JPH057644B2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" The present invention relates to a method of manufacturing a magnetic encoder.
In particular, a magnetic sensor comprising: a spindle shaft having a magnetic recording part on which a magnetized pattern is formed at a predetermined pitch; and a magnetic detection element disposed at a predetermined distance from the spindle shaft and detecting the magnetized pattern. The present invention relates to a manufacturing method suitable for use in manufacturing an encoder.

"Prior Art" Magnetic encoders are generally used as devices for detecting the rotational position, movement position, or speed of control systems in robots, NC devices, etc. A structure shown in FIG. 8 or 9 is known.

The former magnetic encoder 1 shown in FIG. 8 includes a casing 2 and a rolling bearing 3 attached to the casing 2.
A spindle shaft 4 is mounted through the spindle shaft 4, and a magnetic recording body 5 is fitted into a portion of the spindle shaft 4 that protrudes from the casing 2, and has a magnetized pattern M formed on its outer peripheral surface in a predetermined pitch. , a magnetic detection element (MR element) 6 disposed facing the outer peripheral surface of the magnetic recording body 5 at a predetermined interval.
It is composed of:

Moreover, the latter magnetic encoder 7 shown in FIG.
In this case, instead of the former rolling bearing 3, a sliding bearing 8 is used to support the spindle shaft 4 with respect to the casing 2, and a thrust washer 9 and a collar 10 are provided at appropriate positions on the spindle shaft 4, By bringing these thrust washers 9 and collar 10 into sliding contact with the slide bearing 8, the spindle shaft 4 can be positioned along the thrust direction and external forces along that direction can be supported.

These magnetic encoders 1 and 7 cause the magnetic field formed by the magnetized pattern M to act on the magnetic detection element 6, and also cause the magnetic field to be generated by the rotation of the magnetic recording body 5 accompanying the rotation of the spindle shaft 4. By changing the magnetic flux density acting on the detection element 6 and detecting the resulting change in the electrical resistance of the magnetic detection element 6, the control system of the spindle shaft 4, that is, the control system connected to the spindle shaft 4, is controlled. The rotation position, movement position, or speed is detected.

"Problems to be Solved by the Invention" The present invention aims to solve the following problems in the conventional technology described above.

That is, in the magnetic encoder having the above-described magnetization pattern M and the magnetic detection element 6, in order to perform high-precision detection, the vibration of the rotation center of the spindle shaft 4 is suppressed, and the rotating magnetic The distance between the recording body 5 and the magnetic detection element 6 is always kept constant, and the magnetic detection element 6 is
Although it is necessary to maintain a constant magnetic flux density, in both of the conventional magnetic encoders 1 and 7 described above, the casing 2 and the spindle shaft 4 are connected via bearings 3 and 8. Therefore, in order to accurately position the rotation center of the spindle shaft 4 with respect to the casing 2, it is necessary to control the outer diameter of the spindle shaft 4,
The inner and outer diameters of the bearings 3 and 8, as well as the inner diameter of the bearing mounting portion of the casing 2, must be strictly controlled. This is a problem that has led to soaring prices.

In the former case, the casing 2 and the bearing 3
, and the fitting of each bearing 3 with the spindle shaft 4, as well as assembly work at four locations.This also solves the problem of complicating the manufacturing process mentioned above. In the latter case, since the number of constituent members such as the flange 10 and the thrust washer 9 is increased, in addition to the manufacturing process described above, the flange 1
0 formation process and the thrust washer 9 installation process are required, and there are problems that need to be solved, such as a tendency to further complicate the manufacturing process.

Furthermore, the magnetic recording body 5 is moved to the spindle shaft 1.
1 and has a magnetized pattern M applied to its outer periphery, the machining accuracy of the inner and outer surfaces of this magnetic recording body 5 also matches the accuracy of maintaining the distance between the magnetic recording body 5 and the magnetic detection element 6. It greatly affected
In this respect as well, there are factors that restrict the improvement of detection accuracy.

"Means for Solving the Problems" An object of the present invention is to provide a method for manufacturing a magnetic encoder that can effectively solve the above-mentioned conventional problems. In particular, the method for manufacturing a magnetic encoder includes: a spindle shaft having a magnetized pattern formed at a predetermined pitch on its surface; and a magnetic sensing part that rotatably supports the spindle shaft and faces the magnetized pattern. forming an inner casing by insert molding using the spindle shaft as an insert; arranging a circuit element around the inner casing, including a magnetic detection element that is opposed to the magnetized pattern via the magnetic detection section; The present invention is characterized by comprising the following main steps: a step of forming an outer casing around the inner casing and the circuit element to cover them by insert molding, using the inner casing and the circuit element as inserts.

"Operation" The method for manufacturing a magnetic encoder according to the present invention includes:
By forming an internal casing around the spindle shaft by insert molding, the spindle shaft can be directly supported by the casing, making it easy to manage the relative positional relationship between the two, and the magnetic sensing element can also be mounted on the spindle shaft. By facing the magnetized patterns via the magnetic detection part of the internal casing, variations in the distance between each magnetized pattern and the rotation center of the spindle shaft, that is, the distance between the magnetized pattern and the magnetic detection element, can be eliminated. By suppressing variations and forming an outer casing by insert molding to cover the inner casing and magnetic sensing element,
The above-mentioned positional relationship is constrained to maintain its accuracy, and the assembly work is greatly simplified.

``Example'' An example of the present invention will be described below with reference to FIGS. 1 to 7.

First, prior to manufacturing, a cylindrical material is cut to a predetermined length, the outer surface of the material is ground to a predetermined outer diameter, and the shapes of both end surfaces are adjusted.
Furthermore, the spindle shaft 11 is formed by forming a concave groove 11a on the outer circumferential surface near one end.

Next, after cleaning the spindle shaft 11, a magnetization pattern M is applied at a predetermined pitch to the outer peripheral surface near the groove 11a, and magnetization patterns M are applied at predetermined pitches to the outer peripheral surface near the groove 11a.
A mold release agent is applied to a predetermined thickness on the rotary support portions 11b and 11c formed at the locations.

As shown in FIGS. 1 and 2, the spindle shaft 11 subjected to such pretreatment is placed in an injection mold 12, and one end of the spindle shaft 11 is inserted through a fixing core 13. It is supported by the mold 12, and the entire circumference of the other end and the middle part is supported by the mold 12.
Fix it in a supported state.

At this time, cavities 12a and 12b are formed in the mold 12 around the rotational support parts 11b and 11c of the spindle shaft 11, and the cavities 12a and 12b are formed at both ends of the spindle shaft 11.
Hollow portions 12c and 12d that communicate a and 12b
are formed along the length of the spindle shaft 11 and spaced from the spindle shaft 11 .

From this, the cavities 12a to 12 of the mold 12
By injecting resin into d, an inner casing 14 is formed around the spindle shaft 11, as shown in FIG.

Inner casing 14 thus formed
Bearing portions 14a, 14b are brought into contact with the outer circumferential surfaces of the rotational support portions 11b, 11c of the spindle shaft 11, and connecting portions 14c, 14d connect these bearing portions 14a, 14b.
are integrally formed, and both of these bearing parts 14
a, 14b and both connecting portions 14c, 14d, between which the spindle shaft 11 is connected.
A through hole 15 that exposes the magnetized pattern M is formed by forming a through hole perpendicular to the above.

Furthermore, an annular protrusion 16 is formed on the inner peripheral surface of the bearing part 14a that supports the rotation support part 11b, and the annular protrusion 16 is brought into sliding contact with the groove 11a formed in the spindle shaft 11 along the entire circumference. A rectangular groove portion 14e having a predetermined depth is formed by the core 13 on one end surface, and is continuous with the bearing 14a.

Next, the mold release agent applied to the rotation support parts 11b and 11c of the spindle shaft 11 is removed by thermal treatment or chemical treatment.

By removing the mold release agent in this manner, an appropriate amount of water is formed between the spindle shaft 11 and the inner casing 14 around the entire circumference of the spindle shaft 11.
A space is formed between the spindle shaft 11 and the inner casing 14 so that the spindle shaft 11 is rotatably supported.
4 in the longitudinal direction, that is, the thrust direction, of the spindle shaft 11 is restricted.

From this, a rectangular lid 17 as shown in FIG. 3 is attached to the concave groove 14e formed on one end surface of the internal casing 14 to close the end of the bearing part 14a, and the internal casing A circuit element 19 equipped with a magnetic detection element 18 is attached to the circumferential side of the magnetic sensor 14 .

Here, this circuit element 19 will be explained. In this embodiment, it has the following special configuration.

As shown in FIG. 4, the flexible printed circuit board 2 is bent into a U-shape, and the glass is integrally attached to the inner surface of one of the bent ends and supports the magnetic detection element 18. A substrate 21;
It is composed of a plurality of circuit elements 22 attached to appropriate positions on the inner and outer surfaces of the flexible printed circuit board 20, and the magnetic detection element 18,
The circuit element 22 is a flexible printed circuit board 20
are electrically connected to each other by a circuit pattern (not shown) formed on the flexible printed circuit board 20, and to an external connection terminal 24 formed by a protruding piece 23 provided at the other end of the flexible printed circuit board 20. electrically guided.

As shown in FIGS. 5 and 6, this circuit element 19 is connected to the flexible printed circuit board 2.
0 is attached so as to cover one end of the through hole formed in the inner casing 14,
The bent other end is mounted so as to face the other end of the through hole, and the connecting portion of each of these ends is connected to one connecting portion 14c of the inner casing 14.
By attaching it along the inner casing 14, it is attached so as to surround the inner casing 14.

With the circuit element 19 mounted in the inner casing 14 in this manner, the glass substrate 21 is inserted into the through hole 15 to close the through hole 15, and the magnetic detection element 18 attached to the glass substrate 21 is are opposed to the magnetized pattern M of the spindle shaft 11 at a predetermined interval. Furthermore, an external connection terminal 24 formed on the flexible printed circuit board 20 is made to protrude outward from one end surface of the internal casing 14 so as to be substantially orthogonal to the outside.

From this, as shown in Figures 5 and 6,
A closing plate 25 is disposed at the other end of the through hole to cover the through hole, and a circuit element 26 and the like are disposed along the other connecting portion 14d to communicate the internal space of the inner casing 14 with the outside. In addition, an annular spacer 27 is fitted to the other end of the spindle shaft 11, and the external connection terminal 24 is
By fitting the fixing core 28 into the protruding piece 23 forming the circuit element 19 and fitting and supporting the fixing core 28 and the spacer 27 into the injection mold 29, the circuit element 19 is formed. The installed inner casing 14 is placed in the mold 29.

At this time, the inner casing 1 is inside the mold 29.
4, circuit element 19, and internal casing 14
A hollow portion 2 having a substantially rectangular peripheral edge is formed around the spindle shaft 11 that protrudes from the
9a is formed.

Next, after resin is injected into the cavity 29a of the mold 29 and solidified, the mold 29 is removed, and as shown in FIG. A rectangular parallelepiped-shaped outer casing 30 is formed.

External casing 30 thus formed
As a result, the flexible printed circuit board 20 and circuit element 22 of the circuit element 19 are wrapped from the outside,
These movements are restrained, and the flexible printed circuit board 20 and the internal casing 14 are fixed in contact with each other, and their positional relationship is restrained.

In addition, the spacer 27 and the fixing core 28
is removed together with the mold 29, a space is formed between the outer peripheral surface of the other end of the spindle shaft 11 and the outer casing 3, and
A guide hole 31 is provided around the external connection terminal 24 for exposing the external connection terminal 24 to the outside.
is formed, and the former gap ensures relative rotation between the spindle shaft 11 and the internal casing 14, and the latter guide hole 31 allows the external connection terminal 24 (that is, the magnetic detection element 18 and the circuit element 22) and external equipment.

Through the above steps, manufacturing of the magnetic encoder 32 is completed.

According to the manufacturing method of this embodiment, the inner casing 14 is formed around the spindle shaft 11 by insert molding, and the spindle shaft 11 is directly supported by the inner casing 14. Internal casing 1
Since the bearing portions 14a and 14b of No. 4 are formed along the surfaces of the rotational support portions 11b and 11c of the spindle shaft 11, there is no assembly error between the two, and the spindle shaft 11
When applying a mold release agent to form a gap between the inner casing 14 and the inner casing 14, the coating thickness of the mold release agent can be controlled within an ultra-fine range using thin film formation technology, and due to the synergistic effect of these , the relative positional relationship between the two can be managed easily and with high precision.

Moreover, the magnetic detection element 18 is attached to the inner casing 14 in which the spindle shaft 11 is mounted under highly accurate position control, and the magnetic detection element 18 is made to face the magnetization pattern M of the spindle shaft 11. In addition, the magnetized patterns M are directly applied to the surface of the spindle shaft 11, and variations in the distance between each magnetized pattern M and the rotation center of the spindle shaft 11 affect the machining accuracy of the outer surface of the spindle shaft 11. Since it depends only on the distance between the two, highly accurate management can be performed on the interval between the two as well.

The outer casing 30 restricts the positional relationship between the circuit element 19 to which the magnetic detection element 18 is attached and the inner casing 14, making it possible to maintain the above-described accuracy over a long period of time.

Furthermore, by fitting the concave structure 11a of the spindle shaft 11 and the protrusion 16 of the internal casing 14,
As mentioned above, both spindle shafts 11
The relative movement of the spindle shaft 11 in the thrust direction can be restrained, and the shape of these fittings can be easily set by machining the outer surface of the spindle shaft 11, so that the strength of the fitting portion against external force in the thrust direction can be easily increased. Secured.

Therefore, the magnetic encoder 32 can greatly simplify manufacturing and can perform highly accurate detection.
It becomes possible to manufacture

Note that the above-described embodiment is just an example, and various changes can be made based on design requirements and the like.

For example, in order to make the spindle shaft 11 and the internal casing 14 relatively rotatable, in the embodiment described above, a release agent is applied to the surfaces of the rotation support parts 11b and 11c of the spindle shaft 11 to a predetermined thickness. and inner casing 14
By removing the release agent after molding,
An example has been shown in which a predetermined gap is formed between the spindle shaft 11 and the internal casing 14, but instead of this, the gap may be formed by the following method. good.

That is, when molding the inner casing 14, the spindle shaft 11 is heated to thermally expand until it reaches a predetermined outer diameter, and in this state, the inner casing 14 is injection molded around the spindle shaft 11, and then solidified. Later, by cooling the spindle shaft 11 to room temperature and reducing its diameter, a gap between the spindle shaft 11 and the inner casing 14 is created.
This is a method of creating a gap.

Furthermore, if the release agent has good sliding properties, or if a material with excellent slipping properties is used as the molding material for the inner casing 14, there is no need to remove them, and the above-mentioned There is no need to provide one.

FIG. 10 shows another embodiment of the present invention, and FIG. 11 shows the molded state thereof.

In this embodiment, no through hole is formed in the magnetic detection section, and the spindle shaft 11
The casing material wraps around the magnetic detection area of the
A gap 34 is formed between the mold and the spindle shaft 11 so that the thin film 33 is integrally formed. Therefore, when the spindle shaft 11 is insert-molded using such a mold, a thin film 33 is formed as shown in FIG. 11.

If the magnetic encoder is configured by the method according to this embodiment, the circumferential surface of the spindle shaft 11 will be in a completely sealed state, so that the dustproof effect can be enhanced and a thin film 33 of a constant thickness can be formed on the magnetic detection section. Therefore, the magnetic detection element can be easily positioned.

"Effects of the Invention" As explained above, the method for manufacturing a magnetic encoder according to the present invention includes supporting the spindle shaft rotatably around the spindle shaft, the surface of which is provided with a magnetization pattern at a predetermined pitch. forming an internal casing having a magnetic sensing part facing the magnetized pattern by insert molding using the spindle shaft as an insert, around the internal casing facing the magnetic sensing pattern through the magnetic sensing part; a step of forming an outer casing around the inner casing and the circuit element to cover the inner casing and the circuit element by insert molding the inner casing and the circuit element as an insert body; It is characterized by having the above-mentioned main steps, and has the following excellent effects.

The spindle shaft is directly supported by the casing, making it easier to manage the relative positional relationship between the two.
In addition, the magnetization patterns are applied directly to the spindle shaft to suppress variations in the distance between each magnetization pattern and the rotation center of the spindle shaft.
By arranging the magnetic detection element to face the magnetized patterns whose positions are controlled with high precision in this way, the distance between each magnetized pattern and the magnetic detection element is made uniform, and each magnetized pattern acts on the magnetic detection element. By keeping the magnetic flux density constant, it is possible to provide a magnetic encoder that can perform highly accurate detection.

Furthermore, by forming an outer casing that covers the inner casing and magnetic detection element using insert molding, the positional relationship of each component can be restricted and the above-mentioned detection accuracy can be maintained over a long period of time. Enables the provision of magnetic encoders.

Furthermore, when manufacturing the magnetic encoder, it is possible to eliminate as many structural members as possible, simplify the manufacturing process, and simplify the assembly work.

[Brief explanation of the drawing]

Figures 1 to 7 show one embodiment of the present invention, where Figure 1 is a vertical cross-sectional side view showing the state in which the spindle shaft is disposed in the mold, and the second figure is a side view of the spindle shaft arranged in the mold. Fig. 3 is a partially sectional external perspective view showing a state in which the internal casing is formed around the spindle shaft;
The figure is a partially sectional external perspective view showing circuit elements.
Fig. 5 is a vertical cross-sectional side view showing a state where the inner casing with the spindle shaft and circuit elements installed is arranged in the mold, Fig. 6 is a cross-sectional view taken along the - line in Fig. 5, and Fig. 7 is a cross-sectional view taken along the - line in Fig. 5. 8 and 9 are external perspective views showing a part of the magnetic encoder manufactured by one embodiment using phantom lines.
10 and 11 show other embodiments of the present invention, and FIG. 10 shows FIGS. 1 and 11.
The figure is similar to FIG. 3. 11... Spindle shaft, 12, 29...
(For injection molding) Mold, 14...Inner casing,
18...Magnetic detection element, 19...Circuit element, 30
...External casing, 32...Magnetic encoder,
33... Thin film, 34... Interval, M... Magnetized pattern.

Claims (1)

[Scope of Claims] 1. An inner casing surrounding a spindle shaft having a magnetized pattern formed at a predetermined pitch on its surface, rotatably supporting the spindle shaft, and equipped with a magnetic detection section facing the magnetized pattern. a step of forming the spindle shaft by insert molding using the spindle shaft as an insert body, a step of arranging a circuit element including a magnetic detection element that is opposed to the magnetized pattern via the magnetic detection section around the inner casing. , a step of forming an outer casing around the inner casing and the circuit element to cover them by insert molding, using the inner casing and the circuit element as inserts; A magnetic encoder characterized by comprising the above main steps. manufacturing method.