BEARING ASSEMBLY

Abstract: According to known designs magnetic lubricant is used between the bearing-bushing and shaft, and kept therebetween by magnetic forces. The bushing, however, is a permanent magnet made of metal and moreover consists of several segments. The claimed bearing arrangement is based upon a quite different viewpoint, namely to apply a plastic bushing (6) which contains magnetic particles (7). Between the shaft (1) and bushing (6) a small drop of a magnetic lubricant (8) is applied. Due to the magnetic properties of this arrangement a constant lubricant film is obtained. This arrangement is basically simple in design and cheap to manufacture, and particular useful in electromotors for domestic appliances.

Description: The invention relates to a bearing assembly, in particular for an electric motor of a household appliance, comprising a bearing sleeve of a synthetic material forming the running surface of the bearing, a shaft mounted in said sleeve, and a lubricant between the running surface of the sleeve and the shaft, means being provided to retain the lubricant whereby said bearing sleeve consists of a synthetic material in which particles of a magnetic material are imbedded and the lubricant is a magnetic fluid. Such a bearing assembly is disclosed in German patent application DE-A-33 04 623. Electric motors for household appliances should run as quite as possible, which means among other things that the bearings must function optimally. An important condition for this is that the bearings must be well lubricated. In the known bearing assembly, the running surface of the sleeve is also provided with one or more grooves to retain the lubricant. A general problem in the field of journal bearings, with spiral grooves is, that environmental influences, such as comparatively temperatures in the appliance, will cause the lubricant to drain along the shaft out of the grooves of the bearing, so that the sleeve and the electric motor suffer premature wear, resulting in an unacceptably high noise level or worse. The object of the invention is to provide a bearing assembly of the type defined above in which the lubricant will be retained essentially for an indefinite period, and at the same time to provide an economically advantageous bearing by virtue of its form and construction. This object is accomplished in that only a drop of said magnetic lubricant is present between the shaft and the running surface of the bearing sleeve such that the lubricant forms an annular film of small axial breadth relative to the axial dimension of said sleeve. In a bearing so constructed, the magnetic lubricant is very effectively retained by the magnetic flux created by the magnetic particles imbedded in the sleeve, the magnetic fluid being prevented from escaping outside the sleeve because the force of attraction is greater towards the center of the bearing than towards the surroundings of the sleeve. Furthermore, the bearing is less expensive than the known bearing, which requires an additional operation to produce the grooves. Preferably the particles imbedded in the bearing sleeve consist of magnetite. It is noted that a magnetic lubricant is known per se. It consists of a colloidal dispersion of extremely fine particles of a magnetic material in a liquid. The invention will be illustrated in more detail with reference to the embodiment shown in the drawing by way of example, where Fig. 1 shows an axial section of an electric motor of a household appliance with a bearing assembly according to the in-vention, and Fig. 2 shows the bearing assembly drawn to a larger scale. As shown in the drawing, the shaft 1 of the rotor of an electric motor 2 is mounted at one end by a ball bearing 3 and at the other end by a Journal bearing 4 in a housing 5. The Journal bearing 4 comprises a bushing 6 of a synthetic material in which particles 7 of a magnetic material are imbedded. Between the shaft 1 and the bushing 6, a drop of magnetic lubricant 8 is introduced, which owing to the magnetic field set up by the magnetic particles 7 is formed into an annular film around the shaft 1. Note that in Fig. 2 the thickness of the lubricant film 8 has been much exaggerated.

Claims: Bearing assembly, in particular for an electric motor of a houshold appliance, comprising a bearing sleeve (6) of a synthetic material forming the running surface of the bearing, a shaft (1) mounted in said sleeve, and a lubricant (8) between the running surface of the sleeve and the shaft, means being provided to retain the lubricant whereby said bearing sleeve (6) consists of a synthetic material in which particles (7) of a magnetic material are imbedded and the lubricant (8) is a magnetic fluid, characterized in that only one drop of the magnetic lubricant (8) is present between the shaft (1) and the running surface of the bearing sleeve (6) such that the lubricant (8) forms an annular film of small breadth relative to the axial dimension of said sleeve (6). Bearing assembly according to claim 1, characterized in that the particles (7) imbedded in the bearing sleeve consist of magnetite.

Inventors: LANKAMP, HERMAN, DR.
Applicants: SKF INDUSTRIAL TRADING & DEVELOPMENT CO, B.V.
Application year: 1987
Main classification: F16C33
IPC codes: F16C33, H02K5