CN105332914B - A kind of complete smooth screw rotor - Google Patents

Abstract

The invention discloses a kind of complete smooth screw rotor, belong to dry type Twin-screw vacuum pump technical field；The screw rotor end face molded line for being proposed is made up of 7 sections of curves, and be all smoothly connected between adjacent curve, in the absence of cusp, addendum circle arc CD and tooth root circular arc FG are smoothly connected using 1 section of circular arc DE and 1 section of equidistant curve EF of cycloid of mutually conjugation engagement, tooth root circular arc FG and circle involute AB are smoothly connected using the equidistant curve GA of cycloid, are smoothly connected circle involute AB and addendum circle arc CD using circular arc BC；2 screw rotor end face molded line are identical at work, and can realize correct engagement；Thus screw rotor end face molded line makees spiral and launches the screw rotor of generation to be made up of 7 flank of tooth vertically, and is smoothly transitted between whole flank of tooth of screw rotor, eliminates the region for being also easy to produce stress concentration；The screw rotor for being proposed has the advantages that intensity high, good airproof performance, small, long service life of wearing and tearing.

Description

A kind of complete smooth screw rotor

Technical field

The present invention relates to dry type Twin-screw vacuum pump, more particularly to suitable for a kind of complete smooth of dry type Twin-screw vacuum pump Screw rotor.

Background technology

Dry type Twin-screw vacuum pump is a kind of positive-displacement vacuum pump, is by 2 screw rotors that can realize engagement Synchronous incorgruous dual AC power motion, forms periodically variable working chamber volume between 2 screw rotors and pump housing inner chamber, realizes Suction, supercharging and the discharge of gas, form vacuum at the import of pump；Screw rotor be by screw rotor end face molded line vertically Make spiral and launch generation；Therefore screw rotor end face molded line and its conjugation meshing performance directly affect the close of Twin-screw vacuum pump Sealing property, efficiency, area utilization factor.

Conventional screw rotor end face molded line is the combination line style of circle involute, cycloid and circular arc；The invention of China's application Patent (application number 201310170259.6) discloses a kind of screw rotor molded line, is made up of 6 sections of curves, including：Involute, mistake Cross curve, addendum circle arc, cycloid long, tooth root circular arc, easement curve；Patent of invention (the application number of China's application 201510169195.7) a kind of screw rotor molded line is disclosed, is made up of 6 sections of curves, including：Involute, easement curve, tooth top Circular arc, cycloid long, tooth root circular arc, easement curve.

It is to use cycloid long connection addendum circle arc and tooth root circular arc in above-mentioned screw rotor end face molded line, but tooth It is not only slip between tip circle arc and cycloid long, there is cusp；In theory, point can be realized correctly engaging with cycloid； But the screw rotor end face molded line that there is cusp has the disadvantages that：Screw rotor end face molded line has cusp to be caused to be generated Screw rotor there is the rough place of the flank of tooth, easily produce stress concentration at the rough place of the flank of tooth, washed away mutability by fluid Shape, the life-span easy to wear, screw rotor is low, sealing property is poor, gas leakage it is larger, influence Twin-screw vacuum pump the limit it is true Reciprocal of duty cycle and pumping speed.

The content of the invention

The present invention proposes a kind of complete smooth screw rotor to solve the above problems；Its screw rotor end face molded line bag Include 7 sections of curves, using the 1 section of circular arc DE and 1 section of equidistant curve EF of cycloid using mutually conjugation engagement by addendum circle arc CD and Tooth root circular arc FG is smoothly connected, and is smoothly connected tooth root circular arc FG and circle involute AB using the equidistant curve GA of cycloid, uses Be smoothly connected for circle involute AB and addendum circle arc CD by circular arc BC；The cusp in screw rotor end face molded line is eliminated, is obtained Complete smooth screw rotor end face molded line；2 complete smooth screw rotor end face molded line of identical are transported in synchronous incorgruous dual AC power In dynamic, the circular arc of side screw rotor end face molded line, the equidistant curve of cycloid, respectively with opposite side screw rotor end face molded line The equidistant curve of cycloid, circular arc can realize correct engagement；Thus screw rotor end face molded line makees spiral and launches institute vertically The screw rotor of generation, not only meets correct engagement, and its flank of tooth is realized all smoothly transitting；Improve screw rotor Sealing property, intensity, life-span so that the screw rotor can be applied to rotating speed higher, while improve Twin-screw vacuum pump Final vacuum and pumping speed；The screw rotor for being proposed has great importance for improving the performance of Twin-screw vacuum pump.

To achieve these goals, the present invention is adopted the following technical scheme that：

Screw rotor makees synchronous incorgruous dual AC power motion at work, and the conjugation theory of engagement according to molded line determines the fortune The equidistant curve and its relative position of the cycloid being meshed with circular arc under flowing mode, realize the smooth company of circular arc and addendum circle arc Connect, being smoothly connected of the equidistant curve of circular arc and cycloid, the equidistant curve of cycloid and tooth root circular arc are smoothly connected, and obtain full light Sliding screw rotor end face molded line；Thus complete smooth screw rotor end face molded line makees spiral to launch generation complete smooth vertically Screw rotor, the screw rotor for being generated all smoothly transits between having the adjacent flank of tooth in 7 flank of tooth, and 7 flank of tooth；2 The screw rotor end face molded line of individual screw rotor is identical, and can realize correct engagement at work, so as to improve screw rod The combination property of rotor.

A kind of complete smooth screw rotor end face molded line, is made up of 7 sections of curves, is followed successively by：Circle involute AB, circular arc BC, Addendum circle arc CD, circular arc DE, the equidistant curve GA of the equidistant curve EF, tooth root circular arc FG and cycloid of cycloid；The equidistant song of cycloid Line EF be the equidistant curve of cycloid (1) with origin O as pivot, obtained after rotate counterclockwise γ angles；Addendum circle arc CD with Circular arc DE is smoothly connected, and circular arc DE is smoothly connected with the equidistant curve EF of cycloid, the equidistant curve EF and tooth root circular arc FG of cycloid It is smoothly connected, realizes that screw rotor end face molded line is all smoothly connected, in the absence of cusp, while ensures the center of addendum circle arc CD Angle is equal with the central angle of tooth root circular arc FG.

A kind of complete smooth screw rotor, makees spiral and launches generation vertically by complete smooth screw rotor end face molded line, Spiral number of turns are more than 2, are made up of 7 flank of tooth, are followed successively by：Crest top land (11), circular-arc tooth surface (12), pitch face (13), the flank of tooth (14), root face (15), concave tooth face (16), circular-arc tooth surface (17)；These flank of tooth are successively by the tooth in screw rotor end face molded line Tip circle arc CD, circular arc BC, circle involute AB, the equidistant curve GA of cycloid, tooth root circular arc FG, the equidistant curve EF and circular arc of cycloid DE makees spiral and launches generation vertically；Described crest top land (11) smoothly transits with circular-arc tooth surface (17), circular-arc tooth surface (17) with Concave tooth face (16) smoothly transits, and concave tooth face (16) smoothly transit with root face (15), between the adjacent flank of tooth of whole screw rotor All smoothly transit；Intermeshing 2 complete smooth screw rotor end face molded line are identical, thus screw rotor end face molded line institute The complete smooth screw rotor of 2 of generation can realize the correct engagement of whole flank of tooth at work.

A kind of Twin-screw vacuum pump, uses a kind of above-mentioned complete smooth screw rotor.

Beneficial effects of the present invention are：

The screw rotor end face molded line for being proposed does not have cusp, is complete smooth；Thus complete smooth screw rotor end face Molded line makees spiral expansion, the complete smooth screw rotor of generation vertically；At work, 2 of correct engagement can mutually be realized The screw rotor end face molded line of complete smooth screw rotor is identical；Therefore the sealing property and mechanical property of screw rotor are improve Can, improve the final vacuum and pumping speed of Twin-screw vacuum pump.

Brief description of the drawings

Fig. 1 is existing screw rotor end face molded lines.

Fig. 2 is a kind of complete smooth screw rotor end face molded lines for being proposed.

Fig. 3 is the engagement figure of the complete smooth screw rotor end face molded line of proposed 2.

Fig. 4 is engagement figure of the complete smooth screw rotor end face molded line of proposed 2 in different angles.

Fig. 5 is the generating process figure of a kind of complete smooth screw rotor end face molded line for being proposed.

Fig. 6 is the engagement figure of the complete smooth screw rotor of proposed 2.

Fig. 7 is a kind of complete smooth screw rotor figure for being proposed.

In figure：R₁- radius of addendum；R₂- pitch radius；R₃- root radius；R_bThe basic circle of-circle involute half Footpath；301st, 302-screw rotor end face molded line；1st, 3-cycloid；2-circle involute；4-outside circle；5-root circle；6、9— Circle；7th, the equidistant curve of 10-cycloid；8-circle involute；α, β, γ-angle；r₁The radius of-circle (6)；r₂The half of-circle (9) Footpath；11-crest top land；12-circular-arc tooth surface；13-pitch face；14-flank of tooth；15-root face；16-concave tooth face；17-circular arc The flank of tooth；18-root face；19-flank of tooth；20-pitch face；21-circular-arc tooth surface；22-crest top land；23-circular-arc tooth surface；24— Concave tooth face.

Specific embodiment

The invention will be further described with embodiment below in conjunction with the accompanying drawings.

As shown in figure 1, the tie point D between the addendum circle arc CD and cycloid DE of existing screw rotor end face molded line is not for Slick spot, i.e. cusp.

As shown in Fig. 2 a kind of complete smooth screw rotor end face molded line for being proposed is made up of 7 sections of curves, it is followed successively by：Circle Involute AB, circular arc BC, addendum circle arc CD, circular arc DE, the equidistant curve of the equidistant curve EF, tooth root circular arc FG and cycloid of cycloid GA；Using 1 section of circular arc DE and 1 section of equidistant curve EF of cycloid of mutually conjugation engagement by addendum circle arc CD and tooth root circular arc FG light , be smoothly connected for tooth root circular arc FG and circle involute AB using the equidistant curve GA of cycloid by slip, will be justified gradually using circular arc BC The AB and addendum circle arc CD that bursts at the seams is smoothly connected；In 7 sections of curves of described composition screw rotor end face molded line between adjacent curve All it is smoothly connected, in the absence of cusp, forms complete smooth screw rotor end face molded line.

As shown in figure 3, be the engagement figure between 2 complete smooth screw rotor end face molded line (301) and (302), mutually The complete smooth screw rotor end face molded line (301) of 2 of engagement and (302) are identical, at work screw rotor end face molded line (301) composition molded line：Circle involute AB, circular arc BC, addendum circle arc CD, circular arc DE, the equidistant curve EF of cycloid, tooth root circular arc The equidistant curve GA of FG, cycloid, respectively with the composition molded line of screw rotor end face molded line (302)：Circle involute ab, cycloid etc. Can realize correctly nibbling away from curve ga, tooth root circular arc fg, the equidistant curve ef of cycloid, circular arc de, addendum circle arc cd, circular arc bc Close.

As shown in figure 4, being engagement figure of 2 entirely smooth screw rotor end face molded line in different angles, (a)~(i) figures In angle of eccentricity corresponding to each neighbor map be staggered 10 °；That is (a) figure is to (b) figure screw rotor end face molded line (301) dextrorotation Turn 10 °, 10 ° of screw rotor end face molded line (302) rotate counterclockwise；B () figure is suitable to (c) figure screw rotor end face molded line (301) Hour hands rotate 10 °, 10 ° of screw rotor end face molded line (302) rotate counterclockwise；By that analogy；In (a), (b), (c) and (d) figure In, the equidistant curve ef of the cycloid in circular arc DE and screw rotor end face molded line (302) in screw rotor end face molded line (301) Intermeshing；In (f), (g), (h) and (i) figure, the equidistant curve EF and spiral shell of the cycloid in screw rotor end face molded line (301) Circular arc de intermeshings in bar rotor end-face molded line (302)；The composition molded line of screw rotor end face molded line (301)：Circle is gradually opened Line AB, circular arc BC, addendum circle arc CD, circular arc DE, the equidistant curve EF of cycloid, tooth root circular arc FG, the equidistant curve GA of cycloid, point Not with the composition molded line of screw rotor end face molded line (302)：Circle involute ab, the equidistant curve ga of cycloid, tooth root circular arc fg, pendulum The equidistant curve ef of line, circular arc de, addendum circle arc cd, circular arc bc can realize correct engagement.

As shown in figure 5, being a kind of generating process figure of complete smooth screw rotor end face molded line；Complete smooth screw rotor The generating process of profile is as follows：

1. as shown in Fig. 5 (a), 5 sections of curves are generated by below equation, respectively：Cycloid (1), circle involute (2), cycloid (3), outside circle (4) and root circle (5), the equation of each section of curve are as follows：

The equation of cycloid (1) is：

The equation of circle involute (2) is：

The equation of cycloid (3) is：

The equation of outside circle (4) is：

The equation of root circle (5) is：

More than：T-angle parameter, rad；R₁- radius of addendum, mm；R₂- pitch radius, mm；R₃- root radius, mm；R_bThe base radius of-circle involute, mm；r₁- arc radius, mm；r₂- arc radius, mm；

2. as shown in Fig. 5 (b), by cycloid (1) pair-wise offset 2r laterally₁, the curve after skew is counterclockwise further around origin O Rotation γ angles, with origin O as the center of circle, radius is as R₁-r₁Circle intersect, make radius as r by the center of circle of its intersection point₁Circle (6), circle (6) is tangent with outside circle (4), and its point of contact is point D；By cycloid (1) pair-wise offset r laterally₁, the curve after skew is again Around origin O rotate counterclockwise γ angles, obtain the equidistant curve (7) of cycloid, the equidistant curve (7) of cycloid and meanwhile with circle (6) and Root circle (5) is tangent, and its point of contact is respectively E, F, obtains the equidistant curve EF of circular arc DE and cycloid；Angle γ is true by equation below It is fixed：

(x₀,y₀) be following 2 curve intersection point：

x²+y²=(R₁-r₁)²

3. as shown in Fig. 5 (b), circle involute (2) is turned clockwise α angles around origin O, obtains circle involute (8)；Make Be the line segment OC of β with Ox axle clamps angle, line segment OC with origin O as the center of circle, radius is as R₁-r₂Circle intersect, with its intersection point as the center of circle Make radius for r₂Circle (9), circle (9) while tangent with outside circle (4) and circle involute (8), its point of contact is respectively C, B；Obtain Circular arc BC and addendum circle arc CD；Angle [alpha], β are determined by equation below：

4. as shown in Fig. 5 (b), cycloid (3) is turned clockwise β angles, postrotational cycloid is equidistantly inclined to inner side again Move r₂, obtain the equidistant curve (10) of cycloid, the equidistant curve (10) of cycloid and meanwhile with circle involute (8) and root circle (5) phase Cut, its point of contact is respectively A, G；Obtain equidistant curve GA, the circle involute AB and tooth root circular arc FG of cycloid.

As shown in fig. 6, being 2 engagement figures of complete smooth screw rotor, intermeshing 2 complete smooth screw rotors Screw rotor end face molded line it is identical, screw rotor (601) for screw rotor end face molded line make vertically counter-clockwise helical launch Generation, screw rotor (602) makees clock wise spirals and launches generation vertically for screw rotor end face molded line, and screw rod turns at work The crest top land (11) of sub (601), circular-arc tooth surface (12), pitch face (13), the flank of tooth (14), root face (15), concave tooth face (16), circle Curved tooth face (17), root face (18) respectively with screw rotor (602), the flank of tooth (19), pitch face (20), circular-arc tooth surface (21), Crest top land (22), circular-arc tooth surface (23), concave tooth face (24) can realize correct engagement.

It is a kind of complete smooth screw rotor figure shown in Fig. 7, complete smooth screw rotor is by complete smooth screw rotor Profile makees spiral and makees to launch generation vertically, and spiral number of turns are more than 2, are made up of 7 flank of tooth, are followed successively by：Crest top land (11), Circular-arc tooth surface (12), pitch face (13), the flank of tooth (14), root face (15), concave tooth face (16), circular-arc tooth surface (17)；Wherein tooth top Face (11) smoothly transits with circular-arc tooth surface (17), and circular-arc tooth surface (17) smoothly transits with concave tooth face (16), concave tooth face (16) and tooth Root face (15) smoothly transits, and is all smoothly transitted between the adjacent flank of tooth of whole screw rotor.

The characteristics of a kind of complete smooth screw rotor for being proposed is：Complete smooth screw rotor is turned by complete smooth screw rod Sub- profile makees spiral and launches generation vertically, and complete smooth screw rotor end face molded line is made up of 7 sections of curves：Circle involute AB, circular arc BC, addendum circle arc CD, circular arc DE, the equidistant curve GA of the equidistant curve EF, tooth root circular arc FG and cycloid of cycloid, phase All it is smoothly connected between varied curve, in the absence of cusp, can be realized between 2 identical screw rotor end face molded line correct Engagement；Thus the complete smooth complete smooth screw rotor of screw rotor end face molded line generation, comprising 7 flank of tooth, is followed successively by：Tooth top Face (11), circular-arc tooth surface (12), pitch face (13), the flank of tooth (14), root face (15), concave tooth face (16), circular-arc tooth surface (17), phase All smoothly transitted between the adjacent flank of tooth, therefore the mechanical property and meshing performance of screw rotor can be effectively improved, reduce screw rod The abrasion and deformation of rotor, eliminate the region for easily producing stress concentration, and be conducive to air seal；What is thus proposed is complete Smooth screw rotor with intensity and good sealing property higher, while the limit that improve Twin-screw vacuum pump is true Reciprocal of duty cycle and pumping speed.

Although above-mentioned be described with reference to accompanying drawing to specific embodiment of the invention, not to present invention protection model The limitation enclosed, one of ordinary skill in the art should be understood that on the basis of technical scheme those skilled in the art are not Need the various modifications made by paying creative work or deformation still within protection scope of the present invention.

Claims (4)

1. a kind of complete smooth screw rotor, its left screw rotor end face molded line (301) includes 7 sections of curves：Left circle involute AB, The first circular arc BC of a left side, left addendum circle arc CD, left second circular arc DE, the equidistant curve EF of left first cycloid, left tooth root circular arc FG and The equidistant curve GA of left second cycloid；It is characterized in that：Using mutually a 1 section of left side the second circular arc DE of conjugation engagement and 1 section of left side first Be smoothly connected for left addendum circle arc CD and left tooth root circular arc FG by the equidistant curve EF of cycloid, using the equidistant curve of left second cycloid Be smoothly connected for left tooth root circular arc FG and left circle involute AB by GA, using left first circular arc BC by left circle involute AB and left tooth top Circular arc C D is smoothly connected；All it is smoothly connected between adjacent curve in 7 sections of curves of described composition screw rotor end face molded line, In the absence of cusp, complete smooth screw rotor end face molded line is formed；And the complete smooth screw rotor end face molded line of identical 2 Correct engagement can be realized in synchronous incorgruous dual AC power motion, the left circle in left screw rotor end face molded line (301) is gradually opened Line AB, left first circular arc BC, left addendum circle arc CD, left second circular arc DE, the equidistant curve EF of left first cycloid, left tooth root circular arc The equidistant curve GA of FG, left second cycloid, respectively with right screw rotor end face molded line (302) in right circle involute ab, right the The equidistant curve ga of one cycloid, right tooth root circular arc fg, the equidistant curve ef of right second cycloid, right first circular arc de, right outside circle Arc cd, right second circular arc bc can realize correct engagement；

The generation method of left screw rotor end face molded line (301) is as follows：

1. 5 sections of curves are generated by below equation, respectively：First cycloid (1), the first circle involute (2), the second cycloid (3), tooth Tip circle (4) and root circle (5), the equation of each section of curve are as follows：

The equation of the first cycloid (1) is：

The equation of the first circle involute (2) is：

The equation of the second cycloid (3) is：

The equation of outside circle (4) is：

The equation of root circle (5) is：

More than：T-angle parameter, rad；R₁- radius of addendum, mm；R₂- pitch radius, mm；R₃- root radius, mm； R_bThe base radius of-circle involute, mm；r₁- arc radius, mm；r₂- arc radius, mm；

2. by the first cycloid (1) pair-wise offset 2r laterally₁, curve after skew further around origin O rotate counterclockwise γ angles, with With origin O as the center of circle, radius is as R₁-r₁Circle intersect, make radius as r by the center of circle of its intersection point₁First circle (6), first circle (6) tangent with outside circle (4), its point of contact is point D；By the first cycloid (1) pair-wise offset r laterally₁, curve after skew further around Origin O rotate counterclockwise γ angles, obtain the equidistant curve (7) of the first cycloid, and the equidistant curve (7) of the first cycloid is while with One circle (6) and root circle (5) are tangent, and its point of contact is respectively E, F, obtains the equidistant curve of left second circular arc DE and left first cycloid EF；Angle γ is determined by equation below：

$\mathrm{\γ}=-\frac{1}{2}arctan\frac{y_0}{x_0}$

(x₀,y₀) be following 2 curve intersection point：

x²+y²=(R₁-r₁)²

$\left\{\begin{array}{c}x\left(t\right)=2R_2\cos \left(t\right)-(R_1-r_1)\cos \left(2t\right)-2r_1\frac{2R_2\cos \left(t\right)-2(R_1-r_1)\cos \left(2t\right)}{\sqrt{4{R_2}^2-8R_2(R_1-r_1)\cos \left(2t\right)+4{(R_1-r_1)}^2}}\\ x\left(t\right)=2R_2\sin \left(t\right)-(R_1-r_1)\sin \left(2t\right)+2r_1\frac{-2R_2\sin \left(t\right)+2(R_1-r_1)\sin \left(2t\right)}{\sqrt{4{R_2}^2-8R_2(R_1-r_1)\cos \left(2t\right)+4{(R_1-r_1)}^2}}\end{array}\right.$

3. the first circle involute (2) is turned clockwise α angles around origin O, obtains the second circle involute (8)；Make and Ox axle clamps Angle is the line segment OC of β, line segment OC with origin O as the center of circle, radius is as R₁-r₂Circle intersect, be as radius by the center of circle of its intersection point r₂Second circle (9), second circle (9) while tangent with outside circle (4) and the second circle involute (8), its point of contact is respectively C, B； Obtain left first circular arc BC and left addendum circle arc CD；Angle [alpha], β are determined by equation below：

$\mathrm{\α}=tan\left(arccos\frac{R_b}{R_2}\right)-arccos\frac{R_b}{R_2}$

$\mathrm{\β}=tan\left(arccos\frac{R_b}{\sqrt{{R_b}^2+(\sqrt{{(R_1-r_2)}^2-{R_b}^2}+r_2}}\right)-arccos\left(\frac{R_b}{R_1-r_2}\right)-\mathrm{\α}$

4. the second cycloid (3) is turned clockwise β angles, by postrotational cycloid again to inner side pair-wise offset r₂, obtain the second pendulum The equidistant curve (10) of line, the equidistant curve (10) of the second cycloid while tangent with the second circle involute (8) and root circle (5), Its point of contact is respectively A, G；Obtain equidistant curve GA, the left circle involute AB and left tooth root circular arc FG of left second cycloid.

2. a kind of complete smooth screw rotor, a kind of complete smooth screw rotor end face molded line as claimed in claim 1 is along axle Launch generation to spiral is made, it is characterized in that：Spiral number of turns are more than 2, are made up of 7 flank of tooth, are followed successively by：Left crest top land (11), a left side First circular-arc tooth surface (12), left pitch face (13), the left flank of tooth (14), left root face (15), left concave tooth face (16), left second circular arc The flank of tooth (17), these flank of tooth successively by the left addendum circle arc CD in left screw rotor end face molded line (301), left first circular arc BC, Left circle involute AB, the equidistant curve GA of left second cycloid, left tooth root circular arc FG, the equidistant curve EF of left first cycloid and left the Two circular arc DE make spiral and launch generation vertically；In 7 flank of tooth of described composition screw rotor, whole light between the adjacent flank of tooth Slip over and cross, form complete smooth screw rotor.

3. a kind of complete smooth screw rotor as claimed in claim 2, it is characterized in that：Intermeshing 2 complete smooth spiral shells Bar rotor makees spiral and launches generation vertically by same complete smooth screw rotor end face molded line, and left screw rotor (601) is a left side Screw rotor end face molded line (301) makees counter-clockwise helical and launches generation vertically, and right screw rotor (602) is right screw rotor end Face molded line makees clock wise spirals and launches generation vertically, at work the left crest top land (11) of left screw rotor (601), left first Circular-arc tooth surface (12), left pitch face (13), the left flank of tooth (14), left root face (15), left concave tooth face (16), left second circular-arc tooth surface (17) right root face (18), respectively with right screw rotor (602), the right flank of tooth (19), right pitch face (20), right first circle-arc tooth Face (21), right crest top land (22), right second circular-arc tooth surface (23), right concave tooth face (24) can realize correct engagement.

4. a kind of Twin-screw vacuum pump, it is characterized in that：Use screw rotor as claimed in claim 1.