JPH0244395Y2 - - Google Patents

Description

[Detailed description of the invention] "Purpose of the invention" (Industrial application field) The present invention relates to a drive circuit for a linear tracking arm, and in particular a drive circuit for precisely controlling the drive motor of a linear tracking arm. Regarding.

(Prior Art) In general, a tracking arm drive device in a linear tracking type record player has a tracking arm 13 supported by a pivot 14 on a base 12 slidably held on a rail 10, as illustrated in FIG. An optical sensor 16 for detecting the tracking error amount 15 of the tracking arm 13 and a transmission mechanism 17 to which the stress of the drive motor 18 is transmitted are attached to the base 12, and the optical sensor 16 is attached to the base 12. The displacement signal from the sensor 16 is amplified by a control circuit 19, and the output drives the motor 18, so that the tracking arm 13 always follows the record surface (not shown) at a tangential position. ing.

(Problems to be solved by the invention) However, in the above-mentioned conventional linear tracking type arm drive device, firstly, the drive motor 18 has cogging, and there are positions where the motor tends to stop during one revolution. Second, Rail 10
The frictional force that exists between the base and the other sliding parts impedes the smooth operation of the tracking arm 13, and causes the tracking arm 13 to move while exhibiting a so-called measuring motion. The drawback was that it caused vibrations and was reproduced as periodic click noise.

To explain the above phenomenon in detail, in this type of arm drive device, there is a large difference between static friction and dynamic friction, and this means that at the moment when the stress from the motor exceeds the limit of static friction force and the tracking arm 13 moves. This frictional force transfers to dynamic frictional force, and the tracking arm 13 moves at an accelerated rate, which appears as a phenomenon, and when this is repeated, it gives a periodic impact to the tracking arm, which is reproduced as noise. Become.

The present invention has been developed in view of the above points, and its purpose is to drive a linear tracking arm that eliminates unpleasant clicking noises by smoothing the movement of the tracking arm. The purpose is to provide circuits.

"Structure of the invention" (Means for solving the problems) The linear tracking arm drive circuit according to the invention detects the amount of tracking error of the linear tracking arm, and detects the amount of tracking error in accordance with the detected amount. In a linear tracking arm drive circuit configured to perform closed-loop control of a tracking arm drive motor in a direction in which the amount of A signal intermittent means is provided, and an alternating current voltage from an alternating current power source is input as a switching control signal for the signal intermittent means.

(Function) When AC voltage is input from the power supply circuit to the signal intermittent means, this can be used as a switching control signal to generate any signal for controlling the motor in the closed loop, for example, to intermittent the electric power for driving the motor. This allows the motor for driving the tracking arm to operate precisely while resisting static friction, allowing the tracking arm to move smoothly and preventing low-frequency noise and click noise from occurring. can.
In particular, since it is configured to use an AC power source as the switching control signal by the signal intermittent means, the operation is precise, and it is easy and inexpensive to implement.

(Embodiment) An embodiment of a linear tracking arm drive circuit according to the present invention will be described based on FIGS. 1 to 4.

FIG. 1 is a block diagram showing a basic configuration example, in which a tracking arm 1 is pivotally supported on a base 2 running along a rail 3, and is moved in a thrust direction F by a motor 4 and a drive mechanism 5. However, the position can be controlled freely. 6 is the displacement that the tracking arm 1 receives in the thrust direction by tracing on the record disc, that is,
It is an optical angle sensor for detecting the amount of tracking error, and is provided on the base 2, and in the embodiment, the tracking arm is placed between a photointerrupter consisting of a light emitting element 6a and a light receiving element 6b. By interposing a perforated light shielding plate 6c fixed on the first side, the amount of tracking error can be detected. 7 is an amplifier for amplifying the output (displacement amount) from the angle sensor 6, and 8 is a drive amplifier for controlling the motor 4 based on the output signal from the amplifier 7. It consists of Reference numeral 9 denotes _a signal intermittent means interposed in the closed loop _{L ,} and _in the embodiment shown in FIG. , transistor _Q2 is interposed between its emitter and collector in the closed loop, so that main switching is performed. The AC output voltage in the power transformer T is made into a pulsating current by diodes D ₁ and D ₂ , the peak waveform is sliced by a Zener diode Z, and then divided by resistors R ₁ and R ₂ , and further divided by resistors R ₃ The above transistor is stepped down by
It is set to be input to the base of _Q1 . The emitter of the transistor _Q1 is connected to earth GND, and the collector is connected to the base of the transistor _Q2 via a diode _D3 and a resistor _R4 .

To explain an example of the operation in the above configuration, first, a signal corresponding to the amount of tracking error of the tracking arm 1 is output from the angle sensor 6, and then passes through the amplifier 7 to the drive amplifier 8 at the next stage.
A closed loop L that operates the motor 4 in a direction in which the tracking error amount is reduced by the power amplified by
is formed, but the signal intermittent means 9 performs an intermittent operation as described later, and the signal within the closed loop L is interrupted.
The motor 4 is driven by, for example, a pulsating flow with a duty ratio of about 50%.

A pulse of twice the power frequency of the power transformer T, for example, 100 Hz, is input to the base of the transistor Q ₁ , and only when the pulse becomes low level, the transistor Q ₁ is turned on, and its collector voltage is approximately grounded. (GND) potential. Therefore, the base voltage of the transistor Q ₂ becomes approximately the ground potential, and the transistor Q ₂ is turned off.

On the other hand, when the pulse input to the base of transistor Q ₁ becomes high level, transistor Q ₁ is turned off and transistor Q ₂ is turned on, so that the output of amplifier 7 is input to the drive amplifier 8 side, and as described above. The on/off operation is repeated.

In this way, the signal intermittent means 9 has a simple configuration and can perform on/off control at a predetermined frequency, for example, 100 Hz, and can add slight vibration to the rotation of the motor 4. Note that in the configuration example described above, the AC voltage from the AC power supply circuit is used as the switching control signal. It may also be used as a signal. In this case, an alternating current signal or a pulse signal of 30Hz to 300Hz is suitable as the switching control signal. If the switching control signal is below 30Hz, large vibrations will occur in the rotation of the motor 4, making the operation unstable and worsening the S/N ratio. On the other hand, we obtained experimental results that when driven at a high frequency of 300Hz or higher, there is no significant difference compared to when driven with direct current.

As described above, the tracking arm can be moved at a very slow speed while constantly canceling the static friction existing between the base 2 and the rail 3 and in the drive mechanism 5 etc. by the intermittent drive of the motor 4. Since the power applied to the motor is halved when the power is intermittent at a duty ratio of 50%, the rotational speed also decreases, allowing for more delicate speed control. In this way, the tracking arm 1 can be moved faithfully to the record sound groove without stopping, so the tracking arm 1 can be moved faithfully to the record sound groove without stopping.
This does not cause any measuring movement, and the generation of noise associated with this movement can be prevented.

Figures A and B show the movement trajectories of the tracking arm, A is the one according to the present invention and B is the conventional one, in which the moving speed v of the tracking arm on the time axis t is compared. be. FIGS. 4A and 4B are characteristic diagrams at 45 RPM and 50 Hz, comparing vibration components, that is, noise components, applied to the tracking arm. In the conventional device shown in FIG. 3B, the movement speed v fluctuates greatly and it is clear that periodic shocks are applied to the tracking arm, but in the conventional device shown in FIG. 3A, It operates smoothly with little variation in the moving speed v, and does not impart harmful vibrations to the tracking arm 1.

Furthermore, in the device according to the present invention shown in Figure 4A, the noise level has been reduced to about 1/3 compared to the conventional one shown in Figure 4B, and the S/N ratio has been significantly improved. Can be seen.

"Effects of the Invention" According to the linear tracking arm drive circuit according to the present invention, any signal related to motor control within a closed loop for driving the tracking arm is intermittent at a predetermined period by the signal intermittent means. This not only makes the movement of the tracking arm smoother, resulting in better tracing, but also improves S/N because there is no low-frequency noise caused by the measuring movement of the tracking arm, etc.
The ratio can be significantly improved. Moreover, it is configured to input an AC voltage from an AC power supply as a switching signal by the signal intermittent means,
Since the power supply frequency of the commercial power source is used for intermittent operation, there is no need to separately provide an oscillator for intermittent operation, and the system has advantages such as being stable, easy to implement, and inexpensive.

[Brief explanation of the drawing]

1 to 4 show an embodiment of the linear tracking arm drive circuit according to the present invention, FIG. 1 is a block diagram showing the overall configuration, FIG. 2 is a specific circuit configuration diagram, and FIG. 3 is a block diagram showing the overall configuration. The figures are comparative diagrams showing the movement locus of the tracking arm, where Fig. 3A is a locus diagram of the one according to the present invention, Fig. 3B is a locus diagram of the conventional one, and Fig. 4 is a locus diagram of the locus of the conventional one. FIG. 4A is a characteristic diagram of the device according to the present invention, and FIG. 4B is a characteristic diagram of the conventional device. FIG. 5 is a block diagram showing a conventional linear tracking arm drive device. 1...Tracking arm, 2...Base, 3
...Rail, 4...Motor, 5...Drive mechanism,
6... Optical sensor, 7... Amplifier, 8... Drive amplifier, 9... Signal intermittent means, T... Power transformer.

Claims (1)

[Claim for Utility Model Registration] The system is configured to detect the amount of tracking error of the linear tracking arm, and to control the tracking arm drive motor in a closed loop in a direction that reduces the amount of tracking error according to the detected amount. In the drive circuit for the linear tracking arm, a signal intermittent means is provided to intermittent any signal related to motor control in the closed loop at a predetermined period, and an alternating current is used as a switching control signal of the signal intermittent means. A drive circuit characterized in that it is configured to receive an AC voltage from a power source.