A carriage servo unit in a disk player

Abstract: A carriage servo unit in a disk player comprises a pick up (117) for reading information recorded on a disk, a carriage (48) movable in a radial direction of the disk and carrying the pick-up, and a motor (51) for driving the carriage. Switching means (120) are provided for selectively applying a variable carriage drive voltage to the motor. Control means (114) control the switching means (120) to apply the drive voltage to the motor only when an absolute value of the drive voltage exceeds a predetermined voltage (V ref ).

Description: The present invention relates to a carriage servo unit in a disk player, and more particularly to a carriage servo unit which has switching means for selectively applying a variable drive voltage to the motor which drives the pick up carriage. JP-A-53-3138, taken into account for delimitation of the appendend claim 1, discloses an optical pickup driving device with drive voltage switching which employs tracking voltage monitoring to reduce power consumption. FR-A-2526200 discloses a bi-directional carriage servo motor. According to the present invention, there is provided a carriage servo unit in a disk player, comprising: a pick up for reading information recorded on a disk; a carriage movable in a radial direction of the disk and carrying the pick-up; a motor for driving the carriage; switching means for selectively applying a variable carriage drive voltage to the motor; and, control means for controlling the switching means, characterised in that: the control means applies the drive voltage to the motor only when an absolute value of the drive voltage exceeds a predetermined voltage. The present invention provides a carriage servo unit in which power consumption is reduced. Preferably, there is provided short-circuit means for selectively short-circuiting the motor, and the control means controls the short-circuit means to short-circuit the motor when the absolute value of the drive voltage is less than the predetermined voltage. The motor is thereby fixed so that the carriage is not troubled by any motion caused by external vibrations. In the drawings:- Fig. 1 is a block diagram showing the control system of the servo unit; Fig. 2 is a block diagram showing the construction of the carriage servo circuit of Fig. 1; and Fig. 3 is a waveform chart for explaining the circuit operations of Fig. 2. The present invention will now be described in connection with an auto-loading disk player with reference to the accompanying drawings. Fig. 1 shows a block diagram of a control system, in which the control circuit 111 is constructed of a micro computer having a built-in memory, for example. On the basis of the respective signals generated from the grouped control buttons 6, the respective detecting switches 104, 106, 108 and 110 and so on, the control circuit 111 drives a loading mechanism 112, a carriage mechanism 113, the spindle motor 46 and so on at timings to be described later. The carriage mechanism 113 and the spindle motor 46 are driven by the control circuit 111 through a carriage servo circuit 114 and a spindle servo circuit 115. The control circuit 111 also outputs display information to a display 116 for exhibiting a variety of displays. The control circuit 111 is fed with information read out from the disk by a pickup 117 after the information has been processed, e.g., demodulated by a signal processing circuit 118. The control circuit 111 further drives a solenoid plunger 83 through a drive circuit 119. Fig. 2 shows the circuity of the carriage servo circuit 114. As shown, a carriage drive voltage for driving the carriage motor 51 is fed to a bilateral drive circuit 122 through a loop switch 120 and an equalizer circuit 121. The bilateral drive circuit 122 drives the carriage motor 51 in both the forward and backward directions in accordance with the polarity of a drive voltage. This carriage drive voltage is used not only as a non-inverted input of a comparator COMP₁ referenced to the inverted value of a reference voltage +V ref but also as an inverted input of a comparator COMP₂ referenced to the negative reference voltage -V ref . These reference voltage +V ref and -V ref are set to correspond to the insensitive band of the carriage motor 51. The respective outputs of the comparators COMP₁ and COMP₂ become two inputs of an OR gate 123, which generates an output at a high level when the carriage drive voltage is higher than +V ref or lower than -V ref . The output of the OR gate 123 is fed to the loop switch 120 to provide both an on/off control signal for the loop switch 120 and an on/off control signal for a transistor Q acting as a short-circuit for short-circuiting the two ends of the motor 51 through an inverter 124 and a resistor R. In the carriage servo circuit 114 thus constructed, when the drive voltage is within the range from +V ref to -V ref , the output of the OR gate 123 is at a low level. Therefore, the loop switch 120 is turned off (or opened) to open the servo loop. As a result, within the range of the drive voltage from +V ref to -V ref , the bilateral drive circuit 122 receives no drive voltage so that current which is so small as to make no contribution to the start of the motor does not flow, as shown in Fig. 3. Thus, the power consumption can be reduced to the extent of the hatched portion of Fig. 3. At this time, the motor 51 has its two ends short-circuited by the transistor Q in its ON state to have its rotor fixed so that the carriage is not troubled by any motion caused by external vibrations. When the carriage drive voltage is higher than +V ref and lower than -V ref , on the other hand, the output of the OR gate 123 takes the high level so that the loop switch 120 is turned on (or closed) so that the drive of the motor 51 is effected in accordance with the polarity and level of the drive voltage. At this time, the transistor Q is left in its OFF state.

Claims: A carriage servo unit in a disk player, comprising: a pick up (117) for reading information recorded on a disk; a carriage (48) movable in a radial direction of the disk and carrying the pick-up; a motor (51) for driving the carriage; switching means (120) for selectively applying a variable carriage drive voltage to the motor; and, control means (114) for controlling the switching means; characterised in that: the control means (114) applies the drive voltage to the motor only when an absolute value of the drive voltage exceeds a predetermined voltage (V ref ). A unit according to claim 1, further comprising short-circuit means (Q) for selectively short-circuiting the motor, and wherein the control means (114) controls the short-circuit means (Q) to short-circuit the motor when the absolute value of the drive voltage is less than the predetermined voltage (V ref ). A unit according to claim 1 or claim 2, wherein the motor (51) is a bidirectional motor and the drive voltage is a bipolar voltage.

Inventors: ABE HIROYUKI PIONEER ELECRONIC, AOYAGI YOSHIO PIONEER ELECRONI, HAENO AKIRA PIONEER ELECRONIC, IIJIMA TAKAYUKI PIONEER ELECRO, KIMURA TOSHIYUKI PIONEER ELECR, KOBAYASHI KIMITO PIONEER ELECR, MATSUMOTO ISAO PIONEER ELECRON, NAGASHITA TSUNEYOSHI PIONEER E, NAMIKI AKIO PIONEER ELECRONIC, NIINUMA SUSUMU PIONEER ELECRON, NOMURA ISAMU PIONEER ELECRONIC, SHIMOKAWA KAZUTO PIONEER ELECR, WATANABE YOSHIHIKO PIONEER ELE, ABE, HIROYUKI, PIONEER ELECRONIC CORP., AOYAGI, YOSHIO, PIONEER ELECRONIC CORP., HAENO, AKIRA, PIONEER ELECRONIC CORP., IIJIMA, TAKAYUKI, PIONEER ELECRONIC CORP., KIMURA, TOSHIYUKI, PIONEER ELECRONIC CORP., KOBAYASHI, KIMITO, PIONEER ELECRONIC CORP., MATSUMOTO, ISAO, PIONEER ELECRONIC CORP., NAGASHITA, TSUNEYOSHI, PIONEER ELECRONIC CORP., NAMIKI, AKIO, PIONEER ELECRONIC CORP., NIINUMA, SUSUMU, PIONEER ELECRONIC CORP., NOMURA, ISAMU, PIONEER ELECRONIC CORP., SHIMOKAWA, KAZUTO, PIONEER ELECRONIC CORP., WATANABE, YOSHIHIKO, PIONEER ELECRONIC CORP.
Applicants: PIONEER ELECTRONIC CORP, PIONEER ELECTRONIC CORPORATION
Application year: 1986
Main classification: G11B7
IPC codes: G11B21, G11B27, G11B19, G11B17, G11B7