JPH09264276A - Screw rotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a synthetic resin rotor formed around a metallic shaft from falling off from the shaft and to prevent generation of rust in a screw rotor to be assembled to a screw fluid machine. SOLUTION: In a screw rotor in which a synthetic resin rotor 5 is formed around a metallic shaft 1, a spiral groove 3, whose rotating direction is reverse to that of the screw rotor, is formed on the circumferential face of a shaft part coated with a synthetic resin material. The spiral groove 3 consists of a groove face with a circular arc shaped cross section and an outline connecting the connecting parts between the groove face and the adjacent circular arc groove face together by a smooth angle curved line, while stepped parts 7 are arranged in the shaft parts coated by the rotor 5, and the synthetic resin coating is formed on the shaft surface to the rotor 5 continuously.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw rotor of a screw fluid machine such as a screw compressor, a screw vacuum pump, or a screw expander.

[0002]

2. Description of the Related Art Conventionally, a screw rotor assembled in a screw fluid machine (hereinafter, a screw compressor will be described as an example for convenience of description) is provided with a metal shaft in order to improve its workability and reduce its weight. It has been proposed that a synthetic resin rotor is coated and formed on the periphery of the by injection molding. FIG.
Referring to FIG. 6, the drawing is taken along a plane AA [see FIG. 6 (b)] including a rotation axis of a screw rotor (a female rotor is shown in the figure) of this type known in the related art. Although a partial cross-sectional view [Figure (a)] and a front view [Figure (b)] are shown,
The teeth 6 of the rotor 5 are provided on the shaft 1 circumferential surface of these screw rotors.
A single or a plurality of rectangular (square) cross-section grooves 9 or projections having lead angles in the same direction and in the opposite direction to the twisting direction are formed to strengthen the fixing force between the shaft 1 and the rotor 5, and Preventing separation (for example, Japanese Patent Laid-Open No. 6-
No. 123292, JP 1-301976, etc.). These screw rotors do not rust because the rotor surface is made of a synthetic resin material. Therefore, this type of screw rotor is most suitable for a screw compressor (water injection type screw compressor) that injects water into the compression action space.

[0003]

By the way, in a screw rotor in which a groove 9 having a rectangular cross section is formed on the peripheral surface of the shaft 1 and the shaft 1 and the rotor 5 are connected to each other by coating the groove 9 with a synthetic resin material, Due to the difference in the linear expansion coefficient based on the difference in the material of the metal shaft 1 between the metal shaft 1 and the synthetic resin rotor 5 at the time of cooling the synthetic resin rotor after injection molding or due to heat change during the operation and stop of the compressor. Difference in heat shrinkage (shaft ... small heat shrinkage, rotor ...
The amount of heat shrinkage is large) and the fluctuation of the rotational torque due to the fluctuation of the load during operation largely acts, and stress is applied to the corners of the groove of the rotor (synthetic resin part) corresponding to the crests of the groove 9 provided on the shaft surface. Concentration occurs. In the screw rotor of such a type, due to the above-mentioned causes, the rotor 5 moves from the corner of the crest of the groove 9 provided on the surface of the shaft.
Crack 10 is likely to occur toward the bottom of the tooth profile of
During repeated stoppages, the crack spreads and the fixing force between the shaft 1 and the rotor 5 decreases, and finally the shaft and the rotor are separated.

On the other hand, when the screw rotor of the above type is used in the water injection type screw compressor shown in FIG. 7, since the rotor is made of synthetic resin, it has a feature that rust can be prevented. However, the shaft 1 is made of metal,
Further, since the shaft surface between the compression action chamber and the shaft sealing portion (water shaft sealing device) comes into contact with the water supplied to the compression action chamber,
There is a problem that rust is generated on the surface of this shaft. As described above, in the screw rotor of the conventional water-injection screw compressor, when rust occurs on the shaft portion, particularly the shaft surface into which the shaft sealing device for water is fitted, the rust causes the shaft surface to corrode, A shaft diameter of a portion becomes thin and a gap is generated between the shaft sealing device and the shaft surface, or the shaft sealing device itself is damaged, so that the shaft sealing performance is deteriorated.

As a result, the water supplied to the compression chamber leaks toward the shaft end of the shaft of the screw rotor from the gap between the shaft sealing device and the shaft surface, and the water leaks to the bearing portion adjacent to the shaft sealing portion. There is a problem that it flows in and induces deterioration of the lubricating oil and an emulsification phenomenon, which eventually shortens the life of the bearing. Further, due to the deterioration of the performance of the shaft seal portion due to the generation of the rust, the lubricating oil supplied to the bearing portion flows into the compression chamber through the gap between the shaft seal portion and the shaft surface,
There are various problems that water is contaminated by being mixed with cooling / sealing water supplied to the working chamber, and oil is also mixed in discharge air, which adversely affects the equipment used on the consumer side. Therefore, the material of the screw rotor shaft is made of stainless steel, or the surface of the shaft into which the shaft sealing device is fitted is plated or coated with a high rust-proof effect to prevent rust. However, there is a problem that the price and processing cost are high.

Therefore, the present invention eliminates all the problems pointed out above in a screw rotor in which a rotor made of synthetic resin is formed around a metal shaft, and makes the fixing force between the shaft and the rotor strong. In addition, it is an object of the present invention to provide a screw rotor that eliminates concentrated stress in the fixed portion caused by temperature change and prevents rust on the shaft surface in the shaft sealing portion, and that is inexpensive and has good workability.

[0007]

The present invention has the following constituent elements in order to achieve the above object. (1) In a screw rotor in which a rotor made of synthetic resin is formed around a metal shaft, a step is provided on a shaft portion coated with a synthetic resin material, and a spiral groove or a corrugated groove is formed on a surface of the coated shaft portion, A cross section of the spiral groove or the corrugated groove, which is formed by a plane including the axis center line, is formed by a contour line connecting a connecting portion between an arc-shaped groove surface and an adjacent arc-shaped groove surface with a smooth mountain curve, The screw rotor is characterized in that the spiral groove is formed in a direction reverse to the rotation direction of the screw rotor.

(2) In a screw rotor in which a rotor made of synthetic resin is formed around a metal shaft, a step or / and a bulge is provided on the shaft portion covering the synthetic resin material, and the surface of the coated shaft portion is corrugated. A groove or spiral groove is provided, and a cross section of a plane including the axis center line of the corrugated groove or spiral groove is formed by connecting a connecting portion between an arc-shaped groove surface and an adjacent arc-shaped groove surface with a smooth mountain curve. A screw rotor formed by a wire. (3) The shaft surface that is continuous with the synthetic resin rotor is coated with a synthetic resin material, and at least the surface around the axis between the shaft sealing portion on the suction side and the shaft sealing portion on the discharge side of the shaft is formed of the synthetic resin material. The screw rotor according to the above (1) or (2).

[0009]

In the screw rotor in which the rotor made of synthetic resin is formed around the metal shaft, the screw compressor is in operation by providing the spiral groove on the shaft surface in the direction opposite to the rotation direction in the operating state of the screw rotor. Receives a rotational torque in a direction opposite to the load acting on the screw rotor, and a force always acts between the spiral grooves in a direction in which the rotor and the shaft are tightened. By providing a step, a bulge or / and a wavy groove in the shaft portion of the synthetic resin material coating, the movement of the rotor in the axial direction is restrained, and the contact area between the synthetic resin material and the shaft surface is widened so Increase the binding force of.

The cross section of the groove on the shaft circumferential surface has an arc-shaped groove,
By connecting the connecting part with the groove adjacent to that groove by the contour line formed by the smooth mountain curve, the stress generated by the difference in heat shrinkage between the shaft and the rotor (made of synthetic resin) is dispersed in the arc portion, The concentration of stress in the fixed portion between the rotor and the rotor is prevented. Further, when the synthetic resin material is molded, the synthetic resin material is evenly distributed over the entire groove portion, and it is difficult to form a pinhole due to gas entrapment. Therefore, a strong fixing force between the shaft and the rotor can be obtained.

[0011] The contact area between the metal shaft surface and the synthetic resin rotor is increased to increase the fixing force between the two, and
It reduces the generation of stress due to the difference in heat shrinkage and the difference in thermal strain between the two when the compressor is started or stopped. By coating the shaft surface with a synthetic resin continuously with the rotor part, and by covering the shaft surface between the suction side shaft sealing part and the discharge side shaft sealing part with a synthetic resin material, a water jet screw It is possible to prevent rusting of the shaft surface in the shaft sealing portion of the compressor and to extend the life of the shaft sealing device.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the screw rotor of the present invention will be described below with reference to the drawings. Among the requirements constituting the present embodiment, there are the technical levels of ordinary skill in the industry at the time of this application. Within the range, including those that can be variously modified by those skilled in the art, without showing any particular reason,
It is not permitted to limit the scope of the present invention based on only the specific configuration disclosed in the present embodiment.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1A is a schematic side sectional view showing an embodiment of a screw rotor of the present invention, and FIGS. 1B to 1D are enlarged sectional views of spiral grooves or corrugated grooves. In the figure, the metal shaft 1
Is provided with a step 7 by partially reducing the diameter along the axial direction, and on the circumferential surface of the small diameter portion 2, a groove having a groove cross section and a small spiral groove 3 having a circular arc shape, a screw or a corrugated groove. Is provided. In the case of this embodiment, the spiral groove 3 is a single thread screw,
The same action and effect can be obtained even with a multi-thread screw. In FIG. 1B showing an enlarged cross-sectional view of the spiral groove 3, a circular arc shape R
The surface of the groove 3 provided with the surface of 3 and the surface of the adjacent groove 3 ′ are r-finished so as to be connected to the surface of the spiral groove 3 by a smooth curved surface so that there is no corner on the peripheral surface of the shaft. Is forming.

As shown in FIG. 1 (b), the cross section of the spiral groove 3 has a r-finish of the crests 4 different from the radius R of the circular arc groove, for example, a short radius. As shown in, the radius of the r may be set to the same length R as the arc groove, and the arcs may be directly connected to each other. Further, the cross-sectional shape may be a mountain shape in which a straight line is formed between the groove and the arc r forming the mountain, or a substantially Wit screw shape [see FIG. (D)]. Again with reference to FIG. 1A, the spiral groove 3 is a spiral groove in the reverse rotation direction with respect to the rotation direction when the screw rotor operates. That is, when the male rotor operates clockwise when viewed from the suction side shaft end, the spiral groove 3 is pre-configured counterclockwise, and a clockwise spiral groove is formed on the shaft of the female rotor that meshes with the male rotor. To do. On both sides of the thin shaft 2 where the spiral groove 3 is provided, a shaft diameter portion slightly smaller than the diameter of the spiral groove 3 is provided, and a relief portion (groove) of a cutting blade for processing the spiral groove 3 is provided. And

The diameter D ₂ of the small-diameter portion 2 provided with the spiral groove 3 is made smaller than the shaft diameter D ₁ of the intake-side and discharge-side shafts 1 (D ₁
> D ₂ ) and the distance h between the peripheral surface of the coated shaft 2 and the bottom of the tooth groove of the synthetic resin rotor (indicated by the dotted line in the figure) can be made thicker. Even if a crack occurs in the material, it is extremely rare that the crack reaches the tooth space of the rotor. The depth of the groove (mountain) of the spiral groove 3 is relatively shallow as compared with the shaft diameter. For example, within 1% in terms of the diameter ratio, this configuration suppresses the occurrence of heat shrinkage stress generated in the groove-shaped covering portion of the synthetic resin material to a small amount. 6 is axis 1
The teeth of the synthetic resin rotor 5 coated on the above are shown. 7 is axis 1
The axial step of the rotor 5 is supported by the step provided on the. In addition, in order to avoid stress concentration, either a small radius or a chamfer is applied to the corner of the step 7.

In the present embodiment, when the material of the synthetic resin with which the shaft 1 is coated is, for example, a glass phenol resin containing phenol resin and glass fiber as main components, the linear expansion coefficient of the resin is metal (here, , Steel, cast iron), it is possible to suppress the stress generated due to the difference in heat shrinkage between the shaft 1 and the rotor 5 during the operation / stop of the compressor in the compressor using the rotor. it can. The synthetic resin for the rotor is not limited to the above glass phenol resin, and a synthetic resin material satisfying the characteristics such as mechanical strength and having an expansion coefficient close to the linear expansion coefficient of the shaft material is used. Therefore, the component is not limited as long as the stress caused by the thermal fluctuation can be made as small as possible.

FIG. 2 shows a partial sectional view of another embodiment of the screw rotor of the present invention. Among the reference numerals entered in the drawing, the members having the same reference numerals as those in FIG. 1A indicate the members common to the above-described embodiment. The diameter D _{4 of} the shaft portion (the portion where the spiral groove 3 is formed) coated with the synthetic resin material is larger than the shaft diameter D ₃ of the shaft 1 on the suction side and the discharge side (D ₄ > D ₃ ). In this case, the surface area of the portion provided with the spiral (corrugated) groove 3 is increased, and the fixing force between the shaft 1 and the rotor 5 is strengthened.
At this time, since it is not necessary to provide an escape groove for processing the spiral groove 3 on the shaft 1, there is no risk of reducing the strength of the shaft 1. The step 7 provided between the shaft diameter D ₄ and the shaft diameter D ₃ supports the thrust force applied to the synthetic resin rotor 5. The shape of the step 7 has been described above.

In the present embodiment, the distance between the outer peripheral surface of the shaft portion 2'provided with the spiral groove 3 and the outer peripheral surface of the rotor 5 is A ₂ ,
Assuming that the distance between the end surface of the rotor 5 and the shaft portion step 7 provided with the spiral groove 3 is A ₁ , when A ₁ ≈A ₂ , during the cooling of the synthetic resin rotor 5 after molding, Since the cooling rate of the synthetic resin material near the shaft 1 becomes uniform and the internal stress generated in the rotor is reduced, the resin material is less likely to crack. Also in the case of this embodiment, the cross-sectional shape of the spiral groove 3 is as shown in FIG.
The described channel shapes can be implemented.

FIG. 3 is a partial cross-sectional view of another embodiment of the screw rotor of the present invention, in which the shaft 1 on the suction side and the shaft on the discharge side are provided between the shaft seal portion on the suction side and the shaft seal portion on the discharge side. A step is provided thinner than the shaft diameter, and a spiral groove or a wave groove is provided on the shaft peripheral surface of the two small diameter portions. Preferably, a step is provided in a range L having a length longer than the distance between the suction-side and discharge-side water shaft sealing devices and shorter than the distance between the suction-side and discharge-side oil shaft sealing devices. Further, a synthetic resin-coated shaft 8 is formed extending continuously from the both ends of the synthetic resin rotor 5 so as to be integrated with the shaft sealing device. The reference numerals are given in common with the description of FIG. In the case of the present embodiment, since the range L where the step is provided can be made long, the axial length of the portion provided with the spiral groove or the corrugated groove is long, the surface area of the shaft is increased, and the shaft 1 and the synthetic resin rotor are fixed to each other. Will be strengthened. Further, since the shaft into which the water shaft sealing device is fitted is also covered with the synthetic resin, rust does not occur on the rotor, the shaft and the like even when used in the water injection type screw compressor.

FIG. 4 shows a partial cross-section of another embodiment of the screw rotor of the present invention, and the attached reference numerals are the same as those in the drawings shown in FIGS. In the case of the present embodiment, the shaft covering portion of the synthetic resin material forming the shaft sealing portion (spiral groove 3 ₁ ) is larger than the diameter of the shaft covering portion of the synthetic resin material forming the rotor 5 (where the spiral groove 3 is formed). By making the diameter of the portion () that has been subjected to the treatment small, a plurality of steps 7 are provided between the two, and the thickness of the synthetic resin material forming the shaft sealing portion is ensured to prevent the resin material from cracking. Further, by making the groove depth of the spiral groove 3 ₁ smaller than the groove depth of the spiral groove 3, the synthetic resin material forming the shaft sealing portion is prevented from cracking.
The above-mentioned groove is not limited to the spiral groove, and even if a corrugated groove is formed, the same effect can be obtained. In the present embodiment, the diameter of the shaft covering portion (the portion where the spiral groove 3 is formed) is relatively large, and the axial length of the portion where the spiral groove is formed is long. 1 and the synthetic resin rotor 5 can be strengthened.

FIG. 5 shows a partial cross section of another embodiment different from the one described above, and the reference numerals are used in common with the drawings shown in FIGS. This embodiment may be referred to as a modification of the rotor shaft shown in FIG. 4, in which the shaft covering portion of the synthetic resin material of the rotor is formed by a gentle curve, and the expansion portion is formed at the central portion in the longitudinal direction of the shaft 1 as a whole. Is provided. A corrugated groove or a spiral groove 3 is entirely formed on the peripheral surface of the shaft covering portion made of a synthetic resin material.
Is given. According to this embodiment, since the thrust applied to the rotor 5 is dispersedly supported by the arcuate surface of the shaft 1, the stress is not concentrated and the cracking of the resin material can be reduced.

Although not shown, the shaft 1 is further molded by casting, and the shaft portion coated with the synthetic resin material is left as the casting surface (however, the molding sand adhering to the surface is completely removed), and the resin material is coated. If the shaft surface other than the above is finished by machining, the resin enters the irregularities of the casting surface of the shaft covered with the resin material, and the fixing structure between the shaft and the rotor can be strengthened, and the number of processing steps is also saved. be able to.

[0023]

EFFECTS OF THE INVENTION Since the present invention has the structure and operation as described above, the spiral groove or the corrugated groove formed by connecting the peaks and groove sections with a smooth curve is formed on the peripheral surface of the synthetic resin material. By doing so, the stress concentration at the coupling part on the rotor side is relieved,
It is possible to prevent the occurrence of cracks from the joint surface toward the root of the screw rotor groove, as well as the shaft and rotor (synthetic resin part).
It is possible to prevent disengagement between the two and to strengthen and maintain the adherence for a long period of time. By providing a step or expansion section on the shaft, the axial movement of the rotor is restricted, and even if the rotor and the rotor section are separated due to some reason, the inner surface of the casing and the end surface of the rotor will be separated during operation of the compressor. No accident such as contact or seizure will occur.

When used in a water-injection screw compressor, no rust is generated in the part that comes into contact with water, the reliability of the shaft sealing device is improved, and rust and oil are not mixed in the discharge air. In addition, since the deterioration of the lubricating oil and the emulsification phenomenon due to the mixing of water into the lubricating oil can be prevented, the life of the bearing can be extended. Even if the material of the shaft is steel or cast iron, it is not necessary to apply rust-preventive plating or coating to the surface of the shaft, the processing time can be shortened as compared with the conventional device, and the screw rotor can be manufactured at low cost. The rotor is not limited to the rotor of the water injection screw compressor, but can also be used as a rotor of a screw fluid machine such as an oil-cooled screw compressor, an oil-free screw compressor, a screw vacuum pump or a screw expander.

[Brief description of drawings]

FIG. 1 shows a side sectional view and an enlarged partial sectional view of a spiral groove of an embodiment of a screw rotor of the present invention.

FIG. 2 is a side sectional view of another embodiment of the screw rotor of the present invention.

FIG. 3 is a partial side sectional view of another embodiment of the screw rotor of the present invention.

FIG. 4 is a partial side sectional view of another embodiment of the screw rotor of the present invention.

FIG. 5 is a partial side sectional view of a screw rotor according to another embodiment of the present invention.

FIG. 6 shows a partial side sectional view and a front view of an example of a conventionally known screw rotor.

FIG. 7 is a partial side sectional view of a conventionally known water injection type screw compressor.

[Explanation of symbols]

 1 shaft (rotating shaft) 2 small-diameter shaft part 3 spiral groove 4 crest (shaped) part 5 synthetic resin rotor 6 teeth (groove) 7 step 8 synthetic resin material coated shaft sealing part 9 cross-section rectangular groove 10 crack

Claims (3)

[Claims] 1. A screw rotor in which a rotor made of synthetic resin is formed around a metal shaft, and a step is provided on a shaft portion covering the synthetic resin material, and a spiral groove or a corrugated groove is formed on the surface of the covering shaft portion. The cross section of the spiral groove or the corrugated groove taken along a plane including the axial center line is formed by a contour line connecting a connecting portion between an arc-shaped groove surface and an adjacent arc-shaped groove surface with a smooth chevron curve. The screw rotor is characterized in that the spiral groove is formed in a reverse direction with respect to a rotation direction of the screw rotor. 2. A screw rotor in which a rotor made of synthetic resin is formed around a metal shaft, and a step or / and a bulge is provided on a shaft portion covering the synthetic resin material, and a corrugated groove is formed on a surface of the coated shaft portion. Or, a spiral groove is provided, and a cross section of a plane including the axis center line of the corrugated groove or the spiral groove is a contour line that connects a connecting portion between an arc-shaped groove surface and an adjacent arc-shaped groove surface with a smooth mountain curve. A screw rotor characterized by being formed by. 3. A shaft made of synthetic resin, which is continuous with a rotor made of synthetic resin, and is coated on the shaft surface with a synthetic resin material. The screw rotor according to claim 1, wherein the screw rotor is formed by: [0001]