JPH0537677Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to an improvement of a stepping motor drive amplifier, particularly an amplifier circuit for driving a microstep.

[Conventional technology]

Stepping motors pass current (often in a pulsed waveform) through each phase winding sequentially and cyclically.
It is possible to continuously rotate in the same rotational direction by flowing , and the number of rotations is proportional to the number of input current pulses, and to reverse the rotational direction, simply reverse the order in which current is passed through each phase winding. is well known. It has also been known that the stopping position of a stepping motor can be changed by changing the current ratio of each phase winding. This idea concerns a drive amplifier circuit that finely adjusts the stopping position of a stepping motor.
Conventional devices of this type include those shown in FIGS. 8 and 9.

FIG. 8a is a perspective view showing the relationship between a stepping motor and a stepping motor drive amplifier;
In the figure, 6 is a stepping motor, 7 is a rotating rotor of the stepping motor 6, and 9 is a stepping motor drive amplifier for driving the stepping motor 6.

FIG. 8b shows the windings of a stepping motor, and this figure shows four-phase windings 11A to 11D as an example.

Regarding the conventional microstep control of stepping motors, please refer to the document "Basics and Applications of Stepping Motors: Sogo Denshi Publishing: September 1981, Vol. 6.
As explained on pages 52 and later of the ``Edition'', in the case of the two-phase excitation microstep drive system, the windings 11A and 11
When currents IA=IA ₁ and IB=IB ₁ are applied to B and B, respectively, the rotor 7 is positioned at an angle φ ₁ , and IA=IA ₂ and IB=
It is well known that if IB ₂ , the angle becomes φ ₂ . In this case, there is a relationship of tanφ ₁ =IA ₁ /IB ₁ and tanφ ₂ =IA ₂ /IB ₂ .

Now, as shown in FIG. 9a, winding 1 until time t ₁
If the currents IA ₁ and IB ₁ are flowing through 1A and 11B, respectively, and the angle of the rotor 7 is φ ₁ , and it instantaneously changes stepwise to IA ₂ and IB ₂ at time t ₁ , then the rotor 7 moves in an oscillatory manner, as shown in Figure 9b, and finally settles at an angle of φ ₂ . If the time at which the angle φ of the rotor 7 reaches 90% to 110% of the final value φ ₂ is t ₂ , then t ₂ −t ₁ is the time called settling time.

Moreover, the motion shown by the broken line in FIG. 9b shows the case where the motion of the rotor 7 is close to critical braking, and the establishment time in this case is t ₂ '-t ₁ , which is clearly t ₂ - _{t 1}
smaller.

[Problem that the invention attempts to solve]

The conventional stepping motor drive amplifier described above suffers from the vibration phenomenon of the rotor as described above.
Since a long settling time is required, there is a problem that when used in a positioning mechanism of a magnetic disk device, the operation time is unnecessarily long and the function of the magnetic disk device is deteriorated.

This invention has been developed to solve these problems and aims to provide a stepping motor drive amplifier that minimizes settling time.

[Means for solving problems]

The stepping motor drive amplifier according to this invention suppresses the vibration phenomenon of the rotor and shortens the settling time by improving the microstep drive amplifier circuit.

[Effect]

In this invention, since the settling time can be shortened, when it is used in a positioning mechanism of a magnetic disk device, the function thereof is not deteriorated.

[Example of idea]

Hereinafter, embodiments of this invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a case where the stepping motor drive amplifier according to the invention is implemented in a head positioning mechanism of a magnetic disk device. In the figure, 1 is a magnetic disk, 2 is a magnetic head, and 3 is a magnetic disk 1. 4 is a positioning mechanism for the magnetic head 2; 5 is a rack and pinion gear;
6 is a stepping motor, 7 is a rotating rotor of the stepping motor 6, 8 is a head amplifier that amplifies the signal picked up by the magnetic head 2, 9 is a stepping motor amplifier that drives the stepping motor 6, and 10 is a magnetic disk 1. On the upper track, magnetic recording and reproducing operations are performed by opposing magnetic heads 2.

Next, the operation of the apparatus shown in FIG. 1 will be explained. The magnetic head 2 is accurately positioned on the track 10 by a positioning mechanism 4. That is, if the number of the track 10 that the magnetic head 2 is currently facing is known, and the number of the track 10 that the magnetic head 2 is to face next is given, how will the windings of each phase of the stepping motor 6 be shaped? Since the number of pulse currents to be inputted in a certain order is determined, it is sufficient to input the determined number of pulse currents from the amplifier 9 to each phase winding in a determined order. The rotor 7 of the stepping motor 6 rotates by a number of revolutions corresponding to the number of input pulses, and the rack and pinion gear 5 converts the rotational motion into linear motion to drive the positioning mechanism 4 to perform positioning. However, in such positioning, the magnetic head 2 does not accurately face the desired track 10, and an error called off-track often remains. This error is generally detected by a magnetic head from the surface of the magnetic disk on which an error detection track called a servo track is recorded, and the position is corrected in accordance with this error. In this position correction, the current ratio of the current flowing from the amplifier 9 to each winding of the stepping motor 6 is adjusted.

FIG. 2 is a circuit diagram showing the circuit configuration of the stepping motor drive amplifier 9 according to this invention. In the figure, 11 is the winding of the stepping motor.
For convenience of explanation, a case will be explained in which there are four windings A, B, C, and D. Reference numeral 12 denotes a winding selection circuit which selects the corresponding windings A, B, C, and D according to input signals a, b, c, and d, respectively. 13
14 is a current outflow point of the first winding group, and 15 is a current outflow point of the second winding group, which are connected to the winding drive amplifier 13.

The winding 11 is a four-phase winding (which can also be seen as a two-phase winding), and A and C, B and D constitute a pair of windings [see Figure 8b], and A and C constitute a pair of windings. are wound in opposite directions, B and D are wound in opposite directions, and the directions of AC and BD are perpendicular to each other, so no current flows through A and C at the same time. Current is not allowed to flow through B and D at the same time. A and C are the first winding group, B and D
and is called the second winding group. The current inflow ends of the windings 11 are connected in parallel to the positive terminal of the power source. 16 is a second amplifier whose output is applied to the winding drive amplifier 13 as a microstep control voltage 17.
is applied to 18 is an analog signal input;
applied to the second amplifier 16. 19 is a digital operation switching signal, and the winding drive amplifier 13
The switch circuit 20 [consisting of 20A, 20B, and 20c] is controlled. 101 and 102 are control transistors, 103 is a common emitter resistor, and 104 and 105 are control amplifiers. The current from the positive terminal of the power supply is passed through the winding 11,
The current flows through the winding selection circuit 12, the current outflow points 14 and 15, the control transistors 101 and 102, and the resistor 103 to the ground (the negative terminal of the power supply).

Next, the operation of the circuit shown in FIG. 2 will be explained. When the digital operation switching signal 19 becomes logic "H", the switch circuit 20 operates and the 20
A sets the base of the transistor 101 to logic "H", 20B sets the base of the transistor 102 to logic "H", and 20C sets the base of the transistor 101 to logic "H".
3 is short-circuited, the winding drive amplifier 13 is always in a conductive state, and the entire current that is limited by the circuit specifications flows through the winding 11 of the stepping motor. In this state, the stepping motor 6 is rotated in a desired direction and at a desired number of rotations using input signals a, b, c, and d. For example, referring to FIG. 8b, signal a is applied and current flows only through winding 11A to move the rotor 7 of stepping motor 6 in the direction corresponding to winding 11A, then signal a is stopped and signal b is is applied, current is applied only to the winding 11B, the rotor 7 is rotated 90 degrees from the direction corresponding to the winding 11A, and the winding 1 is
1B, then stop signal b, add signal c, apply current to only winding 11C, rotate rotor 7 by another 90 degrees, then stop signal c, add signal d, and wind. The rotor 7 is further rotated by 90 degrees by applying current only to the wire 11D, and then the stepping motor 6 is rotated by the desired number of rotations by stopping the signal d and applying the signal a again. Through such control, the magnetic head 2 is brought approximately onto the desired track 10, and the next step is to perform fine position correction. When moving to fine position correction, the logic of the digital operation switching signal is set to "L". When the digital operation switching signal input 19 is at logic "L", 20A, 20B, and 20C are turned off, and the winding drive amplifier 13 operates in analog mode.
That is, a current proportional to the microstep control voltage 17 is passed through the first winding group 14 and the second winding group 15. In this case, the winding drive amplifier 13 is configured to operate differentially due to the common emitter resistance 103, so when increasing the current in the first winding group 14, the second winding group 15 the current decreases.

Next, the operation of the second amplifier 16 will be described in detail using FIGS. 3, 4, and 5. In FIG. 3, 20 is a digital-to-analog (hereinafter referred to as DA) converter, 21 is a microprocessor,
The digital output of the microprocessor 21 is DA
Applied to converter 20, it generates microstep control voltage 17. FIG. 4 is a diagram showing the relationship between the input digital number d and the output V of the DA converter 20.
When d=d1, V=V1, when d=d2, V=V
2 will occur. Note that although the input d is a digital signal and is therefore discrete, it is represented by a continuous line in the figure. FIG. 5 is a diagram showing the process of controlling the DA converter 20 using the microprocessor 21, and FIG. 5a shows the temporal change in the output d of the microprocessor 21. This indicates that d2 occurs. This output is converted into an analog signal by the DA converter 20, so the time is as shown in Figure 5b.
From t1 to time t2, the voltage increases from V1 to V2 in an analog manner. When this voltage is applied to the winding drive amplifier 13 as the microstep control voltage 17, the positioning mechanism 4 driven by the stepping motor 6 operates smoothly with vibration suppressed, as shown from x1 to x2 in FIG. 5c. It becomes a movement.

6 and 7 show the second amplifier 1 shown in FIG.
In the figure, 22 is a functional amplifier, R1 to R3 are each a resistor, and C is a capacitor. It is well known that when a CR circuit is connected to the feedback path of a functional amplifier as shown in FIG. 6, it becomes an incompletely integrating functional amplifier, where J indicates the input and V indicates the output. FIG. 7a is a diagram showing the temporal change of input J, and at time t1, J=J1 to J
2, but when this input passes through the functional amplifier 22 that performs incomplete integration, it changes exponentially from time t1 to time t2 when it reaches 90% of the final voltage V2, as shown in Figure 7b. Change. When such a signal is applied to the winding drive amplifier 13 as a microstep control voltage 17, the positioning mechanism 14 driven by the stepping motor 6 causes vibration phenomena such as those shown from x1 to x2 in FIG. 7c. The result is a smooth movement with less friction.

[Effect of idea]

As described above, according to this invention, the waveform of the microstep control voltage, which is the output of the second amplifier at the front stage of the winding drive amplifier of the stepping motor, changes in an analog manner, so that vibrations of the rotating rotor of the stepping motor occur. The present invention has the effect of providing a stepping motor drive amplifier that can suppress the noise, shorten the settling time, and perform faster and more precise positioning.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a case where the stepping motor drive amplifier according to this invention is implemented in a head positioning mechanism of a magnetic disk device, FIG. 2 is a circuit diagram showing the circuit configuration of the stepping motor drive amplifier according to this invention, Figures 3 and 4 are block diagrams showing the configuration of the second amplifier, Figure 5 is a time chart, Figure 6 is a block diagram showing another embodiment of the second amplifier, and Figure 7 is a time chart. , FIG. 8, and FIG. 9 are diagrams showing an example of the conventional method. In the figure, 12 is a winding selection circuit, 14 is a current outflow point of the first winding group, 15 is a current outflow point of the second winding group, 1
6 is a second amplifier, 20 is a switch circuit, 101,
102 is a control transistor, 103 is a common emitter resistor, and 104 and 105 are control amplifiers. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Scope of claims for utility model registration] (1) Each phase winding of a stepping motor is
and a driving means for causing the stepping motor to continuously rotate in a desired rotational direction by passing current in a cyclical manner; In a stepping motor drive amplifier having driving means for stopping the stepping motor at an arbitrary angle, the current inflow ends of the windings of each phase of the stepping motor are connected in parallel and connected to the positive terminal of the power supply. A winding selection circuit that selects whether current is to be passed through the wire, and a pair of windings that are wound in opposite directions among the above-mentioned phase windings so that current cannot be caused to flow at the same time due to the selection of the winding selection circuit. Each current outflow point configured by connecting the current outflow ends in parallel to each other, each control transistor whose respective collector is connected to each current outflow point, the connection point where each emitter of each of these control transistors is connected to each other, and the above. A common emitter resistor connected between the negative polarity terminal (ground) of the power supply, each control amplifier connected to apply a respective control voltage to each base of each of the control transistors, and each of these control amplifiers. As an input, a second amplifier that generates a voltage that varies continuously with respect to time; each of the control transistors being controlled by the output of each of the control amplifiers and connected to operate as a differential amplifier circuit by the common emitter resistor; or a switching circuit that switches between short-circuiting the common emitter resistor and connecting the control transistors so that a saturation current flows through them. (2) The second amplifier is composed of a microprocessor and a digital-to-analog converter, and the microprocessor outputs a digital signal that continuously changes with respect to time. The stepping motor drive amplifier described in Section 1. (3) The stepping motor drive amplifier according to claim 1, wherein the second amplifier is constituted by an incompletely integrating function amplifier inputting a rectangular wave voltage. (4) The stepping motor drive amplifier according to claim 1, wherein the second amplifier inputs the tracking error of the magnetic disk device and generates a voltage that continuously changes with respect to time. .