JPS6080176A - Pick-up arm drive device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a drive device for a pickup arm used in a record player or the like.

Conventional structure and problems thereof A conventional device of this type has a structure as shown in FIG. That is, the rotor 1 coaxially fixed to the rotation axis of the arm applies a voltage to the detection coil 2 that is proportional to its rotation speed. 3 is an amplifier that amplifies the output voltage of the detection coil. 4 is a speed control circuit that performs speed control based on the output voltage of the amplifier 3. 5 is a drive circuit that supplies a drive current. 6 is a drive coil.

The operation of the conventional arm drive device configured as described above will be described below.

A voltage proportional to the speed of the arm generated by the detection coil 2 is amplified by the amplifier 2.

Next, the speed control circuit 4 amplifies the error with respect to the reference voltage and outputs a control voltage. The drive circuit 5 causes a current proportional to the control voltage to flow through the drive coil 6. By configuring the control loop as described above, A1, 1 rotates at a constant speed. Furthermore, the logic circuit element switches the direction of rotation of the arm by changing the direction of the drive current. )Sui・lchi8
If switch 8 is turned on, the rotation will be forward, and if switch 8 is turned off, the rotation will be reversed.

However, with the conventional configuration, when some external force is applied to the arm 1 and the arm 1 is stopped/moved or moved in the opposite direction, a large current flows, causing damage to the drive circuit or malfunction. It had

OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional problems and provides an arm drive device that has a simple configuration and prevents malfunctions when an external force is applied to the arm.

Structure of the Invention The present invention uses a comparator to compare the amplified detection coil output voltage with a reference voltage that is switched during forward and reverse rotations, thereby detecting whether the arm is stopped or moved in the opposite direction by an external force. The output voltage of the drive circuit is detected to prevent damage or malfunction of the drive circuit, etc.

DESCRIPTION OF EMBODIMENTS FIG. 2 shows an arm driving device in an embodiment of the present invention. In FIG. 2, 9°10.11 is a voltage dividing resistor for the power supply voltage, 12 is a transistor that is turned on during reverse rotation, 13 is a comparator, and the rest is exactly the same as in FIG. 1.

The operation of the arm driving device of this embodiment configured as described above will be described below. First, Figure 3 shows the comparator 13.
is a graph of voltage. Vcc, -VEE are the power supply voltages of the comparator 13, VF is the positive input voltage of the ratio converter 13 when the arm is rotating in the normal direction, and VR is the positive input voltage of the comparator 13 when the arm is rotating in the reverse direction. The voltage, Vsp, is the negative input voltage of the comparator 13 when the transistor 12 is off, and VsR is the negative input voltage of the comparator 13 when the transistor 13 is on.
This is the input voltage on the negative side of , and the magnitude relationship of the voltages is as shown in Fig. 3. First, the output voltage from the detection coil 1 is amplified by the amplifier 3, and the output signal is input to the comparator 13 and compared with a reference voltage. When the arm is rotating in the normal direction, the input voltage of the comparator is Vp, and since the reference voltage d-transistor 12 is off, it becomes vSF due to the voltage division of the resistors 9 and 10° 11, and the output of the comparator becomes H1. If the arm is stopped or moved in the opposite direction by an external force, the input voltage becomes Ov or less than Ov, so the output of the comparator becomes L. When the arm is reversed, the comparator input voltage (VR) and reference voltage are VO due to the voltage division of resistors 9 and 1Q because transistor 12 is on.
The output of the comparator is L1. If the arm is stopped by an external force or moved in the opposite direction, the input voltage will be Ov or 07.
Therefore, the output of the comparator becomes H. This can be summarized as follows.

Output of comparator As described above, according to this embodiment, by switching the reference voltage of the comparator 13 between forward and reverse rotation, it is possible to accurately detect external force applied to the arm, thereby preventing damage to the drive circuit, etc. To prevent malfunction, do not brake the arm or
It is possible to make a returned paper.

Effects of the Invention The present invention provides a comparator that compares the output obtained by amplifying the back electromotive force of the rotational speed of the pick-up arm with a reference voltage that is switched by forward and reverse rotations, thereby preventing external force from being applied to the pick-up arm. It is possible to realize an excellent pink-up arm drive device that can accurately detect when the pickup arm has stopped and prevent damage or malfunction of the drive circuit, etc., and can brake or return the pickup arm.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional pickup arm drive device, FIG. 2 is a block diagram of a pink-up arm drive device in an embodiment of the present invention, and FIG. 3 is a ratio of pickup arm and drive nl. It is a distribution diagram of σ) input electric power to %13. 1.Pickup arm with magnet connected coaxially, 2.Detection coil, 3.Amplifier, 4.
・Speed control circuit, 6 Drive circuit 6... Drive coil, 7... Logic circuit, 8... Forward/reverse selector switch, 9, 10.11... Fixed resistor, 12...
...Transistor, 13...Comparator.

Claims (1)

[Claims] A pi-qua-y arm, a rotor magnet coaxially connected to the rotation axis of the arm, and a coil that detects the rotation speed of the rotor magnet as a back electromotive force.
A pickup arm drive device comprising: an amplifier that amplifies this back electromotive force; a comparator that compares the output of this amplifier with a reference voltage; and a circuit that switches this reference voltage depending on the rotational direction of the pickup arm.