JPWO2005113984A1 - Screw rotor and screw fluid machine - Google Patents

Abstract

An object of the present invention is to provide a screw-type fluid machine in which the leakage of the screw-type fluid machine is always constant during operation, that is, the clearance of the exhaust chamber is always kept substantially constant. Therefore, in the screw-type fluid machine, the axially perpendicular cross-sectional shape (805) of the tooth profile of the screw rotor, the arc (1) constituting the root, the arc (3) constituting the outer circumference, the outer circumference and the tooth bottom One of the two curves connecting the two is a trochoid curve created at a point on the outer periphery of the mating screw rotor, and the other of the two curves is from the pitch circle by the pitch circle and from the outer periphery and the pitch circle. The tooth bottom is divided into two equal parts, one (7) is formed by a predetermined predetermined curve, and the other (9) is created by one predetermined predetermined curve of the counterpart screw rotor. A tooth shape was formed by the generated curve.

Description

The present invention relates to a screw rotor of a screw-type fluid machine such as a screw-type compressor or screw-type vacuum pump or a screw-type expander, and particularly to a tooth profile curve thereof.

  Conventionally, as a screw type fluid machine (hereinafter, described as an example of a screw type dry vacuum pump), for example, a pair of screw rotors is fixed in a housing via a bearing, and one of the screw rotors is driven by a motor. Then, the two screw rotors are rotated so that they do not interfere with each other by the timing gear fixed to the one screw rotor and the timing gear of the other screw rotor meshing with the timing gear fixed to the one screw rotor. A screw-type dryer that sucks exhaust gas from an intake port formed in the housing on the rotating shaft end side of the screw rotor and transfers the exhaust gas to a discharge port formed in the housing on the other end side of both screw rotors. There is a vacuum pump. There are various combinations of both screw rotors of the screw-type dry vacuum pump. In the present invention, the description will be made assuming that the cross-sectional shapes perpendicular to the axis are the same. The tooth profile curve of the screw rotor of the screw-type dry vacuum pump seals the space formed by both screw rotors and the housing that houses the screw rotors, as seen in the screw rotor tooth profile curve of Cited Document 1, for example. Thus, the transfer chamber is formed, and a tooth profile that improves the sealing effect has been adopted.

The cross-sectional shape of the screw rotor tooth profile shown in the cited document 1 is perpendicular to the rotation axis of the screw rotor, the outer peripheral part of the arc centered on the rotation center of the screw rotor, the tooth bottom part of the arc centered on the rotation center of the screw rotor, And two curved portions connecting the two. One of the curved portions was determined by a trochoid curve created at one point A on the outer periphery of the mating screw rotor. The other curve portion is determined by a sine curve or two involute curves.
JP-A-8-277790

However, the tooth profile of the screw rotor used in the conventional screw type dry vacuum pump is designed only with a curve that can be expressed by a specific function such as a sine curve or two involute curves, but these curves were used. In the tooth type, there is a meshing phase in which interference between screw rotors occurs, and the clearance cannot be zero or some uniform clearance in all the meshing phases. That is, since the gap changes depending on the rotation angle of the rotor, a portion where the gap becomes large is generated, and a problem arises that a large amount of exhaust gas leaks from the large gap. Therefore, the amount of exhaust gas that flows back to the exhaust chamber side is large, and it is difficult to improve the exhaust speed.
Therefore, the present invention has been proposed in view of the above-described problems of the prior art, and the amount of exhaust gas leaking during the transfer of the screw type fluid machine and flowing back to the intake side can be suppressed as much as possible. That is, an object of the present invention is to provide a screw type fluid machine in which the gap between the transfer chambers in the exhaust chamber during operation is always kept substantially constant.

  According to the first aspect of the present invention, the screw having the tooth profile whose axis-perpendicular cross-sectional shape is composed of an arc forming the root, an arc forming the outer periphery, and two curves connecting the outer periphery and the tooth bottom. In the rotor, one of the two curves connecting the outer peripheral portion and the tooth bottom portion is a trochoid curve created at a point on the outer periphery of the meshing partner screw rotor, and the other curve is the outer periphery from the pitch circle. The part and the pitch circle are divided into two equal parts, and one of the two halves is formed with a predetermined curve and the other is divided into two equal parts of the other screw rotor. It is characterized in that a tooth profile perpendicular to the axis is formed as a curve formed by a curve created at the time of meshing by a curve.

  The other curve of the two curves connecting the outer peripheral portion and the tooth bottom portion is divided into even numbers at equal intervals in the radial direction between the outer peripheral portion and the tooth bottom portion in the cross section perpendicular to the rotation axis of the screw rotor. Can be formed by a predetermined curve, and the other can be formed by a curve created by the predetermined curve of the other screw rotor.

  According to the invention of claim 2, the axially perpendicular cross-sectional shape of the tooth profile is constituted by an arc that constitutes the root part, an arc that constitutes the outer peripheral part, and a two-tooth curve that connects the outer peripheral part and the tooth bottom part. In the screw rotor, one tooth-shaped curve of the two tooth-shaped curves connecting the outer peripheral portion and the tooth bottom portion does not interfere with the meshing part of the other screw rotor and is separated from the other space. A tooth profile curve that can be formed by the transfer chamber is formed, and the other tooth profile curve is divided into two equal parts from the pitch circle to the outer peripheral part and from the pitch circle to the tooth bottom part, and one of the two equal parts is formed with a predetermined curve. In addition, the tooth profile perpendicular to the axis is formed as a tooth profile curve formed by a curve created at the time of meshing by one predetermined predetermined curve obtained by dividing the other into two equal parts of the other screw rotor. And

  One of the two tooth-type curves connecting the outer peripheral portion and the tooth bottom portion is a trochoid curve created at a point on the outer periphery of the meshing counterpart screw rotor, particularly when used as a screw type vacuum pump. However, the present invention is not limited to this. The other tooth-shaped curve is an evenly divided portion between the outer peripheral portion and the tooth bottom portion in the radial direction at equal intervals in the cross section perpendicular to the rotation axis of the screw rotor, and the evenly divided half portion is formed by a predetermined predetermined curve, On the other hand, the tooth shape can also be formed by a curve created by the predetermined predetermined curve of the counterpart screw rotor.

  According to a third aspect of the present invention, the one predetermined curve portion divided into two equal parts is formed by an arc and a straight line. If it is possible to select an arrangement and arrangement in which the arc and straight line that constitutes one of the two equal parts are smoothly connected to the tooth bottom part or the outer peripheral part, and further connected to the other one of the two equally divided teeth. There is no limit to the number of combinations of arcs and straight lines. Further, the present invention is not limited to arcs and straight lines.

  According to a fourth aspect of the invention, the predetermined predetermined curve portion is formed by a sine curve. The sine curve can be selected if the arrangement and arrangement can be selected so that one of the two halves is smoothly connected to the root or outer periphery, and the other bisected tooth is also smoothly connected. There is no limit to the number. Also, it is not limited to sine curves. However, in manufacturing the tooth profile, it is easier to form one tooth profile divided into two equal parts by only one curve.

  According to a fifth aspect of the present invention, the pump housing includes an intake port and an exhaust port, and a pair of screw rotors rotatably accommodated in the pump housing so as to rotate while meshing with each other. In a screw-type fluid machine in which a plurality of transfer chambers are formed which are partitioned from each other by meshing portions of both screw rotors and transferred from the inlet side to the exhaust side by rotation of both screw rotors. The tooth profile perpendicular to the axis is formed by an arc that constitutes the root, an arc that constitutes the outer periphery, and two curves that connect the outer periphery and the tooth bottom, and connects the outer periphery and the tooth bottom. One of the two curves is a trochoid curve created at a point on the outer periphery of the mating screw rotor, and the other curve is a pitch circle. Divide the pitch circle into the outer circumference and the pitch circle into the tooth bottom part, one is formed with a predetermined curve, and the other is divided into two equal parts of the mating screw rotor. The tooth shape is formed as a curve formed by a curve created at the time of meshing.

  The other curve of the two curves connecting the outer peripheral portion and the tooth bottom portion is divided into even numbers at equal intervals in the radial direction between the outer peripheral portion and the tooth bottom portion in the cross section perpendicular to the rotation axis of the screw rotor. Can be formed by a predetermined curve, and the other can be formed by a curve created by the predetermined curve of the other screw rotor.

  According to a sixth aspect of the present invention, the pump housing includes an intake port and an exhaust port, and a pair of screw rotors rotatably accommodated in the pump housing so as to rotate while meshing with each other, In a screw-type fluid machine in which a plurality of transfer chambers are formed which are partitioned from each other by meshing portions of both screw rotors and transferred from the inlet side to the exhaust side by rotation of both screw rotors. The cross-sectional shape of the tooth profile perpendicular to the axis is composed of an arc constituting the root, an arc constituting the outer periphery, and a two-tooth curve connecting the outer periphery and the tooth bottom, and the outer periphery and the tooth bottom. Of the two curves to be connected, one of the tooth profile curves does not interfere with the meshing part of the mating screw rotor, and the transfer chambers are adjacent to each other. A tooth profile curve that can be separated from the feeding chamber, and the other tooth profile curve is divided into two equal parts by a pitch circle from the pitch circle to the outer periphery and from the pitch circle to the tooth bottom, and one is formed with a predetermined curve. In addition, the tooth shape is configured as a tooth shape curve formed by a curve created at the time of meshing by one predetermined predetermined curve obtained by dividing the other into two equal parts of the counterpart screw rotor.

  One of the two tooth-type curves connecting the outer peripheral portion and the tooth bottom portion is a trochoid curve created at a point on the outer periphery of the meshing counterpart screw rotor, particularly when used as a screw type vacuum pump. However, the present invention is not limited to this. The other tooth-shaped curve is an evenly divided portion between the outer peripheral portion and the tooth bottom portion in the radial direction at equal intervals in the cross section perpendicular to the rotation axis of the screw rotor, and the evenly divided half portion is formed by a predetermined predetermined curve, On the other hand, the tooth shape can also be formed by a curve created by the predetermined predetermined curve of the counterpart screw rotor.

  The invention according to claim 7 is characterized in that the one predetermined curve portion divided into two equal parts is formed by an arc and a straight line. If it is possible to select an arrangement and arrangement in which the arc and straight line that constitutes one of the two equal parts are smoothly connected to the tooth bottom part or the outer peripheral part, and further connected to the other one of the two equally divided teeth. There is no limit to the number of combinations of arcs and straight lines. Further, the present invention is not limited to arcs and straight lines.

  The invention according to claim 8 is characterized in that the predetermined predetermined curve portion is formed by a sine curve. The sine curve can be selected if the arrangement and arrangement can be selected so that one of the two halves is smoothly connected to the root or outer periphery, and the other bisected tooth is also smoothly connected. There is no limit to the number. Also, it is not limited to sine curves. However, in manufacturing the tooth profile, it is easier to form one tooth profile divided into two equal parts by only one curve.

  According to the first aspect of the present invention, when the screw rotor is meshed and rotated, the screw rotor tooth mold can be easily formed so that the gap between the screw rotors is always constant regardless of the rotation angle.

  According to the invention of claim 2, when the screw rotor is meshed and rotated, the screw rotor tooth mold can be easily formed so that the clearance between the screw rotors is always constant regardless of the rotation angle.

  According to the invention of claim 3, by using an arc for the joint part to the tooth bottom part or the outer peripheral part of one tooth mold divided into two equal parts by the pitch circle, the screw rotor of which the joint part is easily and smoothly connected is used. A tooth mold can be formed.

  According to the fourth aspect of the present invention, one curve that is easily divided into two equal parts by a predetermined pitch circle is easily formed by a minimum of one curve, and is easily and smoothly joined to the joint portion of the tooth bottom portion or the outer peripheral portion. A tooth shape of a screw rotor to which the portions are connected can be formed.

  According to the invention of claim 5, when the screw rotor is meshed and rotated, a screw type fluid machine having a screw rotor tooth shape in which the clearance between the screw rotors is always constant according to the rotation angle is easily obtained. Can be configured.

  According to the invention of claim 6, when the screw rotor is meshed and rotated, a screw type fluid machine having a screw rotor tooth shape in which the clearance between the screw rotors is always constant according to the rotation angle is easily obtained. Can be configured.

  According to the seventh aspect of the invention, the screw rotor of which the joint portion is easily and smoothly connected can be obtained by using an arc for the joint portion to the tooth bottom portion or the outer peripheral portion of one of the tooth molds divided into two equal parts by the pitch circle. A screw-type fluid machine having a tooth shape can be configured.

  According to the invention of claim 8, one curve that is easily divided into two equal parts by a predetermined predetermined pitch circle is formed by a minimum of one curve, and is easily and smoothly joined to the joint portion of the tooth bottom portion or the outer peripheral portion. A screw type fluid machine having a tooth shape of a screw rotor to which parts are connected can be configured.

  Hereinafter, embodiments of the present invention will be described.

  FIG. 1 shows an embodiment of a screw-type dry vacuum pump 100 using the screw rotor of the present invention.

  As shown in FIG. 1, the screw-type dry vacuum pump 100 has two parallel shafts 101 and 102 supported by bearings 111, 112, 113, and 114 in a casing 110, respectively. The screw rotors 103 and 104 having are fixed. One shaft 101 is rotationally driven by a motor 105, and this rotation is transmitted to a timing gear 115 fixed to the other shaft 102 by meshing with the timing gear 106 by a timing gear 106 fixed to the shaft 101. That is, the screw rotors 103 and 104 rotate in synchronization with the timing gears 106 and 115. The casing 110 includes an intake port 107 for taking in exhaust gas in an exhaust chamber (not shown) into the exhaust chamber and an exhaust port 108 for discharging exhaust gas transferred from the intake port 107 side in the exhaust chamber. Yes. By rotating the screw rotors 103 and 104 synchronously with the above configuration, the exhaust gas confined in the transfer chamber in the exhaust chamber formed by the screw rotors 103 and 104 and the casing 110 is axially rotated by the rotation of the screw rotors 103 and 104. Move to and exhaust.

  The action of the screw-type dry vacuum pump includes a suction process for sucking gas into the exhaust chamber from the suction port 107, a transfer process for transporting gas inside the exhaust chamber, and a discharge process for discharging gas from the discharge port 108. ing.

  Here, the air inlet 107 may be arranged on the upper end surface of the housing as shown in FIG. 1, but the air inlet may be arranged on the side surface of the housing at a position overlapping the screw rotor when viewed from the direction perpendicular to the axis. . As for the exhaust port, if the clearance between the upper surface of the exhaust flange 109 and the end surface on the exhaust side of the screw rotor is narrowed between the screw rotors and the clearance between the side surfaces of the screw rotors and the housing at the end, It is possible to adjust the connection timing between the transfer chamber and the discharge-side outside air, and the discharge pressure of the exhaust gas can be changed. Moreover, when the discharge port is vacant at the side end portion of the housing, the exhaust passage and the exhaust port can be enlarged, and in the case of a vacuum pump, the maintainability is improved.

  Further, when a screw-type dry vacuum pump is used for an apparatus that dislikes impurities such as a semiconductor manufacturing apparatus, lubricating oil or the like for lubricating the bearings 111, 112, 113, and 114 and the timing gears 106 and 115 is exhausted. Shaft seals 116, 117, 118, and 119 are provided on the exhaust chamber side between the shaft and the housing so as not to leak into the chamber.

  In the exhaust chamber, a plurality of transfer chambers sealed by a pair of screw rotors and a housing are formed according to the number and number of turns of the screw rotor, and exhaust gas sucked from the intake port 107 is placed in the transfer chamber. The exhaust gas is transferred to the exhaust port 108 according to the confinement and rotation of the screw rotor, and the exhaust gas is discharged from the exhaust port 108.

  The exhaust performance of the screw-type dry vacuum pump during operation varies greatly depending on the sealing degree of the transfer chamber formed in the exhaust chamber. That is, since the exhaust gas flows from the high pressure side to the low pressure side, the exhaust gas confined in the transfer chamber is transferred to the intake port 107 side when the exhaust gas is transferred from the intake port 107 to the exhaust port 108 if the sealing degree is poor. The exhaust performance will deteriorate.

  The transfer chamber is sealed between the outer periphery of both screw rotors and the housing, between the tooth bottom of one screw rotor and the outer periphery of the other screw rotor, and between two curves connecting the outer periphery of each screw rotor and the tooth bottom. Is forming.

  Here, the cross-sectional shape perpendicular to the rotation axis of the screw rotor will be described with reference to FIG. In FIG. 2, between AB is a tooth bottom part, between CD is an outer peripheral part, and between BC and AD are two curves connecting the outer peripheral part and the tooth bottom part. Between BC, a trochoid curve is formed, and between AD, the root side 203 is defined as a circular arc and a straight line with a pitch circle 201 centering on the rotation axis O of the screw rotor having an intermediate diameter between the outer peripheral arc and the root arc. It forms with the curve which combined, and the outer peripheral side 205 is formed with the creation curve.

  If there is a large gap on the seal line, the exhaust gas in the transfer chamber leaks from the gap, resulting in poor exhaust efficiency. The gap along the seal line is a trochoid curve that connects between the outer periphery CD of both screw rotors and the housing, between the tooth bottom of one screw rotor and the outer periphery of the other screw rotor, and between the outer periphery of the screw rotor and the tooth bottom. It is possible to form a tooth profile that can always be operated with a constant gap between the parts. However, in the conventional design, the gap between the AD connecting the outer peripheral portion and the tooth bottom portion changes depending on the rotation angle of both screw rotors during operation. For this reason, when the smallest gap is made the same as that of the other constant gap portion with the smallest gap as a reference, a portion having a large gap is generated in the other curved portion, and the inside of the transfer chamber is formed from this portion. Exhaust gas leaked and flowed back to the intake port side to deteriorate the exhaust efficiency. However, as in the present example, this portion is a curve that combines a circular arc and a straight line on the tooth root side 203 with the pitch circle 201 as a boundary. Since the outer peripheral side 205 is formed by a generating curve, the generating curve portion has a degree of freedom, and a tooth profile that can keep the gap of the meshing portion the same as the gap of other portions during operation is formed Thus, a screw-type dry vacuum pump having extremely good sealing performance can be configured.

  Next, the process of forming the screw tooth mold of this embodiment will be described with reference to FIGS.

  First, in FIG. 3, the root part between AB is formed as an arc centered on the rotation axis O of the screw rotor, the outer peripheral part between CDs is formed as an arc centered on the rotation axis O of the screw rotor, and the distance between BC is formed as a trochoid curve. The rotational axis perpendicular cross-sectional shape of the screw rotor before forming the tooth profile between AD is shown.

  Next, in FIG. 4, the root circle 203 circumscribes the root arc on the root side 203 with the pitch circle 201 centering on the rotation axis O of the screw rotor having a diameter intermediate between the outer arc and the root arc, and the outer arc and the tooth. A circle 301 having a diameter equal to the difference between the bottom arcs is arranged.

  As shown in FIG. 5, a straight line that is half the angle 2θ formed by a straight line connecting the contact point with the root arc of the circle 301 with respect to the central axis O of the screw rotor and a straight line connecting the end point D of the outer peripheral portion. A straight line portion 403 that passes through the intersection point P of L and the pitch circle and contacts the circle 301 on the tooth bottom side is formed, and as shown in FIG. A tooth profile on the tooth bottom side 203 is formed by the straight line portion 403 from 201 to the circle 301.

  Next, as shown in FIG. 7, the other screw rotor 703 having the same shape with respect to the screw rotor 701 is arranged at a position 180 degrees away from the pitch circle 201 by a diameter.

  Next, as shown in FIG. 8, one screw rotor 701 is fixed, and the other screw rotor 703 is moved around one screw rotor 701 in accordance with the positional relationship between the two screw rotors in the operating state while shifting the meshing phase. Rotate.

  At this time, as shown in FIG. 9, in each phase, the outer teeth 901 of one screw rotor 701 do not interfere with the teeth on the other screw rotor. An outer peripheral tooth mold is formed by a creation curve connecting the outermost lines between P and D.

  As described above, the screw rotor 805 has a tooth profile having a cross section perpendicular to the rotation axis as shown in FIG. 10, and a complete tooth profile having a clearance of approximately 0 mm can be obtained at any phase. However, when oil-free operation is performed, thermal expansion is caused in the direction perpendicular to the screw tooth surface due to friction between the screw rotors or compression of exhaust gas, and thus it is necessary to provide a certain gap (0.05 to 0.3 mm). . In this case, if the clearance is corrected by a certain amount (0.025 to 0.15 mm) in the direction perpendicular to the screw tooth surface of each screw rotor with reference to a complete tooth shape with approximately 0 mm, the meshing phase is all uniform. You can get a clear gap.

  In the case of the conventional tooth mold, the part where the gap that becomes the smallest in interference is matched with the gap design minimum value determined from thermal expansion, etc., so a phase in which the gap becomes larger will occur. If the screw-type dry vacuum pump has a rotor, the gap is a constant value depending on the phase, and an optimum design can be performed in consideration of exhaust efficiency, thermal expansion, and the like. As a result, leakage due to the gap can be minimized, exhaust efficiency can be improved, and power consumption can be reduced.

The screw type dry vacuum pump of the present invention is shown. The rotational axis perpendicular cross-sectional shape of the screw rotor of this invention is shown. 1 shows a first process of forming a cross-sectional shape perpendicular to the rotation axis of the screw rotor of the present invention. The 2nd process of forming the rotation axis perpendicular section shape of the screw rotor of the present invention is shown. The 3rd process which forms the rotating shaft right-angle cross-sectional shape of the screw rotor of this invention is shown. The 4th process which forms the rotating shaft right-angle cross-sectional shape of the screw rotor of this invention is shown. 5 shows a fifth process of forming a cross-sectional shape perpendicular to the rotation axis of the screw rotor of the present invention. 6 shows a sixth process of forming a cross-sectional shape perpendicular to the rotation axis of the screw rotor of the present invention. 7 shows a seventh process of forming a cross-sectional shape perpendicular to the rotation axis of the screw rotor of the present invention. 8 shows an eighth process of forming a cross-sectional shape perpendicular to the rotation axis of the screw rotor of the present invention.

Explanation of symbols

100 Screw type dry vacuum pump 110 Casing 101, 102 Shaft 111, 112, 113, 114 Bearing 103, 104 Screw rotor 106, 115 Timing gear 107 Inlet 108 Outlet 109 Exhaust side flange 116, 117, 118, 119 Shaft seal 201 Pitch circle

Claims (8)

  In the screw rotor in which the cross-sectional shape of the tooth profile perpendicular to the axis is composed of an arc that constitutes the root, an arc that constitutes the outer periphery, and two curves that connect the outer periphery and the root, the outer periphery and the root Is a trochoid curve created at a point on the outer periphery of the meshing counterpart screw rotor, and the other curve is 2 from the pitch circle to the outer peripheral portion and from the pitch circle to the tooth bottom portion. Divided into two equal parts, one is formed with a predetermined curve, and the other is created at the time of meshing with one predetermined curve of one of the other screw rotors. A screw rotor characterized in that a tooth profile perpendicular to the axis is formed as a curved line.   In the screw rotor in which the cross-sectional shape of the tooth profile perpendicular to the axis is composed of an arc that forms the root, an arc that forms the outer periphery, and a two-tooth curve that connects the outer periphery and the root, One tooth profile curve of the two tooth profile curves that connect the tooth bottom portion is a tooth profile curve that does not interfere with the meshing part of the other screw rotor and can form a transfer chamber separated from the other space. The other tooth type curve is divided into two equal parts from the pitch circle to the outer peripheral part and from the pitch circle to the tooth bottom part, one of the two equal parts is formed with a predetermined curve, and the other is made into another screw rotor. A screw rotor characterized in that the tooth profile perpendicular to the axis is formed as a tooth profile curve formed by a curve created at the time of meshing by one predetermined predetermined curve divided into two equal parts.   The screw rotor according to claim 1 or 2, wherein the one predetermined predetermined curved portion divided into two equal parts is formed by an arc and a straight line.   The screw rotor according to claim 1 or 2, wherein the predetermined predetermined curve portion is formed by a sine curve.   A pump housing having an intake port and an exhaust port; and a pair of screw rotors rotatably accommodated in the pump housing so as to rotate while meshing with each other, and both screws between the pump housing and each screw rotor In a screw-type fluid machine that forms a plurality of transfer chambers that are separated from each other by the meshing portion of the rotor and are transferred from the intake port side to the exhaust port side by the rotation of both screw rotors, An arc that forms the bottom part, an arc that forms the outer peripheral part, and two curves that connect the outer peripheral part and the tooth bottom part, and one of the two curves that connect the outer peripheral part and the tooth bottom part, A trochoid curve is created at a point on the outer periphery of the mating screw rotor, and the other curve is separated from the pitch circle to the outer periphery by the pitch circle. Divided into two parts from the round circle to the bottom of the tooth, one is formed with a predetermined curve, and the other is divided into two equal parts of the mating screw rotor. A screw-type fluid machine characterized in that a tooth shape is formed as a curve formed by a curved line.   A pump housing having an intake port and an exhaust port; and a pair of screw rotors rotatably accommodated in the pump housing so as to rotate while meshing with each other, and both screws between the pump housing and each screw rotor In a screw-type fluid machine that forms a plurality of transfer chambers that are separated from each other by the meshing portion of the rotor and are transferred from the intake port side to the exhaust port side by the rotation of both screw rotors, It comprises a circular arc that constitutes the bottom part, an arc that constitutes the outer peripheral part, and a two-tooth curve that connects the outer peripheral part and the tooth bottom part, and one of the two curves that connects the outer peripheral part and the tooth bottom part. The mold curve does not interfere with the meshing part of the mating screw rotor, and each transfer chamber can be separated from another adjacent transfer chamber. The tooth profile curve is divided into two equal parts from the pitch circle to the outer periphery and from the pitch circle to the tooth bottom with a pitch circle. A screw type fluid machine characterized in that a tooth shape is formed as a tooth shape curve formed by a curve created at the time of meshing by one predetermined predetermined curve obtained by dividing the rotor into two equal parts.   The screw-type fluid machine according to claim 5 or 6, wherein the one predetermined predetermined curve portion divided into two equal parts is formed by an arc and a straight line.   The screw-type fluid machine according to claim 5 or 6, wherein the predetermined predetermined curve portion is formed by a sine curve.

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