Disc record/reproduce apparatus with brushless motor having rotational speed controlled by a disc

Abstract

A disc record/reproduce apparatus with a brushless dc motor having no separate dedicated position sensor, controls rotation of the dc synchronous motor by back-electromotive force signals developed in windings of the brushless dc motor using a/d converter included in one-chip microprocessor in the first mode, and controls by position and index signals recorded on the disc in the second mode. During start-up, a start-up oscillator is used. The control with a back-electromotive force signal is provided to enable the microprocessor to write a position signal on a disc and provided for inspecting the brushless dc motor independently. In the second mode, functions for executing the back-electromotive force control in the microprocessor is disabled during recording and reproducing of data to prevent overload on the microprocessor which is busy because of communication with an external computer and control of head position.

What is claimed is: 
     
       1. A disc record/reproduce apparatus for recording/reproducing data on/from a sector of a record disc, said disc record/reproduce apparatus having a brushless dc motor for rotating said record disc, said brushless dc motor having a plurality of windings, comprising: (a) drive means responsive to phase signals and an electric power for producing drive signals supplied to the windings of said brushless dc motor respectively to rotate said record disc;   (b) back-electromotive force signal producing means responsive to back-electromotive forces of at least two of said windings of said brushless dc motor for producing back-electromotive force signals;   (c) read/write head means for reading data including a second position signal recorded at every sector from said record disc, the number of said windings and said sector having a given relation therebetween;   (d) microprocessor means including: (I) a/d-converting means responsive to said back-electromotive force signals for converting said back-electromotive force signals into digital back-electromotive force signals;   (II) first position signal detecting means responsive to said digital back-electromotive force signals for producing a first position signal of said brushless dc motor;   (III) start-up clock signal producing means for producing a start-up clock signal;   (IV) start-up detection means responsive to one of said digital back-electromotive force signals for comparing one of said digital back-electromotive force signals with a given intensity value to produce a start-up switching signal;   (V) first switching means responsive to said start-up switching signal for selecting between said start-up clock signal and a third position signal;   (VI) phase signal producing means responsive to an output of said first switching means for producing said phase signals;   (VII) second position signal detecting means responsive to said data read from said record disc for detecting said second position signal;   (VIII) second switching means responsive to a second switching signal for selecting between said first position signal and said second position signal to output as said third position signal;   (IX) speed signal producing means responsive to said third position signal for producing a speed signal in accordance with an interval of succeeding pulses of said third position signal;   (X) comparing means for comparing said speed signal with a second given value to produce a lock-up signal;   (XI) control means for recording/reproducing said data in response to a record command signal including said data and to a reproduce command signal from an external computer, and for causing said a/d-converting means, said first position signal detection means, and said start-up detection means to be disabled in response to said lock-up signal and then producing said second switching signal to select said second position signal as said third position signal in order to prevent overload in processing speed of said microprocessor means; and     (e) speed control means responsive to said speed signal for controlling a speed of said brushless dc motor by controlling said electric power.   
     
     
       2. A disc record/reproduce apparatus as claimed in claim 1, further comprising: disc detection means responsive to the presence of said disc at a given position for producing a disc detection signal;   wherein said control means is further responsive to said disc detection signal for producing said second switching signal to cause said second switching means to output said first position signal as said third position signal in the absence of said record disc.   
     
     
       3. A disc record/reproduce apparatus as claimed in claim 1, further comprising: (a) head positioning means responsive to a positioning signal for positioning said read/write head at a desired track by moving an arm to which said read/write head is provided;   (b) head fixing means having: a permanent magnet fixed on a chassis of said disc record/reproduce apparatus; and   a magnetic plate fixed on said arm; said permanent magnet fixing said read/write head at given position in response to access of said magnetic plate thereto; and     (c) power supply control means responsive to a power save signal for cutting off power supply to said head positioning means; wherein said control means produces said second switching signal to select said first position and produces said power save signal and then produces said positioning signal to cause said positioning means to position said read/write head such that said permanent magnet attracts said magnetic plate, in order to save electric power consumption at said head positioning means.     
     
     
       4. A disc record/reproduce apparatus as claimed in claim 3, further comprising: pulse detection means responsive to an output of said read/write head and said power supply for producing a pulse signal indicative of said data and for sending it to said control means in the presence of said power supply; wherein said second position signal detection means further responds to said power supply to save electric power consumption thereof.   
     
     
       5. A disc record/reproduce apparatus as claimed in claim 1, further comprising: (a) first index signal detection means responsive to one of said digital back-electromotive force signals for producing a first index signal; and   (b) second index signal detection means responsive to said data read from said record disc for detecting a second index signal included in said data at every rotation of said record disc;   wherein said control means, in response to a position-signal-write command from said external computer, produces said second switching signal to cause said second switching means to select said first position signal as said third position signal, produces a position-signal write signal to write said second position signal on said record disc in response to said first position signal, and produces an index-signal write signal to write said second index signal on said record disc in response to said first index signal.   
     
     
       6. A disc record/reproduce apparatus as claimed in claim 1, further comprising: (a) head positioning means responsive to a positioning signal for positioning said read/write head at a desired track by moving an arm to which said read/write head is provided;   (b) head fixing means having: a permanent magnet fixed on said arm; and   a magnetic plate fixed on a chassis of said disc record/reproduce apparatus;   said permanent magnet fixing said read/write head at given position in response to access of said magnetic plate thereto; and     (c) power supply control means responsive to a power save signal for cutting off power supply to said head positioning means;   wherein said control means produces said second switching signal to select said first position and produces said power save signal and then produces said positioning signal to cause said positioning means to position said read/write head such that said permanent magnet attracts said magnetic plate, in order to save electric power consumption at said head positioning means.   
     
     
       7. A disc record/reproduce apparatus as claimed in claim 6, further comprising: pulse detection means responsive to an output of said read/write head and said power supply for producing a pulse signal indicative of said data read from said record disc and for sending it to said control means in the presence of said power supply; wherein said second position signal detection means further responds to said power supply to save electric power consumption thereof.   
     
     
       8. A disc record/reproduce apparatus for recording/reproducing data on/from a sector of a record disc, said disc record/reproduce apparatus having a brushless dc motor for rotating said record disc, said brushless dc motor having a plurality of windings, comprising: (a) drive means responsive to phase signals and an electric power for producing drive signals supplied to the windings of said brushless dc motor respectively to rotate said record disc;   (b) back-electromotive force signal producing means responsive to back-electromotive forces of at least two windings of said brushless dc motor for producing back-electromotive force signals, said back-electromotive force signal producing means being substantially directly connected to said winding;   (c) read/write head means for reading data including a second position signal recorded at every sector from said record disc, the number of said windings and said sector having a given relation therebetween;   (d) first position signal detecting means responsive to said back-electromotive force signals for producing a first position signal of said brushless dc motor;   (e) start-up clock signal producing means for producing a start-up clock signal;   (f) start-up detection means responsive to one of said back-electromotive force signals for comparing one of said back-electromotive force signal with a given intensity value to produce a start-up switching signal;   (g) first switching means responsive to said start-up switching signal for selecting one of said start-up clock signal and a third position signal;   (h) phase signal producing means responsive to an output of said first switching means for producing said phase signals;   (i) second position signal detecting means responsive to said data read from said record disc for detecting said second position signal;   (j) second switching means responsive to a second switching signal for selecting one of said first position signal and said second position signal to output as said third position signal;   (k) speed signal producing means responsive to said third position signal for producing a speed signal in accordance with an interval of succeeding pulses of said position signal;   (l) comparing means for comparing said speed signal with a second given value to produce a lock-up signal;   (m) control means for producing said second switching signal to select said second position signal as said third position signal in response to said lock-up signal; and   (n) speed control means responsive to said speed signal for controlling a speed of said brushless dc motor by controlling said electric power.   
     
     
       9. A disc record/reproduce apparatus as claimed in claim 8, further comprising: (a) command detection means responsive to an external computer for detecting whether a command from said external computer is absent for a given interval;   (b) head positioning means responsive to a positioning signal for positioning said read/write head at a desired position by moving an arm to which said read/write head is provided;   (c) head fixing means having: a permanent magnet fixed on a chassis of said disc reproduce apparatus; and   a magnetic plate fixed on said arm;   said permanent magnet fixing said read head at a given position in response to access of said magnetic plate thereto; and     (d) power supply control means responsive to a power save signal for cutting off power supply to at least a portion of said head positioning means and to said second speed signal producing means;   wherein said control means produces said second switching signal to select said first position signal as said third position signal and produces said power save signal and then produces said positioning signal to cause said head positioning means to position said read/write head such that said permanent magnet attracts said magnetic plate, in order to save electric power consumption at said head positioning means.   
     
     
       10. A disc record/reproduce apparatus as claimed in claim 8, further comprising: (a) first index signal detection means responsive to one of said digital back-electromotive force signals for producing a first index signal; and   (b) second index signal detection means responsive to said data read from said record disc for detecting a second index signal included in said data at every rotation of said record disc;   wherein said control means, in response to a position-signal-write command from an external computer, produces said second switching signal to cause said switching means to select said first position signal as said third position signal, produces a position-signal write signal to write said second position signal on said record disc in response to said first position signal, and produces an index-signal write signal to write said second index signal on said record disc in response to said first index signal.   
     
     
       11. A disc record/reproduce apparatus as claimed in claim 8, further comprising a/d converting means responsive to said back-electromotive force signals for converting said back-electromotive force signals into digital signals, said back-electromotive force signals being produced substantially directly by the windings of said brushless dc motor, said a/d converting means being substantially directly connected to said windings. 
     
     
       12. A disc record/reproduce apparatus as claimed in claim 10, wherein said control means operates to cause said a/d-converting means, said first position signal detection means, and said start-up detection means to be disabled in response to said lock-up signal in order to prevent overload in processing speed of said microprocessor means. .Iadd. 
     
     
       13.  A method for controlling rotational speed of a rotational disc drive to drive a recording disc at a predetermined speed, the disc drive including: a brushless dc motor for rotating the disc, the brushless dc motor having a plurality of windings; a recording/reproducing head for recording/reproducing data on/from a sector of a recording disc having a plurality of sectors; an electrical circuit connected to the recording/reproducing head, and switching means for switchably selecting a control mode for controlling a rotational speed of the brushless dc motor; comprising the steps of: a) feeding a start signal to the plurality of windings for rotating the brushless dc motor;   b) detecting a start of rotation of the brushless dc motor by detecting a back electromotive force generated in the windings;   c) switchably selecting a first control mode for controlling rotational speed of the brushless dc motor responsively to said back electromotive force;   d) detecting whether or not said rotational speed of the brushless dc motor has reached a predetermined value;   e) upon detecting that said rotational speed has reached said predetermined value, switchably selecting a second control mode for controlling said rotational speed of the brushless dc motor responsively to signals recorded on the disc;   f) detecting presence and absence of a record/reproduce command from an external computer to the disc drive;   g) upon detecting absence of said record/reproduce command, fixing the record/reproduce head to a predetermined head position, switchably selecting said first control mode, and cutting off power supply to the electrical circuit connected to the recording/reproducing head. .Iaddend..Iadd.   
     
     
       14.  A method for controlling rotational speed of a rotational disc drive as claimed in claim 13, wherein said step of detecting presence and absence of a record/reproduce command comprises the steps of: setting a timer to a predetermined time interval;   resetting said timer upon each detection of said command; and   determining that said command is absent responsive to an indication by said timer of expiration of said predetermined time interval. .Iaddend..Iadd.15. A method for controlling rotational speed of a rotational disc drive as claimed in claim 13, wherein the electrical circuit connected to the recording/reproducing head comprises a head positioning means, and said step of cutting off power supply comprises cutting off power supply to said head positioning means.   
     
     
        .Iaddend..Iadd.     A method for controlling rotational speed of a rotational disc drive as claimed in claim 13, wherein said step of switchably selecting said first control mode comprises selecting a first phase signal producing means for producing phase signals responsively to said back electromotive force, and said step of switchably selecting said second control mode comprises selecting a second phase signal producing means for producing phase signals responsively to sector signals recorded on the disc, and comprising the further step of applying phase signals produced by the selected one of said first and second phase signal producing means to a drive means for supplying drive signals to the windings of the brushless   
     
     
        dc motor. .Iaddend..Iadd.17.  A disc recording/reproducing control apparatus for controlling rotational speed of a rotational disc drive to drive a recording disc at a predetermined speed, the disc drive including: a brushless dc motor for rotating the disc, the brushless dc motor having a plurality of windings; a recording/reproducing head for recording/reproducing data on/from a sector of a recording disc having a plurality of sectors; an electrical circuit connected to the recording/reproducing head, and switching means for switchably selecting a control mode for controlling a rotational speed of the brushless dc motor; wherein the control apparatus comprises: a) feeding means for feeding a start signal to the plurality of windings for rotating the brushless dc motor;   b) first detecting means for detecting a start of rotation of the brushless dc motor by detecting a back electromotive force generated in the windings;   c) first selecting means for switchably selecting a first control mode for controlling rotational speed of the brushless dc motor responsively to said back electromotive force;   d) second detecting means for detecting whether or not said rotational speed of the brushless dc motor has reached a predetermined value;   e) second selecting means, responsive to said second detecting means detecting that said rotational speed has reached said predetermined value, for switchably selecting a second control mode for controlling rotational speed of the brushless dc motor responsively to signals recorded on the disc;   f) third detecting means for detecting presence and absence of a record/reproduce command from an external computer to the disc drive; and   g) response means, responsive to said third detecting means detecting absence of said record/reproduce command, for fixing the record/reproduce head to a predetermined head position, switchably selecting said first control mode, and cutting off power supply to the electrical circuit   
     
     
        connected to said recording/reproducing head. .Iaddend..Iadd.18.  A disc recording/reproducing control apparatus as recited in claim 17, wherein said apparatus further includes timer means, and said third detecting means comprises: means for setting said timer to a predetermined time interval and for resetting said timer upon each detection of said command; and wherein   said third detecting means determines that said command is absent responsive to an indication by said timer of expiration of said predetermined time interval. .Iaddend..Iadd.19. A disc recording/reproducing control apparatus as recited in claim 17, wherein the electrical circuit connected to the recording/reproducing head comprises a head positioning means, and said response means comprises means for cutting off power supply to said head positioning means. .Iaddend..Iadd.20. A disc recording/reproducing control apparatus as recited in claim 17, wherein said first selecting means comprises a first phase signal producing means for producing phase signals responsively to said back electromotive force, and   said second selecting means comprises a second phase signal producing means for producing phase signals responsively to sector signals recorded on the disc, and   comprising further means for applying phase signals produced by a selected one of said first and second phase signal producing means to a drive means for supplying drive signals to the windings of the brushless dc motor.   
     
     
        .Iaddend..Iadd.21.  A disc recording/reproducing apparatus for recording/reproducing data and a position signal on/from a record disc through a recording/reproducing head provided thereto, said disc recording/reproducing apparatus having a brushless motor including a rotor for rotating said record disc, and circuits connected to said recording/reproducing head, comprising: (a) positional signal producing means for producing a first positional signal from a position signal reproduced by said recording/reproducing head;   (b) position detection means connected to said brushless motor for detecting a position of said rotor thereof to produce a second positional signal representative of said position of said rotor;   (c) starting means responsive to supply of electric power to said disc recording/reproducing apparatus for starting of rotation of said brushless motor;   (d) start up detection means responsive to said starting means for detecting whether a rotational speed of said brushless motor has reached a predetermined value;   (e) command detection means for detecting presence and absence of a record/reproduce command to said recording/reproducing apparatus;   (f) head locking means for locking said recording/reproducing head to a predetermined position;   (g) power supplying means for supplying electric power to said circuits; and   (h) control means responsive to said start up detection means for effecting:   a first mode when said command detection means detects the presence of a recording/reproducing command for a predetermined time interval, wherein said power supplying means supplies said electric power to said circuits and said rotational speed of said brushless motor is controlled by said first positional signal; and   a second mode when said command detection means detects the absence of said recording/reproducing command for said predetermined time interval wherein said rotational speed of said brushless motor is controlled by said second positional signal, said head locking means locks said recording/reproducing head to said predetermined position and said power supplying means cuts off said electric power to said circuits. .Iaddend.