JP5222217B2 - smoke detector - Google Patents

Description

  The present invention relates to a smoke detector that detects smoke and issues a fire alarm.

  Conventionally, a smoke detector that emits a sound when smoke is detected is known (see, for example, Patent Document 1). Conventional smoke detectors use dynamic speakers or piezoelectric speakers as sounding bodies. The piezoelectric speaker includes a piezoelectric vibrator in which a piezoelectric element is bonded to a metal plate, and a support unit that supports the piezoelectric vibrator by being coupled to an outer peripheral portion of the piezoelectric vibrator. In the piezoelectric speaker configured as described above, when a signal voltage is applied to the piezoelectric element, the piezoelectric element contracts and expands, but the metal plate does not contract or expand, and thus the piezoelectric vibrator is bent. Thereby, the piezoelectric speaker can emit sound.

  Such smoke detectors can be installed in various places such as living rooms, bedrooms, stairs, and corridors. Therefore, there is a demand for the smoke detector to be small and thin so as not to disturb the interior design. However, in the dynamic speaker, it is difficult to satisfy the above-mentioned demand while maintaining a sufficient sound pressure as compared with the piezoelectric speaker because of the structure of the drive unit (permanent magnet, voice coil) and the diaphragm (cone). The dynamic speaker also has a problem that when the vibration of the diaphragm increases, the diaphragm comes into contact with a frame that supports the diaphragm and chatter noise is generated.

  On the other hand, since the piezoelectric speaker has a plate shape, the piezoelectric speaker is smaller and thinner and cheaper than the dynamic speaker. In addition, since the piezoelectric speaker only needs to support the outer peripheral portion of the piezoelectric vibrator with the support portion, even if the vibration of the piezoelectric vibrator is large, the piezoelectric vibrator does not contact the support portion other than the outer peripheral portion, As a result, chatter noise unlike a dynamic speaker does not occur.

  However, the above-described piezoelectric speaker has a problem that the sound pressure in the vicinity of the resonance frequency is high, but the sound pressure in other frequencies (particularly in the low frequency region) is low (see the broken line in FIG. 8). In the present specification, the low frequency region means a frequency region of about 1 kHz or less, and the high frequency region means a frequency region exceeding about 1 kHz, but there is no strict boundary between the low frequency region and the high frequency region. .

  In the case of an alarm sound, only the frequency region near 3 kHz is used, whereas in the case of a sound, a low frequency region of 1 kHz or less is also used. For this reason, if the sound pressure level in the low frequency region is low as shown by the broken line in FIG. 8, the sound may not clearly reach a sufficient distance.

  As means for solving the above problem, there is known a piezoelectric speaker in which a piezoelectric vibrator is supported by a support portion via a thin resin plate (see, for example, Patent Document 2). In this piezoelectric speaker 91, as shown in FIG. 9B, the outer peripheral portion of the piezoelectric vibrator 93 and the thin member 92 are coupled, and the thin member 92 coupled to the piezoelectric vibrator 93 is supported by the support section 3. The piezoelectric speaker 91 having the above configuration can lower the resonance frequency and increase the sound pressure in the low frequency region as compared with the case where the support portion directly supports the piezoelectric vibrator.

JP 2008-310732 A Japanese Patent Laid-Open No. 9-271096

  However, even when the conventional piezoelectric speaker 91 using the thin member 92 is employed in the smoke detector, a sufficient sound pressure in the low frequency region cannot be obtained (see the broken line in FIG. 10).

  The present invention has been made in view of the above points, and an object of the present invention is to provide a smoke detector capable of increasing sound pressure not only in a high frequency region but also in a low frequency region.

According to the first aspect of the present invention, there is provided a smoke detection unit for detecting smoke, a sounding body for converting an electric signal into sound, a support unit for supporting the sounding body, and the sound generation when smoke is detected by the smoke detection unit. A circuit unit that outputs the electrical signal to the sounding body so that sound is output from the body, the sounding body being a piezoelectric body made of a piezoelectric element, and having a larger area than the piezoelectric body and laminated on the piezoelectric body. A piezoelectric vibrator having a vibrating plate and a thin member provided around the piezoelectric vibrator in combination with an outer peripheral portion of the piezoelectric vibrator, wherein the thin member includes at least a peak portion and a valley portion. One corrugation is formed in an annular shape, joined to the support portion at the outer periphery, elastically holding the piezoelectric vibrator, and the primary resonance frequency of the sounding body is 600 Hz to 1 kHz, The piezoelectric body and the diaphragm are both A plate shape, the diameter ratio of the diameter of the piezoelectric element to the diameter of the diaphragm is characterized in that 0.40 to 0.46 or less.

  The invention of claim 2 is characterized in that, in the invention of claim 1, the support portion is provided over the entire periphery of the opening portion in the mounting plate in which the opening portion is formed.

  According to a third aspect of the present invention, in the second aspect of the present invention, the lid includes a lid portion in which a plurality of holes are formed, and the support portion is provided so as to protrude from the mounting plate over the entire periphery of the opening of the mounting plate. The lid portion closes the opening so that a space is formed between the lid and the sounding body.

  According to a fourth aspect of the present invention, there is provided the housing according to any one of the first to third aspects, wherein the smoke detecting unit includes a light emitting unit that emits light and the light emitting unit. And a light receiving portion that receives the light, and smoke is optically detected using the light emitting portion and the light receiving portion.

According to the first aspect of the present invention, since the corrugation is formed on the thin member provided around the piezoelectric vibrator, the thin member can also bend and the amplitude of the piezoelectric vibrator can be increased. As for the sound emitted by the body, not only the high frequency region but also the sound pressure in the low frequency region can be increased.
According to the first aspect of the present invention, the sound pressure in the low frequency region can be increased by setting the primary resonance frequency of the sounding body to 600 Hz or more and 1 kHz or less. Can do.
Further, according to the first aspect of the present invention, in the piezoelectric vibrator of the sounding body, the diameter ratio of the diameter of the piezoelectric body to the diameter of the diaphragm is set to 0.40 or more and 0.46 or less, whereby the primary sounding body. The resonance frequency can be lowered and the sound pressure in the low frequency region can be increased to a maximum.

  According to invention of Claim 2, when a sounding body is attached to an attachment board via a support part by providing a support part in the circumference | surroundings of an opening part, it is between the front side and rear surface side of a sounding body. Since no air enters and exits, it is possible to prevent the sound from flowing from the rear side to the front side, and as a result, the sound pressure can be increased.

  According to the invention of claim 3, the front air chamber (space) is formed between the sounding body and the lid portion, so that the front air chamber can be made thin. According to the invention of claim 3, since the frequency region of the peak sound pressure can be expanded to the low frequency side by braking the air sealed in the front air chamber, the sound pressure in the low frequency region is increased. Can do.

  According to the invention of claim 4, when a fire occurs, the smoke detection unit optically detects smoke using the light emitting unit and the light receiving unit in the housing, so that an alarm sound and an alarm sound are output promptly. be able to.

1 is an exploded perspective view of a smoke detector according to Embodiment 1. FIG. It is sectional drawing of the sounding body which concerns on the same as the above. It is a block diagram of the piezoelectric vibrator which concerns on the same as the above. It is a sounding body which concerns on the same as the above, Comprising: (a) is a disassembled perspective view, (b) is a perspective view. It is a figure which shows the manufacturing method of the thin member which concerns on the same as the above in time series. (A) is a diagram for explaining the operation of a sounding body in which a plurality of pairs of peaks and troughs are formed as corrugation, and (b) is for explaining the operation of a sounding body in which one peak is formed as corrugation. (C) is a diagram for explaining the operation of a conventional sounding body without corrugation, and (d) is a diagram for explaining the operation of a conventional sounding body that is a dynamic speaker. It is a sounding body which concerns on the same as the above, Comprising: (a) is sectional drawing, (b) is a model figure. It is a figure which shows the sound pressure level characteristic of the sound which the sounding body which concerns on the same as above, and the sound pressure level characteristic of the sound which the conventional sounding body without a thin member emits. (A) is sectional drawing of the sounding body which concerns on the same as the above, (b) is sectional drawing of the conventional sounding body. It is a figure which shows the sound pressure level characteristic of the sound which the sounding body which concerns on the same as above, and the sound pressure level characteristic of the sound which the conventional sounding body without corrugation generate | occur | produces. (A) is sectional drawing which shows the principal part of the sounding body and cover which concern on the same as the above, (b) is a front view which shows the principal part of a cover. FIG. 6 is a sounding body according to Embodiment 2, wherein (a) is a configuration diagram of a piezoelectric vibrator, and (b) is a diagram showing a change characteristic of a primary resonance frequency with respect to the diameter of the piezoelectric body. It is a sounding body which concerns on the same, Comprising: It is a figure which shows the sound pressure level characteristic when changing the diameter ratio of a piezoelectric material and a diaphragm. It is a sounding body which concerns on Embodiment 3, Comprising: (a) is sectional drawing when a trough and a mountain part are formed as corrugation, (b) is a mountain part and a trough part as corrugation. A sectional view in the case, (c) is a sectional view in the case where only the valley is formed as the corrugation, and (d) is a sectional view in a case where only the peak is formed as the corrugation. It is sectional drawing of the smoke detector which concerns on Embodiment 4.

(Embodiment 1)
First, the configuration of the smoke detector according to the first embodiment will be described. The smoke detector of the present embodiment is a residential fire alarm attached to, for example, a house. As shown in FIG. 1, the smoke detector includes a smoke detector 1 that detects smoke, a sounding body 2 that emits sound by vibration, and a support 3 (see FIG. 2) that supports the sounding body 2. A substrate circuit 4 including a circuit unit for vibrating at least the sounding body 2, a housing 5 in which the respective components 1 to 4 are accommodated, and a base 6 used for mounting to a mounted portion (not shown). I have. Examples of attached parts include living rooms, bedrooms, stairs, and corridors.

  As shown in FIG. 2, the sounding body 2 includes a piezoelectric vibrator 7 and a thin member 8 provided around the piezoelectric vibrator 7. The sounding body 2 emits a sound when smoke is detected by the smoke detection unit 1 (see FIG. 1) in the event of a fire. The sound generated by the sound generator 2 includes, for example, an alarm sound “view, view, view” and an alarm sound “fire”, for example. The alarm sound is emitted by sweeping a sound in a frequency region around 3 kHz. Residents can be informed of the occurrence of a fire by the above warning sound and warning sound. Further, when the remaining battery level is low, the sounding body 2 also emits a notification sound “battery exhausted”.

As shown in FIG. 3, the piezoelectric vibrator 7 has a unimorph structure in which a piezoelectric body 71 and a diaphragm 72 are laminated. Both the piezoelectric body 71 and the diaphragm 72 have a disk shape. The piezoelectric body 71 is composed of a piezoelectric element (piezo element) having an effect of converting an electrical signal into sound (piezoelectric effect). As the piezoelectric element of the present embodiment, lead zirconium titanate having a thickness of 0.05 mm or more and 0.1 mm or less is used. Lead zirconate titanate is a mixed crystal of lead titanate and lead zirconate, which are ternary metal oxides. The density of lead zirconate titanate used in the present embodiment is 8.0 × 10 ³ kg / cm ³ . The diaphragm 72 is made of 42 alloy (iron-nickel alloy containing 42% nickel) having a diameter longer than that of the piezoelectric body 71 and larger, for example, a thickness of 0.05 mm to 0.1 mm. The density of 42 alloy used in this embodiment is 8.15 × 10 ³ kg / cm ³ . The thicknesses of the piezoelectric body 71 and the diaphragm 72 are preferably equal. The diaphragm 72 is bonded to the surface of the piezoelectric body 71 concentrically with the piezoelectric body 71 by, for example, an epoxy adhesive. The surface of the piezoelectric body 71 is provided with an electrode made of silver having a thickness of about 2 μm. A lead wire (not shown) is connected to the electrode. For example, LF solder is used to connect the electrode and the lead wire. When a signal voltage is applied to the electrodes, the piezoelectric body 71 is distorted and the piezoelectric vibrator 7 is vibrated.

  As shown in FIG. 4, the thin member 8 is a resin film formed in a donut shape (annular shape). As the resin film, for example, a thermoplastic resin such as PEI (polyetherimide) or PEN (polyether naphthalate) is used. The thickness of the thin member 8 is not less than 75 μm and not more than 188 μm. A step-shaped portion 81 as shown in FIG. 2 is formed on the inner peripheral portion of the thin member 8. The inner diameter of the step-shaped portion 81 is large enough to fit the piezoelectric vibrator 7 from the periphery. The thin member 8 is bonded to the piezoelectric vibrator 7 with, for example, a silicone adhesive or an epoxy adhesive in a state where the thin member 8 is fitted to the piezoelectric vibrator 7 in the step shape portion 81. Since the step-shaped portion 81 is formed in the thin member 8 as described above, the piezoelectric vibrator 7 can be reliably attached to the thin member 8 and the attachment position can be made constant, so that the sounding body 2 is emitted. Sound pressure and resonance frequency of sound can be stabilized.

  The thin member 8 is fixed to the support portion 3 by being coupled to the support portion 3 at the outer peripheral portion. In the thin member 8, a corrugation 82 including at least one of a valley portion 821 and a mountain portion 822 is formed in an annular shape in all radial directions of the thin member 8. The thin member 8 has a bellows structure that expands and contracts in the outer peripheral direction by the corrugation 82 and elastically holds the piezoelectric vibrator 7. As the corrugation 82, as shown in FIG. 2, valleys 821 and peaks 822 may be alternately formed, only the valleys 821 may be continuously formed, or only the peaks 822 are formed. It may be formed continuously.

  An example of the method for manufacturing the thin member 8 will be described. First, as shown in FIG. 5A, a resin film A having a constant thickness is placed between a mold B and a rubber material C, and the mold B is heated to a predetermined temperature. The mold B is processed into the shape of the corrugation 82. Thereafter, as shown in FIG. 5B, the mold B is pressed against the rubber material C with the resin film A interposed therebetween. Then, as shown in FIG.5 (c), the metal mold | die B is opened and the resin film A is removed. Corrugation 82 is formed on resin film A according to the shape of mold B. Thus, the resin film A in which the corrugation 82 is formed becomes the thin member 8. In the method for manufacturing the thin member 8 described above, the resin film A may be heated instead of heating the mold B. Further, in the method for manufacturing the thin member 8 described above, compressed air may be used instead of the rubber material C.

  The support portion 3 shown in FIG. 2 is provided around the thin member 8 and has a placement surface 31 on which the thin member 8 is placed. The mounting surface 31 is formed with a notch 32. The notch 32 is filled with an adhesive by a dispenser or the like. As the adhesive, a silicone adhesive having a low viscosity or a visible light curable resin is used. Since the adhesive accumulates in the notch 32, the thin member 8 is bonded to the support 3 without being lifted. Thereby, the thin member 8 is reliably attached to the support part 3, and the sound pressure and resonance frequency of the sound which the sounding body 2 emits can be stabilized.

  Next, the operation of the sounding body 2 when the sounding body 2 emits sound will be described. When a signal voltage is applied to the piezoelectric body 71, the piezoelectric body 71 repeatedly contracts and expands, but the diaphragm 72 does not contract or expand. Therefore, as shown in FIG. 6, the piezoelectric vibrator 7 (sound generator 2) Will bend. The sounding body 2 vibrates in the horizontal direction as shown by the arrow in FIG. Due to this vibration, the sounding body 2 emits a sound. In the case of the conventional thin member 92 without corrugation as shown in FIG. 6C, the piezoelectric vibrator 93 of the sounding body 91 is only the above-described vibration. On the other hand, as shown in FIGS. 6A and 6B, the thin member 8 having the corrugation 82 is easily bent at the corrugation 82, and easily expands and contracts in the outer circumferential direction when the corrugation 82 is bent. As a result, the amplitude of the sounding body 2 (piezoelectric vibrator 7) increases, and the sound pressure of the sound emitted by the sounding body 2 increases over the low frequency region and the high frequency region.

  By the way, in the case of the thin member 8 in which a plurality of pairs of valleys 821 and peaks 822 are formed as the corrugation 82 as shown in FIG. On the other hand, as shown in FIG. 6B, in the case of the thin member 8 in which only one peak portion 822 (or valley portion 821) is formed as the corrugation 82, compared to the thin member 8 in FIG. 6A. The amplitude of the sounding body 2 (piezoelectric vibrator 7) increases and the sound pressure at the primary resonance frequency increases. When the sounding body 94 is a dynamic speaker as shown in FIG. 6D, the diaphragm 95 vibrates in the vertical direction. Therefore, as the number of valleys 961 and mountain parts 962 as the corrugation 96 increases, the sounding body 94 increases. The vibration of 94 becomes large.

  Next, the primary resonance frequency of the sounding body 2 will be described. The sounding body 2 shown in FIG. 7A can be regarded as a vibrating structure Q in which the weight G is supported on the support P by the spring J, as shown in FIG. 7B. The primary resonance frequency f of the vibrating structure Q is expressed by Equation 1 where k is the spring constant of the spring J and m is the mass of the weight G.

  Therefore, the primary resonance frequency f0 of the sounding body 2 is expressed by Equation 2 when the spring constant of the thin member 8 is k0 and the mass of the piezoelectric vibrator 7 is m0. The spring constant k0 of the thin member 8 is expressed by Equation 3 where E is the Young's modulus of the thin member 8, h is the thickness of the thin member 8, and L is the length of the thin member 8 in the radial direction.

  Therefore, if the thickness h of the thin member 8 is reduced, the spring constant k0 can be reduced and the primary resonance frequency f0 of the sounding body 2 can be reduced.

  The primary resonance frequency f0 of the sounding body 2 of the present embodiment is set to 600 Hz or more and 1 kHz or less by adjusting the spring constant k0 of the thin member 8 and the mass m0 of the piezoelectric vibrator 7. The spring constant k0 is determined by the Young's modulus E of the thin member 8, the thickness h of the thin member 8, and the radial length L of the thin member 8.

  By the way, in the conventional sounding body that does not have the thin member 8 and the supporting portion directly supports the piezoelectric vibrator, a portion corresponding to the thin member 8 of the present embodiment is a part of the diaphragm. Since the diaphragm is thicker than the thin member, the spring constant k0 is increased. As a result, the conventional sounding body without the thin member 8 has a higher primary resonance frequency f0 than the sounding body 2 of the present embodiment. That is, the sounding body 2 of the present embodiment can lower the primary resonance frequency f0 compared to a conventional sounding body without the thin member 8.

  FIG. 8 shows the sound pressure level characteristic of the sound emitted by the sounding body 2 of the present embodiment (solid line in FIG. 8) and the sound emitted by the sounding body without the thin member 8 (hereinafter referred to as “sounding body of Comparative Example 1”). The sound pressure level characteristics (broken line in FIG. 8) are shown. The sounding body 2 of this embodiment has a configuration in which a doughnut-shaped thin member 8 is bonded to a piezoelectric vibrator 7 having a diameter of 35 mm to have a diameter of 50 mm. The sounding body of Comparative Example 1 is only a piezoelectric vibrator having a diameter of 50 mm. The sound pressure level characteristic of FIG. 8 is the result of measuring the sound pressure level at a position 1 m ahead of the sounding body by applying a voltage of 40 Vp-p to these sounding bodies. The sound pressure level characteristic of the sound emitted by the sounding body 2 of the present embodiment is lower than the sound pressure level characteristic of the sound emitted by the sounding body of Comparative Example 1, and the sound in the low frequency region is lower. The pressure level is also rising.

  Further, when the corrugation 82 is provided on the thin member 8 as shown in FIG. 9A, the spring constant k0 becomes larger than the case of the thin member 92 without corrugation as shown in FIG. 9B. If the outer diameter of the sounding body 2 is increased, the sound pressure increases proportionally, but in order to increase the sound pressure efficiently with a limited outer diameter, the spring constant k0 of the thin member 8 may be changed.

  FIG. 10 shows a sound pressure level characteristic of the sound emitted by the sounding body 2 of the present embodiment (solid line in FIG. 10), and a sounding body without the corrugation on the thin member 92 (hereinafter referred to as “sounding body of Comparative Example 2”) 91. The sound pressure level characteristic (broken line in FIG. 10) of the sound emitted from the sound is shown. The sounding body 2 of the present embodiment has a configuration in which a thin member 8 having a corrugation 82 formed thereon is bonded to a piezoelectric vibrator 7 having a diameter of 35 mm to have a diameter of 50 mm. The sounding body 91 of Comparative Example 2 has a configuration in which a thin member 92 without corrugation is bonded to a piezoelectric vibrator 93 having a diameter of 35 mm so as to have a diameter of 50 mm. The sound pressure level characteristic of FIG. 10 is the result of measuring the sound pressure level at a position 1 m ahead of the sounding body by applying a voltage of 40 Vp-p to these sounding bodies. In both the high frequency region and the low frequency region, the sound produced by the sounding body 2 of this embodiment has a higher sound pressure level than the sound produced by the sounding body 91 of Comparative Example 2. This is particularly noticeable in the low frequency region.

  Next, the smoke detector 1 shown in FIG. 1 will be described. The smoke detection unit 1 optically detects smoke using a light emitting unit and a light receiving unit (not shown). The smoke sensing unit 1 includes an optical base 13 in which a light emitting unit and a light receiving unit are accommodated. The optical base 13 has a plurality of labyrinth walls, each of which is a bent wall, and is covered with an insect net 14. Each labyrinth wall is provided to prevent external light from entering the inside of the optical base 13. The insect screen 14 is formed in a cylindrical shape that matches the outer shape of the optical base 13. The light emitting part and the light receiving part are mounted on the substrate circuit 4. The light emitting unit is provided with an LED as a light source that emits light, and the light receiving unit is provided with a photodiode as a light receiving element that receives light from the light emitting unit. The light emitting unit and the light receiving unit are accommodated in the optical base 13 when the substrate circuit 4 is attached to the optical base 13. At this time, the light receiving unit is disposed in the optical base 13 at a position off the optical axis of the light from the light emitting unit. That is, the light receiving part is not arranged on the optical axis of the light from the light emitting part. Moreover, since external light does not penetrate | invade by each labyrinth wall of the optical base 13, a light-receiving part does not receive external light.

  In the smoke sensing unit 1 having the above structure, when no smoke is present inside the optical base 13, light from the light emitting unit is not received by the light receiving unit. On the other hand, when smoke is present inside the optical base 13, in the smoke sensing unit 1, light from the light emitting unit is scattered by the smoke, and the light receiving unit receives the scattered light. That is, the smoke detector 1 detects smoke when light is received by the light receiver.

  The substrate circuit 4 includes a mounting substrate 41. A circuit unit that vibrates the sounding body 2 is mounted on the mounting substrate 41. This circuit unit outputs an electrical signal to the sounding body 2 so that the sounding body 2 emits a sound when smoke is detected by the smoke sensing unit 1. The mounting substrate 41 is provided with a button 42. The front portion 421 of the button 42 is exposed to the outside from the opening 526 of the cover 52 when the cover 52 is attached to a body 51 (described later) in which the substrate circuit 4 is accommodated. An LED (not shown) is provided on the front portion 421 of the button 42. The LED of the button 42 is turned on when smoke is detected by the smoke detector 1, for example. That is, for example, when smoke is detected by the smoke detection unit 1, the front portion 421 of the button 42 becomes bright. When the front portion 421 of the button 42 exposed to the outside is pressed, the LED of the button 42 is turned off and the sound from the sounding body 2 is stopped.

  The housing 5 is attached to a body 51 in which the smoke detection unit 1 and the board circuit 4 are housed, a cover 52 attached to the front side (upper side in FIG. 1) of the body 51, and a rear side (lower side in FIG. 1) of the body 51. The back cover 53 is provided. The body 51, the cover 52, and the back cover 53 are members formed of a flame retardant ABS material.

  The body 51 includes a disk-shaped bottom surface portion 511. The bottom surface portion 511 is formed with an opening 513 to which the insect screen 14 is attached and an opening 514 into which a battery storage portion 532 described later is inserted. From the outer periphery of the bottom surface portion 511, a cylindrical side surface portion 512 that protrudes in the vertical direction is provided integrally with the bottom surface portion 511. A plurality of opening windows 515, 515... Are formed on the side surface portion 512. The plurality of open windows 515, 515,... Are partitioned by a plurality of window frames that are framed in a lattice shape in order to allow smoke to flow into the smoke sensing unit 1.

  The cover 52 includes a curved front surface portion 521. The front surface portion 521 is integrally provided with a cylindrical side surface portion 522 that protrudes downward from the outer periphery of the front surface portion 521. Moreover, as shown to Fig.11 (a), the front-surface part 521 has the area | region 524 in which the several sound hole (hole part) 523,523, ... was formed. Each sound hole 523 is sufficiently large with respect to the thickness of the cover 52 so that resonance does not occur. On the back surface of the front surface portion 521, a cylindrical rib is provided as a support portion 3 so as to protrude from the periphery of the region 524. As described above with reference to FIG. 2, the sounding body 2 is bonded to the support portion 3 with an adhesive. By this adhesion, a front air chamber 54 is formed between the region 524 and the sounding body 2. Since the entrance and exit of air is blocked between the front air chamber 54 and the rear air chamber 55, sound does not enter the front air chamber 54 from the back surface of the piezoelectric vibrator 7 (the lower surface in FIG. 11A). ing. The cover 52 (except for the region 524) of the present embodiment corresponds to the mounting plate of the present invention, and the region 524 of the present embodiment corresponds to the lid portion of the present invention. In the present embodiment, the region 524 is a part of the cover 52. If the region 524 is removed from the cover 52, the opening formed in the cover 52 at this time is the opening of the present invention. Equivalent to.

  Further, a diffuser 525 serving as a reflector for sound (sound wave) emitted by the sounding body 2 is integrally provided at the center of the area 524 on the back surface of the front surface portion 521. The sound hole 523 is not formed on the surface where the diffuser 525 is provided (see FIG. 11B). The position of the diffuser 525 facing the sounding body 2 is a curved surface (concave surface). The sound pressure distribution is controlled by installing such a diffuser 525 in front of the sounding body 2. That is, the sound (sound wave) emitted directly upward from the sounding body 2 is reflected by the curved surface of the diffuser 525 as indicated by the arrow in FIG. The sound reflected by the diffuser 525 is further reflected by the sound generator 2 and propagates in an oblique direction through the sound hole 523. Thereby, it can prevent that the sound which the sounding body 2 emits becomes pinching directivity. As a result, the smoke detector of this embodiment is suitable for emitting sound toward a wide space such as a detached house.

  As shown in FIG. 1, an opening 526 for exposing the front surface 421 of the button 42 is formed in the front surface 521.

  The back cover 53 includes a disk-shaped bottom surface portion 531. The bottom surface portion 531 is provided with a battery storage portion 532 for storing a battery. After the back cover 53 is attached to the body 51, the battery BT is stored in the battery storage unit 532 from the outside (the lower side in FIG. 1). The battery BT stored in the battery storage unit 532 is electrically connected to the substrate circuit 4.

  The base 6 is engaged with the housing 5 after being attached to an attachment portion (not shown). Thereby, the smoke detector of this embodiment is installed in a to-be-attached part (not shown).

  Next, the operation of the smoke detector according to this embodiment will be described. When smoke is detected by the smoke detection unit 1, a signal voltage is applied to the piezoelectric body 71 by the circuit unit mounted on the substrate circuit 4. Thereafter, the sounding body 2 emits sound by the vibration of the piezoelectric vibrator 7 and the thin member 8. Thereby, an alarm sound or an alarm sound is output from the smoke detector of the present embodiment.

  As described above, according to the present embodiment, the corrugation 82 is formed on the thin member 8 provided around the piezoelectric vibrator 7, whereby the thin member 8 is also bent and the amplitude of the piezoelectric vibrator 7 is increased. Therefore, the sound pressure of the sounding body 2 can be increased not only in the high frequency region but also in the low frequency region. As a result, the smoke detector can clearly output sound when it detects smoke and determines that a fire has occurred.

  Further, according to the present embodiment, when the sounding body 2 is attached to the cover 52 via the support portion 3, no air enters and leaves between the front surface side and the rear surface side of the sounding body 2. From the sound to the front side can be prevented, and as a result, the sound pressure can be increased.

  Furthermore, according to this embodiment, the front air chamber 54 can be made thin by forming the front air chamber 54 between the sounding body 2 and the region 524 of the cover 52. Further, according to the present embodiment, since the frequency region of the peak sound pressure can be expanded to the low frequency side by braking the air sealed in the front air chamber 54, the sound pressure in the low frequency region can be increased. Can do.

  In addition, according to the present embodiment, when a fire occurs, the smoke detecting unit 1 optically detects smoke using the light emitting unit and the light receiving unit in the housing 5, so that an alarm sound and an alarm sound are promptly generated. Can be output.

  Furthermore, according to the present embodiment, the sound pressure in the low frequency region can be increased by setting the primary resonance frequency of the sound generator 2 to 600 Hz or more and 1 kHz or less, so that the sound quality can be improved at the time of sound output. it can.

  In the present embodiment, a 42 alloy plate is used as the vibration plate 72. However, as a modification of the present embodiment, the vibration plate 72 may be another metal plate, or the vibration plate 72 may be a resin plate. It may be. Even with such a configuration, the same effects as in the present embodiment can be obtained. However, since the primary resonance frequency of the sounding body 2 depends on the mass of the piezoelectric vibrator 7 as described above, even if the diaphragm 72 is another metal plate or a resin plate as in this modification, the mass Need to be considered. Moreover, it is necessary to consider bending.

(Embodiment 2)
In the second embodiment, the case where the diameter ratio (r2 / r1) of the diameter r2 of the piezoelectric body 71 to the diameter r1 of the diaphragm 72 is changed in the piezoelectric vibrator 7 shown in FIG.

  FIG. 12B shows a change characteristic of the primary resonance frequency of the piezoelectric vibrator 7 when the diameter r1 of the piezoelectric body 71 is changed while the diameter r1 is fixed to 50 mm. FIG. 12B shows a relative value of the primary resonance frequency with respect to a predetermined frequency, and a0 <a1 <a2 <a3. The primary resonance frequency of the piezoelectric vibrator 7 is minimum when the diameter r2 is around 20 mm. The lower the primary resonance frequency of the piezoelectric vibrator 7, the lower the primary resonance frequency of the sounding body 2 having the thin member 8. Therefore, in order to lower the primary resonance frequency of the sounding body 2 and increase the sound pressure in the low frequency region, it is preferable to set the diameter ratio (r2 / r1) to 0.40 or more and 0.46 or less.

  In FIG. 13, the sound pressure level characteristic (solid line in FIG. 13) of the sound emitted by the sounding body 2 having a diameter ratio (r2 / r1) of 0.4 and the diameter ratio (r2 / r1) is 0.6. The sound pressure level characteristic of the sound emitted by the sounding body 2 (broken line in FIG. 13) is shown. As shown in FIG. 13, the sound emitted by the sounding body 2 having a diameter ratio (r2 / r1) of 0.4 is more than the sound emitted by the sounding body 2 having a diameter ratio (r2 / r1) of 0.6. Thus, the primary resonance frequency is lowered, and the sound pressure level in the low frequency region is high.

  As described above, according to the present embodiment, in the piezoelectric vibrator 7 of the sounding body 2, the diameter ratio (r2 / r1) of the diameter r2 of the piezoelectric body 71 to the diameter r1 of the diaphragm 72 is set to 0.40 or more and 0.46 or less. By doing so, the primary resonance frequency of the sound producing body 2 can be lowered, and the sound pressure in the low frequency region can be raised to the maximum.

(Embodiment 3)
In Embodiment 3, as shown in FIG. 14, the thin member 8 in which the corrugation 82 is formed only in the vicinity of the support portion 3 will be described. As corrugation 82 of this embodiment, both valley part 821 and peak part 822 may be formed as shown in Drawing 14 (a) and (b), and valley part is shown in Drawing 14 (c). Only 821 may be formed, or only the peak portion 822 may be formed as shown in FIG. Compared to the case where the corrugation 82 is formed in all radial directions of the thin member 8, the sounding body 2 having the thin member 8 according to the present embodiment has a particularly large amplitude in the high frequency region, and the sound in the high frequency region. The pressure goes up.

(Embodiment 4)
As shown in FIG. 15, the smoke detector according to the fourth embodiment is different in that the smoke detector 1 and the sounding body 2 are provided separately on a surface plate M that constitutes a ceiling such as a living room. 1 is different from the smoke detector (see FIG. 1). In addition, about the component similar to Embodiment 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  In the present embodiment, an opening N1 is formed in a ceiling substrate N that constitutes the ceiling together with the surface plate M. In the opening N1, the support 3 is attached to the surface plate M, and the sounding body 2 is fixed to the surface plate M via the support 3. The sounding body 2, the support portion 3, and the surface plate M form a hermetically sealed front air chamber P.

  The region M1 of the surface plate M forms a so-called drone cone in which the position facing the sounding body 2 protrudes forward (downward in FIG. 15) in a curved surface (convex shape). As described above, the surface plate M protrudes forward in a curved shape, so that the sound produced by the sounding body 2 can be emitted over a wide range. That is, sound diffusibility can be enhanced. Moreover, the intensity | strength of the area | region M1 of the surface board M can be raised. Furthermore, since the sound emitted from the sound generator 2 can be shifted to the low frequency side by braking the air sealed in the front air chamber P, the sound pressure in the low frequency region can be increased. The surface plate M (other than the region M1) of the present embodiment corresponds to the mounting plate of the present invention, and the region M1 of the surface plate M corresponds to the lid portion of the present invention. In the present embodiment, the region M1 is a part of the surface plate M, but if the region M1 is removed from the surface plate M, the opening formed in the surface plate M at this time is the Corresponds to the opening.

  The smoke detection unit 1 of this embodiment is attached to the front surface of the surface plate M (the lower surface in FIG. 15). Although not shown, the circuit unit that vibrates the sounding body 2 is installed in the vicinity of either the smoke sensing unit 1 or the sounding body 2.

  In the present embodiment, when smoke is detected by the smoke detection unit 1, when a signal voltage is applied to the piezoelectric vibrator 7 of the sounding body 2, the sounding body 2 vibrates and air vibration in the front air chamber P appears. It is transmitted to the face plate M (particularly the region M1). When the surface plate M vibrates, sound is emitted from the ceiling to the living room space.

DESCRIPTION OF SYMBOLS 1 Smoke detection part 2 Sounding body 3 Support part 4 Board circuit 5 Housing 52 Cover (mounting plate)
523 Sound hole (hole)
524 area (lid)
7 Piezoelectric vibrator 71 Piezoelectric body 72 Vibration plate 8 Thin member 82 Corrugation M Surface plate (mounting plate)
M1 area (lid)

Claims (4)

A smoke detector for detecting smoke;
A sounding body that converts electrical signals into sound;
A support for supporting the sounding body;
A circuit unit that outputs the electrical signal to the sounding body so that sound is output from the sounding body when smoke is detected by the smoke sensing unit;
The sounding body is
Including a piezoelectric vibrator having a piezoelectric body made of a piezoelectric element and a diaphragm having a larger area than the piezoelectric body and laminated on the piezoelectric body;
Including a thin member provided around the piezoelectric vibrator in combination with the outer periphery of the piezoelectric vibrator;
In the thin member, a corrugation formed of at least one of a peak portion and a valley portion is formed in an annular shape, joined to the support portion at an outer peripheral portion, and elastically holds the piezoelectric vibrator ,
A primary resonance frequency of the sounding body is 600 Hz to 1 kHz,
Both the piezoelectric body and the diaphragm are disk-shaped, and the diameter ratio of the diameter of the piezoelectric body to the diameter of the diaphragm is 0.40 or more and 0.46 or less .   The smoke detector according to claim 1, wherein the supporting portion is provided over the entire periphery of the opening in the mounting plate in which the opening is formed. A lid having a plurality of holes formed therein;
The support portion is provided to protrude from the mounting plate over the entire periphery of the opening of the mounting plate,
The smoke detector according to claim 2, wherein the lid closes the opening so that a space is formed between the sounding body and the lid. A housing for storing the smoke sensing unit;
The smoke sensing unit includes a light emitting unit that emits light and a light receiving unit that receives light from the light emitting unit, and optically detects smoke using the light emitting unit and the light receiving unit. The smoke detector according to any one of claims 1 to 3 .

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