COMPOSITE CABLE

A composite cable includes a plurality of internal cables and a covering member covering peripheries of the plurality of internal cables. At least one of the plurality of internal cables includes at least one electric wire having a conductor, a first sheath covering a periphery of the at least one electric wire, a shield covering a periphery of the first sheath, and a second sheath covering a periphery of the shield.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority based on Japanese Patent Application No. 2021-158246 filed to Japanese Patent Office on Sep. 28, 2021, and the content of Japanese Patent Application No. 2021-158246 is incorporated by reference in its entirety.

BACKGROUND

The present disclosure relates to a composite cable.

In recent years, an electro mechanical brake (hereinafter also referred to as “EMB”) device using an electric motor or the like is beginning to be proposed in place of a brake device using hydraulic pressure. An electric parking brake device in which a parking brake is electrically operated is also known (see, for example, Japanese Unexamined Patent Application Publication No. 2020-077632).

SUMMARY

The EMB device or the like is connected with an electric wire (also referred to as “power wire”) for supplying electric power to an electric motor, an electric wire (also referred to as “signal wire”) for transmitting output of various sensors that measure parameters such as an angle, and the like. The plurality of electric wires may be covered with a common covering member to serve as a composite cable.

These electric wires are provided with a shield such as a braid that shields electromagnetic noise generated by the electric wires themselves or electromagnetic noise generated outside, and a sheath may be provided outside the shield. The outer sheath may apply a centripetal force to the shield to deform the shield.

When the composite cable is bent in a state where the shield is deformed, local stress concentration may occur in the shield, and the shield may be damaged. When the shield is damaged, there is a problem that the ability to shield electromagnetic noise is deteriorated.

The present disclosure has been made to solve the above problems, and an object is to provide a composite cable that easily suppresses occurrence of damage of a shield.

In order to achieve the above object, the present disclosure provides the following means.

A composite cable of one aspect of the present disclosure includes a plurality of internal cables and a covering member covering peripheries of the plurality of internal cables, and at least one of the plurality of internal cables includes at least one electric wire having a conductor, a first sheath covering a periphery of the at least one electric wire, a shield covering a periphery of the first sheath, and a second sheath covering a periphery of the shield.

In the composite cable of one aspect of the present disclosure, by arranging the electric wire, the first sheath, the shield, and the second sheath in this order from the inside to the outside, the shield is supported by the first sheath arranged on the electric wire side. Therefore, even when the shield receives a force directed from the second sheath toward the electric wire side, the cross-sectional shape of the shield is hardly deformed. Furthermore, even when the composite cable is bent, local stress concentration is less likely to occur in the shield.

By providing the second sheath, the shield and another cable become less likely to come into direct contact with each other. Therefore, the other cable is less likely to be damaged because the shield slides with the other cable.

In the composite cable of one aspect of the present disclosure, by arranging the electric wire, the first sheath, the shield, and the second sheath in this order from the inside to the outside, it is possible to achieve an effect that local stress concentration is less likely to occur in the shield even when the composite cable is bent, and occurrence of damage of the shield is easily suppressed.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, a composite cable1according to one embodiment of the present disclosure will be described with reference toFIG.1. The present embodiment is described with the present disclosure applied to an example in which the composite cable1is a cable used for an EMB device. The composite cable1may be used in a device other than the EMB device.

FIG.1is a cross-sectional view for explaining the configuration of the composite cable1of the present embodiment. As illustrated inFIG.1, the composite cable1is provided with one internal cable10, two power wires20and20, one ground wire30, and an outer sheath (corresponding to covering member)40.

The number of the internal cable10may be two or more. The number of the power wires20and20may be one or three or more. The number of the ground wire30may be two or more.

The internal cable10is a signal wire that propagates electrical signals output from various sensors provided in the EMB device and electrical signals used in a controller area network (CAN). Examples of the various sensors include a load sensor and an angle sensor.

The internal cable10is provided with two twisted electric wires11and11, a first sheath15covering the peripheries of the two electric wires11and11, a shield16covering the periphery of the first sheath15, and a second sheath17covering the periphery of the shield16. The first sheath15is interposed between the two electric wires11.

The electric wire11is a signal wire connected to the sensor in an electrically conductible manner. The two electric wires11and11are in contact with each other and twisted together. The present embodiment is described with the present disclosure applied to an example in which the two electric wires11and11have the same configuration. The electric wire11is provided with a conductor12and a sheath13covering the periphery of the conductor12.

The conductor12is a member formed in an elongated shape, and is a member in which a plurality of conductive metal wires such as copper or an alloy containing copper as a component are twisted. The cross section of the conductor12may be circular, elliptical, or rectangular.

The sheath13is a member formed of a resin material that covers the periphery of the conductor12in a layered manner. As the resin for forming the sheath13, a known resin can be used, and its type is not particularly limited.

The first sheath15is a member formed of a resin material that covers the peripheries of the two electric wires11and11. The first sheath15is a member that supports the shield16. The first sheath15is a columnar member having a solid configuration including two electric wires11and11therein.

The cross section of the first sheath15preferably has a shape in which stress acting on the shield16when the composite cable1is bent is dispersed. Specifically, it is preferable that all sides of the cross section of the first sheath15are formed of curves. The present embodiment is described with the present disclosure applied to an example in which the first sheath15is a columnar member having a substantially circular or substantially elliptical cross section.

An outer peripheral surface of the first sheath15is provided with irregularities for enhancing surface roughness. As a processing method for forming irregularities, embossing in which a plate provided with irregularities is pressed against the outer peripheral surface of the first sheath15can be used. As the surface roughness, 3 µm can be exemplified.

A resin material used as the resin material constituting the first sheath15does not contain a flame retardant and has higher flexibility at low temperature than a resin material containing a flame retardant and constituting the second sheath17described later. As the resin material constituting the first sheath15, a resin material having a Shore D hardness of 80 or less is used, and for example, urethane rubber or silicone rubber is used.

The shield16is a member that is disposed on the outer peripheral surface of the first sheath15and that shields electromagnetic noise. The electromagnetic noise may be generated by power flowing through the electric wire11or may be generated outside the internal cable10.

The present embodiment is described with the present disclosure applied to an example in which the shield16is a braid in which wires formed of a conductive metal material are assembled. For example, the present embodiment is described with the present disclosure applied to an example of copper foil yarn braid. The shield16may be a metallic thin film having conductivity.

The second sheath17is a member formed of a resin material that covers the periphery of the shield16. The second sheath17is a member having a tubular configuration formed in a layered shape along the outer peripheral surface of the shield16.

An outer peripheral surface in the second sheath17is provided with irregularities for enhancing surface roughness. As a processing method for forming irregularities, embossing in which a plate provided with irregularities is pressed against the outer peripheral surface of the second sheath17can be used. As the surface roughness, 3 µm can be exemplified.

The resin material constituting the second sheath17contains a flame retardant. As the resin material constituting the second sheath17, a resin material having a Shore D hardness of 90 or less is used. For example, a polyethylene resin, a fluororesin, or ethylene-propylene-diene rubber (also referred to as EPDM) is used.

As the flame retardant used for the second sheath17, silica (silicon dioxide), a metal hydroxide (magnesium hydroxide or aluminum hydroxide), a bromine-based flame retardant, a phosphoric acid-based flame retardant, a nitrogen-based flame retardant, and a combination of a bromine-based flame retardant and antimony trioxide can be exemplified. The present embodiment is described with the present disclosure applied to an example in which silica is used as a flame retardant.

The number of the electric wires11provided in the internal cable10may be two as described above or three or more. Furthermore, the number of the electric wire11provided in the internal cable10may be one.

The two power wires20and20are power wires for supplying electric power to an electric motor or an actuator provided in the EMB device. The power wire20is provided with a conductor21and a sheath22.

The conductor21is a member formed in an elongated shape, and is a member in which a plurality of conductive metal wires such as copper or an alloy containing copper as a component are twisted. The cross section of the conductor21may be circular, elliptical, or rectangular.

The sheath22is a member formed of a resin material that covers the periphery of the conductor21in a layered manner. As the resin for forming the sheath22, a known resin can be used, and its type is not particularly limited.

One ground wire30is an electric wire used for grounding. The ground wire30is provided with a conductor31and a sheath32. The present embodiment is described with the present disclosure applied to an example in which the composite cable1is provided with the ground wire30, but the composite cable1need not be provided with the ground wire30.

The conductor31is a member formed in an elongated shape, and is a member in which a plurality of conductive metal wires such as copper or an alloy containing copper as a component are twisted. The cross section of the conductor31may be circular, elliptical, or rectangular.

The sheath32is a member formed of a resin material that covers the periphery of the conductor31in a layered manner. As the resin for forming the sheath32, a known resin can be used, and its type is not particularly limited.

The outer sheath40is a member formed of a resin material that covers the periphery of one internal cable10, two power wires20and20, and one ground wire30in a layered manner. As the resin for forming the outer sheath40, a known resin can be used, and its type is not particularly limited.

In the composite cable1having the above-described configuration, the electric wires11and11, the first sheath15, the shield16, and the second sheath17are arranged in this order from the inside to the outside, whereby the shield16is supported by the first sheath15arranged on the electric wire11side. Therefore, even when the shield16receives a force directed from the second sheath17toward the electric wire11side, the cross-sectional shape of the shield16is hardly deformed. Furthermore, even when the composite cable1is bent, local stress concentration is less likely to occur in the shield16, and occurrence of damage of the shield16is easily suppressed.

By providing the second sheath17, the shield16and the power wires20and20and the like become less likely to come into direct contact with each other. Therefore, the shield16slides on the power wires20and20and the like, whereby the power wires20and20and the like become less likely to be damaged.

Since the flame retardant is contained in the material forming the second sheath17, it is easy to impart heat resistance to the internal cable10.

By enhancing the flexibility of the first sheath15as compared with the second sheath17, the internal cable10becomes less likely to be damaged. For example, when the composite cable1is bent, the first sheath15is less likely to be damaged because the flexibility of the first sheath15that is bent more greatly is high.

By forming the first sheath15using a material having a hardness lower than that of the second sheath17, the internal cable10becomes less likely to be damaged. For example, when the composite cable1is bent, the first sheath15is less likely to be damaged because the hardness of the first sheath15that is bent more greatly is low.

By providing the outer peripheral surface of the first sheath15with the irregularities for enhancing surface roughness, the first sheath15and the shield16become easy to be relatively moved. By providing the outer peripheral surface of the second sheath17with the irregularities for enhancing surface roughness, the internal cable10and the outer sheath40become easy to be relatively moved. Therefore, when the composite cable1is bent, distortion becomes less likely to occur in the conductor12of the electric wire11disposed inside the first sheath15.

The first sheath15may be constituted of foamed polyethylene not containing a flame retardant instead of urethane rubber or silicone rubber. In this case, the resin material constituting the second sheath17is not foamed.

By using foamed polyethylene, a plurality of holes are provided inside the first sheath15. This makes it easy to reduce the permittivity of the first sheath15. By lowering the permittivity of the first sheath15, it is easy to lower the characteristic impedance and reduce loss of the current flowing through the conductor12.

The electric wire11of the internal cable10may be a signal wire connected to the sensor in an electrically conductible manner as described above, may be a drain wire in the first sheath15, or may be a power wire for supplying electric power to equipment.

The technical scope of the present disclosure is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present disclosure. For example, the present disclosure is not limited to the embodiments described above, but may be applied to an embodiment in which these embodiments are appropriately combined, and is not particularly limited.