Abstract:
A tray loading apparatus includes a tray, a motor, a drive circuit. The tray is movable between a load position and an unload position. The motor is constructed and arranged for bringing the tray to move from the unload position to the load position. The drive circuit is used for apply a loading voltage to the motor and the loading voltage includes at least one gradually increasing stage. A tray unloading apparatus and an optical disc drive are also provided.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to optical disc drives and, more particularly, to a tray loading/unloading apparatus of an optical disc drive. 
   2. Description of Related Art 
   Optical disc drives, such as video compact disc (VCD) players, digital versatile disc (DVD) players, or computer data disc reading/writing drives are widely used for recording information onto and/or reproducing information from discs. 
   Most optical disc drives use trays to load and unload discs. As shown in  FIG. 7 , a traditional optical disc drive  10  includes a tray  12 , a set of gears  14 , and a motor  16 . The motor  16  connects to the set of gears  14  via a belt  18 . The set of gears  14  meshes with a gear rack  122  formed on the tray  12 . 
   The motor  16  drives the set of gears  14  to rotate via the belt  18 , so as to bring the tray  12  to move linearly between a load position and an unload position. When the tray  12  is ejected out of the traditional optical disc drive  10  to the unload position, an optical disc (not shown) can be placed on/removed from the tray  12 . When the tray  12  is inserted to the load position, the traditional optical disc drive  10  can reproduce/record information from/on the optical disc. 
   A moving speed of the tray  12  is determined by a rotational speed of the motor  16 , and the rotational speed of the motor  16  is controlled by a voltage fed to the motor  16 . In other words, the voltage determines the moving speed of the tray  12 . Referring also to  FIG. 8 , a constant voltage is applied to drive the motor  16 . In order to shorten a(n) loading/unloading time, the constant voltage is usually set to a relatively high voltage value. When the optical disc drive  10  starts loading the tray  12  from the unload position, the voltage applied to the motor  16  increases from zero to a relatively high voltage value instantaneously. Thus the motor  16  accelerates to a high rotational speed in a very short time, this may produce unwanted vibrations on the tray  12 . Similarly, during the end of an unload process, the constant voltage is terminated instantaneously when the tray  12  reaches the unload position. Vibrations may also occur as the tray  12  stops instantly from a high speed in a short time. 
   Therefore, a loading/unloading apparatus which is capable of reducing the unwanted vibrations is desired. 
   SUMMARY OF THE INVENTION 
   A tray loading apparatus includes a tray, a motor, a drive circuit. The tray is movable between a load position and an unload position. The motor is constructed and arranged for bringing the tray to move from the unload position to the load position. The drive circuit is used for apply a loading voltage to the motor and the loading voltage includes at least one gradually increasing stage. 
   A tray unloading apparatus includes a tray, a motor, a drive circuit. The tray is movable between a load position and an unload position. The motor is constructed and arranged for bringing the tray to move from the load position to the unload position. The drive circuit is used for apply an unloading voltage to the motor and the unloading voltage includes at least one gradually decreasing stage. 
   An optical disc drive includes a tray, a motor, a drive circuit, and a control circuit. The tray is movable between a load position and an unload position. The motor is used for driving the tray to move between the load position and the unload position. The drive circuit is used for outputting a voltage to drive the motor. The control circuit is used for sending commands to the drive circuit to control the voltage applied to the motor, wherein the voltage comprise at least one gradually increasing stage when loading the tray and at least one gradually decreasing stage when unloading the tray. 
   Other advantages and novel features will become more apparent from the following detailed description of preferred embodiments when taken in conjunction with the accompanying drawings, in which: 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Many aspects of the tray loading/unloading apparatus can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disc drive. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
       FIG. 1  is a schematic diagram of an optical disc drive in accordance with an exemplary embodiment, the optical disc drive including a motor; 
       FIG. 2  is a schematic diagram showing a first embodiment of a waveform of a loading voltage applied to the motor of  FIG. 1 ; 
       FIG. 3  is a schematic diagram showing a second embodiment of a waveform of a loading voltage applied to the motor of  FIG. 1 ; 
       FIG. 4  is a schematic diagram showing a third embodiment of a waveform of a loading voltage applied to the motor of  FIG. 1 ; 
       FIG. 5  is a schematic diagram showing a first embodiment of a waveform of an unloading voltage applied to the motor of  FIG. 1 ; 
       FIG. 6  is a schematic diagram showing a second embodiment of a waveform of an unloading voltage applied to the motor of  FIG. 1 ; 
       FIG. 7  is a plan view of a traditional optical disc drive, the traditional optical disc drive including a motor; and 
       FIG. 8  is a schematic diagram showing a constant voltage applied to the motor of  FIG. 7 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Reference will now be made to the drawings to describe the preferred embodiment of the present tray loading/unloading apparatus, in detail. 
   Referring to  FIG. 1 , an optical disc drive  20  includes a tray  22 , a set of gears  24 , a motor  26 , a switch  28 , a control circuit  30 , and a drive circuit  32 . The set of gears  24  meshes with a gear rack  222  formed on one side of the tray  22 . The motor  26  drives the tray  22  to linearly move between two positions by engaging with the set of gears  24  therebetween. The two positions include an unload position at which an optical disc can be placed on or removed from the tray  22  and a load position at which a recording and reproducing process can start. 
   The drive circuit  32  is coupled to the control circuit  30  for outputting a loading voltage for driving the tray  22  to move toward the load position and an unloading voltage for driving the tray  22  to move toward the unload position. Both the loading voltage and the unloading voltage are variable. Values of the loading voltage and the unloading voltage determine a rotational speed of the motor  16 . The control circuit  30  is constructed and arranged for sending commands to the drive circuit  32 , thus controlling the values of the loading voltage and the unloading voltage outputted by the drive circuit  32 . 
   The switch  28  is disposed in the optical disc drive  20  for generating signals to indicate whether the tray  22  has reached the load position or the unload position. That is, when the tray  22  reaches the load position, the switch  28  generates a first signal and transmits the first signal to the control circuit  30 . Upon receiving the first signal, the control circuit  30  controls the drive circuit  32  to stop outputting the loading voltage, so as to stop moving the tray  22 . Contrarily, when the tray  22  reaches the unload position, the switch  28  generates a second signal and the second signal is transmitted to the drive circuit  32  so as to stop outputting the unloading voltage. 
     FIG. 2  shows a waveform W 1  of the loading voltage in accordance with a first embodiment. The waveform W 1  includes a first increasing stage L 1 , a second increasing stage L 2 , and a third constant stage L 3 . 
   The first increasing stage L 1  represents an increasing voltage applied to the motor  26  initially. At a first beginning point A of the first increasing stage L 1 , the voltage value outputted by the drive circuit  32  is VA. The voltage value VA is a minimum voltage that can drive the motor  26  to start rotating. Typically, the voltage value VA is 140.625 mV. Since the voltage value VA is relatively low, the motor  26  rotates at a relatively low speed and the tray  22  moves smoothly. 
   The first increasing stage L 1  includes multiple first steps, each representing a loading voltage value. A length of each first step represents a first time interval ΔT 1  of each first step. A height between two adjacent first steps represents a first increment ΔV 1  of the loading voltage value. During the first increasing stage L 1 , the loading voltage value increases by the first increment ΔV 1  after each first time interval ΔT 1 . The loading voltage value remains constant during each of the first time interval ΔT 1 . Thus the rotational speed of the motor  26  increases in steps, and a moving speed of the tray  22  increases in steps accordingly. Optimally, the first increment ΔV 1  is configured to be large enough to drive the motor  26  to accelerate at a proper acceleration so as to increase the moving speed of the tray  22 , but small enough to prevent the tray  22  to vibrate. The tray  22  will move smoothly without heavy collision or vibrations, as there are no sudden high accelerations. 
   N 1  denotes the number of the first steps in the first increasing stage L 1 . During the first increasing stage L 1 , a total loading voltage increment is N 1 ·ΔV 1 . At a first end point B of the first increasing stage L 1 , the loading voltage VB is VA+N 1 ·ΔV 1 . Preferably, the first time interval ΔT 1  is 10 ms, the number of the first steps N 1  is set to 5, and the first increment ΔV 1  is 15.625 mV. The values of ΔT 1 , N 1  and ΔV 1  can be changed according to different optical disc drives. 
   After the first increasing stage L 1 , the second increasing stage L 2  of the loading voltage is applied to the motor  26 . Similarly, the second increasing stage L 2  includes many second steps. A length of each second step in the second increasing stage L 2  is identified as a second time interval ΔT 2 . An increment of the loading voltage between each adjacent second steps in the second increasing stage L 2  is identified as a second increment ΔV 2 . N 2  denotes the number of the second steps in the second increasing stage L 2 . 
   Each of the second time intervals ΔT 2  is longer than each of the first time intervals ΔT 1 , and the second loading voltage increments ΔV 2  approximately equal to the first increments ΔV 1 . The moving speed of the tray  22  increases in steps as the loading voltage increases. 
   The second increasing stage L 2  begins at the first end point B of the first increasing stage L 1  and ends at the second end point C. A total loading voltage increment during the second increasing stage L 2  is N 2 ·ΔV 2 . At the second end point C, the loading voltage VC is VB+N 2 ·ΔV 2 . Preferably, the second time interval ΔT 2  is set to 40 ms, the number of the second steps N 2  is set at 15, and the second increment ΔV 2  is configured to be 15.625 mV. As a result, the loading voltage increases to 234.375 mV during the second increasing stage L 2 . The values of ΔT 2 , N 2 , and ΔV 2  can be changed according to different optical disc drives as well. 
   After the second increasing stage L 2 , the third constant stage L 3  of the loading voltage is applied to the motor  26 . The loading voltage in the third constant stage L 3  is constant and remains at the voltage value VC. The tray  22  loads at a relatively high speed during the third constant stage L 3 . 
   When the tray  22  reaches the load position, the tray  22  triggers the switch  28  to generate the first signal to be transmitted to the control circuit  30 . The control circuit  30  controls the drive circuit  32  to stop outputting the loading voltage after receiving the first signal, so as to stop moving the tray  22 . 
     FIG. 3  shows a waveform W 2  of the loading voltage in accordance with a second embodiment. Compared with the waveform W 1  of  FIG. 2 , a decreasing stage M is added between the second increasing stage L 2  and the third stage L 3 . In the decreasing stage M, the loading voltage decreases linearly. As a result, the voltage of the third constant stage L 3  is lower than VC in the first embodiment. Thus the tray  22  moves at a relatively low speed when the tray  22  approaches the load position, and a sudden stop from a relatively high speed is avoided. 
   In other embodiments, the increasing or decreasing of the voltage can be implemented either linearly or in steps or a combination of both. As shown in  FIG. 4 , a waveform W 3  of a loading voltage in accordance with a third embodiment is illustrated. The increasing and decreasing of the loading voltage are both implemented linearly. 
   In the first stage L 1 , the drive circuit  32  outputs a gradually increasing voltage and vibrations of the tray  22  at the start of loading are thus reduced. At the end of the loading process, the voltage decreases, slowing down the moving speed of the tray  22  so as to reduce the vibrations. 
     FIG. 5  shows a waveform W 4  of the unloading voltage in accordance with a first embodiment. The waveform W 4  includes a first unloading constant stage U 1 , a second unloading decreasing stage U 2  and a third unloading constant stage U 3 . 
   The first unloading constant stage U 1  represents the unloading voltages applied to the motor  26  initially. At a second beginning point D of the first unloading constant stage U 1 , the unloading voltage value is VD. The tray  22  begins moving towards the unload position when the voltage VD is applied on the motor  26 . Optimally, the voltage value VD is a minimum voltage that can drive the motor  26  to start rotating so as to move the tray  22 . Typically, the voltage value VD is 421.875 mV. Since the unloading voltage is relatively low, the motor  26  rotates at a relatively low speed that will not cause vibrations. 
   During the first unloading constant stage U 1 , the unloading voltage remains at a constant voltage value VD. The constant voltage is kept for a first period T 1 . Typically, the first period T 1  is 920 ms. The values of T 1  and VD can be changed according to different optical disc drives. 
   After the first unloading constant stage U 1 , the second unloading decreasing stage U 2  of the unloading voltage is applied to the motor  26 . The second unloading decreasing stage U 2  consists of many third steps, and ΔT 3 , ΔV 3 , and N 3  denotes characteristics of the second unloading decreasing stage U 2 . ΔT 3  represents a third time interval. A first decrement ΔV 3  represents a decrement of the unloading voltage between each adjacent third steps in the second unloading decreasing stage U 2 . N 3  denotes the number of the third steps in the second unloading decreasing stage U 2 . 
   The second unloading decreasing stage U 2  starts at a third end point E and stops at a fourth end point F. During the second unloading decreasing stage U 2 , a total decrement of the unloading voltage is N 3 ·ΔV 3 . At the fourth end point F, the unloading voltage VF is VD−N 3 ·ΔV 3 . Preferably, the third time interval ΔT 3  is set at 80 ms, the number of the third steps N 3  is 8, and the third increment ΔV 3  is configured to be at 15.625 mV. As a result, the unloading voltage decreases 125 mV during the second unloading decreasing stage U 2 . The values of ΔT 3 , N 3 , and ΔV 3  can be changed according to different optical disc drives as well. 
   After the second unloading decreasing stage U 2 , the third unloading constant stage U 3  of the unloading voltage is applied to the motor  26 . The unloading voltage in the third unloading constant stage U 3  is constant and remains at the voltage value VF. The tray  22  unloads at a relatively low speed when the motor  26  is driven by the unloading voltage at the voltage value VF. 
   When the tray  22  reaches the unload position, the tray  22  triggers the switch  28  to generate the second signal to be transmitted to the control circuit  30 . The control circuit  30  controls the drive circuit  32  to stop outputting the unloading voltage based on the second signal, so as to stop moving the tray  22 . 
   After the first unloading constant stage U 1 , the unloading voltage applied to the motor  26  decreases gradually in the second unloading decreasing stage U 2 . Thus the moving speed of the tray  22  decreases gradually, so as to prevent the tray  22  from vibrating. During the third unloading constant stage U 3 , the unloading voltage remains at the voltage value VF and the unloading speed of the tray  22  remains at a lower speed accordingly. Thus the unloading process will not cause vibrations. 
   In other embodiments, as shown in  FIG. 6 , an unloading increasing stage U 0  is employed to increase the unloading speed of the tray  22 . The unloading speed increases gradually so as to maintain the stableness of the tray  22  when unloading starts. Furthermore, the second unloading decreasing stage U 2  lasts until the tray  22  reaches the unload position. 
   In the second unloading decreasing stage U 2 , the drive circuit  32  outputs a gradually decreasing voltage and vibrations of the tray  22  at the end of unloading are thus reduced. During the unloading increasing stage U 0 , the unloading voltage increases gradually so as to reduce the vibrations. 
   The embodiments described herein are merely illustrative of the principles of the present invention. Other arrangements and advantages may be devised by those skilled in the art without departing from the spirit and scope of the present invention. Accordingly, the present invention should be deemed not to be limited to the above detailed description, but rather by the spirit and scope of the claims that follow, and their equivalents.