JPH04364391A - Speed detection circuit - Google Patents

Abstract

PURPOSE:To detect a speed of an optical head without adverse influence to a vibrating characteristic by using a driving coil and a speed detecting coil of a linear motor. CONSTITUTION:The speed sensing circuit comprises a linear motor 31 having a driving coil 13a movable relatively to a magnetic member 31a in a direction crossing a magnetic flux generated by the member 31a, and a speed detecting coil 13b wound on the coil 13a. A relative speed of the coil 13a and the member 31a, i.e., a moving speed of an optical head 3 by the motor 31, is detected by utilizing an electrical change in the coil 13a generated at a moment of crossing the magnetic flux by the coil 13b and an electrical change in the coil 13b.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed detection circuit for detecting the moving speed of an optical head used in an optical disk device for recording information on an optical disk or reproducing information from an optical disk.

0002

2. Description of the Related Art Generally, in an optical disc device that records information on or reproduces information from an optical disc, information is recorded and reproduced using an optical head that moves linearly in the radial direction of the optical disc. This optical head is moved by a linear motor.

The moving speed of the optical head is determined by time-differentiating position information obtained from a photodetector provided on the movable part of the linear motor and an optical scale.
Detected.

As described above, since optical scales and photodetectors have been used to detect speed, if an optical scale or photodetector is attached to the moving part of a linear motor, resonance may occur in the movement of the optical head during high-speed movement. There was a problem in that vibration characteristics were adversely affected.

[0005]

[Problems to be Solved by the Invention] Conventionally, there has been a problem in that vibration characteristics are adversely affected, such as resonance occurring in the movement of the optical head.

[0006] The present invention has been made in view of the above points, and is a speed detection method that can perform speed detection without using an optical scale or photodetector, and can perform speed detection without adversely affecting vibration characteristics. The purpose is to provide circuits.

[0007]

[Means for Solving the Problems] The speed detection circuit of the present invention includes a magnetic material that generates magnetic flux, and a first moving conductor that is movable in a direction that crosses the magnetic flux generated by the magnetic material. , a second conductor for speed detection wound on the first conductor, a moving body that is moved together with the first and second conductors, and controlling the current of the first conductor. A moving means for moving the first and second conductor bodies and the movable body by a detection means for detecting a change; and a detection means for detecting a relative movement speed between the first conductor and the magnetic material using the electrical change caused by the first and second conductors detected by the detection means. It consists of

[0008]

[Operation] In the above-mentioned configuration, the present invention provides a moving first conductive wire that is movable in a direction transverse to the magnetic flux generated by the magnetic material, and a speed at which the first conductive wire is wound on the first conductive wire. A second conductive wire body for detection is provided, and a movable body is moved together with the first and second conductive wire bodies, and by controlling the current of the first conductive wire body, the first and second conductive wire bodies are moving the moving body, detecting electrical changes inside the first and second conductors that occur at the moment when the first and second conductors cross the magnetic flux; The relative movement speed between the first and second conductive wires and the magnetic material is detected using electrical changes caused by the conductive wires.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows a disk device. In other words, a recording medium 1 composed of an optical disk or the like
Spiral grooves (recording tracks) are formed on the surface of the recording medium 1, and the recording medium 1 is rotated by a motor 2 at, for example, a constant speed. This motor 2 is controlled by a motor control circuit 18. Recording and reproduction of information on the recording medium 1 is performed by an optical head (moving body) 3 provided at the bottom of the recording medium 1.

Note that the recording medium 1 uses a recording film in which pits are formed by perforation, but
A recording film or a multilayer recording film that utilizes phase change may be used, and a magneto-optical disk or the like may be used as the recording medium. In the above case, the configuration of the optical head and the like is similarly changed.

An objective lens 6 is held on the optical head 3 by a wire or a leaf spring (not shown), and the objective lens 6 is moved in the focusing direction (optical axis direction of the lens) by a drive coil 5. The coil 4 allows movement in the tracking direction (direction perpendicular to the optical axis of the lens).

Furthermore, the laser light generated by the semiconductor laser oscillator 9 driven by the laser control circuit 14 is
The recording medium 1 is irradiated via the collimator lens 11a, the half prism 11b, and the objective lens 6, and the reflected light from the recording medium 1 is reflected by the objective lens 6 and the half prism 1.
1b, a condensing lens 10a, and a cylindrical lens 10b. The photodetector 8
is composed of four divided photodetection cells 8a, 8b, 8c, and 8d.

The output signal of the photodetection cell 8a of the photodetector 8 is supplied to one end of adders 30a and 30c via an amplifier 12a, and the output signal of the photodetection cell 8b is supplied to one end of the adder 30a, 30c via an amplifier 12a.
2b to one end of adders 30b and 30d,
The output signal of the photodetection cell 8c is supplied to the other end of the adders 30b and 30c via an amplifier 12c, and the output signal of the photodetection cell 8d
The output signal is sent to adders 30a and 3 via amplifier 12d.
It is designed to be supplied to the other end of 0d.

The output signal of the adder 30a is supplied to the inverting input terminal of the differential amplifier OP1.
The output signal of the adder 30b is supplied to the non-inverting input terminal of the adder 30b. Thereby, the differential amplifier OP1 supplies a track difference signal to the tracking control circuit 16 according to the difference between the adders 30a and 30b. This tracking control circuit 16 creates a track drive signal according to the track difference signal supplied from the differential amplifier OP1.

A track drive signal output from the tracking control circuit 16 is supplied to the drive coil 4 in the tracking direction. Further, the track difference signal used in the tracking control circuit 16 is supplied to the linear motor control circuit 17.

The linear motor control circuit 17 controls a drive coil (first conductor) 13a in a linear motor (moving means) 31, which will be described later, in response to a track difference signal from the tracking control circuit 16 and a movement control signal from the CPU 24. A voltage corresponding to the moving speed is applied to the

In the linear motor control circuit 17, a drive coil 13a and a speed detection coil (second conductor) 13b in the linear motor 31, which will be described later, are made of magnetic members (magnetic material).
By using the electrical changes inside the drive coil 13a and the speed detection coil 13b that occur at the moment of crossing the magnetic flux generated from the drive coil 13a and the speed detection coil 13a,
b and the relative speed of the magnetic member 31a, that is, the linear motor 3
A speed detection circuit 40 is provided for detecting the moving speed of the optical head 3 by the optical head 1.

The output signal of the adder 30c is supplied to the inverting input terminal of the differential amplifier OP2, and the output signal of the adder 30d is supplied to the non-inverting input terminal of the differential amplifier OP2. Thereby, the differential amplifier OP2 supplies a signal regarding the focus point to the focusing control circuit 15 according to the difference between the adders 30c and 30d. The output signal of the focusing control circuit 15 is supplied to the focusing drive coil 5, and is controlled so that the laser beam is always in just focus on the recording medium 1.

Each photodetection cell 8a, . . . of the photodetector 8 with focusing and tracking performed as described above
The sum signal of the outputs of the adders 8d, that is, the output signals from the adders 30a and 30b, reflects changes in reflectance from pits (recorded information) formed on the tracks. This signal is supplied to the signal processing circuit 19, and this signal processing circuit 19
Recorded information and address information (track number, sector number, etc.) are reproduced. Further, a recording signal generation circuit 34 as a modulation circuit that modulates the recording signal is provided upstream of the laser control circuit 14.

The reproduction signal (reproduction information) reproduced by the signal processing circuit 19 is outputted to a recording medium control device 33 as an external device via an interface circuit 32.

This disk device also includes a focusing control circuit 15, a tracking control circuit 16, and
A D/A converter 22 used for exchanging information between the linear motor control circuit 17 and the CPU 23 is provided.

Further, the tracking control circuit 16 includes:
The objective lens 6 is moved in response to a track jump signal supplied from the CPU 23 via the D/A converter 22, and the beam light is moved by one track.

The laser control circuit 14, focusing control circuit 15, tracking control circuit 16, linear motor control circuit 17, motor control circuit 18, signal processing circuit 1
9. The recording signal generation circuit 44 and the like are controlled by the CPU 23 via the bus line 20, and the CPU 23 is configured to perform predetermined operations according to a program stored in the memory 24.

The optical head 3, as shown in FIG.
Guide rail 51 fixed to a frame (not shown)
, 52 as guides, it can be moved reciprocally (in the radial direction of the recording medium 1). optical head 3
The carriage 53 is connected to a drive coil 13a as a movable part of the linear motor 31.

As shown in FIGS. 1, 3, and 4, this linear motor 31 includes a yoke-shaped magnetic member 31a,
A permanent magnet (magnet) 32 is adhesively fixed to the inner surface of the magnetic member 31a, a drive coil 13a is provided movably on the magnetic member 31a, and is wound on the drive coil 13a. It is constituted by a speed detection coil 13b.

Drive coil 13a and speed detection coil 13
b moves on the magnetic member 31a according to the voltage applied by the linear motor control circuit 17 and the magnetic field generated from the permanent magnet 32 attached to the magnetic member 31a. As the drive coil 13a moves, the optical head 3 is also moved.

Further, the drive coil 13a and the speed detection coil 13b are connected to a speed detection circuit 40 within the linear motor control circuit 17. This speed detection circuit 40 detects the amount of current flowing through the drive coil 13a and the speed detection coil 13.
By checking the voltage value generated at b, the drive coil 13
a, that is, it outputs a speed signal corresponding to the moving speed of the optical head 3.

The speed detection circuit 40, as shown in FIG.
A resistor R inserted in series with the drive coil 13a to detect the current flowing through the drive coil 13a, the drive coil 13, an amplifier circuit 41 that amplifies and outputs the current flowing through the resistor R, and a The differentiating circuit 42 that differentiates the current value, the amplifying circuit 43 that amplifies and outputs the voltage generated in the speed detection coil 13b, and the outputs of the amplifying circuit 41, the differentiating circuit 42, and the amplifying circuit 43 are added ( It is constituted by an adder circuit 44 that performs (synthesizing).

The amplifier circuit 41 outputs a signal obtained by amplifying the current flowing through the drive coil 13a as shown in FIG. 6(a), and the amplifier circuit 43 outputs a signal as shown in FIG. 6(b). A signal obtained by amplifying the voltage generated by the speed detection coil 13b is output, and the differential circuit 42 outputs a signal (c
) is outputted from the adder circuit 44, and the adder circuit 44 outputs a signal obtained by combining the output signal from the amplifier circuit 43 and the output signal from the differentiator circuit 42, as shown in FIG. 6(d). speed signal) is output.

In such a configuration, the drive coil 13
When a moves, the speed detection coil 13b
A signal also appears. That is, the voltage at both ends of each of the drive coil 13a and the speed detection coil 13b is E.
1, E2, current I1, I2, resistance R1
, R2, the self-inductance is L1, L2, the effective length of each coil is 11, 12, the mutual inductance between the drive coil 13a and the speed detection coil 13b is M, and, common to both, the moving speed is v. , and the air gap magnetic flux density is considered as follows.

E1 = R1 I1 +vB11 -L1 (dI1
/dt)-M(dI2/dt)(1)E2=R2
I2 +vB12 -L2 (dI2 /dt) -M(
dI1 /dt) (2) As a result, the drive coil 13a
When the coupling coefficient of the speed detection coil 13b is 1, the moving speed v is as follows. v=(αE1 −βE2 )−(γI1 −δ
I2) (
3) α, β, γ, and δ are constants. In other words, in order to detect speed with this method, it is sufficient to monitor the voltage and current of both coils. Also,
The current I2 is sufficiently small and the resistance R2
When is also small compared to other terms, it can be approximated as follows. v=αE2 +β(dI1/dt)

(4) α and β are constants

For example, in this case, the speed detection coil 13
By increasing the number of turns of b by using a thinner coil than the drive coil 13a, it is advantageous in that the voltage E2 generated in the speed detection coil 13b can be increased.

The content of Equation 1 above corresponds to the electric signal generated in the drive coil 13a, the content of Equation 2 above corresponds to the electric signal generated in the speed detection coil 13b, and the content of Equation 4 above corresponds to the electric signal generated in the speed detection coil 13b.
The contents correspond to the addition (synthesis) contents of the adder circuit 44.

Next, the operation of detecting the moving speed of the optical head 3 in the above configuration will be explained. A predetermined voltage value is applied by the linear motor control circuit 17 to the drive coil 13a. As a result, the current-carrying drive coil 13a moves on the magnetic member 31a in response to the magnetic field generated from the permanent magnet 31b.

After the current flowing through the drive coil 13a is amplified by the amplifier circuit 41, it is differentiated by the differentiator circuit 42 and output to the adder circuit 44. Speed detection coil 13b
The voltage applied thereto is amplified by the amplifier circuit 43 and output to the adder circuit 44 .

The addition circuit 44 adds the signal from the differentiation circuit 42 ((c) in FIG. 6) and the signal from the amplifier circuit 43 ((b) in FIG. 6) based on the above-mentioned equation 4. By combining these signals, a speed signal as shown in FIG. 6(d) is obtained.

Speed data corresponding to the speed signal from this adder circuit 44 is output to the CPU 23, and
The current moving speed of the optical head 3 is determined from the speed data from the adder circuit 44, and the voltage is again applied to the drive coil 13a by the linear motor control circuit 17 so that the target speed is achieved.

Note that the speed signal waveform shown in FIG. 6(d) shows the state of movement of the optical head 3 by the linear motor 31 when acceleration, stop, acceleration in the opposite direction, and stop are repeated. ing.

As described above, in a linear motor having a drive coil that can move relative to the magnetic member in a direction transverse to the magnetic flux generated by the magnetic member,
By utilizing the electrical changes inside the drive coil and the electrical changes inside the speed detection coil that occur at the moment the drive coil crosses the magnetic flux, the relative speed between the drive coil and the magnetic member, that is, the optical head by the linear motor. The system detects the moving speed of the vehicle. Thereby, speed detection can be performed without using an optical scale or a photodetector, and speed detection can be performed without adversely affecting vibration characteristics.

[0040]

[Effects of the Invention] As detailed above, according to the present invention,
It is possible to provide a speed detection circuit that can perform speed detection without using an optical scale or photodetector, and can perform speed detection without adversely affecting vibration characteristics.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the configuration of a linear motor in an embodiment of the present invention.

FIG. 2 is a block diagram showing a circuit configuration of a disk device according to an embodiment of the present invention.

FIG. 3 is a perspective view showing the configuration of essential parts of the linear motor shown in FIG. 1;

FIG. 4 is a diagram for explaining a speed detection coil wound on a drive coil in the linear motor of FIG. 1;

FIG. 5 is a block diagram showing the circuit configuration of the speed detection circuit in FIG. 2;

FIG. 6 is a diagram showing output signals of each circuit in the speed detection circuit of FIG. 2;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Recording medium, 3... Optical head (moving body), 6... Objective lens, 13a... Drive coil (first conductor), 13b...
Speed detection coil (second conductor), 17... Linear motor control circuit, 23... CPU, 31... Linear motor (moving means), 31a... Magnetic member (magnetic material), 31b... Permanent magnet, 40... Speed detection Circuit, 41, 43...Amplification circuit, 4
2...differentiation circuit, 44...addition circuit, 53...carriage.

Claims (1)

[Claims] Claim 1: A magnetic material that generates magnetic flux, a first conductor for movement that is movable in a direction transverse to the magnetic flux generated by the magnetic material, and a wire wound on the first conductor. A second conducting wire body for detecting the speed being rotated, a moving body that is moved together with the first and second conducting wire bodies, and a first and second conducting wire body by controlling the current of the first conducting wire body. moving means for moving the conducting wire body and the moving body;
a detection means for detecting an electrical change inside the first and second conductors that occurs at the moment when the conductor crosses the magnetic flux; and an electrical change caused by the first and second conductors detected by the detection means. A speed detection circuit comprising: a detection means for detecting the relative movement speed of the first conductor and the magnetic material using the above.