JPH06229385A - Rotor structure for roots displacement compressor - Google Patents

Abstract

PURPOSE:To prevent resin applied as a coating around the outer circumference of a rotor from exfoliating and prevent the surface of the coating of resin from becoming rough. CONSTITUTION:The outer circumference 13 of a rotor 11 is formed flat, holding grooves 15 stretching in the axial direction of the rotor 11 are provided in inflection faces 13c located between projecting curved faces 13a and recessed curved faces 13b of the rotor 11, and the whole circumference of the outer circumference 13 of the rotor 11 is coated with resin 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a rotor of a roots compressor, and more particularly to the structure of a rotor for preventing the resin coated on the outer peripheral surface of the rotor from peeling off.

[0002]

2. Description of the Related Art A technique for coating the outer peripheral surface of a rotor 1 with resin 2 in a roots compressor as shown in FIG. 7 is disclosed in Japanese Utility Model Laid-Open No. 60-153888. FIG. 8 shows an example of a working method for coating the outer peripheral surface of the rotor 1 with resin. As shown in FIG. 8, when coating the resin, it is necessary to flow the resin from the axial direction of the rotor 1. In this way, when the resin is made to flow in from the axial direction of the rotor 1, the resin can be made to flow in linearly, and burrs at the resin injection portion do not occur on the outer peripheral surface of the rotor 1 either.

[0003]

However, when resin is filled from the axial direction of the rotor 1 as shown in FIG.
Due to the influence of the filler mixed in the resin, the shrinkage amount in the resin filling direction (flow direction) B and the direction perpendicular to the resin (rotor circumferential direction) C increases. Therefore, as shown in FIG. 9 and FIG. 10, the resin portion located on the concave curved surface portion 1a of the rotor 1 easily floats in the direction of the arrow D due to the tensile force F due to the contraction, and the resin portion of this portion becomes the outer peripheral surface of the rotor 1. There is a problem that it is easy to peel off from.

Therefore, as shown in FIGS. 11 to 13, unevenness is formed on the outer peripheral surface of the rotor 1. FIG. 11 shows a case where the indentation 3 is formed on the outer peripheral surface of the rotor 1 by shot blasting.
Shows the case where the wedge-shaped groove 4 is formed on the outer peripheral surface of the rotor 1. FIG. 12 shows a case where an arcuate groove 5 is formed on the outer peripheral surface of the rotor 1.

FIG. 14 shows a state in which the resin 2 is coated on the outer peripheral surface of the rotor 1 on which the indentations 3 have been formed by shot blasting, and the resin 2 contracts.
As shown in FIG. 14, the surface of the resin 2 is smooth before the resin 2 contracts, but when the resin 2 contracts, the resin 2
A concave-convex surface 2a is formed on the surface according to the indentation 3. This phenomenon similarly occurs when the grooves 4 and 5 are formed on the outer peripheral surface of the rotor 1 as shown in FIGS. 12 and 13.

Therefore, conventionally, the thickness of the coating of the resin 2 is increased, and as shown in FIG. 15, the resin surface having the uneven surface 2a is cut by the cutting tool 6 to finish the resin surface to a predetermined accuracy. Work was needed. Therefore, in this case, there is a problem that the cost increases due to the cutting work.

The present invention focuses on the above problems, and prevents the resin coated on the outer peripheral surface of the rotor from being peeled off and prevents the surface of the coated resin from becoming uneven. The purpose is to provide.

[0008]

In order to achieve this object, a rotor structure of a roots compressor according to the present invention is a roots compressor provided with a cocoon-shaped rotor, in which the outer peripheral surface of the rotor is formed smooth. A holding groove extending in the axial direction of the rotor is provided on the curved surface portion located between the convex curved surface portion and the concave curved surface portion of the rotor, and resin is coated on the entire outer peripheral surface of the rotor.

[0009]

In the rotor structure of the roots compressor having such a structure, the outer peripheral surface of the rotor is formed smooth, so that even if the resin coated on the outer peripheral surface of the rotor contracts, the surface of the resin becomes uneven. Does not occur. Therefore, the work of cutting the surface of the resin becomes unnecessary.

Further, since the holding groove extending in the axial direction of the rotor is provided in the curved surface portion located between the convex curved surface portion and the concave curved surface portion of the rotor, the resin portion solidified in the holding groove is the rotor. Will be engaged. Therefore, almost no tensile force acts on the resin located on the concave curved surface,
The peeling of the resin located on the concave curved surface portion is prevented.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the rotor structure of a roots compressor according to the present invention will be described below with reference to the drawings.

1 to 6 show an embodiment of the present invention. In FIG. 1, reference numeral 11 indicates a rotor of the roots compressor. A rotary shaft 12 is attached to the center of the rotor 11. The rotor 11 has a cocoon-shaped cross section. As a result, the outer peripheral surface 13 of the rotor 11 has two
One convex curved surface portion 13a and two concave curved surface portions 13b are formed. Two reduction holes 14 are formed in the rotor 11 for weight reduction.

The rotor 11 is made of a metal member and is manufactured by extrusion molding. That is, the rotor 11
Is manufactured by being extruded from a cocoon-shaped mold. As a result, the outer peripheral surface 13 of the rotor 11 is formed smooth. A holding groove 15 extending in the axial direction of the rotor 11 is provided in the variable curved surface portion 13c located between the convex curved surface portion 13a and the concave curved surface portion 13b of the rotor 11. The holding groove 15 is also formed by extrusion molding.

Since the holding groove 15 is located on the curved surface portion 13c, the rotor 11 is provided with four holding grooves 15 as shown in FIG. As shown in FIG. 5, the holding groove 15 has a rectangular cross section. The outer peripheral surface 13 of the rotor 11 is coated with a resin 16. The resin 16 has a uniform film thickness except for the holding groove 15.

Next, the operation of this embodiment will be described. FIG. 6 shows an operation for coating the rotor 16 with the resin 16. As shown in FIG. 6, the rotor 11 is set in the mold 21, and the molten resin 16 a injected from the injection molding machine 22 is transferred to the gate 21 a of the mold 21.
It is filled into the outer peripheral side of the rotor 11 via. Rotor 11
The molten resin 16a filled in the outer periphery of the rotor adheres to the outer peripheral surface 13 of the rotor 11 and flows into the holding groove 15 provided in the outer peripheral surface 13. As a result, the outer peripheral surface 13 of the rotor 11 and the outer peripheral portions of both end surfaces of the rotor 11 are covered with the resin 16.

The resin 16 coated on the outer peripheral surface 13 of the rotor 11 is solidified and contracted by cooling after being taken out from the mold 21. The shrinkage rate of the resin 16 after molding is
When the coating film thickness of the resin 16 is about 1.5 mm,
It is about 0.1% in the filling direction (flow direction) of the molten resin 16a, that is, the axial direction of the rotor 11, and about 0.5% in the direction perpendicular to the flowing direction of the molten resin 16a, that is, the circumferential direction of the rotor 11. As described above, since the shrinkage rate of the resin 16 is larger in the rotor circumferential direction, a large tensile force acts on the resin 16 along the circumferential direction of the outer peripheral surface 13 of the rotor 11.

Here, since a part of the resin 16 is engaged with the holding groove 15 provided on the outer peripheral surface 13 of the rotor 11,
The tensile force due to the shrinkage of the resin 16 hardly acts on the concave curved surface portion 13b on the outer peripheral surface 13. Therefore, the resin 16 located on the concave curved surface portion 13b is less likely to float from the outer peripheral surface 13, and the resin 16 is prevented from peeling off. Further, the holding groove 15 also has a function of preventing the resin 16 from being separated from the outer peripheral surface 13 due to the centrifugal force generated by the rotation of the rotor 11.

Since the outer peripheral surface 13 of the rotor 11 is formed smoothly by extrusion molding, as shown in FIG.
Resin 16 coated on the outer peripheral surface 13 of the rotor 11
Even if the resin shrinks, the surface of the resin 16 does not have irregularities. The width W of the holding groove 15 provided on the outer peripheral surface 13
Is significantly smaller than the length of the rotor 11 in the circumferential direction, and since the number provided is 4 on the entire circumference, the unevenness of the surface of the resin 16 due to the holding groove 15 can be substantially ignored. it can. Therefore, the work of cutting the surface of the resin 16 is also unnecessary.

As described above, since it is not necessary to cut the surface of the resin 16, it is possible to reduce the film thickness of the resin during coating. The shrinkage amount of the resin 16 is greatly affected by the film thickness H, and the shrinkage amount can be made smaller as the film thickness is thinner. Therefore, in this embodiment, the outer peripheral surface 13 of the resin 16 is reduced.
It is possible to further reduce the tensile force along the circumferential direction, and it is possible to enhance the effect of preventing the resin 16 located on the concave curved surface portion 13b from peeling off.

[0020]

According to the present invention, the following effects can be obtained.

(1) Since the holding groove extending in the axial direction of the rotor is provided in the curved surface portion located between the convex curved surface portion and the concave curved surface portion of the rotor, the resin portion solidified in the holding groove is formed. It can be engaged with the rotor. Therefore, even if the coated resin largely contracts in the circumferential direction of the rotor, the transmission of the contracting force can be blocked by the engagement with the groove of the rotor, and the peeling of the resin located on the concave curved surface portion of the rotor can be prevented. To be done.

(2) Since the outer peripheral surface of the rotor is formed to be smooth, even if the resin coated on the outer peripheral surface of the rotor contracts, unevenness does not occur on the surface of the resin. Therefore, the work of cutting the surface of the resin becomes unnecessary.

(3) Since it is not necessary to cut the surface of the resin, it is possible to reduce the film thickness of the resin by an amount that does not require a cutting allowance, and it is possible to reduce the amount of resin used. Further, since the film thickness of the resin can be made small, the amount of contraction of the resin in the rotor circumferential direction can be made small, and the tensile force due to the contraction of the resin can be made even smaller. This makes it possible to further enhance the effect of preventing the resin located on the concave curved surface portion of the rotor from peeling off.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a rotor structure of a roots compressor according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a partially enlarged sectional view of a rotor surface in FIG.

4 is a perspective view of the rotor of FIG. 1. FIG.

5 is a partial enlarged cross-sectional view of the holding groove of FIG.

FIG. 6 is a cross-sectional view showing a work process when coating the outer peripheral surface of the rotor of FIG. 4 with resin.

FIG. 7 is a cross-sectional view showing an example of a rotor in a conventional roots compressor.

8 is a perspective view showing a resin flow state during the resin coating operation of FIG. 7 and a resin contraction state after the coating operation.

9 is a cross-sectional view showing a peeled state of the resin when the resin coated on the rotor of FIG. 7 contracts.

FIG. 10 is a partially enlarged sectional view of FIG.

11 is a partially enlarged cross-sectional view showing a resin coating state when an indentation is formed on the outer peripheral surface of the rotor of FIG. 7 by shot blasting.

FIG. 12 is a partially enlarged cross-sectional view showing a resin coating state when a wedge-shaped groove is formed on the outer peripheral surface of the rotor of FIG.

13 is a partially enlarged cross-sectional view showing a resin coating state when arc-shaped grooves are formed on the outer peripheral surface of the rotor of FIG.

FIG. 14 is a partially enlarged cross-sectional view showing a state in which the resin coated on the outer peripheral surface of the rotor of FIG. 11 is contracted.

FIG. 15 is a cross-sectional view showing a work process of cutting the surface of the resin of FIG.

[Explanation of symbols]

 11 rotor 13 outer peripheral surface 13a convex curved surface portion 13b concave curved surface portion 13c variable curved surface portion 15 holding groove 16 resin

Claims (1)

[Claims] 1. A roots compressor provided with a cocoon-shaped rotor, wherein an outer peripheral surface of the rotor is formed to be smooth, and a variable curved surface portion located between a convex curved surface portion and a concave curved surface portion of the rotor,
A rotor structure for a roots compressor, wherein a holding groove extending in the axial direction of the rotor is provided, and resin is coated over the entire outer peripheral surface of the rotor.