JPH081179B2 - Screw rotors such as oil-cooled screw compressors - Google Patents

Description

TECHNICAL FIELD The present invention relates to an oil-cooled screw rotor such as an oil-cooled screw compressor applied to a screw compressor, a vacuum pump, an expander, or the like. is there.

(Prior Art) Generally, when determining the tooth profile of a screw rotor such as a screw compressor as shown in FIG. 6, first, a function F (x) representing the tooth profile of the trailing end of the male rotor 11 is appropriately determined. . Further, when this function F (x) is determined, the function f (x) representing the forward side portion of the female rotor tooth 12 created by this portion is uniquely determined. Next, female rotor
A function G (x) representing the shape of the portion from the end point E of this function f (x) portion (point A to point E) of 12 to the addendum circle 13 is appropriately determined. Further, when this function G (x) is determined, the function g (x) representing the trailing side tooth root portion of the male rotor 11 created by this portion is uniquely determined.

In the conventional function G (x) part, whether the center of curvature of the part is on the follower side (Japanese Patent Publication No. 60-41238, Japanese Patent Publication No. 56-17559), or the center of curvature is on the forward side, It is determined to be on the pitch circle (Japanese Patent Laid-Open No. 60-153486).

(Problems to be Solved by the Invention) The tooth profile of the screw rotor influences the performance of the screw compressor and the like, and it is desirable to reduce the seal line length and blowhole area. However, as shown in FIG. 5, the seal line length and the blow hole area have contradictory properties, and there is a relationship that if one is made smaller, the other becomes larger.

The seal line and the blow hole are well-known ones, though there are some differences in expression from the conventional ones, and are described in detail, for example, in Japanese Patent Publication No. 56-17559. To briefly explain this, the seal line is a line that separates the tooth groove on the high pressure side from the tooth groove on the low pressure side adjacent to it, and the blow hole is the tooth of the male rotor and the tooth of the female rotor that meshes with it. And a casing, which is formed by a collective portion of the casing and a casing, and which is a substantially V-shaped void serving as a communication portion between the high-pressure side space and the low-pressure side space adjacent thereto.

FIG. 5 shows this relationship in an easy-to-understand manner, where the horizontal axis represents the seal line length and the vertical axis represents the size of the blowhole area. In the case of a conventional tooth profile, the above relationship is a curve.
It is represented by II. That is, as described above, the blowhole area increases when the seal line length is reduced, and the blowhole area decreases when the seal line length is increased.
This relationship will be described more specifically with reference to FIGS. 6 to 10.

The broken line in FIG. 6 is the seal line, and in order to make it easier to understand the creation of the rotor, the direction in which the female rotor 12 and the male rotor 11 are indicated by the two-dot chain line arrow (the direction opposite to the rotor rotation direction during operation) ), The xy plane (rotor axis shown in FIG. 6) of each seal point of the above function F (x) and f (x) part and each function G (x) and g (x) part. The projection locus on a right-angled section) is shown. That is, if the seal points of the functions F (x) and f (x) are projected on the cross section perpendicular to the axis along with the above rotation, the seal line AB is continuously moved from the point A to the point B, and the function G (x ) And g (x) seal points continuously move from point D to point B and seal line DB
When the respective seal points reach the point B on the seal line, the teeth of the female and male rotors 12 and 11 disengage from each other. In other words, when the two rotors are rotated by a predetermined angle, they separate at a point E which is a connection point on the tooth profile between the functions G (x) and f (x). Therefore, the point B on the seal line corresponds to the point E on the tooth profile.

Further, in order to shorten the seal line, the function G '(x) is indicated by the one-dot chain line in FIG. 6, that is, the portion between the point E'on the tooth profile and the point dG is corrected, and It suffices that the teeth of the female and male rotors 12 and 11 are quickly separated from each other, and in this case, the projection locus of the seal line on the xy plane is the curve D'B'A (dots) shown by the broken line in FIG. D'is a point on the seal line in the case of this modified tooth profile, which corresponds to the point D described at the beginning). And
The point on the tooth profile corresponding to the point B'on this seal line is E '.

Needless to say, the locus of each seal point when rotated 360 ° in the rotor rotation direction during operation is the same as that shown in FIG. 6 as long as it is created.

Reference numerals 15 and 14 denote pitch circles of the female and male rotors 12 and 11.

FIG. 7 is based on the case where there is a point A which is the tip of the male rotor on the line connecting the centers of the rotors of the sealing points of the functions F (x) and f (x) (rotor rotation angle φ = 0. ) Rotor rotation angle φ (in the case of a screw rotor, if the rotation angle φ of the rotor is fixed, it can be considered as the distance (horizontal axis) in the rotor axis direction from the reference point to the seal point) 6 shows the relationship with the distance (vertical axis) from the reference point (point A) measured along the movement trajectory of the seal point on the xy plane, that is, on the paper surface of FIG. 6, and points a and d are shown in FIG. Point A corresponds to point A and D in the upper case, and point b corresponds to point B in FIG. That is, the vertical axis of FIG. 7 represents the length measured from the reference point along the seal line (projection locus on the xy plane) shown by the broken line of FIG. 6, and the horizontal axis represents the rotor rotation angle. However, as described above, the rotor rotation angle is equal to the distance in the axial direction of the rotor (distance in the direction perpendicular to the paper surface in FIG. 6) and 1
There is a one-to-one relationship, and it can be seen as a distance in the axial direction of the rotor. Therefore, using the distance in the rotor axis direction on the horizontal axis and the length measured along the seal line in FIG. 6 on the vertical axis,
(Length squared on the horizontal axis + length squared on the vertical axis) _1/2 . Therefore, the length of the solid line measured from the point a in FIG. 7 (corresponding to the broken line DBA in FIG. 6) or the length of the chain line measured from the point a (broken line D ′ in FIG. 6)
(Corresponding to B'A) represents the actual length of the seal line from the reference point measured three-dimensionally. That is, the actual length of the seal line DBA is equal to the sum of the lengths of the curves ab and db in FIG. 7, and the corrected seal line D'B'A described above is used.
The actual length of is equal to the sum of the curves ab ', b'd', which length is almost determined by the position of the points B, B '. If the point B in FIG. 6 is changed to a point B ′ located closer to the point A, the point b is changed to the point b ′ as shown by the alternate long and short dash line in FIG.
It can be seen that the point d moves to the point d'and the length of the seal line becomes shorter. In FIG. 7, φ _B and φ _B ′ are male and female rotors.
Point 12 and point 11 on the seal line in FIG.
Shows the rotor rotation angle corresponding to. φ _D is a rotation angle corresponding to the points D and D ′ on the seal line in FIG. 6 (the points dG and dg on the tooth profile contact each other).

Next, looking at the blowhole, as shown in FIG. 8, l _MF : The shortest distance between the female rotor and the male rotor l _MC : Between the male rotor and the cusp C (the chevron portion of the rotor chamber wall) Shortest distance l _FC : Defined as the shortest distance between the female rotor and the cusp C.

Fig. 9 shows the change curves of the above distances l _MF , l _MC , and l _FC , where the horizontal axis represents the rotor rotation angle φ or the distance in the rotor axial direction and the vertical axis represents the distance. , The horizontal axis and the vertical axis are the same as those in FIG. 9, but can be represented as shown in FIG. 10 by leaving only the smaller one of the distance l _MC and the distance l _MF + l _FC . Here, the meaning of leaving only the smaller one of l _MC and l _MF + l _FC is as follows.

Leakage of compressed gas from the space X to the space Y shown in FIG. 8 influences the performance of the compressor. The amount of this leakage is determined in a plane by the smaller one of the distance l _MC and the distance l _MF . Considering three-dimensionally, the distance l in FIG.
The gap shown by _MF is actually the distance l _MF + l _FC
Can be considered to have a size of. Therefore,
The actual amount of compressed gas leakage is determined by the smaller of the distance l _MC and the distance l _MF + l _FC , and when considering the performance of the compressor, this smaller distance is important.

Note that, for convenience, the distance l _FC is below the distance curve indicating the distance l _MC . In the above representation, the blowhole area is the area surrounded by the points s, t, u, v in FIG. Here, the angle φ _c is the point A at the tip of the male rotor.
Is an angle that reaches the cusp C shown in FIG. 8 and has a fixed value, and the point B in FIG. 6 is the same as in the case of FIG.
Is changed to the point B ', as shown in Fig. 10, the angle φ
_B changes to the angle φ _B ′, the portion indicating the distances l _MC and l _FC changes as indicated by the alternate long and short dash line, and the points s, t, u change to the points s ′, t ′, u ′.

Therefore, when considering the conventional tooth profile in which the center of curvature of the function G (x) is on the following side, the female and male rotors 12, 11
When the rotor rotation angle φ _B is changed to φ _B ′, the seal line length is shortened as can be understood from FIG. 7, while the distance l _MF , l _FC is understood as understood from FIG.
State where st and tu of the part are substantially translated, that is, s', t ', u',
There is a problem that it becomes an area surrounded by v, which causes an increase in blowhole area.

This is because in the case of the conventional tooth profile, the point E on the tooth profile in FIG. 6 is moved to a point E ′ located farther from the tooth tips of the female rotor in an attempt to shorten the length of the seal line. That is, if the timing of separating the male rotors 12 and 11 is advanced, the gap between the rotors in the portion ahead of the point where the rotors separate will be widened, and the blowhole area will increase.

On the other hand, as shown in FIG. 11, in an actual oil-cooled compressor or the like, a predetermined minute rotor gap is provided for a theoretical tooth profile with zero rotor gap, and a female rotor and a male rotor are provided.
The oil 16 between 12 and 11 provides a seal between the tooth spaces 17 and 18 on both sides of the oil 16. The sealing effect at the oil 16 portion can be increased as the female and male rotors 12 and 11 have relative speeds and hydraulic pressure is generated by the wedge effect. That is,
When the relative speed of the female and male rotors 12 and 11 is 0, the oil pressure generated in the oil 16 portion becomes small, and the sealing effect of the oil 16 deteriorates.

For this reason, in the prior art described in the above-mentioned JP-A-60-153486 in which the center of curvature of the function G (x) portion is on the pitch circle of the female rotor, the relative speed of the female and male rotors at the seal point is There is a problem that it becomes 0 and the sealing effect deteriorates.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and shortens the length of the seal line and reduces the increase amount of the blowhole area due to this, which is an oil-cooled screw compressor. It is intended to provide a screw rotor of

(Means for Solving the Problem) In order to solve the above problem, the present invention is represented by an arbitrary function F (x) capable of creating a female rotor tooth profile at the tip end portion on the trailing side of a male rotor tooth. The part represented by the function G (x) from the end of the part represented by the function f (x) on the forward side of the female rotor tooth created by the part to the tip circle of the female rotor tooth is represented by the function f ( x) and the shape represented by the function G (x) is partly or entirely up to the tip circle, the center of curvature of which is the pitch circle of the female rotor tooth. Formed to be on the forward side on the outside.

(Embodiment) Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a screw rotor of an oil-cooled screw compressor or the like according to the present invention, which rotates in a direction shown by an arrow by a solid line in the drawing, but a tooth surface of a meshing portion of female and male rotors 2 and 1 shows only, curve a _M ~ which towards the tooth bottom tracking side tooth surfaces of the male rotor 1 from the tooth tip corresponds to the function F (x) section
B _M and each part of the curves B _{M to} C _M and the curves C _{M to} D _M corresponding to the function g (x), and the advancing side tooth surface of the female rotor 1 moves from the tooth root to the tooth tip. and curves _a F .about.B _F corresponding to f (x) portion, the curve corresponding to the function G (x) section _B F -C _F, are formed from each part of the curve _C F to D _F. However, the geometrical meanings of the above parts are as follows.

A _{M to} B _M : A circle centered on O ₃ B _{M to} C _M : Creation curve of the female rotor 1 by the curves B _{F to} C _F Curve C _{M to} D _M : Creation of the female rotor 1 curve from C _{F to} D _F curve a _F .about.B _F: male creation curve by curve _a M .about.B _M of the rotor 2 B _F ~C _F: in a circle around the point _{O 1,} the point _{O 1} is _B F ~
It is on the forward side of the _CF section and outside the pitch circle 3.

C _F to D _F: a circle around the point _{O 2,} the point _{O 2} is _{C F}
The point _DF is located on the tip circle on the trailing side of the portion _DF .

Here, as shown in FIG. 2, the function representing the tooth profile of the conventional screw rotor is attached with a suffix 1, and the function representing the tooth profile of the present screw rotor is attached with a suffix 2, and both screw rotors are compared. To do.

It should be noted that FIG. 2 shows only the tooth profile of the female rotor in order to avoid complicating the figure, and the tooth profile of the male rotor is shown as F.
Only the (x) part is displayed.

As described above, the function G ₁ (x) part is connected to the function f (x) part at the point E. Further, the function G ₂ (x) part is connected to the function f (x) part at a point B _F closer to the point A _F ,
From there to a point C _F near the point E, the shape represented by the function f (x) and a short distance, however, the gap between the rotors, that is, it is actually not allowed to bring the rotors into contact with each other, and the rotors are not in contact with each other. And a shape separated by a distance ε larger than the rotor gap, which is the minimum gap for this,
The points C _{F to} D _F have a shape similar to the shape represented by the function G ₁ (x). As a result, the seal line functions than the function G _{1 (x)} as shown in FIG. 3 G ₂
The value is smaller in the case of (x). On the other hand, the blowhole area becomes larger in the case of the function G ₂ (x) than in the case of the function G ₁ (x) as shown in FIG.
Rotor rotation angle φ _BF ~ φ _E and function G at ₁ (x)
Distance between rotor rotation angle φ _BF and φ _{CF at 2} (x)
l _MF is ε, and the area of this part is sufficiently smaller than the whole area. Further, in addition, in the same way as the conventional tooth profile, since the center of curvature on the tip side from the point B _F is on the side following the female rotor tooth, as shown by the curved line I in FIG. It bends in the direction away from the male rotor tooth as it goes from _BF to the tip side. On the other hand, in the case of the tooth profile of the present screw rotor, since the center of curvature is on the forward side of the female rotor tooth on the tooth tip side from the point B _F , the curve I
It bends toward the side of the male rotor tooth that is opposite to the direction, that is, with a very small gap from the male rotor tooth. Therefore, it can be understood that in the case of the present screw rotor, even if the seal line length is shortened, the increased blowhole area is extremely small, which is not so different from the case of the function G ₁ (x). Also, the center of curvature of the function f (x) is always on the forward side of this part, and the function G
_{Since the} center of curvature of the curves B _{F to} C _F of the ₂ (x) section is also on the forward side, the distance ε can be made sufficiently small.

That is, in the case of the present screw rotor, even if the length of the seal line is shortened, the increase in the blowhole area can be sufficiently reduced. In other words, regarding the relationship between the seal line length and the blowhole area, the conventional tooth profile was on the line of curve II shown in FIG. 5, whereas the tooth profile of the present screw rotor is shown in FIG. It becomes a point in the range shaded inside the curve II shown in.

It should be noted that, although FIG. 3 corresponds to FIG. 7 and FIG. 4 corresponds to FIG. 10, the symbols used in both figures do not necessarily correspond to FIG. In the description related to FIG. 10, basically, the points on the seal line are described, whereas in the description related to FIGS. 3 and 4, the points on the tooth profile are basically described. It depends on

Further, the center of curvature of the above curves B _{F to} C _F is the pitch circle 3.
Since it is on the outer side of the rotor, a relative speed is generated between the female and male rotors 2 and 1, and along with this, hydraulic pressure is generated in the oil between the female and male rotors 2 and 1, and the sealing performance is improved.

(Effect of the Invention) As is clear from the above description, according to the present invention, it is represented by an arbitrary function F (x) capable of creating the female rotor tooth profile of the tip end portion on the trailing side of the male rotor tooth. Function G (x) from the end of the portion represented by the function f (x) on the forward side of the female rotor tooth created by the portion to the tip circle of the female rotor tooth
The part represented by the function f (x) is different from the shape represented by the function f (x), and part or all of the part represented by the function G (x) up to the tip circle is The center of curvature is formed on the forward side outside the pitch circle of the female rotor teeth.

Therefore, as described above, the seal line length can be shortened without increasing the blowhole area so much, and the performance of the screw compressor or the like can be improved.

Further, since the center of curvature that is on the forward side is on the outside of the pitch circle, a relative speed is generated between the female and male rotors in the function G (x) part, and as a result, hydraulic pressure is generated and the seal is generated. This has the effect of improving the performance and improving the performance of the screw compressor and the like.

[Brief description of drawings]

FIG. 1 is a partial front view showing a meshing portion of a screw rotor according to the present invention, and FIGS. 2, 3, and 4 show tooth profiles in which the screw rotor shown in FIG. 1 and a conventional screw rotor are compared. Partial front view showing the movement of the seal point, the area of the blow hole, FIG. 5 shows the relationship between the seal line length and the blow hole area in the case of the conventional tooth profile, and FIG. 6 shows the conventional FIG. 7 is a diagram showing the meshing portion of the screw rotor and the trajectory of the seal point. FIG. 7 is a diagram showing the relationship between the rotor rotation angle or the distance from the reference point in the rotor axial direction and the distance from the reference point of the seal point. Figure 8 shows distance l
_FC , l _MF , l _MC partial front view for explanation, Fig. 9 shows the rotor axial angle or the distance from the reference point in the axial direction of the rotor l _FC , l
Fig. 10 shows the relationship between _MF and l _MC, and Fig. 10 shows the distance in the rotor axial direction from the rotor rotation angle or reference point, the distance l _MC and the distance (l
Figure showing the relationship with the smaller distance of _MF + l _FC ),
FIG. 11 is a partial sectional view showing a state of oil between the male and female rotors. 1 ... Female rotor, 2 ... Male rotor, 3 ... Pitch circle.

Claims (1)

[Claims] 1. A female rotor tooth created by a portion (A _{M to} B _M ) represented by an arbitrary function F (x) capable of creating a female rotor tooth profile on the trailing end of a male rotor tooth. Of the part (A _{F to} B _F ) represented by the function f (x) on the advancing side of the part from the end of the tip circle (4) of the female rotor tooth to the part (B _F D _F ) is different from the shape represented by the function f (x), and a part or all of the portion represented by the function G (x) up to the tip circle is its center of curvature. A screw rotor for an oil-cooled screw compressor or the like, wherein (O ₁ ) is on the forward side outside the pitch circle (3) of the female rotor teeth.