SCREW VACUUM PUMP

Abstract

A screw vacuum pump includes a male rotor, a female rotor, a stator, and a drive motor/motors. A screw gear portion of the male rotor, a screw gear portion of the female rotor, and the stator cooperatively form a gas working chamber. The stator has an inlet port and an outlet port. At least one of the male rotor and the female rotor has a rotor hollow portion which is opened on at least one end face side in a rotation-axis longitudinal direction of the male rotor and/or the female rotor. The drive motor is at least partially received in the rotor hollow portion.

Description

TECHNICAL FIELD

This invention relates to a screw vacuum pump.

BACKGROUND ART

In a semiconductor device manufacturing apparatus, a liquid crystal panel manufacturing apparatus, or a solar panel manufacturing apparatus, a serious problem arises in a device manufacturing process if oil backflow occurs from a pump into a process chamber of the device manufacturing apparatus. Accordingly, use is generally made of, what is called, a dry pump, a mechanical booster pump, or a turbomolecular pump in which there is no occurrence of contact between suction gas and oil.

However, since molecular weights of process gas, carrier gas, generated gas, and so on are broad, i.e. from 1 to one hundred and several tens, the current situation is that the above-mentioned pumps are selectively used depending on their pumping characteristics for those various gases and their inherent pumping regions.

On the other hand, since the pumping speed is lowered depending on the kind of gas to be exhausted, a pump having a high pumping speed is inefficiently used and therefore a problem exists that it is not possible to reduce the power consumption or to place the pump near the apparatus due to the pump size being large.

Further, with respect to general dry pumps and mechanical booster pumps, a serious problem exists that product is deposited inside the pump between an inlet port and an outlet port, resulting in a short maintenance time.

In this regard, a screw vacuum pump has a feature that it can be used in a region from the atmospheric pressure to 0.5 Pa and that it is possible to prevent the pressure in the pump from sharply increasing near an outlet port, to prevent abnormal heat generation, and to reduce the power consumption, and has a feature that even if a large amount of product is formed, it is possible to rake out the product to the exterior of the pump by screw tooth surfaces.

Conventionally, as such a screw vacuum pump, there is known a screw vacuum pump described in Patent Document 1.

This conventional screw vacuum pump comprises a male rotor and a female rotor engaging each other, a stator receiving therein the male rotor and the female rotor, a first shaft and a second shaft serving as rotation shafts of the male rotor and the female rotor, bearings for the first shaft and the second shaft, and a drive motor for rotating the first shaft and the second shaft.

The bearings and the drive motor are disposed outside the male rotor or the female rotor, i.e. the male rotor or the female rotor, the bearings, and the drive motor are aligned in a rotation-axis longitudinal direction.

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PRIOR ART DOCUMENT

Patent Document

Patent Document 1: JP-A-2004-263629

SUMMARY OF THE INVENTION

Problem to be Solved by the Invention

However, since the male rotor or the female rotor, the bearings, and the drive motor are aligned in the rotation-axis longitudinal direction in the conventional screw vacuum pump, there has been a problem that the pump size in the rotation-axis longitudinal direction becomes large.

While the pump is running, drive heat is generated from the drive motor. Consequently, members or devices around the drive motor should be designed taking into account the influence of this drive heat of the drive motor. As a result, there has been a problem that the flexibility of design of the pump components is impaired.

Therefore, this invention is intended to solve the conventional problems, that is, it is an object of this invention to achieve a reduction in pump size in the rotation-axis longitudinal direction.

It is another object of this invention to provide a screw vacuum pump that ensures the flexibility of design of pump components.

Means for Solving the Problem

A screw vacuum pump of the present invention comprises a male rotor and a female rotor respectively having, on their outer peripheral sides, screw gear portions engaging each other, a stator receiving therein the male rotor and the female rotor, and a drive motor/motors for rotating the male rotor and the female rotor, wherein the screw gear portion of the male rotor, the screw gear portion of the female rotor, and the stator cooperatively form a gas working chamber, the stator has an inlet port and an outlet port adapted to communicate with one end and the other end of the gas working chamber, at least one of the male rotor and the female rotor has a rotor hollow portion which is opened on at least one end face side of the male rotor and/or the female rotor in a rotation-axis longitudinal direction, and the drive motor is at least partially received in the rotor hollow portion, and thus, resolved the foregoing problems. If a structure is employed in which the hollow portions are provided in both male and female rotors and the motors are placed in the respective hollow portions (i.e. the number of motors is two), heat rise due to heat generation of the motors becomes uniform in the male rotor and the female rotor, resulting in the same thermal expansion, thus achieving an effect that an engagement gap therebetween is maintained uniform. On the other hand, if a structure is employed in which the hollow portion is provided in one of the male rotor and the female rotor and the motor is placed in the hollow portion (i.e. the number of motors is one), it is possible to suppress the motor cost while reducing the pump size and increasing the flexibility of installation of an exhaust system.

Effect of the Invention

According to this invention, since the drive motor/motors is/are at least partially received in the rotor hollow portion/portions, it is possible to reduce the pump size in the rotation-axis longitudinal direction. Further, since it is possible to make most of the drive heat of the drive motor/motors stay inside the male rotor or/and the female rotor and thus to reduce the influence of the drive heat of the drive motor/motors on the pump components other than the male rotor and the female rotor, it is possible to achieve high flexibility of design of the pump components.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view schematically showing a screw vacuum pump according to a first embodiment of this invention.

FIG. 2 is an explanatory diagram conceptually showing circulation paths of lubricating oil.

FIG. 3 is a perspective view showing a male rotor.

FIG. 4 is an explanatory diagram exemplarily showing screw gear portions of the male rotor and a female rotor.

FIG. 5 is a perpendicular-to-axis cross-sectional view of the male rotor and the female rotor.

FIG. 6 is a plan view schematically showing a screw vacuum pump according to a second embodiment of this invention.

FIG. 7 is a perspective view showing a male rotor of a screw vacuum pump according to a modification of this invention.

MODE FOR CARRYING OUT THE INVENTION

Hereinbelow, embodiments of this invention will be described with reference to the drawings.

First Embodiment

First, as shown in FIGS. 1 and 2, a screw vacuum pump 100 according to a first embodiment of this invention comprises a pair of a male rotor 110 and a female rotor 120 that are disposed in engagement with each other while maintaining an engagement gap therebetween and are rotated synchronously in opposite directions (driven synchronously by a non-illustrated inverter), a stator 130 receiving therein the male rotor 110 and the female rotor 120, drive motors 140A and 140B for rotating the male rotor 110 and the female rotor 120, rotation shafts (rotation axes) 150A and 150B fixed to the male rotor 110 and the female rotor 120, bearings 160Aa, 160Ab, 160Ac, 160Ba, 160Bb, and 160Bc for the rotation shafts 150A and 150B, a pair of gears 170A and 170B (which prevent contact between the male and female screw rotors in abnormality and, in particular, which significantly reduce vibration and noise due to backlash of gears at the time of starting and stopping rotation of the rotors) attached to one-end portions of the rotation shafts 150A and 150B, oil supply means 180 for supplying lubricating oil to later-described pump components by centrifugal force due to rotation of the rotation shafts 150A and 150B, and a cooling device 190 for water-cooling the lubricating oil.

The male rotor 110, the female rotor 120, and the stator 130 cooperatively form a gas working chamber which transfers and compresses a gas.

As shown in FIGS. 1, 3, and 4, the male rotor 110 and the female rotor 120 respectively have, on their outer peripheral sides, screw gear portions 111 and 121 which engage each other while maintaining an engagement gap therebetween.

As shown in FIGS. 1, 3, and 4, the screw gear portions 111 and 121 of the male rotor 110 and the female rotor 120 each comprise an unequal lead unequal inclination angle screw portion 111a, 121a disposed on an inlet port 134 side for transferring and compressing a gas, and an equal lead screw portion 111b, 121b with one lead or a plurality of leads which is continuous with the unequal lead unequal inclination angle screw portion 111a, 121a for transferring the gas.

In the unequal lead unequal inclination angle screw portions 111a and 121a, a tooth lead angle changes according to a rotation angle of the male rotor 110 and the female rotor 120 so that the volume of a V-shaped gas working chamber formed by the male rotor 110, the female rotor 120, and the stator 130 changes to decrease, thereby carrying out transfer and compression and carrying out compression and exhaust near an outlet port 135.

In the unequal lead unequal inclination angle screw portions 111a and 121a, since transfer, compression, and exhaust are carried out, the temperature of the male rotor 110 and the female rotor 120 becomes uniform.

As shown in FIGS. 1, 3, and 4, the male rotor 110 and the female rotor 120 have rotor hollow portions 112 and 122 which are opened on both end face sides of at least one of the male rotor 110 and the female rotor 120 in a rotation-axis longitudinal direction, i.e. which pass through the male rotor 110 and the female rotor 120 in the rotation-axis longitudinal direction.

The perpendicular-to-axis cross-sectional shape of each of the rotor hollow portions 112 and 122 is circular.

As shown in FIG. 1, the stator 130 comprises a stator body portion 131 receiving therein the male rotor 110 and the female rotor 120, a first support portion 132 fixed to the stator 130 and supporting the drive motors 140A and 140B and the bearings 160Aa, 160Ab, 160Ba, and 160Bb, a second support portion 133 fixed to the stator 130 and supporting the bearings 160Ac and 160Bc, and the inlet port 134 and the outlet port 135 formed in the stator body portion 131 for communicating with one end and the other end of a gas working chamber.

As shown in FIG. 1, the first support portion 132 is partially received in the rotor hollow portions 112 and 122.

As shown in FIG. 1, the drive motors 140A and 140B are partially received in the rotor hollow portions 112 and 122 of the male rotor 110 and the female rotor 120, respectively, and are synchronously controlled by the inverter (not illustrated).

As shown in FIG. 1, the drive motor 140A is disposed between the bearings 160Aa and 160Ab.

As shown in FIG. 1, the drive motor 140B is disposed between the bearings 160Ba and 160Bb.

As shown in FIG. 1, the rotation shafts 150A and 150B are partially received in the rotor hollow portions 112 and 122.

As shown in FIG. 1, the rotation shafts 150A and 150B respectively have flange portions 151A and 151B extending toward and fixed to inner peripheral walls of the rotor hollow portions 112 and 122.

As shown in FIG. 1, the bearing mechanisms of the rotation shafts 150A and 150B are formed by the bearings 160Aa and 160Ba disposed on the inlet port 134 side, the bearings 160Ac and 160Bc disposed on the outlet port 135 side, and the bearings 160Ab and 160Bb disposed between the bearings 160Aa and 160Ac and between the bearings 160Ba and 160Bc.

The gears 170A and 170B are attached to the rotation shafts 150A and 150B and function to prevent contact between the screw gear portion 111 of the male rotor 110 and the screw gear portion 121 of the female rotor 120 at the time of occurrence of abnormality and in particular to reduce vibration and noise due to backlash of the screw gear portions 111 and 121 at the time of starting and stopping rotation of the male and female rotors 110 and 120.

The oil supply means 180 serves to supply the lubricating oil to the pump components and, as shown in FIG. 2, comprises an oil storage portion 181 storing the lubricating oil, push-up heads 182 each for pushing up the lubricating oil from the oil storage portion 181 by centrifugal force and drag effect, and oil flow paths 183 each for supplying the lubricating oil, pushed up by the push-up head 182, to the pump components.

FIG. 2 is a diagram for conceptually explaining the circulation paths of the lubricating oil by hatching the respective portions associated with the circulation paths of the lubricating oil. In FIG. 2, arrows are given for conceptually explaining the circulation paths of the lubricating oil, but not for showing specific circulation paths of the lubricating oil.

As shown in FIG. 2, the oil storage portion 181 is a space formed in the lower part of the stator 130 for storing the lubricating oil. In this oil storage portion 181, a cooling pipe 191 of the later-described cooling device 190 is disposed.

As shown in FIG. 2, each push-up head 182 has a through hole passing through in a vertical direction and an inner peripheral surface of this through hole is formed in a tapered shape which increases in diameter from lower to upper. The push-up heads 182 are fixed to lower ends of the rotation shafts 150A and 150B so that while the screw vacuum pump 100 is driven, the push-up heads 182 are configured to rotate along with the rotation shafts 150A and 150B, thereby pushing up the lubricating oil from the oil storage portion 181 by the tapered inner peripheral surfaces, centrifugal force due to the rotation of the rotation shafts 150A and 150B, and the drag effect.

Each oil flow path 183 is a circulation path that is formed at a position physically isolated from the above-mentioned gas working chamber, that supplies the lubricating oil, pushed up by the push-up head 182, to the pump components, and that again returns the lubricating oil, supplied to the pump components, to the oil storage portion 181. The lubricating oil flows along inner walls defining the oil flow paths 183 and simultaneously flows in the form of mist in the hollow oil flow paths 183. Specifically, in this embodiment, as shown in FIG. 2, the lubricating oil is pushed up from the oil storage portion 181 by the push-up heads 182 to move upward by centrifugal force in the hollow portions formed in the rotation shafts 150A and 150B and is ejected to the outside of the rotation shafts 150A and 150B near upper portions of the bearings 160Aa and 160Ba. Then, the ejected lubricating oil is supplied into the bearings 160Aa and 160Ba, then flows in the form of mist in hollow portions formed between the bearings 160Aa and 160Ba and the drive motors 140A and 140B and simultaneously flows along inner walls defining the hollow portions, and then is supplied into the drive motors 140A and 140B. Then, the lubricating oil exiting the drive motors 140A and 140B flows in the form of mist in hollow portions formed between the drive motors 140A and 140B and the bearings 160Ab and 160Bb and simultaneously flows along inner walls defining the hollow portions, and then is supplied into the bearings 160Ab and 160Bb. Then, the lubricating oil exiting the bearings 160Ab and 160Bb flows in the form of mist in hollow portions formed between the bearings 160Ab and 160Bb and the synchronous gears 170A and 170B and simultaneously flows along inner walls defining the hollow portions, and then is supplied to the synchronous gear 170A, 170B side. The lubricating oil supplied to the synchronous gear 170A, 170B side is supplied to surfaces of the synchronous gears 170A and 170B, including a meshing portion between the synchronous gears 170A and 170B. Then, the lubricating oil is supplied into the bearings 160Ac and 160Bc and is again returned to the oil storage portion 181. Lubricating oil supply portions may be arbitrarily set according to a carrying-out mode.

The cooling device 190 is for water-cooling the lubricating oil stored in the oil storage portion 181 and, as shown in FIG. 2, comprises the cooling pipe 191 disposed in the oil storage portion 181 for circulating cooling water and a cooling pump 192 for supplying the cooling water into the cooling pipe 191. In FIG. 1, illustration of the cooling device 190 is omitted.

As shown in FIG. 5, engagement of the male rotor 110 and the female rotor 120 is located outside gear engagement pitch circles SA and SB determined by a distance between the rotation shaft (rotation axis) 150A of the male rotor 110 and the rotation shaft (rotation axis) 150B of the female rotor 120 and the numbers of teeth of the male rotor 110 and the female rotor 120.

As a consequence, there are no tooth surfaces where the tooth-surface speeds of the screw gear portion 111 and the screw gear portion 121 are equal to each other, thereby achieving an operation of raking out sucked reaction product or the like and thus achieving an effect of raking out the reaction product to the exterior of the pump.

Symbols DA and DB shown in FIG. 5 represent the outer diameters of the male rotor 110 and the female rotor 120.

In this embodiment thus obtained, since the drive motors 140A and 140B are partially received in the rotor hollow portions 112 and 122, it is possible to reduce the pump size in the rotation-axis longitudinal direction.

Since it is possible to make most of the drive heat of the drive motors 140A and 140B stay inside the male rotor 110 and the female rotor 120 and thus to reduce the influence of the drive heat of the drive motors 140A and 140B on the pump components other than the male rotor 110 and the female rotor 120, it is possible to achieve high flexibility of design of the pump components.

Further, since the drive motors 140A and 140B are partially received in the rotor hollow portions 112 and 122, the drive heat generated from the drive motors 140A and 140B causes the temperature of the screw gear portions 111 and 121 of the male rotor 110 and the female rotor 120 to be uniform so that thermal expansion of the screw gear portion 111 of the male rotor 110 and that of the screw gear portion 121 of the female rotor 120 can be maintained on the same level. Therefore, the engagement gap between the screw gear portions 111 and 121 of the male rotor 110 and the female rotor 120 is maintained uniform without localization. As a consequence, there is no engagement contact between the screw gear portions 111 and 121 so that the engagement gap is made stable and, therefore, it is possible to prevent back diffusion from the outlet port 135 side, thereby reducing the power consumption and achieving stable operation of the screw vacuum pump 100.

The drive motors 140A and 140B are disposed between the bearings 160Aa and 160Ab and between the bearings 160Ba and 160Bb.

This makes it possible to ensure a certain distance between the bearings 160Aa and 160Ab and between the bearings 160Ba and 160Bb for reliably receiving the rotation shafts and to effectively use spaces between the bearings 160Aa and 160Ab and between the bearings 160Ba and 160Bb as installation spaces for the drive motors 140A and 140B, thereby further reducing the pump size in the rotation-axis longitudinal direction. That is, since the motors are placed inside the screw rotors, the external size of the pump can be largely reduced. While a conventional pump cannot be disposed near a semiconductor device manufacturing apparatus, a liquid crystal panel manufacturing apparatus, or a solar panel manufacturing apparatus, this motor built-in screw pump can be disposed near the apparatus or under a chamber so that it is possible to largely improve an apparatus installation space.

Further, since the male rotor 110 and the female rotor 120 have the unequal lead unequal inclination angle screw portions 111a and 121a on the inlet port 134 side and the equal lead screw portions 111b and 121b on the outlet port 135 side and since the engagement of the male rotor 110 and the female rotor 120 is located outside the gear engagement pitch circles SA and SB determined by the distance between the axes of the male rotor 110 and the female rotor 120 and the numbers of teeth of the male rotor 110 and the female rotor 120, it is possible to increase the compression ratio, to obtain the effect of raking out the product, and to maintain the stable pumping speed down to 0.5 Pa.

Second Embodiment

Next, a screw vacuum pump 200 according to a second embodiment of this invention will be described with reference to FIG. 6.

Herein, the structures, other than a drive motor 240, of the screw vacuum pump 200 according to the second embodiment are totally the same as those described above. Therefore, by reading 100s symbols shown in the description relating to the screw vacuum pump 100 of the first embodiment and shown in FIGS. 1 to 5 as 200s symbols, explanation of the structures other than the drive motor 240 is omitted.

As shown in FIG. 6, in the screw vacuum pump 200 according to the second embodiment of this invention, the single drive motor 240 as a drive source common to a male rotor 210 and a female rotor 220 is received in a rotor hollow portion 212 formed in the male rotor 210.

The drive motor 240 rotates a rotation shaft 250A and a drive force of the drive motor 240 is synchronously transmitted also to a rotation shaft 250B through synchronous gears 270A and 270B. In order to rotate the other screw rotor, the synchronous gears 270A and 270B are formed larger in width and stronger than the gears 170A and 1708 of the first embodiment.

Also in the second embodiment, oil supply means 280 and a cooling device (not illustrated) configured in the same manner as in the first embodiment are provided. However, since there is no difference other than the number of drive motors to be supplied with lubricating oil, illustration and explanation thereof are omitted.

Also in this embodiment, since the motor is placed inside the screw rotor, the external size of the pump can be largely reduced. While a conventional pump cannot be disposed near a semiconductor device manufacturing apparatus, a liquid crystal panel manufacturing apparatus, or a solar panel manufacturing apparatus, this motor built-in screw pump can be disposed near the apparatus or under a chamber so that it is possible to largely improve an apparatus installation space.

MODIFICATION

Next, a modification common to the first and second embodiments of this invention will be described with reference to FIG. 7.

In the above-mentioned first and second embodiments, as shown in FIGS. 1 and 6, the description has been given assuming that the screw gear portions 111 and 121, 211 and 221 of the male rotor 110, 210 and the female rotor 120, 220 each have the unequal lead unequal inclination angle screw portion 111a, 121a, 211a, 221a and the equal lead screw portion 111b, 121b, 211b, 221b with one lead or a plurality of leads.

In this modification, as shown in FIG. 7, screw gear portions 311 and 321 of a male rotor 310 and a female rotor 320 each comprise a first equal lead screw portion 311a, 321a which is disposed on an inlet port 335 side, an unequal lead unequal inclination angle screw portion 311b, 321b which is continuous with the first equal lead screw portion 311a, 321a, and a second equal lead screw portion 311c, 321c with one lead or a plurality of leads which is continuous with the unequal lead unequal inclination angle screw portion 311b, 321b.

FIG. 7 shows only the male rotor 310.

In the first embodiment, the second embodiment, and the modification, the description has been given assuming that the screw gear portions of the male rotor and the female rotor each have the unequal lead unequal inclination angle screw portion and the equal lead screw portion. However, each screw gear portion may be designed to have only an unequal lead unequal inclination angle screw portion.

Further, size design and combination of an unequal lead unequal inclination angle screw portion and an equal lead screw portion may be properly set according to a carrying-out mode.

DESCRIPTION OF SYMBOLS

110, 210 male rotor

111, 211 screw gear portion

111 a unequal lead unequal inclination angle screw portion

111 b equal lead screw portion

112, 212 rotor hollow portion

120, 220 female rotor

121, 221 screw gear portion

121 a unequal lead unequal inclination angle screw portion

121 b equal lead screw portion

122, 222 rotor hollow portion

130, 230 stator

131, 231 stator body portion

132, 232 first support portion

133, 233 second support portion

134, 234 inlet port

135, 235 outlet port

140A drive motor

140B drive motor

240 drive motor

150A, 250A rotation shaft

150B, 250B rotation shaft

151A, 251A flange portion

151B, 251B flange portion

160Aa, 260Aa bearing

160Ab, 260Ab bearing

160Ac, 260Ac bearing

160Ba, 260Ba bearing

160Bb, 260Bb bearing

160Bc, 260Bc bearing

170A, 170B gear

270A, 270B synchronous gear

180, 280 oil supply means

181 oil storage portion

182 push-up head

183 oil flow path

190 cooling device

191 cooling pipe

192 cooling pump

310 male rotor

311 screw gear portion

311 a first equal lead screw portion

311 b unequal lead unequal inclination angle screw portion

311 c second equal lead screw portion

312 rotor hollow portion

Claims

1. A screw vacuum pump comprising a male rotor and a female rotor respectively having, on their outer peripheral sides, screw gear portions engaging each other, a stator receiving therein the male rotor and the female rotor, and a drive motor/motors for rotating the male rotor and the female rotor, the screw gear portion of the male rotor, the screw gear portion of the female rotor, and the stator cooperatively form a gas working chamber,the stator has an inlet port and an outlet port adapted to communicate with one end and the other end of the gas working chamber,at least one of the male rotor and the female rotor has a rotor hollow portion which is opened on at least one end face side of the male rotor and/or the female rotor in a rotation-axis longitudinal direction, andthe drive motor is at least partially received in the rotor hollow portion.

2. The screw vacuum pump according to claim 1, wherein the male rotor and the female rotor respectively have the rotor hollow portions,the drive motors are provided in the number of two, andthe respective drive motors are at least partially received in the rotor hollow portions of the male rotor and the female rotor, respectively.

3. The screw vacuum pump according to claim 1, wherein the screw vacuum pump further comprises rotation shafts at least partially received in the rotor hollow portion/portions and fixed to at least one of the male rotor and the female rotor and at least two bearings for each of the rotation shafts, andwherein the drive motor is disposed between the bearings.

4. The screw vacuum pump according to claim 1, wherein the stator comprises a stator body portion receiving therein the male rotor and the female rotor and a support portion partially received in the rotor hollow portion/portions and supporting the drive motor/motors and/or the bearings.

5. The screw vacuum pump according to claim 1, wherein each of the screw gear portions of the male rotor and the female rotor comprises an unequal lead unequal inclination angle screw portion disposed on the inlet port side and an equal lead screw portion with one lead or a plurality of leads which is continuous with the unequal lead unequal inclination angle screw portion.

6. The screw vacuum pump according to claim 1, wherein each of the screw gear portions of the male rotor and the female rotor comprises a first equal lead screw portion disposed on the inlet port side, an unequal lead unequal inclination angle screw portion continuous with the first equal lead screw portion, and a second equal lead screw portion with one lead or a plurality of leads which is continuous with the unequal lead unequal inclination angle screw portion.

7. The screw vacuum pump according to claim 1, wherein engagement of the male rotor and the female rotor is located outside gear engagement pitch circles determined by a distance between a rotation axis of the male rotor and a rotation axis of the female rotor and the numbers of teeth of the male rotor and the female rotor.

8. The screw vacuum pump according to claim 1, wherein the screw vacuum pump further comprises rotation shafts fixed to at least one of the male rotor and the female rotor and oil supply unit for supplying lubricating oil, andwherein the oil supply means unit comprises an oil storage portion storing the lubricating oil, push-up heads fixed to the rotation shafts for pushing up the lubricating oil from the oil storage portion by the use of rotation of the rotation shafts, and oil flow paths for supplying the lubricating oil, pushed up by the push-up heads, to predetermined portions.

9. The screw vacuum pump according to claim 8, wherein the screw vacuum pump further comprises a cooling device for cooling the lubricating oil.