JPH11177258A - Fixing structure for signal cable and electronic equipm ent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize ground line of a signal cable in terms of potential and to prevent noise transmitted through the ground line from flowing into a casing. SOLUTION: A land 9 formed by extending a part of a ground pattern 8 is provided for the ground pattern 8 of a flexible cable 4. The land 9 is fixed to the casing in a state where it is inserted into the casing sharing a frame ground through a resistor ring 11 being an impedance member having a specified frequency characteristic and a high dielectric ring 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal cable fixing structure for reducing noise radiated from a signal cable housed in a housing of an electronic device, and to an electronic device.

[0002]

2. Description of the Related Art Conventionally, a signal cable connected between a plurality of printed wiring boards housed in a housing of an electronic device has a problem in transmitting a clock signal or an image data signal which is a high frequency signal. In order to reduce radiated noise, measures are taken such as shortening the length of the signal cable as much as possible, making the signal cable as close as possible to the inner wall of the housing, or shielding the signal cable.

However, depending on the internal structure of the electronic device, it may be extremely difficult to implement the countermeasure by the above-described means, or a great cost burden may be required to implement the countermeasure. is there. Furthermore, even if it is possible to take measures to reduce radiation noise as in the above-described means, the measures alone may, for example, be CISPR · P
ub. In some cases, the noise standard such as 22 cannot be satisfied. Specifically, there is a case where the magnitude of the noise radiated from the shielded cable does not fall within the standard value even though the shielded cable is used as the signal cable as a measure against radiation noise.

Therefore, conventionally, for example, Japanese Patent Application Laid-Open No. 9-8315
As disclosed in Japanese Patent Laid-Open Publication No. 5 (1993) -5, a shielded cable which is a ground wire of a shielded cable is fixed by fixing the shielded cable with a plurality of clamp members made of a conductive metal provided inside a metal casing. Has been taken to conduct the electric current to the frame ground of the casing, which is more stable in terms of electric potential, and to suppress noise radiated from the shielded cable.

[0005]

However, in the above-described conventional measures for suppressing radiation noise, since the ground line of the signal cable is connected to the frame ground of the housing, noise transmitted through the ground line is reduced. It flows into the housing. Then, depending on the frequency of the noise, resonance may occur in a system formed by the signal cable and the housing, and noise at a specific frequency may increase. Therefore, the effect of suppressing radiation noise may be worsened.

Accordingly, the present invention provides a signal cable fixing structure and an electronic device which can stabilize the ground line of a signal cable in terms of potential and further prevent noise conducted through the ground line from flowing into a housing. The purpose is to do.

[0007]

In order to achieve the above object, a signal cable fixing structure according to the present invention fixes a signal cable wired inside a housing also serving as a frame ground of an electronic device to the housing. For fixing a signal cable, wherein the signal cable is provided with a ground wire, and the signal cable is connected to the housing in a state where the ground wire is conducted to the housing via an impedance member. It is characterized by being fixed.

Accordingly, the ground line of the signal cable is more stabilized in terms of potential, so that noise radiated from the signal cable is suppressed. Further, since the ground line of the signal cable and the housing are connected via the impedance member, the flow of noise transmitted through the ground line into the housing is suppressed.

Preferably, the impedance member has a characteristic of attenuating a frequency component of noise transmitted through the ground line.

Further, it is preferable that the impedance member is constituted by at least one of a resistor member, a dielectric member, a magnetic member and an inductor member.

Further, it is preferable that the impedance member has a structure in which at least two of a resistor member, a dielectric member, a magnetic member, and an inductor member are connected in series.

Further, the signal cable may be a flexible cable in which a ground pattern and a signal pattern as the ground line are provided on a flexible base material.

[0013] Further, the flexible cable is locked to the housing with a land portion formed by extending a part of the ground pattern being electrically connected to the housing via the impedance member. Thereby, it is preferable to adopt a configuration fixed to the housing.

[0014] Further, it is preferable that the land portion is configured to be locked to the housing together with the impedance member by a screw member.

Further, the signal cable may be a shielded cable in which a signal line is covered with a shield line as the ground line.

Further, the shielded cable is gripped by a cable gripping member made of a conductive member via the impedance member, and the cable gripping member is locked to the housing by a locking member made of a conductive member. Thereby, it is preferable to adopt a configuration fixed to the housing.

Further, it is preferable that the shield wire is covered by the impedance member.

In addition, it is preferable that the impedance member is constituted by one of a resistor member, a dielectric member and a magnetic member.

Further, it is preferable that the impedance member has a structure in which at least two of a resistor member, a dielectric member and a magnetic member are overlapped.

Further, the impedance member may be provided only at a portion of the shielded cable gripped by the cable gripping member.

Further, the impedance member is formed in an annular shape by one of a resistor member, a dielectric member, and a magnetic member, and is provided so as to be fitted into the shielded cable. Is preferred.

Further, the impedance member is formed in a concentric annular shape by at least two of a resistor member, a dielectric member, and a magnetic member, and is provided so as to fit through the shielded cable. Is preferred.

According to another aspect of the present invention, there is provided an electronic apparatus having a housing also serving as a frame ground, and a signal cable wired inside the housing. It is characterized by being fixed to the housing by a structure.

Thus, the potential of the ground line of the signal cable is more stabilized and the noise radiated from the signal cable is suppressed, and the flow of the noise from the ground line to the housing is suppressed.

[0025]

Next, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) FIG. 1 is a perspective view showing a fixing structure of a signal cable of an electronic device according to a first embodiment of the present invention, and FIG. It is a perspective view which expands and shows a part.

As shown in FIG. 1, a plurality of printed wiring boards 3 are provided inside a housing 2 of the electronic device 1. A flexible cable 4 as a signal cable is connected between the printed wiring boards 3 via a connector 5, and a signal is transmitted between the printed wiring boards 3.

As shown in FIG. 2, the flexible cable 4 has a signal pattern 7 and a ground pattern 8 (hereinafter, referred to as a "GND pattern 8") on the surface of a base member 6 made of a flexible insulating member. It is formed and configured. Signal pattern 7 and GND pattern 8
Is connected to a printed wiring (not shown) provided on the printed wiring board 3 via a connection terminal 5 a provided on the connector 5. In addition, the flexible cable 4 is formed of the housing 2 (see FIG. 1) by a plurality of cable fixing structures 13.
It is fixed to. The housing 2 is formed of a metal member made of a conductive material, an insulating plastic member having an inner wall coated with a conductive member, or the like, and these conductive members are connected to ground (earth). . Therefore, the housing 2 functions as a frame ground.

FIG. 3 is an enlarged perspective view of the cable fixing structure shown in FIG. 2, and FIG. 4 is a sectional view of the cable fixing structure shown in FIG.

As shown in FIGS. 3 and 4, the cable fixing structure 13 includes the land 9 formed by extending a part of the GND pattern 8 of the flexible cable 4 and the land 9 in the housing 2 (FIG. 4). ) And a high dielectric ring 10 and a resistor provided between the land 9 and the head of the screw 12 such as a washer. And a ring 11. Thereby, the GND pattern 8 and the housing 2
Is conducted through the resistor ring 11, the high dielectric ring 10, and the screw 12. The resistor ring 11 and the high dielectric ring 10 are impedance members having specific impedances, and these impedance members have specific frequency characteristics.

As shown in FIG. 4, the surface of the flexible cable 4 is covered with an overcoat material 14, so that the patterns 7, 8 are protected from oxidation and protected from dust and the like.

According to the above-described cable fixing structure 13 of the present embodiment, the GND pattern 8 of the flexible cable 4 is connected to the casing 2 which is a potential ground frame ground. Therefore, the GND pattern 8 of the flexible cable 4 is more stabilized in terms of potential, and noise radiated from the flexible cable 4 is suppressed.

Further, the GND pattern 8 and the housing 2 are
Since the connection is made via the resistor ring 11 and the high dielectric ring 10, which are impedance members having specific frequency characteristics, the flow of noise transmitted through the GND pattern 8 into the housing 2 is suppressed. As a result, it is possible to prevent the occurrence of resonance in the system formed by the signal cable and the housing and increase in noise at a specific frequency.
Radiation noise can be suppressed well.

As the impedance member, in addition to the resistor ring 11 and the high dielectric ring 10 described above, an inductor member formed in a coil shape or a ring shape similar to the resistor ring 11 shown in FIG. A magnetic material such as a ferrite core formed on the substrate may be used. Further, it is preferable that the frequency characteristic of the impedance member be set to a characteristic capable of attenuating a frequency component of noise to be removed.

The number of the cable fixing structures 13 is set according to the length of the flexible cable 4. That is, as the length of the flexible cable 4 used in the electronic device 1 increases, more cable fixing structures 13 are provided. Therefore, even when a long flexible cable must be used for structural reasons or the like, the GND pattern of the flexible cable is satisfactorily connected to the housing, so that noise radiated from the flexible cable is suppressed. .

(Second Embodiment) FIG. 5 is a perspective view showing a fixing structure of a signal cable of an electronic device according to a second embodiment of the present invention, and FIG. It is a perspective view which expands and shows a part.

As shown in FIG. 5, the housing 2 of the electronic device 21
A plurality of printed wiring boards 23 are installed inside 2. A shielded cable 24 as a signal cable is connected between the printed wiring boards 23 via a connector 25, and signals are transmitted between the printed wiring boards 23.

As shown in FIG. 6, the signal line 28 and the shield line 29 of the shielded cable 24 (see FIG. 7 and the like) are provided on the printed wiring board 23 via connection terminals 25a provided on the connector 25. Connected to a printed wiring (not shown). Further, the shielded cable 24 is secured to the housing 22 by a plurality of cable holding members 26.
(See FIG. 5) to form a signal cable fixing structure. The configuration of the housing 22 is the same as that of the housing 2 described with reference to FIG.

FIG. 7 is an enlarged perspective view showing a fixing structure of the signal cable composed of the shielded cable and the cable gripping member shown in FIG. 5 and the like. FIG. 8 is a sectional view of the fixing structure of the signal cable shown in FIG. It is.

As shown in FIGS. 7 and 8, in the shielded cable 24 of the present embodiment, a plurality of signal lines 28 are covered with a shield line 29 having a function as a ground line. Further, the shield wire 29 is coated with a resistance material coating 30, and the resistance material coating 30 is coated with a high dielectric material coating 31.

The shielded cable 24 is clamped by a cable holding member 26, and the cable holding member 26 is fixed to the housing 22 (see FIG. 8) by screws 27 with screws. As a result, the shield wire 29 and the housing 22 are electrically connected via the resistance material coating 30, the high dielectric material coating 31, and the cable gripping member 26. The resistance material coating 30 and the high dielectric material coating 31 are impedance members having a predetermined impedance, and these impedance members have specific frequency characteristics.

As described above, the shielded cable 24 in which the shielded wire 29 is covered with the resistive material coating 30 and the high dielectric material coating 31 is clamped by the cable gripping member 26 and fixed to the housing 22 to form a shield. The shield wire 29 of the cable 24 is connected to the housing 22, which is a frame ground that is stabilized in potential. Therefore,
The shielded wire 29 of the shielded cable 24 is more stabilized in potential, and noise radiated from the shielded cable 24 is suppressed.

Further, the shield wire 29 and the housing 22
Since the connection is made via the resistance material coating 30 and the high dielectric material coating 31 which are impedance members having specific frequency characteristics, the noise transmitted through the shield wire 29 into the housing 22 is suppressed. As a result, it is possible to prevent the occurrence of resonance in the system formed by the signal cable and the housing and increase in noise at a specific frequency, and thus it is possible to satisfactorily suppress radiation noise.

As in the case of the cable fixing structure 13 described with reference to FIG. 3 and the like, the number of the cable gripping members 26 is set according to the length of the shielded cable 24. That is, as the shielded cable 24 used in the electronic device 21 becomes longer, more cable gripping members 26 are provided. Therefore, even if a long shielded cable must be used for structural reasons, the shielded cable of the shielded cable is well connected to the housing.
Noise radiated from the shielded cable is suppressed.

Next, a modified example of the fixing structure of the signal cable composed of the shielded cable and the cable gripping member shown in FIG. 7 and the like will be described with reference to FIG. 9 and FIG. FIG. 9 is a perspective view showing a modification of the signal cable fixing structure shown in FIG. 7 and the like, and FIG. 10 is a cross-sectional view showing a modification of the signal cable fixing structure shown in FIG.

As shown in FIGS. 9 and 10, the shielded cable 41 according to the present modification is configured by covering a plurality of signal lines 46 with a shielded wire 47. That is,
In the shielded cable 41, the shielded wire 47 is exposed. A resistor ring 45 is attached to the portion of the shielded cable 41 where the cable gripping member 42 is clamped, and a high dielectric ring 44 is further attached to the resistor ring 45. The resistor ring 45 and the high dielectric ring 44 are impedance members having a predetermined impedance, and these impedance members have specific frequency characteristics.

In this modification, the high dielectric ring 44 is clamped by the cable gripping member 42, and the cable gripping member 42 is fixed to the housing 22 (see FIG. 10) by screws 43 with screws. As a result, the shield wire 47 and the housing 22 are electrically connected via the resistor ring 45, the high dielectric ring 44, and the cable holding member 42.

Also in this modified example, the shielded wire 47 of the shielded cable 41 is connected to the housing 22 which is the frame ground, similarly to the signal cable fixing structure shown in FIG. And the noise radiated from the shielded cable 41 is suppressed. Furthermore, since the shield wire 47 and the housing 22 are connected via the resistor ring 45 and the high dielectric ring 44, which are impedance members having specific main numerical characteristics, the shield wire 47 is conducted. Noise housing 22
Is prevented from flowing into. As a result, an increase in specific frequency noise due to resonance can be prevented, so that radiation noise can be suppressed well.

As the impedance member, in addition to the resistor ring 45 and the high dielectric ring 44, an inductor member such as an annular ferrite core similar to the resistor ring 45 shown in FIG. May be used. Further, it is preferable that the frequency characteristic of the impedance member be set to a characteristic capable of attenuating a frequency component of noise to be removed.

[0050]

As described above, according to the present invention, the signal cable is fixed to the housing of the electronic device while the ground wire of the signal cable is conducted to the housing of the electronic device via the impedance member. The ground line is electrically stable, and noise radiated from the signal cable can be suppressed. Further, since it is possible to prevent an increase in noise at a specific frequency due to resonance occurring in a system formed by the signal cable and the housing, it is possible to satisfactorily suppress radiation noise.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a fixing structure of a signal cable of an electronic device according to a first embodiment of the present invention.

FIG. 2 is an enlarged perspective view showing a portion A inside the electronic device shown in FIG. 1;

FIG. 3 is an enlarged perspective view showing the cable fixing structure shown in FIG. 2;

FIG. 4 is a sectional view of the cable fixing structure shown in FIG. 3;

FIG. 5 is a perspective view showing a fixing structure of a signal cable of an electronic device according to a second embodiment of the present invention.

6 is an enlarged perspective view showing a portion B inside the electronic device shown in FIG. 5;

FIG. 7 is an enlarged perspective view showing a signal cable fixing structure including the shielded cable and the cable gripping member shown in FIG. 5 and the like.

FIG. 8 is a sectional view of the signal cable fixing structure shown in FIG. 7;

FIG. 9 is a perspective view showing a modified example of the signal cable fixing structure shown in FIG. 7 and the like.

FIG. 10 is a sectional view showing a modification of the signal cable fixing structure shown in FIG. 9;

[Explanation of symbols]

 1, 21 Electronic equipment 2, 22 Housing 3, 23 Printed wiring board 4 Flexible cable 5, 25 Connector 5a, 25a Connection terminal 6 Base material 7 Signal pattern 8 Ground pattern 9 Land 10, 44 High dielectric ring 11, 45 Resistance Body ring 12, 27, 43 Screw 13 Cable fixing structure 14 Overcoat material 24, 41 Shielded cable 26, 42 Cable gripping member 28, 46 Signal wire 29, 47 Shield wire 30 Resistive material coating 31 High dielectric material coating

Claims (16)

[Claims] 1. A signal cable fixing structure for fixing a signal cable wired inside a casing also serving as a frame ground of an electronic device to the casing, wherein the signal cable is provided with a ground wire. And
The signal cable fixing structure, wherein the signal cable is fixed to the housing in a state where the ground wire is conducted to the housing via an impedance member. 2. The signal cable fixing structure according to claim 1, wherein the impedance member has a characteristic of attenuating a frequency component of noise transmitted through the ground line. 3. The impedance member is a resistor member,
3. The device according to claim 1, comprising at least one of a dielectric member, a magnetic member, and an inductor member.
The fixing structure of the signal cable according to the paragraph. 4. The impedance member is a resistor member,
3. The signal cable fixing structure according to claim 1, wherein at least two of the dielectric member, the magnetic member, and the inductor member are connected in series. 5. The signal cable according to claim 1, wherein the signal cable is a flexible cable in which a ground pattern and a signal pattern as the ground line are provided on a flexible base material. Fixed structure of signal cable. 6. The flexible cable is locked to the housing while a land portion formed by extending a part of the ground pattern is electrically connected to the housing via the impedance member. The signal cable fixing structure according to claim 5, wherein the signal cable is fixed to the housing. 7. The signal cable fixing structure according to claim 6, wherein the land portion is locked to the housing together with the impedance member by a screw member. 8. The signal cable fixing structure according to claim 1, wherein the signal cable is a shielded cable having a signal line covered with a shield line as the ground line. 9. The shielded cable is held by a cable holding member made of a conductive member via the impedance member, and the cable holding member is locked to the housing by a locking member made of a conductive member. 9. The signal cable fixing structure according to claim 8, wherein the signal cable is fixed to the housing. 10. The signal cable fixing structure according to claim 8, wherein the shield wire is covered with the impedance member. 11. The signal cable fixing structure according to claim 10, wherein the impedance member comprises one of a resistor member, a dielectric member, and a magnetic member. 12. The signal cable fixing structure according to claim 10, wherein the impedance member is formed by stacking at least two of a resistor member, a dielectric member, and a magnetic member. 13. The signal cable fixing structure according to claim 9, wherein the impedance member is provided only at a portion of the shielded cable gripped by the cable gripping member. 14. The method according to claim 13, wherein the impedance member is formed in an annular shape by one of a resistor member, a dielectric member, and a magnetic member, and is provided so as to fit through the shielded cable. The fixing structure of the described signal cable. 15. The impedance member is formed in a concentric annular shape by at least two of a resistor member, a dielectric member, and a magnetic member, and is provided so as to fit through the shielded cable. The signal cable fixing structure according to 1. 16. A housing also serving as a frame ground,
16. An electronic device comprising: a signal cable wired inside the housing;
An electronic device, wherein the electronic device is fixed to the housing by the signal cable fixing structure described in (1).