Abstract:
A direction reversing apparatus for a rotary motor of a microcassette tape transport includes a motor (14) having substantially the same characteristic for the forward and reverse motor rotation directions for driving a recording tape, and a motor controller (12) for setting a motor speed to a given speed. The reversing apparatus further includes a switch (16) coupled between the motor (14) and the motor controller (12) for reversing the direction of rotation of the motor (14).

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to apparatus for reversing a rotatory direction of a motor, which is used for an auto-reverse type microcassette tape recorder. 
     A stable rotation is required for a motor used in a tape deck, because the stability of rotation greatly influences the wow and flutter characteristics of the tape deck. To this end, a motor for a one-motor type reversible tape deck is generally provided with two servo circuits, one for a forward rotation and the other for a reverse rotation. The reason for this is that the rotary characteristic of the motor has a transfer function expressed by a ratio of a mechanical output to an electric input of the motor, which depends on the rotary direction of the motor. In view of assembling such servo systems into a miniature mechanism such as a microcassette deck, the two-servo system encounters a difficulty that a restricted space rejects its use. The employment of the two-servo system increases the occurence of troubles in the servo circuits and the number of adjusting steps, resulting in an increase of cost to manufacture. 
     A motor with much the same characteristics for both the forward and the reverse rotations of the motor has recently been developed and put into a practical use. Such a motor has found its application in a so-called direct drive motor (DD) widely used in disc players or tape recorders currently being marketed. As far as the inventor knows, a miniature type device such as a microcassette tape recorder never employed a motor rotation direction reversing circuit capable of controlling the motor equally well in both the forward and reverse directions by a single servo system. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the invention is to provide a motor rotation reversing apparatus for use in a microcassette recorder which is capable of controlling a motor rotation in a forward direction and a reverse direction by a single control circuit. 
     To achieve the above object of the invention, there is provided a motor rotation reversing apparatus comprising: a motor with the substantially the same characteristic for a forward rotation and reverse rotation, which drives a microcassette tape transport; a motor control means for setting a motor speed to a given value; and a switch means for switching the direction of a motor drive current, the switch means being disposed between the motor and the motor control means. 
     In the motor rotation reversing apparatus with such a construction, transfer functions, as complex functions expressed each by a ratio of a mechanical output of the motor to an electric input, are substantially the same for the forward rotation and the reverse rotation of the motor. Also, the transfer function of the motor control means is fixed in value. Therefore, the transfer function of a rotation control loop (servo loop) is invariable, irrespective of the direction of a motor rotation. This indicates that a rotation performance of the motor is the same for the forward rotation and the reverse rotation. This implies that only a one time adjustment of the motor speed is satisfactory for both the forward and reverse direction of the motor rotation. These useful features may be attained by the mere combination of a single motor and a single motor control circuit. The results from the use of the motor rotation reversing circuit of the present invention provide a miniaturization of the device size, a cost reduction of the device, and an improvement of the reliability of the device. 
     The above and other objects, and features, advantages and uses will be apparent as the description proceeds, when considered with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of a tape transport mechanism or an example of the structure of a tape transport deck to which the invention is applied; 
     FIG. 2 is a schematic diagram of an embodiment of a motor rotation reversing apparatus according to the invention; 
     FIG. 3 illustrates in block and circuit forms a modification of the motor rotation reversing apparatus shown in FIG. 2; 
     FIG. 4 illustrates in block and circuit forms a modification of the circuit shown in FIG. 3; and 
     FIG. 5 is a circuit diagram of a conventional motor controller used in the circuits shown in FIGS. 2 to 4. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Some preferred embodiments of the invention will be described referring to the accompanying drawings. In the description, like reference symbols designate like or equivalent portions or parts in the several views for simplicity of explanation. 
     Referring first to FIG. 1, there is shown a mechanism of a typical example of an auto-reverse tape transport of the center capstan type to which the invention is applied. The transport is for a microcassette. No elaboration of the transport mechanism will be given, with a mere description as to how a motor 14 to which the invention is applied is actually utilized. In FIG. 1, a capstan 15 driven by the motor 14 rotates uniformly in both clockwise and counterclockwise direction to draw the tape across record/playback heads 102A, 102B. For further details of the transport mechanism and its related electronic circuit, reference should be made to Japanese patent application Nos. 141616/&#39;78 corresponds to U.S. application Ser. No. 90,900 filed Nov. 5, 1979 now U.S. Pat. No. 4,309,727, issued Jan. 5, 1982) and 41601/&#39;79 (corresponds to U.S. application Ser. No. 134,064 filed Mar. 26, 1980 now U.S. Pat. No. 4,318,139, issued Mar. 2, 1982 assigned to the assignee (Olympus Optical Co. Ltd.) of the present patent application. 
     FIG. 2 shows an embodiment of the motor rotation reversing apparatus according to the invention. A first output terminal of a motor control circuit 12 supplied with power from a power source 10, is connected through a first contact a of a switch S1 to a first terminal of a motor 14. The motor control circuit 12 may be constructed by using model TCA955 speed regulator IC made by SIEMENS Co. Ltd. in West German, for example. The connection of the TCA955 with the motor 14 is described in detail in the application note published by this company. It is evident that the control circuit 12 is not limited to the TCA955. The motor suitable for the motor 14 is, for example, a DC servo motor with a frequency generator of which the forward and reverse characteristics are the same. Such a motor is, for example, model MMX-5 provided from Matsushita Electric Co. Ltd., Japan or model LS16-TA provided from Copal Electric Co. Ltd., Japan. 
     The second output terminal of the control circuit 12 is connected to the second terminal of the motor 14, through a first contact c of a switch S2. A second contact b of the switch S1 is connected to the first contact c of the switch S2 and a second contact d of the switch S2 is connected to the first contact a of the switch S1. The switches S1 and S2 are of the double gang two contact type (i.e., combined they form a double pole-double throw switch) and generally designated by reference numeral 16. The switch 16 is switched interlockingly with an operation mode switching mechanism of a tape deck transport shown in FIG. 1. For example, it is switched in a reverse or rewind mode. Upon the switching, the current direction of the current fed to the motor 14 is switched to the direction indicated by an arrow A or by an arrow B. With the switching of the current direction, the rotation direction of the motor 14 is reversed or inverted. 
     A servo detection signal e s  corresponding to a motor speed of the motor 14 has the number of pulses corresponding to the number of rotations of the motor 14. The servo system so operates as to fix the frequency of the pulse. When the transfer function of the motor 14 is substantially common for the forward and reverse rotations, reversing the rotation of the motor 14 by the switch 16 provides no change of the servo characteristic. 
     Referring to FIG. 3, there is shown a motor reversing circuit in which the switch 16 shown in FIG. 2 is replaced by an electronic switch. The first output terminal Q of a flip-flop 18 is connected to the bases of NPN transistors S10 and S30, by way of respective resistors R10 and R30. The second output terminal Q of the flip-flop 18 is connected to the bases of NPN transistors S20 and S40, via respective resistors R20 and R40. The emitters of the transistors S30 and S40 are connected to the second output terminal of the motor control circuit 12. The first output terminal of the motor control circuit 12 is connected to the collectors of the transistors S10 and S20. The emitter of the transistor S10 and the collector of the transistor S40 are connected to the first terminal of the motor 14. The second terminal of the motor 14 is connected to the emitter of the transistor S20 and the collector of the transistor S30. 
     The motor reversing circuit shown in FIG. 3 operates in the following manner. Assume that the flip-flop 18 is set at the time of a forward reproduction or playback. In this case, the flip-flop 18 has logical &#34;1&#34; at the first output terminal Q and logical &#34;0&#34; at the second output terminal Q. With these logical states of the outputs of the flip-flop 18, the transistors S10 and S30 are turned on while the transistors S20 and S40 are turned off. Current fed out of the first output terminal of the control circuit 12 flows in the direction of an arrow A, through the transistor S10, the motor 14 and the transistor S30. At this time, the motor 14 is in the forward rotation mode. 
     The reverse reproduction mode follows. In this case, the flip-flop 18 is reset and Q=&#34;0&#34; and Q=&#34;1&#34;. In turn, the transistors S20 and S40 are turned on while the transistors S10 and S30 are turned off. Then, the direction of the current flowing into the motor 14 as is indicated by an arrow B and reverses the rotation of the motor 14. 
     As seen from the foregoing, the motor reversing circuit according to the present invention can control the motor 14 in the same way in both the forward and reverse directions of rotation by using the single motor control circuit 12. 
     A modification of the embodiment in FIG. 3 is shown in FIG. 4. Although the FIG. 3 embodiment uses NPN type transistors for the switch transistors S10 to S40, the FIG. 4 embodiment uses combination of the NPN and PNP type transistors. In the forward rotation of the motor 14, logical levels &#34;1&#34; and &#34;0&#34; at the output terminals Q and Q of the flip-flop 18 turn on an NPN transistor S30 1  and a PNP transistor S10 1 . In the reverse rotation of the motor 14, logical levels &#34;0&#34; and &#34;1&#34; at the output terminals Q and Q turn on a PNP transistor S20 1 , and an NPN transistor S40 1 . In FIG. 4, a frequency generator 14 1  for generating the servo detection signal e s  and the motor 14 are separately illustrated. FIGS. 2 and 3 are illustrated on the assumption that the generator 14 1  is contained in the motor 14. The servo detection signal e s  may be obtained, with bridge-detection, by detecting power caused by a counter electromotive force of the armature in the motor 14, alternatively. 
     FIG. 5 shows a circuit diagram of the type device disclosed in the application note published by SIEMENS Co. In FIG. 5, there are illustrated the output terminals 1 and 2 of the control circuit 12 shown in FIGS. 2 to 4 and an input circuit of the servo detection signal e s . Note here that the constructions disclosed above do not limit the present invention, but may be modified and changed variously within the scope of the invention. For example, the double-gang two-contact type switch 16 shown in FIG. 2 may be substituted by an electronic switch (not shown) using a thyristor. Conversely, the switch circuits S10 to S40 may be replaced by a mechanical switch of four-gang type.