CN106762837B

CN106762837B - Centrifugal fan volute for range hood

Info

Publication number: CN106762837B
Application number: CN201611168217.9A
Authority: CN
Inventors: 翁建松; 余旭锋; 郑幸; 田涛; 茅忠群; 诸永定; 李斌
Original assignee: Ningbo Fotile Kitchen Ware Co Ltd
Current assignee: Ningbo Fotile Kitchen Ware Co Ltd
Priority date: 2016-12-16
Filing date: 2016-12-16
Publication date: 2023-04-14
Anticipated expiration: 2036-12-16
Also published as: CN106762837A

Abstract

The invention discloses a centrifugal fan volute for a range hood, which comprises a front cover plate, a rear cover plate and an air outlet, wherein an air inlet hole is formed in the front cover plate, the center of the air inlet hole is a first origin of coordinates, and a current collector is arranged at the air inlet hole, and the centrifugal fan volute is characterized in that: the lower part of the front cover plate and the position of the corresponding side of the air outlet are provided with bending parts, the bending parts incline towards the direction of the rear cover plate, and the current collector is eccentrically arranged relative to the first coordinate origin and the direction of the bending parts. The left lower corner of the volute is bent, and the current collector is deviated to the left lower corner, so that the flow field fluctuation of the left lower corner is improved, the asymmetric characteristic of the volute is weakened, the circumferential air inflow of the impeller is adjusted, the air inflow of each runner blade of the impeller is more uniform, the vortex is reduced, and the purpose of noise reduction is achieved.

Description

Centrifugal fan volute for range hood

Technical Field

The invention relates to a range hood, in particular to a volute of a centrifugal fan for the range hood.

Background

Along with the change of living environment of people and the improvement of life quality, the requirements on the range hood are higher and higher. The fan that domestic range hood adopted mostly is multi-wing centrifugal fan, inhales, exhausts. Centrifugal fans generally consist of a volute, a motor, an impeller, etc. The working principle of the centrifugal fan is that the motor drives the impeller to rotate to apply work to airflow and the airflow is discharged from the radial direction through the diffusion effect of the volute.

The volute of the centrifugal fan is designed by adopting an approximate logarithmic spiral line or an approximate Archimedes spiral line, the volute is gradually expanded, for example, the volute molded line of the centrifugal fan for the range hood disclosed by the Chinese patent with the application number of 201110118687.5 is formed by smoothly transitionally connecting a first straight line, a first arc line, a second arc line, a spiral line and a second straight line, and the spiral line is a constant-speed spiral line; also, as disclosed in the chinese patent application No. 201220245605.3, a double-sided air intake type range hood volute structure includes an air outlet fixing plate, a volute front plate and a volute rear plate which are arranged in parallel, and a volute side plate for connecting the volute front plate and the volute rear plate, wherein both the volute front plate and the volute rear plate are provided with circular air inlets, and the edge contour line of the volute front plate includes a first straight line, a second straight line, a first circular arc, a second circular arc, a third straight line, a third circular arc, a fourth circular arc, a fifth circular arc, a fourth straight line and a fifth straight line which are connected in sequence; the fifth straight line is in contact with the air outlet fixing plate, and the second straight line and the third straight line are both vertical to the fifth straight line; the contour of the volute back plate is consistent with that of the volute front plate, and all points are in one-to-one correspondence.

The volute design mode inevitably causes the nonuniformity of the flow in each flow channel in the axial direction of the impeller, and simultaneously, because the air inlet quantity at the front part of the impeller of the multi-wing centrifugal fan is far smaller than the middle part and the rear part of the impeller, vortexes exist at the front part of the volute and the back of a current collector, the two factors cause the maximum turbulent kinetic energy at the lower left corner of the volute and the most chaotic flow, and the maximal vortexes of the impeller in the blade flow channel at the lower left corner become one of the noise sources of the multi-wing centrifugal fan.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a centrifugal fan volute for a range hood, which can reduce noise and solve the problems in the prior art.

The technical scheme adopted by the invention for solving the technical problems is as follows: the utility model provides a centrifugal fan spiral case for range hood, includes front shroud, back shroud and air outlet, the fresh air inlet has been seted up on the front shroud, the center of fresh air inlet is first origin of coordinates, fresh air inlet department is provided with collector, its characterized in that: the lower part of the front cover plate and the position of the corresponding side of the air outlet are provided with bending parts, the bending parts incline towards the direction of the rear cover plate, and the current collector is eccentrically arranged relative to the first coordinate origin and the direction of the bending parts.

In order to better reduce the flow, improve the flow field and reduce the noise, the eccentric angle formed by the connecting line of the center of the current collector and the first coordinate origin and the included angle between the connecting line and the vertical direction is gamma, gamma is more than or equal to 25 degrees and less than or equal to 35 degrees, the eccentric distance between the center of the current collector and the first coordinate origin is L, and L is more than or equal to 10mm and less than or equal to 18mm.

Preferably, in order to further compress the flow field and ensure that the fan system has larger air pressure, the molded line of the front cover plate is formed by sequentially connecting a first straight line, a first circular arc, a second circular arc, a third circular arc, a fourth circular arc, a fifth circular arc, a sixth circular arc and a first termination straight line, and the adjacent straight line segment and the circular arc segment or the adjacent circular arc segment and the circular arc segment are tangent at the intersection point.

Preferably, a first bending point is arranged between the fourth arcs, a second bending point is arranged between the sixth arcs, a connecting line of the first bending point and the second bending point forms a bending line, and the front cover plate is bent towards the rear cover plate at the bending line to form the bending portion.

Preferably, an included angle between a connecting line of the first bending point and the first origin of coordinates and the vertical direction is beta 1, an included angle between a connecting line of the second bending point and the first origin of coordinates and an included angle between a connecting line of the first bending point and the first origin of coordinates are beta 2, beta 1 is larger than or equal to 10 degrees and smaller than or equal to 20 degrees, beta 2 is larger than or equal to 60 degrees and smaller than or equal to 80 degrees, the bending angle of the bending part is theta, and theta is larger than or equal to 110 degrees and smaller than or equal to 130 degrees.

Preferably, for further compression flow field, guarantee that fan system has great wind pressure, noise reduction, the molded lines datum line of front shroud is for coordinate, the size of first coordinate origin relatively:

(1) A first straight line, the coordinates of the starting point being (33.27, 228.6) and the coordinates of the end point being (3.3, 173.9);

(2) The curvature radius (Ra) of the first circular arc is 18.9mm, and the origin coordinates of the curvature radius are (18.9, 163.1);

(3) The curvature radius of the second circular arc is 84.6mm, the origin coordinate of the curvature radius is (45, 223.4), and the starting point coordinate is (11.4, 145.8);

(4) The curvature radius of the third circular arc is 138.9mm, the origin coordinate of the curvature radius is (4,3.7), and the starting point coordinate is (29.5, 140.3);

(5) The curvature radius of the fourth circular arc is 178.1mm, the origin coordinate of the curvature radius is (-35.2,4.2), and the starting point coordinate is (142.9,2);

(6) The curvature radius of the fifth circular arc is 155.8mm, the origin coordinates of the curvature radius are (-49.7, -12.8), and the coordinates of the starting point are (-150.7, 131.4);

(7) The curvature radius of the sixth circular arc is 322.3mm, the origin coordinate of the curvature radius is (116.3,0), and the starting point coordinate is (-205, -24.5);

(8) A first end straight line, a start point coordinate (-188.3, 104.9), an end point coordinate (-145.4, 229.1);

the datum line is deviated outwards by 5mm to form an outer boundary line, the datum line is deviated inwards by 5mm to form an inner boundary line, and the molded line of the front cover plate is positioned in a molded band formed between the outer boundary line and the inner boundary line.

Preferably, the molded line of the rear cover plate is formed by sequentially connecting a seventh circular arc, an eighth circular arc, a ninth circular arc, a tenth circular arc, a fifth circular arc, a sixth circular arc and a second termination straight line, and adjacent straight line segments and circular arc segments or adjacent circular arc segments and circular arc line segments are tangent at the intersection point.

The rear cover plate is provided with a second origin of coordinates, the projection of the first origin of coordinates on the plane where the rear cover plate is located is superposed with the second origin of coordinates, and the coordinates and the sizes of the molded line datum line of the rear cover plate relative to the second origin of coordinates are as follows:

(1) The curvature radius of the seventh circular arc is 18.9mm, the origin coordinate of the curvature radius is (18.9, 163.1), and the starting point coordinate is (0.3, 159.8);

(2) The curvature radius of the second circular arc is 84.6mm, the origin coordinate of the curvature radius is (45, 223.4), and the starting point coordinate is (11.4, 145.8);

(3) The curvature radius of the ninth circular arc is 138.9mm, the origin coordinate of the curvature radius is (4,3.7), and the starting point coordinate is (29.5, 140.3);

(4) The curvature radius of the tenth circular arc is 178.1mm, the origin coordinate of the curvature radius is (-35.2,4.2), and the starting point coordinate is (142.9,2);

(5) The curvature radius of the eleventh circular arc is 155.8mm, the origin coordinates of the curvature radius are (-49.7, -12.8), and the coordinates of the starting point are (-150.7, 131.4);

(6) The curvature radius of the twelfth circular arc is 322.3mm, the origin coordinate of the curvature radius is (116.3,0), and the starting point coordinate is (-205, -24.5);

(7) A second end line, start point coordinates (-188.3, 104.9), end point coordinates (-168.6, 159.8);

the molded line of the rear cover plate is positioned in a curve band which is deviated inwards and outwards by 5mm by the reference line (L4).

Compared with the prior art, the invention has the advantages that: the left lower corner of the volute is bent, and the current collector is deviated to the left lower corner, so that the flow field fluctuation of the left lower corner is improved, the asymmetric characteristic of the volute is weakened, the circumferential air inflow of the impeller is adjusted, the air inflow of each runner blade of the impeller is more uniform, the vortex is reduced, and the purpose of noise reduction is achieved.

Drawings

FIG. 1 is a schematic view of a volute of the present invention;

FIG. 2 is a schematic view of a volute of the present invention;

FIG. 3 is a schematic view of a front cover plate of the present invention;

FIG. 4 is a schematic view of the profile of the front cover plate according to the present invention;

FIG. 5 is a profile view of the volute back cover of the present invention;

FIG. 6 is a schematic view of a collector of a volute of the present invention;

fig. 7 is a schematic view of the profile range of the front cover plate according to the present invention.

Detailed Description

The invention is described in further detail below with reference to the accompanying examples.

Referring to fig. 1 to 3, a centrifugal fan volute for a range hood includes a front cover plate 11, a rear cover plate 12, and a volute annular wall 13 connected between the front cover plate 11 and the rear cover plate 12, and an air outlet 14 is formed on the volute. The volute is internally provided with an impeller 2, the front cover plate 11 is provided with an air inlet hole 111, the rear cover plate 12 is provided with a mounting hole 121, so that the motor 3 can be mounted, the center of the air inlet hole 111 and the center of the mounting hole 121 are both on the axis of the impeller 2, the center of the air inlet hole 111 is a first origin of coordinate O1, the center of the mounting hole 121 is a second origin of coordinate O2, namely, the projection of the first origin of coordinate O1 on the plane of the rear cover plate 12 coincides with the second origin of coordinate O2.

A bent part 112 is formed at the lower part of the front cover plate 11 and the position of the side corresponding to the air outlet 14 (the lower left corner of the front cover plate 11), the bent part 112 inclines towards the direction of the rear cover plate 12, and the bent part 112 is connected with the volute annular wall 13, so that a flow channel at the position in the volute is narrowed, flow field fluctuation is improved, and noise is reduced. The air inlet hole 111 of the front cover plate 11 is provided with a current collector 15, and the current collector 15 is eccentrically arranged towards the direction of the bent part 112 relative to the center of the air inlet hole 111. An included angle formed by a connecting line of the center O3 of the current collector 15 and the first coordinate origin O1 and the vertical direction is gamma, and the gamma is more than or equal to 25 degrees and less than or equal to 35 degrees. The eccentric distance between the center O3 of the current collector 15 and the first origin of coordinates O1 is L, L is more than or equal to 10mm and less than or equal to 18mm, see FIG. 6.

Through bending the lower left corner of the volute and offsetting the lower left corner of the current collector, the flow field fluctuation of the lower left corner is improved, the asymmetric characteristic of the volute is weakened, the circumferential air inlet of the impeller is adjusted, so that the air inlet of each flow channel blade of the impeller 2 is more uniform, the vortex is reduced, and the purpose of noise reduction is achieved.

Referring to fig. 4, the molded line of the front cover plate 11 is formed by sequentially connecting a first straight line IA, a first arc AB, a second arc BC, a third arc CD, a fourth arc DE, a fifth arc EF, a sixth arc FG, and a first termination straight line GH. The adjacent straight line segments and arc line segments or the adjacent arc line segments and arc line segments are tangent at the intersection point, for example, the third arc CD and the fourth arc DE are tangent at point D.

The fourth arc DE has a first bending point K, the sixth arc FD has a second bending point J, and the front cover 11 is bent toward the rear cover 12 at a bending line KJ, which is a connection line between the first bending point K and the second bending point J, thereby forming the above-mentioned bent portion 112. The position of a bending line KJ is determined by angles beta 1 and beta 2, the included angle between a connecting line of a first bending point K and a first coordinate origin O1 and the vertical direction is beta 1, the included angle between a connecting line of a second bending point J and the first coordinate origin O and the included angle between the connecting line of the first bending point K and the first coordinate origin O is beta 2, the angle between the connecting line of the second bending point J and the first coordinate origin O is beta 1 which is more than or equal to 10 degrees, and the angle between the connecting line of the second bending point J and the first coordinate origin O is beta 2 which is more than or equal to 20 degrees, and the angle between beta 2 which is more than or equal to 60 degrees and less than or equal to 80 degrees; the bending angle of the bending part 112 is theta, and theta is more than or equal to 110 degrees and less than or equal to 130 degrees. More preferably, β 1 is 16 °, β 2 is 73.5 °, and θ is 60 °.

Specifically, the molded-line reference line L1 of the front cover plate 11 has the following coordinates and dimensions (relative to the first origin O1):

(1) A first straight line IA, the coordinates of the starting point I are (33.27, 228.6), and the coordinates of the ending point a are (3.3, 173.9);

(2) The first arc AB has a radius of curvature (Ra) of 18.9mm and a radius of curvature origin a coordinate of (18.9, 163.1).

(3) The radius of curvature (Rb) of the second circular arc BC is 84.6mm, the origin B of the radius of curvature is (45, 223.4) and the starting point B is (11.4, 145.8).

(4) The radius of curvature (Rc) of the third circular arc CD is 138.9mm, the origin C coordinate of the radius of curvature is (4,3.7), and the starting point C coordinate is (29.5, 140.3).

(5) The radius of curvature (Rd) of the fourth circular arc DE is 178.1mm, the origin D coordinate of the radius of curvature is (-35.2,4.2), and the starting point D coordinate is (142.9,2).

(6) The curvature radius (Re) of the fifth circular arc EF is 155.8mm, the origin E coordinate of the curvature radius is (-49.7, -12.8), and the starting point E coordinate is (-150.7, 131.4).

(7) The sixth circular arc FG has a radius of curvature (Rf) of 322.3mm, a radius of curvature origin F coordinate of (116.3,0), and a starting point F coordinate of (-205, -24.5).

(8) The first end straight line GH, G point coordinate (-188.3, 104.9), H point coordinate (-145.4, 229.1).

Referring to fig. 7, the reference line L1 is shifted outward by 5mm to form an outer boundary line L2, the reference line L1 is shifted inward by 5mm to form an inner boundary line L3, and the profile of the front cover plate 11 is located within a curve band formed between the outer boundary line L2 and the inner boundary line L3.

The molded line of the front cover plate 11 is different from the currently used spiral line, and comprises a starting straight line IA and a first stopping straight line GH, and the middle of the starting straight line IA and the first stopping straight line GH are connected through a plurality of sections of circular arcs. The distances between the impeller 2 and the second arc BC and the third arc CD behind the starting straight line IA are not gradually increased, so that a flow field is compressed, and a fan system is ensured to have larger air pressure; the later arc line sections DE, EF and FG are gradually diffused outwards, and dynamic pressure is converted into static pressure. After the volute is well matched with the impeller and the motor, the fan system has larger air pressure, air quantity and efficiency, and meanwhile, the noise is lower.

The molded line of the rear cover plate 12 is formed by sequentially connecting a seventh circular arc A1B1, an eighth circular arc B1C1, a ninth circular arc C1D1, a tenth circular arc D1E1, an eleventh circular arc E1F1, a twelfth circular arc F1G1 and a second termination straight line G1H 1. The adjacent straight line segments and the adjacent arc line segments, or the adjacent arc line segments and the adjacent arc line segments are tangent at the intersection point, for example, the ninth arc C1D1 and the tenth arc D1E1 are tangent at the point D1.

Specifically, the molded-line reference line L4 of the rear cover plate 12 has the following coordinates and dimensions (relative to the second origin O2):

(1) The curvature radius (Ra 1) of the seventh circular arc A1B1 is 18.9mm, the origin A1 of the curvature radius is (18.9, 163.1), and the coordinate of the point A1 is (0.3, 159.8).

(2) The radius of curvature (Rb 1) of the eighth circular arc B1C1 is 84.6mm, the origin B1 of the radius of curvature is (45, 223.4), and the starting point B1 is (11.4, 145.8).

(3) The ninth circular arc C1D1 has a radius of curvature (Rc 1) of 138.9mm, a coordinate of origin C1 of the radius of curvature of (4,3.7), and a coordinate of origin C1 of (29.5, 140.3).

(4) The radius of curvature (Rd 1) of the tenth circular arc D1E1 is 178.1mm, the coordinate of the origin D1 of the radius of curvature is (-35.2,4.2), and the coordinate of the starting point D1 is (142.9,2).

(5) The curvature radius (Re 1) of the eleventh circular arc E1F1 is 155.8mm, the origin E1 of the curvature radius is (-49.7, -12.8) and the origin E1 of the curvature radius is (-150.7, 131.4).

(6) The curvature radius (Rf) of the twelfth circular arc F1G1 is 322.3mm, the origin F1 coordinate of the curvature radius is (116.3,0), and the starting point F1 coordinate is (-205, -24.5).

(7) The second end straight line G1H1, G1 point coordinate (-188.3, 104.9), H point coordinate (-168.6, 159.8).

Similarly, the profile of the rear cover plate 12 is located within a curve band which is shifted inward and outward by 5mm with respect to the above-mentioned reference line L4.

Claims

1. The utility model provides a centrifugal fan spiral case for range hood, includes front shroud (11), back shroud (12) and air outlet (14), inlet air hole (111) have been seted up on front shroud (11), mounting hole (121) have been seted up on back shroud (12), the center of inlet air hole (111) is first origin of coordinates (O1), inlet air hole (111) department is provided with collector (15), its characterized in that: a bending part (112) is formed at the position of the lower part of the front cover plate (11) and the corresponding side of the air outlet (14), the bending part (112) inclines towards the direction of the rear cover plate (12), and the current collector (15) is eccentrically arranged relative to the first coordinate origin (O1) and towards the direction of the bending part (112).

2. The volute of the centrifugal fan for a range hood according to claim 1, wherein: an eccentric angle formed by an included angle between a connecting line of the center (O3) of the current collector (15) and the first coordinate origin (O1) and the vertical direction is gamma, gamma is more than or equal to 25 degrees and less than or equal to 35 degrees, an eccentric distance between the center (O3) of the current collector (15) and the first coordinate origin (O1) is L, and L is more than or equal to 10mm and less than or equal to 18mm.

3. The volute of the centrifugal fan for the extractor hood according to claim 1 or 2, wherein: the molded line of the front cover plate (11) is formed by sequentially connecting a first straight line (IA), a first circular Arc (AB), a second circular arc (BC), a third circular arc (CD), a fourth circular arc (DE), a fifth circular arc (EF), a sixth circular arc (FG) and a first termination straight line (GH), and adjacent straight line sections and circular arc sections or adjacent circular arc sections and circular arc line sections are tangent at an intersection point.

4. The volute of the centrifugal fan for a range hood according to claim 3, wherein: the novel folding corner is characterized in that a first bending point (K) is arranged on the fourth circular arc (DE), a second bending point (J) is arranged on the sixth circular arc (FD), a connecting line of the first bending point (K) and the second bending point (J) forms a bending line (KJ), and the front cover plate (11) is bent towards the direction of the rear cover plate (12) at the bending line (KJ) to form the bending portion (112).

5. The volute of the centrifugal fan for a range hood according to claim 4, wherein: the included angle between the connecting line of first bending point (K) and first origin of coordinate (O1) and the vertical direction is beta 1, the line of second bending point (J) and first origin of coordinate (O1), the included angle between the connecting line of first bending point (K) and first origin of coordinate (O1) is beta 2, beta 1 is not less than 10 degrees and not more than 20 degrees, beta 2 is not less than 60 degrees and not more than 80 degrees, the angle of bending of the bending portion (112) is theta, theta is not less than 110 degrees and not more than 130 degrees.

6. The volute of the centrifugal fan for a range hood according to claim 3, wherein: the coordinate and the size of the molded line reference line (L1) of the front cover plate (11) relative to the first coordinate origin (O1) are as follows:

(1) A first straight line (IA), with the coordinates of the starting point (I) being (33.27, 228.6) and the coordinates of the end point (a) being (3.3, 173.9);

(2) The curvature radius (Ra) of the first circular Arc (AB) is 18.9mm, and the coordinate of the origin (a) of the curvature radius is (18.9, 163.1);

(3) The curvature radius (Rb) of the second circular arc (BC) is 84.6mm, the coordinate of the origin (B) of the curvature radius is (45, 223.4), and the coordinate of the starting point (B) is (11.4, 145.8);

(4) The radius of curvature (Rc) of the third circular arc (CD) is 138.9mm, the coordinate of the origin (C) of the radius of curvature is (4,3.7), and the coordinate of the starting point (C) is (29.5, 140.3);

(5) The curvature radius (Rd) of the fourth circular arc (DE) is 178.1mm, the coordinate of the origin (D) of the curvature radius is (-35.2,4.2), and the coordinate of the starting point (D) is (142.9,2);

(6) The curvature radius (Re) of the fifth circular arc (EF) is 155.8mm, the coordinate of the origin (E) of the curvature radius is (-49.7, -12.8), and the coordinate of the starting point (E) is (-150.7, 131.4);

(7) The radius of curvature (Rf) of the sixth circular arc (FG) is 322.3mm, the coordinate of the origin (F) of the radius of curvature is (116.3,0), and the coordinate of the starting point (F) is (-205, -24.5);

(8) A first end straight line (GH), coordinates (-188.3, 104.9) of a start point (G) point, coordinates (-145.4, 229.1) of an end point (H);

the reference line (L1) is deviated 5mm outwards to form an outer boundary line (L2), the reference line (L1) is deviated 5mm inwards to form an inner boundary line (L3), and the molded line of the front cover plate (11) is positioned in a molded line formed between the outer boundary line (L2) and the inner boundary line (L3).

7. The volute of the centrifugal fan for the extractor hood according to claim 1 or 2, wherein: the molded line of the rear cover plate (12) is formed by sequentially connecting a seventh circular arc (A1B 1), an eighth circular arc (B1C 1), a ninth circular arc (C1D 1), a tenth circular arc (D1E 1), a fifth circular arc (E1F 1), a sixth circular arc (F1G 1) and a second termination straight line (G1H 1), and adjacent straight line sections and circular arc line sections or adjacent circular arc line sections and circular arc line sections are tangent at the intersection point.

8. The volute of the centrifugal fan for use in a range hood according to claim 7, wherein: the rear cover plate (12) is provided with a second origin of coordinate (O2), the projection of the first origin of coordinate (O1) on the plane where the rear cover plate (12) is located coincides with the second origin of coordinate (O2), and the molded line datum line (L4) of the rear cover plate (12) is in a coordinate and size relative to the second origin of coordinate (O2):

(1) The curvature radius (Ra 1) of the seventh circular arc (A1B 1) is 18.9mm, the coordinates of the origin (A1) of the curvature radius are (18.9, 163.1), and the coordinates of the starting point (A1) are (0.3, 159.8);

(2) The curvature radius (Rb 1) of the eighth circular arc (B1C 1) is 84.6mm, the coordinate of the origin (B1) of the curvature radius is (45, 223.4), and the coordinate of the starting point (B1) is (11.4, 145.8);

(3) The curvature radius (Rc 1) of the ninth circular arc (C1D 1) is 138.9mm, the coordinate of the origin (C1) of the curvature radius is (4,3.7), and the coordinate of the starting point (C1) is (29.5, 140.3);

(4) The curvature radius (Rd 1) of the tenth circular arc (D1E 1) is 178.1mm, the coordinate of the origin (D1) of the curvature radius is (-35.2,4.2), and the coordinate of the starting point (D1) is (142.9,2);

(5) The curvature radius (Re 1) of the eleventh circular arc (E1F 1) is 155.8mm, the coordinates of the origin (E1) of the curvature radius are (-49.7, -12.8), and the coordinates of the starting point (E1) are (-150.7, 131.4);

(6) The curvature radius (Rf) of the twelfth circular arc (F1G 1) is 322.3mm, the coordinate of the origin (F1) of the curvature radius is (116.3,0), and the coordinate of the starting point (F1) is (-205, -24.5);

(7) A second end straight line (G1H 1), a coordinate (-188.3, 104.9) of the start point (G1), and a coordinate (-168.6, 159.8) of the end point (H);

the molded line of the rear cover plate (12) is positioned in a curve band which is deviated inwards and outwards by 5mm by the reference line (L4).