JPH02123959A - Stepping motor - Google Patents

Abstract

PURPOSE:To obtain a low-cost, high-accuracy servomotor by coaxially providing the first rotor of a stepping motor and the second rotor thereof minutely turning through an electromagnetic force generator means, by step-driving the first rotor and further by performing a minute displacement between steps via the second rotor through said electromagnetic force generator means. CONSTITUTION:A pulse current is successively supplied to a plurality of coils 8 of a stepping motor 6 to turn a rotating shaft 2 step by step. When an electric current flows through a coil 14A in a minute displacement generator 7, a gear 12 is driven in the direction A via the tooth form of a yoke 13A. Also, when an electric current flows through a coil 14B, the gear 12 is driven in the direction A' via the tooth form of a yoke 13B. When the magnitude of supply currents to the coils 14A and 14B is changed appropriately relatively, a minute displacement between steps can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a stellar pin motor, and more particularly to a stepping motor used for a tracking servo for accurately tracking a recording track by a magnetic head or the like.

[Prior Art] Conventionally, this type of tracking servo mechanism has generally been based on a voice coil type servo motor that utilizes magnetic force, or a double chipper type mechanism. Note that in a system called a double stepper, basic steps are performed by one stepping motor, and a second stepping motor provided separately is used to perform control so as to perform minute displacements.

[Problems to be Solved by the Invention] However, when using the conventional voice coil type servo motor as described above, the structure of the motor itself is complicated, so the cost tends to be high, and a large current is required for driving. Further, the double chipper type also has a complicated structure including the control mechanism including the operating section, and is expensive.

The purpose of the present invention is to focus on the above-mentioned conventional problems, and to solve the problems, it is an object of the present invention to provide a stepping device suitable for tracking servo that has a simple structure, can freely control minute displacements, and can be obtained at a low cost. Our goal is to provide motors.

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a first rotor that is driven in steps, a rotor that is arranged around the first rotor, and that drives the first rotor in a predetermined manner. In a stepping motor having a stator having a plurality of coils that are driven step by step, a second rotor fixed coaxially with the first rotor, and arranged opposite to the second rotor, The present invention is characterized by comprising an electromagnetic force generating means for rotating the second rotor.

[Function] According to the present invention, the first rotor of the stepping motor performs step drive and the second rotor is rotated by the electromagnetic force generating means.
The first rotor of the stepping motor is provided coaxially with the rotor, and the first rotor of the stepping motor is driven in steps, and the second
Since the minute displacement between steps is made via the rotor, it is possible to efficiently carry out high-precision servo at a fixed price.

[Examples] Examples of the present invention will be described below in detail and specifically based on the drawings.

1 and 2 show one embodiment of the invention.

Here, 1 is a stepping motor and 2 is its rotating shaft, and in this example, it rotates! A screw thread 3 is carved in the extending portion of i[lI2, and the seek position of a helad carriage (not shown) held in a state of being screwed with the screw thread 3 can be driven and controlled by rotation of the rotating shaft 2. . 4 is a housing of the motor 1; 5 is a bearing that pivotally supports the rotating shaft 2; the housing 4 is directly connected to a stepping motor section 6 that functions as a stepping motor, and is capable of rotating the rotating shaft 2 by a minute angle; A minute displacement generating section 7 is provided.

Roughly speaking, 8 is a plurality of coils constituting the stator of the stepping motor section 6, 9 is a yoke that holds the coil 8, and 10 is a yoke that holds the coil 8;
is a collar member that holds the magnet 11 around the rotating shaft 2, and the rotating shaft 2, collar member lO, and magnet 11 constitute a rotor of the motor section 6. The configuration of the stepping motor section 6 is similar to a conventional one. In contrast,
As shown in FIG. 2, the minute displacement generating section 7 includes a rotor 12 made of a conductive material in the form of a gear whose gears are cut at a step angle for minute displacement, and a position opposite to the tips of the teeth of the gear 12. It is composed of comb-shaped yokes 13^ and 13B in which a plurality of corresponding tooth patterns are formed, and electromagnetic force generating means consisting of coils 14A and 14B provided on each of these yokes 13A and 13B.

Incidentally, the stepping motor section is driven at a constant angle θ for each step, and the number of steps a during one rotation is therefore determined by the relationship between the number of gear cuts n of the gear 12 and the number of steps a, as shown in FIG. If the number of teeth is n=axb (integer), then the yoke 13A at any step.

The positional relationship between the teeth of gear 13B and gear 12 is the same.

For example, in FIG. 2, when θ=18° and a=20, n=20X 2 =40 may be set. In this setting, the yoke 13A,
If 13B is installed at a predetermined position, the same magnetic flux effect, that is, minute displacement can be achieved in any step. In addition, the number of teeth n and the yoke 13A facing thereto,
Of course, the larger the number of teeth in 13B, the more magnetic circuits can be constructed and a stronger retraction force can be obtained with less current.

Note that the rotor 12 made of a conductive material is coaxially fixed to the rotating shaft 2.

In the stepping motor 1 configured in this way,
By sequentially supplying pulse current to the plurality of coils 8 of the stepping motor section 6, the rotating shaft 2 is rotated one step at a time.
Furthermore, in this example, the minute displacement generating section 7 can perform minute displacement between one step. That is, in the minute displacement generating section 7, when a current is applied to the coil 14A +, the gear 12 is moved in the A direction through the teeth of the yoke 13A, and when current is applied to the coil 148, it is caused to move in the direction of A through the teeth of the yoke 13B. Gear 12 is A
’ direction.

Therefore, the current supplied to the coil 14A and the coil 14B
By relatively appropriately changing the strength of the current supplied to the stepping motor section 6, it is possible to perform minute displacement between steps.Moreover, while performing such minute displacement, the current supplied to the stepping motor section 6 is Therefore, no extra power is consumed, and minute displacement can be efficiently performed.

In the above embodiment, the gear 12 is made of a conductive material, but it goes without saying that it may be made of a magnet.

FIG. 3 shows another embodiment of the invention. In this example, the tooth profile of the gear part 12, which is the second rotor, is formed on a surface perpendicular to the shaft 2. Therefore, the tooth profiles of the yokes 13A and 1311 are also provided at positions facing the above tooth profile. . Note that 15 is a spacer for fixing the yokes 13A and 13B to the housing 4.

The operation of the stepping motor 21 configured in this manner is the same as that described in the first embodiment, and the explanation thereof will be omitted.

[Effects of the Invention] As described above, according to the present invention, the first rotor of the step-driven motor section, the second rotor fixed coaxially, and the second rotor facing the second rotor are provided. Since it is equipped with an electromagnetic force generating means that rotates the second rotor, it is possible to efficiently perform high-precision servo with a simple structure, and it is highly reliable and can generate high torque with a small current. As a result, a stepping motor suitable for tracking servo can be provided.

Furthermore, the present invention has a feature in that the shapes of the teeth provided on both the rotor and the yoke of the minute displacement means can be freely set to suit the minimum displacement.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of the configuration of a stepping motor according to the present invention, FIG. 2 is a front view showing an example of the configuration of its minute displacement means, and FIG. 3 is a cross-sectional view showing the configuration of another embodiment of the present invention. It is a diagram. DESCRIPTION OF SYMBOLS 1...Stepping motor, 2...Rotating shaft, 4...Housing, 6...Stepping motor part, 7...Minute displacement generating part, 8j4A, 14B...Coil, 9.13A, 13B ... Yoke, IO ... collar member, 12 ... gear (rotor).

Claims (1)

[Claims] 1) A first rotor that is driven in steps, and a plurality of coils that are arranged around the first rotor and drive the first rotor in predetermined steps. A stepping motor having a stator, a second rotor fixed coaxially with the first rotor, and a stepping motor arranged opposite to the second rotor and capable of rotating the second rotor. A stepping motor characterized by comprising an electromagnetic force generating means for moving the stepping motor.