Method for manufacturing a cable connection structure and cable connection structure

Abstract

This technology ensures reliable cable connections without compromising the ease of connection work. [Solution] The power cable conductor is placed inside a cylindrical sleeve, and compression is performed from the outside of the sleeve using a die to form an indentation that is recessed in the radial direction of the sleeve (S20). In the step of forming the indentation (S20), the die used has an indentation pin with a protruding shape corresponding to the indentation, and when the compression is performed, there is a gap in which the parts other than the indentation pin are separated from the cylindrical outer surface of the sleeve.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a cable connection structure and a cable connection structure.

Background Art

[0002] When connecting a pair of power cables, the conductors may be connected by compressing a sleeve (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] The present disclosure provides a technique capable of reliably performing cable connection and without impairing the connection workability.

Means for Solving the Problems

[0005] According to one aspect of the present disclosure, a step of forming an indentation recessed in the radial direction of the sleeve by performing compression using a die from the outside of the sleeve with the conductor of the power cable disposed in the cylindrical sleeve is provided, in the step of forming the indentation, as the die, an indentation pin having a protrusion shape corresponding to the indentation and having a gap where a portion other than the indentation pin is separated from the outer cylindrical surface of the sleeve when the compression is performed is used A method for manufacturing a cable connection structure is provided.

Effects of the Invention

[0006] According to the present disclosure, cable connection can be reliably performed, and the connection workability is not impaired. [Brief explanation of the drawing]

[0007] [Figure 1] This flowchart shows an example of a procedure for manufacturing a cable connection structure according to one embodiment of the present disclosure. [Figure 2] This is an explanatory diagram showing an example of the configuration of a die used in a method for manufacturing a cable connection structure according to one embodiment of the present disclosure. [Figure 3A] This is a plan view showing an example of the configuration of an eccentricity prevention jig used in a method for manufacturing a cable connection structure according to one embodiment of the present disclosure. [Figure 3B] This is a side view showing an example of the configuration of an eccentricity prevention jig used in a method for manufacturing a cable connection structure according to one embodiment of the present disclosure. [Figure 4] This is an explanatory diagram showing an example of the axial position arrangement of a die and an eccentricity prevention jig in a method for manufacturing a cable connection structure according to one embodiment of the present disclosure. [Figure 5] This is an explanatory diagram showing an example of a pre-compressed state in a method for manufacturing a cable connection structure according to one embodiment of the present disclosure. [Figure 6] This is an explanatory diagram showing an example of the compressed state in a method for manufacturing a cable connection structure according to one embodiment of the present disclosure. [Figure 7] This is an explanatory diagram showing an example of another arrangement of dies in a method for manufacturing a cable connection structure according to one embodiment of the present disclosure. [Figure 8] This is an explanatory diagram showing yet another example of a die arrangement in a method for manufacturing a cable connection structure according to one embodiment of the present disclosure. [Figure 9] This is an explanatory diagram showing an example of the configuration of a cable connection structure according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0008] [Description of Embodiments in this Disclosure] <Insights gained by the inventor> First, I will explain the findings obtained by the present inventor.

[0009] In recent years, in order to reduce the weight of power cables and the manufacturing cost of power cables, the application of conductors containing aluminum has been increasing. However, when connecting power cables having such aluminum conductors, an aluminum oxide film is formed on the outer periphery of the conductor strands, and since this film is insulating and becomes an obstacle factor during connection, it has been necessary to break the oxide film.

[0010] Under the situation where the conductor strands have an oxide film as described above, the following problems may occur in the connection of power cables.

[0011] For example, in the method of compressing a sleeve so that the cross section becomes hexagonal, as in the method applied to conventional copper conductors, the sleeve length required to reduce the contact resistance between the sleeve and the aluminum conductor has been long.

[0012] Also, for example, in the method of welding an aluminum conductor, the mechanical strength of the welded part may decrease or the working time related to welding may become long.

[0013] Also, for example, in the method of tightening a bolt inserted radially from the outer periphery of the sleeve toward the aluminum conductor, it has been difficult to sufficiently break the oxide film of the conductor strands with the flat surface at the tip of the bolt. For this reason, the electrical resistance of the conductor connection part tends to increase.

[0014] In order to solve these problems, the inventor has considered a method of forming an indent recessed in the radial direction of the sleeve. By forming such an indent, the crushing of the conductor can be increased, and the oxide film of the conductor strands can be broken. Thereby, the contact area between the sleeve and the conductor can be increased. As a result, the contact resistance between the sleeve and the conductor can be reduced, and the sleeve length can be suppressed. Also, by increasing the contact area between the sleeve and the conductor, the tensile strength can be increased.

[0015] Regarding the formation of an indentation, for example, if the power cable to be connected is a submarine cable, the indentation can be formed by compressing a sleeve using a large dedicated compressor having, for example, four compression cylinders on a laying ship. Hereinafter, the compression of the sleeve for forming an indentation is also referred to as "indentation compression".

[0016] When power cables applying aluminum conductors are widely used in the future, indentation compression of the sleeve will also be required in the connection structure of power cables laid in underground tunnels. In this case, it is desirable that the indentation compression can be performed using a small compressor (for example, a general-purpose 200t compressor) that has been conventionally used for compressing a sleeve with a hexagonal cross-section.

[0017] In such a small general-purpose compressor, it is common to compress the sleeve using a compression die (hereinafter, also simply referred to as a "die") that can be attached to the compressor. However, regarding indentation compression, for example, in the case of compressing a sleeve with a hexagonal cross-section, if a die having a compression surface with the same shape as the outer shape of the sleeve is used, there is a risk that the die and the sleeve will stick together due to the influence of indentation formation. The sticking of the die and the sleeve causes deterioration of workability when connecting the cables, and thus its occurrence should be avoided beforehand.

[0018] Therefore, as a result of earnestly studying the relationship between the sleeve and the die, the inventor has found a configuration that can surely perform cable connection and does not impair the connection workability.

[0019] The following disclosure is based on the above findings found by the inventor.

[0020] <Embodiments of the present disclosure> Next, the embodiments of the present disclosure will be listed and described.

[0021] [1] The manufacturing method of the cable connection structure according to one aspect of the present disclosure is The process includes a step of forming an indentation in the radial direction of the sleeve by compressing the conductor of the power cable from the outside of the sleeve using a die while the conductor is placed inside a cylindrical sleeve, In the process of forming the indentation, the die used has indentation pins with a protruding shape corresponding to the indentation, and has a shape that, when compressed, separates the portion other than the indentation pins from the outer surface of the sleeve. This configuration ensures secure cable connections by forming an indentation, and even when indentation compression is performed, the gap between the die and sleeve prevents them from sticking together, thus not compromising the ease of connection when making cable connections.

[0022] [2] In the method for manufacturing the cable connection structure described in [1] above, Prior to compression using the die, the process includes a step of positioning an eccentricity prevention jig to position the sleeve and the die. With this configuration, the eccentricity prevention jig can prevent misalignment of the die and indent pin relative to the sleeve.

[0023] [3] In the method for manufacturing the cable connection structure described in [2] above, The process of forming the indent is as follows: With the eccentricity prevention jig in place, the tip of the indent pin is brought into contact with the outer surface of the sleeve to perform a preliminary compression of the sleeve by the indent pin; After the initial compression, the process involves performing the main compression to form the indentation with the eccentricity prevention jig removed, Includes. With this configuration, preliminary compression is performed with the eccentricity prevention jig in place, and then the eccentricity prevention jig is removed before the main compression is performed. This ensures that the indentation is reliably formed while avoiding misalignment of the die and indent pin relative to the sleeve, and the eccentricity prevention jig does not interfere with indentation formation.

[0024] [4] In the method for manufacturing the cable connection structure described in [2] or [3] above, The die is provided with a jig support portion on the surface of the sleeve facing the outer surface of the sleeve, which constitutes the placement location of the eccentricity prevention jig. The jig support portion is formed in a shape that corresponds to multiple arrangement configurations of the eccentricity prevention jig. With this configuration, when forming indentations at different locations on the sleeve, the eccentricity prevention jig can be positioned in a manner appropriate to each location, ensuring that indentations are formed appropriately and reliably at each location.

[0025] [5] In the method for manufacturing the cable connection structure described in [2], [3] or [4] above, In the step of arranging the eccentricity prevention jig, the eccentricity prevention jig is arranged such that it is positioned at least on the downward side in the direction of gravity of the sleeve. With this configuration, positioning is performed using gravity and an eccentricity prevention jig, ensuring reliable positioning without complicating the configuration.

[0026] [6] In the method for manufacturing a cable connection structure described in any one of [1] to [5] above, The die has an elastic member attached to the indent pin, and the elastic member contacts the outer surface of the sleeve before the tip of the indent pin. With this configuration, the use of elastic members allows for stable positioning by the eccentricity prevention jig, and because elastic deformation is possible, the elastic members do not interfere with indentation formation.

[0027] [7] In the method for manufacturing a cable connection structure described in any one of [1] to [6] above, The process of forming the indent is repeated while moving the position where the indentation is formed. This configuration creates indentations at different points on the sleeve, which is very useful for ensuring secure cable connections without compromising the ease of cable connection work.

[0028] [8] A cable connection structure relating to another aspect of the present disclosure is: A pair of power cables, A cylindrical sleeve enclosing each conductor of the pair of power cables, The sleeve comprises an indentation formed on the outer surface of the sleeve so as to be recessed in the radial direction of the sleeve, An indented compression section and a non-compression section are arranged at different positions in the axial direction of the sleeve. The indentation compression portion includes the indentation formation area and has a cross-sectional shape in which the cylindrical outer shape of the sleeve is deformed into a non-circular shape. The non-compressible portion has a cross-sectional shape that maintains the cylindrical outer shape of the sleeve before the formation of the indentation. This configuration ensures reliable cable connection by incorporating indentations. Furthermore, the indentation compression section, including the indentation formation area, is allowed to deform into a non-circular shape in relation to the outer diameter of the sleeve. Moreover, by providing a non-compression section, deformation in the sleeve axial direction from the indentation compression section can be released, preventing interference between the deformations of the indentations themselves. As a result, even when performing indentation compression using a die, for example, it becomes easy to avoid compromising the workability when forming the indentations.

[0029] [Details of the embodiments of this disclosure] Next, an embodiment of the present disclosure will be described below with reference to the drawings. However, the present disclosure is not limited to these examples, and all modifications are intended to be included in the meaning and scope equivalent to the claims, as indicated by the claims.

[0030] <One Embodiment of the Present Disclosure> (1) Power cables and cable connection structures A brief description of the schematic configuration of a power cable and cable connection structure (cable connection part) according to one embodiment of this disclosure will be provided.

[0031] In this embodiment, a pair of power cables are connected by a cable connection structure. That is, the cable connection structure is located at the connection point of the pair of power cables.

[0032] In the following, "axial direction" of a power cable refers to the direction along the central axis of the power cable. "Radial direction" of a power cable refers to the direction from the central axis of the power cable toward the outer circumference. "Circumferential direction" of a power cable refers to the direction along the outer circumference of the power cable. The same terminology as for power cables can be used for components of cable connection structures (for example, sleeves, which will be described later).

[0033] [Power Cables] Power cables are formed, for example, as solid-insulated cables (CE cables or CV cables: Crosslinked polyethylene (PE) insulated PE or PVC sheathed cable, also called XLPE cables) which are high-voltage transmission cables.

[0034] Specifically, a power cable, for example, has a conductor surrounded by a cable internal semiconducting layer, cable insulation layer, cable external semiconducting layer, water absorption layer, cable metal shielding layer, etc., and further has a cable outer perimeter structure consisting of a corrosion protection layer, a base yarn layer, iron wire sheath (armor), yarn layer, etc. However, a power cable is not limited to this configuration, and any configuration in which the conductor is surrounded by a covering is acceptable, even if it is a configuration based on other known technologies.

[0035] The conductor is constructed, for example, by twisting multiple conducting strands together in a spiral. The conducting strands constituting the conductor include, for example, aluminum or an aluminum alloy and have an aluminum oxide film on their outer surface. However, the conductor is not limited to this configuration and may also be constructed according to other known technologies.

[0036] In power cables, the covering material for the conductor is stripped in stages from the tip of the conductor toward the opposite side (this is known as "step stripping"). As a result, power cables have a portion of the conductor exposed at the end edge. Hereafter, this exposed portion of the conductor may be referred to as the "exposed portion."

[0037] This configuration with exposed portions makes it possible to connect a pair of power cables to each other in this embodiment. In this case, the pair of power cables are arranged with their conductor axes aligned and their exposed portions facing each other. In the following, one of the pair of power cables may be referred to as the "first power cable," and the other as the "second power cable."

[0038] [Cable connection structure] The cable connection structure is configured to connect a pair of power cables. Specifically, the cable connection structure includes at least the pair of power cables described above, and a sleeve (conductor connection tube) arranged to surround the exposed portion of each power cable. Furthermore, the outer circumference of the sleeve includes, for example, a sleeve cover, an insulating tube (rubber connection tube, rubber unit, insulating unit), a protective tube (metal tube), and a filler material.

[0039] Regarding the cable connection structure, the configuration of the outer circumference of the sleeve may be based on publicly known technology, and a detailed explanation thereof is omitted here. Furthermore, such configuration is not limited to those described above, and may be based on other publicly known technologies.

[0040] (sleeve) A sleeve is provided to surround the connection point between conductors, for example, to connect the conductors of a pair of power cables. Here, a "connection point (connection part)" refers to the point (part, location) where a pair of conductors abut each other and their ends are close together.

[0041] Specifically, the sleeve is formed, for example, as a cylindrical metal tube having a hollow section. A pair of exposed conductors, including a connection point, are inserted into the hollow section of the sleeve, and the pair of conductors are connected. Examples of metals that make up the sleeve include aluminum and aluminum alloys.

[0042] The sleeve is formed, for example, as a through-tube with a hollow section passing through it. However, it is not limited to a through-tube; for example, it may have a partition wall in the axial center of the sleeve that closes the hollow section. This prevents water from propagating through the conductor.

[0043] In this embodiment, the sleeve has, for example, a plurality of indentations. The indentations are formed to be recessed in the radial direction of the sleeve. That is, the indentations locally compress the conductor in the radial direction of the sleeve.

[0044] By forming such indentations, the conductor can be compressed more significantly, and the oxide film on the conductor strands can be broken. This increases the contact area between the sleeve and the conductor. As a result, the contact resistance between the sleeve and the conductor can be reduced. Furthermore, increasing the contact area between the sleeve and the conductor can increase the tensile strength.

[0045] In other words, the cable connection structure of this embodiment ensures a secure connection between a pair of power cables through the sleeve and indentation described above.

[0046] Further details regarding sleeves and indentations will be explained later.

[0047] (2) Method for manufacturing cable connection structure Next, the method for manufacturing the cable connection structure according to this embodiment, that is, the method for connecting the conductors of a pair of power cables in this embodiment, will be described with reference to Figures 1 to 8.

[0048] As shown in Figure 1, the manufacturing method of the cable connection structure of this embodiment comprises, broadly speaking, a preparation step (step 10, hereafter steps will be abbreviated as "S"), a conductor connection step (S20), and a covering step (S30).

[0049] (S10: Preparation process) First, as a preparation step (S10), at least a pair of power cables and a sleeve, which will constitute the cable connection structure described above, are prepared. Furthermore, covering members such as sleeves, sleeve covers, and insulating tubes are also prepared.

[0050] Then, for each pair of power cables, stripping is performed in steps on one end to create an exposed section where the conductor is exposed.

[0051] Furthermore, in the preparation step (S10), the die to be used in the conductor connection step (S20) and the compressor to be used in the conductor connection step (S20) are prepared. Details of the die to be prepared will be described later. As for the compressor, any compressor that performs the compression process using the die will suffice, for example, a general-purpose compressor such as a 200t compressor is prepared.

[0052] (S20: Conductor connection process) After the preparation process (S10) is completed, at the power cable laying site, the conductor connection process (S20) is performed using a sleeve to connect the conductors of a pair of power cables. To do this, first, the pair of power cables are butted together inside the sleeve with the axes of their conductors aligned. In other words, the conductors of each power cable are placed inside the cylindrical sleeve. Then, with the sleeve enclosing the conductors of each power cable, compression is performed from the outside of the sleeve using a die to form an indentation that is recessed in the radial direction of the sleeve, thereby connecting the conductors of the pair of power cables using the sleeve.

[0053] In this embodiment, the die used has the following configuration.

[0054] (Dice composition) As shown in Figure 2, the die 1 comprises a pair of halved die pieces 11a and 11b, each of which is formed to compress the sleeve 3 containing the conductor 2 from two opposing directions.

[0055] To perform this type of compression, each die piece 11a, 11b has its outer surface formed in a shape (for example, semicircular) that allows it to be mounted on a compressor.

[0056] Furthermore, each die piece 11a, 11b has indent pins 12a, 12b with a projection shape corresponding to the indent. Here, the projection shape corresponding to the indent specifically refers to a convex shape that has a male-female relationship with the concave indent. Each indent pin 12a, 12b in each die piece 11a, 11b has a curved tip shape and is arranged so that it faces each other when compressed against the sleeve 3 (i.e., their respective tips face each other). The indent pins 12a, 12b may be straight from the curved tip towards the die pieces 11a, 11b, or they may have a so-called draft angle (slope). The slope is preferably about 1 to 5 degrees.

[0057] An elastic member may be attached to at least one of the indent pins 12a and 12b. As the elastic member, for example, a compression coil spring 13 is used, wound around the indent pin 12b so as to protrude from the tip of one of the indent pins 12b. However, it is not necessarily required to be a compression coil spring 13; other elastic members that perform a similar function (details will be described later) may be used.

[0058] Incidentally, the die used to compress sleeve 3 is generally such that the shape of the inner surface of each die piece corresponds to the shape of the outer surface of sleeve 3 after compression (i.e., the outer surface of the cylinder) (i.e., the shapes are in a male-female relationship).

[0059] In contrast, in this embodiment, the inner circumferential surfaces of each die piece 11a, 11b (i.e., the surfaces facing the outer surface of the sleeve 3) have a shape that, apart from the indent pins 12a, 12b, separates from the outer circumferential surface of the sleeve 3 when the sleeve 3 is compressed. Specifically, the shape of the inner circumferential surface of each die piece 11a, 11b is formed to include a pin arrangement portion 14, a projection portion 15, and a jig support portion 16.

[0060] The pin arrangement section 14 is where the indent pins 12a and 12b are positioned. The compression coil spring 13, which is an elastic member, is also positioned in the pin arrangement section 14.

[0061] The projection 15 is located between the pin arrangement portion 14 and the jig support portion 16, and is shaped to protrude closer to the sleeve 3 than the pin arrangement portion 14 and the jig support portion 16. In other words, the protruding top of the projection 15 is the part of the inner circumferential surface of the die pieces 11a and 11b that is closest to the sleeve 3. The protruding top of the projection 15 is, for example, made of a curved surface concentric with the sleeve 3, but because there is a gap between the sleeves 3, it is a curved surface with a larger diameter than the outer circumferential surface of the sleeves 3. Specifically, when the sleeves 3 are compressed, the protruding top of the projection 15 is configured such that the curved surface has an inner diameter of approximately +3 to 10%, more preferably +6 to 8%, compared to the outer diameter of the outer circumferential surface of the sleeves 3. Therefore, the inner diameter of each die piece 11a, 11b when the sleeve is compressed is approximately +3 to 10%, more preferably +6 to 8%, of the outer diameter of the outer surface of the sleeve 3.

[0062] The jig support portion 16 is the part where the eccentricity prevention jig 4, described later, is placed, and has a shape that includes a corner portion 17 corresponding to one side of the eccentricity prevention jig 4. The corner portion 17 is formed on both sides of the pin placement portion 14 on each die piece 11a, 11b. Then, for example, the placement location of one eccentricity prevention jig 4 is formed by the combination of the corner portions 17 on both sides of the pin placement portion 14. In that case, when the eccentricity prevention jig 4 is placed in the placement location, each die piece 11a, 11b will be supported in a manner along the divided surface. Hereinafter, this manner may also be called the "horizontal orientation" or the "0° orientation". However, the placement location of the eccentricity prevention jig 4 is not limited to this configuration, and may also be formed by a combination of the corner portion 17 on one die piece 11a and the corner portion 17 on the other die piece 11b. In that case... When the eccentricity prevention jig 4 is placed in its designated location, it is supported in such a manner that each die piece 11a, 11b straddles the divided surface. Hereafter, this configuration may also be referred to as the "vertical configuration" or the "90° directional configuration." In other words, the jig support portion 16 is formed in a shape that corresponds to multiple configurations of the eccentricity prevention jig 4. More specifically, by appropriately combining each corner portion 17 to form a location, it is possible to accommodate multiple configurations of the eccentricity prevention jig 4.

[0063] (Configuration of the eccentricity prevention jig) The eccentricity prevention jig 4, supported by such a jig support portion 16, is used to position the sleeve 3 and the die 1 when compressing the sleeve 3 using the die 1.

[0064] To this end, in this embodiment, the eccentricity prevention jig 4 is formed from, for example, a metal or resin member having a rectangular parallelepiped shape, as shown in Figures 3A and 3B. One face of the rectangular parallelepiped has a pair of corners 41 that are supported by the corners 17 of the jig support portion 16 that constitute the placement location of the eccentricity prevention jig 4. The face opposite to this face is provided with a recessed portion 42 having a curved shape corresponding to the cylindrical outer surface of the sleeve 3. By having such a cross-sectional shape, the eccentricity prevention jig 4 can position the sleeve 3 and the die 1.

[0065] Furthermore, the eccentricity prevention jig 4 has a notch 43 to accommodate the indent pins 12a and 12b in the die 1. The presence of the notch 43 allows the eccentricity prevention jig 4 to be placed in the location formed by the jig support 16 of the die 1, even when the die 1 has indent pins 12a and 12b, and also allows it to be removed from that location.

[0066] (Details of the conductor connection process) In this embodiment, as shown in Figure 1, in the conductor connection process (S20), the conductors 2 of a pair of power cables are connected to each other by sequentially going through the die and jig placement process (S21), the preliminary compression process (S22), the jig removal process (S23), and the final compression process (S24), using the die 1 and eccentricity prevention jig 4 described above.

[0067] (S21: Die and jig placement process) First, as shown in Figure 2, the die 1 is positioned on the sleeve 3, which encloses the conductor 2, so that the sleeve 3 is sandwiched between the pair of die pieces 11a and 11b. Furthermore, prior to compressing the sleeve 3 using the die 1, an eccentricity prevention jig 4 is placed between the sleeve 3 and the die 1.

[0068] The eccentricity prevention jig 4 is positioned by supporting its corner portion 41 on the corner portion 17 that constitutes the jig support portion 16 of the die 1. By positioning the eccentricity prevention jig 4 on the jig support portion 16 of the die 1, the sleeve 3 can be supported on its outer circumferential surface by the recess portion 42 of the eccentricity prevention jig 4. Therefore, even if the inner circumferential surface of the die 1 has a gap separating it from the outer circumferential surface of the sleeve 3, the eccentricity prevention jig 4 positions the sleeve 3 and the die 1, thereby preventing misalignment of the indentation pins 12a and 12b relative to the sleeve 3 (i.e., misalignment of the indentation formation position).

[0069] The die 1 and the eccentricity prevention jig 4 are arranged such that, for example, the die pieces 11a and 11b of the die 1 sandwich the sleeve 3 from above and below. In other words, the indent pins 12a and 12b face each other along the vertical direction. In this case, the eccentricity prevention jig 4 is positioned horizontally (0° direction configuration) utilizing the corner 17 of the die piece 11b located on the lower side. Therefore, the eccentricity prevention jig 4 is positioned at least below the sleeve 3 in the direction of gravity, so the action of gravity can be used to position the sleeve 3 and the die 1.

[0070] Furthermore, the die 1 and the eccentricity prevention jig 4 are arranged such that, as shown in Figure 4, the indentation pins 12a and 12b of the die 1 are positioned in the axial direction of the sleeve 3 at the indentation formation position relative to the sleeve 3. In this case, if the eccentricity prevention jig 4 is formed with an axial dimension smaller than the axial dimension of the sleeve 3 and larger than the axial dimension of the die 1, the stability when positioning the sleeve 3 and die 1 using the eccentricity prevention jig 4 can be improved.

[0071] When arranging the die 1 and the eccentricity prevention jig 4, if a compression coil spring 13 is attached to at least the indent pin 12b located on the downward side in the direction of gravity, the compression coil spring 13 will be able to contact the outer surface of the sleeve 3 before the tip of the indent pin 12b. In other words, the sleeve 3 will also be supported by the compression coil spring 13. Therefore, if a compression coil spring 13 is attached, the stability when positioning the sleeve 3 and the die 1 can be further enhanced by using the compression coil spring 13 in combination with the eccentricity prevention jig 4.

[0072] (S22: Pre-compression process) After positioning the die 1 and the eccentricity prevention jig 4, the next step is to bring the tips of the indent pins 12a and 12b into contact with the outer circumferential surface of the sleeve 3 while the eccentricity prevention jig 4 is still in place, thereby performing a preliminary compression of the sleeve 3 by the indent pins 12a and 12b. Specifically, the die pieces 11a and 11b that sandwich the sleeve 3 are moved closer together by the compressor until the tips of the indent pins 12a and 12b contact the outer circumferential surface of the sleeve 3, thereby creating a state in which the sleeve 3 can be held by the indent pins 12a and 12b (a state of preliminary compression).

[0073] At this time, since the eccentricity prevention jig 4 remains in place, even if there is a gap between the inner surface of the die 1 and the outer surface of the sleeve 3, no misalignment of the indent pins 12a and 12b relative to the sleeve 3 will occur.

[0074] Furthermore, even if a compression coil spring 13 is attached to the indent pin 12b, the presence of the compression coil spring 13 does not hinder the pre-compression process because the compression coil spring 13 undergoes elastic deformation.

[0075] (S23: Jig removal process) After performing preliminary compression on the sleeve 3 with the indent pins 12a and 12b, the eccentricity prevention jig 4, which is in its positioned state, is removed from between the sleeve 3 and the die 1. The eccentricity prevention jig 4 can be removed by using the notch 43 of the eccentricity prevention jig 4 and pulling the eccentricity prevention jig 4 out in the direction that the indent pin 12b passes through the open end of the notch 43.

[0076] Even after removing the eccentricity prevention jig 4 in this manner, as shown in Figure 5, the temporary compression by the indent pins 12a and 12b remains, so no misalignment of the indent pins 12a and 12b relative to the sleeve 3 occurs.

[0077] (S24: Main compression process) After removing the eccentricity prevention jig 4, the main compression to form the indent is performed while maintaining the state in which the eccentricity prevention jig 4 is removed. This main compression to form the indent is sometimes called "indent compression." Specifically, as shown in Figure 6, from a state of preliminary compression in which the tips of the indent pins 12a and 12b abut against the outer surface of the sleeve 3, the die pieces 11a and 11b are further moved by the compressor in a direction that brings them closer together, causing the indent pins 12a and 12b to bite into the sleeve 3 in the direction of its axis, thereby forming a radially recessed indentation in the sleeve 3. The indentations are formed by the indent pins 12a and 12b at opposite positions on either side of the axis of the sleeve 3.

[0078] Even under this compressed state, the minimum inner diameter of the inner surface of the die 1 is larger than the outer diameter of the outer surface of the sleeve 3, and the die 1 has a shape that creates a gap between it and the outer surface of the sleeve 3 (see, for example, symbol S in Figure 6). Therefore, interference between the inner surface of the die 1 and the outer surface of the sleeve 3 does not occur at locations other than the indent pins 12a and 12b.

[0079] After the indentation is formed, the compression by die 1 is released, and die 1 is detached from the outer circumference of sleeve 3. At this time, even if the outer shape of sleeve 3 is deformed due to the formation of the indentation, the inner surface of die 1 has a gap separating it from the outer surface of sleeve 3, and this gap acts as a release, preventing die 1 and sleeve 3 from becoming stuck together. Therefore, die 1 can be detached from sleeve 3 smoothly, and any deterioration in workability that would result from this can be avoided.

[0080] (S25: Repeated check) After that, it is determined whether all the indentations to be formed on sleeve 3 have been completed. If they are not completed, the relative position of die 1 with respect to sleeve 3 is moved, and the above-described steps (S21 to S24) are repeated.

[0081] Specifically, first, the relative position of the sleeve 3 and the die 1 is moved to position the die 1 in a different location from the previously indented position. The relative position can be moved, for example, only in the axial direction of the sleeve 3, only in the circumferential direction of the sleeve 3, or both in the axial and circumferential directions of the sleeve 3.

[0082] If the relative position of the sleeve 3 is to be moved in the axial direction, the die 1 is positioned at a predetermined distance in the axial direction from the position where the indentation has already been formed. The predetermined distance is, for example, at least the diameter size of the indentation pins 12a and 12b (radius size × 2) plus the axial size of the uncompressed portion 33 of the cable connection structure, which will be described in detail later. In this way, in the axial direction of the sleeve 3, there is a formation region of the uncompressed portion 33 between adjacent indentations.

[0083] Furthermore, if the relative position of the sleeve 3 is to be moved in the circumferential direction, the die 1 is positioned at a position rotated in the circumferential direction from the position where the indentation has already been formed. This rotation results in a different arrangement of the die 1 relative to the sleeve 3 from the aforementioned arrangement where the die pieces 11a and 11b sandwich the sleeve 3 from above and below.

[0084] Another arrangement configuration is, for example, as shown in Figure 7, in which the die pieces 11a and 11b of the die 1 sandwich the sleeve 3 from the left and right directions. In other words, the indent pins 12a and 12b face each other along the horizontal direction. In this case, the eccentricity prevention jig 4 is positioned vertically (90° direction configuration) using the respective corners 17 of each die piece 11a and 11b. Therefore, even when the die pieces 11a and 11b are arranged in a configuration where the indent pins 12a and 12b face each other horizontally, the eccentricity prevention jig 4 can be positioned on the lower side of the sleeve 3 in the direction of gravity, and the action of gravity can be used to position the sleeve 3 and the die 1.

[0085] Even in this arrangement, after the die 1 and the eccentricity prevention jig 4 are placed (S21), temporary compression is performed using the indent pins 12a and 12b (S22), and then the eccentricity prevention jig 4 is removed (S23), and the main compression is performed on the sleeve 3 (S24) to form the indent.

[0086] Furthermore, as another arrangement, for example, as shown in Figure 8, the die pieces 11a and 11b of the die 1 sandwich the sleeve 3 so that the indent pins 12a and 12b face each other along directions that are inclined at approximately 45° from the vertical and horizontal directions. In this arrangement as well, the process of forming the indents through each step (S21 to S24) is the same as in the arrangement described above.

[0087] In the case of such an inclined arrangement, it is preferable that the eccentricity prevention jig 4 has a recessed portion 42 configured as follows. When the eccentricity prevention jig 4 is positioned between the sleeve 3 and the die 1, the edge of the recessed portion 42 is positioned outside the axis of the sleeve 3 in terms of horizontal positional relationship (see symbol L in Figure 8). In other words, the eccentricity prevention jig 4 has a horizontal positional relationship such that the axis of the sleeve 3 is contained within the recessed portion 42. With this configuration, even when the die pieces 11a and 11b are arranged in an inclined manner, the direction in which the center of gravity of the sleeve 3 and the conductor 2 acts will not fall outside the range of the recessed portion 42 of the eccentricity prevention jig 4. Therefore, the eccentricity prevention jig 4 can appropriately position the sleeve 3 and the die 1 while utilizing the action of gravity.

[0088] As described above, in this embodiment, the conductor connection step (S20) is performed by sequentially going through the die and jig placement step (S21), the preliminary compression step (S22), the jig removal step (S23), and the final compression step (S24) to form the indentations. Then, each of the above steps (S21 to S25) is repeated while moving the indentation formation position in at least one direction, either axial or circumferential, of the sleeve 3 until all the indentations to be formed are completed.

[0089] (S30: Coating process) After the conductor connection process (S20) is completed, the outer circumference of the sleeve 3 after indentation is covered with, for example, a sleeve cover, insulating tube, protective tube, filler, etc.

[0090] The coating of the outer circumference of sleeve 3 can be done using publicly known techniques, and a detailed explanation of this will be omitted here.

[0091] The cable connection structure of this embodiment is manufactured as described above.

[0092] (3) Details of sleeves and indentations in cable connection structures Next, the cable connection structure obtained by the manufacturing method described above will be explained with reference to Figure 9, paying particular attention to the sleeve and indentation in the cable connection structure. Note that in Figure 9, other components of the cable connection structure other than the sleeve 3 and indentation 5 are not shown.

[0093] As shown in Figure 9, in this embodiment, the sleeve 3 in the cable connection structure has a first region 31a that encloses a first power cable (not shown) and a second region 31b that encloses a second power cable (not shown), along the axial direction of the sleeve 3. Multiple indentations 5 are formed in each of the first region 31a and the second region 31b, thereby connecting the first power cable and the second power cable with the axes of their conductors aligned.

[0094] For sleeve 3, for example, a cylindrical shape with an outer diameter of φ62 mm and an axial length of 200 mm is used. However, it is not limited to this, and other sizes may also be used. In any case, the outer shape of sleeve 3 before the formation of indentation 5 is, for example, approximately circular. Multiple indentations 5 are formed on such sleeve 3 by following the cable connection method described above.

[0095] The indentations 5 are formed in pairs on the same circumference of the sleeve 3, facing each other with the axis of the sleeve 3 in between. Each of the multiple indentations 5 is formed, for example, with a diameter of φ15 mm, a depth of 15 mm from the outer surface of the sleeve 3, and a pitch of 20 mm between adjacent indentations in the axial direction. However, it is not limited to this, and other sizes are also possible. The illustrated example shows a case where two pairs of indentations 5 are formed on the same circumference, but it is not necessarily limited to this, and it is sufficient to have at least one pair of indentations 5 formed on the same circumference.

[0096] Furthermore, the indents 5 are formed such that if the indentation formation locations on the same circumference of the sleeve 3 are considered as one "row," then multiple rows are arranged at different positions in the axial direction of the sleeve 3. In the example shown, four rows of indentation formation locations are shown in each of the first region 31a and the second region 31b, but this is not necessarily the only option, and the number of indentation rows can be appropriately set according to the axial length of the sleeve 3, etc.

[0097] Furthermore, the indents 5 may be formed such that their positions differ from each other in adjacent columns along the axial direction of the sleeve 3. The example shown illustrates a configuration where two pairs of indents 5 are formed in a given column at 0°, 90°, 180°, and 270°, and two pairs of indents 5 are formed in the adjacent column at positions shifted by 45°. However, the configuration is not necessarily limited to this example; the indent positions in each column may be shifted in different angular directions, or the indent positions in each column may be aligned in the same angular direction.

[0098] In all configurations, the indents 5 in adjacent columns along the axial direction of sleeve 3 are formed in a positional relationship where they are separated from each other. In other words, there is a region between adjacent columns where no indent 5 is formed.

[0099] With the above configuration, after the formation of the indentation 5, indentation compression areas 32, which include the area where the indentation 5 is formed, and uncompressed areas 33, which are areas where the indentation 5 is not formed, are arranged at different axial positions on the outer circumferential surface of the sleeve 3. Specifically, multiple indentation compression areas 32 (for example, four each in the first area 31a and the second area 31b) and multiple uncompressed areas 33 (for example, three between each indentation compression area 32) are arranged alternately along the axial direction of the sleeve 3.

[0100] The indentation compression section 32 is the region that includes the area where the indentation 5 is formed, and has a cross-sectional shape in which the cylindrical outer shape (i.e., the shape of the outer surface) of the sleeve 3 is deformed into a non-circular shape. Specifically, the indentation compression section 32 is deformed in such a way that the area where the indentation 5 is formed is crushed due to the effect of die compression, and as a result the cross-sectional shape, which was approximately circular before indentation formation, becomes non-circular. However, the non-circular shape after deformation does not match the shape of the inner surface of the die 1, and is different from the shape of the inner surface, because there is a gap between the inner surface of the die 1 and the outer surface of the sleeve 3.

[0101] On the other hand, the uncompressed portion 33 located between the indented compression portions 32 is a region where the indentation 5 has not been formed, and has a cross-sectional shape that maintains the cylindrical outer shape (i.e., the shape of the outer circumferential surface) of the sleeve 3 before the indentation was formed. Therefore, since the cross-sectional shape maintains the outer circumferential surface of the sleeve, the uncompressed portion 33 has, for example, a substantially circular cross-sectional shape.

[0102] In other words, in the cable connection structure of this embodiment, indented compression sections 32 and uncompressed sections 33 are arranged alternately along the axial direction of the sleeve 3.

[0103] Furthermore, the indented compression section 32 has a non-circularly deformed cross-sectional shape. This deformation of the cross-sectional shape of the indented compression section 32 can occur because a gap exists between the inner circumferential surface of the die 1 and the outer circumferential surface of the sleeve 3, and this gap acts as a relief. In other words, the presence of a gap in the die 1 allows for deformation of the cross-sectional shape of the indented compression section 32 (particularly deformation of the sleeve 3 in the radial direction).

[0104] Furthermore, since the indentation compression section 32 is adjacent to the non-compression section 33, the non-compression section 33 acts as a buffer against axial deformation of the sleeve 3 in the indentation compression section 32, preventing interference between the deformations of the indentations 5 in adjacent indentation compression sections 32. Leaving the region as a non-compression section 33 means not making the formation pitch of the indentations 5 in each row more compact than necessary. In other words, this is based on a technical concept that is clearly different from the general technical concept of making the formation pitch compact.

[0105] Considering the above, the cable connection structure of this embodiment, in which the indented compression section 32 and the uncompressed section 33 are arranged alternately, can be said to be unique to the cable connection method obtained by following the procedure of the cable connection method of this embodiment.

[0106] (4) Summary of this embodiment According to this embodiment, one or more of the following effects are achieved.

[0107] (a) In this embodiment, the die 1 used in the conductor connection process (S20) has indent pins 12a and 12b, and when indent compression is performed, it has a shape in which the parts other than the indent pins 12a and 12b are separated from the outer surface of the sleeve 3. Therefore, according to this embodiment, the cable connection between the first power cable and the second power cable can be reliably achieved by forming the indentation 5 by indentation compression. Moreover, even when indentation compression is performed, the die 1 and the sleeve 3 do not become stuck together due to the gap between them, and the ease of connection during cable connection is not impaired. In other words, according to this embodiment, cable connections can be made reliably without compromising the ease of connection work.

[0108] (b) In this embodiment, prior to indentation compression using die 1, in die / jig arrangement step (S21), an eccentricity prevention jig 4 supported by die 1 is arranged to position the sleeve 3 and die 1. Therefore, according to this embodiment, even if the inner circumferential surface of the die 1 has a gap separating it from the outer circumferential surface of the sleeve 3, the eccentricity prevention jig 4 positions the sleeve 3 and the die 1, thus preventing misalignment of the indentation pins 12a and 12b relative to the sleeve 3 (i.e., misalignment of the indentation formation position). In other words, according to this embodiment, it is possible to avoid compromising the ease of connection work when connecting cables, and even in that case, cable connections can be reliably made by preventing misalignment of the indentation formation position.

[0109] (c) In this embodiment, in the preliminary compression step (S22), preliminary compression is performed using the indent pins 12a and 12b with the eccentricity prevention jig 4 in place, and then in the main compression step (S24), main compression (i.e., indentation compression) is performed using the indent pins 12a and 12b with the eccentricity prevention jig 4 removed. Therefore, according to this embodiment, since the positioning state by the eccentricity prevention jig 4 is maintained by pre-compression, the indentation 5 can be reliably formed during the main compression while avoiding misalignment of the die 1 and indentation pins 12a, 12b relative to the sleeve 3. Moreover, since the eccentricity prevention jig 4 is removed before the main compression, the eccentricity prevention jig 4 does not interfere with indentation formation.

[0110] (d) In this embodiment, the jig support portion 16 provided on the die 1 is formed in a shape that corresponds to multiple arrangement configurations of the eccentricity prevention jig 4. Therefore, according to this embodiment, when forming indentations 5 at different locations in the circumferential direction of the sleeve 3, the eccentricity prevention jig 4 can be positioned in a manner appropriate to each location, such as selecting either a horizontal orientation (0° direction orientation) or a vertical orientation (90° direction orientation), and the indentations 5 can be formed appropriately and reliably at any location.

[0111] (e) In this embodiment, the eccentricity prevention jig 4 is positioned such that it is located at least on the downward side in the direction of gravity of the sleeve 3. Therefore, according to this embodiment, the positioning of the sleeve 3 and die 1 by the eccentricity prevention jig 4 can be performed by utilizing the action of gravity, thus ensuring reliable positioning. Moreover, by utilizing the action of gravity, the configuration does not become complicated for positioning purposes.

[0112] (f) In this embodiment, at least an elastic compression coil spring 13 is attached to the indent pin 12b, so that the sleeve 3 can also be supported by the compression coil spring 13. Therefore, according to this embodiment, the stability when positioning the sleeve 3 and die 1 can be further enhanced by using the indentation pin 12b and the compression coil spring 13 together. Moreover, since the compression coil spring 13 is elastically deformable, it does not interfere with indentation formation.

[0113] (g) In this embodiment, in the conductor connection step (S20), the die and jig placement step (S21), the preliminary compression step (S22), the jig removal step (S23), and the final compression step (S24) are repeated while moving the indentation formation position in at least one direction in the axial or circumferential direction of the sleeve 3 until all of the indentations 5 to be formed have been formed. Therefore, according to this embodiment, indentations 5 are formed at different locations on the outer surface of the sleeve 3, which is very useful for ensuring reliable cable connections. Moreover, this does not impair the ease of cable connection work.

[0114] (h) In this embodiment, the cable connection structure after the formation of the indentation 5 includes an indentation compression portion 32 along the axial direction of the sleeve 3, which includes the location where the indentation 5 is formed and has a non-circularly deformed cross-sectional shape, and a non-compression portion 33 which maintains the cylindrical outer shape of the sleeve 3 before the indentation is formed. A cable connection structure with such a configuration can be said to be unique to the cable connection method obtained by following the procedure of the cable connection method of this embodiment. Therefore, according to the cable connection structure of this embodiment, reliable cable connection can be achieved by providing the indentation 5. Furthermore, the indentation compression section 32, which includes the location where the indentation 5 is formed, is allowed to deform into a non-circular shape. Moreover, by providing the non-compression section 33, axial deformation from the indentation compression section 32 can be released, and the deformation of the indentations 5 does not interfere with each other. As a result, even when performing indentation compression using a die 1, for example, it becomes easy to avoid a loss of workability when forming the indentation 5. In other words, the cable connection structure of this embodiment ensures reliable cable connection without compromising the ease of connection.

[0115] <Other embodiments of this disclosure> Although one embodiment of the present disclosure has been described in detail above, the present disclosure is not limited to the above-described embodiment and can be modified in various ways without departing from its essence.

[0116] The above embodiment illustrates a case where the power cable is configured as a solid-insulated cable, but it is not limited to this and can be applied to other configurations as well. The power cable may be configured as an underwater cable, a land cable, or an underground cable.

[0117] In the embodiments described above, the case in which the conductor strands contain aluminum or an aluminum alloy and have an aluminum oxide film on their outer circumference was explained. However, the conductor may be configured as a so-called strand-insulated conductor. That is, the conductor strands may contain, for example, copper or a copper alloy and have an insulating coating on their outer circumference.

[0118] The embodiments described above describe a case where the conductor strands in both power cables have an oxide coating or insulating coating on their outer circumference, but the disclosure is not limited to this case. It is sufficient that the conductor strands in at least one of the pair of power cables have an oxide coating or insulating coating on their outer circumference.

[0119] In the embodiments described above, the case in which the sizes (hole diameter, recess depth) of the multiple indentations 5 are equal to each other was explained, but this disclosure is not limited to this case. The sizes of the multiple indentations 5 may be different to each other.

[0120] In the embodiments described above, a case was described in which, regarding the arrangement of multiple indentations 5, one column has indentations 5 formed in the 0°, 90°, 180°, and 270° directions, and the adjacent column has indentations 5 formed at a position shifted by 45°. However, this disclosure is not limited to this case. The arrangement of multiple indentations 5 may be different from the embodiments described above, as long as it is predetermined.

[0121] Although the application of a compound was not mentioned in the embodiments described above, a compound may be applied in this disclosure. For example, if the conductor 2 and sleeve 3 include aluminum or an aluminum alloy, a compound containing minerals may be provided between the inner surface of the sleeve 3 and the outer surface of the conductor 2. This prevents oxygen from entering the sleeve 3 and prevents the reformation of the aluminum oxide film. As a result, electrical resistance can be stably reduced. [Explanation of symbols]

[0122] 1 die 2 conductors 3 sleeves 4. Eccentricity prevention jig 5 indents 11a Dice piece 11b Dice Pieces 12a Indentation pin 12b Indentation pin 13 Compression coil spring 14 Pin configuration section 15 Protrusion 16 Jig support part 17 Corner 31a 1st area 31b 2nd area 32 Indentation Compression Section 33 Uncompressed section 41 Corner 42 Recessed area 43 Notch

Claims

1. The process includes a step of forming an indentation in the radial direction of the sleeve by compressing the conductor of the power cable from the outside of the sleeve using a die while the conductor is placed inside a cylindrical sleeve, In the process of forming the indent, the die used has indentation pins with a protruding shape corresponding to the indent, and has a shape that, when compressed, separates the parts other than the indentation pins from the outer surface of the sleeve. A method for manufacturing a cable connection structure.

2. Prior to compression using the die, the procedure includes a step of positioning an eccentricity prevention jig to position the sleeve and the die. A method for manufacturing the cable connection structure according to claim 1.

3. The process of forming the indent is as follows: With the eccentricity prevention jig in place, the tip of the indent pin is brought into contact with the outer surface of the sleeve to perform a preliminary compression of the sleeve by the indent pin; After the initial compression, the process involves performing the main compression to form the indentation with the eccentricity prevention jig removed, A method for manufacturing a cable connection structure according to claim 2, including the method described above.

4. The die is provided with a jig support portion on the surface of the sleeve facing the outer surface of the sleeve, which constitutes the placement location of the eccentricity prevention jig. The jig support portion is formed in a shape that corresponds to multiple arrangement configurations of the eccentricity prevention jig. A method for manufacturing a cable connection structure according to claim 2 or 3.

5. In the step of arranging the eccentricity prevention jig, the eccentricity prevention jig is arranged such that it is located at least on the downward side of the sleeve in the direction of gravity. A method for manufacturing a cable connection structure according to claim 4.

6. The die has an elastic member attached to the indent pin, and the elastic member contacts the outer surface of the sleeve before the tip of the indent pin. A method for manufacturing the cable connection structure according to claim 3.

7. The process of forming the indent is repeated while moving the position where the indent is formed. A method for manufacturing the cable connection structure according to claim 1.

8. A pair of power cables, A cylindrical sleeve enclosing each conductor of the pair of power cables, The sleeve comprises an indentation formed on the outer surface of the sleeve so as to be recessed in the radial direction of the sleeve, An indented compression section and a non-compression section are arranged at different positions in the axial direction of the sleeve. The indentation compression portion includes the indentation formation area and has a cross-sectional shape in which the cylindrical outer shape of the sleeve is deformed into a non-circular shape. The non-compressible portion has a cross-sectional shape that maintains the cylindrical outer shape of the sleeve before the indentation is formed. Cable connection structure.

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