A kind of gear

Abstract

The present application discloses a gear, wherein the spoke plate includes a first spoke plate, a second spoke plate and a plurality of connecting columns; the first spoke plate and the second spoke plate are arranged along the rotation axis direction of the helical gear; the first spoke plate is closer to the tooth top of the tooth portion and is provided with two first surfaces which are both perpendicular to the rotation axis and away from each other; the second spoke plate includes a body and a plurality of connecting bodies; the body is annular and is provided with two second surfaces which are both perpendicular to the rotation axis and away from each other; the inner edge of the connecting body is connected to the outer edge of the body, and the connecting body is provided with two third surfaces which are away from each other, and the two line segments formed by the two third surfaces on the cross section passing through the rotation axis are parallel to each other and are both inclined relative to the rotation axis, and the inclination direction is radially outward close to the first surface; the connecting column extends along the rotation axis direction, and is used to connect the first surface and the second surface which are opposite to each other. The above-mentioned gear has an innovative configuration and is lightweight under the premise of ensuring that the stress requirements are met.

Description

Technical Field

[0001] This application relates to the field of gears. Background Art

[0002] The transmission system is one of the three key moving components of a helicopter and is an essential power transmission component for the power output of a turboshaft engine. Its performance largely determines the overall performance of the helicopter. As the core component of the transmission system, helical gears / helical gear trains have always attracted the attention of researchers. In terms of the design optimization of helical gears, preliminary research has been carried out by scholars at home and abroad. These studies mainly focus on the size optimization of conventional solid-configuration helical gears, and most of the research is carried out under simple working conditions and single-disciplinary conditions, and the weight reduction potential of advanced optimization design techniques has not been fully explored. In particular, with the significant increase in the demand for the transmission power of the reducer in the transmission system, the loads borne by helical gears are becoming larger and more complex, their own structural dimensions are larger and heavier, and the dynamic problems are more prominent. The need for lightweight design under complex working conditions is more urgent. Summary of the Invention

[0003] The purpose of this application is to overcome the above-mentioned defects or problems in the background art and provide a gear. The web of this gear has an innovative configuration and can achieve lightweight while meeting the stress requirements of the helical gear.

[0004] To achieve the above purpose, the following technical solutions are adopted:

[0005] A gear, which sequentially includes an axle part, a web, and a tooth part that are integrally connected to each other from the inside to the outside in the radial direction. Among them, the web includes a first web, a second web, and a plurality of connecting columns; both the first web and the second web are connected to the axle part and the tooth part and are arranged along the rotation axis direction of the gear; the first web is closer to the tooth tip of the tooth part and is circular, and it is provided with two first surfaces that are both perpendicular to the rotation axis and face away from each other; the second web includes a body and a plurality of connecting bodies that are integrally connected to each other; the body is circular, its inner edge is connected to the axle part, its outer edge is connected to each connecting body, and it is provided with two second surfaces that are both perpendicular to the rotation axis and face away from each other; each connecting body is arranged circumferentially around the rotation axis, the outer edge of the connecting body is connected to the tooth part and is provided with two third surfaces that face away from each other, and two line segments formed by the two third surfaces of the same connecting body in the cross-section passing through the rotation axis are parallel to each other and are both inclined relative to the rotation axis, and the inclination direction is radially outward and close to the first surface; the connecting columns extend along the rotation axis direction and are close to the outer edge of the body, and they are used to connect the opposite first surfaces and second surfaces; each connecting column is evenly distributed around the rotation axis.

[0006] Further, a plurality of first holes are circumferentially and uniformly distributed on the first web plate around the rotation axis. The first holes penetrate through the two first surfaces in the direction of the rotation axis, and their openings are located at the outer edge of the first web plate.

[0007] Further, the number of the connecting bodies is equal to the number of the first holes and is twice the number of the connecting columns, and the connecting bodies and the first holes are correspondingly arranged with the connecting columns at an interval of one each.

[0008] Further, the number of the connecting columns is 7.

[0009] Further, the projection of the connecting column on the projection plane perpendicular to the rotation axis is elliptical, and its minor axis is located on the plane passing through the rotation axis.

[0010] Further, the projection of the first hole on the projection plane is sequentially composed of a first straight line segment, a first arc segment and a second straight line segment; both the first straight line segment and the second straight line segment are connected to the outer edge of the first web plate and are tangent to the first arc segment; the first straight line segment and the second straight line segment are also located on the plane passing through the rotation axis.

[0011] Further, the interval between adjacent connecting bodies forms a second hole. The projection of the second hole on the projection plane is sequentially composed of a second arc segment, a third straight line segment, a third arc segment, a fourth arc segment, a fifth arc segment, a fourth straight line segment, and a sixth arc segment, wherein the second arc segment and the sixth arc segment are connected to the inner edge of the tooth part, and the fourth arc segment is located on the projection of the outer edge of the body.

[0012] Further, the area of the second hole on the projection plane is larger than the area of the first hole on the projection plane.

[0013] Further, a fillet is provided at the joint of the outer edge of the first web plate and the inner edge of the tooth part.

[0014] Further, when the tangential component force of the tooth engagement force on the tooth is less than or equal to 81000 N, the axial component force of the tooth engagement force is less than or equal to 23000 N, the radial component force of the tooth engagement force is less than or equal to 53000 N, and the rotational speed is less than or equal to 323 rpm, if the total mass of the tooth part is less than or equal to 20 kg, the yield strength of the material used for the web plate is greater than or equal to 700 Mpa and the material density is less than or equal to 7.86 g / cm 3 , then when 93 ≤ R0 ≤ 113 and 186.4 ≤ R1 ≤ 201.32, the following parameters of the web plate are: R2 = R1 - 40.32; R3 = R1 - 51.4; R4 = 175; w0 = 50; w3 = 8; ∝ = 160°; a = 2tan7.5°×R3; b = 18; r1 = 12.5; r2 = r3 = r4 = r ( = 7.5; r6 = 2; ∠O1OO2 = 3°; ∠O1OS = 7.5°; ∠OSR = 25.5°; ∠ROQ = 15°; ∠OQP = 165°; where, R0 is the radius of the inner edge of the web plate, in mm; R1 is the radius of the outer edge of the web plate, in mm; R2 is the radius of the outer edge of the body, in mm; R3 is the distance between the center of the projection of the connecting column on the projection plane and the rotation axis, in mm; R4 is the distance between the center of the first arc segment and the rotation axis, in mm; w0 is the distance between the first surface of the first web plate away from the body and the second surface of the body away from the first web plate, in mm; w1 is the distance between two first surfaces, in mm; w2 is the distance between two second surfaces, in mm; w3 is the distance between two third surfaces, in mm. ∝ is the angle between the intersection line of the third surface in the cross-section passing through the rotation axis and the intersection line of the second surface in the same cross-section; a is the major axis length of the projection of the connecting column on the projection plane, in mm; b is the minor axis length of the projection of the connecting column on the projection plane, in mm; r1 is the radius of the first arc segment, in mm; r2 is the radius of the second arc segment, in mm; r3 is the radius of the third arc segment, in mm; r4 is the radius of the fifth arc segment, in mm; r ( is the radius of the sixth arc segment, in mm; r6 is the radius of the chamfer at the junction of the outer edge of the first web plate and the inner edge of the tooth part, in mm; ∠O1OO2 is the angle between the perpendicular from the center of the projection of the connecting column to the rotation axis and the perpendicular from the center of the first arc segment of the corresponding first hole to the rotation axis; ∠O1OS is the angle between the perpendicular from the center of the projection of the connecting column to the rotation axis and the perpendicular from the intersection point of the extension line of the fourth straight line segment of the corresponding second hole and the inner edge of the tooth part to the rotation axis; ∠OSR is the angle between the perpendicular from the intersection point of the extension line of the fourth straight line segment and the inner edge of the tooth part to the rotation axis and the fourth straight line segment; ∠ROQ is the angle between the perpendicular from the intersection point of the extension line of the fourth straight line segment and the outer edge of the body to the rotation axis and the perpendicular from the intersection point of the extension line of the third straight line segment and the outer edge of the body to the rotation axis; ∠OQP is the angle between the perpendicular from the intersection point of the extension line of the third straight line segment and the outer edge of the body to the rotation axis and the third straight line segment.

[0015] Compared with the prior art, the above solution has the following beneficial effects:

[0016] The web of the gear involved in this application is composed of a first web, a second web and several connecting columns, which is lighter in weight and meets the requirements of stress and deformation. Compared with the web of the helical gear in the prior art, weight reduction is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments, the following briefly introduces the drawings that need to be used:

[0018] Figure 1 Is the front view of the helical gear in the embodiment;

[0019] Figure 2 Is Figure 1 The sectional view taken along the M-M direction of

[0020] Figure 3 Is Figure 2 The partial enlarged view of the X part of

[0021] Figure 4 Is the bottom view of the helical gear in the embodiment;

[0022] Figure 5 Is Figure 4 The sectional view taken along the N-N direction of

[0023] Figure 6 Is Figure 4 The partial enlarged view of the Y part of

[0024] Figure 7 Is the rear view of the helical gear in the embodiment;

[0025] Figure 8 Is Figure 7 The partial enlarged view of the Z part of

[0026] Description of the main reference numerals:

[0027] Gear 1; Tooth part 4; Web 3; First web 31; First hole 311; Second web 32; Body 321; Connecting body 322; Second hole 323; Shaft part 2. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] In the claims and the specification, unless otherwise defined, the terms "first", "second" or "third", etc., are used to distinguish different objects rather than to describe a specific order.

[0029] In the claims and the specification, unless otherwise defined, the terms "center", "lateral", "longitudinal", "horizontal", "vertical", "top", "bottom", "inner", "outer", "upper", "lower", "front", "rear", "left", "right", "clockwise", "counterclockwise", etc. indicate the orientation or positional relationship based on the orientation and positional relationship shown in the drawings, and are only for the convenience of simplified description, rather than implying that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation.

[0030] In the claims and the specification, unless otherwise defined, the term "fixed connection" or "fixedly connected" shall be understood in a broad sense, that is, any connection method without displacement relationship and relative rotation relationship between the two, that is, including non-detachable fixed connection, detachable fixed connection, being integrally formed, and being fixed connected through other devices or elements.

[0031] In the claims and the specification, unless otherwise defined, the terms "comprise", "have" and their variants mean "including but not limited to".

[0032] The technical solutions in the embodiments will be clearly and completely described below with reference to the drawings.

[0033] See Figure 1 and Figure 2 , Figure 1 show the structure of gear 1 in the embodiment. Gear 1 in this embodiment is a helical gear. Gear 1 sequentially includes a shaft portion 2, a web 3, and a tooth portion 4 that are integrally formed with each other from the inside to the outside in the radial direction. Among them, there are no improvements to the shaft portion 2 and the tooth portion 4 in this application, and they will not be elaborated here.

[0034] As Figure 2 shown, the web 3 includes a first web 31, a second web 32, and a plurality of connecting columns; both the first web 31 and the second web 32 are connected to the shaft portion 2 and the tooth portion 4 and are arranged along the rotation axis O direction of gear 1.

[0035] As Figure 3 shown, the first web 31 is closer to the tooth tip of the tooth portion 4 and is annular, and it is provided with two first surfaces that are both perpendicular to the rotation axis O and face away from each other. As Figure 4 and Figure 5 shown, a plurality of first holes 311 are circumferentially distributed around the rotation axis O on the first web 31. The first holes 311 penetrate through the two first surfaces in the rotation axis O direction, and their openings are at the outer edge of the first web 31. As Figure 6As shown, the projection of the first hole 311 on the projection plane perpendicular to the rotation axis O is successively composed of a first straight line segment AB, a first arc segment BD, and a second straight line segment CD; both the first straight line segment AB and the second straight line segment CD are connected to the outer edge of the first web 31 and are tangent to the first arc segment BD; the first straight line segment AB and the second straight line segment CD are also located in the plane passing through the rotation axis O. As Figure 3 As shown, a fillet is provided at the connection between the outer edge of the first web 31 and the inner edge of the tooth part 4.

[0036] As Figure 3 As shown, the second web 32 includes a body 321 and a plurality of connecting bodies 322 that are integrally connected to each other. As Figure 7 As shown, the body 321 is in an annular shape, its inner edge is connected to the shaft part 2, and its outer edge is connected to each connecting body 322. As Figure 3 As shown, the body 321 is provided with two second surfaces that are both perpendicular to the rotation axis O and face away from each other. As Figure 7 As shown, the connecting bodies 322 are arranged circumferentially around the rotation axis O. The outer edge of the connecting body 322 is connected to the tooth part 4 and is provided with two third surfaces that face away from each other. The two line segments formed by the two third surfaces of the same connecting body 322 in the cross-section passing through the rotation axis O are parallel to each other and are both inclined relative to the rotation axis O, and the inclination direction is along the radial direction and outward close to the first surface. As Figure 8 As shown, the interval between adjacent connecting bodies 322 forms a second hole 323. The projection of the second hole 323 on the projection plane is successively composed of a second arc segment EF, a third straight line segment FG, a third arc segment GH, a fourth arc segment HI, a fifth arc segment IJ, a fourth straight line segment JK, and a sixth arc segment KL. Among them, the second arc segment EF and the sixth arc segment KL are connected to the inner edge of the tooth part 4, and the fourth arc segment HI is located on the projection of the outer edge of the body 321. Generally, the area of the second hole 323 on the projection plane is larger than the area of the first hole 311 on the projection plane.

[0037] As Figure 3 As shown, the connecting column extends along the rotation axis O and is close to the outer edge of the body 321, and it is used to connect the first surface and the second surface that face each other. As Figure 6 As shown, the projection of the connecting column on the projection plane perpendicular to the rotation axis O is in an elliptical shape, and its minor axis is located in the plane passing through the rotation axis O. As Figure 5 As shown, each of the connecting columns is evenly distributed around the rotation axis O. In this embodiment, the number of connecting columns is 7.

[0038] As Figure 5 and Figure 7 As shown, the number of connecting bodies 322 is equal to the number of the first holes 311 and is twice the number of connecting columns. In this embodiment, it is 14. The connecting bodies 322 and the first holes 311 correspond to the connecting columns at intervals of one.

[0039] In this embodiment, the gear 1 operates under the conditions that the tangential component force of the tooth engagement force on the tooth is less than or equal to 81000 N, the axial component force of the tooth engagement force is less than or equal to 23000 N, the radial component force of the tooth engagement force is less than or equal to 53000 N, and the rotational speed is less than or equal to 323 rpm. And the total mass of the tooth part 4 can be less than or equal to 20 kg. The yield strength of the material used for the web 3 is equal to 700 Mpa and the material density is equal to 7.86 g / cm 3 .

[0040] As a specific design guide, such as Figure 6 and Figure 8 shown, when 93 ≤ R0 ≤ 113 and 186.4 ≤ R1 ≤ 201.32, the following parameters of the web 3 are:

[0041] R2 = R1 - 40.32;

[0042] R3 = R1 - 51.4;

[0043] R4 = 175;

[0044] w0 = 50;

[0045]

[0046] w3 = 8;

[0047] ∝ = 160°;

[0048] a = 2tan7.5° × R3;

[0049] b = 18;

[0050] r1 = 12.5;

[0051] r2 = r3 = r4 = r ( = 7.5;

[0052] r6 = 2;

[0053] ∠O1OO2 = 3°;

[0054] ∠O1OS = 7.5°;

[0055] ∠OSR = 25.5°;

[0056] ∠ROQ = 15°;

[0057] ∠OQP = 165°;

[0058] Among them,

[0059] R0 is the radius of the inner edge of the web 3, with the unit of mm;

[0060] R1 is the radius of the outer edge of the web 3, with the unit of mm;

[0061] R2 is the radius of the outer edge of the body 321, with the unit of mm;

[0062] R3 is the distance between the center of the projection of the connecting column on the projection plane and the rotation axis O, with the unit of mm;

[0063] R4 is the distance between the center of the first arc segment and the rotation axis O, with the unit of mm;

[0064] w0 is the distance between the first surface of the first web 31 away from the body 321 and the second surface of the body 321 away from the first web 31, with the unit of mm;

[0065] w1 is the distance between the two first surfaces, with the unit of mm;

[0066] w2 is the distance between the two second surfaces, with the unit of mm;

[0067] w3 is the distance between the two third surfaces, with the unit of mm.

[0068] ∝ is the angle between the intersection line of the third surface and the rotation axis O in the cross-section and the intersection line of the second surface in the same cross-section; a is the length of the major axis of the projection of the connecting column on the projection plane, with the unit of mm;

[0069] b is the length of the minor axis of the projection of the connecting column on the projection plane, with the unit of mm;

[0070] r1 is the radius of the first arc segment BD, with the unit of mm;

[0071] r2 is the radius of the second arc segment EF, with the unit of mm;

[0072] r3 is the radius of the third arc segment GH, with the unit of mm;

[0073] r4 is the radius of the fifth arc segment IJ, with the unit of mm;

[0074] r ( is the radius of the sixth arc segment KL, with the unit of mm;

[0075] r6 is the radius of the chamfer at the joint of the outer edge of the first web 31 and the inner edge of the tooth part 4, with the unit of mm;

[0076] ∠O1OO2 is the angle between the perpendicular line from the center O1 of the projection of the connecting column to the rotation axis O and the perpendicular line from the center O2 of the first arc segment BD of the corresponding first hole 311 to the rotation axis O;

[0077] ∠O1OS is the angle between the perpendicular line from the center O1 of the projection of the connecting column to the rotation axis O and the perpendicular line from the intersection point S of the extension line of the fourth straight line segment JK of the corresponding second hole 323 and the inner edge of the tooth part 4 to the rotation axis O;

[0078] ∠OSR is the angle between the perpendicular line from the intersection point S of the extension line of the fourth straight line segment JK and the inner edge of the tooth part 4 to the rotation axis O and the fourth straight line segment JK;

[0079] ∠ROQ is the angle between the perpendicular line from the intersection point R of the extension line of the fourth straight line segment JK and the outer edge of the body 321 to the rotation axis O and the perpendicular line from the intersection point Q of the extension line of the third straight line segment FG and the outer edge of the body 321 to the rotation axis O;

[0080] ∠OQP is the angle between the perpendicular line from the intersection point Q of the extension line of the third straight line segment FG and the outer edge of the body 321 to the rotation axis O and the third straight line segment FG, where P is the intersection point of the extension line of the third straight line segment FG and the inner edge of the tooth part 4.

[0081] In this embodiment, specifically, the value of R0 is 90 mm, the value of R1 is 201.4 mm, the value of R2 is 161.08 mm, the value of R3 is 150 mm, the value of w1 is 10 mm, the value of w2 is 8 mm, and the value of a is 39.5 mm. The volume of the web 3 is 1.597×10 6 mm 3 , and the mass is 12.556 kg.

[0082] If the web 3 for the same environment is solid, its volume is 5.239*10 6 mm 3 , and the mass is 41.181 kg. Therefore, the web 3 in this embodiment has a smaller volume and lighter mass compared with the solid web, and the mass can be reduced by 69.511%, achieving a good lightweight effect.

[0083] Perform a static analysis on the web 3 in the embodiment. The mesh division size is 2 mm, and the number of network elements is 1,487,575. The maximum equivalent stress (von-Mises stress) of the web 3 is between 614.78 MPa and 691.92 MPa, and the stress is less than the material yield strength of 700 MPa. Therefore, reliable operation can be ensured.

[0084] Although this embodiment is directed to helical gears, those skilled in the art can know that the above web structure can also be used for other types of gears.

[0085] The above description of the specification and the embodiment is used to explain the protection scope of the present application, but does not constitute a limitation on the protection scope of the present application.

Claims

1. A gear, which sequentially includes a shaft portion, a web and a tooth portion that are integrally connected to each other from the inside to the outside in the radial direction, and is characterized in that: The web includes a first web, a second web and a plurality of connecting columns; both the first web and the second web are connected to the shaft portion and the tooth portion and are arranged along the rotation axis direction of the gear; The first web is closer to the tooth tip of the tooth portion and is annular, and is provided with two first surfaces that are both perpendicular to the rotation axis and face away from each other; The second web includes a body and a plurality of connecting bodies that are integrally connected to each other; the body is annular, its inner edge is connected to the shaft portion, its outer edge is connected to each connecting body, and it is provided with two second surfaces that are both perpendicular to the rotation axis and face away from each other; each connecting body is arranged circumferentially around the rotation axis, the outer edge of the connecting body is connected to the tooth portion and is provided with two third surfaces that face away from each other, and two line segments formed by the two third surfaces of the same connecting body in the cross-section passing through the rotation axis are parallel to each other and are both inclined relative to the rotation axis, and the inclination direction is to approach the first surface radially outward; The connecting columns extend along the rotation axis direction and are close to the outer edge of the body, and are used to connect the first surface and the second surface that face each other; each connecting column is evenly distributed around the rotation axis; A plurality of first holes are evenly distributed circumferentially around the rotation axis on the first web, the first holes penetrate through the two first surfaces in the rotation axis direction, and open at the outer edge of the first web; The projection of the connecting column on the projection plane perpendicular to the rotation axis is elliptical, and its minor axis is located on the plane passing through the rotation axis; The projection of the first hole on the projection plane is sequentially composed of a first straight line segment, a first arc segment and a second straight line segment; both the first straight line segment and the second straight line segment are connected to the outer edge of the first web and are both tangent to the first arc segment; the first straight line segment and the second straight line segment are also located on the plane passing through the rotation axis; The interval between adjacent connecting bodies forms a second hole, and the projection of the second hole on the projection plane is sequentially composed of a second arc segment, a third straight line segment, a third arc segment, a fourth arc segment, a fifth arc segment, a fourth straight line segment, and a sixth arc segment, wherein the second arc segment and the sixth arc segment are connected to the inner edge of the tooth portion, and the fourth arc segment is located on the projection of the outer edge of the body.

2. A gear according to claim 1, characterized in that, The number of the connecting bodies is equal to the number of the first holes and is twice the number of the connecting columns, and the connecting bodies and the first holes are both corresponding to the connecting columns at an interval of one.

3. A gear according to claim 2, characterized in that, The number of the connecting columns is 7.

4. A gear according to claim 3, characterized in that, The area of the second hole on the projection plane is larger than the area of the first hole on the projection plane.

5. A gear according to claim 4, characterized in that, The joint of the outer edge of the first web and the inner edge of the tooth portion is rounded.

6. A gear according to claim 5, characterized in that, When the tangential component of the meshing force on the tooth of the gear is less than or equal to 81000 N, the axial component of the meshing force on the tooth is less than or equal to 23000 N, the radial component of the meshing force on the tooth is less than or equal to 53000 N, and the rotational speed is less than or equal to 323 rpm, if the total mass of the tooth part is less than or equal to 20 kg, the yield strength of the material used for the spoke is greater than or equal to 700 Mpa and the material density is less than or equal to 7.86 g / cm 3 , then When and then The following parameters of the web are: ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； Among them, is the radius of the inner edge of the web, in mm; is the radius of the outer edge of the web, in mm; is the radius of the outer edge of the said body, in mm; is the distance between the center of the projection of the connecting column on the projection plane and the rotation axis, with the unit of mm; is the distance between the center of the first arc segment and the rotation axis, with the unit of mm; is the distance between the first surface of the first web away from the body and the second surface of the body away from the first web, with the unit of mm; is the distance between the two first surfaces, in mm; is the distance between the two second surfaces, in mm; is the distance between the two third surfaces, in millimeters (mm); is the included angle between the intersection line of the third surface in the cross-section passing through the rotation axis and the intersection line of the second surface in the same cross-section; is the major axis length of the projection of the connecting column on the projection plane, with the unit of mm; is the minor axis length of the projection of the connecting column on the projection plane, with the unit of mm; is the radius of the first arc segment, in mm; is the radius of the second arc segment, in mm; is the radius of the third arc segment, in mm; is the radius of the fifth arc segment, in mm; is the radius of the sixth arc segment, in mm; is the radius of the chamfer at the joint of the outer edge of the first web plate and the inner edge of the tooth part, with the unit of mm; The angle between the perpendicular line from the center of the projection of the connecting column to the rotation axis and the perpendicular line from the center of the first arc segment of the corresponding first hole to the rotation axis; The included angle between the perpendicular line from the center of the projection of the connecting column to the rotation axis and the perpendicular line from the intersection point of the extension line of the fourth straight line segment of the corresponding second hole and the inner edge of the tooth part to the rotation axis; The angle between the perpendicular line from the intersection point of the extension line of the fourth straight line segment and the inner edge of the tooth part to the rotation axis and the fourth straight line segment; is the angle between the perpendicular line from the intersection point of the extension line of the fourth straight line segment and the outer edge of the body to the rotation axis and the perpendicular line from the intersection point of the extension line of the third straight line segment and the outer edge of the body to the rotation axis; The included angle between the perpendicular line from the intersection point of the extension line of the third straight line segment and the outer edge of the body to the rotation axis and the third straight line segment.

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