CN107110156A

CN107110156A - Screw vacuum pump

Info

Publication number: CN107110156A
Application number: CN201580072378.5A
Authority: CN
Inventors: 田中智成; 铃木敏生
Original assignee: Ulvac Inc
Current assignee: Ulvac Inc
Priority date: 2015-01-05
Filing date: 2015-12-15
Publication date: 2017-08-29
Anticipated expiration: 2035-12-15
Also published as: JP6446476B2; KR20170102324A; CN107110156B; KR101883894B1; TW201634812A; JPWO2016110902A1; WO2016110902A1; TWI670418B

Abstract

Screw vacuum pump with a pair of screw rotors, once a curve for constituting the axle vertical-sectional shape of helical tooth is created by epitrochoid curve, then the mutual gap of the helical tooth of two screw rods rotor is big in pivot side, and is become narrow gradually to its outer circumferential side.First curve is when based on gap between two helical tooths (the 22a, 22b) flank of tooth being zero, the coordinate (X radially for the epitrochoid curve that the point on the second circular arc of paired another screw rotor is created_t, Y_t) and the correction angle (α) that is calculated with following formula (formula 1) coordinate is modified, connect revised each coordinate (X=X_tCos α-Y_tSin α, Y=X_tsinα+Y_tCos α) draw curve.【Formula 1】

Description

Screw vacuum pump

Technical field

The present invention relates to a kind of screw vacuum pump, it has the helical tooth that has that the hand of spiral is opposite, pitch is equal respectively A pair of screw rotors, by this pair of screw rotors to be mutually twisted but discontiguous state is stored in the housing, and pass through two spiral shells The synchronous rotary of bar rotor and from one end air-breathing of housing from the other end spue.

Background technology

This screw vacuum pump is for example known patent document 1.In this before example, the axle vertical section shape of helical tooth First circular arc of the shape centered on constituting the pivot by screw rotor in its bottom of the tooth portion；Constitute turning with screw rod for its tooth crest The second circular arc centered on the pivot of son；And the first circular arc and the first curve of the second circular arc and the second song are connected respectively Line is created and formed.Also, the epitrochoid that point of first curve on the second circular arc of paired another screw rotor is created Curve is created and formed, and the virtual rack (ラッ Network) that the second curve is made up of defined curve, which is created, to be formed.

The gas of air entry suction from housing is limited between screw rotor and housing by this screw vacuum pump, by one Compress while transporting, from the discharge opening discharge of housing on side.Now, if the gap between the flank of tooth of two helical tooths of increase is to ensure spiral shell If rotation tooth is not interfered with each other each other, then increased by the capacity of returns of the gas of the clearance backflow, cause the decline of pump capacity.Cause This, should consider the thermal expansion corresponding with the use environment of screw vacuum pump and machining accuracy etc., and design again makes a pair of spiral shells Gap between the flank of tooth of two helical tooths when bar rotor is engaged but do not contacted each other is whole radially equal and as much as possible at it Small (such as 0.05mm).

Herein, find in above-mentioned previous example, once the first circular arc of connection and the second circle are created with epitrochoid curve First curve of arc, then the mutual gap of the helical tooth of two screw rods rotor is big in pivot side, and gradually becomes to its outer circumferential side It is narrow.This is considered as the pitch of the helical gear due to any distance (R) place of the radial direction in the pivot to screw rotor Caused by angle (θ p) is different.Therefore, the present inventor etc. is had been found that according to the rotation with screw rotor by constantly research The pitch angle (θ p) for turning center distance (R) place calculates correction angle (α), and the seat of epitrochoid curve is corrected on this basis Mark, so that it may make the gap between the flank of tooth of two helical tooths whole radially equal at it.

Prior art literature

Patent document

【Patent document 1】Patent Publication is into 8-189485 publications

The content of the invention

The invention technical problem to be solved

Present invention research based on more than is made, and its problem is to provide a kind of be mutually twisted in a pair of screw rotors but not The equal screw vacuum pump in gap between the flank of tooth of two helical tooths during contact.

Solve the means of technical problem

To solve above-mentioned problem, screw vacuum pump of the invention, it is characterised in that：And have respectively the hand of spiral it is opposite, A pair of screw rotors of the equal helical tooth of pitch, this pair of screw rotors are to be mutually twisted but discontiguous state is accommodated in shell In body, spued by the synchronous rotary of two screw rods rotor from one end air-breathing of housing from the other end, the axle of helical tooth is vertically cutd open First circular arc of the face shape centered on constituting the pivot by screw rotor in its bottom of the tooth portion；Constitute its tooth crest with spiral shell The second circular arc centered on the pivot of bar rotor；And the first circular arc and the first curve of the second circular arc and are connected respectively Two curves create form, on the axle vertical section of screw rotor, by X-direction of two direction of principal axis of orthogonal radial direction with Y direction, the of paired another screw rotor that the first curve is when based on the gap between the flank of tooth of two helical tooths being zero Coordinate (the X radially for the epitrochoid curve that point on two circular arcs is created_t=2Acos θ-r_dCos (2 θ), Y_t=2Asin θ-r_dSin (2 θ), A are the half of the distance between the pivot of two screw rods rotor, r_dRadius, the θ for being the second circular arc are rotations Angle) and the correction angle (α) that is calculated with following formula (formula 1) coordinate is modified, connect revised each coordinate (X= X_tCos α-Y_tSin α, Y=X_tsinα+Y_tCos α) draw curve.

【Formula 1】

(still, P is the pitch of helical tooth, and R is that radial distance, DG to the center of the rotary shaft of screw rotor are spirals The half of distance between the flank of tooth of tooth.)

Using the present invention, correction angle is calculated according to the pitch angle (θ p) at distance (R) place of the pivot to screw rotor (α), two helical tooths when correcting the coordinate of epitrochoid curve, therefore can make a pair of screw rotors be mutually twisted but not contact Gap between the flank of tooth is whole radially equal and small as best one can at it.

In the present invention, it is preferred to which second curve is combined by epicycloid curve and involute curve.

Brief description of the drawings

Fig. 1 is the profile of the structure for the screw vacuum pump for illustrating embodiments of the present invention.

Fig. 2 (a) is that figure, (b) of the axle section shape for showing helical tooth are the axle vertical-sectional shapes for showing helical tooth Figure, (c) be show two helical tooths be mutually twisted but discontiguous state axle vertical cross section.

Fig. 3 (a) be cut off using the internal diameter of the helical tooth as a screw rotor figure of the screw rotor, (b) be with The figure of the screw rotor is cut off as the internal diameter of the helical tooth of another screw rotor.

Fig. 4 is the chart for the reason for gap for illustrating that the helical tooth of a pair of screw rotors is mutual changes.

Fig. 5 is the chart of the amendment for the coordinate for illustrating the first curve.

Embodiment

Reference picture 1, SP is the screw vacuum pump of embodiments of the present invention.Screw vacuum pump SP has cylindric housing 1, it is provided with and (does not scheme with the connecting tube from equipment (vacuum chamber etc.) to be vacuumized in the side (being upside in Fig. 1) of housing 1 Show) air entry 11 that freely connects.It is provided with to spue the gas in housing 1 in the opposite side (being downside in Fig. 1) of housing 1 and arrives Outside discharge opening 12.Also, a pair of screw rotors 2₁、2₂With with integrally formed its helical tooth 22a of rotary shaft 21a, 21b, 22b is mutually twisted but discontiguous state is accommodated in the operating space 1a in housing 1.In the following description, use with Fig. 1 institutes On the basis of the posture shown, with a pair of screw rotors 2₁、2₂Rotary shaft 21a, 21b extension direction be above-below direction, with it just The direction of friendship is the term in the expression direction of left and right directions.

Above housing 1 opening and lower aperture by the airtight air-breathing side cover 13a for keeping its internal operating space 1a and Discharge side cover 13b is closed.Bearing 3a, 3b are assembled with respectively on air-breathing side cover 13a and discharge side cover 13b, and support respectively Pair of right and left screw rotor 2₁、2₂Rotary shaft 21a, 21b upper and lower end.Further, the lower end of rotary shaft 21a, 21b Portion extends to discharge side cover 13b lower section, outside be inserted with respectively be mutually twisted and homomorphosis gear 4a, 4b.And then, Right screw rotor 2₁Rotary shaft 21a lower end be provided with connector 5a, with the company being arranged in the drive shaft 61 of motor 6 Joint 5b is connected and the power of motor 6 is introduced into rotary shaft 21a.Thus, two screw rods rotor 2₁、2₂It is synchronized with each other reverse Rotation, screw rotor 2 is limited to by the gas sucked from the air entry 11 of housing 1₁、2₂Between housing 1 and transport, in spiral Tooth 22a, 22b terminal part are compressed and protruded from discharge opening 12.

Screw rotor 2₁、2₂Each helical tooth 22a, 22b be respectively formed as the distance of these helical tooths 22a, 22b to each other (height of above-below direction) is that pitch P (or pin) is equal and its hand of spiral is opposite.The axle of each helical tooth 22a, 22b tooth form Shown in section shape and axle vertical-sectional shape such as Fig. 2 (a)~(c), by constitute its bottom of the tooth portion (in Fig. 2 (b) for Ta-Tb it Between) the pivot tc by rotary shaft 21a, 21b centered on the first circular arc t1, constituted its tooth crest and (be in Fig. 2 (b) Between Tc-Td) with screw rotor 2₁、2₂Pivot centered on tc the second circular arc t2 and respectively connection first justify Arc t1 and the second circular arc t2 the first curve t3 (be in Fig. 2 (b) Tb-Tc between) and the second curve t4 (is Td- in Fig. 2 (b) Between Ta) create form.Second curve t4 is for example combined by epicycloid curve and involute curve.

Herein, learn once constituting a screw rotor 2₁Each helical tooth 22a the first curve t3 by another screw rod turn Son 2₂The second circular arc t2 on the epitrochoid curve that creates of point create and form, then helical tooth 22a, 22b is mutual Gap such as Fig. 3 (a) and (b) are shown, big in the pivot tc sides of rotary shaft 21a, 21b, are become narrow gradually to its outer circumferential side.This Be considered as due to helical tooth 22a, 22b at arbitrary distance (R) place to pivot tc radial directions pitch angle (θ p) no Together, i.e. as shown in figure 4, arbitrary distance (R) for example is set into A, B, C for the arc length (girth) of the circle of radius, by them Caused by angle, θ p1, θ p2, θ p3 for being formed when being highly connected from pitch is different.Accordingly, it would be desirable to will be angularly by helical tooth The clearance amendment of 22a, 22b to each other is fixed value.

In the present embodiment, the first curve t3 is when based on the gap between two helical tooth 22a, 22b flank of tooth being zero Another screw rotor 2₂The second circular arc t2 on the coordinate (X radially of epitrochoid curve that is created of point_t=2Acos θ-r_dCos (2 θ), Y_t=2Asin θ-r_dSin (2 θ), A are two screw rods rotors 2₁、2₂Pivot tc between distance one Halfth, r_dRadius, the θ for being the second circular arc t2 are the anglecs of rotation) and the correction angle (α) that is calculated with following formula (formula 1) coordinate is entered Row amendment, connects revised each coordinate (X=X_tCos α-Y_tSin α, Y=X_tsinα+Y_tCos α) draw curve.

【Formula 1】

I.e. reference picture 5, when using above-mentioned epitrochoid curve as the first curve t3, draws bent as shown by dashed lines in Fig. 5 Line (X_t=2Acos θ-r_dCos (2 θ), Y_t=2Asin θ-r_dsin(2θ).Also, consider and screw rotor 2₁、2₂Rotation Center tc distance (R), pitch angle (θ p) now can be represented with following formula (formula 2).

【Formula 2】

Then, when the distance that should move the position for being zero from the gap between two helical tooth 22a, 22b flank of tooth is set to ij When, ij can be represented with following formula (formula 3), can be deformed into following formula (formula 4).Now, P is helical tooth 22a, 22b pitch, and R is To the radial distance at the center of rotary shaft 21a, 21b, DG is the half of the distance between helical tooth 22a, 22b flank of tooth.

【Formula 3】

【Formula 4】

According to above-mentioned various (formula 2)~formula (formula 4), correction angle (α) is represented by above-mentioned formula (formula 1), by its table Show in Figure 5, as indicated by chain dotted lines.In addition, Fig. 5 is shown with (X, Y)=0,0 is screw rotor 2₁、2₂Pivot when Coordinate system, be that Fig. 2 (b) institutes diagrams rotates figure corresponding to the state after 180 °.

Once correction angle (α) is determined as described above, between the flank of tooth that two helical tooth 22a, 22b are corrected based on correction angle (α) Epitrochoid curve of gap when being zero coordinate (X_t, Y_t), then the first curve t3 be Fig. 5 in connect coordinate shown in solid (X=X_tCos α-Y_tSin α, Y=X_tsinα+Y_tCos α) curve.Using above-mentioned embodiment, according to screw rotor 2₁, 2₂The pivot tc pitch angle (θ p) at distance (R) place calculate correction angle (α), correct the coordinate of epitrochoid curve, Therefore a pair of screw rotors 2 can be made₁、2₂Gap between the flank of tooth of two helical tooth 22a, 22b when being mutually twisted but not contacting is at it It is whole equal in the radial direction and small as best one can.

Embodiments of the present invention are illustrated above, but the present invention is not limited in the above.In above-mentioned reality Apply in mode, cycloidal curve and involute curve are combined beyond being to form the second curve t4 in case of, it is not limited to This, for example, can also be sine curve, cycloidal curve, clothoid.Further, screw rotor 2₁、2₂Radical can also not be one Root but more than two.

Description of reference numerals

1 ... housing, 2₁, 2₂... screw rotor, 21a, 21b ... rotary shaft, 22a, 22b ... helical tooth, the circular arcs of t1 ... first, The circular arcs of t2 ... second, the curves of t3 ... first, the curves of t4 ... second.

Claims

1. a kind of screw vacuum pump, it is characterised in that：

With a pair of screw rotors for having the hand of spiral is opposite, pitch is equal helical tooth respectively, this pair of screw rotors are with phase Mutually occlusion but discontiguous state is stored in the housing, by the synchronous rotary of two screw rods rotor from one end air-breathing of housing from The other end spues,

First circle of the axle vertical-sectional shape of helical tooth centered on constituting the pivot by screw rotor in its bottom of the tooth portion Arc；The second circular arc centered on constituting the pivot by screw rotor of its tooth crest；And connect respectively the first circular arc and First curve of the second circular arc and the second curve, which are created, to be formed,

On the axle vertical section of screw rotor, two direction of principal axis using orthogonal radial direction as X-direction and Y direction,

Second circle of paired another screw rotor that the first curve is when based on the gap between the flank of tooth of two helical tooths being zero Coordinate (the X radially for the epitrochoid curve that point on arc is created_t=2Acos θ-r_dCos (2 θ), Y_t=2Asin θ- r_dSin (2 θ), A are the half of the distance between the pivot of two screw rods rotor, r_dRadius, the θ for being the second circular arc are the anglecs of rotation) The coordinate is modified with the correction angle (α) calculated with following formula (formula 1), revised each coordinate (X=X is connected_tcos α-Y_tSin α, Y=X_tsinα+Y_tCos α) draw curve.

【Formula 1】

<mrow> <mi>&alpha;</mi> <mo>=</mo> <mfrac> <mrow> <mi>D</mi> <mi>G</mi> </mrow> <mrow> <mi>R</mi> <mi> </mi> <mi>sin</mi> <mrow> <mo>(</mo> <msup> <mi>tan</mi> <mrow> <mo>-</mo> <mn>1</mn> </mrow> </msup> <mo>(</mo> <mfrac> <mi>P</mi> <mrow> <mn>2</mn> <mi>&pi;</mi> <mi>R</mi> </mrow> </mfrac> <mo>)</mo> <mo>)</mo> </mrow> </mrow> </mfrac> </mrow>

(wherein, P is the pitch of helical tooth, and R is that radial distance, DG to the center of the rotary shaft of screw rotor are helical tooths The half of distance between the flank of tooth.)

2. screw vacuum pump according to claim 1, it is characterised in that second curve is by epicycloid curve and gradually opens Line curve combination is formed.