JPH0319918B2 - - Google Patents

Description

Detailed Description of the Invention Technical Field The present invention relates to a pair of rotors used in a screw machine that compresses or expands a compressible fluid;
In particular, it concerns its tooth profile. PRIOR ART In general, a screw rotor with an asymmetric tooth profile used in compressors for compressible fluids, etc. has two types: a male rotor with the main part of the tooth profile outside the pitch circle of the rotor, and a male rotor with the main part of the tooth profile outside the pitch circle of the rotor. Usually, a male rotor with a plurality of teeth and a female rotor with a slightly larger number of teeth are engaged, and the tip circle of the male rotor is The diameter and the pitch circle diameter of the female rotor are set to be approximately equal. A pair of screw rotors of this type are placed in two cylindrical spaces whose axes are parallel to each other and whose diameter is equal to the outer diameter of each rotor, and where the distance between the axes is less than the sum of their mutual radii. It is rotatably housed in a short casing with a space whose axial length is the same as the axial length of the rotor, and both open ends of the casing are closed with end plates, and suction ports are provided at the required locations. A screw compressor or expander is constructed by providing a discharge port and a discharge port.
[See Figures 3a and 3b] When the above-mentioned device is used as a compressor, the female rotor is rotated counterclockwise and the male rotor is rotated clockwise in the figure. Regarding the tooth profile curve of a female rotor, the front side in the rotational direction of the curve forming the tooth groove is called the forward tooth profile, and the curve on the rear side in the rotational direction is called the following tooth profile.As for the curve forming the tooth profile of a male rotor, In this case, the curve on the front side in the rotational direction is called the advancing side tooth profile, and the curve on the rear side in the rotational direction is called the following side tooth profile curve. When the device is used as an expander, the respective curves function in the opposite manner, but in the description herein, they are all discussed as being used as a compressor. Figures 1a and 1b of the screw rotor shown above show the tooth profile curves seen when the rotor is cut along a plane perpendicular to the rotor rotation axis, that is, the tooth profile curves of the screw rotor at the longitudinal end face of each rotor. The tooth profile is a tooth profile curve that has been conventionally used by the present applicant (see Japanese Utility Model Publication No. 54-25552), and its characteristics are as follows. That is, in the figure, 1 is a male rotor, 2 is a female rotor that meshes with the male rotor 1 , and these rotors 1 and 2 are respectively centered on the rotation center (pitch circle center).
By rotating in the direction of the arrow in the casing (not shown) around 3 and 4, it functions as a fluid compressor. 15 and 16 are the pitch circles of the male rotor 1 and female rotor 2 , respectively;
And the straight line connecting each rotation center 3 and 4 is pitch circle 1
5 and 16, or the pitch point. (1) Female rotor tooth profile (a) Forward side On the lines 3 and 4, from the deepest point 12 at the center of the tooth profile of the female rotor to the tip 11 of the tooth profile, connect the contact points of the pitch circles 15 and 16 of both the female and male rotors ( pitch point)
17 as a center and a radius of r ₄ , and further, between the outer portions 11 and 10 of the curve, a tangent to the arcs 11 and 12 of radius r ₄ from the pitch circle center (rotation center) 4 of the female rotor. The curve between 12 and 13 at the bottom of the groove of the female rotor is made into an arc centered on the rotation center 4 of the female rotor and has a radius r ₂ , and the outer diameter of the tip circle matches the pitch circle 16 of the female rotor. let (b) Follow-up side Let the curves 13 to 14 on the follow-up side of the groove of the female rotor be an epitrochoid curve created by point 8 of the male rotor. (2) Male rotor tooth profile (A) Forward side The curve from the center vertex 7 of the male rotor tooth profile to the point 6 on the root side of the tooth profile is centered at the contact point 17 of the pitch circles 15 and 16 of both the female and male rotors. , an arc with radius r ₃ smaller than the radius r ₄ by the clearance required for rotation, and the distance from point 6 to root 5 is formed by a straight line between tips 10 and 11 of the female rotor. Let the envelope curve be (b) Follower side The curve between points 7 and 8 on the follower side of the tooth profile of the male rotor is centered at the rotation center 3 of the male rotor and has a radius r ₁
The curve from point 8 to dedendum point 9 is an epicycloid curve created by the tooth tip 14 of the opposing female rotor, and the groove bottom diameter between 5 and 9 is By aligning point 8 with the pitch circle 15 of the male rotor, the contact line of the female and male rotors on the ridge line along the thread reaches the intersection line of the compression chamber closure side of the cylinder that accommodates both rotors. stipulated in Further, the point 8 is formed far away from the straight line connecting the rotation centers 3 and 4 of each rotor. Since the tooth profile of both rotors is defined as above, (a) the short-circuit leakage space (blow hole) between the compression chambers can be made virtually zero, and the tooth tips of the female rotor can be made pitch-perfect. By matching the circular diameter, interference between the tips of the female rotor's teeth at the root of the male rotor's teeth is eliminated, and the closing effect is improved. (b) By moving the point 8 on the male rotor tooth profile far away from the straight line connecting the rotation centers 3 and 4 of both the female and male rotors, a space 18 is created at the contact area between the low-pressure side end plate and the male and female rotors. However, since the rate of volumetric expansion accompanying the rotation of the rotor is small, there is little power loss due to the vacuum generation effect based on volumetric expansion. Although there are advantages such as, the following problems are also pointed out. That is, (c) the space volume is small (the stroke volume is small). (d) Because the bottom of the female rotor tooth profile is uneven, the sealing performance is not good and it is difficult to measure the dimensions during processing. Furthermore, the outer shape of the cutter becomes complicated, making it difficult to process. (e) Since the trailing side curve of the female rotor tooth profile forms a point, the sealing point is easily worn and the sealing effect is difficult to maintain. (f) Since the pressure angle is almost equal to 0 near the pitch circle, it is difficult to machine the tooth profile with high precision, and the tool life is shortened. Especially when hobbing screw rotors, the life of the hobbing tool is shortened. Figure 1a shows the phase of the tooth profiles of both rotors immediately after point 8 of the male rotor tooth profile of the rotor having the above-mentioned tooth profile and the curve 13 to 14 of the female rotor tooth profile begin to come into contact; By rotating about 20 degrees, the phase shown in Figure 1b is reached, but since the contact surface indicated by the reference numeral 18' in Figure 1a expands into a space such as 18 in Figure 1b, a vacuum space is created in this area. I decided to create
It is preferable that the space volume not be large, since the necessary power (unrelated to compression) is consumed. The above-mentioned tooth profile has a small rate of volumetric expansion, so the power loss is small. For example, one of the conventional tooth profiles used by other companies,
The tooth profile of the rotor used in the screw rotor machine described in Publication No. 56-17559 is as shown in Figure 2a,
In the figure, components denoted by the same reference numerals as in FIG. 1 are the same members. In Fig. 2, (1) Female rotor tooth profile (a) Forward side 28-29: Circular arc with radius r' ₁ centered at point 36 on straight line 17-29. 29-30; radius centered on pitch point 17
arc of r′ ₂ . (b) Following side 30-31; Epitrochoid curve formed by point 23 on the male rotor tooth profile. 31-32; A straight line passing through the rotation center 4 of the female rotor. 32-33; Arc having its center on the pitch circle 16. 33-34; Arc centered on rotation center 4. 34-35; Arc having its center on the pitch circle 16. (2) Male rotor tooth profile (a) Forward side 21-22; female rotor tooth profile 28-29 (radius centered on point 36 on straight line 17-29)
arc of r′ ₁ ). 22-23; radius centered on pitch point 17
arc of r′ ₂ . (b) Following side 23-24; Epitrochoid curve formed by point 31 on the female rotor tooth profile. 24-25; Creation curve by straight line 31-32. 25-26; Arc having its center on the pitch circle 15. 26-27; Arc centered on rotation center 3. 27-21; Arc having its center on the pitch circle 15. However, the capacity of the illustrated space (vacuum creation space) 18 is larger than that of the tooth profile illustrated in the first figure. Further, when both the female and male rotors are in the rotational position shown in FIG. 2a, both rotors are at points 31 and 30.
and 76 are in contact with each other with a slight clearance that prevents leakage from the working space. The three contact points create a space 79 on the forward side of the tooth profile (above the X axis in the figure).
is formed, while the following side of the male rotor tooth profile (X
A space 18 is similarly formed below the shaft. Now, on the suction side end surface 74 (see Figure 3), as both the female and male rotors rotate in the direction of the arrow, the volume of the space 18 gradually expands, forming a significantly larger vacuum space as described above. do. On the other hand,
On the discharge side end face 75 (see FIG. 3), the space 79 gradually reduces its volume as both rotors rotate, and eventually reaches a volume close to zero. Therefore, the gas trapped in the space 79 is abnormally pressurized, and in the case of an oil-cooled rotary compressor, a compression action space is provided in the closed space for cooling, sealing, and lubrication. Since the lubricating oil injected into the rotor remains, the fluid becomes compressed, causing the female and male rotors to generate abnormal vibrations and noise, and in extreme cases, accelerate rotor wear and damage. Furthermore, since an excessive rotational torque is required and an excessive load is applied to the rotor and casing, power loss is large, and the service life of the bearing is shortened. In order to solve the above-mentioned problems, the special public
As described in Japanese Patent Publication No. 214693 and Japanese Patent Publication No. 58-131388 [see Figure 2b]. A bypass hole 77 is bored in the inner wall surface 75 of the discharge side casing,
Means is provided to allow the residual gas and lubricating oil to escape through the bypass hole into a separate low-pressure working space or suction side space, or to increase the volume of the bypass hole 77 to prevent them from flowing into the low-pressure working space. However, the structure is complicated and the cost is high. Purpose Therefore, the present invention solves the problems raised without losing the above-mentioned advantages of the tooth profile shown in the first drawing conventionally used by the present applicant, or by reducing the losses based thereon as much as possible. In particular, it prevents wear of the sealing point to prevent a reduction in efficiency over long-term use, and also prevents the wear of the sealing point, which is formed on the inner wall of the discharge side casing when the discharge port is closed just before the end of the discharge process. Prevent abnormal vibrations and noise caused by the reduction of closed spaces, and smoothly
The purpose of the present invention is to provide a new tooth profile that ensures operation without overload and solves problems in forming process. The detailed configuration and effects thereof will be made clear in the description of the embodiments described below. Configuration The present invention comprises: 1. A screwdriver consisting of a female rotor and a male rotor that rotate around two parallel axes while meshing with each other.
In a rotor, the main part of each tooth profile of a female rotor is formed within the pitch circle of the same rotor, and the main part of each tooth profile of a male rotor is formed outside the pitch circle of the same rotor, In each tooth profile curve formed in a plane perpendicular to the rotational axis of each rotor, at least the trailing side tooth profile of the rotor has a straight line connecting the rotation center of each rotor along one side from the tooth tip to the tooth root side. A circular arc with a radius R ₁ centered at the rotation center of the male rotor, sandwiching a central angle θ ₂ when viewed from above, and a radius line connecting the ends of the arc and the rotation center of the male rotor, the center of which is drawn. An arc of radius R ₄ that is inscribed in an arc of radius R ₁ , and an epicycloid curve created by the intersection of the female rotor's following side tooth profile curve and the rotor's pitch circle, and the arc of radius R ₄ The center position is formed far away from the straight line connecting the rotation centers of each rotor, and the trailing side tooth profile of the female rotor is formed along a part of the trailing side tooth profile of the male rotor from the tooth bottom to the tooth tip side. A screw rotor characterized in that it consists of an envelope formed by a circular arc with a radius _R4 . 2 A screwdriver consisting of a female rotor and a male rotor that rotate in mesh around two parallel axes.
The rotor is a female rotor, and the main part of each tooth profile of the female rotor is formed within the pitch circle of the rotor,
Each tooth profile of the male rotor is of the type in which the main part is formed outside the pitch circle of the same rotor, and in each tooth curve formed in a plane perpendicular to the rotation axis of each rotor, the tooth profile is on the forward side of the female rotor. The tooth profile runs from the tooth tip to the bottom side on a straight line connecting the rotation centers of each rotor, with the apex at a position outside the pitch circle of the female rotor, and an angle of θ ₁ when looking at the straight line to one side. The tooth profile on the following side consists of an arc with a radius R _{2 circumscribing an arc with a radius R 3 drawn} with the apex as the center and an arc with the radius R ₃ , the center of which is on the extension line of the sandwiching straight line, and the following side tooth profile is Along the tooth root side to the tooth tip side, at least an arc with the radius R ₃ and a radius R ₄ forming a part of the trailing side tooth profile of the male rotor.
and the envelope formed by the arc of radius R ₄ , and the tooth bottom of the female rotor is formed by the arc of radius R 3 and the envelope formed by the arc of radius R ₄ . The forward tooth profile of the male rotor is connected to the envelope line smoothly or by a common tangent, while the forward tooth profile of the male rotor is connected to the radius of the forward tooth profile of the female rotor along the tooth root to the tooth tip side.
The following tooth profile is formed by an envelope formed by an arc of radius R ₂ and an envelope formed by an arc of radius R ₃ , and the following tooth profile extends from the tooth tip to the root side. Looking at the straight line connecting the rotation centers of each rotor on one side, there is an arc with a radius R ₁ centered on the male rotor's rotation center, sandwiching the center angle θ ₂ , and an arc with a radius R ₁ from the male rotor rotation center on the other end. An epicycloid curve created by the intersection of an arc of radius R ₄ inscribed in the arc of radius R ₁ , drawn with the center on the extended radius line, and the pitch circle of the female rotor's trailing side tooth profile. and,
A screw rotor characterized in that the center position of a circular arc with a radius R ₄ forming a part of the following side tooth profile of the male rotor is formed far away from a straight line connecting the rotation centers of each rotor. One embodiment of the present invention will now be described with reference to the accompanying drawings. FIG. 3 shows a compressor for compressible fluid constructed by incorporating the screw rotor of the present invention, FIG. 3a is a cross-sectional view taken along line A-A in FIG. 3b, and FIG. It is a longitudinal cross-sectional view taken along the line BB shown in FIG. In the figure, reference numeral 1 denotes a male rotor, which is rotatably driven by a rotating shaft 60 connected to a drive device (not shown), and which cooperates with a support shaft 61 extending symmetrically to the shaft 60 with respect to the rotor 1 . , the rotor 1 is attached to the bearing portions 64 and 6 of each end plate 62 and 63.
5, it is rotatably supported. 2 is a female rotor that meshes with male rotor 1 ;
The rotor 2 is also rotatably supported by the end plates 62 and 63 by rotating shafts extending from each end surface thereof. Reference numeral 66 denotes a casing that surrounds the outer periphery of a pair of mutually meshing rotors 1 and 2 , and includes a low-pressure side end plate 62 having a suction port 67 and a discharge port at each end surface in the longitudinal axis direction. High pressure side end plate 63 with 68
A working space 69 is formed by the rotor tooth groove surface, the inner wall of the casing, and the inner sides of both end plates,
and compartmentalize. The working space 69 has a suction port 67 and a discharge port 6 that communicate with a low pressure passage 70 and a high pressure passage 71, respectively, for working fluid in the casing.
It has 8. The cross section of the casing 66 has two cylindrical spaces arranged in parallel, and the distance between their center axes is smaller than the sum of the radii of each cylindrical space. Therefore, both cylindrical spaces have mutually overlapping parts, and the inner walls of both spaces A ridgeline 72 appears at the intersection. The female rotor 2 has six grooves in which each spiral groove runs along the rotational axis (longitudinal) direction and is usually twisted by 200 degrees around the axis, and the grooves are located inside the pitch circle of the rotor 2 . The height of the teeth separating the grooves is limited to the pitch circumference, and the groove shape is approximately an inwardly concave curve. The male rotor 1 usually has four helical teeth, and each tooth is twisted about 300 degrees along the rotational axis (longitudinal) direction. The tooth height of the teeth is located outside the pitch circle of the rotor, and grooves are provided between the teeth into which the teeth of the female rotor 2 fit, and the tooth profile cross section is approximately
Consists of an outwardly convex curve. The working space 69 is divided into a V-shape, and after the rotation of the rotors closes the communication between the suction port 67 of the low-pressure side end plate 62 and the working space, the meshing line of both rotors moves (the rotation of both rotors Due to the accompanying relative), the volume of the partitioned working space is reduced compared to that at the time of closure, and the compressible fluid in the working space, which has been adiabatically compressed and becomes high pressure and high temperature, will eventually reach high pressure. Discharge port 6 bored in side end plate 63
8 and is discharged to the high pressure chamber 71 side. During this period, the rotor teeth, the mesh between the groove surfaces, the sliding surfaces between the casing inner wall and the sliding surfaces between the rotor end surface and the inner surfaces of both end plates are lubricated and airtightly maintained (sealed), and the compressible fluid is In order to cool the heat generated by adiabatic compression, cooling lubricant is applied to the nozzle 73.
is injected into the working space through the The screw rotor of the present invention relates to the tooth profiles of both rotors used in the above-mentioned compressor. Figures 4a and 4b show the tooth profile curves of each rotor seen when the screw rotor is cut along a plane perpendicular to each rotation axis, and in the figures, 1 indicates a male rotor;
3 is the rotation center of the rotor, 15 is the pitch circle of the rotor, and the male rotor 1 rotates around the rotation center 3 in the direction of the arrow. 2 is a female rotor that meshes with the male rotor 1 and rotates around the rotation center 4 in the direction of the arrow.
16 is the pitch circle of the female rotor, which touches the pitch circle 15 on the straight line connecting the rotation centers 3 and 4. The point of contact between pitch circles 15 and 16 is pitch point 17.
The diameter ratio of both pitch circles 15 and 16 is 2/3.
Note that 18 is a space close to a vacuum generated at the contact portion. Referring to Figure 4b, (1) Tooth profile curve of female rotor (a) Tooth profile on the forward side, along the tooth tip to the bottom side, (a) Between 47 and 48: Connects rotation centers 3 and 4 The apex is the center point 52 of a circular arc of radius R ₃ that is on a straight line and outside the pitch circle 16, and the center is a point 53 that is on a straight line with an angle θ ₁ = 40° to 46° between it and the straight line. An arc of radius R ₂ circumscribing an arc of radius R ₃ , drawn by (b) Between 48 and 49; An arc with a central angle θ ₁ =40° to 46° drawn with radius R ₃ centered on the point 52. Also, 1.05≦R ₃ /R ₁ -1/2PCD≦1.3, but PCD; pitch circle diameter of male rotor R ₃ /R ₁ -1/2 The larger PCD is than 1, and the smaller θ ₁ is. The smaller the
The pressure angle near the pitch circle of the tooth profile curve constituting 48-49 can be increased, making it easier to form the tooth profile with a hob, and the closer R ₃ /R ₁ -1/2PCD is to 1, the more Also, the smaller θ ₁ is, the more 48-49
It is possible to increase the pressure _angle near the pitch circle of _the tooth profile curve that makes up the tooth profile, making it easier to form the tooth profile with a hob. The larger ₁ is, the thicker the tooth profile of the female rotor can be. In this example, the pressure angle is set in a range that can be made sufficiently large and a tooth thickness that is sufficient in terms of strength can be ensured, and θ ₁ ,
R ₃ was defined as above. (b) Follower side tooth profile, along the tooth bottom to tooth tip side, (c) Between 49 and 51; An arc with a radius R ₁ (3-44) centered on the rotation center 3 of the male rotor 1 is the center angle When θ ₂ = 4° to 8°, the radius is centered at point 54 on the radius line 3-44.
Arc 44-45 on the tooth profile curve drawn by R ₄
envelope by. (d) Between 50 and 50' is on the straight line connecting the envelope 49-51 formed by the arc 44-45, which is a part of the tooth profile curve of the male rotor, and the rotation centers 3 and 4, and is located outside the pitch circle 16. center 5
The common tangent with the arc 48-49 having a radius _R3 having a radius of 2, and the section 50-50 _' may be smoothly connected using a gentle curve comparable to the arc of the radius R1. (e) Between 51 and 47 is the circumference of pitch circle 16. (2) Tooth profile curve of male rotor (a) Tooth profile on the advancing side, along the tooth root to tooth tip side, (f) Between 41 and 42: Envelope curve formed by arcs 47 and 48 on the tooth profile curve on the female rotor 2 side . (g) Between 42 and 43 is an envelope formed by arcs 48 and 49 on the tooth profile curve on the female rotor 2 side. (b) Follower side tooth profile, along the tooth tip to tooth root side, (h) Between 43 and 44; An arc with center angle θ ₂ = 4° to 8° drawn with radius R 1 and centered on rotation center ₃ . . The larger θ ₂ is, the smaller the space 18 can be, and the smaller θ ₂ is, the smaller the space 18 is.
a male rotor between -44 and 50-50';
The gap between the female rotors can be reduced. In this embodiment, the space 18
can be made sufficiently small, and the curve 43-
The above numerical value for θ ₂ was determined as a range in which the gap between the male rotor and the female rotor between 44 and 50-50' can be made to such an extent that it does not pose a practical problem. (i) Between 44 and 45; An arc with radius R ₄ centered on point 54 and having its center on radius 3 and 44. In relation to the value of θ ₂ in the above (h), the position of the center point 54 of the circular arc with radius R ₄ is set far away from the straight line 3-4. (j) 45-46 is the intersection 51 of the tooth profile curve 49-51 of the female rotor 2 and the pitch circle 16.
The epicycloid curve created by (k) Between 46 and 41 is the circumference of pitch circle 15 of the male rotor. As an example, each radius and angle in the tooth profile shown in FIG. 4 is shown in Table 1. Table 1 [Table] Pitch circle diameter effect of [Table] Since the tooth profile curve of the screw rotor of the present invention is as described above, (1) Under the conditions of (h) and (i), (a) Radius The center point 54 of the arc 44-45 of R ₄ is
By providing it on the radius line 3-44 extending from the rotation center 3 of the male rotor 1 , as shown in FIG. The angle θ ₅ with the perpendicular line l can be made smaller than the angle θ′ ₅ when it is provided on the radial line 17-44 extending from the center point 17, and the following side tooth profile curve of the male rotor is aligned with each rotation center. The distance from the straight line 3-4 connecting the two approaches the female rotor follow-up side tooth profile curve, and the vacuum creation space 18 can be made smaller. (b) In the conventional tooth profile shown in Fig. 2a, just before the end of the discharge process and when the discharge port is closed, the space 79 formed on the forward side of the male rotor is Volume decreases. Therefore, the compressed gas and seal lubricating oil trapped in the space 79 are abnormally pressurized. In the tooth profile of the present invention, a space corresponding to the space 79 is generated in the compression process, but the line 44-45 of the male rotor tooth profile forms an angle θ ₂ (=4 Radius line 3-4 that intersects across ゜~8゜)
An arc of radius R ₄ whose center 54 is located on 4,
Moreover, the center 54 is far away from the straight line 3-4, and is further away from the line 50- of the female rotor tooth profile.
50' is the circular arc 44- of the male rotor tooth profile.
It is a common tangent between the envelope formed by 45 and the circular arc of radius R ₃ or a gentle curve about the same as radius R ₁ , and is the line 42- of the male rotor tooth profile.
Since 43 is an envelope formed by the circular arcs 48-50 of the female rotor tooth profile, the confined volume of the space can be made as small as possible. Further, on the discharge side end face, as both rotors rotate, the portions formed by the envelopes of both tooth shapes separate, thereby communicating the space with the suction side. As a result, when the discharge port is closed immediately before the end of the discharge process, over-compression of compressed air or compression of liquid in the space can be avoided, resulting in noise, abnormal vibration, unexpected wear, and bearing damage. etc. will not occur. Furthermore, the conventional technique proposed by Japanese Patent Application Publication No.
It is not necessary to provide a bypass hole 77 (see Fig. 2b) as described in JP-A-58-214693 and JP-A-58-131383, and the structure is simple.
Moreover, an inexpensive screw compressor can be provided. (c) In the figure, by increasing θ ₂ and forming the center 54 of the circular arc with radius R ₄ far away from the straight line 3-4, the space 18 can be further reduced. That is, while both rotors rotate from the phase shown in FIG. 4a to the phase shown in FIG. 4b, the rate of volumetric expansion of the space 18 is relatively small, so power loss due to vacuum creation is small. (2) Under the condition (j), as shown in Figure 9, the blowhole is so narrow that it hardly poses a problem in practice. In the figure, members having the same reference numerals as those in FIG. 4b are the same as those shown in the same figure, and have the same functions and effects, so a description thereof will be omitted. 72 is a ridgeline where the two cylindrical space peripheral walls provided in the casing 66 intersect, and is also the meshing point of the teeth of both rotors. (3) Based on _the condition (c) above, as shown in FIG . 49-51, the wear resistance is improved compared to a case where the same point of the male rotor tooth profile becomes an inflection point, and the original compression efficiency is maintained over a long period of time. (b) When lubricating oil E is supplied between the contact surfaces of both curves 44-45 and 49-51, since the mutual sliding surfaces are curved in the same direction, a wedge effect is created due to the sliding action. This can improve the lubrication and sealing properties of the surface. (4) From the condition (i) above, (a) The conventionally important points as sealing points [see point 8 on the tooth profile curve in Figure 1b and point 23 on the tooth profile curve in Figure 2a] However, because it was a discontinuous point, it was difficult to accurately measure the position and difficult to process with high precision, but now 44-45 is smoothly connected with a circular arc and a continuous curve , it becomes easy to measure the position, and it is possible to process with high precision. (b) By eliminating discontinuous points on the tooth profile curve, the cutter can be manufactured easily and the service life of the tool can be extended. (5) Based on the conditions in (b), as shown in Fig. 6, the angle θ ₃ between the tangent to the tooth profile curve at point 48 and the straight line connecting the rotation center 4 of the female rotor to point 48 is , that at an approximate point on an arc of radius 17-49 drawn with pitch point 17 as the center,
Since it can be made larger compared to θ' ₃ , the curve 48-
Since the pressure angle near the pitch circle of the tooth profile curve constituting 49 becomes larger, the machining accuracy of the tooth formation shape can be improved and the tool life can be extended. (6) According to the condition (a) above, compared to the case where the center point 53 of the arc 47-48 is on the same side of the arc 48-49 as the center point 52 of the same arc, with reference to FIG. A straight line tangent to the arc 47-48 at point 47 and the rotation center 4 of the female rotor.
Since the angle θ ₄ between the curve and the straight line connecting the point 47 can be increased, the pressure angle near the pitch circle of the arc can be increased, which is effective in improving machining accuracy and tool life. (7) From the conditions (f) and (g) above, in conjunction with the conditions (a) and (b), (a) By creating an envelope curve of arcs 47-48 and 48-50, wear resistance is improved. can improve sex. (b) When lubricating oil is interposed between both sliding surfaces, the fifth
As shown in the figure, the lubricating oil creates a wedge effect due to the sliding of the contact surfaces, which improves the lubrication effect and sealing performance on the same surfaces. As described in detail above, according to the first invention of the present application, the following side tooth profile of the male rotor is measured along the tooth tip to the tooth root side, and the center angle θ is a circular arc with a radius _{R 1 that} has its center at the rotation center of the male rotor and which has its center on a radial line extending from the rotation center of the male rotor to the other end of said arc, and which has said radius R ₁ between the two corners; It is formed by a circular arc with a radius R ₄ drawn so as to be inscribed in the circular arc, and an epicycloid curve created by the intersection of the following side tooth profile of the female rotor and the pitch circle of the same rotor, and the center position of the circular arc with the radius R ₄ . is formed far away from the straight line connecting the rotation centers of each rotor, and the following side tooth profile of the female rotor is formed along a radius that forms part of the following side tooth profile of the male rotor from the tooth bottom to the tooth tip side. Since it is formed by the envelope formed by the arc of R ₄ , the space (vacuum creation space) created at the contact area between the suction side end plate and the male and female rotors when both rotors mesh and rotate can be reduced. is possible,
In addition to reducing power loss due to vacuum creation,
Short-circuit leakage spaces (blowholes) can be virtually eliminated. In addition, in the follow-up side tooth profile of the screw rotor, the lubricating oil applied to the contact surface of the tooth profile curve produces a wedge effect due to the sliding of the contact surface, improving lubricity and sealing performance.
The durability of the sliding surface can also be improved. Further, according to the second invention of the present application, in addition to the above configuration, the forward tooth profile of the female rotor is aligned from the tooth tip to the bottom side on a straight line connecting the rotation centers of each rotor. The apex is at a position outside the pitch circle, the center is on an extension of the straight line that sandwiches the angle of θ ₁ when looking at the above straight line on one side, and the radius R is circumscribed by an arc of radius R ₃ drawn with the above apex as the center. ₂
The forward tooth profile of the male rotor is formed by the circular arc of radius R _{2 and the circular arc of radius R 3} , and the forward tooth profile of the male rotor is formed by the circular arc of radius R ₂ of the forward tooth profile of the female rotor and the circular arc of radius R ₃ Since it is formed by an envelope curve formed by Reduce losses. In addition, short-circuit leakage spaces (blow holes) can be virtually eliminated, and the wedge effect of the lubricating oil supplied to the sliding surfaces provides lubrication to the sliding surfaces in the following tooth profile and advancing tooth profile of the screw rotor. By achieving improved performance and sealing performance, and preventing abnormal vibrations and noises that occur when the discharge port is closed immediately before the end of the discharge process on the inner wall surface of the discharge side casing, and by increasing the pressure angle near the pitch circle, By forming a tooth profile with excellent workability, hobbing becomes easier and the life of the tool can be extended. As described above, according to the present invention, a practically useful screw
rotor can be provided.

[Brief explanation of the drawing]

Figures 1 and 2 are tooth profile curves of conventionally used screw rotors, and Figures 1a and 1b are tooth profile curves used by the present applicant in which the meshing phase of a pair of rotors is different. In this case, Fig. 2a is an example of a tooth profile used by another company, Fig. 2b is a partial sectional view of the discharge side cylinder of a screw compressor, and Figs. 3a and 3b are rotor machines implementing the screw rotor of the present invention. 4a and 4b show the tooth profile curves of a pair of rotors of the screw rotor of the present invention, and when the meshing phases are different, respectively, FIGS. 5 to 8 9 is a drawing showing a part of the tooth profile for explaining the tooth profile curve of the rotor of the present invention, and FIG. 9 is a diagram illustrating the presence or absence of blowholes in the screw rotor of the present invention. 1 ...Male rotor, 2 ...Female rotor, 3 and 4...Rotor rotation center, 15 and 16...Pitch circle, 18...Vacuum creation space.

Claims (1)

[Scope of Claims] 1. A screw rotor consisting of a female rotor and a male rotor that rotate in mesh around two parallel axes, and each tooth profile of the female rotor has a main portion within the pitch circle of the same rotor. Each tooth profile of the male rotor is of a type in which the main portion is formed outside the pitch circle of the rotor, and each tooth profile curve formed in a plane orthogonal to the rotation axis of each rotor has at least The following side tooth profile of the male rotor is a radius centered at the male rotor's rotation center, extending from the tooth tip to the tooth root side, and sandwiching the center angle θ ₂ when looking at one side from the straight line connecting the rotation centers of each rotor. An arc of R ₁ and
A circular arc of radius R ₄ inscribed in the circular arc of radius R ₁ drawn with the center on the radius line connecting the circular arc end and the rotation center of the male rotor, the following side tooth profile curve of the female rotor, and the pitch circle of the same rotor. _An epicycloid curve created by the intersection with A screw rotor characterized in that the envelope line is formed by an arc of radius R ₄ that forms a part of the following side tooth profile of the male rotor along the tooth bottom to the tooth tip side. 2. A screw rotor consisting of a female rotor and a male rotor that rotate in mesh around two parallel axes, each tooth profile of the female rotor having its main portion formed within the pitch circle of the same rotor, and the male rotor Each tooth profile is of the type in which the main part is formed outside the pitch circle of the same rotor, and among the tooth profile curves formed in the plane orthogonal to the rotation axis of each rotor, the tooth profile on the forward side of the female rotor is , along the tooth tip to the tooth bottom side, on the straight line connecting the rotation centers of each rotor, with the apex at a position outside the pitch circle of the female rotor, and a straight line sandwiching the angle θ ₁ when looking at the straight line on one side. The tooth profile on the following side consists of an arc of radius R ₂ circumscribing an arc of radius R ₃ drawn with the apex as the center, and an arc of radius R ₃ . It is formed by an envelope formed by an arc of radius R ₄ that extends from
While the arc of R ₃ and the envelope are connected smoothly or by a common tangent, the forward tooth profile of the male rotor has a radius R ₂ of the forward tooth profile of the female rotor along the tooth root to the tooth tip side.
An envelope formed by an arc of radius R 3 and an envelope formed by an arc of radius R ₃ , and the following tooth profile runs from the tooth tip to the root side,
Looking at the straight line connecting the rotation centers of each rotor on one side, there is a circular arc with a radius R ₁ centered on the male rotor's rotation center, sandwiching the center angle θ ₂ , and an arc with a radius R ₁ from the male rotor rotation center on the other end. The radius inscribed in the arc of radius R ₁ drawn with the center on the extended radius line
The radius R ₄ is composed of an epicycloid curve created by the intersection of the circular arc of R 4 and the following tooth profile of the female rotor and the same pitch circle, and also forms a part of the following tooth profile of the male rotor _. A screw rotor characterized in that the center position of the arc of is formed far away from the straight line connecting the rotation centers of each rotor.