Cable for differential serial transmission

Abstract

Provided is a cable including: at least two signal cables formed of first and second signal cables for differential transmission; a third cable for ground; a fourth cable for power supply; a metal sheet adapted to cover the first and second signal cables; a coating material adapted to house the first and second signal cables covered with the metal sheet, and the third and fourth cables; and a magnetic powder-mixed resin filled into an inner space of the coating material and prepared by mixing magnetic powder with a resin.

Claims

1. A cable, comprising: at least a first signal cable and a second signal cable for differential transmission; a third cable for ground; a fourth cable for power supply; a metal sheet configured to cover the first signal cable and the second signal cable; a coating material configured to house the first signal cable, the second signal cable, the third cable and the fourth cable; and a magnetic powder-mixed resin filled into a space between an inner peripheral surface of the coating material and the metal sheet, the third cable, and the fourth cable, wherein the magnetic powder-mixed resin is a mixture of magnetic powder and a resin.

2. The cable according to claim 1, wherein a mixing ratio of the magnetic powder in the magnetic powder-mixed resin is 70 wt % or more.

3. The cable according to claim 1, wherein the magnetic powder is one of ferrite or permalloy.

4. The cable according to claim 1, wherein the first signal cable is twisted with the second signal cable.

5. The cable according to claim 1, wherein each of the first signal cable and the second signal cable comprises a plurality of copper wires and an aramid fiber.

6. The cable according to claim 5, further comprising a coating film of an insulation resin on each of the first signal cable and the second signal cable.

7. The cable according to claim 1, wherein each of the third cable and the fourth cable comprises a plurality of copper wires and an aramid fiber.

8. The cable according to claim 7, further comprising a coating film of an insulation resin on each of the third cable and the fourth cable.

9. The cable according to claim 1, further comprising a drain, wherein the drain is covered with the metal sheet.

10. The cable according to claim 1, wherein a transmission via the cable is based on a USB standard.

11. The cable according to claim 1, further comprising: a ferrite core configured to surround a partial section of the cable; and a molding resin on an outer side of the ferrite core.

12. The cable according to claim 11, wherein the molding resin is mixed with the magnetic powder.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIGS. 1A to 1C are schematic diagrams used to describe problems in the case of using a braided wire.

(2) FIG. 2 is a horizontal sectional view of a cable according to a first embodiment of the present disclosure.

(3) FIG. 3 is a perspective view of an exemplary cable according to the first embodiment of the present disclosure.

(4) FIG. 4 is a graph illustrating frequency characteristics of magnetic permeability of a magnetic powder-mixed resin.

(5) FIG. 5 is a graph used to describe signal transmission characteristics of the present disclosure.

(6) FIG. 6 is a graph used to describe signal transmission characteristics of the present disclosure.

(7) FIG. 7 is a horizontal sectional view of a cable according to a second embodiment of the present disclosure.

(8) FIGS. 8A and 8B are a schematic diagram and a horizontal sectional view of a cable according to a third embodiment of the present disclosure.

(9) FIG. 9 is a schematic diagram of a cable according to a fourth embodiment of the present disclosure.

(10) FIG. 10 is a connection diagram of the cable according to the fourth embodiment of the present disclosure.

(11) FIG. 11 is a graph of impedance frequency characteristics of a common mode choke coil for a signal.

(12) FIG. 12 is a graph of impedance frequency characteristics of a common mode choke coil for power source.

(13) FIG. 13 is a graph of insertion loss frequency characteristics of noise removal capacitor.

(14) FIG. 14 is a cross-sectional view of an exemplary USB connector.

(15) FIG. 15 is a graph of frequency characteristics of a loss factor of a molding resin.

(16) FIG. 16 is a cross-sectional view of another exemplary USB connector.

MODE FOR CARRYING OUT THE INVENTION

(17) In the following, embodiments of the present disclosure will be described with reference to the drawings. Note that the description will be provided in the following order.

(18) <1. First Embodiment>

(19) <2. Second Embodiment>

(20) <3. Third Embodiment>

(21) <4. Fourth Embodiment>

(22) <5. Modified Example>

(23) Note that the embodiments described below are preferred concrete examples of the present disclosure and various kinds of technically preferred limitations are provided, however; the scope of the present disclosure is not limited to these embodiments unless otherwise provided with a description that particularly limits the present disclosure in the following description.

1. First Embodiment

(24) Cable Structure

(25) FIG. 2 is a horizontal sectional view of a cable according to a first embodiment of the present disclosure. The first embodiment is an example in which the present disclosure is applied to USB cable (USB Standard Type-A and Type-B). The USB cable has four cables (electric wires) including: a pair of cables formed of a first signal cable 21a and a second signal cable 21b for differential transmission (differential mode); a power cable 22; and a ground cable 23. Each of these cables 21a, 21b, 22, and 23 has a periphery of a conductive wire 24 as a core wire coated with an insulation film 25.

(26) As the conductive wire 24, any one of a structure using copper and formed of a single conductive wire and a structure of a strand wire formed as one conductive wire by twisting thin conductive wires together may be used. In the case of using the strand wire, there may be a structure in which an aramid fiber thread 42 is disposed in a center portion of a plurality of copper wires 41 and the copper wires 41 and the thread 42 are twisted together as illustrated in FIG. 3 in order to ensure tensile strength and flexibility of a wire material. An insulation resin is provided for a portion obtained by twisting the copper wires 41 and the thread 42 together. The structure of FIG. 3 may be adopted by any one of the signal cables 21a, 21b, power cable 22, and ground cable 23. The signal cables 21a, 21b may be formed as a wire pair, for example.

(27) The signal cables 21a and 21b are covered with a metal sheet 26. The metal sheet 26 may adopt a structure covered with copper or an aluminum foil, a structure of wrapping an aluminum ribbon around the signal cables 21a and 21b, and a structure of combining these two methods. Since the metal sheet 26 is not connected to the ground, there is an advantage of having no big tail problem caused by using a braided wire.

(28) The signal cables 21a and 21b covered with the metal sheet 26, the power cable 22, and the ground cable 23 are covered with a coating material 27. The magnetic powder-mixed resin 28 is filled into the coating material 27. The magnetic powder-mixed resin 28 intervenes between an inner peripheral surface of the coating material 27 and the signal cables 21a and 21b, power cable 22, and ground cable 23. Since the signal cables 21a and 21b are covered with the metal sheet 26, a signal can be transmitted without influence of the magnetic powder-mixed resin 28.

(29) As the insulation film 25 of the conductive wire 24 and the coating material 27, various kinds of materials can be used. For example, materials such as polyethylene, polypropylene, polyvinyl chloride (PVC), and elastomer can be used.

(30) The magnetic powder-mixed resin 28 is obtained by mixing magnetic powder with a synthetic resin. An exemplary synthetic resin is styrene elastomer. Besides, synthetic resins such as olefin elastomer and PVC may also be used. Exemplary magnetic powder is NiZn-based ferrite. According to an exemplary mixture ratio, ferrite is 89 wt %. As the magnetic powder, NiCuZn-based ferrite, MnZn-based ferrite, and magnetic powder of soft magnetic metal-base, copper-base, magnesium-base, lithium-base, zinc-base, iron-base (e.g., permalloy), and cobalt-base may also be used.

(31) The mixture ratio is not limited to the above-described percentage. The higher the mixture ratio of the magnetic powder is, the better a characteristic to absorb high-frequency noise can be achieved. However, since mechanical characteristics such as moldability, flexibility, and tensile strength are deteriorated, a ratio is set so as to satisfy both characteristics. Generally, the high-frequency noise can be absorbed when the ratio of ferrite is 70 wt % or more and 95% or less.

(32) FIG. 4 illustrates frequency characteristics of magnetic permeability of the magnetic powder-mixed resin 28 obtained by mixing NiZn-based ferrite with a styrene elastomer compound at the above-described ratio.

(33) Transmission Characteristics of First Embodiment

(34) In the above-described first embodiment of the present disclosure, the signal cables 21a, 21b are shielded by the metal sheet 26, and an outer side thereof is coated with the magnetic powder-mixed resin 28, and furthermore, the outside thereof is coated with the coating material 27. With this structure, it is confirmed that signal can be properly transmitted.

(35) As a reference example 1, differential transmission of a high-frequency signal is performed with two cables corresponding to the signal cables 21a, 21b. In this case, a shielding material like the metal sheet 26 is not provided at the cables. Additionally, a ferrite core having a cylindrical body is used as a member corresponding to the magnetic powder-mixed resin 28, and each of the cables is set so as to pass through a center hole of the ferrite core. The two ferrite cores where the respective cables pass through near an input port, and two ferrite cores where the respective cables pass through near an output port are used.

(36) A coil is formed by the cable passing through the center hole of the ferrite core having a cylindrical shape (or ring shape). Therefore, the higher the frequency is, the higher impedance is. Additionally, when current flows in the coil formed of the ferrite core, there is an effect that energy is lost by a magnetic loss generated at the ferrite core, and impedance (resistant component) is increased. Impedance characteristics in the case of using the ferrite core are determined by a material of the ferrite core, a size of the cylindrical body formed by the ferrite core (length, diameter, and diameter of the center hole), the number of turns, and the like. The structure where the cable passes through the center hole of the cylindrical body formed of the ferrite core is referred to as one turn, and the structure where the cable is once wound around the cylindrical body is referred to as two turns. The more the number of turn is, the higher the impedance is.

(37) Thus, in the case of the reference example 1 in which the ferrite core is used without covering the signal cable with the metal sheet, transmission characteristics illustrated in FIG. 5 are obtained. In other words, signal transmission is not normally performed by the ferrite core. A horizontal axis represents a frequency, and a vertical axis represents an insertion loss.

(38) Next, a study result of transmission characteristics related to a reference example 2 having a structure in which two cables same as the reference example 1 are provided as a twist pair and further covered with a braided shield is illustrated as frequency characteristics indicated by a dotted line in FIG. 6. Similar to FIG. 5, a horizontal axis represents a frequency, and a vertical axis represents an insertion loss. As illustrated in FIG. 6, in the case of the reference example 2, a signal is transmitted from an input side to an output side with little attenuation amount. Therefore, signal transmission is normally performed.

(39) Furthermore, transmission characteristics related to a structure in which each of the cables is made to pass through a ferrite core (the one same as the reference example 1) in the reference example 2 (structure similar to the present disclosure) are indicated as a solid line in FIG. 6. As it can be grasped from the graph of FIG. 6, even when the ferrite core is provided, the transmission characteristics can be little changed by providing a shield. Therefore, the first embodiment of the present disclosure can normally transmit a signal even when the outside of the signal cables 21a, 21b for differential transmission is covered with the magnetic powder-mixed resin 28.

2. Second Embodiment

(40) A second embodiment of the present disclosure applied to a Type-C newly added in accordance with the USB 3.1 standard will be described with reference to FIG. 7. FIG. 7 is a horizontal sectional view of the second embodiment. A first embodiment described above can be applied to any one of a Type-A and a Type-B of the USB standard. The standard of the Type-C can perform bidirectional transmission and power supply, and supports a maximum data transfer rate (10 Gbps (USB 3.1 standard)).

(41) As illustrated in FIG. 7, similar to the first embodiment, signal cables 21a, 21b each attached with an insulation film are covered with a metal sheet 26, and a power cable 22 and a ground cable 23 each attached with an insulation film are provided. The signal cables 21a, 21b are referred to as C-signal cables (for differential transmission).

(42) In the second embodiment, A-signal cables (for differential transmission) 31a, 31b and a drain 31c are covered with a metal sheet 33, B-signal cables (for differential transmission) 32a, 32b and a drain 32c are covered with a metal sheet 34. The drains 31c and 32c do not have any insulation film.

(43) In the above-described second embodiment also, each of the cables is shielded by a coating material 27 and a magnetic powder-mixed resin 28 in a manner similar to the first embodiment. Therefore, problems such as noise emission to the outside and noise entrance from the outside can be suppressed. Furthermore, since the respective signal cables are covered with the metal sheets 26, 33, and 34, the magnetic powder-mixed resin 28 prevents occurrence of a problem of not normally performing a high-frequency signal transmission.

3. Third Embodiment

(44) A third embodiment of the present disclosure will be described with reference to FIGS. 8A and 8B. A coating material 27 in a partial section at an appropriate place (one or plural places) of a cable according to above-described first embodiment is removed, and a magnetic powder-mixed resin 28 is exposed. A ferrite core 35 molded in a cylindrical shape is disposed in the section where the magnetic powder-mixed resin 28 is exposed. An inner diameter of the ferrite core 35 is formed slightly larger than an outer diameter of the magnetic powder-mixed resin 28.

(45) Furthermore, a molding resin 36 to cover an entire portion of the ferrite core 35 is provided. The molding resin 36 is a molding resin mixed with ferrite. Thus, noise removal performance can be improved by inserting the ferrite core 35 in the middle of the cable and covering the same with the molding resin 36. Meanwhile, the coating material 27 is not necessarily removed, and the molding resin 36 does not necessarily include ferrite.

4. Fourth Embodiment

(46) Next, a fourth embodiment of the present disclosure will be described. As illustrated in FIG. 9, the fourth embodiment relates to anti-noise measures for a cable having an exemplary form in which a standard USB connector (Type-A) 71 is connected to one end of a cable 61 and a micro (suitably abbreviated as ) USB connector (Type-A) 81 is connected to the other end. The standard USB connector (hereinafter simply referred to as USB connector) 71 is connected to a host side (personal computer, electric charger (so-called AC adapter), and the like) and the USB connector 81 is connected to a device side (smartphone, tablet, and the like). As the cable 61, a cable having excellent noise suppression performance according to the above-described present disclosure or a cable with an existing shield is used.

(47) As illustrated in FIG. 5, for example, the USB connector 71 is connected to a receptacle of a personal computer 70, and the USB connector 81 is connected to a receptacle of a mobile terminal 80. The USB connector 71 has following pin arrangement.

(48) Pin 1: Vbus, Pin 2: D, Pin 3: D+, Pin 4: GND

(49) The USB connector 81 has following pin arrangement.

(50) Pin 1: Vbus, Pin 2: D, Pin 3: D+, Pin 4: ID, Pin 5: GND

(51) Two terminals on one side of a common mode choke coil (also may be referred to as common mode filter) 72 are connected to data terminals D and D+ of the USB connector 71. Two terminals on the other side of the common mode choke coil 72 are connected to two terminals on one side of a common mode choke coil 82 provided at the USB connector 81 via the cable 61. Two terminals on the other side of the common mode choke coil 82 are connected to the data terminals D and D+.

(52) Two terminals on one side of a common mode choke coil 73 are connected to power source terminals Vbus and GND of the USB connector 71. A noise removal capacitor 74 is inserted between two terminals on the other side of the common mode choke coil 73. The two terminals on the other side of the common mode choke coil 73 are connected to power source terminals Vbus and a GND via the cable 61 and ferrite beads 83 and 84 provided at the USB connector 81. An identification resistance 85 is connected between an identification terminal ID and the power source terminal GND.

(53) The two common mode choke coils 72 and 82 are inserted to a data transmission line, but one of these common mode choke coils may also be omitted. A common mode choke coil for a power line may also be provided instead of the ferrite beads in USB connector 81. Meanwhile, in the case of the connector standard of a USB Type-C, the connector can be used in both the host side and the device side. Therefore, in this case, common mode choke coils are needed to be mounted on the both-side connectors.

(54) The common mode choke coil is formed by winding two coils around a common core in opposite directions. In the common mode choke coils 72 and 82, coils are respectively inserted into two data lines. In the common mode choke coil 73, coils are respectively inserted into two power lines.

(55) The common mode choke coil allows signal current to pass in a differential mode, and can remove noise current of the common mode. In other words, in the case of the differential mode, flow directions of current flowing in the two coils are opposite and the current does not function as an inductor. In the case of a common mode, the current flowing in the two coils flows in the same direction and functions as the inductor. Since noise is the common mode, the noise can be removed. Actually, since a magnetic flux generated in each coil partly becomes a leaked magnetic flux, an inductance component does not become zero. Therefore, there may be a case where such an inductance component cannot be ignored in a region having an extremely high signal frequency. Furthermore, noise can be removed by the noise removal capacitor 74. Noise having a high frequency can be removed by the ferrite beads 83 and 84.

(56) Thus, by improving noise removal performance for power transmission, it is possible to prevent a reception level of the mobile terminal 80 from being degraded due to noise generated in an electric charger or a personal computer connected with the USB connector 71.

(57) FIG. 11 illustrates impedance frequency characteristics of the common mode choke coil 72 (82) for a signal. Characteristics indicated by a solid line 86 are the impedance frequency characteristics relative to the common mode, and a dotted line 87 indicates the impedance frequency characteristics relative to the differential mode. For example, impedance relative to the differential mode is low in the vicinity of 100 MHz, and little influence is given to signal transmission.

(58) FIG. 12 illustrates impedance frequency characteristics of the common mode choke coil 73 for a power source. Characteristics indicated by a solid line 88 are the impedance frequency characteristics relative to the common mode, and a dotted line 89 indicates the impedance frequency characteristics relative to the differential mode. For example, impedance relative to both of the common mode and the differential mode is relatively high in the vicinity of 100 MHz, and a high frequency component (namely, noise) can be suppressed in both of the modes.

(59) FIG. 13 illustrates insertion loss frequency characteristics of the noise removal capacitor 74. For example, a value of the capacitor 74 is set to 1.5 F. Noise can be suppressed by the capacitor 74.

(60) In the fourth embodiment, measures for shielding the USB connector 71 and the USB connector 81 are additionally taken. FIG. 14 is a schematic cross-sectional view of, for example, the USB connector 71 taken along an A-A line in FIG. 9. Components of the common mode choke coils 72, 73 and the like are mounted on a printed circuit board 91.

(61) The printed circuit board 91 and the common mode choke coils 72, 73 have a structure covered with a resin. The resin is formed of: a layer of a non-conductive resin 92 such as polypropylene adapted to directly cover the common mode choke coils 72, 73; and a layer of a conductive resin 93 located outside thereof. The conductive resin 93 is a resin that is obtained by filling carbon in a resin and can be molded, and has a shielding effect against electromagnetic waves, such as absorption and reflection. A resin (ferrite resin) that is obtained by filling ferrite in a resin and can be molded may also be used instead of the conductive resin 93.

(62) A method of manufacturing the USB connector 71 thus configured will be described. Chip components (common mode choke coils 72, 73 and the like) for anti-noise measures are mounted on the printed circuit board 91, and then the connector and the printed circuit board 91 are soldered. After that, primary molding is performed with the non-conductive resin 92 while a wire material is connected to the printed circuit board 91 by soldering. Next, molding is performed with the conductive resin 93 (or ferrite resin), and a connector portion is formed. Since only the resin is used for manufacture, a manufacturing time can be shortened, and furthermore, since covering is provided with the resin without any clearance, shielding performance can be improved.

(63) FIG. 15 illustrates frequency characteristics of an exemplary loss factor of the ferrite resin. For example, illustrated are frequency characteristics when polypropylene is used and a weight filling rate of ferrite is 80%. As it can be grasped from FIG. 15, when the frequency is low, the loss factor of approximately 4 can be obtained.

(64) As illustrated in FIG. 16, it may also be possible to have a structure in which the outer side of the above-described USB connector 71 is covered with a non-conductive resin 94. In other words, that is the structure in which the chip components for anti-noise measures are covered with a three-layer structure (non-conductive resin 92, conductive resin 93, and non-conductive resin 94). The three-layer structure can implement more improved shield performance.

5. Modified Example

(65) While the embodiments of the present disclosure have been concretely described above, the present disclosure is not limited to the above-described embodiments, and various kinds of modifications can be made on the basis of the technical idea of the present disclosure. For example, the configuration, methods, processes, shapes, materials, and values exemplified in the above-described embodiments are merely examples, and as the case may be, a configuration, a method, a process, a shape, a material, and a value different therefrom may also be used. For example, the present disclosure may also be applicable to a cable or a connector of the USB Type-C standard.

(66) Additionally, not limited to the USB cable, the present disclosure may be applicable to a cable of HDMI (registered trademark), a cable of Institute of Electrical and Electronics Engineers (IEEE) 1394, and the like. In other words, in the case of the standard of the HDMI (registered trademark), various kinds of packet data of a video and an audio is transmitted by a system called transition minimized differential signaling (TMDS). As for TMDS channels, three channels for data and one channel for a clock are prepared. For example, a transmission line of the channels for data and a clock are covered with a metal sheet and a magnetic powder-mixed resin is filled, thereby achieving effects similar to those described above.

(67) Note that the present disclosure can also have the following configurations.

(68) (1)

(69) A cable including: at least two signal cables formed of first and second signal cables for differential transmission; a third cable for ground; a fourth cable for power supply; a metal sheet adapted to cover the first and second signal cables; a coating material adapted to house the first and second signal cables covered with the metal sheet, and the third and fourth cables; and a magnetic powder-mixed resin filled into an inner space of the coating material and prepared by mixing magnetic powder with a resin.

(70) A cable including: at least two signal cables formed of first and second signal cables for differential transmission; a third cable for ground; a fourth cable for power supply; a metal sheet to cover the first and second signal cables; a coating material adapted to house the first and second signal cables covered with the metal sheet, and the third and fourth cables; and a magnetic powder-mixed resin filled into a space generated after housing the cables in an inner space of the coating material and prepared by mixing magnetic powder with a resin.

(71) (2)

(72) The cable recited in (1), wherein a mixing ratio of magnetic powder of the magnetic powder-mixed resin is 70 wt % or more.

(73) (3)

(74) The cable recited in (1) or (2), wherein the magnetic powder is ferrite or permalloy.

(75) (4)

(76) The cable recited in any one of (1), (2), and (3), wherein the first and second cables are twisted together.

(77) (5)

(78) The cable recited in any one of (1), (2), (3), and (4), wherein the first and second signal cables are formed of a plurality of copper wires and an aramid fiber.

(79) (6)

(80) The cable recited in (5), wherein a coating film of the first and second signal cables formed of the plurality of copper wires and the aramid fiber is formed of an insulation resin.

(81) (7)

(82) The cable recited in any one of (1), (2), (3), (4), (5), and (6), wherein the third and fourth cables are formed of a plurality of copper wires and an aramid fiber.

(83) (8)

(84) The cable recited in (7), wherein a coating film of the third and fourth cables formed of the plurality of copper wires and the aramid fiber is formed of an insulation resin.

(85) (9)

(86) The cable recited in any one of (1), (2), (3), (4), (5), (6), (7), and (8), wherein a drain is covered with the metal sheet together with the first and second signal cables.

(87) (10)

(88) The cable recited in any one of (1), (2), (3), (4), (5), (6), (7), (8), and (9) used for transmission based on a USB standard.

(89) (11)

(90) A cable including a ferrite core adapted to surround a partial section of a cable recited in (1), and provided with a molding resin on an outer side of the ferrite core.

(91) (12)

(92) The cable recited in (11), wherein the molding resin is mixed with magnetic powder.

(93) (13)

(94) The cable recited in (11), wherein a coating material in the partial section is removed.

REFERENCE SIGNS LIST

(95) 21a, 21b, 31a, 31b, 32a, 32b Signal cable 22 Power cable 23 Ground cable 26, 33, 34 Metal sheet 27 Coating material 28 Magnetic powder-mixed resin