Method of controlling reel driven tape recorder

Abstract: A recording and/or reproducing apparatus which includes no pinch roller and no capstan and wherein the converging time to a rotated speed upon starting of feeding of a tape can be reduced and the tape can be fed stably at the rated speed during recording and/or reproduction of the tape is disclosed. A rotary encoder for detecting a period of rotation is disposed between a recording and/or reproducing head and a take-up side reel, and deviation from a predetermined reference value is calculated from the period of rotation detected by the rotary encoder. On start-up the period of 1/n rotations is measured and used to determine the deviation. After one rotation has been completed the deviation is determined from the period of a whole rotation.

Description: This invention relates to a recording and/or reproducing apparatus for a recording medium in the form of a tape, and more particularly to a method of controlling the speed of rotation of a reel to feed a recording medium in the form of a tape at a fixed speed. Recording and/or reproducing apparatus wherein, for example, a magnetic tape accommodated in a tape cassette housing or an open reel tape is employed as a recording medium are spread widely. In the recording and/or reproducing apparatus, normally a capstan and a pinch roller are contacted with a magnetic tape and the speed of rotation of the capstan is controlled to rotate at a fixed speed to feed the magnetic tape at a fixed speed. In order to realize feeding of the tape at a fixed speed in a recording and/or reproducing apparatus of the reel drive type, it is one of possible measures to detect the speed of feeding of the tape and perform velocity servo control of a reel motor in response to the detected speed. A suitable one of means to detect the tape feeding speed involves employment of a rotary encoder having a roller which contacts with and is rotated by the tape when the tape is fed. By the way, in a recording and/reproducing apparatus of the reel drive type, when the take-up side reel (reel spindle meshed with the take-up side reel) is driven to rotate at a fixed speed, the diameter of the tape wound on the reel varies gradually, and consequently, the load to the tape varies and the tape feeding speed varies. While depending upon the length of the tape, the tape feeding speed immediately before the tape is taken up completely sometimes varies, for example. by two times or more comparing with that immediately after feeding of the tape is started from its starting end. Accordingly, even where a same recording medium is used, it is not compatible both with recording and/or reproducing apparatus of the reel drive type and recording and/or reproducing apparatus of the capstan type, which are spread widely at present. Further, a recording and/or reproducing apparatus of the reel drive type is not suitable as a recording and/reproducing apparatus for which fidelity in sound quality is required since the frequency characteristic and the S/N (signal to noise) ratio are varied from the starting end to the last end of the tape by the variation of the tape feeding speed. From those reasons, recording and/or reproducing apparatus of the reel drive type have a problem in that they are not suitable for practical use while they have an advantage in that they are simplified in construction due to absence of a capstan. For example, a recording and/or reproducing apparatus is disclosed in Japanese Patent Laid-Open No. Heisei 3-134848 wherein a rotating roller is contacted with a magnetic tape and a reel is driven in response to the difference between a period of rotation of the rotating roller and a reference period of rotation for the rotating roller without using a capstan and a pinch roller. When the tape stops, naturally a reel must stop, and therefore, in order to realize fixed speed feeding of the tape with a recording and/reproducing apparatus of the reel drive type, upon starting feeding of the tape, rotation of the reel must be raised rapidly to the speed for fixed speed rotation. However, it is not possible for the reel to continue, also when the recording and/or reproducing apparatus is in a stopping condition, its rotation at a fixed speed like a capstan, and from the necessity for the rising operation, much time is required until feeding of the tape reaches the predetermined speed. This gives rise to such serious problems as failure in recording at a starting end and a variation in musical interval upon reproduction. Further, even during recording or reproduction, when the tape feeding speed is displaced by a significant amount from the predetermined speed, much time is required for recovery, resulting in such problems as failure in recording at a starting end and a variation in musical interval upon reproduction. Further, when it is tried to realize fixed speed feeding of the tape with a recording and/or reproducing apparatus of the reel drive type, it is one of available measures to detect the tape feeding speed and control the speed of rotation of the reel motor by servoing control. However, the tape feeding speed is not always detected precisely due to vibrations applied to the apparatus from the outside, a momentary variation of the operating voltage or an influence of irregularity in thickness, wrinkles and so forth of the magnetic tape. Thus, it is a problem that rotation of the reel motor is liable to be placed out of control by an error in detection of the tape feeding speed arising from some of the factors just described. Accordingly, it is difficult to realize fixed speed feeding making use of a rotational servo mechanism. One of possible means for detecting the tape feeding speed involves a rotary encoder having roller which contacts with and is rotated by the tape so that pulses are generated from the rotary encoder. In this instance, where the rotary encoder is constructed so as to generate a large number of pulses during one rotation of the roller, a high resolution is obtained so that information of the tape feeding speed is obtained at a short interval of time and servoing control of a high responsibility is obtained. However, the construction requires a large size for the tape feeding speed detecting means and particularly for the roller and the pulse generating means, which is not preferable. On the other hand, where the rotary encoder is constructed so as to generate one pulse or a small number of pulses for one rotation of the roller, reduction in size of the tape feeding speed detecting means can be achieved, but since information of the tape feeding speed can be obtained only at a comparatively long interval of time, servoing control of a high responsibility cannot be achieved and a delay in servoing control may be resulted. Further, even during recording or reproduction, when the tape feeding speed is displaced by a significant amount from the predetermined speed, much time is required for recovery, resulting in such problems as failure in recording at a starting end and a variation in musical interval upon reproduction. Furthermore, when the speed is detected by means of the rotary encoder, a slip between the tape and the roller makes it difficult to detect the speed accurately. Accordingly, there is a problem in that it is difficult to achieve accurate servoing control. For example, if the back tension of the supply side reel is insufficient, the contacting pressure or the contacting area between the roller and the tape is rendered unstable so that a slip may be produced between the roller and the tape. On the other hand, when it is tried to obtain sufficient back tension of the supply side reel to eliminate such a possible slip as described just above, then complication of the structure, increase of the torque of the take-up side reel and employment of a motor of a large size and a high power for such increase, increase of the power dissipation and so forth are involved. Further, a rise of the slip torque may result in damage to the tape. It is an object of the present invention to provide a method of controlling the reel drive of a recording and/or reproducing apparatus which is high in responsiveness upon starting and high in accuracy in speed of feeding of a tape. It is further object of the present invention to provide a method of controlling the reel drive of a recording and/or reproducing apparatus wherein a rise to a predetermined speed upon starting of feeding of a tape is performed rapidly. According to the present invention, there is provided a controlling method for a reel motor of a recording and/or reproducing apparatus which includes no capstan and no pinch roller and wherein a rotatable member is contacted with a recording medium in the form of a tape to measure a period of rotation of said member and a reel is driven to rotate by a reel motor in accordance with the period of rotation thus measured, characterized by comprising the steps of: measuring upon starting of feeding of the tape-formed recording medium, a 1/n rotation period T of said member by rotation detection means, n being a natural number larger than 1, and changing over an effective servo system to a first servo system which calculates a deviation d in accordance with the thus calculated 1/n rotation period; servo controlling said reel motor in accordance with the thus calculated deviation d; determining whether or not said member has rotated one rotation; changing over, in response to determination of one rotation of said member, the effective servo system to a second servo system which calculates a deviation d in accordance with a whole rotation period measured by said rotation detection means; and servo controlling said reel motor in accordance with the thus calculated deviation d. By obtaining speed information in a 1/n, e.g. 1/4 rotation of the roller only upon starting of feeding of the tape-formed recording medium, a rapid servoing operation is allowed, and a rise to the rated speed (for example, 4.76 cm/sec in a compact cassette tape) can be performed in a short period of time. Further, where driving of the reel motor using an initial value upon starting of feeding of the tape-formed recording medium is performed only when the power source is turned on or only upon starting of feeding of a tape-formed recording medium for the first time after loading of the tape-formed recording medium into the recording and/or reproducing apparatus but the reel motor is driven, upon starting of feeding in any other case, using a servo control value obtained immediately before the last stopping of feeding, since a servoing operation is started from a condition considerably proximate to that at the rated speed upon any other starting of feeding than starting of feeding when the power source is turned on or starting of feeding for the first time after loading of the tape-formed recording medium into the recording and/or reproducing apparatus, a rise to the rated speed can be performed in a very short period of time. The present invention will be further described by way of example in the following description, taken in conjunction with the accompanying drawings, in which like parts or elements are denoted by like reference characters, and in which:- Fig. 1 is a block diagram of a recording and/or reproducing apparatus described for reference; Fig. 2 is a flow chart illustrating operation of the recording and/or reproducing apparatus of Fig. 1; Figs. 3(a) and 3(b) are time charts showing output signals of a rotary encoder and a waveform shaping circuit of the recording and/or reproducing apparatus of Fig. 1; Fig. 4 is a block diagram of a recording and/or reproducing apparatus, which operates according to the method of the present invention; Fig. 5 is a flow chart illustrating operation of the recording and/or reproducing apparatus of Fig. 4; Figs. 6(a) and 6(b) are flow charts showing subroutines of the flow chart of Fig. 5; Figs. 7(a) and 7(b) are time charts showing output signals of a rotary encoder and a waveform shaping circuit of the recording and/or reproducing apparatus of Fig. 4; Figs. 8(a) to 8(d) are time charts illustrating servoing conditions of the recording and/or reproducing apparatus of Fig. 4; Fig. 9 is a block diagram of a further recording and/or reproducing apparatus described for reference; Fig. 10 is a flow chart illustrating operation of the recording and/or reproducing apparatus of Fig. 9; Figs. 11(a) and 11(b) are time charts illustrating servoing conditions of the recording and/or reproducing apparatus of Fig. 17; Fig. 12 is a block diagram of a yet further recording and/or reproducing apparatus described for reference; Fig. 13 is a flow chart illustrating operation of the recording and/or reproducing apparatus of Fig. 12; Figs. 14(a) to 14(h) are time charts illustrating a servoing condition of the recording and/or reproducing apparatus of Fig. 12; Fig. 15 is a schematic view of a reel drive structure of a recording and/or reproducing apparatus to which the present invention is applied; Fig. 16(a) is a perspective view showing a mounted condition of a rotary encoder in a recording and/or reproducing apparatus to which the present invention is applied, Fig. 16(b) is a partial perspective view of a roller of the rotary encoder, and Fig. 16(c) is a diagrammatic view schematically showing an electric construction of the rotary encoder; Figs. 17(a) and 17(b) are schematic sectional views illustrating a detecting operation of the rotary encoder shown in Figs. 16(a) to 16(c); Figs. 18 to 34 are perspective views showing different mechanical arrangements of a magnetic head or heads and a rotary encoder in a recording and/or reproducing apparatus to which the present invention can be applied; Fig. 35 is a schematic plan view of a compact cassette tape; and Fig. 36 is a schematic plan view of a micro cassette tape. Referring first to Fig. 1, there is shown for reference in block diagram a recording and/or reproducing apparatus. A magnetic block diagram a recording and/or reproducing apparatus. A magnetic tape 1 is wound on a supply reel 2 and a take-up reel 3 and accommodated in a body of a tape cassette not shown. The magnetic tape 1 is loaded in position and fed in the recording and/reproducing apparatus when a recording and/or reproducing operation for audio information or the like is performed by a magnetic head 10. The magnetic tape 1 is fed when the take-up reel 3 is driven to rotate by a reel motor 11. Referring also to Fig. 15, rotation of the reel motor 11 is transmitted to a flywheel 13 by way of a belt 19 so that a drive shaft 14 provided on the flywheel 13 is rotated. A take-up reel receiver 15 is held in contact with the drive shaft 14 by way of a rubber belt 16 provided on a circumferential face of the take-up reel receiver 15. Consequently, when the drive shaft 14 rotates, the take-up reel receiver 15 is rotated by the drive shaft 14 to rotate a reel driving shaft 17 mounted on the take-up reel receiver 15. Then, when the tape cassette 4 is loaded in position as indicated by a broken line in Fig. 15, a hub of the take-up reel 3 is engaged with the reel driving shaft 17, and consequently, the take-up reel 3 is rotated by the reel driving shaft 17 to feed the magnetic tape 1. The supply reel 2 has a reel shaft 18 thereon. A rotary encoder 12 is provided in order to detect the feeding speed of the magnetic tape 1 and includes a roller 12a, a shutter plate 12b provided on the roller 12a, a photo-diode 12c serving as a light outputting element, and a phototransistor 12d for detecting an optical output of the photo-diode 12c and converting it into an electric signal. Referring now to Figs. 16(a) to 16(c), the roller 12a is mounted for rotation on a frame 12e, and a photo-reflector 12f in the form of a single chip element including the photo-diode 12c and the phototransistor 12d is mounted on a base plate 12g below the roller 12a. The photo-reflector 12f has a window 12f 1 and another window 12f 2 formed therein so that light from the photo-diode 12 is outputted through the window 12f 1 while light to be detected by the photo-transistor 12d is admitted through the window 12f 2 . The shutter plate 12b is formed on a lower face of the roller 12a opposing to the photo-reflector 12f such that, when the angular position of the shutter plate 12b with respect to the photo-reflector 12f is varied by rotation of the roller 12a, light emitted from the photodiode 12c is admitted into the photo-transistor 12d or intercepted from entering the photo-transistor 12d. In particular, referring also to Figs. 17(a) and 17(b), the roller 12a and the shutter plate 12b are mounted for rotation around a shaft 12a 1 relative to the frame 12e, and accordingly, when the roller 12a is contacted with the magnetic tape 1 as shown in FIG. 1, as the magnetic tape 1 is fed, the roller 12a is rotated by the magnetic tape 1 and rotates the shutter plate 12b. Here, when the shutter plate 12b is at such a rotational position as shown in Fig. 17(a) relative to the photo-reflector 12f, light emitted from the photo-diode 12c and outputted through the window 12f 1 is intercepted by the shutter plate 12b, and consequently, it is not detected by the photo-transistor 12d. On the other hand, when the shutter plate 12b is at another rotational position as shown in Fig. 17(b) relative to the photo-reflector 12f, light emitted from the photo-diode 12c and outputted through the window 12f 1 is not intercepted by the shutter plate 12 and is introduced into the phototransistor 12d through the window 12f 2 . Accordingly, admission or non-admission of light into the photo-transistor 12d is repeated each time the roller 12a rotates 1/4 rotation. Consequently, such a detection waveform as indicated, for example, by Fig. 3(a), 7(a) or 14(a) is output from the phototransistor 12d. It is to be noted that the roller 12a has such a diameter that it rotates four rotations for one second when the magnetic tape 1 is fed at a rated speed (4. 76 cm/sec with a compact cassette tape). Referring back to FIG. 1, a waveform shaping circuit 20 shapes the wave form of an output of the photo-transistor 12d, which may have some distortion, into a rectangular wave form. In particular, the waveform shaping circuit 20 has a predetermined threshold level having a hysteresis for the output Sa of the rotary encoder 12 of Fig. 3(a), 7(a) or 14(a) and produces such a waveform shaped output Sb as seen from Fig. 3(b), 7 (b) or 14(b). A rotation time measurement section 21 calculates a time required for one rotation of the roller 12a. One rotation of the roller 12a corresponds to a period T in Fig. 3(b), 7(b) or 14(b), that is, a period from the rising edge (or the falling edge) of a pulse to the rising edge (or the falling edge) of a second pulse next to the first pulse. A deviation calculation section 22 holds in advance therein information (hereinafter referred to as rated period information T ⊘25 ) of the period of one rotation of the roller 12a at a rated speed in feeding of the magnetic tape 1. It is to be noted that, since the roller 12a is rotated four rotations for one second when the magnetic tape 1 is fed at the rated speed, the rated period information T ⊘25 is 0. 25 seconds. The deviation calculation section 22 calculates a deviation d using the rated period information T ⊘25 and the period T of an actual one rotation inputted thereto. In particular, the deviation d is calculated in accordance with the following equation: d = T-T ⊘25 T ⊘25 A gain coefficient generation section 23 outputs a coefficient K to be used for setting of a servo gain. It is to be noted that, when the coefficient K should always be kept equal to K = 1, the gain coefficient generation section 23 need not be provided. However, by setting the coefficient K to a predetermined value, the servo gain can be set to a desired value and the responsiveness of a servoing operation which will be hereinafter described can be set arbitrarily. A control constant generation section 24 generates a control constant A calculated in accordance with a functional expression between a range of speed of rotation of the reel motor 11 and a servo control value L which will be hereinafter described. The control constant A is used to obtain a servo control value L which appropriately coincides with the range of variation of rotation of the reel motor 11, and accordingly, the control constant A is a fixed value peculiar to the apparatus. The control constant A is calculated in accordance with the following equation: A = (L MAX - L MIN ) * N MIN N MAX - N MIN where N MAX is a speed of rotation of the reel motor 11 at the starting end of the magnetic tape 1, N MIN is a speed of rotation of the reel motor 11 at the last end of the magnetic tape 1, L MAX is a servo control value at the starting end of the magnetic tape 1, and L MIN is a servo control value at the last end of the magnetic tape 1. The recording and/or reproducing apparatus further includes a control output calculation section 25 for calculating and outputting a servo control value L N . and an output storage section 26 for storing the servo control value L N is output from the control output calculation section 25 and supplying the servo control value L N to a data conversion section 27 which will be hereinafter described. The servo control value L N supplied to the output storage section 26 is stored as a servo control value L in the output storage section 26, and the servo control value L is fed back as a servo control value in a preceding control cycle to the control output calculation section 25 and used for calculation of a servo control value L N . The control output calculation section 25 calculates, using the deviation d, the gain coefficient K, the control constant A and the servo control value L thus fed back, a servo control value L N for a current control cycle in accordance with the following expression: L N = L + d * A * K The data conversion section 27 converts the servo control value L supplied thereto from the output storage section 26 into a reference value for a servoing operation. For example, the data conversion section 27 converts the servo control value L into a resistance value, a voltage value, a pulse width or a pulse period corresponding to the servo control value L. In the apparatus, the servo control value L is converted into a PWM (pulse width modulation) signal having a corresponding "L period" (period of a low level) with respect to a fixed "H period" (period of a high level). Accordingly, the servo control values L MAX and L MIN used for calculation of the control constant A described above represent the pulse widths of an "L period" of the PWM signal at the starting end and the last end of the magnetic tape 1. A motor servo circuit 28 converts the PWM signal supplied thereto, for example, into a voltage value or a resistance value and supplies a servo output EM to the reel motor 11 so that the voltage value or resistance value obtained by the conversion may coincide with a drive voltage value (or resistance value) fed back thereto from the reel motor 11 to control driving of the reel motor 11 so as to minimize the deviation d. In the recording and/or reproducing apparatus having such a construction as described above, servoing control is performed so that the speed of rotation of the reel motor 11 may be kept substantially constant while the magnetic tape 1 is fed from the starting end to the last end thereof. A servoing operation for the speed of rotation of the reel motor 11 is illustrated in the flow chart of FIG. 2, Referring to FIGS. 1 and 2, when the magnetic tape 1 is fed, the roller 12a is rotated by the magnetic tape 1, and thereupon, rotational speed information Sa is outputted from the rotary encoder 12 to the waveform shaping circuit 20 and a waveform shaped output Sb is outputted from the wave form shaping circuit 20. In response to the waveform shaped output Sb, a one rotation period T of the roller 12a is measured by the rotation time measurement section 21 (step F101). Then, using the one rotation period T, a deviation d is calculated in the deviation calculation section 22 as described above, and the deviation d is supplied to the control output calculation section 25 (step F102). The control output calculation section 25 calculates a servo control value L N for a current control cycle from the deviation d, a gain coefficient K, a control constant A and another servo control value L in a preceding control cycle (step F103), and supplies the servo control value LN to the output storage section 26 so that it may be stored into the output storage section 26 (step F104). The servo control value L thus stored is converted into a PWM signal by the data conversion section 27 (step F105), and in response to the PWM signal, the motor servoing circuit 28 develops a servo output EM to control driving of the reel motor 11 (step F106). The sequence of operations described above is repeated, and as the operations proceed, the speed of rotation of the reel motor 11 decreases gradually in accordance with the diameter of the magnetic tape 1 wound on the take-up reel 3 while the feeding speed of the magnetic tape 1 is kept substantially constant. Referring now to Fig. 4 there is shown a recording and/or reproducing apparatus which operates according to the the method of the present invention. In the recording and/or reproducing apparatus, a one rotation detection section 40 counts the rising edges of pulses Sb outputted from the waveform shaping circuit 20 to detect that the roller 12a has been rotated one full rotation after starting of feeding of the magnetic tape 1. In the recording and/or reproducing apparatus, a detection pulse is obtained for each one fourth rotation of the roller 12a, and accordingly, when the rising edge of the third pulse is counted, the one rotation detection section 40 develops an output of one rotation detection. A one quarter rotation time measurement section 41 calculates a period of one quarter rotation of the roller 12a from the output Sb of the wave form shaping circuit 20. One quarter rotation of the roller 12a corresponds to a period of T/4 in Fig. 7(b), that is, a period from the rising edge to the falling edge of a pulse. A deviation calculation section 42 holds in advance therein in one quarter rotation period information (hereinafter referred to as 1/4 rated period information T ⊘25 Q) at the rated speed in feeding of the magnetic tape 1. It is to be noted that here the 1/4 rated period information T ⊘25 Q is information for 0.0625 seconds. The deviation calculation section 42 calculates a deviation d using the 1/4 rated period information T ⊘25 Q and the actual 1/4 rotational period (T/4) inputted thereto from the one quarter rotation time measurement section 41. In this instance, the deviation d is calculated in accordance with the following equation: d = 4/T - T ⊘25 Q T ⊘25 Q A switching circuit 43 has a contact SW1 to which the deviation d outputted from the deviation calculation section 22 is supplied and another contact SW2 to which the deviation d outputted from the deviation calculation section 42 is supplied. Upon starting of feeding of the magnetic tape 1, the switching circuit 43 is switched to the contact SW2, but in response to a one rotation detection output of the one rotation detection section 40, the switching circuit 43 is switched to the contact SW1. In the recording and/or reproducing apparatus of the construction described above, except upon starting of feeding of the magnetic tape 1, servoing control is executed in accordance with a servo control value L N obtained by calculation of the equation (3) above in accordance with a deviation d calculated from a one rotation period of the roller 12a obtained from the deviation calculation section 22, and consequently, the speed of rotation of the reel motor 11 is controlled so that the feeding speed of the magnetic tape 1 may be kept substantially constant from the starting end to the last end of the magnetic tape 1. In this instance, a servo responsiveness is set in response to a value of the gain coefficient K described above. If the gain coefficient K is varied in response to the value of the deviation d similarly as in the second embodiment described above, then a rise of the feeding speed of the magnetic tape 1 to the rated speed upon starting of rotation of the reel can be achieved comparatively rapidly as seen from Fig. 8(c). Even where such coefficient variation control is performed, there still is some limitation in reduction of the rise time of the motor to the rated speed. In order to realize a better recording and/or reproducing apparatus of the reel drive type, it is desired to further reduce the rise time of the motor as seen from Fig. 8(d). Therefore, in the recording and/or reproducing apparatus operating according to the method of the invention, upon starting of feeding of the magnetic tape 1, a deviation d is calculated by the deviation calculation section 42 using 1/4 period information T ⊘25 Q obtained from the one quarter rotation time measurement section 41 and is used in execution of servoing control. A servoing operation for the speed of rotation of the reel motor 11 in the recording and/or reproducing apparatus is illustrated in Fig. 5. Referring to Figs. 4 and 5, when feeding of the magnetic tape 1 is to be started, the switching circuit 43 is first controlled to be connected to the contact SW2 (step F301), and consequently, a servoing operation based on 1/4 rotation period measurement of the roller 12a is executed (step F302). Details of the servoing operation are illustrated in Fig. 6(b). Referring to Fig. 6(b), a 1/4 rotation period (T/4) is measured by the one quarter rotation time measurement section 41 (step F501), and a deviation d is calculated by calculation of the equation (6) given hereinabove by the deviation calculation section 42 (step F502). The deviation d is supplied by way of the switching circuit 43 to the control output calculation section 25, in which a servo control value LN is calculated by calculation of the equation (3) given hereinabove (step F503). It is to be noted that an initial value is stored in the output storage section 26 as a servo control value L in a preceding control cycle which is to be used for calculation of a servo control value L N in a first control cycle, and the initial value is used for calculation of a servo control value L N in a first control cycle. The servo control value L N is supplied to and stored as a servo control value L into the output storage section 26 (step F504), and the thus stored servo control value L is converted into a PWM signal by the data conversion section 27 (step F505). The motor servo circuit 28 develops a servo output EM in response to the PWM signal to effect driving control of the reel motor 11 (step F506). The processing of Fig. 6(b) is executed until the roller 12a is rotated one full rotation, that is, executed for each one quarter rotation of the roller 12a and accordingly executed four times for each one rotation. Referring back to Fig. 5, if completion of one rotation of the roller 12a is detected by the one rotation detection section 40 at step F303, then the switching circuit 43 is controlled to be switched to the contact SW1 (step F304), and then, a servoing operation based on one rotation period measurement of the roller 12a is executed (step F305). Details of the servoing operation at step F305 are illustrated in Fig. 6(a). Referring to Fig. 6(a), when the roller 12a is rotated so that rotation speed information Sa is outputted from the rotary encoder 12 to the waveform shaping circuit 20 and a waveform shaped output Sb is outputted from the waveform shaping circuit 20, a one rotation period T of the roller 12a is measured by the rotation time measurement section 21 (step F401). Then a deviation d is calculated using the one rotation period T by the deviation calculation section 22 as described above and is supplied to the control output calculation section 25 by way of the switching circuit 43 (step F402). The control output calculation section 25 calculates a servo control value L N for a current control cycle similarly (step F403) and supplies the servo control value L N to the output storage section 26 so that it is stored as a servo control value L (step F404). The thus stored servo control value L is converted into a PWM signal by the data conversion section 27 (step F405), and the motor servo circuit 28 develops a servo output EM in response to the PWM signal to effect driving control of the reel motor 11 (step F406). Referring now to Fig. 9, there is shown for reference in block diagram a recording and/or reproducing apparatus. The reference recording and/or reproducing apparatus is constructed such that a servo control value set as an initial value into the output storage section 26 is used only upon first starting of feeding of the magnetic tape 1 after loading of a cassette or turning on of the power source. In particular, if, upon starting of feeding of the magnetic tape 1, driving of the reel motor is started using a predetermined initial value every time and a deviation d or a tape position TP is calculated from a feeding condition of the tape 1 by rotation of the motor to effect servoing control, then the period of time until servoing control for a first control cycle is executed (feedback period of the servo system) is a time necessary for a rise of feeding at all, and consequently, a rising operation to the rated speed cannot be decreased any more. Therefore, the initial value is used only at necessary minimum opportunities, and in any other case, servoing control is started with a servo control value L in a preceding control cycle. For example, when it is considered that reproduction or recording (FWD) and stopping are repeated as seen from Fig. 11(a), if servoing control is started for each reproducing or recording operation, a period which cannot be shortened occurs and delays a rise to the rated speed as seen from Fig. 11(a). However, an initial value must be used without fail only upon starting of first feeding of the magnetic tape 1 after loading of a cassette or turning on of the power source. In any other case, it is suitable to use a servo control value L in a preceding control cycle (that is, a control cycle immediately before stopping). By using a servo control value L in a preceding control cycle in this manner, further reduction of the time can be realized for starting of feeding of the magnetic tape 1 for the second or following time after a cassette is loaded in position or the power source is turned on as seen from Fig. 11(b). Referring back to Fig. 9, the recording and/or reproducing apparatus of the seventh embodiment of the present invention includes an initial value generation section 50 for outputting and placing an initial value into the output storage section 26, a power source turning off signal generation section 51, and a cassette absence detection signal generation section 52. A servoing operation of the recording and/or reproducing apparatus is illustrated in Fig. 10. Referring to Figs. 9 and 10, the initial value generation section 50 normally supervises detection signals from the power source turning off signal generation section 51 and the cassette absence detection signal generation section 52 (steps F802 and F803), and only when any of the detection signals is detected, the initial value generation section 50 outputs an initial value to the output storage section 26 (step F801). Then, while the magnetic tape 1 is being fed, servoing control based on calculation of a deviation d is executed (steps F804 to F810). It is to be noted that the processing at steps F805 to F810 is similar to that of Fig. 6(a). Here, even when feeding of the magnetic tape 1 is stopped once, unless a detection signal from the power source turning off signal generation section 51 or the cassette absence detection signal generation section 52 is detected, the initial value generation section 50 does not output the initial value (No at step F802, and No at step F803). Accordingly, a last servo control value L in a control cycle immediately before stopping is maintained in the output storage section 26. Consequently, when feeding of the magnetic tape 1 is resumed, the reel motor 11 is started in response to the servo control value L stored in the output storage section 26. Due to the operation described above, the period of time, which has not been reduced formerly, can be reduced for starting of feeding of the magnetic tape 1 in any of the second and following control cycles after loading of a cassette or turning on of the power source as seen from Fig. 10(b). The initial control steps F801 to F804 may also be used with the method of the present invention. In that case it is possible in addition to reduction of the time upon starting of feeding of the magnetic tape in the first control cycle after loading of a cassette or turning on of the power source, to remarkably reduce the time upon starting of feeding of the magnetic tape in any of the second and following control cycles. Referring now to Fig. 12, there is shown for reference in block diagram a recording and/or reproducing apparatus. The recording and/or reproducing apparatus includes a one quarter rotation period storage section 36 which stores the last four 1/4 rotation periods (T/4) of the roller 12a outputted from the one quarter rotation period measurement section 21. In particular, the one quarter rotation period storage section 36 holds the last one quarter rotation period (T/4) available at present as a period TM 1 in a recording area 36a and holds three one quarter rotation periods (T/4) obtained in the preceding three control cycles as periods TM 2 to TM 4 in recording areas 36b to 36d, respectively. The holding operation can be realized, for example, by means of data control by address shifting of the memory areas or by constituting the one quarter rotation period storage section from a shift register. An addition section 37 calculates a one rotation period T of the roller 12a using data held in the one quarter rotation period storage section 36, that is, the periods TM 1 to TM 4 . The one rotation period T is the sum of the last four one quarter rotation periods (T/4). Accordingly, it can be presented by the following equation: T = TM 1 + TM 2 + TM 3 + TM 4 In the recording and/or reproducing apparatus having the construction described above, servoing control is executed in accordance with a servo control value L N obtained by calculation of the equation (3) given hereinabove based on a deviation d calculated from a one rotation period of the roller 12a obtained from the deviation calculation section 22 during feeding of the magnetic tape 1, and the speed of rotation of the reel motor 11 is controlled so that the feeding speed of the magnetic tape 1 may be kept substantially constant from the starting end to the last end of the magnetic tape 1. Further, while only two pulses are outputted during one rotation of the roller 12a, since in this recording and/or reproducing apparatus, a one rotation period T is calculated and a deviation d is calculated by the deviation calculation section 42 to execute servoing control each time one quarter period information (T/4) is obtained from the one quarter rotation time measurement section 21, a fine servoing operation is realized in units of a short time. The servoing operation for the speed of rotation of the reel motor 11 in the recording and/or reproducing apparatus of the present embodiment is illustrated in Fig. 13. Referring to Figs. 12 and 13, during feeding of the magnetic tape 1, a one quarter rotation period (T/4) of the roller 12a is measured by the one quarter rotation time measurement section 21 (step F1101) and is supplied to the one quarter rotation period storage section 36. Thereupon, shifting of stored data is executed in the one quarter rotation period storage section 36. In particular, the period TM 3 is shifted to the period TM 4 : the period TM 2 is shifted to the period TM 3 : and the period TM 1 is shifted to the period TM 2 , and then, the newly inputted one quarter rotation period (T/4) is held as the period TM 1 (steps F1102 to F1105). In short, the last four one quarter rotation periods (T/4) are held in the one quarter rotation period storage section 36. The periods TM 1 to TM 4 held in the one quarter rotation period storage section 36 are supplied to the addition section 37, in which a period T of one rotation of the roller 12a is calculated by calculation of the equation (7) given hereinabove (step F1106). Then, the deviation calculation section 22 calculates a deviation d by calculation of the equation (1) given hereinabove (step F1107). The deviation d is supplied to the control output calculation section 25, in which a servo control value L N is calculated by calculation of the equation (3) given hereinabove (step F1108). The servo control value L N is supplied to and stored as a servo control value L into the output storage section 26 (step F1109), and the thus stored servo control value L is converted into a PWM signal by the data conversion section 27 (step F1110). The motor servo circuit 28 develops a servo output EM in response to the PWM signal to effect driving control of the reel motor 11 (step F1111). The sequence of operations described above is repeated, and as the operations proceed, the speed of rotation of the reel motor 11 decreases gradually in accordance with the feeding position of the magnetic tape 1, that is, the diameter of the magnetic tape 1 wound on the take-up reel 3. Accordingly, the feeding speed of the magnetic tape 1 is kept substantially constant. Consequently, a recording medium such as, for example, a compact cassette tape is compatible with a recording and/or reproducing apparatus of the capstan type, and besides, the frequency characteristic and the S/N ratio are not fluctuated from the starting end to the last end of the magnetic tape and a recording or reproducing operation is achieved with fidelity. Furthermore, a one rotation period T of the roller 12a is calculated, for each one quarter rotation of the roller 12a, from periods TM 1 to TM 4 held in the one quarter rotation period storage section 36 as seen from Figs. 14(a) to 14(h), and a servo control value L is obtained from the one rotation period T. In short, fine servoing control in units of a one quarter rotation time of the roller 12a is executed. Accordingly, a delay in servoing control is eliminated, and a recovering operation to the rated speed is achieved rapidly when the tape feeding speed is displaced by a great amount from a predetermined speed, for example, during recording and/or reproduction or a like case. Besides, the rotary encoder 12 can be constructed with a small size which only outputs a small number of (two) pulses by one rotation of the roller 12a. In the method of the invention, the period of one rotation can be determined by summing the n periods of 1/n rotation, n = e.g. 4, as described above. Mechanical Arrangements The servo control system for a reel motor which employs the rotary encoder 12 as a tape feeding speed detection means as described above will be described subsequently with reference to Figs. 18 to 34 which show different mechanical arrangements of the servo control system. As seen from Figs. 18 to 34, the magnetic head 10 (10a, 10b, 10c, 10a(F), 10a(R), 10b(F), 10b(R), 10c(F) and 10c(R) and the rotary encoder 12 (12(F), 12 (R) are secured to a head base 19 mounted on a mechanism chassis 19a so that, when the head base 19 is slidably moved, they are inserted into the tape cassette through a window in a front wall of the tape cassette until they are contacted with the magnetic tape. It is to be noted that the recording medium to be used in any of the mechanical arrangements may be either a compact cassette tape or a micro cassette tape, whose structure is shown in Fig. 35 or 36. Referring first to Fig. 35 which shows a compact cassette tape, a magnetic tape 1 is wound around a supply reel 2 and a take-up reel 3 and accommodated in a housing 4, and a tape path is set by a pair of guide rollers so that the magnetic tape 1 is fed while it is exposed to the outside through windows 8a to 8e formed in a front wall of the housing 4. In the window 8c, a pad 6 for contacting with the rear face of the magnetic tape 1 is secured to a leaf spring 6a and disposed in front of the front face of a shield plate 7. Referring now to Fig. 36 which shows a micro cassette tape, a magnetic tape 1 is wound around a supply reel 2 and a take-up reel 3 and accommodated in a housing 4, and a tape path is set by a pair of guide rollers so that the magnetic tape 1 is fed while it is exposed to the outside through windows 9a to 9e formed in a front wall of the housing 4. A pair of pads 6 for contacting with the rear face of the magnetic tape 1 are secured to a leaf spring 6a in the windows 9b and 9d, respectively. The head 10 and the rotary encoder 12 are disposed in the following manner in the mechanical arrangements of the recording and/or reproducing apparatus of the present invention which uses a compact cassette tape or a micro cassette tape of the construction described above. <Arrangement 1 (Fig. 18)> Recording medium: compact cassette tape Tape feeding: one-directional feeding Magnetic head: erasing/recording/reproducing head 10a ... inserted through window 8c Rotary encoder: rotary encoder 12 ... inserted through window 8e Accordingly, the rotary encoder 12 is contacted with the magnetic tape 1 in the tape path between the magnetic head 10 and the take-up reel 3. <Arrangement 2 (Fig. 19)> Recording medium: compact cassette tape Tape feeding: one-directional feeding Magnetic head: erasing/recording/reproducing head 10b ... inserted through window 8e Rotary encoder: rotary encoder 12 ... inserted through window 8c Accordingly, the rotary encoder 12 is contacted with the magnetic tape 1 with the magnetic tape 1 held between the rotary encoder 12 and the pad 6 (refer to Fig. 35). <Arrangement 3 (Fig. 20)> Recording medium: compact cassette tape Tape feeding: one-directional feeding Magnetic head: recording/reproducing head 10b ... inserted through window 8c erasing head 10c ... inserted through window 8b Rotary encoder: rotary encoder 12 ... inserted through window 8e Accordingly, the rotary encoder 12 is contacted with the magnetic tape 1 in the tape path between the magnetic head 10 and the take-up reel 3. <Arrangement 4 (Fig. 21)> Recording medium: compact cassette tape Tape feeding: one-directional feeding Magnetic head: recording/reproducing head 10b ... inserted through window 8c erasing head 10c ... inserted through window 8a Rotary encoder: rotary encoder 12 ... inserted through window 8e Accordingly, the rotary encoder 12 is contacted with the magnetic tape 1 in the tape path between the magnetic head 10 and the take-up reel 3. <Arrangement 5 (Fig. 22)> Recording medium: compact cassette tape Tape feeding: normal/reverse bi-directional feeding Magnetic head: recording/reproducing head 10b ... inserted through window 8c normal direction erasing head 10c(F) ... inserted through window 8b reverse direction erasing head 10c(R) ... inserted through window 8d Rotary encoder: normal direction rotary encoder 12(F) ... inserted through window 8e reverse direction rotary encoder 12(R) ... inserted through window 8a Accordingly, when the magnetic tape 1 is fed in the normal direction, the normal direction rotary encoder 12(F) is contacted with the magnetic tape 1 in the tape path between the magnetic head 10 and the take-up reel 3, but when the magnetic tape 1 is fed in the reverse direction. the reverse direction rotary encoder 12(R) is contacted with the magnetic tape 1 in the tape path between the magnetic head 10 and the supply reel 2 which functions as a take-up reel when the magnetic tape 1 is fed in the reverse direction. <Arrangement 6 (Fig. 23)> Recording medium: compact cassette tape Tape feeding: normal/reverse bi-directional feeding Magnetic head: normal direction erasing/recording/ reproducing head 10a(F) ... inserted through window 8e reverse direction erasing/recording/reproducing head 10a(R) ... inserted through window 8a Rotary encoder: normal/reverse bi-directional rotary encoder 12 ... inserted through window 8c Accordingly, the normal/reverse bi-directional rotary encoder 12 is contacted with the magnetic tape 1 with the magnetic tape 1 held between the rotary encoder 12 and the pad 6 (refer to Fig. 35). <Arrangement 7 (Fig. 24)> Recording medium: micro cassette tape Tape feeding: one-directional feeding Magnetic head: recording/reproducing head 10b ... inserted through window 9d erasing head 10c ... inserted through window 9e Rotary encoder: rotary encoder 12 ... inserted through window 9c Accordingly, the rotary encoder 12 is contacted with the magnetic tape 1 in the tape path between the magnetic head 10 and the take-up reel 3. <Arrangement 8 (Fig. 25)> Recording medium: micro cassette tape Tape feeding: one-directional feeding Magnetic head: recording/reproducing head 10b ... inserted through window 9d erasing head 10c ... inserted through window 9e Rotary encoder: rotary encoder 12 ... inserted through window 9b Accordingly, the rotary encoder 12 is contacted with the magnetic tape 1 in the tape path between the magnetic head 10 and the take-up reel 3 with the magnetic tape 1 held between the rotary encoder 12 and the pad 6 (refer to Fig. 36). <Arrangement 9 (Fig. 26)> Recording medium: micro cassette tape Tape feeding: one-directional feeding Magnetic head: erasing/recording/reproducing head 10a ... inserted through window 9d Rotary encoder: rotary encoder 12 ... inserted through window 9c Accordingly, the rotary encoder 12 is contacted with the magnetic tape 1 in the tape path between the magnetic head 10 and the take-up reel 3. <Arrangement 10 (Fig. 27)> Recording medium: micro cassette tape Tape feeding: one-directional feeding Magnetic head: erasing/recording/reproducing head 10a ... inserted through window 9d Rotary encoder: rotary encoder 12 ... inserted through window 9b Accordingly, the rotary encoder 12 is contacted with the magnetic tape 1 in the tape path between the magnetic head 10 and the take-up reel 3 with the magnetic tape 1 held between the rotary encoder 12 and the pad 6 (refer to Fig. 36). <Arrangement 11 (Fig. 28)> Recording medium: micro cassette tape Tape feeding: one-directional feeding Magnetic head: erasing/recording/reproducing head 10a ... inserted through window 9d Rotary encoder: rotary encoder 12 ... inserted through window 9a Accordingly, the rotary encoder 12 is contacted with the magnetic tape 1 in the tape path between the magnetic head 10 and the take-up reel 3. Further, in this instance, the location of contact is in the proximity of one of the guide rollers 5 (refer to Fig. 36). <Arrangement 12 (Fig. 29)> Recording medium: micro cassette tape Tape feeding: one-directional feeding Magnetic head: recording/reproducing head 10b ... inserted through window 9d erasing head 10c ... inserted through window 9e Rotary encoder: rotary encoder 12 ... inserted through window 9a Accordingly, the rotary encoder 12 is contacted with the magnetic tape 1 in the tape path between the magnetic head 10 and the take-up reel 3. Further, in this instance, the location of contact is in the proximity of one of the guide roller 5 (refer to Fig. 36). <Arrangement 13 (Fig. 30)> Recording medium: micro cassette tape Tape feeding: normal/reverse bi-directional feeding Magnetic head: normal direction recording/reproducing head 10b(F) ... inserted through window 9d reverse direction recording/reproducing head 10b(R) ... inserted through window 9b normal direction erasing head 10c(F) ... inserted through window 9e reverse direction erasing head 10c(R) ... inserted through window 9a Rotary encoder: normal/reverse bi-directional rotary encoder 12 ... inserted through window 9c Accordingly, when the magnetic tape 1 is fed in the normal direction. the normal/reverse bi-directional rotary encoder 12 is contacted with the magnetic tape 1 in the tape path between the magnetic head 10 (10b(F)) and the take-up reel 3, but when the magnetic tape 1 is fed in the reverse direction, the normal/reverse bi-directional rotary encoder 12 is contacted with the magnetic tape 1 in the tape path between the magnetic head 10 (10b(R)) and the supply reel 2 which functions as a take-up reel when the magnetic tape 1 is fed in the reverse direction. <Arrangement 14 (Fig. 31)> Recording medium: micro cassette tape Tape feeding: normal/reverse bi-directional feeding Magnetic head: normal direction erasing/recording/ reproducing head 10a(F) ... inserted through window 9d reverse direction erasing/recording/reproducing head 10a(R) ... inserted through window 9b Rotary encoder: normal/reverse bi-directional rotary encoder 12 ... inserted through window 9c Accordingly, when the magnetic tape 1 is fed in the normal direction, the normal/reverse bi-directional rotary encoder 12 is contacted with the magnetic tape 1 in the tape path between the magnetic head 10 (10a(F)) and the take-up reel 3, but when the magnetic tape 1 is fed in the reverse direction, the normal/reverse bi-directional rotary encoder 12 is contacted with the magnetic tape 1 in the tape path between the magnetic head 10 (10a(R)) and the supply reel 2 which functions as a take-up reel when the magnetic tape 1 is fed in the reverse direction. <Arrangement 15 (Fig. 32)> Recording medium: micro cassette tape Tape feeding: one-directional feeding Magnetic head: erasing/recording/reproducing head 10a ... inserted through window 9b Rotary encoder: rotary encoder 12 ... inserted through window 9a Accordingly, the rotary encoder 12 is contacted with the magnetic tape 1 in the tape path between the magnetic head 10 and the take-up reel 3. Further, in this instance, the location of contact is in the proximity of one of the guide rollers 5 (refer to Fig. 36). <Arrangement 16 (Fig. 33) > Recording medium: micro cassette tape Tape feeding: one-directional feeding Magnetic head: recording/reproducing head 10b ... inserted through window 9b erasing head 10c ... inserted through window 9d Rotary encoder: rotary encoder 12 ... inserted through window 9a Accordingly, the rotary encoder 12 is contacted with the magnetic tape 1 in the tape path between the magnetic head 10 and the take-up reel 3. Further, in this instance, the location of contact is in the proximity of one of the guide rollers 5 (refer to Fig. 36). <Arrangement 17 (Fig. 34)> Recording medium: micro cassette tape Tape feeding: one-directional feeding Magnetic head: recording/reproducing head 10b ... inserted through window 9b erasing head 10c ... inserted through window 9d Rotary encoder: rotary encoder 12 ... inserted through window 9c Accordingly, the rotary encoder 12 is contacted with the magnetic tape 1 in the tape path between the magnetic head 10 (erasing head 10c) and the take-up reel 3. Further, in this instance, the location of contact is between the recording/reproducing head 10b and the erasing head 10c. As described above. the rotary encoder 12 (or 12(F) or 12(R)) is either contacted with the magnetic tape 1 in the tape path section between the magnetic head 10 and the take-up reel 3 (supply reel 2 upon feeding in the reverse direction), that is, in the section in which tension of a certain magnitude is obtained irrespective of the magnitude of back tension provided by the supply side reel, or contacted with the magnetic tape 1 with the magnetic tape 1 held between the rotary encoder 12 and the pad 6. Consequently. a good contacting condition (good in contacting force and contacting area) is obtained between the roller 12a of the rotary encoder 12 and the magnetic tape 1, and a slip can be eliminated from occurring between the roller 12a and the magnetic tape 1. Accordingly, accurate tape feeding speed information can be obtained. Where, in addition to the arrangement and construction described above, the position at which the rotary encoder 12 is inserted into the tape cassette is set to a position in the proximity of one of the guide rollers 5 where good tape tension is obtained as in the arrangement 11, 12 or 16, a good contacting condition can be obtained. Also where the rotary encoder 12 is inserted into the tape cassette between the recording/reproducing head 10b and the erasing head 10c as in the arrangement 17 described above, a good contacting condition can be assured similarly. It is to be noted that naturally the present invention can be applied not only to the arrangements described above but also to various arrangements and can be applied widely to recording apparatus constructed only for recording, reproducing apparatus constructed only for reproduction, recording and reproducing apparatus and so forth which use a recording medium such a compact cassette tape, a micro cassette tape, an open reel tape, a digital audio tape or the like.

Claims: A controlling method for a reel motor of a recording and/or reproducing apparatus which includes no capstan and no pinch roller and wherein a rotatable member (12a) is contacted with a recording medium in the form of a tape (2) to measure a period of rotation of said member and a reel is driven to rotate by a reel motor in accordance with the period of rotation thus measured, characterised by comprising the steps of: measuring (F501) upon starting of feeding of the tape-formed recording medium, a 1/n rotation period T of said member by rotation detection means (12), n being a natural number larger than 1, and changing over (F301) an effective servo system to a first servo system (41, 42) which calculates (F502) a deviation d in accordance with the thus calculated 1/n rotation period; servo controlling (F505, F506), said reel motor in accordance with the thus calculated deviation d; determining (F303) whether or not said member has rotated one rotation; changing over (F304), in response to determination of one rotation of said member, the effective servo system to a second servo system (21, 22) which calculates a deviation d in accordance with a whole rotation period measured (F401) by said rotation detection means (12); and servo controlling (F405, F406) said reel motor in accordance with the thus calculated deviation d. A controlling method according to claim 1, wherein the step of servo controlling said reel motor in accordance with the deviation d calculated in accordance with the 1/n rotation period includes the steps of: measuring (F501) a 1/n rotation period T/n of said roller by said rotation detection means; calculating (F502) a deviation d from the 1/n rotation period T/n obtained at the measurement step and a predetermined rated period T ⊘25 ; calculating (F503) a servo control value L N for a present control cycle from the thus calculated deviation d, a gain coefficient K, a control constant A and a servo control value L in the last control cycle; storing (F504) the thus calculated servo control value L N for the present control cycle as a servo control value L in the last control cycle; converting (F505) the thus stored servo control value L into a PWM signal; and controlling (F506) driving of said reel motor (11) in response to the PWM signal obtained by the conversion. A method according to claim 1 or 2, wherein the step of servo controlling said reel motor (11) in accordance with the deviation d calculated in accordance with the one rotation period includes the steps of: measuring (F401) a one rotation period T by said rotation detection means; measuring (F402) a deviation d from the one rotation period T obtained at the measurement step and a predetermined rated period T ⊘25 ; calculating (F403) a servo control value L n for a present control cycle from the thus calculated deviation d, a gain coefficient K, a control constant A and a servo control value L in the last control cycle; storing (F404) the thus calculated servo control value L N for the present control cycle as a servo control value L in the last control cycle; converting (F405) the thus stored servo control value L into a PWM signal; and controlling (F406) driving of said reel motor in response to the PWM signal obtained by the conversion. A method according to any one of claims 1 to 3, further comprising the steps of: determining (F802) a loaded condition of a cassette; determining (F803) whether the power source is on or off; determining (F804) whether or not the tape is being fed; executing, when it is determined that the tape is being fed, servo control in accordance with the deviation; and storing (F801) an initial value into said storage means when it is detected that no cassette is loaded or the power source is off. A controlling method for a reel motor according to claim 1, 2, 3 or 4, wherein the step of detecting a whole period of rotation includes the steps of measuring (F1101) a 1/n rotation period, n being a natural number, successively storing (F1102-F1105) the last n measured values obtained by n measurements of a one rotation period, and adding (F1106) the n stored measured values to calculate a one rotation period.

Inventors: NAKANO YOSHITOMO, SHIMIZU KUNIO, NAKANO, YOSHITOMO, SHIMIZU, KUNIO
Applicants: SONY CORP, SONY CORPORATION
Application year: 1993
Main classification: G11B15
IPC codes: G11B15