive gear is made larger than that of a driven gear in an oil pump having a housing and a cover member made of aluminum. It is described that the body clearance, that is, the clearance between the outer peripheral surface of the driven gear and the inner peripheral wall of the main housing and the tooth clearance (the clearance between the meshing teeth of the driven gear and the driven gear) referred to in the publication are reduced. I have.

[0006]

By the way, the oil pumps described in the above publications are characterized in that the pump chamber expands at a high temperature and the end faces of the drive gear and the driven gear and the inner walls of the pair of housings in the axial direction. No clearance measures are described. If the clearance in the axial direction is also unnecessarily large, it may cause a reduction in the function of sealing the discharge volume portion and the suction volume portion as in the case of the tooth tip clearance.

Therefore, the clearance in the axial direction is set to zero or a negative value at the time of manufacturing, and an allowable clearance is formed as the temperature rises, so that the rotation of the drive gear and the driven gear in the pump chamber is performed. Is performed smoothly. However, if the axial clearance is set to 0 or minus at the time of manufacturing, a frictional force acts between the gear end face and the opposing inner wall at the time of low temperature in the early stage of startup, and there is a problem that heat is generated and seizure or wear is accelerated. This burning and abrasion are dealt with by the lubricating action of oil (lubricating oil) held between the gear end face and the opposed inner wall due to the surface roughness of the drive gear and the driven gear, but they are not sufficient.

An object of the present invention is to provide an oil pump capable of simultaneously ensuring a sealing function at high temperatures and preventing abrasion or seizure at low temperatures.

[0009]

In order to solve the above problems, the inventors of the present invention have conducted various studies, and have studied the relationship between the gear end faces of the drive gear and the driven gear made of iron-based sintered metal and the opposed inner walls of the pair of housings. The present invention has been completed by considering one of them as a lubricated surface made of a film of a different material which does not cause abrasion or seizure and the other as an uneven surface which sufficiently retains lubricating oil.

That is, the oil pump of the present invention has a drive gear made of an iron-based sintered metal having a plurality of external teeth and internal teeth having one more tooth than the drive gear, and the drive gear is inscribed. A driven gear; and a pair of housings accommodating the drive gear and the driven gear in a pump chamber defined by an inner wall facing the respective axial end faces of the drive gear and the driven gear and an inner peripheral wall inscribing the outer peripheral surface of the driven gear. In the oil pump, at least one of the opposed inner walls of the pair of housings or the axial end surfaces of the drive gear and the driven gear is subjected to shot peening.

[0011]

In the oil pump according to the present invention, the shot peening is performed on the axial end faces of the drive gear and the driven gear, or on the opposing inner walls of the pair of housings abutting on the axial end faces. Fine irregularities are formed, lubricating oil and hydraulic oil can be sufficiently held between the mating member surface and the shot-peened member surface, and come into contact with the axial end surfaces of the drive gear and the driven gear. Lubricity between the opposing inner walls of the pair of housings can be reliably ensured.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In an oil pump according to the present invention,
Minute irregularities formed by shot peening
It is preferably about several tens of microns. In the oil pump of the present invention, it is preferable that a lubricating film having high wear resistance is attached to the opposite inner walls of the pair of shot-peened housings or the other end faces of the drive gear and the driven gear in the axial direction. As the lubricating film having high wear resistance, a fluorine-based coating agent, a linear aromatic polymer, nickel fluoride plating, or the like can be used, and the film can be formed by coating, dipping, showering, or other means.

As a result, the frictional resistance between the top land of the shot peened member surface and the surface of the film is reduced, and the lubricating oil or hydraulic oil held between the shot peened member surface and the film is reduced. Coupled with the lubricating effect, the lubricating properties between the axial end faces of the drive gear and the driven gear and the opposing inner walls of the pair of housings abutting on the end faces are further improved, and heat generation, seizure or wear can be further reduced.

In the oil pump of the present invention, the axial clearance between the drive gear and the driven gear and the pair of inner walls of the housing in the axial direction can be zero or negative. By adopting the present invention in an assembly in which the above-mentioned axial clearance is set to 0 or a minus state, the frictional resistance between the axial end surfaces of the drive gear and the driven gear and the opposing inner walls of the pair of housings in the initial stage of starting is reduced. It is possible to reduce heat generation and seizure wear.

The drive gear and the driven gear are
It is preferable to be molded from the same material, and since the same material has the same linear expansion coefficient, the thickness can be set to be the same,
It is possible to prevent a difference in clearance between the drive gear and the driven gear due to a temperature change. If the drive gear and the driven gear cannot be formed of the same material due to required performance or the like, the clearance may be appropriately set according to the linear expansion coefficient of each material.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An oil pump according to the present invention will be specifically described with reference to the embodiments shown in the drawings. As shown in FIG. 1, the basic configuration of the oil pump is a drive gear 1 made of an iron-based sintered metal having external teeth 11 having a predetermined number of trochoid teeth.
2 and internal teeth 13 inscribed with external teeth 11 of drive gear 12
, And a first housing 15 and a second housing 16 made of aluminum die cast and connected in the axial direction.

Drive gear 12 and driven gear 14
As shown in FIG. 3 and FIG. 2, is a spur gear having the same thickness between its axial end faces (gear end faces) 18, 19 and 20, 21. As shown in FIGS. 2 and 3, the internal teeth 13 of the driven gear 14 and the external teeth 11 of the drive gear 12 correspond to the external teeth 11 of the drive gear 12.
4, one less than the internal teeth 13. By eccentricizing the drive gear 12 with respect to the center of the driven gear 14 in accordance with the number of teeth, a predetermined number of the volume portions 17 (FIG. 1) are provided between the drive gear 12 and the external teeth 11 and the internal teeth 13 of the driven gear 14. ) Is formed.

As shown in FIG. 4, the first housing 15 includes a boss 23 having a shaft hole 22 formed therein, and the boss 23
Drive gear 12 and driven gear 1 formed outside
4 and a flange portion 26 having an inner peripheral wall 25 that inscribes the outer peripheral surface of the driven gear 14. The opposite inner wall 24 is formed with a discharge port 27 opening to a predetermined number of volumes 17 and a suction port 28 opening to another predetermined number of volumes 17. The suction port 28 communicates with a suction port 29 a opened on the outer peripheral side of the flange 26 via a suction passage 29 formed in a thick portion of the flange 26. Discharge port 27
Is connected to a discharge port 30a opened on the outer peripheral side of the flange portion 26 via a discharge passage 30 formed in a thick portion of the flange portion 26.

As shown in FIG. 5, the second housing 16 includes a boss 41 having a shaft hole 40 formed therein, and the boss 41
And an opposing inner wall 34 opposing the opposing inner wall 24 of the first housing 15 is formed in the inner diameter region of the outer part 33. The second housing 16 is shown in FIG.
As shown in FIG. 5, the pump chamber is formed by the opposed inner wall 34 of the second housing 16 and the inner peripheral wall 25 and the opposed inner wall 24 of the first housing 15 by being fastened to the first housing 15 in the axial direction. Drive gear 1 in pump room
The driven gear 14 in which the internal gear 2 is inscribed is stored.

The opposed inner wall 34 of the second housing 16 faces the discharge port 27 of the first housing 15 and opens to a predetermined number of volumes 17 and faces the discharge port 35 and the suction port 28 of the first housing 15. Another predetermined number of volumes 1
A suction port 36 opening to 7 is formed. The discharge port 35 and the suction port 36 are recesses for expanding the discharge volume and the suction volume by the predetermined volume 17, respectively, and include a flange 26 outside the opposed inner wall 24 of the first housing 15 in addition to the volume 17. The first housing 15 communicates with the discharge port 27 and the suction port 28 of the first housing 15 through communication ports 31b and 31a in the middle of the discharge passage 30 and the suction passage 29 that pass through.

Drive gear 1 housed in the pump chamber
2 and the driven gear 14, the outer peripheral surface 37 of the driven gear 14 is in sliding contact with the inner peripheral wall of the first housing 15, the gear end surfaces 19 and 21 are in contact with the opposed inner wall 34 of the second housing 16, and the gear end surfaces 18 and 20 are It comes into contact with the opposing inner wall 24 of one housing 15. The above is a general configuration. In the oil pump of this embodiment, the gear end faces 18, 19 of the drive gear 12 and the gear end faces 20, 21 of the driven gear 14 are covered with a fluorine-based coating agent. In addition, the opposing inner wall 24 of the first housing 15 and the opposing inner wall 34 of the second housing 16 are subjected to a shot peening process, and irregularities of several to several tens of microns are formed on the front wall surface.

Incidentally, the surface roughness of the outer peripheral surface 37 of the driven gear 14 and the surface roughness of the inner wall surface 25 of the first housing 15 slidably in contact with the outer peripheral surface 37 are the surface roughness during molding or the surface roughness during cutting. It is. The drive gear 12 and the driven gear 14 were formed by sintering a predetermined iron-based metal material. That is, an iron-based metal material (powder) was molded using a mold, the molded gear material was sintered by a sintering furnace, and then forged by a mold. Gear material obtained by forging,
The gear end faces 18 to 21 were machined by cutting. The distance between the gear end faces 18 and 19 (the thickness of the drive gear 12 and the driven gear 14) at the time of this cutting is the distance between the opposed inner walls 24 and 34 when the first housing 15 and the second housing 16 are fastened in the axial direction. (The axial length of the pump chamber) or a predetermined amount larger than that.

The drive gear 12 and the driven gear 14 having the gear end surfaces 18 to 21 having a predetermined surface roughness formed by the above-described cutting cover the respective gear end surfaces 18 to 21 with, for example, a fluorine-based coating agent. The coating with the coating agent was performed, for example, by dipping. Next, the first housing 15 and the second housing 16 are formed by die-casting an aluminum material using a mold, and then forming the opposing inner walls 24 and 34 by cutting or the like. The molded product was formed by spraying, for example, a steel ball on the opposed inner walls 24 and 34 at a predetermined speed by compressed air or centrifugal force to form a hardened layer of several tens of microns and irregularities of several microns in depth on the surface.

Next, in an assembling step, a drive shaft (not shown) was inserted into a shaft hole 12a (see FIG. 3) of the drive gear 12, and a driven gear 14 was fitted so as to inscribe the drive gear 12. One side of the drive shaft of the drive gear 12 fitted with the driven gear 14 is inserted through the shaft hole 22 of the first housing 15 and the other side is inserted through the shaft hole 31 of the second housing 16. The clearance between the opposed inner wall 24 and each of the gear end faces 18 and 20, and the opposed inner wall 34 and each of the gear end faces 19 of the second housing 16,
A predetermined number of bolts 39 (see FIG. 1) were used so that the clearance with the bolt 21 became the above set value. Thus, the oil pump was assembled. The holes of the bolt 39 are omitted in FIGS.

According to the oil pump manufactured as described above, the gear end faces 18 to 21 of the drive gear 12 and the driven gear 14 are coated with a fluorine-based coating agent,
Since the opposing inner walls 24, 34 of the first housing 15 and the second housing 16 are formed with irregularities of a predetermined degree, lubricating oil is held in the concavities and convexities on the opposing inner walls 24, 34 and the top land having the irregularities. Can slide on the surface of the fluorine-based coating agent without frictional resistance. The lubricating oil held in the concavities and convexities on the opposing inner walls 24 and 34 can make the sliding of the top land smoother.

The opposed inner walls 24 and 34 and the gear end faces 18 to
The lubricity of the oil pump 21 is not lost at the time of high temperature from the start, especially at the time of start, and heat generation, seizure or abrasion can be guaranteed for a long time, and the durability of the oil pump can be improved.
On the other hand, at the time of high temperature, the clearance in the axial direction of the oil pump (the clearance between the opposed inner wall 24 of the first housing 15 and each of the gear end faces 18, 20 and the second housing 1).
6) (clearance between the opposing inner wall 34 and each of the gear end faces 19, 21) can be set to 0 or minus, and the sealing function between the discharge side and the suction side can be sufficiently ensured.

[0027]

As described above, according to the present invention, the clearance between the drive gear and the driven gear housed in the pump chambers of the pair of housings in the axial direction with respect to the housing wall surface can be reduced, and the effect of preventing liquid leakage on the discharge suction side. An oil pump with high (seal function) and excellent durability is obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an oil pump according to one embodiment.

FIG. 2 is a diagram showing a driven gear of the oil pump.

FIG. 3 is a view showing a drive gear of the oil pump.

FIG. 4 is a view showing a first housing of the oil pump.

FIG. 5 is a view showing a second housing of the oil pump.

[Description of Signs] 12: Drive gear, 14: Driven gear, 15: First housing, 16: Second housing, 18 to 21: Gear end face with lubricating film adhered, 24, 34: Opposing inner walls subjected to shot peening processing .

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3H041 AA02 BB03 CC03 CC07 CC08 CC09 CC13 CC15 CC19 DD04 DD05 DD31 DD33 DD38 3H071 AA03 BB02 CC01 CC26 CC27 CC28 CC31 CC44 EE05 EE06

Claims (2)

[Claims] 1. A drive gear made of an iron-based sintered metal having a plurality of external teeth, a driven gear having internal teeth having one more tooth than the drive gear and inscribed with the drive gear; An oil pump comprising: a pair of housings accommodating the drive gear and the driven gear in a pump chamber defined by an inner wall facing each axial end surface of the driven gear and an inner peripheral wall inscribing the outer peripheral surface of the driven gear; An oil pump characterized in that shot peening is performed on at least one of the opposed inner walls of the housing or the axial end surfaces of the drive gear and the driven gear. 2. A lubricating film having high wear resistance is attached to the opposite inner walls of the pair of housings that have been subjected to the shot peening processing or to the other axial end surfaces of the drive gear and the driven gear. Oil pump.