JPH11141479A - Screw rotor of screw compressor or the like - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screw rotor of a screw compressor which is capable of improving workability of rotor working and dimension accuracy and improving durability of a cutter for rotor working. SOLUTION: This screw rotor is constituted of a female rotor F provided with a tooth flank fixed by curves b to f constituted of curves b to c forming the forwarding side tooth flank of a female rotor tooth TF created by a tooth end tip part of an arbitrarily fixed male rotor tooth TM, circularly-arc shaped curves e to f forming a seal edge S at the forwarding side tip part of the tip outer peripheral surface of the female rotor tooth TF and curves c to e which are interposed between the curves b to c and the curves e to f, are smoothly connected with the curves b to c and the curves e to f and are formed with a curvature which continuously or discontinuously becomes larger as the curves c to e approach the curves e to f and a male rotor M which is provided with a follow-up side tooth flank created by a tooth flank fixed by the curves c to f and is formed so as to be engaged with the female rotor F.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw rotor for a screw type compressor, a screw type vacuum pump, a screw type compressor applied to a screw type expander, and the like.

[0002]

2. Description of the Related Art At first, a screw rotor called a symmetrical tooth profile was used for a screw compressor.
In 965, Swedish company SRM developed an asymmetric tooth profile screw rotor with excellent volumetric efficiency.

In Japanese Patent Publication No. 51-14723, as shown in FIG. 8, a tooth groove G and a seal edge S of a female rotor F are inside a female rotor pitch circle, and the seal edge S is a female rotor tooth. It is formed at the intersection of a straight line portion 32 following a generating curve 31 defining the advancing-side tooth surface of the TF and an arc 33 forming the tip outer peripheral surface of the female rotor tooth TF forming a part of the rotor outer periphery. A toothed screw rotor has been proposed in which the smooth circular convex portion 34 conforms to the concave following curve 35 of the female rotor tooth TF. By adopting such a tooth profile, it is possible to continuously perform the operation without changing the cutter, similarly to the tooth surface processing. In FIG. 8, M indicates a male rotor.

[0004]

In the case of the screw rotor shown in FIG. 8, with respect to the shape of the outer peripheral surface of the distal end of the female rotor tooth TF, the seal edge S is positioned at the end of the outer peripheral surface of the distal end, and thus the same as the tooth surface machining. Furthermore, the processing of the seal edge S can be performed without changing the cutter. However, the seal edge S of the female rotor tooth TF is located at the end of the outer peripheral surface of the distal end, and the corner portion rather than a curved surface that gradually bends from the seal edge S to the linear portion 32 on the forward side of the female rotor tooth TF. Continue to form. Such a shape is not preferable for processing the bottom of the male rotor M that is paired with the female rotor F, as described below.

FIG. 9 shows a cutter 5 for processing the male rotor M.
FIG. 10 is an enlarged view of a portion surrounded by a circle III at the tip of the cutter 51. 11 shows the relative temporal displacement of the cutter 51 during machining of the male rotor M with respect to the male rotor M at regular time intervals, and FIG. 12 is an enlarged view of a portion surrounded by a circle IV in FIG. It is. FIG.
In FIG. 12, the locus of the cutter 51 is concentrated near the bottom of the tooth groove of the male rotor M, especially near the right tooth surface in each drawing, that is, near the tooth surface a side, as can be seen from FIG. Since the cutter 51 moves along the tooth surface A, an error in the shape of the cutter 51 itself and an error in the operation of the cutter 51 are easily reflected on the tooth surface of the male rotor M on the side to be machined. Further, the processing by the minute projections 52 at the tip of the cutter 51 will continue for a longer time than the other parts of the cutter 51, and this projection 52
The thermal expansion and abrasion due to the rise in temperature are also intensified accordingly.
As a result, the dimensional accuracy of the portion processed by the protruding portion 52 and the portion corresponding to the seal edge S described above also deteriorates.

As can be seen from FIGS. 9 to 12, the protruding portion 52 at the tip of the cutter 51 forms a relatively sharp corner, so that the protruding portion 52 is formed when the male rotor M is machined. And the dimensional accuracy of the male rotor M is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and has been made in consideration of the above circumstances, and has been made in consideration of a screw type capable of improving workability of rotor processing, dimensional accuracy, and durability of a cutter for rotor processing. An object of the present invention is to provide a screw rotor such as a compressor.

[0008]

In order to solve the above-mentioned problems, the present invention forms an advancing-side tooth surface of a female rotor tooth TF formed by a tip end portion of an arbitrarily defined male rotor tooth TM. Curves b to c and an arc-shaped curve e forming a seal edge S at the forward end of the outer peripheral surface of the tip end of the female rotor tooth TF.
To f, curves bc and ef, smoothly connect to curves bc and ef, and curve e to
A female rotor F having a tooth surface defined by curves b to f formed by curves c to e having a curvature that increases continuously or discontinuously as f approaches f, and is determined by the curves c to f. The female rotor F is provided with a follower tooth surface created by the tooth surface, and the male rotor M is formed so as to mesh with the female rotor F.

[0009]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a male rotor M and a female rotor F of a screw rotor such as a screw compressor according to the present invention.
3 shows a tooth surface shape of a meshing portion with the above. When driving,
The male rotor M and the female rotor F rotate in the directions indicated by arrows A and B. In FIG. 1, the lower side of the male rotor tooth TM is referred to as an advancing-side tooth surface and the upper side thereof is referred to as a following-side tooth surface. The lower side is referred to as a forward tooth side, and the upper side is referred to as a following side tooth side.

The forward tooth flank of the female rotor tooth TF represented by the curves b to c is a generating curve determined by an arbitrarily determined tip of the male rotor tooth TM. Further, the contour of the seal edge S at the forward end portion represented by the curves e to f of the female rotor tooth TF has an arc shape. The curves b to c and the curves e to f are curves formed with a curvature that increases continuously or discontinuously as the curves approach the curves e to f. For example, in the example shown in FIG. Ｄd and curves cｅe composed of curves d〜e of a radius of curvature R2 (R1> R2) smoothly connected thereto.

That is, in the case of the example shown in FIG. 1, two curves of two kinds of curvature which increase discontinuously are adopted.
The present invention is not limited to this, and may employ more than two types of curves, including those in which the number is increased to infinity and the curvature continuously changes. . On the other hand, the male rotor M, which forms a pair with the female rotor F and meshes with the female rotor F, has a shape having a follow-side tooth surface created by the tooth surface determined by the curves c to f.

As described above, since the seal edge S is located at the intersection of the curves b to e defining the shape of the advancing-side tooth surface of the female rotor tooth TF and the outer peripheral surface of the tip end of the female rotor tooth TF, the same cutter is used. Processing of the tooth surface of the female rotor F and the seal edge S becomes possible. Therefore, the workability of the processing of the female rotor F,
Dimensional accuracy can be improved. Further, as will be described later with reference to the drawings, the dimensional accuracy of processing the groove at the bottom of the male rotor M corresponding to the seal edge S of the female rotor F, and the durability of the cutter for processing the bottom of the tooth are improved. It has become.

Further, in the case of the example shown in FIG. 1, the seal edge S is formed outside the pitch circle PF of the female rotor F. And by forming like this, male,
When the distance between the centers (OM, OF) of the female rotor remains unchanged, the stroke volume can be increased as compared with the conventional screw rotor. As a result, for the same stroke volume,
The size of the device can be reduced.

FIG. 2 shows a cutter 21 for processing a male rotor M of the screw rotor according to the present invention, and FIG.
It is the figure which expanded the part enclosed with the circle | round | yen III inside. Cutter 2
A protrusion 22 for forming a groove at the bottom of the male rotor M corresponding to the seal edge S of the female rotor F on the outer periphery of the tip of the female rotor F
Are formed. It can be seen that the corners of the protrusion 22 shown in FIGS. 2 and 3 are less sharp than the protrusion 42 of the conventional cutter 41 shown in FIGS. 10 and 11. Therefore, the protruding portion 22 shown in FIGS. 2 and 3 has a larger heat capacity, a lower degree of damage due to overheating during processing of the seal edge S, and a smaller wear amount. As a result, the dimensional accuracy of the male rotor M is also improved.

FIG. 4 is a graph showing the change over time of the relative position of the cutter 21 with respect to the male rotor M when machining the bottom of the male rotor M by the cutter 21, more specifically, the machining of the groove at the bottom corresponding to the seal edge S. Are shown at regular time intervals, and FIG. 5 is an enlarged view of a portion surrounded by a circle V in FIG. Compared with the conventional cutter 41 when the male rotor M shown in FIGS. 11 and 12 is machined, the cutter 21 shown in FIGS. You can see that it is kept. Therefore, a rise in temperature at the tip of the cutter 21 during the above processing is suppressed. This also improves the dimensional accuracy of the male rotor M.

Incidentally, the radius of curvature R _{1 of} the curves c to d and the curvature R ₂ of the curves de to e shown in FIG. 1 greatly affect the following parameters. First, the radius of curvature R ₁ is related to the blowhole area which greatly affects the performance of a screw compressor or the like. The blow hole means a gap peculiar to a screw compressor or the like generated between a pair of male rotor teeth TM and female rotor teeth TF meshing with each other and a wall surface of the rotor chamber. In other words, in the case of a compressor or a vacuum pump when the blowhole area increases, the compressed gas in the tooth grooves of both rotors leaks back to the adjacent tooth grooves of lower pressure, which is one of the parameters indicating the performance of the compressor and the like. There is a problem that the volume efficiency is reduced.

As an example, the radii of curvature R1 (mm), R2
6 and 7 show calculation results on the relationship between (mm) and the blowhole area Sb (mm ² ). The blow hole area Sb greatly depends on the radius of curvature R1, and the radius of curvature R1
It decreases with the increase of. In contrast, it can be seen that the blow hole area Sb hardly depends on the radius of curvature R2. That is, it is preferable to increase the radius of curvature R1.

Next, as shown in FIG. 5, the smaller the radius of curvature R2 is, the larger the relative movement of the cutter 21 with respect to the male rotor M when machining the tooth grooves of the male rotor M, especially at the bottom thereof. It can be seen that the cutting point is constantly moving. Therefore, the wear and temperature rise of the cutter 21 do not concentrate in one place,
The manufacturing error of the male rotor M is concentrated in one place and is not integrated, so that dimensional accuracy can be easily ensured. Further, as shown in FIG.
Since the shape of No. 2 is rounded toward the outside as compared with the cutter 51 shown in FIG. Is less likely to occur.

[0019]

As is apparent from the above description, according to the present invention, the curve forming the forward tooth surface of the female rotor tooth TF formed by the tip of the male rotor tooth TM arbitrarily determined. b to c, and arcuate curves ef forming a seal edge S at the forward end of the outer peripheral surface of the distal end of the female rotor tooth TF.
And between the curves b to c and the curves e to f, and the curves b to
Curves b to f, which are smoothly connected to c and curves e to f, and are formed by curves c to e formed with curvatures that increase continuously or discontinuously as they approach curves e to f. A female rotor F having a tooth surface and a male rotor M having a following tooth surface created by the tooth surfaces determined by the curves c to f and formed so as to mesh with the female rotor F are provided. . For this reason, it is possible to improve the workability and dimensional accuracy of the rotor processing and the durability of the rotor processing cutter.

[Brief description of the drawings]

FIG. 1 is a view showing a contour shape of a cross section perpendicular to an axis of a meshing portion of a screw rotor according to the present invention.

FIG. 2 is a view showing a cutter for machining a male rotor of the screw rotor shown in FIG. 1;

FIG. 3 is an enlarged view of a portion surrounded by a circle I in FIG.

FIG. 4 is a diagram showing relative time-dependent displacement of the cutter with respect to the male rotor at regular time intervals during machining of the male rotor by the cutter shown in FIG. 2;

FIG. 5 is an enlarged view of a portion surrounded by a circle II in FIG.

FIG. 6 is a diagram showing a relationship between a radius of curvature R1 (mm) and a blow hole opening area Sb (mm ² ).

FIG. 7 is a diagram showing a relationship between a radius of curvature R2 (mm) and a blow hole opening area Sb (mm ² ).

FIG. 8 is a view showing a conventional screw rotor.

FIG. 9 is a view showing a male rotor machining cutter of the screw rotor shown in FIG. 8;

FIG. 10 is an enlarged view of a portion surrounded by a circle III in FIG. 9;

11 is a diagram showing, at regular time intervals, relative temporal displacement of the cutter with respect to the male rotor when the male rotor is machined by the cutter shown in FIG. 9;

FIG. 12 is an enlarged view of a portion surrounded by a circle IV in FIG. 11;

[Explanation of symbols]

 M Male rotor F Female rotor TM Male rotor tooth TF Female rotor tooth S Seal edge R1, R2 Radius of curvature

Claims (1)

[Claims] 1. Curves b to c forming the forward-side tooth surface of the female rotor tooth TF formed by the tip of the male rotor tooth TM arbitrarily determined, and the advance of the outer peripheral surface of the distal end of the female rotor tooth TF. An arc-shaped curve e forming a seal edge S at the side end
To f, curves bc and ef, smoothly connect to curves bc and ef, and curve e to
A female rotor F having a tooth surface defined by curves b to f formed by curves c to e having a curvature that increases continuously or discontinuously as f approaches f, and is determined by the curves c to f. A screw rotor such as a screw compressor, comprising: a follower-side tooth surface created by the tooth surface; and a male rotor M formed to be meshable with the female rotor F.