Speed alarm system for an automobile

[57] ABSTRACT

A speed alarm system for an automobile comprises a speed detector connected to the output of a generator for generating an output proportional in magnitude to a travelling speed of an automobile; a speed detector for detecting the travelling speed set to a predetermined level; an alarm signal generator operative to receive an output of the speed detector to generate two alarm signals displaced in phase from each other; and a sound reproducing device for generating from two speakers alarm sounds obtained by amplifying the outputs of the alarm signal generators.

Claims, 14 Drawing Figures

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ΓΆΤΕΝΪΕΟ JAN 71975

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PATENTED JAN 71975

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SHEET 3 OF 7

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PATENTED JAN 71975

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PATENTED JAN 71975

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SHEET 5 OF 7

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PATENTED JAN 71975

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SHEET 7 OF 7

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SPEED ALARM SYSTEM FOR AN AUTOMOBILE

BACKGROUND OF THE INVENTION

This invention relates to a speed alarm system of an automobile.

Recently, traffic accidents are increased in number with a wide acceptance of automobile and, particularly, excess speed results in an increased number of accidents.

A variety of devices are designed to give a warning to the drive when excess speed is attained. The speed alarm devices are designed to light a lamp and sound a buzzer when a present speed is encountered. A lamp alarm is liable to be overlooked by the driver focussing his attention to the foreground. An alarm buzzer is difficult to draw the driver’s attention due to its monotonous tone.

An object of this invention is to provide a speed alarm system for an automobile, capable of giving forth alarm sounds which easily attract the driver’s attention.

SUMMARY OF THE INVENTION

A speed detector is incorporated into an automobile and connected to the output of a generator for generating an output proportional in magnitude to the output of a travelling speed of an automobile. A speed setting device is coupled to the speed detector, is capable of being set to a predetermined speed and is operated when an output level corresponding to the setting speed is received from the speed detector. An alarm sound signal wave generator is operated by the operation of the speed setting device and generated desired alarm sound signal waves from two output terminals of the signal wave generator. The alarm sound signal wave generator is connected to a dual channel sound generating signal and generates alarm sounds from two speakers connected to the sound reproducing device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an automobile speed alarm system according to this invention;

FIGS, 2A and 2B are schematic circuits of FIG. 1;

FIG. 3 is a graphical representation showing a relation between the output voltage of a generator and the speed of an automobile;

FIG. 4 is a waveform of each part of a circuit of FIG. 2;

FIG. S is a graphical representation showing a relation in sound volume between alarm sounds and car stereo performance sounds;

FIG. 6 is a perspective view showing the interior of an automobile equipped with a speed alarm system;

FIG. 7 shows a connection between the speed alarm system, a generator and a car stero set;

FIG. 8 is a perspective view showing the speed alarm device;

FIG. 9 is a side cross-sectional view showing the speed alarm device;

FIG. 10 is a perspective view showing a speed setting switch section;

FIG. 11 is a perspective view showing a mounting bracket of the speed alarm system; and

FIGS. 12 and 13 are a front view and a side view, respectively, of the speed alarm system incorporated into the speed alarm system.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1 there is shown a speed setting device 20 adapted to be set selectively to a control speed as stipulated in a Road Traffic Law. When the travelling speed of an automobile reaches the setting speed, that is, the travelling speed exceeds the setting speed set at the speed setting device 20, a speed detector 21 is operated. The speed detector is coupled to an alarm signal generator 22. An output signal of the detector as generated upon coincidence of the setting speed with the travelling speed is fed to an alarm signal generator 22 to cause it to be operated. The alarm signal generator 22 has two output terminals and adapted to generator alarm signals shifted in phase from each other. The output terminals of the alarm signal generator are connected, respectively, to the input terminals corresponding to the left and right channels of the dual channel sound reproducing device 23.

The sound reproducing device is a dual channel sound reproducing device, for example a car stereo set such as a stereo tape player or a car stereo cartridge tape recorder and an FM car stereo receiver. At the normal time, a stereophonic performance or broadcasting is effected and, at the warning time, alarm signals from the alarm signal generator 22 are amplified and generated from a speaker. At this time, a stereophonic performance sound is also generated from the speaker. The sound reproducing device is also so designed that an electric power is supplied from another line when a speed detecting device 21 is operated. Even when the car stereo set is not used, alarm sounds can be generated due to a constant supply of electric current from said another line.

Let us now explain the detailed circuit of the alarm sound system of FIG. 2.

A generator 25 incorporated into an automobile generates an AC output voltage nearly proportional to the travelling speed of the automobile, as shown in FIG. 3. One end of the generator is grounded and the other end of the generator is connected to a speed level setting adjuster 26. The level setting adjuster consists of resistors R1-R6 and a multicontact change-over switch 27. Each of the resistors R1-.R6 has one end connected to the output of the generator 25 and the other end connected to any one of the contacts of the change-over switch 27. A neutral contact of the changeover switch is grounded through a resistor R7 and connected to a rectifier circuit 28 consisting of a diode DI and a smoothing capacitor Cl. The level setting adjuster 26 is constituted of resistors whose resistances are accurately determined to correspond to respective travelling speeds based on the Road Traffic Law and, therefore, a more accurate speed setting is obtained than it is constituted of a potentiometer or continually variable resistor.

The output of the rectifying circuit 28 is connected through a biasing resistor R9 to a Schmitt circuit 29 including a first and a second transistor Tri and Tr2 and grounded through a resistor R8. The output of the Schmitt circuit, that is, the collector of the transistor Tr2, is connected through a resistor R33 to the base of a third transistor Tr₃. The collector of the third transistor is coupled to the base of each of parallel-connected amplification transistors Tr4, Tr5 and Tr6 in a. drive circuit 30.

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The alarm signal generating circuit 22 is connected through a resistor 10 to the output of the drive circuit 30 and consists of a modulation wave oscillating circuit 31, a first and a second modulation wave form shaping circuit 32 and 33, a sound signal oscillation circuit 34 and an output circuit 35 consisting of a differential circuits 351 and 352 and a filter 353. The modulation wave signal oscillating circuit 31 includes two transistors Tr7 and Tr8 and constitutes a conventional astable multivibrator having two output ends. The first modulation wave form shaping circuit 32 consists of a capacitor C3a connected to one output of the astable multivibrator 31, a breeder or voltage dividing circuit consisting of resistors R13a and R14a, a transistor circuit including a resistor R15a and a transistor Tr9 connected to the breeder circuit, and a wave form shaping capacitor C4a connected between the emitter and the collector of the transistor Tr9. The second modulation wave form shaping circuit 33 constitutes the same circuit arrangement as the first modulation wave form shaping circuit and includes a capacitor C3b, resistors R13b, R14b and R15b, a transistor TrlO and a capacitor C4b. The outputs of both the modulation wave form shaping circuits 32 and 33 are coupled, respectively, to diodes D4 and D5 of the output circuit 35. The sound signal oscillating circuit 34 constitutes an astable multivibrator including transistors Trll and Trl2, resistors R16-R19 and capacitors C5a and C5b. The output of the astable multivibrator 34 is coupled on the diodes D4 and D5. The diode D4 is coupled through a first DC blocking circuit 351 consisting of a blocking capacitor C6 and a resistor R20 to a first filter circuit 353 consisting of resistors R22, R23, R24 and capacitors C8 and C9. The diode D5 is coupled through a second DC blocking circuit 352 including a blocking capacitor C7 and a resistor R21 to a second filter circuit 354 consisting of resistors R25, R26 and R27 and capacitors CIO, and Cll. The outputs from both the filter circuits are supplied, respectively, to electric amplifiers 44L and 44R of the sound reproducing device 23.

The dual channel sound reproducing device 23 is a car stereo tape player having a left channel including a reproducing head 40L, a preamplifier 41L, a sound volume adjuster 42L, a level setting resistor 43L and the electric amplifier 44L; a right channel including a reproducing head 40R, a preamplifier 41R, a level setting resistor 43R and the electric amplifier 44R; a series connection of an electric power switch 45, a diode 46 and a smoothing circuit 47; and a tape drive motor 48 connected between ground and a junction present between the power switch 45 and a diode 46. The diode 46 is provided to prevent a supply of an output from the drive circuit to the motor 48 when the power switch 45 is opened. The collector of each of transistors Tr4, Tr5 and Tr6 in the drive circuit 30 is connected in a forward direction to a diode D2. The diode D2 is provided to prevent a supply of a DC current into the drive circuit 30 when the power switch 45 is thrown in.

Explanation is now made of the circuit operation of the speed alarm system.

First of all, the level setting adjuster 26 is set to a control speed, 80 km/h for example, as stipulated by the Road Traffic Law. The generator 25 generates an AC output voltage nearly proportional to a travelling speed of an automobile, as shown in FIG. 3. The AC output voltage so generated is set, through resistors R3 and R7 of the level setting adjuster 26, to a predetermined level, rectified in a rectifying circuit 28 consisting of a diode DI and a capacitor Cl and supplied through a resistor R9 to the base of the transistor Tri of the

Schmitt circuit 29.

Suppose that the travelling speed of the automobile exceeds a setting speed and the output voltage of the rectifying circuit reaches a predetermined potential.

Then, the transistor Tri is turned ON and the transistor Tr2 is turned OFF. When the collector potential of the transistor Tr2 is raised to cause the transistor Tr3 to turn ON, the transistors Tr4, Tr5 and Tr6 of the drive circuit 30 are operated. This causes a DC power to be supplied through a resistor R10 to an alarm signal generator 22 and through diode D2 to the smoothing circuit 47 of the sound reproducing device 23. When the DC power is supplied to the alarm signal generator 22, the astable multivibrator 31 is operated to cause signals opposite in phase to each other, as shown in FIGS. 4a and 4b, to be generated from the two output terminals of the astable multivibrator. These signals are shaped, by the first and second modulation wave form shaping circuits 32 and 33, to wave forms shown in FIGS. 4c and 4d. The outputs supplied through resistors R31 and R32 from the first and second modulation circuits 32 and 33 modulate output signals supplied through diodes D4 and D5 from the astable multivibrator 34. The output signals of the astable multivibrator 34 and the modulated signals are respectively shown in FIGS. 4e to 4g. The DC portions of the modulated signals are eliminated at the first and second blocking circuits 351 and 352 to obtain signals as shown in FIGS. 4H and 41. These modulated signals are filtered at the first and second filter circuits to obtain wave forms shown in FIGS. 4j and 4k. Since the two modulated signals or alarm signals so filtered are obtained through modification of the output signals of the astable multivibrator 34 by the signal alternately generated from the two output terminals of the astable multivibrator 31, these alarm output signals are shifted in phase from each other. When these alarm signals, after amplified by the amplifiers 44L and 44R of the stereo player set, are supplied to the left and right channel speakers 24R and 24L intermittent sounds shifted in time from each other are generated from the left and right speakers to alarmingly provide stereophonic alarm signals. At this time, an indication circuit 37 receives intermittent signals alternatively from the first and second modulation circuits 32 and 33 to cause the transistors Trl3 to effect an on-off operation. This causes a lamp 38 connected to the transistor Trl3 to flicker in synchronization with the alarm sounds of speakers, thereby too attracting the attention of the driver.

With the above sound reproducing system, when a cartridge is incorporated into the car stereo set to cause the power source switch 45 of the stereo set to be thrown in to permit the car stereo set to be played, the alarm sounds are generated from the speakers together with performance sounds where the alarm device is operated. Suppose that the car stereo set is not in a playing position when the alarm device is operated, the drive circuit 30 feeds DC electric powers to the amplifiers of the car stereo set, where they are amplified. The amplified alarm signals are supplied to the speaker, and alarm sounds are generated from the speakers.

The alarm device is so designed that its sound volume is varied according to the sound volume set up by the adjuster of the car stereo set, with a predetermined dif3,859,629 ference in level left therebetween. That is, an alarm signal current is flowed through resistors R24 and R27 of the filter circuit and resistors 43L and 43R into the sound volume adjusting resistors 42L and 42R to cause a voltage drop to take place across the adjusting resistors 42L and 42R and resistors 43L and 43R. The voltage drop across the resistors 42L and 42R and 43L and 43R provides an input voltage to the amplifiers 44L and 44R. Therefore, adjustment of the sound volume adjusting resistors 42L and 42R causes the level of the level alarm signal to be varied at the input terminal of the amplifiers 44L and 44R. When the sound volume is so adjusted, alarm sounds are generated from the speaker with a predetermined difference in level between the performance signal and the alarm signal. The difference in level between the signals, or sound volumes, is provided by selecting a desired value of the resistors 43L and 43R. The sound volume level relation between the alarm sound and the performance sound is shown in FIG. 5.

The alarm system is so designed that an operational accuracy is not varied relative to a temperature variation. A circuit device using a semiconductor element is generally susceptible to influence due to a temperature variation. For this reason, such circuit device is provided with a temperature compensating means. However, provision of the temperature compensating means makes the circuit of the device intricate in design and, furthermore, an expensive circuit device results. According to the alarm system of this invention, a temperature compensation is made by a generator having an opposite temperature characteristic to that of a semiconductor and no particular temperature compensating means is necessary. That is, when a temperature variation takes place at the AC generator, an output level of the AC generator whose generating voltage is dropped with a temperature rise is varied in an opposite direction to a detection level of the Schmitt circuit whose temperature is varied and the output variation of the semiconductor circuit device is cancelled by the output variation of the generator. The device as a whole has, in effect, a constant temperature characteristic.

Let us now explain the above alarm system as incorporated into an automobile.

As shown in FIG. 6, a speed alarm device 50 is mounted to a dash-board 51 at the front of the driver’s seat of the automobile, and electrically coupled to a sound reproducing device 23, a car stereo set for example, adjacent to the device 50. The output line of the car stereo set 23 is connected to two speakers 24L and 24R disposed at the rear of a backward seat of the automobile. The speed alarm device, as shown in FIG. 7, is coupled to the output of a generator 56 for generating an electric power through rotation of the engine 54. The generator 56 is connected to a speedometer 57. The generator 56 is mechanically connected to a shaft of a flexible cable 55 toward speedometer 57.

The speed alarm device 50 has a metal fitting 61 by means of which, as shown in FIG. 8, an indication window 58 is mounted at the front of a casing 59 and an operating knob 60 is secured to the bottom of the casing 59. A printed circuit board 63, onto which electrical parts elements 62 constituting an electrical circuit shown in FIG. 2 of the device are mounted, is accommodated into the alarm device 50 as shown in FIG. 9. The rear end of the substrate 63 is inserted into a groove 73 provided between projections 71 and 72 projecting from the back face of the casing 59. A preset switch 64 of the speed setting device is provided at the forward bottom portion of the casing. A shaft 65 extends through the bottom of the casing and towards the outside of the casing. An operating knob 60 is fitted over an operating section 66 of the shaft 65. The preset switch 64 is secured fixedly to the bottom of the case by a fastening nut 67α and a nut 67b. The print substrate 63 is arranged on the top of the speed setting switch 64 and electrically connected to a switch contact and an electrical circuit of the print substrate. A rotatable long shaft 68 is connected integrally to the shaft 65 of the speed setting switch 64 and extends vertically in the casing 59. A rotatable drum 69 is mounted to, and rotated with, the shaft 68. The rotatable drum 69 is made of, for example, a transparent or semitransparent synthetic resin, and characters, such as 40 km/h, 60 km/h, 80 km/h etc., representative of respective control speeds are printed on the outer periphery of the drum 69. A doughnut-shaped cavity 74 is formed within the drum 69. An indication lamp 70 is disposed opposite to an indication window 58 and within the cavity 74. The indication lamp is mounted on the print substrate 63 and electrically connected to the electrical circuit of the print substrate.

With the above structure, when the operating knob 60 is rotated stepwise, the speed setting switch 64 is switched to cause the rotatable drum 69 to be rotated to permit the characters of the control speeds visually observed from the indication window 58 to be varied. When the operating knob 60 is stopped upon appearance of a desired character, the alarm device 50 is set to a speed control indicated by the character.

A front covering 75 having the indication window 58 is formed from synthetic resin, plastics, for example, and detachably mounted to the casing body 59. A groove 76 is provided in the upper inner surface of the front cover 75 and a projection 77 is provided on the lower outer surface of the front covering. The upper forward end of the casing body 59 has a section 78 bent into L-shape in cross section and an engaging pawl 79 at the lower forward end of the casing body. The front covering 75 is mounted to the casing 59 by engaging the forward end of the bent section 77 with the groove 76 while engaging the projection 77. The engaging pawl 79 is located in the recess 80 provided in the bottom of the casing 59, as shown in FIG. 10, in a manner that the shaft 65 of the preset switch extends through the recess and the pawl. The engaging pawl 79 consists of a washer portion 81, a leg portion and a pawl. When the front cover 75 is mounted to the casing 59, the pawl 83 is snap-fitted on the projection to hold the front covering 75 in position. When the pawl 83 is unsnapped from the projection, the front cover 75 is removed from the front covering 75.

Let us now explain the method in which the speed alarm device 50 is incorporated into the dash-board 51 of an automobile.

As shown in FIG. 11, a bracket 85 has a frame 86 and a side plate 87 provided on one side of the frame. Two openings 88 are provided one at one side and one at the other side of the frame 86. At the top surface of the frame are formed three openings 89. Three openings 90 are provided at the side plate 87. When the alarm device 50 is mounted through the bracket 85 to the bottom portion of the dash-board of the automobile,

3,859,629 the bracket 85 is mounted to the lower portion of the dash-board, as shown in FIG. 12, by a bolt 91 passed through the central opening provided at the top surface of the bracket 85. The bracket arm 61 is mounted to one side of the bracket 85 in a manner to permit a hole 5 61a of the bracket arm to align with the opening 88 of the bracket. The alarm device 50 is secured to the bracket 85 by bolt and nut means inserted into the aligned hole and opening.

As shown in FIG. 13 the alarm device is mounted 10 through the bracket 85 to the dash-board 51 by inserting a bolt into the opening of the side plate 87 of the bracket 85.