JPH0319919B2 - - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pair of screw rotors used in a screw machine that transports a compressible fluid while compressing or expanding it, and in particular to its tooth profile. Prior Art A screw rotor with an asymmetric tooth profile, which is generally used in compressors for compressible fluids, has 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 is meshed with a female rotor with a slightly larger number of teeth than that of the male rotor, and the diameter of the tip of the male rotor is adjusted. and the pitch circle diameter of the female rotor are set to be approximately equal. A pair of screw rotors of this type are constructed 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 shorter than the sum of their radii. In addition, it is rotatably housed in a casing having 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 fluid is supplied to the required locations. A screw compressor or expander is constructed by providing a suction port and a discharge port. [See Figures 3a and 3b] When the above 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 the female rotor,
Among the curves that form the tooth grooves, the curve on the front side in the rotational direction is called the forward side tooth profile, and the curve on the rear side in the rotational direction is called the follower tooth profile. The curved line will be referred to as the advancing side tooth profile, and the curve on the rear side in the rotational direction will be referred to as the following side tooth profile. When the device is used as an expander, the names of the respective curves are reversed; however, in the specification of the present invention and the explanations in the drawings, the names related to the tooth profile curves are explained in accordance with the above definitions in all cases. do. Figures 1a and 1b show each tooth profile curve seen when the rotor is cut by a plane perpendicular to the rotational axis of the screw rotor, that is, the tooth profile of the screw rotor at the end surface of the longitudinal axis of each rotor. This shows the meshing state, and Figure 1a shows the phase of the tooth profiles of both rotors immediately after the female rotor tooth profile following side tooth tip curve and the male rotor tooth profile following side tooth tip curve begin to contact. Then, the male rotor rotates about 20 degrees and rotates through the phase shown in Figure 1b, that is, the state in which the highest part of the tooth profile curve of the male rotor and the deepest part of the tooth profile groove of the female rotor are opposed to each other. The above-mentioned tooth profile curve is a tooth profile that has been practiced 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 centered around their respective rotation centers (pitch circle centers) 3 and 4, By rotating in the direction of the arrow within the casing (not shown), it functions as a fluid compressor. 15 and 16
are male rotor 1 and female rotor 2 , respectively.
The straight line connecting the rotation centers 3 and 4 of the pitch circle passes through the tangent point 17 of the pitch circles 15 and 16, that is, the pitch point 17. Referring to Figure 1b, (1) Female rotor tooth profile (a) Forward curve; on straight lines 3 and 4, from point 12 at the deepest point in the tooth profile center of the female rotor to tip 1 of the tooth profile
0 direction, centering on pitch point 17 r ₄
A circular arc 11-1 with radius r 4 passes through the rotation center ₄ of the female rotor between the circular arc 11-12 having a radius of
Formed by straight lines 10 to 11 that are in contact with 2,
The curve between 12 and 13 at the bottom of the female rotor groove is
Radius R ₂ centered on the rotation center 4 of the female rotor
The outer diameter of the tip circle is made to match the pitch circle 16 of the female rotor. (b) Follow-up side curve: 1 on the follow-up side of the female rotor groove
Let curves 3 to 14 be epitrochoid curves created by point 8 on the tooth profile of the male rotor. It is formed by smoothly connecting the above curves. (2) Male rotor tooth profile (a) Advance side curve; center apex 7 of male rotor tooth profile
The curve from to point 5 toward the tooth root side is
The center is the contact point (pitch point) 17 of the pitch circles 15 and 16 of both the female and male rotors, and the radius is
Let it be a circular arc whose radius is _r3 , which is smaller than r4 by the amount of clearance required for rotation, and let the area from point 6 to tooth base 5 be the envelope formed _by the straight line between tooth tips 10 and 11 of the female rotor. . (b) Follow-up side curve: The curve between points 7 and 8 on the follow-up side of the male rotor tooth profile is a circular arc whose center is the male rotor's rotation center (center of the pitch circle) 3 and radius R ₁ , and the tooth profile starts from point 8. The curve leading to origin 9 is
By making the epicycloid curve created by the opposing point 14 on the tip of the tooth of the female rotor, and making the diameter between 9 and 5 of the bottom of the tooth groove coincide with the pitch circle 15 of the male rotor, point 8 is ,
The contact line of both the female and male rotors on the ridge line along the thread is determined so as to reach the intersection line of the compression chamber closing side of the cylinder that accommodates both rotors.
Further, the point 8 is formed far away from the straight line (X axis) connecting the rotation centers 3 and 4 of each rotor. Since the conventional tooth profile shown in Figure 1b is defined as described above, (a) blowholes between the working spaces can be made substantially zero. (b) Point 8 of the male rotor tooth profile as shown in Figure 1b.
By forming the space 18 far away from the X axis, the volume expansion rate of the space 18 created at the tooth-shaped contact area between the low-pressure side end plate and the male and female rotors as the rotor rotates will be as described below. So-called
Since it is smaller than the SRM tooth profile, there is no power loss due to vacuum generation effect based on volumetric expansion. While there are advantages, the following problems have also been pointed out. In other words, (c) the space volume is small (the stroke volume is small). (d) Because the groove bottom of the female rotor tooth profile is uneven,
It cannot be said that the sealing performance is good, and it is difficult to measure dimensions during processing. Furthermore, the profile of the cutter is uneven and complicated, resulting in poor processing efficiency. (E) Since the curve on the follower side of the tooth profile is created as a point, the sealing point is easily worn and the sealing effect is difficult to maintain (efficiency decreases with long-term use). (f) Since the pressure angle of the tooth profile near the pitch circle becomes almost 0, it is difficult to machine the tooth profile with high precision, and the life of the machining tool is shortened. Especially when hobbing a screw rotor, the life of the hobbing tool is shortened. Note that the contact surface 18' in the initial meshing phase of both tooth profiles shown in FIG. 1a becomes space 18 in the phase shown in FIG.
As a result of creating a vacuum space in this part, the power required for this (unrelated to the compression operation) is consumed, so it is preferable that the volume of the space 18 is not increased. The characteristic tooth profile described above has a smaller rate of volumetric expansion than those described below. 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, and in the figure, the components with the same symbols as in Figure 1 are the same members as those in Figure 1. Therefore, its explanation will be omitted. Note that the meshing phase of the tooth profile in FIG. 2a corresponds to that shown in FIG. 1b. In the same figure, (1) Female rotor tooth profile (a) Advance side curve 28-29: Circular arc with radius r' ₁ centered on point 36 on straight line 17-29, 29-30: Centered on pitch point 17 radius
arc of r′ ₂ . (B) Follow-up side curve 30-31; Epitrochoid curve based on point 23 on the tooth profile of the male rotor, 31-32; Part of a straight line passing through the rotation center 4 of the female rotor, 32-33; Centered on the pitch circle 16. 33-34; An arc centered on the rotation center 4; 34-35; An arc centered on the pitch circle 16. (2) Male rotor tooth profile (a) Advance side curve 21-22; female rotor tooth profile 28-29 (radius centered on point 36 on straight line 17-29)
Envelope curve by arc of r' ₁ ), 22-23; radius centered at pitch point 17
arc of r′ ₂ . (b) Follow-up side curve 23-24; Epitrochoid curve by point 31 on the female rotor tooth profile, 24-25; Generation curve by straight line 31-32, 25-26; Circular arc having its center on pitch circle 15, 26- 27; Arc centered on the rotation center 3; 27-28; Arc centered on the pitch circle 15. However, the volume of the illustrated vacuum space (vacuum creation space) 18 is, compared to the tooth profile illustrated in No. 1b,
It has become a much bigger thing. Furthermore, when both the female and male rotors are in the rotational position shown in Figure 2a, both rotors are at points 31 and 3.
They are in contact at three locations 0 and 76 with a slight clearance that does not cause leakage from the working space. The three contact points create a space 7 on the forward side of the tooth profile (above the X axis in the figure).
8 is formed, and a space 18 is similarly formed on the following side of the male rotor tooth profile (below the X axis). Now, on the suction side end face 74 (see Figure 3) side, 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 78 gradually reduces its volume as both rotors rotate, and eventually reaches a volume close to zero. Therefore, the gas trapped in the space 78 is abnormally pressurized, and in the case of an oil-cooled rotary compressor, the gas trapped in the space 78 is compressed by the female and male rotors and the cylinder wall in the closed space. The lubricating oil injected for cooling, sealing, and lubrication remains in the formed compression space.
Under the state of liquid compression, the female and male rotors generate abnormal vibrations and noise, which in extreme cases accelerates 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, in the past, special public
As described in Japanese Patent Publication No. 58-214693 and Japanese Patent Publication No. 58-131388, referring to FIG. 2b, a bypass hole 77 is bored in the inner wall surface 75 of the discharge side casing, and a separate Means is provided to allow the residual gas and lubricating oil to escape into the 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. The structure becomes complicated,
It had the disadvantage of high cost. Purpose: Therefore, the screw rotor of the present invention solves the problem without losing the advantages of the tooth profile shown in FIG. In particular, in order to prevent wear of the sealing points so that there is no reduction in efficiency during long-term use, on the inner wall surface of the discharge side casing, when the discharge port is closed immediately before the end of the discharge process, Preventing abnormal vibrations and noise caused by the reduction of the closed space that is formed,
The purpose is to provide a new tooth profile that ensures smooth and overload-free operation and solves problems in cutting. The detailed configuration and effects thereof will be made clear in the description of the following examples. Configuration The present invention provides a screw rotor consisting of a pair of female and male rotors that rotate in mesh around two parallel axes, wherein the main part of each tooth profile of the female rotor is located within its pitch circle. of the female rotor, and the main part of each tooth profile of the male rotor is formed outside the pitch circle, in each tooth profile curve formed in a plane orthogonal to the rotation axis of each rotor, at least A part of the curve of the trailing tooth profile is an envelope formed by an arc of radius R ₄ that forms part of the trailing tooth profile of the male rotor, along the tooth bottom to the tooth tip side, and the female rotor. It is a circular arc with a radius R ₇ centered on the outside of the concave shape of the tooth groove, and the curve of a part of the trailing side tooth profile of the male rotor runs from the tooth tip to the root side, and the rotation center of each rotor. Radius centered at the center of rotation of the male rotor, sandwiching the center angle θ ₂ when looking at the straight line connecting them on one side.
an arc of radius R ₅ , and an arc of radius R ₄ that has its center on a radial line extending from the rotation center of the male rotor to the other end of said arc and is tangent to an arc of radius R ₅ drawn around said rotation center; , the envelope formed by the arc of radius R ₇ of the trailing tooth profile of the female rotor, and the center of the arc of radius R ₄ forming the trailing tooth profile of the male rotor is the center of rotation of each rotor. A screw rotor is characterized by being formed far away from the straight line connecting the two. 2 A screwdriver consisting of a female rotor and a male rotor that rotate in mesh around two parallel axes.
In a type of rotor in which the main part of each tooth profile of a female rotor is formed within the pitch circle, and the main part of each tooth profile of a male rotor is formed outside the pitch circle, the rotation axis of each rotor In each tooth profile curve formed in a plane _orthogonal to an envelope formed by a circular arc, a circular arc with a radius R ₇ having a center on the outside of the concave shape of the tooth space of the female rotor, and the circular arc with a radius R ₇ ,
The tooth profile on the forward side of the female rotor is located on a straight line connecting the rotation centers of each rotor from _the tooth bottom to the tooth tip, and the female rotor An arc having a radius R 1 and having a center outside the pitch circle of the rotor and sandwiching a corner having a center angle θ ₁ when looking at the straight line on one side, and _the radius R ₁
An arc of radius R ₂ that has a center on the opposite side of the center point of the arc and is tangent to the arc of radius R ₁ ,
It has a center on the outside of the concave shape of the tooth groove of the female rotor,
It consists of the circular arc with radius R ₂ and the circular arc with radius R ₆ that is in contact with the pitch circle, and the tooth bottom of the female rotor is formed by the circular arc with radius R ₁ and the circular arc with radius R ₄ . On the other hand, the following side tooth profile of the male rotor is connected to the envelope line by a common tangent line or a smooth curve.On the other hand, the following side tooth profile of the male rotor is An arc of radius R ₅ that is centered at the rotation center of the male rotor, sandwiching an angle θ ₂ , and a circular arc that has its center on a radial line extending from the rotation center of the male rotor to the other end of the arc, and has its center on the rotation center of the male rotor. _{An envelope formed by an arc of radius R 4 tangent} to an arc of radius R ₅ drawn with
Similarly, the center of the arc of radius R ₄ , which forms the envelope formed by the circular arc of radius R ₈ and forms the following side tooth profile of the male rotor, is far away from the straight line connecting the rotation centers of each rotor. The forward tooth profile of the male rotor is the same as the radius of the forward tooth profile of the female rotor from the tooth tip to the root side.
An envelope formed by an arc of radius R ₁ and an envelope formed by an arc of radius R ₂ ,
A screw rotor is also characterized in that it consists of an envelope formed by an arc of radius R ₆ , and one embodiment thereof 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.
The figure is a side sectional view along line A-A in figure b,
FIG. 3b is a cross-sectional view taken along the line BB shown in FIG. 3a. In the figure, 1 is a male rotor that is rotationally driven by a rotating shaft 60 connected to a drive device (not shown), and the shaft 60 is connected to the rotor 1.
The rotor 1 is rotatably supported by bearings 64 and 65 of each end plate 62 and 63 in cooperation with a support shaft 61 extending in a symmetrical position. Reference numeral 2 denotes a female rotor that meshes with the male rotor 1 , and the rotor 2 is also rotatably supported by 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 high-pressure side end plate having a discharge port 68 on its longitudinal end face. 63, and a working space 69 is formed and divided by the rotor tooth groove surface, the inner wall of the casing, and the inner sides of both end plates. The working space 69 includes a low-pressure passage 70 and a high-pressure passage 7 for the working fluid in the casing.
1, a suction port 67 and a discharge port 68 respectively communicate with
has. 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 are A ridgeline 72 appears at the intersection. The female rotor 2 has six grooves in which each helical groove runs along the rotation axis (longitudinal) direction and is usually twisted by 200 degrees around the axis, and the grooves are located inside the pitch circle 16 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 by the groove surface and tooth surface of the rotor, their engagement line, and the inner surface of the high-pressure side end plate.
After the communication between the suction port 67 of No. 2 and the working space is closed, the volume of the partitioned working space is closed due to the movement of the meshing line of both rotors (relatively as the rotors rotate). The compressible fluid, which has been compressed and has become high pressure due to the reduction of the working space, is transferred to the high pressure chamber 71 side. Exhale. 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 is characterized by the tooth profile curves of both rotors used in the above-mentioned compressor, and FIG. It shows four states of a pair of tooth profile curves with different meshing phases when cut by a plane perpendicular to the axis, and Fig. 4e is an enlarged view of the tooth profile of the tooth bottom of the female rotor and the tooth tip of the male rotor. be. Moreover, the meshing phase progresses in the direction from figure a to figure d. In the figure, 1 is the male rotor, _On is the rotation center of the rotor, 15 is the pitch circle of the rotor, and male rotor 1 is the rotation center.
Rotate in the direction of the arrow (clockwise) around _On . 2 is a female rotor that meshes with the male rotor 1 and rotates in the direction of the arrow (counterclockwise) around the rotation center _Of . 16 is a pitch circle of the rotor 2 , which is in contact with the pitch circle 15 on the straight line connecting the rotation centers On _{and Of} of both rotors. The above point is pitch point _O3 . Note that 18, _18-1 , _18-2 ... are vacuum created spaces generated at the contact portions of the tooth profile curves of both rotors. In Figure 4d, (a) tooth profile of the female rotor, (a) trailing side tooth profile, along the tooth root to tooth tip side, (1) C ₂ −B ₂ ; part of the tooth profile curve of the male rotor;
Envelope by arc C ₁ −B ₁ with radius R ₄ .
It touches the curve B ₂ −A ₂ at point B ₂ . (2) B ₂ −A ₂ ; Radius R having the center point O ₇ on a straight line perpendicular to the envelope C ₂ −B ₂ at point B ₂ and on a tangent to the pitch circle 16 of the female rotor. ₇ arc and touches the curve A ₂ − H ₂ at point A ₂ . (3) A ₂ −H ₂ ; A circular arc with a small radius R ₈ and having its center O ₈ on the straight line connecting the points O ₇ and A ₂ above. (b) Along the tooth profile on the advancing side, from the root to the tooth tip, (4) C ₂ −E ₂ ; On the straight line connecting the rotation center O _n of the male rotor and the rotation center O _f of the female rotor,
Point located outside pitch circle 16 of female rotor
An arc of radius R ₁ with angle θ ₁ centered at O ₁ .
It touches the curve E ₂ −F ₂ at point E ₂ . Here, θ ₁ = 40° ~ 46°, 1.05≦
R ₁ /R ₅ -1/2PCD≦1.3 However, PCD is the pitch circle diameter of the male rotor. The larger R ₁ /R ₅ −1/2PCD is than 1, the smaller θ ₁ , the smaller C ₂ −E ₂
The pressure angle near the pitch circle of the tooth profile curve constituting can be increased (see also Figures 7 and 8), and the closer R ₁ /R ₅ -1/2PCD is to 1, the more θ The larger ₁ is, the thicker the teeth of the female rotor can be. In this example, R ₁ is the range in which the pressure angle can be made sufficiently large and a tooth thickness sufficient in terms of strength can be ensured.
The above range is selected for and θ ₁ . (5) C′ ₂ −D′ ₂ ; Envelope B ₂ −C 2 formed by arc B ₁ −C ₁ which is a part of the tooth profile curve of the male rotor (point C ₂ on the line is also a straight line _{Of −O )} and a radius on the straight line O _f −O _n with the center O ₁ outside the pitch circle 16.
Common tangent of R ₁ with arc D ₂ −E ₂ . Note that the distance between C' ₂ and D' ₂ may be smoothly connected using a gentle curve having the same radius as R ₅ . (6) E ₂ −F ₂ ; An arc with radius R ₂ centered on point O ₂ located on the extension of the straight line connecting points O ₁ and E ₂ . It touches the curve F ₂ −G ₂ at point F ₂ . (7) F ₂ −G ₂ ; Centered on the straight line connecting points O ₂ and F ₂
An arc of radius R ₆ with O ₆ . Curve G ₂ at point G ₂
-Touches _H2 . (8) G ₂ −H ₂ ; Matches the outer diameter. Curve at point H ₂
Touches A ₂ − H ₂ . The width of G ₂ − H ₂ is PCD×
(0.004 to 0.01) mm. (b) Male rotor tooth profile curve (a) The trailing side tooth profile, along the tooth tip to the root side, (9) D ₁ −C ₁ ; Central angle θ ₂ around the rotation center O _n of the male rotor , an arc of radius R ₅ . It touches the curve C ₁ −B ₁ at point C ₁ . Among the above, θ ₂ = 4° to 8° The larger θ ₂ is, the smaller the space 18 can be, and the smaller θ ₂ is, the smaller the curves D ₁ −C ₁ , C′ ₂ −D′ ₂ , the gap between the male and female rotors can be reduced. In this embodiment, the space 18 can be made sufficiently small, and the curve C' ₂
The above range for θ _{2 is shown as a range in which the gap between the male and female rotors between −D′ 2 can} be made to such an extent that it does not pose a problem in practice. (10) C ₁ −B ₁ ; Point C ₁ on the male rotor tooth profile curve
An arc D ₁ − with the center O ₄ on the straight line connecting the rotation center O _n of the same rotor and the radius R ₅ above
An arc of small radius R ₄ tangent to C ₁ . It touches the curve B ₁ −A ₁ at point B ₁ . (11) B ₁ −A ₁ ; Envelope of arc B ₂ −A ₂ which is a part of female rotor tooth profile. Curve A ₁ at point A ₁
-Touches H ₁ . (12) A ₁ −H ₁ ; Part of female rotor tooth profile, arc
Envelope due to A ₂ − H ₂ . (b) Progressive tooth profile, along the tooth tip to tooth root side, (13) D ₁ −E ₁ ; Envelope line by arc C ₂ −E ₂ that is a part of the female rotor tooth profile. Curve E ₁ at point E ₁
−F ₁ and touches the curve D ₁ −C ₁ at point D ₁ . (14) E ₁ −F ₁ ; Part of female rotor tooth profile, arc
Envelope due to E ₂ −F ₂ . Curve F ₁ − G ₁ at point F ₁
come into contact with (15) G ₁ −H ₁ ; Matches the tooth root diameter. Curve at point H ₁
Touches A ₁ − H ₁ . As an example, each radius and angle in the tooth profile shown in FIG. 4 is shown in Table 1. [Table] Pitch circle diameter effect of [Table] Since the screw rotor tooth profile curve of the present invention is formed as described above, (1) The center point O ₄ of the arc C ₁ −B ₁ with radius R ₄ is By providing it on the radial line extending from the rotation center O _n of the male rotor, the point C _1
The angle _{θ 7} formed by _{the tangent} line _at The trailing side tooth profile curve is far away from the straight line Of _{- O n} connecting the rotation centers of both rotors and approaches the female rotor trailing side tooth profile curve, so that the space 18 can be made smaller. (2) The center point of the arc C ₁ −B ₁ in relation to the central angle θ ₂
Since O ₄ is formed at a large distance from the straight line _Of - O _n , the space 18 can be further reduced. As described above, as shown in Figures 4b to 4c, the rate at which the volume of the space 18 expands as the two rotors rotate is small, so the loss of power consumed in creating the vacuum is small. (3) Based on the conditions stated in item (2), the space 78 on the forward side of the male rotor tooth profile formed when the discharge port is closed immediately before the end of the discharge process due to the meshing of both the female and male rotors [Fig. 2a] [Reference]], a communication passage having a small area that does not reduce its performance is formed between the thread of the rotor and the adjacent working space on the suction side (low pressure side). Therefore, the overcompressed gas trapped in the space 78 and the remaining lubricating oil for seals, etc. are discharged into the adjacent low-pressure side working space through the communication path, so that the discharge port is closed immediately before the end of the discharge process. At times, overcompression of compressed gas and compression of liquid within the space 78 are eliminated, and accompanying noise, abnormal vibration, unexpected wear, and bearing damage do not occur. Furthermore, the prior art proposed in JP-A-58
It is possible to provide a screw compressor that does not require the provision of a bypass hole 77 (see Figure 2b) as described in Japanese Patent Laid-open No. 214693 and Japanese Patent Application Laid-open No. 131383/1983, has a simple structure, and is inexpensive. can. (4) Let the curve B ₁ −A ₁ be the envelope of the arc B ₂ −A ₂ which is a part of the female rotor tooth profile curve, and let the arc A ₂
−H ₂ is an arc with a small radius R ₈ , so the fourth
Referring to Figure a, the blowhole can be made to a size that does not pose a problem in practice. In addition, in the same figure, 1 is the male rotor, O _n is its center of rotation,
15 is the pitch circle of the male rotor, 2 is the female rotor, _Of is its rotation center, 16 is the pitch circle of the female rotor, 66 is the casing of both rotors,
72 is a ridgeline where the male and female rotor inner wall surfaces of the casing intersect. (5) Referring to Fig. 6, the curve B ₂ - _{A 2} is an arc having the center O ₇ outside the concave shape of the tooth space of the female rotor, so the curve shown in Figs. 4d and 6
The profile of the cutter that cuts and forms the tooth profile of the same rotor is much smaller than when C ₂ - B ₂ is extended to the top of the pitch circle 16 or when the straight line connecting the center of rotation _Of and point B ₂ is extended to the pitch circle 16. Since the skirt tends to widen and the pressure angle θ ₃ can be increased, the machining accuracy of the tooth profile can be improved and the tool life can be extended. (6) The pressure angle θ ₃ near the pitch circle is expressed as the arc B ₂ −A ₂
can be made larger than θ' ₃ when extended to H' ₂ above the pitch circle 16, which improves the machining accuracy of the tooth profile and extends the tool life. (7) Referring to Fig. 7, the angle θ ₄ between the tangent to the tooth profile curve at point E ₂ and the O _f −E ₂ straight line is calculated using the arc C ₂
−E ₂ can be made larger than the similar angle θ′ ₄ when the center is on the pitch circle 16, so C ₂
-The pressure angle near the pitch circle of the curve forming ₂ can be increased. (8) Referring to Figure 8, the angle θ ₅ between the tangent to the tooth profile curve at point F ₂ and the Of _{−F 2} straight line can be increased (θ ₅ > θ′ ₅ ). The pressure angle near the pitch circle of the curve composing E ₂ −F ₂ can be increased. (9) Referring to Figure 9, the F ₂ - G ₂ curve is an arc with the center O ₆ outside the concave shape of the tooth space of the female rotor, so the arc E ₂ - _{F 2} can be directly converted into a pitch circle 1.
Compared to the case where the length is extended to 6, damage to the side surface of the hob cutter during hobbing of the rotor can be prevented, the life of the tool can be extended, and the machining accuracy of the tooth profile can be improved. (10) The tangent line of the tooth profile curve at point _G2 on the same curve,
The angle θ ₆ formed with the _Of − G ₂ straight line can be increased (θ ₆ >θ′ ₆ ), and the pressure angle around the pitch circle of the curve forming F ₂ −G ₂ can be increased. As described above, the pressure angle of the tooth profile curve can be increased, the machining accuracy of the tooth profile can be improved, and the tool life can be extended. (11) Arc B ₂ −A ₂ , A ₂ −H ₂ , C ₂ −E ₂ , E ₂ −F ₂ ,
The respective tooth profile curves meshing with F ₂ −G ₂ and C ₁ −B ₁ are defined by envelopes B ₁ −A ₁ , A ₁ −H ₁ , D ₁ −E ₁ , E ₁ formed by circular arcs, respectively. −F ₁ , F ₁ −
Since G ₁ and C ₂ −B ₂ are set, wear resistance can be improved. (12) Referring to Figure 10, as mentioned above, if the sliding surfaces curve in the same direction and lubricant e is supplied between them, the movement of both sliding surfaces causes the oil to , it can produce a wedge effect and improve the lubrication of the tooth surface and the sealing performance of the sliding surface. (13) Conventionally, although it is an important sealing point, it is a discontinuous point [see number 8 in Figure 1b and number 23 in Figure 2], so not only calipers and micrometers but also three-dimensional measurement methods have been used. However, since the tip of the filler f was spherical, it was difficult to measure the position accurately. That is, FIG. 11a, FIG. 11b
11c, if there is a discontinuous point in the tooth profile curve, the exact position of the discontinuous point cannot be determined because the position of contact with the filler f cannot be determined even when measuring the same point. However, C ₁ −B ₁
If the curve is an arc and a continuous curve, such a problem will not occur and measurement will be easier.
Therefore, it is easy to process and form an accurate tooth profile curve. As detailed above, according to the first invention of the present application, a part of the trailing side tooth profile curve of the female rotor is traced from the tooth bottom to the tooth tip side, and a part of the trailing side tooth profile of the male rotor is An envelope formed by an arc of radius R ₄ and an arc of radius R ₇ having its center outside the concave shape of the tooth space of the female rotor,
A part of the male rotor's follow-up side tooth profile curve, along the tooth tip to the tooth root side, and the center of rotation of the male rotor is located at a center angle of θ ₂ when looking at one side with a straight line connecting the rotation centers of each rotor. An arc of radius R ₅ with center at and
An arc with a radius R 4 that has its center on a radial line extending from the rotation center of the male rotor to the other end of the arc and is tangent to an arc with a radius R ₅ drawn with the rotation center as the center, and the following side of the _female rotor. The rotation center of each rotor is the center of the circular arc of radius R ₄ that forms part of the tooth profile and the envelope of the circular arc of radius R ₇ that forms the following side tooth profile of the male rotor. Since it is located far away from the straight line connecting the two, the space created at the contact area between the suction side end plate and the male/female rotor (vacuum creation space) can be reduced, reducing the power loss spent on creating the vacuum, and preventing short circuits. The leakage space (blowhole) can be made smaller, and the lubricity and durability of both sliding surfaces can also be improved due to the wedge effect of the lubricating oil on the follower side tooth profile of the screw rotor. Further, according to the second invention of the present application, the following tooth profile of the female rotor is formed by an arc of radius R ₄ that forms a part of the following tooth profile of the male rotor along the tooth bottom to the tooth tip side. The envelope formed,
A female rotor is formed by a circular arc with a radius R ₇ having a center O ₇ on the outside of the concave shape of the tooth groove of the female rotor, and a circular arc with a small radius R _{8 that is in contact with the circular arc with the radius R 7 and} its pitch circle 16. The forward tooth profile of the tooth is centered on the straight line connecting the rotation centers of each rotor along the tooth bottom to the tooth tip side, outside of the pitch circle of the female rotor.
O ₁ , with a radius R ₁ sandwiching _{the center angle θ 1 when} looking at the straight line on one side; _an arc of radius R ₂ that is tangent to the arc of ₁ ;
The tooth bottom of the female rotor is formed by a circular arc with a radius R ₆ that is in contact with the pitch circle 16, and the tooth bottom of the female rotor is formed by a common tangent between the envelope formed by the circular arc with the radius R ₁ and the circular arc with the radius R ₄ . On the other hand, connect the male rotor's trailing side tooth profile from the tooth tip to the root side, and sandwich the center angle θ ₂ between the straight line connecting the rotation centers of each rotor on one side. A circular arc with a radius R ₅ having its center at the rotation center, and a circular arc with a radius R ₅ centered on the rotation center and having its center on a radial line extending from the rotation center of the male rotor to the other end of said arc. A tangent arc of radius R ₄ and
An envelope formed by an arc of radius R ₇ of the trailing side tooth profile of the female rotor and an envelope formed by a circular arc of radius R ₈ , and the advancing side tooth profile of the male rotor is Radius R ₁ of the forward tooth profile of the female rotor from the tooth tip to the root side
The envelope formed by the arc of and also the radius
A radius formed by an envelope formed by an arc of radius R ₂ and an envelope formed by an arc of radius R ₆ , forming the following side tooth profile of the male rotor.
Since the center of the arc of _R4 is located far away from the straight line connecting the rotation centers of each rotor, the space created at the contact area between the suction side end plate and the male and female rotors (vacuum creation space) can be reduced, and the vacuum It is possible to reduce the power loss spent on formation, reduce the short-circuit leakage space (blowhole), and prevent abnormal vibrations and noise that occur when the discharge port is closed on the inner wall surface of the discharge side casing immediately before the end of the discharge process. , the lubricating oil creates a wedge effect on the following tooth profile and the advancing tooth profile of the screw rotor, improving lubricity, sealing performance, and durability, and further increasing the pressure angle of the tooth profile curve. Therefore, the machinability of the tooth profile curve is excellent, the life of the hobbing tool can be extended, and hobbing can be easily performed. That is, 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 Figure 1a,
FIG. 1b shows that when a pair of rotors with tooth profiles used by the applicant's company have different meshing phases, the second
Figure a is an example of a tooth profile used by another company, Figure 2b is a partial sectional view of its discharge cylinder, and Figures 3a and 3b are a side sectional view and a cross sectional view of a rotor machine equipped with the screw rotor of the present invention. Figures 4a to 4d show the tooth profile curves of a pair of rotors in an embodiment of the screw rotor of the present invention, in which the meshing phase changes in the direction from figure a to figure d, respectively. Fifth
10 are partially enlarged explanatory diagrams of tooth profile curves for explaining the characteristics of the screw rotor tooth profile curve of the present invention, and FIGS. 11a to 11c are explanatory diagrams for measuring rotor tooth profile curves. 1...Male rotor, 2...Female rotor, On _{and Of} ...Rotor rotation center, 15 and 16
...Pitsuchien, 18...Vacuum creation space.

Claims (1)

[Scope of Claims] 1. A screw rotor consisting of a pair of female and male rotors that rotate in mesh around two parallel axes, wherein the main part of each tooth profile of the female rotor lies within its pitch circle. In the case of a type in which the main part of each tooth profile of the male rotor is formed outside the pitch circle, at least the tracking of the female rotor in each tooth profile curve formed in a plane orthogonal to the rotation axis of each rotor. The curve of a part of the side tooth profile is defined by an envelope formed by an arc of radius R 4 that forms part of the trailing side tooth profile of the male rotor, along the tooth root side and the tip side of the tooth, and an envelope line formed by a circular arc with a radius of R ₄ that forms part of the trailing side tooth profile of the male rotor. It consists of a circular arc with a radius of R ₇ centered on the outside of the concave shape of the tooth space, and the curve of a part of the trailing side tooth profile of the male rotor runs from the tooth tip to the root side, and the center of rotation of each rotor. An arc of radius R ₅ centered at the rotation center of the male rotor, sandwiching a corner with a center angle θ ₂ when the connecting straight lines are viewed on one side, and a radius line extending from the rotation center of the male rotor to the other end of the arc. , and consists of an envelope formed by an arc of radius R ₄ tangent to an arc of radius R ₅ drawn around the center of rotation, and an arc of radius R ₇ of the trailing side tooth profile of the female rotor. ,and,
The radius R ₄ forming the following side tooth profile of the male rotor
A screw rotor characterized in that the center of the arc of is formed far away from the straight line connecting the rotation centers of each rotor. 2. A screw rotor consisting of a female rotor and a male rotor that rotate in mesh around two parallel axes, and the main part of each tooth profile of the female rotor is as follows:
In the case of a type in which the main part of each tooth profile of the male rotor is formed within the pitch circle, and the main part of each tooth profile of the male rotor is formed outside the pitch circle, the tooth profile curve formed in the plane perpendicular to the rotation axis of each rotor has a small In both cases, the trailing side tooth profile of the female rotor is an envelope formed by an arc with a radius R ₄ that forms a part of the trailing side of the male rotor along the tooth bottom to the tooth tip side.
The tooth profile on the forward side of the female rotor consists of a circular arc with a radius R ₇ centered on the outside of the concave shape of the tooth groove of the female rotor, the circular arc with the radius R ₇ , and a small circular arc with a radius R ₈ that is tangent to the pitch circle. is located on the straight line connecting the rotation centers of each rotor along the tooth bottom to the tooth tip side, and has its center outside the pitch circle of the female rotor, and when the straight line is viewed on one side, the central angle θ is _{A circular arc with a radius R 1 sandwiching a} corner of
An arc of radius R ₂ that is tangent to an arc of R ₁ and has a center on the outside of the concave shape of the tooth space of the female rotor, and has said radius R ₂
and an arc of radius R ₆ that is tangent to the pitch circle, and the tooth bottom of the female rotor has a radius of
A common tangent or a smooth curve connects the arc of R ₁ and the envelope formed by the arc of radius R _4. On the other hand, the following side tooth profile of the male rotor is Along the side, an arc of radius R 5 centered at the center of rotation of the male rotor, sandwiching an angle of center angle θ ₂ with a straight line connecting the rotation centers of each rotor on one side, and an arc of radius R ₅ from the center of rotation of the male rotor to the a circular arc with a radius R ₄ that has its center on a radial line extending to the other end of the circular arc and is in contact with a circular arc with a radius R ₅ drawn around the rotation center;
Consists of an envelope formed by an arc of radius R ₇ of the female rotor's trailing side tooth profile and an envelope formed by a circular arc of radius R ₈ , and also forms the male rotor's trailing side tooth profile. The center of the circular arc with radius R ₄ is formed far away from the straight line connecting the rotation centers of each rotor, and the forward tooth profile of the male rotor is formed along the tooth root side from the tooth tip to the forward tooth profile of the female rotor. radius of R ₁
The envelope formed by the arc of and also the radius
A screw rotor comprising an envelope formed by an arc of radius R ₂ and an envelope formed by an arc of radius R ₆ .