Background Art As shown in Fig. 4, a typical conventional brushless motor comprises a plurality of coils 34 fixed on printed board 36 by soldering and magnet 35 fixed on rotor frame 32, opposing to coil 34 with a gap.

A brushless motor of above configuration has been provided with coils wound by metal wire. Nowadays, however, along with recent advance in printed wired board technology, a different coil manufacturing method is disclosed, e. g., in the Japanese publication of patent application No. S57- 68565, No. S57-186940, No. S57-68656 or No. S58-33958 such that to apply a printed pattern of a conductive coil pattern on film 40 composed of epoxy resin, polyester resin and polyimide resin or the like to form coil sheet 44, and laminate a lot of those coil sheets 44 to form a multilayer coil, as shown in Fig. 5.

Such multilayer coil is advantageous to make a compact motor because conventional core wound by metal wire is not necessary and wire winding density is high.

But conventional multilayer coil mentioned above needs an additional process to apply an adhesive layer evenly on a plurality of respective coil sheets 44 for bonding, which results in a problem of production cost increase.

Additionally, the coil sheet composed of plastic or composite materials

has a poor thermal proof and are easily affected by ambient temperature.

Therefore, operation conditions such as ambient temperature for a brushless motor must be restricted to prevent an unstable movement caused by heat generation due to copper loss and iron loss.

Consequently, a following coil configuration is disclosed to solve the above problems in conventional multilayer coil, in the Japanese publication of patent application No. H5-336712 such that, as shown in Fig. 6, to continue the manufacturing steps of : (a) forming a conductive coil pattern on a glass substrate, (b) providing the conductive coil pattern with a glass coating, and (c) forming a conductive coil pattern further on the glass coating, and finally, applying a glass coating on the top surface to produce a multilayer coil.

Generally, however, the glass used for such multilayer substrate has drawbacks of low impact proof and short life performance.

Disclosure of Invention A multilayer ceramic coil is disclosed in this invention wherein a plurality of ceramic layers having coil patterns printed with conductive paste and connected the coil patterns of respective layers electrically via thru-holes are laminated to form a single multilayer ceramic structure comprising a plurality of phases of coil.

Brief Description of Drawings Fig. 1 is a cross-sectional view of a motor used in the exemplary

embodiment of the present invention.

Fig. 2A is front view of patterns of a multilayer ceramic coil used in the exemplary embodiment of the present invention.

Fig. 2B is a cross-sectional view of a multilayer ceramic coil used in the exemplary embodiment of the present invention.

Fig. 2C is an outline view of a multilayer ceramic coil used in the exemplary embodiment of the present invention.

Fig. 3 is an exploded perspective view of a coil pattern of one phase of the coil pattern used in the first preferred embodiment of the present.

Fig. 4 is a cross-sectional view of a conventional motor.

Fig. 5 is an exploded perspective view of a multilayer ceramic coil of a conventional motor.

Fig. 6 is an exploded perspective view of a multilayer ceramic coil of another conventional motor.

Best Mode for Carrying Out the Invention The present invention is described by following preferred embodiment with reference to drawings.

Exemplary Embodiment Fig. 1 shows a motor used in the exemplary embodiment of the present invention. A cross-sectional view of the motor is shown in Fig. 1. As shown in Fig. 1, rotation axis 1 is secured rotor frame 2 vertically. Multilayer ceramic coil 4 is fastened on bearing 3 by means of housing. Bearing 3 holds rotation axis rotatably. Magnet 5 is secured on rotor frame 2 opposing to multilayer ceramic coil 4 with a gap.

Delivering excitation current to multilayer ceramic coil 4, attraction and repulsion of magnet against multilayer ceramic coil 4 produces rotating force

of motor.

Fig. 2A shows exploded views of configuration of multilayer ceramic coil 4, Fig. 2B shows a cross-sectional view of the multilayer ceramic coil and Fig. 2C shows an outline view of the multilayer ceramic coil.

Coil patterns 4a and 4b printed on ceramic layer 4c are electrically connected alternately via thru-hole 4d. Coil patterns 4a and 4b of respective phases are electrically connected to crossing pattern 4e.

In addition, each phase terminal is electrically connected to outlet electrode 4g by means of terminal pattern 4f. Outlet electrodes 4g are mounted at four corners of multilayer ceramic coil 4. Outlet electrodes 4g are soldered on printed wired board 6 to secure multilayer ceramic coil 4 on the board.

Next, a procedure to form a coil pattern on multilayer ceramic is described in detail with reference to Fig. 3. Fig. 3 is an exploded view of winding formation for a phase of multilayer coil pattern.

(a) Connect terminal pattern 51 electrically to winding top of coil pattern 53a, formed on one layer below, via thru-hole 52a.

(b) Connect winding end of coil pattern 53a electrically to winding top of coil pattern 53b of the formation, formed on further one layer below, via thru-hole 52b.

(c) Laminate coil patterns 53a and 53b from top to bottom to form patterned-coil 55a in this way, via thru-holes 52a and 52b.

(d) Similarly, laminate coil patterns 53a and 53b from bottom to top to form patterned-coil 55b, via thru-holes 52a and 52b.

(e) Moreover, connect winding end of coil pattern 53a on the bottom layer of patterned-coil 55a electrically to one end of crossing pattern 54, formed on further one layer below, via thru-hole 52b.

(f) Connect another end of crossing pattern 54 electrically to winding top of coil pattern 53a, formed on the bottom of patterned-coil 55b, via thru-hole 52a, to provide patterned-coil 55a and patterned-coil 55b with an electrical connection to an other phase of coil.

(g) Finally, connect winding end of coil pattern 53a on the uppermost layer of patterned-coil 55b electrically to terminal pattern 56 via thru-hole 52b to provide a patterned-coil having multiple outlet electrodes.

The multilayer ceramic coil disclosed in the present invention has such a configuration that conductive coil patterns are embedded and laminated in multilayer ceramic structure to provide a coil formation to which excitation current of the motor is fed, which can solve problems in conventional art.

The multilayer ceramic coil has a plurality of ceramic layers having coil patterns printed using conductive paste, connected to the coil patterns of respective layers electrically via thru-holes and laminated to form a single multilayer ceramic structure including a plurality of phases of patterned-coil.

In addition, terminals of coil pattern formed inside of the multilayer ceramic structure are electrically connected to outlet electrodes disposed on surrounding surfaces of the multilayer ceramic coil to form terminals for feeding excitation current for motor.

The present invention is not limited to the exemplary example mentioned above but can be used for various application within the concept of this invention.

As mentioned above, the multilayer ceramic coil for use in motor adopts ceramic as an innovative coating material. A motor equipped with the multilayer ceramic coil generates a stable torque force because the

multilayer ceramic coil has a higher thermal proof compared with coils provided by plastic, composite materials or glass and has a good heat conductivity. Additionally, the motor shows a reliable performance in various ambient conditions.

Industrial Applicability The present invention discloses a multilayer ceramic coil and a motor using the same. A multilayer ceramic coil for use in motor is configured with conductive coil patterns embedded and laminated in a multilayer ceramic structure to provide a coil formation to which excitation current for the motor is supplied.