Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1998-07-21
2001-02-06
Young, Lee (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
Reexamination Certificate
active
06182350
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to the art of electric motors. This invention is specifically concerned with electric motors for driving piston pumps used in anti-locking brake devices for vehicles and the like.
2. Description of Related Art
Generally, examples of electric motors for driving piston pumps of this type include arrangements wherein the piston is caused to move reciprocally in the radial direction with respect to the armature shaft of the driving motor, e.g., arrangements used for anti-locking brakes. An example of such an arrangement is disclosed in Japanese Unexamined patent Publication No. 2-207184. In this arrangement, bearing of the armature shaft is accomplished by a pair of bearings provided at either side of an eccentric shaft linked to the piston side. The armature shaft is press fit to the inner ring of the pair of bearings. The armature shaft is press fit to the bearings when the shaft is aligned with each of the bearings. In the event that the outer rings of the bearings are press fit to the pump housing side, freedom in the radial direction is lost, and in the case that there is misalignment in both of the bearings, press fitting of the armature shaft cannot be performed for all practical purposes. Accordingly, the bearings are arranged so as to be loosely inserted into the pump housing to ensure freedom in the radial direction, however slight, thus handling misalignment.
However, with such an arrangement, not only does wobbling of the bearings in the radial direction due to receiving the load from the piston moving in the aforementioned radial direction cause noise and deterioration of pump performance, but other parts become necessary in order to prevent the bearings (which have been inserted loosely) from moving in the axial direction, requiring extra parts and complicated assembly. Because it is necessary to provide a space for setting a jig for assembling both bearings in a pump housing separately from a space for piston pump components, the resulting space for piston pump components becomes smaller, which creates a problem in that freedom in layout for the piston pump components in a pump housing is reduced.
In order to deal with such problems, an arrangement has been disclosed in Japanese Unexamined patent Publication No. 7-184344, wherein grooves are provided in the bearing outer ring and the member of the pump housing to which the bearing is to be inserted. Resin material is inserted into the aforementioned grooves so as to restrict movement in the axial and radial direction.
However, with such an arrangement, the endurance of the resin material is problematic, and not only is there the possibility that the bearings may return to the original state of being inserted loosely due to deterioration and the like of the resin over prolonged usage periods, but there is the problem that resin material in the grooves decreases work efficiency.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to solve the above-mentioned problems. The invention includes an electric motor which drives a piston pump such that the load from the piston pump side acts upon the armature shaft in a radial direction.
In accordance with a first aspect of the invention, an electric motor for driving a piston pump is disclosed which comprises a yoke including a yoke bearing located at an opening of the yoke, a pump housing connected to the yoke and including a first pump housing bearing located in the pump housing. An armature shaft extends between the yoke bearing and the first pump housing bearing and includes an eccentric shaft tip portion, and a second pump housing bearing, smaller in diameter than the first pump housing bearing, located on the eccentric shaft tip portion of the armature shaft. An inner cylinder portion of the pump housing comprises the sequential formation of a first pump housing bearing support portion by which the first pump housing bearing is supported, a second pump housing bearing moveable support portion which is smaller in diameter than the first pump housing bearing support portion and by which the second pump housing bearing is moveably supported, a temporary supporting portion which is smaller in diameter than the second pump housing bearing moveable support portion and configured to support the second pump housing bearing in a temporarily supported state and an inserting hole portion for inserting a jig from a side of the pump housing that is opposite a side to which the yoke is connected and for pressing the jig against an inner ring of the second pump housing bearing to press fit the inner ring to the eccentric shaft tip portion of the armature shaft.
Such an arrangement allows a small through hole to be placed in the piston housing for passing through a jig for pressing the inner ring of the second pump housing bearing, rather than a through hole corresponding with the outer diameter of the second pump housing bearing for inserting the second pump housing bearing to one side thereof from the other side. While the second pump housing bearing cannot be assembled to the pump housing from the side opposite to the side to which the yoke is assembled, this arrangement is advantageous in that the freedom in layout of the piston pump components provided within the pump housing is improved.
In accordance with a second aspect of the invention, the method of assembly involves the steps of bearing one end of the armature shaft of the electric motor by a yoke with a yoke bearing, bearing the other end of the armature shaft by a pump housing with a first pump housing bearing, press fitting the one end of the armature shaft to an inner ring of the yoke bearing, press fitting the other end of the armature shaft to an inner ring of the first pump housing bearing, press fitting an outer ring of the first pump housing bearing to the pump housing, and assembling an outer ring of the yoke bearing to the yoke.
Such an arrangement does away with axial and radial direction wobbling of the bearings bearing the armature shaft even in the event that load from the piston pump acts upon the armature shaft in the radial direction, thus reducing noise and contributing to improved pump performance.
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patent: 4994699 (1991-02-01), Shiina
patent: 5057730 (1991-10-01), Yoshida
patent: 5203071 (1993-04-01), Niemela
patent: 5347187 (1994-09-01), Tsuzaki et al.
patent: 5564909 (1996-10-01), Rischen et al.
patent: 5620311 (1997-04-01), Wetzel
patent: 5635778 (1997-06-01), Fujita et al.
patent: 5678299 (1997-10-01), Mochizuki et al.
patent: 5777407 (1998-07-01), Ishida et al.
patent: 5844334 (1998-12-01), Sasaki et al.
patent: 5854522 (1998-12-01), Iwata et al.
patent: 2-207184 (1990-08-01), None
patent: 5-83372 (1993-11-01), None
patent: 6-10471 (1994-02-01), None
patent: 7-184344 (1995-07-01), None
Hagiwara Hiroshi
Iwata Masato
Mitsuba Corporation
Oliff & Berridg,e PLC
Vereene Kevin G.
Young Lee
LandOfFree
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