CN101210556B - Roots dry type vacuum pump rotor capable of directly discharging to air and processing technique thereof - Google Patents

Abstract

The invention relates to a design of a Roots pump, in particular to a rotor of a Roots dry vacuum pump which discharges directly into atmosphere and processing technology thereof. The processing technology substitutes a waist arc for an involute to design a rotor block, the rotor block is separately processed and then assembled with a spigot shaft. The processing steps are as follows: (1) processing the rotor block: a ductile cast iron bar is selected as roughcast; processing method: firstly processing the outer surface and the two end surfaces of the bar, incising the bar according to the thickness of the rotor block, then processing other two surfaces (outer circular surface and inner circular surface) of the rotor block, finally incising the bar into the rotor block with needed thickness according to application requirements; (2) joining two rotor blocks and a pin roll into a whole via a pin hole. The invention has the advantages of simple processing technology, low cost, high versatility of parts, suitability for IC equipments, etc.

Description

A kind of roots dry vacuum pump rotor and processing technology thereof of discharging directly into atmosphere

Technical field

The present invention relates to Roots Pumps Design, specifically a kind of roots dry vacuum pump rotor and processing technology thereof of discharging directly into atmosphere.

Background technique

IC equipment industry is the important industry of national development strategy.In IC equipment industry, 70% need of work is requiring to carry out for example chemical vapor deposition, ion injection, evaporation, sputter, epitaxial growth, etching, encapsulation, detection etc. under the harsh vacuum environment to cleanliness.In each bar IC production line, all to use a large amount of acquisitions and obtain equipment with the dry vacuum of keeping the clean vacuum environment.Middle-grade technology IC production line with 2.5 ten thousand 8 inches wafers of a monthly output is an example, needs usually with thousands of of various dry vacuum pumps, and investment accounts for about 20% of equipment investment.As one of key equipment of IC equipment, dry vacuum obtains equipment because industrial technology threshold height, production and sales are monopolized by major company of external a few family always, occupied the market share more than 95% in the world as weak former, general of the Germany of Japan, Britain Edward, German Lay treasured, French Alcatel etc., domestic production producer does not almost form the product of industrialization.

Roots pump is developed by Roots blower, the dry type Roots pump that comprises high vacuum multi-stage roots pump, middle vacuum Roots blower pump and discharging directly into atmosphere, being widely used in industries such as chemical industry, papermaking, metallurgy, film preparation, food, also is a kind of vacuum pump commonly used in the IC equipment industry.The research of domestic Roots pump and making early, but it is actually rare to be suitable for the dried pump of Roots that IC equipment industry is strict with, and causes the long-term dependence on import of this equipment.

Roots rotor is the most key part of Roots pump.At the dry type Roots pump that is used for IC equipment industry, the cost of production of a pair of roots rotor accounts for about 40% of overall cost.

The development of the dried pump of discharging directly into atmosphere Roots is as follows:

1854, American Israelis FRANCIS M.ROOTS and PHILAND H.ROOTS two brothers on the basis of rotary blower, invented Roots blower (P.H.ROOTS.ROTARY BLOWER[P] .USPATENT.No.30157.1860.9; F.M.ROOTS.ROTARY PUMP[P] .US PATENT.No.325276.1885.9), and applied for multinomial U. S. Patent successively, and molded lines is revised.In subsequently nearly 150 years, many scholars and machinist revise Roots's molded lines in succession and develop, to satisfy the demand of different occasions.

1900, American RALPH C.ENYART did improvement to Roots's molded lines, had invented Roots type transmission pump as shown in Figure 1.1954, Roots pump appearred; After Roots pump is used 20 years, Germans such as CLAUSWINKELSTRATER are used for this structure the design of Roots pump, but thereby invented dry type Roots pump with ventilation type structure discharging directly into atmosphere (CLAUS WINKELSTRATER, et al.ROTARY-PISTON MACHINE[P] .US PATENT.No.3817667.1974.6).German scholar JHenning write articles (J Henning, H lang.Roots pumps for high difference pressures with cooling bygas circulation[J] .Vacuum 1976:26 (7): 273-276; J.Henning, H.Lang.WGK_Cpumps:Gas-cooled roots pumps-chemical series.Journal of Vacuum Science andTechnology[J] .1978, Vol.15 No.2, pp.784.) introduced the air cooling principle of the dried pump of this Roots, ultimate pressure, pumping performance, energy consumption and heating temperature control etc., point out that this pump adopts two roots rotor axles in the fixing cantilever beam type structure of gear end, the lubricant oil that guarantees gear does not enter into vacuum pump chamber, be particularly suitable for extracting and contain a large amount of condensable gas and chemical emission in the semi-conductor industry, obtain the vacuum environment that cleaning does not have oil.(L.C.Valdes, Renaud Theis, et al.Calculating transient flows through ducts of nonconstantrectangular shape.Vacuum 1997:48 (839-843) such as France scholar L.C.Valdes; L.C.Valdes, Benoit Barthod, et al.Accurateprediction of intemal leaks in stationary dry roots vacuum pumps.Vacuum1999:52 (451-459)), derived by the conductance calculating of transition flow under the non-constant rectangular cross-section, and studied under the non-operating condition static leakage theory by the dried pump of ventilation type Roots gap in conjunction with the Knudsen-Dong rule, and verify by test, but once pointed out: the Knudsen-Dong rule is not suitable for the running simulation of the dried pump of Roots.

Domesticly start late for specializing in then of discharging directly into atmosphere Roots pump.(Cao Yu such as Cao Yu, Luo Gensong. the heat Balance Calculation of ventilation type discharging directly into atmosphere Roots pump and unit [J]. vacuum, 2002, (2) .) carried out the heat Balance Calculation of ventilation type discharging directly into atmosphere Roots pump and unit, point out that it has characteristics such as big, the allowable pressure reduction height of pumping speed, pollution-free, low power consumption.Duan Yongli (Duan Yongli, multistage three leaf dry type Roots pump Study on Several Problems [M], Shenyang: Northeastern University's Master's thesis, 2004) has analyzed the cooling effect of ventilation type three leaf roots rotors.Wang Xiaohu, Zhang Baofu etc. (Wang Xiaohu, Yu Linghua, Zhang Baofu, Luo Gensong is applicable to a kind of molded lines of rotor [J] of ventilation type discharging directly into atmosphere Roots pump. vacuum, 2005, (5)) studied the composition of an Arc Cycloid molded breadth two lobe rotor molded lines.Li Decai etc. have studied the Magneticfluid Seal Technique that Roots's sense is collapsed.

The dried pump of ventilation type Roots satisfied IC equipment industry the operating temperature height, long-term operation is stable, noise is low, maintenances is simple, clean the numerous requirements of no wet goods, is very promising a kind of dry type Roughing pump.At present, have high input etc. the restraining factors except that processing and matching requirements precision height, difficulty of processing are big, disposable, design theory is in urgent need to be improved, especially comprises the determining of reduction, gap of improvement, the processing cost of Roots's molded lines, the calculating of leakage rate, the thermodynamic analysis in the pump etc.

Summary of the invention

Be processed into big, the disposable deficiency that has high input, can not be used for the IC equipment of difficulty in the prior art in order to overcome, the object of the present invention is to provide that a kind of processing technology is simple, cost is low, roots dry vacuum pump rotor and processing technology thereof that part universality is strong, be applicable to the novel discharging directly into atmosphere of IC equipment.

To achieve these goals, technological scheme of the present invention is as follows:

The roots dry vacuum pump rotor of discharging directly into atmosphere: the multi-stage rotor group is installed on the central shaft, and the minimum range δ of two rotor waist circular arcs engagement was between 0.08mm～0.14mm when the rotor set on two central shafts was meshing with each other; Its rotor set is divided into three parts: adopt pin-and-hole location, bolt to be connected between left rotor piece, bearing pin and the right rotor block, left and right rotor block and bearing pin;

The whole outer contour of described rotor block all is made up of circular arc, promptly is made up of periphery, two waist discs and inner headed face; Described multi-stage rotor group inter-stage rotor thickness is by successively decreasing in proportion to the direction of air outlet end from the suction port end; The minimum range of two rotor waist circular arcs engagement is:

${\mathrm{\&delta;}}_{\min }=\min \left\{\sqrt{\begin{array}{c}{[(x_1-x_2+A)\cos \mathrm{\&gamma;}-A+({\mathrm{<figure-callout\; id="1"\; label="y"\; filenames="H061F5910220070123E000032.png"\; state="\{\{state\}\}">y</figure-callout>}}_1+y_2)\sin \mathrm{\&gamma;}]}^2\\ +{[(x_1+x_2-A)\sin \mathrm{\&gamma;}-(y_1-y_2)\cos \mathrm{\&gamma;}]}^2\end{array}}\right\}$

Wherein: A is two rotor centre distances, x ₁Be the dynamic abscissa of left rotor waist circular arc, x ₂Be the dynamic abscissa of the epitrochanterian waist circular arc of correspondence, y ₁Be the dynamic y coordinate of left rotor waist circular arc, y ₂Dynamic y coordinate for the epitrochanterian waist circular arc of correspondence;

The dynamic y coordinate of the dynamic abscissa of left rotor waist circular arc and left rotor waist circular arc draws according to following formula:

$\left\{\begin{array}{c}{x}_1=x_0+R_1\cos {\mathrm{\&alpha;}}_1\\ {\mathrm{<figure-callout\; id="1"\; label="y"\; filenames="H061F5910220070123E000032.png"\; state="\{\{state\}\}">y</figure-callout>}}_1=R_1{\sin \mathrm{\&alpha;}}_1\end{array}\right.$ α ₀≤α ₁≤β ₀

Wherein: x ₀Be the center of circle abscissa of waist circular arc, α ₀Be the initial angle of waist circular arc, α ₁Be the angle of spread of waist circular arc, β ₀Be the end angle of waist circular arc, R ₁Be left rotor left part radius of arc;

The dynamic abscissa of corresponding rotor waist circular arc, the dynamic y coordinate of corresponding rotor waist circular arc draws according to following formula:

$\left\{\begin{array}{c}{x}_2=A-R_1{\sin \mathrm{\&alpha;}}_2\\ y_2=x_0+R_1\cos {\mathrm{\&alpha;}}_2\end{array}\right.$ α ₀≤α ₂≤β ₀

Wherein: A is two rotor centre distances, x ₀Be the center of circle abscissa of waist circular arc, α ₀Be the initial angle of waist circular arc, α ₂Be the angle of spread of the epitrochanterian waist circular arc of correspondence, β ₀End angle for the waist circular arc.

Its processing technology: with waist circularity substitution involute design rotor block, the processing rotor piece is assembled with central shaft more separately; Step is as follows:

1) processing rotor piece: blank is selected the spheroidal graphite cast iron bar for use; Processing method: process outer surface and two end faces of bar earlier, by required rotor block thickness cutting, two faces of all the other of processing rotor piece (periphery and inner headed face) then;

2) two rotor blocks and bearing pin are fused by pin-and-hole.

Also can strengthen the foundry goods diameter, processing method can be processed two end faces of bar earlier, on end face, accomplish fluently the center hole of waist circular arc, the periphery of car rotor block, inner headed face, vertical line cuts into identical two-part then, the center hole that utilization processes is finished the processing of residue bi-side, cuts into rotor block by thickness proportion at last.

The present invention has following advantage:

1. the rotor of structure of the present invention has replaced the working surface of original rotor complexity with the cylndrical surface, can cut down finished cost significantly.

2. the rotor block of Sun Huaiing can directly be changed, and is convenient to safeguard.Because the present invention adopts left and right rotor block and bearing pin package assembly, in case when local failure such as rotor outer surface generation crackle, spot corrosion, scuffing was arranged, the replacing rotor block can be reused, and has reduced maintenance cost, has improved the working life of Roots pump.

3. part universality is strong, and processing technology is simple.The present invention makes respectively and processes rotor block and axle, can use different materials according to different qualities, thereby improve the versatility of part, more helps producing in batches.

4. because the rotor of structure of the present invention adopts periphery at waist, compare to the eel-like figure roots rotor that in the past adopts inner headed face, intensity obviously increases, and structure is more durable.

5. adopt the dried pump of Roots of rotor of the present invention, can satisfy the operating temperature height, long-term operation is stable, noise is low, maintenances is simple, clean no wet goods demand, be specially adapted to IC and equip industry.

Description of drawings

Fig. 1 is Roots's transmission pump structural drawing of American RALPH C.ENYART invention.

Fig. 2 is roots rotor mesh schematic representation (power rotor group and a driven rotor group).

Fig. 3 is the constitutional diagram (driven rotor group) of involute-type Roots molded lines.

Fig. 4 is the composition and the rotor structure figure (left rotor is an example) of circularity substitution Roots molded lines.

Fig. 5 is the 3 d effect graph of roots rotor spindle unit.

Fig. 6 is the comparison diagram of the λ-c curve of two kinds of Roots's molded lines.

Fig. 7 is the gap distribution figure of roots rotor.

Fig. 8 a is the blank design sketch of roots rotor.

Fig. 8 b is the rotor block connection diagram of roots rotor.

Embodiment

Below in conjunction with embodiment and accompanying drawing the present invention is described in further detail.

For simplicity, take this opportunity to illustrate earlier the composition of involute-type Roots molded lines rotor.

Involute is a kind of molded lines that rotor design is usually selected for use, and basic circle equates, bearing of trend pair of opposite involute, is desirable pitch curve.The schematic representation of a pair of involute-type roots rotor engagement is referring to Fig. 2.

Since roots rotor from symmetry properties, only its molded lines of 1/4 is studied, other each several parts can draw according to symmetry properties.Be example with the molded lines of rotor in second quadrant now, the molded lines of involute roots rotor constitutes as shown in table 1.

The theory shaped wire of table 1 involute-type roots rotor is formed

The theory shaped wire of involute-type roots rotor can be derived according to the theory of engagement and mathematical computations.As Fig. 3, under the driven rotor group left part on circular arc A2B2 and the driven rotor group right part center of circle of circular arc C 2D2 be the center O 2 of rotor set central shaft, and conjugate curve each other.The radius R 1 (referring to Fig. 3) of circular arc A2B2 is half of pump chamber diameter d under the driven rotor group left part, and the radius R 3 (referring to Fig. 3) of circular arc C 2D2 is the radius R of circular arc A2B2 under two rotor centre distance A and the driven rotor group left part on the driven rotor group right part ₁Difference.The radius size of two circular arcs and subtended angle size all influence the volumetric efficiency of Roots pump and the sealing effect of rotor and rotor, rotor and pump chamber inwall.

Involute rule really is complicated slightly.Power rotor group right part involute B1C1 and driven rotor group left part involute B2C2 be conjugate curve (referring to Fig. 2) each other mutually, mainly play under circular arc A1B1 on the power rotor group right part and the power rotor group right part between the circular arc C 1D1, and be connected transitional function between the circular arc C 2D2 on circular arc A2B2 and the driven rotor group left part under the driven rotor group left part.By regulating basic circle and the initial angle of driven rotor group left part involute B2C2, can control the shape of rotor, play a major role for " fat ", " thin " of rotor, i.e. the size of the volumetric efficiency of intense influence pump chamber.According to the theory of engagement, the intersection point of intermeshing two involutes and pitch circle must be on the 45 bisector, as Fig. 2 on two rotors.Because symmetry properties, the pressure angle of involute that intermeshing two involutes are corresponding with the intersection point of pitch circle is half of whole pressure angle of involute.During design, can be according to above-mentioned conclusion and the actual involute Base radius of selecting for use, in conjunction with the intersection point of intermeshing two involutes and pitch circle (also for driven rotor group left part under the intersection point of circular arc C 1D1 under circular arc A2B2 and the power rotor group right part) determine the initial angle α and the end angle β of involute, be the position that C2 point and B2 are ordered, as Fig. 3.Under the driven rotor group left part under circular arc A2B2 and the power rotor group right part central angle of circular arc C 1D1 also determine thereupon.Solid line as shown in Figure 3 is a profile line, is its theory shaped wire.

The actual molded lines of involute-type roots rotor can be on the basis of theoretical molded lines, and each segment type line can obtain along contract half of post gap of normal direction, and dotted outline as shown in Figure 2 is its actual molded lines.At this moment, gap delta occurs between two rotors, this is the dry vacuum pump necessary gap of turning round.

The structure of roots rotor of the present invention and molded lines improve:

For Roots pump, the minimum range δ of two rotor waist circular arcs engagements requires very high to the processing and the assembly precision of roots rotor usually between 0.05mm～0.80mm.Equip the industry elevated operating temperature, contain under the dust granules situation especially for use in IC, if the machining accuracy of roots rotor can not get guaranteeing, roots rotor very likely bumps behind expanded by heating in the running even is stuck so, gently then rotor scratches, noise is unusual, heavy then termination of pumping shutdown, burn-down of electric motor, causes great production accident etc.Adopt the molded lines processing of involute roots rotor comparatively difficult, common processing method is design specialized lathe or last Cutter Body Processing with Machining Center, and expends a large amount of man-hours, has directly increased the cost of rotor.

Consider the convenience of processing, the present invention has done improvement to the involute-type rotor, replaces involute with one section circular arc, forms Roots's molded lines rotor by three sections circular arcs.In four quadrants coordinate axes and true origin symplex structure, present embodiment is that example is illustrated with the left rotor molded lines in second quadrant, the whole outer contour of molded lines of rotor all is made up of circular arc, specifically form by left rotor left part circular arc A3B3 and left rotor right part circular arc C 3D3 and waist circular arc B3C3, the left rotor left part circular arc A3B3 and the left rotor right part circular arc C 3D3 center of circle are true origin O3, and the center of circle of waist circular arc is the perpendicular bisector of line segment of waist circular arc two-end-point line and the intersection point (referring to the O4 point of Fig. 4) of coordinate axes; Waist circular arc and central shaft equal diameter.Radius also can determine by mapping or programming calculating is learnt.With the rotor behind the circularity substitution involute, as shown in Figure 4, its outer contour all is made up of circular arc.

In the processing design, the waist circular arc can be designed to and the central shaft equal diameter, and like this, a rotor set can divide work three parts to form: left rotor piece, bearing pin and right rotor block, adopt pin-and-hole location, bolted mode between left and right rotor block and the bearing pin, make up and the formation rotor set.Its tomograph as shown in Figure 5.Present embodiment is 5 groups, and by the direction from the suction port end to the air outlet end, rotor thickness successively decreases in proportion.The ratio of successively decreasing between group is 12: 8: 8: 3: 3.

Describe the blank and the processing technology of roots rotor below in detail:

According to the scheme of circularity substitution involute, design rotor block as shown in Figure 4, machine the back separately and assemble formation roots pump rotor group with central shaft.Rotor block is selected spheroidal graphite cast iron for use, and machining blanks can be directly with the casting bar, shown in Fig. 8 a.Add man-hour, can process outer surface and two end faces of bar earlier, press rotor block thickness cutting, the periphery of processing rotor piece, inner headed face then, processing is easier to, and can process on engine lathe.

Also can strengthen the foundry goods diameter, process two end faces of bar earlier, on end face, accomplish fluently the center hole of waist circular arc, the periphery of car rotor block, inner headed face, vertical line cuts into identical two-part then, the center hole that utilization processes is finished the processing of residue bi-side, cuts into rotor block by thickness proportion at last.Then, with two rotor blocks and bearing pin by pin-and-hole fuse (getting pin-and-hole) at a rotor block and axle central authorities.As Fig. 8 b, the component diagram for the roots rotor piece connects needs for structure representation is clear, does not put into central shaft among the figure.

Adopt the rotor shaft of this structure to have many good qualities, the one, replaced the working surface of original rotor complexity with the cylndrical surface, reduced processing cost significantly; The 2nd, in case when local failure such as rotor outer surface generation crackle, spot corrosion, scuffing is arranged, change rotor block and can reuse, reduced maintenance cost, improved the working life of Roots pump; The 3rd, rotor block and axle are made respectively and are processed, and can use different materials according to different qualities, and improve the versatility of part, more help producing in batches; The 4th, the rotor waist of this structure adopts periphery, compares to the eel-like figure roots rotor that in the past adopts inner headed face, and intensity obviously increases, and structure is more durable.

Relatively see the invention effect structure from volumetric efficiency

, molded lines of rotor identical for the pump chamber physical dimension formed close Roots pump, and the theoretical pumping speed that adopts involute to obtain is often bigger, and promptly volumetric efficiency is bigger.The following describes with of the influence of circularity substitution involute pumping speed.

Definition form factor c is the ratio of pump chamber diameter and two rotor centre distances, and Fig. 6 provides the λ-c curve of the volumetric efficiency λ of involute roots rotor molded lines and circularity substitution type Roots molded lines of the present invention with shape coefficient c variation.The form factor excursion of involute-type roots rotor is 1＜c≤1.466, and corresponding volumetric efficiency excursion is 0＜λ≤0.5102; The excursion of the form factor c of corresponding circularity substitution type roots rotor is 1＜c≤1.466, and corresponding volumetric efficiency excursion is 0＜λ≤0.4784.

As seen from Figure 6, in form factor c≤1.318 scopes, the volumetric efficiency of two kinds of roots rotor molded lines is very nearly the same, and the volumetric efficiency of circularity substitution type roots rotor also is better than the involute-type roots rotor; And in form factor c 〉=1.318 scopes, along with the increase of form factor c, the advantage that the volumetric efficiency of involute-type roots rotor is big is just more and more obvious.When c=1.36, both differ 1.67%, and when form factor c=1.40, this difference expands 4.52% to, reaches 11.3% when form factor c=1.45.But it is pointed out that simultaneously that when form factor c increases to a certain degree it is very narrow that the circular arc of rotor head and waist becomes, and is unfavorable for the sealing between rotor and the pump chamber, is unfavorable for the raising of pump performance on the contrary.Take all factors into consideration, the scope of generally getting form factor c is 1.2≤c≤1.4, and in this scope, both volumetric efficiencies differ the most very much not can surpass 5%.That is to say, use the circularity substitution involute, little to the volumetric efficiency influence of pump chamber.

The distribution of back lash of the present invention:

Because the waist circular arc of two rotor blocks is eccentric arc, is engaged with each other and does not follow the theory of engagement, so the gap distribution situation must investigate described two waist circular arcs engagement the time.

As shown in Figure 2, a pair of roots rotor is done the engagement rotation by direction as shown.If the power rotor group clockwise rotates angle-γ, then the driven rotor group rotates counterclockwise angle γ.As shown in Figure 4, the center of circle of setting up with left rotor left part circular arc A3B3 and left rotor right part circular arc C 3D3 is true origin O3, and X-axis and Y-axis are the plane right-angle coordinate of coordinate axes.Because of replacing involute with circular arc, then for waist circular arc B3C3, its center of circle O4 makes its equation in coordinates be:

$\left\{\begin{array}{c}{x}_1=x_0+{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="H061F5910220070123E000032.png"\; state="\{\{state\}\}">R</figure-callout>}}_1\cos {\mathrm{\&alpha;}}_1\\ {\mathrm{<figure-callout\; id="1"\; label="y"\; filenames="H061F5910220070123E000032.png"\; state="\{\{state\}\}">y</figure-callout>}}_1={\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="H061F5910220070123E000032.png"\; state="\{\{state\}\}">R</figure-callout>}}_1{\sin \mathrm{\&alpha;}}_1\end{array}\right.$ α ₀≤α ₁≤β ₀ (1)

Wherein: x ₀Be the center of circle abscissa of waist circular arc, α ₀Be the initial angle of waist circular arc, α ₁Be the angle of spread of waist circular arc, β ₀Be the end angle of waist circular arc, R1 is a left rotor left part radius of arc.

Then be corresponding epitrochanterian waist circular arc, get by transformation of coordinates with the part that the waist circular arc is meshed:

$\left\{\begin{array}{c}{x}_2=A-{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="H061F5910220070123E000032.png"\; state="\{\{state\}\}">R</figure-callout>}}_1{\sin \mathrm{\&alpha;}}_2\\ y_2=x_0+{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="H061F5910220070123E000032.png"\; state="\{\{state\}\}">R</figure-callout>}}_1\cos {\mathrm{\&alpha;}}_2\end{array}\right.$ α ₀≤α ₂≤β ₀ (2)

Wherein: A is two rotor centre distances, x ₀Be the center of circle abscissa of waist circular arc, α ₀Be the initial angle of waist circular arc, α ₂Be the angle of spread of the epitrochanterian waist circular arc of correspondence, β ₀End angle for the waist circular arc.

Then according to Rotating Transition of Coordinate, the minimum range of the present invention's two rotor waist circular arcs engagement is:

${\mathrm{\&delta;}}_{\min }=\min \left\{\sqrt{\begin{array}{c}{[(x_1-x_2+A)\cos \mathrm{\&gamma;}-A+({\mathrm{<figure-callout\; id="1"\; label="y"\; filenames="H061F5910220070123E000032.png"\; state="\{\{state\}\}">y</figure-callout>}}_1+y_2)\sin \mathrm{\&gamma;}]}^2\\ +{[(x_1+x_2-A)\sin \mathrm{\&gamma;}-(y_1-y_2)\cos \mathrm{\&gamma;}]}^2\end{array}}\right\}---\left(3\right)$

Wherein: x ₁Be the dynamic abscissa of left rotor waist circular arc, x ₂Be the dynamic abscissa of the epitrochanterian waist circular arc of correspondence, y ₁Be the dynamic y coordinate of left rotor waist circular arc, y ₂Dynamic y coordinate for the epitrochanterian waist circular arc of correspondence.

In formula (1), (2), (3), the angle of spread α of left rotor waist circular arc is only arranged ₁Angle of spread α with the epitrochanterian waist circular arc of correspondence ₂Be unknown number, can pass through two-dimensional search, can draw the minimum value δ in gap _Min(minimum range δ fluctuates between 0.08mm～0.14mm).By research waist radius of arc is 30, two rotor center square A=46, gap delta ₁The roots rotor of circularity substitution involute profile during=0.11mm if turning over 0 °～90 ° gap distribution in the scope from the left rotor horizontal position calculates, obtains distribution curve as shown in Figure 7.As can be seen from Figure 7, the distribution error in gap belongs to the acceptable margin of error in ± 0.025mm, and is little to the influence of the pumping performance of the thermodynamic property of rotor and entire pump.

Claims (7)

1. the roots dry vacuum pump rotor of a discharging directly into atmosphere, it is characterized in that: the multi-stage rotor group is installed on the central shaft, and the minimum range δ of two rotor waist circular arcs engagement was between 0.08mm～0.14mm when the rotor set on two central shafts was meshing with each other; Its rotor set is divided into three parts: adopt pin-and-hole location, bolt to be connected between left rotor piece, bearing pin and the right rotor block, left and right rotor block and bearing pin.

2. the roots dry vacuum pump rotor of discharging directly into atmosphere according to claim 1, it is characterized in that: the whole outer contour of described rotor block all is made up of circular arc, promptly is made up of periphery, two waist discs and inner headed face.

3. the roots dry vacuum pump rotor of discharging directly into atmosphere according to claim 1, it is characterized in that: described multi-stage rotor group inter-stage rotor thickness is by successively decreasing in proportion to the direction of air outlet end from the suction port end.

4. the roots dry vacuum pump rotor of discharging directly into atmosphere according to claim 1, it is characterized in that: the minimum range δ of two rotor waist circular arcs engagement is:

${\mathrm{\&delta;}}_{\min }=\min \left\{\sqrt{\begin{array}{c}{[(x_1-x_2+A)\cos \mathrm{\&gamma;}-A+(y_1+y_2)\sin \mathrm{\&gamma;}]}^2\\ +{[(x_1+x_2-A)\sin \mathrm{\&gamma;}-(y_1-y_2)\cos \mathrm{\&gamma;}]}^2\end{array}}\right\}$

Wherein: A is two rotor centre distances, x ₁Be the dynamic abscissa of left rotor waist circular arc, x ₂Be the dynamic abscissa of the epitrochanterian waist circular arc of correspondence, y ₁Be the dynamic y coordinate of left rotor waist circular arc, y ₂Be the dynamic y coordinate of the epitrochanterian waist circular arc of correspondence, γ rotates counterclockwise the angle for the driven rotor group;

The dynamic abscissa x of left rotor waist circular arc ₁Dynamic y coordinate y with left rotor waist circular arc ₁Draw according to following formula:

$\left\{\begin{array}{c}{x}_1=x_0+R_1\cos {\mathrm{\&alpha;}}_1\\ y_1=R_1\sin {\mathrm{\&alpha;}}_1\end{array}\right.{,\mathrm{\&alpha;}}_0\&le;{\mathrm{\&alpha;}}_1{\&le;\mathrm{\&beta;}}_0$

Wherein: x ₀Be the center of circle abscissa of waist circular arc, α ₀Be the initial angle of waist circular arc, α ₁Be the angle of spread of waist circular arc, β ₀Be the end angle of waist circular arc, R ₁Be left rotor left part radius of arc;

The dynamic abscissa x of corresponding rotor waist circular arc ₂, the dynamic y coordinate y of corresponding rotor waist circular arc ₂Draw according to following formula:

$\left\{\begin{array}{c}{x}_2=A-R_1\sin {\mathrm{\&alpha;}}_2\\ y_2=x_0+R_1\cos {\mathrm{\&alpha;}}_2\end{array}\right.{,\mathrm{\&alpha;}}_0\&le;{\mathrm{\&alpha;}}_2{\&le;\mathrm{\&beta;}}_0$

Wherein: A is two rotor centre distances, x ₀Be the center of circle abscissa of waist circular arc, α ₀Be the initial angle of waist circular arc, α ₂Be the angle of spread of the epitrochanterian waist circular arc of correspondence, β ₀End angle for the waist circular arc.

5. processing technology by the roots dry vacuum pump rotor of the described discharging directly into atmosphere of claim 1, it is characterized in that: with waist circularity substitution involute design rotor block, the processing rotor piece is assembled with central shaft more separately; Step is as follows:

1) processing rotor piece: blank is selected the spheroidal graphite cast iron bar for use; Processing method: process outer surface and two end faces of bar earlier, by required rotor block thickness cutting, two faces of all the other of processing rotor piece then;

2) two rotor blocks and bearing pin are fused by pin-and-hole.

6. as the roots dry vacuum pump rotor processing technique of discharging directly into atmosphere as described in the claim 5, it is characterized in that: described two faces are periphery and inner headed face.

7. as the roots dry vacuum pump rotor processing technique of discharging directly into atmosphere as described in the claim 5, it is characterized in that: also can strengthen the foundry goods diameter, processing method can be processed two end faces of bar earlier, on end face, accomplish fluently the center hole of waist circular arc, the periphery of car rotor block, inner headed face, vertical line cuts into identical two-part then, utilizes the center hole that processes to finish the processing of residue bi-side, cuts into rotor block by thickness proportion at last.

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