JPH0470713B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a drive circuit for a moving device that moves an optical pickup or the like using a differential transmission system.

[Conventional technology]

For optical discs, especially compact discs, the pitch between spiral tracks is 1.6 μm when using an optical pickup to reproduce information on the disc.
is extremely small, and the feed rate of the optical pick-up is 1
The speed is extremely slow at 10 μm per second, so in order to move the optical pickup stably, it is necessary to increase its speed reduction ratio. On the other hand, in order to access the disk to the desired track position at high speed, the pick-up must be fed at a high speed, for example, 10 seconds per second.
If you move an optical pickup in cm, there is a difference of 10 ⁴ times compared to when reading information, and when using a moving device designed with a large reduction ratio, it is difficult to perform high-speed access; If the reduction ratio is made small to enable high-speed feed, the speed during normal regeneration will be very low and will barely touch the starting voltage, resulting in unstable driving such as repeated stopping and starting.For this reason, for example, a differential transmission system moving device The present applicant has previously proposed a moving device in which an optical pickup is moved by means of an optical pickup. The specific structure of the above-mentioned pick-up moving device will be explained below with reference to FIGS. 3 to 5.

FIG. 3 is a schematic diagram showing the feeding mechanism of the pick-up moving device, and FIG. 4 is a plan view showing the pulley portion of FIG. 3. The optical pickup device 1 includes a moving table 2.
The movable table 2 is configured to slide along a guide rail 3 supported between the fixed parts. A rotary pulley 4 as shown in FIG. 2 is disposed on the movable table 2. As shown in FIG. That is, as shown in FIG. 4, the rotary pulley 4 is pivotally attached to a shaft 5 protruding from the movable table 2, and is composed of first and second drums 4a and 4b having the same diameter. Wires 7 and 6 are wound around the drums 4a and 4b, respectively. That is, one end of the wire 6 is hooked onto a pulley 8 fitted to the rotating shaft of the first motor _M1 , and then hooked onto a pulley 10 disposed on the opposite side of the first motor _M1 . The wire 6 is connected endlessly to the other end of the wire 6 wound around the wire 6. One end of the other wire 7 is hooked onto a pulley 9 fitted to the rotating shaft of the second motor _M2 , and then hooked onto a pulley 11 located on the opposite side of the second motor _M2 . Similarly, it is connected endlessly to the other end of the wire 7 wound around the drum 4a. Furthermore, in order to apply tension to the wires 6, 7, respectively, springs 12, 13 are interposed between the rotation shafts of the pulleys 10, 11 and the outer fixed portions, so that the pulleys 10, 11 are Tension is applied by biasing in the direction of arrow B in Figure 3. For this purpose,
The pulleys 10 and 11 are configured to be freely movable in the axial direction of the guide rail 3.

According to the above configuration, if pulley 8 and pulley 9
If the diameters of the pulleys 10 and 11 are equal, and the first motor _M1 and the second motor _M2 are rotating in the same direction, the entire pulley 4 rotates with respect to the shaft 5. However, the moving table 2 does not move in either direction along the guide rail 3. now,
If the first and second motors M ₁ and M ₂ are rotated at the same rotation speed and in opposite directions as shown by the arrows in FIG. Now, in Figure 3, move to the right. That is, the moving speed V of the moving table 2 is the rotational speed of the first motor _M1 .
V _M1 and the rotation speed V _M2 of the second motor M ₂ have the following relationship: V∞V _M1 −V _M2 (1).

Here, the rotational direction of the second motor _M2 is the same as that of the first motor M2.
If the opposite direction is positive for the motor _M1 , then V∞V _M1 +V _M2 (2), and the speed V is the sum of the rotational speeds of both motors. If the moving speed V of the moving platform 2 is constant, both motors M ₁ and M ₂ need to act differentially. Therefore, if both motors M ₁ and M ₂ are rotated at the same speed, the moving table 2 will move fastest and will be equal to the speed of the wires 6 and 7. Now the first motor M ₁ is 90%
If the speed is V _M1 + V _M2 , the former is 1 + 1
= 2, whereas the latter is 1-0.9 = 0.1, and the moving speed V is 1/20. The rotation ratio of both is 99
If you convert it to %, you will get 1/200 as the moving speed V.

An example of such a drive circuit is shown in FIG. 1st
motor M ₁ and second motor M ₂ respectively.
and second tachogenerators T ₁ and T ₂ , and drive amplifiers A ₅ and A ₄ via feedback circuits β ₁ and β ₂ .
to drive the first and second motors M ₁ and M ₂ . This causes the first and second motors M ₁ and M ₂ to be servoed to rotate at a rotational speed proportional to the input voltage V _S . Here, the tacho generator
Even without feedback circuits β ₁ and _{β 2 ,} if DC motors are used as the first and second motors M ₁ or M _{2 ,} the speeds of these motors will correspond to the applied voltage. Therefore, such a tachogenerator and feedback circuit can be omitted. In the example of FIG. 3 in which tachogenerators T ₁ and T ₂ or feedback circuits β ₁ and β ₂ are provided, the input voltage V _S is applied to the drive amplifier A ₄ via the inverting amplifier A ₅ . That is, in the inverting amplifier _A5 , a reverse voltage -V _S of the input voltage V _S is obtained, but a variable resistor V _R is inserted between this reverse voltage - V _S and the input voltage V _S , The output of the slider of the variable resistor _VR is input to the drive amplifier _A4 . Now, when the slider of the variable resistor V _R is turned all the way to the input voltage V _S side, the same voltage V _S is applied to the first and second motors M ₁ and M ₂ , and both rotate at the same speed. becomes.
Conversely, if you turn it all the way to the reverse voltage - V _S side, the rotation speed will be the same in the opposite direction. Therefore, the variable resistor is used to control the movement of the moving table 2 from maximum movement to stopping.
_VR allows you to freely set the speed reduction ratio, including the reduction ratio. That is, the moving device V of the pick-up 1 can be varied with the variable resistor _VR with respect to the input voltage V _S , and the first and second moving servos for the pick-up
The rotational speed of the motors M ₁ and M ₂ can be electrically set. Therefore, by setting an appropriate rotation speed during playback, and during fast forwarding, the position of the slider of the variable resistor _VR can be changed to allow high speed movement.
Also, by applying bias voltages -V _B1 and -V _B2 to drive amplifiers A ₃ and A ₄ , respectively, when there is no input voltage V _S , both motors M ₁ and M ₂ are differentially rotated at a constant speed. If the movable table 2 is stopped, the influence of hysteresis at the time of starting the motor can be eliminated.

[Problem that the invention seeks to solve]

The differential mechanism described above allows the pickup to be operated differentially, but its motor drive circuit not only uses two servo systems and is quite complex, but also requires independent servo control between the two motors. Because of this, variations in parts became a problem, and it was necessary to have parts with matching characteristics.

[Means for solving problems]

The present invention has been made to solve the above-mentioned drawbacks, and its means are such that a movable table on which an optical system such as a pick-up is mounted is driven by first and second motors, and the first (or second) ) is added to the second (or first) motor and subjected to servo control.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2. FIG. 1 is a schematic diagram showing a feeding mechanism of a pickup moving device, and FIG. 2 is a system diagram of the present invention. In FIG. 1, a movable table 2 including an optical pickup 1 is movable left and right along guide rails 3a and 3b. A first drive motor _M1 is disposed on a fixed part such as a chassis, and the screw S is rotated by the first drive motor _M1 . On the other hand, a second drive motor _M2 is attached to the moving table 2, and a worm gear G
are in mesh with each other, and when the screw S is pressed against the gear G by rotation of the worm gear G, for example, the movable table 2 is moved from side to side. Also a second drive motor _M2
When the screw S is not rotating and only the first rotary motor _M1 is rotating, the moving table 2 can be moved left and right by pressing the gear G toward the screw S due to the rotation of the screw S. Therefore, if the moving speed of the screw S is V ₁ to the right and the circumferential speed of the gear G that meshes with the screw S is V ₂ counterclockwise, the moving speed V of the moving table 2 will be V = V ₁ + V ₂ . . Therefore, if the first and second motors are driven as described above, the speeds of both motors will be the sum of the speeds, and the movable table 2 can be moved at a very high speed. Also, if one drive motor is rotated in the opposite direction, for example, if the second drive motor _M2 is set to _-V2 , the high speed V of the moving table 2 becomes V= _{V1 -V2} , and the first and second motors rotate. Even if the moving table 2 is moving, the moving table 2 is stopped.

FIG. 2 is a system diagram of such a pick-up moving device. _T1 is an input terminal to which a motor drive signal is applied, and the first motor is connected via the first drive circuit 14.
The second motor _M2 is controlled by adding a drive circuit ₁₅ that drives the second motor _M2 using the output from the tachogenerator _T1 that drives the first motor _M1 and detects the rotation of the first motor M1. With this circuit configuration, V=
In order to perform V ₁ + V ₂ servo, the second drive circuit 1 is required.
In order to perform positive servo control with 5 and servo with V = V ₁ - _{V 2} , the bias voltage applied to terminal T ₂ may be switched so that the second drive circuit 15 performs negative servo control. .

〔Effect of the invention〕

Since the present invention is constructed as described above, there may be slight product variations in parts such as the first and second motors, and the present invention has the feature that the initial purpose can be achieved with a simple circuit.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an embodiment of the pick-up moving device of the present invention, FIG. 2 is a system diagram of the pick-up moving device of the present invention, FIG. 3 is a schematic diagram of a conventional pick-up moving device, and FIG. 4 1 is an enlarged plan view of the pulley portion of FIG. 1, and FIG. 5 is a wiring diagram of a conventional motor drive circuit. 1... Optical pick-up, 2... Moving table, 4...
Rotating pulley, 6, 7... wire, 12, 13...
Spring, 14, 15... Drive circuit, M ₁ , M ₂
...first and second motors, T...tachogenerator.

Claims (1)

[Claims] 1. In a moving device that moves a moving table on which a pick-up, etc. is placed, by driving it with first and second motors, the moving table is fed and rotated in the moving direction of the moving table driven by the first drive motor. a screw, a gear that meshes with the screw and moves together with the moving table, a second motor that drives the gear, and a first motor drive circuit that drives the first motor;
a second motor drive circuit for driving the second motor; a detection means for detecting the rotational speed of the first or second motor; and a detection means for detecting the rotational speed of the first or second motor; A moving device drive circuit comprising: a control circuit that performs control in addition to the control input of the motor drive circuit, and performs servo control using a rotational speed difference between the first and second motors as a moving speed of the moving base.