JPH0451674B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a male and female screw rotor used in a screw compressor, etc., and more particularly to an asymmetric screw rotor having a tooth profile suitable for mass production by hobbing. .

(Prior Art) As is well known, the screw compressor was invented by Mr. Krigar of Germany around 1878, and various improvements have been made since then. The rotor that was initially provided was called a symmetrical toothed rotor, but in 1965, the Swedish company SRM (Svenska Rotstaa Maskinaa Aktivorag) offered an asymmetrical toothed rotor with extremely superior volumetric efficiency. This asymmetric toothed rotor can be seen, for example, in Japanese Patent Publication No. 56-17559. This asymmetric toothed rotor has also been improved year by year. The present applicant has already provided an improved type, for example, in Japanese Patent Application Laid-Open No. 59-196988. A schematic diagram of this improved type is shown in FIG.

The rotor shown in FIG. 5 is designed to increase its theoretical volume, and its tooth profile has the following characteristics. In the figure, M indicates a male rotor, and F indicates a female rotor.

1 Female Rotor Tooth Profile The female rotor F has an addendum Af outside the pitch circle Pf of each tooth, and a dedendum Df inside the pitch circle Pf of each tooth bottom. The advancing side tooth profile and the following side tooth profile are as follows.

A Forward side tooth profile ・The space between dd ₂ and e ₂ is the pitch circle Pf, the male and female rotor F,
It is a circular arc whose center is the intersection point m with the line connecting the center points Of and Om of M. Note that point d ₂ is the center point Of,
It is a point on the line connecting Om ・The line between e ₂ − f ₂ is a tangent line passing through point e ₂ and point f ₂
is a point on the pitch circle Pf.

- The space between f ₂ and g ₂ is a circular arc centered on point S on a line that passes through point f ₂ and is perpendicular to line e ₂ - f ₂ .
Note that the point g ₂ is a point on a circular arc centered on the center Of.

(b) Follow-up side tooth profile - The area between d ₂ and c ₂ is a generation curve created by the point d ₁ of the male rotor M.

- The area between c ₂ and b ₂ is a circular arc centered on point t on the tangent to pitch circle Pf passing through point b ₂ (a point on pitch circle Pf).

・The space between b ₂ and a ₂ is an arc centered on point q on pitch circle Pf. Note that point _a2 is a point on a circular arc centered on the center Of.

2 Male rotor tooth profile The male rotor M has a dedendum Dm corresponding to the addendum Af of the female rotor F. The advancing side tooth profile and the following side tooth profile are as follows.

A. Forward side tooth profile ・d ₁ - e ₁ is an arc centered on the intersection m of the pitch circle Pm and the line connecting the center points Of and Om of the male and female rotors, and is the arc d ₂ of the female rotor F mentioned above.
-e ₂ is supported. Note that point d ₁ is the center point Of,
It is a point on the line connecting Om.

・The line e ₁ −f ₁ −g ₁ is the line e ₂ −f ₂ −g ₂ of the female rotor F.
This is the creation curve created by. In addition, f ₁ is a point on the pitch circle Pm, and g ₁ is a point on the male rotor M.
It is a point on the root circle of the tooth.

(b) Follow-up side tooth profile - Between d ₁ and b ₁ is a generated curve created by the circular arc c ₂ - b ₂ of the female rotor F. Note that the point _b1 is a point on the pitch circle Pm.

- The space between b ₁ and a ₁ is an arc corresponding to the arc of the female rotor F, b ₂ - _{a 2} . Note that point _a1 is a point on the root circle of the male rotor M.

(Problems to be Solved by the Invention) Incidentally, although the tooth-shaped rotor described above has a large theoretical volume and is therefore very excellent in volumetric efficiency, it has a major problem in that it is not suitable for hobbing.
The reason why this rotor is not suitable for hobbing is that the rotor tooth profile has many sharp edges. This sharp edge can be seen at the point _a2 of the female rotor F, the shield edge E of the female rotor F, the seal groove E' of the male rotor M, and the point _d1 of the male rotor. Furthermore, the radius of the corresponding arc b ₁ -a _{1 of the male rotor M corresponding to the arc b 2 -a 2 of the} female rotor F is extremely small, and this arc portion b ₁ -a ₁ is the same as that of the male rotor. Since it constitutes one corner of the groove bottom of M, the corner also has an angle close to a right angle (sharp edge).

In this way, if the rotor tooth profile has many sharp edges, the tooth profile of the rotor machining tool must also have many corresponding sharp edges. However, the sharp edge portion of the tool tooth profile is prone to wear and chipping, and therefore machining can only be performed about 3 to 5 times at a time, and the tool must be frequently reground. When machining a rotor with this kind of tooth profile using a hob,
Because hobbing is a method of machining using generating motion, the time involved in cutting each tooth tip of the hob is long.
Therefore, the formation of a sharp edge at the tip of each tooth of the hob is a fatal reason why hobbing for the purpose of mass production cannot be put to practical use. In other words, the seal groove on the bottom of the tooth of the male rotor M is the biggest reason why hobbing cannot be put to practical use.

Therefore, conventionally, processing has been carried out using a full-length milling cutter.

Also, the point between d ₂ and c ₂ of the female rotor F is the point of the male rotor M.
This is a generation curve created by d ₁ and depends on the number of teeth and the position of the point d ₁ , that is, the seal point, so undercuts may appear prominently, making it difficult to grasp the shape and making it difficult to determine the tooth shape. This was considered to be one of the difficulties mentioned above.

The present invention was made in view of such problems,
The objective is to provide a rotor tooth profile that is suitable for hobbing, has a shape that is easy to grasp during generating processing, and does not cause undercuts, and at the same time can maintain the same volumetric efficiency as conventional screw compressors. do.

(Means for Solving the Problems) In order to solve the above problems, the present invention eliminates the sharp edge in the rotor tooth profile, makes the undercut portion of the female rotor a predetermined arc shape instead of a generating curve, and increases the number of teeth. , which is not affected by the position of the sealing point of the male rotor.

That is, it consists of a female rotor F with seven teeth and a male rotor M with six teeth meshing with the female rotor F, and has the following rotor tooth profile.

Tooth profile a of the female rotor The forward tooth profile is the pitch circle Pf and each center point Of of the male and female rotors,
Radius centered at the intersection O ₂ with the line connecting Om
The arc d ₂ - _{e 2} of SR ₁ , the arc e _{2 - f 2 of radius SR 2 having the center point O 3 on the extension of the straight line O 2 - e 2 , the} point S on the pitch circle Pf, and the female rotor. Center point
A straight line f ₂ - _{g 2} that intersects the line connecting Of at an angle α at point S, a generated curve g ₂ - h ₂ created by the arc g ₁ - h ₁ of the male rotor M, and the tip circle Cf It is formed by connecting the above arc h ₂ −a ₂ and in order.

However, the point d ₂ is the outermost point of a circular arc having a central angle of 5 to 15 degrees with respect to the straight line connecting the center points O ₂ and Of.

A seal edge Ef is provided between the arc h ₂ −a ₂ and protrudes outward from the tip circle Cf.

b The following tooth profile is an arc d ₂ −c ₂ with radius SR ₃ centered on point O ₆
and an arc c ₂ −b ₂ of radius SR ₄ centered at point O ₅
, and a generation curve b ₂ −a ₂ created by the arc b ₁ −a ₁ of the male rotor M, and are formed by connecting in order.

Tooth profile a of the male rotor The forward tooth profile is the pitch circle Pf and each center point Of of the male and female rotors,
A generation curve e ₁ created by the circular arc d ₁ - e ₁ with a radius equal to the radius SR ₁ centered on the intersection O ₁ with the line connecting Om and the circular arc e ₂ - f ₂ of the female rotor F. −f ₁ , a generated curve f ₁ −g ₁ created by the straight line f ₂ −g ₂ of the female rotor F, and an arc g ₁ −h ₁ with radius SR ₅ centered on point O ₆
, the arc h ₁ −a ₁ on the root circle Bm, and are connected in order.

However, the point d ₁ is the outermost point of a circular arc having a central angle of 5 to 15 degrees with respect to the straight line connecting the center points O ₁ and Of.

No seal groove is formed on the arc _h1 − _a1 .

A seal edge Em is provided between the arc d ₁ and e ₁ inside the tip circle Cm.

b The following tooth profile is a generated curve d1-c1 created by the circular arc _{d2 - c2} of the female rotor F, and _a generated curve _c1 generated by the circular arc _c2 - _b2 of the female rotor F. −b ₁ and an arc b ₁ −a ₁ with radius SR ₆ centered at point O ₇
and are connected in order.

(Embodiment) FIG. 1 or FIG. 4 shows an embodiment of the present invention.
Since the symbols in the drawings correspond to the symbols used to explain the structure of the invention, the explanation of the tooth profile of this embodiment will be omitted.

Although the outline of the teeth of the male and female rotors according to the present invention is as described above, the detailed shape of the seal edge Ef protruding between the arcs a ₂ - h ₂ of the female rotor F and the arc d ₁ - e ₁ of the male rotor M are as follows. Seal edge formed on the part
The detailed shape of Em is shown in FIGS. 3 and 4, respectively.

In the present invention, the seal edge Ef of the female rotor F has a significantly smaller height than that of the conventional example, and has an arcuate shape. Incidentally, in the conventional example shown in FIGS. 6 and 7, the height dimension of this seal edge was the target (outside diameter of the male rotor) x 3 x 10 ^-3 , but in the present invention,
This is set to approximately (outer diameter of male rotor) x 5 x 10 ^-4 . Further, a part of the arc d ₁ -e ₁ of the male rotor M is cut out to form a seal edge Em in an arc shape.

The characteristics of the tooth profiles of the male and female rotors F and M according to the present invention are, first of all, that no sharp edges are formed. This can be clearly seen by comparing with the conventional example shown in FIG. That is, in place of the sharp edge point _a2 in the conventional example, in the present invention, the generated curve _b2 - _a2 is formed by the circular arc _b1 - _a1 of the male rotor M. For this reason, the arc b ₁ −a ₁ , that is, the bottom corner of the tooth in the present invention, can be determined in advance to a shape that is easy to hob, and the arc
It is angularly widened compared to the root corner formed by b ₁ − _{a 1} (generated curve by point a ₂ ). Also,
In the present invention, no seal groove is formed in the tooth bottom of the male rotor M, and therefore, there is no sharp edge associated with the seal groove. in this way,
In the present invention, since the rotor tooth profile is free of sharp edges, the tooth profile of the hob for processing the rotor can also be free of sharp edges, thereby making it possible to put the hob for processing the rotor into practical use.

Second, the undercut portion of the female rotor F, that is, the d ₂ -c ₂ portion, is shaped into an arc so that difficult points in cutting can be managed at the time of designing the tooth profile.

Thirdly, the straight line f ₂ −g ₂ portion of the tooth profile of the female rotor F is arbitrarily determined by the angle α, and it is possible to easily adjust the backlash of the male and female rotors by minute changes in this angle α. be. Therefore, contact can be obtained only on the forward pitch circle, and so-called multi-point contact can be avoided, so noise and vibration can be prevented.

Fourth, the number of teeth of the male rotor M is 6, and the number of teeth of the female rotor F is 7, making the rotor tooth profile particularly suitable for a high compression ratio, small capacity screw compressor.

On the other hand, in terms of volumetric efficiency, the rotor tooth profile according to the present invention is not inferior to the conventional examples shown in FIGS. 6 and 7.

First, the portion of the circular arc b ₂ - _{a 2} of the tooth tip of the female rotor F has a smaller protrusion amount compared to the conventional example, so the blowhole area is increased accordingly, and in this respect it is inferior to the conventional example. However, on the other hand, the length d ₁ -c ₂ in FIG. 6 is shortened by shifting the d ₁ point, and the length of the seal line is shortened by this amount. Therefore, this part of the present invention and the conventional example each have advantages and disadvantages, and there is almost no difference between the two in terms of volumetric efficiency.

Next, the relationship between volumetric efficiency and the fact that the seal groove is removed from the tooth bottom of the male rotor M to make the tooth bottom flat will be explained.

In Fig. 7 and Fig. 5, the current tooth surface clearance dimension
If Cl (normally (male rotor outer diameter) x 4 x 10 ^-4 ) is set equally for both and the tooth surface gap area of both is compared, the difference will be found on both sides of the seal edge Ef in the present invention (Fig. 5). parts, i.e. shown in a checkered pattern
The parts T ₁ and T ₂ and the parts on both sides of the seal groove E' in the conventional example (Fig. 7), that is, shown in the grid pattern.
This is the difference between the T ₃ and T ₄ parts. Incidentally, in the conventional example, the width of the seal groove E' needs to be sufficiently larger than the width of the seal edge E. Normally, the width of seal edge E is (male rotor outer diameter)
× 5 × 10 ^-3 , and the width of the seal groove E' is (outer diameter of male rotor) × 0.015. This is based on the fact that there is a certain backlash between the male and female rotors when they are installed in a compressor, and that there is a gap between the starting position and the escape position of the seal edge E with respect to the seal groove E'. This is to avoid interference between the seal edge E and the seal groove E'. On the other hand, in the present invention, the above areas T ₁ and T ₂
In order to reduce the height of the seal edge Ef, the height of the seal edge Ef is set to be significantly smaller than about 50 μm, that is, about 1/6 of the seal edge E of the conventional example shown in FIG. Therefore, the area T ₁ + in the present invention
T ₂ can be made approximately equal to or smaller than the area T ₃ +T ₄ in the conventional example. The area between the tooth surfaces around the seal edge affects the amount of compressed air leaking to the suction side, which in turn affects the compression efficiency, but for the reasons mentioned above, in the present invention, the seal groove is formed from the bottom of the male rotor tooth. Even if it is removed, by making the height of the seal edge of the female rotor as small as possible, the area between the tooth surfaces around the seal edge can be made equal to or less than that of a conventional seal, thereby preventing a decrease in volumetric efficiency.

In the present invention, the male and female rotors are meshed so that the portion d ₂ -c ₂ of the female rotor F is an arc, and the portion d ₂ -c ₂ creates an arc of the portion d ₁ -c ₁ of the male rotor M. Therefore, even if a local flaw occurs in the arc d ₁ −c ₁ , the effect on the seal line is local and there is an advantage that there is little adverse effect. On the other hand _, in the conventional example shown in _{FIG .}
Since the male and female rotors mesh as if creating a point, if a scratch occurs at point _d1 , the effect on the seal line will be very large.

(Effects of the Invention) As is clear from the above description, according to the present invention, sharp edges are eliminated by making the seal edges in the rotor tooth profile into arc shapes without causing a decrease in volumetric efficiency, and hobbing is facilitated. In addition, the sharp edges of the hobkage are eliminated, resulting in a long life.

In addition, the shape of the root part of the female rotor is an arc shape that is determined in advance at the design stage, and there is no need to worry about undercuts due to generation machining of this part as in the past. This has the effect of improving productivity on the processing line.

[Brief explanation of drawings]

1 to 5 illustrate the present invention, FIG. 1 is a diagram showing the main part of the tooth profile of the screw rotor, FIG. 2 is a sectional view perpendicular to the axis of the screw rotor, and FIG. Figure 4 is an enlarged view of the main parts shown in Figure 1.
FIG. 5 is an enlarged sectional view of a main part showing the tooth tip of the male rotor in FIG. 1, FIG. FIG. 7 is an enlarged cross-sectional view of a main part similar to FIG. 4 showing the meshing state of the seal edge of the female rotor and the seal groove of the male rotor in FIG. 5, which shows the tooth profile of a conventional screw rotor. F...Female rotor, M...Male rotor, a ₁ , b ₁ ,
c ₁ , d ₁ , e ₁ , f ₁ , g ₁ , h ₁ ...each point on the male rotor tooth profile,
a ₂ , b ₂ , c ₂ , d ₂ , e ₂ , f ₂ , g ₂ , h ₂ ... each point of the female rotor tooth profile, Ef, Em ... seal edge.

Claims (1)

[Scope of Claims] 1. A screw rotor for a screw compressor or the like, comprising a female rotor F having seven teeth and a male rotor M meshing with the female rotor F having six teeth, and having the following rotor tooth profile. Tooth profile a of the female rotor The forward tooth profile is the pitch circle Pf and each center point Of of the male and female rotors,
Radius centered at the intersection O ₂ with the line connecting Om
The arc d ₂ - _{e 2} of SR ₁ , the arc e _{2 - f 2 of radius SR 2 having the center point O 3 on the extension of the straight line O 2 - e 2 , the} point S on the pitch circle Pf, and the female rotor. Center point
A straight line f ₂ - _{g 2} that intersects the line connecting Of at an angle α at point S, a generated curve g ₂ - h ₂ created by the arc g ₁ - h ₁ of the male rotor M, and the tip circle Cf It is formed by connecting the above arc h ₂ −a ₂ and in order. However, the point d ₂ is the outermost point of a circular arc having a central angle of 5 to 15 degrees with respect to the straight line connecting the center points O ₂ and Of. A seal edge Ef is provided between the arc h ₂ −a ₂ and protrudes outward from the tip circle Cf. b The following tooth profile is an arc d ₂ −c ₂ with radius SR ₃ centered on point O ₆
and an arc c ₂ −b ₂ of radius SR ₄ centered at point O ₅
, and a generation curve b ₂ −a ₂ created by the arc b ₁ −a ₁ of the male rotor M, and are formed by connecting in order. Tooth profile a of the male rotor The forward tooth profile is the pitch circle Pm and each center point Of of the male and female rotors,
A generation curve e ₁ created by the circular arc d ₁ - e ₁ with a radius equal to the radius SR ₁ centered on the intersection O ₁ with the line connecting Om and the circular arc e ₂ - f ₂ of the female rotor F. −f ₁ , a generated curve f 1 −g ₁ created by _the straight line f ₂ −g ₂ of the female rotor F, and an arc g ₁ −h ₁ with radius SR ₅ centered on point O ₆
, the arc h ₁ −a ₁ on the root circle Bm, and are connected in order. However, the point d ₁ is the outermost point of a circular arc having a central angle of 5 to 15 degrees with respect to the straight line connecting the center points O ₁ and Of. No seal groove is formed on the arc _h1 − _a1 . A seal edge Em is provided between the arc d ₁ and e ₁ inside the tip circle Cm. b The following tooth profile is a generated curve d1-c1 created by the circular arc _{d2 - c2} of the female rotor F, and _a generated curve _c1 generated by the circular arc _c2 - _b2 of the female rotor F. −b ₁ and an arc b ₁ −a ₁ with radius SR ₆ centered at point O ₇
and are connected in order.