Measuring and testing – Rotor unbalance – Combined static and dynamic
Reexamination Certificate
2002-04-30
2004-05-18
Jules, Frantz F. (Department: 3617)
Measuring and testing
Rotor unbalance
Combined static and dynamic
C301S005210
Reexamination Certificate
active
06736007
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention concerns a tire/wheel assembly assembling method, a tire/wheel assembly assembling line, a wheel, and a wheel manufacturing method, which improve the working efficiency in assembling together a tire and a wheel and improve the outer appearance of the wheel.
2. Description of the Related Art
A tire/wheel assembly (car wheel) used in an automobile or other vehicle is comprised of a wheel and a tire, which is assembled onto the wheel. The wheel has an annular rim, onto which the tire is assembled, and a disk, which is welded to the rim and to which the hub of the shaft of a vehicle is fixed by means of bolts, etc.
Such wheels and tires are non-uniform in weight, dimensions, rigidity, etc. due to the scattering that occurs in the respective manufacturing processes. The uniformity of weight is referred to as balance. The condition in which balance is not achieved is called unbalance, and there is static unbalance and dynamic unbalance. Static unbalance refers to the non-uniformity of weight distribution that exists in the circumferential direction in the still condition and causes vibration of the car body in the vertical direction. Dynamic unbalance refers to the non-uniformity of weight distribution that exists in the rotating condition and causes vibration of the car body in the vertical and lateral directions as well as steering shimmy. The uniformity of the dimensions is referred to as “runout”, and there is radial runout (referred to hereinafter as “RRO”), which is the runout in the radial direction (vertical runout), and lateral runout, which is the runout in the width direction (lateral runout). The uniformity of rigidity is referred to as “force variation”, and there is radial force variation (referred to herein after as “RFO”), which is the variation of force in the radial direction, and lateral force variation, which is the variation of force in the width direction. Among these characteristics, a large unbalance and RFV in particular cause vibration of a vehicle. The unbalance and RFV must thus be lessened.
Balance in the direction around the rotation axis and in the direction of the rotation axis must thus be achieved with a tire/wheel assembly, in which a tire and a wheel are assembled together. However, if a wheel and tire are assembled together without consideration of the abovementioned static balance of the wheel and tire, unbalance in the direction around the rotation axis and in the direction of the rotation axis will occur. The condition in which the balance in the direction around the rotation axis is not achieved is static unbalance, and if static balance is not achieved, vibration in the vertical direction will occur during travel. The condition in which the balance in the direction of the rotation axis is not achieved is dynamic unbalance, and if dynamic balance is not achieved, vibration in the vertical and lateral directions will occur and cause steering shimmy, etc.
Since non-uniformity exists in the wheel alone and the tire alone as described above, in order to lessen the non-uniformity, the non-uniformity of the tire/wheel assembly, with which the wheel and tire are assembled together, is lessened as much as possible. Various methods are thus employed as methods of assembling a tire/wheel assembly. Two representative assembling methods shall be described below.
As a first method, there is the method of reducing the RFV of the tire/wheel assembly. With this method, a tire and a wheel are assembled together upon performing phase matching of the maximum point of the RFV of the tire with the minimum point of the RRO (so-called low point) of the wheel. By this assembling method, the tire/wheel assembly as a whole is made to approach a circular shape and the vibration in the vertical direction during the rotation of the tire/wheel assembly is reduced. Here, if the light point of the tire, which is the lightest part in the weight distribution in the circumferential direction of the tire, and the heavy point of the wheel, which is the heaviest part in the weight distribution in the circumferential direction of the wheel, are at mutually close positions, the static unbalance of the tire and the static unbalance of the wheel cancel each other out to lessen the static unbalance of the tire/wheel assembly as a whole. However, if assembly is performed with priority given to matching the direction of the maximum point of the RFV of the tire with the direction of the minimum point of RRO of the wheel as mentioned above, the light point of the tire and the heavy point of the wheel will normally not be matched and balance weights must be added further.
Thus in order to determine the weight and position of attachment of the balance weights after assembly, the tire/wheel assembly is set on an unbalance measuring device (referred to hereinafter as a “balancer”) and the weight and position (angle) of the unbalance of the tire/wheel assembly are measured. After measurement, balance weights (lead, etc.), which correspond to the weight of the unbalance, are attached to the rim of the wheel at locations corresponding to the position of the unbalance to adjust the balance, and the measurement of unbalance and adjustment of the balance weights are repeated until the amount of unbalance becomes less than or equal to a fixed amount. In order to improve the efficiency of the balance weight attachment work, the position of attachment of the air valve, which becomes the heavy point, is used as a guide-line for the attachment position of the balance weights. Balance weights are normally attached at two locations at the outer side and the inner side of the wheel.
A second method is the method of lessening the unbalance of the tire/wheel assembly. With this method, the tire and wheel are assembled together upon performing phase matching of the light point of the static unbalance of the tire and the heavy point of the static unbalance of the wheel. By this assembly, the static unbalances of both the tire and wheel cancel each other out so that the static unbalance of the tire/wheel assembly as a whole is lessened and the vibration in the vertical direction during travel can be restrained. After assembly, the RFV is improved using a tire fitter. Furthermore, if unbalance still remains in the tire/wheel assembly, the weight and position (angle) of the unbalance of the tire/wheel assembly are measured using a balancer in order to lessen the unbalance. Balance weights, corresponding to the weight of the unbalance, are then attached to the rim of the wheel at locations corresponding to the unbalance.
In particular with this method, since an air valve for supplying compressed air into the tire is attached to the rim of the wheel, the weight of this air valve is taken into account and the air valve attachment position is used as the heavy point of the wheel in many cases. Thus in this case, the light point of the static unbalance of the tire is phase matched with the air valve attachment position of the wheel.
As has been described above, with both methods, the setting of the heavy point of the static unbalance of the wheel to the air valve attachment position is effective in providing a guideline for assembly that can be judged readily. However, since the weight of an air valve is not so high, in the case where the scattering of the weight distribution is large among the respective products due to manufacturing errors of the wheel body, this scattering may override the weight of the air valve and the heavy point of the wheel as a whole may not necessarily coincide with the air valve attachment position. In relation to this problem, Japanese Unexamined Patent Publication No. 2000-170843 discloses an invention of a method for making the heavy point of the static unbalance of the wheel coincident with the air valve attachment position. With this invention, for each of the members, which comprise the air valve, for example, the air valve body, the cap that covers the air inlet of the air valve, etc., a plurality of types that dif
Ichinose Hidemi
Kashiwai Mikio
Sato Shiro
Takagi Hisamitsu
Watanabe Shin-ichi
Armstrong Kratz Quintos Hanson & Brooks, LLP
Jules Frantz F.
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