JP2016196859A - Compressor, and screw rotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compressor including a screw rotor, for actualizing a smaller gap between female and male rotors in consideration of a heat deformation amount.SOLUTION: The compressor includes the screw rotor including at least a pair of a female rotor 2 and a male rotor 1, and a compressor body casing forming a compression chamber together with the screw rotor. Each of the female rotor and the male rotor is taper-shaped at its discharge and suction side end faces so that the outer diameter on the suction side is larger than the outer diameter on the discharge side. The taper amount of each of the female rotor and the male rotor is equal to or larger than a difference in heat deformation amount between the tooth bottoms on the discharge and suction side end faces of each rotor, and is equal to or smaller than a difference in heat deformation amount between the tooth tips thereof. The sum of the taper amounts is equal to or smaller than the sum of the difference in heat deformation amount between the tooth bottoms of one rotor and the difference in heat deformation amount between the tooth tips of the other.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a compressor and a screw rotor, and relates to a tapered compressor and screw rotor having different outer diameters on a suction side and a discharge side.

A screw compressor is known as a compressor for compressing gas.
There are two types of screw compressors: an oil supply type that injects and injects oil into a compression chamber that compresses gas, an oilless type that does not inject oil, and a water injection type that injects and injects water into an oilless type, and a dry type that does not inject There is.

  In the dry type, adiabatic compression without cooling of compressed air by oil or water is performed, so that the compressed gas becomes high temperature, and the rotor and casing of the compressor main body constituting the compression chamber become high temperature. In addition, the dry type does not have a lubricating effect due to oil or water or a sealing effect that suppresses leakage of compressed gas from the compression chamber, so there is no direct contact drive at the screw part, and a minute amount between the male and female rotors or between the rotor and casing. It is designed to drive at a high speed with a clear gap. For this reason, the rotor and casing are subject to thermal deformation during operation, and the gap between the male and female rotors and the gap between the rotor and casing are greatly different from those during assembly. There is a problem that contact between both rotors or between the rotor and the casing increases, which increases the possibility of the compressor being stopped or the compressor air end being stuck.

  In order to prevent such a problem, in general, the dimensions of the rotor at the time of assembly are set in consideration of thermal deformation during operation, that is, it is manufactured so as to increase the gap at the time of assembly.

  There exists patent document 1 as such a prior art example. Patent Document 1 discloses that the shape of the screw rotor is such that the temperature increases during operation, that is, a tapered rotor having different radial dimensions on the discharge side having a large thermal expansion amount and on the suction side having a relatively low temperature and a small thermal expansion amount. In order to make the cross-sectional tooth profile on the discharge side and the suction side close to the target similarity, the difference in thermal deformation at the tooth bottom of both cross sections using different leads on the advance surface and the reverse surface Disclosed is a multiple lead tooth profile that is a tooth profile that is moved to the outer peripheral side only.

  According to Patent Document 1, a tapered rotor having a tooth shape close to the tooth shape of the discharge side cross section and the suction side cross section, which are different in size and having a target similar shape, is formed along the axial direction using a tooth surface grinder or the like. It can be realized by a normal processing method (hereinafter referred to as “pulling processing”) in which processing is performed while the amount of radial pull-up is constant.

Japanese Patent No. 2619468

  However, since Patent Document 1 uses the difference in the amount of thermal deformation at the roots of both cross sections as the pull-up amount, the effect cannot be expected so much in practice. In other words, the amount of thermal deformation is approximately proportional to the radial dimension, while the amount of pulling up is a constant amount regardless of the radial dimension. In the portion close to, the tooth profile is smaller than the originally desired similar tooth profile. Therefore, the gap between the rotors and the gap between the rotor and the casing are also larger than the gap formed by the tooth shape having the desired shape.

Further, in Patent Document 1, the amount of multiple leads in each male and female rotor is set to an amount that eliminates the interference portion between the target tooth profile and the lifting tooth profile, but in this determination method, the portion that does not interfere with the male and female rotors is also deleted. Therefore, there is a problem that the tooth profile becomes thinner than necessary.
A screw rotor and a compressor that take into account the amount of thermal deformation with higher accuracy are desired.

  In order to solve the above problem, for example, the configuration described in the claims is applied. That is, a compressor including a screw rotor including at least a pair of female rotors and a male rotor, and a compressor body casing that forms a compression chamber together with the screw rotors, wherein the male rotor and the female rotor are disposed on the discharge side and the suction side. The end surface has a taper shape in which the outer diameter on the suction side is larger than the outer diameter on the discharge side, and the taper amount of each of the male rotor and the female rotor is the heat of the tooth bottom on the discharge side and the suction side end face of each rotor. The difference between the amount of deformation and the difference between the amount of thermal deformation of the tooth tip and the difference of the amount of thermal deformation of the tooth tip is the sum of the respective taper amounts. It is the structure which is below the sum with the difference of deformation amount.

According to the present invention, the male and female rotors have tooth shapes that compensate for thermal deformation with each other, and leakage of compressed gas from the compression working chamber can be reduced.
Other problems, configurations, and effects of the present invention will become apparent from the following description.

(A) is a prior art example and is a perspective view schematically showing a state where male and female screw rotors are engaged with each other, and (b) is a top view schematically showing the state where these male and female rotors are observed from above. is there. The partial cross section of the female rotor by the conventional "base raising of a tooth base" as a comparative example is shown. The partial cross section of the male rotor by the conventional "tooth base reference pulling up" as a comparative example is shown. The partial cross section at the time of the male-and-female rotor meshing | engaging by the conventional system "base raising of a tooth base" as a comparative example is shown. The partial cross section by "tooth tip standard pulling up" of the female rotor by one Example to which this invention is applied is shown. The partial cross section by "tooth tip standard pulling up" of the male rotor by one Example to which this invention is applied is shown. The partial cross section at the time of raising the raising amount of the male and female rotor by a present Example on the basis of "tooth tip" or "tooth bottom" is shown. The partial cross section at the time of raising the raising amount of the male and female rotor by a present Example on the basis of "tooth tip" or "tooth bottom" is shown. It is explanatory drawing of the multiple lead process for deleting the interference part of the male and female rotor by a present Example.

  Hereinafter, embodiments for carrying out the invention will be described in detail with reference to the drawings.

First, a conventional example of a general tapered rotor will be described with reference to FIGS.
FIG. 1A is a perspective view schematically showing a state in which a male rotor 1 and a female rotor 2 of a screw compressor main body (also referred to as “air end”) are engaged with each other. In the compressor main body, a tooth space formed by the male rotor 1 and the female rotor 1 and a compressor main body casing (not shown) installed on the outer peripheral side thereof is referred to as a compression chamber (or a compression working chamber). As the rotor is rotated inward by the drive source, the compression chamber advances toward the discharge side end face and is narrowed, and the suction port 3 provided on the upper side (only the position is schematically shown in the figure). ) Is gradually compressed. The compressed air in the compression chamber that has been moved to the discharge side is discharged from the discharge port 4 (only the position is schematically shown by a dotted line in the figure) formed at a position substantially opposite to the rotor end surface. Air of a desired pressure is obtained.

FIG. 1B shows a schematic view of each rotor observed from above. Both the male rotor 1 and the female rotor 2 have a tapered shape in which the outer diameter on the suction side is large and the outer diameter decreases toward the discharge side (dotted line). Note that FIG. 1B shows a large difference in diameter between the suction side and the discharge side for convenience of explanation, but the actual difference in diameter is slight. The difference in diameter is the difference in the degree of thermal expansion caused by the difference in temperature. For example, the outer diameter of the rotor is 100 (mm), and the linear expansion coefficient of the rotor material is 10 ⁻⁵ (1 / K). Assuming that the temperature difference between the discharge side and the suction side is 100 (K), the difference in the expansion amount of the outer diameter portion is about 0.1 (mm).

  FIG. 2 schematically shows a partial cross section of one groove on the suction side and discharge side of the tooth profile of the female rotor 2. In the drawing, the “discharge side tooth profile” of the female rotor 2 indicates a tooth shape before thermal expansion on the discharge side (hereinafter referred to as “processed tooth profile”). The “suction side target tooth profile” of the female rotor 2 indicates a tooth profile before thermal expansion on the suction side. The shape of the “suction-side target tooth profile” is substantially similar to the “discharge-side tooth profile”, but the outer diameter is increased by a small amount of thermal expansion during operation. In this way, by using a small tooth profile on the discharge side and a large tooth profile on the suction side, the tooth profile on the discharge side and the suction side is approximately the same size during operation, so that the clearance between both rotors and between the rotor and casing is appropriate. It has become. Note that O2 is the rotation axis, and “suction side tooth profile circle” and “discharge side tooth profile circle” indicate the trajectories of the outermost diameter portions of “suction side target tooth profile” and “discharge side tooth profile”, respectively.

  By the way, in actually manufacturing a tapered rotor, it is difficult to make the tooth profiles on both sides of the discharge and suction similar. For example, when using the most common tooth surface grinder, the advancing surface and the reversing surface are processed by setting a constant grinding wheel lifting amount and each lead (an example of a tooth profile in that case, (Indicated in the figure as "pull tooth profile"). In this conventional example, the pull-up amount h2 between the “discharge-side tooth profile” and the “suction-side target tooth profile” is the pull-up difference, and as a result, the root diameter of the “pull-up tooth profile” is However, in the vicinity of the tooth tip, the “pull-up tooth profile” becomes smaller than the “suction-side target tooth profile”. Thus, the method of using the difference between the roots of the “discharge-side tooth profile” and the “suction-side target tooth profile” as the pull-up amount is referred to as “base-lifting”.

  FIG. 3 schematically shows a partial cross section of one groove on the suction side and the discharge side of the tooth profile of the male rotor 1. “Discharge side tooth profile” indicates the outer diameter shape on the suction side before thermal expansion, and “Suction side target tooth profile” indicates the outer diameter shape on the suction side before thermal expansion. In addition, O1 is a rotation axis, and “suction side tooth tip circle” and “discharge side tooth tip circle” indicate rotation trajectories of the outermost diameter portions of “suction side target tooth profile” and “discharge side tooth profile”, respectively. .

  In the case of the male rotor 1 as well, with the “suction-side target tooth profile” as the target, the grinding wheel is pulled up and the lead is set and feed processing is performed. As in the case of the above, a phenomenon occurs in which the “lifting tooth profile” becomes smaller in the vicinity of the tooth tip than the “suction side target tooth profile”.

  FIG. 4 schematically shows a partial cross section of one groove on the suction side and discharge side of the tooth profile of both the male and female rotors. This figure shows a combination of the “pulling teeth” of FIGS. 2 and 3, where the bottom of the female rotor 2 and the top of the male rotor 1 are connected to the axes O 1 and O 2. Are located at the same time, that is, they are in the most engaged state. At this time, the gap between the rotors is large between the tooth bottom of the female rotor 2 and the vicinity of the tooth tip of the male rotor 1. In this way, when the tooth root reference pull-up tooth profiles are combined, the clearance between the meshed parts, especially in the vicinity of the tip of the tooth, increases, and the amount of compressed gas leakage increases accordingly. The problem that it cannot be obtained arises.

  Based on the above problems, a male rotor 10 and a female rotor 20 according to an embodiment to which the present invention is applied will be described with reference to FIGS. In the present embodiment, the pull-up amount of the male and female rotors is based on the difference between the discharge-side tooth profile and the suction-side target tooth profile at the “tooth tip” (hereinafter referred to as “tooth tip reference pull-up”). One.

  FIG. 5 schematically shows a partial cross section for one groove on the suction side and the discharge side of the female rotor 20. Unlike the female rotor 2 (FIG. 2) in the above-described conventional example, the diameter of the root portion is larger than that of the “suction side target tooth profile” and the diameter of the tooth tip portion is the same. The tooth profile becomes larger than the “target tooth profile”. That is, in this embodiment, polishing is performed by “pickup of the tooth tip reference” from the h2 which is the difference of the tooth bottom portion to the tooth tip difference X2, and the relationship of h2 <X2 is satisfied.

  The amount of pull-up is defined based on the tooth tip because the rotor tooth has other characteristics such as the shape of the screw rotor that the rotor outer diameter side is thinner than the rotor core side, the drive source, etc. The core side near the rotor shaft that is connected to and contacted with the other member is because the thermal expansion coefficient on the tooth tip side is larger than that on the core side due to the mechanical characteristics that the heat dissipation effect is relatively high in terms of heat conduction. This is because it is suitable for narrowing the gap between the rotor at the tooth bottom portion and the tooth tip during driving.

  FIG. 6 schematically shows a partial cross section for one groove on the suction side and the discharge side of the male rotor 10. Similar to the female rotor 20, the pull-up amount X1 is polished by “tooth tip reference pull-up” with h1 <X1. The diameter of the tooth bottom part is larger than the “suction side target tooth profile”, and the diameter of the tooth tip part is the same, and is generally larger than the “suction side target tooth form”.

Thus, since the outer diameter of the rotor is increased by the “tooth tip reference pulling up”, it can be said that the gap between the rotors is smaller than that in the case of “tooth base reference pulling up” when the rotors are engaged with each other.
Here, if the pull-up amount becomes larger than necessary, one tooth tip comes into contact with the other tooth bottom, so the pull-up amount needs to take into account the amount of thermal deformation of each rotor. That is, it is preferable that the sum of the pull-up amounts of the two rotors is equal to or less than the sum of the difference in the thermal deformation amount of the tooth bottom of one rotor and the difference of the thermal deformation amount of the tooth tip of the other rotor. An example satisfying such a relationship will be described below.

  FIG. 7 shows one groove when both rotors are combined when the male rotor 10 is pulled up with the “base lift amount (h2)” and the female rotor 20 is pulled up with the “tip top pull amount (X2)”. The partial cross section of is schematically shown. FIG. 4 shows the advancing surface portion in particular. However, compared to the case where both rotors are set to the tooth base reference lifting amounts h1 and h2 (FIG. 4), the tooth bottom portion of the female rotor 20 and the tooth tip portion of the male rotor 10 are shown. It is possible to reduce the gap between the rotors in the vicinity. The pull-up amount h2 of the male rotor 10 is a thermal deformation amount considering the thermal expansion coefficient of the tooth bottom portion having a smaller diameter, and the pull-up amount X2 of the female rotor 20 is a tooth having a larger diameter. Since the amount of thermal deformation takes into account the coefficient of thermal expansion of the tip portion, the amount of thermal deformation due to the difference in diameter between the tooth bottom portion and the tooth tip portion is complemented by the male and female rotors. Thereby, the leak amount of compressed gas becomes small and the improvement of performance is realizable.

  8, contrary to FIG. 7, a portion corresponding to one groove when the male rotor 10 is set to the “tooth tip reference pull-up amount (X1)” and the female rotor 20 is set to “tooth base reference pull-up amount (h2)”. The partial cross section of is schematically shown. Even in this case, it is possible to reduce the clearance between the rotors in the vicinity where the bottom of the female rotor meshes with the male rotor tip.

  In the examples shown in FIGS. 7 and 8, one is the “tooth base reference pull-up amount (h)” and the other is “tooth tip reference pull-up amount (X)”. The lifting amount may be an intermediate lifting amount between the respective “tooth base reference lifting amount (h)” and “tooth tip reference lifting amount (X)”.

  On the other hand, even if one of the rotors is set to “upper root reference pulling” and the other rotor is set to “upper tip reference pulling”, the tooth forms of the male rotor 10 and the female rotor 20 interfere as shown by hatching in FIGS. A portion (hereinafter referred to as “interference portion T”) may occur. In such a case, it is necessary to delete the interference portion T (including thermal deformation and a set gap) for either one or both rotors by multi-lead processing.

  With reference to FIG. 9, a method of deleting the interference portion T by multi-lead machining and a multi-lead tooth profile formed as a result will be described. This figure shows the forward surfaces of the female rotor 20 and the male rotor 10. The pulling-up tooth profile in the figure is a tooth profile obtained by the “tooth tip reference lifting” shown in FIG. In order to eliminate the interference part T, the lead on the advancing surface is made smaller than the basic lead value, that is, the winding angle on the discharge side and the suction side is made larger. This increase in the winding angle is shown as the double lead rotation angle in the figure. By changing the lead value, the “pull-up tooth profile” is processed into a rotated shape like a multi-lead tooth profile, and the interference portion with the male rotor 10 is deleted. It is possible to realize a tooth profile that is larger than the “tooth base reference lifting” tooth profile and does not interfere with both the male and female rotors as compared with the “tooth base reference lifting” tooth profile shown in the drawing.

Such multi-lead processing will be further described with reference to FIGS. 7 and 8 described above.
As described above, FIG. 7 shows that the pulling amount of the female rotor 20 is “tooth tip reference pulling amount (X2)”, and the pulling amount of the male rotor 10 is “tooth base reference pulling amount (h1)”. In this case, the rotor gap and the interference portion T, which are a combination of both rotors, are shown, and Fig. 8 shows a case where the pulling amount is opposite to Fig. 7.

  7 and FIG. 8, the gap between the rotors in the tooth tip portion and the tooth bottom portion is approximately the same, but there is a difference in the size of the interference portion T. This is because when the male rotor 10 and the female rotor 20 are pulled up by the same pulling amount, the female rotor 20 has more teeth, and the pulling direction and the radial direction are close to each other for one groove. This is because the tooth profile is closer to the “suction target tooth profile” than in the case of the male rotor 10. When the interference part T becomes large, the value of the rotation angle to be deleted increases due to the multiple leads, and even parts that do not need to be reduced are deleted and thinned. Therefore, it can be said that the method of FIG. 7 in which the lifting amount of the female rotor 20 is larger than the lifting amount of the male rotor 10 is preferable.

  DESCRIPTION OF SYMBOLS 1 ... Male rotor, 2 ... Female rotor, 10 ... Male rotor, 20 ... Female rotor, h1 * h2 ... Tooth base reference pull-up amount, X1 / X2 ... Tooth tip reference pull-up amount, T ... Interference part

Claims (4)

A compressor comprising: a screw rotor including at least a pair of female rotors and male rotors; and a compressor body casing that forms a compression chamber together with the screw rotors,
Male and female rotors
At the discharge side and suction side end faces, the suction side has an outer diameter that is larger than the discharge side outer diameter,
The taper amount of each of the male rotor and the female rotor is greater than or equal to the difference between the thermal deformation amounts of the roots of the discharge side and suction side end surfaces of each rotor and less than the difference between the thermal deformation amounts of the tooth tips. The compressor in which the sum of the amounts is equal to or less than the sum of the difference in thermal deformation amount of the tooth bottom of one rotor and the difference in thermal deformation amount of the tooth tip of the other rotor.   2. The compressor according to claim 1, wherein a portion that interferes with rotation of the male rotor and the female rotor is deleted by multi-lead processing. The compressor according to claim 1 or 2,
A compressor in which the taper amount of the female rotor is larger than the taper amount of the male rotor. A screw rotor that includes at least a pair of female and male rotors, and compresses gas by meshing by rotation of both rotors,
Male and female rotors
At the discharge side and suction side end faces, the suction side has an outer diameter that is larger than the discharge side outer diameter,
The taper amount of each of the male rotor and the female rotor is greater than or equal to the difference between the thermal deformation amounts of the roots of the discharge side and suction side end surfaces of each rotor and less than the difference between the thermal deformation amounts of the tooth tips. A screw rotor in which the sum of the amounts is equal to or less than the sum of the difference in thermal deformation amount of the tooth bottom of one rotor and the difference of thermal deformation amount of the tooth tip of the other rotor.

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