GB2313483A

GB2313483A - Coils for electromagnetic actuators

Info

Publication number: GB2313483A
Application number: GB9704044A
Authority: GB
Inventors: Jae-Won Yi; Chul-Woo Lee; Yong-Hoon Lee
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 1996-05-22
Filing date: 1997-02-27
Publication date: 1997-11-26
Anticipated expiration: 2017-02-27
Also published as: CN1166023A; NL1005379C2; FR2749103A1; JP2855111B2; GB2313483B; JPH09330812A; GB9704044D0; KR970076542A

Abstract

At least two coils (12, 14) are wound around a bobbin (10) and connected in parallel to decrease coil resistance and as a result, increase the driving current and sensitivity of the actuator. The actuator includes a lens for focusing a laser beam precisely on an optical disc to read out data stored in the optical disc. The bobbin (10) supports the lens which is movable by the actuator in a track direction of the disc or towards and away from the disc.

Description

METHOD FOR WINDING COILS OVER AN APPARATUS AND TO THE SO WOUND APPARATUS The present invention relates to a method of winding coils over an apparatus and to such an apparatus and particularly, though not exclusively, to driving an actuator for tracing a position in an optical recording/reproducing device, and more particularly to a method for winding coils capable of increasing driving current in an actuator driven by a voltage-driven servo.

Figure 1 shows a conventional actuator 20 with an object lens 28 mounted on the top of a bobbin 10, which is to focus a laser beam precisely on an optical disc to read out data stored in the optical disc. The bobbin 10 fixedly supports the object lens 28.

A focus coil 24 wound over a circumference of the bobbin 10 is supplied with a driving current from a servo circuit (not shown) to move the bobbin 10 vertically.

Further, a track coil 22 wound over front and rear sections of the bobbin 10 is supplied with a driving current from the servo circuit to move the bobbin 10 horizontally. A holder 26 for fixing a spring which supports the bobbin 10 is mounted on a side of the bobbin 10.

Figure 2 schematically shows how a coil is wound over a circumference of the bobbin 10 according to the prior art, and Figure 3 shows an equivalent circuit diagram of Figure 2. Referring to Figures 2 and 3, a first coil 12 is wound in series over a circumference of the bobbin 10 from top to bottom in a specific direction (counter-clockwise, in the drawing). In detail, a single coil is wound continuously from a starting point to an ending point in series in a specific direction.

In the prior art, in order to increase the driving sensitivity of the bobbin 10, the wound number of the first coil 12 which is wound in series must increase.

However, the increase of the wound number of the first coil 12 may cause an increase in the coil resistance, resulting in a decrease of the input current. Thus, the first coil 12 is subject to a heat generation and the current applied to the first coil 12 is limited to a specific value, thereby causing a lowering of a driving force in a track direction and a focus direction.

It is therefore an aim of preferred embodiments of the present invention to provide a method for winding coils in parallel.

It is another aim of preferred embodiments of the present invention to provide a coil winding method capable of reducing coil resistance.

It is still another aim of preferred embodiments of the present invention to provide a coil winding method capable of increasing a driving current and a driving sensitivity.

It is yet still another aim of preferred embodiments of the present invention to provide a coil winding method capable of increasing a driving force in a track and focus direction of a bobbin.

It is further still another aim of preferred embodiments of the present invention to provide a coil winding method capable of increasing an AC sensitivity of an actuator.

According to an aspect of the present invention, there is provided a method for winding coils over an apparatus using AC power characterized by winding at least two or more coils over the apparatus using the AC power, so as to reduce coil resistance and thus increase a driving current applied to said apparatus.

Suitably, said coils are wound in parallel from a plurality of starting points to a plurality of ending points.

According to a second aspect of the present invention, there is provided a method for winding coils over a bobbin in an actuator including an object lens for focusing a laser beam precisely on an optical disc to read out data stored in the optical disc, a bobbin for supporting the object lens, coils for moving the bobbin in a focus direction or a track direction, and a holder for supporting the bobbin characterized by winding at least two or more coils over the bobbin so as to reduce coil resistance and thus increase a driving current applied to the bobbin.

Suitably, the wound number of the coils is two.

According to the present invention in a third aspect, there is provided an apparatus around which are wound a plurality of electrically conductive coils.

Suitably, the apparatus further comprises any one or more of the features of the accompanying description, claims, abstract and/or drawings, in any combination.

The present invention will become more apparent in the light of the following detailed description of an exemplary embodiment thereof taken with the attached drawings in which: Figure 1 is a schematic diagram of an actuator in an optical recording/reproducing apparatus according to the prior art; Figure 2 shows how a coil is wound over a bobbin according to the prior art; Figure 3 is an equivalent circuit diagram of Figure 2; Figure 4 shows how coils are wound over a bobbin according to an embodiment of the present invention; Figure 5 is an equivalent circuit diagram of Figure 4; Figure 6 shows how coils are wound over an apparatus using an AC power according to another embodiment of the present invention; and Figure 7 is an equivalent circuit diagram of Figure 6 A coil winding method according to embodiments of the present invention will be described in detail hereinbelow with reference to the attached drawings, in which the like numerals represents like elements.

Referring to Figures 4 and 5, a first coil 12 and a second coil 14 are wound in parallel, in a specific direction, over a circumference of a bobbin 10 starting from the top of the bobbin. It should be noted that the number of coils wound in parallel over the circumference of the bobbin 10 can be two or more, in answer to a need.

It can be readily appreciated from the above description that since the first and second coils 12, 14 are wound in parallel over a circumference of the bobbin 10, the coil resistance may decrease drastically, resulting in an increase of the driving current, i.e., the driving sensitivity.

The above description will be more apparent from the following equations (1) through (3). Namely, in the case in which two coils are wound in parallel, the high frequency band sensitivity of an actuator is in proportion to a driving force.

High Frequency Band Sensitivity Driving Force (F) Biln (1) where "B" represents a magnetic field, "i" a current, "1" a coil length, and "n" the wound number of the coil.

Here, the current is determined by following equation (2): i (current) = V (voltage) / R (coil resistance) ..(2) If equation (1) is substituted for equation (2) High Frequency Band Sensitivity BVln/R (3) It is therefore readily understood from the above description that although the wound number of the coils in case where the coils are wound in parallel is the same as that in case where a coil is wound in series, the total resistance (1/R) of the coils 12, 14 is reduced to become 1/Rl2 + 1/Rl4. Namely, the coil resistance decreases by four times, and thus the driving current with respect to the same voltage increases by four times. Therefore, the driving sensitivity also increases by four times.

As described above, the coil winding method according to an embodiment of the present invention is capable of increasing the driving current and driving sensitivity, and also increasing a driving force to the track and focus directions of the bobbin. Further, an AC sensitivity of the actuator is also improved.

Referring to Figures 6 and 7, shown is a coil winding method which may be employed for an apparatus using an AC power according to another embodiment of the present invention, in which a plurality of coils (1, 2, .., n-1, n) are wound in parallel over a circumference of the apparatus 16 using an AC power starting from the upper section in a specific direction. Namely, at least two or more coils are wound in parallel starting at coil starting points to coil ending points in a specific direction.

Accordingly, the resistance of the coils wound in parallel over the apparatus 16 using the AC power is reduced drastically, thereby resulting in an increase of driving current and driving sensitivity, in accordance with equations (1) to (3).

As described above, since the coil winding method according to embodiments of the present invention winds a plurality of coils in parallel (in the prior art, the coil is wound in series) over an apparatus using AC power, the coil resistance is reduced drastically, resulting in an increase of the driving current and driving sensitivity.

The preferred embodiment of the present invention are given by way of example, and as a means for explaining the use and manufacture of the present invention. The embodiment are subject to routine modification by those of ordinary skill in the art. The present invention is not limited to the illustrative embodiments, but is defined by the appended claims.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A method for winding coils over an apparatus using AC power, characterized by winding at least two or more coils over the apparatus using the AC power, so as to reduce coil resistance and thus increase a driving current applied to said apparatus.

2. A method for winding coils as claimed in claim 1, wherein said coils are wound in parallel from a plurality of starting points to a plurality of ending points.

3. A method for winding coils over a bobbin in an actuator including an object lens for focusing a laser beam precisely on an optical disc to read out data stored in the optical disc, a bobbin for supporting the object lens, coils for moving the bobbin in a focus direction or a track direction, and a holder for supporting the bobbin, characterized by winding at least two or more coils over the bobbin so as to reduce coil resistance and thus increase a driving current applied to the bobbin.

4. A method for winding coils as claimed in claim 3, wherein said coils are wound in parallel from a plurality of starting points to a plurality of ending points.

5. A method for winding coils as claimed in claim 3 or claim 4, wherein the wound number of the coils is two.

6. A method for winding coils, substantially as described herein.

7. An apparatus around which are wound a plurality of electrically conductive coils.

8. An apparatus according to claim 7, further comprising any one or more of the features of the accompanying description, claims, abstract and/or drawings, in any combination.

9. An apparatus substantially as described herein, with reference to and as shown in Figures 4 and 5 or 6 and 7 of the accompanying drawings.