JPH01315244A - Axial flux type brushless motor - Google Patents

Abstract

PURPOSE:To reduce in diameter and thickness and to decrease the jitter, of a rotating speed by forming a small gap between a rotor permanent magnet and a stator yoke, and mounting a printed sheet formed with a printed coil in the gap. CONSTITUTION:A rotor 50 is composed of a bracket 14 secured to a rotary shaft 12, a rotor yoke 16 secured to the bracket 14, and a rotor permanent magnet 52 secured to the yoke 16. A gap between the magnet 52 and a stator yoke 56 is approx. 0.3mm. The yoke 56 is so attached as to be buried in a base 54, and a plated through-hole both-side printed sheet 58 copper-lined adheres to a polyimide film base material on the base 54. A printed coil pattern and a driving circuit are provided on the both-side printed sheet 58.

Description

[Detailed Description of the Invention] Table of Contents Existing Fields of Industrial Application Prior Art Problems to be Solved by the Invention Means for Solving the Problems Implementation Examples Summary of the Effects of the Invention Concerning an axial flux type brushless motor, The aim is to provide a low-cost axial flux brushless motor with a small diameter and thin profile and low rotational speed jitter and flutter.The rotor is created by magnetizing a disk-shaped magnet with multiple poles in the direction parallel to the rotation axis. In an axial flux type brushless motor, which has an armature coil on the stator side and a stator yoke that serves as a magnetic path for the rotor magnetic flux, the motor drive is made of a flexible wood film as a base material. A printed sheet having a circuit pattern and a printed coil consisting of two layers of conductive coil patterns, one on the front and one on the back, with through-hole plated parts formed on other parts, is attached to the disc-shaped magnet and the stator yoke. At the same time, a magnetic pole position detecting element of a disc-shaped magnet is provided on the printed sheet, and a speed signal of one waveform per rotation generated by the magnetic pole position detecting element is detected as a rotational speed. The system is configured by providing a control means for controlling the system.

INDUSTRIAL APPLICATION FIELD The present invention relates to an axial flux type brushless motor.

Brushless motors, which use non-contact electronic commutation instead of a commutator, are highly reliable in terms of lifespan and electrical noise.
Adoption in various devices is progressing.

Since this brushless motor has a high degree of structural freedom, it is easy to make it lighter, thinner, shorter, and smaller, and its uses are expanding as a direct drive motor that can easily maintain relative mechanical precision between equipment and the motor. There is a high demand for scanner motors for laser beam printers for office automation equipment.

The axial flux type (axial gap type) brushless motor, which is a type of brushless motor, has a structure in which a disc-shaped magnet is multi-polarized in the magnetization direction parallel to the rotation axis and used as a rotor, so it has a simple structure and is thin. It is suitable for use in high-precision devices such as cassette tape recorders, video tape recorders, and scanner motors for laser beam printers, as it generates little torque due to changes in the magnetic attraction force between the rotor magnet and stator yoke. Widely used in applications requiring high speed rotation.

BACKGROUND ART FIG. 15 is a schematic exploded perspective view of a conventional axial flux type brushless motor, and FIG. 16 is a vertical cross-sectional view thereof. Rotor yoke 1 fixed to 14
6 and rotor permanent magnets (in the direction of the rotating shaft 12 fixed to the rotor yoke 16) that are alternately magnetized into a plurality of poles (
The rotor magnet 18 includes a rotor magnet (rotor magnet) 18, an annular member 20 fixed to the lower surface of the outer periphery of the rotor yoke 16, and an annular FG magnet 22 attached to the annular member 20. In the illustrated conventional example, the rotor permanent magnet 18 is polarized into eight poles.

A housing 24 constitutes the stator side, and two bearings 28 and 3 are provided between the housing 24 and the rotating shaft 12.
0 are provided, and the rotating shaft 12 is rotatably supported by these bearings.

Further, the second sleeve is a sleeve, and a preload spring 32 is installed between the sleeve 26 and the housing 24 and between the bearings 28 and 30.
is interposed. A stopper 34 prevents the bearing 30 from coming off.

36 is a stand fixed to the housing 24. stand 3
A stator yoke 38 made of, for example, a silicon steel plate is provided on the stator 6, and a printed wiring board 40 is provided on the stator yoke 38. Printed wiring board 4
0, there are six armature coils 42, an FC coil 44 for rotational speed detection, and a Hall element 4 for rotor phase detection.
6 is provided. Armature coil 42 of this conventional example
is a three-phase drive in which opposing armature coils are driven simultaneously. The phase relationship between the rotor permanent magnet 18 and the armature coil 42 is detected by the Hall element 46, and the phase and current magnitude of the armature coil 42 to be excited are set to ensure smooth rotation. .

The housing 24, the stand 36, the stator yoke 38, and the printed wiring board 40 on which the armature coil 42, the FG coil 44, and the Hall element 46 are provided constitute the stator side of the motor. The FC coil 44 is designed to generate a speed signal for speed control by changing the intersecting magnetic flux with the FC magnet 22.

The above-mentioned wire-wound brushless motor has the disadvantage of increasing the overall thickness of the motor. A flat brushless motor in which multiple layers of stator coils are stacked is disclosed.

According to this publication, it is not clear how to form multiple layers of stator coils on the printed circuit board (the structure in Figure 10 of the publication is not clear), but it is fixed compared to conventional brushless motors. The motor can be made thinner by making the child coil layer thinner.

Problems to be Solved by the Invention In order to improve the cost performance of printer devices, etc., they are becoming increasingly thinner and smaller (for example, thickness less than 20 cm, diameter less than 500 m), and rotational speed jitter (high frequency component of speed fluctuation) and flutter (speed fluctuation). low frequency components) are small (for example, ±
(0.015% or less), a low-cost axial flux type brushless motor is required. There are three main factors that impede these demands:

(1) Usually, when designing the magnetic circuit of a motor, it is designed to maximize the torque per unit power consumption of the coil, that is, the motor constant. The gap is approximately equal to the thickness of the rotor magnet. Because of this design, there is a problem that the rotor inertia is small relative to the thickness of the motor, and even if closed-loop speed control is performed, the motor is susceptible to external disturbances and is prone to jitter and flutter.

(2) Since the arrangement of the FG coil and FG magnet includes eccentricity and pitch deviation, errors are included in the speed signal that generates multiple waveforms in one rotation. Even if closed-loop speed control is performed using this speed signal, there is a problem in that jitter and flutter in the rotational speed cannot be suppressed. For example, if the precision of the FG coil, FG magnet, and their mounting is increased so that the speed signal error is less than 1/10 of the required specification value for jitter and flutter, it becomes expensive. Furthermore, if used as a motor magnetic circuit, FC is placed on the outermost periphery, which is the part that generates the largest torque.
Since the motor is provided with a coil and an FG magnet, there is a problem in that the generated torque is small despite the motor's large outer diameter.

(3) Since the coil is made of wire, it is difficult to automate the soldering of its terminals, and the soldering must be done manually, resulting in high labor costs.

The flat brushless motor described in JP-A-62-123952 mentioned above still has an FG magnet and an FG coil, and therefore cannot solve the above-mentioned problem (2). Furthermore, since a plurality of layers of stator coils are formed on a rigid printed circuit board, there is a limit to how thin the stator coil portion can be made.

The present invention has been made in view of these points, and its purpose is to reduce jitter and rotational speed with a small diameter and thin structure.
To provide a low-cost axial flux type brushless smoke with small flutter.

Means for solving the problem A disk-shaped magnet is magnetized with multiple poles parallel to the rotation axis and used as a rotor, and fixed on the stator side to serve as a magnetic path for the armature coil and rotor magnetic flux. An axial flux type brushless smoke with a child yoke has two layers on the front and back, with a motor drive circuit pattern formed on one part of the flexible wood film as a base material and a through-hole plated part formed on the other part. A printed sheet having a printed coil composed of a conductive coil pattern is provided such that the printed coil is mounted in the gap between the disc-shaped magnet and the stator yoke. Further, a magnetic pole position detecting element of a disc-shaped magnet is provided on the printed sheet, and a control means is provided for controlling the rotational speed by using a speed signal of one waveform per rotation generated by the magnetic pole position detecting element.

The control means may use, for controlling the rotational speed, speed signals having one waveform for one rotation of a plurality of rotations occurring at angular positions shifted from each other. In order to suppress losses such as eddy current loss,
Although it is desirable to form the stator yoke from a soft ferrite material, the stator yoke is formed by winding a ferromagnetic strip material coated with an insulator or a ferromagnetic wire material with a circular cross section in a spiral shape around the rotation axis. may be formed.

Furthermore, in order to particularly suppress eddy current loss, the stator yoke may be constructed of a plurality of concentric magnetic rings centered around the rotation axis of the rotor.

Furthermore, when the motor rotates at high speed, eddy current loss increases due to fluctuations in the magnetic flux leaking not only to the stator yoke but also to the stator housing that fixes the bearing, causing a problem in which motor efficiency decreases. In order to prevent magnetic flux, a ring-shaped non-magnetic rotor member, a soft magnetic rotor member, a high resistivity soft magnetic stator member, or a high resistivity non-magnetic member is placed opposite the side surface of the disc-shaped magnet. A stator member may also be provided.

Function The axial flux type brushless smoke of the present invention has the following features:
One of its features is that it does not use a design method that maximizes the motor constant. In other words, by forming the gap between the disc-shaped magnet and the stator yoke to be smaller than the thickness of the magnet, the entire motor can be made thin, and by making the rotor relatively thick, high inertia can be achieved. , it is possible to suppress jitter and flutter by increasing the inertia of the rotor. In order to maximize the thickness of the disc-shaped magnet within a given finite motor thickness, it is necessary to make the gap between the magnet and the stator yoke as small as possible. The ultimate coil for this purpose is a single sheet coil.

In order to make a thin sheet coil, it is necessary to use a film-like printed sheet instead of a rigid printed circuit board as the base material, and it is desirable to form conductive coil patterns on both the front and back sides of this printed sheet.

In order to simplify the motor configuration and eliminate the concept of installing coil parts, it is necessary to create the printed coil at the same time as the wiring pattern of the drive circuit. As is well known, in order to avoid patterns crossing each other, the simplest wiring pattern for the drive circuit is a two-layer copper foil pattern including through-hole plating parts.

Further, multilayering of three or more layers is not necessary in the drive circuit.

Therefore, it is desirable that the coil pattern be formed from two layers of conductive coil patterns formed on both the front and back surfaces of the printed sheet including the through-hole plated portions. If the coil is multi-layered with three or more layers, processing of the connection part (soldering, resistance welding, gluing, etc.) is required, which is disadvantageous for simplification. It just forms a sexual coil pattern,
It has the advantage that no treatment of the connection is required.

Conventional motors use the speed signal from the FG coil and FG magnet for speed control, but in the present invention, the FG coil and FC magnet are abolished, and the speed signal of one waveform per revolution generated by the magnetic pole position detection element is used. is used to control the rotational speed, so jitter and fluff in the rotational speed can be suppressed compared to conventional motors. The servo band for closed-loop control decreases because the number of signal waveforms per rotation for speed signal generation decreases, but this increases the inertia of the rotor and reduces the eccentricity error and angle division error of the conventional FG coil and FG magnet. Since the amount not included can be compensated for by an equivalent reduction in disturbance, jitter and fluff in the rotational speed do not increase. Furthermore, since the outer peripheral portion occupied by the FG coil and the FG magnet can be removed, the outer diameter of the motor can be reduced, and the number of parts can be reduced, resulting in lower costs.

When the stator yoke is made of soft ferrite material, eddy current loss during high speed rotation can be reduced. Instead of adopting soft ferrite material, the stator yoke can be formed by spirally winding ferromagnetic strips or wires, or by dividing the stator yoke into multiple concentric magnetic rings. Since the flowing eddy current can be divided, the total eddy current loss can be reduced. Since there is no break in the magnetic circuit in the rotational direction of the motor, configuring the stator yoke in this manner does not cause an increase in vibration or torque fluctuation.

To prevent leakage of magnetic flux, if a ring-shaped soft magnetic member is provided on the rotor side, the magnetic flux will actively pass through this soft magnetic member, exerting a magnetic shielding effect, and prevent magnetic flux from leaking to the stator side. Therefore, eddy current loss can be suppressed. Additionally, if a ring-shaped non-magnetic member is provided on the rotor side to ensure a sufficient distance between the side surface of the disc-shaped magnet and the stator, magnetic flux leakage to the stator can be prevented without reducing rotor inertia. be able to. On the other hand, if a ring-shaped high-resistivity soft magnetic member is provided on the stator side, the magnetic shielding effect of this member can prevent leakage of magnetic flux to the housing and suppress eddy current loss. If a ring-shaped high resistivity non-magnetic member is provided on the stator side instead of the high resistivity soft magnetic member and a sufficient distance is secured between the side surface of the disc-shaped magnet and the stator conductive member, the housing It is possible to suppress magnetic flux leakage to
As a result, eddy current loss can be suppressed.

Embodiments The present invention will be explained in detail below based on embodiments shown in the drawings. In the description of this embodiment, the same components as those of the conventional structure shown in FIGS. 15 and 16 will be described with the same reference numerals.

Referring first to FIGS. 1 and 2, there are shown respectively an exploded perspective view and a vertical sectional view of an embodiment of the present invention. Rotor 5
0 is a bracket 14 fixed to the rotating shaft 12, a rotor yoke 16 fixed to the bracket 14, and a permanent rotor fixed to the rotor yoke 16 and magnetized into multiple poles alternately in the direction of the rotating shaft 12. It is composed of a magnet 52.

In this embodiment, the rotor permanent magnet 52 is, for example, a ferrite magnet with a diameter of 40 mm and a thickness of 5 mm, and is polarized into eight poles.

24 is a housing that constitutes the stator side, and this housing 24 has two bearings 28 and 3 spaced apart in the vertical direction.
0 is provided to rotatably support the rotating shaft 12.

26 is a sleeve, and this sleeve and the housing 24
A preload spring 32 is interposed between the bearings 28 and 30 and between the bearings 28 and 30.

A stopper 34 serves to prevent the bearing 30 from being pulled out. An aluminum stand 54 is fixed to the housing 24, and a stator yoke 56 made of soft ferrite having high resistivity is attached to this stand 54.

In this example, the gap between rotor permanent magnets 52 and stator yoke 56 is approximately 0.30. The coil constant of the coil that can be mounted in such a small gap is small, and the motor constant is also small, so the output torque is relatively small. Therefore, it is necessary to suppress loss torque. Particularly at high speed rotations, it is necessary to suppress eddy current loss, which is proportional to the square of the rotational speed. Therefore, as described above, the yoke 56 made of soft ferrite was adopted as the stator yoke. The stator yoke 56 is mounted so as to be embedded in the base 54, and as shown in FIG. 1, the extended surface of the base 54 and the upper surface of the stator yoke 56 form a flat plane with no difference in level. .

On the stand 54 (on the stator yoke 56 in the coil part as seen in FIG. 2), a copper-clad double-sided printed sheet 58 with through-hole plating is adhered to a polyimide film base material with a thickness of 0.05 mm. . Double-sided print sheet 5
On the back surface of 8, six second-layer conductive coil patterns 60 made of copper are formed. A second layer conductive coil pattern 68 is also formed on the surface of the double-sided printed sheet 58, and the conductive patterns on the front and back sides also connect opposing coils to form a three-phase coil (see FIG. 3).

Electronic components constituting a drive circuit 62 for closed loop speed control are mounted on the surface of the double-sided printed sheet 58, and three Hall elements 64 for detecting the phase of the rotor 500 are mounted by soldering. This Hall element 6
The terminal No. 4 is drawn out of the coil pattern 68 by a chip-shaped connection component 66, and is connected to a lead pattern (not shown). Instead of using such a chip-shaped connection component 66, a flat-packaged elongated Hall element extending to an external lead pattern portion may be used.

In this way, the printed coil patterns 60, 68 and the drive circuit 62 are provided on the double-sided printed sheet 58, and since the double-sided printed sheet 58 is shared as a substrate, the number of parts is reduced, and the printed coil pattern is formed by laminating films. Since this is a two-layered coil pattern formed on both the front and back sides of a single printed sheet, the production of the printed coil pattern does not increase the cost.

For example, DC 24V power is supplied to the connector provided on the double-sided printed sheet 58.

Reference is now made to FIGS. 3 and 4. FIG. 3 shows the coil patterns formed on both the front and back surfaces of the printed sheet, and FIG. 4 shows the flow of excitation current in the one-phase coil when two layers are connected in series. As shown in FIGS. 3 and 4, the first layer coil pattern 60 formed on the back surface of the printed sheet 58 and the second layer coil pattern 68 formed on the front surface are connected in series. ing. In FIG. 4, 60 is a first layer printed coil pattern that faces each other diagonally, and 68 is a second layer printed coil pattern that faces each other diagonally. Since they are connected in series, the first layer printed coil pattern 60 and the second printed coil pattern 68 are coil patterns that rotate in opposite directions. The excitation current is supplied to the drive circuit 62 as indicated by the arrow.
The second layer print flows through the pattern 72 formed on the front surface of the double-sided print sheet 58 to one side of the first layer printed coil pattern 60 formed on the back surface, and then flows through the through hole to the second layer print formed on the surface of the print sheet 580. It is introduced into one side of the coil pattern 68. The excitation current from one of the second layer printed coil patterns 68 is transmitted through the pattern 73 formed on the front surface of the double-sided printed sheet 58 to the first layer printed coil pattern 6o formed on the back surface.
Then, it flows through the other side of the second layer printed coil pattern 68 formed on the surface, and flows into the drive circuit 62 via the pattern 74 formed on the surface of the double-sided printed sheet 58.

In the axial flux type brushless smoke having the above-described configuration, the rotor magnet 1 is attached to the stator yoke 56.
Since the fluctuating magnetic flux due to the rotation of 8 flows, an eddy current is generated due to the fluctuating magnetic flux, and as a result, there is a problem in that eddy current loss occurs. In the embodiment described above, this eddy current loss is reduced by employing a soft ferrite material for the stator yoke, but as shown in FIG. It may be divided into 56c. With this configuration, the eddy current is divided and flows through each magnetic ring, so that the total eddy current loss can be reduced. Further, since there is no break in the magnetic circuit in the rotational direction of the motor, even if the stator yoke is divided, no increase in vibration or torque fluctuation occurs.

FIG. 6 shows another configuration for preventing eddy current loss, in which an annular groove 54a is provided in an aluminum base 54 centered on the rotating shaft of a motor (not shown). 24 is a housing on the stator side, and a stand 54 is fixed to this housing 24. Reference numeral 76 denotes a ferromagnetic strip material coated with an insulator such as epoxy resin, and the stator yoke 77 is formed by winding this ferromagnetic strip material 76 in a spiral shape around the rotating shaft in the annular groove 54a. do. Suitable materials for the strip include silicon steel plates, permalloy having a high magnetic flux density, and the like. When a silicon steel plate is used, it is preferable that the silicon content is 1 to 2.5%, and a silicon steel plate with a thickness of, for example, 0.6 to 1 mm and a width of about 3 wings can be used. When a silicon steel plate having a width of 3InI11 is used, it is desirable that the depth of the annular groove 54a is also 3 mm so that the upper surface of the base 54 and the upper surface of the stator yoke 77 are flat without any step.

Between the ferromagnetic strips 76 and between the ferromagnetic strips 76 and the stand 54
To fix the stator yoke 76, an adhesive is applied in advance to the surface coating layer of the ferromagnetic material strip 76, and after the stator yoke 77 is assembled, the stator yoke 77 is heated and melted and bonded. Stator yoke 7
The outermost periphery of the ferromagnetic material strip 76 is pressed against the side surface of the annular groove 54a formed in the base 54 by the springback of the ferromagnetic material strip 76 and fixed by adhesive.

When the stator yoke 77 is formed in this manner, the eddy current is divided in the thickness direction of the ferromagnetic strip 76, so that the total eddy current loss can be much reduced compared to the conventional configuration. Furthermore, since there is no break in the magnetic circuit in the rotational direction, no increase in vibration or torque fluctuation occurs due to stator yoke division.

FIG. 7 shows another embodiment for reducing eddy current loss. In this embodiment, an insulator wire 78 with a circular cross section coated with an insulator such as epoxy resin is inserted into the annular groove 54a. Stator yoke 77
form. Since the cross section is circular, there is no directionality in arranging the wire rods 78, and there is an advantage that workability is better than the embodiment shown in FIG. The material of the ferromagnetic wire 78 is as follows:
Similar to the embodiment shown in FIG. 6, silicon steel plate or permalloy having a high magnetic flux density is preferable. The diameter of the wire 78 is preferably about 2 mm, for example.

For example, permanent magnets with high energy products such as barium ferrite and rare earth magnets rotate at high speeds (e.g. 110
00 rpm), there is a problem in that eddy current loss caused by fluctuations in magnetic flux leaking not only to the stator yoke but also to the housing of the stator (stator) that fixes the bearing becomes large, and the efficiency of the motor decreases. In other words, magnetic flux leaks from the side of the permanent magnet into the non-magnetic brass housing.
Eddy current loss occurs here. In order to prevent this eddy current loss, the configurations shown in FIGS. 8 to 11 can be considered.

First, referring to the first embodiment shown in FIG. 8, in this embodiment, a non-magnetic ring 80 is fixed to a portion of the flange 140 facing the side surface of the rotor magnet 52. This non-magnetic ring 80 ensures a distance between the side surface of the permanent magnet 52 and the stator's conductive housing 24, thereby preventing leakage of magnetic flux to the stator. The material of the non-magnetic ring 80 may be conductive or insulating, but it is preferable to use a material with a high specific gravity, such as brass, to ensure rotor inertia. The non-magnetic ring 80 is attached to the flange 1 of the rotor.
It may be configured integrally with 4.

In the second embodiment shown in FIG. 9, a soft magnetic ring 82 is fixed to the side surface of the flange 14 facing the permanent magnet 52. The material of the soft magnetic ring 82 is, for example, a cold rolled steel plate, and its magnetic shielding effect suppresses eddy current loss without leaking magnetic flux inside the ring 82. Since this soft magnetic ring 82 actively passes magnetic flux and short-circuits it, the thickness t of the ring 82 can be thinner than the thickness of the non-magnetic ring 80 of the first embodiment shown in FIG. There is an advantage that the effective width of the permanent magnet 52 can be increased.

FIG. 10 shows a third embodiment for preventing magnetic flux leakage, in which a soft magnetic ring 84 with high resistivity is fixed to the conductive housing 24 of the stator. The magnetic flux from the permanent magnet 52 is passed through this high-resistivity soft magnetic ring 84, and its magnetic shielding effect prevents leakage of magnetic flux to the housing 24 and suppresses eddy current loss. As the material of the ring 84, for example, a composite material of a powdery soft magnetic material such as soft ferrite and a bonding material can be adopted.

FIG. 11 shows a fourth embodiment for preventing magnetic flux leakage, and in this embodiment, a high resistivity non-magnetic ring 86 is attached to the conductive housing 24 facing the inner side surface of the permanent magnet 52. ing.

This ring 86 is made of wood and is attached to the housing 24 with adhesive. The ring 86 has a protrusion 8
6a is provided, and this protrusion 86a and the flange 1
The protruding portion 14a of No. 4 acts as a labyrinth seal to prevent oil droplets of lubricant of the bearing from scattering. This high resistivity non-magnetic ring 86 ensures a sufficient distance between the inner side surface of the permanent magnet 52 and the conductive housing 24,
This prevents leakage of magnetic flux to the housing 24.

Generation of a speed signal used to control the rotational speed will be explained below.

In the present invention, as described above, the FG magnet and the FG coil are abolished, and the output of the Hall element for detecting the phase of the rotor is used for controlling the speed of the rotor. Since the rotor permanent magnet 52 of this embodiment is polarized into eight poles, the output voltage of the Hall element has four waveforms per revolution as shown in FIG. 12. This Hall element voltage is shaped into a rectangular wave by a waveform shaping circuit 87, and divided into 1/4 by a frequency dividing circuit 88 to obtain 1 pulse/1 rotation, which is used as a speed signal.

Through closed-loop speed control using this speed and signal, it is possible to suppress rotational speed jitter and flange to ±0.005% or less with respect to the rated rotational speed of 400 Orpm in the 3-phase 6-coil axial flux type brushless smoke as described above. was completed.

Furthermore, there is also a method of shifting the rotation angle (phase) of the Hall element voltage outputted in four waveforms per rotation, and using a four-phase speed signal of the negative one-rotation waveform. FIG. 13 is a schematic diagram showing the generation of four-phase speed signals, and FIG. 14 is a block diagram of a speed control system using such four-phase speed signals. In FIG. 13, the Hall element voltage is shaped into a rectangular wave by a waveform shaping circuit 89, and the frequency is divided by 1/4 by a frequency dividing circuit 90 to generate four signals of one pulse/one rotation whose phases are shifted from each other. generated and used as a speed signal.

Reference numeral 91 denotes an edge selection circuit, which serves to instruct the frequency dividing circuit 90 as to the order in which pulses are sequentially multiplied by -.

FIG. 14 shows a block diagram of a speed control system that uses the four-phase speed signals of one waveform per revolution generated in this way, and the four-phase output signals from the frequency divider circuit 90 whose phases are shifted from each other are It is compared with the speed command value, and the four deviation counters 93 generate four systems of deviation signals from the speed command value, which are manually input to the multiplexer 94. The multiplexer 9 receives a data select signal input from the edge selection circuit 91.
The four deviation signals manually inputted in step 4 are sequentially switched and outputted according to the rotation angle in the same way as the excitation phase switching.

A phase compensation circuit 95 compensates the phase of the output signal of the multiplexer 94, a voltage amplification circuit 96 amplifies the voltage, and then inputs it to a driver 97 to drive the motor 92 to rotate.

If controlled in this way, the phase delay of the loop transfer function caused by the Hall element 64 will be smaller than when one speed signal is used as shown in FIG. 12, the servo band will be improved, and the motor will be less susceptible to disturbance It has the advantage of being stronger. Furthermore,
By using the outputs of three Hall elements whose angular positions and phases are shifted by 120 degrees, the number of phases of the speed signal can be increased, and the servo band can be further improved.

Effects of the Invention As detailed above, the present invention forms a small gap between the rotor permanent magnet and the stator yoke, and forms printed coils on both the front and back sides of the gap using a wood film as a base material. Since the motor is configured to be mounted with a printed sheet, the motor has a small diameter, a low profile, and high inertia.As a result, it is possible to provide a low-cost motor with small rotational speed jitter and flange. Furthermore, since the rotor has high inertia, FC magnets and FG coils can be eliminated, and a speed signal with one waveform per rotation without detection errors is used to control the rotational speed, resulting in a highly accurate motor. can.

In addition, the increase in eddy current loss due to the increase in gap magnetic flux density caused by reducing the gap between the rotor permanent magnet and stator yoke can be suppressed by forming the stator yoke from a soft ferrite material. . This eddy current loss can also be suppressed by dividing the stator yoke concentrically or by winding a wire or a strip in a spiral manner.

[Brief explanation of the drawing]

Fig. 1 is an exploded perspective view of an embodiment of the present invention, Fig. 2 is a vertical sectional view of the embodiment, Fig. 3 is a schematic diagram showing an example of a coil pattern on a printed sheet, and Fig. 4 is a two-layer series connection. Fig. 5 is an explanatory diagram showing the flow of eddy current in the stator yoke when the stator yoke is divided into concentric circles, and Fig. 6 is a schematic diagram showing the flow of excitation current in the one-phase coil of the stator yoke. Fig. 7 is a block diagram of yet another embodiment of the stator yoke, Fig. 8 is a longitudinal sectional view of the first embodiment for preventing leakage magnetic flux, and Fig. 9 is a block diagram of the first embodiment of the stator yoke. 10 is a longitudinal sectional view of the third embodiment for preventing leakage magnetic flux; FIG. 11 is a longitudinal sectional view of the fourth embodiment for preventing leakage magnetic flux; 12. The figure is a schematic diagram showing the generation of the speed signal, and Fig. 13 shows the 4
A schematic diagram showing the generation of phase speed signals, Fig. 14 is a block diagram of a speed control system using four-phase speed signals, Fig. 15 is an exploded perspective view of the conventional example, and Fig. 16 is a longitudinal section of the conventional example. It is a diagram. 12... Rotating shaft, 14... Flange, 16... Rotor yoke, 24... Housing, 52... Rotor permanent magnet, 54... Stand, 56... Stator yoke, 58...Double-sided printed sheet, 60...First phase printed coil pattern, 62...
Drive circuit, 64... Hall element, 68... Second phase printed coil pattern, 76...
Ferromagnetic strip material, 78... Ferromagnetic wire material, 80... Non-magnetic material ring, 82... Soft magnetic material ring, 84... High resistivity soft magnetic material ring, 86... High Resistivity non-magnetic ring, 87.89... Waveform shaping circuit, 88.90... Frequency dividing circuit, 91... Edge selection circuit, 93... Deviation counter, 94... Multiplexer.

Claims (1)

[Scope of Claims] (1) A disc-shaped magnet (52) is magnetized with multiple poles in a direction parallel to the rotation axis (12) and used as a rotor (50), with an armature on the stator side. In an axial flux type brushless motor equipped with a stator yoke (56) that serves as a magnetic path for the coil and rotor magnetic flux, the motor drive circuit (62) pattern is formed on a part of a flexible wood film as a base material. and a printed coil consisting of two layers of conductive coil patterns (60, 68) on the front and back having through-hole plated portions formed on other parts, the printed coil is attached to the disk. The magnetic pole position detecting element (64) of the disc-shaped magnet (52) is mounted on the printed sheet (58) so as to be mounted in the gap between the disc-shaped magnet (52) and the stator yoke (56). An axial flux type brushless motor, comprising: a control means that uses a speed signal of one waveform per rotation generated by the magnetic pole position detection element (64) to control the rotational speed. (2) The axial flux type brushless motor according to claim 1, wherein the control means uses, for controlling the rotational speed, a plurality of speed signals having one waveform per rotation generated at angular positions shifted from each other. (3) The stator yoke (5
6. The axial flux type brushless motor according to claim 1, wherein the axial flux type brushless motor is made of a soft ferrite material. (4) The stator yoke is formed by winding a ferromagnetic strip material (76) coated with an insulator or a ferromagnetic wire material (78) with a circular cross section in a spiral shape around the rotating shaft. The axial flux type brushless motor according to claim 1. (5) The stator yoke (
The axial flux type brushless motor according to claim 1, wherein the axial flux type brushless motor (56) is constituted by a plurality of concentric magnetic rings (56a to 56c) centered around the rotation axis of the rotor. (6) A claim characterized in that a ring-shaped soft magnetic member (82) is provided on the rotor side, facing the side surface of the disc-shaped magnet (52) that faces the conductive member of the stator. The axial flux type brushless motor described in 1. (7) The axial flux type brushless motor according to item 6, characterized in that a ring-shaped non-magnetic member (80) is provided in place of the ring-shaped soft magnetic member (82). (8) Disk-shaped magnet (52
) A ring-shaped high resistivity soft magnetic member (84) is provided on the stator side, facing the side surface of the stator.
Axial flux type brushless motor described. (9) The axial flux type brushless according to claim 8, characterized in that a ring-shaped high-resistivity non-magnetic member (86) is provided in place of the ring-shaped high-resistivity soft magnetic member (84). motor.