Measuring and testing – Tire – tread or roadway – Tire inflation testing installation
Reexamination Certificate
2002-02-06
2003-09-02
Williams, Hezron (Department: 2855)
Measuring and testing
Tire, tread or roadway
Tire inflation testing installation
C073S146000
Reexamination Certificate
active
06612164
ABSTRACT:
TECHNICAL FIELD
The present invention generally relates to sensors, and more particularly relates to sensor for contactlessly measuring forces which act on the tire of a wheel, especially during driving.
BACKGROUND OF THE INVENTION
In view of the increasingly dense traffic and larger engines of motor vehicles, controlled intervention in the brake—and engine—system based on measured data of vehicle dynamics has attained greater significance, since errors in the driver's, driving behavior can be compensated to a certain extent in this way. The forces acting on the vehicle and, in particular, on the tires play a special part in these types of control operations. Whereas it is possible, as such, to obtain the driving dynamics data of a vehicle through the rotary behavior of the wheels of a vehicle, more recent developments strive to measure the forces acting on the tires of the vehicle in order to obtain an input value that is even more suitable for motor vehicle control systems.
Thus, for example, DE-PS 39 37 966 discloses the possibility of measuring the forces acting on a tire on all three coordinates by means of sensors positioned in the tire. This known principle is complicated and prone to failure. Another disadvantage of the prior-art solution is that it is difficult to mount the tires, since the sensor signals from the tire have to be transmitted to an amplifier on the rim and then from the amplifier to a sensor arranged on the rim, from where they are then contactlessly transmitted to the vehicle body. The above-mentioned document makes no statement concerning the type of transmission between the sensors and the amplifier within the tire. If such a transmission inside the tire is handled by means of lines, then mounting the tires becomes difficult because the connecting lines between the sensor and the amplifier inside the tire must not be damaged during the mounting process.
On the other hand, DE-OS 19744611 discloses that the distance of a measuring point on the inner surface of a tire can be measured by a sensor arranged on the rim without contacts in order to determine the air pressure in the tire.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to measure, in a simple manner, transverse forces and longitudinal forces acting on the tire during driving, with the above-mentioned advance work of inserting sensors in the tires and the problems involved in mounting the tires being avoided.
The object of the present invention is solved with method for contactlessly detecting the change in position of a measuring point (
11
) on or in a tire (
1
) on the basis of a force (
7
) by means of a sensor (
9
) acting on the tire (
3
) of a wheel especially during driving, with the sensor (
9
) being in a fixed stationary position in relation to the rim (
2
) of the wheel, wherein a source of radiation is present and by means of the sensor the change in position of the measuring point (
11
) in the longitudinal and/or transverse direction (y,x) in relation to the running surface of the tire is detected.
Hence, the invention in principle consists of measuring, by means of a sensor arranged on the rim, the change in position of at least one measuring point on the tire in a longitudinal direction and, in particular, also in a transverse direction in relation to the running surface of the tire, thereby determining the forces.
This gives rise to numerous advantages. In principle, it is now possible to contactlessly measure forces in the tire contact area. Since the sensor (or sensors) are not embedded in the tires, the sensor is not lost when the tire is changed. Due to the contactless detection of the change in position of the measuring point, it becomes much easier to mount the tires since there are no connecting cables between the tire and rim. Moreover, the sensor is extensively protected against being damaged by particularly serious tire deformations (driving over edge of sidewalk, flat tire). In addition, the fact that the sensors are not arranged in the running surface of the tire should have a positive effect on the performance of the tire and its load-carrying ability.
SUMMARY OF THE INVENTION
In order to mount the sensor in a particularly well protected manner, the present invention teaches fastening the sensor directly to the rim, whereby a particularly stable reference point is obtained. It is not necessary for the sensor to be in direct contact with the rim base. It can also be arranged on a toe connected to the rim, which protrudes radially outwards and, thus, exhibits a smaller distance to the inner surface of the tire. In this way, more precise measurements can be carried out under certain conditions, because the maximum shift angle as viewed from the sensor is increased significantly. Also, the sensitivity of the system can be increased by reducing the distance between the sensor and measuring point, since the contactless transmission distance for the radiation or electromagnetic fields being applied is shortened considerably.
The system of the present invention measures not only in a longitudinal direction (circumferential direction) and transverse direction of the running surface of the tire, but also (essentially) radially in relation to this. On the basis of the deflection of the running surface of the tire in the tire contact area that can be determined in this way, important parameters regarding vehicle dynamics such as, for example, tire pressure, load of the vehicle, strength of the running surface etc., can also be determined.
Basically, the measuring point can be located anywhere on the tire provided it is ensured that the sensor can detect changes in the position of the measuring point in the desired directions. Thus, for example, the measuring point may be arranged on the sidewall of the tire for measuring the circumferential direction. Moreover, it need not be on the surface of the inner surface of the tire, but can also be inserted in the tire, as long as the sensor can definitely measure changes in position.
If the measuring point is positioned on the inner surface of the tire, it can also be designed in a particularly simple manner as a passive transducer which reflects the radiation emitted by the sensor in a suitable way to the sensor. If transversal forces are to be measured, the measuring point should be located below the running surface of the tire, since this is where the greatest movements of the measuring point in a transverse direction occur.
The location information on the measuring point detected by the sensor are particularly accurate when the sensor operates at the same angle-of-rotation position as that of the measuring point of the wheel, so that such disturbance variables as, for example, torsion in both directions due to the tire contact area, vibration knot in the tire, imbalances etc. can be eliminated by forming the difference of the measured values. The angle-of-rotation position can be determined with sufficient accuracy by means of so-called maximum formation. For this purpose, for example using only one single measuring point, the transverse displacement in the x direction and/or the change in distance in the z direction (deflection) is measured at constant time intervals, which, given constant rotational speeds, correspond to equal angle-of-rotation distances.
If the measuring point passes through the tire contact area, a comparably large change in the z and x directions will be detected, and this can be used for determining the maximum displacements and, hence, the angle-of-rotation position of the wheel. It is not necessary for the location coordinates of only one single measuring point to be detected always during one certain angle-of-rotation position only in order to determine the active forces. Rather the same measuring point (or also several measuring points) can be measured one after the other by one single or several sensors in different angle positions. This, for example, may be important if the deflection of the tire contact area is to be related to the distance of the measuring point without
Continental Teves AG & Co. OHG
Ferguson Marissa
Williams Hezron
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