JPH02294240A - Rotor structure of stepping motor - Google Patents

Abstract

PURPOSE:To improve properties of an apparatus by forming two permanent magnets around a resin-molded spacer secured to a rotor. CONSTITUTION:A resin-molded spacer 33 is secured to the end 32a on the side opposite to the lead screw 31 of the rotor shaft 32 of a rotor 30 and said spacer 33 has magnet-securing parts 33a, 33b almost at its both ends. Also, projecting parts 33d, 33g are formed at both ends of the spacer 33. A resin magnet is used as a magnet 34 and in two rows of said magnet-securing parts 33a, 33b of the spacer 33, respective ring magnets 34a, 34b are molded into shapes projecting from respective projecting parts 33d, 33g of the spacer 33. Then, said magnet 34 is connected by two joints 34c, 34d between said ring magnets 34a, 34b.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an improved rotor structure in step motors, particularly small step motors.

[Conventional technology]

Stepper motors are widely used to accurately position or steg feed various driven members, and open control systems allow relatively inexpensive equipment to perform the desired positioning action. In modern printers, floppy disk drives, etc., in order to drive the print head or write/read head with high precision, it is common to use a step motor to move the carriage carrying these heads. A small step motor is essential for such a drive.

The structure of a general step motor will be explained below using a motor for a floppy disk drive as an example. FIG. 2 shows an assembled sectional view of the step motor.

A rotor 5 is rotatably supported on the motor base body 1 in one thrust direction and one radial direction by a bearing ball 6 of a pivot bearing 2 in point contact, and in the other radial direction by a pusher 4. It is held movably. The rotor 5 is composed of a rotor shaft 7 on which a lead screw 6 is formed, a magnet holding seat 8 press-fitted into the rotor shaft 7, and a magnet 9 held by the magnet holding seat 8.

A stator 10 is arranged around the magnets 9 of the rotor 5. The stator 10 has a coil wire 1 wound in two rows.
1, a winding frame 12 for winding the coil wire 11, an outer stator core body 16 and an inner stator core body 14 for holding the winding frame 12 and generating a magnetic field according to the current flowing to the coil wire 11. and a mounting plate 16 that holds the stator core 15.

A thrust spring 18 is arranged on the back side of the rotor 5 and supports the rotor 5 in the thrust direction in cooperation with the thrust ball 17, and a thrust spring 18 is arranged on the back side of the rotor 5, and a thrust spring 18 is arranged on the back side of the rotor 5 to support the rotor 5 in the thrust direction in cooperation with the thrust ball 17.
It has a structure covered with a rear force bar 19.

Next, the action will be explained.

By passing current through the coil wire 11, the stator coil 71
5K magnetic poles are formed, and the rotor 5 is rotated in steps by the action of the magnet 9. This step rotation of the rotor 5 causes a lead screw 6 formed on the rotor shaft 7 to feed and drive a magnetic head (not shown) with high precision.

Incidentally, an actual rotor conventionally has a structure as shown in the cross-sectional view of FIG. 3 or FIG. 4. FIG. 3 shows a cross-sectional view of a magnet-integrated rotor.

An end 23a of a rotor shaft 26 opposite to the lead screw 22 is formed with a lead screw 22 in the rotor 21.
A cylindrical magnet 24 having a hollow cylindrical shape is fitted and fixed therein.

In the case of such a magnet-integrated rotor, the specific gravity of the magnet is 4.
Since it is heavy, about .about.6 mm, the moment of inertia is large, making it difficult to accurately position it as a step motor, which poses a problem in terms of accuracy.

Further, FIG. 4 shows a sectional view of a rotor in which a spacer is arranged between the shaft and the magnets. In the rotor 25, a rotor seat 28 made of metal such as AiB or F is press-fitted and fixed to the end 27a of the rotor shaft 27 opposite to the lead screw 26, on which the lead screw 26 is formed, as shown in FIG. The magnet 29 is attached to the rotor seat 28 as two ring-shaped magnets 29a and 29b.
a and 28b by adhesive. The ring-shaped magnets 29a, 29b are fixed to magnet fixing portions 28a, 28b formed at both axial ends of the rotor seat 28 at positions corresponding to the two rows of coil wires 11 shown in FIG. The shape of the rotor seat 28 has a ring-shaped recess 28C in the center sandwiched between ring-shaped magnets 29a and 29b, and a ring-shaped magnet 29 at the boundary between the recess 28C and each magnet fixing part 28a and 28b.
Ring-shaped convex portion 28d for positioning a and 29b
．． 28e is formed.

To assemble this rotor 25, first, the rotor seat 2
A ring-shaped magnet 29a,
29b is cured and fixed by applying an adhesive to each, and the rotor seat 28 is press-fitted and fixed to the end 27a of the rotor shaft 27 on which the lead screw 26 is formed to complete the process.

[Problem to be solved by the invention]

However, in the rotor structure shown in FIG.
Since 2a and 22b are fixed by adhesive, there is no need for adhesive. This method requires a huge number of man-hours, and also requires a large number of man-hours to press-fit and fix the rotor seat onto the rotor shaft, so that only very expensive rotors can be obtained. This is a major drawback in response to the demand for lower costs of devices such as floppy disk drives.

In addition, quality problems may occur during bonding and compression work.

Furthermore, since the adhesive is bonded with a gap, the eccentricity of the magnet becomes large, resulting in deterioration of characteristics, which is an obstacle to improving the performance of small step motors.

An object of the present invention is to provide a step motor rotor structure that is low in cost, has small variations in quality, and has good characteristics.

[Means to solve the problem]

The gist of the present invention to achieve the above object is to provide a step motor comprising a rotor, a stator core, and a stator coil assembly, in which a resin-molded base is fixed to the shaft of the rotor, and at least [Embodiment] The embodiment of the present invention will be described in detail below with reference to the drawings.

1 is a cross-sectional view of a rotor according to the present invention, FIG. 5 is a cross-sectional view of the rotor shown in FIG. 1 when viewed from a direction perpendicular to the plane of the paper, and FIG. 6 is a cross-sectional view taken along the line AA in FIG.

60 is a rotor, and the rotor 60 has a rotor shaft 62 with a lead screw 31 formed at one end.
A spacer 66 formed with a finger is fixed to the end 32a on the opposite side of the second lead screw 61. The shape of the smoother 66 includes magnet fixing parts 33a and 33b at almost both ends of the smoother 66, which correspond to the two rows of coil wires 11 shown in FIG. 2, and a recessed part 53C in the center. There is. There is no particular need to form this recess 33C. And magnet fixing parts 66a, 33b and recessed part 33C
There is a protrusion 3 on the border for positioning and holding the magnet.
3e and 33f, there are also convex portions 53 at both ends of the spacer 360.
d and 33g are each formed.

The magnets 34 are made of clear resin magnets, and each H-ring shaped magnet 64a is attached to the two rows of magnet fixing parts 33a and 33b of the spacer 63.
, 34b are formed to protrude from each convex portion of the spacer 33.

The magnet 64 improves workability, which will be described later, by connecting two rows of ring-shaped magnets 34a and 34b with two connecting portions 34C and 34d.

Of course, there are two joints (・
However, two locations are not necessarily required, and processing can be performed at one location. In order to form the connecting portions 64C, 34d, cutout portions 3)h, 35i are formed in the baser 66.

Furthermore, since it is possible that the adhesion between the metal rotor shaft 62 and the sugar beet smoother 66 is weak, the rotor shaft 32 is provided with one or several detents 32b.

7 and 8 illustrate the structure of an embodiment of the rotor curve of the present invention. 7 is a sectional view taken along line FF in FIG. 8, and FIG. 8 is a sectional view taken along line EE in FIG.

The rotors shown in FIGS. 7 and 8 are almost the same as the rotor shown in FIG. The central protrusion 47e has the same diameter, the lower surface of the connecting portion 48d of the ring-shaped magnet 48 is the same as the surface of the magnet fixing portions 47a and 47b of the spacer 47, and the upper surface of the connecting portion 48d is located at the center of the spacer 47. The diameter is the same as that of the protrusion 47e.

Next, a method of forming the rotor 30 will be explained.

The rotor 60 uses a two-step molding method. That is, FIGS. 9 to 11 show a rotor molding method according to the present invention.

Figure 9 shows the method of molding the subesa, which is shown in Figure 6.
B sectional view, FIG. 10 is a BB sectional view in FIG. 6 showing the magnet forming method, and FIG. 11 is a C-C sectional view in FIG. 10.
FIG.

To explain with reference to FIG. 1, first, the rotor shaft 62 on which the lead screw 31 is formed is set in the mold 65,
The upper mold 66 and lower mold 67 are combined. Then, sugar beet (in the embodiment, the material is PBT) is injected into the spacer-shaped mold portion 69 through sprues 68 provided at two locations. As a result, the spacer 36 is molded. Next, the mold is changed, and the rotor shaft 62 on which the spacer 66 is formed is set in the mold 40 shown in FIG. 8, and the upper mold 41 and the lower mold 42 are brought together. Then, as shown in FIG. 9, magnet powder (in the embodiment, the material is a Nd-Fe-B magnet) is poured into the resin through two sprues 46 provided in two notches 66h provided in the spacer 66. A mixed and kneaded m-fat material (in the example, the material is nylon 12) is injected into a magnet-shaped mold part 44 and molded. At this time, if a sprue 46 is provided on the ring-shaped magnet 34a side, the resin material will flow through the connecting parts 34C and 34d and also flow to the other ring-shaped magnet 54b side, and the two rows of ring-shaped magnets 34a and 3
4b can be formed.

〔Effect of the invention〕

As is clear from the above, since two rows of magnets are formed with a joint, molding is possible, and since both the spacer and magnets are formed by molding, a rotor can be provided at a very low cost. We were able to achieve great results.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a rotor according to the present invention, FIG. 2 is an assembled cross-sectional view of a step motor, FIG. 3 is a cross-sectional view of a magnet-integrated rotor, FIG. Figure 5 is a cross-sectional view of the rotor in Figure 1 when viewed from a direction perpendicular to the page.
6 is a cross-sectional view taken along the line A-A in FIG. 5, FIG. 7 is a cross-sectional view taken along line FF in FIG. 8 showing another embodiment of the present invention, and FIG. 8 is a cross-sectional view taken along line E-E in FIG. FIG. 9 shows how to form the subesa 24,
29, 34...Magnet, 36...Subasa, 34a, 34b...Ring magnet, 34c, 3
4d...Connection part, 35, 40...Mold, 68, 46...Gate, 39, 44...Mold part. The top view and Figure 11 are cross-sectional views taken along the line C-C in Figure 10.
...Motor base body, 5, 21, 25, 30...Rotor, 6, 22,
26, 61...Lead scree 7, 26, 27
, 62... Rotor shaft, 9... Rotor magnet, 10... Stator coil, 11... Coil wire, Figure 1! s4 figure figure 5 figure 6 question l figure figure figure figure

Claims (1)

[Claims] A stator coil having a rotor having a permanent magnet fixed to the shaft, a stator core disposed around the rotor, a stator coil core integrally arranged with the stator core, and a coil wire wound around the stator coil core. In the step motor including the assembly, a resin-molded spacer is fixed to the shaft of the rotor, and two permanent magnets connected at at least one point are formed around the spacer. A step motor rotor structure featuring: