Method and gauge for measuring the tread depth of a motor vehicl

Details Method and gauge for measuring the tread depth of a motor vehicl Method and gauge for measuring the tread depth of a motor vehicl

1997-01-24

1999-04-20

Biegel, Ronald

Measuring and testing

Tire, tread or roadway

Tire inflation testing installation

356 308, 356356, G01B 1102

Patent

active

058958452

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The invention relates to a method and a measuring device for measuring the tread depth of of a tyre of a motor vehicle comprising: surface of the motor vehicle tyre to generate a light spot thereon; spot; and measured value indicative of the tread depth of one or more tread grooves of the tyre tread.
The tread pattern of tyres of motor vehicles is a quite essential safety feature. The tread of the tyre permits rain water on the road surface to flow off laterally, whereby floating of the tyre and loss of ground contact (aquaplaning) is avoided. This is of particular importance with modern passenger cars driving at high velocity. Therefore, a minimum depth of the tread is laid down by law in many countries. In Germany, for example, this minimum depth is 1.6 millimeters. Even with a tread depth of less than 3.0 millimeters, the water displacement is reduced by 30 percent of the value obtained with new tyres. The tread of motor vehicle tyres is subjected to heavy wear. This wear can, however, only difficultly be recognized by the owner of the vehicle. Tread depth is measured, if at all, from time to time in a repair shop, where measuring instruments for the measurement thereof are available.


PRIOR ART

German patent application 4,316,984 discloses a method and a device for automatically determining the tread depth of motor vehicle tyres. A partially transparent measuring plate is provided on the floor of a measuring station. A measuring head is located below the measuring plate. The measuring head has a laser and an image resolving sensor as a triangulation unit. In order to measure the tread depth, the tyre rolls over the measuring plate or the tyre is placed on the measuring plate. Then, the laser generates a light spot on the tread surface. The position of the light spot is observed by the sensor. The output signals from the sensor are applied to a signal processing unit, which determines the measure of the tyre tread. The measuring head is mounted on a carriage and is movable transversely to the rolling direction of the tyre.
With the device described in this German patent application 4,316,984, measurement of the tyre tread, necessarily, takes place under load, whereby the tread bars of the tyre tread are radially compressed in the region of the contact area of the tyre. In order to avoid a falsified measuring result, the laser is aligned such that the laser beam hits the tyre tread outside the contact surface of the tyre.
In order to be able to determine the tyre tread also with contaminated tyres, an outlet nossle for water directed to the tyre tread is provided in the region of the measuring plate, which directs a jet of water onto the tyre tread before or during measurement. Furthermore, a self-cleaning equipment is provided, which is to clean the measuring plate itself contaminated by the cleaning of the tyre.
This automatic device cannot ensure that an area of the tyre representative of the tyre tread is scanned. Therefore, in order to increase the probability of a representative measurement, a number of measuring plates and measuring heads are provided one behind the other in the rolling direction of the tyre.
German patent application 1,809,459 described a method and a device for automatically determining the tread depth of motor vehicle tyres in moving traffic. The measuring principle is similar to the measuring principle described in DE 4,316,984. A slot-shaped opening is provided in the road surface. A measuring device is arranged in a pit under this opening. A photoelectric contact is actuated by the tyre to be measured. This contact triggers an electronic flashlight. A narrow light strip is generated by the electronic flashlight. The light strip is sharply imaged on the tyre surface through the slot-shaped opening. Because of the tread of the tyre surface, the light strip is reflected as a stepped line, the height of the steps being proportional to the tread depth. The stepped light strip image is imaged on a photographic layer at an enlarged scale by a telescope and a came

REFERENCES:
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patent: 5245867 (1993-09-01), Sube et al.
patent: 5789668 (1998-08-01), Coe et al.
patent: 5790243 (1998-08-01), Herr

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