JP2024099955A - Power Cable Terminations - Google Patents

Abstract

[Problem] To provide a power cable terminal connection part capable of suppressing the formation of a gap between the inner surface of a fitting hole into which a bushing with a conductive wire inserted therethrough is fitted and the outer peripheral surface of the bushing while improving watertightness. [Solution] A power cable terminal connection part 1 in which a terminal end of a power cable 11 is electrically connected to a conductor wire 12 to be connected includes a bushing 2 into which the conductor wire 12 is inserted, and a holding member 4 integrally having a power cable holding part 4A that holds the terminal end of the power cable 11 and a bushing holding part 4B that holds the bushing 2. The bushing holding part 4B is cylindrical with a fitting hole 400 into which the bushing 2 is fitted, the fitting hole having an opening at an end face 40a, and an inner surface 400a of the fitting hole including an inner peripheral surface 400b of an opening end 401 of the bushing holding part 4B elastically contacts the bushing 2, and the opening end 401 of the bushing holding part 4A is highly elastic. [Selected Figure] Figure 3

Description

The present invention relates to a power cable termination connection part used, for example, in railway vehicles.

Conventionally, as described in Patent Document 1, for example, railway vehicles are supplied with high voltage power of 25 kV or 20 kV from a pantograph, and this high voltage power is sent to a main transformer via a circuit breaker, where the voltage is reduced to a specified voltage value, and then the main converter converts the frequency and outputs the power to the main motor. The circuit breaker and the main transformer are connected by a power cable. The applicant has proposed the terminal connection part of this power cable described in Patent Document 2.

In the power cable termination connection section described in Patent Document 2, the central conductor of the power cable is connected to the equipment side conductor inside the cable holder via a compression terminal. The equipment side conductor is inserted into a tapered bushing. The cable holder has an insulator made of a polymer material and a semi-conductor made of a polymer material that has been made conductive by a conductive agent. The semi-conductor has the function of reducing the concentration of an electric field.

The cable holder is integrally formed into a T-shape with a holding tube portion that holds the end of the power cable and a connecting tube portion that extends perpendicular to the holding tube portion and holds the bushing. The connecting tube portion has a fitting hole that opens into the end face of the connecting tube portion and into which the bushing fits. The connecting tube portion has elasticity that causes it to expand in diameter when the bushing fits into it, and the inner surface of the fitting hole fits tightly against the outer circumferential surface of the bushing.

JP 2014-19208 A Patent No. 7040662

It is desirable that the power cable termination connection part configured as described above ensures high watertightness so that moisture does not penetrate into the inside of the cable holder through the small gap between the outer circumferential surface of the bushing and the inner surface of the fitting hole. In order to improve watertightness, it is possible to increase the tightening margin, especially at the open end of the fitting hole, but if this tightening margin is made too large, a gap will be created between the outer circumferential surface of the bushing and the inner surface of the fitting hole in parts other than the open end, and there is a risk of discharge occurring in this gap. Such discharge can cause damage to the cable holder and the bushing.

The present invention aims to provide a power cable termination connection part that can prevent a gap from being formed between the inner surface of the fitting hole into which the bushing fits and the outer peripheral surface of the bushing while improving watertightness.

The present invention aims to solve the above problems and provides a power cable termination connection part in which a termination of a power cable is electrically connected to a conductor wire to be connected, the power cable termination connection part comprising a bushing through which the conductor wire is inserted, and a holding member integrally having a power cable holding part that holds the termination of the power cable and a bushing holding part that holds the bushing, the bushing holding part being tubular with a fitting hole into which the bushing fits opening at its end face, the inner surface of the fitting hole including the inner peripheral surface of the opening end of the bushing holding part being in elastic contact with the bushing, and the opening end of the bushing holding part being highly elastic.

The power cable termination connection part of the present invention can improve watertightness while preventing the formation of a gap between the inner surface of the fitting hole into which the bushing fits and the outer peripheral surface of the bushing.

1 is a cross-sectional view of a power cable termination connection portion according to a first embodiment. 1A is a side view of the third semi-conductor as viewed from a direction perpendicular to the axial direction of the cylindrical holding portion, and FIG. 1B is a side view of the third semi-conductor as viewed along the axial direction of the cylindrical holding portion. 1A is a partial cross-sectional view of a bushing holding portion, and FIG. 2 is a cross-sectional view taken along line AA in FIG. 1. 11A to 11C are cross-sectional views showing examples of configurations in which the axial length of the highly elastic body is changed in three ways. 1 is a partial cross-sectional view of a bushing including a portion of a conical portion and a cylindrical portion. 1 is a graph showing the face distance from a reference point on the horizontal axis and the tightening force of the bushing on the vertical axis. FIG. 11 is a partial cross-sectional view of a power cable termination connection portion according to a second embodiment.

[First embodiment]
A power cable connection terminal according to a first embodiment of the present invention will be described with reference to Fig. 1 to Fig. 7. Fig. 1 is a cross-sectional view of a power cable connection terminal 1. The power cable connection terminal 1 is provided, for example, under the floor of a railway vehicle, and electrically connects an end of a power cable 11 between a circuit breaker and a main transformer to a conductor wire 12 to be connected. The power cable 11 transmits high voltage power for driving a main motor of the railway vehicle.

The power cable 11 has a central conductor 111 formed by twisting together a number of strands 110, an insulating layer 112 that covers the central conductor 111, a number of shield wires 113 arranged to surround the outer periphery of the insulating layer 112, and a sheath 114 that covers the outer periphery of the number of shield wires 113. The power cable 11 has a terminal end that is connected to the power cable terminal connection part 1 and is stripped in stages. Specifically, the sheath 114 is removed to expose the multiple shield wires 113 and the insulating layer 112, and the insulating layer 112 is further removed to expose the central conductor 111.

A compression terminal 10 is attached to the central conductor 111 exposed from the insulating layer 112. The compression terminal 10 has a cylindrical crimped portion 101 that is crimped to compress the central conductor 111, and a flat connecting portion 102 that is integral with the crimped portion 101. The crimped portion 101 is formed with a receiving hole 101a that receives the central conductor 111. The connecting portion 102 is formed with a through hole 102a.

The power cable terminal connection part 1 includes a bushing 2 through which a conductor wire 12 is inserted, an insulating plug 3 arranged at a position where the compression terminal 10 is sandwiched between the bushing 2, a holding member 4 that holds the power cable 11, the bushing 2, and the insulating plug 3, a protective cap 5 that protects the insulating plug 3, a male screw 61, a nut 62, and a washer 63 for connecting the compression terminal 10 and the conductor wire 12, a metal tubular member 7 fixed to the holding member 4, and a waterproofing treatment part 8 that prevents water from entering the inside of the tubular member 7. The bushing 2 has an insertion hole 200 formed in its center, and the conductor wire 12 is inserted into this insertion hole 200.

The conductor wire 12 has a female thread 120 that opens on the longitudinal end face 12a of the portion inserted into the bushing 2, and one end of a male thread 61 is screwed into the female thread 120. The male thread 61 is inserted into a through hole 102a formed in the connection part 102 of the compression terminal 10 and protrudes toward the insulating plug 3. The nut 62 is screwed into the male thread 61 protruding toward the insulating plug 3, and a washer 63 is interposed between the nut 62 and the connection part 102 of the compression terminal 10. The nut 62 presses the connection part 102 of the compression terminal 10 against the end face 12a of the conductor wire 12 via the washer 63.

The bushing 2 is made of a hard insulator such as epoxy resin. The bushing 2 has a stepped shape that integrally includes a partially conical cone-shaped portion 21 and a cylindrical portion 22 whose outer diameter is larger than the maximum outer diameter of the cone-shaped portion 21. The cone-shaped portion 21 has the largest outer diameter at the base end 211 on the cylindrical portion 22 side, and the outer diameter becomes smaller toward the tip end 212 on the compression terminal 10 side. The cylindrical portion 22 protrudes along the conductor wire 12 from the end surface 20a of the base 20, which has an even larger diameter than the cylindrical portion 22. The cone-shaped portion 21 has a flat tip surface 212a at the tip end 212. The tip surface 212a of the cone-shaped portion 22 is the end surface on the connection side of the power cable 11 and the conductor wire 12 in the bushing 2, and faces the connection portion 102 of the compression terminal 10.

The insulating plug 3 comprises a molded insulator 31, a high-voltage electrode 32 provided at one end of the insulator 31, and a voltage detector electrode 33 provided at the other end of the insulator 31. The high-voltage electrode 32 is formed with a countersunk hole 32a corresponding to the shape of the nut 62, and a female thread 320 into which the male thread 61 screws. The voltage detector electrode 33 is formed with a tool fitting hole 33a into which the tip of a tool such as a socket wrench fits. The insulator 31 is molded integrally with the high-voltage electrode 32 and the voltage detector electrode 33.

The protective cap 5 is made of a semiconductive rubber material and is formed in a cylindrical shape with a bottom, having a disk-shaped bottom wall 51 and a cylindrical side wall 52 integrally formed therewith. The bottom wall 51 covers the insulating plug 3. The inner peripheral surface 52a of the side wall 52 is formed with an annular protrusion 521 for fixing to the holding member 4.

The tubular member 7 has the central conductor 111 and insulating layer 112 of the power cable 11 inserted therethrough, and also houses the multiple shield wires 113 and a portion of the longitudinal direction of the sheath 114. The tubular member 7 is made of a metal having high conductivity, such as brass or an aluminum alloy. The multiple shield wires 113 are led out of the sheath 114 inside the tubular member 7, folded back around the outer periphery of the sheath 114, and led out to the outside of the tubular member 7 from between the outer periphery 114a of the sheath 114 and the inner periphery 7a of the tubular member 7.

The multiple shield wires 113 led out to the outside of the tubular member 7 are electrically connected to the tubular member 7 by multiple connection terminals 71 and bolts 72. The tubular member 7 is also electrically grounded by connecting a first earth wire 91 to it by a bolt 73. The first earth wire 91 has an earth wire body 911 made of an insulated wire whose core is covered with an insulator, and an earth terminal 912 attached to the tip of the earth wire body 911, and the earth terminal 912 is fixed to the tubular member 7 by a bolt 73.

The waterproofing treatment section 8 is formed by wrapping waterproof tape 81 around the outer circumference of the tubular member 7 and the sheath 114 multiple times, and then covering the waterproof tape 81 with a heat shrink tube 82.

The holding member 4 is integrally formed in a T-shape with a power cable holding portion 4A that holds the end of the power cable 11, a bushing holding portion 4B that holds the bushing 2, and an insulating plug holding portion 4C that holds the insulating plug 3. The power cable holding portion 4A is cylindrical and extends in the longitudinal direction of the power cable 11, and has a linear insertion hole 410 formed in the center thereof into which the central conductor 111 and insulating layer 112 of the power cable 11 are inserted. The bushing holding portion 4B is formed in a cylindrical shape that surrounds the conical portion 21 and cylindrical portion 22 of the bushing 2.

The bushing holding portion 4B and the insulating plug holding portion 4C extend in a direction perpendicular to the extension direction of the power cable holding portion 4A and are aligned along the axial direction of the conductor wire 12. The connection portion 102 of the compression terminal 10 is disposed between the bushing holding portion 4B and the insulating plug holding portion 4C. The bushing holding portion 4B has a fitting hole 400, into which the bushing 2 fits, that opens to the end face 40a on the base 20 side. This end face 40a corresponds to the open end face of the fitting hole 400. The bushing holding portion 4B is restricted in its relative movement with the bushing 2 in the axial direction of the conductor wire 12 by the female thread 320 of the high voltage electrode 32 in the insulating plug 3 being screwed into the male thread 61.

When assembling the power cable terminal connection part 1, the bushing 2 is inserted into the fitting hole 400 from the end face 40a side of the bushing holding part 4B, and the inner surface 400a of the fitting hole 400 elastically contacts the bushing 2. Here, "elastically contacts" means that the bushing holding part 4B is elastically deformed so that the inner diameter of the fitting hole 400 expands when the bushing 2 is inserted, and the inner surface 400a of the fitting hole 400 elastically contacts the outer peripheral surface of the bushing 2 without any gaps due to the restoring force of the bushing holding part 4B.

The holding member 4 also has an insulator 40 made of a polymer-based material, and first to third semi-conductors 41 to 43 made of a polymer-based material to which a conductive agent has been dispersed to impart conductivity. The insulator 40 is provided across the holding tube portion 4A, the bushing holding portion 4B, and the insulating plug holding portion 4C, and is formed integrally with the first to third semi-conductors 41 to 43. The first to third semi-conductors 41 to 43 reduce the electric field around the power cable 1. The third semi-conductor 43 also has a shielding function that prevents the electric field around the compression terminal 10, the conductor wire 12, the male screw 61, the nut 62, and the washer 63 from leaking to the outside.

The insulator 40 and the first to third semi-conductors 41 to 43 are made of a soft material with a lower elastic modulus than the bushing 2. Here, the elastic modulus is the tensile modulus expressed by the ratio of the tensile stress per unit cross-sectional area to the elongation occurring in the stress direction, and the larger this value is, the less likely the material is to elongate. As the polymer-based material of the insulator 40 and the first to third semi-conductors 41 to 43, for example, silicone rubber, ethylene propylene rubber (EPM), ethylene propylene diene rubber (EPDM), etc. can be used. That is, in this embodiment, the insulator 40 and the first to third semi-conductors 41 to 43 are rubber molded bodies. As the conductivity imparting agent for the first to third semi-conductors 41 to 43, for example, conductive fine powder such as carbon black can be used.

The insulator 40 is formed by injecting a molten polymer material into the cavity of a mold in which the first to third semi-conductors 41 to 43, which have been molded in advance, are placed. The heat of the polymer material melts part of the surface of the first to third semi-conductors 41 to 43, and they become integrated with the insulator 40.

The first semi-conductor 41 surrounds the compression terminal 10 together with a part of the insulating layer 112 of the power cable 11 from the end of the retaining tube portion 4A to the bushing retaining portion 4B and the insulating plug retaining portion 4C. The second semi-conductor 42 is aligned with the first semi-conductor 41 in the longitudinal direction of the power cable 11 and is disposed closer to the tubular member 7 than the first semi-conductor 41. The central conductor 111 and insulating layer 112 of the power cable 11 are inserted into the center of the second semi-conductor 42.

Figure 2(a) is a side view of the third semi-conductor 43 as viewed from a direction perpendicular to the axial direction of the retaining tube portion 4A, and Figure 2(b) is a side view of the third semi-conductor 43 as viewed along the axial direction of the retaining tube portion 4A. Figures 2(a) and (b) show the second earth wire 92 along with the third semi-conductor 43.

The third semi-conductor 43 integrally comprises a cylindrical portion 431 that covers the outer periphery of the insulator 40 in the bushing holding portion 4B and the insulating plug holding portion 4C, a tubular portion 432 that covers the outer periphery of the insulator 40 that is on the outer periphery side of the crimping portion 101 of the compression terminal 10, and a pair of protruding pieces 433, 434 formed by protruding from the outer periphery 432a of the tubular portion 432. The cylindrical portion 431 is formed with an annular recess 430 that engages with the protrusion 521 of the side wall 52 of the protective cap 5. The outer periphery 431a of the cylindrical portion 431 is linear and parallel to the conductor wire 12 in a side view, except for the portion where the recess 430 is formed.

The pair of protruding pieces 433, 434 are used to fix the third semi-conductor 43 to a mold for molding the insulator 40. The pair of protruding pieces 433, 434 are formed with through holes 433a, 434a, respectively. In addition, the second earth wire 92 is connected to one of the pair of protruding pieces 433, 434, i.e., the protruding piece 433, so that the third semi-conductor 43 is electrically grounded.

The second earth wire 92 has an earth wire body 921 made of an insulated electric wire whose core is covered with an insulator, and an earth terminal 922 attached to the tip of the earth wire body 921. The earth terminal 922 is attached to one of the protruding pieces 433 by a bolt 64 and a nut 65. The threaded portion 641 of the bolt 64 is inserted into the through hole 433a of the one of the protruding pieces 433.

Figure 3(a) is a partial cross-sectional view of the bushing holding portion 4B. Figure 3(b) is an external view of the bushing 2. Figure 4 is a cross-sectional view taken along line A-A in Figure 1. In Figure 3(a), the inner surface 400a of the fitting hole 400 before the bushing 2 is inserted into the fitting hole 400 is indicated by a solid line, and the inner surface 400a of the fitting hole 400 when the bushing 2 is inserted is indicated by a two-dot chain line. The area between the solid line and the two-dot chain line is the tightening margin of the inner surface 400a of the fitting hole 400. It is desirable that the tightening margin of the outer periphery of the cylindrical portion 22 is smaller than the tightening margin of the outer periphery of the conical portion 21. By making the tightening margin of the outer periphery of the cylindrical portion 22 smaller than the tightening margin of the outer periphery of the conical portion 21, a gap is less likely to occur between the outer periphery of the bushing 2 and the inner surface 400a of the fitting hole 400, and discharge from this gap can be suppressed.

3(b), a flat annular step surface 22b oriented toward the compression terminal 10 is formed between the outer circumferential surface 21a of the conical portion 21 and the outer circumferential surface 22a of the cylindrical portion 22 of the bushing 2. These outer circumferential surfaces 21a, 22a and step surface 22b form the outer surface of the bushing 2. Chamfered portions R1, R2, and R3 are formed between the outer circumferential surface 21a of the conical portion 21 and the step surface 22b, between the step surface 22b and the outer circumferential surface 22a of the cylindrical _portion 22, and between the outer circumferential surface _22a of the cylindrical portion ₂₂ and the end surface 20a of the base 20, respectively.

The inner surface 400a of the fitting hole 400 has an opening side inner surface 400b that elastically contacts the outer circumferential surface 22a of the cylindrical portion 22 of the bushing 2, a rear side inner surface 400c that elastically contacts the outer circumferential surface 21a of the conical portion 21, and an annular elastic contact surface 400d that elastically contacts the step surface 22b. The inner surface 400a of the fitting hole 400 is formed by the insulator 40, and the outer circumferential side of the insulator 40 that contacts the outer periphery of the bushing 2 is surrounded by the cylindrical portion 431 of the third semi-conductor 43.

Hereinafter, the portion of the bushing retaining portion 4B that corresponds to the outer periphery of the cylindrical portion 22 of the bushing 2 will be referred to as the open end 401, and the portion that corresponds to the outer periphery of the conical portion 21 of the bushing 2, which is located further back in the fitting hole 400 than the open end 401, will be referred to as the inner body portion 402. The open end 401 is formed thinner than the inner body portion 402 in accordance with the difference in outer diameter between the conical portion 21 and the cylindrical portion 22 of the bushing 2. Figure 4 shows a cross section of the power cable termination connection portion 1 at the open end 401.

The opening side inner circumferential surface 400b is the inner circumferential surface of the opening side end portion 401. The rear side inner circumferential surface 400c is the inner circumferential surface of the rear side body portion 402. In other words, when the power cable termination connection portion 1 is assembled as shown in FIG. 1, the inner surface 400a of the fitting hole 400, including the inner circumferential surface (opening side inner circumferential surface 400b) of the opening side end portion 401 of the bushing holding portion 4B and the inner circumferential surface (rear side inner circumferential surface 400c) of the rear side body portion 402, is in elastic contact with the outer surface (outer circumferential surfaces 21a, 22a and step surface 22b) of the bushing 2.

It is desirable that the power cable terminal connection part 1 is highly watertight so that moisture does not penetrate between the inner surface 400a of the fitting hole 400 and the bushing 2 to the connection part between the power cable 11 and the conductor wire 12. In addition, if there is a gap between the inner surface 400a of the fitting hole 400 and the bushing 2, there is a risk of discharge occurring in this gap, so it is desirable that the inner surface 400a of the fitting hole 400 is in contact with the bushing 2 without any gaps.

On the other hand, the thickness of the opening end 401 of the bushing retaining portion 4B is thinner than the thickness of the rear body portion 402, so it is difficult to ensure a tightening margin, particularly at the opening end 401, and it is also difficult to ensure the tightening force (surface pressure acting on the outer surface of the bushing 2) that tightens the bushing 2. Therefore, in this embodiment, the opening end 401 of the bushing retaining portion 4B is made more elastic than the rear body portion 402. Here, high elasticity specifically means that the inner diameter is less likely to expand, and high elasticity can also be said to be high rigidity. In other words, in order to expand the opening end 401 by a predetermined amount, a greater force is required than when expanding the rear body portion 402 by the same amount.

In this embodiment, the bushing holding portion 4B has a highly elastic body 44, which makes the opening end 401 highly elastic. As shown in FIG. 4, the highly elastic body 44 is formed in a ring shape around the entire circumference of the opening end 401. The highly elastic body 44 is embedded in the cylindrical portion 431 of the third semi-conductor 43 in the bushing holding portion 4B. In this embodiment, the highly elastic body 44 is in the shape of an endless band.

The highly elastic body 44 may be embedded in the insulator 40 at the opening end 401, or may be embedded between the insulator 40 at the opening end 401 and the cylindrical portion 431 of the third semi-conductor 43. The highly elastic body 44 does not necessarily have to be formed as an integral ring, and may be, for example, a plurality of arc-shaped segments arranged in the circumferential direction of the opening end 401 to form a ring as a whole. Furthermore, the highly elastic body 44 is not limited to an endless belt shape, and may be, for example, a configuration in which a wire is wound in a coil shape.

The highly elastic body 44 is made of a material whose elastic modulus is higher than that of the insulator 40 and the third semi-conductor 43. Here, the elastic modulus of the highly elastic body 44 is a tensile elastic modulus, which is obtained from the relationship between tensile stress and tensile strain in a tensile test conforming to JIS K7113 or the like. In this embodiment, the highly elastic body 44 is made of cylindrical plastic. The elastic modulus of the highly elastic body 44 is, for example, 10 MPa or more and 100 MPa or less. On the other hand, the elastic modulus of the insulator 40 and the third semi-conductor 43 is, for example, 1.3 MPa. In this case, the elastic modulus of the highly elastic body 44 is 7.7 times or more and 77 times or less than that of the insulator 40 and the third semi-conductor 43. The highly elastic body 44 may be formed of conductive plastic, and an earth wire may be connected to the highly elastic body 44 for electrical grounding.

In this embodiment, one axial end face 44a of the highly elastic body 44 is exposed to the end face 431a of the cylindrical portion 431 of the third semi-conductor 43. This configuration makes it easier to hold the highly elastic body 44 in the mold used for injection molding when the third semi-conductor 43 is injection molded. The end face 44a of the highly elastic body 44 is covered by the insulator 40 during the subsequent molding of the insulator 40, and the entire highly elastic body 44 is covered by the bushing retaining portion 4B.

By increasing the elasticity of the opening end 401, even if the tightening margin at the opening end 401 is smaller than that at the rear body 402, the opening inner circumferential surface 400b can be pressed against the bushing 2 with the same tightening force as the rear inner circumferential surface 400c, ensuring high watertightness. In addition, because the tightening margin at the opening end 401 is smaller than that at the rear body 402, the deformation of the opening end 401 when the bushing 2 is fitted into the fitting hole 400 is small, and the occurrence of a gap between the rear inner circumferential surface 400c and the outer circumferential surface 21a of the conical portion 21 can be suppressed.

In other words, if the opening end 401 expands significantly when the bushing 2 is fitted into the fitting hole 400, the rear body portion 402 also expands in diameter, which can easily cause gaps to form between the outer peripheral surface 21a at the base end 211 of the conical portion 21 and the rear inner peripheral surface 400c. However, in this embodiment, the opening end 401 is made highly elastic, which can prevent such gaps from occurring.

It is desirable that the other axial end face 44b of the highly elastic body 44 be located at the same position as the annular elastic contact surface 400d or at the rear body portion 402 in the axial direction of the fitting hole 40. This allows the effect of the high elasticity of the opening side end portion 401 to be fully exerted.

Next, referring to Figures 5 to 7, the axial length and elastic modulus of the highly elastic body 44 are changed, and the tightening force (stress generated in the bushing retaining portion 4B) with which the bushing retaining portion 4B tightens the bushing 2 is evaluated for six patterns: patterns 1 to 5 and pattern 6 without the highly elastic body 44.

FIG. 5(a) is a cross-sectional view showing a configuration example in which the axial length of the high elastic body 44 is L ₁ , and the end face 44b of the high elastic body 44 is at the same position as the annular elastic contact surface 400d in the axial direction of the fitting hole 40. FIG. 5(b) is a cross-sectional view showing a configuration example in which the axial length L ₂ of the high elastic body 44 is 1.5 times L ₁ , and a part of the axial direction including the end face 44b of the high elastic body 44 is arranged in the back side body part 402. FIG. 5(c) is a cross-sectional view showing a configuration example in which the axial length L ₃ of the high elastic body 44 is 3 times L ₁ , and a part of the axial direction including the end face 44b of the high elastic body 44 is arranged further back than the configuration example of FIG. 5(b). The length L ₁ is 10 mm as an example. The radial thickness of the high elastic body 44 shown in FIGS. 5(a) to (c) is 0.5 mm as an example.

Table 1 shows the axial length and elastic modulus of the highly elastic body 44 for each of patterns 1 to 6.

Fig. 6 is a partial cross-sectional view of the bushing 2 including a part of the conical portion 21 and the cylindrical portion 22. Point P0 shown in Fig. ₆ is the boundary point between the end surface 20a of the base 20 and the chamfered portion _R3 . Point _P1 is the boundary point between the chamfered portion _R3 and the outer circumferential surface 22 of the cylindrical portion 22. Point _P2 is the boundary point between the outer circumferential surface 22 of the cylindrical portion 22 and the chamfered portion _R2 . Point _P3 is the boundary point between the chamfered portion _R2 and the step surface 22b. Point _P4 is the boundary point between the step surface 22b and the chamfered portion _R1 . Point _P5 is the boundary point between the chamfered portion _R1 and the outer circumferential surface 21a of the conical portion 21.

Point _P0 is a reference point that is the starting point for erecting the cylindrical portion 22 of the bushing 2 from the base 20. The projection distance from point _P0 to point _P1 , the projection distance from point _P0 to point _P2 , and the projection distance from point _P0 to point _P5 are, for example, 5 mm, 10 mm, and 21 mm, respectively. Note that the length _L4 of the cylindrical portion 22 in the axial direction of the bushing 2 is, for example, 11 mm.

7 is a graph showing the tightening force of the bushing 2 on the vertical axis, with the horizontal axis representing the surface distance from point _P0 . On the vertical axis, the force in the direction of tightening the bushing 2 is represented by - (minus). In order to suppress the occurrence of a gap between the inner surface 400a of the fitting hole 400 and the bushing 2 while ensuring high watertightness, it is desirable that the difference between the tightening force acting on the outer peripheral surface 22a of the cylindrical portion 22 and the tightening force acting on the outer peripheral surface 21a of the conical portion 21 is not too large. More specifically, when the tightening force acting on the outer peripheral surface 21a of the conical portion 21 at point _P5 is _F1 and the tightening force acting on the outer peripheral surface 22a of the cylindrical portion 22 at point _P2 is _F2 , it is desirable that the value of _F2 / _F1 is 0.5 or more and 1.2 or less.

The elastic modulus of the highly elastic body 44 is preferably 10 MPa or more and 100 MPa or less. If the elastic modulus of the highly elastic body 44 is less than 10 MPa, the fastening force acting on the outer peripheral surface 22a of the cylindrical portion 22 is insufficient, and if the elastic modulus of the highly elastic body 44 exceeds 1000 MPa, the fastening force is too large, making it difficult to insert the bushing 2 into the fitting hole 400. Furthermore, by setting the elastic modulus of the highly elastic body 44 to be 10 MPa or more and 100 MPa or less, the value of _F2 / _F1 is 0.5 or more and 1.2 or less, as shown in Fig. 7, and high watertightness can be ensured.

The axial length of the highly elastic body 44 may be shorter than _L1 , and the position of the end face 44b of the highly elastic body 44 in the axial direction of the fitting hole 400 may be aligned with the outer circumferential surface 22a of the cylindrical portion 22 in the radial direction of the bushing 2. Even in this case, high watertightness can be ensured in a portion of the opening side end 401 that has been made highly elastic by the highly elastic body 44. In other words, it is sufficient that at least a portion of the opening side end 401 that corresponds to the outer circumferential side of the cylindrical portion 22 of the bushing retaining portion 4B has been made highly elastic.

The axial length of the highly elastic body 44 should be 0.8 to 1.5 times the length of the cylindrical portion 22 in the axial direction of the bushing 2. If the axial length of the highly elastic body 44 is too short relative to the length of the cylindrical portion 22, the effect of improving watertightness is not necessarily sufficient, and if the axial length of the highly elastic body 44 is too long relative to the length of the cylindrical portion 22, the impact on parts other than the cylindrical portion 22 will be significant.

[Second embodiment]
Next, a power cable termination connection part according to a second embodiment will be described with reference to Fig. 8. In the first embodiment, the opening end 401 is made highly elastic by the highly elastic body 44 embedded in the bushing holding part 4B, but in the second embodiment, the opening end 401 is made highly elastic by using rubber materials having different elastic moduli.

Figure 8 is a cross-sectional view showing a part of the power cable terminal connection part according to the second embodiment. In this configuration example, a high-elasticity rubber material having a higher elasticity (tensile elasticity) than the rubber material of the rear trunk part 402 is used for the cylindrical part 431 of the third semi-conductor 43 at the opening end 401 and the elastic body 40. In Figure 8, the high-elasticity part 43A in which a high-elasticity rubber material is used in the cylindrical part 431 of the third semi-conductor 43, and the high-elasticity part 40A in which a high-elasticity rubber material is used in the insulator 40 are shown in gray shading. The ratio of the tensile elasticity of the rubber material constituting the high-elasticity parts 40A and 43A to the tensile elasticity of the rubber material constituting the insulator 40 of the rear trunk part 402 is greater than 1. The other configurations of the power cable terminal connection part according to the second embodiment are the same as those of the first embodiment.

The third semi-conductor 43 having such a high elasticity portion 43A can be molded, for example, by injecting a polymer material that will become the high elasticity portion 43A into a mold for molding the third semi-conductor 43, and then injecting a polymer material that will become the other portions of the third semi-conductor 43. The same applies to the molding method of the insulator 40 having the high elasticity portion 40A. Note that if the third semi-conductor 43 has the high elasticity portion 43A, the insulator 40 does not need to have the high elasticity portion 40A. Also, if the insulator 40 has the high elasticity portion 40A, the third semi-conductor 43 does not need to have the high elasticity portion 43A.

In this way, in the second embodiment, the elastic modulus (tensile elastic modulus) of at least a portion of the rubber material of the opening side end 401 of the bushing retaining portion 4B is higher than the elastic modulus (tensile elastic modulus) of the rubber material of the other portions, thereby making the opening side end 401 highly elastic. As a result, the second embodiment can also achieve the same effect as the first embodiment. Note that the high elasticity portions 40A, 43A can be made of a rubber material whose tensile elastic modulus has been increased by adding an additive to the base resin of the resin composition that constitutes the rubber material.

(Summary of the embodiment)
Next, the technical ideas grasped from the first and second embodiments described above will be described by using the reference numerals and the like in the embodiments. However, the reference numerals and the like in the following description do not limit the components in the claims to the members and the like specifically shown in the embodiments.

[1] A power cable terminal connection part (1) in which a terminal end of a power cable (11) is electrically connected to a conductor wire (12) to be connected, the power cable terminal connection part (1) includes a bushing (2) through which the conductor wire (12) is inserted, and a holding member (4) integrally including a power cable holding part (4A) for holding the terminal end of the power cable (11) and a bushing holding part (4B) for holding the bushing, the bushing holding part (4B) is cylindrical with a fitting hole (400) into which the bushing (2) fits, the fitting hole (400) opening at the end face (40a), the inner surface (400a) of the fitting hole (400) including the inner peripheral surface (400b) of the opening end (401) of the bushing holding part (4B) is in elastic contact with the bushing (2), and the opening end (401) of the bushing holding part (4B) is highly elastic. Power cable terminal connection part (1).

[2] The bushing (2) has a conical portion (21) whose outer diameter decreases toward the connection portion with the power cable (11), and a cylindrical portion (22) whose outer diameter is larger than the maximum outer diameter of the conical portion (21), and the bushing holding portion (4B) has at least a portion of the opening side end (401) that corresponds to the outer periphery of the cylindrical portion (22) that is made highly elastic, the power cable terminal connection portion (1) described in [1] above.

[3] The bushing holding portion (4B) has a rubber molded body (third semi-conductor 43 and insulator 40) molded to surround the conical portion (21) and the cylindrical portion (22) of the bushing (2), and a highly elastic body (44) embedded in the rubber molded body (43, 40), the elastic modulus of the highly elastic body (44) is higher than the elastic modulus of the rubber molded body (43, 40), and the opening side end (401) of the bushing holding portion (4B) is made highly elastic by the highly elastic body (44), the power cable terminal connection portion (1) described in the above [2].

[4] The power cable terminal connection part (1) described in [3] above, in which the highly elastic body (44) is formed in a ring shape around the entire circumference of the opening side end part (401).

[5] The bushing retaining portion (4B) is a power cable termination connection portion (1) described in [1] or [2] above, in which the elastic modulus of the rubber material of at least a portion of the opening end portion (401) is higher than the elastic modulus of the rubber material of the other portions.

Although the first and second embodiments of the present invention have been described above, these embodiments do not limit the invention according to the claims. It should also be noted that not all of the combinations of features described in the embodiments are necessarily essential to the means for solving the problems of the invention.

Reference Signs List 1...Power cable terminal connection part 11...Power cable 12...Conductor wire 2...Bushing 21...Conical part 22...Cylindrical part 4...Retaining member 40...Insulator (rubber molded body)
400: fitting hole 400a: end face 400a: inner face 400b: inner circumferential face 401: opening side end 43: third semi-conductor (rubber molded body)
44: Highly elastic body 4A: Power cable holding portion 4B: Bushing holding portion

Claims (5)

A power cable terminal connection portion in which a terminal end of a power cable is electrically connected to a conductor wire to be connected,
a bushing through which the conductor wire is inserted;
a holding member integrally including a power cable holding portion that holds the terminal end of the power cable and a bushing holding portion that holds the bushing,
the bushing holding portion is tubular and has a fitting hole, into which the bushing is fitted, open at an end surface of the fitting hole,
an inner surface of the fitting hole, including an inner circumferential surface of an opening end of the bushing holding portion, is in elastic contact with the bushing,
The opening side end of the bushing holding portion is made highly elastic.
Power cable termination connections. the bushing has a conical portion whose outer diameter decreases toward a connection portion with the power cable, and a cylindrical portion whose outer diameter is larger than the maximum outer diameter of the conical portion,
At least a part of the opening side end portion of the bushing holding portion, which corresponds to the outer circumferential side of the cylindrical portion, is made highly elastic.
2. The power cable termination of claim 1. the bushing holding portion includes a rubber molded body molded so as to surround the conical portion and the cylindrical portion of the bushing, and a highly elastic body embedded in the rubber molded body,
the elastic modulus of the high-elastic body is higher than the elastic modulus of the rubber molded body,
The opening side end of the bushing holding portion is made highly elastic by the highly elastic body.
3. The power cable termination of claim 2. The highly elastic body is formed in an annular shape around the entire circumference of the opening side end portion.
4. The power cable termination of claim 3. the elastic modulus of the rubber material of at least a portion of the opening side end of the bushing holding portion is higher than the elastic modulus of the rubber material of the other portion;
3. A power cable termination according to claim 1 or 2.

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