JPH0246796B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a male and female screw rotor used in a screw compressor or the like, and particularly to an asymmetric tooth profile 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 Activorag) has provided an asymmetrically toothed rotor with very good volumetric efficiency. This asymmetric toothed rotor can be seen, for example, in Japanese Patent Publication No. 56-17559. By the way, as is known, there are two types of screw compressors: an oil-cooled type that supplies lubricating oil into the rotor chamber to improve cooling and sealing effects, and a non-lubricated type that does not supply any lubricating oil to the rotor chamber. In recent years, there has been an increasing demand for clean air with low voltage (about 7ata) in the electronics and food industries, etc., so there has been a desire to improve the performance of oil-free screw compressors.

Against this background, the present applicant also proposed a tooth profile for an oil-free type with a large theoretical process volume, for example, in the patent application Sho.
58-44682 (Japanese Unexamined Patent Publication 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 ・d ₂ - e ₂ is the pitch circle Pf, 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
It is a point on the line connecting Of and 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 area 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 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 the point d ₁ is a point on the line connecting the center points Of and Om.

・The line e ₁ - (f ₁ ) - g ₁ is the line e ₂ - (f ₂ ) of the female rotor F.
This is the generation curve created by −g ₂ .
Note that the point f ₁ is a point on the pitch circle Pm, and g ₁
is a point on the root circle of the male rotor M.

(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 interval 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.

However, with this tooth profile, the tooth thickness of the female rotor is thin, and an oil-free single-stage machine cannot withstand high pressure (approximately 7ata).

In addition, although the tooth-shaped rotor has a large theoretical volume and therefore has excellent 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 is located at point _a2 of the female rotor F, the seal edge E of the female rotor F, and the seal groove of the male rotor M.
E′, seen at point d ₁ of the male rotor. Furthermore, the radius of the corresponding arc a ₁ -b 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 a ₁ -b ₁ is the same as that of the male rotor. M
Since it constitutes one corner of the groove bottom, 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 a large number of 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 re-sharpened frequently. When machining a rotor with this kind of tooth profile using a hob,
Since hobbing is a method of machining using a generating motion, the time involved in cutting each tooth tip of the hob is longer, and the above-mentioned chipping is more likely to occur.
The formation of sharp edges 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 particular, the existence of the seal groove at the bottom of the teeth of the male rotor M is the biggest reason why hobbing cannot be put to practical use.

Therefore, in the past, each tooth was machined using a full-length milling cutter.

Technical problem of the present invention Therefore, the technical problem to be solved by the present invention is to provide a tooth profile that has mechanical strength that can withstand high pressure of about 7ata in an oil-free single-stage machine, and that increases the theoretical volume. By reducing the sharp edge in the rotor tooth profile as much as possible while ensuring the
The purpose is to create a shape that is suitable for hobbing and at the same time maintains the volumetric efficiency of compressors and the like to the same level as conventional ones.

Summary of the present invention In order to achieve the above technical problem, the present invention was constructed as follows. A detailed explanation will be given below with reference to FIGS. 1, 2, and 3.

FIG. 1 shows the tooth profiles of the male rotor M and the female rotor F. As shown in the figure, there is an addendum Af on the outside of the pitch circle Pf of each tooth of the female rotor F,
Inside the pitch circle Pm at the bottom of each tooth of the male rotor M, there is a dedendum Dm corresponding to the addendum Af.

1 Female rotor tooth profile The advancing side tooth profile and following side tooth profile of the female rotor are as follows.

A. Forward side tooth profile ・The space between d ₂ and e ₂ is an arc with radius SR ₁ centered on the intersection point O ₁ of the pitch circle Pf and the line connecting the center points (axes) Of and Om of the male and female rotors. be.
Note that the point d ₂ is a point on the line connecting the center points Of and Om, and is also a point on the root circle Bf.

・The center point between e ₂ − f ₂ is on the extension of radius O ₁ − e ₂
It is an arc of radius SR ₂ with O ₂ . In addition, the point
f ₂ is located inside the pitch circle PfPf.

・f ₂ −g ₂ is a circular arc with radius SR ₃ centered on point O ₃ on radius O ₂ −f ₂ . In addition, point g ₂ is the tip circle
It is a point on Cf.

・The space between g ₂ and a ₂ is an arc along the tip circle Cf.

(b) Follow-up side tooth profile - Between d ₂ and c ₂ is a generated curve created by the circular arc d ₁ and c ₁ of the male rotor M.

・The space between c ₂ and b ₂ is an arc with radius SR ₅ centered on point O ₅ . Note that point _b2 is a point on pitch circle Pf. Further, at point _b2 , the tangent of the arc _c2 - _b2 and the tangent of the pitch circle Pf intersect at right angles, and the arc _c2 - _b2 and the generating curve _d2 - _c2 are circumscribed with each other.

・b ₂ −a ₂ is an arc with radius SR ₇ centered on point O ₇ on pitch circle Pf.

2 Male rotor tooth profile The forward side tooth profile and follower side tooth profile of the male rotor are as follows.

A. Forward side tooth profile ・The space between d ₁ and e ₁ is an arc whose center is 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 whose radius is equal to the radius SR ₁ , This corresponds to the circular arc d ₂ −e ₂ of the female rotor. Note that the point _d1 is a point on the line connecting the center points Of and Om, and is also a point on the outer circumferential circle Cm.

- The interval between e ₁ and f ₁ is a generated curve created by the arc e ₂ - f ₂ of the female rotor F. Note that the point _f1 is located outside the pitch circle Pm.

- The interval between f ₁ and g ₁ is a generated curve created by the arc f ₂ - _{g 2} of the female rotor F.

・The space between g ₁ and f ₁ is an arc along the root circle Bm.

B Follower side tooth profile - The area between d ₁ and c ₁ is an arc with radius SR ₄ centered on point O ₄ .

- Between c ₁ and b ₁ is a generated curve created by the arc b ₂ - _{c 2} of the female rotor F. Note that the point _b1 is a point on the pitch circle Pm. Also, the arc d ₁ −c ₁
is inscribed in this generating curve c ₁ −b ₁ .

・b ₁ −a ₁ is a circular arc with radius SR ₈ centered on point O ₈ on pitch circle Pm.

The outline of the teeth of the male and female rotors according to the present invention is as described above, but the detailed shape of the seal edge Ef protruding between the arcs a ₂ - g ₂ of the female rotor F, and the seal edge Em of the male rotor M, that is, the arc _d1 − _c1
The detailed shape of the vicinity of is shown in FIGS. 2 and 3, respectively.

In the present invention, the seal edge Ef is
The height dimension is significantly smaller than that of the conventional example. Incidentally, in the conventional example shown in Figs. 5 and 6, the height dimension of this seal edge is approximately <
(Female rotor outer diameter) × 3 × 10 ^-3 μm>, but in the present invention, this is < (Female rotor outer diameter) × 5 ×
It is set to about 10 ^-4 μm. Also, a part Ru of the forward side of the point d ₁ of the male rotor M, that is, the arc d ₁ −e ₁
is cut out to make a part of the forward side of point _d1 protrude from the other part, thereby forming a seal edge Em.

The characteristics of each tooth profile of the male and female rotors F, M according to the present invention are, firstly, the seal edge Ef of the female rotor F.
and a part of the seal edge of male rotor M,
It does not form a sharp edge. This can be clearly seen by comparing it with the conventional example shown in FIG. That is, in place of the sharp edge point a ₂ in the conventional example, in the present invention, it is formed as a circular arc b ₂ −a ₂ , and therefore, the circular arc b ₁ −a ₁ in the present invention, that is, the tooth bottom corner, is the circular arc in the conventional example. It is angularly widened compared to the root corner formed by b ₁ − _{a 1} . Further, 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. As described above, in the present invention, since the sharp edge in the rotor tooth profile is minimized, the sharp edge in the tooth profile of the hob for processing the rotor can also be significantly reduced. It becomes possible to put the hob into practical use.

In addition, in the above rotor tooth profile, the female rotor F
The starting point f ₂ of the arc with radius SR ₃ is located inside the pitch circle Pf, while the point f ₁ of the male rotor corresponding to this point f ₂ is located outside the pitch circle Pm. , the thickness of each tooth of the female rotor F is thicker than in the conventional example, and the rigidity is increased, while the width of the tooth bottom of the male rotor M is widened. Therefore, from this point as well, the rotor tooth profile according to the present invention is suitable for hobbing.

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. 5 and 6.

First of all, the area of the circular arc d ₁ - _{c 1} of the tooth tip of the male rotor M is a point in the conventional example, but the area of the blowhole is increased by making it an arc, as compared to the point in the conventional example. Although it is inferior to the conventional example in this respect, on the other hand, the length of the seal line formed between this portion and the tooth surface of the female rotor F is shortened. 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. 6 and Fig. 4, the current tooth surface clearance dimension
Cl<Normal (male rotor outer diameter) x 4 x 10 ^-4 μm) is set equally for both, and if 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. 4). parts, i.e. shown in a checkered pattern
The T ₁ and T ₂ parts and the parts on both sides of the seal groove E' in the conventional example (Fig. 6), that is, the lattice 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 the seal edge E is male rotor outer diameter x 5.
×10 ^-3 μm, and the width of the seal groove E′ is male rotor outer diameter × 0.015 μm. 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 arranged in such a way that the portion d ₁ -c ₁ of the seal edge Em of the male rotor M is an arc, and the portion d ₁ -c ₁ creates an arc of the portion d ₂ -c ₂ of the female rotor F. The arc
Even if a local flaw occurs in d ₂ - c ₂ , the effect on the seal line is local and there is an advantage that there is little negative impact. On the other hand, in the conventional example shown in FIG. 5, the male and female rotors are meshed so that the point d ₁ of this seal edge portion of the male rotor forms a point d ₂ −c ₂ of the female rotor, so the point d ₁ If a scratch occurs on the seal line, the effect on the seal line will be very large.

[Brief explanation of drawings]

1 to 4 illustrate the present invention; FIG. 1 is an axis-perpendicular sectional view showing the main parts of the screw rotor; FIG. 2 is an enlarged sectional view of the main parts showing the tooth tips of the female rotor in FIG. 1; 3 is an enlarged cross-sectional view of the main part showing the seal edge portion of the male rotor in FIG. 1, FIG. 4 is an enlarged cross-sectional view of the main part showing the engagement state between the seal edge of the female rotor and the tooth bottom of the male rotor in FIG. 1, Fifth
The figure is a cross-sectional view at right angles to the axis showing the main parts of a conventional screw rotor, and FIG. 6 is similar to FIG. 4, which shows the engagement state between the seal edge of the female rotor and the seal groove of the male rotor in FIG. FIG. F...Female rotor, M...Male rotor, a ₁ , b ₁ ,
c ₁ , d ₁ , e ₁ , f ₁ , g ₁ ...Each point on the male rotor tooth profile, a ₂ ,
b ₂ , c ₂ , d ₂ , e ₂ , f ₂ , g ₂ ...each point on the female rotor tooth profile,
Ef, Em...Seal edge.

Claims (1)

[Claims] 1. The female rotor F has an addendum Af outside the pitch circle Pf of each tooth, while the male rotor M has a dedendum Dm corresponding to the addendum Af inside the pitch circle Pm of each tooth bottom. A screw rotor, such as a screw compressor, characterized by having the following rotor tooth profile. Female rotor tooth profile The forward tooth profile is the pitch circle Pf and the center points Of, Om of the male and female rotors.
An arc of radius SR ₁ centered at the intersection point O ₁ with the line connecting
d ₂ − e ₂ , an arc e 2 ₋ f 2 with radius SR ₂ with center point O ₂ on the extension of radius O ₁ − e ₂ , and center on point O ₃ on _radius O ₂ − f ₂ . It is formed by sequentially connecting the arc f ₂ - _{g 2} with radius SR ₃ , the arc g ₂ - _{a 2} on the tip circle Cf, and However, the point d ₂ is a point on the line connecting the center points Of and Om, and is also a point on the root circle Bf. Point f ₂ is located inside the pitch circle Pf. A seal edge Ef is provided between the arc g ₂ −a ₂ and protrudes outward from the tip circle Cf. The following side tooth profile is formed by a generation curve d ₂ - _{c 2} created by the arc d ₁ - c ₁ of the male rotor M, an arc c ₂ - b ₂ of radius SR ₅ centered on point O ₅ , and pitch. It is formed by sequentially connecting an arc b ₂ −a ₂ of radius SR ₇ centered on point O ₇ on circle Pf and . However, point _b2 is a point on pitch circle Pf. Tooth profile of the male rotor The tooth profile on the forward side is the pitch circle Pm and the center point Of of the male and female rotors,
Centered at the intersection m with the point connecting Om and the above radius
An arc _d1 - _e1 with a radius equal to _SR1 , a generation curve _e1 - _f1 created by the above-mentioned arc _e2 - _f2 of the female rotor F, and an arc _f2 - _g2 of the female rotor F. The generated curve f ₁ −g ₁ created by , the arc g ₁ −a ₁ on the root circle Bm, and are connected in order. However, the point _d1 is a point on the line connecting the center points Of and Om, and is also a point on the root circle Bf. Point f ₁ is located outside the pitch circle Pm. No seal groove is formed on the arc _g1 − _a1 . The following side tooth profile is a generation curve created by the circular arc d ₁ - c ₁ of radius SR ₄ centered on point O ₄ on the line connecting the center points Of and Om and the above circular arc b ₂ - c ₂ of the female rotor F. c ₁ - b ₁ and an arc b _{1 - a 1} of radius SR ₈ centered on point O ₈ on the pitch circle Pm are connected in order. However, point _b1 is a point on the pitch circle.