JP2009275586A - Screw tooth form - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screw tooth form accurately machining the tip end of the screw tooth form of a male rotor in comparison with the past and improving performance of a screw compressor. <P>SOLUTION: This screw tooth form 20 is so configured that in the screw compressor including a compressor body 21 composed of a pair of female and male screw rotors 23, 24, the tip end 32 of the male rotor 24 is formed into a circular arc with the center of the rotating shaft of the male rotor 24 as a center point, and the circular arc of the tip end 32 of the male rotor 24 is formed on a short virtual circular arc 34 of the circular arc divided into two at an intersection of a virtual male rotor shape 40 as the shape of the male rotor 24 with a clearance in a position closest to the female rotor 23 set to substantially zero when the female rotor 23 is rotated and a circular arc with the center of the male rotor 24 as the center point. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a screw tooth profile.

  The tip of the conventional male rotor is generally shaped as shown in FIG. That is, with respect to the rotational direction R, the forward tooth profile 10 is an arc centered on B on the pitch circle centered on the male rotor rotational axis A, and the follower tooth profile 11 is between the tip of the male rotor and B. An arc centered on C. Although there is a difference depending on the size of the radius, it has such a shape.

  As shown in FIG. 5, the distal end portion 13 of the male rotor 12 shown in Patent Document 1 is an important part that determines the gap ε1 between the male rotor 12 and the female rotor 14 and the gap ε2 between the male rotor 12 and the casing 15. . The processing accuracy of the tip 13 greatly affects the performance of the screw compressor. In particular, the accuracy of the gap of ε2 greatly depends on the processing accuracy of the tip portion 13 of the male rotor 12.

However, since the tip portion 13 of the male rotor 12 has been cut with a cutter or the like simultaneously with other portions, there is a limit to machining with high accuracy.
Japanese Patent Publication No. 60-41238

  An object of the present invention is to provide a screw tooth profile that can process the tip portion of the screw tooth profile of the male rotor with higher accuracy than the conventional one and improve the performance of the screw compressor.

  As a means for solving the above-mentioned problems, the screw tooth profile of the present invention is a screw compressor in which a compressor main body is constituted by a pair of male and female screw rotors, and the tip of the male rotor is rotated by the male rotor. The arc at the tip of the male rotor is formed as an arc centered on the center of the shaft, and the gap at the position closest to the female rotor when the female rotor rotates is substantially zero. The virtual male rotor shape, which is the shape of the male rotor, is formed on the shorter virtual arc of the arc divided by the intersection of the arc centered on the center of the male rotor. Is.

  With this configuration, the gap at the position where the tip of the male rotor formed on an arc centered on the center of the rotation axis of the male rotor is closest to the female rotor when the female rotor rotates is substantially omitted. By forming the virtual male rotor shape, which is the shape of the male rotor being zero, and the short virtual arc of the arc divided and bisected at the intersection of the male rotor with the arc, the female rotor and the male rotor The possibility of interference with the rotor tip can be reduced.

  Furthermore, it is preferable that the part formed in the advance side tooth profile in the tip portion of the male rotor is formed longer than the part formed in the following side tooth profile. With this configuration, the female rotor and the tip of the male rotor may interfere with each other as compared with the case where the part formed in the forward side tooth profile is formed to be the same as or shorter than the part formed in the following side tooth profile. Can be reduced.

  According to the present invention, the performance of the screw compressor can be improved by processing the tip portion of the screw tooth profile of the male rotor with high accuracy by polishing instead of cutting with a cutter or the like.

  Since the forward tooth profile has a larger clearance with the female rotor, the portion formed on the forward tooth profile of the tip of the screw tooth profile of the male rotor is longer than the portion formed on the follower tooth profile. If formed, it is possible to reduce the possibility of interference between the female rotor and the tip of the screw tooth shape of the male rotor.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a sectional view in the axial direction of rotors 23 and 24 of a rotor casing 22 of a screw compressor main body 21 having a screw tooth profile 20 according to the present invention. FIG. 2 shows a partially enlarged view of the screw tooth profile 20 in the male and female rotors 23 and 24 engaged with each other.

1) Female rotor tooth profile The female rotor 23 has an addendum Af of 2 to 3% with the best compression efficiency on the outside of various pitch circles Pf, and has a denden dam Df on the inside of the pitch circle Pf of each tooth bottom 25. ing. The advance side tooth profile 26 and the follow side tooth profile 27 are as follows.

B) Advance side tooth profile 26
The space between d _{2 and} e ₂ is an arc having a radius R ₁ centering on the intersection l between the pitch circle Pf and the line connecting the center points (axis centers) Of and Om, and ∠d ₂ le ₂ is In order to set the tooth thickness from the tooth base to the tooth tip to a suitable value, it is set to 45 to 55 degrees. D ₂ is a point on the line connecting the center points Of and Om.

The space between e _{2 and} f ₂ is an arc of radius R ₂ having a center point O ₂ on an extension line of radius l−e ₂ . The arc e ₂ -f ₂ is inflected at a point e _{2 with} respect to the arc d ₂ -e ₂ . It should be noted that the point _{f 2} is a point on the pitch circle Pf.

The space between f _{2 and} g ₂ is an arc with a radius R ₃ having a center point O ₃ on the radius O ₂ -f ₂ . Incidentally, the point g ₂ is in contact with the addendum circle Cf at a point on the addendum circle Cf of radius Rf.

· Between g _{2 and} h ₂ is an arc along the tip circle Cf. The dimension between them is 0.5 to 1.5 mm, and it is preferable to have the same effect as the protective function at the time of contact between the rotor and the casing which the conventional tooth profile seal edge has.

B) Tracking side tooth profile 27
The space between d _{2 and} c ₂ is a creation curve created by the arc d ₁ -c ₁ of the male rotor 24.

· _C 2 -a ₂ between are arc having a radius _{R 5} around the point _{O 5.} Note that the point a ₂ is a point on the pitch circle Pf, the point O ₅ is a tangent line R ₅₁ in contact with the pitch circle Pf at the point a ₂ , a generating curve d ₂ -c ₂ and an arc c _{2 at the} point c ₂ . This is the intersection of the common normal R ₅₂ with -a ₂ . The arc c ₂ -a ₂ is inflected at the point c _{2 with} respect to the generating curve d ₂ -c ₂ .

The space between a _{2 and} h ₂ is a creation curve created by the point a ₁ of the male rotor 24. It should be noted that the point h ₂ is a point on the addendum circle Cf.

The h ₂ -a ₂ -c ₂ -d ₂ -e ₂ -f ₂ -g ₂ -h ₂ constitutes one sixth of the tooth profile of the female rotor 23.

2) Male rotor tooth profile The male rotor 24 has an addendum Am on the outside of the pitch circle Pm of each tooth 28, and has a denden dam Dm on the inside of the pitch circle Pm of each tooth bottom 29. The advance side tooth profile 30 and the follow side tooth profile 31 are as follows.

B) Advance side tooth profile 30
· _D 1 -e ₁ between the respective center points of the pitch circle Pm and male and female rotors 23, 24 Of, centered on the intersection m of the line connecting the Om, and the arc of the radius _R substantially equal to the radius _{R 1} to the ₁ ' And corresponds to the arc d ₂ -e ₂ of the female rotor 23. Thus, ∠d ₁ me ₁ is at the same angle as ∠d ₂ le ₂ . Incidentally, the point _{d 1} is the point of a line connecting the center point Of, the Om.

· Between e ₁ -f ₁ is a creation curve created by the arc e ₂ -f ₂ of the female rotor 23. It should be noted that the point _{f 1} is on the pitch circle Pm.

-Between f ₁ -g ₁ is a creation curve created by the arc f ₂ -g ₂ of the female rotor 23. Incidentally, _{g 1} is a point on the dedendum Cm.

· _G 1 -h ₁ while is a circular arc along the dedendum Cm radius Rm.

B) Tracking side tooth profile 31
The space between d _{1 and} c ₁ is an arc with a radius R ₄ having a center point O ₄ on the straight line Of-Om. Radius _{R 4} is 20-30% approximately of the radius of the arc _{R 1} centered on the point m is on the male rotor pitch circle Pm.

The space between c _{1 and} a ₁ is a creation curve created by the arc c ₂ -a ₂ of the female rotor 23. Note that the point a ₁ is a point on the pitch circle Pm.

A section between a _{1 and} h ₁ is a creation curve created by the point h ₂ of the female rotor 23.

The h ₁ -a ₁ -c ₁ -d ₁ -e ₁ -f ₁ -f ₁ -g ₁ -h ₁ constitute one fifth of the tooth profile of the male rotor 24.

FIG. 3 shows a partially enlarged view of the shape of the male rotor 24 near the point d ₁ of the screw tooth profile. The tooth profile of the male rotor 24 is a substantially rectangular shape having a height H and a width W in the radial direction from the point d ₁ (W = Wa + Wb, a width Wa from the d ₁ to the forward tooth profile 30 and a width Wb from the follow tooth profile 31). The tip 32 is provided. The width W direction of the distal end portion 32 is a shape formed in a part of an arc whose center point is the center Om of the rotation axis of the male rotor 24. Other than the tip portion 32 of the male rotor 24 is cut by a cutter, but the tip portion 32 is processed by polishing. If the shape is ensured after polishing, the height H from d _{1 of the} tip 32 protruding radially from the point d ₁ may be zero.

  The distal end portion 32 of the male rotor 24 is formed in an arc having the center of the rotation axis of the male rotor 24 as the center point Om, and by limiting the range in which the arc is formed, the male rotor 24 having the distal end portion 32 is formed. Even if the shape of the screw tooth shape is larger than the shape of the screw tooth shape of the conventional male rotor 12, it does not interfere with the male and female rotors 23,24.

  Specifically, as shown in FIG. 3, the arc of the distal end portion 32 of the male rotor 24 is the intersection (α1 and α2) of the arc centered on the center of the rotation axis of the female rotor 23 and the male rotor 24. Is formed within the virtual arc 33 (within the range of Wmax) defined by.

  In addition, if the edge part of the circular arc of the front-end | tip part 32 is formed in the position very close to the intersections (alpha) 1 and (alpha) 2 of the said circular arc, interference with the female rotor 23 and the male rotor 24 will arise. Therefore, in order to avoid the interference, first, when the female rotor 23 rotates, the gap at the position closest to the female rotor 23 (point p in FIG. 3) becomes substantially zero (that is, the male and female rotors are Assume a virtual male rotor shape 40 that is the shape of the male rotor in the case of substantially contact). The tip of the virtual male rotor shape 40 and the virtual arc 34 (within the range of Wmax ′) defined by the intersection (α1 ′ and α2 ′) of the arc centered on the center of the rotation axis of the male rotor 24 An arc of the portion 32 is formed. Note that the virtual arc 34 is naturally shorter than the virtual arc 33. In addition, this virtual arc 34 can be rephrased as the shorter one of the virtual male rotor shape 40 and the arc bisected at the intersection (α1 ′ and α2 ′) of the arc centered on the center of the male rotor 24. it can.

For example, the male rotor 24 diameter 150 mm, an arc of radius _{R 1} centered on m 'is 32.5 mm, the arc radius _{R 4} centered at _{O 4} is 13.6 mm, and 50μ clearance of the rotor 23, 24 Then, the width (Wmax ′) of the arc having the center point Om as the center of the rotation axis of the male rotor 24 that does not interfere with the female rotor 23 is 3.7 mm. This width of 3.7 mm is sufficient for processing by polishing.

  The distal end portion 32 is formed in a width W narrower than the width Wmax ′, and the distal end portion 32 is processed by polishing. Parts other than the tip 32 are cut by a conventional cutter.

  Compared to the conventional tooth profile, except for the male rotor tip 32, it is the same, so the tip 32 can be processed with high accuracy while ensuring the same strength as the conventional one, and the performance of the screw compressor Can be improved.

Further, as shown in FIG. 3, the radius R ₁ ′ of the arc centered on m of the advancing side tooth surface 30 is larger than the radius R _{4 of} the arc centered on O ₄ of the following side tooth surface 31. Therefore, as shown in FIG. 3, the length W _{1 of the} portion that does not interfere with the female rotor 23 on the advance side tooth surface 30 side is longer than the length W ₂ on the follow side tooth surface 31 side. There is a space in the gap with the female rotor 23. Therefore, if the width Wa of the portion formed on the forward tooth surface 30 of the arc of the tip portion 32 of the male rotor 24 is longer than the width Wb of the portion formed on the following tooth surface 31, Even if the arc of the portion 32 has the same width W, the width Wa of the portion formed on the forward side tooth surface 30 is the same as the width Wb of the portion formed on the following side tooth surface 31 or from the width Wb. The possibility that the female rotor 23 and the distal end portion 32 of the male rotor 24 interfere with each other can be reduced as compared with the case where the length is short.

The rotor axial direction sectional view of the rotor casing of the screw compressor which has the screw tooth profile concerning this invention. The partial enlarged view of the screw tooth profile in the male and female rotors which mesh. Partially enlarged view showing a d ₁ near the shape points of the screw tooth profile of the male rotor. The figure which shows a part of front-end | tip of the screw tooth profile of the conventional male rotor. The figure which shows gap | interval (epsilon) 1 of a male rotor and a female rotor and the clearance gap (epsilon) 2 of a casing and a rotor which the front-end | tip part of the conventional screw tooth shape determines.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 Screw tooth shape 21 Screw compressor main body 23 Female rotor 24 Male rotor 30 Advance side tooth profile 31 Follow-up side tooth profile 32 Tip part 34 Virtual arc 40 Virtual male rotor shape

Claims (2)

In the screw compressor in which the compressor body is constituted by a pair of male and female screw rotors,
The tip of the male rotor is formed into an arc centered on the center of the rotation axis of the male rotor, and the arc of the tip of the male rotor is in contact with the female rotor when the female rotor rotates. The short of the arc divided into two at the intersection of the virtual male rotor shape, which is the shape of the male rotor where the gap at the closest position is substantially zero, and the arc centered on the center of the male rotor A screw tooth profile characterized by being formed on a virtual arc of the other side.   2. The screw tooth profile according to claim 1, wherein a portion formed in the forward-side tooth profile of the tip portion of the male rotor is formed longer than a portion formed in the following-side tooth profile.

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