WO2005113984A1

WO2005113984A1 - Screw rotor and screw type fluid machine

Info

Publication number: WO2005113984A1
Application number: PCT/JP2005/009415
Authority: WO
Inventors: Tsuyoshi Nachi
Original assignee: Nabtesco Corporation
Priority date: 2004-05-24
Filing date: 2005-05-24
Publication date: 2005-12-01
Also published as: US20080193317A1; CN1961153A; JPWO2005113984A1; KR20070027558A; TW200607926A; EP1750011A1

Abstract

A screw type fluid machine so designed that the leakage from the screw type fluid machine is always constant during operation, that is, the gap in an exhaust chamber is always kept substantially constant. Thus, in a screw type fluid machine, the axis-orthogonal sectional shape (805) of the tooth form of a screw rotor is formed by curved lines including an arc (1) constituting the tooth bottom, an arc (3) constituting the outer periphery, and two curved lines that connect the outer periphery with the tooth bottom, wherein one (5) of the two curved lines is a trochoidal curved line generated by points on the outer periphery of a mating screw rotor, while the other of the two curved lines is bisected by the pitch circle into two portions, one from the pitch circle to the outer periphery, and the other from the pitch circle to the tooth bottom; the portion from the pitch circle to the tooth bottom (7) is formed by a predetermined curved line, while the portion from the pitch circle to the outer periphery (9) is formed by the curved line, generated by the bisected predetermined curved line, of the mating screw rotor to complete a tooth form shape.

Description

Specification

Screw rotor and screw type fluid machine

Technical field

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

[0002] Conventionally, as a screw type fluid machine (hereinafter, described by taking a screw type dry vacuum pump as an example), for example, a pair of screw rotors is fixed in a nozzle through a bearing. One is driven by a motor, and both screw rotors 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 that matches the timing gear fixed to the one screw rotor. In this way, the intake rotor exhaust gas formed in the housings at the ends of the rotating shafts of both screw rotors is sucked, and discharged to the discharge ports formed in the housings at the other end sides of both screw rotors. There is a screw-type dry vacuum pump that transfers and discharges gas. The two screw rotors of the screw-type dry vacuum pump have various types of threading, but in the present invention, the ones having the same shape in the cross section perpendicular to the axis will be described. The tooth profile of the screw rotor of the screw dry vacuum pump is, for example, a space formed by the two screw rotors and a housing for accommodating the two screw rotors, as seen in the screw rotor tooth profile of Patent Document 1. Toothing was used to form the transfer chamber in a sealed manner and to improve the sealing effect.

[0003] The cross-sectional shape perpendicular to the rotation axis of the tooth profile of the screw rotor shown in the cited document 1 has an outer peripheral portion of an arc centered on the rotation center of the screw rotor and a root portion of an arc centered on the rotation center of the screw rotor. And two curved portions connecting the outer peripheral portion and the tooth bottom portion. One of the curves is

Is determined by the trochoid curve created at one point A on the outer circumference of the mating screw rotor. Was. The other curve was determined by a sine curve and two involute curves.

Patent Document 1: Japanese Patent Application Laid-Open No. 8-277790

Disclosure of the invention

Problems to be solved by the invention

[0004] 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 represented by a specific function such as a sine curve or two involute curves! However, in the tooth form using these curves, when interference occurs between the screw rotors, there is a phase, and in all cases, the gap cannot be set to 0 or a uniform gap in all phases. That is, since the gap changes depending on the rotation angle of the rotor, a portion where the gap becomes large occurs, and a problem occurs that the exhaust gas being transferred leaks from the large gap in a large amount. Therefore, it is difficult to increase the exhaust speed because the amount of exhaust gas flowing backward to the exhaust chamber is large.

In view of the above, the present invention has been proposed in view of the above-described problems of the related art, and it is possible to minimize the amount of exhaust gas leaking during transfer of a screw type fluid machine and flowing backward to the intake side. 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.

Means for solving the problem

[0005] According to the invention of claim 1, the cross-sectional shape of the tooth profile at right angles to the axis is formed by an arc forming the tooth bottom, an arc forming the outer circumference, and two curves connecting the outer circumference and the tooth bottom. In one of the screw rotors described above, one of the two curves connecting the outer peripheral portion and the tooth bottom portion is a trochoidal curve created at a point on the outer periphery of the mating screw rotor, and the other is a curved line. Halving the outer circumference from the pitch circle and the tooth bottom from the pitch circle, forming one of the two halves with a predetermined curve, and the other half of the other screw rotor The cross-sectional shape perpendicular to the axis of the tooth profile is configured as a curve formed by a curve created at the time of fitting by a predetermined curve.

[0006] The other of the two curves connecting the outer peripheral portion and the tooth bottom portion is an even-numbered radially-divided portion between the outer peripheral portion and the tooth bottom portion in a cross section perpendicular to the rotation axis of the screw rotor. The tooth shape can also be formed by forming a half of the divided part with a predetermined curve, and the other half by a curve created by the predetermined curve of the mating screw rotor. .

[0007] According to the invention of claim 2, the tooth profile has an arc-shaped cross-section perpendicular to the axis, an arc forming the tooth bottom, an arc forming the outer circumference, and a two-tooth-shaped curve connecting the outer circumference and the tooth bottom. In the screw rotor composed of: the one tooth profile curve of the two tooth profile curves connecting the outer peripheral portion and the tooth bottom portion does not interfere with the combined portion of the other screw rotors and the other space. 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 determined in advance. Profile of the tooth profile as a tooth profile curve formed by a curve created at the time of mating by one predetermined curved line that is formed by dividing the other into two equal parts of the other screw rotor Is constituted.

[0008] One tooth profile curve of the two-tooth profile connecting the outer peripheral portion and the tooth bottom is created at a point on the outer periphery of the mating screw rotor, particularly when used as a screw vacuum pump. It is best to choose a trochoid curve that is not limited to this. In the other tooth profile curve, the outer circumferential portion and the root portion are evenly divided in the radial direction at equal intervals in a cross section perpendicular to the rotation axis of the screw rotor, and the evenly divided half portion is formed by a predetermined curve. On the other hand, the tooth shape can also be formed by a curve created by the predetermined curve of the mating screw rotor.

[0009] According to the invention of claim 3, the one predetermined bisected curved portion is formed by an arc and a straight line. It is possible to select an arrangement and an arrangement such that the arc and the straight line that constitute one of the two halves are smoothly connected to the tooth bottom or the outer periphery, and are also smoothly connected to the other half of the tooth. If possible, there is no limit on the number of combinations of arcs and straight lines. The invention is not limited to only arcs and straight lines.

[0010] According to the invention of claim 4, the predetermined curved portion is formed by a sine curve. If it is possible to select an arrangement and an arrangement such that the sine curve is such that one of the two halves is smoothly connected to the tooth bottom or the outer peripheral portion, and the other is also smoothly connected to the other half of the tooth. There is no limit on the number of curves. Also, rhino It is not limited to curves. However, in terms of manufacturing the tooth profile, it is easier to form one tooth profile that is bisected by only one curve.

[0011] According to the invention of claim 5, there is provided a pump nozzle and a housing having an intake port and an exhaust port, and a pair of screw rotors rotatably housed in the pump housing so as to rotate while engaging with each other. A screw chamber in which a plurality of transfer chambers are partitioned between the pump housing and each screw rotor at a joint portion of the two screw rotors and are transferred from an intake port side to an exhaust port side by rotation of the two screw rotors. In a fluid machine, the cross-sectional shape perpendicular to the axis of the tooth profile of a screw rotor is constituted by an arc forming a tooth bottom, an arc forming an outer circumference, and two curves connecting the outer circumference and the tooth bottom. One of the two curves connecting the outer circumference and the tooth root is a trochoidal curve created at a point on the outer circumference of the mating screw rotor, and the other is a trochoidal curve. The pitch circle force is divided into two parts at the outer peripheral part and the pitch circle force at the tooth bottom part by the switch circle, one part is formed with a predetermined curve, and the other part is divided into two parts of the counterpart screw rotor. It is characterized in that the tooth shape is configured as a curve formed by a curve created at the time of a predetermined curve.

[0012] The other curve of the two curves connecting the outer peripheral portion and the tooth bottom portion is an even-numbered radially-divided portion between the outer peripheral portion and the tooth bottom portion in a cross section perpendicular to the rotation axis of the screw rotor. The tooth shape can also be formed by forming a half part obtained by dividing into several parts by a predetermined curve, and the other half by a curve created by the predetermined curve of the mating screw rotor. .

[0013] According to the invention of claim 6, there is provided a pump nozzle and a housing having an intake port and an exhaust port, and a pair of screw rotors rotatably housed in the pump housing so as to rotate while engaging with each other. A screw chamber in which a plurality of transfer chambers are partitioned between the pump housing and each screw rotor at a joint portion of the two screw rotors and are transferred from an intake port side to an exhaust port side by rotation of the two screw rotors. In a fluid machine, the cross-sectional shape of the tooth profile of a screw rotor perpendicular to the axis is composed of an arc forming a tooth bottom, an arc forming an outer circumference, and a two-tooth curve connecting the outer circumference and the tooth bottom. One tooth profile curve of the two curves connecting the outer peripheral portion and the tooth bottom portion is changed to the shape of the mating screw rotor. Each transfer chamber has a tooth profile curve that does not interfere with the mating portion and can be separated from another adjacent transfer chamber, and the other tooth profile curve is a pitch circle with a pitch circle. The force is divided into two equal parts at the bottom of the tooth, one is formed by a predetermined predetermined curve, and the other is created at the time of engagement by one predetermined curve that is bisected by the other side screw rotor. It is characterized in that the tooth shape is configured as a tooth shape curve formed by the curved lines.

[0014] One of the two-tooth-shaped curves connecting the outer peripheral portion and the tooth bottom is formed at a point on the outer periphery of the mating screw rotor, particularly when used as a screw-type vacuum pump. It is best to choose a trochoid curve that is not limited to this. In the other tooth profile curve, the outer circumferential portion and the root portion are evenly divided in the radial direction at equal intervals in a cross section perpendicular to the rotation axis of the screw rotor, and the evenly divided half portion is formed by a predetermined curve. On the other hand, the tooth shape can also be formed by a curve created by the predetermined curve of the mating screw rotor.

[0015] According to the invention of claim 7, the one predetermined bisected one curved portion is formed by an arc and a straight line. It is possible to select an arrangement and an arrangement such that the arc and the straight line that constitute one of the two halves are smoothly connected to the tooth bottom or the outer periphery, and are also smoothly connected to the other half of the tooth. If possible, there is no limit on the number of combinations of arcs and straight lines. The invention is not limited to only arcs and straight lines.

According to the invention of claim 8, the predetermined curved portion is formed by a sine curve. If it is possible to select an arrangement and an arrangement such that the sine curve is such that one of the two halves is smoothly connected to the tooth bottom or the outer peripheral portion, and the other is also smoothly connected to the other half of the tooth. There is no limit on the number of curves. It is not limited to the sign curve. However, in terms of manufacturing the tooth profile, it is easier to form one tooth profile that is bisected by only one curve.

The invention's effect

[0017] According to the invention of claim 1, when the screw rotors are rotated together, the tooth profile of the screw rotor can be easily formed such that the gap between the screw rotors is always constant regardless of the rotation angle. Can be formed. [0018] According to the invention of claim 2, when the screw rotors are rotated together, the tooth profile of the screw rotor can be easily formed such that the gap between the screw rotors is always constant regardless of the rotation angle. Can be formed.

[0019] According to the invention of claim 3, the joint portion is easily and smoothly connected by using the arc at the joint portion to the tooth bottom portion or the outer peripheral portion of one tooth mold divided into two equal parts by the pitch circle. The tooth profile of the screw rotor can be formed.

[0020] According to the invention of claim 4, one curve is easily formed into two equal parts by a predetermined predetermined pitch circle using at least one curve, and is easily formed at the joint portion of the tooth bottom portion or the outer peripheral portion. Thus, it is possible to form a tooth profile of the screw rotor in which the joints are smoothly connected.

According to the invention of claim 5, the screw type fluid having the tooth profile of the screw rotor such that the gap between the screw rotors is always constant depending on the rotation angle when the screw rotors are rotated together. The machine can be easily configured.

[0022] According to the invention of claim 6, the screw type fluid having the tooth profile of the screw rotor such that when the screw rotor is rotated together, the gap between the screw rotors is always constant depending on the rotation angle. The machine can be easily configured.

[0023] According to the invention of claim 7, the joint portion is easily and smoothly connected by using the arc at the joint portion to the tooth bottom portion or the outer peripheral portion of one of the tooth molds bisected by the pitch circle. A screw type fluid machine having a screw rotor tooth form can be configured.

[0024] According to the invention of claim 8, one of the curves is easily divided into two equal parts by a predetermined predetermined pitch circle with at least one curve, and is easily formed at the joint portion of the tooth bottom portion or the outer peripheral portion. A screw-type fluid machine having a tooth profile of a screw rotor with a smoothly connected joint can be configured.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described.

Example 1

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

[0027] As shown in FIG. 1, the screw dry vacuum pump 100 has two casings in a casing 110. The parallel shafts 101, 102 are supported by bearings 111, 112, 113 and 114, respectively, to which screw rotors 103, 104 having screw grooves matching each other are fixed. One of the shafts 101 is driven to rotate by a motor 105, and the rotation is transmitted by a timing gear 106 fixed to the shaft 101 to a timing gear 115 fixed to the other shaft 102 in accordance with the timing gear 106. That is, the screw rotors 103 and 104 are synchronously rotated by the timing gears 106 and 115. The casing 110 has an intake port 107 for taking exhaust gas in an exhaust chamber (not shown) into the exhaust chamber and an exhaust port 108 for exhausting exhaust gas transferred from the intake port 107 side in the exhaust chamber. Have. By rotating the screw rotors 103 and 104 in synchronization 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 rotated by the screw rotors 103 and 104 to rotate the shaft. Move in the direction and exhaust.

[0028] The operation of the screw-type dry vacuum pump is as follows: a suction process of sucking gas from the intake port 107 into the exhaust chamber, a transfer process of transferring gas inside the exhaust chamber, and a discharge process of discharging gas from the exhaust port 108. It is made up of

[0029] Here, the intake port 107 may be arranged on the upper end surface of the housing as shown in Fig. 1, but the intake port is arranged on the side surface of the housing at a position overlapping with the screw rotor when viewed from the direction perpendicular to the axis. You may. As for the exhaust port, if the gap between the upper surface of the exhaust side flange 109 and the screw rotor exhaust side end face is narrowed at the end in the same way as the gap between both screw rotors and the gap between both screw rotor side faces and the housing, the position and size of the exhaust port By changing the height, the connection timing between the transfer chamber and the outside air on the discharge side can be adjusted, and the discharge pressure of the exhaust gas can be changed. When the housing has an exhaust port at the side end, the exhaust passage and the exhaust port can be enlarged, and in the case of a vacuum pump, the maintainability is improved.

When a screw-type dry vacuum pump is used in an apparatus such as a semiconductor manufacturing apparatus that does not want to mix impurities, a lubricating oil for lubricating the bearings 111, 112, 113 and 114 and the timing gears 106 and 115 is used. Shaft seals 116, 117, 118, and 119 are provided on the side of the exhaust chamber between the shaft and the housing so as not to leak into the exhaust chamber. In the exhaust chamber, a plurality of chambers are formed in accordance with the number of turns and the number of turns of the screw rotor, and a plurality of chambers are formed in the exhaust chamber. Is confined in the transfer chamber, and the exhaust gas is transferred to the outlet 108 according to the rotation of the screw rotor, and the exhaust gas is discharged from the outlet 108.

[0032] The evacuation performance of the screw dry vacuum pump during operation greatly changes depending on the degree of sealing of the transfer chamber formed in the evacuation chamber. In other words, since the exhaust gas flows from the high pressure side to the low pressure side, if the degree of sealing is poor, the exhaust gas trapped in the transfer chamber while the exhaust gas is being transferred from the intake port 107 to the exhaust port 108 will be exhausted. It leaks to the side, and the exhaust performance deteriorates.

The transfer chamber is hermetically sealed between the outer peripheral portions of both screw rotors and the housing, between the tooth bottom of one screw port and the outer peripheral portion of the other screw rotor, and between the outer peripheral portion of each screw rotor and the tooth bottom. A seal line is formed between the curves.

Here, the cross-sectional shape of the screw rotor perpendicular to the rotation axis will be described with reference to FIG. In Fig. 2, two curves connecting the outer circumference and the bottom are shown between AB and the outer circumference, between CD and outer circumference, between BC and AD. BC is formed by a trochoidal curve, and AD is formed by a straight line on the bottom side 203 with a pitch circle 201 centered on the rotation axis O of the screw rotor having a diameter between the outer circumference arc and the bottom circle. And the outer peripheral side 205 is formed by a creation curve.

[0035] If there is a large gap on the seal line, there is a portion, and the exhaust gas from the transfer chamber leaks from the gap, resulting in poor exhaust efficiency. The gap along the seal line is a trochoid curve connecting the outer periphery of both screw rotors, between the CD and the housing, between the tooth bottom of one screw rotor and the outer periphery of the other screw rotor, and connecting the outer periphery of the screw rotor and the tooth bottom. It is possible to form a tooth profile that can be operated while maintaining a constant gap between the parts. However, in the conventional design, the gap between the outer circumference and the AD connecting the tooth bottom changes with the rotation angle of both screw rotors during operation. Therefore, when the smallest gap is set to be the same as the other constant gap portion based on the portion where the gap is smallest, a portion having a large gap is formed in the other curved portion, and the transfer chamber is formed from the portion. Exhaust gas leaks and flows back to the intake port side, thereby deteriorating the exhaust efficiency. Since the tooth bottom side 203 is formed by a curve combining an arc and a straight line with the pitch circle 201 as a boundary, and the outer peripheral side 205 is formed by a creation curve, the creation curve portion has a degree of freedom. It is possible to form a tooth profile in which the gap at the joint portion can always be held the same as the gap at other portions, and it is possible to configure a screw dry vacuum pump having extremely good sealing performance.

Next, a forming process of the screw tooth form of the present embodiment will be described with reference to FIGS.

First, in FIG. 3, an arc centered on the rotation axis O of the screw rotor is the root between the teeth AB, an arc centered on the rotation axis O of the screw rotor is the outer circumference between the CDs, and a trochoid curve is shown between BC. Fig. 3 shows a cross-sectional shape perpendicular to the rotation axis of the screw rotor before forming and forming a tooth profile between ADs.

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

As shown in FIG. 5, an angle 2 ° between a straight line connecting the center axis O of the screw rotor and the contact point with the root arc of the circle 301 and a straight line connecting the end point D of the outer peripheral portion is formed. A straight line portion 403 that passes through the intersection P of the half-length straight line L and the pitch circle and that is in contact with the circle 301 on the root side is formed. As shown in FIG. 6, the tooth bottom of the circle 301 and the straight line portion 403 are in contact with each other. The portion and the straight portion 403 from the pitch circle 201 to the circle 301 form a tooth profile on the root side 203.

Next, as shown in FIG. 7, another screw rotor 703 having the same shape is arranged at a position apart from the screw rotor 701 by a diameter of the pitch circle 201 with a phase shift of 180 °.

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

At this time, as shown in FIG. 9, the teeth of one screw rotor 701 are prevented from interfering with the tooth roots 901 of the other screw rotor in each phase so that the outer peripheral teeth 901 of the other screw rotor 701 do not interfere. A creation curve connecting the outermost line of the bottom teeth 903 between P and D forms the outer tooth form.

As described above, the screw rotor 805 has a tooth profile having a cross section perpendicular to the rotation axis as shown in FIG. With all phases, a complete tooth profile with a gap of almost Omm can be created. However, when operating without oil, thermal expansion in the direction perpendicular to the screw tooth surface occurs due to friction between the two screw rotors and compression of exhaust gas, etc., so it is necessary to provide a certain gap (0.05 to 0.3 mm). You. In this case, if a certain amount (0.025 to 0.15 mm) is corrected in the direction perpendicular to the screw tooth surface of each screw rotor based on the complete tooth shape with the above-mentioned clearance of almost Omm, all phases are uniform and uniform. You can get a good gap.

In the case of the conventional tooth form, the portion where the gap that interferes the least becomes the same as the gap design minimum value that determines the force such as thermal expansion, so that a phase in which the gap becomes large occurs. In the case of the screw-type dry vacuum pump having the screw rotor in the example, the gap is constant depending on the phase, and an optimal design can be performed in consideration of the exhaust efficiency, thermal expansion, and the like. As a result, leakage due to gaps can be minimized, and exhaust efficiency can be increased and power consumption can be reduced.

Brief Description of Drawings

FIG. 1 shows a screw-type dry vacuum pump of the present invention.

FIG. 2 shows a cross section perpendicular to the rotation axis of the screw rotor of the present invention.

FIG. 3 shows a first step of forming a cross section perpendicular to the rotation axis of the screw rotor of the present invention.

FIG. 4 shows a second step of forming a cross section perpendicular to the rotation axis of the screw rotor of the present invention.

FIG. 5 shows a third step of forming a cross section perpendicular to the rotation axis of the screw rotor of the present invention.

FIG. 6 shows a fourth step of forming a cross section perpendicular to the rotation axis of the screw rotor of the present invention.

FIG. 7 shows a fifth step of forming a cross section perpendicular to the rotation axis of the screw rotor of the present invention.

FIG. 8 shows a sixth step of forming a cross section perpendicular to the rotation axis of the screw rotor of the present invention.

FIG. 9 shows a seventh step of forming a cross section perpendicular to the rotation axis of the screw rotor of the present invention.

FIG. 10 is a view showing an eighth step of forming a cross section perpendicular to the rotation axis of the screw rotor of the present invention.

[0046] 100 screw dry vacuum pump

110 casing

101, 102 shaft m, 112, 113, 114 bearing

103, 104 Screw rotor

106, 115 Timing gear

107 Inlet

108 outlet

109 Exhaust side flange

116, 117, 118, 119 axes

201 pitch circle

Claims

The scope of the claims

[1] In the screw rotor, wherein the tooth profile has a cross-section perpendicular to the axis formed by an arc forming a tooth bottom, an arc forming an outer circumference, and two curves connecting the outer circumference and the tooth bottom. One of the two curves connecting the shaft part and the tooth bottom is a trochoidal curve created at a point on the outer circumference of the mating screw rotor, and the other curve is from the pitch circle to the outer circumference and the pitch circle. Of the screw rotor, and one of the two halves is formed by a predetermined curve, and the other is formed by a predetermined curve of one of the other screw rotors. A screw rotor characterized in that a cross-section perpendicular to the axis of the tooth profile is formed as a curve formed by a curve created at times.

[2] In the screw rotor in which the cross-sectional shape perpendicular to the axis of the tooth profile is composed of an arc forming the tooth bottom, an arc forming the outer circumference, and a two-tooth curve connecting the outer circumference and the tooth bottom, The transfer chamber is formed so that one of the two tooth curves connecting the outer peripheral part and the tooth bottom part does not interfere with the joint portion of the other screw rotor and is separated from the other space. 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 parts is formed as a predetermined predetermined curve, and the other is formed. A screw characterized by forming a tooth profile curve perpendicular to the axis as a tooth profile curve formed by a curve created at the time of engagement by one of two predetermined predetermined curves of another screw rotor. Rotor.

3. The screw rotor according to claim 1, wherein the one predetermined curved portion divided into two equal parts is formed by an arc and a straight line.

4. The screw rotor according to claim 1, wherein the predetermined curved portion is formed by a sine curve.

[5] A pump housing having an intake port and an exhaust port, and a pair of screw rotors rotatably housed in the pump housing so as to rotate while meshing with each other, wherein the pump nosing and each screw rotor are provided. In the screw type fluid machine in which a plurality of transfer chambers are separated from each other at a joint portion of the two screw rotors and are transferred from the intake port side to the exhaust port side by the rotation of the two screw rotors, The cross-sectional shape of the tooth profile perpendicular to the axis is defined by the arc that forms the tooth bottom, the arc that forms the outer periphery, The trochoid curve formed by a point on the outer circumference of the mating screw rotor is formed of two curves connecting the peripheral portion and the root portion, and one of the two curves connecting the outer peripheral portion and the root portion is formed. The other curve is divided into two equal parts at the outer circumference and the pitch circular force at the bottom of the tooth with the pitch circle, and the other curve is formed with a predetermined curve, and the other at the other end of the counterpart screw rotor. A screw-type fluid machine characterized in that the tooth shape is configured as a curve formed by a curve created at the time of fitting by one of the predetermined curves that are divided

[6] A pump housing having an intake port and an exhaust port, and a pair of screw rotors rotatably housed in the pump housing so as to rotate while meshing with each other, wherein the pump nosing and each screw rotor are provided. In the screw type fluid machine in which a plurality of transfer chambers are separated from each other at a joint portion of the two screw rotors and are transferred from the intake port side to the exhaust port side by the rotation of the two screw rotors, The cross-sectional shape of the tooth profile perpendicular to the axis is constituted by an arc forming the tooth bottom, an arc forming the outer circumference, and a two-tooth curve connecting the outer circumference and the tooth bottom. the tooth-shaped curve of one of the ^two curves connecting, that interfere with the嚙合portion of the mating screw rotor separates the different transfer chambers Mugu and each transfer chamber is adjacent Of the other tooth profile curve, the pitch circle force is divided equally into the outer peripheral portion and the tooth bottom portion from the pitch circle by the pitch circle, and one is formed by a predetermined predetermined curve, and the other is formed by A screw type fluid machine characterized in that a tooth profile is formed as a tooth profile curve formed by a curve created at the time of engagement by one of two predetermined predetermined curves of the side screw rotor

7. The screw-type fluid machine according to claim 5, wherein the one of the predetermined two predetermined curved portions is formed by an arc and a straight line.

8. The screw fluid machine according to claim 5, wherein the predetermined curved portion is formed as a sine curve.