Abstract:
An apparatus measures and indicates the speeds of a vehicle at the beginning and end of braking of the vehicle by counting as many vehicle speed representative pulse signals as indicative of the speed per hour of the vehicle which are gated during the time that the desired number of clock pulses are counted in response to the beginning and end of braking of the vehicle, respectively.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a braking vehicle speed measuring apparatus for measuring the initial and final braking speeds of a vehicle under braking. 
     Known systems for measuring the initial braking speed of a vehicle during the initial braking period and the final braking speed upon completion of the braking have been such that at the beginning and end of the braking action the measure reads the vehicle speeds by means of the speedometer attached to the vehicle or alternatively the measurements are made by such means as a fifth wheel attached to the vehicle exclusively for vehicle speed measuring purposes. Another system has been proposed in which the output of a vehicle speed sensor designed to generate a number of pulses proportional to the vehicle speed is subjected to digital-to-analog conversion and then recorded in a data recorder or the like and at the same time the initial and final braking speeds are obtained from the marked beginning and end of the braking action. 
     However, these known systems have the disadvantages of being low in measuring accuracy, requiring the attachment to a vehicle of such large means as a fifth wheel, being unable to easily measure the braking vehicle speed of a vehicle, etc. 
     SUMMARY OF THE INVENTION 
     With a view to overcoming the foregoing deficiencies in the prior art, it is the object of the present invention to provide an improved braking vehicle speed measuring apparatus in which while the speed of a vehicle is measured at predetermined intervals irrespective of braking of the vehicle, noting the fact that the vehicle speed does not change rapidly due to the inertia of the vehicle, the vehicle speed just before the beginning of braking is detected as the initial braking speed and the vehicle speed just after the completion of the braking is detected as the final braking speed and which is thus easily attachable to any types of vehicles, excellent in accuracy and compact in construction. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing the overall construction of an embodiment of the present invention. 
     FIG. 2 is a circuit diagram of the control signal generating unit shown in FIG. 1. 
     FIG. 3 is a circuit diagram of the vehicle speed detecting unit shown in FIG. 1. 
     FIG. 4 is a circuit diagram of the initial speed measuring unit shown in FIG. 1. 
     FIG. 5 is a circuit diagram of the final speed measuring unit shown in FIG. 1. 
     FIG. 6 is a circuit diagram of the indicator unit shown in FIG. 1. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The present invention will now be described in greater detail with reference to the illustrated embodiment. 
     Referring to FIG. 1 illustrating the overall construction of the embodiment, numeral 1 designates a control signal generating unit for receiving at its terminal 1a the ON or OFF signal of a brake switch operatively associated with the brakes of a vehicle so as to detect braking of the vehicle and generate control signals for suitably operating the various units. Numeral 2 designates a vehicle speed detecting unit for generating a number of pulse signals proportional to the speed of the vehicle, 3 an initial speed measuring unit for measuring the vehicle speed at predetermined intervals irrespective of the presence or absence of the braking and memorizing the vehicle speed just before the beginning of the braking in response to a control signal from the control signal generating unit 1, and 4 a final speed measuring unit for measuring the final braking speed in response to a control signal applied from the control signal generating unit 1 in a predetermined time interval just following the completion of the braking. Numeral 5 designates an indicator unit for digitally indicating the measurements of the initial speed measuring unit 3 and the final speed measuring unit 4. 
     The operation as well as the circuit construction of the various units of FIG. 1 will now be described with reference to their detailed circuit diagrams shown in FIGS. 2 to 6. Referring to FIG. 2 showing the control signal generating unit 1, the wiring cable interconnecting the brake switch and the brake warning light of the vehicle is extended and connected to the terminal 1a. As a result, when the brakes are applied, the vehicle battery voltage is applied to the terminal 1a and the voltage is hereinafter referred to as a brake signal BR. Numeral 11 designates a limiter and waveform reshaping circuit for the brake signal, which comprises clipper diodes 111 and 112, a noise absorbing capacitor 113, a NAND gate 114 which exhibits hysteresis to prevent generation of noise due to chattering of the switch, etc. The output signal of the NAND gate 114 is designated as BR. Numeral 12 designates a clock signal generating circuit comprising a CR oscillator 121, a waveform reshaping NAND gate 122 which exhibits hysteresis and a frequency divider 123 employing the known TOSHIBA IC TC4040, thus generating a clock signal φ 2  of about 1 KHz at a terminal 1e connected to the Q 2  terminal of the frequency divider 123. Numeral 13 designates a control circuit responsive to the output of the brake signal limiter and waveform reshaping circuit 11 and the clock signals φ 2  to generate an initial speed latch signal L at a terminal 1b and a final speed measurement start signal ST at a terminal 1c and it comprises a latch signal generating circuit 131 and an inverter 132. When the brake signal BR is applied to the terminal 1a, the signal BR goes to a &#34;0&#34; level. This releases the resetting of the latch signal generating circuit 131 of the control circuit 13 so that an initial speed latch signal L is generated from its first stage 1 and then its second stage 2 goes to a &#34;1&#34; level, thus causing its clock enable terminal CE connected to the second stage to go to the &#34;1&#34; level and thereby completing a series of operations. The inverter 132 inverts the signal BR and the resulting signal is delivered as a final speed measurement start signal ST. 
     In FIG. 3 showing the vehicle speed detecting unit 2, numeral 21 designates a vehicle speed sensor including a magnet 211 connected to the speedometer cable shaft and a reed switch 212 for generating four pulse signals WH for every revolution of the magnet 211, and 22 a reshaping circuit for reshaping the signal from the vehicle speed sensor 21 and it comprises a resistor 221, a noise absorbing capacitor 222, a transistor 223, a noise absorbing capacitor 224 and a NAND gate 225 which exhibits hysteresis to prevent generation of noise due to chattering of the switch. The resulting output signal W represents the reshaped vehicle speed signal. Numeral 23 designates a frequency multiplier circuit for receiving the vehicle speed signal W and the clock signals φ 2  at its terminal 2a to generate at its terminal 2b a pulse signal 2W of a frequency which is two times that of the signal W, and it comprises an inverter 231, counters 232 and 233 each employing the known TOSHIBA IC TC4017 and an OR gate 234. 
     In FIG. 4 showing the initial speed measuring unit 3, numeral 31 designates an initial speed gating signal generating circuit comprising an OR gate 311, a counter 312 employing the TOSHIBA IC TC4040, an inverter 313, a decade counter 314 employing the TC4017 and an AND gate 315. Assuming now that the output Q n  of the counter 312 goes to the &#34;1&#34; level at a certain time, the output of the OR gate 311 connected to the output Q n  goes to the &#34;1&#34; level and thereafter the application of the clock signals φ 2  to the clock terminal CL is prevented until a &#34;1&#34; level signal is applied to the reset terminal R and the output Q n  goes again to the &#34;0&#34; level. When the output Q n  of the counter 312 goes to the &#34;1&#34; level, the inverter 313 connected to the output Q n  generates a &#34;0&#34; level output. As a result, the resetting of the decade counter 314 is released so that in response to the clock signals φ 2  applied through a terminal 3a, a single pulse signal is generated from each of its first and second stages 1 and 2. The output of the first stage 1 is a latch signal l and the output of the second stage 2 is a reset signal r. Since the second stage 2 of the counter 314 is connected to the reset terminal R of the counter 312, when the reset signal r is generated, the counter 312 is reset so that its output Q n  goes to the &#34;0&#34; level and the OR gate 311 is opened, thus allowing the application of the clock signals φ 2  to the counter 312. Then the output Q n  again goes to the &#34;1&#34; level at a certain later time and thereafter the previously mentioned operations are repeated. The interval between the time that the output Q n  goes to the &#34;0&#34; level and the time that the output Q n  goes to the &#34;1&#34; level or the time interval during which the output of the inverter 313 is held at the &#34;1&#34; level is determined by the oscillation frequency of the CR oscillator 121. In this case, the oscillation frequency is selected to become 706 msec in accordance with the following calculation. When the vehicle is running at 60-Km/h, the speedometer cable shaft is rotated at 637 rpm and the frequency of the vehicle speed signal W is given by ##EQU1## This frequency is increased by two times so that the frequency of the signal 2W applied to the terminal 3b becomes 84.92 Hz and thus ##EQU2## is required for counting the signals so as to give &#34;60&#34; (corresponding to the vehicle speed in terms of Km/h). As a result, the output of the inverter 313 is maintained at the &#34;1&#34; level for 706 msec during which the AND gate 315 is opened to pass 60 pulse signals applied through the terminal 3b. The output of the AND gate 315 represents an initial speed data V a . 
     Numeral 32 designates an initial speed counting circuit for counting and latching the initial speed data V a  and it comprises BCD counters 321, 322 and 323 each using the TOSHIBA IC TC4518 and data latches 324, 325, 326, 327, 328 and 329 each using the TC4042. The data latches 324, 325 and 326 are responsive to the latch signal l to latch the contents of the BCD counters at intervals of 706 msec irrespective of the brake signal, and the data latches 327, 328 and 329 latch the contents of the data latches 324, 325 and 326 in response to the initial speed latch signal L which is applied to a terminal 3c after the application of the brake signal. The thus latched data represents the initial braking speed. The outputs of the data latches 327, 328 and 329 represent three BCD digits at output terminals A 1  to D 1 , A 2  to D 2  and A 3  to D 3 , respectively, with the A 1  to D 1  representing the least significant digit. 
     In FIG. 5 showing the final speed measuring unit 4, numeral 41 designates a final speed gating signal generating circuit comprising an OR gate 411, a counter 412 using the TOSHIBA IC TC4040, a NOR gate 413, a decade counter 414 using the TC4017 and an AND gate 415. Assume now that the brakes are applied at a certain time and are released at a later time. In response to the application of the brakes, the final speed measurement start signal ST applied to a terminal 4b goes to the &#34;1&#34; level and the output Q n  of the counter 412 goes to the &#34;0&#34; level. In response to the releasing of the brakes the signal ST goes to the &#34;0&#34; level so that the resetting of the counter 412 is released and the counter 412 starts to count the clock signals φ 2  applied through a terminal 4a and the OR gate 411. At this time, the two inputs of the NOR gate 413 are at the &#34;0&#34; level so that the reset terminal R of the decade counter 414 is at the &#34;1&#34; level and the counter 414 is not in operation. In the like manner as the initial speed measuring unit 3, after the expiration of 706 msec the output Q n  of the counter 412 goes to the &#34;1&#34; level so that the resetting of the decade counter 414 is released and the counter 414 generates a latch signal l&#39; and a reset signal r&#39;. When the output Q n  goes to the &#34;1&#34; level, the counter 412 stops counting. A final speed data V r  represents the signals 2W applied to a terminal 4c and passed during the interval of 706 msec. Numeral 42 designates a final speed counter circuit for counting and latching the final speed data V r  and it comprises BCD counters 421, 422 and 423 each using the TOSHIBA IC TC4518 and data latches 424, 425 and 426 each using the TC4042. The data V r  is counted by the BCD counters 421, 422 and 423 and then latched in the data latches 424, 425 and 426 in response to the latch signal l&#39;. The contents of the BCD counters are reset in response to the reset signal r&#39;. The outputs of the data latches 424, 425 and 426 represent three BCD digits at output terminals A&#39; 1  to D&#39; 1 , A 2  &#39; to D 2  &#39; and A 3  &#39; to D 3  &#39;, respectively, with the A 1  &#39; to D 1  &#39; representing the least significant digit. 
     In FIG. 6 showing the indicator unit, numeral 51 designates an initial speed indicating circuit, and 52 a final speed indicating circuit. The circuits 51 and 52 respectively comprise decoders 511, 512, 513 and 521, 522, 523 each using the TOSHIBA IC5002, current limiting resistors 514 and 524 (each 7×3=21) and displays 515, 516, 517 and 525, 526, 527 each employing the TOSHIBA LED TLR-312. The BCD outputs of the initial speed measuring unit 3 and the final speed measuring unit 4 are converted by the decoders 511, 512, 513, 521, 522 and 523 to 7-segment signals which are in turn digitally displayed by the displays. 
     While, in the embodiment described above, the vehicle speed is indicated digitally by the digital displays, the vehicle speed may be indicated analogically on a meter through D/A conversion or the vehicle speed may be measured in the form of an output which can be recorded on a pen recorder or the like. 
     Further, while the presence or absence of braking is determined in accordance with the output signal of the brake switch, if the presence of braking is determined in dependence on the presence of an acceleration greater than a predetermined value, the application of the brakes may be sensed by a G sensor or acceleration sensor to use its output signal in place of the brake signal used in the above-described embodiment. 
     Further, it is possible to add a device for calculating an approximate braking energy in accordance with the initial and final braking speeds detected by the apparatus of this invention. 
     Still further, while, in the above-described embodiment, the vehicle speed sensor used generates four pulses per revolution, it is possible to replace it with one which generates a greater number of pulses so as to further improve the accuracy and decrease the vehicle speed measuring time. 
     It will thus be seen from the foregoing detailed description that the apparatus of this invention has a great advantage that the speed of a vehicle is measured at predetermined intervals irrespective of braking of the vehicle so that the vehicle speed just before the beginning of braking is detected as the initial braking speed and the vehicle speed just after the completion of the braking is detected as the final braking speed, thus making it possible to detect both the initial and final braking speeds with a very high degree of accuracy, making it possible to easily mount the apparatus and making the apparatus itself compact in construction.