JPS58849Y2 - Rotation state detection device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a rotational state detection device that obtains a speed detection signal corresponding to the rotational speed of a rotating body and a phase detection signal corresponding to the rotational phase of this rotating body. Therefore, it is most suitable for being incorporated into a motor that requires speed control, or a brushless motor in which the coils constituting the armature coil are sequentially energized.

Generally, in motors that need to rotate at a constant speed (e.g., capstan drive motors for tape recorders, spade motors for VTRs, etc.), the rotational phase of a rotating ring that rotates integrally with the motor shaft is detected by a rotational phase detection device. The current supplied to the armature coil of the motor is sequentially switched based on this detection signal.

Such a rotational phase detection device can be broadly classified into three methods as described below.

The first method is a so-called optical method, in which the rotational phase of the rotor is detected by a light emitting source and a light receiving element, and a detection signal corresponding to the rotational phase of the rotating ring is obtained from this light receiving element. be.

The second method uses a so-called magnetically sensitive element, such as a Hall element, which detects the leakage magnetic flux of a permanent magnet fixed to a rotating ring, and detects the leakage magnetic flux from the Hall element according to the rotational phase of the rotating ring. This is to obtain a detection signal.

The third method is a so-called capacitance variable method, in which a capacitance variable section is configured on the outer circumferential surface of a rotating ring, a plurality of electrodes are arranged near the rotation trajectory of this rotating ring, and these multiple electrodes are A detection signal corresponding to the rotational phase of the rotating ring is obtained based on the capacitance change between the electrodes.

Each rotational phase detection device has its advantages and disadvantages, but in the first method, the voltage of the power supply supplied to the light emitting source, The current level must be constant.

Therefore, it is necessary to stabilize the power source, and when a light source lamp is used as a light source, there is a drawback that the lamp is easily disconnected.

Regarding the second method, it is necessary to attach a magnetic shielding plate to the permanent magnet to distinguish between positions where leakage magnetic flux is obtained and positions where leakage magnetic flux is not obtained.

This is to clarify the level change of the detection signal obtained from the Hall element, and therefore has the disadvantage that not only is the motor assembly work troublesome, but also the number of parts increases.

Regarding the third method, the present applicant has filed a patent application filed in 1972-
Since there is a rotational state detection device already proposed as No. 11875, this will be explained below.

Note that an example is shown in which this rotational state detection device is incorporated into a three-phase, four-pole brushless motor.

FIGS. 1 to 4 show one specific example in which a rotation speed and phase detection device is incorporated into a brushless motor,
FIG. 1 is a front view showing a state in which the rotational speed/phase detection device 1 is attached to a motor bracket 2 and a motor rotating shaft 3. As shown in FIG.

FIG. 2 is a sectional view taken along line II-II in FIG.
The figure is a sectional view taken along line III-III in FIG. 2.

As shown in FIG. 2, in the center of the motor bracket 2,
An oil-impregnated bearing 11 is press-fitted, and the motor rotating shaft 3 is inserted through this bearing 11.

The motor bracket 2 includes a case 4 of a rotational speed/phase detection device, annular first and second electrodes 5 and 6 for speed detection housed in the case, three third electrodes 14 for phase detection, 15, 16, an insulating member 7, and a lid 8 are attached, respectively.

Further, a rotating ring 9 is fixed to the rotating shaft 3 of the motor with screws 10 via a boss 17 made of an insulating material, and is configured to rotate together with the rotating shaft 3.

The case 4 has first and second electrodes 5, 6 and a third electrode 14.
, 15, 16, and is made of an insulating material such as synthetic resin.

An insertion hole 4a for inserting the motor rotating shaft 3 is formed in the center of the case 4, and a screw hole 4a for fixing the case 4 to the racket 2 is formed around the outer periphery.
12b and 12C (7) insertion holes are formed at approximately 120° intervals.

Further, the case 4 is formed with a recess 4C that is concentric with the rotating shaft 3, and includes the first and second electrodes 5, 6 and the third electrode 1.
4, 15, and 16 are stored and held.

As shown in FIG. 1, the lead portions 5b, 6b of the first and second electrodes 5.6 and the third electrodes 14, 15.16 are attached to the cylindrical portion 4e of the case 4 around the outer periphery of the recessed portion 4C. A notch 4d for pulling out each is formed to have the same depth as the recess 4C.

First and second electrodes 5, 6 and third electrodes 14, 15.16
can be made of a metal plate, such as brass, phosphor bronze, aluminum, etc.

As shown by dotted lines in FIG. 1, a large number of tooth shapes 5a, 5a are formed on the inner peripheral surfaces of these electrodes 5, 6, and lead portions 5b, 6b are formed on a part of the outer periphery. has been done.

These first electrodes 5 and second electrodes 6 have exactly the same shape, and have respective tooth shapes 5a and 6a with an annular insulating member 7 in between.
are arranged so as to face each other at a predetermined interval.

Further, as shown in FIG. 3, the third electrodes 14, 15, 16 for rotational phase detection have a cylindrical surface facing the rotating ring 9, and lead portions 14b, 15 for signal extraction.
b, 16 b.

And these third electrodes 14, 15, 16 each have a diameter of 60
They are arranged concentrically with the rotation ring 9 at intervals of .degree. with a slight gap between them.

Note that these first, second and third electrodes 5, 6 and 14,
15.16 is the cover body 8 which is made of insulating material with screws 13 a
, 13 b , and 13 C to the case 4 , it is held between the lid 7 and the case 4 by the insulating member 7 made of a ring-shaped sheet.

The rotary ring 9 attached to the motor rotation shaft 3 has a second
As shown in the figure, it is fixed by press fit or adhesive to a boss 17 made of synthetic resin or the like and having a small diameter portion 17a.

This rotary ring 9 has almost the same shape as the later-described modification shown in FIG. 4, but the tooth profile 9a extends a little further downward compared to the case shown in FIG.

The rotating ring 9 is made of a conductive material such as brass, aluminum, or mild steel.

On the outer circumferential surface facing the first and second electrodes 5 and 6, tooth profiles with the same pitch as the first and second electrodes 5 and 6 are formed, as shown by dotted lines in FIG. ,15.16
As shown in FIG. 3, notches 19 a and 19 b having a notch width of 60° are formed on the outer circumferential surface facing each other at positions facing each other.

The rotary ring 9 is made by integrally molding the boss 17 and the cylinder 9 using a synthetic resin such as ABS resin or polyacetal resin, and then metal plating or coating the outer peripheral surface thereof.

Alternatively, it may be coated with metal vapor deposition.

Alternatively, the rotating ring 9 may be a dielectric body integrally molded with the above-mentioned synthetic resin or the like.

The rotating ring 9 connects the first, second and third electrodes 5, 6 and 14.
, 15 and 16, the boss 17 is positioned at an appropriate position and screwed to the motor rotating shaft 3 so that the boss 17 rotates while facing the bosses 15 and 16 with a slight gap in the radial direction.

Here, when the rotating ring 9 rotates with the rotation of the rotating shaft 3, a capacitance is generated between the first electrode 5 and the second electrode 6, and a capacitance is generated between the second electrode 6 and the third electrode 14, depending on this rotation. 15.16
The capacitance between the

That is, the tooth profile 9a of the rotating ring 9 and the first and second electrodes 5.
Depending on the opposing state of the peaks and troughs with the tooth profiles 5a, 5a of 6, a detection signal with a frequency proportional to the rotational speed can be obtained from the lead parts 5b, 6b of the first or second electrodes 5, 6. can.

Further, depending on the facing state of the notches 19 a and 19 b of the rotating ring 9 and the third electrodes 14 and 15.16, a detection signal representing the rotational phase is transmitted to the respective lead portions of the third electrodes 14 and 15.16. 14 b , 15 b , and 16 b .

If a switching element (not shown) that operates according to the capacitance change is provided corresponding to each third electrode 14, 15, 16, the switching element can be turned on according to the rotational phase of the rotating ring 9.・It becomes possible to switch to the off state.

Therefore, if a coil constituting an armature coil (not shown) is connected to each switching element, each coil can be sequentially energized according to the rotational phase of the rotating ring 9.

Next, FIG. 4 is a side view showing one modification of the above-mentioned rotating ring 9.

The rotating ring 9 in FIG. 4 is press-fitted into the small diameter portion of the insulating boss 17, as described above.

A tooth profile 9a having the same pitch as the tooth profile of this electrode 5 is formed on the circumferential surface of the rotating ring 9 facing the first fixed electrode 5.

The peripheral surface facing the second electrode 6 is a flat curved surface with no tooth profile formed thereon.

Further, cutouts 19 a and 19 b similar to those described above are formed on the peripheral surface facing the third electrodes 14 and 15.16.

Although not shown, the first electrode 5 and the third electrode 14
, 15 and 16 may have the same shape as the above-described embodiment shown in FIGS. 1 to 3, and the second electrode 6 may be an annular electrode having a lead portion 6b but no tooth profile.

When configured in this way, the following effects can be obtained.

That is, the capacitance change JC between the first electrode 5 and the second electrode 6 is approximately equal to the capacitance change C1 formed between the first electrode 5 and the rotating ring 9 and the second electrode 6 and rotating ring 9
Since the change in capacitance formed between C2 and C2 becomes a series capacitance, it becomes as follows.

Therefore, by eliminating the tooth profile on the circumferential surfaces of both the second electrode 6 and the rotating ring 9 facing the second electrode 6 on its outer circumferential surface, C2 in the first equation can be increased.

Note that in this case as well, the minimum value of C1 is approximately 0, so as a result, the overall capacitance change (C) can be increased.

A similar effect also occurs regarding the capacitance change between the second electrode 6 and the third electrodes 14, 15, 16.

Furthermore, in the specific examples shown in FIGS. 1 to 3 described above, there is a defect that the rotational speed detection signal is superimposed on the phase detection signal, but by changing the rotating ring 9 and the second electrode 6 as described above, Such inconvenience is resolved.

Next, FIGS. 5 to 7 show another specific example of the rotational speed/phase detection device, in which FIG. 5A is an axial cross-sectional view similar to FIG. 2, and FIG. 5B is a rotational speed/phase detection device. FIG. 3 is a perspective view of a portion of the ring.

Note that the same parts as in FIG. 2 are denoted by the same reference numerals, and explanations thereof will be omitted.

In FIGS. 5A and 5B, a rotating ring 20 attached to the motor rotating shaft 3 is made of a conductive material, and has a tooth profile 20 a for detecting rotational speed and a tooth profile 20 a for detecting rotational phase.
Ring-shaped protruding portion 20 having notches 20 C at intervals of °
b is formed around it.

This rotating ring 20 is press-fitted or bonded to the insulating boss 17.

Alternatively, the rotating gear 20 and the boss 17 may be integrally molded from synthetic resin, and the tooth profile 20a and the protruding strip 20b may be plated or metal vapor-deposited.

The annular first and second fixed electrodes 21.22 and the third electrodes 23, 24.25 centripetally arranged at 60° intervals are formed of thin metal plates such as brass, phosphor bronze, and aluminum. , on the inner periphery of the first and second electrodes 21,22,
Tooth profile 21 of the rotating ring 20 with the same pitch as the tooth profile 20 a
a, 22a are formed in the same way as in FIG.

As shown in FIG. 5A, these first and second electrodes 21.
22 are arranged to sandwich the toothed shape 20a of the rotating ring 20.

Further, the third electrode 23, 24, 25 is connected to the second electrode 22
The protrusion 20b of the rotary ring 20 is sandwiched between the electrode and the protrusion 20b.

According to the above configuration, when the tooth profile 20 a of the rotary ring 20 rotates, a tooth profile is formed between the tooth profile 21 a of the first electrode 21 and the tooth profile 22 a of the second electrode 22, which are arranged opposite to the tooth profile 20 a. The capacitance between the electrodes changes depending on whether there are peaks of 20a or valleys.

This means that the crest of the tooth profile 20a of the rotating ring 20 is
When facing the peaks of the tooth profiles 21a and 22a of the second electrode 21.22, the capacitance is equivalent to when these tooth profiles 21a and 221 are close to each other by the tooth thickness of the tooth profile 20a of the rotating ring 20. This is because change occurs.

Similarly, the ring-shaped convex portion 20 of the rotating ring 20
The second electrode 22 and the third electrode 23, 24 depending on the facing state of the notch 20C and the third electrode 23, 24.
．． The capacitance of each of 25 changes.

As a result, the lead portions 21b of the first and second electrodes 21.22
, 22b, and the third electrode 23,
24.25 respective lead portions 23 b , 24 b ,
Rotational phase detection signals can be obtained from each of the signals 25b and 25b.

If a switching element that operates according to the capacitance change is provided corresponding to each of the third electrodes 23, 24, 25, the switching element can be switched between on and off states according to the rotational phase of the rotating ring 20. becomes possible.

Therefore, if the coils constituting the armature coil are connected to each switching element, each coil can be sequentially energized according to the rotational phase of the rotating ring 20.

Note that the rotating ring 20 can also be formed of an insulating or dielectric material such as synthetic resin.

In this case, the rotation of the rotating ring 20 causes a change in the capacitance between the electrodes.

Further, the second electrode 22 may be annular with no tooth profile 22a formed on its periphery.

In the rotational speed/phase detection device configured as described above, the capacitance change to be detected is determined by the facing area of each fixed electrode, the gap, and the tooth profile of the rotating ring or the thickness of the ring-shaped protrusion.

Therefore, the detection signal is not affected by the surface runout of the rotating ring 20.

Therefore, a very stable detection signal can be obtained.

FIG. 6 is a partially detailed perspective view showing a modification of the rotating ring and electrodes of the rotational speed/phase detecting device shown in FIG. 5. FIG.

As shown in FIG. 6, the rotating ring 26 has a nearly circular disk shape, and a number of recesses 26C are provided on its upper end surface to form a tooth profile 26a for detecting rotational speed. Notch 26b for rotational phase detection on the end face is 1
They are formed at 80° intervals.

That is, the tooth profile 20 a of the rotating ring 20 in FIG. 5A
It has a structure in which the ring-shaped protruding portion 20b and the ring-shaped protruding portion 20b are integrated.

In other words, the rotary ring 9 shown in FIG. 4 is made even more flat, and the tooth profile 9a and the notches 19a, 19b are made deeper.

A first electrode 21 faces the tooth profile 26 a, and third electrodes 23, 24 .
25 are arranged with rotating rings 26 sandwiched therebetween.

The second electrode 27 is a disk-shaped electrode whose outer diameter is somewhat smaller than the inner diameter of the annular first electrode 21, and is opposed to the upper surface of the rotating ring 26 and is on the same plane as the first electrode 21. located within.

In this case, the second electrode 27 may be provided with a plurality of mounting arms extending outward from the electrode and having a step at its base with respect to the electrode surface.

Therefore, as the rotating ring 26 rotates, the capacitance between each electrode changes, so that a rotation speed detection signal is transmitted between the first electrode 21 and the second electrode 27, and the third electrode 23, 24 .
Rotational phase detection signals can be obtained from between the electrode 25 and the second electrode 27, respectively.

In addition, according to the configuration shown in FIG. 6, since the opposing area between the second electrode 27 and the rotating ring 26 can be made very large,
02 in the first equation can be increased.

Therefore, the capacitance change J between the first electrode 21 and the second electrode 27
As can be seen from the first equation, C is approximately equal to C (capacitance change between the first electrode and the rotating ring), and the amplitude of the detection signal can be substantially increased.

Also rotating ring 26 and electrodes 21.27 and 23.2
4.

25 can be made more flat, it is possible to make the rotation speed/phase detection device flat as a whole.

The first, second, and third electrodes shown in FIGS. 5 and 6 can be formed by punching or etching a thin metal plate made of brass, aluminum, stainless steel, or the like.

Alternatively, these electrodes may be formed by etching a printed circuit board on which a metal layer is formed.

However, the rotational state detection devices shown in FIGS. 1 to 3 and the rotational state detection devices shown in FIGS. 5 and 6 configured as described above both detect the rotational phase of the rotating ring. requires three third electrodes.

When increasing the number of armature coils in order to change the specifications of the brushless motor's rotational speed, rotational torque, etc., the number of third electrodes for rotational phase detection should be adjusted according to the number of coils. Must be increased.

Therefore, in such a case, the structure of the brushless motor becomes complicated and the number of parts increases.

Furthermore, it takes time and effort to assemble the brushless motor, and these factors combine to increase production costs.

On the other hand, when converting the capacitance change of the third electrode for rotational phase detection as described above into a change in voltage level, for example, a method is used in which a carrier wave signal with a frequency of about IMHz is modulated according to the capacitance change.

Therefore, as the number of third electrodes increases, the number of lead wires connecting these third electrodes and the switching elements also increases.

In such a case, a carrier wave signal or a modulated frequency signal is likely to leak from one lead wire to another lead wire.

Furthermore, the speed detection signal may be superimposed on the phase detection signal due to leakage, and this may cause uneven rotation in the brushless motor.

The present invention has been devised to correct the above-mentioned defects, and includes: (a) a first tooth profile portion used to detect the rotational speed; and a first tooth profile portion used to detect the rotational phase. annular phase detection portions are respectively formed around the variable capacitance body and rotate together with the rotary body; (C) a second fixed electrode as a common electrode arranged so as to be close to and opposite to the rotation locus of the variable capacitance body; (d) a third fixed electrode disposed close to and opposite to the annular phase detection portion of the capacitance variable body; (e) a third fixed electrode disposed close to and opposite to the annular phase detection portion of the capacitance variable body; at least one variable permittivity member that is partially attached and has a dielectric constant different from that of the variable capacitance body, and the capacitor rotates as the rotating body rotates. Depending on the rotational state of the variable body (1), the amount of electrostatic charge between the first and second fixed electrodes, the capacitance between the second and third fixed electrodes, and 5' !, ・The speed detection signal is obtained from the first or second fixed electrode, and the phase detection signal is obtained from the second or third fixed electrode. With this configuration, it is possible to accurately detect the rotational speed and rotational phase of the rotating body with a very simple configuration, and the capacitance for rotational phase detection is connected to the rotational phase of the annular phase detection portion. It is extremely easy to configure the capacitance variable body so that it changes to a desired state accordingly.

Next, a first embodiment of the present invention will be described based on FIGS. 7 to 12.

The brushless motor described below is assumed to have a three-phase, four-pole structure, and parts that operate in the same way as the rotational state detection device shown in Figs. Omitted.

7 and 8 show a specific example in which the rotational speed and phase detection device of the present invention is incorporated into a brushless motor, with FIG. 7 being an axial cross-sectional view, and FIG. 7 is a sectional view taken along the line ■-■ in FIG. 7.

Notches 30 and 31 having a notch width of 120° are formed at positions facing each other at the lower end of the tooth profile 9a formed on the rotating ring 9 made of a conductive material.

As shown in FIG. 8, two dielectric bodies 32 and 33 formed into arc shapes are attached to these notches 30 and 31 by adhesive or the like.

The dielectric 32 may be formed by molding, for example, phenol resin with a relative dielectric constant ε of about 8 to 10, and the dielectric 33 may be formed by molding, for example, polycarbonate whose relative permittivity ε is about 3 to 4. It may be something that has been done.

Therefore, the relative permittivity ε8 of the portion of the outer peripheral surface of the rotating ring 9 where the third electrode should face depends on the relative permittivity ε8 of the rotating ring 9 and the relative permittivity ε3 of each of the dielectrics 32 and 33.
It will change every 60 degrees.

On the other hand, as the third electrode for rotational phase detection, only the third electrode 14 is used, as shown in FIG. 8, and the other third electrodes 15 and 16 described above are omitted.

Therefore, only one notch 4d is required to be formed in the case 4, and the structure of the case 4 can be simplified.

Here, the capacitance C between the second electrode 6 and the third electrode 14
As is clear from the equation (■), we get the following.

However, C3 is a capacitance determined according to the dielectric constant ε8 of the dielectrics 32 and 33.

Note that when the rotating ring 9 is made of a conductive substance, this capacitance is determined by the space with a relative dielectric constant of 1 that exists between the second and third electrodes 6 and 14 and the rotating ring 9. .

Therefore, when the third electrode 14 and the outer circumferential surface of the rotating ring 9 face each other, the capacitance C between the second electrode 6 and the third electrode 14 is determined by the formula (2).

Therefore, when the rotating ring 9 rotates half a turn in the direction of the arrow A in FIG. 8, the capacitance C between the second electrode 6 and the third electrode 14 changes in three stages.

Further, when the rotating ring 9 rotates once, the change in the capacitance C as described above is repeated twice.

Note that the outer circumferential surface of the rotating ring 9 may be deformed as shown in FIG.

In this case, the capacitance C between the second electrode 6 and the third electrode 14 changes as described above based on FIG. 4.

If such a change in capacitance C is converted into a change in voltage level, for example, the switching element is switched between on and off operating states according to the rotational phase of the rotating ring 9, thereby controlling the armature coil. It becomes possible to sequentially energize the constituent coils.

Next, a motor drive circuit incorporating the above-mentioned rotational speed/phase detection device will be explained.

FIG. 10 is a block diaphragm showing a motor drive circuit when the above-mentioned rotational speed/rotational position detection device is incorporated into a brushless motor.

First, the circuit configuration will be described. Numeral 35 is a carrier wave generation circuit, which generates a frequency signal having a frequency of about IMHz, for example.

C indicates the capacitance between the second electrode 6 and the third electrode 14, and the resistance R is the load resistance.

Further, Co indicates the capacitance between the first electrode 5 and the second electrode 6, and the resistance R8 is a load resistance.

By the way, the impedance Xc of the capacitance C with respect to the frequency signal is as follows, where f is the frequency.

Therefore, as the rotating ring 9 rotates, the capacitance C changes, so the voltage drop across the load resistor R changes in accordance with the change in the capacitance C.

In addition, since the capacitance C8 acts in the same manner on the frequency f, the voltage drop across the load resistor R8 is
It will change depending on the change in capacitance C6.

Therefore, the load resistances R, R. The voltage signal obtained between both ends of the signal is obtained by AM modulating the frequency signal based on the capacitance change of the capacitors C, C,.

36a and 36b are AM demodulation circuits, which may be composed of, for example, a rectifier circuit and a low-pass filter;
From the voltage signal obtained between both ends of the load resistances R, R,
An AM demodulated signal from which a carrier wave component with a frequency of IMHz is removed can be obtained.

Further, these AM demodulation circuits 36a and 36b may be provided with a waveform shaping circuit (not shown), which allows the AM demodulation circuits 36a and 36b to
From the M demodulation circuit 36a, AM demodulation signals 40 having three different voltage levels as shown in FIG. 11A are obtained.

On the other hand, from the AM demodulation circuit 36b, a continuous pulse signal 41 as shown in FIG.

Reference numeral 37 denotes a level identification circuit, which compares a reference voltage obtained from a reference voltage generation circuit (not shown) with the voltage level of the AM demodulated signal 40.

Note that the level identification circuit 37 is connected to the coil L1. L2. It is composed of three series with different reference voltages corresponding to L3.

Then, from this level identification circuit 37, the first
Drive signal 42.4 as shown in Figure 1B to Figure 11D
3.44 is obtained.

Transistors TR, TR2, TR3 are switching transistors, each having a collector at voltage level E.

are connected to the DC power supply of the coils L, , L2 ., whose collectors constitute the armature coils. Connected to L3.

Therefore, when the drive signal 42 is supplied to the transistor TR1, the transistor TR is turned on according to the time width of its rising portion, and a current 11 flows through the coil L1.

Similarly, when the drive signal 43 is supplied to the transistor TR2, this transistor TR2 is turned on according to the time width of the rising portion thereof, and when the driving signal 44 is supplied to the transistor TR3, the width of the rising portion of the transistor TR2 is turned on. This transistor TR3 is turned on depending on the time width.

Therefore, when the transistor TR2 is on, the coil L
A current I2 flows through the coil L3, and a current I2 flows through the coil L3 when the transistor TR3 is on.

On the other hand, 38 is a frequency-voltage conversion circuit (hereinafter referred to as a conversion circuit), which converts a change in the frequency of the AM demodulated signal 41, in other words, a change in the rotational speed of the rotating ring 9, into a change in voltage level. It is.

This conversion circuit 38 is configured to, for example, form a triangular wave signal with a predetermined slope from the AM demodulated signal, sample the slope portion of this triangular wave with a predetermined reference sampling pulse, and perform frequency-voltage conversion. It's good to be there.

Alternatively, frequency-voltage conversion may be performed using the frequency characteristics of a low-pass filter.

A control signal 45 as shown in FIG. 12B is obtained from the conversion circuit 38, and this control signal 45 is supplied to the base of the control transistor TR4.

By the way, the voltage level V of the control signal 45 changes depending on the rotational speed of the rotating ring 9, as is clear from FIG. 12B.

Therefore, in the motor drive circuit shown in FIG.
As the rotational speed of the rotating ring 9 increases, the voltage level (2) of the control signal 45 decreases.

As a result, the current flowing through the transistor TR4 1. ■2
．． Since the amount of current flowing through I3 decreases, the rotational speed of the rotating ring 9 gradually decreases.

In this way, the rotational speed of the rotating ring 9 is controlled according to the change in the capacitance C6 between the first electrode 5 and the second electrode 6.

Further, the coils L, L2 . It is possible to sequentially energize L3.

Next, the circuit operation of the motor drive circuit shown in FIG. 10 constructed as described above will be described.

First, the case where the rotating ring 9 and the third electrode 14 correspond to each other will be described. The capacitance C is determined as shown by the equation (2), and the capacitance value is small.

Therefore, the impedance shown by equation (2) increases, and the voltage drop across the load resistor R decreases.

Therefore, the voltage level of the AM demodulated signal 40 becomes a as shown in FIG. 11A, and the drive signal 42 is obtained from the level identification circuit 17.

As a result, the transistor TR is turned on, and a current 1 flows through the coil L1.

The amount of this current (1) is controlled by the transistor TR4 as described above.

Next, the rotating ring 9 rotates to connect the dielectric 33 and the third electrode 3.
3 corresponds to the capacitance C of the dielectric material 33.
It becomes large according to the dielectric constant ε5 of .

Therefore, the impedance shown by the equation (2) is smaller than that without the dielectric 33, and the voltage drop across the load resistor R becomes higher.

Therefore, the voltage level of the AM demodulated signal 40 becomes vb as shown in FIG. 11A, and the drive signal 43 is obtained from the level identification circuit 37.

As a result, the transistor TR2 is turned on, and a current 2 flows through the coil L2.

The amount of this current (2) is controlled by the transistor TR4 as described above.

Next, the rotating ring 9 rotates to connect the dielectric 32 and the third electrode 1.
4 corresponds to the capacitance C of the dielectric material 32.
It becomes large according to the dielectric constant ε8 of .

Therefore, the impedance shown by equation (2) is smaller than that corresponding to the dielectric 33, and the voltage drop across the load resistor R is higher than that in the above case.

Therefore, the voltage level of the AM demodulated signal 40 becomes VC as shown in FIG. 11A, and the drive signal 44 is obtained from the level identification circuit 37.

As a result, the transistor TR3 is turned on, and a current 3 flows through the coil L3.

The amount of this current (3) is controlled by the transistor TR4 as described above.

In this way, on the outer peripheral surface of the rotating ring 9 and on the third electrode 1
4, a dielectric material 32 having a different dielectric constant ε8
．． 33 makes it possible to detect the rotational phase of the rotating ring 9 very easily.

By the way, when changing the specifications such as rotation I and torque of a brushless motor, the number of magnetic poles of a permanent magnet (not shown) that rotates integrally with the rotating ring 9 may be increased, or the number of magnetic poles of a permanent magnet (not shown) that rotates integrally with the rotating ring 9 may be increased, or the coils that constitute the armature coil may be changed. increase the number.

In such a case, the outer peripheral surface of the rotating ring 9 has a relative dielectric constant ε
If 8 different dielectrics are installed according to the number of coils, the rotating ring 9 can be installed without increasing the number of third electrodes for rotational phase detection.
It becomes possible to detect the rotational phase of.

Therefore, even if the number of coils increases, the structure of the brushless motor does not become complicated, the number of assembly steps does not increase, and no extra effort is required.

Next, a second embodiment of the present invention will be described based on FIGS. 13 to 15.

Note that the same reference numerals are given to parts that operate in the same way as in the first embodiment, and the explanation thereof will be omitted.

FIG. 13 shows two types of dielectrics 32 and 33 with different relative dielectric constants ε5 attached to the rotating ring 9, and two third electrodes 14.
．． 15 is a cross-sectional view of the main parts of the brushless motor to show the positional relationship with the brushless motor 15. FIG.

The dielectric 32 attached to the outer peripheral surface of the rotating ring 9 has 12
The dielectrics 33 are molded at 0° intervals, and the dielectrics 33 are molded at 60° intervals as in the previous case.

The dielectrics 32 are mounted at positions facing each other, and the dielectrics 33 are also mounted at positions facing each other.

On the other hand, the third electrode 14.15 for rotational position detection is
As shown in the figure, they are arranged along the rotation locus of the rotary ring 9 at intervals of 60° from each other.

Then, when the rotating ring 9 rotates in the direction of the arrow A in FIG. Both have the same capacitance value.

Next, the rotating ring 9 rotates in the direction of the arrow hole in FIG.
When the third electrode 14 corresponds to the dielectric 32 and the third electrode 15 corresponds to the dielectric 33, the capacitance value of the capacitance C of the third electrode 15 becomes small.

From this state, the rotating ring 9 further rotates, and the third electrode 1
4 corresponds to the dielectric 33 and the third electrode 15 corresponds to the dielectric 32, the capacitance C of the third electrode 14 becomes large.

FIGS. 14A and 14B show the third electrode 14 as described above.
．． 15 shows voltage levels of demodulated signals obtained from two demodulation circuits 36a based on changes in capacitance C of 15.

Therefore, if the motor drive circuit shown in FIG. 10 is changed to the one shown in FIG. 15, it becomes possible to sequentially turn on the transistors TR, TR2, and TR3 as in the case described above.

That is, the voltage levels of the two AM demodulated signals 46 and 47 obtained from the two AM demodulation circuits 36 a and 36 b are as follows:
The rotation ring 9 remains at the same level while rotating from 0 to 60 degrees.

Then, while the rotating ring 9 rotates 60 to 120 degrees, the voltage level of the AM demodulated signal 46 is high, and one of the A
The voltage level of M demodulated signal 47 becomes low.

Next, while the rotating ring 9 rotates 120 to 180 degrees, the voltage levels of the AM demodulated signals 46 and 47 are reversed between 60 and 120 degrees.

Therefore, by comparing the voltage levels of the AM demodulated signals 46 and 47 while the rotating ring 9 makes a half rotation, it becomes possible to detect the rotational phase at every 60° interval.

The AM demodulated signals 46 and 47 are then supplied to a gate circuit 50 configured by a phase inversion circuit (not shown) and an AND circuit (not shown).

As a result, drive signals are obtained from the gate circuit 50 at intervals of 60° as the rotating ring 9 rotates, and are sequentially supplied to the bases of the transistors TR, TR2, TR3.

Therefore, the coils L,, L2. As mentioned above, L3 has a current of 11. ■2. I3 flows, and the amount of current is controlled by transistor TR.

Note that the rotating ring 9 rotates the next half turn, in other words, 180
The above-mentioned operation is repeated during rotation of ~360 degrees.

In this way, two types of dielectrics 32.33 are attached at predetermined intervals on the outer peripheral surface of the rotating ring 9, and the capacitance that changes based on the dielectric constant ε of the third electrode 14.
5, the rotational phase of the rotating ring 9 can also be detected.

In this case, there is no need to compare the voltage levels of the AM demodulated signals 46 and 47, and therefore the motor drive circuit can be simplified.

Further, since the number of third electrodes 14, 15 can be reduced by at least one more than the number of energized phases of the motor, the structure of the brushless motor can be simplified.

As described above, the present invention includes a first tooth-shaped portion used for detecting the rotational speed and an annular phase detection portion used for detecting the rotational position, which are commonly formed around the variable capacitance body. Further, a second fixed electrode was provided which is common to the capacitance for obtaining the speed detection signal and the capacitance for obtaining the phase detection signal.

Therefore, the rotational speed and rotational phase of the rotating body can be accurately detected with a very simple configuration, and the configurations of the detection circuit and the speed/phase control circuit of the rotating body can also be simplified.

Further, at least one variable permittivity member having a dielectric constant different from that of the variable capacitor is partially attached to the annular phase detection portion of the variable capacitor.

Therefore, it is extremely easy to configure the capacitance variable body so that the capacitance between the second and third fixed electrodes changes to a desired state according to the rotational phase of the annular phase detection portion.

[Brief explanation of the drawing]

Figures 1 to 6 are filed in Japanese Patent Application No. 521187 by the applicant.
This shows an example of the rotational state detection device already proposed as No. 5, in which Fig. 1 is a front view showing the rotational speed/phase detection device attached to the motor bracket and the motor rotation shaft, and Fig. 2 1 is a sectional view taken along line II-II in FIG. 1, FIG. 3 is a sectional view taken along line III-III in FIG. be. Figures 5A to 6 are patent applications filed in 1982-11 by the applicant.
This shows another specific example of the rotational speed/phase detection device already proposed as No. 875, in which FIG. 5A is an axial cross-sectional view similar to FIG. 2, and FIG. FIG. 6 is a partially detailed perspective view showing a modification of the rotating ring and electrodes of the rotational speed/phase detecting device shown in FIG. 5. FIG. 7 to 12B show the first embodiment of the present invention, and FIG. 7 shows the rotation speed/phase detection device attached to the motor bracket and the motor rotation shaft in the axial direction. 8 is a sectional view taken along the line ■--■ in FIG. 7, FIG. 9 is a side view showing one modification of the rotating ring shown in FIGS. 7 and 8, and FIG. FIG. 8 is a circuit diagram showing a motor drive circuit for rotationally driving the brushless motor; FIG.
Figures 1B to 11D are waveform diagrams of the drive signal obtained from the level identification circuit, Figure 12A is a waveform diagram showing changes in the pulse width of the AM demodulated signal according to the rotation speed of the brushless motor, and Figure 12B is the waveform diagram of the drive signal obtained from the level identification circuit. FIG. 3 is a waveform diagram of a control signal for controlling the rotational speed of a motor. 13 to 15 show a second embodiment of the present invention, and FIG. 13 shows a brushless motor showing the positional relationship between the dielectric attached to the rotating ring and the fixed electrode for phase detection. The cross-sectional view, Figures 14A and 14B, are two A
FIG. 15 is a waveform diagram showing changes in the voltage level of the M demodulated signal, and is a circuit diagram of a motor drive circuit for rotationally driving the brushless motor shown in FIG. 13. In addition, in the symbols used in the drawings, 5 is the first electrode, 6 is the second electrode, 9 is the rotating ring, 14 is the third electrode, 3
2 and 33 are dielectric materials.

Claims (1)

[Claims for Utility Model Registration] A rotational state detection device configured to obtain a speed detection signal corresponding to the rotational speed of a rotating body and a phase detection signal corresponding to the rotational phase of this rotating body, (a) A first tooth-shaped portion used to detect the rotational speed and an annular phase detection portion used to detect the rotational phase are respectively formed around the first tooth-shaped portion and are integrated with the rotating body. a rotating capacitance variable body; (b) a first fixed electrode having a second tooth-shaped portion disposed so as to be close to and opposite to the rotation locus of the first tooth-shaped portion of the capacitance variable body; (C); (d) a second fixed electrode as a common electrode arranged so as to be close to and opposite to the rotation locus of the variable capacitance body; (d) arranged to be close to and opposite to the annular phase detection portion of the variable capacitance body; (e) a third fixed electrode partially attached to the annular phase detection portion of the variable capacitance body and having a dielectric constant different from that of the variable capacitance body; at least one type of variable permittivity member, and the capacitance between the first and second fixed electrodes varies depending on the rotational state of the variable capacitance body that rotates with the rotating body. and the capacitance between the second and third fixed electrodes are configured to vary, respectively, and the speed detection signal is obtained from the first or second fixed electrode, and the capacitance between the second or third fixed electrode is changed. A rotation state detection device configured to obtain the phase detection signal from a fixed electrode.