JPH0442554B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a screw rotor such as a screw compressor, and particularly to a tooth profile of a screw rotor suitable for a low-pressure, large-capacity screw compressor.

(Prior art) Conventionally, the tooth profile of the screw rotor of a screw compressor is a male rotor with 4 teeth and a female rotor with 6 teeth (hereinafter, the tooth profile in which these mesh with each other is referred to as 4-6 tooth profile). (3Kgf/cm ² g) for oil-free screw compressors (hereinafter referred to as 4-6α tooth profile, Japanese Patent Application Laid-Open No. 196988), high pressure (7Kgf/cm ² g) ) For oil-cooled screw compressors, there is one (hereinafter referred to as 4-6β tooth profile) designed to improve the sealing effect by an oil film.

Furthermore, by using a male rotor with 5 teeth and a female rotor with 6 teeth (hereinafter, the tooth profile in which these teeth mesh is referred to as 5-6 tooth profile), a high-pressure (7 kgf/cm ² g) oil-free screw compressor. Especially suitable for hobbing (hereinafter referred to as 5-6γ tooth profile).
252252) is also available.

(Problems to be Solved by the Invention) However, although the above tooth profile is intended for high efficiency for use in medium and high pressure screw compressors, it is difficult to process, and
f/cm ² g), which has the problem of not being suitable for large-capacity screw compressors.

On the other hand, in recent years, low-pressure, large-capacity screw compressors have been required for waste heat recovery equipment, etc.
It is desired to develop a new tooth profile to replace the conventional tooth profile.

Therefore, in order to meet these demands, the present invention aims to provide a screw rotor for a screw compressor or the like that is easy to process and has a tooth profile suitable for low pressure and large capacity.

(Means for Solving the Problems) In order to achieve the above object, the present invention aims to improve the male rotor by increasing the tooth gap by reducing the number of teeth and by increasing the height of the tooth end (hereinafter referred to as addendum) of the female rotor. Considering that an increase in the height of the tooth base (hereinafter referred to as dedendum) increases the stroke volume and achieves a large capacity, the tooth profile (hereinafter referred to as , 3-4 tooth profile) is developed as a tooth profile for the screw rotor of a screw compressor that is easy to process and suitable for low pressure and large capacity.

When the distance between the centers of the male and female rotors and the rotor length are limited, if the addendum is increased by increasing the tip circle, the bottom of the other tooth will be gouged out during generating gear cutting, resulting in a larger dedendum. The stroke volume will increase. But in this case,
As the female rotor's addendum grows, the lower teeth of the male rotor gouge out, creating an undercut. Therefore, it is necessary to set the addendum of the female rotor somewhat large to increase the stroke volume, and at the same time, to minimize the undercut by rounding the corners of the tips of the teeth of the female rotor.

However, rounding the corners of the tooth tips of the female rotor tends to increase so-called blowholes and reduce volumetric efficiency. In the 4-5α tooth profile, the curvature of the corner of the tooth tip of the female rotor is reduced to form a sharp edge to reduce blowholes in order to improve volumetric efficiency.

When there are many teeth like this 4-5α tooth profile,
Undercuts due to an increase in addendum or sharp edges at the corners of the tooth tips do not occur noticeably.

However, when the number of teeth is small, such as a 3-4 tooth profile, the undercut is noticeable in shape even if the amount is small, making it impossible to bob the male rotor.
As described above, the sharpening of the tooth tips of the female rotor reduces blowholes and improves volumetric efficiency, but it increases undercuts and makes machining difficult. However, since the purpose of the present invention is to provide a tooth profile suitable for low pressure and large capacity, a slight increase in blowholes will not lead to a decrease in volumetric efficiency if the pressure is low.

Therefore, the present invention maintains the volumetric efficiency to a certain level, increases the stroke volume by increasing the addendum of the female rotor, and reduces undercut by rounding the corners of the female rotor's tooth tips. , to facilitate hobbing.

That is, the present invention includes a female rotor (F) having 4 teeth,
It consists of a male rotor (M) with a number of teeth of 3 that meshes with the rotor, and has the following rotor tooth profile.

Female rotor tooth profile (a) The forward tooth profile is an arc (d) of radius (SR ₁ ) centered on the intersection (O ₂ ) of the pitch (Pf) and the line connecting the center points (Of, Om) of the male and female rotors. ₂ −e ₂ ) and the center point (O ₃ ) on the extension of the straight line (O ₂ −e ₂ )
_An arc _{( e 2 − f 2 )} of _radius (SR ₂ ) with ), an arc (h ₂ − j ₂ ) of radius (SR ₄ ) centered on the point (O ₅ ) on the straight line (O ₄ − h ₂ ), and an arc (j ₂ ) on the tip circle (Cf) −a ₂ ) and are connected in order.

However, the point (d ₂ ) is on the line connecting the center points (Of, Om) and is also on the root circle (Bf), and the point (f ₂ ) is on the inside of the pitch circle (Pf). positioned.

(b) The following tooth profile is created by the generation curve (d ₂ − c ₂ ) created by the circular arc (d ₁ − c ₁ ) of the male rotor (M) and the _radius (SR ₅ ) arc (c ₂ − b ₂ ), an arc ( _{b 2} − _{a 2} ) of radius (SR ₆ ) centered on point (O ₇ ) on the straight line (O ₆ − b ₂ ), and It will be connected.

(c) The addendum (Af) is 3 to 6% of the diameter of the pitch circle (Pf).

(d) Radius (SR ₄ ) and radius (SR ₆ ) are 10-50% of addendum (Af).

Male rotor tooth profile (a) The forward tooth profile is defined by the arc (d ₁ − l ₁ ) on the tip circle (Cm), the line connecting the pitch circle (Pm) and each center point (Of, Om) of the male and female rotors. A circular arc (l ₁ −e ₁ ) with a radius equal to the radius (SR ₁ ) centering on the intersection point (O ₁ ) and a center point (O ₃ ) on the extension of the straight line (O ₁ −e ₁ )
_A generated curve _{( f 1 - g 1} ), a generation curve (g ₁ - h ₁ ) created by the arc (g ₂ - h ₂ ) of the female rotor (F), and the arc (h ₂ - _{j 2} ) of the female rotor (F). ), the arc (j _{1 −a 1} ) on _the root circle (Bm), and are connected in order.

However, the point (d ₁ ) is on the line connecting the center point (Of, Om) and on the tip circle (Cm), and the point (f ₁ ) is on the tip circle (Cm). It is located in

(b) Point (O ₈ ) on the line where the follower tooth profile connects the center point (Of ₂ Om)
An arc (d ₁ − c ₁ ) with radius (SR ₇ ) centered at
, a generation curve (c ₁ −b ₁ ) created by the arc (c 2 −b 2 ) of the female rotor (F), and a generation curve (c ₁ −b ₁ ) created by the arc (b ₂ −a ₂ ) of the female rotor (F). It is formed by connecting the generating curve (b ₁ − _{a 1} ) in order.

(c) The tangent to the arc (c ₁ − b ₁ ) at the intersection (Op) of the pitch circle (Pm) and the arc (c ₁ − b ₁ ), and the line connecting the intersection (Op) and the center point (Om) The angle (α ₁ ) formed by this is 10 to 30° toward the following side.

(Example) FIGS. 1 to 3 show an example 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.

In this embodiment, the tooth tips of the male rotor M and the female rotor F have seal edges Em and Ef, respectively, as shown in FIGS. 2 and 3. That is, the seal edge Em is formed by the edge of the triangular groove l ₁ k ₁ m ₁ provided on the tip of the tooth of the male rotor M (arc l ₁ - e ₁ ),
The seal edge Ef is cut into a trapezoidal shape (k ₂ l ₂ m ₂ n ₂ ) on the tooth tip of the female rotor F.

The tooth profile having the above configuration has the following characteristics compared to the conventional tooth profile. First of all, it has a 3-4 tooth profile, which has fewer teeth than the conventional 4-6 tooth profile and 5-6 tooth profile. Due to this reduction in the number of teeth, if the center distance is the same and the rotor length is the same, the tooth space becomes larger and the stroke volume increases.

Second, the addendum Af of the male rotor F is 3 to 6% of the pitch circle Pf, which is larger than the conventional approximately 2%. This is the center distance Of−
Tip circle when Om and rotor length are limited
Increase Cf (i.e. increase addendum Af)
In addition, the dedendum of the male rotor of the other side is
Dm is increased to widen the tooth space and increase the stroke volume.

Third, the pitch circle Pm of the male rotor M and the follow-up tooth profile (in this specification, for the male rotor, the side in the rotational direction is referred to as the forward tooth profile with the tooth as a reference, the tooth profile is referred to as the forward tooth profile, and the side in the counter rotation direction is referred to as the forward tooth profile). on the following side, the tooth profile is called the following tooth profile) and the intersection Op (hereinafter simply the intersection point).
The straight line connecting the center point Om and the center point Om is the intersection point.
The angle α ₁ (hereinafter simply referred to as tooth space angle α ₁ ) with the tangent to the following tooth profile in Op is 10 to 10 to the following side.
It is limited to 30°. If the angle α ₁ of this tooth space is small and the root of the tooth is gouged, hobbing becomes difficult. Conversely, if α ₁ becomes large, the corner of the tooth tip of the female rotor F (arc a ₂ − b ₂ , b ₂ −c ₂ )), the blowhole increases, which is undesirable.

Fourth, the forward side of the tooth tip of the female rotor F (in this specification, for the female rotor, the side in the rotation direction with respect to the tooth groove is referred to as the forward side, the tooth profile is referred to as the forward tooth profile, and the side in the counter rotation direction is referred to as the forward tooth profile). On the following side, the tooth profile is called the following tooth profile.) Radius of the corner formed by the arc h ₂ − _{j 2}
The radius SR ₆ of the corner formed by SR ₄ and the following arc b ₂ −a ₂ is limited to 10 to 50% of the addendum Af. These arcs h ₂ −j ₂ and b ₂ −a ₂ correspond to the male rotor M
are the main bodies that create the arcs h ₁ −j ₁ and b ₁ −a ₁ of the tooth groove portion, respectively, and the magnitude of their curvature determines the magnitude of the angle α ₁ of the tooth groove.

On the other hand, the size of the curvature of the circular arc b ₂ −a ₂ forming the follower tooth profile among these circular arcs directly influences the size of the area of the blowhole. As shown in Fig. 4, a blowhole is a hole for compressed gas that is formed between the time when the tooth tips of the male rotor M are separated from the casing S and before they come into contact with the teeth of the female rotor F. At the point where point _C1 , which is the tip of the tooth, and point _C2 of the tooth of the female rotor F touch, an arc _c1 - _b1 forming the follower tooth profile of the male rotor M, and an arc c having the follower tooth profile of the female rotor F. ₂ -b ₂ -a ₂ and the area of an approximate triangle B (area indicated by a dotted pattern in the figure) formed by an extension line from the inner wall of the casing S on the female rotor F side. In this case, if the radius SR ₆ of the arc b ₂ - _{a 2} is small (indicated by a broken line in the figure), the area of the blowhole is
The area indicated by the diagonal line pattern) will be reduced.

Therefore, when the curvature of the corner of the tooth tip of the female rotor F is small (SR ₆ is small), the tooth space angle α ₁
becomes smaller and the root of the tooth tends to be greatly gouged,
Although hobbing becomes difficult, the area B of the blowhole is reduced and the volumetric efficiency is improved. On the other hand, when the curvature is increased (SR ₆ is increased), the angle of the tooth space increases and hobbing becomes easier, but the area B of the blowhole increases and no improvement in volumetric efficiency can be expected. On the other hand, the magnitude of the curvature (the magnitude of SR ₄ ) of the corner on the forward side of the tooth tip of the female rotor F (the part forming the arc h ₂ - j ₂ of the forward tooth profile) is unrelated to the blowhole, but Since it is related to the size of the gouge of the tooth root of the male rotor M, it is preferable to have a larger value in consideration of ease of machining.

From the above point of view, the radius SR ₄ and SR ₆ are conventionally
In addition to increasing the addendum Af, which was the same as the addendum Af, as described above, making it the same value as the addendum Af as in the past would result in a decrease in volumetric efficiency, so in the present invention, By limiting the upper limit to 50% of the addendum Af, volumetric efficiency is maintained, and the lower limit is kept to 10% of the addendum Af so that the angle α ₁ of the tooth space of the male rotor M falls within the range of 10 to 30°. , which facilitates hobbing.

(Effects of the Invention) As is clear from the above description, according to the present invention, hobbing of the screw rotor is easy, and even if the center distance and rotor length of the female rotor and male rotor are made the same, the volumetric efficiency is improved. It is possible to increase the stroke volume without causing a decrease, making it a screw compressor suitable for low pressure and large capacity.

[Brief explanation of the drawing]

Fig. 1 is a tooth profile diagram of the screw rotor according to the present invention, Fig. 2 is an enlarged view showing the seal edge portion of the tooth tip of the male rotor in Fig. 1, and Fig. 3 is a tooth profile diagram of the female rotor in Fig. 1. Enlarged view showing the seal edge part of
FIG. 4 is an enlarged view showing the blowhole portion in the tooth profile meshing shown in FIG. 1. F...Female rotor, M...Male rotor, _a1 to _h1 , _j1
...Each point on the male rotor tooth profile, b ₂ ~ h ₂ , j ₂ ...Each point on the female rotor tooth profile, Af...Addendum of the female rotor,
SR ₄ ...Radius of the forward corner of the male rotor tooth tip,
SR ₆ ...Radius of the trailing side corner of the tooth tip of the female rotor,
α ₁ ...The angle of the tooth space of the male rotor.

Claims (1)

[Claims] 1. A screw compressor comprising a female rotor (F) with 4 teeth and a male rotor (M) with 3 teeth meshing with the female rotor (F), and having the following rotor tooth profile: etc. screw rotor. Tooth profile of the female rotor (a) The forward tooth profile is an arc of radius (SR ₁ ) centered on the intersection (O ₂ ) of the pitch circle (Pf) and the line connecting the center points (Of, Om) of the male and female rotors. d ₂ −e ₂ ) and the center point (O ₃ ) on the extension of the straight line (O ₂ −e ₂ )
_An arc _{( e 2 − f 2 )} of _radius (SR ₂ ) with ), an arc (h ₂ − j ₂ ) of radius (SR ₄ ) centered on the point (O ₅ ) on the straight line (O ₄ − h ₂ ), and an arc (j ₂ ) on the tip circle (Cf) −a ₂ ) and are connected in order. However, the point (d ₂ ) is on the line connecting the center points (Of, Om) and is also on the root circle (Bf), and the point (f ₂ ) is on the inside of the pitch circle (Pf). positioned. (b) The following tooth profile is created by the generation curve (d ₂ − c ₂ ) created by the circular arc (d ₁ − c ₁ ) of the male rotor (M) and the _radius (SR ₅ ) arc (c ₂ − b ₂ ), an arc ( _{b 2} − _{a 2} ) of radius (SR ₆ ) centered on point (O ₇ ) on the straight line (O ₆ − b ₂ ), and It will be connected. (c) The addendum (Af) is 3 to 6% of the diameter of the pitch circle (Pf). (d) Radius (SR ₄ ) and radius (SR ₆ ) are 10-50% of addendum (Af). Male rotor tooth profile (a) The forward tooth profile is defined by the arc (d ₁ − l ₁ ) on the tip circle (Cm), the line connecting the pitch circle (Pm) and each center point (Of, Om) of the male and female rotors. A circular arc (l ₁ −e ₁ ) with a radius equal to the radius (SR ₁ ) centering on the intersection point (O ₁ ) and a center point (O ₃ ) on the extension of the straight line (O ₁ −e ₁ )
_A generated curve _{( f 1 - g 1} ), a generation curve (g ₁ - h ₁ ) created by the arc (g ₂ - h ₂ ) of the female rotor (F), and the arc (h ₂ - _{j 2} ) of the female rotor (F). ), the arc (j _{1 −a 1} ) on _the root circle (Bm), and are connected in order. However, the point (d ₁ ) is on the line connecting the center point (Of, Om) and on the tip circle (Cm), and the point (f ₁ ) is on the tip circle (Cm). It is located in (b) Point (O ₈ ) of the following tooth profile on the line connecting the center point (Of, Om)
An arc (d ₁ − c ₁ ) with radius (SR ₇ ) centered at
, a generation curve (c ₁ - b ₁ ) created by the arc (c 2 - b 2 ) of the female rotor (F), and a generation curve (c ₁ - b ₁ ) created by the arc (b ₂ - _{a 2} ) of the female rotor (F). It is formed by sequentially connecting the generating curve (b ₁ − _{a 1} ) and . (c) The tangent to the arc (c ₁ − b ₁ ) at the intersection (Op) of the pitch circle (Pm) and the arc (c ₁ − b ₁ ), and the line connecting the intersection (Op) and the center point (Om) angle (α ₁ )
is 10 to 30° toward the following side.