JP2015074283A - Vehicular alarm apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicular alarm apparatus with a sound pressure adjustment of an alarm sound with a desired tone secured.SOLUTION: In order to warn a vehicle condition requiring attention in a vehicle by an alarm sound and cause the alarm sound whose continuation period of turning on-off at a high set frequency being higher than a given boundary frequency to appear at a low set frequency being lower than the boundary frequency, a vehicular alarm apparatus 1 includes: a control unit 10 including a pulse generator 16 that generates a pulsing digital sound signal S0 that is turned on-off in an amplitude V0, and an MPU 12 that performs pulse-width modulation in accordance with an instruction of a computer program stored in memory 14; a low-pass filter 20 for attenuating a signal component of a high set frequency of the sound signal output from the control unit 10 and letting a signal component of a low set frequency of the sound signal to pass; and a piezoelectric buzzer 50 for issuing the alarm sound in the vehicle as a result of a voltage being applied, the voltage in accordance with an amplitude of the sound signal output from the low-pass filter 20.

Description

  The present invention relates to a vehicle alarm device that emits an alarm sound in a vehicle.

  Conventionally, in a vehicular alarm device, a piezoelectric buzzer that emits an alarm sound when a voltage is applied is widely used as a relatively cheap buzzer with a simpler structure than an electromagnetic buzzer.

  In the one disclosed in Patent Document 1 as one type of such a vehicle alarm device, the sound pressure of the alarm sound is adjusted by controlling the voltage applied to the piezoelectric buzzer according to the oscillation pulse output from the microcomputer. Here, in particular, in the one disclosed in Patent Document 1, the degree of sound pressure attenuation is changed by so-called pulse width modulation that variably controls the on-duty ratio of an oscillation pulse in a configuration in which a capacitor is connected in parallel to a piezoelectric buzzer. .

JP-A-8-207660

  However, when the on-duty ratio of the oscillation pulse is changed by the method disclosed in Patent Document 1, the sound pressure of the alarm sound emitted from the piezoelectric buzzer changes with the timbre, which may impair the reliability.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a vehicle alarm device that adjusts the sound pressure of an alarm sound that secures an intended tone color.

  The invention disclosed in order to solve the above-described problem is a low set frequency (fl) in which an intermittent period (Ti) that is turned on / off at a high set frequency (fh) higher than a predetermined boundary frequency (fb) is lower than the boundary frequency. ), A control unit (10) for pulse-width modulating the acoustic signal, the control unit for variably controlling the on-duty ratio (Rh) of the acoustic signal in the intermittent period, and the sound output from the control unit A low-pass filter (20) that attenuates a signal component of a high setting frequency in the signal and passes a signal component of a low setting frequency in the acoustic signal, and a voltage corresponding to the amplitude of the acoustic signal output from the low-pass filter A piezoelectric buzzer (50) that emits an alarm sound in the vehicle when applied is provided.

  In the present invention, the on-duty ratio of the intermittent period is set for an acoustic signal that is pulse width modulated so that the intermittent period that is turned on and off at a high set frequency higher than the boundary frequency appears at a low set frequency that is lower than the boundary frequency. Variable control. As a result, the acoustic signal output from the control unit to the low-pass filter has an amplitude that follows the variable control value of the on-duty ratio due to the attenuation of the signal component of the high setting frequency and the passage of the signal component of the low setting frequency. This signal is given during the intermittent period. At this time, the voltage applied to the piezoelectric buzzer is determined according to the amplitude of the acoustic signal to be output from the low-pass filter at a low set frequency. Therefore, the sound pressure of the alarm sound emitted from the piezoelectric buzzer with the tone color corresponding to the low set frequency also follows the variable control value of the on-duty ratio. Therefore, it is possible to achieve the sound pressure adjustment of the alarm sound while ensuring the desired tone color.

  According to another disclosed invention, the high set frequency is set to the frequency of the sound wave in the non-audible range. In this invention, even if the signal component of the high setting frequency that remains due to attenuation is superimposed on the intermittent period of the acoustic signal output at the low setting frequency from the low-pass filter, the alarm of the high setting frequency that becomes a non-audible sound is superimposed. The sound does not substantially affect the timbre. Therefore, it is possible to increase the reliability of the effect for adjusting the sound pressure of the alarm sound that secures the expected tone color.

  Further, according to another disclosed invention, the intermittent period is fixed. In this invention, not only the acoustic signal output from the control unit to the low-pass filter, but also the acoustic signal output from the low-pass filter at a low set frequency is fixed. According to this, the alarm sound emitted from the piezoelectric buzzer during the fixed intermittent period of the low set frequency can be a timbre with high stability.

It is a block diagram which shows the alarm device for vehicles by one Embodiment of this invention. It is a graph which shows the characteristic of the alarm device for vehicles of Drawing 1. It is a graph which shows the characteristic of the alarm device for vehicles of Drawing 1. It is a block diagram which shows the modification of FIG.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, a vehicle alarm device 1 according to an embodiment of the present invention includes a control unit 10, a low-pass filter 20, an amplifier 30, and an alarm sound to warn a vehicle situation that requires attention in a vehicle. A pull-down resistor 40 and a piezoelectric buzzer 50 are provided. In addition, the apparatus 1 generates an alarm sound for warning a passenger in the vehicle, for example, a door opening state, a light forgetting to turn off, a seat belt not worn state, a battery voltage drop state, a tire pressure drop state, etc. In order to emit, it is provided in the instruments in the vehicle.

  The control unit 10 includes an MPU 12, a memory 14, and a pulse generator 16. The MPU 12 determines whether or not an alarm sound is necessary by executing a computer program stored in the memory 14. As a result, the MPU 12 instructs the pulse generator 16 to generate the acoustic signal S0 when an alarm sound is necessary. The pulse generator 16 is composed of a sound generator, for example, and generates an acoustic signal S0 in accordance with a command from the MPU 12.

  Specifically, the pulse generator 16 performs pulse width modulation on the pulsed digital acoustic signal S0 that is turned on / off at the amplitude V0 in accordance with a command from the MPU 12. As shown in FIGS. 2 and 3, in such pulse width modulation, the pulse generator 16 has a low set frequency fl having a substantially constant value lower than a predetermined boundary frequency fb and a high set value having a substantially constant value higher than the boundary frequency fb. The frequency fh is set to the acoustic signal S0.

  Here, in particular, if one period Tl is from the start of the intermittent period Ti in which the on period Th of the acoustic signal S0 is intermittent to the end of the interruption period Ts in which the acoustic signal S0 is continuously turned off immediately after the period Ti, The repetition frequency 1 / Tl of the periods Ti and Ts is set to the low set frequency fl. At this time, the low set frequency fl is set to a sound wave frequency in an audible range such as 2 kHz, for example. At this time, the ratio Rl (= 100 × Ti / Tl) of the intermittent period Ti in the cycle Tl is fixed to a substantially constant value such as 50% in the present embodiment. As a result, the intermittent period Ti is also fixed.

  Further, in the intermittent period Ti repeatedly appearing at the low set frequency fl set in this way, the frequency at which the acoustic signal S0 is turned on and off is assumed to be N when the intermittent number of the on period Th (that is, the number of pulses in the period Ti) is N. N / Ti is set to the high set frequency fh. At this time, the high set frequency fh is set to a sound wave frequency in a non-audible range such as 62.5 kHz, for example. At this time, the on-duty ratio Rh (= 100 × Th × N / Ti) as the ratio of the acoustic signal S0 to the on-period Th in the intermittent period Ti is variable in the range of 0 to 100%, for example, in this embodiment. Be controlled. 2 shows an example in which the on-duty ratio Rh is variably controlled to 50%, and FIG. 3 shows an example in which the on-duty ratio Rh is variably controlled to 100%.

  As a result of the pulse width modulation as described above, the signal component necessary for generating the alarm sound is given to the acoustic signal S0 because the intermittent period Ti that turns on and off at the high set frequency fh appears at the low set frequency fl. Signal.

  As shown in FIG. 1, the low-pass filter 20 is an L-type primary low-pass filter and includes a filter resistor 22 and a filter capacitor 24. The filter resistor 22 is connected in series between the output side of the pulse generator 16 and the input side of the amplifier 30. The filter capacitor 24 is connected to the filter resistor 22 in parallel with the amplifier 30 and is grounded on the opposite side of the resistor 22.

  In the low-pass filter 20 having such a configuration, the cutoff frequency is set to be substantially equal to the boundary frequency fb, which is the setting reference for the frequencies fl and fh, in the pulse generator 16. With this setting, the low-pass filter 20 attenuates the signal component of the high setting frequency fh in the acoustic signal S0 output from the pulse generator 16, and passes the signal component of the low setting frequency fl in the signal S0. As a result, the low-pass filter 20 outputs an acoustic signal S1 that is continuously turned on in the intermittent period Ti and continuously turned off in the intermittent period Ts, out of one cycle Tl of the low set frequency fl shown in FIGS. It is generated as an output signal to 30 (see FIG. 1). At this time, the amplitude (specifically, the average amplitude within the period Ti) V1 of the output-side acoustic signal S1 in the intermittent period Ti is a value that is variably controlled as the on-duty ratio Rh of the input-side acoustic signal S0 during the synchronization period Ti. Increases or decreases following. For example, the amplitude V1 in FIG. 2 in which the variable control value is reduced to 50% with respect to the amplitude V1 in FIG. 3 in which the variable control value of the on-duty ratio Rh is 100% is the same as the variable control value. To decrease. As described above, the acoustic signal S1 output from the low-pass filter 20 to the amplifier 30 maintains the amplitude V1 that follows the on-duty ratio Rh throughout the intermittent period Ti of the low set frequency fl, thereby substantially reducing the ratio Rl. The signal is an on-duty ratio.

  As shown in FIG. 1, the amplifier 30 is a grounded-emitter transistor amplifier circuit, and includes an amplifier transistor 32, an emitter resistor 34, a collector resistor 36, and a rectifier diode 38. In this embodiment, the amplifying transistor 32 is a bipolar transistor whose emitter is grounded via an emitter resistor 34. The collector of the amplification transistor 32 is connected to a rectifier diode 38 via a collector resistor 36, and the diode 38 is further connected to the battery power supply 2 of the vehicle. The base of the amplification transistor 32 is connected to an output terminal provided between the filter resistor 22 and the filter capacitor 24 in the low-pass filter 20. When the acoustic signal S1 is input from the low-pass filter 20 to the base of the amplifying transistor 32, a voltage Vc obtained by amplifying the amplitude V1 of the signal S1 is generated between both ends of the collector resistor 36 as shown in FIGS. To be applied. At this time, in this embodiment, the amplitude V1 of the acoustic signal S1 is amplified by a gain of 1 or more according to the resistance value ratio of the resistors 34 and 36, whereby the voltage Vc across the collector resistor 36 is obtained. . For example, here, the emitter current I (see FIG. 1) in the case of FIG. 3 in which the resistance value of the emitter resistor 34 is 100Ω, the resistance value of the collector resistor 36 is 1 kΩ, and the on-duty ratio Rh is variably controlled to 100% is 10 mA. To do. In this example, the voltage Vc is amplified to about 10 V across the collector resistor 36 as compared to across the emitter resistor 34 to which 1 V is applied.

  As shown in FIG. 1, the pull-down resistor 40 is connected to the filter resistor 22 in parallel with the filter capacitor 24 and the amplifier 30, and is grounded on the opposite side of the resistor 22. By such connection and grounding, the pull-down resistor 40 can maintain the base potential of the amplification transistor 32 at zero potential and maintain the transistor 32 in the off state even when the output of the acoustic signal S0 from the pulse generator 16 is interrupted. It has become.

  The piezoelectric buzzer 50 is mainly composed of a piezoelectric element such as lead zirconate titanate (PZT), and the collector resistor 36 is connected in parallel to each of the collector of the amplification transistor 32 and the rectifier diode 38. . With this connection, when the voltage Vc across the collector resistor 36 fluctuates according to the on / off state of the acoustic signal S <b> 1 input from the low-pass filter 20 to the amplifier 30, the voltage Vc is applied to the piezoelectric buzzer 50. As a result, the piezo-electric element that constitutes the piezoelectric buzzer 50 vibrates according to the fluctuation of the applied voltage Vc, so that an alarm sound is generated. 2 and 3, the applied voltage Vc is obtained by amplifying the amplitude V1 of the acoustic signal S1 following the variable control value of the on-duty ratio Rh during the intermittent period Ti of the low set frequency fl (specifically Specifically, the average voltage in the period Ti). As a result, the sound pressure of the alarm sound emitted from the piezoelectric buzzer 50 at the low set frequency fl also follows the variable control value of the on-duty ratio Rh.

  Hereinafter, the function and effect of the device 1 described above will be described.

  In the apparatus 1, for the acoustic signal S0 subjected to pulse width modulation, an intermittent period Ti that is turned on / off at a high set frequency fh higher than the boundary frequency fb appears at a low set frequency fl lower than the boundary frequency fb. The on-duty ratio Rh of Ti is variably controlled. As a result, the acoustic signal S0 output from the control unit 10 to the low-pass filter 20 follows the variable control value of the on-duty ratio Rh by the attenuation of the signal component of the high set frequency fh and the passage of the signal component of the low set frequency fl. The signal S1 which gives the amplitude V1 thus obtained in the intermittent period Ti of the low set frequency fl. At this time, the applied voltage Vc to the piezoelectric buzzer 50 is determined according to the amplitude V1 of the acoustic signal S1 to be output from the low-pass filter 20 at the low set frequency fl. Therefore, the sound pressure of the alarm sound emitted from the piezoelectric buzzer 50 with a tone color corresponding to the low set frequency fl also follows the variable control value of the on-duty ratio Rh. Therefore, it is possible to achieve the sound pressure adjustment of the alarm sound while ensuring the desired tone color.

  Further, in the apparatus 1, even if the signal component of the high set frequency fh remaining due to attenuation is superimposed on the intermittent period Ti of the acoustic signal S1 output from the low pass filter 20 at the low set frequency fl, the non-audible region The alarm sound of the frequency fh that becomes a sound wave does not substantially affect the timbre. Therefore, it is possible to increase the reliability of the effect for adjusting the sound pressure of the alarm sound that secures the expected tone color.

  Furthermore, in the apparatus 1, not only the acoustic signal S0 output from the control unit 10 to the low-pass filter 20, but also the acoustic signal S1 output from the low-pass filter 20 at the low set frequency fl is fixed. According to this, the alarm sound emitted from the piezoelectric buzzer 50 during the fixed intermittent period Ti of the low set frequency fl can be highly timbre-stable.

  Furthermore, in the apparatus 1, the voltage V1 applied to the piezoelectric buzzer 50 is generated by amplifying the amplitude V1 of the acoustic signal S1 output from the low pass filter 20 following the variable control value of the on-duty ratio Rh. According to this, the adjustment range of the sound pressure following the variable control value of the on-duty ratio Rh can be increased.

(Other embodiments)
Although one embodiment of the present invention has been described above, the present invention is not construed as being limited to the embodiment, and can be applied to various embodiments without departing from the gist of the present invention. it can.

  Specifically, as a first modification, as shown in FIG. 4, a piezoelectric buzzer 50 in which the collector resistor 36 is not provided and the emitter resistor 34 is connected in parallel to the emitter of the amplification transistor 32 is opposite to the emitter. It may be grounded on the side. In this case, the amplification gain by the amplifier 30 is substantially 1.

  As a second modification, for example, a secondary low-pass filter other than the L-type primary low-pass filter may be employed for the low-pass filter 20. Further, as the third modification, other than the amplifier circuit using the bipolar transistor, for example, an amplifier circuit using a field effect transistor, an amplifier circuit using an operational amplifier, or the like may be adopted for the amplifier 30. Furthermore, as a fourth modification, the pull-down resistor 40 may not be provided.

  As a fifth modification, the boundary frequency fb is reduced by a low-pass filter as long as the function of attenuating the signal component of the high set frequency fh in the acoustic signal S0 and passing the signal component of the low set frequency fl of the signal S0 is achieved. It may be different from 20 cut-off frequencies. Further, as a sixth modification, the intermittent period Ti may be changed by variably controlling the ratio Rl of the intermittent period Ti in the cycle Tl. Furthermore, as a seventh modification, the high set frequency fh may be set to the frequency of the sound wave in the audible range.

1 Vehicle alarm device, 10 control unit, 16 pulse generator, 20 low-pass filter, 22 filter resistor, 24 filter capacitor, 30 amplifier, 32 amplification transistor, 34 emitter resistor, 36 collector resistor, 50 piezoelectric buzzer, fb boundary frequency, fh High setting frequency, fl Low setting frequency, Rh On-duty ratio, S0, S1 acoustic signal, Ti intermittent period, V0, V1 amplitude, Vc voltage

Claims (4)

The acoustic signal is subjected to pulse width modulation so that an intermittent period (Ti) that turns on and off at a high set frequency (fh) higher than a predetermined boundary frequency (fb) appears at a low set frequency (fl) lower than the boundary frequency. A control unit (10) that variably controls an on-duty ratio (Rh) of the acoustic signal in the intermittent period;
A low-pass filter (20) for attenuating the signal component of the high set frequency in the acoustic signal output from the control unit and passing the signal component of the low set frequency of the acoustic signal;
A vehicular alarm device comprising: a piezoelectric buzzer (50) that emits an alarm sound in a vehicle when a voltage corresponding to the amplitude of the acoustic signal output from the low-pass filter is applied.   The vehicle alarm device according to claim 1, wherein the high set frequency is set to a frequency of a sound wave in a non-audible range.   The vehicle alarm device according to claim 1, wherein the intermittent period is fixed.   The amplifier (30) for generating the voltage to be applied to the piezoelectric buzzer by amplifying the amplitude of the acoustic signal output from the low-pass filter. The vehicle alarm device according to one item.

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