WO2024189738A1 - Encoder having flexible cable - Google Patents

Abstract

The present invention provides a highly reliable encoder in which an FPC cable does not come into close proximity to or contact with an electronic component. The encoder comprises: a printed circuit board with an electronic component; a flexible cable in connection with a connector, which is mounted on the printed circuit board; and a cover constructed to cover the printed circuit board and the flexible cable. The cover has a protrusion that can come into contact with the flexible cable. The protrusion is constructed to bend the flexible cable such that the minimum distance between the flexible cable and the electronic component is equal to or greater than a permissible distance determined on the basis of a function of the encoder.

Description

Encoder with flexible cable

This disclosure relates to an encoder having a flexible cable.

As sensors for detecting the rotational position of each axis of a robot, encoders such as optical encoders attached to the motors that drive each axis are known. One well-known example is an optical encoder that has a housing formed of a main body and a cover, and has a flexible cable (FPC cable) arranged inside the housing (see, for example, Patent Document 1).

Similarly, a magnetic rotary encoder having a housing formed of a main body and a cover and an FPC cable disposed inside the housing is also well known (see, for example, Patent Document 2).

Japanese Patent Application Publication No. 06-174496 JP 2008-249343 A

In an encoder that has an FPC cable inside a cover or housing, if the FPC cable comes close to or comes into contact with electronic components such as an LSI placed inside the cover, the noise tolerance of the encoder may decrease or the temperature of the electronic components may rise excessively. Therefore, there is a demand for technology that provides a highly reliable encoder in which the FPC cable does not come close to or into contact with electronic components.

One aspect of the present disclosure is an encoder comprising a printed circuit board having electronic components, a flexible cable connected to a connector mounted on the printed circuit board, and a cover configured to cover the printed circuit board and the flexible cable, the cover having a protrusion capable of contacting the flexible cable, and the protrusion configured to bend the flexible cable so that the minimum distance of the flexible cable relative to the electronic components is equal to or greater than an allowable distance determined based on the function of the encoder.

1 is a schematic cross-sectional side view of an encoder according to a first embodiment. FIG. 2 is a schematic perspective view of a cover of the encoder of FIG. 1 . 1 is a schematic cross-sectional side view of an encoder according to a comparative example. FIG. 11 is a schematic cross-sectional side view of an encoder according to a second embodiment. FIG. 11 is a schematic plan view of an encoder according to a third embodiment.

(First embodiment)
1 is a schematic cross-sectional side view of an encoder 10 according to a first embodiment of the present disclosure. The encoder 10 is, for example, an optical encoder attached to a motor such as a servo motor that drives each axis of a robot, and detects the rotational angle position of a rotating shaft 12 of the motor. The encoder 10 has a slit plate 14 formed with a plurality of slits (not shown) and configured to rotate integrally with the rotating shaft 12, and a light-emitting unit 16 such as an LED and a light-receiving unit 18 such as a photosensor that are arranged opposite each other with the slit plate 14 in between.

The light-emitting unit 16 is disposed on a mounting plate 20 for mounting the encoder 10 to a predetermined location on a motor or the like. The light-receiving unit 18 is disposed on a first surface (e.g., the downward surface) of a printed circuit board (PCB) 22 disposed opposite the mounting plate 20, and generates a signal based on the light from the light-emitting unit 16 received through the slit plate 14. An electronic component 24 such as an LSI is mounted on a second surface (e.g., the upward surface) of the printed circuit board 22. In addition to LSIs, the electronic component 24 can also include integrated circuits and electronic circuits that perform arithmetic processing, such as microcomputers and DSPs (digital signal processors).

The electronic component 24 generates information (data) about the rotational position of the rotating shaft 12 based on the signal generated by the light receiving unit 18. The data generated by the electronic component 24 is output to the outside via a flexible cable (FPC cable in the illustrated example) 28 connected to a connector 26 mounted on the PCB 22.

As shown in Figures 1 and 2, the encoder 10 has a cover 30 configured to cover the PCB 22 and the FPC cable 28 in order to protect the electronic components 24 mounted on the PCB 22 from the outside. The FPC cable 28 is connected by soldering or the like to a connection part 36 disposed in an opening 34 formed on the side of the cover 30, and the connection part 36 is connected to an external device (not shown) that processes the output data of the encoder 10 by a cable or the like (not shown).

The inner surface of the cover 30 is provided with a protrusion 32 that can come into contact with the FPC cable 28, and the protrusion 32 is configured to come into contact with and bend the flexible cable 28 so that the minimum distance of the FPC cable 28 to the electronic component 24 is equal to or greater than the allowable distance determined based on the noise tolerance and other functions of the encoder 10. This allowable distance will be described later.

As a comparative example, FIG. 3 shows an example of the configuration of an encoder in which the cover does not have a protrusion. Note that components that may be the same as those in the first embodiment are given reference numbers that are 100 larger than the reference numbers in the first embodiment, and detailed descriptions are omitted.

Generally, due to constraints of the manufacturing equipment for the encoder 110, the FPC cable 128 is considerably longer than the distance between the components (here, the electronic component 124 and the connector 126) that are connected by the FPC cable 128. Since the FPC cable 128 is flexible, it may come into contact with the electronic component 124.

Electronic components such as LSIs are easily affected by noise, and the FPC cable itself can be a path for noise. Therefore, as shown in FIG. 3, when the FPC cable 128 comes into contact with the electronic component 124, the electronic component 124 is adversely affected, which can result in a decrease in the noise tolerance of the encoder 110. Even if the FPC cable 128 is not in contact with the electronic component 124, a similar decrease in noise tolerance can occur just by being close to the electronic component 124 within the allowable distance. Furthermore, contact with the FPC cable 128 can cause an undesirable temperature rise in the electronic component 124, which can reduce its function as an encoder.

In the first embodiment, therefore, a protrusion 32 that can come into contact with the FPC cable 28 is provided on the inner surface of the cover 30, and the degree of bending of the FPC cable 28 is controlled so that the FPC cable 28 does not come into contact with the electronic component 24 or approach within an allowable distance, thereby reliably preventing a decrease in noise tolerance caused by the FPC cable 28 and an excessive temperature rise in the electronic component 24.

In this embodiment, "close (less than the allowable distance)" means that the FPC cable 28 is not in contact with the electronic component 24, but is close enough to cause a substantial decrease in the noise resistance of the encoder. According to the present disclosure, the FPC cable 28 is maintained by the protrusion 32 at a distance from the electronic component that is greater than the allowable distance at which the noise resistance is not decreased. In other words, the allowable distance in this embodiment means, for example, the minimum distance between the FPC cable 28 and the electronic component 24 at which the noise resistance is not decreased, and can be empirically determined based on the noise resistance required for the encoder. Alternatively, the allowable distance can be determined based on the amount of temperature rise in the electronic component 24 that may affect the function of the encoder, and more specifically, the allowable distance can be empirically determined so that the amount of temperature rise in the electronic component 24 due to contact or proximity with the FPC cable 28 is equal to or less than the maximum value at which the function of the encoder is not impaired. The allowable distance can be various values depending on the size and structure of the encoder, and is, for example, 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm.

The position, size and shape of the protrusion 32 can be appropriately determined based on the arrangement and shape of the electronic component 24. For example, in the first embodiment shown in Figures 1 and 2, the protrusion 32 is arranged above, and preferably directly above, the electronic component 24 in a direction perpendicular to the surface of the PCB 22, and in a plan view (when viewed in a direction perpendicular to the surface of the PCB 22) (see Figure 5 described below), the electronic component 24 has a substantially rectangular shape, while the protrusion 32 has a shape (here, substantially circular) that encompasses the electronic component 24. Alternatively, the tip of the protrusion 32 may have substantially the same shape as the electronic component 24 in a plan view. In addition, the distance between the tip of the protrusion 32 (the lower end in Figure 1) and the electronic component 24 is preferably short enough that the bent FPC cable 28 cannot be interposed between the tip and the electronic component 24, and is, for example, 1 to 5 mm.

These protrusions 32 are arranged and shaped in such a way that no matter how the FPC cable 28 is deformed or bent, the FPC cable 28 is prevented from contacting or coming into close proximity with the electronic components 24, preventing a decrease in noise resistance, etc.

There are no particular restrictions on the material that constitutes the cover 30 and the protrusions 32; for example, resin or metal can be used. Furthermore, the protrusions 32 may be attached to the cover 30 by adhesive or other means after being molded into a predetermined shape, or may be molded integrally with the cover 30. With regard to the latter, for example, molding the cover 30 and the protrusions 32 integrally with resin is advantageous in terms of cost.

Second Example
4 is a schematic side cross-sectional view of an encoder 10a according to the second embodiment. In the second embodiment, only the parts different from the first embodiment will be described, and the components of the second embodiment that may be similar to those of the first embodiment will be given the same reference numerals as those of the first embodiment, and detailed descriptions thereof will be omitted.

In the first embodiment, the protrusion 32 and the electronic component 24 overlap in a plan view (more specifically, the protrusion 32 encompasses the electronic component 24), whereas in the second embodiment, the protrusion 32a provided on the inner surface of the cover 30a is disposed between the electronic component 24 and the connector 26. In the second embodiment, the FPC cable 28 can be intentionally entangled with the protrusion 32a, thereby ensuring that the minimum distance of the FPC cable 28 from the electronic component 24 is equal to or greater than the allowable distance determined based on the noise tolerance of the encoder 10a. Therefore, in the second embodiment, a decrease in the noise tolerance of the encoder 10a is also prevented. The position, size, and shape of the protrusion 32a can be appropriately selected so that the FPC cable 28 can be suitably entangled.

(Third Example)
5 is a schematic plan view of an encoder 10b according to the third embodiment. In the third embodiment, only the parts different from the first embodiment will be described, and the components of the third embodiment that may be similar to those of the first embodiment will be given the same reference numerals as those of the first embodiment, and detailed descriptions thereof will be omitted.

In the first and second embodiments, there is one protrusion, but the third embodiment has multiple (two in the illustrated example) protrusions 32, 32b. The third embodiment is advantageous, for example, when there are multiple electronic components with which the FPC cable 28 should not come into contact or be close to, from the standpoint of noise immunity. When two electronic components 24, 24b are arranged at a certain distance apart as in the illustrated example, by providing the cover 30b with protrusions 32, 32b that respectively encompass the electronic components 24, 24b in a plan view, it becomes possible to suitably bend the FPC cable 28 so that it does not come into contact with or be close to the electronic components, regardless of the number of electronic components.

In the third embodiment, the size and shape of each protrusion 32a can be selected as appropriate, but for example, if the surface is curved, such as with cylindrical protrusions 32, there is an effect of suppressing damage to the FPC cable 28 due to contact with the protrusions 32.

The manufacturing process for the encoder in the above embodiments can be appropriately selected and determined based on the position and shape of the protrusions. For example, in the first embodiment shown in FIG. 1, when attaching the cover 30, instead of moving it vertically from above the PCB 22 in the direction of its surface, it is attached by sliding it from the right side to the left side, which allows the FPC cable 28 to bend appropriately as shown in FIG. 1.

On the other hand, in the second embodiment shown in FIG. 4, when attaching the cover 30a, it is moved vertically from above the PCB 22 in the direction of its surface, which makes it easy to suitably entangle the FPC cable 28 with the protrusions 32a. In this way, by appropriately selecting the approach direction of the cover according to the arrangement and shape of the protrusions, it is also easy to automate the assembly and manufacturing of the encoder.

The above-mentioned embodiments can be combined as appropriate. For example, it is possible to configure an encoder having both a protrusion 32 disposed directly above the electronic component 24 as in the first embodiment, and a protrusion 32a disposed between the electronic component 24 and the connector 26 as in the second embodiment.

In the above embodiments, an optical rotary encoder has been described, but the present disclosure is not limited to this. For example, the present disclosure can also be applied to magnetic encoders and linear encoders that have a configuration in which the FPC cable can abut or come into close proximity to an electronic component.

According to the present disclosure, the FPC cable can be bent so that it does not come into contact with electronic components or come within an allowable distance by using a simple means such as a cover with protrusions, and this makes it possible to prevent a decrease in the noise tolerance of the encoder. This makes it possible to provide a highly reliable encoder at low cost.

Although the present disclosure has been described in detail, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible to these embodiments without departing from the gist of the present disclosure, or without departing from the spirit of the present disclosure derived from the contents described in the claims and their equivalents. These embodiments can also be implemented in combination. For example, in the above-mentioned embodiments, the order of each operation and the order of each process are shown as examples, and are not limited to these. The same applies when numerical values or formulas are used to explain the above-mentioned embodiments.

The following notes are further provided with respect to the above embodiment and modified examples.

(Appendix 1)
An encoder comprising: a printed circuit board having electronic components; a flexible cable connected to a connector mounted on the printed circuit board; and a cover configured to cover the printed circuit board and the flexible cable, wherein the cover has a protrusion capable of contacting the flexible cable, and the protrusion is configured to bend the flexible cable so that a minimum distance of the flexible cable from the electronic components is equal to or greater than an allowable distance determined based on the function of the encoder.

(Appendix 2)
The encoder of claim 1, wherein the protrusion is provided above the electronic component in a direction perpendicular to the surface of the printed circuit board.

(Appendix 3)
The encoder of claim 2, wherein the tip of the protrusion has a shape that is substantially identical to or encompasses the surface shape of the electronic component when viewed in a direction perpendicular to the surface of the printed circuit board.

(Appendix 4)
2. The encoder of claim 1, wherein the protrusion is disposed between the electronic component and the connector.

(Appendix 5)
The encoder according to any one of claims 1 to 4, wherein the cover has a plurality of the protrusions.

(Appendix 6)
6. The encoder according to claim 1, wherein the allowable distance is determined based on a noise tolerance of the encoder.

(Appendix 7)
The encoder according to any one of appendixes 1 to 5, wherein the allowable distance is determined based on an amount of temperature rise of the electronic components that may affect the function of the encoder.

10, 10a, 10b Encoder 12 Rotating shaft 14 Slit plate 16 Light emitting portion 18 Light receiving portion 20 Mounting plate 22 PCB
24 Electronic component 26 Connector 28 FPC cable 30 Cover 32, 32a, 32b Protrusion 34 Opening 36 Connection portion

Claims (7)

a printed circuit board having electronic components;
a flexible cable connected to a connector mounted on the printed circuit board;
a cover configured to cover the printed circuit board and the flexible cable,
An encoder, wherein the cover has a protrusion that can abut against the flexible cable, and the protrusion is configured to bend the flexible cable so that the minimum distance of the flexible cable to the electronic component is greater than or equal to an allowable distance determined based on the function of the encoder. The encoder of claim 1, wherein the protrusion is provided above the electronic component in a direction perpendicular to the surface of the printed circuit board. The encoder according to claim 2, wherein the tip of the protrusion has a shape that is substantially the same as or includes the surface shape of the electronic component when viewed in a direction perpendicular to the surface of the printed circuit board. The encoder of claim 1, wherein the protrusion is disposed between the electronic component and the connector. An encoder as described in any one of claims 1 to 4, wherein the cover has a plurality of the protrusions. An encoder according to any one of claims 1 to 5, wherein the allowable distance is determined based on the noise tolerance of the encoder. An encoder according to any one of claims 1 to 5, wherein the allowable distance is determined based on the amount of temperature rise of the electronic components that may affect the function of the encoder.

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