Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1998-01-12
2002-11-12
Vo, Peter (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S596000, C029S598000, C029S605000, C029S606000, C310S261100, C310S270000, C310S049540, C310S234000, C156S172000, C156S275500, C264S272200
Reexamination Certificate
active
06477763
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a rotating part of an electrically driven machine, a direct-current motor for a motor vehicle comprising such a rotating part and a method for making such a rotating part.
BACKGROUND OF THE INVENTION
Direct-current motors for electric fans in motor vehicles are known which comprise an inductor with permanent magnets and a wire-wound armature. This armature has a support and a generally ring-shaped winding formed of strands wound around the support. The circulation of a current in the strands placed in the magnetic field generated by the inductor gives rise to a Laplace force in the strands which causes the rotation of the armature around its axis. The strands comprise rectilinear sections, parallel to the axis of the armature, and at the end thereof intermediate sections connected to the commutator or to another rectilinear section. The Laplace force essentially occurs only in the rectilinear sections.
The inactive intermediate sections are disposed and fitted together at the axial end faces of the winding to occupy a reduced space. These thus form bulges called armature leading-out wires. The spatial requirement of the leading-out wires in the axial direction of the motor is large, and may be equal to the length of the active rectilinear sections. The axial spatial requirement of the motor itself therefore depends to a great extent on the axial spatial requirement of the leading-out wires. In the motor industry, inter alia, there is today an increasing demand for motors having a reduced axial spatial requirement.
Moreover, the dimension of the winding in the axial direction, which is large, is matched with a tolerance range which is itself large. It follows that the parts of a motor adjacent to the winding occupy positions which take this tolerance range into consideration. The axial spatial requirement of the motor is therefore doubly increased.
Furthermore, the volumetric distribution of the strands parallel to the axes and of the leading-out wires is generally irregular. This poor distribution creates a weight imbalance or mass imbalance, which it is necessary to compensate by rebalancing the armature after production before mounting in the motor. This compensation forms an operation which becomes increasingly delicate as the initial lack of balance increases.
One problem is therefore of providing a method for producing a wire-wound rotating part having leading-out wires which have a reduced axial dimension and a reduced tolerance range associated with this dimension, and distributed more regularly than the leading-out wires of the above-mentioned rotating parts.
From the prior art, particularly the English translation of the abstract of the Japanese patent JP-4 275 050 (Fujitsu General Ltd), the production of a wound stator having a reduced axial dimension is known by winding the strands onto the sheet metal pack, then disposing the sheet metal pack with its winding in a press comprising two clamping jaws having opposite coaxial annular compression faces. The first clamping jaw has a core onto which the sheet metal pack with its winding is threaded. When the press is closed, the end of the core penetrates into a cavity of the second clamping jaw intended for this purpose. Then the two clamping jaws are brought closer to one another to perform the axial compression of the winding.
Thus, the compression force causes the crushing of the leading-out wires in the axial direction and brings about a great reduction in the axial spatial requirement of the winding.
However it is known that to produce the wire-wound rotating part of an electrically driven machine, it is advantageous to proceed as follows:
attach a bare sheet metal pack onto a shaft;
then fix a commutator onto the shaft in a temporary position spaced from the sheet metal pack;
then wind the strands simultaneously onto the sheet metal pack and the commutator; and finally
bring the commutator closer to the sheet metal pack to place it in its permanent position.
This method facilitates the production of the winding. The teaching of the abstract of the above-mentioned Japanese document cannot be used in these conditions, as it relates to a winding of a fixed part of an electrically driven machine which is provided with neither a shaft nor a commutator.
One object of the invention is to propose a method for producing a rotating part of an electrically driven machine enabling the winding to be produced simultaneously on the sheet metal pack and on the commutator in the temporary position before placing the commutator in the permanent position, whilst obtaining the above-mentioned advantages of the axial compression of the winding.
SUMMARY OF THE INVENTION
With a view to the achievement of this object, according to the invention there is specified a method for producing a wire-wound rotating part for an electrically driven machine, including stages consisting of:
attaching a sheet metal pack and a commutator onto a shaft, the commutator being spaced from the sheet metal pack; and
winding conductive strands onto the sheet metal pack and the commutator to form a generally ring-shaped winding,
the method also including the step consisting simultaneously of compressing the winding in an axial direction of the winding, and bringing the commutator closer to the sheet metal pack.
Thus, the temporary position of the commutator facilitates the production of the winding on the commutator and sheet metal pack. Moreover all the advantages of the axial compression of the winding are obtained. Furthermore, certain strands have an end connected to the commutator and another end connected to the axial end face of the winding directed towards the commutator. During the axial compression of the winding simultaneously with the displacement of the commutator, the two ends of these strands are displaced in the same direction in the axial direction of the shaft. Consequently, between these two ends no traction occurs which is likely to alter or break the strand, and the excess of strands adjacent to the commutator does not produce any masses from which short circuits could result. The risk of contact, or shocks, between the strands is reduced. This method generally enables the deterioration of the insulating sheath or of the insulating varnish of the strands to be avoided to a great extent during compression, which deterioration could in the opposite case cause short circuits between the strands. In particular, the crushing of the strands which could cause the cutting of some of them is avoided.
The method advantageously includes during compression the phase consisting of guiding strand sections extending from the commutator to the sheet metal pack.
Thus the above-mentioned drawbacks are further avoided, for the strands adjacent to the commutator, i.e. the formation of masses, their crushing or their excessive traction, from which a contrario the alteration of the insulating material of the strands and short circuits between them could result.
The guiding phase advantageously includes the operation consisting of keeping each of the said strand sections in a fixed radial plane determined in relation to the shaft.
It involves a particularly simple manner of producing this guidance.
Conductive strands having an outer sheath made of thermosetting material are advantageously wound onto the support, and during the compression stage the winding is heated to a temperature at least equal to the setting temperature of this material.
Thus the strands are immobilised in the compression position of the winding. Therefore the service life of the obtained arrangement of the strands is prolonged.
The winding is advantageously heated by circulating electric current in the strands.
Thus it is not necessary to use a press equipped with its own heating means.
Before the compression stage, a hot liquid substance which can harden on cooling is advantageously applied onto the strands, and the compression stage is extended until the cooling of the substance.
It involves another manner of obtaining the immobilisation of
Desesquelles Pierre-François
Pigeau Jean-Michel
Santander Eduardo
Templer Dominique
Morgan & Finnegan , LLP
Tugbang A. Dexter
Valeo Systemes d'Essuyage
Vo Peter
LandOfFree
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