JP2003036739A - Communication cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication cable which has a structure of a pair of twisted cables as for a conductor but gives a very small change in characteristic impedance, even if a twisted pitch is changed or a cable is bent. SOLUTION: Two conductors 11a, for example, spaced at a certain distance apart and placed in parallel are covered by an insulator to be unified to give a flat cable 11. The flat cable 11 is twisted to form a communication cable 12, which maybe referred as a flat twisted pair cable. Two conductors 11a are unified by the insulator 11b and the distance between conductors changes very little even if a twisted pitch changes, consequently causing a very small impedance change. Accordingly, the cable will have increased resistance against electromagnetic flux noise from the outside by changing a twisting pitch while keeping a characteristic impedance constant. The cable does not need to be designed separately to meet each case of different degrees of electromagnetic flux noise. The constant distance between conductors assure the stable characteristic impedance in whatever path the cable may take, no interference caused whether straight or a curved path. The cable does not need to be designed individually for different vehicles requiring different number of bending points.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication cable for suppressing the influence of electromagnetic induction noise by twisting, and more particularly to a communication cable suitable for use as a communication line for an in-vehicle LAN mounted on an automobile. .

[0002]

2. Description of the Related Art Conventionally, as a communication cable for LAN, for example, as shown in FIG. 10, two single-core insulated wires 1 in which a single conductor 1a is covered with an insulator 1b are twisted together. A twisted pair cable 2 is known in which the influence of electromagnetic induction noise is suppressed. The twist pitch P of the twisted pair cable 2 depends on the performance of the twisting machine, but considering the strength of electromagnetic induction noise received from the outside, a twist pitch of about 15 mm to 60 mm is generally used. The twisted pair cable 2 is also used as a communication line for an in-vehicle LAN of an automobile, but in this case, it is usually wired as a wire harness in the automobile.

[0003]

When the twist care cable 2 is used as the communication line for the in-vehicle LAN, the required specifications for the characteristic impedance of the communication line to be used depend on the communication protocol of the in-vehicle LAN to be mounted. Therefore, it is necessary to satisfy this required specification. If the required specifications are not satisfied, there is a problem that the communication waveform is reflected at the terminal end or branch of the bus, the waveform is distorted, and a communication error occurs.

By the way, the characteristic impedance of the twisted pair cable 2 changes depending on the permittivity between the two conductors 1a. The greater the permittivity, the greater the characteristic impedance, and the smaller the permittivity, the smaller the characteristic impedance. Therefore, the dielectric constant of the insulator 1b is an important factor when designing a twisted pair cable that satisfies the required specifications. However, even with a twisted pair cable that satisfies the required specifications, when the in-vehicle LAN system is actually installed in an actual vehicle, there are places that are easily affected by the electromagnetic induction noise generated from external devices depending on the wiring route of the communication line, An error may occur. In such a case, generally, the twisting pitch P of the twisted pair cable 2 is further shortened to improve resistance to external electromagnetic induction noise (noise resistance). On the other hand, if the twist pitch of the twisted pair cable is changed to improve resistance to electromagnetic induction noise from the outside, the characteristic impedance also changes. This is because changing the twist pitch changes the distance between the conductors 1a, and consequently changes the dielectric constant between the conductors. FIG. 11 is a graph showing the frequency characteristics of the characteristic impedance when the twist pitch P of the twisted pair cable 2 shown in FIG. 10 is changed to 15 mm, 40 mm, and 60 mm. It can be seen that the impedance is changing.

As described above, when the twist pitch of the twisted pair cable is changed, the characteristic impedance also changes. Therefore, if the twist pitch is changed to improve the resistance to electromagnetic induction noise from the outside, the influence of reflection is affected. There is a problem that it becomes easy to receive, and the performance as a communication line deteriorates. There is also a method of designing a cable whose characteristic impedance satisfies the specifications after making the twist pitch as short as possible in order to secure resistance to electromagnetic induction noise from the beginning of design, but it may result in over-spec. Many, as a matter of course, the shorter the twist pitch, the longer the amount (length) of the electric wire used, resulting in an increase in cost.

[0006] Further, in the case of a vehicle having different mounting equipment,
Since the strength of electromagnetic induction noise generated from various electrical components is different, the twisted pair cable used as a communication line, even with the same in-vehicle LAN protocol, has resistance to external electromagnetic induction noise and the required specifications of the communication protocol. In consideration of the two points with the characteristic impedance that is
Since it has to be individually designed and cannot be mass-produced as a general-purpose product, there is a problem that the cost is increased.

Further, although not shown in the drawing, the wire harness mounted in the vehicle is wired in a complicated route corresponding to the device arrangement and space, and therefore there are many places where the wire harness is wired in a bent state. . In such a bent portion, in the twisted pair cable 2 of FIG. 10, the two single-core insulated electric wires 1 are separated from each other and the distance between the conductors 1a is increased as shown in FIG. The difference in opening distance is different). In this way, opening the distance between the conductors at the bent portion also causes a change in the characteristic impedance, and even if the requirements for the characteristic impedance are satisfied in the linear arrangement state, the condition when assembled in the vehicle There is a problem that the required specifications may not be satisfied in (the state where the bent portion exists).

Further, in vehicles having different wiring routes,
Since the number of bends is also different, in the worst case, a twisted pair cable that meets the required specifications for characteristic impedance must be individually designed for each vehicle with a different wiring route, which increases the cost. There is also.

The present invention has been made in view of the above circumstances, and has been described above as a structure in which the conductor has a twisted pair cable structure and the characteristic impedance does not significantly change even when the twist pitch is changed or bent. The purpose is to solve the problems of the conventional twisted pair cable.

[0010]

The communication cable of the present invention for solving the above-mentioned problems is characterized in that a plurality of conductors are twisted in a state of being insulated from each other inside an integral insulator. .

A second aspect of the present invention is characterized in that the communication cable of the first aspect is formed by twisting a multicore insulated electric wire in which a plurality of conductors are arranged in parallel at intervals and integrally insulated.

A third aspect of the present invention is characterized in that the multi-core insulated electric wire according to the second aspect is a flat cable whose insulator has a substantially flat outline.

A fourth aspect of the present invention is characterized in that the flat cable according to the third aspect is a two-core flat cable.

A fifth aspect of the present invention is characterized in that the flat cable according to the third aspect is obtained by arranging a plurality of single-core insulated wires in parallel and integrally joining them by an adhesive or welding.

A sixth aspect of the present invention is characterized in that the communication cable of the first aspect is formed by integrally bonding a plurality of single-core insulated electric wires twisted together by an adhesive or welding.

A seventh aspect of the present invention is characterized in that the communication cable of the first aspect is formed by twisting a plurality of multi-core insulated electric wires obtained by arranging a plurality of conductors in parallel at intervals and integrally performing insulation treatment. To do.

An eighth aspect of the present invention is characterized in that the communication cable of the first aspect is used as a wire harness mounted on a vehicle.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1B shows a communication cable 12 according to an embodiment of the present invention. The communication cable 12 of this embodiment has two conductors 11 as shown in FIG.
The two-core flat cable 11 is formed by twisting (twisting) as shown in FIG. . Regarding the method of manufacturing the communication cable 12, the flat cable 11 of FIG. 1A may be twisted after being manufactured, or may be twisted at the time of manufacturing. Also,
As a specific structure of the two-core flat cable 11 as in the embodiment, various structures can be used as shown in FIGS. Two conductors 11 spaced apart
The outline (cross-sectional shape) of the insulator 11b for integrally insulating a is conceivable as shown in the drawing, but is arbitrary. The distance between the two conductors 11a is not particularly specified, and the conductor 11a itself may be a twisted wire. Further, as a flat cable, as shown in FIG.
3 are arranged side by side in parallel, and a flat cable 14 integrally joined by adhesive or welding (joint portion by adhesive or welding is shown by 13c) is used, and the flat cable 14 is twisted as shown in FIG. The communication cable 15 can also be constructed (twisted). In FIG. 5, the conductor of the single-core insulated wire 13 is indicated by 13a, and the insulator is indicated by 13b. Further, not only a two-core flat cable, but also a three-core or more flat cable can be used. In short, any structure may be used as long as it has a structure in which a plurality of conductors are arranged in parallel at intervals and are integrally insulated.

The communication cable 12 has a structure which can be called a flat twisted pair cable, but since the two conductors 11a which are in a twisted relationship with each other are integrated by the insulator 11b, the single core insulated wire is used. Compared with the conventional twisted pair cable 2 of FIG. 10 in which two 1's are twisted together, even if the twisting pitch P changes, the change in the distance between the conductors 11a is extremely small. Therefore, the change in the dielectric constant between the conductors 11a is small, and the change in the characteristic impedance is also extremely small. FIG. 2 shows the twist pitch P of the communication cable (flat twisted pair cable) 12 of the above embodiment.
It is a graph showing the frequency characteristics of the characteristic impedance when is changed to 15 mm, 40 mm, and 60 mm, and it can be seen that even if the twist pitch P is changed, the change in the characteristic impedance is extremely small compared to FIG. 11.

As described above, this communication cable 12
According to the method, since the change in the characteristic impedance is extremely small even if the twist pitch P changes, the twist pitch P is changed to maintain the resistance (noise resistance) to external electromagnetic induction noise while keeping the characteristic impedance constant. It will be possible to improve. Further, it is not necessary to unnecessarily shorten the twist pitch, and cost reduction can be realized.

In addition, even if the strength of the electromagnetic induction noise generated from various electric components is different in vehicles with different installed equipment, it is possible to set the twist pitch corresponding to the noise strength without changing the characteristic impedance. So
If the same in-vehicle LAN protocol is used, mass production as a general-purpose product is not required, considering the two points of resistance to electromagnetic induction noise from the outside and characteristic impedance, which is the required specification of the communication protocol. Therefore, cost reduction can be realized in this respect as well.

Further, in this communication cable 12, since the two conductors 11a are integrated by the insulator 11b,
Even if the conductors 11a are bent as shown in FIG. 3, the distance between the conductors 11a does not depend on the bend R and is always constant. As described above, the distance between the conductors 11a does not change even in the bent portion, and therefore the characteristic impedance is stable in any wiring path. Therefore, as in the conventional twisted pair cable 2 shown in FIGS. In the linear arrangement state (FIG. 10), even if the required specifications of the characteristic impedance are satisfied, the state of being assembled to the vehicle (the state where the bending portion exists:
In FIG. 12), it is possible to avoid the problem that the required specifications may not be satisfied.

Further, since the distance between the conductors does not change even in the bent portion as described above, it is necessary to individually design twisted pair cables for each vehicle even in vehicles having different wiring routes (and therefore different numbers of bent portions). Since it can be mass-produced as a general-purpose product, cost reduction can be realized.

The communication cable of the present invention is preferably constructed by using a flat cable as described above, but in short, a plurality of conductors are twisted in a state of being insulated from each other inside an integral insulator. As long as the communication cable 16 shown in FIG. 6 is used, for example, two conductors 16a are provided inside the insulator 16b having a circular cross section.
May be twisted at intervals. In this case, since the twist pitch cannot be recognized from the appearance of the communication cable 16, if it is essential to be able to recognize the twist pitch from the appearance, some means such as printing a spiral line on the outer peripheral surface may be taken. .

Further, as shown in FIG. 7, two conductors 17
Two-core insulated electric wire (multi-core insulated electric wire) 17 in which a is arranged in parallel at intervals and is integrally insulated with an insulator 17b having a circular cross section.
Can be twisted (twisted) to form a communication cable having substantially the same appearance as the communication cable 16 of FIG.
The insulated wire 17 has basically the same structure as the flat cables 11 shown in FIG. 4 except the outline of the insulator, and cannot be simply called a "flat" cable.

Further, as shown in FIG. 8 (a), for example, two single-core insulated wires 13 twisted together are shown in FIG.
Alternatively, as shown in (b), the communication cable 19 may be configured by integrally joining with an adhesive or welding (the joint portion by the adhesive or welding is indicated by 13c). The obtained communication cable 19 is the communication cable 15 shown in FIG.
Is almost the same as. The state of FIG. 8 (a) corresponds to a conventional twisted pair cable because the two single-core insulated electric wires 13 are not joined.

FIG. 9 shows still another embodiment of the present invention. In this embodiment, two two-core flat cables 11 shown in FIG. 9 (a), such as FIG. 4, are twisted together as shown in FIG. 9 (b) to form a communication cable 20. In this communication cable 20, each of the individual flat cables 11 is in a twisted (twisted) state, so that the flat cable 11 acts not only as a flat cable but as a twisted pair cable, and each of the above-described embodiments. The same effect as in the case of is obtained.

In the above description, the case of application to the in-vehicle LAN has been described, but the present invention is not limited to the in-vehicle LAN, but a general L
It can also be used as a communication line for AN applications. Furthermore, L
The present invention can be used not only for AN applications but also for various applications such as sensor signals and speakers, as an alternative to the twisted pair cables currently used.

[0029]

According to the communication cable of the present invention, since a plurality of conductors are twisted in a state of being insulated from each other inside an integral insulator, the following various effects are exhibited. Even if the twisting pitch changes, the distance between conductors does not change much and the characteristic impedance changes very little, so the twisting pitch can be changed while maintaining the characteristic impedance constant to improve resistance to electromagnetic induction noise from the outside. It is possible to let Further, it is not necessary to unnecessarily shorten the twist pitch, and cost reduction can be realized. Even if the intensity of electromagnetic induction noise generated from various electrical components is different, simply changing the twist pitch to correspond to the noise intensity does not require individual design and can be mass-produced as a general-purpose product. Also in this respect, cost reduction can be realized.

Since the distance between the conductors does not change even in the bent portion (the characteristic impedance is stable in any wiring path), even if the required specifications of the characteristic impedance are satisfied in the linear arrangement state, It is possible to avoid the problem that the required specifications cannot be satisfied in a state where the vehicle is assembled (a state in which a bent portion exists). Since the distance between the conductors does not change even at the bend,
Even vehicles having different wiring routes (different bending points) do not need to be individually designed for each vehicle, and can be mass-produced as general-purpose products, and also in this respect, cost reduction can be realized.

If the communication cable of the present invention is constructed by twisting (twisting), for example, a two-core flat cable or the like, its manufacture is easy and preferable. Further, when the present invention is used as a wire harness for a vehicle, the effects of the present invention described above are remarkably exhibited.

[Brief description of drawings]

FIG. 1 is a view for explaining an embodiment of a communication cable of the present invention, (a) is a perspective view of a flat cable, and (b) is a flat cable.
FIG. 3A is a perspective view of a communication cable of one embodiment of the present invention configured by twisting (twisting) the flat cable of (A).

2 is a diagram showing frequency characteristics of characteristic impedance when the twist pitch is set to 15 mm, 40 mm, and 60 mm in the communication cable of FIG. 1 (B), and is compared with the conventional example of FIG.

FIG. 3 is a diagram illustrating a state in which the communication cable of FIG. 1B is bent, and is compared with the conventional example of FIG.

4A to 4D are cross-sectional views showing various examples of flat cables used for the communication cable of FIG. 1B.

FIG. 5 is a view for explaining still another embodiment of the communication cable of the present invention, (a) is a perspective view of a flat cable in which two insulated electric wires are integrally joined by welding, and (b) is (a). FIG. 3 is a perspective view of a communication cable of an embodiment of the present invention configured by twisting (twisting) the flat cable of FIG.

FIG. 6 is a perspective view showing still another embodiment of the communication cable of the present invention.

7 is a diagram illustrating an example of manufacturing the communication cable of FIG.

FIG. 8 is a view for explaining still another embodiment of the communication cable of the present invention, (a) is a perspective view showing a state in which two insulated electric wires are twisted together, and (b) is a line in (a). FIG. 3 is a perspective view of a communication cable of an embodiment of the present invention configured by integrally joining the insulators of the insulated wire of the book with an adhesive or welding.

FIG. 9 shows an embodiment of the communication cable according to claim 6, (a) is a perspective view showing a state in which two two-core flat cables are arranged, and (b) is two of (a). It is a front view of the cable for communication of an embodiment of the present invention constituted by twisting core flat cables.

FIG. 10 is a perspective view of a conventional communication cable (twisted pair cable).

11 is a diagram showing the frequency characteristics of the characteristic impedance when the twist pitch is 15 mm, 40 mm, and 60 mm in the twisted pair cable of FIG.

FIG. 12 is a diagram illustrating a state when the twisted pair cable in FIG. 10 is bent.

[Explanation of symbols]

11, 14 Flat cable (multi-core insulated wire) 11a, 13a, 16a conductors 11b, 13b, 16b insulator 12, 15, 16, 19, 20 Communication cable 13 Single insulated wire 13c Bonding part by adhesive or welding P twist pitch

Claims (8)

[Claims] 1. A communication cable, characterized in that a plurality of conductors are twisted in a state of being insulated from each other inside an integral insulator. 2. The communication cable according to claim 1, wherein a plurality of conductors are arranged in parallel at intervals and are integrally insulated to form a multi-core insulated electric wire. 3. The communication cable according to claim 2, wherein the multi-core insulated electric wire is a flat cable in which the outline of the insulator is substantially flat. 4. The communication cable according to claim 3, wherein the flat cable is a two-core flat cable. 5. The communication cable according to claim 3, wherein the flat cable is formed by arranging a plurality of single-core insulated wires in parallel and integrally joining them by an adhesive or welding. 6. The communication cable according to claim 1, wherein a plurality of single-core insulated wires twisted together are integrally joined by an adhesive or welding. 7. The communication cable according to claim 1, wherein a plurality of multi-core insulated electric wires in which a plurality of conductors are arranged in parallel at intervals and integrally insulated are twisted together. 8. The communication cable according to claim 1, which is used as a wire harness mounted on a vehicle.