DE2735670A1 - SCREW ROTORS - Google Patents

Description

Inventor: Dieter Mosemaim, Berlin

Bernhard Seiffer, Berlin 2 7 35670

Z.-authorized representative: Pafceufc-Infc. Ullrich Scheffler

-V

Screw rotors

The field of application of the invention relates to a pair of rotors for a screw rotor machine, preferably for compressing a compressible working medium

A screw rotor machine generally has a housing with a work space with high pressure and low pressure ports, which a high-pressure and a low-pressure chamber are connected.

In the working area there are combing main and secondary rotors arranged, which have helically extending interlocking ridges and grooves.

The tooth gaps formed between the tooth parts and the circumference of the working space form V-shaped working chambers, which are limited at the base ends by stationary normal planes to the rotors.

Each of these V-shaped working chambers comprises a part of one Groove of the main rotor and part of a groove of the secondary rotor · Each groove part of the secondary rotor has a rear first flank and a front second plank. The transverse seal in ten-point engagement of the rotors takes place along a so-called contact line, the shape of which is determined by the shape of the tooth flank. She provides one uninterrupted spatial line.

This contact line is the geometric location of such flank points of the main rotor teeth and the secondary rotor tooth gaps, which in the Tooth meshing come into sealing proximity. Due to the largely Contact-free sealing determines the flank shape in the area of the contact line and the contact line length Leakage volume flow to the low pressure side and take as well as the position of the contact line on the tooth influences the technical properties of the rotor profile.

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Known technical solutions There are known symmetrically and asymmetrically profiled tooth flank contours.

With the latter, different profile shapes are used for the first and second tooth flanks in a plane normal to the rotor axes of rotation.

Sections of epitrochoids, spicycloids, circular arcs, ellipses and involutes have so far been used as contour judgments of the tooth flanks, these curves being the predominant part of a Form tooth flank.

In the known asymmetrical profiles, the point-generated profile curves were used for the essential contour sections of the first tooth flank and circular arcs generated for the second flank, either on the main or on the Secondary rotor are arranged, used

Disadvantages of point-generated profile sections are the long contact line length, the large trapped volume during the extension process, and the susceptibility to damage to the Sealing edge and the associated leakage losses that make the profile unusable. Another disadvantage is the high relative speeds of flank parts that are in sealing proximity interact and poor power transmission and lubrication conditions in tooth meshing, which are caused by unfavorable pressure conditions and oil stripping and are particularly disadvantageous in the case of the secondary rotor drive, since almost the entire compressor drive power is transferred to the tooth flanks of the main rotor in this flank. The second flank performs Use of the circular arcs, which are designed as essential contour parts, with the opposite flank generated by migrating points for reduction in size of the geometric flow rate.

In all known profiles, especially for the secondary rotor drive, it is disadvantageous that the transition of the tooth flank on the pitch circle of the secondary rotor from the pitch circle inside to the pitch circle outside Area takes place in steps. That's for the manufacture -z. B. for hobbing - unfavorable. With other profiles, the transition takes place by changing the radius of curvature at the pitch circle, which is disadvantageous for the power transmission ratios is.

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In addition, such profiles have a not optimally executed addendum with regard to the blowing gap.

Object of the invention

In addition to the requirement for a with regard to the flank shape Flow rate and compressor drive power optimally formed contact line, good manufacturability at low costs by milling in the single tooth gap milling process and hobbing process, good flank pressure ratios of the rotors, whose secondary rotor is driven by a motor and requires robustness against profile damage.

The known rotor profiles only partially meet these requirements and do not have an optimally executed flank profile.

Essence of the invention

The object of the invention is to create an optimal rotor profile, which has improved parameters - with the highest possible degree of volume utilization and with the largest possible theoretical delivery volume, with a high degree of delivery and efficiency through one good compromise between contact line length and blow gap size, with an improved outside of the secondary rotor pitch circle Addendum and with good power transmission ratios and good lubrication ratios in meshing with R ^ pt- and Auxiliary rotor drive.

According to the invention the object is achieved in that at the first Tooth flank of the secondary rotor is an optimized combination of several curve parts at a curve point outside the pitch circle starting in the sequence involute piece that extends to a curve point within the pitch circle close to it, Circular arc with convex flank curvature, circular arc with concave flank curvature, envelope curve to an elliptical section of the main rotor, whose center of the ellipse lies on the pitch circle of the main rotor and a circular arc in the sole part of the first tooth flank, whose center is on the pitch circle of the secondary rotor are arranged.

According to the invention, the second tooth flank of the secondary rotor is of this type formed that of one within the pitch circle close to

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Part of the circle lying point starting a section of a "conchoid of the circle ** is arranged, which is the essential Contour part and which is a circular arc-shaped sole part the second tooth flank, the center of which is located on the pitch circle of the secondary rotor. The individual curved pieces of the first and second secondary rotor tooth flanks are designed in such a way that they connect to one another and merge into one another without kinks. The main rotor flanks are the corresponding conjugate profiles, taking profile corrections into account to achieve a favorable clearance distribution in such a way that the Play between the involute parts of the main rotor flank and the secondary rotor flank is minimized compared to the other flank clearances is.

As a special design, there is an optimized rotor profile with a tooth tip located outside the pitch circle, the as an addendum, the height of which makes up 4 to 6 percent of half the outer rotor diameter, the first tooth flank of which starting at the radially outermost flank point has the following contour composition: 5 to 10 percent of the radial extent the tooth flank is designed as a section of an epicycloid, the envelope curve of which is free of edges on the main rotor, 6 to 12 percent of the tooth height is part of an involute, the base circle of which lies within the sub-rotor pitch circle. 2 to 6 percent of the tooth height consists of a circular arc that has a convex curvature on the tooth flank and its outermost point has a radial tangent, 15 to 3p percent of the tooth height consists of an arc of a circle concave flank curvature, the radius being optimized in such a way that the entire tooth flank of the main rotor is free of edges remains and a wander point is generated,

4o to 7o percent of the ten height is an envelope curve for an am Main rotor arranged slipsection, its center point is on the pitch circle of the main rotor, 1 to 4 percent of the tooth height consists of an arc of a circle with the center on the secondary rotor pitch circle.

The second tooth flank of this particular embodiment is advantageous in the following way, starting at the radially outermost point optimally executed:

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■ ι

4 to 11 percent of the tooth height, outside the secondary rotor pitch circle lying, are part of an epicycloid, ddren belonging to it Envelope curve on the main rotor has an edge-shaped counter flank delivers,

5 to 12 percent of the tooth height is then part of it an involute whose base circle is within the sub-rotor pitch circle and which is joined by the conchoid within the pitch circle,

7o to 9o percent of the tooth height is part of the conchoid of the circle that is tangent to the sub-rotor part circle from the outside and the diameter of which has been calculated so that the conchoid section and the involute section adjoin each other with a radial tangent,

1 to 4 percent of the tooth height is an arc with the center formed on the secondary rotor pitch circle.

An advantageous distribution of the game results if one considers the theoretical Maintains the tooth flank contour of the main rotor and the backlash-free theoretical tooth flank contour of the secondary rotor according to the equation

^S f ^{= S} k ^ ^sin Y ^{+ cos} T "* ^ ⁸¹¹ ° ^

corrected, where jp is the profile pitch angle on the pitch circle and ^ is the direction of the correction shift.

The profile according to the invention has in the area of the entire radial Extension of the 1st and 2nd secondary rotor tooth flanks no point-generated contour parts. The secondary rotor profile is throughout Plank area free of edges. The main rotor tooth is only in a very limited part of the dedendum with regard to a small one Blow joint surface is point-generated and has none on the secondary rotor tooth sealing edges.

The dedendum is the one located within the main rotor pitch circle Flank part that meshes with the addendum of the secondary rotor tooth.

The profile according to the invention represents an optimal combination, as it has advantageous technical and technological properties united.

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The degree of delivery n "d efficiency are improved by the favorable shape of the contact line ζ v / i see the rotors and by reducing the blow gap of the first tooth flank of the secondary rotor within the secondary rotor pitch circle in the meshing and by reducing the blow gap, which is created by the design of the first tooth flank of the Secondary rotor is reached in the area of the addendum.

The power transmission and lubrication conditions in the vicinity of the Pitch circles are improved as a result of the involute profile shape, so that this profile in the area of power transmission properties has a helical gear and is suitable for the secondary rotor drive in an advantageous manner. The profile is insensitive to profile edge damage, as only punctual, momentary interruptions in the event of damage occur at the contact line of the rotors. Compared to the symmetrical circular arc profile, the profile has a profile around 3 percent higher volume utilization. The milling knife shape for milling the tooth gaps in the single milling process is improved in that the slope 4 ^ to the Tooth flanks of the secondary rotor in the area of the largest knife width and of the main rotor in the area of the smallest knife width enlarged so that the number of possible cuts the milling knife for contour grinding by more than three times elevated.

Embodiment

1t a section of a screw rotor profile perpendicular to the axes of rotation of the main and secondary rotors

Fig. 2t A line of contact between the rotors.

Fig. 1 shows a groove of the secondary rotor 13 and the tooth of the main rotor 14 which is in engagement with it in a section perpendicular to the rotor axes of rotation. The groove of the secondary rotor contains the following profile sections cycloid 1, involute 2 with its base circle within the pitch circle 1o, conchoid 3 of a circle outside of the pitch circle 1o, circular arc 4 with center on the pitch circle 1o, envelope curve 5 to an am

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Main rotor tooth arranged ellipse with center on the Main rotor pitch circle 11, circular arc 6 with concave curvature, circular arc 7 with convex curvature. The shape of the main rotor tooth consists of the corresponding conjugated profile sections.

In Fig. 2, the projection of the theoretical contact line of the rotors along the rotor axes of rotation is shown. The axis plane 12 and the intersection line 9 represent the rotors Housing bores are shown.

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Claims (1)

Claim 1. Pair of rotors for a screw rotor machine, preferably for compressing a compressible working medium with a main rotor with four teeth, the crests and grooves of which are arranged essentially outside the pitch circle and the ridges are substantially convex in shape; and with a secondary rotor with six teeth, its crests and grooves are arranged essentially within the pitch circle and largely have a concave shape, wherein the meshing rotor tooth parts with their tooth gap spaces form V-shaped working chambers and each Groove part of the secondary rotor, which in each case forms one leg of a V-shaped working chamber, a first rear tooth flank which faces the housing end wall on the high-pressure side and has a front second flank, facing the housing end wall on the lower side of the pressure is, characterized in that in a normal section to the rotor axis of rotation at the first Tooth flank of the secondary rotor is an optimized combination of several curve parts at a curve point outside the pitch circle is arranged starting, which consists of an involute piece that extends up to a curve point within the Partial circle, located close to this, leads, which is followed by a circular arc with a convex flank shape, the one This is followed by an arc of a circle with a concave flank curvature, followed by an envelope curve to a segment of the ellipse Main rotor arranged, the center of the ellipse is on the pitch circle of the main rotor and this envelope curve The arc of a circle follows, which forms the radially innermost flank area of the first tooth flank and its center point 809813/0692 ORIGINAL INSPECTH) the pitch circle of the secondary rotor and on the second Tooth flank from one within the pitch circle close to Starting point in a partial circle, an optimized combination of several parts of the curve in a standard section is arranged to the rotor axis of rotation, starting with a portion of a conchoid of the circle, which is the essential The contour part and which is joined by the radially innermost plank part, which is an arc of a circle the center point is formed on the pitch circle of the secondary rotor, the individual curve pieces of the first and second secondary rotor tooth flanks merge into one another without kinks and the main rotor tooth flanks the corresponding ones are conjugated profiles or envelopes. 2. rotor pair for a screw rotor machine according to claim in an optimized version with an outside of the Tooth tip located on a pitch circle, the addendum, whose height is 4 to 6 percent of half the outer rotor diameter constitutes, characterized in that the profile of the first tooth flank from 5 to 1o percent radial extension, which is referred to as the tooth height, as a section of an epicycloid whose envelope curve on the main rotor is free of edges, 6 to 12 percent of the tooth height as a section of an involute, the base circle of which is within the secondary Kötort sub-circle lies, 2 to 6 percent of the tooth height as a circular arc piece that has a convex curvature on the tooth flank and its outermost point has a radial tangent, 15 to 3o percent of the tooth height as a concave arc of a circle Flank curvature with an optimized radius in such a way that the entire tooth flank of the main rotor is created 4-0 to 70 percent of the tooth height as an envelope curve for the blip section and 1 to 4 percent of the tooth height executed as a circular arc, and that on the second tooth flank outside the pitch circle 4 to 11 percent of the tooth height as part of an epicycloid, whose corresponding envelope curve on the main rotor provides an edge-free opposite flank, 809813/0692 5 to 12 percent of the tooth height as a section of an involute, the radially outermost point of which is outside the pitch circle and the base circle of the involute lies within the sub-rotor pitch circle, then in optimized combination 7o is designed to 9o percent of the tooth height as the portion of the conchoid of the circle which is tangent to female rotor pitch circle of Removing sen and whose diameter is carried out so that KonchoidentdLlstück and Evolvententeilstück radial tangent line adjoin one another and from 1 to 4 x percent of the tooth height as a circular arc. 3 rotor pair for a screw rotor machine according to claim 2, characterized in that that the play between the involute parts of the main and lifting rotor tooth flanks compared to the other flank play is minimized. 4. rotor pair for a screw rotor machine according to claim 3 » characterized in that the theoretical play distribution follows equation 1. 809813/0692