Flexible flat cable and power feeding device

Abstract

To provide a flexible flat cable that satisfies performance in which not only characteristic impedance of a communication conductor but also other electrical characteristics are required.SOLUTION: A flexible flat cable 1 is formed by covering a plurality of conductors including at least a pair of communication conductors 2, whose characteristic impedance is adjusted, by an insulator 3, where a thickness dimension T is 5 times the thickness dimension t of the communication conductor 2 or less, and an aspect ratio (width dimension W / thickness dimension t) being a ratio between the width dimension W and the thickness dimension t of the communication conductor 2 is a predetermined value set corresponding to the length dimension of the communication conductor 2 or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a flexible flat cable and a power supply device formed by covering a conductor including a communication conductor for transmitting a communication signal with an insulator.

Background Art

[0002] As a conventional flexible flat cable, there is known one having a plurality of communication conductors, an insulating material layer covering the plurality of communication conductors, and a shield layer formed outside one of the insulating material layers (see, for example, Patent Document 1).

[0003] The conventional flexible flat cable adjusts the characteristic impedance of the communication conductor by adjusting the thickness dimension and relative permittivity of the insulating material layer and by adjusting the capacitance between the communication conductor and the shield layer.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the conventional flexible flat cable, although the characteristic impedance of the communication conductor is adjusted, other electrical characteristics such as insertion loss, reflection loss, and mode conversion characteristics are not adjusted. When other electrical characteristics do not satisfy predetermined performance, there is a possibility that the communication performance deteriorates.

[0006] An object of the present invention is to provide a flexible flat cable and a power supply device that satisfy the performance required not only for the characteristic impedance of the communication conductor but also for other electrical characteristics.

Means for Solving the Problems

[0007] The flexible flat cable according to the present invention is a flexible flat cable formed by covering a plurality of conductors including at least a pair of communication conductors whose characteristic impedance is adjusted with an insulator, wherein the thickness dimension is 5 times or less the thickness dimension of the communication conductors, and the aspect ratio (width dimension / thickness dimension), which is the ratio of the width dimension to the thickness dimension of the communication conductors, is a predetermined value or less set according to the length dimension of the communication conductors.

[0008] Further, in the flexible flat cable according to the present invention, it is preferable that a conductive layer is formed on at least one surface side in the thickness direction.

[0009] Further, in the flexible flat cable according to the present invention, when the variable representing the aspect ratio is Y and the variable representing the length dimension (mm) of the communication conductors is X, it is preferable that the relationship Y≦-0.033X + 43.4 is satisfied.

[0010] Further, it is preferable that the power supply device according to the present invention includes a flexible flat cable.

Advantages of the Invention

[0011] According to the present invention, it is possible to suppress a decrease in bending performance, and to adjust the characteristic impedance of a pair of communication conductors and set electrical characteristics such as insertion loss, reflection loss, and mode conversion characteristics so as to satisfy the required performance. Therefore, it is possible to improve the communication performance of communication via a pair of communication conductors.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0013] <First Embodiment> Fig. 1 shows the first embodiment of the present invention and is a cross-sectional view of a flexible flat cable.

[0014] The flexible flat cable 1 of the present invention is applied, for example, in a vehicle, to a steering roll connector as a power supply device provided at a connection portion between a steering column on the vehicle body side and a steering shaft on the steering wheel side, a slide door harness as a power supply device provided at a connection portion between the vehicle body side and a slide door, a movable portion such as a slide seat harness provided at a connection portion between the vehicle body side and a slide seat, or a stationary portion such as inside an ECU or a connection between ECUs. The movable portion such as a slide seat harness provided at a connection portion between the vehicle body side and a slide seat is, for example, a wiring support portion described in JP-A-2010-149807. Further, the flexible flat cable 1 of the present invention is applicable not only to vehicles but also to devices that need to communicate between one device and another device. Further, the flexible flat cable 1 of the present invention is applicable to a steering device that can store an operation member such as a steering wheel. The steering device that can store an operation member such as a steering wheel is, for example, the steering device described in JP-A-2021-169259. For example, the flexible flat cable 1 of the present invention is applicable to a steering roll connector as a rotary connector (not shown) provided in the operation support portion of JP-A-2021-169259, and wiring (not shown) between the operation support portion and the holding portion. Furthermore, the flexible flat cable 1 of the present invention is used alone as one flexible flat cable 1 or in a state where a plurality of flexible flat cables 1 are laminated.

[0015] The flexible flat cable 1 forms part of a communication circuit for transmitting electrical signals. Here, the communication circuit including a pair of communication conductors described later is used, for example, in differential signal transmission of LVDS (Low Voltage Differential Signaling) that performs high-speed transmission using a low-voltage and low-amplitude signal, and signal transmission in communication standards such as CAN (Controller Area Network), CAN FD (Flexible Data Rate), CAN XL (Extra Long), and Ethernet (100BASE-T1, 10BASE-T1S). The transmission speed of the communication signal transmitted via the flexible flat cable 1 is generally 100 Mbps or less, but may be higher than 100 Mbps if necessary.

[0016] Here, for example, in the communication standard of CAN, the characteristic impedance of the communication circuit is adjusted within the range of 90 Ω or more and 140 Ω or less. Also, in the communication standard of 100BASE-T1, the characteristic impedance of the communication circuit is adjusted within the range of 90 Ω or more and 110 Ω or less.

[0017] The flexible flat cable 1 is formed in a flexible strip shape. As shown in FIG. 1, the flexible flat cable 1 has a pair of communication conductors 2 for transmitting electrical signals for communication and an insulator 3 covering the pair of communication conductors 2.

[0018] Each of the pair of communication conductors 2 is made of a member having high conductivity, which is made of a metal material such as tinned copper, aluminum, silver, or an alloy material containing copper, aluminum, silver, etc. The pair of communication conductors 2 may be formed by plating the surface of another member. The conductivity of the pair of communication conductors 2 is, for example, 10×10 6It is preferably above S / m. Each of the pair of communication conductors 2 has a rectangular cross-section (for example, the width dimension W is 0.8 mm and the thickness dimension t is 35 μm), and is arranged with a spacing S (for example, 0.6 mm) in the width direction of the flexible flat cable 1. Here, for each of the pair of communication conductors 2, the aspect ratio (width dimension W / thickness dimension t), which is the ratio of the width dimension W to the thickness dimension t, is not more than a predetermined value set according to the length dimension of the pair of communication conductors 2. Specifically, the relationship between the length dimension of the communication conductor 2 and the aspect ratio is preferably such that, when the variable representing the aspect ratio is Y and the variable representing the length dimension (mm) of the communication conductor 2 is X, Y ≤ -0.033X + 43.4 is satisfied.

[0019] The insulator 3 has a pair of insulating material layers (not shown) that cover the pair of communication conductors 2 from both sides in the thickness direction of the flexible flat cable 1, and an adhesive layer (not shown) for joining the pair of insulating material layers to each other with the communication conductors 2 arranged. The insulator 3 has a relative permittivity of, for example, 3.6.

[0020] The pair of insulating material layers are made of film-like members made of insulating materials such as PET, PVC, and polyimide. The pair of insulating material layers have rigidity and flame retardancy according to the usage state of the flexible flat cable 1.

[0021] The adhesive layer is made of an adhesive made of polyester, polyethylene, etc. The adhesive layer has heat resistance according to the usage state of the flexible flat cable 1 so that the arrangement of the pair of communication conductors 2 can be maintained in a high-temperature environment.

[0022] Here, the thickness dimension T of the flexible flat cable 1 is not more than 5 times the thickness dimension t of the pair of communication conductors 2.

[0023] When the flexible flat cable 1 configured as described above is used to connect one device and another device, a differential transmission line is formed between the one device and the other device.

[0024] The characteristic impedance of a pair of communication conductors 2 is determined by the width dimension W and thickness dimension t of the communication conductors 2, the distance S between the pair of communication conductors, and the relative permittivity of the insulator 3.

[0025] Also, regardless of the relative permittivity of the insulator 3, when the aspect ratio of a pair of communication conductors 2 is reduced by increasing the thickness dimension t or the width dimension W, the electrical resistance becomes smaller compared to the case where the aspect ratio is large, and the insertion loss, which is the loss of power input from one end and output from the other end, becomes smaller.

[0026] Also, regardless of the relative permittivity of the insulator 3, when the aspect ratio of a pair of communication conductors 2 is reduced by increasing the thickness dimension t or the width dimension W, the electrical resistance becomes smaller compared to the case where the aspect ratio is large, and it becomes possible to stabilize the characteristic impedance over the entire range of the signal frequency. As a result, when the inductance and capacitance of the pair of communication conductors 2 do not change, the reflection loss, which is the ratio of the reflected power to the input power, becomes smaller.

[0027] Also, regardless of the relative permittivity of the insulator 3, by reducing the aspect ratio of a pair of communication conductors 2, the mode conversion characteristic, which is the amount of conversion from the normal mode to the common mode, becomes smaller.

[0028] For example, in a flexible flat cable 1 where the width dimension W of each of the pair of communication conductors 2 is 0.8 mm, the thickness dimension t is 0.035 mm, the distance S between the pair of communication conductors 2 is 0.6 mm, and the relative permittivity of the insulator 3 is 3.6, the aspect ratio (W / t) is 22.9. When the length dimension of this flexible flat cable 1 is about 400 mm or less, it satisfies the performance requirements for electrical characteristics such as characteristic impedance, insertion loss, reflection loss, and mode conversion characteristics. That is, it is preferable that the aspect ratio is 30 or less when the length dimension of the communication conductors 2 is 400 mm or less.

[0029] Also, for example, in a flexible flat cable 1 where the width dimension W of each of a pair of communication conductors 2 is 0.9 mm, the thickness dimension t is 0.140 mm, the interval S between the pair of communication conductors 2 is 0.6 mm, and the relative permittivity of the insulator 3 is 3.6, the aspect ratio (W / t) is 6.4. When the length dimension of this flexible flat cable 1 is about 1000 mm or less, it satisfies the performance requirements for electrical characteristics such as characteristic impedance, insertion loss, return loss, and mode conversion characteristics. That is, it is preferable that the aspect ratio is 10 or less when the total length of the communication conductor 2 is 1000 mm or less.

[0030] Thus, according to the flexible flat cable of the present embodiment, the flexible flat cable 1 is formed by covering a plurality of conductors including at least a pair of communication conductors 2 whose characteristic impedance is adjusted with an insulator 3, and the thickness dimension T is 5 times or less the thickness dimension t of the communication conductor 2, and the aspect ratio (width dimension W / thickness dimension t), which is the ratio of the width dimension W to the thickness dimension t of the communication conductor 2, is a predetermined value or less set according to the length dimension of the communication conductor 2.

[0031] Thereby, for the pair of communication conductors 2, it becomes possible to set electrical characteristics such as insertion loss, return loss, and mode conversion characteristics so as to satisfy the required performance while adjusting the characteristic impedance, and thus it becomes possible to improve the communication performance of communication via the pair of communication conductors 2.

[0032] Also, when the variable representing the aspect ratio is Y and the variable representing the length dimension (mm) of the communication conductor 2 is X, it is preferable to satisfy the relationship Y ≦ -0.033X + 43.4.

[0033] Thereby, by adjusting the aspect ratio according to the length dimension of the communication conductor 2, it is possible to improve the communication performance and suppress a decrease in the bending performance of the flexible flat cable 1.

[0034] Also, the power supply device includes the flexible flat cable 1.

[0035] By connecting a member that moves relative to another member with the flexible flat cable 1, movement of the other member relative to the one member is allowed, and when transmitting a communication signal between the one member and the other member, improvement in communication performance can be achieved.

[0036] <Second Embodiment> FIG. 2 shows a second embodiment of the present invention and is a cross-sectional view of the flexible flat cable. The same components as those in the first embodiment are denoted by the same reference numerals.

[0037] As shown in FIG. 2, the flexible flat cable 1 of the present embodiment has a conductive layer 4 that covers one surface in the thickness direction.

[0038] The conductive layer 4 is arranged at an interval h in the thickness direction of the flexible flat cable 1 with respect to each of the pair of communication conductors 2.

[0039] In the flexible flat cable configured as described above, the characteristic impedance of the pair of communication conductors 2 is determined by the width dimension W and thickness dimension t of each of the pair of communication conductors 2, the interval S between the pair of communication conductors 2, the relative dielectric constant of the insulator 3, and the interval h between the pair of communication conductors 2 and the conductive layer 4.

[0040] Further, the pair of communication conductors 2, regardless of the relative dielectric constant of the insulator 3 and the interval h between the pair of communication conductors 2 and the conductive layer 4, when reducing the aspect ratio by increasing the thickness dimension t or increasing the width dimension W, compared with the case where the aspect ratio is large, the electrical resistance becomes smaller, and the insertion loss, which is the loss of power input from one end and output from the other end, becomes smaller.

[0041] Further, regardless of the relative permittivity of the insulator 3 and the distance h between the pair of communication conductors 2 and the conductive layer 4, when the aspect ratio is reduced by increasing the thickness dimension t or increasing the width dimension W of the pair of communication conductors 2, the electrical resistance becomes smaller compared to the case where the aspect ratio is large, and it becomes possible to stabilize the characteristic impedance over the entire range of the signal frequency. As a result, when the inductance and capacitance of the pair of communication conductors 2 do not change, the reflection loss, which is the ratio of the reflected power to the input power, becomes smaller.

[0042] Further, regardless of the relative permittivity of the insulator 3 and the distance h between the pair of communication conductors 2 and the conductive layer 4, by reducing the aspect ratio, the mode conversion characteristic, which is the amount of conversion from the normal mode to the common mode, becomes smaller.

[0043] For example, in the flexible flat cable 1 where the width dimension W of each of the pair of communication conductors 2 is 0.1 mm, the thickness dimension t is 0.035 mm, the distance S between the pair of communication conductors 2 is 0.6 mm, the relative permittivity of the insulator 3 is 3.6, and the distance h between the pair of communication conductors 2 and the conductive layer 4 is 0.0054 mm, the aspect ratio (W / t) is 2.9. When the total length of this flexible flat cable 1 is about 1000 mm or less, it satisfies the performance requirements for electrical characteristics such as characteristic impedance, insertion loss, reflection loss, and mode conversion characteristics. That is, it is preferable that the aspect ratio is 10 or less when the length dimension of the communication conductor 2 is 1000 mm or less.

[0044] Also, for example, in a flexible flat cable 1 where the width dimension W of each of a pair of communication conductors 2 is 0.3 mm, the thickness dimension t is 0.070 mm, the interval S between the pair of communication conductors 2 is 0.6 mm, the relative permittivity of the insulator 3 is 3.6, and the interval h between the pair of communication conductors 2 and the conductive layer 4 is 0.0054 mm, the aspect ratio (W / t) is 4.2. When the total length of this flexible flat cable 1 is about 1000 mm or less, it satisfies the performance requirements for electrical characteristics such as characteristic impedance, insertion loss, return loss, and mode conversion characteristics. That is, it is preferable that the aspect ratio is 10 or less when the length dimension of the communication conductor 2 is 1000 mm or less.

[0045] Thus, according to the flexible flat cable of the present embodiment, similar to the first embodiment, it has high bending performance, and for a pair of communication conductors 2, it is possible to adjust the characteristic impedance and set the electrical characteristics such as insertion loss, return loss, and mode conversion characteristics to meet the required performance. Therefore, it is possible to improve the communication performance of communication via a pair of communication conductors 2.

[0046] Also, it is preferable that the conductive layer 4 is formed on at least one surface side in the thickness direction.

[0047] Thereby, by arranging the conductive layer 4, it becomes easy to adjust the characteristic impedance of a pair of communication conductors 2.

[0048] In the above-described first and second embodiments, each of the pair of communication conductors 2 is shown to have a rectangular cross-section as illustrated in FIGS. 1, 2, and 3(a), but the present invention is not limited thereto. As the pair of communication conductors, as shown in FIG. 3(b), the cross-section may be circular, or as shown in FIG. 3(c), it may be a stranded wire formed by twisting thin wires together. By forming the cross-section of each of the pair of communication conductors 2 into a circular shape, the aspect ratio (W / t) becomes 1, making it possible to improve the performance in terms of insertion loss, reflection loss, and mode conversion characteristics. Further, as the aspect ratio (W / t) of each of the pair of communication conductors 2 decreases, the thickness dimension t becomes larger with respect to the width dimension W, which may increase the rigidity of the flexible flat cable 1 and reduce the bending performance.

[0049] In the second embodiment, the flexible flat cable 1 having the conductive layer 4 covering one surface in the thickness direction is shown, but the present invention is not limited thereto, and conductive layers may be disposed on both surfaces in the thickness direction. Further, the conductive layer does not need to cover the entire length of one or both surfaces in the thickness direction of the flexible flat cable. For example, it may cover a part of one or both surfaces in the thickness direction of the flexible flat cable, such as being disposed at intervals in the longitudinal direction.

[0050] In the first and second embodiments, the flexible flat cable 1 including only the pair of communication conductors 2 as a plurality of conductors is shown, but the present invention is not limited thereto. The flexible flat cable may include other conductors in addition to the pair of communication conductors, such as a conductor for power transmission for transmitting driving power between one device and another device. Further, the flexible flat cable may include two or more pairs of communication conductors.

Examples

[0051] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples.

[0052] In the examples, for each of a plurality of types of flexible flat cables 1 in which the width dimension W, thickness dimension t, and aspect ratio (W / t) of a pair of communication conductors 2 are different from each other, the electrical characteristics of the mode conversion characteristics of characteristic impedance, insertion loss, and return loss when the length dimension is changed are shown as the results of tests on whether the required performance is satisfied.

[0053] Fig. 4 is a list of the width dimension W, thickness dimension t, and aspect ratio (W / t) of a pair of communication conductors 2 of eight types (A to H) of flexible flat cables 1 used in the tests.

[0054] In the tests, a plurality of flexible flat cables 1 of the above eight types with their overall lengths changed were each connected to a vector network analyzer (VNA), and an evaluation was made on whether each electrical characteristic satisfied the required performance based on the communication standard of Ethernet (100BASE-T1). The tests were conducted in an environment with the frequency of the input electrical signal in the range of 300 kHz or more and 1 GHz or less, at room temperature (23°C ± 3°C), and atmospheric pressure.

[0055] Here, for the characteristic impedance, it is determined that the required performance is satisfied when the measured value is 100 ± 10 Ω.

[0056] Also, for the insertion loss, it is determined that the required performance is satisfied when the measured value is equal to or greater than a predetermined standard value (300 kHz to 66.6 MHz).

[0057] Also, for the return loss, it is determined that the required performance is satisfied when the measured value is equal to or less than a predetermined standard value (300 kHz to 66.6 MHz).

[0058] Also, for the mode conversion characteristics, it is determined that the required performance is satisfied when the measured value is equal to or less than a predetermined standard value (300 kHz to 200 MHz).

[0059] FIG. 5 is a graph plotting whether or not the electrical characteristics meet the required performance in the relationship between the aspect ratio and the length dimension of each of the eight types of communication conductors 2 in FIG. 4.

[0060] As shown in FIG. 5, when the length dimension of the flexible flat cable 1 (communication conductor 2) is 100 mm, it was confirmed that all the communication conductors 2 from A to H meet the performance required for electrical characteristics.

[0061] Also, when the length dimension of the flexible flat cable 1 (communication conductor 2) is 400 mm, the communication conductors 2 from A to E, G, and H meet the performance required for electrical characteristics, but it was confirmed that the communication conductor 2 of F with an aspect ratio of 40 does not meet the performance required for electrical characteristics.

[0062] Furthermore, when the length dimension of the flexible flat cable 1 (communication conductor 2) is 1000 mm, the communication conductors 2 from A to D, G, and H meet the performance required for electrical characteristics, but it was confirmed that the communication conductor 2 of E with an aspect ratio of 22.8 and the communication conductor 2 of F with an aspect ratio of 40 do not meet the performance required for electrical characteristics.

[0063] That is, as shown in FIG. 5, the length dimension of the flexible flat cable 1 (communication conductor 2) and the aspect ratio have a correlation, and it is preferable that the communication conductor 2 reduces the aspect ratio when increasing the length dimension. The aspect ratio of the communication conductor 2 is preferably 10 or less when the length dimension of the communication conductor 2 is 1000 mm, preferably 30 or less when the length dimension of the communication conductor 2 is 400 mm, and preferably 40 or less when the length dimension of the communication conductor 2 is 100 mm. That is, the relationship between the aspect ratio and the length dimension of the communication conductor 2 is preferably satisfied by Y≦-0.033X + 43.4, where the variable representing the aspect ratio is Y and the variable representing the length dimension (mm) of the communication conductor 2 is X.

Description of Symbols

[0064] 1 Flexible flat cable 2 Communication conductor 3 Insulator 4 Conductive layer

Claims

1. A flexible flat cable formed by covering a plurality of conductors including at least a pair of communication conductors whose characteristic impedance is adjusted with an insulator, the thickness dimension is 5 times or less the thickness dimension of the communication conductor, the aspect ratio (width dimension / thickness dimension), which is the ratio of the width dimension to the thickness dimension of the communication conductor, is equal to or less than a predetermined value set according to the length dimension of the communication conductor flexible flat cable.

2. A conductive layer is formed on at least one surface side in the thickness direction The flexible flat cable according to Claim 1.

3. When the variable representing the aspect ratio is Y and the variable representing the length dimension (mm) of the communication conductor is X, Y ≦ -0.033X + 43.4 satisfying the relationship of The flexible flat cable according to Claim 1.

4. A power supply device comprising the flexible flat cable according to any one of Claims 1 to 3 power supply device.

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