Communications: electrical – Audible indication
Reexamination Certificate
2000-03-14
2002-09-24
Hofsass, Jeffery (Department: 2632)
Communications: electrical
Audible indication
C340S384500, C340S384730, C116S13700R, C116S14200R
Reexamination Certificate
active
06456193
ABSTRACT:
The present invention relates to an electric horn of a motor vehicle, and particularly to a controlling method and apparatus of constant-frequency sound production for the electric horn. This invention also relates to a method for producing a signal source which has constant-frequency and continuous, adjustable duty cycles.
Nowadays, the basic sound-production theory for an electric horn of a motor vehicle is that the horn uses an electromagnget to drive a diaphragm, which then pushes the air and produces sound. The attractions of the electromagnet in that kind of horns are controlled by a contact. When the horn works, since the contact is operating at a very high frequency (generally 300-600 Hz), the on-off of the large electric current may generate a big spark. The corrosion of the contact caused by the electric spark makes the horn short life and at the same time continuously makes it deviate from the standard frequency and sound level both of which are set when the horn is off the production line. It brings about some disadvantages such as sound variations, sound reduction, and noise increase. Furthermore, it is very difficult to make the sounding frequency consistent with the inherent mechanical resonant point (frequency) of the horn to achieve the maximum sounding efficiency and maximum energy savings. In recent years with the developments of the electronic technology, various kinds of electronic devices have been invented to replace the contact, wherein an electric circuit instead of the contact is used to generate pulse currents (signals) for the electromagnet to drive the diaphragm. However, since they are adjusted in accordance with the inherent mechanical resonant point of each horn individually, all the electronic devices are constituted by circuits with their frequencies adjusted via resistors and capacitors, such as various kinds of multi-harmonic oscillators, time-base circuits, pulse width adjusting and controlling circuits. Since this kind of circuit is influenced by temperature and voltage features of semiconductor devices and resistors and capacitors, its output frequency being influenced by the environmental temperature and the motor vehicle's voltage, it can not be kept stably at the frequency consistent with the inherent mechanical resonant frequency of the horn. Therefore, although the above said horn has a longer life than the horns with a contact, it still has some disadvantages For example, the variations of the environmental temperature and the motor vehicle's voltage result in changes of the driving frequency of the circuit which finally cause the frequency of the horn sound to change and the output sound level greatly reduce. So far it has not been used widely.
A quartz crystal oscillator or a highly stable oscillator within some semiconductor chips has high stability of frequency, generally up to several dozens of PPM, but it can only generate a frequency of 2-1/N when using ordinary frequency dividing method. However, the inherent mechanical resonant frequency of a horn is at a frequency point between 300 and 600 HZ, therefore these general frequency dividing methods can't be used here. Although frequency division can be effected by a digital voltage controlled oscillator (VCO), it exists a problem that the pulse width can not be arbitrarily adjusted. So it is not applicable to be used in a horn for its too high cost relative to a horn and its complicated adjusting method.
An object of the invention is, with respect to the problems in the prior art, to design and provide a method and apparatus which uses a constant-frequency oscillator such as a quartz crystal oscillator to generate a stabilized reference signal, then via a monolithic-processor controls the reference signal, corrects its frequency according to the inherent acoustic parameters of each horn to generate a driving signal, and then makes the horn to achieve the optimum sounding effect when driven by the generated electronic driving signal, thereby overcomes the problems such as the sound variations (frequency variations) and unstable output sound level which are not solved in the prior art.
According to the first aspect of this invention, there is provided a control method of constant-frequency sound production for an electric horn, the above said method includes the following steps: generating a reference pulse signal of a constant frequency; pre-dividing the reference pulse signal generated by the generating step into a predetermined level which is near a certain frequency at the work frequency range of the horn; correcting the frequency of the pulse signal generated in the step of pre-dividing based on the predetermined frequency parameters of the horn so as for the frequency of output pulse signal to be consistent with the said certain frequency; adjusting the duty cycle of the frequency-corrected pulse signal based on the predetermined duty cycle parameters so as for the horn to achieve the optimum sounding characteristics; buffering and power-amplifying the signal output from the duty cycle correcting unit; then sending the buffered and amplified pulse signal into the electric horn to drive the electric horn to work.
In the above first aspect of this invention, the said certain frequency in the frequency correcting step is the mechanical resonant frequency of the electric horn.
According to the second aspect of this invention, there is provided a controlling method of constant-frequency sound production for an electric horn by microprocessor, the said method includes the following steps: generating a reference pulse signal of constant frequency; according to the predetermined frequency parameters of the horn and the predetermined duty cycle parameters, simultaneously adjusting the frequency and the duty cycle of the generated reference pulse signal using the microprocessor so that the pulse signal generated subsequently has a predetermined frequency and duty cycle, wherein the said predetermined frequency which is very near the mechanical resonant frequency and in the electric horn's working frequency range, the predetermined duty cycle is enough for the horn to achieve the optimum sounding characteristics; buffering and power amplifying the signal output from the adjusting step; then sending the buffered and amplified frequency signal into the electric horn so as to drive the electric horn to work.
According to the third aspect of this invention, there is provided an control apparatus of constant-frequency sound production for an electric horn, the said apparatus includes: a reference signal generating unit for generating a reference pulse signal of constant frequency; a pre-dividing unit for pre-dividing the reference signal generated by the reference signal generating unit into a predetermined level which is near a frequency in the working frequency range of the electric horn; a frequency correcting unit for correcting the frequency of the pulse signal generated in the pre-dividing unit based on the predetermined frequency parameters of the horn so that the output pulse signal frequency is consistent with a certain frequency within the working frequency range of the electric horn's diaphragm; a duty cycle adjusting unit for adjusting the duty cycle of the frequency-corrected pulse signal based on the predetermined duty cycle parameters so as for the horn to achieve the optimum sounding characteristics; a buffering and amplifying unit for buffering and power amplifying of the signal output from the duty cycle correcting unit; then sending the buffered and amplified pulse signal into the electric horn to drive the electric horn to work.
In the said apparatus in the above third aspect of this invention, the said pre-dividing unit, the said frequency correcting unit and the said duty cycle adjusting unit may be implemented by a monolithic-processor, and also may be constituted by a microprocessor or a which includes CPUL, I/O, RAM, ROM (EPROM, EEPROM, FLASH or other devices having similar memory function) or other similar devices. Furthermore, in the cas
Burns Doane Swecker & Mathis L.L.P.
Goins Davetta W.
Hofsass Jeffery
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