JPS6029960B2 - sound generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sound generator, that is, a non-contact type buzzer, and in particular,
The present invention relates to a sound generator particularly suitable for use in a motor vehicle to provide an audible and visual warning indication when one or more predetermined conditions occur.

Current federal regulations require all motor vehicles to be equipped with a device that provides a four to eight second audible warning when an attempt is made to operate the motor vehicle without a seat belt properly fastened.

Typically such devices take the form of a buzzer unit controlled by a bimetallic timer circuit adjusted to expire within an appropriate amount of time. The warning light must also be activated at the same time as the buzzer, but according to federal regulations,
It is necessary for the audible alarm to operate even if there is no warning light or if the warning light is malfunctioning. “
The same buzzer may be used to provide a "headlights off" alarm and a "key left in ignition" alarm. Such devices are sufficient for their intended purpose. However, there are certain drawbacks inherent in devices using bimetal elements.

A bimetallic element typically operates to open a circuit by causing the element to warp when it is heated by a heating coil wrapped around it. However, to produce the desired time delay, the physical orientation of the bimetallic element must be manually adjusted so that the deflection of the bimetallic element interrupts the circuit at the appropriate time. Additionally, the thin heating wires that are wrapped around the bimetallic elements typically must be spot welded together with the other components of the circuit rather than simply being flow brazed. It is therefore clear that manufacturing a buzzer unit with bimetallic elements is a very labor-intensive process and therefore adds considerable manufacturing costs to the basic component costs of the unit. Furthermore, in that bimetallic elements are temperature-responsive devices, the time delay provided by bimetallic elements is affected by changes in ambient temperature. Therefore, the accuracy of the unit will be significantly compromised if it is subjected to significant temperature changes. Additionally, unless adequate heat dissipation is provided, the substantial heat generated by the bimetallic elements can cause problems for other circuit elements. Therefore, the main objective of the present invention is to design an acoustic generator using a resistor with a positive temperature coefficient (PTC) to create the necessary time delay.
The purpose is to eliminate the drawbacks inherent in the use of bimetal elements.

The idea of using a PTC resistor in place of a bimetal element is not new and has already been attempted in the past, but certain problems always arise that make it impossible to simply replace the bimetal element with a PTC resistor. In particular, since the resistance value of the PTC resistor is temperature sensitive, simply connecting the PTC resistor in a series circuit with the lamp and logic line will not result in a circuit that will function satisfactorily over the required temperature range. Furthermore, if the lamp burns out or is removed, the change in the resistive characteristics of the circuit will prevent the PTC resistor from timing out. Additionally, when a resistor is inserted in parallel with the lamp to provide a pull-down resistance in the event of a lamp failure, the additional drop across the resistor prevents the lamp from properly lighting. As a result, due to these obstacles, PTC resistors have not been used despite their obvious promise. The present invention uses one PTC resistor as the main heating element, another PTC resistor as the switch element of the lamp, and a third PTC resistor as the logic switch element of the logic signal timing the acoustic generator. The above problem is solved by devising a circuit that utilizes a unique triple PTC element.

The problems caused by the use of PTC resistors as described above are thus eliminated. In particular, because the switch element controlling lamp operation is provided with a separate logic switch element separate from the heating element, the circuit continues to function properly and for a specified period of time regardless of the absence or failure of the lamp. Gives an audible alarm. In addition, the use of separate heating elements reduces the unit's delay time to 4.0 over a wide range of ambient temperatures.
It is held within a specific time of 8 seconds. Importantly, PTC elements are inexpensive, do not require separate manual adjustments to set delay times, yet can be flow-brazed onto printed circuit boards with other circuit elements. Therefore,
Significant manufacturing costs can be saved when producing a sound generator according to the invention. Further objects and advantages of the invention will become apparent from the following detailed description of preferred embodiments of the invention, taken in conjunction with the accompanying drawings.

Referring now to FIG. 1, an acoustic generator 10 according to the present invention
A cross-sectional view of the assembled state is shown.

The acoustic generator 10 described herein is very small in size, approximately 6.25 skins (2.5 inches) square by 2.5 arcs (1 inch) high, and is very inexpensive to manufacture. ,
However, it is especially suitable for mass production. The acoustic generator 10' according to the invention is therefore suitable for use in motor vehicles as a warning device to indicate the existence of various predetermined conditions. In particular, the present invention protects the driver from driving when the headlights remain on even after the ignition system is turned off, when the key is left in the ignition position, and when attempting to operate the vehicle without properly fastening the seat belt. It can be used to give a warning when something happens. As stated above, current federal regulations require that an audible warning signal be provided for 4 to 8 seconds when the seat belt is not buckled when the vehicle is started. The control circuit of generator 10 according to the present invention may also be used to time a seat belt warning signal to a motor vehicle at a specified time over a wide range of ambient temperatures. The sound generator 10 essentially comprises a diaphragm 24 which is caused to vibrate by an electromagnetic coil 30 and thus generate sound.

The electromagnetic coil 30 is electrically driven by an oscillation circuit (FIG. 4). The diaphragm 24 is connected to the cover 12 of the unit.
18 and held in place by a foam gasket 26 and a plastic retaining ring 28. This retaining ring 28 is simply snapped onto the bulge 25 of the cover 12 as shown. Therefore, a closed acoustic cavity 18 is formed within the concave height of the cover 12. It is important to note that although the Sougetsu 18 is closed, it is not hermetically sealed.

In particular, the diameter of the diaphragm 24 is the same as that of the overhang 2 of the cover 12.
Please note that the inner diameter is slightly smaller than the inner diameter of 5. Therefore, the presence of a porous foam gasket 26 around the diaphragm 24 allows air to slowly leak out from around the diaphragm 24 even if a pressure differential is maintained on both sides of the diaphragm. Therefore, the diaphragm 24 will not bend or bulge even if the air within the closed acoustic ear 18 is heated or cooled by changes in ambient temperature. Furthermore, this slow air leakage allowed around the diaphragm 24 also results in tension or compression forces being imposed on the diaphragm 24 over a wide ambient temperature range due to the difference in expansion coefficients between the cover 12 and the diaphragm 24. To prevent. However, at the same time, the seal formed around the diaphragm 24 by this foamed gasket 26 is due to the relatively fast movement of air caused by the vibration of the diaphragm 24 when excited by the electromagnetic coil 301. It is in a sealed state that could be considered a cavity. Generally speaking, the seal formed by diaphragm 24, foam gasket 26, and retaining ring 28 is
If a sustained pressure difference occurs due to a change in ambient temperature, air leakage can occur to balance the pressure difference across the diaphragm, but the diaphragm 24 vibrates at the frequency at which this device produces sound. This allows the closed cavity 18 to be considered sealed if rapid air movement occurs. The magnitude and sound quality of the radiated sound generated by the sound generator of the present invention are as follows:
A diaphragm 2 having a mass M, a compliance Cr provided by the intumescent gasket 26, and a compliance Cc provided by the air in the closed cavity 18.
It is mainly determined by the characteristics of the resonant acoustic system consisting of four components.

This physical configuration can be shown to be equivalent to an electrical series resonant circuit, where M is the inductance L
and C is equivalent to the capacitance C. Therefore, the resonant frequency f of this system is given by the following equation.
・ f = 7 tassels of cloth In the acoustic generator of the present invention, this frequency is transmitted through the oscillation circuit (the fourth
(Fig.) is selected to be the same as the operating frequency.

As mentioned above, the diaphragm 24 is caused to vibrate by the "pulling and pushing forces" exerted on the diaphragm by the pole pieces 32 of the electromagnetic coil 30.

As is well known to those skilled in the art, in order for diaphragm 24 to vibrate properly, pole pieces 32 and diaphragm 24 must
It is important that there is an appropriate air gap between In known devices, individual manual arrangements are still required to set the correct air gap. However, in the sound generator according to the present invention, the air gap between the pole piece 32 and the diaphragm 24 is automatically set to an appropriate distance when the unit is assembled. In particular, the printed circuit board 16 to which the electromagnetic coil 30 is securely secured is connected to the diaphragm 24 by a pair of support posts 54 integral to the cover 12.
The support posts 54 are spaced a predetermined distance from each other and are ferro-coupled with a pair of support posts 56 that are integral to the case 14 of the unit. Each of the support posts 54 has a protrusion 55 projecting from its end, which extends through a hole in the circuit board 16;
Then, it fits into a hole in the upper part of the opposing support post 56 protruding from the case 14. In this manner, when the cover 12 is heated and laminated to the case 14, the printed circuit board 16 is mounted on the diaphragm 24 such that the pole piece of the coil 30 mounted thereon is automatically spaced the appropriate distance from the diaphragm 24. 24. Therefore, when the unit is assembled, an appropriate air gap 52 is set.
Referring now to FIG. 2, an acoustic generator 10 according to the present invention
Case 14 is shown in detail.

As previously mentioned, a closed acoustic cavity 18 is formed within the recessed window of the cover 12 and above the diaphragm. Furthermore, case 1
An acoustic ear 22 is also formed below the diaphragm 24 within the diaphragm 24. The closed ear 18 above the diaphragm 24 constitutes the primary acoustic cavity of the unit, while the diaphragm 24
The lower boat cavity 22 constitutes the secondary acoustic cavity of the unit. The secondary acoustic cavity 8 and 22 are attached by a series of holes 20 formed in the case 14 of the unit 10.

The secondary acoustic cavity 22 is boated to tune it to the main frequency of the oscillator circuit.

In particular, the size and number of acoustic boats 20 are selected such that the effective boat dimensions of the open acoustic boats 22 resonate at the main frequency of the diaphragm 24. In other words, by changing the number and/or dimensions of the acoustic boats 20, the volume of the sound generated by the acoustic generator 101 can be changed. 6a and 5b, the manner in which electromagnetic coil 30 is mounted to printed circuit board 16 is shown in detail.

Electromagnetic coil 30 consists of multiple turns of magnetic wire 36 wound around a plastic bobbin 34. The bobbin 34 has three mounting legs 38-40 integral therewith, which are used to secure the coil 30 to the printed circuit board 16. Specifically, mounting legs 39 and 40 are first inserted through a pair of holes 46 and 47, respectively, in printed circuit board 16, coil 30 is then swung downward, and locking tabs at the ends of remaining mounting legs 38 are inserted. This leg 38 is inserted into the third hole 48 of the printed circuit board 16 until the leg 42 engages the underside of the printed circuit board 16. It is therefore apparent that the coil 30 is easily secured to the printed circuit board 16 without the need for special clips or mounting screws. Referring now specifically to FIG. 5b, one end 44 of coil wire 36 is wrapped around and terminated onto mounting leg 401, and the other end 43
Note that the mounting leg 39 is wrapped around and the termination is connected thereto.

The process of wrapping and terminating the wire 36 around the mounting legs 39 and 40 of the bobbin 34
This is done when the wire 36 is first mechanically wrapped around the wire 36 and does not require any additional manual intervention. Accordingly, as is readily apparent from the accompanying drawings, when coil 30 is mounted to a printed circuit board as described above, ends 43 and 44 of coil wire 36 are connected to suitable copper pads on the underside of printed circuit board 16. 50 and 51, respectively. Thus, the connection of coil wire 36 to printed circuit board 16 can be flow brazed with other electrical components on printed circuit board 16 in a conventional manner. Thereby,
Labor-intensive additional operations are eliminated. Referring now to FIG. 4, a circuit diagram of a timing control circuit for sound generator 10 in accordance with the present invention is shown. The illustrated control circuit provides a 4 to 8 second audible alarm upon receipt of a signal indicating that the seat belt is not properly fastened;
Also, the headlights remained on even after I turned off the ignition system.)
It is used to issue a continuous audible alarm when a signal is received indicating that the Additionally, appropriate panel lamps are activated to provide a visual alarm signal consistent with the audible alarm thus issued. Although not included in the circuit shown, with slight circuit modifications the circuit could easily be adapted to provide additional alarms such as "key in ignition", "door ajar", etc. can. Generally, the control circuitry includes timing circuitry, logic circuitry for determining the existence of certain predetermined conditions, oscillator circuitry, and drive circuitry for driving the electromagnetic coil assembly. The timer circuit is essentially 3 of the type shown in Figures 6a and 6b.
Consists of a heavy PTC element. As is clear from FIGS. 6a and 6b, a pair of cavities 82 are formed in the metallized portion of the surface of this element.
By simply carving and 84, three separate PTC resistors are created on one disk 80'. Separate leads 86 and 88 are attached to each of the three metallized surface areas, and one lj-de 90 is attached to the rear surface of disk 80. Thus, separate PTC resistances are created between lead 90 and each of the three front leads 86-88. PTC resistors are characterized by their rapid change in resistance at a given temperature and their temperature coefficient of resistance.

The temperature at which the temperature coefficient of PTC increases rapidly is called the "transition temperature." The characteristic transition temperature of PTC resistance is PTC
The resistance is determined by the specific porcelain composition based on barium titanate. Characteristically, the temperature coefficient of PTC resistance is typically low and constant below its transition temperature. Thus, for example, the resistance of a PTC resistor varies from 5 ohms below its transition temperature to 5 kilohms above its transition temperature. Referring now to FIG. 7, there is shown a simplified circuit diagram illustrating the particular manner in which triple PTC elements are utilized in the present invention. Basically, three PTC resistors are used for three separate purposes: one PTC resistor (Rad) is used as the main heating element of PTC element 60, and the other PTC resistor (R
ac) is used as a switch element to control the operation of the seat belt warning lamp, and the third PTC resistor (
Rab) is used as a logic switch element that provides a logic signal that controls the operation of the electromagnetic coil. As will be readily apparent to those skilled in the art, the basic triple P shown in FIG.
The TC timing circuit is readily applicable to a wide variety of uses other than timing control circuits for automotive seat belt warning units. In practice, in virtually any case where a bimetallic element is used to provide the sea bream signal, the bimetallic element can be replaced with the triple PTC circuit shown in FIG. effect can be obtained. Additionally, PTC timing circuits can be used in many applications where the use of bimetallic elements is not possible or practical. When the circuit is first powered, all three PTC resistors have their nominal resistance values.

A high level signal is therefore present on logic line 74 and lamp 73 is activated. However, because a substantial current is drawn through the heating element Rad, the entire PTC element 60 begins to heat up simply because three resistors are placed in the same PTC element. Furthermore, although the PTC resistors Rab and Rac heat up to some extent by their own current conduction, due to the added resistance in their current path, this effect is small compared to the heat transferred from the heating element Rad. It's not significant. When the transition temperatures of Rab and Rac of the two switch elements are reached, these two PTC
The resistance of the resistor increases significantly, thereby causing the lamp 73
and causes the signal on logic line 74 to go low.

If lamp 73 is removed from the circuit or if lamp 73 burns out, the logic PTC resistor R
It is important to note that the operation of ab is not affected in any way. However, if logic line 74 were simply coupled to the midpoint of PTC resistor Rac and alarm lamp 73 (shown in phantom), the logic line would never go low if the lamp failed. This is because the pull-down resistance of the lamp is lost. Additionally, if an additional resistor were connected in parallel with lamp 73 to eliminate this condition (also shown in phantom), the increased voltage drop across this resistor would prevent the lamp from igniting properly. .
Therefore, the triple PTC configuration described herein is required in order for logic line 74 to operate regardless of lamp circuit failure. Of course, when power is finally removed from the main heating element Rad, the temperature of the triple PTC element 60 will rapidly return to its ambient temperature condition and the temperature of the two switch elements R
The effective resistance values of ab and Rac similarly return to their initial minimum values. Therefore, as shown in FIGS. 6a and 6b, the lamp PTC resistance Rac
It must be large enough so that its resistance below the transition temperature of is low enough to light the lamp brightly. Similarly, the heated PTC resistor Rad provides sufficient heat to cause the logic PTC resistor Rab to exceed the transition temperature of the PTC element 60 within a specified 4 to 8 second time period even if the lamp burns out. must be large enough to occur. Furthermore, as shown, the lamp PT
Preferably, a C resistor Rac is disposed between the heating PTC resistor Rad and the logic PTC resistor Rab, so that the lamp PTC resistor is heated relatively evenly and the lamp gradually dims. can be prevented. Now, referring to FIG. 4, the triple PTC element 60 is
It is clear that it is followed by a control circuit as shown in the figure. In particular, the heating element PTC resistor Rad is connected between the terminal of the igniter and ground, and the PTC element Rac
is connected between the terminal of the ignition system and the terminal connected to the seat belt warning lamp, and the PTC resistor Rab, which is a logic switch element, is connected between the terminal of the ignition system and the logic line 74.
is connected between. A pull-down resistor R9 connected between logic line 74 and ground together with PTC resistor Rab forms a voltage divider network that determines the switching time of the signal on logic line 74. In particular, the value of resistor R9 is selected such that the signal on logic line 74 switches from a high state to a low state within a specified time period of 4 to 8 seconds. If the seat belt is not fastened when the ignition system is turned on, node 72 is pulled to ground potential despite the high level signal sent from the ignition system terminals through resistor RI.

When the signal at the coupling point 72 is at a low level, the oscillation circuit 75
, especially the Noah Gate 68 therein. Conversely, if the seat belt is properly fastened when the ignition is turned on, the signal at node 72 will be high, thereby disabling oscillator circuit 75. Connection point 7
In the state in which the oscillation circuit 75 is enabled by the low level signal of 2, the oscillation circuit 75 starts oscillating when the logic enable signal is received from the output of the NOR gate 64.

As previously discussed, upon initiation of ignition, the signal on logic line 74 will be high for a predetermined 4 to 8 seconds, causing the output signal of NOR gate 64 to be low for a corresponding 4 to 8 seconds. When the output signal of NOR gate 64 is low and the signal at node 72 is low, oscillator circuit 75 oscillates and provides a square wave drive signal to the base of transistor QI through resistor R5. Thereby, a substantially triangular current waveform is induced in coil LI, which in turn causes the diaphragm to vibrate at the frequency of the current waveform and generates an audible alarm signal. When the signal on logic line 74 goes low after the specified 4 to 8 seconds, the output from NOR gate 64 goes high and oscillator circuit 7
Disable 5. Additionally, the control circuit shown herein may also be used to provide a persistent warning signal when the headlights remain on after the ignition has been turned off.

This is accomplished by connecting the panel lamp terminal, which indicates the status of the headlights, to the other input of NOR gate 64 through resistor R7. Since the state of the headlights is relevant only when the ignition system is turned off, the terminal of the ignition system is connected to the other input of the NOR gate 64 via a resistor R2, an inverter 62, and a diode D2. Therefore, when the ignition is turned on, the signal at this input of the Noah gate 64 is pulled low, disabling the headlight input signal. However, when the ignition device is turned off,
The high level signal from the panel lamp terminal is Noah gate 64
, thereby enabling the oscillator circuit 75. This is because the signal at node 72 is also low since the igniter is off. Therefore, an audible warning is generated that lasts until the headlights are turned off. As mentioned above, oscillator circuit 75 also drives transistor QI with a square wave output signal. However, the square wave signal has many harmonics and therefore does not provide a good driving signal for the coil LI. Of course, rather than a pure sine wave oscillator (which requires very expensive circuitry and does not generate harmonics) a square wave oscillator circuit 75 is used.
However, the current actually induced through the coil LI is
The square wave signal is converted into an "approximate" sine wave by the inductance of the coil LI and the resistance value of the resistor R6 connected in parallel with the coil LI. The current signal flowing through the coil LI is therefore further triangulated, which sufficiently approximates a sinusoidal signal and causes the diaphragm to be 1/2 to produce a purer acoustic than if driven by a direct square wave signal. It vibrates in only one mode. In particular, by coarsely matching this triangular drive signal with the characteristics of the resonant acoustic system described above, the acoustic generator according to the invention produces a substantially pure sinusoidal acoustic output. It will thus be apparent that the present invention provides a low cost sound generator that is capable of producing relatively pleasant yet clear audible sounds and that is easily mass-produced.

As noted above, the present invention is particularly suited for use as an automobile alarm system, but may also find use in a wide variety of other applications where an inexpensive, reliable, yet low cost sound generator is desired. Easy to apply. Although a preferred embodiment of this invention has been described, it will be apparent to those skilled in the art that changes and modifications can be made without departing from the scope of this invention.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the sound generator according to the present invention in a roughly erected state, FIG. 2 is a diagram showing the case of the sound generator shown in FIG. 1, and FIG. 4 is a circuit diagram of a control circuit according to the invention; FIGS. 5a and 5b are detailed illustrations of how to mount the electromagnetic coil on a printed circuit board; FIG. Figures 6a and 6b show a triple PT of the type used according to the invention.
FIG. 7, which shows the C element, is a simplified circuit diagram of a PTC timing circuit forming a part of the control circuit of FIG. 4. 10... Sound generator, 12... Cover, 1
4... Case, 16... Printed circuit board, 18... Atsushi (acoustic cavity), 20...
・・Hole (boat), 22・・・・−・Acoustic cavity, 24・
...Diaphragm, 26...Foaming gasket, 28...Plastic retaining ring, 30
..... Electromagnetic coil, 32 ..... Electrode piece, 3
4... Plastic bobbin, 36... Magnetic wire, 52... Air gap, 54, 56...
...Support post. -1- -Sanki. 1. Thirty-three. ↓ 11”. 4. rIL dead, Hakuranto 1 old-yo, Ran, F Ko. Une, F Tsuneko/Ran FE Nico 2.

Claims (1)

[Claims] 1. An acoustic generator suitable for use in a motor vehicle for generating an audible signal timed in relation to a visible signal by a lamp of the motor vehicle, comprising a diaphragm and for causing said diaphragm to vibrate by repeated energization. an electromagnetic coil, an oscillator for repeatedly energizing the electromagnetic coil, and a control circuit including timing means for controlling enabling of the oscillator and energizing of the lamp;
The timing means includes a positive temperature coefficient resistive element consisting of a PTC body having a transition temperature;
The object has conductive contact surface layers on separate first and second surfaces, said first conductive surface layer on separate first and second surfaces.
and a third contact area, said contact areas being electrically isolated from each other and forming a plurality of PTC resistance means in association with said second electrically conductive surface layer, said contact areas comprising: The first and second contact areas are distributed such that the third contact area is larger than the third contact area, and the second contact area is located between the first contact area and the third contact area. wherein the first contact area is connected to a power source end, and the second contact area is connected between the power source and the lamp to control energization of the lamp. and wherein the third contact area is connected between the power source and the oscillator and is adapted to control enabling of the oscillator.