Electricity: magnetically operated switches – magnets – and electr – Magnets and electromagnets – With magneto-mechanical motive device
Reexamination Certificate
1999-01-26
2001-01-16
Donovan, Lincoln (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Magnets and electromagnets
With magneto-mechanical motive device
C335S255000
Reexamination Certificate
active
06175291
ABSTRACT:
BACKGROUND TO THE INVENTION
The invention relates to an electromagnet, comprising a magnet coil which receives an armature movable longitudinally with respect to the coil axis and having an armature rod, and comprising a support of the armature or of the armature rod in a core serving also for the guidance of the magnetic field.
Electromagnets have a wide range of application, for example, as actuating or pressure-regulating magnets. In particular, such magnets are employed, for example, in automatic transmissions of vehicles. Owing to the operating conditions which exist there, in particular in an oil sump, the presence of a high degree of fouling and great temperature differences, the above-described electromagnets are subject to exacting requirements.
The above-described electromagnets are usually constructed in such a way that one or more slide bearings are provided, in particular in the core material of the electromagnet, in order to support and guide the movable element of the electromagnet, namely the armature or the armature rod. As a rule, the bearing is an axial slide bearing which takes up the forces occurring parallel to the coil axis or to longitudinal extent of the rod. These slide bearings or slide-bearing bushes involve a relatively high outlay in respect of mounting. The region which receives the armatures or the armature rod must have a corresponding receiving bore for the slide-bearing bush. For the fitting of the bearing a tolerance must be provided which must be precisely designed in accordance with the bearing quality. This results in a corresponding outlay in respect of the fitting of the bearing.
Since a plurality of slide rings (=as bearings) are also provided for the support of the armature rod, the various bearings must be mounted in an aligned manner. Since a misalignment or radial run-out cannot be ruled out in this case, this also leads to a further tolerance. Since the above-described electromagnets may be employed in areas subject to high temperature fluctuations, these temperature fluctuations must also be taken into account with a corresponding bearing play.
As a result, owing to air-gap losses and frictional hysteresis, the efficiencies of the magnets are relatively poor. Owing to the large bearing play, there is also a susceptibility to fouling and the increased risk of the fouling leading to disruption of the operation of the electromagnet. Moreover, the relatively low precision owing to the large bearing play is also responsible for a relatively poor magnetic circuit, since the bearing plays also lead to relatively large losses at the air gaps which cannot be compensated for. Furthermore, the fitting of the slide-bearing bushes involves a relatively high outlay, since, as described, these bushes require a precise receiving bore. Additional outlay is involved in avoiding an axial displacement of the bearings through the fitting of suitable securing means. Lastly, the fitting of the bearings also takes up additional installation space.
Since the reliability of the above-described electromagnet depends on the accuracy of the support, it is necessary specifically to monitor the support, with corresponding outlay in terms of production and inspection, in order to achieve a satisfactory quality.
BRIEF SUMMARY OF THE INVENTION
The present invention has the object of developing an electromagnet such that the latter can be produced with higher precision and thus a higher quality, at low manufacturing costs.
This invention is achieved by an electromagnet as described at the outset, i.e., an electromagnet comprising a magnet coil which receives an armature movable longitudinally with respect to the coil axis and having an armature rod, and comprising a support for the armature or armature rod in a core serving also for the guidance of the magnetic field. According to the invention direct support of the armature and/or of the armature rod on a surface of the core is provided. The direct support of the armature means that the fitting of the bearing bushes is dispensed with. This gives rise to an immediate advantage in terms of manufacture. Since no bearings are used any more, misalignment or radial run-out is minimized. The outlay in respect of adjustment or calibration of the position, or axial securing against undesired slipping of the bearing bushes, is no longer necessary either.
In a preferred configuration of the invention, there is provision for a bore, preferably a precision bore, to be provided in the core, on the inner surface of which core the armature or the armature rod is supported, in particular without a separate bearing, and the rod assumes the supporting function. The use of the precision bore is retained from the known electromagnet. This precision bore was necessary anyway to achieve an appropriate quality of the orientation of the bearing after the fitting of the bush. Since the use of an additional bearing is deliberately dispensed with, the supporting function is assigned to the rod. Besides supporting the armature rod in a bore, however, it is also possible to support the armature on a surface, of any nature whatsoever, of the core, or to guide it on this surface.
In a preferred configuration of the invention, it is proposed that the armature rod is made of a nonmagnetic bearing material. By using a nonmagnetic bearing material as the material for the armature rod, the magnetic properties of the magnet are not impaired. In particular, the magnetic field lines guided in the core are not deflected by such a configuration, which ultimately could lead to an impairment of the efficiency of the device.
There is provision for the armature to comprise a plurality of elements—the armature body and the armature rod. According to the invention, elements of the armature assume the direct support on a surface of the core. Besides the use of the armature rod, however, it is also possible to support the armature body correspondingly in a core element. Such a configuration allows, for example, a double support of the armature by means of the armature body and the armature rod to be provided. In order to achieve as high an efficiency as possible, there is provision to form the armature body from a ferromagnetic material. The armature in this case comprises a plurality of elements consisting of different materials which are appropriately welded, adhesively bonded or caulked, or connected in some other way, to one another.
Besides the configuration in which one armature rod is arranged on the armature body, however, it is also possible to arrange two armature rods. The support of the armature may in this case be provided either via the two armature rods or via the armature body alone, in which case the armature rods merely assume controlling functions.
It has been found here that the surface, which slides on the surface of the core, of the armature or of the armature rod is harder than the surface of the core. It has been found here that the surface of the armature/the armature rod is from 2× to 10×, but preferably from 3× to 5× harder than the stationary sliding surface of the core. In order to establish an appropriate ratio of hardnesses, recourse may be had to the methods for hardening the surfaces known in the prior art.
The preferred materials employed here are brass or known bronze alloys or other known bearing metals, such as lead bronzes, tin bronzes, aluminium bronzes or copper, lead, zinc, tin with appropriate added alloys of other materials, such as lead, copper, antimony, aluminium, zinc. The compositions of these alloys are known from the prior art. Appropriate choice of the alloy makes it possible to optimize the armature rod also with regard to the temperature range employed.
The advantages of the configuration according to the invention reside in the markedly reduced manufacturing outlay in respect of these electromagnets. At the same time, the precision of the rod guidance is increased, thereby also resulting in air-gap conditions of greater definition and precision. The magnetic air-gap losses can
Hanka Manfred
H{umlaut over (a)}ring Reinhard
Kleinert Dieter
Mang Helmut
Scherer Georg
Dipl- Ing. Wolfgang E. Schultz
Donovan Lincoln
Jacobson Price Holman & Stern PLLC
Nguyen Tuyen T.
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