CN202756246U - Equal-teeth and top width single-head varying pitch screw rotor - Google Patents

Abstract

The utility model discloses an equal-teeth and top width single-head varying pitch screw rotor which is formed by sequential connecting of a root face, an inclined tooth face, a tooth top face and a transitional tooth face. A rotor spiral guide is increased in linear mode from an air exhaust end to a suction end along a spiral spread angle. The width of an axial direction of the inclined tooth face is gradually is largened thereupon, while the width of the tooth top face always keeps unchangeable. Compared with existing variable varying pitch screw rotors, the molded line rotor is comparatively small at the width of a tooth top of the suction end, therefore, big interstage suction volume is formed and the molded line rotor has a big volume utilization coefficient, and therefore, under the same structural parameter, the equal-teeth and top width single-head varying pitch screw rotor has a big theoretical pumping speed. On the contrary, the molded line rotor is comparatively big at the width of the tooth top of the air exhaust end, has strong interstage leakage resistance capability, and can enable gas interstage leakage return flow to reduce, and therefore, equal-teeth and top width single-head varying pitch screw rotor is beneficial to improving a limitation vacuum degree and an actual effective pumping speed.

Description

A kind of single head varying pitch screw rotor that waits tooth top width

Technical field

The utility model relates to screw type oil-free vacuum pump technical field, particularly a kind of single head varying pitch screw rotor that waits tooth top width.

Background technique

The oil free screw pump have pumping speed wide ranges, simple and compact for structure, pumping chamber element without friction, the life-span is long, energy consumption is low, without characteristics such as oil pollutions, be widely used in the industrial fields such as semiconductor, medicine, food, chemical industry.Screw rotor is the parts of bleeding of most critical in the screw vacuum pump, is directly determining service behaviour and the working life of pump, its manufacturing cost account for whole screw pump overall cost near half.The Profile Design of screw rotor then is the most critical technology in the whole screw pump design.Wherein the screw rotor of single head variable pitch because it has inner precompressed exhaust mode, is compared with the constant lead screw rotor, has outstanding energy-saving and noise-reducing advantage, therefore enjoys artificer and the user's of rotors for dry double-screw vacuum pump favor.Existing many technician have designed the single head varying pitch screw molded lines of rotor of various structures form.

Although it is varied that the structure of existing single head varying pitch screw molded lines of rotor consists of, but its common structure characteristic is: in the process that is diminished gradually to exhaust end by suction end along with the helical pitch (pitch) of screw rotor, the tooth top width in the rotor flute profile (and corresponding tooth root is wide) also narrows down to equal proportion thereupon gradually.Because the gap between rotor tooth end face and the pump housing internal surface is the main leakage way that the gas inter-stage backflows in the rotor exhaust process, the tooth top width of rotor flute profile then is equivalent to the degree of depth of this leakage way, tooth top width is wider, leakage way is darker, the blocking capability that inter-stage is leaked is stronger, and then the gas backflow amount between the adjacent two-stage is just less.The tooth top width of existing single head varying pitch screw molded lines of rotor is narrowed down to exhaust end gradually by suction end, the blocking capability that then inter-stage is leaked more and more a little less than.And screw vacuum pump in the course of the work, and the closer to exhaust end, gas pressure and interstage pressure are poor just larger, and the result appeared at the suction end interstage pressure poor hour, and the flute profile tooth top width is unnecessarily very large, causes on the contrary the volumetric efficiency of pump less than normal; And poor when very large at the exhaust end interstage pressure, the unreasonable situation that instead the flute profile tooth top width diminishes and cause the gas backflow amount to increase.This directly causes, and the aspirated volume utilization factor of screw vacuum pump is little and the leakage rate of totally backflowing is large, thereby causes the main performance index ultimate vacuum of screw vacuum pump to reduce and the consequence of actual speed of exhaust decline.

If in screw rotor Profile Design process, have a mind to keep rotor flute profile tooth top width constant all the time, then can effectively avoid the appearance of the problems referred to above, thereby improve the pumping performance index of screw vacuum.

The model utility content

Problem for the prior art existence, the purpose of this utility model provides a kind of single head varying pitch screw rotor that waits tooth top width, guarantee in minimum value the process with the spiral angle of spread linear increase of rotor helical pitch by exhaust end, the tooth top width of rotor remains constant, so that having stronger inter-stage, rotor leaks blocking capability, reduce the gas inter-stage and leak regurgitation volume, be conducive to improve the ultimate vacuum of vacuum pump and the purpose of actual effective pumping speed thereby reach.

The technical solution of the utility model is achieved in that a kind of single head varying pitch screw rotor that waits tooth top width, connected and composed successively by tooth flank, pitch face, Topland and the transition flank of tooth, the rotor helical-screw helical pitch with the spiral angle of spread by exhaust end to the linear increase of suction end, it is large that the axial width of pitch face becomes thereupon gradually, and the width of Topland remains constant.

Described tooth flank, pitch face, Topland and the transition flank of tooth are to make variable-pitch auger by the profile that root circle curve, involute curve, top circle curve and changeover portion curve connect and compose successively to launch and generate.

With the axle center of screw rotor exhaust end face as true origin, point to rotor suction end direction as the Z axis forward take rotor axis, set up the rectangular coordinate system Oxyz that describes molded lines of rotor, root circle curve of the present utility model, involute curve, top circle curve and changeover portion curve satisfy following condition:

Described root circle section curve, satisfy following formula:

$\begin{array}{c}x=\frac{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HDA00002011218700011.png,HDA00002011218700021.png"\; state="\{\{state\}\}">d</figure-callout>}}{2}\cos (t_1+\mathrm{\&tau;})\\ y=\frac{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HDA00002011218700011.png,HDA00002011218700021.png"\; state="\{\{state\}\}">d</figure-callout>}}{2}\sin ({\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="HDA00002011218700011.png,HDA00002011218700012.png"\; state="\{\{state\}\}">t</figure-callout>}}_1+\mathrm{\&tau;})\end{array}---\left(1\right)$

In the formula, x is abscissa, and y is y coordinate, and d is root diameter, and τ is the spiral angle of spread, t ₁Be formal parameter.

Described involute curve, satisfy following formula:

$\begin{array}{c}x=\frac{a\left(\mathrm{\&tau;}\right)}{2}\&CenterDot;[\cos ({\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="HDA00002011218700011.png,HDA00002011218700021.png"\; state="\{\{state\}\}">t</figure-callout>}}_2+\mathrm{\&tau;})+{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="HDA00002011218700011.png,HDA00002011218700021.png"\; state="\{\{state\}\}">t</figure-callout>}}_2\&CenterDot;\sin ({\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="HDA00002011218700011.png,HDA00002011218700021.png"\; state="\{\{state\}\}">t</figure-callout>}}_2+\mathrm{\&tau;})]\\ y=\frac{a\left(\mathrm{\&tau;}\right)}{2}\&CenterDot;[\sin ({\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="HDA00002011218700011.png,HDA00002011218700021.png"\; state="\{\{state\}\}">t</figure-callout>}}_2+\mathrm{\&tau;})-{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="HDA00002011218700011.png,HDA00002011218700021.png"\; state="\{\{state\}\}">t</figure-callout>}}_2\&CenterDot;\cos ({\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="HDA00002011218700011.png,HDA00002011218700021.png"\; state="\{\{state\}\}">t</figure-callout>}}_2+\mathrm{\&tau;})]\end{array}---\left(2\right)$

α in the formula (τ) is the involute base circle diameter (BCD), t ₂Be formal parameter.

Described top circle curve, satisfy following formula:

$\begin{array}{c}x=\frac{D}{2}\cos ({\mathrm{<figure-callout\; id="3"\; label="t"\; filenames="HDA00002011218700011.png,HDA00002011218700021.png"\; state="\{\{state\}\}">t</figure-callout>}}_3+\mathrm{\&tau;})\\ y=\frac{D}{2}\sin ({\mathrm{<figure-callout\; id="3"\; label="t"\; filenames="HDA00002011218700011.png,HDA00002011218700021.png"\; state="\{\{state\}\}">t</figure-callout>}}_3+\mathrm{\&tau;})\end{array}---\left(3\right)$

In the formula, D is tip diameter, t ₃Be formal parameter.

Described changeover portion curve refers to have from the connection teeth tip circle of meshing characteristic and any one curve of root circle, and the optimal case that this transition curve is selected is single cycloid transition curve or double cycloid transition curve, wherein,

Described single cycloid transition curve, satisfy following formula:

$\begin{array}{c}x=\frac{d+\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="HDA00002011218700011.png,HDA00002011218700021.png"\; state="\{\{state\}\}">D</figure-callout>}}{2}\cos (t_{41}+\mathrm{\&tau;})-\frac{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="HDA00002011218700011.png,HDA00002011218700021.png"\; state="\{\{state\}\}">D</figure-callout>}}{2}\cos (2t_{41}+\mathrm{\&tau;})\\ y=\frac{d+\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="HDA00002011218700011.png,HDA00002011218700021.png"\; state="\{\{state\}\}">D</figure-callout>}}{2}\sin (t_{41}+\mathrm{\&tau;})-\frac{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="HDA00002011218700011.png,HDA00002011218700021.png"\; state="\{\{state\}\}">D</figure-callout>}}{2}\sin ({2t}_{41}+\mathrm{\&tau;})\end{array}---\left(4\right)$

In the formula, t ₄₁Be formal parameter.

Described double cycloid transition curve comprises hypocycloid and epicycloid, wherein, and hypocycloid, satisfy following formula:

$\begin{array}{c}x=\frac{d+\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="HDA00002011218700011.png,HDA00002011218700021.png"\; state="\{\{state\}\}">D</figure-callout>}}{2}\cos (t_{421}{+\mathrm{\&beta;}}_{421}+\mathrm{\&tau;})-\frac{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="HDA00002011218700011.png,HDA00002011218700021.png"\; state="\{\{state\}\}">D</figure-callout>}}{2}\cos (2t_{421}+{\mathrm{\&beta;}}_{421}+\mathrm{\&tau;})\\ y=\frac{d+\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="HDA00002011218700011.png,HDA00002011218700021.png"\; state="\{\{state\}\}">D</figure-callout>}}{2}\sin (t_{421}+{\mathrm{\&beta;}}_{421}+\mathrm{\&tau;})-\frac{\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="HDA00002011218700011.png,HDA00002011218700021.png"\; state="\{\{state\}\}">D</figure-callout>}}{2}\cos ({2t}_{421}+{\mathrm{\&beta;}}_{421}+\mathrm{\&tau;})\end{array}---\left(5\right)$

In the formula, t ₄₂₁Be formal parameter, β ₄₂₁For regulating the angle.

The epicycloid equation

$\begin{array}{c}x=\frac{d+\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="HDA00002011218700011.png,HDA00002011218700021.png"\; state="\{\{state\}\}">D</figure-callout>}}{2}\cos (t_{421}+\mathrm{\&tau;})-\frac{D+\mathrm{<figure-callout\; id="4"\; label="d"\; filenames="HDA00002011218700011.png"\; state="\{\{state\}\}">d</figure-callout>}}{4}\cos (2t_{422}+\mathrm{\&tau;})\\ y=-\frac{d+\mathrm{<figure-callout\; id="2"\; label="D"\; filenames="HDA00002011218700011.png,HDA00002011218700021.png"\; state="\{\{state\}\}">D</figure-callout>}}{2}\sin (t_{422}+\mathrm{\&tau;})+\frac{D+\mathrm{<figure-callout\; id="4"\; label="d"\; filenames="HDA00002011218700011.png"\; state="\{\{state\}\}">d</figure-callout>}}{4}\cos ({2t}_{422}+\mathrm{\&tau;})\end{array}---\left(6\right)$

In the formula, t ₄₂₂Be formal parameter.

The formula of the above-mentioned molded line that employing cylindrical-coordinate system or other form system of coordinates are explained also belongs to the row of the utility model.

Described profile is in the variable pitch expansion process, the base circle diameter (BCD) of involute curve is gradually to suction end by exhaust end and diminishes, the occupied angle of involute curve increases gradually, and the angle that top circle curve and root circle Curves occupy reduces gradually, the lead of screw of rotor was directly proportional situation about changing with the spiral angle of spread under, the tooth top width of rotor tooth form face and tooth root were wide constant all the time.

Root circle curve, involute curve, top circle curve and changeover portion curve are in the axial screw expansion process, and axial coordinate all satisfies following formula:

$z=\frac{p_0}{2\mathrm{\&pi;}}(\mathrm{\&tau;}+{\mathrm{\&lambda;\&tau;}}^2)---\left(7\right)$

Relation between described lead of screw p and the spiral angle of spread τ satisfies:

$p=p_0(1+2\mathrm{\&lambda;\&tau;})---\left(8\right)$

Involute curve in the profile is connected between root circle curve and the top circle curve, and the generation circular diameter a (τ) of this involute curve is diminished with spiral angle of spread τ to suction end gradually by exhaust end, and formula is as follows:

$\begin{array}{c}\arctan \sqrt{{\left(\frac{D}{a\left(\mathrm{\&tau;}\right)}\right)}^2-1}-\arctan \sqrt{{\left(\frac{e}{a\left(\mathrm{\&tau;}\right)}\right)}^2-1}-\sqrt{{\left(\frac{D}{a\left(\mathrm{\&tau;}\right)}\right)}^2-1}+\sqrt{{\left(\frac{e}{a\left(\mathrm{\&tau;}\right)}\right)}^2-1}\\ =3\mathrm{\&pi;}-\mathrm{\&tau;}-\frac{1}{2\mathrm{\&lambda;}}+\frac{1}{2\mathrm{\&lambda;}}\sqrt{1-\frac{8\mathrm{\&pi;B\&lambda;}}{p_0}+4\mathrm{\&lambda;\&tau;}+4{\mathrm{\&lambda;}}^2{\mathrm{\&tau;}}^2}\end{array}---\left(9\right)$

In the formula, e is the rotor pitch diameter, and B is tooth top width, and λ is the variable pitch coefficient, p ₀Be the initial helical pitch of the rotor of exhaust end.

Described rotor helical-screw expansion direction is left-handed or dextrorotation;

The beneficial effects of the utility model: the single head varying pitch screw rotor structure that the flute profile tooth top width that the utility model proposes is constant, at the minimum value p of rotor helical pitch by exhaust end ₀In the linear process that increases of the spiral angle of spread, the tooth top width of rotor remains constant.Compare with existing various single head varying pitch screw rotors, this molded line rotor is at the addendum width less of suction end, thereby form larger inter-stage aspirated volume, larger volumetric efficiency is arranged, therefore under identical structural parameter, have larger theoretical pumping speed; Otherwise this molded line rotor is relatively large at the addendum width of exhaust end, has stronger inter-stage and leaks blocking capability, can make the gas inter-stage leak the regurgitation volume reduction, thereby is conducive to improve ultimate vacuum and the actual effective pumping speed of vacuum pump.

Description of drawings

Fig. 1 is the exhaust end profile view of the tooth top width single head of waiting take single cycloid as transition curve varying pitch screw rotor;

Fig. 2 is the screw rotor plan view that generates according to rotor end-face molded line shown in Figure 1;

Fig. 3 is the exhaust end profile view of the tooth top width single head of waiting take double cycloid as transition curve varying pitch screw rotor;

Fig. 4 is the screw rotor plan view that generates according to rotor end-face molded line shown in Figure 3;

Among the figure, 1. root circle curve; 2. involute curve; 3. top circle curve; 4. the transition curve that consists of of single cycloid; 5. tooth flank; 6. pitch face; 7. Topland; 8. the recessed flank of tooth; 9. the transition curve that consists of of double cycloid; 10. straight-sided flank.

Embodiment

Below in conjunction with accompanying drawing mode of execution of the present utility model is done detailed explanation of a step.

Embodiment one:

Present embodiment provides a kind of single head varying pitch screw rotor that waits tooth top width, at the profile of its a certain cross-section as shown in Figure 1.Curve abc section is root circle curve 1, curve cde section is involute curve 2, curve efg section is top circle curve 3, the transition curve 4 of curve gha section for being consisted of by single cycloid, four sections curves join in order, and (the terminal c such as root circle curve abc is connected with the starting point c of involute curve cde, the terminal e of involute curve cde is connected with the starting point e of top circle curve efg, the terminal g of top circle curve efg is connected with the starting point g of the transition curve gha that single cycloid consists of, the end of the transition curve gha that single cycloid consists of is connected with the starting point a of root circle curve abc, consists of profile).

Make the structural drawing that waits tooth top width single head varying pitch screw rotor that the dextrorotation variable-pitch auger launches to generate as shown in Figure 2 based on this profile.By finding out among Fig. 2, the Profile of AT of this screw rotor comprises the fillet surface that tooth flank 5, pitch face 6, Topland 7 and recessed flank of tooth 8(are generated by single cycloid) 8.The lead of screw of rotor (pitch) by the right side exhaust end to the left suction end become gradually greatly, P3＞P2＞P1 is directly proportional with the spiral angle of spread as shown in Figure 2; But the width B of its Topland 7 is constant all the time, as shown in Figure 2 B3=B2=B1=B; The occupied axial length of pitch face 6 is then more and more longer, as shown in Figure 2 L3＞L2＞L1.

According to the formula of formula (1)～formula (9), it is as follows that the present embodiment provides the structural parameter that wait tooth top width single head varying pitch screw rotor of certain model rotors for dry double-screw vacuum pump: tip diameter D=186mm; Root diameter d=62mm; Pitch diameter e=(d+D)/2=124mm; The initial helical pitch p of the rotor of exhaust end ₀=80mm; Variable pitch coefficient lambda=0.0198944; Tooth top width B=28mm; Working rotor district total length L=480mm.Its structural drawing as shown in Figure 2, its spiral number of turns be 4 the circle.

Embodiment two:

Present embodiment provides a kind of single head varying pitch screw rotor that waits tooth top width, at the profile of its a certain cross-section as shown in Figure 3, curve abc section is root circle curve 1, curve cde section is involute curve 2, curve efg section is top circle curve 3, curve gha section is the transition curve 9 that double cycloid consists of, four sections curves join in order, and (the terminal c such as root circle curve abc is connected with the starting point c of involute curve cde, the terminal e of involute curve cde is connected with the starting point e of top circle curve efg, the terminal g of top circle curve efg is connected with the starting point g of the transition curve gha that single cycloid consists of, the end of the transition curve gha that single cycloid consists of is connected with the starting point a of root circle curve abc, consists of profile).

Make the structural drawing that waits tooth top width single head varying pitch screw rotor that left-handed variable-pitch auger launches to generate as shown in Figure 4 based on this profile.By finding out among Fig. 4, the Profile of AT of this screw rotor comprises tooth flank 5, pitch face 6, Topland 7 and straight-sided flank (fillet surface that the transition curve that is made of double cycloid generates) 10.The lead of screw of rotor (pitch) by the right side exhaust end to the left suction end become gradually greatly, P3＞P2＞P1 is directly proportional with the spiral angle of spread as shown in Figure 4; But the width B of its Topland 7 is constant all the time, as shown in Figure 2 B4=B3=B2=B1=B; The occupied axial length of pitch face 6 is then more and more longer, as shown in Figure 2 L4＞L3＞L2＞L1.

According to the formula of formula (1)～formula (9), it is as follows that present embodiment provides the structural parameter that wait tooth top width single head varying pitch screw rotor of certain model rotors for dry double-screw vacuum pump: tip diameter D=188mm; Root diameter d=62mm; Pitch diameter e=(d+D)/2=125mm; The initial helical pitch p of the rotor of exhaust end ₀=80mm; Variable pitch coefficient lambda=0.0198944; Tooth top width B=28mm; Working rotor district total length L=562.5mm.Its structural drawing as shown in Figure 4, its spiral number of turns be 4.5 the circle.

Although more than described embodiment of the present utility model, but the one skilled in the art is to be understood that, these only illustrate, and can make various changes or modifications to these mode of executions, and not deviate from principle of the present utility model and essence.Scope of the present utility model is only limited by appended claims.

Claims (7)

1. single head varying pitch screw rotor that waits tooth top width, it is characterized in that: the Profile of AT of this screw rotor is connected and composed successively by tooth flank (5), pitch face (6), Topland (7) and the transition flank of tooth (8), rotor helical-screw helical pitch (P1, P2, P3) with the spiral angle of spread by exhaust end to the linear increase of suction end, axial width (the L1 of pitch face (6), L2, L3) become gradually large thereupon, and the width of Topland (7) (B1, B2, B3) remain constant.

2. the single head varying pitch screw rotor that waits tooth top width according to claim 1, it is characterized in that: described tooth flank (5), pitch face (6), Topland (7) and the transition flank of tooth (8) are to make variable-pitch auger by the profile that root circle curve (abc), involute curve (cde), top circle curve (efg) and changeover portion curve (gha) connect and compose successively to launch and generate.

3. the single head varying pitch screw rotor that waits tooth top width according to claim 2, it is characterized in that: described profile is in the variable pitch expansion process, the base circle diameter (BCD) of involute curve (cde) is gradually to suction end by exhaust end and diminishes, the occupied angle of involute curve (cde) increases gradually, and top circle curve (efg) and the occupied angle of root circle curve (abc) reduce gradually, the lead of screw of rotor was directly proportional situation about changing with the spiral angle of spread under, the tooth top width of rotor tooth form face and tooth root were wide constant all the time.

4. the single head varying pitch screw rotor that waits tooth top width according to claim 1, it is characterized in that: the relation between described lead of screw p and the spiral angle of spread τ satisfies following formula:

$p=p_0(1+2\mathrm{\&lambda;\&pi;})$

In the formula, p ₀Be the initial helical pitch of the rotor of exhaust end, λ is the variable pitch coefficient, and τ is the spiral angle of spread.

5. the single head varying pitch screw rotor that waits tooth top width according to claim 2, it is characterized in that: the involute curve in the profile (cde) is connected between root circle curve (abc) and the top circle curve (efg), the generation circular diameter a (τ) of this involute curve (cde) is diminished with spiral angle of spread τ to suction end gradually by exhaust end, satisfies following formula:

$\begin{array}{c}\arctan \sqrt{{\left(\frac{D}{a\left(\mathrm{\&tau;}\right)}\right)}^2-1}-\arctan \sqrt{{\left(\frac{e}{a\left(\mathrm{\&tau;}\right)}\right)}^2-1}-\sqrt{{\left(\frac{D}{a\left(\mathrm{\&tau;}\right)}\right)}^2-1}+\sqrt{{\left(\frac{e}{a\left(\mathrm{\&tau;}\right)}\right)}^2-1}\\ =3\mathrm{\&pi;}-\mathrm{\&tau;}-\frac{1}{2\mathrm{\&lambda;}}+\frac{1}{2\mathrm{\&lambda;}}\sqrt{1-\frac{8\mathrm{\&pi;B\&lambda;}}{p_0}+4\mathrm{\&lambda;\&tau;}+4{\mathrm{\&lambda;}}^2{\mathrm{\&tau;}}^2}\end{array}$

In the formula: D is the rotor tooth outside diameter circle, and e is the rotor pitch diameter; B is tooth top width, and α (τ) is the involute base circle diameter (BCD).

6. the single head varying pitch screw rotor that waits tooth top width according to claim 2, it is characterized in that: the changeover portion curve (gha) of connection teeth tip circle curve (efg) and root circle curve (abc) is the arbitrary curve that has from meshing characteristic in the profile.

7. the single head varying pitch screw rotor that waits tooth top width according to claim 1, it is characterized in that: the rotor helical-screw expansion direction is left-handed or dextrorotation.

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