Brushless motor

A brushless motor has a field part 20, three-phase coils 21, 22, and 23, a drive block 40 for supplying a power to the coils in accordance with output signals of a position detecting block 30, and a rotation detecting block 10 for producing a rotation signal and a direction signal by using output signals of the position detecting block 30. The rotation detecting block 10 has a shaped position signal producing circuit 11 for producing plural-phase shaped position signals, a rotation signal producing circuit 12 for producing the rotation signal synchronized with the shaped position signals, and a direction signal producing circuit 13 for producing the direction signal in correspondence with levels of the shaped position signals at a timing of a level change of the rotation signal.

BACKGROUND OF THE INVENTION 
The invention relates to a brushless motor for rotating a disk or the like. 
Recently, in a brushless motor for rotating a disk or the like, a waveform 
shaping circuit is used for detecting a rotation of the motor in order to 
measure a rotational speed of the motor. As disclosed in, for example, the 
unexamined published Japanese patent application (TOKKAI) SHO 63-256013, 
the waveform shaping circuit is configured so as to produce a pulse signal 
by shaping an alternating signal of a frequency proportional to the 
rotational speed of the motor. 
FIG. 27 shows configurations of a detector and the waveform shaping circuit 
which are used in detection of the rotation in the prior art. In an 
optical disk 2002 attached to a rotor shaft 2001, slits are formed at 
regular angular intervals. A light emitting diode 2010 and a 
phototransistor 2011 are attached to a support member 2003 fixed to the 
stator, so as to face each other across the slits of the optical disk 
2002. A detection signal from the phototransistor 2011 is amplified by a 
linear amplifier circuit 2020, and an alternating signal 2101 is output. 
Accordingly, in response to the rotation of the optical disk 2002, the 
alternating signal 2101 of a frequency which is proportional to the 
rotational speed of the rotor is generated in the phototransistor 2011 and 
the amplifier circuit 2020. 
A first comparator block 2110 having no hysteresis receives the alternating 
signal 2101, and produces a shaped signal 2141 which is obtained by 
comparing and shaping the alternating signal 2101. The first comparator 
block 2110 comprises a comparator 2111, an inverting circuit 2112, and a 
DC voltage source 2113. A second comparator block 2120 having a 
predetermined hysteresis width corresponding to resistors 2121 and 2122 
produces another shaped signal 2142 which is obtained by comparing and 
shaping the alternating signal 2101 by using the predetermined hysteresis 
width. The second comparator block 2120 comprises the resistors 2121 and 
2122, a comparator 2123, and an inverting circuit 2124. The shaped signals 
2141 and 2142 are supplied to a pulse generating block 2130. The pulse 
generating block 2130 comprises an inverting circuit 2131, an AND circuit 
2132, and OR circuits 2133 and 2134. The pulse generating block 2130 
outputs a pulse signal 2150, the level of which is changed during a time 
period from a leading edge of the shaped signal 2141 to that of the shaped 
signal 2142. As a result, the rotational speed of the motor can be 
measured on the basis of the pulse signal 2150. 
However, in the conventional brushless motor, many detection parts and 
detection devices are required to attach to the rotor and the stator in 
order to generate the alternating signals. Consequently, the number of 
mechanical parts is large and the production of the motor is complicated. 
In particular, the optical disk 2002 having slits must be attached to the 
rotor, and the light emitting diode 2010 and the phototransistor 2011 must 
be attached to the stator. As a result, the conventional brushless motor 
has problems that the production cost is high and that the space for such 
parts is large. 
In the conventional brushless motor, moreover, the pulse signal 2150 can be 
used for measurement of the rotational speed but cannot be used for 
detection of a rotational direction. In many applications for rotating the 
disk or the like, it is required also to detect the rotational direction. 
In the above-mentioned conventional configuration, some detection parts 
for detecting the rotational direction must be additionally disposed. 
As the two comparator blocks 2110 and 2120 are used for shaping the same 
alternating signal 2101, the circuitry of the conventional brushless motor 
has a complex configuration. In order to simplify the circuitry, it may be 
contemplated that only the first comparator block 2110 having no 
hysteresis is used, and the second comparator block 2120 and the pulse 
generating block 2130 are omitted. However, since the first comparator 
block 2110 has no hysteresis, many noise pulses are generated at timings 
when the edges of the shaped signal 2141 are generated, by high-frequency 
noises contained in the alternating signal 2101. The pulse signal from the 
first comparator block 2110 cannot be used as the signal for measuring the 
rotational speed. 
On the contrary, in order to simplify the circuitry, it may be contemplated 
that only the second comparator block 2120 having hysteresis is used, and 
the first comparator block 2110 and the pulse generating block 2130 are 
omitted. However, since the second comparator block 2120 has hysteresis, 
timings of the edges of the shaped signal 2142 are shifted from the 
respective zero-crossing points of the input alternating signal 2101 by a 
value corresponding to the hysteresis width. Both the pulse width and the 
pulse period of the shaped signal 2142 are varied by an amplitude 
modulation component contained in the alternating signal 2101. Therefore, 
the pulse signal of the second comparator block 2120 cannot be 
sufficiently as the signal for measuring the rotational speed. 
Although the two comparator blocks are used in the conventional brushless 
motor, the output signal has noise pulses when the alternating signal 2101 
contains noises larger than the hysteresis width of the second comparator 
block 2120. In mass production, there are large variations in the 
amplitude of the alternating signal 2101. Therefore, the hysteresis width 
must be set to a value sufficiently smaller than the estimated minimum 
amplitude in mass-produced motors, and the margin for noises is reduced 
remarkably. 
BRIEF SUMMARY OF THE INVENTION 
Briefly stated, the present invention comprises a brushless motor. The 
brushless motor includes a field means for generating a magnetic field 
flux by using a permanent magnet; plural-phase coils interlinking with the 
magnetic field flux; position detecting means for detecting the relative 
position between the field means and the coils and for obtaining 
plural-phase position signals which vary in a continuous manner; rotation 
detecting means for obtaining a rotation signal and a direction signal in 
correspondence with output signals of the position detecting means; 
command means for outputting an activation command signal; and drive means 
for supplying electric power to the coils in correspondence with the 
activation command signal and the corresponding position signals. 
The rotation detecting means comprise a shaped position signal producing 
means for producing three-phase shaped position signals which are 
electrically different from each other in phase and are based upon 
three-phase output signals of the position detecting means; rotation 
signal producing means for obtaining the rotation signal which is 
synchronized with the shaped position signals; and direction signal 
producing means for obtaining the direction signal in response to a level 
of one of the shaped position signals coincident with a level change of 
the rotation signal. 
In the brushless motor of the present invention, the three-phase shaped 
position signals, different from each other in phase, are produced by 
shaping the three-phase output signals of the position detecting means. 
The rotation signal is produced by using the shaped position signals, and 
the direction signal is produced in response to a level of one of the 
shaped position signals coincident with a level change of the rotation 
signal. 
According to this configuration, because the position signals of the 
brushless motor are used, no additional parts are required. Furthermore, 
by using the three-phase shaped position signals, the rotation signal and 
the direction signal are hardly affected by noise contained in the 
three-phase output signals of the position detecting means. 
The brushless motor of another aspect comprises field means for generating 
a magnetic field flux by using a permanent magnet; plural-phase coils 
interlinking with the magnetic field flux; position detecting means for 
detecting the relative position between the field means and the coils and 
for obtaining plural-phase position signals which vary in a continuous 
manner; rotation detecting means for obtaining a rotation signal and a 
direction signal in correspondence with output signals of the position 
detecting means; command means for outputting an activation command 
signal; and drive means for supplying electric power to the coils in 
correspondence with the activation command signal and to the corresponding 
position signals. 
The rotation detecting means comprises shaped position signal producing 
means for producing three-phase shaped position signals A, B, and C which 
are electrically different from each other in phase based upon three-phase 
output signals of the position detecting means; rotation signal producing 
means for eliminating noises coincident with a level change of the 
rotation signal by using a pair of the shaped position signals A and B and 
for obtaining the rotation signal which is synchronized with either of the 
shaped position signals A and B, and direction signal producing means for 
obtaining the direction signal in correspondence with a level of the 
shaped position signal C coincident with a level change of the rotation 
signal. 
In a specific brushless motor of the present invention, the rotation 
detecting means comprises the shaped position signal producing means, the 
rotation signal producing means and the direction signal producing means. 
The shaped position signal producing means waveform-shapes the three-phase 
output signals of the position detecting means, and produces the 
three-phase shaped position signals A, B, and C which are electrically 
different from each other in phase. The rotation signal producing means 
eliminates the noise coincident with the level change of the rotation 
signal by using the pair of shaped position signals A and B, and obtains 
the rotation signal synchronized with either of the shaped position 
signals A and B. The direction signal producing means obtains the 
direction signal in response to the level of the shaped position signal C 
coincident with a level change of the rotation signal. 
According to this configuration, the rotation signal is produced from a 
pair of the shaped position signals A and B so as to eliminate the noise 
contained in the shaped position signal A or B, and for synchronizing the 
rotation signal with either of the shaped position signals A or B. Even 
when the shaped position signal A or B is produced by using comparators 
having no hysteresis, the rotation signal is not influenced by noise 
contained in the shaped position signals and a level change (edge) of the 
rotation signal occurring exactly at a zero-crossing point of the output 
signal of the position detecting means. Furthermore, the direction signal 
is obtained in response to the level of the shaped position signal C 
coincident with the level change of the rotation signal. In other words, 
the rotation signal does not contain noise pulses, and the level of the 
shaped position signal C is stable during the level change of the rotation 
signal resulting in stable detection of the direction signal. 
The brushless motor of another aspect comprises a field means for 
generating a magnetic field flux by using a permanent magnet; plural-phase 
coils interlinking with the magnetic field flux; position detecting means 
for detecting the relative position between the field means and the coils 
and for obtaining plural-phase position signals which vary in a continuous 
manner; rotation detecting means for obtaining a rotation signal and a 
direction signal in correspondence with the output signals of the position 
detecting means; command means for outputting an activation command 
signal; and drive means for supplying electric power to the coils in 
correspondence with the activation command signal and the corresponding 
position signals. 
The rotation detecting means comprises shaped position signal producing 
means for producing three-phase shaped position signals A, B, and C, which 
are electrically different from each other in phase, based upon 
three-phase output signals of the position detecting means; first rotation 
signal producing means for: (1) eliminating noises coincident with a level 
change of the first rotation signal by using a pair of the shaped position 
signals A and B, and (2) for obtaining the first rotation signal which is 
synchronized with either of the shaped position signals A and B; second 
rotation signal producing means for: (1) eliminating noise coincident with 
a level change of the second rotation signal by using another pair of the 
shaped position signals B and C, and (2) for obtaining the second rotation 
signal which is synchronized with either of the shaped position signals B 
and C; rotation signal output means for outputting the rotation signal in 
correspondence with at least one of the first and second rotation signals; 
and direction signal producing means for obtaining the direction signal in 
correspondence with the level of the second rotation signal coincident 
with a level change of the first rotation signal. 
In another specific embodiment of the brushless motor of the present 
invention, the rotation detecting means comprises the shaped position 
signal producing means, the first rotation signal producing means, the 
second rotation signal producing means, the rotation signal output means, 
and the direction signal producing means. The shaped position signal 
producing means waveform-shapes the three phase output signals of the 
position detecting means, and produces the three-phase shaped position 
signals A, B, and C. The first rotation signal producing means eliminates 
the noise coincident with a level change of the first rotation signal by 
using the pair of the shaped position signals A and B, and obtains the 
first rotation signal synchronized with either of the shaped position of 
the shaped position signals A and B. The second rotation signal producing 
means eliminates the noise coincident with a level change of the second 
rotation signal by using another pair of the shaped position signals B and 
C, and obtains the second rotation signal synchronized with either of the 
shaped position signals B and C. The rotation signal output means outputs 
the first or second rotation signal as the rotation signal. The direction 
signal producing means obtains the direction signal in response to the 
level of the second rotation signal coincident with the level change of 
the first rotation signal. 
According to this configuration, the rotation signal is produced from the 
pair of the shaped position signals A and B or B and C so as to eliminate 
the noise contained in the shaped position signals. As the first and 
second rotation signals do not contain noise pulses, the stable detection 
of the direction signal is always enabled. 
The brushless motor of another aspect comprises field means for generating 
a magnetic field flux by using a permanent magnet; plural-phase coils 
interlinking with the magnetic field flux; position detecting means for 
detecting the relative position between the field means and the coils and 
for obtaining plural-phase position signals which vary in a continuous 
manner; rotation detecting means for obtaining a rotation signal and a 
direction signal in correspondence with the output signals of the position 
detecting means; command means for outputting an activation command 
signal; and drive means for supplying electric power to the coils in 
correspondence with the activation command signal corresponding to the 
position signals. 
The rotation detecting means comprises shaped position signal producing 
means for producing three-phase shaped position signals A, B, and C which 
are electrically different from each other in phase, based upon 
three-phase output signals of the position detecting means; first rotation 
signal producing means for: (1) eliminating noise coincident with a level 
change of the first rotation signal by using a pair of the shaped position 
signals A and B, and (2) obtaining the first rotation signal which is 
synchronized with either of the shaped position signals A and B; second 
rotation signal producing means for eliminating noise coincident with a 
level change of the second rotation signal by using another pair of the 
shaped position signals B and C, and for obtaining the second rotation 
signal which is synchronized with either of the shaped position signals B 
and C; third rotation signal producing means for eliminating noise 
coincident with a level change of the third rotation signal by using 
another pair of the shaped position signals C and A, and for obtaining the 
third rotation signal which is synchronized with either of the shaped 
position signals C and A; rotation signal output means for synthesizing 
the first, second, and third rotation signals with each other, and for 
outputting a synthesized signal as the rotation signal; and direction 
signal producing means for obtaining the direction signal in 
correspondence with the level of the second rotation signal coincident 
with a level change of the first rotation signal. 
In another specific embodiment of a brushless motor of the present 
invention, the rotation detecting means comprises the shaped position 
signal producing means, the first rotation signal producing means, the 
second rotation signal producing means, the third rotation signal 
producing means, the rotation signal output means, and the direction 
signal producing means. The shaped position signal producing means 
waveform-shapes the three-phase output signals of the position detecting 
means, and produces the three-phase shaped position signals A, B, and C. 
The first rotation signal producing means eliminates the noise coincident 
with the level change of the first rotation signal by using the pair of 
the shaped position signals A and B. The second rotation signal producing 
means eliminates the noise coincident with the level change of the second 
rotation signal by using another pair of the shaped position signals B and 
C, and the third rotation signal producing means eliminates the noise 
coincident with the level change of the third rotation signal by using 
another pair of the shaped position signals C and A. The rotation signal 
output means combines the first, second, and third rotation signals so as 
to output the rotation signal. The direction signal producing means 
obtains the direction signal in response to the level of the second 
rotation signal coincident with the level change of the first rotation 
signal. 
According to this configuration, each of the first, second, and third 
rotation signals is produced by using a pair of the shaped position 
signals so as to eliminate the noise contained in the shaped position 
signals. The output rotation signal of the rotation signal output means 
has a frequency higher than that of the shaped position signals. As a 
result, the direction signal occurring in response to the level of the 
second rotation signal coincident with the level change of the first 
rotation signal is stably obtained. 
A brushless motor which is used for rotating a disk, comprises field means 
for generating a magnetic field flux by using a permanent magnet; 
plural-phase coils interlinking with the magnetic field flux; position 
detecting means for detecting the relative position between the field 
means and the coils, and for obtaining plural-phase position signals which 
vary in a continuous manner; rotation detecting means for obtaining a 
rotation signal and a direction signal in correspondence with output 
signals of the position detecting means; command means for outputting a 
direction command signal and an activation command signal so as to produce 
a forward torque in a rotation command operation and a reverse direction 
in a stop command operation; drive means for supplying electric power to 
the coils in correspondence with the activation command signal 
corresponding to the position signals; and stop operation means for 
stopping rotation of the motor in correspondence with the direction 
command signal and the direction signal. 
The rotation detecting means comprises shaped position signal producing 
means for producing plural-phase shaped position signals which are 
electrically different from each other in phase, based upon output signals 
of the position detecting means; rotation signal producing means for 
producing the rotation signal synchronized with the shaped position 
signals; and direction signal producing means for producing the direction 
signal in correspondence with a rotation of the field means by using the 
plural-phase shaped position signals. 
The stop operation means comprises activation changing means for supplying 
the required electric power to the coils in correspondence with the 
activation command signal and the direction command signal when either the 
direction command signal indicates a forward rotation command or the 
direction signal indicates a forward rotation, and for stopping activation 
of the coils when the direction command signal indicates a reverse 
rotation and the direction signal indicates a reverse direction. 
The stop operation means further includes: (1) stop detecting means for 
outputting a stop operation signal when the time interval of the rotation 
signal command signal becomes larger than a predetermined value in the 
stop command operation, and (2) unloading means for unloading the disk in 
response to the stop operation signal. 
In the brushless motor of the present invention suitable for rotating the 
disk, the field means generates the magnetic field flux by using a 
permanent magnet. The plural-phase coils are disposed so as to interlink 
with the magnetic field flux. The position detecting means detects the 
relative position between the field means and the coils, and the position 
detecting means generates plural-phase continuously variable position 
signals. The rotation detecting means generates the rotation signal and 
the direction signal in response to the output signals of the position 
detecting means. The command means outputs the direction command signal 
and the activation command signal so as to produce the forward torque in 
the rotation command operation and so as to produce the reverse torque in 
the stop command operation. The drive means supplies the electric power to 
the coils in response to the activation command signal corresponding to 
the position signals. The stop operation means stops the motor rotation in 
accordance with the direction command signal and the direction signal. 
Furthermore, the rotation detecting means comprises the shaped position 
signal producing means, the rotation signal producing means, and the 
direction signal producing means. The shaped position signal producing 
means waveform-shapes the output signals of the position detecting means, 
and produces the plural-phase shaped position signals which are 
electrically different from each other in phase. The rotation signal 
producing means produces the rotation signal in synchronization with the 
rotation of the field means, by using the shaped position signals. The 
direction signal producing means produces the direction signal 
corresponding to the rotational direction of the field means, by using the 
plural-phase shaped position signals. The stop operation means comprises 
the activation changing means, the stop detecting means, and the unloading 
means. When the direction command signal indicates the forward rotation 
command or the direction signal indicates the forward rotation, 
the-activation changing means allows the drive means to supply the coils 
with the required electric power in response to the activation command 
signal, so as to produce a forward torque or a reverse torque 
corresponding to the direction command signal. When the direction command 
signal indicates the reverse rotation command and the direction signal 
indicates the reverse rotation, the activation changing means stops the 
activation of the coils. After the time interval of the level change of 
the rotation signal becomes larger than a predetermined value, the stop 
detecting means outputs the stop operation signal. The unloading means 
unloads the disk in response to the stop operation signal. 
According to this configuration, the accurate rotation signal and the 
correct direction signal used for measuring the rotation of the field 
means are produced by the output signals of the position detecting means. 
In the rotation command operation, the forward rotation of the motor is 
controlled by the rotation signal. When the operation of the motor is 
transferred from the rotation command operation to the stop command 
operation, the direction command signal is, at first, changed from the 
forward rotation command to the reverse rotation command. The motor 
produces a reverse torque corresponding to the direction command signal 
and reduces the rotational speed rapidly. The beginning of the reverse 
rotation of the motor is instantaneously detected by the change of the 
detection signal. The activation of the motor coils is stopped by the 
activation changing means as soon as the reverse rotation is detected. The 
stop detecting means confirms the stop of the rotation of the field means 
by the time interval of the rotation signal, and it outputs the stop 
operation signal. The unloading means unloads the disk in response to the 
stop operation signal. As a result, the disk is unloaded in a very short 
time period in response to the stop command operation, and damage of the 
disk due to the unloading operation is prevented because of the 
confirmation by the stop detecting means.

DETAILED DESCRIPTION OF THE INVENTION 
Hereinafter, embodiments of the present invention will be described with 
reference to the accompanying drawings. 
&lt;&lt;FIRST EMBODIMENT&gt;&gt; 
FIG. 1 through FIG. 8 show a brushless motor of a first embodiment of the 
present invention which is used for rotating a disk. FIG. 1 shows an 
entire configuration of the motor. A field part 20 shown in FIG. 1 is 
mounted on the rotor and forms plural magnetic field poles by a permanent 
magnet, thereby generating a magnetic field flux. Three-phase coils 21, 
22, and 23 are mounted on the stator and arranged so as to be electrically 
separated from each other by a predetermined angle (corresponding to 120 
degrees in an electrical angle) with respect to interlinkage with the 
magnetic flux of the field part 20. An electric power (a voltage or a 
current) is supplied in correspondence with the relative position between 
the field part 20 and the three-phase coils, thereby rotating the field 
part 20 and the disk attached to the rotor. 
FIG. 2 specifically shows configurations of the field part 20 and the 
three-phase coils 21, 22, and 23. In an annular permanent magnet 102 
attached to the inner side of the rotor 101, the inner and end faces are 
magnetized so as to form four poles, thereby constituting the field part 
20 shown in FIG. 1. An armature core 103 is disposed at a position of the 
stator which opposes the poles of the permanent magnet 102. Three salient 
poles 104a, 104b, and 104c are disposed in the armature core 103 at 
intervals of 120 degrees in a mechanical angle. Three-phase coils 105a, 
105b, and 105c (corresponding to the three-phase coils 21, 22, and 23 
shown in FIG. 1) are wound on the salient poles 104a, 104b, and 104c in 
winding slots 106a, 106b, and 106c formed between the salient poles, 
respectively. Among the coils 105a, 105b, and 105c, phase differences of 
120 degrees in the electrical angle are established with respect to the 
interlinkage with the magnetic flux from the permanent magnet 102 (the 
mechanical angle of one set of N and S poles corresponds to the electrical 
angle of 360 degrees). Three position detecting elements 107a, 107b, and 
107c (for example, Hall elements which are magnetoelectrical converting 
elements) are arranged on the stator. The end face poles of the permanent 
magnet 102 are detected, thereby obtaining three-phase position signals 
corresponding to the relative position between the field part and the 
coils. In the embodiment, the coils and the position detecting elements 
are shifted in phase by the electrical angle of 90 degrees (45 degrees in 
the mechanical angle). When driving signals in the same phase with the 
detection signals of the position detecting elements are applied to the 
coils, a rotation force in a predetermined direction can be obtained 
continuously. 
A position detecting circuit 31 of a position detecting block 30 shown in 
FIG. 1 detects the relative position between the field part 20 and the 
three-phase coils 21, 22, and 23, and outputs three-phase output signals 
which analoguely vary and are electrically different in phase from each 
other. In the embodiment, the position detecting circuit 31 outputs two 
sets of three-phase output signals a, b, and c and three-phase output 
signals d, e, and f. The three-phase output signals a, b, and c are 
supplied to a rotation detecting block 10, and the three-phase output 
signals d, e, and f are supplied to a drive block 40. 
The rotation detecting block 10 of FIG. 1 comprises a shaped position 
signal producing circuit 11 connected to the position detecting circuit 
31, a rotation signal producing circuit 12 connected to the shaped 
position signal producing circuit 11, and a direction signal producing 
circuit 13. The shaped position signal producing circuit 11 shapes the 
three-phase output signals a, b, and c of the position detecting block 30 
and obtains three-phase shaped position signals A, B, and C. The rotation 
signal producing circuit 12 obtains a rotation signal F in which noises 
are eliminated, by using a pair of the shaped position signals A and B. 
The direction signal producing circuit 13 obtains a direction signal J in 
correspondence with a level of the shaped position signal C of the other 
phase at a timing of a level change of the rotation signal F (i.e., a 
timing when an edge of the rotation signal F is produced). 
FIG. 3 specifically shows configurations of the position detecting circuit 
31 of the position detecting block 30, and the shaped position signal 
producing circuit 11, the rotation signal producing circuit 12, and the 
direction signal producing circuit 13 in the rotation detecting block 10. 
Position detecting elements 131, 132, and 133 in the position detecting 
circuit 31 correspond to the position detecting elements 107a, 107b, and 
107c shown in FIG. 2. DC voltages (+Vcc and -Vcc: Vcc=+5 V, -Vcc=-5 V) of 
DC power sources 121 and 122 are applied to the position detecting 
elements 131, 132, and 133 via resistors 123 and 124. Differential 
position signals g1 and g2 corresponding to the detected magnetic field of 
the field part 20 (corresponding to the permanent magnet 102 of FIG. 2) 
are detected at output terminals of the position detecting element 131. 
The position signals g1 and g2 are differentially amplified by an 
operational amplifier circuit 141 and resistors 142, 143, 144, and 145, 
and the output signal a of a first phase which analoguely varies in the 
same phase with the position signal g1 is output. Similarly, differential 
position signals h1 and h2 corresponding to the detected magnetic field of 
the field part 20 are output at output terminals of the position detecting 
element 132. The position signals h1 and h2 are differentially amplified 
by an operational amplifier circuit 146 and resistors 147, 148, 149, and 
150, and the output signal b of a second phase is obtained. Furthermore, 
differential position signals i1 and i2 corresponding to the detected 
magnetic field of the field part 20 are output at output terminals of the 
position detecting element 133. The position signals i1 and i2 are 
differentially amplified by an operational amplifier circuit 151 and 
resistors 152, 153, 154, and 155 and the output signal c of a third phase 
is output. The output signals d, e, and f of the position detecting 
circuit 31 coincide with the output signals a, b, and c, respectively, and 
are supplied to the drive block 40. As the rotational movement of the 
field part 20 proceeds, the output signals a, b, and c and the output 
signals d, e, and f of the position detecting circuit 31 vary analoguely 
so as to constitute two sets of three-phase signals which have a desired 
electrical phase difference. The position signals g1, g2, h1, h2, and i1, 
and i2 constitute six phases in total, and the signals g1 and g2, h1 and 
h2, or i1 and i2 are in reversed phase relationships. In the embodiment, 
the signals of reversed phase relationships are not counted in the number 
of phases. Consequently, the six position signals obtained from the three 
position detecting elements 131, 132, and 133 constitute three-phase 
signals. 
The shaped position signal producing circuit 11 of the rotation detecting 
block 10 is configured by three comparators 161, 162, and 163. The 
comparator 161 outputs the shaped position signal A by shaping the output 
signal a of the position detecting circuit 31. Similarly, the comparator 
162 outputs the shaped position signal B by shaping the output signal b, 
and the comparator 163 outputs the shaped position signal C by shaping the 
output signal c. 
FIG. 4 shows a concrete configuration of the comparator 161. Transistors 
202, 203, 204, 205, 206, and 207 compare the analog output signal a with a 
predetermined voltage (in the embodiment, the ground potential). When the 
output signal a is higher than the predetermined voltage, a transistor 209 
is turned on and a transistor 211 is turned off. As a result, the shaped 
position signal A of the comparator 161 becomes "H" (the high-potential 
state, and, in the embodiment, Vcc). By contrast, when the output signal a 
is lower than the predetermined voltage, the transistor 209 is turned off 
and the transistor 211 is turned on. As a result, the shaped position 
signal A of the comparator 161 becomes "L" (the low-potential state, and, 
in the embodiment, the ground potential). Constant current sources 201, 
208, and 210 supplies currents of a predetermined value. In this way, the 
comparator 161 compares the output signal a of the position detecting 
circuit 31 with the predetermined voltage without setting hysteresis, and 
changes the level of the shaped position signal A to "H" or "L" in a 
digital manner at the zero-crossing point of the output signal a of the 
position detecting circuit 31. The comparators 162 and 163 operate in the 
same manner, and change the levels of the shaped position signals B and C 
to "H" or "L" in a digital manner at the respective zero-crossing points 
of the output signals b and c of the position detecting circuit 31, 
respectively. 
The rotation signal producing circuit 12 in the rotation detecting block 10 
of FIG. 3 receives a pair of the shaped position signals A and B. In the 
rotation signal producing circuit 12, an inverting circuit 172 and an AND 
circuit 171 produce an AND signal D of a negation of the signal B and the 
signal A, and the AND signal D is supplied to the set terminal of a 
set-reset flip-flop circuit 175. An inverting circuit 174 and an AND 
circuit 173 produce an AND signal E of the negation of the signal A and 
the signal B, and the AND signal is supplied to the reset terminal of the 
flip-flop circuit 175. As a result, the digital rotation signal F 
synchronized with the shaped position signal A or B is obtained at the 
output terminal of the flip-flop circuit 175. 
The direction signal producing circuit 13 in the rotation detecting block 
10 of FIG. 3 has a first flip-flop circuit 182 and a second flip-flop 
circuit 183. The first flip-flop circuit 182 latches a level of the shaped 
position signal C by using a leading edge (a timing when a level of the 
rotation signal F is changed from "L" to "H") of the rotation signal F as 
a clock signal, and outputs a first direction signal G. The second 
flip-flop circuit 183 latches the level of the shaped position signal C by 
using a falling edge (the timing when the level of the rotation signal F 
is changed from "H" to "L") of the rotation signal F as the clock signal, 
and outputs a second direction signal H via an inverting circuit 184. An 
AND circuit 185 functioning as a direction signal output circuit composes 
the first and second direction signals G and H to produce a direction 
signal J. 
The operation of the rotation detecting block 10 of FIG. 3 will be 
described in detail with reference to FIGS. 9A through 9M. The abscissae 
of FIGS. 9A through 9M indicate the time. In FIGS. 9A through 9M, the 
forward rotation state is carried out in the left side of the one-dot 
chain line, and the state is changed to the reverse rotation state at the 
one-dot chain line. In the forward rotation state, the output signals a, 
b, and c of the position detecting block 30 change as three-phase analog 
signals which are electrically different in phase from each other see 
FIGS. 9A to 9C!. In the shaped position signal producing circuit 11 of the 
rotation detecting block 10, the waveforms of the output signals a, b, and 
c are shaped by the comparators 161, 162, and 163, respectively, and the 
shaped position signals A, B, and C are produced. As the comparator 161 
has a simple configuration having no hysteresis, the timing (the edge 
timing) of a level change of the shaped position signal A corresponds 
exactly to the zero-crossing point of the output signal a. When the output 
signal a has noises, minute noise pulses are generated in the shaped 
position signal A see FIG. 9D!. Similarly, as the comparator 162 has no 
hysteresis, the timing of a level change of the shaped position signal B 
corresponds to the zero-crossing point of the output signal b. When the 
output signal b has noises, minute noise pulses are generated in the 
shaped position signal B see FIG. 9E!. Furthermore, as the comparator 163 
has no hysteresis, the timing of a level change of the shaped position 
signal C corresponds to the zero-crossing point of the output signal c. 
When the output signal c has noises, minute noise pulses are generated in 
the shaped position signal C see FIG. 9F!. In the rotation signal 
producing circuit 12, the AND signal D see FIG. 9G! and the AND signal E 
see FIG. 9H! are produced by using a pair of the shaped position signals 
A and B, and the AND signals D and E are used as the set signal and the 
reset signal, respectively. As a result, the flip-flop circuit 175 outputs 
the rotation signal F in which the noises are eliminated see FIG. 9I!. 
The rotation signal F is synchronized with the shaped position signal A 
during the forward rotation, and the level change of the rotation signal F 
is generated at the timing of a level change of the shaped position signal 
A. As a result, the rotation signal F has a waveform which is in phase 
with the shaped position signal A. The rotation signal F is synchronized 
with the shaped position signal B during the reverse rotation. 
The first flip-flop circuit 182 of the direction signal producing circuit 
13 receives the shaped position signal C and holds the level of the shaped 
position signal C at the timing of the leading edge of the rotation signal 
F, and the first direction signal G is obtained see FIG. 9K!. As a 
result, the first direction signal G is "H" during the forward rotation, 
and the first direction signal G is changed to "L" at a first timing of 
the leading edge of the rotation signal F in the reverse rotation. 
Similarly, the second flip-flop circuit 183 receives the shaped position 
signal C and holds the level of the shaped position signal C at the timing 
of the falling edge of the rotation signal F, and obtains the second 
direction signal H is obtained via the inverting circuit 184 see FIG. 
9L!. As a result, the second direction signal H is "H" during the forward 
rotation, and the second direction signal H is changed to "L" at a first 
timing of the falling edge of the rotation signal F in the reverse 
rotation. Therefore, the direction signal J in correspondence with the 
first and second direction signals G and H is "H" during the forward 
rotation, and the direction signal J is changed to "L" at a first timing 
of the edge of the rotation signal F in the reverse rotation see FIG. 
9M!. FIG. 9J shows a waveform of a direction command signal L which will 
be described later. When the direction command signal L is changed from 
the forward rotation command ("H" level) to the reverse rotation command 
("L" level), the reverse direction torque is generated by the motor 
operation which will be described later, thereby decelerating the motor 
and then causing the motor to be reversely rotated (actually, the time 
period of the reverse rotation is short). 
The drive block 40 of FIG. 1 comprises a distributing circuit 41, a first 
drive circuit 42, a second drive circuit 43, and a third drive circuit 44. 
FIG. 5 shows a configuration of the drive block 40. The distributing 
circuit 41 of the drive block 40 receives the three-phase output signals 
d, e, and f of the position detecting block 30. Differential amplifier 
circuits 234, 235, and 236 amplify the difference voltages between the 
output signals d, e, and f and a predetermined voltage signal (in the 
embodiment, the ground potential) and output the amplified voltages. A 
corrected activation command signal n in correspondence with an activation 
command signal w of a command block 50 is supplied to the distributing 
circuit 41 (the corrected activation command signal n will be described in 
detail later). Multiplier circuits 231, 232, and 233 multiply the output 
signals of the differential amplifier circuits 234, 235, and 236 with the 
corrected activation command signal n, and output distributed signals m1, 
m2, and m3, respectively. The first drive circuit 42 supplies a driving 
voltage Va to the terminal of the coil 21 by power-amplifying the 
distributed signal m1. The second drive circuit 43 supplies a driving 
voltage Vb to the terminal of the coil 22 by power-amplifying the 
distributed signal m2. The third drive circuit 44 supplies a driving 
voltage Vc to the terminal of the coil 23 by power-amplifying the 
distributed signal m3. As a result, the driving voltages Va, Vb, and Vc 
distributed by the output signals d, e, and f of the position detecting 
circuit 31 are supplied to the three-phase coils 21, 22, and 23, 
respectively. The electric power (a voltage or a current) supplied to the 
coils 21, 22, and 23 is controlled in correspondence with the corrected 
activation command signal n (i.e., the activation command signal w). As 
the output signals d, e, and f of the position detecting block 30 are 
changed according to the rotation of the field part 20, a continuous 
torque is obtained. 
In the embodiment, a forward torque is generated when the corrected 
activation command signal n is positive, and a reverse torque is generated 
when the corrected activation command signal n is negative. 
Furthermore, when the corrected activation command signal n is zero, the 
generated torque becomes zero so that the activation of the coils is 
stopped. 
The command block 50 of FIG. 1 comprises a command signal producing circuit 
51, a rotational speed detecting circuit 52, a stop command circuit 53, 
and a switch circuit 54. The rotational speed detecting circuit 52 
measures a time interval (the period or the half period) of the level 
change of the rotation signal F of the rotation detecting block 10, and 
changes analoguely the output signal (control signal) v of the rotational 
speed detecting circuit 52 in correspondence with the measurement result. 
That is, when the rotational speed is low, the control signal v of the 
rotational speed detecting circuit 52 has the positive maximum voltage, 
and, when the rotational speed is nearly equal to a predetermined 
rotational speed, the control signal v has a required positive voltage in 
correspondence with the rotational speed. In the case of the forward 
rotation command operation, the switch circuit 54 is connected so that the 
control signal v of the rotational speed detecting circuit 52 is supplied 
to the command signal producing circuit 51. In the case of the stop 
command operation, the switch circuit 54 is connected so that an output 
voltage signal (stop command signal) u of the stop command circuit 53 is 
supplied to the command signal producing circuit 51. 
FIG. 6 shows a configuration of the command block 50. The command signal 
producing circuit 51 amplifies the signal passed through the switch 
circuit 54 by a non-inverting amplifier circuit 262 and resistors 263 and 
264, and it outputs the activation command signal w. A comparator 265 of 
the command signal producing circuit 51 compares the voltage signal from 
the switch circuit 54 with a predetermined voltage (in the embodiment, the 
ground potential), and outputs the direction command signal L. For 
example, the comparator 265 may have the circuitry shown in FIG. 4. The 
direction command signal L is "H" level in the case of the forward 
rotation command, and the signal is "L" level in the case of the reverse 
rotation command. The stop command circuit 53 has a voltage source 261 and 
outputs the stop command signal u which has a predetermined negative 
voltage. In the case of the stop command operation, as the connection of 
the switch circuit 54 is changed so as to pass the stop command signal u 
of the stop command circuit 53, the activation command signal w of the 
command signal producing circuit 51 becomes a negative voltage 
corresponding to the stop command signal u, and the direction command 
signal L is changed to "L" level which is the reverse rotation command. In 
the case of the forward rotation command operation, the switch circuit 54 
operates so as to pass the control signal v of the rotational speed 
detecting circuit 52, and each of the activation command signal w and the 
direction command signal L of the command signal producing circuit 51 have 
a value in correspondence with the control signal v, thereby controlling 
the rotational speed of the motor. 
A stop operation block 60 of FIG. 1 comprises an activation changing 
circuit 61 and a stop detecting circuit 62. FIG. 7 shows a configuration 
of the activation changing circuit 61. The activation changing circuit 61 
receives the activation command signal w and the direction command signal 
L of the command signal producing block 50, and also the direction signal 
J of the rotation detecting block 10. When the direction command signal L 
indicates the forward rotation command (L="H") or the direction signal J 
indicates the forward rotation (J="H"), the output signal (activation 
changing signal) K of an AND circuit 274 becomes "L", thereby turning off 
a switch circuit 271. As a result, the activation command signal w is 
output as the corrected activation command signal n. That is, the 
corrected activation command signal n coincides with the activation 
command signal w and the normal activation of the coils is conducted. When 
the direction command signal L indicates the reverse rotation command 
(L="L") and the direction signal J indicates the reverse rotation (J="L"), 
the activation changing signal K of the AND circuit 274 becomes "H", 
thereby turning on the switch circuit 271. As a result, the activation 
command signal w is interrupted by the resistor 270 and the switch circuit 
271, so that the corrected activation command signal n becomes zero. When 
the corrected activation command signal n becomes zero, the drive block 40 
operates so as to stop the activation of the three-phase coils 21, 22, and 
23. In this embodiment, the driving voltages Va, Vb, and Vc have the same 
potential and no current flows through the coils 21, 22, and 23. That is, 
the activation of the coils 21, 22, and 23 is halted, and the rotation of 
the motor is stopped. The stop detecting circuit 62 of the stop operation 
block 60 of FIG. 1 receives the rotation signal F of the rotation 
detecting block 10. When it is detected that the interval of the level 
change of the rotation signal F becomes larger than a predetermined value, 
the stop detecting circuit 62 judges that the stop state is established 
and outputs a stop operation signal X, thereby causing the operation of 
unloading or ejecting the disk as described later. 
FIG. 8 shows a configuration for rotating the disk. A rotation shaft 281 
and a turn table 282 are attached to the rotor 282 (corresponding to the 
field part 20 of FIG. 1) of a motor part 280. As required, the disk 290 on 
which information has been recorded is slightly pressed against the turn 
table 282 by a damper 283 so as to contact therewith. The disk 290 is 
rotated together with the rotor field part of the motor part 280. When the 
disk 290 is rotated by the motor part 280, digital information is recorded 
onto or reproduced from the disk 290 by an optical pickup (not shown). 
When the disk 290 is to be ejected in order to replace the disk with 
another one, the motor part 280 is transferred from the rotation command 
operation to the stop command operation. Specifically, the stop command 
signal u of the stop command circuit 53 is supplied to the command signal 
producing circuit 51, and the activation command signal w and the 
direction command signal L are adjusted to indicate the reverse rotation 
command. The drive block 40 distributively supplies a reverse rotation 
driving signal to the coils 21, 22, and 23 so as to decelerate rapidly the 
field part 20. The activation changing circuit 61 detects the reverse 
rotation of the field part 20 by the polarity of the direction signal J of 
the rotation detecting block 10, and then stops the activation of the 
coils 21, 22, and 23 as soon as the direction signal J becomes the reverse 
rotation. Immediately after the stop of the activation, the field part 20 
and the disk 290 remain to be rotated reversely at a low speed. Therefore, 
the stop detecting circuit 62 checks the rotation signal F of the rotation 
detecting block 10. When there occurs no level change of the rotation 
signal F over the predetermined period, the stop operation signal X is 
changed from "L" level to "H" level. In response to the level change of 
the stop operation signal X, an ejection driving block 291 starts to 
operate. Thereby, an ejection part 292 is moved and the disk 290 is 
detached from the turn table 282. Then, the disk 290 is moved to a 
predetermined unloading position (ejection position). In this way, the 
operation of unloading or ejecting the disk 290 is conducted after the 
stop of the rotation of the field part 20 is detected and confirmed. 
Consequently, as the unloading operation is not conducted while the disk 
290 is rotated, a damage of the disk 290 due to the unloading operation 
can be prevented. 
Next, the operation of the embodiment will be described. When the disk 290 
is mounted as shown in FIG. 8, the motor part 280 rotates the turn table 
282 and the disk 290 at a predetermined rotational speed in order to 
reproduce information recorded on the disk 290 or record information onto 
the disk 290. For this purpose, the switch circuit 54 of the command block 
50 of FIG. 1 is connected to the rotational speed detecting circuit 52. 
The rotational speed detecting circuit 52 measures the rotational speed on 
the basis of the period or the half period of the rotation signal F of the 
rotation detecting block 10, and outputs the control signal v. The command 
signal producing circuit 51 outputs the activation command signal w and 
the direction command signal L in correspondence with the control signal 
v. During the speed control operation, the activation command signal w is 
a signal for generating a forward torque, and the direction command signal 
L indicates the forward rotation command (L="H"). Therefore, the 
activation changing circuit 61 and the stop detecting circuit 62 in the 
stop operation block 60 exert no effective operation. In other words, the 
corrected activation command signal n coincides with the activation 
command signal w. The position detecting circuit 31 of the position 
detecting block 30 detects the relative position between the field part 20 
and the three-phase coils 21, 22, and 23, and outputs the three-phase 
output signals d, e, and f and the three-phase output signals a, b, and c 
which are electrically different from each other in phase. The 
distributing circuit 41, the first drive circuit 42, the second drive 
circuit 43, and the third drive circuit 44 in the drive block 40 
distributes the electric power in correspondence with the activation 
command signal w to the three-phase coils 21, 22, and 23 corresponding to 
the output signals d, e, and f of the position detecting circuit 31. As a 
result, a forward torque for maintaining the forward rotation at the 
predetermined rotational speed is generated. On the other hand, the shaped 
position signal producing circuit 11 of the rotation detecting block 10 
waveform-shapes the three-phase output signals a, b, and c of the position 
detecting circuit 31, and produces the three-phase shaped position signals 
A, B, and C which are electrically different from each other in phase. The 
rotation signal producing circuit 12 eliminates the noises by using a pair 
of the shaped position signals A and B, and produces the rotation signal F 
synchronized with the shaped position signal A or B. In the embodiment, 
the rotation signal F coincides with the shaped position signal A during 
the forward rotation, and the rotation signal F coincides with the shaped 
position signal B during the reverse rotation. The direction signal 
producing circuit 13 produces the direction signal J in correspondence 
with the level of the shaped position signal C at one kind or both kinds 
of the timings of level change (i.e., at least one of the leading edge and 
the falling edge) of the rotation signal F. In this way, the disk 290 is 
rotated in the forward rotation direction at the predetermined speed. 
When the disk 290 is to be ejected, the connection of the switch circuit 54 
in the command block 50 of FIG. 1 is changed to the stop command circuit 
53. The stop command signal u (the predetermined negative voltage) is 
supplied to the command signal producing circuit 51 from the stop command 
circuit 53. Consequently, the activation command signal w of the command 
signal producing circuit 51 has the predetermined negative voltage, and 
the direction command signal L indicates the reverse rotation command 
(L="L"). At this time, the disk 290 and the field part 20 continue to 
rotate in the forward direction by inertia. The level of the rotation 
signal F is changed at the period corresponding to the rotational speed, 
and the direction signal J remains to indicate the forward rotation 
(J="H"). As a result, under this state, the stop operation block 60 exerts 
no effective operation. In other words, the corrected activation command 
signal n coincides with the activation command signal w. The distributing 
circuit 41, the first drive circuit 42, the second drive circuit 43, and 
the third drive circuit 44 in the drive block 40 distributes the electric 
power in correspondence with the activation command signal w to the 
three-phase coils 21, 22, and 23 corresponding to the output signals a, b, 
and c of the position detecting circuit 31. As a result, a reverse torque 
for the reverse rotation is generated. The disk 290 and the field part 20 
are rapidly decelerated by the reverse torque, and finally start to rotate 
in the reverse direction. When the disk 290 and the field part 20 
reversely rotate, the rotation detecting block 10 detects the beginning of 
the reverse rotation, and changes the direction signal J so as to indicate 
the reverse rotation (J="L"). When the direction command signal L 
indicates the reverse rotation command and the direction signal J is 
changed to indicate the reverse rotation, the activation changing circuit 
61 operates so as to make the corrected activation command signal n zero 
(the ground potential). As a result, the activation of the threephase 
coils 21, 22, and 23 is stopped, and the driving torque is not generated. 
However, the disk 290 and the field part 20 are caused to continue to 
rotate in the reverse direction by inertia, and a certain period must 
elapse until they stop completely. The stop detecting circuit 62 measures 
the time interval of the level change of the rotation signal F. When there 
occurs no level change over the predetermined period, the stop detecting 
circuit 62 judges that the disk 290 stops, and changes the stop operation 
signal X from "L" to "H." When the stop operation signal X is changed to 
"H," the ejection driving block 291 and the ejection part 292 operate to 
conduct the unloading operation (ejection operation) on the disk 290. 
In the brushless motor of the embodiment, the rotation signal for measuring 
the rotational speed and the direction signal for measuring the rotational 
direction are produced by using the position signals obtained by the 
position detecting elements of the brushless motor. Therefore, it is 
entirely unnecessary to add further parts to the structure of the motor. 
Accordingly, a simple motor configuration can be realized. 
In the rotation detecting block, the noises at the timing of level change 
of the rotation signal are eliminated by using the two-phase shaped 
position signals. Therefore, an erroneous operation does not occur in the 
rotational speed measurement using the rotation signal. As the direction 
signal is obtained in correspondence with the level of the shaped position 
signal of the third phase at the timing of a level change of the rotation 
signal, the level of the shaped position signal of the third phase becomes 
stable at the timing of a level change of the rotation signal, and it is 
possible to obtain the direction signal correctly. In particular, even 
when the shaped position signals A, B, and C contain the noises at each 
edge, it is possible to obtain the rotation signal F and the direction 
signal J from which the noises are completely eliminated. 
The rotation signal producing circuit comprises the flip-flop circuit in 
which the AND signal of the shaped position signal A and the negation of 
the shaped position signal B is supplied to the set terminal and the AND 
signal of the shaped position signal B and the negation of the shaped 
position signal A is supplied to the reset terminal. The rotation signal F 
is obtained from the output terminal of the flip-flop circuit. Therefore, 
the rotation signal F which is free from the noises can be easily produced 
by a very simple configuration. 
When the position signal of the position detecting circuit (or an output 
signal which is in the same phase with the position signal) is 
waveform-shaped by the comparator having no hysteresis to obtain the 
shaped position signal A, it is possible to use the comparator which is 
very simply configured. Furthermore, the effect of the amplitude 
modulation component contained in the position signal can be eliminated, 
and hence the period or half period of the rotation signal is not 
disturbed by the amplitude modulation. In other words, it is possible to 
obtain the rotation signal for measuring the rotational speed correctly. 
The direction signal producing circuit comprises the edge-trigger type 
flip-flop circuit which receives the level of the shaped position signal C 
at the timing of level change of the rotation signal. The direction signal 
is obtained from the output terminal of the flip-flop circuit. Although 
simple circuitry is used, the direction detection can be surely conducted. 
The direction signal producing circuit comprises: the first flip-flop 
circuit of the edge-trigger type which receives the level of the shaped 
position signal C at one kind of the timing of level change (the leading 
edge) of the rotation signal and which outputs the first direction signal; 
the second flip-flop circuit of the edge-trigger type which receives the 
level of the shaped position signal C at the other kind of the timing of 
level change (the falling edge) of the rotation signal and which outputs 
the second direction signal; and the direction signal output circuit (AND 
circuit) which produces the direction signal J in correspondence with the 
first and second direction signals. According to this configuration, the 
direction signal can be detected each time when the level of the rotation 
signal is changed, thereby enabling the reverse rotation to be detected 
rapidly and surely. 
In the shaped position signal producing circuit, the waveforms of the 
three-phase output signals in correspondence with the plural-phase 
position signals of the position detecting circuit are shaped to produce 
the three-phase shaped position signals A, B, and C, by the three 
comparators having no hysteresis. Although such very simply comparators 
are used, it is possible to detect the rotation signal and the direction 
signal which are free from noise pulses. 
The brushless motor of the embodiment comprises the stop operation block 
which stops the motor rotation in correspondence with the direction 
command signal of the command block and the direction signal of the 
rotation detecting block. The stop operation block comprises the 
activation changing circuit which allows the electric power in 
correspondence with the activation command signal to be supplied to the 
coils by the operation of the drive block when the direction command 
signal indicates the forward rotation command or the direction signal 
indicates the forward rotation, and stops the activation of the coils when 
the direction command signal of the command block indicates the reverse 
rotation command and the direction signal of the rotation detecting block 
indicates the reverse rotation. Accordingly, the rotor field part can be 
decelerated and stopped for a very short time period. In other words, the 
brushless motor has an excellent responsibility. 
The brushless motor comprises: the stop detecting circuit of the stop 
operation block which outputs the stop operation signal when the time 
interval of the level change of the rotation signal is larger than the 
predetermined value; and the ejection process block (the ejection driving 
block and the ejection part) which unloads the disk in correspondence with 
the stop operation signal. After the stop of the rotation of the disk is 
surely detected, the disk can be ejected safely, so that the disk is 
prevented from being damaged during the unloading process. Consequently, 
the brushless motor suitable for rotating the disk can be realized. 
&lt;&lt;SECOND EMBODIMENT&gt;&gt; 
FIGS. 10 and 11 show a configuration of a brushless motor of a second 
embodiment of the present invention. FIG. 10 shows an entire configuration 
of the motor. In the embodiment, the number of detected phases of the 
position signals of the position detecting block 30 is decreased to two, 
so that the position detecting elements can be reduced to two. The 
components which are identical with those of the first embodiment are 
designated by the same reference numerals. That is, the motor structure is 
identical with that of FIG. 2 (however, the number of the position 
detecting elements is two), the drive block 40 with that of FIG. 5, the 
command block 50 with that of FIG. 6, the activation changing circuit 61 
of the stop operation block 60 with that of FIG. 7, and the relationships 
between the motor and the disk with those of FIG. 8. Their duplicated 
description is omitted. 
FIG. 11 shows a configuration of a position detecting circuit 301 of the 
position detecting block 30 using two-phase position signals. The position 
detecting circuit 301 comprises a three-phase signal producing circuit 
302. Two position detecting elements 311 and 312 of the position detecting 
circuit 301 correspond to two of the position detecting elements 107a, 
107b, and 107c of FIG. 2. DC voltages (+Vcc and -Vcc) of DC power sources 
314 and 315 are applied to the elements 311 and 312 via resistors 316 and 
317. Differential position signals g1 and g2 corresponding to the magnetic 
field of the field part 20 (corresponding to the permanent magnet 102 of 
FIG. 2) are generated at output terminals of the position detecting 
element 311. The position signals g1 and g2 are differentially amplified 
by an operational amplifier circuit 321 and resistors 322, 323, 324, and 
325 in the three-phase signal producing circuit 302, and an output signal 
a of a first phase is output. Similarly, differential position signals i1 
and i2 corresponding to the magnetic field of the field part 20 are 
generated at output terminals of the position detecting element 312. The 
position signals i1 and i2 are differentially amplified by an operational 
amplifier circuit 326 and resistors 327, 328, 329, and 330 in the 
three-phase signal producing circuit 302, and an output signal c of a 
second phase is output. An operational amplifier circuit 331 and resistors 
332, 333, and 334 in the three-phase signal producing circuit 302 compose 
the output signals a and c with each other so as to produce an output 
signal b of a third phase. Output signals d, e, and f of the position 
detecting circuit 301 coincide with the output signals a, b, and c, 
respectively, and are supplied to the drive block 40. According to the 
rotational movement of the field part 20, the output signals a, b, and c, 
and the output signals d, e, and f of the position detecting circuit 301 
vary analoguely so as to constitute two sets of three-phase signals which 
have a predetermined electrical phase difference. In other words, the 
three-phase signal producing circuit 302 produces three-phase signals by 
using the two-phase position signals g1 and g2, i1 and i2, and supplies 
the three-phase signals to the rotation detecting block 10 and the drive 
block 40. In the embodiment, the position signals g1 and g2, and i1 and i2 
are in reversed phase relationships, and the signals of reversed phase 
relationships are not counted in the number of phases. 
The shaped position signal producing circuit 11 of the rotation detecting 
block 10 of FIG. 11 is configured by three comparators 161, 162, and 163, 
and outputs the shaped position signal A, B, and C obtained by 
waveform-shaping the output signals a, b, and c, respectively. The 
rotation signal producing circuit 12 receives the two-phase shaped 
position signals A and B. In the rotation signal producing circuit 12, the 
inverting circuit 172 and the AND circuit 171 produce the AND signal D of 
the negation of the signal B and the signal A, and the AND signal D is 
supplied to the set terminal of the set-reset type flip-flop circuit 175. 
The inverting circuit 174 and the AND circuit 173 produce the AND signal E 
of the negation of the signal A and the signal B, and the AND signal is 
supplied to the reset terminal of the flip-flop circuit 175. As a result, 
the digital-type rotation signal F in synchronization with the shaped 
position signal A (or the shaped position signal B) is obtained at the 
output terminal of the flip-flop circuit 175. The direction signal 
producing circuit 13 has the first flip-flop circuit 182 of the 
edge-trigger type, and the second flip-flop circuit 183 of the 
edge-trigger type. The first flip-flop circuit 182 latches the level of 
the shaped position signal C by using the leading edge of the rotation 
signal F as the clock signal, and outputs the first direction signal G. 
The second flip-flop circuit 183 latches the level of the shaped position 
signal C by using the falling edge (the timing when the level of the 
rotation signal F is changed from "H" to "L") of the rotation signal F as 
the clock signal, and outputs the second direction signal H via the 
inverting circuit 184. The AND circuit 185 functioning as the direction 
signal output circuit produces and outputs the direction signal J in 
correspondence with the first and second direction signals G and H. 
In the embodiment, the three-phase output signals a, b, and c, and the 
output signals d, e, and f are produced by using the two-phase position 
signals obtained from the two position detecting elements, whereby the 
desired operation of the brushless motor is realized. Therefore, the 
number of the position detecting elements can be reduced and the motor 
structure can be very simplified. 
Generally, a position signal contains harmonic components. Therefore, the 
output signal b composed by the two-phase position signals with each other 
has a distorted waveform. In the brushless motor of the embodiment, the 
shaped position signal A is produced by shaping the position signal 
appearing in the position detecting element (or the output signal a), and 
the rotation signal F synchronized with the shaped position signal A is 
produced. Therefore, the rotation signal F can be suitable to use an 
accurate and correct rotational speed measurement. The shaped position 
signal C is produced by shaping the position signal appearing in another 
position detecting element (or the output signal c), and the level of the 
shaped position signal C becomes stable at the timing of a level change of 
the rotation signal F. Therefore, the direction signal J can be measured 
stably. 
&lt;&lt;THIRD EMBODIMENT&gt;&gt; 
FIGS. 12 and 13 show a brushless motor of a third embodiment of the present 
invention. FIG. 12 shows an entire configuration of the motor. In the 
embodiment, the rotation detecting block comprises a first rotation signal 
producing circuit 352 and a second rotation signal producing circuit 353, 
so that the rotation signal F and the direction signal J can be obtained 
accurately. The components identical with those of the above-mentioned 
embodiments are designated by the same reference numerals. That is, the 
motor structure is identical with that of FIG. 2, the drive block 40 with 
that of FIG. 5, the command block 50 with that of FIG. 6, the activation 
changing circuit 61 of the stop operation block 60 with that of FIG. 7, 
the relationships between the motor and the disk with those of FIG. 8, and 
the position detecting circuit 301 of the position detecting block 30 with 
that of FIG. 11. Their duplicated description is omitted. 
The rotation detecting block 350 comprises a shaped position signal 
producing circuit 351, a first rotation signal producing circuit 352, a 
second rotation signal producing circuit 353, a rotation signal output 
circuit 354, and a direction signal producing circuit 355. 
FIG. 13 specifically shows configurations of the position detecting circuit 
301 of the position detecting block 30, and the shaped position signal 
producing circuit 351, the first rotation signal producing circuit 352, 
the second rotation signal producing circuit 353, the rotation signal 
output circuit 354, and the direction signal producing circuit 355 in the 
rotation detecting block 350. The position detecting circuit 301 of the 
position detecting block 30 is identical with that shown in FIG. 11, and 
the motor structure is identical with that of FIG. 2 (however, the number 
of the position detecting elements is reduced to two). Their detailed 
description is omitted. 
The operations of the portions of the rotation detecting block 350 of FIG. 
13 will be described in detail with reference to the waveforms of the 
signals shown in FIGS. 14A through 14L. The abscissae of FIGS. 14A through 
14L indicate the time. In FIGS. 14A through 14L, the forward rotation 
state is carried out in the left side of the one-dot chain line, and the 
state is changed to the reverse rotation state at the one-dot chain line. 
The shaped position signal producing circuit 351 of the rotation detecting 
block 350 of FIG. 13 is configured by three comparators 461, 462, and 463. 
The comparators 461, 462, and 463 receive the output signals a, b, and c 
of the position detecting circuit 301, respectively see FIGS. 14A to 
14C!, and output the shaped position signal A, B, and C by 
waveform-shaping the output signals, respectively see FIGS. 14D to 14F!. 
The comparators 461, 462, and 463 are configured in the same manner as 
those shown in FIG. 4. 
The first rotation signal producing circuit 352 receives a pair of the 
shaped position signals A and B. In the first rotation signal producing 
circuit 352, an inverting circuit 472 and an AND circuit 471 produce the 
AND signal of the negation of the signal B and the signal A, and the AND 
signal is supplied to the set terminal of a set-reset type flip-flop 
circuit 475. An inverting circuit 474 and an AND circuit 473 produce the 
AND signal of the negation of the signal A and the signal B, and the AND 
signal is supplied to the reset terminal of the flip-flop circuit 475. As 
a result, a digital-type first rotation signal P is obtained at the output 
terminal of the flip-flop circuit 475. The level of the first rotation 
signal P is changed in synchronization with the shaped position signal A 
during the forward rotation, and changed in synchronization with the 
shaped position signal B during the reverse rotation. In the first 
rotation signal P, the noises at the timing of level change are eliminated 
see FIG. 14G!. 
The second rotation signal producing circuit 353 receives another pair of 
the shaped position signals B and C. In the second rotation signal 
producing circuit 353, an inverting circuit 482 and an AND circuit 481 
produce an AND signal of the negation of the signal C and the signal B, 
and the AND signal is supplied to the set terminal of a set-reset type 
flip-flop circuit 485. An inverting circuit 484 and an AND circuit 483 
produce an AND signal of the negation of the signal B and the signal C, 
and the AND signal is supplied to the reset terminal of the flip-flop 
circuit 485. As a result, a digital-type second rotation signal R is 
obtained at the output terminal of the flip-flop circuit 485. The level of 
the second rotation signal R is changed in synchronization with the shaped 
position signal B during the forward rotation, and changed in 
synchronization with the shaped position signal C during the reverse 
rotation. In the second rotation signal R, the noises at the timing of 
level change are eliminated see FIG. 14H!. 
The rotation signal output circuit 354 is configured by a buffer circuit 
478, and outputs the first rotation signal P as the rotation signal F of 
the rotation detecting block 350. During the forward rotation, therefore, 
the level of the rotation signal F is changed in synchronization with the 
shaped position signal A. 
The direction signal producing circuit 355 has a first flip-flop circuit 
492 of the edge-trigger type, and a second flip-flop circuit 493 of the 
edge-trigger type. The first flip-flop circuit 492 latches the level of 
the second rotation signal R (more correctly, the negation of the signal 
R) by using the leading edge of the first rotation signal P as the clock 
signal, and outputs a first direction signal G. The second flip-flop 
circuit 493 latches the level of the second rotation signal R by using the 
falling edge of the first rotation signal P as the clock signal, and 
outputs a second direction signal H. An AND circuit 485 functioning as the 
direction signal output circuit produces a direction signal J in 
correspondence with the first and second direction signals G and H see 
FIGS. 14J to 14L!. FIG. 14I shows a waveform of a direction command signal 
L. When the direction command signal L is changed from the forward 
rotation command ("H" level) to the reverse rotation command ("L" level), 
the reverse direction torque is generated by the motor operation, thereby 
decelerating the motor and then causing the field part 20 to be rotated 
reversely (actually, the time period of the reverse rotation is short). 
In FIG. 12, the field part 20, the three-phase coils 21, 22, and 23, the 
drive block 40, the command block 50, and the stop operation block 60 are 
the same as those of the above-mentioned first embodiment (FIG. 1), and 
their detailed description is omitted. 
Also in the brushless motor of the embodiment, as the rotation signal F and 
the direction signal J are produced by using the position signals of the 
position detecting elements, it is entirely unnecessary to add further 
parts to the structure of the motor. Accordingly, a simple motor 
configuration can be realized. In the brushless motor of the embodiment, 
the three-phase output signals a, b, and c, and the output signals d, e, 
and f are produced by using the two-phase position signals obtained from 
the two position detecting elements. Therefore, the motor structure can be 
very simplified. 
In the rotation detecting block, the noises at the timing of level change 
of the first rotation signal P are eliminated by using a pair of the 
shaped position signals A and B, and the noises at the timing of level 
change of the second rotation signal R are eliminated by the using another 
pair of the shaped position signals B and C. Furthermore, one of the first 
and second rotation signals P and R is used as the rotation signal F. 
Therefore, an erroneous operation does not occur in the rotational speed 
measurement using the rotation signal F. The direction signal J is 
obtained correctly in correspondence with the level of the second rotation 
signal R at the timing of a level change of the first rotation signal P, 
since the first and second rotation signals P and R are free from the 
noises and the level of the second rotation signal R becomes stable at the 
timing of a level change of the first rotation signal P. Therefore, even 
when the shaped position signals A, B, and C contain the noises at each 
edge, it is possible to obtain the rotation signal F and the direction 
signal J from which the noises are completely eliminated. 
In the same manner as the above-mentioned first embodiment, the brushless 
motor of the embodiment comprises the stop operation block which stops the 
motor rotation in correspondence with the direction command signal of the 
command block and the direction signal of the rotation detecting block. 
The stop operation block comprises the activation changing circuit. When 
the direction command signal indicates the forward rotation command or the 
direction signal indicates the forward rotation, the activation changing 
circuit allows the electric power in correspondence with the activation 
command signal to be supplied to the coils. When the direction command 
signal of the command block indicates the reverse rotation command and the 
direction signal of the rotation detecting block indicates the reverse 
rotation, the activation changing circuit stops the activation of the 
coils. When the stop command is issued, therefore, the rotor of the motor 
and the field part can be decelerated and stopped for a short time period. 
In other words, the brushless motor has an excellent responsibility. 
The brushless motor comprises the stop detecting circuit of the stop 
operation block which outputs the stop operation signal when the time 
interval of the level change of the rotation signal F is larger than the 
predetermined value, and the process block (the ejection driving block and 
the ejection part) which unloads the disk in correspondence with the stop 
operation signal. Therefore, the stop of the rotation of the disk can be 
surely detected, so that the disk is prevented from being damaged during 
the unloading process. Consequently, a brushless motor suitable for 
rotating a disk can be realized. 
&lt;&lt;FOURTH EMBODIMENT&gt;&gt; 
FIGS. 15 through 17 show a brushless motor of a fourth embodiment of the 
present invention. FIG. 15 shows an entire configuration of the motor. In 
the embodiment, the motor structure of the first embodiment is modified so 
that the positional relationships between the coils and the attached 
positions of position detecting elements are shifted from each other by 
the electrical angle of about 30 degrees. This configuration allows the 
position detecting elements to be disposed between the salient poles of 
the armature core, whereby the motor structure can be miniaturized. The 
components which are identical with those of the above-mentioned 
embodiments are designated by the same reference numerals. That is, the 
drive block 40 is identical with that of FIG. 5, the command block 50 with 
that of FIG. 6, the stop operation block 60 with that of FIG. 7, and the 
relationships between the motor and the disk with those of FIG. 8. Their 
duplicated description is omitted. 
A field part 520 shown in FIG. 15 is mounted on the rotor and forms plural 
magnetic field poles by means of a magnetic flux generated by a permanent 
magnet, thereby generating a magnetic field flux. Three-phase coils 521, 
522, and 523 are mounted on the stator and arranged so as to be 
electrically separated from each other by a predetermined angle 
(corresponding to 120 degrees in the electrical angle) with respect to the 
interlinkage with the magnetic flux generated by the field part 520. A 
required electric power is distributively supplied to the three-phase 
coils 521, 522, and 523 in accordance with the relative position between 
the field part 520 and the coils, thereby rotating the field part 520 and 
the disk attached to the rotor. 
FIG. 16 specifically shows configurations of the field part 520 and the 
three-phase coils 521, 522, and 523. In an annular permanent magnet 602 
attached to the inner side of the rotor 601, the inner and end faces are 
magnetized so as to form four poles, thereby constituting the field part 
520 shown in FIG. 15. An armature core 603 is placed at a position of the 
stator which opposes the poles of the permanent magnet 602. Three salient 
poles 604a, 604b, and 604c are disposed in the armature core 603 at 
intervals of 120 degrees in the mechanical angle. Three-phase coils 605a, 
605b, and 605c (corresponding to the three-phase coils 521, 522, and 523 
shown in FIG. 15) are wound on the salient poles 604a, 604b, and 604c by 
using winding slots 606a, 606b, and 606c, respectively. Among the coils 
605a, 605b, and 605c, phase differences of 120 degrees in the electrical 
angle are established with respect to the interlinkage with magnetic flux 
from the permanent magnet 602. Three position detecting elements 607a, 
607b, and 607c (for example, Hall elements which are magnetoelectrical 
converting elements) are arranged on the stator. The pole of the end face 
of the permanent magnet 602 is detected, thereby obtaining three-phase 
position signals corresponding to the relative position between the field 
part and the coils. In the embodiment, the coils and the position 
detecting elements are shifted in phase by the electrical angle of 120 
degrees (60 degrees in the mechanical angle). The position detecting 
elements are disposed in winding slots between the salient poles. As a 
result, the position detecting elements can be disposed in the motor, 
whereby the motor structure can be miniaturized. Since the position 
detecting elements are disposed with being shifted, driving signals 
shifted by 30 degrees with respect to the position signals of the position 
detecting elements are applied to the coils, thereby obtaining a rotation 
force in a predetermined direction. 
FIG. 17 shows a configuration of the position detecting circuit 531 of the 
position detecting block 530. Position detecting elements 631, 632, and 
633 of the position detecting circuit 531 correspond to the position 
detecting elements 607a, 607b, and 607c shown in FIG. 16. DC voltages 
(+Vcc and -Vcc) of DC power sources 621 and 622 are applied to the 
elements 631, 632 and 633 via resistors 623 and 624. Differential position 
signals g1 and g2 corresponding to the magnetic field of the field part 
520 (corresponding to the permanent magnet 602 of FIG. 16) are detected at 
output terminals of the position detecting element 631. The position 
signals g1 and g2 are differentially amplified by an operational amplifier 
circuit 641 and resistors 642, 643, 644, and 645, and an output signal a 
which varies in the same phase of the position signal g1 is obtained. 
Similarly, position signals h1 and i1 are output from output terminals of 
the position detecting elements 632 and 633, respectively. The position 
signals g1, h1, and i1 are three-phase signals which have a phase 
difference of 120 degrees in the electrical angle. The position signals g1 
and i1 are differentially amplified by an operational amplifier circuit 
651 and resistors 652, 653, 654, and 655, and an output signal d 
proportional to a signal (g1-i1) is obtained. As a result, the output 
signal d is a signal shifted in phase by 30 degrees in the electrical 
angle from the position signal g1. Similarly, an output signal e 
proportional to a signal (h1-g1 ) is obtained by an operational amplifier 
circuit 661 and resistors 662, 663, 664, and 665. The output signal e is a 
signal shifted by 30 degrees from the position signal h1. Similarly, an 
output signal f proportional to a signal (i1-h1) is obtained by an 
operational amplifier circuit 671 and resistors 672, 673, 674, and 675. 
The output signal f is a signal shifted by 30 degrees from the position 
signal i1. The output signals b and c of the position detecting circuit 
531 coincide with the output signals e and f, respectively. The output 
signals d, e, and f are three-phase signals which have a phase difference 
of 120 degrees in the electrical angle and which are shifted in phase by 
30 degrees from the three-phase position signals g1, h1, and i1, 
respectively. The three-phase output signals d, e, and f are supplied to 
the drive block 40, and a required electric power is distributed to the 
coils 521, 522, and 523 according to the three-phase signals d, e, and f 
so as to produce a torque of the motor. On the other hand, the three-phase 
output signals a, b, and c of the position detecting circuit 531 which are 
electrically different from each other in phase are supplied to the 
rotation detecting block 10. 
The operations of the rotation detecting block 10 shown in FIG. 17 will be 
described with reference to waveforms of the signals shown in FIGS. 18A 
through 18M. The abscissae of FIGS. 18A through 18M indicate the time. In 
FIGS. 18A through 18M, the forward rotation state is carried out in the 
left side of the one-dot chain line, and the state is changed to the 
reverse rotation state at the one-dot chain line. The three-phase output 
signals a, b, and c of the position detecting circuit 531 are three-phase 
signals, although they have phase differences not equal to each other in 
the electrical angle. Specifically, the phase difference between the 
output signals a and b is about 150 degrees, that between the output 
signals b and c is about 120 degrees, and that between the output signals 
c and a is about 90 degrees see FIGS. 18A to 18C!. The three comparators 
161, 162, and 163 of the shaped position signal producing circuit 11 
output shaped position signal A, B, and C by waveform-shaping the output 
signals a, b, and c of the position detecting circuit 531, respectively 
see FIGS. 18D to 18F!. The rotation signal producing circuit 12 receives 
a pair of the shaped position signals A and B. In the rotation signal 
producing circuit 12, the inverting circuit 172 and the AND circuit 171 
produce the AND signal D of the negation of the signal B and the signal A, 
and the AND signal D is supplied to the set terminal of the set-reset type 
flip-flop circuit 175 see FIG. 18G!. The inverting circuit 174 and the 
AND circuit 173 produce the AND signal E of the negation of the signal A 
and the signal B, and the AND signal is supplied to the reset terminal of 
the flip-flop circuit 175 see FIG. 18H!. As a result, the digital-type 
rotation signal F in synchronization with the shaped position signal A (or 
the shaped position signal B) is obtained at the output terminal of the 
flip-flop circuit 175 see FIG. 18I!. 
The direction signal producing circuit 13 has the first flip-flop circuit 
182 of the edge-trigger type, and the second flip-flop circuit 183 of the 
edge-trigger type. The first flip-flop circuit 182 latches the level of 
the shaped position signal C by using the leading edge of the rotation 
signal F as the clock signal, and outputs the first direction signal G. 
The second flip-flop circuit 183 latches the level of the shaped position 
signal C by using the falling edge of the rotation signal F as the clock 
signal, and outputs the second direction signal H via the inverting 
circuit 184. The AND circuit 185 functioning as the direction signal 
output circuit produces and outputs the direction signal J in 
correspondence with the first and second direction signals G and H see 
FIGS. 18K to 18M!. FIG. 18J shows a waveform of the direction command 
signal L. When the direction command signal L is changed from the forward 
rotation command ("H" level) to the reverse rotation command ("L" level), 
the reverse direction torque is generated, thereby decelerating the motor 
and then causing the field part to be reversely rotated (actually, the 
time period of the reverse rotation is short). 
The drive block 40, the command block 50, and the stop operation block 60 
in FIG. 15, and the relationships between the motor and the disk are 
identical with those of the above-mentioned first embodiment. Their 
detailed description is omitted. That is, the drive block 40 is identical 
with that of FIG. 5, the command block 50 with that of FIG. 6, the stop 
operation block 60 with that of FIG. 7, and the relationships between the 
motor and the disk with those of FIG. 8. 
In the brushless motor of the embodiment, the distributive driving is 
conducted on the basis of the output signals obtained by shifting the 
phases of the position signals. Therefore, the position detecting elements 
can be freely arranged. For example, the position detecting elements can 
be disposed between the salient poles of the armature core, with the 
result that the motor structure can be miniaturized. 
As shown in the embodiment, the phase differences among the three-phase 
output signals a, b, and c supplied to the rotation detecting block are 
not restricted to 120 degrees. The minimum phase difference may be about 
30 degrees. 
&lt;&lt;FIFTH EMBODIMENT&gt;&gt; 
FIGS. 19 and 20 show a brushless motor of a fifth embodiment of the present 
invention. FIG. 19 shows an entire configuration of the motor. In the 
embodiment, the number of detected phases of the position detecting block 
of the above-mentioned fourth embodiment is decreased to two, so that the 
position detecting elements can be reduced to two. The components which 
are identical with those of the fourth embodiment are designated by the 
same reference numerals. That is, the motor structure is identical with 
that of FIG. 16 (however, the number of the position detecting elements is 
two), the drive block 40 with that of FIG. 5, the command block 50 with 
that of FIG. 6, the stop operation block 60 with that of FIG. 7, and the 
relationships between the motor and the disk with those of FIG. 8. Their 
duplicated description is omitted. 
FIG. 20 shows a configuration of a position detecting circuit 701 of the 
position detecting block 530 using two position detecting elements. The 
position detecting circuit 701 comprises a three-phase signal producing 
circuit 702. The position detecting elements 711 and 712 of the position 
detecting circuit 701 correspond to two of the position detecting elements 
607a, 607b, and 607c of FIG. 16. DC voltages (+Vcc and -Vcc) of DC power 
sources 714 and 715 are applied to the elements 711 and 712 via resistors 
716 and 717. Differential position signals g1 and g2 corresponding to the 
magnetic field of the field part 520 (corresponding to the permanent 
magnet 602 of FIG. 16) are detected at output terminals of the position 
detecting element 711. The position signals g1 and g2 are differentially 
amplified by an operational amplifier circuit 721 and resistors 722, 723, 
724, and 725 of the three-phase signal producing circuit 702, and an 
output signal a of a first phase which analoguely varies in the same phase 
with the position signal g1 is obtained. Similarly, differential position 
signals i1 and i2 are detected at output terminals of the position 
detecting element 712. The position signals i1 and i2 are differentially 
amplified by an operational amplifier circuit 726 and resistors 727, 728, 
729, and 730 of the three-phase signal producing circuit 702, and an 
analogue signal j which varies in the same phase with the position signal 
i1 is obtained. The signals a and j are two-phase signals which have a 
phase difference of 120 degrees in the electrical angle. An output signal 
d of a first phase proportional to a signal (a-j) is output by an 
operational amplifier circuit 735 and resistors 736, 737, 738, and 739. 
The output signal d is a signal shifted in phase by 30 degrees in the 
electrical angle from the position signal g1. An operational amplifier 
circuit 741 and resistors 742, 743, and 744 compose the signals a and j at 
a ratio of 2:1 so as to produce an output signal e of a second phase. An 
operational amplifier circuit 751 and resistors 752, 753, and 754 compose 
the signals a and j at a ratio of 1:2, and an operational amplifier 
circuit 755 and resistors 756, 756, and 758 amplifies inversely the 
composed signal so as to produce an output signal f of a third phase. The 
output signals b and c of the position detecting circuit 701 coincide with 
the output signals e and f, respectively. The output signals d, e, and f 
of the three-phase signal producing circuit 702 are three-phase signals 
produced from the two-phase position signals g1 and i1. The output signals 
d and f are shifted in phase from the position signals g1 and i1 by 30 
degrees in the electrical angle, respectively. The three-phase output 
signals d, e, and f are supplied to the drive block 40, and a required 
electric power is distributed to the coils 521, 522, and 523 in accordance 
with the output signals d, e, and f, thereby generating a motor torque. 
The three-phase output signals a, b, and c of the position detecting 
circuit 701 which have different phases are supplied to the rotation 
detecting block 10. The phase difference between the output signals a and 
b is about 150 degrees, that between the output signals b and c is about 
120 degrees, and that between the output signals c and a is about 90 
degrees. The configuration and operation of the rotation detecting block 
10 of FIG. 20 are identical with those of the above-mentioned fourth 
embodiment and shown in FIG. 17, and hence their detailed description is 
omitted. 
The drive block 40, the command block 50, and the stop operation block 60 
in FIG. 19, and the relationships between the motor and the disk are 
identical with those of the above-mentioned fourth embodiment. Their 
detailed description is omitted. That is, the drive block 40 is identical 
with that of FIG. 5, the command block 50 with that of FIG. 6, the stop 
operation block 60 with that of FIG. 7, and the relationships between the 
motor and the disk with those of FIG. 8. 
In the brushless motor of the embodiment, the three-phase output signals a, 
b, and c, and the three-phase output signals d, e, and f are produced by 
using two-phase position signals obtained from the two position detecting 
elements, whereby the desired operation of the brushless motor is 
realized. Therefore, the number of the position detecting elements can be 
reduced and the motor structure can be very simplified. 
Generally, as a position signal contains harmonic components, the composed 
signal b has a distorted waveform. To comply with this, in the brushless 
motor of the embodiment, the shaped position signal A is produced by 
shaping the position signal appearing in the position detecting element, 
and the rotation signal F synchronized with the shaped position signal A 
is produced. Therefore, the rotation signal F can be used for accurate and 
correct rotational speed measurement. 
&lt;&lt;SIXTH EMBODIMENT&gt;&gt; 
FIGS. 21 and 22 show a brushless motor of a sixth embodiment of the present 
invention. FIG. 21 shows an entire configuration of the motor. In the 
embodiment, the rotation detecting block 350 shown in the third embodiment 
and comprising the first and second rotation signal producing circuits is 
used. The components which are identical with those of the above-mentioned 
embodiments are designated by the same reference numerals. That is, the 
field part 520, the three-phase coils 521, 522, and 523, the position 
detecting block 530, the drive block 40, the command block 50, and the 
stop operation block 60 are identical with those of the above-mentioned 
fifth embodiment, and their detailed description is omitted. Moreover, the 
motor structure is identical with that of FIG. 16 (however, the number of 
the position detecting elements is reduced to two). The rotation detecting 
block 350 of FIG. 21 comprises the shaped position signal producing 
circuit 351, the first rotation signal producing circuit 352, the second 
rotation signal producing circuit 353, the rotation signal output circuit 
354, and the direction signal producing circuit 355. FIG. 22 specifically 
shows configurations of the position detecting block 530 and the rotation 
detecting block 350. FIGS. 23A through 23L show waveforms of signals in 
the rotation detecting block 350. The abscissae of FIGS. 23A through 23L 
indicate the time. In FIGS. 23A through 23L, the forward rotation state is 
carried out in the left side of the one-dot chain line, and the state is 
changed to the reverse rotation state at the one-dot chain line. The 
configuration of the position detecting circuit 701 of the position 
detecting block 530 is identical with that of the above-mentioned fifth 
embodiment of FIG. 20, and its detailed description is omitted. One set of 
three-phase output signals d, e, and f is produced on the basis of 
two-phase position signals g1 and g2, and i1 and i2 of the two position 
detecting elements 711 and 712, and supplied to the drive block 40. The 
other set of three-phase output signals a, b, and c is produced and 
supplied to the rotation detecting block 350 see FIGS. 23A to 23C!. In 
the brushless motor of the embodiment, as shown in FIG. 22, the output 
signals e and f coincide with the output signals c and b, respectively. 
The configuration of the rotation detecting block 350 is substantially 
identical with that of the third embodiment of FIG. 13, and the components 
having the same function are designated by the same reference numerals (in 
the embodiment, however, an inverting circuit 760 is added to the shaped 
position signal producing circuit 351). The shaped position signal 
producing circuit 351 of FIG. 22 is configured by the three comparators 
461, 462, and 463 and the inverting circuit 760. The shaped position 
signal producing circuit 351 waveform-shapes the output signals a, b, and 
c of the position detecting circuit 701 and outputs the three-phase shaped 
position signal A, B, and C, respectively see FIGS. 23D to 23F!. The 
comparators 461, 462, and 463 are configured in the same manner as those 
shown in FIG. 4. 
The first rotation signal producing circuit 352 receives a pair of the 
shaped position signals A and B. In the first rotation signal producing 
circuit 352, the inverting circuit 472 and the AND circuit 471 produce the 
AND signal of the negation of the signal B and the signal A, and the AND 
signal is supplied to the set terminal of the set-reset type flip-flop 
circuit 475. The inverting circuit 474 and the AND circuit 473 produce the 
AND signal of the negation of the signal A and the signal B, and the AND 
signal is supplied to the reset terminal of the flip-flop circuit 475. As 
a result, the digital-type first rotation signal P is obtained at the 
output terminal of the flip-flop circuit 475. The level of the first 
rotation signal P is changed in synchronization with the shaped position 
signal A during the forward rotation, and changed in synchronization with 
the shaped position signal B during the reverse rotation. In the first 
rotational signal P, the noises at the timing of level change are 
eliminated see FIG. 23G!. 
The second rotation signal producing circuit 353 receives another pair of 
the shaped position signals B and C. In the second rotation signal 
producing circuit 353, the inverting circuit 482 and the AND circuit 481 
produce the AND signal of the negation of the signal C and the signal B, 
and the AND signal is supplied to the set terminal of the set-reset type 
flip-flop circuit 485. The inverting circuit 484 and the AND circuit 483 
produce the AND signal of the negation of the signal B and the signal C, 
and the AND signal is supplied to the reset terminal of the flip-flop 
circuit 485. As a result, the digital-type second rotation signal R is 
obtained at the output terminal of the flip-flop circuit 485. The level of 
the second rotation signal R is changed in synchronization with the shaped 
position signal B during the forward rotation, and changed in 
synchronization with the shaped position signal C during the reverse 
rotation. In the second rotation signal R, the noises at the timing of 
level change are eliminated see FIG. 23H!. 
The rotation signal output circuit 354 is configured by the buffer circuit 
478, and outputs the first rotation signal P as the rotation signal F of 
the rotation detecting block 350. During the forward rotation, therefore, 
the level of the rotation signal F is changed in synchronization with the 
shaped position signal A. Since the shaped position signal A is obtained 
by waveform-shaping the output signal a which is in the same phase with 
the position signal g1, the rotation signal F corresponds to a shaped 
position signal of the position signal g1. 
The direction signal producing circuit 355 has the first flip-flop circuit 
492 of the edge-trigger type, and the second flip-flop circuit 493 of the 
edge-trigger type. The first flip-flop circuit 492 latches the level of 
the second rotation signal R (more correctly, the negation of the signal 
R) by using the leading edge of the first rotation signal P as the clock 
signal, and outputs the first direction signal G. The second flip-flop 
circuit 493 latches the level of the second rotation signal R by using the 
falling edge of the first rotation signal P as the clock signal, and 
outputs the second direction signal H. The AND circuit 495 functioning as 
the direction signal output circuit produces the direction signal J in 
correspondence with the first and second direction signals G and H see 
FIGS. 23J to 23L!. FIG. 23I shows a waveform of the direction command 
signal L. When the direction command signal L is changed from the forward 
rotation command ("H" level) to the reverse rotation command ("L" level), 
the reverse torque is generated, thereby decelerating the motor and then 
causing the field part to be rotated reversely (actually, the time period 
of the reverse rotation is short). 
The drive block 40, the command block 50, and the stop operation block 60 
in FIG. 21, and the relationships between the motor and the disk are the 
same as those of the above-mentioned fifth embodiment, and their detailed 
description is omitted. That is, the drive block 40 is identical with that 
of FIG. 5, the command block 50 with that of FIG. 6, the stop operation 
block 60 with that of FIG. 7, and the relationships between the motor and 
the disk with those of FIG. 8. 
In the brushless motor of the embodiment, as the rotation signal F and the 
direction signal J are produced by using the position signals of the 
position detecting elements, it is entirely unnecessary to add further 
parts to the structure of the motor. Accordingly, a simple motor 
configuration can be realized. The three-phase output signals a, b, and c 
are produced by using the two-phase position signals of the two position 
detecting elements. Therefore, the motor structure can be very simplified. 
In the rotation detecting block, the shaped position signal A is produced 
by shaping the output signal a which is in the same phase with the 
position signal g1 of the position detecting element, and the rotation 
signal F synchronized with the shaped position signal A is obtained by 
using a pair of the shaped position signals A and B. Therefore, an 
erroneous operation does not occur in the rotational speed measurement. 
In the three-phase shaped position signals A, B, and C, the phase 
difference between the shaped position signals A and B is 90 degrees, that 
between the shaped position signals B and C is 60 degrees, and that 
between the shaped position signals C and A is 150 degrees (or 30 
degrees). The first rotation signal P is produced by using the shaped 
position signals A and B, and the second rotation signal R is produced by 
using the shaped position signals B and C. Furthermore, the direction 
signal in correspondence with the level of the second rotation signal R at 
the timing of level change of the first rotation signal P is obtained. 
Therefore, the first and second rotation signals P and R and the direction 
signal are all stable so that no noises are contained. In other words, 
even when the shaped position signals A, B, and C contain the noises at 
each edge, it is possible to obtain the rotation signal F and the 
direction signal J without noises. 
&lt;&lt;SEVENTH EMBODIMENT&gt;&gt; 
FIGS. 24 and 25 show a brushless motor of a seventh embodiment of the 
present invention. FIG. 24 shows an entire configuration of the motor. In 
the embodiment, the configuration of the rotation detecting block of the 
first embodiment is modified so that the period of the rotation signal is 
shortened to one third of that of the position signal, thereby increasing 
the frequency of the rotational speed measurement. 
In FIG. 24, the field part 20, the three-phase coils 21, 22, and 23, the 
drive block 40, the command block 50, and the stop operation block 60 are 
the same as those of the above-mentioned first embodiment, and their 
detailed description is omitted. The motor structure is identical with 
that of FIG. 2. 
A rotation detecting block 800 of FIG. 24 comprises a shaped position 
signal producing circuit 801, a first rotation signal producing circuit 
802, a second rotation signal producing circuit 803, a third rotation 
signal producing circuit 804, a rotation signal output circuit 805, and a 
direction signal producing circuit 806. 
FIG. 25 specifically shows configurations of the position detecting block 
30 and the rotation detecting block 800. FIGS. 26A through 26G show 
waveforms of signals in the rotation detecting block 800. The abscissae of 
FIGS. 26A through 26G indicate the time. The configuration of the position 
detecting circuit 31 of the position detecting block 30 is identical with 
that of the above-mentioned first embodiment of FIG. 3, and its detailed 
description is omitted. Three-phase position signals g1 and g2, h1 and h2, 
and i1 and i2 appearing in the three position detecting element 131, 132, 
and 133 are differentially amplified to produce three-phase output signals 
d, e, and f, and three-phase output signals a, b, and c. The output 
signals d, e, and f are supplied to the drive block 40, and the output 
signals a, b, and c to the rotation detecting block 800. In the 
embodiment, the output signals a, b, and c coincide with the output 
signals d, e, and f, respectively. 
The shaped position signal producing circuit 801 of the rotation detecting 
block 800 is configured by three comparators 861, 862, and 863. The shaped 
position signal producing circuit 801 waveform-shapes the output signals 
a, b, and c of the position detecting circuit 31 and outputs the 
three-phase shaped position signal A, B, and C see FIGS. 26A to 26C!. The 
comparators 861, 862, and 863 are configured in the same manner as those 
shown in FIG. 4. 
The first rotation signal producing circuit 802 receives a pair of the 
shaped position signals A and B. In the first rotation signal producing 
circuit 802, an inverting circuit 872 and an AND circuit 871 produce the 
AND signal of the negation of the signal B and the signal A, and the AND 
signal is supplied to the set terminal of a set-reset type flip-flop 
circuit 875. An inverting circuit 874 and an AND circuit 873 produce the 
AND signal of the negation of the signal A and the signal B, and the AND 
signal is supplied to the reset terminal of the flip-flop circuit 875. As 
a result, the digital-type first rotation signal P is obtained at the 
output terminal of the flip-flop circuit 875. The level of the first 
rotation signal P is changed in synchronization with the shaped position 
signal A during the forward rotation, and changed in synchronization with 
the shaped position signal B during the reverse rotation. In the first 
rotation signal P, the noises at the timing of level change are eliminated 
see FIG. 26D!. 
The second rotation signal producing circuit 803 receives another pair of 
the shaped position signals B and C. In the second rotation signal 
producing circuit 803, an inverting circuit 877 and an AND circuit 876 
produce the AND signal of the negation of the signal C and the signal B, 
and the AND signal is supplied to the set terminal of a set-reset type 
flip-flop circuit 880. An inverting circuit 879 and an AND circuit 878 
produce the AND signal of the negation of the signal B and the signal C, 
and the AND signal is supplied to the reset terminal of the flip-flop 
circuit 880. As a result, the digital-type second rotation signal R is 
obtained at the output terminal of the flip-flop circuit 880. The level of 
the second rotation signal R is changed in synchronization with the shaped 
position signal B during the forward rotation, and changed in 
synchronization with the shaped position signal C during the reverse 
rotation. In the second rotation signal R, the noises at the timing of 
level change are eliminated see FIG. 26E!. 
The third rotation signal producing circuit 804 receives another pair of 
the shaped position signals C and A. In the third rotation signal 
producing circuit 804, an inverting circuit 882 and an AND circuit 881 
produce an AND signal of the negation of the signal A and the signal C, 
and the AND signal is supplied to the set terminal of a set-reset type 
flip-flop circuit 885. An inverting circuit 884 and an AND circuit 883 
produce an AND signal of the negation of the signal C and the signal A, 
and the AND signal is supplied to the reset terminal of the flip-flop 
circuit 885. As a result, a digital-type third rotation signal N is 
obtained at the output terminal of the flip-flop circuit 885. The level of 
the third rotation signal N is changed in synchronization with the shaped 
position signal C during the forward rotation, and changed in 
synchronization with the shaped position signal A during the reverse 
rotation. In the third rotation signal N, the noises at the timing of 
level change are eliminated see FIG. 26F!. 
The rotation signal output circuit 805 is configured by an exclusive OR 
circuit 890 to which the first, second, and third rotation signals P, R, 
and N are supplied, and the exclusive OR circuit 890 outputs the rotation 
signal F. When an odd number of the first, second, and third rotation 
signals P, R, and N are "H" level, the rotation signal F is "H," and, when 
an even number of the rotation signals are "H" level, the rotation signal 
F is "L" see FIG. 26G!. Since the first, second, and third rotation 
signals P, R, and N are the digital signals with a phase difference of 120 
degrees, the rotation signal F is a high-frequency pulse signal with one 
third of a period of the shaped position signal. That is, the period of 
the rotation signal F is one third of that of the position signal g1. 
The direction signal producing circuit 806 has a first flip-flop circuit 
892 of the edge-trigger type, and a second flip-flop circuit 893 of the 
edge-trigger type. The first flip-flop circuit 892 latches the level of 
the second rotation signal R (more correctly, the negation of the signal 
R) by using the leading edge of the first rotation signal P as the clock 
signal, and outputs the first direction signal G. The second flip-flop 
circuit 893 latches the level of the second rotation signal R by using the 
falling edge of the first rotation signal P as the clock signal, and 
outputs the second direction signal H. An AND circuit 895 functioning as 
the direction signal output circuit produces the direction signal J in 
correspondence with the first and second direction signals G and H and 
outputs the direction signal. 
In addition to the effects of the first embodiment, the brushless motor of 
the embodiment can attain an effect that the period of the rotation signal 
F is shortened to one third and the rotational speed detecting circuit 52 
of the command block 50 can conduct the rotational speed measurement of a 
high frequency. As a result, the gain of the rotational speed control can 
be set to be high and hence accurate measurement and control can be 
realized. 
The configurations of the above-mentioned embodiments may be modified in 
various manners. For example, the coil for each phase may be configured by 
connecting a plurality of sub-coils in series or in parallel. Each coil 
may consist of a concentrated winding, or a distributed winding, or may be 
an air-core coil having no salient pole. The connection of the three-phase 
coils is not restricted to the Y-connection and the .DELTA.-connected 
coils may be used. The position detecting elements are not restricted to 
Hall elements and other magnetoelectrical converting elements. The 
relative positional relationships among the coils and the position 
detecting elements may be variously modified. The configuration of the 
field part is not restricted to that of the above-mentioned embodiments. 
Furthermore, the number of poles is not limited to four. 
The drive block is not restricted to the one which distributes three-phase 
driving voltages in accordance with the output signals of the position 
detecting circuit. The drive block may distribute three-phase driving 
currents. The drive block is not restricted to the one which supplies an 
analog-like driving voltage to the coils, and may be configured so as to 
supply a PWM driving pulse voltage to the coils in accordance with a PWM 
signal (Pulse-Width Modulation signal) of a pulse width in correspondence 
with the distributed signals. 
The configurations of the command block and the stop operation block are 
not restricted to those of the above-mentioned embodiments. For example, 
the activation changing circuit may directly stop the command signal 
producing circuit, the distributing circuit, the drive circuits, or the 
like. The drive block may select the coil to be activated in 
correspondence with not only the output signals of the position detecting 
block but also the direction command signal. 
The timing of level change of the rotation signal produced in the rotation 
detecting block may be set to coincide with the timing of level change of 
the shaped position signal A in both the forward rotation and the reverse 
rotation. The mechanical configuration of the coupling between the disk 
and the motor shaft, or the ejection part for unloading is not restricted 
to that of the above-mentioned embodiments. 
It is a matter of course that the invention may be variously modified 
without departing from the spirit of the present invention, and such 
modifications are within the scope of the present invention.