Patent Grant
8209850
It is known from U.S. Pat. No. 6,092,278 to provide ignition voltage for a spark plug in an internal combustion engine by use of a high voltage step-up transformer mounted directly above the spark plug. The high voltage transformer utilizes a magnetic core having a pencil-shape, and thus has become commonly known as a “pencil core”.
Such a pencil core is shown at 10 in prior art FIG. 1 from the '278 patent and is formed of a plurality of stacked thin magnetic metal laminations 11 of varying width, but having a substantially constant thickness and a same length so that a substantially circular profile as shown in prior art FIG. 2 results.
In order to maintain the stack as a unified body, it is known in the '278 patent to provide a plurality of embossments 12A, 12B, 12C in the laminations 11 so that the embossment of an upper lamination fits into the inside of an embossment of the following lamination and so on until the last lamination at the bottom. This is most clearly shown in FIG. 2 which is a cross-section taken along line II-II in FIG. 1.
It is also known as shown in FIG. 1 to provide vertical rectangular channels 8 and 9 at end faces of the pencil core where the channels are formed from individual cutouts in each of the laminations. These channels 8 and 9 are used to keep the core vertically aligned as it proceeds through a die.
There are a number of disadvantages to such a pencil core. First, the steps 13 shown in FIG. 2, the embossments 12A, B, C, and the cutouts to form channels 8 and 9 result in a decreased electrical performance of the core. Also not as much electrical steel is provided for a given core diameter because of the steps 13.
It is known from U.S. Pat. No. 6,501,365 to provide a substantially circular pencil core 14 as shown in prior art FIG. 3. According to the '365 patent, such a circular pencil core is manufactured with the following steps.
First, the individual laminations 16 of a constant length corresponding to the length of the desired finished pencil core are cut but with varying width (such as by blanking in a stamping die). Thereafter the laminations 16 are stacked to form a stacked assembly which is clamped and subjected to a mechanical machining so that the stepped dotted portions 15 of the laminations 16 are removed. However, this mechanical machining produces burrs on the lateral portions of the laminations at the lateral edges and these burrs provide undesired electrical conductive paths between laminations which may produce electrical shorts. The mechanical machining also produces undesired smears which may also create electrical shorts.
It is thus necessary to remove the burrs and the smears, such as by electro-chemical etching, for example. The burrs and smears are indicated at 18 in FIG. 3.
Thereafter, as shown in prior art FIG. 4, the end faces 19 and 20 of the machined and de-burred/de-smeared core stack 14 are welded to form the finished pencil core.
The above manufacturing procedure has a number of disadvantages. The welds at the ends decrease the electrical performance of the core. Furthermore, the process is complicated and requires the electro-chemical etching removal of the burrs and smearing. Furthermore, during the machining process, the loose laminations of the stack must be clamped together during the machining process prior to the welding.
It is an object to provide an improved pencil core with improved electrical performance and method for manufacturing the improved pencil core.
In a method for manufacturing pencil cores a continuous strip of electrical steel is provided. The continuous strip is cut to create a plurality of starting strips as laminations each having a length longer than a desired length of the pencil cores and at least one of the strips having a strip width at least equal to or larger than a desired diameter of a cross-section of the pencil cores. The starting strips are provided with a bonding layer. The starting strips are stacked and then heated and cured to create a bonded stack. The bonded stack is machined to a substantially circular cross-section. Without a de-burring or de-smearing operation after the machining, the machined bonded stack is cut to create a plurality of pencil cores of the desired length. The pencil cores created by the method are substantially round, and have no welds at end faces.
FIGS. 5A-5D′ show a preferred embodiment of an improved manufacturing method to create a substantially circular pencil core of improved electrical performance; and
FIGS. 6A-6D′ show an alternative embodiment of an improved method for manufacturing to create a substantially circular pencil core of improved electrical performance.
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the preferred embodiments/best mode illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, and such alterations and further modifications in the illustrated device and such further applications of the principles of the invention as illustrated as would normally occur to one skilled in the art to which the invention relates are included.
FIGS. 5A-5D′ show the improved manufacturing method for manufacturing a substantially circular pencil core of improved electrical performance. As shown in
The continuous strip 21 is preferably provided with a bonding layer 27 at the top and bottom of strip 21 (and possibly even covering the opposite edges). Preferred bonding adhesives to use as a material for the bonding layer are the Rembrandtin Emersol EB 548 as described in the data sheet labeled “TDS EB 548” dated 2008, and the DuPont Voltatex as described in data sheet “Datasheet Voltatex(R)” dated Aug. 30, 2004, both of which are incorporated herein by reference. Preferably the adhesive is applied and dried, and then later heated and cured for bonding after stacking the starting strips described hereafter. This bonding material layer 27 is shown in the side view of
Alternatively, the starting strips 23 may be coated with the bonding adhesive layer 27 after they have been cut into the starting strips.
In either of the above processes, the bonding layer 27 may be provided on one side only.
The continuous strip 21 may be provided by slitting or shearing to the desired width 24 described above.
The length of the starting strips 23, although being a multiple of the final length of the pencil core, is selected to be a length which is manageable for following steps.
Although the bonding material layer 27 is preferably heat cured, other types of bonding material for the bonding layer may be provided where the bonding material or bonding agent is activated via other methods such as ultrasound, UV, pressure, etc.
As shown in
As shown in
In
As alternatively shown in FIG. 5D′, instead of combining the machining and cutting in a single station, a separate machining station 7 may be provided for receiving the bonded strip stack 30 which then outputs a machined bar stock 60 to its separate cutting station 33 which then cuts the bar stock to create the finished cut to length pencil cores 34.
Significantly, unlike the method described in the '365 patent, very surprisingly and unexpectedly, no additional de-burring and/or de-smearing process is required after the machining to create the substantially circular finished pencil cores. This is because the bonding as a result of the heating and curing in the bonding and curing oven so intimately bonds together the adjacent starting strip laminations 23 in such a close and intimate fashion that no smearing or burring occurs during the machining operation. This is one of many significant advantages of the present improved method. Another major advantage is the creation of a relatively long bonded stack for use in creating the final pencil cores. Also electrical performance is better since there are no retaining embossments, no cutouts for channels at the end faces, and no welds at the end faces of the pencil cores, for holding the laminations together.
In an alternate embodiment as shown in FIGS. 6A-6D′, beginning with the step illustrated in
As shown in
As shown in
As shown in
Alternatively, as shown in FIG. 6D′, instead of using a combined machining and cutting station, a separate machining station 51 receives the bonded stack 48 and machines it to create a machined bar stock 70 which is then fed to a separate cutting station 52 to create the final finished pencil cores 53 cut to the appropriate length.
As was explained in the embodiment of the method of FIG. 5A-5E′, de-burring and/or de-smearing is surprisingly and unexpectedly not required after the machining as indicated in explaining the embodiment of the method of FIGS. 5A-5E′. Also no retaining embossments are required, no cutouts for channels at the end faces, and no welds are required at the end faces of the pencil cores for holding the laminations together.
In summary, the resulting pencil core has a relatively higher electrical performance since it has substantially no steps at a periphery, does not have embossments for holding the laminations together, does not have cutouts for channels at the end faces, and there are no welds at the end faces. Also fewer method steps are required for manufacture. Furthermore, more steel is provided for a given core diameter by elimination of the steps at ends of the laminations. And significantly, because of the intimate bonding, subsequent to machining no de-burring and de-smearing processes are necessary.
While preferred embodiments have been illustrated and described in detail in the drawings and foregoing description, the same are to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention both now or in the future are desired to be protected.
| Number | Name | Date | Kind |
|---|---|---|---|
| 3875660 | Kobayashi et al. | Apr 1975 | A |
| 4413406 | Bennett et al. | Nov 1983 | A |
| 4848684 | Sasaki et al. | Jul 1989 | A |
| 5037706 | Lin et al. | Aug 1991 | A |
| 5906040 | Kawano et al. | May 1999 | A |
| 5986532 | Kikuta et al. | Nov 1999 | A |
| 6025770 | Okamoto et al. | Feb 2000 | A |
| 6092278 | Latkow | Jul 2000 | A |
| 6363599 | Bajorek | Apr 2002 | B1 |
| 6501365 | Elliott et al. | Dec 2002 | B1 |
| 6744342 | Dechristofaro et al. | Jun 2004 | B2 |
| 20080042505 | Gerster et al. | Feb 2008 | A1 |
| Number | Date | Country |
|---|---|---|
| 20318993 | Apr 2004 | DE |
| 55160318 | Dec 1980 | JP |
| 9007860 | Jan 1997 | JP |
| 2002170727 | Jun 2002 | JP |
| WO 9916092 | Apr 1999 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20110234361 A1 | Sep 2011 | US |
