JP7781666B2 - Outer rotor for internal gear pump - Google Patents

Description

The present invention relates to an outer rotor used in an internal gear pump and attached to the outer periphery of an inner rotor.

Many vehicles that run on engines are equipped with an oil pump that circulates engine cooling oil. One type of oil pump is an internal gear pump, which circulates oil by rotating an inner rotor and an outer rotor attached to the outer periphery of the inner rotor. Patent Document 1 discloses a prior art technique related to an outer rotor for an internal gear pump.

Patent Document 1 discloses that the use of resin as the material for the outer rotor of an internal gear pump can improve sliding properties.

Japanese Patent Application Publication No. 11-247766

The inventors conducted research and found that when outer rotors for internal gear pumps are resin-molded, a certain percentage of them contain large dimensional errors. Outer rotors for internal gear pumps with large dimensional errors may not be able to achieve the specified performance and quality of the product.

The objective of this invention is to provide an outer rotor for an internal gear pump with improved dimensional accuracy.

According to the present disclosure, the device is made of a resin material and has a generally cylindrical shape,
The inner circumferential surface is formed with a plurality of valleys with which the external teeth of the inner rotor can mesh, and bulging portions that bulge toward the center and are located between these valleys,
a first side surface portion, which is one side surface of the bulging portion, having a general surface portion and a first recess portion formed in a recessed shape relative to the general surface portion;
an interior of the bulging portion is a gap portion formed in a gap shape from a second side surface portion, which is the other side surface of the bulging portion, toward the first recess portion;
There is provided an outer rotor for an internal gear pump, characterized in that a groove is formed along the outer edge of the first recess.

This disclosure makes it possible to provide an outer rotor for an internal gear pump with improved dimensional accuracy.

FIG. 2 is a plan view of the outer rotor for the internal gear pump according to the first embodiment. FIG. 2 is an enlarged view of part 2 of FIG. 1. 3 is a cross-sectional view taken along line 3-3 of FIG. 2. FIG. 2 is a bottom view of the outer rotor for the internal gear pump shown in FIG. 1 . FIG. 5A is a diagram for explaining the dimensional accuracy of an outer rotor for an internal gear pump according to a comparative example, and FIG. 5B is a diagram for explaining the dimensional accuracy of an outer rotor for an internal gear pump according to an embodiment. FIG. 10 is a cross-sectional view of an outer rotor for an internal gear pump according to a second embodiment.

An embodiment of the present invention will be described below with reference to the attached drawings.

Example 1
Referring to Figure 1, the outer rotor 20 for an internal gear pump (hereinafter abbreviated as "outer rotor 20") is a substantially cylindrical resin part provided on the outer periphery of the inner rotor 10. The outer rotor 20 can be made of a fiber-reinforced plastic containing carbon fiber or glass fiber.

The inner circumferential surface 21 of the cylindrical outer rotor 20 is formed with five valleys 22 with which the external teeth 11 of the inner rotor 10 can mesh, and bulges 23 that bulge out toward the center C between these valleys 22. In other words, the inner circumferential surface 21 of the outer rotor 20 is composed of alternating valleys 22 and bulges 23.

Note that although the explanation has been given assuming four external teeth 11 and five valley portions 22, any number of external teeth 11 and valley portions 22 can be selected as long as there is one more valley portion than the number of external teeth.

Center C is the axial center of the outer rotor 20, and the center of the inner rotor 10 is offset from center C of the outer rotor 20. For example, when the inner rotor 10 rotates due to engine power, the outer rotor 20 rotates as it is pushed by the external teeth 11.

Refer to Figure 2. The first side surface portion 25, which is one side surface of the bulge portion 23 (the surface formed at one end of the outer rotor 20 relative to the axial direction), includes a general surface portion 26 that forms one end surface of the outer rotor 20, and a first recessed portion 27 that is recessed in the axial direction relative to this general surface portion 26. The first recessed portion 27 is formed in a position corresponding to one end of the bulge portion 23.

See also Figure 3. The first recess 27 includes a groove portion 27a formed in a groove shape along the outer edge of the first recess 27. The groove portion 27a surrounds the entire outer periphery of the first recess 27 and is formed to a position deeper than the first recess 27. A gate mark 27b is formed in approximately the center of the first recess 27. The gate mark 27b is formed by the resin injection port when the resin material is poured into the molding die. See Figure 1. A gate mark 27b is formed in each of the multiple first recesses 27 formed.

See Figures 3 and 4. The other side of the bulge 23 (the surface formed at the other end of the outer rotor 20 relative to the axial direction) is referred to as the second side surface 31. The interior of the bulge 23 is a gap 32 that extends from the second side surface toward the first recess 27. The gap 32 is a bottomed recess that has a generally elliptical shape when viewed from the second side surface 31.

Refer to Figures 1 and 3. When viewed from the first side surface portion 25 as a reference, the gap bottom surface portion 32a, which is the bottom of the gap portion 32, is formed at a position inside the groove portion 27a (see also the two-dot chain line extending upward from the corner of the gap bottom surface portion 32a shown in Figure 3). Furthermore, when viewed from the first side surface portion 25 as a reference, the gate mark 27b is formed in a portion that overlaps with the gap portion 32.

The effects of the outer rotor 20 described above will now be explained.

Please refer to Figures 5A and 5B. Figure 5A shows an outer rotor 120 according to a comparative example, and Figure 5B shows an outer rotor 20 according to an embodiment. The outer rotor 120 according to the comparative example and the outer rotor 20 according to the embodiment differ in the presence or absence of a groove 27a. That is, the outer rotor 120 according to the comparative example does not have a groove on the outer edge of the first recess 127, while the outer rotor 20 according to the embodiment has a groove 27a on the outer edge of the first recess 27.

The inventors resin-molded multiple outer rotors 120 according to the comparative example and multiple outer rotors 20 according to the example, and measured their dimensions. They found that the outer rotors 20 according to the example had smaller dimensional variations between individual products. This led them to realize that dimensional accuracy can be improved by forming grooves 27a along the outer edge of the first recess 27. The reason for this is explained below.

See Figure 5A. The outer rotor 120 has only the first recess 127 formed therein, and no groove 27a (see Figure 5B) is formed on the outer edge of the first recess 127. In this outer rotor 120, the thickness of the thickest portion is D1.

See Figure 5B. A groove 27a is formed on the outer edge of the first recess 27 of the outer rotor 20. The thickness of the thickest portion of this outer rotor 20 is D2.

See also Figure 5A. Comparing D1 of the outer rotor 120 without the groove 27a and D2 of the outer rotor 20 with the groove 27a formed along the outer edge of the first recess 27, D1 > D2. In other words, the outer rotor 20 with the groove 27a formed had a thinner wall thickness at its thickest point.

The outer rotor 20 has grooves 27a, which allow for a uniform overall thickness. Furthermore, the formation of grooves 27a allows for a larger surface area. These factors allow for more uniform cooling of the entire rotor during resin molding, which is believed to prevent the occurrence of so-called sink marks. Preventing the occurrence of sink marks improves dimensional accuracy. This means that an outer rotor 20 with improved dimensional accuracy can be provided.

Example 2
Next, a second embodiment of the present invention will be described with reference to the drawings.

Figure 6 shows the cross-sectional configuration of the outer rotor 20A according to the second embodiment. The same reference numerals are used for parts common to the first embodiment, and detailed descriptions will be omitted.

The bottom of the gap 32A, that is, the gap bottom surface 32Aa, includes a second recess 32Ab recessed toward the first recess 27. Furthermore, the gap bottom surface 32Aa is formed in a position where at least a portion of the edge of the gap bottom surface 32Aa overlaps with the groove 27a (see the two-dot chain line extending upward from the corner of the gap bottom surface 32Aa).

This type of outer rotor 20A also achieves the desired effects of the present invention. Furthermore, the outer rotor 20A according to Example 2 also achieves the following effects:

The gap bottom surface 32Aa includes a second recess 32Ab that recesses toward the first recess 27. This allows for a more uniform overall thickness and a larger surface area. This allows for more uniform cooling of the entire outer rotor 20A, more effectively suppressing the occurrence of sink marks and improving dimensional accuracy.

Furthermore, when viewed from the first side surface portion 25, the gap bottom surface portion 32Aa is formed in a position where at least a portion of the edge of this gap bottom surface portion 32Aa overlaps with the groove portion 27a. This shortens the length from the edge of the gap bottom surface portion 32Aa to the groove portion 27a. This makes it possible to make the overall thickness more uniform, allowing the entire outer rotor 20A to be cooled more uniformly. This further reduces the occurrence of sink marks and improves dimensional accuracy.

Note that while the outer rotor for an internal gear pump according to the present invention has been described as being used in an oil pump for a vehicle, it can also be applied to oil pumps used in other vehicles and to internal gear pumps other than oil pumps.

Also, while the example described above uses fiber-reinforced plastic as the material, it is also possible to use resin that does not contain fibers. Furthermore, when using fiber-reinforced plastic, it is also possible to use different fibers such as carbon fiber in addition to glass fiber.

Furthermore, each embodiment can be combined as appropriate. For example, the edge of the bottom surface of the void portion that does not have a second recess may overlap the groove portion. Also, the bottom surface of the void portion that has a second recess may be formed in a position that is inside the groove portion.

In other words, as long as the functions and effects of the present invention are achieved, the present invention is not limited to the examples.

The outer rotor for an internal gear pump of the present invention is suitable for use in a vehicle oil pump.

DESCRIPTION OF SYMBOLS 10... Inner rotor 11... External teeth 20, 20A... Outer rotor for internal gear pump 21... Inner peripheral surface 22... Root portion 23... Bulging portion 25... First side surface portion 26... General surface portion 27... First recessed portion, 27a... Groove portion 31... Second side surface portion 32, 32A... Gap portion, 32a, 32Aa... Gap portion bottom surface portion, 32Ab... Second recessed portion C... Center

Claims (2)

It is made of a resin material and is roughly cylindrical in shape.
The inner circumferential surface is formed with a plurality of valleys with which the external teeth of the inner rotor can mesh, and bulging portions that bulge toward the center and are located between these valleys,
a first side surface portion, which is one side surface of the bulging portion, having a general surface portion and a first recess portion formed in a recessed shape relative to the general surface portion;
an interior of the bulging portion is a gap portion formed in a gap shape from a second side surface portion, which is the other side surface of the bulging portion, toward the first recess portion;
a groove portion is formed along an outer edge of the first recess ,
An outer rotor for an internal gear pump, wherein a bottom surface of the gap, which is a bottom of the gap, includes a second recess recessed toward the first recess . 2. The outer rotor for an internal gear pump according to claim 1, wherein, when viewed from the first side surface portion, a bottom surface portion of the gap, which is the bottom of the gap, is formed in a position where at least a portion of the edge of the bottom surface portion of the gap overlaps with the groove portion.