Screw assembly and vacuum pump

Abstract

The application provides a screw assembly and a vacuum pump, and relates to the field of dry screw vacuum pumps.The screw assembly comprises a first screw rotor and a second screw rotor;an end face profile of the first screw rotor comprises a cycloid AB, a dedendum circle arc segment BC, a cycloid CD, an involute DE and a addendum circle arc segment EA connected in sequence;an end face profile of the second screw rotor comprises a cycloid A'B', a dedendum circle arc segment B'C', a cycloid C'D', an involute D'E' and an addendum circle arc segment E'A' connected in sequence;the connection point A of the cycloid AB and the addendum circle arc segment EA is engaged with the cycloid A'B';the dedendum circle arc segment BC is engaged with the addendum circle arc segment E'A';the connection point E of the involute DE and the addendum circle arc segment EA is engaged with the cycloid C'D';the involute DE is engaged with the involute D'E';the gas is transported;the processing efficiency is improved;and the processing cost is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of dry screw vacuum pumps, in particular, to a screw assembly and a vacuum pump. BACKGROUND

[0002] The dry screw vacuum pump is a volumetric vacuum pump, which usually realizes the suction, pressurization and discharge of gas by periodically changing the volume of the working cavity formed between the two screw rotors and the inner cavity of the pump body through the synchronous high-speed reverse rotation of the two screw rotors. The existing dry screw vacuum pump has a complex structure, and the design of the involute and circular arc segment in the end face profile of the two rotors in the vacuum pump is unreasonable, which may cause the poor structure design of the vacuum pump and the meshing sharp point problem, thereby causing the rotors to be unable to be closely meshed. SUMMARY

[0003] The present application provides a screw assembly and a vacuum pump to solve the technical problems of meshing sharp point and the rotors being unable to be closely meshed during the rotation of the two rotors.

[0004] The embodiments of the present application can be implemented as follows:

[0005] In a first aspect, the present application provides a screw assembly, comprising a first screw rotor and a second screw rotor with the same end face profile and opposite rotation directions;

[0006] The end face profile of the first screw rotor comprises a cycloid AB, a dedendum circle arc segment BC, a cycloid CD, an involute DE and a addendum circle arc segment EA connected in sequence, and the end face profile of the second screw rotor comprises a cycloid A'B', a dedendum circle arc segment B'C', a cycloid C'D', an involute D'E' and an addendum circle arc segment E'A' connected in sequence;

[0007] During the rotation and meshing of the first screw rotor and the second screw rotor, the connection point A of the cycloid AB and the addendum circle arc segment EA is meshed with the cycloid A'B', the dedendum circle arc segment BC is meshed with the addendum circle arc segment E'A', the connection point E of the involute DE and the addendum circle arc segment EA is meshed with the cycloid C'D', and the involute DE is meshed with the involute D'E'.

[0008] In the above embodiments, the end face profiles of the first screw rotor and the second screw rotor are the same and have opposite rotation directions, so as to realize the symmetry of the profile and the structural consistency of the first screw rotor and the second screw rotor, thereby improving the matching meshing degree of the first screw rotor and the second screw rotor and realizing the closely meshing of the two screw rotors during work.

[0009] In an optional embodiment, the parametric equation of the cycloid AB is:

[0010] x = Rm * sin(2 * t) - 2A * sin(t);

[0011] y = 2A * cos(t) - Rm * cos(2 * t);

[0012] wherein t is a variable, x and y are rectangular coordinates of a point on the cycloid AB, the circle on which the dedendum circular arc segment BC lies and the circle on which the addendum circular arc segment EA lies are concentric circles, the center of the circle on which the dedendum circular arc segment BC lies is the center of the first screw rotor 100, the circle on which the dedendum circular arc segment B’C’ lies and the circle on which the addendum circular arc segment E’A’ lies are concentric circles, the center of the circle on which the dedendum circular arc segment B’C’ lies is the center of the second screw rotor 200, 2A is the center distance of the first screw rotor 100 and the second screw rotor 200, and Rm is the radius of the addendum circle of the screw rotor.

[0013] In the above embodiment, a rectangular coordinate system is established with the center of the addendum circle and the center of the dedendum circle as the coordinate origin, and the line shape of the cycloid AB can be determined by continuously inputting the variable t according to the parametric equation of the cycloid AB.

[0014] In an optional implementation, the value range of t is 0≤t≤arccos(2A / (2*Rm)).

[0015] In the above embodiment, the specific curve segment of the cycloid AB is determined according to the value range of t. By limiting the value range of t to 0~arccos(2A / (2*Rm)), the sharp point phenomenon at the cycloid AB of the end face profile is avoided, thereby improving the meshing and sealing of the two screw rotors.

[0016] In an optional implementation, the parametric equation of the cycloid CD is:

[0017] x = -Rm * sin(2 * t) - 2A * sin(t);

[0018] y = 2A * cos(t) - Rm * cos(2 * t);

[0019] wherein t is a variable, x and y are rectangular coordinates of a point on the cycloid AB, the circle on which the dedendum circular arc segment BC lies and the circle on which the addendum circular arc segment EA lies are concentric circles, the center of the circle on which the dedendum circular arc segment BC lies is the center of the first screw rotor 100, the circle on which the dedendum circular arc segment B’C’ lies and the circle on which the addendum circular arc segment E’A’ lies are concentric circles, the center of the circle on which the dedendum circular arc segment B’C’ lies is the center of the second screw rotor 200, 2A is the center distance of the first screw rotor 100 and the second screw rotor 200, and Rm is the radius of the addendum circle of the screw rotor.

[0020] In the above embodiment, a rectangular coordinate system is established with the centers of the addendum circle and the dedendum circle as the origin. Based on the parametric equation of the cycloid CD, the shape of the cycloid CD can be determined by continuously inputting the variable t.

[0021] In an optional implementation, the value of t is 0 ≤ t ≤ arccos(2A / (2*Rm)).

[0022] In the above embodiment, the specific curve segment of the cycloidal CD is determined based on the range of values ​​for t. By limiting the range of values ​​for t to 0 to arccos(2A / (2*Rm)), the formation of sharp angles at the cycloidal CD of the end face profile is avoided, thereby improving the meshing and sealing performance of the two screw rotors.

[0023] In an optional implementation, the parametric equation of the involute DE is:

[0024]

[0025]

[0026] Where t is a variable, x and y are the rectangular coordinates of a point on the cycloid CD, line L is a straight line passing through the center of the first screw rotor and tangent to the cycloid CD, Ro is the distance from the intersection of line L and the cycloid CD to the center of the first screw rotor, Rm is the radius of the addendum circle of the screw rotor, and Rd is the radius of the root circle of the screw rotor.

[0027] In the above embodiment, a rectangular coordinate system is established with the centers of the addendum circle and the dedendum circle as the origin. According to the parametric equation of the involute DE, the line shape of the involute DE can be determined by continuously inputting the variable t. Ro is also the base circle radius of the involute DE. The base circle radius is the minimum radius of the theoretical profile of the cam, which can ensure that the involute DE is tangent to the cycloid CD, ensuring that the tool can smoothly transition during the machining process and avoiding the phenomenon of poor transition.

[0028] In an optional implementation, the range of values ​​for t is:

[0029]

[0030] In the above embodiment, a rectangular coordinate system is established with the centers of the addendum circle and the dedendum circle as the origin. Based on the range of values ​​for t, the specific curve segment of the involute DE is determined. By limiting the range of values ​​for t to (Rd^2 / Ro^2-1)^0.5 to (Rm^2 / Ro^2-1)^0.5, the formation of acute angles at the involute DE of the end face profile is avoided, thereby improving the meshing and sealing performance of the two screw rotors.

[0031] In an alternative embodiment, the helix equation of the screw rotor is:

[0032] x = Rm * cos(t);

[0033] y = Rm * sin(t);

[0034]

[0035] where t is a variable, and x, y, and z are the coordinates of points on the helix of the screw rotor.

[0036] The helix of the screw rotor consists of multiple sequentially connected helix segments. P1 is the starting end pitch of the nth helix segment. The starting end of the nth helix segment is connected to the terminating end of the (n - 1)th helix segment. P2 is the terminating end pitch of the nth helix segment. The terminating end of the nth helix segment is connected to the starting end of the (n + 1)th helix segment. The gap between adjacent two helical teeth is the pitch. z1 is the axial length of the (n - 1)th helix segment, and t1 is the rotation angle of the (n - 1)th helix segment. The rotation angle is the angle that a point on the helix segment rotates around the axis in the projection plane perpendicular to the axis of the rotor during the process of moving from one end to the other end of the helix segment.

[0037] where n ≥ 1, and when n = 1, z1 = 0 and t1 = 0°.

[0038] In the above embodiment, according to the helix parametric equation, continuously inputting the variable t can determine the line type of the helix of the screw rotor, and can make the helices formed by two screw rotors mesh tightly.

[0039] In an alternative embodiment, the value range of t is t1 < t < t2, where t2 is the rotation angle of the outer helix of the nth helix segment around its own axis.

[0040] In the above embodiment, according to the value range of t, the specific curve segment of the helix is determined. By limiting t within t1 to t2, the helices formed by two screw rotors can mesh tightly.

[0041] In a second aspect, the present invention provides a vacuum pump, including the screw component according to any one of the foregoing embodiments.

[0042] The beneficial effects of the screw assembly and vacuum pump provided in this invention include: by having the same end face profiles, opposite rotation directions, and self-meshing capability of the first and second screw rotors, the symmetry of the profiles and the structural consistency of the first and second screw rotors are achieved, thereby improving the matching and meshing degree of the first and second screw rotors, increasing processing efficiency and reducing processing costs. Compared with existing vacuum pumps or conventional pumps, the structure is more compact and avoids the phenomenon of poor transition, enabling the two screw rotors to mesh tightly during operation. Attached Figure Description

[0043] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a schematic diagram of the screw assembly structure provided in an embodiment of the present invention;

[0045] Figure 2 This is a schematic diagram of the end face profile of the screw rotor provided in an embodiment of the present invention.

[0046] Icons: 10 - Screw assembly; 100 - First screw rotor; 200 - Second screw rotor. Detailed Implementation

[0047] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0048] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0049] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0050] In the description of this invention, it should be noted that if terms such as "upper," "lower," "inner," or "outer" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed, they are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0051] Furthermore, the terms "first" and "second" are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0052] It should be noted that, where there is no conflict, the features in the embodiments of the present invention can be combined with each other.

[0053] A dry screw vacuum pump is a positive displacement vacuum pump. Dry screw vacuum pumps typically achieve gas intake, pressurization, and discharge through the synchronous, counter-rotating double-rotation motion between two screw rotors.

[0054] Dry screw vacuum pumps are widely used in modern industry to obtain dry, low-pollution high vacuum environments. Due to their structural characteristics, they maintain stable performance under working pressures of 10,000 Pa to 100,000 Pa, and are therefore widely used in semiconductors, photovoltaics, LCD panels, and other fields. The screw rotor of the dry screw vacuum pump is the core component in its development.

[0055] Therefore, the good end-face profile meshing performance, the good sealing effect of the concave and helical tooth surfaces formed by the end face and the helix, and the high area utilization coefficient represent the current cutting-edge trend in screw pump rotor design. Existing dry screw vacuum pumps have complex structures, and unreasonable design of involute and arc segments in the end-face profiles of the two rotors can lead to poor vacuum pump structural design and meshing point problems, resulting in rotors not meshing tightly.

[0056] Based on the above issues, please refer to Figure 1 and Figure 2 The present invention provides a vacuum pump (not shown), which includes a pump body (not shown) and a screw assembly 10 disposed on the pump body. The screw assembly 10 includes a first screw rotor 100 and a second screw rotor 200. By causing the first screw rotor 100 and the second screw rotor 200 to rotate synchronously at high speed in opposite directions, the gas is transported.

[0057] Furthermore, the end face profile of the first screw rotor 100 includes a cycloid AB, a tooth root arc segment BC, a cycloid CD, an involute DE, and a tooth tip arc segment EA connected end to end in sequence, and the end face profile of the second screw rotor 200 includes a cycloid A'B', a tooth root arc segment B'C', a cycloid C'D', an involute D'E', and a tooth tip arc segment E'A' connected end to end in sequence.

[0058] In this embodiment, during the rotational meshing of the first screw rotor 100 and the second screw rotor 200, the connection point A between the cycloid AB and the tooth tip arc segment EA meshes with the cycloid A'B', that is, the profile point A meshes with the cycloid A'B'; the tooth root arc segment BC meshes with the tooth tip arc segment E'A'; the connection point E between the involute DE and the tooth tip arc segment EA meshes with the cycloid C'D', that is, the profile point E meshes with the cycloid C'D'; and the involute DE meshes with the involute D'E'. Similarly, the cycloid AB meshes with the profile point A', the cycloid CD meshes with the profile point E, the tooth tip arc segment EA meshes with the tooth root arc segment B'C', and the involute D'E meshes with the involute DE, thereby realizing the mutual meshing of the first screw rotor 100 and the second screw rotor 200 to complete the gas transport.

[0059] It should be noted that the end face profiles of the first screw rotor 100 and the second screw rotor 200 are the same but have opposite directions of rotation to achieve symmetry of the profiles and structural consistency of the first screw rotor 100 and the second screw rotor 200. This improves the matching and meshing degree of the first screw rotor 100 and the second screw rotor 200, increases processing efficiency, reduces processing costs, and avoids the phenomenon of poor transition.

[0060] Furthermore, the parametric equation of the cycloid AB is:

[0061] x = Rm*sin(2*t) - 2A*sin(t);

[0062] y = 2A*cos(t) - Rm*cos(2*t);

[0063] Where Rm is the radius of the addendum circle of the screw rotor, Rd is the radius of the root circle of the screw rotor, the circle containing the root arc segment BC is concentric with the circle containing the addendum arc segment EA, the center of the circle containing the root arc segment BC is the center of the first screw rotor 100, the circle containing the root arc segment B'C' is concentric with the circle containing the addendum arc segment E'A', the center of the circle containing the root arc segment B'C' is the center of the second screw rotor 200, 2A is the center distance between the first screw rotor 100 and the second screw rotor 200, i.e., 2A=Rm+Rd, t is a variable, and x and y are the rectangular coordinates of points on the cycloid AB.

[0064] It should be noted that before determining the cycloid AB, the radius Rm of the addendum circle arc segment EA and the radius Rd of the dedendum circle arc segment BC can be determined first. After establishing a rectangular coordinate system, with the origin as the center, the addendum circle and dedendum circle can be obtained based on Rm and Rd.

[0065] In this embodiment, a rectangular coordinate system is established with the centers of the addendum circle and the dedendum circle as the origin. Based on the parametric equation of the cycloid AB, the shape of the cycloid AB can be determined by continuously inputting the variable t.

[0066] Specifically, the value of t is in the range of 0 ≤ t ≤ arccos(2A / (2*Rm)), which determines the specific curve segment of the cycloid AB. By limiting the value of t to 0~arccos(2A / (2*Rm)), the formation of acute angles at the cycloid AB on the end face profile is avoided, thus improving the meshing and sealing performance of the two screw rotors.

[0067] Furthermore, the parametric equation of the cycloid CD is:

[0068] x = -Rm*sin(2*t) - 2A*sin(t);

[0069] y = 2A*cos(t) - Rm*cos(2*t);

[0070] In this embodiment, similarly, the shape of the cycloidal CD can be determined by continuously inputting the variable t according to the parametric equation of the cycloidal CD using the aforementioned coordinate axes.

[0071] Specifically, the value of t is 0 ≤ t ≤ arccos(2A / (2*Rm)), which determines the specific curve segment of the cycloidal CD. By limiting the value of t to the above range, the formation of sharp angles at the cycloidal CD of the end face profile is avoided, thus improving the meshing and sealing performance of the two screw rotors.

[0072] It should be noted that after the cycloid CD is determined, a straight line L is drawn through the center of the circle, i.e., the origin of the coordinate system, under the above coordinate axis, and this straight line L is tangent to the cycloid CD. The distance from the intersection point of the straight line L and the cycloid CD to the center of the circle is Ro.

[0073] Furthermore, the parametric equation of the involute DE is:

[0074]

[0075]

[0076] Where x and y are the rectangular coordinates of a point on the cycloid CD, line L is the line that passes through the center of the first screw rotor and is tangent to the cycloid CD, Ro is the distance from the intersection of line L and the cycloid CD to the center of the first screw rotor. It can be understood that Ro is also the base circle radius of the involute DE. The base circle radius is the minimum radius of the theoretical profile of the cam, Rm is the radius of the addendum circle of the screw rotor, and Rd is the radius of the root circle of the screw rotor.

[0077] In this embodiment, similarly, the shape of the involute DE can be determined by continuously inputting the variable t according to the parametric equation of the involute DE using the aforementioned coordinate axes; and Ro is also the base circle radius of the involute DE, which can ensure that the involute DE is tangent to the cycloid CD, ensuring that the tool can smoothly transition during the machining process.

[0078] Specifically, the range of values ​​for t is:

[0079] This determines the specific curve segment of the involute DE. By limiting the value of t to the aforementioned range, the formation of acute angles at the involute DE of the end face profile is avoided, thereby improving the meshing and sealing performance of the two screw rotors.

[0080] Furthermore, the helix equation of the screw rotor is:

[0081] x = Rm * cos(t);

[0082] y = Rm*sin(t);

[0083]

[0084] Where x, y, and z are the coordinates of points on the helix of the screw rotor.

[0085] Where t is a variable, x, y and z are the coordinates of a point on the helix of the screw rotor. The helix of the screw rotor is composed of multiple helical segments connected in sequence. P1 corresponds to the pitch at the starting end of the nth helical segment. The starting end of the nth helical segment is connected to the ending end of the (n-1)th helical segment. P2 corresponds to the pitch at the ending end of the nth helical segment. The ending end of the nth helical segment is connected to the starting end of the (n+1)th helical segment. The gap between two adjacent helical teeth is the pitch. z1 is the axial length of the (n-1)th helical segment. t1 is the rotation angle of the helix of the (n-1)th helical segment. The rotation angle of the helix is ​​the rotation angle of a point on the projection plane perpendicular to the axis of the rotor as it moves from one end of the helix to the other.

[0086] Where n≥1, and when n=1, z1=0, t1=0°.

[0087] It should be noted that the (n - 1)-th segment represents the previous segment of the n-th helical line. When n = 1, it indicates whether there is a helical segment in front of the n-th segment. At this time, the n-th helical line serves as the first helical segment.

[0088] In the above embodiments, according to the parametric equation of the helical line, continuously inputting the variable t can determine the line type of the helical line of the screw rotor, and can make the helical lines formed by the two screw rotors be closely meshed.

[0089] Specifically, the value range of t is t1 < t < t2, where t2 is the rotation angle of the helical line of the n-th helical segment, thereby determining the specific curve segment of the helical line.

[0090] It can be understood that in the case where the pitch P1 at the starting end of the screw rotor is equal to the pitch P2 at the terminating end of the screw rotor, the above parametric equation is an equal pitch equation; in the case where the pitch P1 at the starting end of the screw rotor is not equal to the pitch P2 at the terminating end of the screw rotor, the above parametric equation is a variable pitch equation.

[0091] In addition, it should be noted that since the screw rotor is composed of multiple different helical segments, a multi-segment parametric equation is required. Therefore, when the above parametric equation is used as the equation of the first helical line, z1 is 0; when the above parametric equation is used as the equation of the second helical line, z1 is the axial length of the previous helical line; when the above parametric equation is used as the equation of the third helical line, z1 is the axial length of the previous two helical lines, and so on.

[0092] The rotation angle of the helical line of the screw rotor is the angle by which the outermost helical line of the screw rotor rotates around the axis of the screw rotor. In other words, during the process of a point on the helical segment moving from one end to the other along its helical line, the rotation angle of this point around the axis on the projection plane perpendicular to the axis of the rotor is the rotation angle of the helical line.

[0093] It can be understood that on the first helical line, the starting end of the helical line can be regarded as the starting point of the helical line rotation, and the rotation angle of the helical line at this starting point is the starting angle, and this angle is 0°, and the axial length of the first helical line extending helically along the axis of the screw rotor is z1.

[0094] For example, the starting angle t1 of the first helical line is 0, and t2 can be 360°, that is, during the process of a point on the helical segment moving from one end to the other along the helical line, this point rotates one week around the axis of the rotor; in the case of the second helical line, t1 is 360°, and t2 can be 420°; in the case of the third helical line, t1 is 420°, and t2 can be 720°. Of course, the angles are not limited to the above settings, as long as t1 < t < t2 is ensured. The above data are only for illustration and not for specific limitation.

[0095] Therefore, based on the above helical parameter equation, by continuously inputting the variable t to obtain multiple helical segments, the shape of the screw rotor helical can be determined.

[0096] It is understandable that, since the end face profiles of the first screw rotor 100 and the second screw rotor 200 are the same, the process of determining the cycloid A'B', tooth root arc segment B'C', cycloid C'D', involute D'E', and tooth tip arc segment E'A' of the end face profile of the second screw rotor 200 is exactly the same as that of the first screw rotor 100, and will not be repeated here.

[0097] Specifically, please refer to Figure 1 , Figure 1 This is a schematic diagram of the end face profile of the screw rotor. It should be noted that... Figure 1 The three spirals and their corresponding parameters shown are for illustrative purposes only and do not represent actual proportional relationships.

[0098] like Figure 1 The screw rotor's helix is ​​divided into three segments: segment 1, segment 2, and segment 3, connected sequentially. If segment 1 is the end of the screw rotor, then when calculating the first helical segment, n = 1, z1 = 0, t1 = 0°, and t2 is the rotation angle of the first helical segment around the rotor axis. At this time, P1 corresponds to... Figure 1 The pitch at point A, P2 corresponds to Figure 1 The pitch at point B can be determined manually, and the specific line shape of the first helical segment can be determined by substituting the above parameters into the above formula.

[0099] Similarly, when calculating the second spiral segment, n=2. In this case, the first segment is considered the preceding segment of the second segment, and the third segment is considered the following segment of the second segment. P1 corresponds to... Figure 1 The pitch at point B corresponds to the pitch at point C, t1 is the rotation angle of the first helical segment around the rotor axis, t2 is the rotation angle of the second helical segment around the rotor axis, and z1 corresponds to the axial length of the first helical segment, i.e., as shown... Figure 1 As shown in the figure, H1 can be used to determine the specific line shape of the second spiral segment by substituting the above parameters into the above formula;

[0100] The calculation of the spiral segment in the third segment is the same as that in the second segment, and will not be repeated here.

[0101] By calculating the helical segments of the first, second, and third sections respectively, the shape of the rotor's helix can be determined, thereby ensuring that the helices formed by the two screw rotors can mesh tightly.

[0102] In summary, the embodiments of the present invention provide a screw assembly 10 and a vacuum pump, wherein the end face profiles of the first screw rotor 100 and the second screw rotor 200 are the same but have opposite rotation directions, so as to achieve the symmetry of the profiles and the structural consistency of the first screw rotor 100 and the second screw rotor 200, thereby improving the matching and meshing degree of the first screw rotor 100 and the second screw rotor 200, improving processing efficiency and reducing processing costs, making the structure more compact, eliminating leakage triangles after assembly, facilitating processing with full parametric design, having a high area utilization coefficient, and avoiding the phenomenon of poor transition.

[0103] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A screw assembly (10) characterized by, The first screw rotor (100) and the second screw rotor (200) have the same end surface profile and opposite rotation directions; The end surface profile of the first screw rotor (100) comprises a cycloid AB, a dedendum circle arc segment BC, a cycloid CD, an involute DE and a addendum circle arc segment EA connected in sequence, and the end surface profile of the second screw rotor (200) comprises a cycloid A'B', a dedendum circle arc segment B'C', a cycloid C'D', an involute D'E' and an addendum circle arc segment E'A' connected in sequence; During the meshing of the first screw rotor (100) and the second screw rotor (200), the connection point A of the cycloid AB and the addendum circle arc segment EA meshes with the cycloid A'B', the dedendum circle arc segment BC meshes with the addendum circle arc segment E'A', the connection point E of the involute DE and the addendum circle arc segment EA meshes with the cycloid C'D', and the involute DE meshes with the involute D'E'. The helix equation of the screw rotor is: x = Rm*cos(t); y = Rm*sin(t); wherein t is a variable, x, y and z are coordinates of a point on the helix of the screw rotor, the helix of the screw rotor is composed of a plurality of helical segments connected in sequence, P1 corresponds to the start end pitch of the nth helical segment, the start end of the nth helical segment is connected with the end of the (n-1)th helical segment, P2 corresponds to the end pitch of the nth helical segment, the end of the nth helical segment is connected with the start end of the (n+1)th helical segment, the gap between adjacent two helical teeth is the pitch, z1 is the axial length of the (n-1)th helical segment, and t1 is the rotation angle of the (n-1)th helical segment, which is the angle of the point on the helical segment rotating around the axis as the center in the process of moving from one end to the other end of the helical segment in the projection plane perpendicular to the axis of the rotor; wherein n is greater than or equal to 1, and when n = 1, z1 = 0 and t1 = 0°; The value range of t is t1 < t < t2, wherein t2 is the rotation angle of the nth helical segment.

2. The screw assembly (10) according to claim 1, characterized in that The parametric equation of the cycloid AB is: x = Rm*sin(2*t)-2A*sin(t); y = 2A*cos(t)-Rm*cos(2*t); wherein t is a variable, x and y are rectangular coordinates of a point on the cycloid AB, the circle where the dedendum circle arc segment BC is located is concentric with the circle where the addendum circle arc segment EA is located, the center of the circle where the dedendum circle arc segment BC is located is the center of the first screw rotor (100), the circle where the dedendum circle arc segment B'C' is located is concentric with the circle where the addendum circle arc segment E'A' is located, the center of the circle where the dedendum circle arc segment B'C' is located is the center of the second screw rotor (200), 2A is the center distance of the first screw rotor (100) and the second screw rotor (200), and Rm is the radius of the addendum circle of the screw rotor.

3. The screw assembly (10) according to claim 2, characterized in that The t has a value range of 0≤t≤arccos(2A / (2*Rm)).

4. The screw assembly (10) of claim 1, wherein, The parametric equation of the cycloid CD is: x=-Rm*sin(2*t)-2A*sin(t); y=2A*cos(t)-Rm*cos(2*t); Wherein, t is a variable, x and y are the rectangular coordinates of a point on the cycloid CD, the center of the tooth root circle arc segment BC is the center of the first screw rotor (100), the center of the tooth root circle arc segment B'C' is the center of the second screw rotor (200), 2A is the center distance of the first screw rotor (100) and the second screw rotor (200), and Rm is the radius of the addendum circle of the screw rotor.

5. The screw assembly (10) according to claim 4, characterized in that The t has a value range of 0≤t≤arccos(2A / (2*Rm)).

6. The screw assembly (10) of claim 1, wherein, The parametric equation of the involute DE is: Wherein, t is a variable, x and y are the rectangular coordinates of a point on the cycloid CD, the straight line L is a tangent line passing through the center of the first screw rotor and the cycloid CD, Ro is the distance from the intersection point of the straight line L and the cycloid CD to the center of the first screw rotor, Rm is the radius of the addendum circle of the screw rotor, and Rd is the radius of the dedendum circle of the screw rotor.

7. The screw assembly (10) according to claim 6, characterized in that The t has a value range of:

8. A vacuum pump, characterized by The screw assembly (10) according to any one of claims 1-7. The screw assembly (10) according to any one of claims 1-7.

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