A speed sensor and a manufacturing method thereof

Abstract

The present invention provides a speed sensor and a manufacturing method thereof. The speed sensor includes a bracket, a fixed seat, a chip, and a back magnet. Among them, the bracket has a first groove recessed along its thickness direction; the fixed seat is disposed in the first groove, and the fixed seat is provided with a second groove. For the speed sensor with this structure, one end of the mounting portion abuts against the back magnet through the notch of the second groove, the mounting cavity matches the mounting portion. After the mounting portion is inserted into the mounting cavity, both end faces of the mounting portion tightly abut against the first wall surface and the back magnet respectively. The gap between the mounting portion and the back magnet is small, and the injection-molded plastic will not enter the gap between the mounting portion and the back magnet, so that there is no plastic isolation between the mounting portion and the back magnet and the gap between the two is small, and the sensor signal transmission is stable; and through the setting of the mounting cavity, the chip and the back magnet can ensure close contact without being encapsulated as a whole first, which can reduce the production cost of the sensor.

Description

Technical Field

[0001] The present invention relates to the technical field of sensors, and particularly relates to a speed sensor and a manufacturing method thereof. Background Art

[0002] Most sensors are magnetoelectric sensors based on the Hall effect, and have the characteristics of high sensitivity to magnetic fields, stable output signals, high frequency response, strong anti-electromagnetic interference ability, simple structure, and convenient use. Currently, they are widely used in the traction systems and braking systems of high-speed railway locomotives, urban rail vehicles, electric vehicles, new energy vehicles, and other fields.

[0003] The speed sensor includes a chip and a back magnet. To ensure the stability of the output signal of the sensor, the chip and the back magnet need to be attached together. In the prior art, the chip and the back magnet are generally encapsulated into a whole and then installed in a bracket. For the speed sensor with such a structure, the chip and the back magnet need to be encapsulated first and then installed in the bracket, resulting in high production costs of the sensor. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defect of high production costs of the speed sensor in the prior art.

[0005] To this end, the present invention provides a speed sensor, including

[0006] a bracket having a first groove recessed along its thickness direction; the two opposite side walls of the first groove along the length direction of the bracket are respectively a first wall surface and a second wall surface;

[0007] a fixing seat disposed in the first groove, a second groove recessed from the outside to the inside is provided at a first end of the fixing seat close to the first wall surface, and a second end of the fixing seat opposite to the first end abuts against the second wall surface;

[0008] a chip including an installation portion extending along the thickness direction of the bracket and an extension portion bent toward the length direction of the bracket;

[0009] a back magnet disposed in the second groove, and an end surface of a third end of the back magnet facing the first wall surface is flush with an outer wall surface of the notch of the second groove;

[0010] an installation cavity is formed between the first wall surface, the two side walls of the first groove in the width direction of the bracket, and the notch of the second groove, which is matched with and for tightly clamping the installation portion;

[0011] the installation portion is clamped in the installation cavity, and two ends of the installation portion respectively abut against the first wall surface and the back magnet.

[0012] Optionally, for the above speed sensor, first abutting portions and second abutting portions are respectively provided at both ends of the notch of the second groove in the width direction of the bracket;

[0013] An installation cavity is defined among the first wall surface, the first abutting portion, the second abutting portion and the notch of the second groove.

[0014] Optionally, for the above speed sensor, a blocking portion protruding towards the installation cavity is provided at the bottom of the notch of the second groove. The blocking portion is located between the first abutting portion and the second abutting portion, and the inner side wall of the blocking portion abuts against the end face of one end of the back magnet;

[0015] An installation cavity is defined among the first wall surface, the first abutting portion, the second abutting portion, the blocking portion and the notch of the second groove.

[0016] Optionally, for the above speed sensor, at least one elastic member is provided at the second end of the fixing base. The second end abuts against the second wall surface through the elastic member, and the elastic member applies a biasing force towards the direction of the first wall surface to the fixing base and the back magnet under the abutting force of the second wall surface.

[0017] Optionally, for the above speed sensor, there are at least two elastic members, and two of the elastic members are arranged on opposite sides of the end face of the second end.

[0018] Optionally, for the above speed sensor, one end of any elastic member is formed on the second end, and the other end bends inwards towards the middle of the fixing base and abuts against the second wall surface.

[0019] Optionally, for the above speed sensor, a first protruding portion protrudes upwards from the top of the fixing base;

[0020] An installation hole extending along the length direction of the bracket is provided on the extension portion, and the installation hole is sleeved and fixed on the first protruding portion.

[0021] Optionally, for the above speed sensor, the extension portion has two electrode ends;

[0022] The speed sensor further includes two conductive components. The conductive components correspond to the electrode ends one by one, and one end of the conductive component penetrates into the bracket and is electrically connected to the respective corresponding electrode end, and the other end extends out of the bracket.

[0023] Optionally, for the above speed sensor, the first groove is a stepped groove. The groove located below is for installing the fixing base, and the groove located above is for installing the conductive component and the electrode end.

[0024] The present invention provides a manufacturing method for a speed sensor, comprising the following steps:

[0025] Injection-mold a fixed seat outside the back magnet and form an opening of a second groove on the fixed seat for the end face of the third end of the back magnet to leak out;

[0026] Install the fixed seat into a first groove of a bracket. The two opposite side walls of the first groove along the length direction of the bracket are respectively a first wall surface and a second wall surface; make the first end of the fixed seat close to the first wall surface, and the second end of the fixed seat opposite to the first end abuts against the second wall surface; an installation cavity for tightly clamping the installation part of the chip is formed between the first wall surface of the first groove, the two side walls of the first groove in the width direction of the bracket, and the opening of the second groove;

[0027] Install the installation part of the chip in the installation cavity so that the two opposite surfaces of the installation part respectively tightly abut against the end face of the third end of the back magnet and the first wall surface.

[0028] The technical solution of the present invention has the following advantages:

[0029] 1. The speed sensor provided by the present invention includes a bracket, a fixed seat, a chip, and a back magnet. Among them, the bracket has a first groove recessed along its thickness direction; the two opposite side walls of the first groove along the length direction of the bracket are respectively a first wall surface and a second wall surface; the fixed seat is arranged in the first groove, the first end of the fixed seat close to the first wall surface is provided with a second groove recessed from the outside to the inside, and the second end of the fixed seat opposite to the first end abuts against the second wall surface; the chip includes an installation part extending along the thickness direction of the bracket and an extension part bent towards the length direction of the bracket.

[0030] For the speed sensor with such a structure, one end of the installation part abuts against the back magnet through the opening of the second groove, the installation cavity matches the installation part. After the installation part is installed in the installation cavity, the two end faces of the installation part respectively tightly abut against the first wall surface and the back magnet. The gap between the installation part and the back magnet is small, and the injection-molded plastic will not enter the gap between the installation part and the back magnet, so that there is no plastic isolation between the installation part and the back magnet and the gap between them is small, and the sensor signal transmission is stable; and through the setting of the installation cavity, the chip and the back magnet do not need to be encapsulated into one body first to ensure their close contact, which can reduce the production cost of the sensor.

[0031] 2. The manufacturing method of the speed sensor provided by the present invention first injection-molds a fixing seat outside the back magnet and forms a notch of a second groove for the third-end end face of the back magnet to leak out, which can firmly fix the back magnet in the second groove of the fixing seat. At the same time, the notch of the second groove reserved by injection molding allows the back magnet to abut against the installation part of the chip. Then, the fixing seat is installed in the first groove of the bracket, and the second end of the fixing seat abuts against the second wall surface. An installation cavity is formed among the first wall surface of the first groove, the two side walls of the first groove in the width direction of the bracket, and the notch of the second groove. The installation part of the chip is installed in the installation cavity so that the opposite end faces of the installation part respectively abut against the third-end end face of the back magnet and the first wall surface. Through the setting of the installation cavity, the chip and the back magnet can be ensured to be in close contact without being first encapsulated as a whole, which can reduce the manufacturing cost of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0033] Figure 1 Schematic diagram of the speed sensor provided in Embodiment 1 of the present invention;

[0034] Figure 2 Top view of the speed sensor after removing the sealant in the first groove;

[0035] Figure 3 Schematic diagram of the internal structure of the speed sensor;

[0036] Figure 4 For Figure 3 First-angle schematic diagram after removing the chip;

[0037] Figure 5 For Figure 3 Second-angle schematic diagram after removing the chip;

[0038] Figure 6 Schematic diagram of the bracket;

[0039] Figure 7 Schematic diagram of the cooperation of the fixing seat, the chip and the conductive component;

[0040] Figure 8 First-angle schematic diagram of the cooperation between the fixing seat and the back magnet;

[0041] Figure 9 Second-angle schematic diagram of the cooperation between the fixing seat and the back magnet;

[0042] Figure 10 Schematic diagram of a fixed seat;

[0043] Figure 11 Schematic diagram of the usage state of a speed sensor.

[0044] Description of reference numerals:

[0045] 1 - Bracket; 11 - First groove; 111 - First wall surface; 112 - Second wall surface; 2 - Fixed seat; 21 - Second groove; 22 - First abutting portion; 23 - Second abutting portion; 24 - Blocking portion; 25 - Elastic member; 26 - First protruding portion; 31 - Mounting portion; 32 - Extension portion; 4 - Back magnet; 5 - Conductive component; 6 - Mounting cavity. Specific embodiments

[0046] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0047] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0048] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "mounted", "connected", "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0049] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0050] Embodiment 1

[0051] This embodiment provides a speed sensor, as Figures 1 to 5As shown in the figure, it includes a bracket 1, a fixed seat 2, a chip, and a back magnet 4.

[0052] Among them, the bracket 1 has a first groove 11 recessed along its thickness direction; the two opposite side walls of the first groove 11 along the length direction of the bracket 1 are respectively a first wall surface 111 and a second wall surface 112; the fixed seat 2 is arranged in the first groove 11, and a second groove 21 recessed from the outside to the inside is provided at the first end of the fixed seat 2 close to the first wall surface 111, and the second end of the fixed seat 2 opposite to the first end abuts against the second wall surface 112; the chip includes a mounting portion 31 extending along the thickness direction of the bracket 1 and an extending portion 32 bent toward the length direction of the bracket 1. The back magnet 4 is arranged in the second groove 21, and the end surface of the third end of the back magnet 4 facing the first wall surface 111 is flush with the outer wall surface of the notch of the second groove 21; the first wall surface 111, the two side walls of the first groove 11 in the width direction of the bracket 1, and the notch of the second groove 21 enclose an installation cavity 6 for tightly clamping the mounting portion 31; the mounting portion 31 is clamped in the installation cavity 6, and both ends of the mounting portion 31 respectively abut against the first wall surface 111 and the back magnet 4.

[0053] The chip sensitive source is located in the mounting portion 31, and the mounting portion 31 abuts against the first wall surface 111, and the first wall surface 111 serves as the reference surface during the sensor test. The usage state of the sensor is as Figure 11 shown, with its reference surface facing and approaching the trigger wheel to measure the rotational speed of the trigger wheel.

[0054] For the speed sensor with this structure, one end of the mounting portion 31 abuts against the back magnet 4 through the notch of the second groove 21. The installation cavity 6 matches the mounting portion 31. After the mounting portion 31 is inserted into the installation cavity 6, both end faces of the mounting portion 31 tightly abut against the first wall surface 111 and the back magnet 4 respectively. The gap between the mounting portion 31 and the back magnet 4 is small, and the injection-molded plastic will not enter the gap between the mounting portion 31 and the back magnet 4, so that there is no plastic isolation between the mounting portion 31 and the back magnet 4 and the gap between them is small, and the sensor signal transmission is stable; and through the setting of the installation cavity 6, the chip and the back magnet 4 do not need to be encapsulated into one body first to ensure their close contact, which can reduce the production cost of the sensor.

[0055] Specifically, referring to Figures 7 to 10 the figure, the fixed seat 2 further includes a first abutting portion 22, a second abutting portion 23, a blocking portion 24, an elastic member 25, and a first protruding portion 26. The first abutting portion 22 and the second abutting portion 23 are respectively arranged at both side ends of the notch of the second groove 21 in the width direction of the bracket 1 ( Figure 5On the upper and lower sides thereof), the first abutting portion 22 and the second abutting portion 23 abut against the first wall surface 111. At the bottom of the notch of the second groove 21, there is a blocking portion 24 protruding towards the installation cavity 6. The blocking portion 24 is located between the first abutting portion 22 and the second abutting portion 23. An installation cavity 6 is formed between the first wall surface 111 and the first abutting portion 22, the second abutting portion 23, the blocking portion 24 and the notch of the second groove 21. The inner side wall of the blocking portion 24 abuts against one end face of the back magnet 4, so that each face of the back magnet 4 firmly abuts against the inner wall surface of the second groove 21, preventing the back magnet 4 from moving or shaking relative to the fixed seat 2, and further ensuring that the back magnet 4 is in close contact with the installation portion 31 of the chip.

[0056] The elastic members 25 are arranged at the second end of the fixed seat 2. There are two elastic members 25, and the two elastic members 25 are located on the opposite sides of the fixed seat 2 along the width direction of the bracket 1. One end of the elastic member 25 is integrally formed on the fixed seat 2, and the other end is bent inwards towards the middle of the fixed seat 2 and abuts against the second wall surface 112. The elastic members 25 apply a biasing force to the fixed seat 2 and the back magnet 4 in the direction towards the first wall surface 111, further making the back magnet 4 in close contact with the installation portion 31 of the chip, and the installation portion 31 in close contact with the first wall surface 111. The back magnet 4 is in close contact with the installation portion 31 of the chip to ensure the stability of signal transmission; the first wall surface 111 serves as the reference surface of the sensor, and the installation portion 31 is in close contact with the first wall surface 111, effectively ensuring the accuracy of the reference surface and improving the stability of signal transmission.

[0057] The first protruding portion 26 is provided at the top of the fixed seat 2. The extending portion 32 of the chip is perpendicular to the installation portion 31. The extending portion 32 is provided with an installation hole extending along the length direction of the bracket 1. The installation hole is sleeved on the first protruding portion 26, and then the first protruding portion 26 is thermally riveted and welded to the extending portion 32 to further position the chip and prevent the chip from shaking or moving. The chip is only bent once as a whole, with fewer bending times, which is convenient for positioning the installation portion 31 in the installation cavity 6 and ensuring the accuracy of its position.

[0058] The speed sensor further includes two conductive components 5. For example, the conductive components 5 are conductive sheets. The extending portion 32 has two electrode ends respectively connected to the two conductive components 5. Refer to Figure 6 , the first groove 11 is a stepped groove. The lower groove is for installing the fixed seat 2, and the upper groove is for installing the conductive components 5 and the electrode ends.

[0059] One end of the conductive component 5 passes through the bracket 1 and is electrically connected to the corresponding electrode end, and the other end extends out of the bracket 1 and is connected to the circuit board. By connecting the circuit board and the chip through the conductive component 5, it is avoided that the chip is directly connected to the circuit board. The circuit board is fixed inside the bracket 1, and the positioning of the circuit board inside the bracket 1 affects the accuracy of the chip positioning, ensuring that the chip is in close contact with the back magnet 4.

[0060] The first groove 11 is sealed by sealant filling to form a sealing cover, which seals the back magnet 4 and the chip inside the bracket 1, preventing moisture and oil pollution from contaminating the chip circuit, causing the chip to short-circuit, and ensuring the normal operation of the chip. Compared with the prior art where the chip and the back magnet 4 are first encapsulated and then installed in the bracket 1, and then secondary potting encapsulation is carried out, the overall sensor of the present invention only needs to be encapsulated once at the end, saving production costs.

[0061] As the first alternative embodiment of Embodiment 1, the elastic member 25 can also be provided on both ends of the second end of the fixed seat 2 along the depth direction of the second groove 21; or the elastic member 25 can be separately provided from the fixed seat 2, and the number of the elastic members 25 can be one, three, four, etc., as long as the elastic member 25 is provided at the second end of the fixed seat 2 and can apply a biasing force towards the first wall surface 111 to the back magnet 4 and the fixed seat 2 to press the chip tightly against the first wall surface 111.

[0062] Embodiment 2

[0063] This embodiment provides a manufacturing method of a speed sensor, including the following steps:

[0064] Inject and mold the fixed seat 2 outside the back magnet 4 and form an opening of the second groove 21 on the fixed seat 2 for the third end face of the back magnet 4 to leak out; integrally inject and mold two elastic members 25 on the second end of the fixed seat 2 opposite to the opening of the second groove 21;

[0065] Install the fixed seat 2 into the first groove 11 of the bracket 1. The two opposite side walls of the first groove 11 along the length direction of the bracket 1 are respectively the first wall surface 111 and the second wall surface 112; make the first end of the fixed seat 2 close to the first wall surface 111, and the two elastic members 25 on the second end of the fixed seat 2 abut against the second wall surface 112; an installation cavity 6 for tightly clamping the installation part 31 of the chip is formed between the first wall surface 111 of the first groove 11, the two side walls of the first groove 11 in the width direction of the bracket 1, and the opening of the second groove 21;

[0066] Install the installation part 31 of the chip into the installation cavity 6 so that the two opposite surfaces of the installation part 31 respectively tightly abut against the third end face of the back magnet 4 and the first wall surface 111;

[0067] Inject sealant into the first groove 11 for potting and sealing to seal the back magnet 4 and the chip inside the bracket 1.

[0068] In this manufacturing method, a fixing base 2 is injection-molded outside the back magnet 4 first, and a notch of a second groove 21 for exposing the third end face of the back magnet 4 is formed. The back magnet 4 can be firmly fixed in the second groove 21 of the fixing base 2, preventing a gap between the back magnet 4 and the inner surface of the fixing base 2 and the back magnet 4 from shaking in the fixing base 2. At the same time, the notch of the second groove 21 reserved by injection molding can be used for the back magnet 4 to abut against the mounting portion 31 of the chip. The back magnet 4 is stably positioned through the fixing base 2, so that the back magnet 4 is in close contact with the chip mounting portion 31, improving the signal transmission stability.

[0069] Then, the fixing base 2 is installed in the first groove 11 of the bracket 1, and the mounting portion 31 of the chip is installed in the installation cavity 6 so that the opposite end faces of the mounting portion 31 respectively abut against the third end face of the back magnet 4 and the first wall surface 111. Through the setting of the installation cavity 6, the chip and the back magnet 4 can be ensured to be in close contact without being encapsulated into one body first, which can reduce the manufacturing cost of the sensor. The elastic member 25 on the second end of the fixing base 2 applies a pressure towards the first wall surface 111 to the fixing base 2, further making the chip mounting portion 31 in close contact with the back magnet 4 and the mounting portion 31 in close contact with the first wall surface 111.

[0070] Obviously, the above embodiments are only examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A speed sensor, characterized in that, including a bracket (1) having a first groove (11) recessed in its thickness direction; the two opposite side walls of the first groove (11) along the length direction of the bracket (1) are a first wall surface (111) and a second wall surface (112) respectively; a fixing seat (2) disposed in the first groove (11), a second groove (21) recessed from the outside to the inside is provided at the first end of the fixing seat (2) close to the first wall surface (111), and the second end of the fixing seat (2) opposite to the first end abuts against the second wall surface (112); a chip including a mounting portion (31) extending in the thickness direction of the bracket (1) and an extension portion (32) bent toward the length direction of the bracket (1); a back magnet (4) disposed in the second groove (21), and the end surface of the third end of the back magnet (4) facing the first wall surface (111) is flush with the outer wall surface of the notch of the second groove (21); a mounting cavity (6) matching and for tightly clamping the mounting portion (31) is formed between the first wall surface (111), the two side walls of the first groove (11) in the width direction of the bracket (1), and the notch of the second groove (21); the mounting portion (31) is clamped in the mounting cavity (6), and the two ends of the mounting portion (31) respectively abut against the first wall surface (111) and the back magnet (4); at least one elastic member (25) is provided on the second end of the fixing seat (2), the second end abuts against the second wall surface (112) through the elastic member (25), and the elastic member (25) is subjected to the abutting force of the second wall surface (112) to apply a biasing force to the fixing seat (2) and the back magnet (4) in the direction toward the first wall surface (111); a first protrusion (26) protrudes upward from the top of the fixing seat (2); a mounting hole extending in the length direction of the bracket (1) is provided on the extension portion (32), and the mounting hole is sleeved and fixed on the first protrusion (26).

2. The speed sensor according to claim 1, characterized in that, first abutting portions (22) and second abutting portions (23) are respectively provided at the two side ends of the notch of the second groove (21) in the width direction of the bracket (1); the mounting cavity (6) is formed between the first wall surface (111), the first abutting portion (22), the second abutting portion (23), and the notch of the second groove (21).

3. The speed sensor according to claim 2, characterized in that, a blocking portion (24) protruding toward the mounting cavity (6) is provided at the bottom of the notch of the second groove (21), the blocking portion (24) is located between the first abutting portion (22) and the second abutting portion (23), and the inner side wall of the blocking portion (24) abuts against one end surface of the back magnet (4); the mounting cavity (6) is formed between the first wall surface (111), the first abutting portion (22), the second abutting portion (23), the blocking portion (24), and the notch of the second groove (21).

4. The speed sensor according to any one of claims 1 to 3, characterized in that, the elastic members (25) are at least two, and two of the elastic members (25) are disposed on the opposite sides of the end surface of the second end.

5. The speed sensor according to claim 4, characterized in that, One end of any of the elastic members (25) is formed on the second end, and the other end is bent inwardly towards the middle of the fixed seat (2) and abuts against the second wall surface (112).

6. The speed sensor according to any one of claims 1 to 3, characterized in that, The extension portion (32) has two electrode ends; The speed sensor further includes two conductive members (5), the conductive members (5) correspond to the electrode ends one by one, and one end of the conductive member (5) is inserted into the bracket (1) and electrically connected to the corresponding electrode end, and the other end extends out of the bracket (1).

7. The speed sensor according to claim 6, characterized in that, The first groove (11) is a stepped groove. The groove located below is for installing the fixed seat (2), and the groove located above is for installing the conductive member (5) and the electrode end.

8. A method for manufacturing a speed sensor, characterized in that, Including the following steps: Injection-mold the fixed seat (2) outside the back magnet (4) and form a notch of the second groove (21) on the fixed seat (2) for the third end face of the back magnet (4) to leak out; Install the fixed seat (2) into the first groove (11) of the bracket (1). The two opposite side walls of the first groove (11) along the length direction of the bracket (1) are the first wall surface (111) and the second wall surface (112) respectively; make the first end of the fixed seat (2) close to the first wall surface (111), and the second end of the fixed seat (2) is opposite to the first end and abuts against the second wall surface (112); the first wall surface (111) of the first groove (11), the two side walls of the first groove (11) in the width direction of the bracket (1), and the notch of the second groove (21) enclose an installation cavity (6) for tightly clamping the installation portion (31) of the chip; Install the installation portion (31) of the chip in the installation cavity (6) so that the opposite two surfaces of the installation portion (31) tightly abut against the third end face of the back magnet (4) and the first wall surface (111) respectively.

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