Crimp terminal

[0002] The present invention relates to a crimp terminal for connecting electric wires by crimping, and more particularly to an improvement of conductor engaging grooves (serrations) which are formed on an inner face of a bottom plate part, etc. of the terminal, and advantageously contribute to an improvement of electrical connecting performance as well as an improvement of mechanical connecting performance between the terminal and conductors of the electric wires.

[0003] FIGS. 6 and 7 show examples of related-art crimp terminals.

[0004] A crimp terminal 1 as shown in FIG. 6 is the crimp terminal for screw fitting, and includes a terminal portion 2 for screw fitting which has a screw insertion hole 2aformed at its distal end, a conductor crimping portion 4 and a sheath crimping portion 5 which are provided in order behind the terminal portion 2. These portions are integrally formed of a sheet of metal plate by stamping process.

[0005] The conductor crimping portion 4 is a portion for connecting bare conductors 7bby crimping, which are exposed by removing an insulation sheath 7afrom a sheathed electric wire 7, as also shown in FIG. 8. The conductor crimping portion 4 has a bottom plate part 4aon which the bare conductors 7bare placed, and a pair of crimp claws 4bwhich are adapted to be crimped onto the bare conductors 7bplaced on this bottom plate part 4a, by a crimping equipment 9 (See FIG. 9).

[0006] The sheath crimping portion 5 is a portion for crimping the sheathed electric wire 7 to fix it together with the insulation sheath 7a, and includes a bottom plate part 5aon which the sheathed electric wire 7 is placed, and a pair of crimp claws 5bwhich are crimped onto the sheathed electric wire 7 placed on the bottom plate part 5a, by the crimping equipment 9 (See FIG. 9).

[0007] The crimping equipment 9 is a kind of pressing apparatus which includes, as shown in FIGS. 9 and 10, an anvil 9afor supporting the bottom plate parts 4a, 5aof the conductor crimping portion 4 and the sheath crimping portion 5, and two crimpers 9b, 9cprovided above the anvil 9aso as to move up and down for respectively crimping the crimp claws 4band the crimp claws 5b.

[0008] Meanwhile, a crimp terminal 11 as shown in FIG. 7, is a relaying crimp terminal for connecting conductors of a plurality of sheathed electric wires 12a, 12b, 12ctogether in a bundle, and has a bottom plate part 11aon which a plurality of bare conductors 13 are placed, and a pair of crimp claws 11bwhich are extended from both sides of the bottom plate part 11aand adapted to be crimped onto the bare conductors 13 placed on the bottom plate part 11a, by a crimping equipment. The bottom plate part 11aand the crimp claws 11bare integrally formed of a sheet of metal plate by stamping process.

[0009] It has been known that in order to enhance electrical connecting performance and mechanical connecting performance between the bare conductors and the bottom plate parts of these crimp terminals, a plurality of conductor engaging grooves 17 in a concave shape (hereinafter referred to as “serrations”) extending in a direction intersecting axes of the bare conductors (usually, in a perpendicular direction) are provided on an inner face 16 of the bottom plate part, etc. of the terminal to be contacted with the bare conductors, as shown in FIGS. 11 and 12.

[0010] In this case, all the serrations have a groove width and a groove depth of the same size, and are in the same shape.

[0011] When the crimp claws 4b, 11bhave been crimped, groove edges of the serrations 17 are intensively pressed so as to adequately bite the bare conductors 7b, 13 on the surface, and both the mechanical connecting performance and the electrical connecting performance can be improved, ensuring reliability of the connection by crimping.

[0012] By the way, in order that oxidized coatings formed by oxidation on the surfaces of the conductors may be removed when the edges of the serrations 17 have bitten the bare conductors 7b, 13 by the edges, it is necessary for the serrations 17 to be set to have a large amount of bite, and it is necessary to make the serrations 17 deep for an increase of the amount of bite.

[0013] On the other hand, in case where the serrations have been set to have a large amount of bite, stresses will be converged on crimped areas of the conductors when a tensile force is exerted on the bare conductors 7b, 13 from outside. As the results, the bare conductors 7b, 13 will be likely to be broken, resulting in deterioration of the mechanical connecting performance.

[0014] Under the circumstances, in order that improvements of the electrical connecting performance and the mechanical connecting performance may be obtained while keeping their balance, the depth of the serrations 17 and crimping amounts of the crimp claws can be determined in consideration of outer diameters of the bare conductors.

[0015] However, there have been many cases in which the crimp terminals employed in a wire harness or the like for a motor vehicle must connect the sheathed electric wires having various diameters, or must crimp the conductors having different outer diameters together in a bundle.

[0016] For this reason, it is extremely difficult to determine the depth of the serrations 17 and the crimping amounts of the crimp claws so that improvements of both the electrical connecting performance and the mechanical connecting performance can be obtained while keeping their balance. For example, in case where a plurality of the bare conductors having different outer diameters have been crimped together in a bundle, even though the large diametered bare conductors may be improved both in the electrical connecting performance and the mechanical connecting performance, the small diametered bare conductors may be too much engaged by the serrations 17, resulting in a probability that even a slight tensile force may break the bare conductors.

[0017] Moreover, in case where the mechanical connecting performance is intended to be ensured, by setting the depth of the serrations 17 according to the bare conductor having the smallest diameter among the bare conductors 7b, 13 to be crimped, there has been such an anxiety that in the bare conductors having the larger diameters, the edges of the grooves cannot sufficiently remove the oxidized coatings on the surfaces of the conductors, incurring defective electrical connecting performance.

[0018] In order to eliminate such disadvantages contradicting each other, a crimp terminal 21 as shown in FIGS. 13 and 14 has been proposed.

[0019] This crimp terminal 21 is disclosed in Japanese Patent Publication No. JP 59-165390A, and includes two conductor crimping portions 23, 24 having different crimping amounts. The conductor crimping portion 23 positioned at a proximal end side of the bare conductors forms a crimping part having a small amount of bite of the serrations with respect to the conductors, by adjusting a height of the crimp claws 23b, 23band controlling a crimper 26bin a crimping equipment 26 so as to obtain a smaller crimping amount.

[0020] On the other hand, the conductor crimping portion 24 which is positioned at a distal end side of the bare conductors forms a crimping part having a large amount of bite of the serrations with respect to the conductors, by adjusting a height of the crimp claws 24b, 24band controlling a crimper 26cin the crimping equipment 26 so as to obtain a larger crimping amount.

[0021] In this manner, by providing two types of the conductor crimping portions 23, 24 having different crimping amounts, incomplete or excessive amount of bite by the serrations has been eliminated, even in case where the bare conductors having small diameters and large diameters are mixed, and both the electrical connecting performance and the mechanical connecting performance have been able to be improved.

[0022] However, in the crimp terminal 21 as shown in FIGS. 13 and 14, an increase in number of the conductor crimping portions 23, 24 has incurred a problem that a structure of the terminal has become complicated and large-sized. In addition, the crimping equipment 26 has become also complicated due to an addition of the crimper 26c, and there has arisen a problem that cost for the equipment might be increased.

[0023] It is therefore an object of the invention to provide a crimp terminal in which, on occasion of crimping operation when the bare conductors of both small diameters and large diameters are mixed, an excessive or incomplete bite in any conductor can be eliminated, without incurring a complicated and large-sized structure of the crimp terminal, and also without incurring a complicated crimping equipment, and both electrical connecting performance and mechanical connecting performance can be improved at a low cost.

[0024] In order to achieve the above object, according to the present invention, there is provided a crimp terminal for crimping at least one bare conductor of at least one sheathed electric wire, comprising:

[0025] a bottom plate, on which the at least one bare conductor is placed;

[0026] a pair of crimp craws, extending from the bottom plate to crimp the at least one bare conductor placed on the bottom plate; and

[0027] a plurality of serrations formed at least on an inner face of the bottom plate to bite the at least one bare conductor crimped by the crimp claws,

[0028] wherein at least one of the serrations has a depth different from a depth of each another serration.

[0029] In this construction, when the crimping operation is performed, the shallow serration will prevent an excessive bite thereby to attain improvement of the mechanical connecting performance, and on the other hand, the deep serration will prevent the oxidized coating from remaining due to an incomplete bite thereby to attain improvement of the electrical connecting performance.

[0030] Further, the serrations having different depths can ensure appropriate amounts of bite with respect to both the bare conductors having a small diameter and a large diameter, although no additional crimping structure is required.

[0031] Therefore, on occasion of crimping operation when the bare conductors having both a small diameter and a large diameter are mixed, an excessive or incomplete bite with respect to either conductor can be eliminated, without incurring a complicated and large-sized structure of the crimp terminal, and also without incurring a complicated crimping equipment, and both the electrical connecting performance and the mechanical connecting performance can be improved at a low cost.

[0032] Preferably, a depth of a serration situated closer to an end of the bottom plate at which the sheathed electric wire is placed is shallower than a depth of another serration.

[0033] When plural sheathed electric wires are placed at both ends of the bottom plate, it is preferable that depths of serration closer to the both ends of the bottom plate are shallower than a depth of another serration.

[0034] In these cases, it is possible to decrease an amount of bite between the serrations and the bare conductors at the proximal end side of the bare conductors, so that deterioration of the mechanical connecting performance due to an excessive bite can be reliably prevented.

[0035] Preferably, a depth of a center portion of the at least one serration in an extending direction thereof is shallower than depths of both end portions thereof.

[0036] The above objects and advantages of the present invention will become more apparent by describing in detail preferred exemplary embodiments thereof with reference to the accompanying drawings, wherein:

[0037] FIG. 1 is a developed view of a conductor crimping portion of a crimp terminal according to a first embodiment of the present invention;

[0038] FIG. 2 is a cross sectional view of the conductor crimping portion shown in FIG. 1;

[0039] FIG. 3 is a sectional view taken along a line D—D of FIG. 1;

[0040] FIG. 4 is a sectional view taken along a line E—E of FIG. 3, showing a crimp terminal according to a second embodiment of the present invention;

[0041] FIG. 5 is a sectional view of a conductor crimping portion, showing a crimp terminal according to a third embodiment of the present invention;

[0042] FIG. 6 is a perspective view of a related-art crimp terminal;

[0043] FIG. 7 is a side view of a related-art relaying crimp terminal;

[0044] FIG. 8 is a cross sectional view of a conductor crimping portion of the related-art crimp terminals;

[0045] FIG. 9 is a front view of a crimping equipment for conducting crimping operation of crimp claws on the crimp terminal;

[0046] FIG. 10 is a sectional view taken along a line B—B of FIG. 9;

[0047] FIG. 11 is a sectional view taken along a line A—A of FIG. 8;

[0048] FIG. 12 is a sectional view taken along a line C—C of FIG. 11;

[0049] FIG. 13 is a perspective view of a related-art crimp terminal of two-step crimping type; and

[0050] FIG. 14 is a vertical sectional view of a crimping equipment for conducting crimping operation of the crimp terminal shown in FIG. 13.

[0051] Now, preferred embodiments of a crimp terminal according to the present invention will be described in detail, referring to the accompanying drawings.

[0052] A crimp terminal 31 according to a first embodiment is a crimp terminal for screw fitting which is integrally formed of a metal plate by stamping process. As shown in FIG. 1, the crimp terminal 31 is constructed in such a manner that in order from its proximal end side, a sheath crimping portion 33 and a conductor crimping portion 35 are continuously provided.

[0053] The sheath crimping portion 33 has a bottom plate part 33aon which a sheathed electric wire 37 is placed, and a pair of crimp claws 33bextended from both sides of the bottom plate part 33a. By crimping a pair of the crimp claws 33bonto the sheathed electric wire 37 together with the insulation sheath 37aby the crimping equipment 9 (See FIGS. 9 and 10), the sheathed electric wire 37 is secured.

[0054] As shown in FIG. 2, the conductor crimping portion 35 has a bottom plate part 35aadapted to support bare conductors 37bwhich are exposed by removing an insulation sheath 37afrom one end portion of the sheathed electric wire 37, and a pair of crimp claws 35bextended from both sides of this bottom plate part 35a. By crimping a pair of the crimp claws 35bonto the bare conductors 37bby the crimping equipment 9, the sheathed electric wire 37 is fixed.

[0055] The conductor crimping portion 35 is provided with three conductor engaging grooves, so-called serrations 41, 42, 43 which extend in a direction intersecting axes of the bare conductors 37b, on inner faces of the bottom plate part 35aand the crimp claws 35bto be contacted with the bare conductors 37b.

[0056] These serrations 41, 42, 43 act in such a manner that edges of the grooves may bite the bare conductors 37bwhen the crimp claws 35bhave been crimped, and electrical connecting performance and mechanical connecting performance between the bare conductors 37band the conductor crimping portion 35 may be enhanced. A width w is the same in all the grooves.

[0057] However, in this embodiment, among the three serrations 41, 42 and 43, the serration 41 located adjacent to an end of the bottom plate portion 35acorresponding to a proximal end side of the bare conductors 37bis set to have a groove depth h1 which is smaller than a groove depth h2 of the other two serrations 42, 43 which are located adjacent to a center and adjacent to a distal end of the bottom plate part 35a, so that the serrations 41, 42, 43 may have different amounts of bite with respect to the bare conductors 37b.

[0058] In the crimp terminal 31 constructed in this manner, when the bare conductors 37bon the bottom plate part 35ahave been crimped by crimping operation of the crimp claws 35b, respective edges of the serrations 41, 42, 43 are adapted to bite the bare conductors 37bon the surface. On this occasion, the serration 41 having the smaller groove depth h1 will be prevented from excessively biting the conductors 37b, thus enhancing the mechanical connecting performance with an appropriate bite.

[0059] On the other hand, the serrations 42, 43 having the larger groove depth h2 will remove an oxidized coating formed on the surfaces of the bare conductors 37bwith a deep bite, thus enhancing the electrical connecting performance.

[0060] Although the above described function has been described referring to a case in which the bare conductors to be applied have a small outer diameter, it is apparent that in case where the bare conductors have a large outer diameter, the serrations 42, 43 having the large groove depth h2 can ensure an appropriate amount of bite which is suitable for both the electrical connecting performance and the mechanical connecting performance. Therefore, such an inconvenience that either one of the electrical connecting performance and the mechanical connecting performance may become defective will not occur.

[0061] Moreover, in the above described embodiment, the groove depths of the three serrations 41, 42, 43 are set in a plurality of different sizes so as to ensure appropriate amounts of bite with respect to both the bare conductors 37bhaving a small diameter and a large diameter, and so, any additional structure or the like to the conductor crimping portion on the crimp terminal 31 is absolutely unnecessary.

[0062] Accordingly, even in case where the bare conductors having a large diameter and a small diameter are mixed, excessive or incomplete amount of bite can be eliminated with respect to the conductors of any size, without incurring a complicated or large-sized structure of the crimp terminal 31, and also without incurring a complicated crimping equipment. Thus, both the electrical connecting performance and mechanical connecting performance can be improved at a low cost.

[0063] Further in the present embodiment, the serration 41 located corresponding to the proximal end side of the bare conductors 37bhas been set to have the smaller groove depth than the groove depth of the other serrations 42, 43 which are located adjacent to the center part of the bottom plate part 35a, as shown in FIG. 3. As the results, it is possible to decrease the amount of bite between the groove and the conductors at the proximal end side of the bare conductors 37b, and deterioration of the mechanical connecting performance due to an excessive bite can be reliably prevented.

[0064] Next, a second embodiment of the present invention will be described referring to FIG. 4, which is a sectional view taken along a line E—E of FIG. 3. Specifically, in the first embodiment, the groove depths of the serrations 41, 42, 43 are constant inside the respective serrations 41, 42, 43. However, in this embodiment, in the serration 42 located in the middle, a depth h3 at a center part of the groove is set to be smaller than a depth h2 at both end parts of the groove.

[0065] With this structure, the center part of the serration 42 located in the middle of the three serrations can be positively utilized for engaging a small diametered conductor. Meanwhile, the large depth h2 at the both end parts of this serration 42 can attain a deep bite, and improved electrical connecting performance can be obtained. Structures of other parts in this embodiment are the same as in the preceding embodiment.

[0066] It is to be noted that although the crimp terminal for screw fitting has been illustrated in the above described embodiments, the present invention can be applied to the relaying crimp terminal which is adapted to connect a plurality of electric wires together by crimping, as a third embodiment of the invention.

[0067] In this embodiment, it is desirable that among three serrations 61, 62, 63 provided on an inner face of a conductor crimping portion 55, the serrations 61 and 63 located at both end parts are set to have a small groove depth h1 so as to contribute to mechanical connection, and the serration 62 located in the center is set to have a large groove depth h2 so as to contribute to electrical connection.

[0068] Although the present invention has been shown and described with reference to specific preferred embodiments, various changes and modifications will be apparent to those skilled in the art from the teachings herein. Such changes and modifications as are obvious are deemed to come within the spirit, scope and contemplation of the invention as defined in the appended claims.

[0069] For example, number of the serrations to be provided on the inner face of the conductor crimping portion is not limited to the above described embodiment. An arbitrary number of more than two can be selected.