JPS58148652A - Cylinder motor - Google Patents

Abstract

PURPOSE:To reduce the size and to increase the efficiency of a cylinder motor by forming electrodes of specific shape on the pole surfaces of a rotor and a stator and obtaining rotary position detection signals of a rotor magnet and a video head by utilizing the variation in static capacity between the poles. CONSTITUTION:A cylinder motor which records and reproduces a video signal via video heads 14, 14' by rotating an upper cylinder 12 is formed by mounting on an adapter 47 a stator having a stator yoke 3 and on a shaft 7 a rotor having a magnet 4. Thin-plate-shaped conductors 25, 25', 24 and 26, 26', 26'', 27, 28, 29 are respectively formed as specific shapes on the pole surfaces of the coil 10 and magnet 4 to be opposed at the ultrafine air gaps. Accordingly, the rotary position detection signal and rotary speed signal can be produced between the rotor magnet 4 and the video heads 14, 14' from the variations of the static capacity between them, thereby reducing the size of the motor.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention detects (2) position detection signals of rotor magnets directly connected to the rotating shaft of the rotor, video head rotational position detection signals, etc. by changing the # tolerance accompanying rotation. The present invention relates to a cylinder motor configured to obtain the following.

Figure 1 shows an example of the structure of a conventional cylinder motor, where 141 is an overall vertical cross-sectional view (al is a plan view of the motor stator section).A structure in which a 11v x 5-phase flat brushless DC motor is built into the lower cylinder. In the figure, the rotor magnet 4 has multi-pole magnetic poles whose plane is magnetized equally divided into fan shapes, and the back magnetic poles are short-circuited by the rotor yoke 8 made of an E material such as iron, and the front magnetic poles are short-circuited. It is attached to the rotating shaft 7 via the rotor boss 5 with tIi1+!IA facing upward.The rotor boss 5 is press-fitted or in contact with the l!l!1 rotating shaft 7.To the two bearings that support the rotating shaft 7 6'VC is provided with upper and lower ICs of the lower cylinder 9 using rolling bearings.

The motor stator is rotated with the stator coil 10 facing downward and facing the magnetic poles of the rotor magnet 4.

They are arranged on the upper part of the child magnet 4 and fixed to the upper peripheral edge N of the side wall of the lower cylinder 9. The stator coil 10 is a wire-wound coil with a flat structure in which the number of coil poles per phase is the same as the number of magnet magnetic poles, and is stacked and fixed on the flat annular stator yoke 3. On the outer periphery of the stator coil 10, three magnetic field detection elements 1.1', 1" are fixed together with the wiring board 2 at a predetermined angular interval (50"3), and the side surface of the rotor magnet 4 The leakage magnetic field in the direction is detected and its rotational position It is detected.The distribution board 2 is provided in a cutout part of a part of the side wall of the motor built-in part of the lower cylinder 9. The secondary core 16 of the rotating transformer is fixed above the stator.A flywheel 17 is fixed to the rotating shaft 7 at the bottom of the lower cylinder 9. .

Two tack magnets 18° and 18' are attached to the flywheel 17 with their polarities reversed. Tack magnets 118' are attached to each video 14 and 14' respectively.
The position corresponds to Tack magnet 18.
At the radial position v11 through which the rotor magnet 18' rotates, a magnetic field detection element 19 is separately installed to amplify the magnetic pole position signal of the rotor magnet 4 detected at the bottom 1'' of the lower cylinder 9 by a drive electronic circuit (not shown). Then, 1 pulse signal is formed and 1 pulse signal is formed.
The rotor magnet 4 is driven to rotate by supplying the ml stator coil 'roy control 4fft, and the upper cylinder 12 is rotated. As the upper cylinder 12 rotates, a video head 14, 14' attached thereto scans the surface of a video tape (not shown) running in contact with it, thereby recording and reproducing video signals on the tape. The tack magnet 18.18' on the flywheel 1 and the magnetic field detection element 19 constitute a position detection section of the video head 14.14'.
．． The rotational speed of the 0-top cylinder 120, which generates a pair of positive and negative tack signals for controlling the rotational phase at the same time as identification of the 14', is determined by the back electromotive force generated in the frequency e signal generation coil built into the stator coil 10. This is done by adjusting the frequency of the acid pressure to FVg and controlling the motor input using a one-child circuit.

A cylinder motor I'lf with such a conventional structure has a mountain
A magnetic field detection element is installed on the outer circumference of the stator coil. (2) Since the configuration uses the lateral magnetic field of the trochanter magnet to cause the potential to lateralize, a certain amount or more of lateral leakage magnetic flux is required. tIB noise increases and motor efficiency decreases.

(21) In the case of a structure in which a magnetic material such as ferrite is used in the magnetic field transverse element, cogging torque is generated between the magnetic flux of the rotor magnet and rotational unevenness.

(Since the rotational speed signal frequency is low, the loop gain of the control circuit is correspondingly low (stability against disturbances is low).

t47 Since the stator coil is composed of a powder-wound coil, the coil thickness is thick (and it is difficult to make the coil pole shape and dimensions uniform) (the degree of pole arrangement is low. Furthermore, the coil area is small and the winding coefficient is low. Small. Therefore, the motor size is large and the torque fluctuation is also large.

(Since the tank detection section 51 is also externally attached to the cylinder, the cylinder size tends to become large and it is difficult to position the tank detection section with respect to the video head position.

(6) The stator coil, rotational position detection sensor, and tack sensor are manufactured separately using their own manufacturing technology, and then combined to form the motor stator, resulting in low assembly accuracy and low assembly man-hours. There are many, and the cost is high.

There are drawbacks such as.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the above-mentioned prior art and to provide a cylinder direct drive motor that is easy to manufacture, small in size, has high volumetric efficiency, high smooth rotation, and high controllability.

In order to achieve the above object, the cylinder motor of the present invention has the following features: (1) Conductor electrodes are provided on both the rotor side fixed to the upper cylinder rotating shaft and the stator side fixed to the lower cylinder side, and conductive electrodes are provided between the two electrodes. The configuration is such that the rotational position detection signal of the rotor magnet of the shaft-directly coupled brushless motor, the rotational position detection No. 100 (tack signal) of the video head, etc. is obtained from the capacitance formed in the shaft-directly connected brushless motor.

(27 The static electrode conductor on the rotor side is provided on the magnetic pole surface of the rotor magnet, and the electrostatic electrode conductor on the stator side is provided on the top of the stator coil. Reduced man-hours and made it more compact.

(3) The main feature is that at least the stator coil and the stator-side electrostatic electrode are formed into a pattern by manufacturing means such as etching so that they can be manufactured and assembled easily and with high precision.

The present invention will be explained below based on examples.

! FIG. 12 is a longitudinal cross-sectional view of an example of the structure of the cylinder motor of the present invention, and FIG. 3 is a plan structural view of the magnetic pole surface portion of the rotor magnet 4 and the surface portion of the stator coil 10 of the same motor, #I
FIG. 4 is a circumferential development view of the rotor side-1 of FIG. 3 of the electrode 20 and the stator side electrostatic electrode 21. This cylinder motor has a structure in which a flat DC three-phase brushless motor is directly connected to the bottom of the lower cylinder. The stator yoke 5 and stator coil 10 of the motor are fixed on the surface of the adapter 47, covered with a shield case 11 to form a stator part, and fixed to the lower part of the lower cylinder with the opening facing downward. Further, the rotor magnet 4 is directly connected to the shaft 7, facing the pole face of the stator coil 10. This cylinder motor has rotor magnet nod 4
A thin plate-shaped conductor is sandwiched between the magnetic pole surface of the rotor magnet and the pole surface of the stator coil 10 to detect the rotational position detection section of the rotor magnet side 4, the rotational speed detection section, and the rotational position detection section of the video nozzle 14° 14'. This is an example where . Thin plate conductors 25, 25', 24 and 26, 26' are provided on the pole face of the stator coil 10 and the magnetic pole face of the rotor magneto 4, respectively.
, 26'', 27, 29, and 28 are fixed to the surface of a thin insulator 2λ23 and are arranged to face each other with a small gap between them.The conductor 2 on the rotor magnet m-pole surface and the stator coil From the capacitance formed between the conductors 2426', 26', and 27 on the pole surfaces, a rotational position detection signal of the rotor magnet 4 and a rotational position d configuration signal of the video head 1414' (hereinafter referred to as a tack signal) are generated. Also, from the electrostatic capacitance formed between the conductor 24 on the rotor magnet pole surface and the conductors 2a and 29 on the other surface of the stator coil, 1 g is formed.
A rotational position signal of the first trochanter is generated. The above-mentioned capacitance changes in proportion to the 40 rotations of the rotor magnet as the area of the opposing conductor changes. Conductor 25 on the magnet side
has a planar shape corresponding to the magnetization polarity of the rotor magnet, and in this example, the north pole part has a wide area and the south pole part has a narrow area. Since this example is an 8-pole magnet, the large and small area parts are arranged at a 45° pitch. Further, the conductor 25' has a shape in which a part of the conductor 25 is integrally protruded in the radial direction, and is provided at a position corresponding to the video head 14. The stator side conductors 2426', 26' are also provided at positions t11 corresponding to the pole positions of the stator coil 10, so that three-phase position signals can be generated. In this example, the three conductor portions are arranged at a pitch of 120°. The tack signal is obtained by being superimposed on the rotational position signal. The conductor 26 is connected to the other two conductors 26 corresponding to the conductor 25'.
The conductor 25 has a shape that is longer in the radial direction than the conductor 25.
The inner edge of the conductor 27 is located at a position facing the annular conductor 27, so that a constant capacitance can always be formed at any rotational position.

The capacitance change output is taken out from the conductors 26, 26', 26" and the conductor 27. Also, the conductor 24 on the rotor magnet side
are provided at equal angular pitches along the outermost periphery, facing conductors 2 & 29 on the stator coil side to form a capacitance that changes periodically with rotation, and is proportional to the rotation speed of the rotor magnet. Frequency signal (FG multiplied signal is generated. In the case of this structure example, the FG repeats 18 times per rotation.
Can generate double signal. FG times the capacitance change signal conductor 28.2
Take it out from the terminal number 9.

Figure 5 is a basic circuit diagram for converting capacitance changes as rotation information signals of the cylinder motor of the present invention into voltage signals. Figure 5 and Figure 7 are explanations of the conversion principle and output waveforms of each part It is a diagram. .

The detection unit @go in FIG. 5 includes a detector 40 inside.

The capacitance C formed between the rotating and fixed electrodes and changing with rotation is connected to the detection circuit 15OK through the terminal 5t52.

In the detection circuit 50, a resistor R and an inductance L are connected in series, and by connecting a capacitor C, R, L, C
The series together form an Is@ path. Carrier oscillator 41 is connected to detection circuit 30 at terminals 55,56. Assuming that the angular frequency of the carrier signal output from the carrier oscillator 41 is 0 and the amplitude is 4, a signal voltage EC of the following formula is generated between both terminals 5152 of the capacitor C.

If the generation angular frequency of the O carrier oscillator 410 is set to a low value in the above-mentioned series, it is possible to amplitude-modulate the voltage EC from Ecl to Ecs in accordance with the change from CI to C2 of the capacitance C, as shown in Fig. 1146. Therefore, the steeper the resonance characteristic of this resonant circuit, the greater the amplitude modulation and the greater the amplification factor. If the obtained variable aIII (w band voltage Ec is input to a detector 40 consisting of a diode 37, a resistor 38, and a capacitor 39 and envelope-detected, the output terminal 34
54, it is possible to obtain a signal voltage Eoμt corresponding to the capacitance change.

FIG. 8 is a diagram showing an example of the configuration of a rotation information signal detection circuit for a cylinder motor according to the first embodiment shown in FIGS. 2 to 4. FIG. 5th above
Rotation position 1 for 5-phase power supply control using 4 systems of detection circuits shown in the figure
1 signal EutμEast wEautw and an FG multiplied signal autFG for rotational speed control are obtained.

Figure wJ9 shows an example of the configuration of the cylinder motor drive circuit of the first embodiment. A rotational position signal, a rotational speed signal, and a tack signal generated in the motor body as capacitance change signals are each converted into voltage signals by a detection circuit 30 and amplified by an amplifier 6 by 60', 60''. U-phase signal is sent to amplifier 6
0, the V phase signal is sent to the amplifier 60', and the W phase signal is sent to the amplifier 60'.
0', the speed signal is amplified by amplifier 60#. Further, each signal is then processed according to its purpose. The rotational position signal is input to an energization signal forming circuit 51, which generates a pulse for operating a drive circuit 52. Kaku1g11 circuit 5
2 controls the current from the power source to the stator coil 10 of the motor in accordance with the output pulses of the WL signal forming circuit 51 and the signals of the control system to provide rotational driving force to the rotor magnet of the motor. Since the tack signal is superimposed on the U-phase rotational position signal amplified by the amplifier 60, this signal is also input to a signal processing electronic circuit to separate the tack signal.

The signal processing electronic circuit consists of a comparator 61, a phase adjustment circuit 62, a pulse forming circuit 6B, and a phase comparison circuit 64, each of which separates, delays, and pulses the voltage signal and compares the phase with a reference signal to generate a phase error signal. The motor drive circuit 5
Input to 2.

The pulse forming circuit 6s uses a logic circuit to form pulse signals corresponding to the positions of the two video heads. The drive circuit 52 operates to control the input to the motor coil 10 so as to make the phase error signal zero, thereby controlling the rotational phase of the motor. After the rotational speed signal is amplified, it is converted into a voltage signal proportional to the rotational speed by an FV converter 53 and input to a comparator 55. Here, it is compared with a reference voltage corresponding to a predetermined speed, and the error signal is inputted as an output to the drive circuit 52 to control the rotational speed and maintain it at a predetermined value.

FIG. 10 is an explanatory diagram of the process of separating the tack signal from the position signal to form a video head rotational position signal in the signal processing electronic circuit of FIG. 9. U-phase amplified signal-U
is compared with the reference voltage EVpt by the comparator 61 and the tack pulse P
, obtain (separation). Next, the phase adjustment circuit 62 delays the tack pulse P1 by a predetermined amount (until the time when the video head starts scanning the tape) to produce pulse 8. The pulse forming circuit 65 counts a predetermined value using the high frequency clock signal CP starting from the rising time (tl) of the pulse to form a phase detection signal with a duty of 50. At the time (t,) when the phase detection signal P1 changes from a high level to a low level, the first video head starts scanning the magnetic tape, and at the time (tl) when the phase detection signal P1 changes from a low level to a high level, the video head m2 starts scanning the magnetic tape. Start scanning the magnetic tape. By this method, the phase detection signal 1 of the duty sob is obtained. By forming the two video heads, the rotational positions (phases) of the two video heads can be detected. In the cylinder motor of the 1d41 practical example shown in FIGS. 2 to 410 above, the rotational position detection sensor section is
The tack signal generation section and the rotational speed (number 1! generation section (FG)) are provided on the same plane in the motor electromagnetic section, and the rotational position detection sensor section is also used as the tack signal generation section.With this configuration, the cylinder motor can be made smaller. It can be made into a simple structure, and there is no cogging force based on sensors, etc., so low rotational unevenness can be achieved.Also, it is possible to easily arrange conductors with high accuracy and subdivide the arranged conductors, so accurate position detection is possible. Accurate power supply control and high-rate Φhigh-precision rotational speed signal generation are possible, which also allows for highly smooth rotation.Also, since the configuration uses static capacitance changes to obtain signals, it is possible to generate high-precision rotational speed signals. It is possible to always obtain a signal with stable characteristics without being affected by the noise.The signal level and waveform are also quiet.
It can be easily selected by adjusting the area and opposing gap size to I14. There is no influence of the magnet's rotating magnetic field or the coil's passing electromagnetic field. Rotation 11 @ Each conductor for the Seiden electrode on the fixed side and the insulator provided under it can be made of thin material, so they can be made of a thin material, so they can be made of a thin material, so it is possible to improve the magnetic circuit efficiency and coil efficiency in the electromagnetic part of the motor. If the structure is formed as a patterned conductor, it can be made at low cost and high precision.

In the first embodiment described above, one conductor electrode is provided for each rotational position detection sensor section, but if a plurality of conductor electrodes are provided, detection errors can be averaged and alleviated, and detection accuracy can be further improved. . It is also possible to have a structure in which conductive electrodes such as rotational position detection sensor conductors are provided on both the front and back surfaces of the insulator to increase the number of conductive electrodes. Further, in this embodiment, the flat motor is disposed at the bottom of the lower cylinder with the stator above and the rotor magnet below, but other arrangements may be used.

Figure 5 @ 11 is an explanatory diagram when the stator coil 10 is also formed with a patterned conductor by etching, plating, etc.
3 is a plan view of the coil, and 3 is a partial cross-sectional view of the coil. This example has a structure with coil poles on the front and back surfaces of the sheet. The coil pole areas 70 and 70' are formed, and an insulating material 76 is applied to each surface.With this structure, the stator coil 10 can be made thin and have a highly flat shape.

Moreover, the coil efficiency can be improved by increasing the coil pole area, and the motor efficiency can be improved. It is possible to make the release shape uniform and to improve the precision of the pole arrangement, and also to reduce torque fluctuations.

FIG. 12 shows the structure of a sheet-like coil in which eight coil poles made of the patterned conductor described above are formed on each of the front and back planes at equal intervals of 1c, and are connected in series through a through hole 80 provided at the center of the coil pole with 8 valleys on the front and back poles. In the example, (al is a plan view, (hl is a laminated cross-sectional view when laminating these to form a 5-phase coil. On the upper part, there is provided a sheet 21 formed of the conductor #A described in the first embodiment with a pattern like the stator coil.As in this example, the stator coil and the conductor #A are etched or etched. By forming a patterned conductor through plating, etc., the entire structure can be made thin, highly flat, and
Can be made into a high-precision array. Furthermore, since such a stator section can be manufactured using the same manufacturing method, it can be manufactured at low cost.

, @15 is a second embodiment of the cylinder motor of the present invention, (α) is a plan view of the rotor-side electrostatic electrode, and (h) is a plan view of the stator electrostatic electrode. This example also has a three-phase, eight-pole, and twenty-four-coil configuration. In this example, the silent gig poles on the rotor side and stator side are configured to generate a rotation position signal and a tack signal of the rotor magnet as rotation information. This example also has a rotor side electrode pattern (on the 1st rotor magnet magnetic pole surface, the stator 11411
The electrode pattern is fixed on the stator coil. The stator coil 10 and the electrostatic Ill pole are constructed of patterned conductors. The feature of this embodiment is that the stator-side electrostatic electrode 21 has only one pair of output pins, and a capacitance 11 change signal is obtained as a single-phase output. Rotor side polarization pattern 25
In this case, the area of one period consisting of the pair of magnet magnetic poles N and S is divided into six equal parts in the circumferential direction, and the electric area is sequentially changed in a stepwise manner. Among these, the pattern at the position corresponding to the video head position 11 has a pattern shape with an additional step of lc. The stator a electrode pattern 26 has a shape in which one pattern extends in the radial direction within a pair of magnet magnetic poles N and S. The position of this wide area pattern portion is such that the stator side electrode 21 is fixed on the surface of the stator coil 10 at a predetermined position aIK corresponding to the stator coil pole position. One of the four wide-area pattern sections includes a tack signal generation pattern 25' on the rotor side and a tack signal generation pattern 25' per rotation.
A pattern section 46 for generating a tack signal is provided opposite to each other. From the output terminal of the stator #* pole pattern 2427, a 6- or 7-step level shift is produced depending on the rotational position of the rotor magnet 4. This
is input to a voltage converting electronic circuit as shown in FIG. 5, converted to a single voltage deviation signal, and further converted to a three-phase motor signal to drive the motor.

Figure 514 is a circuit signal waveform diagram of the cylinder motor drive circuit of the second embodiment. The 6-step and 7-step change polarization signals obtained during stator coil pattern 2 to 4 to 27 are input to the detection circuit 30, where they are converted into amplified voltage signals, and then further amplified by the buffer 110. At the output terminal of the buffer 110, 6-stage and 7-stage outputs of IJ4J are obtained. This signal output; 4 is further inputted to one end of the next-stage comparator E11-64, and the other end of the comparators 81-86 is set to each predetermined reference voltage level, so that the output waveforms of the comparators 81-86!
Ii1~(G is obtained. The 5-phase coil energization control signal is within~
C) is formed by combining them with a logic circuit, and the tack signal is formed from white. FG flaw signal for rotational speed control is obtained from the back electromotive force of the stator coil. The tack signal and FG flaw signal processing method after amplification is the same as in the case of the cylinder motor in the first embodiment. Since the cylinder motor of the second embodiment has a single-phase capacitive sensor structure, the structure of the poles on the stator side is simple and there is no need to locate the correlation, so that the 'Wt pole arrangement n degrees can be highly elliptical IfVr- This has the advantage that the wiring between the upper motor and the circuit can be reduced.

In the above embodiment, the electrostatic electrode conductor is manufactured in front of the pattern conductor and is fixed on the other surface of the rotor #If1 or on the stator rail surface. It is also within the scope of the present invention to form a pattern directly on the surface or to have a structure in which the stator side electrode portion is integrated with the patterned stator coil. Further, the motor may be a cylindrical motor or one having a phase number other than five phases.

In addition, although the embodiment uses a structure in which the electrode area is changed to obtain a change in capacitance, there is also a method of changing the gap size between opposing electrodes, which is also within the scope of this patent. The static electrode for tack signal generation may be provided separately from the #electrode for rotational position detection signal generation, or may be integrated with the FG electrode. Further, in the embodiment, the electrostatic electrode conductor is provided in the gap '#tM1 of the motor, but it may be provided in a location other than this.

According to the present invention, when using a cylinder motor, (1) the rotational position sensor of the rotor magnet, the rotational position detection section and the rotational speed detection section of the video head can be constructed of thin conductors such as patterned conductors. Reduction of man-hours,
It is possible to make it thinner. In particular, when the stator coil is also a sheet coil, the entire motor stator section except the stator yoke can be manufactured using the same technique such as etching, making it possible to significantly reduce costs, create a thinner structure, and improve efficiency.

(21 sensors, each detection part, and the stator coil can be arranged with high accuracy and uniform in shape and size, and the conductors of the sensor and detection part can be subdivided into multi-level signals, multiple signals, and high-frequency signals, so high Accurate control is possible.A cylinder motor particularly suitable for digital control can be configured.

(3) Since there is no cogging torque in the sensor or each detection section, low rotational unevenness can also be achieved from this point of view. In addition, since there is no temperature tL% characteristic, accurate rotation information can be obtained regardless of temperature changes, and a cylinder motor with always stable controllability can be constructed.

You can get the effect of the number.

[Brief explanation of drawings]

Fig. 1 is a structural diagram of a conventional cylinder motor, Fig. 2 is a longitudinal sectional view of a first embodiment of the cylinder motor of the present invention, and Fig. 3 is a longitudinal cross-sectional view of a first embodiment of the cylinder motor of the present invention.
The figure is a plan view of the magnetic pole surface of the rotor magnet and the surface of the stator coil in the motor section of the cylinder motor in figure 2. 5
The figure is a detection circuit diagram that converts capacitance changes into voltage changes, Figures 6 and 7 are explanatory diagrams of the conversion principle and output waveforms of each part,
Fig. 8 is a rotation information signal detection circuit diagram of the cylinder motor of the m1 embodiment, and Fig. 9 is an overall drive circuit diagram of the cylinder motor 1.
．． The i@1o diagram is a signal waveform diagram of the signal processing electronic circuit section of the m9 diagram, Figure 11 is a basic structural diagram of a patterned conductor coil, Figure 12 is a structural diagram of an 8-pole 3-phase coil using a patterned conductor coil, Figure 13 is a diagram of the second embodiment of the cylinder motor of the present invention, Figure wJ14 is its drive circuit diagram, and Figure 15 is 41M1.
4 is a signal waveform diagram of each part of the circuit of FIG. 4. FIG. 4... Rotor magnet, 10-... Stator coil,
20... Rotor side electrostatic electrode, 21... Stator side electrostatic electrode, 24, 25.25'... Rotor side electrostatic electrode conductor, 26.26'. 26", 27.28.29.46...Stator side 'W
L electrode conductor. No. j (a-) Fig. 2 jl 4 Fig. 7 e QcO) G:D G:De GOD (I:
DGRID, IQWO)σ:Dσ:Dσ=℃σ=
Dσ=℃σ: Fuσ: Dσ=DC Fig. 5 No. 6 y"I Fig. 1 y Fig. rod fj (a-) ri O Leaf Iz eye 'lJI511 (b)

Claims (1)

[Scope of Claims] t. A cylinder motor for a VTR that records and reproduces video signals by rotating an upper cylinder to which a video head is fixed and causing the video head to helically scan the video tape surface, comprising: a rotor magnet on the rotation axis of the upper cylinder; It is a direct-coupled shaft drive structure using a DC brushless motor with a motor stator including a coil fixed to the lower cylinder side, and conductor electrode parts are installed on the rotor side including the upper cylinder and rotor magnet, and on the fixed side including the lower cylinder. , and forms a dampness between the two conductor poles that changes as the rotor side rotates, and detects at least one rotational position of the rotor magnet by the one-step change, and generates a detection signal and a video head. A cylinder motor characterized in that it is configured to receive a door rotation position detection signal.