Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Mechanical measurement system
Reexamination Certificate
1998-06-16
2003-03-04
Wachsman, Hal (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Mechanical measurement system
C702S056000, C702S076000, C702S183000, C702S191000, C381S071400, C381S086000, C700S280000, C703S008000
Reexamination Certificate
active
06529838
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of and an apparatus for predicting vehicle interior noise (vehicle interior sound), and more particularly, to a method of and an apparatus for predicting vehicle interior noise in which the vehicle interior noise caused by an irregular road surface can be easily predicted.
2. Description of the Related Art
In recent years, the demands of ordinary consumers for less noise have increased. In the same way, automobile buyers are also asking for vehicles making less noise. One way of reducing the noise of an automobile is to reduce the noise generated inside a vehicle by the excitation, via the suspension, of the vehicle body by the exciting force generated on the tires when a vehicle travels over a slightly uneven road surface such as a tough paved road or the like, (i.e. road noise). If the tire, as one part of the vehicle, is focused on as the phenomenon causing this road noise, then generally, from the standpoint of the vehicle, the quality of the vehicle is altered by the specifications of the tire, such as structure and quality of the materials. From the standpoint of the tire, the level and tone quality of the noise is altered by the specifications of the vehicle. Thus it is clear that the characteristics of both the tire and the vehicle are linked together. At sites of product development of tires or the like, it has been experienced, though not so frequently, that the superiority and inferiority between tires having different specifications may be reversed due to the specifications of the vehicles used in the running tests.
A method of predicting road noise which uses experimental values in combination is described in “Trend of the Study on Road Noise” (Automobile Technology, Vol. 49, No. 1, 1995, pp. 88-93).
In this reference, from a long-term point of view, it is ideal if vehicle internal noise up to a frequency of about 500 Hz such as road noise can be predicted by a calculation model using a finite element method or the like, and it is a matter of course that such research is being advanced. However, in the present state, high accuracy is not obtained even if the vibration analysis of a structual body such as a vehicle body having a complicated and enormous degree of variance is effected up to a high frequency (approximately 500 Hz). Accordingly, it is stated in the reference that the method using experimental values in combination is the mainstream.
This method using experimental values in combination is also called a transfer function synthesis method or a substructure synthesis method. In this method, a vehicle is separated into two components, i.e., a vehicle body and a suspension, and vibration noise within the vehicle is predicted from the vibration characteristics of each of the components. The vibration characteristics (i.e., transfer function or frequency response function) of each of the components may be obtained by the calculation model using the finite element method, or may be obtained by using experimental values. Alternatively, the finite element method and experimental values can be used in combination.
When the finite element method and the experimental value are used in combination, the vibration characteristics of the suspension are obtained by the calculation model using the finite element method, the vibration characteristics of the vehicle body, at a point located above the point where the suspension is mounted, are obtained by using a frequency response function which has been actually measured, and the system characteristics from axle input to vehicle interior noise are obtained in accordance with the transfer function synthesis method. In order to predict road noise by this method, it is necessary to have an exciting force input to the system. As a result, in this method, a driving-point innertance matrix (3×3) at the time the axle is excited is actually measured, the acceleration (three orthogonal axial directions) of the vehicle axle portion when the vehicle is actually running on a rough road surface is measured, and the measured value of this acceleration is multiplied by the inverse matrix of the innertance matrix. The exciting force input to the axle is thereby estimated by inverse operation. At this time, in order to minimize error s generated by using the measured data in the calculated values of the inverse matrix, the accuracy of prediction is improved by applying a mathematical technique such as singular value decomposition. The interior noise serving as an output is predicted by finally multiplying the exciting force input to the axle, which was estimated in this way, with the system transfer function.
A principal object of the above-described conventional road noise predicting method is to obtain a guideline for improving the two components on the vehicle side, i.e., the suspension and the vehicle body. The input from the tire is obtained as a representative value by the aforementioned inverse operation, and is provided only as a boundary condition. Accordingly, it is not appropriate to use in obtaining a guideline for improving the tire.
Moreover, from the standpoint of the tire, it is sufficient if the characteristics of the vehicle are simply taken as being the total characteristics of the vehicle above the axle only. Thus, it is not always necessary to subdivide the vehicle components into suspension model transfer characteristics and vehicle body transfer characteristics. However, in the above-described conventional road noise predicting method, the vehicle is divided into two components. Accordingly, it is not practical only to improve the tire and thereby a simpler method is desired.
Further, it is considered that the above-described conventional road noise predicting method is applied to the tire, that the respective tires having different specifications are subjected to the above-described inverse operation, and that the road noises of the respective tires having different specifications are compared. However, in order to implement this, it is necessary that the respective tires having different specifications be replaced and mounted on the axles and that the vehicles on which the tires are mounted be subjected to actual running. As a result, it is the same as when the tires are replaced on the actual vehicle and the interior sound is directly evaluated. A drawback arises in that a great amount of time and labor is required.
SUMMARY OF THE INVENTION
The present invention was developed in order to solve the above-described drawbacks, and the object thereof is to provide an apparatus for and a method of predicting vehicle interior noise in which road noise can be easily predicted by using a transfer function synthesis method.
The principle of the present invention will be explained. Firstly, the components of a vehicle as a whole which affect road noise are broken down into two parts, i.e., the tires and the portion of the vehicle above the axles, and the above-described transfer function synthesis method is applied.
As described above, with regard to the components of the vehicle, since the calculation model in which the vehicle is broken down into the suspension and the vehicle body is not practical, it is appropriate to use the actually-measured transfer function. In the original transfer function synthesis method, transfer characteristics, which are obtained by exciting the axle of the vehicle on which a tire is not mounted, should be used as the transfer characteristics from the axle of the vehicle to the vehicle interior sound. However, in order to obtain the transfer characteristics by exciting the axle of a vehicle on which a tire is not mounted, it is necessary that a state which is the same as the state in which a tire is mounted on the axle and a load is applied thereto be created in a state in which a tire is not mounted on the axle and without applying excessive force thereto. Accordingly, it is necessary to provide enormously complicated equipment in the experiment, and a great number of technical difficultie
Horiuchi Mamoru
Kudo Ken
Suto Akira
Yamashita Tsuyoshi
Yoshimura Yuichi
Bridgestone Corporation
Wachsman Hal
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