JP2005204215A - Electro-acoustic transducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a full-band type dynamo-electric electro-acoustic transducer which can reduce cost, without complicating its structure or the manufacturing steps. <P>SOLUTION: The electro-acoustic transducer includes a frame 10, and an inner magnetic circuit 20 is housed in a recess 11 of the frame 10. An annular elastic member 25 is mounted in an elastic member mounting portion 14 of the frame 10, and an edge portion 31 of an approximately dome-shaped diaphragm 30 is placed on the elastic member 25. An annular elastic member 26 is placed on the edge portion 31, and the edge portion 31 is held between the elastic members 25, 26. A protective cover 40, which covers the diaphragm 30 and fixes the elastic member 26, is mounted to the frame 10. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a full-band electrodynamic electroacoustic transducer for use in headphones, microphones, and the like.

  Conventionally, literature relating to a full-band electrodynamic electroacoustic transducer that reproduces sound over a wide band (for example, 3 Hz to 100 KHz) from a low frequency range to a high frequency range includes, for example, the following: .

Japanese Patent No. 3005436 (FIG. 1)

Supervised by Tamon Saeki, “New Edition Speaker and Enclosure Encyclopedia” Seikodo Shinkosha, November 26, 2003, 5th edition, p. 27, FIG. 1, FIG.

  FIG. 1 of Patent Document 1 and this explanatory note describe the technology of an all-band electrodynamic electroacoustic transducer. This electroacoustic transducer is composed of a frame having a recess for storing a magnetic circuit in the center, a magnetic pole (yoke), a center pole (plate), and a permanent magnet (magnet), and an inner magnet stored in the recess. Type magnetic circuit, a diaphragm in which the edge portion of the outer periphery of the dome shape is bonded to the outer edge of the frame, and a cylinder mounted on the back surface of the diaphragm and suspended in a gap (gap) of the magnetic circuit And a voice coil (movable coil). A columnar protrusion is formed at the center of the recess in the frame, and the columnar protrusion is fitted into a through-hole formed in each of the magnetic pole, the central pole, and the permanent magnet, and the magnetic A circuit is fixed to the frame.

  In this type of electroacoustic transducer, the magnetic circuit can be fixed to the frame simply by fitting the through holes of the magnetic pole, the central pole and the permanent magnet to the columnar projection, so that the assembly of the electroacoustic transducer is easy. There is an effect of becoming.

  However, the conventional electroacoustic transducer has the following problems.

  FIG. 5 is a schematic partial configuration diagram showing a longitudinal section of a diaphragm in the conventional electrodynamic electroacoustic transducer described in FIG. 1 of Patent Document 1 and FIG. 3 of Non-Patent Document 1. FIG. 6 is a diagram illustrating the frequency response (output sound pressure frequency characteristics) of FIG. 5 described in FIG.

  In FIG. 5, the diaphragm 1 has a substantially dome shape, and a cylindrical voice coil 2 is adhered to the back surface of the central portion side with an adhesive. The voice coil 2 is suspended in the magnetic pole gap of the magnetic circuit. An edge 1a on the outer periphery of the diaphragm 1 is bonded to an outer edge 3a of the frame with an adhesive.

In this type of electroacoustic transducer, for example, when a voice current of an electric signal is passed through the voice coil 2, the voice coil 2 is driven up and down according to the principle of electromagnetic action (Fleming's left-hand rule). This driving force f is expressed by the following equation.
f = B ・ L ・ i (dyne)
Where B: Magnetic flux density of magnetic pole gap (gauss)
L: Length of voice coil 2 in a magnetic field (cm)
i: voice current (A)

  The driving force f increases or decreases linearly in proportion to the audio current i. Thereby, the diaphragm 1 to which the voice coil 2 is attached moves up and down in proportion to the current change, and emits sound.

  The frequency response shown in FIG. 6 is obtained by automatically measuring the sound pressure level at a point of 1 m on the reference axis so as to form a continuous curve corresponding to the frequency, as described in Non-Patent Document 1. In this frequency response, the frequency range to be reproduced is called the effective frequency band FB, and the output sound pressure level is within the range of the low frequency resonance frequency fo indicating the low frequency limit and the high frequency resonance frequency fh indicating the high frequency limit. The frequency range of the low-frequency reproduction limit L and the high-frequency reproduction limit H in which -10 dB is reduced is shown. The characteristic is divided into two parts: a flat characteristic of the piston vibration region PB and a divided vibration region DB composed of a complicated vibration region of the diaphragm 1. In the full-band type, the entire effective frequency band FB from the low frequency reproduction limit L to the high frequency reproduction limit H is used.

  The characteristics of the bass range are substantially determined by the value of the bass resonance frequency fo and the value of the resonance sharpness Qo, and the output sound pressure decreases in inverse proportion to the square of the frequency below the bass resonance frequency fo. From the low sound range to the middle sound range, the characteristics are substantially flat because of the piston vibration region PB in which the vibration system vibrates substantially integrally. In the middle sound range, the influence of the edge portion 1a around the diaphragm 1 appears and vibrates in the opposite phase with respect to the diaphragm 1 due to resonance, so that the sounds from the diaphragm 1 and the edge portion 1a cancel each other out. A dip called D occurs. In the high sound range, the diaphragm 1 cannot perform piston vibration and becomes a divided vibration area DB in which each part of the diaphragm 1 vibrates in a complicated manner, so that many peak dips occur. At the high frequency limit, high frequency resonance occurs mainly at the frequency determined by the stiffness and mass of the central portion of the diaphragm 1 and the mass of the voice coil 2, and the peak at this high frequency limit (high frequency reproduction limit H) ends. Sound pressure drops suddenly.

  Conventionally, in a relatively large electroacoustic transducer such as a cone-shaped speaker, the area of the edge portion 1a is reduced, a dumping agent is applied, or a bonding structure in order to minimize the mid-sound valley D. Etc. have been devised.

  However, since the diameter of the diaphragm 1 is small in a small electroacoustic transducer such as a headphone, a single diaphragm structure is usually employed. In such a single diaphragm structure, the area of the edge portion 1a is reduced. Then, there is a possibility that the fixing strength becomes small and the frame is peeled off from the outer edge portion 3a of the frame. In order to prevent this, even if a dumping agent is applied or a device such as a bonding structure is devised, it is difficult to secure a necessary processing area because the diameter of the diaphragm 1 is small. In addition, as another device, a multi-way method using three diaphragms for low, medium and high sounds, or two diaphragms for low / medium and medium / high sounds is adopted. Although there are some which improve the sound quality by suppressing the valley D of the middle tone as much as possible, there is a problem that the structure and the manufacturing process become complicated and the cost is increased.

  The object of the present invention is to solve the problems of the prior art and to provide a small electroacoustic transducer capable of reducing the cost without complicating the structure and the manufacturing process.

  In order to solve the above-mentioned problem, in the all-band electrodynamic electroacoustic transducer according to the present invention, a recess for housing a magnetic circuit is formed at the center, and an annular elastic member mounting portion is formed around the recess. And an inner magnet type magnetic circuit. The magnetic circuit includes a magnetic pole, a center pole, a gap between the magnetic pole and the center pole, and a permanent magnet, and is housed and fixed in a recess of the frame.

  Furthermore, in the electroacoustic transducer of the present invention, a diaphragm having an almost dome shape and having an edge portion on the outer periphery of the dome shape, and a voice coil mounted on the back surface of the diaphragm and suspended in the gap, An annular elastic member (or first and second elastic members) that is mounted on the elastic member mounting portion and sandwiches the edge portion, and is attached to the frame to cover the diaphragm and the elastic member. And a protective cover to be fixed.

  According to the first, second, fourth, and fifth aspects of the invention, since the edge portion of the diaphragm is sandwiched between the elastic members, the valley of the middle sound is suppressed to be reduced, and the sound quality in the effective frequency band is improved. improves. In addition, since the diaphragm has a structure in which the edge portion is sandwiched between the elastic members, the diaphragm can be easily attached, which facilitates the manufacture of the electroacoustic transducer and enables cost reduction. .

  According to the invention of claim 3, since the protective cover and the diaphragm can be fixed only by engaging the protective cover with the frame by the engaging concavo-convex portion, the manufacturing becomes easier and the cost is reduced. It becomes possible.

  In the full-band electrodynamic electroacoustic transducer according to the present invention, a concave portion for housing a magnetic circuit is formed at the center, and an annular elastic member mounting portion (for example, a concave groove) is formed around the concave portion. Has a frame. An inner magnet type magnetic circuit composed of a magnetic pole, a center pole, a gap between these magnetic poles and the center pole, and a permanent magnet is housed and fixed in the recess. An annular elastic member is attached to the elastic member mounting portion, and an edge portion on the outer periphery of the diaphragm having a substantially dome shape is held by the elastic member. The elastic member is composed of a single elastic member or first and second elastic members. The first and second elastic members are each composed of, for example, an elastic O-ring.

  A voice coil is mounted on the rear surface of the diaphragm, and this voice coil is suspended in the gap. A protective cover that covers the diaphragm and fixes the elastic member is attached to the frame. A detachable engaging concavo-convex portion is formed at a place where the frame and the protective cover are attached.

(Constitution)
1A and 1B are configuration diagrams of an all-band electrodynamic electroacoustic transducer showing Embodiment 1 of the present invention. FIG. 1A is a longitudinal sectional view and FIG. B) is a plan view with the protective cover and the diaphragm removed. FIG. 2 is a plan view of the diaphragm in FIG.

  This all-band electrodynamic electroacoustic transducer is a small electroacoustic transducer used for headphones or the like, and has a resin-made frame 10 that houses the transducer body. The frame 10 has a circular plane, a concave portion 11 having a substantially circular plane for accommodating a magnetic circuit is formed at the center thereof, and a cylindrical projection 12 is erected at the center of the concave portion 11. The through hole of the protrusion 12 is a duct for adjusting sound quality. A plurality of vent holes 13 are formed on the outer periphery of the recess 11, and an annular elastic member mounting portion 14 is provided on the outer periphery of the vent holes 13. The elastic member mounting portion 14 is constituted by a concave groove, and an annular outer wall portion 15 is erected on the outer periphery thereof. An engaging recess 16 is formed on the outer surface side of the outer wall portion 15.

  On the outer periphery of the concave portion 11 on the bottom surface side of the frame 10, another concave portion 17 is formed corresponding to the vent hole forming region. A plurality of air holes 13 penetrate through the bottom surface of the recess 17, and a sound absorbing material 18 such as a nonwoven fabric is stuck in the recess 17. A terminal 19 that is an electrical terminal is provided on a part of the outer periphery of the recess 11. The recessed portion 11, the projecting portion 12, the vent hole 13, the elastic member mounting portion 14, the outer wall portion 15, the engaging recessed portion 16, and the recessed portion 17 of the frame 10 are integrally formed by, for example, insert molding using a resin. ing.

  An inner magnet type magnetic circuit 20 is fitted in the recess 11 of the frame 10. The magnetic circuit 20 includes a flat circular cap-shaped magnetic pole 21 having a through hole 21a at the center, a disk-shaped permanent magnet 22 having a through hole 22a at the center, and a through hole 23a at the center. A disc-shaped center pole 23, and a magnetic pole 21 and a gap 24 between the center poles 23. In the cap-shaped magnetic pole 21, the through hole 21 a is fitted to the outer periphery of the protruding portion 12 in a state where the cap-shaped magnetic pole 21 is reversed. The permanent magnet 22 is mounted on the magnetic pole 21 in a state where the through hole 22 a is fitted to the protrusion 12. The center pole 23 is placed on the permanent magnet 22 in a state where the through hole 23 a is fitted to the protrusion 12. The top of the protrusion 12 is caulked by ultrasonic welding or the like, and the center pole 23 is fixed by the caulking portion. A gap 24 is formed between the outer peripheral surface of the center pole 23 and the inner peripheral surface of the magnetic pole 21.

  A first elastic member (for example, a 0-ring having a circular cross section having elasticity such as silicon rubber) 25 is inserted into the annular elastic member mounting portion 14. On the O-ring 25, an edge portion 31 at the outer edge of the substantially dome-shaped diaphragm 30 is placed, and a second elastic member (for example, silicon rubber or the like) placed on the edge portion 31 has elasticity. The edge portion 31 is held between the O-ring 26 having a circular cross section and the O-ring 25.

  The substantially dome-shaped diaphragm 30 has a single diaphragm structure formed of a plastic film or the like, the plane is circular, and the diameter of the flat edge portion 31 of the outer edge is equal to that of the annular elastic member mounting portion 14. The dimensions are almost the same as the diameter. An annular flat coil fixing portion 32 is formed at a position corresponding to the gap in the diaphragm 30, and the inner side of the coil fixing portion 32 swells in a circular arc shape and covers the center pole 23. Between the coil fixing | fixed part 32 and the edge part 31, it swells in cross-sectional arc shape, and the corrugation 33 is formed here. The corrugation 33 is a convex or concave rib-shaped fold, and is radiated. The corrugation 33 softens the peaks and valleys of the response in the treble resonance region where the diaphragm 30 divides and vibrates. It is formed in order to give the board 30 strength.

  A cylindrical voice coil 34 is bonded to the back surface of the coil fixing portion 32, and the voice coil 34 is suspended in the gap 24. A cap-shaped protective cover 40 having a circular plane is attached to the outer wall portion 15 of the frame 10 so as to cover the diaphragm 30. The protective cover 40 has a function like a baffle plate that prevents a decrease in sound pressure by preventing the wraparound of air pressure associated with the vibration of the vibration plate 30 and also has a function of fixing the O-ring 26 and is formed of resin or the like. Has been. On the outer edge of the protective cover 40, an outer wall portion 41 that is fitted to the outer wall portion 15 on the frame 10 side is erected, and the outer surface of the outer wall portion 41 is detachably fitted into the engaging recess 16 on the frame 10 side. The engaging convex part 42 is protrudingly provided. A plurality of sound emitting holes 43 are formed on the upper surface of the protective cover 40.

(Example of manufacturing method)
3A to 3C are manufacturing process diagrams illustrating an example of a method for manufacturing the electroacoustic transducer of FIG.

  The electroacoustic transducer of FIG. 1 is manufactured by the following processes (1) to (3), for example.

(1) Step of FIG. 3A The through-hole 21a of the magnetic pole 21, the through-hole 22a of the permanent magnet 22, and the through-hole 23a of the center pole 23 are sequentially fitted to the protrusions 12 of the frame 10, and their magnetic poles. 21, the permanent magnet 22 and the center pole 23 are stacked to form the magnetic circuit 20. And if the top part of the projection part 12 is crimped by ultrasonic welding etc., the magnetic circuit 20 will be fixed in the recessed part 11 of the flame | frame 10, and the gap 24 of the fixed space | interval will be formed between the magnetic pole 21 and the center pole 23. Is done.

(2) Step of FIG. 3B The O-ring 25 is inserted into the elastic member mounting portion 14 of the frame 10. A voice coil 34 is bonded in advance to the back surface of the coil fixing portion 32 of the diaphragm 30, and the edge portion 31 of the diaphragm 30 is placed on the O-ring 25 while the voice coil 34 is inserted into the gap 24.

(3) Step of FIG. 3C A 0 ring 26 is placed on the edge portion 31 of the diaphragm 30 surrounded by the outer wall portion 15 of the frame 10. Next, if the outer wall 41 on the protective cover 40 side is put on the outer surface of the outer wall 15 on the frame 10 side and the protective cover 40 is pressed, the engaging convex part 42 on the outer wall 41 side will be on the outer wall 15 side. Fit into the engaging recess 16. As a result, the protective cover 40 is attached to the frame 10 and is fixed in a state where the O-ring 26 is slightly pressed by the outer edge of the inner surface of the protective cover 40. Thereafter, when the sound absorbing material 18 is adhered in the recess 17 on the bottom surface side of the frame 10 and the lead wire of the voice coil 34 is soldered to the terminal 19, the production of the electroacoustic transducer of FIG. 1 is completed.

  For example, when manufacturing headphones using such an electroacoustic transducer, the electroacoustic transducer is fixed in a headphone case (not shown), and an ear pad (ear pad) is attached to the opening of the headphone case. Thus, a desired headphone can be manufactured.

(Operation)
For example, when an audio current is supplied to the terminal 19, this audio current flows through the voice coil 34. Then, since the voice coil 34 vibrates up and down according to the electromagnetic action, the diaphragm 30 moves up and down in proportion to the current change and emits sound. This sound is radiated to the outside from the sound emission hole 43 of the protective cover 40.

  In the full-band type electroacoustic transducer of the first embodiment, since the entire effective frequency band FB as shown in FIG. 6 is used, the vibration system vibrates almost integrally from the low range to the mid range. Due to the piston vibration range PB, the frequency characteristics are substantially flat. In the conventional electroacoustic transducer, the influence of the edge portion around the diaphragm appears in the middle sound range, and the vibration vibrates in the opposite phase to the diaphragm due to resonance, the sounds from the diaphragm and the edge portion cancel each other, and the middle valley D A dip called However, in the first embodiment, since the edge portion 31 of the diaphragm 30 is sandwiched from above and below by two O-rings 25 and 26 having a circular cross section having elasticity, the edge portion 31 and the O-rings 25 and 26 are separated from each other. The contact area (that is, the area of the support point of the edge portion 31) is small, and the left and right sides of the edge portion 31 do not easily swing up and down around the support point, and the edge portion 30 is interlocked with the vibration of the diaphragm 30. Vibrate in the same phase. Therefore, vibration in the opposite phase of the edge portion 31 due to resonance is suppressed, and the mid-sound valley D is reduced. At this time, the elastic force or the like of the O-rings 25 and 26 may be set to a desired value in advance through experiments or the like so that the suppression effect is maximized.

  In the high sound range, the diaphragm 30 becomes unable to perform piston movement and tends to become a divided vibration region DB in which each part of the vibration plate 30 vibrates in a complicated manner. However, since the corrugation 33 is formed, the high frequency resonance region in which the vibration is divided. The peaks and troughs of the response are relaxed and a flatter frequency characteristic can be obtained. At this time, the position where the corrugation 33 is applied, the size and number of irregularities, and the like may be set to desired values in advance so as to obtain a flatter frequency characteristic.

(Effects etc.)
In Example 1, the following effects (I) to (III) are obtained.

  (I) Since the edge portion 31 of the diaphragm 30 is sandwiched from above and below by the two O-rings 25 and 26, the middle sound valley D is suppressed to be reduced. In addition, since the correlation 33 is formed on the diaphragm 30, the frequency characteristics in the high sound range are flattened. Therefore, the overall sound quality in the effective frequency band FB is dramatically improved.

  (II) Since the magnetic circuit 20 is assembled by fitting the magnetic pole 21, the permanent magnet 22 and the central pole 23 to the protrusion 12, the magnetic circuit 20 can be easily assembled. Moreover, since the diaphragm 30 has a structure in which the edge portion 31 is sandwiched from above and below by the two O-rings 25 and 26, the diaphragm 30 can be easily attached. Accordingly, the electroacoustic transducer can be easily manufactured, and the cost can be reduced.

  (III) Since the protective cover 40 and the diaphragm 30 can be fixed simply by fitting the engaging convex portion 42 on the protective cover 40 side into the engaging concave portion 16 on the frame 10 side, the manufacturing becomes easier and the cost is lower. Can be realized. Note that an engaging convex portion may be provided on the frame 10 side and an engaging concave portion may be formed on the protective cover 40 side.

  FIGS. 4A to 4C are cross-sectional views showing another example of the structure of the elastic member for sandwiching the edge portion 31 according to the second embodiment of the present invention.

  In FIG. 4A, the edge portion 31 is sandwiched between annular elastic members 25A and 26A having a substantially semicircular cross section. In FIG. 4B, the edge portion 31 is sandwiched between annular elastic members 25B and 26B having a triangular cross section. The elastic members 25A, 26A, 25B, and 26B are formed of, for example, an elastic material such as silicon rubber. Even when such elastic members 25A, 26A, 25B, and 26B are used, the same operations and effects as in the first embodiment are achieved. Is obtained. The cross sections of the elastic members 25A, 26A, 25B, and 26B may be changed to other shapes such as a square.

  In FIG. 4C, an annular elastic member 25C having a substantially U-shaped cross section is provided, and an annular protrusion 26C or a plurality of protrusions 26C arranged at predetermined intervals are formed on the upper and lower sides of the elastic member 25C. Has been. The elastic member 25C and the protrusion 26C are formed of an elastic material such as silicon rubber, for example. The edge portion 31 inserted inside the elastic member 25C is pressed and clamped from above and below via the upper and lower protrusions 26C. Even when such an elastic member 25C is used, substantially the same operations and effects as those of the first embodiment can be obtained. Note that the edge portion 31 may be sandwiched between the upper and lower sides of the elastic member 25C without providing the protruding portion 26C.

  As described above, in order to change the suppression force according to the size of the middle valley D, the elastic member that sandwiches the edge portion 31 can be deformed into various shapes and structures.

  The present invention is not limited to the first and second embodiments, and other modifications are possible. As a third embodiment which is this modification, for example, there are the following (i) and (ii).

  (I) The elastic member mounting portion 14 in FIG. 1 is configured by a groove having a concave cross section, but may have other configurations. For example, the elastic member mounting portion 14 has a flat shape and the outer wall portion 15 of the outer edge is made higher than that in FIG. At this time, the outer diameters of the O-rings 25 and 26 and the elastic members 25A to 25C and 26A to 26C are made slightly larger than the inner diameter of the outer wall portion 15. In this way, the O-rings 25 and 26 and the elastic members 25A to 25C and 26A to 26C are flat in the outer wall portion 15 by the elastic force of the O-rings 25 and 26 and the elastic members 25A to 25C and 26A to 26C. It is held on the elastic member mounting portion 14. Moreover, since the elastic member mounting portion 14 has a flat shape, this formation is facilitated.

  (Ii) The frame 10, the magnetic circuit 20, the diaphragm 30, the protective cover 40, and the like may be changed to shapes and structures other than those illustrated.

  The electroacoustic transducer of the present invention can be used for various devices such as headphones and microphones using the electroacoustic transducer.

1 is a configuration diagram of an all-band electrodynamic electroacoustic transducer showing Example 1 of the present invention. FIG. It is a top view of the diaphragm in FIG. It is a manufacturing process figure which shows an example of the manufacturing method of the electroacoustic transducer of FIG. It is sectional drawing which shows the other structural example of the elastic member which shows Example 2 of this invention. It is a typical partial block diagram which shows the diaphragm of the conventional electrodynamic electroacoustic transducer. It is a figure which shows the frequency response (output sound pressure frequency characteristic) of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Frame 11 Concave part 14 Elastic member mounting part 15,41 Outer wall part 16 Engagement recessed part 20 Magnetic circuit 21 Magnetic pole 22 Permanent magnet 23 Center pole 24 Gap 30 Diaphragm 31 Edge part 34 Voice coil 40 Protective cover 42 Engaging convex part

Claims (5)

A full-band electrodynamic electroacoustic transducer,
A frame in which a recess for storing a magnetic circuit is formed in the center, and an annular elastic member mounting portion is formed around the recess;
An internal magnetic circuit composed of a magnetic pole, a central pole, a gap between the magnetic pole and the central pole, and a permanent magnet, housed in the recess and fixed;
A diaphragm having an almost dome shape and having an edge portion on the outer periphery of the dome shape;
A voice coil mounted on the back surface of the diaphragm and suspended in the gap;
An annular elastic member mounted on the elastic member mounting portion and sandwiching the edge portion;
A protective cover attached to the frame and covering the diaphragm and fixing the elastic member;
An electroacoustic transducer comprising: A full-band electrodynamic electroacoustic transducer,
A frame in which a recess for storing a magnetic circuit is formed in the center, and an annular elastic member mounting portion is formed around the recess;
An internal magnetic circuit composed of a magnetic pole, a central pole, a gap between the magnetic pole and the central pole, and a permanent magnet, housed in the recess and fixed;
An annular first elastic member mounted on the elastic member mounting portion;
A diaphragm having an approximately dome shape, and an outer peripheral edge portion of the dome shape placed on the first elastic member;
A voice coil mounted on the back surface of the diaphragm and suspended in the gap;
An annular second elastic member placed on the edge portion and sandwiching the edge portion together with the first elastic member;
A protective cover attached to the frame and covering the diaphragm and fixing the second elastic member;
An electroacoustic transducer comprising:   The electroacoustic transducer according to claim 1 or 2, wherein a concavo-convex portion for detachable engagement is formed at an attachment portion between the frame and the protective cover.   3. The electroacoustic transducer according to claim 2, wherein each of the first and second elastic members is an elastic O-ring.   The electroacoustic transducer according to claim 2, wherein the elastic member mounting portion includes a concave groove that receives the first elastic member.

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