Speedometer tester
First Claim
1. In combination, with a driven vehicle wheel having a threaded element projecting outwardly therefrom and provided as a standard part thereof, apparatus for determining the accuracy of the vehicle speedometer comprising:
- a testing unit for evaluating the speed of said vehicle corresponding to the rotative speed of said driven vehicle wheel, said testing unit having means for receiving a train of electrical pulses corresponding to said wheel rotative speed, computing means responsive to said pulses for determining vehicle speed corresponding to said wheel rotative speed, and means for indicating to a testing unit operator said determined vehicle speed,a device for producing said electrical pulses at a repetition rate proportional to said wheel rotative speed,said device including a magnetic component threadably mounted on said element for rotation therewith along a predetermined path of travel about the rotative axis of said wheel, and pulse output means associated with said testing unit having a sensor independent of said vehicle, said testing unit having means for positioning said sensor at a point adjacent said component path of travel, andsaid sensor being capable of detecting the presence of said component as it passes the sensor in proximal relationship thereto to cause said pulse output means to deliver said train of pulses to said testing unit receiving means.
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Accused Products
Abstract
The speedometer of a stationary vehicle is evaluated for accuracy and calibrated regardless of vehicle tire size. The powered driven wheel or wheels is/are disengaged from road contact and a detachable housing member with a permanent magnet therein is releasably threaded onto the tire valve stem. A sensor associated with a testing unit is positioned adjacent the housing member so that as the wheels are driven at selected speeds, as indicated by the vehicle speedometer, a train of electrical pulses derived from the sensor is delivered to the testing unit at a rate proportional to the wheel rotative speed. This pulse information, in conjunction with a compensated reference signal generated by a scaler circuit, is processed by computing circuitry in the testing unit resulting in a digital display indicating the actual vehicle speed. The scaler circuit includes a tire size selector providing the testing unit with a number of reference frequencies corresponding to a range of selectable tire sizes.
9 Citations
16 Claims
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1. In combination, with a driven vehicle wheel having a threaded element projecting outwardly therefrom and provided as a standard part thereof, apparatus for determining the accuracy of the vehicle speedometer comprising:
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a testing unit for evaluating the speed of said vehicle corresponding to the rotative speed of said driven vehicle wheel, said testing unit having means for receiving a train of electrical pulses corresponding to said wheel rotative speed, computing means responsive to said pulses for determining vehicle speed corresponding to said wheel rotative speed, and means for indicating to a testing unit operator said determined vehicle speed, a device for producing said electrical pulses at a repetition rate proportional to said wheel rotative speed, said device including a magnetic component threadably mounted on said element for rotation therewith along a predetermined path of travel about the rotative axis of said wheel, and pulse output means associated with said testing unit having a sensor independent of said vehicle, said testing unit having means for positioning said sensor at a point adjacent said component path of travel, and said sensor being capable of detecting the presence of said component as it passes the sensor in proximal relationship thereto to cause said pulse output means to deliver said train of pulses to said testing unit receiving means. - View Dependent Claims (2, 3, 4, 5)
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6. Apparatus for testing the speedometer of a vehicle having a wheel provided with a tire which has a predetermined, unloaded radius in free rotation and which undergoes deformation when in contact with a road surface to present a smaller radius over the area of surface contact, said apparatus comprising:
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input means for producing a train of electrical pulses having a repetition rate proportional to the speed of rotation of said wheel, compensated oscillator means for producing a reference signal having a frequency representative of a reduced, effective radius of the wheel caused by said tire deformation, computing means coupled with said input means and said compensated oscillator means and responsive to said pulse train and said reference signal for determining the speed of the vehicle corresponding to the rotative speed of the wheel of said effective radius, and display means coupled with the output of said computing means for indicating the speed of the vehicle in predetermined units of measure.
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7. In apparatus for testing the accuracy of a vehicle speedometer where means is employed for producing a train of repetitive electrical pulses at a rate proportional to the speed of rotation of a driven vehicle wheel, said pulses used as input along with a generated reference signal for processing by computing means resulting in a determinable indication of vehicle speed the improvement comprising:
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said reference signal is generated by selectively operable means producing a frequency dependent upon the size of a tire on said wheel, including means for generating a time base signal of fixed frequency, and scaler circuitry responsive to said time base signal for dividing the frequency thereof by any number over a range of numbers corresponding to a range of tire sizes, and a tire size selector connected with said circuitry for selecting a divisor within said range of numbers to cause said scaler circuitry to deliver said reference signal. - View Dependent Claims (8)
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9. A method of testing the speedometer of a stationary vehicle having a driven wheel from which a treaded projection extends, said method comprising the steps of:
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raising said driven wheel to an elevation where a tire thereon is out of engagement with the road surface, removably securing a component to said projection having a characteristic that enables the component to be sensed as the wheel rotates and the component passes in proximal relationship to a sensor therefor;
driving said wheel, producing a train of electrical pulses having a repetition rate proportional to the speed of rotation of the wheel, in response to said sensor positioned adjacent the path of travel of said component, andprocessing said pulse train to determine the speed of the vehicle corresponding to the rotative speed of the wheel. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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Specification