An easily machined convex rotor profile with maximum form factor for pumps

Abstract

The present invention discloses an easy-to-process convex rotor profile with a maximum shape coefficient for a pump, which is composed of half-lobe profiles symmetrically adjacent to each other in the circumferential direction with a pitch circle twice the number of leaves, wherein the half-lobe profile is composed of three parts, namely, a peak transition connection arc, a peak conjugate profile, and a valley transition connection arc connected end to end, and the corresponding endpoints and connection points are, in order, a peak point located on the peak symmetry axis, a starting point, a midpoint, and a valley point located on the valley symmetry axis. The present invention has, firstly, the largest shape coefficient and volume utilization coefficient among similar convex rotors; and, secondly, has the most easily processable profile structure among similar convex rotors.

Description

Technical Field

[0001] The invention belongs to the technical field of rotor pumps, and in particular relates to a convex rotor profile structure with a maximum shape coefficient and easy processing. Background Art

[0002] The convex rotor pump is a type of positive displacement pump that uses the inlet vacuum suction generated by the rotation of two convex rotors (referred to as rotors) to transport the fluid medium to the outlet. It was first used in Roots vacuum pumps and is widely used. Among them, the non-contact rotor pair formed by two identical rotors is the core component of the pump, and the number of rotor blades is usually 2 to 4.

[0003] The volume utilization coefficient of the rotor = "the volume of the part of the blade slot used to extrude the medium in the volume of the rotor top cylinder / the volume of the rotor top cylinder" ∝ "1-1 / the square of the rotor shape coefficient", which is the most important indicator for measuring pump performance. The larger the shape coefficient, the larger the volume utilization coefficient and the better the pump performance. Therefore, in the design of the rotor profile, it is always hoped to obtain a larger volume utilization coefficient by adopting the maximum shape coefficient.

[0004] For common easy-to-process rotors with ordinary profile structures, the size of the shape coefficient is directly determined by the shape of the conjugate segment in the rotor profile, where the conjugate segment consists of two parts: the peak conjugate profile outside the pitch circle and the valley conjugate profile inside the pitch circle. Although the shape coefficient of ordinary rotors can be further improved after applying the high-profile technology of CN109630407B, the structure of the high-profile profile is relatively complex and relatively difficult to process.

[0005] Although CN109812413B provides general criteria and calculation methods for the upper limit shape coefficients of different conjugate profiles, for example, the upper limit shape coefficients that can be obtained for the most common involute shape are 1.6177, 1.4638, 1.3655 for 2-leaf, 3-leaf, and 4-leaf, 1.6699, 1.4770, 1.3680 for arc shape, and 1.5, 1.3333, 1.25 for cycloid shape. However, it does not solve the fundamental problem of what specific shape of the conjugate profile is when the rotor can obtain the maximum shape coefficient. Summary of the invention

[0006] The present invention aims at solving the fundamental problem in the background technology, provides a special construction condition when the valley conjugate profile is contracted and gathered on the pitch circle, directly calculates the maximum shape coefficient that the rotor can obtain and determines the geometric shape of the peak conjugate profile.

[0007] To achieve the above purpose, the technical solution of the present invention is as follows:

[0008] A convex rotor profile for a pump with a maximum shape coefficient that is easy to process, is composed of half-leaf profiles that are circumferentially symmetrically adjacent to each other with a pitch circle that is twice the number of leaves, and is characterized in that the half-leaf profile is composed of three parts, namely, a peak transition connecting arc, a peak conjugate profile, and a valley transition connecting arc that are connected end to end, and the corresponding endpoints and connection points are, in sequence, a peak point located on the peak symmetry axis, a starting point, a midpoint point, and a valley point located on the valley symmetry axis.

[0009] The half-leaf profile is formed by the peak symmetry axis and the valley symmetry axis, the intersection of the peak symmetry axis and the valley symmetry axis is the rotor center, and the angle between the peak symmetry axis and the valley symmetry axis is the center angle of the half-leaf profile uniquely determined by the number of rotor blades.

[0010] The intersection of the peak symmetry axis and the pitch circle is the peak node.

[0011] The intersection of the valley symmetry axis and the pitch circle is the valley node.

[0012] The midpoint of the nodal arc between the peak node and the valley node is the midpoint node, any point on the nodal arc between the peak node and the midpoint node is the instantaneous node, the nodal circle tangent at the instantaneous node is the instantaneous tangent line, the straight line segment between the instantaneous node and the midpoint is the instantaneous arc chord, the mirror symmetry line of the instantaneous arc chord about the instantaneous tangent line is the instantaneous radius line, and the endpoint of the non-instantaneous node on the instantaneous radius line is the instantaneous contour point.

[0013] The peak transition connection arc is an arc between the peak point and the starting point with the peak node as the circle center and "(shape coefficient - 1) x pitch circle radius" as the radius.

[0014] The peak conjugate contour is a trajectory line of the instantaneous contour points when the instantaneous node moves continuously from the mid-node to the peak node.

[0015] The valley transition connection arc is an arc between a mid-node and a valley node with the valley node as the center and "(shape coefficient - 1) x pitch circle radius" as the radius.

[0016] The shape coefficient = 1 + the length between nodes in the peak node / the radius of the pitch circle, that is, 1.7654, 1.5176, and 1.3902 for 2 leaves, 3 leaves, and 4 leaves, which are the maximum values ​​among all peak conjugate contour shapes.

[0017] The two inter-blade transition connecting arcs symmetrical about the valley symmetry axis can be made into standard arcs that can be processed simultaneously with standard tools by fine-tuning the pitch circle radius. In addition, there is no valley conjugate contour on the inner side of the pitch circle, so the contour of the rotor is relatively simple and the processing is relatively easy.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The pump of the present invention has an easy-to-process convex rotor profile with a maximum shape coefficient. First, it has the largest shape coefficient and volume utilization coefficient among similar convex rotors; second, it has a profile structure that is easiest to process among similar convex rotors. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Other features, objectives and advantages of the present invention will become more apparent from a reading of the detailed description of non-limiting embodiments made with reference to the following accompanying drawings.

[0021] Figure 1 Construct a schematic diagram for the convex rotor half blade profile with the maximum shape factor.

[0022] Wherein: O, rotor center, 0, peak point, 1, starting point, 2, midpoint, 3, valley point, 4, peak node, 5, valley node, 6, instantaneous node, 7, instantaneous contour point; O40, peak symmetry axis, O35, valley symmetry axis, 01, peak transition connecting arc, 12, peak conjugate contour, 23, valley transition connecting arc, ρ, length of instantaneous diameter line, θ, instantaneous center angle, 62, instantaneous arc chord, 67, instantaneous diameter line, 68, instantaneous tangent line, α, angle between instantaneous diameter line and peak symmetry axis, r, pitch circle radius, ε, shape coefficient, φ, center angle of half-leaf contour, N, number of rotor blades, λ, volume utilization coefficient. DETAILED DESCRIPTION

[0023] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0024] like Figure 1As shown, a convex rotor profile with a maximum shape coefficient for a pump of the present invention is easy to process, and is composed of half-lobe profiles circumferentially symmetrically adjacent to the pitch circle of twice the number of blades. The half-lobe profile is composed of three parts, namely, a peak transition connection arc 01, a peak conjugate profile 12, and a valley transition connection arc 23, which are smoothly connected end to end. The corresponding endpoints and connection points are, in sequence, a peak point 0 located on the peak symmetry axis, a starting point 1, a midpoint 2, and a valley point 3 located on the valley symmetry axis O35. Among them, the half-lobe profile is formed by the peak symmetry axis O40 and the valley symmetry axis O35. The intersection of the peak symmetry axis O40 and the valley symmetry axis O35 is the rotor center O. The angle between the peak symmetry axis O40 and the valley symmetry axis O35 is the center angle φ of the half-lobe profile uniquely determined by the number of rotor blades. The intersection of the peak symmetry axis O40 and the pitch circle is the peak node 4, the intersection of the valley symmetry axis O35 and the pitch circle is the valley node 5, the midpoint of the pitch circle arc between the peak node 4 and the valley node 5 is the midpoint 2, and the peak node 4 and the midpoint are connected. Any point on the 2 pitch circle arcs is the instantaneous node 6; the pitch circle tangent at the instantaneous node 6 is the instantaneous tangent line 68, the straight line segment between the instantaneous node 6 and the mid node 2 is the instantaneous arc chord 62; the mirror symmetry line of the instantaneous arc chord 62 about the instantaneous tangent line is the instantaneous radial line 67, the endpoint of the non-instantaneous node on the instantaneous radial line 67 is the instantaneous contour point 7, ρ is the length of the instantaneous radial line, θ is the instantaneous center angle (the center angle of the pitch circle arc between the instantaneous node and the mid node), r is the pitch circle radius, ε is the shape coefficient, N is the number of rotor blades, and λ is the volume utilization coefficient.

[0025] Under the premise that the pitch circle radius r and the number of leaves N are given, the peak symmetry axis O40, peak node 4, mid-node 2, valley node 5, half-leaf contour central angle φ, and valley symmetry axis O35 are all uniquely determined.

[0026] First, when the instantaneous radial line 67 and the instantaneous arc chord 62 are symmetrical about the instantaneous tangent line 68:

[0027]

[0028] The peak conjugate profile 12 is uniquely constructed;

[0029] Secondly, from ε = 1 + the length between nodes in the peak node / the radius of the pitch circle r, we get:

[0030]

[0031] And taking the peak node 4 and the valley node 5 as the circle center and r×(2-ε) as the radius, a peak transition connection arc 01 and a valley transition connection arc 23 are constructed respectively;

[0032] Then, by further deduction of the volume utilization coefficient calculation, we get:

[0033]

[0034] The upper limit shape factor ε of the involute rotor j and its volume utilization coefficient λj of

[0035]

[0036] In comparison, the shape coefficient of the rotor of the present invention is respectively increased by 9.13% under 2 blades, 3.68% under 3 blades and 1.81% under 4 blades, and the volume utilization coefficient is respectively increased by 8.06% under 2 blades, 5.38% under 3 blades and 3.72% under 4 blades.

[0037] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention.

Claims

1. An easy-to-machine convex rotor with a maximum shape coefficient for a pump, comprising a rotor profile consisting of half-lobe profiles symmetrically adjacent to each other in the circumferential direction of a pitch circle twice the number of lobes, characterized in that: The half-leaf contour is composed of three parts: a peak transition connecting arc, a peak conjugate contour, and a valley transition connecting arc connected end to end. The corresponding endpoints and connection points are, in sequence, a peak point, a starting point, a midpoint located on the peak symmetry axis, and a valley point located on the valley symmetry axis. The intersection of the peak symmetry axis and the pitch circle is the peak node, the midpoint of the pitch circle arc between the peak node and the valley node is the midpoint, any point on the pitch circle arc between the peak node and the midpoint is an instantaneous node, the pitch circle tangent at the instantaneous node is an instantaneous tangent, the straight line segment between the instantaneous node and the midpoint is an instantaneous arc chord, and the instantaneous arc chord is a tangent line. The mirror symmetry line of the instantaneous tangent line is the instantaneous diameter line, the endpoint of the non-instantaneous node on the instantaneous diameter line is the instantaneous contour point, the peak transition connection arc is the arc between the peak point and the starting point with the peak node as the center and (shape coefficient-1)×the pitch circle radius as the radius, the peak conjugate contour is the trajectory line of the instantaneous contour point when the instantaneous node moves continuously from the midnode to the peak node, the valley transition connection arc is the arc between the midnode and the valley node with the valley node as the center and (shape coefficient-1)×the pitch circle radius as the radius, and the shape coefficient=1+the length between the peak node and the midnode / the pitch circle radius.

2. A convex rotor for a pump with a maximum shape factor that is easy to process as claimed in claim 1, characterized in that: The half-leaf profile is formed by a peak symmetry axis and a valley symmetry axis, the intersection of the peak symmetry axis and the valley symmetry axis is the rotor center, and the angle between the peak symmetry axis and the valley symmetry axis is the center angle of the half-leaf profile uniquely determined by the number of rotor blades.

3. A convex rotor for a pump with a maximum shape factor that is easy to process as claimed in claim 1, characterized in that: The intersection of the valley symmetry axis and the pitch circle is the valley node.

Images