Rolling bearing unit with a rotating speed measuring device

Details Rolling bearing unit with a rotating speed measuring device Rolling bearing unit with a rotating speed measuring device

1999-01-15

2001-11-27

Snow, Walter (Department: 2862)

Electricity: measuring and testing

Electrical speed measuring

Including speed-related frequency generator

C324S207250, C384S448000

Reexamination Certificate

active

06323640

ABSTRACT:

The present invention refers to a roller bearing unit, in particular for the hub of a vehicle wheel, of the kind equipped with a sealing device and a device for measuring the rotating speed of the outer race.
Known measuring devices of the aforementioned type comprise an encoder wheel in the form of an annular disc of magnetised plastic or rubber material, which is rotatably secured to the rotating ring of the bearing. In some well-known types of device, the encoder wheel is forcefully fitted onto the rotating ring of the bearing or onto an element fixedly connected to it. It has however been found that encoder wheels of this type do not stand up very well to the stress to which they are subjected when they are forcefully fitted; furthermore, encoder wheels fitted in this way are exposed to the action of external contaminating agents such as water, dust, mud, metal particles from nearby brake devices etc; when said contaminating agents come into contact with said encoder wheels their performance tends to be impaired and the signal produced by a sensor which picks up variations in magnetic flow generated by the rotating encoder wheel can be adversely affected.
In other well-known types of device, such as that described in Italian patent application No. TO97A000371 (not yet available to the public as of the date of the present application) the encoder wheel is integrated into the sealing device of the bearing unit. While this kind of alternative presents certain advantages in some respects, the encoder wheel is however fitted in such a way as to present a restricted surface for the sensor to read.
An aim of the present invention is to achieve a robust, reliable arrangement which ensures that the encoder wheel does not risk being damaged during assembly, transport or use.
Another aim of the present invention is to achieve an arrangement of reduced overall dimensions, housing the encoder wheel between the axial dimensions of the bearing unit.
Another aim of the present invention is to obtain maximum intensity from the magnetic field generated by the encoder wheel, and to obtain a larger reading surface for the sensor in use facing the encoder wheel.
Another aim of the present invention is to propose a method which can also be applied to conventional bearing units, without having to modify them in order to mount an encoder wheel onto said conventional bearing units.
A further aim of the present invention is to achieve an arrangement which protects the magnetised wheel from sudden extreme changes in temperature caused by vehicle brake devices located near the hub.
These and other objectives and advantages, which will be better understood hereinafter, are achieved according to the present invention by a roller bearing unit, in particular for the hub of a vehicle wheel, the bearing comprising a radially outer rotating race, a radially inner stationary race, a sealing device between said races and a device for measuring the rotating speed of the outer race, wherein said measuring device comprises an encoder wheel in the form of a radially oriented annular disc of magnetised plastic or rubber material, characterised in that the bearing comprises a metallic annular insert adapted for fixing the encoder wheel to the bearing outer race, said insert forming: an outer cylindrical portion for forcefully fitting to an outer surface of the outer race; a radial wall portion concurring in forming an annular seat for accommodating the encoder wheel, said wall portion extending radially inwardly so as to co-operate with said sealing device to close the gap between said races; a portion joining said outer cylindrical portion and said radial wall portion, said joining portion being the part on which an axial thrust is exerted for performing said force fitting.


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