A multi-point engagement screw rotor of a twin screw pump

Abstract

The application discloses a kind of multi-point engagement screw rotors of double screw pump, convex screw rotor (1) is double-end screw, one half of left section line (101) is made of 4 curves, in order to: tooth root circular arc AB, first cycloid BC, addendum elliptic arc CD, second cycloid DE;Concave screw rotor (2) is three-end screw, one third of right section line (201) is made of 2 curves and 2 points, in order to: addendum circular arc ab, first point b, elliptic arc envelope line bcd, second point d;Convex screw rotor (1) addendum has recess, and the tooth root of concave screw rotor (2) has protrusion;The recess of convex screw rotor (1) addendum and the protrusion of concave screw rotor (2) tooth root are correctly engaged;The design of the engagement of two screw rotors can effectively reduce the internal leakage of double screw pump, improve volumetric efficiency, and the double screw pump using such section line can better adapt to high-pressure environment, and the tooth profile section line is simple in composition, and easy to manufacture.

Description

TECHNICAL FIELD

[0001] The present application relates to screw pump, particularly to a kind of multi-point engagement screw rotor of double screw pump. BACKGROUND

[0002] Double screw pump is a kind of positive displacement pump, by two mutually engaged screw rotors form multiple closed cavities in pump body, under the drive of gear, a pair of screw rotors do double rotation in pump cavity, sealed cavity continuously from the inlet of pump moves to the outlet of pump, complete medium suction, pressurization and discharge process, realize the delivery of liquid.Double screw pump has the remarkable characteristics of no pulsation, small vibration, high reliability, good stability, strong self-priming ability, and is widely used in oil field, shipbuilding industry, petrochemical industry, food industry.

[0003] Double screw pump leakage determines the volumetric efficiency of double screw pump, internal leakage is the main reason of pump leakage, the gap leakage between screw rotors and between rotor and shell of double screw pump greatly influences the conveying performance of pump.For the design of leakage gap, under the premise of ensuring that no interference occurs when the rotor operates, it is required to reduce the interdental leakage as much as possible.The existing screw rotor engagement surface is single-point engagement, and the double screw pump of this design is prone to reduce sealing performance during operation due to screw rotor wear.The existing double screw pump screw rotor tooth top and tooth bottom are horizontal structure, and the leakage channel formed when screw rotors engage exists obvious internal leakage under high pressure, which reduces the volumetric efficiency of pump.China patent (patent number CN201720524780.9) proposes a full smooth double screw pump rotor, which uses two circular arcs and their envelope to replace the commonly used point engagement trochoid, which relieves the wear problem at the sharp point, realizes smooth connection between the constituting curves and correct engagement, and improves the sealing performance, but the tooth top and tooth top of this screw rotor are still horizontal structure, which exists obvious internal leakage under high pressure, and the volumetric flow of this tooth type is small. SUMMARY

[0004] In order to reduce the internal leakage of double screw pump and improve the volumetric efficiency of double screw pump, the present application proposes a kind of multi-point engagement screw rotor of double screw pump, which has large volumetric flow, and the screw end face profile can realize three-point engagement, so that the screw rotor has multiple seals.The convex screw rotor has a groove at the tooth top, the concave screw rotor has a protrusion at the tooth root, and the groove at the tooth top of the convex screw rotor and the protrusion at the tooth root of the concave screw rotor can realize correct engagement.The special design of the engagement gap makes the leakage channel more tortuous and long, which can effectively reduce the internal leakage of double screw pump, thereby improving the volumetric efficiency of the pump.The tooth profile is simple in composition, easy to optimize design, and convenient for processing and manufacturing.

[0005] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0006] A multi-point meshing screw rotor of a twin screw pump, comprising: a convex screw rotor and a concave screw rotor.

[0007] The convex screw rotor is a double-headed screw, the tooth profile of each head is identical and uniformly distributed along the circumference, the left section profile of the convex screw rotor is 180° center symmetric about its rotation center O1, that is, the left section profile is completely coincident with itself after rotating 180° counterclockwise or clockwise around its rotation center O1; one half of the left section profile of the convex screw rotor is composed of four curves, in the clockwise direction, they are: tooth root circular arc AB, first cycloid BC, tooth tip elliptic arc CD, and second cycloid DE.

[0008] The concave screw rotor is a triple-headed screw, the tooth profile of each head is identical and uniformly distributed along the circumference, the right section profile of the concave screw rotor is 120° center symmetric about its rotation center O2, that is, the right section profile is completely coincident with itself after rotating 120° counterclockwise or clockwise around its rotation center O2; one third of the right section profile of the concave screw rotor is composed of two curves and two points, in the counterclockwise direction, they are: tooth tip circular arc ab, first point b, elliptic arc envelope line bcd, and second point d.

[0009] The left section profile and the right section profile can realize correct meshing under the counter-rotating motion of the convex screw rotor and the concave screw rotor with a transmission ratio of 3:2; the meshing conditions of the curves are: the tooth root circular arc AB on the left section profile meshes with the tooth tip circular arc ab on the right section profile, the first cycloid BC on the left section profile meshes with the first point b on the right section profile, the tooth tip elliptic arc CD on the left section profile meshes with the elliptic arc envelope line bcd on the right section profile, and the second cycloid DE on the left section profile meshes with the second point d on the right section profile; the left section profile and the right section profile can realize three-point meshing during the counter-rotating motion.

[0010] The tooth tip elliptic arc CD is axially spirally developed along the left helix line to form a left tooth tip surface with a groove, and the depth of the groove ranges from 0.1mm to 2mm; the elliptic arc envelope line bcd is axially spirally developed along the right helix line to form a right tooth groove surface with a protrusion, and the height of the protrusion ranges from 0.1mm to 2mm; during the counter-rotating motion, the groove on the left tooth tip surface of the convex screw rotor can mesh correctly with the protrusion on the right tooth groove surface of the concave screw rotor.

[0011] The left tooth tip surface with a groove of the convex screw rotor forms two-point meshing with the inner wall surface of the pump cavity.

[0012] The left cross-sectional profile is developed along a left helical line to generate a convex screw rotor; the right cross-sectional profile is developed along a right helical line to generate a concave screw rotor; wherein the pitch of the concave screw rotor is 1.5 times of the pitch of the convex screw rotor.

[0013] The multi-point meshing screw rotor of the double screw pump is established with the rotation center O1 of the convex screw rotor as the origin of the rectangular coordinate system, and the equation of the composition curve of the left cross-sectional profile of the convex screw rotor is:

[0014] The parametric equation of the dedendum circular arc AB is:

[0015] In the formula, t is an angle parameter; R1 is a dedendum circle radius;

[0016] The parametric equation of the first cycloid BC is:

[0017] In the formula, R2 is a addendum circle radius; L is a center distance between two screws;

[0018] The parametric equation of the addendum elliptical arc CD is:

[0019] In the formula, m is an elliptical long semi-axis length; n is an elliptical short semi-axis length;

[0020] The parametric equation of the second cycloid DE is:

[0021] The multi-point meshing screw rotor of the double screw pump is established with the rotation center O2 of the concave screw rotor as the origin of the rectangular coordinate system, and the equation of the composition curve of the right cross-sectional profile of the concave screw rotor is:

[0022] The parametric equation of the addendum circular arc ab is:

[0023] The parametric equation of the elliptical arc envelope line bcd is:

[0024]

[0025] In the formula, is an intermediate variable.

[0026]

[0027] The beneficial effects of the present application are:

[0028] ①The screw rotor profile proposed adopts an elliptical arc and its envelope line in the case of a transmission ratio of 3:2, the screw end face profile exists three-point meshing, the sealing performance is improved, the leakage is reduced, and the wear is improved.

[0029] The recess and protrusion structure at the meshing position of the two screw rotors makes the leakage channel zigzag and narrow, effectively reduces the internal leakage of the double screw pump, and thus improves the volumetric efficiency of the double screw pump.

[0030] The tooth profile is simple in structure, easy to optimize and design, and convenient to manufacture. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 Fig. 1 is a left sectional profile (101) of a convex screw rotor (1).

[0032] Figure 2 Fig. 2 is a right sectional profile (201) of a concave screw rotor (2).

[0033] Figure 3 Fig. 3 is a meshing diagram of the left sectional profile (101) and the right sectional profile (201).

[0034] Figure 4 Fig. 4 is a three-point meshing diagram of the left sectional profile (101) and the right sectional profile (201).

[0035] Figure 5 Fig. 5 is a three-dimensional view of the convex screw rotor (1).

[0036] Figure 6 Fig. 6 is a three-dimensional view of the concave screw rotor (2).

[0037] Figure 7 Fig. 7 is a meshing diagram of the convex screw rotor (1) and the concave screw rotor (2).

[0038] Figure 8 Fig. 8 is a sectional view of the convex screw rotor (1) and the concave screw rotor (2) in meshing.

[0039] In the figure: 1-convex screw rotor; 2-concave screw rotor; 3-pump cavity; 11-left tooth top surface; 21-right tooth groove surface; 31-pump cavity inner wall surface; 101-left sectional profile; 201-right sectional profile; AB-tooth root circular arc; BC-first cycloid; CD-tooth top elliptical arc; DE-second cycloid; ab-tooth top circular arc; bcd-elliptical arc envelope; R1-tooth root radius; R2-tooth top radius; n1, n2, n3-meshing points DETAILED DESCRIPTION

[0040] The application will be further described below with reference to the accompanying drawings.

[0041] As Figure 1The diagram shows the left cross-sectional profile 101 of the convex screw rotor 1. The convex screw rotor 1 is a double-headed screw, with identical tooth profiles on each head, evenly distributed along the circumference. The left cross-sectional profile 101 of the convex screw rotor 1 is 180° centrally symmetrical about its rotation center O1, meaning that after rotating 180° counterclockwise or clockwise around its rotation center O1, the left cross-sectional profile 101 completely coincides with itself. Half of the left cross-sectional profile 101 of the convex screw rotor 1 consists of four curve segments, arranged clockwise as follows: tooth root arc AB, first cycloid BC, tooth tip elliptical arc CD, and second cycloid DE. A rectangular coordinate system is established with the rotation center O1 as the origin. The equations of the constituent curves of the left cross-sectional profile 101 of the convex screw rotor 1 are:

[0042] The parametric equation of the tooth root arc AB is:

[0043] In the formula, t is the angle parameter; R1 is the root circle radius;

[0044] The parametric equation of the first cycloid BC is:

[0045] In the formula, R2 is the tooth tip circle radius; L is the center distance between the two screws;

[0046] The parametric equation for the elliptical arc CD at the tooth tip is:

[0047] In the formula, m is the length of the major semi-axis of the ellipse; n is the length of the minor semi-axis of the ellipse.

[0048] The parametric equation of the second cycloid DE is:

[0049] like Figure 2 The diagram shows the right cross-sectional profile 201 of the concave screw rotor 2. The concave screw rotor 2 is a three-headed screw, with each head having the same tooth profile, evenly distributed along the circumference. The right cross-sectional profile 201 of the concave screw rotor 2 is symmetrical about its rotation center O2 at a 120° angle, meaning that after rotating 120° counterclockwise or clockwise around its rotation center O2, the right cross-sectional profile 201 completely coincides with itself. One-third of the right cross-sectional profile 201 of the concave screw rotor 2 consists of two curve segments and two points, which, in the counterclockwise direction, are: tooth tip arc ab, first point b, elliptical arc envelope bcd, and second point d. A rectangular coordinate system is established with the rotation center O2 as the origin. The equations of the constituent curves of the right cross-sectional profile 201 of the concave screw rotor 2 are:

[0050] The parametric equation for the tooth tip circle ab is:

[0051] The parametric equation of the envelope of the elliptic arc bcd is:

[0052]

[0053] wherein, is an intermediate variable.

[0054]

[0055] As Figure 3 shown, is the meshing diagram of the left cross-sectional profile 101 and the right cross-sectional profile 201, the left cross-sectional profile 101 and the right cross-sectional profile 201 can achieve correct meshing. The left cross-sectional profile 101 of the convex screw rotor 1 and the right cross-sectional profile 201 of the concave screw rotor 2 can achieve correct meshing under the counter-rotating motion with a transmission ratio of 3:2; the meshing conditions of each curve are as follows: the tooth root circular arc AB on the left cross-sectional profile 101 meshes with the tooth crest circular arc ab on the right cross-sectional profile 201, the first cycloid BC on the left cross-sectional profile 101 meshes with the first point b on the right cross-sectional profile 201, the tooth crest elliptic arc CD on the left cross-sectional profile 101 meshes with the elliptic arc envelope bcd on the right cross-sectional profile 201, and the second cycloid DE on the left cross-sectional profile 101 meshes with the second point d on the right cross-sectional profile 201.

[0056] As Figure 4 shown, is the three-point meshing diagram of the left cross-sectional profile 101 and the right cross-sectional profile 201, the left cross-sectional profile 101 and the right cross-sectional profile 201 can achieve three-point meshing during the counter-rotating motion, which improves the sealing performance of the screw rotor, reduces leakage, and improves wear.

[0057] As Figure 5 shown, is a three-dimensional diagram of the convex screw rotor 1, the left cross-sectional profile 101 is axially spirally developed along the left helix to generate the convex screw rotor 1, and the convex screw rotor 1 is a double-headed constant-pitch screw. The tooth crest elliptic arc CD is axially spirally developed along the left helix to form a left tooth crest surface 11 with a groove, and the depth of the groove ranges from 0.1 mm to 2 mm.

[0058] As Figure 6 shown, is a three-dimensional diagram of the concave screw rotor 2, the right cross-sectional profile 201 is axially spirally developed along the right helix to generate the concave screw rotor 2, and the concave screw rotor 2 is a three-headed constant-pitch screw. The elliptic arc envelope bcd is axially spirally developed along the right helix to form a right tooth groove surface 21 with a protrusion, and the height of the protrusion ranges from 0.1 mm to 2 mm.

[0059] As Figure 7 shown, is a meshing diagram of the convex screw rotor 1 and the concave screw rotor 2, wherein the pitch of the concave screw rotor 2 is 1.5 times the pitch of the convex screw rotor 1. The two screw rotors can achieve correct meshing under the counter-rotating motion with a transmission ratio of 3:2, the groove at the tooth crest of the convex screw rotor 1 and the protrusion at the tooth root of the concave screw rotor 2 can achieve correct meshing, and there is no interference or part not participating in meshing.

[0060] like Figure 8 The diagram shows a cross-sectional view of the screw rotor meshing point. The convex screw rotor 1 has a groove at the tooth tip, while the concave screw rotor 2 has a protrusion at the tooth root. During twin-screw operation, the groove at the tooth tip of the convex screw rotor 1 and the protrusion at the tooth root of the concave screw rotor 2 mesh correctly, resulting in a tortuous and narrow leakage channel at the meshing gap, effectively reducing internal leakage of the screw pump. The grooved left tooth tip surface 11 of the convex screw rotor 1 meshes with the inner wall surface 31 of the pump chamber 3 at two points, further reducing axial internal leakage of the twin-screw pump.

[0061] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A multi-point meshing screw rotor for a twin screw pump, comprising: The convex screw rotor (1) and the concave screw rotor (2) are characterized in that: The convex screw rotor (1) is a double-head screw, and the tooth profile of each head is the same and uniformly distributed along the circumference; the left section line (101) of the convex screw rotor (1) is 180° center-symmetrical about its rotation center O1, that is, the left section line (101) is completely coincident with itself after being rotated by 180° counterclockwise or clockwise about the rotation center O1; one half of the left section line (101) of the convex screw rotor (1) is composed of four curves in the clockwise direction, which are, in sequence, the dedendum circular arc AB, the first cycloid BC, the addendum elliptic arc CD, and the second cycloid DE; The concave screw rotor (2) is a three-head screw, and the tooth profile of each head is the same and uniformly distributed along the circumference; the right section line (201) of the concave screw rotor (2) is 120° center-symmetrical about its rotation center O2, that is, the right section line (201) is completely coincident with itself after being rotated by 120° counterclockwise or clockwise about the rotation center O2; one third of the right section line (201) of the concave screw rotor (2) is composed of two curves and two points in the counterclockwise direction, which are, in sequence, the addendum circular arc ab, the first point b, the elliptic arc envelope bcd, and the second point d; The left section line (101) and the right section line (201) can realize correct meshing under the counter-rotating motion of the convex screw rotor (1) and the concave screw rotor (2) with a transmission ratio of 3:2; the meshing conditions of the curves are as follows: the dedendum circular arc AB on the left section line (101) meshes with the addendum circular arc ab on the right section line (201), the first cycloid BC on the left section line (101) meshes with the first point b on the right section line (201), the addendum elliptic arc CD on the left section line (101) meshes with the elliptic arc envelope bcd on the right section line (201), and the second cycloid DE on the left section line (101) meshes with the second point d on the right section line (201); during the counter-rotating motion, the left section line (101) and the right section line (201) can realize three-point meshing; The addendum elliptic arc CD is axially spirally developed along the left helix to form a left addendum surface (11) with a groove, and the depth of the groove ranges from 0.1 mm to 2 mm; the elliptic arc envelope bcd is axially spirally developed along the right helix to form a right tooth groove surface (21) with a protrusion, and the height of the protrusion ranges from 0.1 mm to 2 mm; during the counter-rotating motion, the groove at the left addendum surface (11) of the convex screw rotor (1) can mesh correctly with the protrusion at the right tooth groove surface (21) of the concave screw rotor (2); The left addendum surface (11) with a groove of the convex screw rotor (1) forms two-point meshing with the inner wall surface (31) of the pump cavity (3); The left section line (101) is axially spirally developed along the left helix to generate the convex screw rotor (1); the right section line (201) is axially spirally developed along the right helix to generate the concave screw rotor (2); the pitch of the concave screw rotor (2) is 1.5 times that of the convex screw rotor (1); A right-angle coordinate system is established with the rotation center O1 of the convex screw rotor (1) as the origin, and the equation of the composed curve of the left cross-sectional profile (101) of the convex screw rotor (1) is: The parametric equation of the tooth root circular arc AB is: In the formula, t is an angle parameter; R1 is the tooth root circle radius; The parametric equation of the first cycloid BC is: In the formula, R2 is the addendum circle radius; L is the center distance of the two screws; The parametric equation of the addendum ellipse arc CD is: In the formula, m is the length of the major axis of the ellipse; n is the length of the minor axis of the ellipse; The parametric equation of the second trochoid DE is: A right-angle coordinate system is established with the rotation center O2 of the concave screw rotor (2) as the origin, and the equation of the composed curve of the right cross-sectional profile (201) of the concave screw rotor (2) is: The parametric equation of the addendum circle arc ab is: The parameter equation of the elliptic arc envelope line bcd is: In the formulae, is an intermediate variable.

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