JPH1061562A - Internal gear pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal gear pump for enabling smooth meshing by restraining the reduction of the number of teeth while reducing the slip ratio in meshing parts of an external gear and an internal gear. SOLUTION: In an internal gear pump in which an internal gear 5 rotatably mounted in a housing 1 and an external gear 7 arranged eccentric from the internal gear 5 and to be roated and driven are meshed with each other to feed out fluid, the tooth tip 7b of the external tooth 7a of the external gear 7 is set to the gear center side from a pitch circle P of the gear, and the tooth profile of the internal tooth 5a of the internal gear 5 is formed into such a shape as to be formed by a cutter having the tooth profile of the external tooth 7a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal gear pump that rotates by rotating an internal gear and an external gear in mesh with each other to deliver a fluid.

[0002]

2. Description of the Related Art Conventional inscribed internal gear pumps include a type in which a crescent-shaped crescent is arranged between an internal gear and an external gear, and a type without a crescent. In the former type, fluid is conveyed by rotating the tip of both gears while sliding on the inner and outer circumferences of the crescent. In the latter type, on the opposite side of the portion where the two gears mesh most deeply, the tips of the two gears slide and rotate with each other to carry the fluid between the two gears. Regardless of the type, to increase the tooth height of each tooth to increase the discharge capacity of the pump, to increase the number of teeth to suppress the discharge pulsation of the pump, and to ensure the durability of the pump In order to reduce noise, it is required to increase the meshing ratio of the two gears to reduce the slip ratio, and to suppress noise, reduce caption. In particular, in the latter type having no crescent, it is important to reduce fluid leakage between both gears. As a technique belonging to the latter type, there is, for example, Japanese Patent Application No. 56-106321 (Japanese Patent Application No. 57-79290). The present invention
This is a particularly improved tooth shape of a pump called “Eaton pump”.

[0003]

[Problems to be Solved by the Invention] Japanese Patent Application No. 56-1063
In the gear No. 21, the pitch circle of the external gear is kept away from the center of the tooth height so as to be coincident with the tip circle in order to secure a high tooth height and increase the number of teeth. In manufacturing the two gears, the external gear is formed by the internal teeth in order to ensure a sufficient meshing. However, when the external gear is created with internal teeth, as shown in FIG.
b interferes with the cutting blade 14 of the cutter having the shape of the internal gear 5, and both ends thereof are cut as shown by vertical hatching. Therefore, the meshing portion (contact portion) between the external tooth and the internal tooth is only the contact portion between the root side of the external tooth surface and the ending side of the internal tooth surface, resulting in a distance from the pitch circle passing through the tooth tip. Becomes If the meshing portion moves away from the pitch circle in this way, the slip ratio between the two gears increases by that amount, and the durability deteriorates. Therefore, the position of the pitch circle is limited, and as a result, the tooth height and the number of teeth are limited. The problem arises.

[0004] If the diameter of the pitch circle is set to a small diameter, the slip ratio can be reduced and the durability of the gear can be improved. However, if the pitch circle is set to be small without changing the number of teeth, the module becomes As the size becomes smaller, the tooth height becomes lower and the discharge capacity of the pump decreases. In general, the pitch circle is determined by a module corresponding to the tooth height and the number of teeth. Therefore, if the diameter of the pitch circle is reduced without changing the discharge capacity of the pump, the number of teeth of each gear decreases. The decrease in the number of teeth increases the pitch of the teeth (the angle of one tooth) in the gear, so that the meshing ratio decreases, the rotation fluctuation of the gear increases, and smooth meshing becomes difficult. There is a problem that it leads to an increase.

[0005]

SUMMARY OF THE INVENTION The present invention reduces the slip ratio at the meshing portion between an external gear and an internal gear,
In order to provide an internal gear pump that enables smooth meshing while suppressing a decrease in the number of teeth, the tip of the external teeth of the external gear is set closer to the gear center than the pitch circle of the external gear. ,
The tooth profile of the internal teeth of the internal gear is a tooth surface shape created by a cutter having the tooth profile of the external teeth.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention has an external gear which is eccentrically disposed in an internal gear rotatably mounted in a housing and is driven to rotate. The present invention is applied to an internal gear pump that meshes and rotates to deliver a fluid. The tip of the external gear of the external gear is set at the center of the gear from the pitch circle of the external gear, and the tooth profile of the internal gear of the internal gear is created using the cutter formed on the external tooth profile. Tooth surface shape.

When the internal teeth of the internal gear are formed by using the external teeth of the external gear, the interference portion between the external teeth and the internal teeth becomes a portion away from the pitch circle, and the meshing portion of the two gears becomes the pitch. It is a portion close to the circle, that is, a contact portion between the tooth flank side of the external tooth flank and the tooth root side of the internal tooth flank, so that the slip ratio is reduced and the durability is improved.

When the meshing portion of both gears approaches the pitch circle,
It is possible to increase the diameter of the pitch circle without considering the relationship with the slip ratio, and if the tooth height is to be increased or if the tooth height is not increased, it is necessary to increase the number of internal teeth and external teeth it can. This means that the pitch angle per tooth is narrowed, the rotation fluctuation error is reduced, and the internal teeth and the external teeth can be smoothly meshed.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. The internal gear type pump shown in FIGS. 1 and 2 has side housings 2 and 3 joined to each side of a ring-shaped housing main body 1 by a plurality of bolts 4 to form a cylindrical space 8 therein. ing. The internal gear 5 is slidably fitted to the inner peripheral surface of the space 8.

A drive shaft 6 is inserted through a hole provided in the center of the side housing 3 via a seal member (not shown). An external gear 7 is fitted on the drive shaft 6 on the same axis. The external gear 7 is formed to have a smaller diameter than the diameter of the internal gear 5, and is disposed eccentrically with respect to the center O of the internal gear 5. The external gear 7 is formed with 12 teeth, and the internal gear 5 is formed with one more 13 teeth. The external gear 7 is the internal gear 5
Are completely meshed with each other on the upper side in the drawing, and the tooth tips are brought into contact with each other on the lower side in the drawing. In the side housing 3, an inflow opening 9 and an outflow opening 10 communicating with the inside of the space 8 are provided.
They are formed on the left and right with reference to the center of the housing. The inflow opening 9 has an inlet 11 for fluid supplied from outside the pump, and the outflow opening 10 has a fluid outlet 12.
Are in communication with each other.

In this embodiment, when the external gear 7 is rotated in the counterclockwise direction, the external gear 7 is formed between the respective teeth of the external gear 7 and the internal gear 5 located on the inflow opening 9. Oil as a liquid is taken into a space defined by the external gear 7 and the internal gear 5 located on the side of the outflow opening 10 and compressed and discharged in a space formed between the respective teeth. .

The tooth profile of the external gear 7 used in the internal gear pump is not particularly limited, and may be the same as the improved Eaton gear in the prior art.

The internal gear 5 has the same shape as the external gear 7 shown in FIG. 3 formed by an NC processing machine (not shown) numerically controlled by a computer.
The tooth profile is created by cutting with a cutter 7 ′ provided with. The cutter 7 ′ has an external tooth 7 a of the external gear 7.
The tooth tip 7b 'corresponding to the tooth tip 7b is set closer to the gear center than the pitch circle P of the external gear 7. The pitch circle of the internal gear 5 is outside the tooth bottom, that is, a circle having a larger diameter than the tooth circle, and the pitch circles of the two gears 5 and 7 overlap each other at a point where the gears 5 and 7 mesh with each other most deeply. .

When the internal gear 5 is created by rotating the cutter 7 'in the direction of the arrow a while sliding the cutter 7' in the direction of the paper, the tip 5b of the internal teeth 5a and the tip 7b 'of the cutter 7' Will interfere. Then, both ends of the inner teeth 5a on the tip 5b side are indicated by hatched portions X in the figure, so that the cutter 7 'is formed.
Of the internal gear 5.
The shape of c becomes the same tooth surface shape as the shape of the external teeth 7a '.

With respect to the internal gear 5 configured as described above,
As shown in FIG. 4, when the external gear 7 whose tooth height h is set to be slightly smaller than the tooth height of the cutter 7 ′ is actually meshed,
The meshing portions Y1 and Y2 between the internal teeth 5a of the internal gear 5 and the external teeth 7a of the external gear 7 are near the pitch circle P. Therefore, the slip rate when the external gear 7 rotates is reduced, the load on the internal teeth 5a and the external teeth 7a is reduced, and the durability of the external gear 7 and the internal gear 5 is improved.

The external gear 7 side is used as a cutter 7 'to form internal teeth 5a.
When the meshing portions Y1 and Y2 between the outer teeth 7a and the outer teeth 7a are close to the pitch circle P, the pitch circle P in this embodiment is moved outward from the tip 7b of the outer teeth 7a as shown by a two-dot chain line in FIG. It is also possible to form a large-diameter pitch circle P1.

When the pitch circle P has a large diameter, the tooth height h is increased to increase the pump discharge amount,
Alternatively, the number of teeth of each gear can be increased. When the number of teeth of the gear is increased, the pitch per tooth is reduced, and the engagement ratio between the external teeth 7a and the internal teeth 5a is increased. Therefore, the rotation error of the external teeth 7a with respect to the rotation of the external gear 7 is reduced, and the gear rotates smoothly, so that the load applied to the tooth tip and the meshing noise are reduced.

When the pitch circle P of the external gear 7 is increased in diameter,
Since the engagement between the internal gear 5 and the external gear 7 ends early,
The joint Y1 located in the moving direction of the external teeth 7a is quickly separated in the oil suction process. That is, a space Z formed between the tooth tip 7b and the concave portion 5c, and a space X formed between the concave portion 7c of the external gear 7 and the tooth portion 5a of the internal gear 5
The communication with the space 1 is performed quickly, the negative pressure in the space Z is prevented, and the occurrence of caption in the space can be suppressed.

[0019]

According to the present invention, since the meshing portion between the internal gear and the external gear is near the pitch circle of the external gear, the slip ratio is reduced and the durability of the gear is improved. Further, since the slip ratio is small and advantageous, the pitch circle can be increased and the tip of the external gear can be positioned outside, so that the number of teeth of the gear can be increased and the meshing ratio can be improved and the discharge pulsation can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic structural view of an inscribed internal gear pump showing one embodiment of the present invention.

FIG. 2 is a side sectional view of an inscribed internal gear pump.

FIG. 3 is an enlarged cross-sectional view showing a state in which an internal gear is processed by an external gear cutter.

FIG. 4 is an enlarged view showing a meshing state of the external gear and the internal gear.

FIG. 5 is an enlarged sectional view showing a processing state of an external gear by a conventional internal gear cutter.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Housing 5 Internal gear 5a Internal tooth 7 External gear 7a External tooth 7b Tip P, P1 Pitch circle

Claims (1)

[Claims] 1. An internal gear rotatably mounted in a housing, and an external gear which is eccentrically arranged in the internal gear and driven to rotate, and the two gears mesh with each other. An internal gear pump for rotating and delivering fluid, wherein the tip of the external teeth of the external gear is set closer to the center of the gear than the pitch circle of the external gear, and the tooth profile of the internal teeth of the internal gear Wherein the external gear has a tooth flank shape created by the external toothed cutter.