Cable manufacturing method

Abstract

To improve flexural durability of a cable including interposition.SOLUTION: A method of manufacturing a cable comprises: an aggregate formation step of forming a stranded wire aggregate made by stranding a plurality of electric wires and inclusions; a tape winding step of winding a tape member around the stranded wire aggregate; and a sheath formation step of extruding a melted sheath material around the tape member to form a sheath which covers the tape member. The inclusion is formed into a hollow with a resin material that starts thermal contraction at a temperature lower than the melting point of the sheath material. In the sheath formation step, the sheath material heated to a temperature exceeding the melting point is extruded around the tape member, and the inclusion is thermally contracted.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a cable.

Background Art

[0002] A harness (sometimes referred to as a "wire harness") in which a connector is provided at at least one end of a cable (composite cable) including a plurality of electric wires is known. One of the conventional cables constituting the harness includes a plurality of electric wires and an intervening member, a tape member, and a sheath. The plurality of electric wires and the intervening member are collectively twisted to form a twisted wire aggregate. The tape member is wound around the twisted wire aggregate, and the sheath covers the tape member (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Generally, a cable including an intervening member has inferior bending durability compared to a cable not including an intervening member. Therefore, it is required to suppress a decrease in the bending durability of the cable due to including an intervening member.

[0005] An object of the present invention is to suppress a decrease in the bending durability of a cable including an intervening member.

Means for Solving the Problems

[0006] A method for manufacturing a cable according to one embodiment includes a bundle formation step of forming a bundle of stranded wires and an intervening wire by twisting together a plurality of electric wires and an intervening wire; a tape wrapping step of wrapping a tape member around the bundle of stranded wires; and a sheath formation step of extruding molten sheath material around the tape member to form a sheath that covers the tape member. The intervening wire is formed hollow from a resin material that begins to shrink under heat at a temperature below the melting point of the sheath material. In the sheath formation step, the sheath material heated to a temperature above its melting point is extruded around the tape member to cause the intervening wire to shrink under heat. [Effects of the Invention]

[0007] According to the present invention, a cable is realized in which the reduction in bending durability is suppressed even while including an intervening material. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-section of the cable. [Figure 2] This is a process diagram for the manufacturing method of cables. [Figure 3] This is an explanatory diagram of the aggregate formation process. [Figure 4] This is an explanatory diagram of the tape winding process. [Figure 5] This is an explanatory diagram of the sheath formation process. [Figure 6] This is a schematic diagram of a harness using cables. [Figure 7] This is a schematic diagram of a vehicle equipped with a wiring harness. [Modes for carrying out the invention]

[0009] Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. In all drawings used to describe the embodiment, the same or substantially the same components and elements will be denoted by the same reference numerals. Furthermore, components and elements that have already been described will not be described again in principle.

[0010] (Cable overview) To facilitate understanding of the present invention, a cable manufactured by the cable manufacturing method according to the present invention will be described first. Note that the cable described below is merely one example of a cable manufactured by the cable manufacturing method according to the present invention.

[0011] Figure 1 is a cross-sectional view of a cable 1 manufactured by the cable manufacturing method according to the present invention. The cross-section of the cable 1 shown in Figure 1 is perpendicular to the longitudinal direction of the cable 1.

[0012] Cable 1 comprises a stranded wire bundle 2, a tape member 3, and a sheath 4. While the application of Cable 1 is not particularly limited, it is suitable for use as a cable in vehicle harnesses and robot arm harnesses. Harnesses using Cable 1 will be described in more detail later.

[0013] (Twisted wire assembly) The stranded wire assembly 2 is composed of multiple twisted wires and intervening materials. More specifically, the stranded wire assembly 2 is composed of two power supply wires 11 and 12, one signal wire 20, and two intervening materials 31 and 32.

[0014] The power wires 11 and 12, the signal wire 20, and the intervening elements 31 and 32 are all twisted together in the same direction. More specifically, the power wires 11 and 12, the signal wire 20, and the intervening elements 31 and 32 are twisted clockwise within the cross-section shown in Figure 1.

[0015] (power wire) In the following explanation, power supply wire 11 may be referred to as "power supply wire 11," and power supply wire 12 may be referred to as "power supply wire 12." Also, power supply wire 11 and power supply wire 12 may be collectively referred to as "power supply wire 10" or "power supply wire 10."

[0016] The power supply line 10 is an insulated wire including a central conductor 13 and an insulator 14 covering the central conductor 13. The outer diameter of the power supply line 10 can be changed as appropriate, but in this embodiment, the outer diameter of the power supply line 10 is approximately 3 mm. In this embodiment, the power supply line 11 and the power supply line 12 are in contact with each other.

[0017] The central conductor 13 is formed of a highly conductive wire such as copper. The insulator 14 is formed of an insulating resin. Further, the central conductor 13 is a stranded wire in which a plurality of wires are twisted together. Also, the insulator 14 is formed of, for example, crosslinked PE (polyethylene) or flame-retardant crosslinked PE (polyethylene).

[0018] (Signal wire) In the following description, the signal wire 20 may sometimes be referred to as the "signal line 20". The signal line 20 is an insulated wire including a pair of core wires 21a, 21b and an inner sheath 22 covering the core wires 21a, 21b. Viewed another way, the signal line 20 is a multi-core wire including a pair twist wire 21 formed by twisting a pair of core wires 21a, 21b together and an insulator covering the pair twist wire 21. Note that the pair of core wires 21a, 21b are twisted counterclockwise (left-handed) within the cross section shown in FIG. 1. That is, the twisting direction of the pair twist wire 21 is opposite to the twisting direction of the stranded wire assembly 2.

[0019] The outer diameter of the signal line 20 can be changed as appropriate, but in this embodiment, the outer diameter of the signal line 20 is approximately 4.3 mm. That is, the outer diameter of the signal line 20 is larger than the outer diameter of the power supply line 10. In this embodiment, the signal line 20 is in contact with the power supply line 11 and the power supply line 12.

[0020] The core wires 21a, 21b are insulated wires including a central conductor 24 and an insulator 25 covering the central conductor 24. Each central conductor 24 is a stranded wire in which a plurality of wires are twisted together. Also, each insulator 25 is formed of, for example, crosslinked PE (polyethylene) or flame-retardant crosslinked PE (polyethylene).

[0021] The internal sheath 22 is formed from a soft resin that is highly flexible and durable. In this embodiment, the internal sheath 22 is formed from a soft thermoplastic urethane.

[0022] Furthermore, the cable 1 according to this embodiment does not have a shielding conductor covering the power line 10 and the signal line 20. In other words, there is no conductive material capable of shielding electromagnetic waves between the power line 10 and the signal line 20. This configuration is according to the usage conditions of the cable 1, which will be explained later, and does not intentionally exclude cables that have a shielding conductor covering the power line 10 and the signal line 20.

[0023] However, cable 1, in which the power lines 10 and signal lines 20 are not covered by a shield conductor, has superior flexibility and bending resistance, as well as being lighter and having lower manufacturing costs, compared to cables of other embodiments in which the power lines 10 and signal lines 20 are covered by a shield conductor.

[0024] (intervention) In the following description, intervening elements 31 and 32 may be collectively referred to as “intervening element 30”. Intervening element 30 is positioned between adjacent power lines 10 and signal lines 20 in the circumferential direction. More specifically, intervening element 31 is positioned in the air gap 5 between power line 11 and signal line 20, and intervening element 32 is positioned in the air gap 6 between power line 12 and signal line 20.

[0025] Intervening element 30 has an outer diameter that allows it to simultaneously contact the power line 10 or signal line 20 and the tape member 3. Alternatively, intervening element 30 has an outer diameter that prevents it from simultaneously contacting the power line 10, signal line 20, and tape member 3. For example, intervening element 31, which is placed in the gap 5, can simultaneously contact the power line 11 or signal line 20 and the tape member 3, but it will not simultaneously contact the power line 11, signal line 20, and tape member 3.

[0026] Each intervening element 30 is a hollow tube. In other words, each intervening element 30 is a tube. More specifically, each intervening element 30 is hollow and formed from a resin material that begins to shrink when heated above a predetermined temperature. That is, the intervening element 30 is a heat-shrinkable tube. The intervening element 30 (heat-shrinkable tube) shown in Figure 1 has already been heat-shrinkable.

[0027] The resin material forming the intervening 30 only needs to begin thermal shrinking at a temperature below the melting point of the resin material forming the sheath 4 (sheath material), and there are no other particular restrictions. In this embodiment, the intervening 30 is formed of a polyolefin resin whose shrinkage initiation temperature is 115°C. The sheath material and its melting process will be explained in more detail later.

[0028] The intervening 30 is primarily positioned during the manufacturing of the cable 1 with the purpose of making the outer shape (cross-sectional shape) of the cable 1 (sheath 4) closer to a circular or nearly circular shape. More specifically, the intervening 30 is positioned during the process of forming the sheath 4 around the tape member 3 with the purpose of making the outer shape of the cable 1 (sheath 4) closer to a circular or nearly circular shape.

[0029] (Tape material) The tape member 3 is spirally wrapped around the stranded wire assembly 2 to prevent the sheath 4 from getting between multiple electric wires (power wire 11, power wire 12, and signal wire 20). The tape member 3 is, for example, a strip of paper or nonwoven fabric. In this embodiment, the tape member 3 is in contact with power wire 11, power wire 12, and signal wire 20.

[0030] The tape member 3 is wound in the opposite direction to the twisting direction of the stranded wire assembly 2. By winding the tape member 3 in the opposite direction to the twisting direction of the stranded wire assembly 2, the coiling and waviness of the cable 1 are reduced.

[0031] (sheath) The sheath 4 is made of an insulating resin. The sheath 4 is provided around the tape member 3 and covers the tape member 3. The sheath 4 is made of a soft resin that is highly flexible and durable. In this embodiment, the sheath 4 is made of urethane with a melting point of 185°C. More specifically, in this embodiment, the sheath 4 is made of thermoplastic urethane with a melting point of 185°C.

[0032] (How to manufacture cables) Next, an example of a method for manufacturing cable 1 will be described. The cable manufacturing method described here includes at least the steps shown in Figure 2. Specifically, the cable manufacturing method includes at least a bundle formation step, a tape winding step, and a sheath formation step.

[0033] (Aggregation formation process) The assembly formation process is the process of forming the stranded wire assembly 2 shown in Figure 3. In this process, multiple electric wires and intervening materials are prepared and twisted together in the same direction. More specifically, power lines 11 and 12, signal lines 20, and intervening materials 31 and 32 are prepared and twisted together in the same direction. This process can be carried out, for example, using a stranding machine.

[0034] As previously mentioned, the intervening elements 31 and 32 constituting the stranded wire assembly 2 shown in Figure 1 have already undergone thermal shrinkage. However, the intervening elements 31 and 32 constituting the stranded wire assembly 2 shown in Figure 3 have not undergone thermal shrinkage. In other words, no heat is applied to the stranded wire assembly 2, including the intervening elements 31 and 32, during this process. At the very least, no heat exceeding the shrinkage start temperature of the intervening elements 31 and 32 is applied to the stranded wire assembly 2.

[0035] (Tape wrapping process) The tape winding process involves winding the tape member 3, shown in Figure 4, around the stranded wire assembly 2, shown in Figure 3. In this process, the tape member 3 is wound around the stranded wire assembly 2 while it is being transported in the longitudinal direction. More specifically, the strip-shaped tape member 3 is wound spirally around the stranded wire assembly 2. At this time, the winding direction of the tape member 3 is opposite to the twisting direction of the stranded wire assembly 2.

[0036] (Sheath formation process) The sheath formation process involves forming a sheath 4, shown in Figure 5, around the tape member 3, shown in Figure 4. In other words, the sheath formation process involves covering the stranded wire assembly 2, around which the tape member 3 is wound, with the sheath 4.

[0037] In this process, the molten sheath material is extruded around the tape member 3 wound around the stranded wire assembly 2 to form the sheath 4. More specifically, the thermoplastic urethane is heated to a temperature above its melting point (185°C) to melt it. For example, the thermoplastic urethane is heated to a temperature between 200°C and 230°C to melt it.

[0038] Furthermore, heating thermoplastic polyurethane to a temperature above its melting point is done to increase its fluidity.

[0039] Next, the molten thermoplastic urethane is extruded around the tape member 3 wound on the stranded wire assembly 2 to form a sheath 4. This process can be carried out, for example, using an extruder.

[0040] In this process, a high-temperature resin material is supplied around the stranded wire assembly 2. More specifically, thermoplastic urethane at 200°C to 230°C is supplied around the stranded wire assembly 2. As a result, the intervening materials 31 and 32 contained in the stranded wire assembly 2 are heated to above their shrinkage start temperature (115°C) and undergo thermal shrinkage.

[0041] From another perspective, the sheath formation process is a process that forms the sheath 4 and simultaneously uses the heat of the sheath material to thermally shrink the intervening elements 31 and 32. When the outer diameter of the intervening element 30 decreases due to thermal shrinkage, the ratio of the cross-sectional area of ​​the intervening element 30 to the cross-sectional area of ​​the gaps 5 and 6 between the power line 10 and the signal line 20 decreases in a cross-sectional view.

[0042] For example, when the outer diameter of the intervening 31 shown in Figure 5 decreases due to thermal shrinkage, the ratio of the cross-sectional area of ​​the intervening 30 to the cross-sectional area of ​​the gaps 5 and 6 between the power line 10 and the signal line 20 decreases in a cross-sectional view. Alternatively, before this process is performed, the intervening 31 is in contact with three things: the power line 11, the signal line 20, and the tape member 3 (see Figure 4). On the other hand, after this process is performed, the intervening 31 is in contact with two things: the signal line 20 and the tape member 3, but not with the power line 11 (see Figure 5).

[0043] In other words, the sheath formation process creates "play" inside the stranded wire assembly 2. As a result, the stranded wire assembly 2 shown in Figure 5 (which is substantially the same as the stranded wire assembly 2 shown in Figure 1) has improved flexibility and bending resistance compared to the stranded wire assembly 2 shown in Figure 4.

[0044] Furthermore, after the sheath formation process, the intervening 30 may be in contact with the power line 10 and the tape member 3, but not with the signal line 20. Also, one intervening 30 may be in contact with the power line 10 and the tape member, while the other intervening 30 is in contact with the signal line 20 and the tape member 3. Moreover, there may be cases where the intervening 30 is in contact with the power line 10 and the signal line 20, but not with the tape member 3.

[0045] (Harness) Figure 6 is a schematic diagram of a harness 40 using the cable 1 shown in Figure 1. The harness 40 comprises the cable 1 and a connector attached to at least one end of the cable 1. More specifically, the harness 40 comprises a connector 41 attached to one end of the cable 1 and connectors 42, 43 attached to the other end of the cable 1.

[0046] The ends of the power line 10 and signal line 20 of cable 1 extend from both ends of the sheath 4, respectively. Alternatively, both ends of the sheath 4 are removed, exposing the ends of the power line 10 and signal line 20.

[0047] Furthermore, removing both ends of the sheath 4 exposes not only the ends of the power line 10 and signal line 20, but also the ends of the intervening material 30. The exposed portion of the intervening material 30 can be cut off at any time.

[0048] In the following explanation, the ends of the power lines 10 and signal lines 20 located on the left side in Figure 6 may be referred to as the "left end," and the ends of the power lines 10 and signal lines 20 located on the right side in Figure 6 may be referred to as the "right end." However, this distinction is merely for the convenience of explanation.

[0049] Connector 41 is attached to the left end of the exposed power wire 10, and connector 42 is attached to the right end of the exposed power wire 10. Connector 43 is attached to the right end of the exposed signal wire 20.

[0050] A wheel speed sensor 44 is attached to the left end of the exposed signal wire 20. The wheel speed sensor 44 is a magnetic sensor that detects changes in the surrounding magnetic field and outputs a signal according to the detection result.

[0051] (Example of harness usage) Figure 7 is a schematic diagram of a vehicle 50 equipped with a harness 40. The vehicle 50 is equipped with an electric parking brake (EPB). More specifically, an electric motor 60 for the EPB is mounted on a wheel 51. In addition, an EPB control unit 61 is provided in an ECU (electronic control unit) 62 mounted on the vehicle body 52.

[0052] The electric motor 60 for the EPB drives a piston to which brake pads are attached. When the piston is driven in the first direction by the electric motor 60 for the EPB, the brake pads are pressed against the disc rotor, generating braking force. On the other hand, when the piston is driven in the second direction by the electric motor 60 for the EPB, the brake pads move away from the disc rotor, and the braking force is lost.

[0053] When predetermined conditions are met, the EPB control unit 61 supplies a drive current to the EPB electric motor 60 for a predetermined time (for example, 1 second) to move the piston in the first direction. For example, when the parking brake operating switch 70 is operated by the driver from the off state to the on state, the EPB control unit 61 supplies a drive current to the EPB electric motor 60 for a predetermined time to move the piston in the first direction.

[0054] Furthermore, when predetermined conditions are met, the EPB control unit 61 supplies drive current to the EPB electric motor 60 and moves the piston in the second direction. For example, when the driver operates the parking brake actuation switch 70 from the ON state to the OFF state, or when the accelerator pedal is pressed, the EPB control unit 61 supplies drive current to the EPB electric motor 60 and moves the piston in the second direction.

[0055] In other words, the electric parking brake installed in the vehicle 50 remains activated after the parking brake activation switch 70 is turned ON, until the parking brake activation switch 70 is turned OFF or the accelerator pedal is pressed.

[0056] Vehicle 50 is equipped with an anti-lock braking system (ABS) in addition to an electric parking brake. More specifically, an ABS sensor 44 is located near the wheels 51. Furthermore, an ABS control unit 63 is provided in the ECU (electronic control unit) 62 mounted on the vehicle body 52.

[0057] The ABS control unit 63 controls the braking system based on the output of the ABS sensor 44. For example, the ABS control unit 63 intermittently activates the braking system based on the output of the ABS sensor 44 to prevent wheel lock-up.

[0058] The harness 40 electrically connects the ECU 62 and the electric motor 60 for the EPB. More specifically, a connector 41 (Figure 6) on the harness 40 is connected to a connector on the electric motor 60 for the EPB. Also, a connector 42 (Figure 6) on the harness 40 is connected to a connector on the junction box 64. When connector 42 is connected to the connector on the junction box 64, the power lines 10 of the harness 40 are electrically connected to the group of wires inside the junction box 64. As a result, the ECU 62 and the electric motor 60 for the EPB are electrically connected, and drive current is supplied to the electric motor 60 for the EPB based on the control of the EPB control unit 61.

[0059] The harness 40 electrically connects the ECU 62 and the ABS sensor 44. More specifically, the wheel speed sensor 44 (Figure 6) on the harness 40 is positioned near the wheel 51 as an ABS sensor. Also, the connector 43 (Figure 6) on the harness 40 is connected to a connector provided on the relay box 64. When the connector 43 is connected to the connector on the relay box 64, the signal line 20 of the harness 40 is electrically connected to the group of wires inside the relay box 64. As a result, the ECU 62 (ABS control unit 63) and the ABS sensor 44 are electrically connected, and the braking system is controlled based on the output of the ABS sensor 44.

[0060] In other words, the power lines 10 provided by the harness 40 form a power supply path for supplying drive current to the electric motor 60 for the EPB. In addition, the signal lines 20 provided by the harness 40 form a signal transmission path for transmitting signals output from the ABS sensor 44 to the ECU 62 (ABS control unit 63).

[0061] As previously stated, the cable 1 used in harness 40 does not have a shielded conductor. More specifically, there is no conductive material capable of shielding electromagnetic waves between the power line 10 and the signal line 20 of cable 1.

[0062] Therefore, if current flows through the power line 10, the electromagnetic waves generated by this current may electrically affect the signals transmitted through the signal line 20. However, the electric parking brake installed in the vehicle 50 operates mainly when the vehicle 50 is stopped. In other words, the drive current supplied to the electric motor 60 for the EPB via the power line 10 is mainly when the vehicle 50 is stopped.

[0063] On the other hand, the ABS system installed in vehicle 50 operates while vehicle 50 is in motion. In other words, the ABS system does not operate when vehicle 50 is stopped. Another way of looking at it is that when the vehicle is stopped (vehicle speed is zero), no signal is output from the ABS sensor 44, and no signal is transmitted via the signal line 20. At the very least, even if the signal transmitted via the signal line 20 is affected in some way, that effect can be ignored.

[0064] Therefore, in this embodiment, the shield conductor is omitted in order to prioritize the flexibility and bendability of the cable 1 and harness 40.

[0065] For convenience, only one wheel 51 is shown in Figure 7, but the vehicle 50 has four wheels, including the wheel 51 shown in the figure. The electric motor 60 for the EPB and the ABS sensor 44 may be provided on all four wheels, or only on the front wheels or only on the rear wheels.

[0066] The present invention is not limited to the embodiments described above, and various modifications are possible without departing from its spirit. For example, the combination of the intervening material 30 and the sheath material 4 can be appropriately determined based on the shrinkage start temperature of the intervening material 30 and the melting point of the sheath material 4. Also, the internal sheath 22 shown in Figure 1 can be omitted.

[0067] The power line 10 of the harness 40 (cable 1) can also be used to supply drive current to the electric motor of the electromechanical brake (EMB). In this case, since current flows through the power line 10 even while the vehicle is running, it is preferable to provide a shielded conductor on at least one of the power line 10 and the signal line 20.

[0068] The wheel speed sensor 44 in the harness 40 can be replaced with other sensors. For example, the wheel speed sensor 44 can be replaced with a temperature sensor or an air pressure sensor.

[0069] The signal line 20 of harness 40 (cable 1) can also be used to transmit signals for controlling the vibration damping device installed in the vehicle, or signals for controlling the EMB (Electromagnetic Mixer). [Explanation of symbols]

[0070] 1…Cable, 2…Stranded wire assembly, 3…Tape material, 4…Sheath, 5,6…Air gap, 10,11,12…Power wire (power line), 13…Center conductor, 14…Insulator, 20…Signal wire (signal line), 21…Paired stranded wire, 21a,21b…Core wire, 22…Internal sheath, 24…Center conductor, 25…Insulator, 30,31,32…Interlayer, 40…Harness, 41,42,43…Connector, 44…Wheel speed sensor (ABS sensor), 50…Vehicle, 51…Wheel, 52…Vehicle body, 60…Electric motor for EPB, 61…EPB control unit, 62…ECU (Electronic Control Unit), 63…ABS control unit, 64…Relay box, 70…Parking brake actuation switch

Claims

1. A process for forming a stranded wire assembly in which multiple electric wires and intervening materials are twisted together, A tape winding step in which a tape member is wrapped around the stranded wire assembly, The process includes a sheath forming step of extruding molten sheath material around the tape member to form a sheath that covers the tape member, The intervening is formed hollow by a resin material that begins to shrink at a temperature below the melting point of the sheath material. A method for manufacturing a cable, wherein in the sheath forming step, the sheath material, heated to a temperature above its melting point, is extruded around the tape member to cause the intervening to thermally shrink.

2. The method for manufacturing a cable according to claim 1, wherein in the sheath forming step, the sheath material heated to 200°C or higher is extruded around the tape member.

3. The method for manufacturing a cable according to claim 2, wherein the intervening is formed of a polyolefin resin that begins to shrink at 115°C.

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