JPH0515045B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultra-thin, compact, and inexpensive printed coil unit for an actuator. Actuator here consists of a coil, a magnetic circuit, etc., and converts electrical energy into mechanical energy using electromagnetic force, and refers to, for example, a motor, linear motor, rotary actuator, linear actuator, etc. .

[Conventional technology and its problems]

BACKGROUND ART In recent years, as audio equipment, video equipment, OA equipment, etc. have significantly advanced and become smaller and thinner, the actuators used in these equipment have also been desired to be smaller and thinner.

Taking a rotary actuator as an example of an actuator used in such equipment, as shown in FIG. What is desired is a structure consisting of a coil unit 12 which is a laminate of printed coil sheets having a spiral conductor pattern 3 corresponding to the magnetic poles of the magnet. Since this printed coil sheet is extremely thin compared to a wire-wound coil, an actuator using a printed coil unit obtained by laminating printed coil sheets can have a considerably thinner gap between the yoke plate 13 and the magnet 10. As a result, the magnetic field at the position where the coil is present becomes stronger and the torque increases.

Incidentally, in actuators, the magnetic detection element 8 is used to switch the current flowing through the coil, but with the introduction of printed coil units, the thickness of the coil part has become significantly thinner, making it possible to reduce the distance between the magnet and the yoke plate. became more magnetic, making it difficult to place them. Magnetic detection elements include Hall elements and magnetoresistive elements, but these are all considerably thicker than the above-mentioned printed coil unit, and conventionally these magnetic detection elements 8 have been formed into coils as shown in FIG. 2B, for example. The unit 12 is placed on top of the unit 12 with a large gap so that it does not get caught in the opposing magnet 10. However, when the magnetic sensing elements are arranged in this way, the distance between the magnet and the coil becomes large, and the advantage of the printed coil sheet, which allows it to be wound thinly, cannot be utilized. Furthermore, if the magnetic detection element is placed outside the main magnetic flux of the magnet in order to achieve a thinner profile, the magnetic detection sensitivity will decrease, making it necessary to increase the sensitivity of the amplifier for the magnetic detection element, making it difficult to obtain a good S/N ratio. Cost increases.

[Means and actions to solve the problem]

The present invention solves the above problems by embedding a thin magnetic sensing element in a portion of the printed coil sheet other than the spiral conductor pattern.

In other words, the present invention is directed to one or more printed coil sheets placed facing a magnet having one or more magnetic poles on the same plane, or one or more of them. A printed coil unit for a small actuator made of a laminate, wherein the printed coil sheet has one or more spiral patterns on the same plane,
and one or more magnetic sensing elements having a thickness equal to or thinner than the thickness of the printed coil sheet are embedded in a single layer of the printed coil sheet and in a portion other than the spiral conductor pattern. This is a printed coil unit for small actuators.

FIG. 1 shows an example of an actuator incorporating the printed coil unit of the present invention.

The printed coil sheet used in the present invention is
The printed coil may be manufactured by any manufacturing method, such as etching, plating, or a combination thereof, but the printed coil manufactured by the manufacturing method described in Japanese Patent Application Laid-Open No. 57-91590. A sheet is preferred. Moreover, the size of 0.1 to 2 mm is particularly effective. The linear density of the coil portion is preferably 2 to 20 lines/mm, more preferably 5 to 20 lines/mm. FIG. 3 shows an example of a printed coil sheet used in the present invention. The magnet is N
When there are n poles and south poles, 2n spiral patterns 3 are formed on both sides of the printed coil sheet support 2. Figure 3 shows a case where the magnet is magnetized with four north poles and four south poles, and eight spiral conductor patterns 3
This is an example where . Note that the two spiral conductor patterns on the front and back sides of the printed coil sheet support 2 are counted as one spiral conductor pattern.
Generally, the spiral conductor pattern 3 is arranged on the same plane and its center coincides with the axis 11 of the actuator and the center of the magnet 10 shown in FIG.

If necessary, the conductor patterns 3 present on both sides of the printed coil sheet support 2 are electrically connected through the through holes 6. The printed coil sheet support 2 may be of any material as long as it has electrical insulation properties, and for example, glass epoxy substrates, polyimide films, epoxy resins, etc. are preferably used. Further, any method for forming the through hole 6 may be used.

FIG. 4 is an example of a printed coil sheet for a linear actuator used in the present invention. One or more spiral conductor patterns are arranged on the same straight line as the sliding direction, and FIG. 4 shows a case where there are two spiral conductor patterns. Similarly to the flat brushless motor, the printed coil sheet for the linear actuator is also connected to the conductor patterns 3 present on both sides of the printed coil sheet support 2 via through holes 6 so as to be electrically conductive, as necessary.

The thickness of the magnetic sensing element must be less than or equal to the thickness of the printed coil sheet to which the element is attached.

The magnetic detection element 8 is embedded in a printed coil sheet constituting the coil unit. The state of "embedding" here means that the entirety of the magnetic sensing element, including the sensing part 14 and the part in which it is molded, is contained within the thickness of the printed coil sheet, as shown in FIGS. 5A and 5B. There are also states. Therefore,
The magnetic detection element cannot protrude from the surface of the printed coil sheet at all. Here, the sensitive part refers to a part of the magnetic detection element that has the ability to convert the strength of a magnetic field into an electrical signal. Any magnetic detection element can be used as long as it can convert changes in the magnetic field into electrical signals, but
For example, a Hall element, a magnetoresistive element, etc. are used.

If the element is thinner than the thickness of the printed coil sheet, it is necessary to deform the spiral conductor pattern of the printed coil sheet other than the printed coil sheet to which the element is attached in the coil unit to match the position and shape of the element. This increases the degree of freedom in designing spiral conductor patterns. In particular, as the magnetic detection element used in the present invention, a face down bonded or lead bonded Hall element is particularly preferable. Such an element is 0.6
It is possible to manufacture products with a thickness of mm or less, and even products thinner than 0.4 mm.

Further, the shape of the element may be any shape, but a pentagonal or triangular shape is particularly preferable when the element is arranged in a region facing the outer periphery where the corners of the spiral conductor pattern are rounded and deformed.

Although the magnetic detection element 8 may be embedded in any printed coil sheet constituting the coil unit, it is preferable to embed it entirely in one of the printed coil sheets constituting the coil unit. When magnetic sensing elements are embedded in one printed coil sheet, the distances from the magnet to each magnetic sensing element are exactly the same, and the strength of the magnetic field that each element receives is constant. In addition, holes for positioning and embedding all magnetic detection elements can be punched all at once using a mold on one printed coil sheet.
The mutual positional accuracy of the magnetic detection elements can also be increased. As a result, the timing of switching the current flowing through each coil becomes accurate, and uneven rotation and uneven thrust of the linear actuator can be suppressed.

Further, it is preferable that the printed coil sheet in which the magnetic detection element is embedded is placed on the side of the coil unit closest to the magnet. With this arrangement, the magnetic field received by the magnetic detection element becomes stronger, the output of the magnetic detection element becomes higher, and the current switching timing becomes more accurate. Furthermore, by embedding a magnetic detection element in the printed coil sheet closest to the magnet, a part of the coil that contributes to torque is removed, reducing the contribution to torque, and reducing the torque contribution to the magnet between each printed coil. Can balance. Therefore, the effect of reducing torque unevenness can be expected.

In the case of a flat brushless motor, it is preferable that the position on the printed coil sheet in which the magnetic sensing element is embedded satisfies the following two conditions at the same time.
The first condition is that the inner diameter of the magnet is r ₁ and the outer diameter is
When r ₂ , and when R is the distance from the center of the magnet to the center of the sensing part of the magnetic detection element, R is r ₁ × 1.2
≦R≦r ₂ ×1.1, and further satisfies r ₁ ×1.4≦R≦r ₂ ×1.0. Whether R is small or large, the magnetic field becomes weaker and the magnet position detection accuracy decreases. The second condition for embedding the magnetic detection element is that it should be located between the spiral conductor patterns or in a portion facing the inner and outer peripheries, excluding the spiral conductor patterns 3 and their central portions 5. Two or more magnetic detection elements are arranged depending on the driving method, but in many cases, the arrangement pitch in the circumferential direction does not match the arrangement pitch of the spiral conductor pattern. In other words, even if one magnetic detection element is placed in an empty space between the spiral conductor patterns, the positions of other magnetic detection elements overlap with the spiral conductor patterns. Therefore, a part of the spiral conductor pattern that contributes to the actuator torque is sacrificed to slightly deform the pattern, and a magnetic detection element is embedded there. For example, the seventh
It may be done as shown in Figures A, B, C or D.

In addition, in the case of a linear actuator, the position of the printed coil sheet in which the magnetic detection element is embedded is 2.
As can be seen from the graph of the relationship between the distance from the center of the magnet and the strength of the magnetic field shown in Figure 8(B), the first condition is:
When the distance from the axial center of the magnet to the center of the sensing part of the magnetic detection element 8 is R, R≦/2+d (d is the distance between the magnet and the coil), and R≦ Preferably, it is l/2+d/2. When R is larger than 1/2+d, the magnetic field becomes weaker and the magnet position detection accuracy decreases. The second condition for the position of embedding the magnetic detection element is that it be located on the spiral conductor pattern 3 and excluding the center part 5 of the conductor pattern, and as shown in FIGS. 9A and B, Part is preferred.

A method for embedding a magnetic detection element in a printed coil sheet is, for example, by making a hole in the printed coil sheet using a press, inserting the element, and fixing the hole with an adhesive. It is preferable to make the hole in the same shape as the outer shape of the element, such as a triangle or a rectangle, since this improves positional accuracy. As shown in Fig. 10, the simplest and most accurate example is to use a triangular magnetic sensing element and make a V-shaped notch 15 on a part of the outer periphery of the printed coil sheet that matches the outer shape of the element. An example of this method is to simultaneously provide a triangular magnetic detection element in the V-shaped notch 15 when machining the mold for both the inner and outer diameters and fix it with adhesive. A liquid or sheet-like epoxy or phenol adhesive is used to fix the magnetic detection element to the printed coil sheet. In addition, when punching out a hole or notch into which the magnetic sensing element is inserted using a mold, the positioning of the magnetic sensing element with respect to the coil can be done by marking the photomask on the printed coil sheet in advance and using it. Accuracy is also significantly improved.

As described above, a coil unit is formed by laminating a plurality of printed coil sheets in which magnetic sensing elements are embedded, or a plurality of printed coil sheets that do not include magnetic sensing elements. In some cases, a printed coil sheet in which a magnetic detection element is embedded may be used alone. Any adhesive can be used for this lamination as long as it can fix the coils and provide insulation between the coils, but for example, epoxy or phenol adhesives can also be used, or semi-cured adhesive can be used on both sides of the insulating film. You may also use an adhesive sheet that has been applied with a coating.

Embodiments of the printed coil unit of the present invention are listed below, but the present invention is not limited to these embodiments in any way.

Example 1 Using photolithography technology and electrolytic copper plating, a spiral conductor pattern was formed in each region of a flat donut shape with an outer diameter of 20 mmφ and an inner diameter of 7 mmφ divided at a central angle of 45°, with 8 poles on both the front and back sides with an insulating layer in between. Two printed coil sheets were created. For each printed coil sheet, one pole of the spiral conductor pattern on both sides was made smaller, and a space was created on the outer periphery of the coil sheet for embedding a Hall element. Each spiral conductor pattern has a through hole in the center to electrically connect opposing patterns with an insulating layer in between, and adjacent patterns on the same plane have opposite coil winding directions. I made it. An insulating overcoat resin was applied to both sides of the printed coil sheet. The thickness of both printed coil sheets including the overcoat layer was 0.3 mm.

Next, the above-mentioned printed coil sheets formed on the same substrate are molded one by one using a bushing mold.
The coil sheets were cut and separated into flat donut-shaped printed coil sheets. At this time, at the same time, a notch is made in the mold to embed an equilateral triangular Hall element with a side of 2.3 mm and a thickness of 0.3 mm at a predetermined location on the outer periphery so that the sensing part is 9 mm from the center of the axis. It was then cut and formed.

A 42 μm thick Nitto Denko adhesive sheet (Nitto Fixtures TK-2532) was placed on the yoke plate obtained by cutting a 1 mm thick silicon rigid plate, and the above printed coil sheet was placed on top of the 42 μm thick adhesive sheet (Nitto Fixtures TK-2532). Insert the Hall element so that it does not come out from the surface of the printed coil sheet and do not dent it, then spread the aforementioned adhesive sheet on top of it, and place the second printed coil sheet at a central angle with respect to the first printed coil sheet. 22.5 degrees apart, and in the same manner as before, the laminate in which the Hall element was fitted was placed between a hot press machine and heat-pressed under conditions of 120° C. and 10 kg/cm ² for 1 hour.

In this way, the obtained laminate of the coil unit and yoke plate was used as a rare earth sintered magnet (samarium-cobalt 2
-17 series, maximum energy product 20MGOe (Mega Gauss Oersted)) is divided into 45° sections in the circumferential direction, and magnets are magnetized alternately with 4 N poles and 4 S poles in the direction perpendicular to the surface. 10 flat brushless motors with a total thickness of 3.1 mm from the upper end of the magnet to the lower end of the yoke plate via the printed coil unit, and a distance (gap) between the magnet and yoke plate of 1.1 mm. Obtained.

These motors are measured using a back electromotive force measurement method, which is one of the methods for evaluating motor characteristics, in which the motor to be measured is rotated at a constant rotation speed using another rotor and the electromotive force generated from the motor coil is measured. When we measured the back electromotive force of the coil on the side closer to the magnet and the coil on the side different from the magnet, we found that the sum of the back electromotive force of both printed coils, which is an indicator of the overall torque of the motor at 2400 rpm, is the same as that of the 10 motors. The average is 2.08V, and the difference between the back electromotive force, which indicates the difference in the contribution of the two printed coils to the motor torque, is the average of 10 motors.
It was 0.174V.

Also, during the measurement of each voltage above, 5 mA was applied to the Hall element.
The average value of the 10 motors was that the output of the Hall element for the coil near the magnet was 280 mV, and the output of the Hall element for the coil far from the magnet was 280 mV. Output is 248m
It was V.

Comparative Example 1 Two equilateral triangular Hall elements each having a side of 2.3 mm and a thickness of 0.9 mm are placed on the side closer to the magnet so that the sensing part is 9 mm from the axis center and the center angle between the elements is 22.5°. Three flat brushless motors were made that were exactly the same as in Example 1, except that they were adhered to the one-pole spiral conductor pattern of the printed coil sheet using an instant adhesive Tackback ^R manufactured by Loctite. The total thickness of the obtained motors from the upper end of the magnet to the lower end of the yoke plate was 4.0 mm, and the distance (gap) between the magnet and the yoke plate was 2.0 mm.

When the motor characteristics of these motors were evaluated, the sum of the back electromotive force of the two printed coil sheets in the motor at 2400 rpm was 1.49V on average for the three motors.

Also, during the measurement of each voltage above, 5mA is applied to the Hall element.
When the peak-to-peak voltage of the output voltage of the Hall element on both printed coil sheets was measured by passing a current of
It was hot. The central angle between Hall elements calculated from the phase difference of the output waveform is 21.8° for each angular motor.
They were 22.6° and 23.1°.

Example 2 Using photolithography technology and electrolytic copper plating, a spiral conductor pattern was formed in each region of a flat donut shape with an outer diameter of 20 mmφ and an inner diameter of mmφ separated into a central angle of 45°, 8 stations on both the front and back sides with an insulating layer in between. Two printed coil sheets were created. One printed coil sheet has 8 poles of spiral conductor patterns arranged evenly, and the other one has one pole of the spiral conductor patterns on both sides made smaller, and a place for embedding a Hall element on the outer periphery of the coil sheet. I opened it. Each spiral conductor pattern has a through hole in the center to electrically connect opposing patterns with an insulating layer in between, and adjacent patterns on the same plane have opposite coil winding directions. I made it. An insulating overcoat resin was applied to both sides of the printed coil sheet. The thickness of both printed coil sheets including the overcoat layer was 0.3 mm.

Next, the above-mentioned printed coil sheets formed on the same substrate are molded one by one using a bushing mold.
The coil sheets were cut and separated into flat donut-shaped printed coil sheets. At this time, the printed coil sheet in which the Hall elements are embedded is also equipped with two equilateral triangular Hall elements, each with a side of 2.3 mm and a thickness of 0.3 mm, at a predetermined location on the outer periphery, with each sensing part located 9 mm from the center of the shaft. Then, a notch for embedding the elements was cut using a mold so that the central angle between the elements was 22.5°.

A 42 μm thick Nitto Denko adhesive sheet (Nitto Fixtures TK-2532) is placed on a yoke plate obtained by cutting a 1 mm thick silicon rigid plate, and the printed coil sheet without the above notch is placed on top of it. Place the above-mentioned adhesive sheet on top of it, make a notch for the second sheet, place the printed coil sheet with the center angle shifted by 22.5 degrees from the first printed coil sheet, and make a hole in the notch. To prevent the element from jumping out from the printed coil sheet surface,
The laminate, which had been fitted so as not to be dented, was placed in a hot press and heat-pressed at 120° C. and 10 kg/cm ² for 1 hour.

The thus obtained laminate of the coil unit and yoke plate was used as a rare earth sintered magnet (samarium-cobalt 2
-17 series, maximum energy product 20MGOe (Mega Gauss Oersted)) is divided into 45° sections in the circumferential direction, and magnets are magnetized alternately with 4 N poles and 4 S poles in the direction perpendicular to the surface. 10 flat brushless motors with a total thickness of 3.1 mm from the upper end of the magnet to the lower end of the yoke plate via the printed coil unit, and a gap of 1.1 mm between the magnet and the yoke plate. Obtained.

When we evaluated the motor characteristics of these motors, we found that the sum of the back electromotive force of the two printed coils in the motor at 2400rpm was 2.09V on average for 10 motors, and the back electromotive force of both coils was The average difference for the 10 motors was 0.038V.

Also, during the measurement of each voltage above, 5mA is applied to the Hall element.
When the peak-to-peak voltage of the output voltage was measured by passing a current of
It was V.

The central angle between the Hall elements calculated from the phase difference of the output waveforms was within 22.5±0.3° for all 10 units.

〔Effect of the invention〕

In the printed coil unit of the present invention, each of the printed coil sheets constituting the unit is thin, and a magnetic detection element with a thickness less than the thickness of the printed coil sheet is embedded therein. The gap between the yoke plates can be made sufficiently small, resulting in an ultra-thin actuator.

In particular, by embedding all the magnetic detection elements in one of the printed coil sheets that make up the coil unit, the magnetic fields received by the magnetic detection elements are equalized, the output voltage of each element is made equal, and If the printed coil sheet embedded with the magnetic sensing element is placed on the side closest to the magnet, the actuator torque of the printed coil sheet on the side closest to the magnet will be affected by deforming the coil pattern to embed the magnetic sensing element. Since the contribution is reduced, it is possible to equalize the contribution of each printed coil sheet to the torque at the same time, resulting in a small and thin actuator with high rotational stability.

[Brief explanation of the drawing]

Figures 1A and 1B are each a small actuator incorporating the printed coil unit of the present invention.
FIG. 2A is an exploded view and a sectional view showing an example.
B is an exploded view and a sectional view of a conventional small actuator, respectively. FIGS. 3A, 3B, and 3C show one example of a printed coil sheet used in the present invention, and are, in order, a front plan view, a back plan view, and a view taken along the line A-A'. FIGS. 4A and 4B are an example of a printed coil sheet for a linear actuator used in the present invention, and are a front view and a view taken along the line A-A', respectively.
In FIG. 5, A, B, and C are cross-sectional views illustrating the state in which magnetic detection elements are "embedded" in a printed coil sheet according to the present invention, and A and B in FIGS. 6 and 8 are printed coils according to the present invention, respectively. 2 is a cross-sectional view of an actuator incorporating the unit, and a graph showing the relationship between the distance from the center of the actuator and the strength of the magnetic field. FIG. 7 and FIG. 9 are surface views of a printed coil sheet showing examples of preferred embedding positions of magnetic sensing elements. FIG. 10 is a surface view of a printed coil sheet provided with a notch for embedding a magnetic detection element. Figure 11 and 1st
Figure 3, A, B, and C are, in order, a cross-sectional view of the small brushless motor obtained in Examples 1 and 2, a plan view of the printed coil sheet on the side closer to the magnet, and a plan view of the printed coil sheet on the side farther from the magnet. Yes, first
2A, B, and C are, in order, a cross-sectional view of the small brushless motor obtained in Comparative Example 1, a plan view of the printed coil sheet on the side closer to the magnet, and a plan view of the printed coil sheet on the side farther from the magnet. 1, 1a, 1b...Printed coil sheet, 2
...Printed coil sheet support, 3...Spiral conductor pattern, 4...Through hole land, 5...
... Central part of spiral conductor pattern, 6 ... Through hole, 7 ... External connection terminal, 8 ... Magnetic detection element, 9 ... Insulating overcoat resin, 10 ...
Magnet, 11... Shaft, 12... Coil unit, 1
3... Yoke plate, 14... Sensing section in the magnetic detection element, 15... Notch for embedding the magnetic detection element.

Claims (1)

[Claims] 1. A printed coil unit for a small actuator consisting of one or more printed coil sheets or a laminate thereof, which are placed facing a magnet having one or more magnetic poles magnetized on the same plane. and the printed coil sheet is arranged on the same plane.
One or more magnetic sensing elements having one or more spiral conductor patterns and having a thickness equal to or thinner than the printed coil sheet are in a single layer of the printed coil sheet and are other than the spiral conductor pattern. A printed coil unit for a small actuator characterized by being embedded in the part. 2. When two or more magnetic detection elements are embedded, all the magnetic detection elements are embedded in the same printed coil sheet so that the distance from the magnet surface is substantially the same. Printed coil unit for small actuator. 3. The printed coil unit for a small actuator according to claim 2, wherein all the magnetic detection elements are embedded in the printed coil sheet closest to the magnet.