Terminal fitting connecting structure

A connecting structure has a male terminal (10) including a tab (13) and a female terminal (20) including a rectangular connecting tube (23) that receives the tab (13). A louver spring (30) is housed in the connecting tube (23) and has two spaced apart contact piece rows (31) each including juxtaposed resilient contact pieces (35) with contact portions (36) facing each other. The tab (13) resiliently contacts the contact portions (36) by being inserted between the contact portions (36) while resiliently displacing the contact piece rows (31) at the opposite sides. Inclined surfaces (15, 16) are formed adjacent a tip of the tab (13) of the male terminal (10) to gradually thin the tab (13) toward the tip. The inclined surfaces (15, 16) are formed so that the positions of base end edges (15A, 16A) connected to flat surfaces 14A differ in forward and backward directions.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a connecting structure for male and female terminal fittings.

2. Description of the Related Art

U.S. Pat. No. 7,150,660 andFIG. 10herein disclose a connecting structure for high-current terminal fittings. As shown inFIG. 10, this connecting structure has a male terminal1with a tab2in the form of a relatively thick tongue and a female terminal3with a rectangular connecting tube4into which the tab2is to be inserted. A louver spring5is housed in the connecting tube4. The louver spring5has two contact piece rows each including a plurality of juxtaposed resilient contact pieces6. The contact piece6has contact portions6A arranged to face each other while being spaced apart. On the other hand, inclined surfaces7are formed on opposite surfaces of a tip of the tab2and taper the tip for guiding purposes.

The tab2of the male terminal1is guided into the louver spring5when being inserted into the connecting tube4of the female terminal3and thrusts itself between the contact portions6A at the opposite sides while resiliently displacing the rows of the resilient contact pieces6at the opposite sides. Thus, the tab2is sandwiched resiliently between the contact portions6A at the opposite sides for electrically connecting the tab2and the louver spring5, and consequently the male and female terminal fittings1,2.

A variation of an insertion force of the tab2is shown by a characteristic curve x ofFIG. 9. Specifically, the tip of the tab2contacts the contact portions6A of the resilient contact pieces6at the opposite sides and then the tab2is pushed in while resiliently displacing the resilient contact pieces6, i.e. receiving an insertion load to gradually increases. The tab2receives a largest load when base end edges7A of the inclined surfaces7pass the contact portions6A and then the load gradually decreases. More particularly, a load peak is reached when the tab2is inserted a predetermined distance after the base end edges7A of both inclined surfaces7contact the contact portions6A. This is thought to be because the base end edges7A pass the contact portions6A at a delayed timing due to a backward displacement of the louver spring5or inclination of the resilient contact pieces6resulting from a housing tolerance of the louver spring5. At any rate, this conventional connecting structure is such that the base end edges7A of both inclined surfaces7on the tip of the tab2simultaneously pass the contact portions6A of the rows of the resilient contact pieces6at the opposite sides. Thus, a large insertion load is received during a connecting operation, i.e. a large insertion force (about 75N) is necessary, which has been a problem in ensuring a smooth connecting operation.

The present invention was developed in view of the above situation and an object thereof is to reduce an insertion force by a simple structural change.

SUMMARY OF THE INVENTION

The invention relates to a terminal fitting connecting structure, comprising a male terminal with a tab; and a female terminal including a connecting tube into which the tab is inserted. The connecting tube preferably is substantially rectangular. Contact portions are provided at positions substantially equidistant from the leading end of the connecting tube of the female terminal on substantially facing surfaces of the connecting tube to sandwich the tab in a thickness direction. The contact portion at least at one side is provided on a resilient contact piece arranged on the facing surface, and the tab resiliently contacts the contact portions by being inserted between the contact portions while resiliently displacing the resilient contact piece. Inclined surfaces are formed on opposite surfaces of the tab of the male terminal to gradually thin the tab toward the tip and the respective inclined surfaces are formed such that the positions of base end edges connected to flat surfaces of the tab differ in forward and backward directions.

When being at least partly inserted into the connecting tube portion of the female terminal, the tab of the male terminal is pushed in while resiliently displacing the resilient contact piece. First, as the base end edge of the inclined surface located more forward passes the corresponding contact portion, a relatively small first peak of an insertion force is reached. Thereafter, as the base end edge of the inclined surface located more backward passes the corresponding contact portion, a similarly relatively small second peak of an insertion force is reached. In other words, in the case of inserting the tab, the insertion force is distributed to have relatively small peaks at two positions, with the result that the insertion force is reduced. Further, a reduction in the insertion force is dealt with by a simple structural change of making the positions of the respective base end edges different in forward and backward direction.

Both inclined surfaces of the tab of the male terminal may have the same angle of inclination so that middle positions of both inclined surface in a thickness direction of the tab are displaced from a center of the tab in the thickness direction. Alternatively, the inclined surfaces of the tab of the male terminal may extend at different angles of inclination in obliquely upward and downward directions from tip edges at the middle thickness position of the tip surface of the tab.

Resilient contact pieces preferably are arranged substantially symmetrically on the facing surfaces of the connecting tube of the female terminal.

A louver spring preferably is housed in the connecting tube of the female terminal and preferably has contact piece rows with juxtaposed resilient contact pieces arranged to substantially face each other while being spaced apart. The tab is inserted between the contact piece rows at opposite sides in the louver spring member while resiliently displacing the contact piece rows.

Excessive deformation preventing portions preferably are provided on rear edge portions of the facing surfaces in the connecting tube of the female terminal while being spaced apart by a distance substantially equal to the thickness of a flat portion of the tab of the male terminal.

The inclined surfaces of the tab of the male terminal preferably are formed in an area of the tab that projects back from the rear edge of the connecting tube when the tab is inserted a proper distance into the connecting tube.

The flat surfaces of the tab substantially face the excessive deformation preventing portions at the rear side when the tab is inserted by the proper amount.

A distance between the projecting ends of the upper and lower excessive deformation preventing portions preferably is slightly longer than the thickness of the flat portion of the tab.

Positioning pieces of the louver spring preferably enter positioning holes or recesses of the connecting tube and/or locking pieces of the louver spring pass respective locking portions of the connecting tube to restore and engage the inner surfaces of the locking portions when the louver spring is inserted to a proper position.

The peripheral edge of the tip surface of the tab may be rounded.

The inclined surfaces may be provided over substantially the full width of the tab.

To reduce an overall level of the insertion force of the tab, it is more effective if the inclination of the inclined surfaces is more moderate and the lengths of the inclined surface are longer. On the other hand, the length of the tip portion projecting from the rear edge of the connecting tube when the tab is inserted by a proper amount is limited, for example, to avoid interference with a core of a wire connected to a barrel by crimping. Here, if inclined surfaces are formed beyond the projecting area of the tip portion of the tab, base ends of the inclined surfaces engage with the excessive deformation preventing portions provided on the rear edge of the connecting tube. Therefore a function of preventing shaking and twisting movements of the tab cannot be fulfilled sufficiently.

In contrast, the upper and lower inclined surfaces are formed only in the projecting area of the tip of the tab while being inclined as moderately as possible. Thus, the flat surfaces of the tab face the excessive deformation preventing portions on the rear edge when the tab is inserted by the proper amount. As a result, the function of preventing shaking and twisting movements of the tab can be fulfilled reliably.

Accordingly, it is possible to reduce an insertion force by a simple structural change of the male terminal.

These and other objects, features and advantages of the invention will become more apparent upon reading the following detailed description of preferred embodiments and accompanying drawings. It should be understood that even though embodiments are separately described, single features thereof may be combined to additional embodiments.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

One particular embodiment of the present invention is described with reference toFIGS. 1 to 9.

In this embodiment is illustrated high-current terminal fittings used e.g. for a power supply line of an electric vehicle, a hybrid vehicle or the like. As shown inFIG. 1, a connecting structure includes a pair of a male terminal10and a female terminal20connectable to each other.

The male terminal10is formed by press-working a conductive (particularly metal) plate with good electrical conductivity such as copper alloy and having a relatively large thickness (e.g. 1.5 mm). A tab13in the form of a tongue piece particularly with a substantially constant width is formed before a wire connection portion to be connected to an unillustrated wire, the wire connection portion particularly comprising a barrel11to be crimped, bent or folded and connected to an end of a core of the unillustrated insulated wire. A base end portion of the tab13is slightly widened, and a locking hole or recess12used to retain the male terminal10in a male housing (not shown) is formed.

Inclined surfaces15,16for guiding purpose are formed on or near a tip portion of the tab13. Particularly, the inclined surfaces15,16are provided substantially over the full width extension of the tab13(see e.g.FIG. 2). These are described in detail later.

On the other hand, the female terminal20is structured to have a built-in louver spring member30. As also shown inFIGS. 5 and 6, the female terminal20is likewise formed by press-working a conductive (particularly metal) plate with good electrical conductivity such as copper alloy and having a relatively large thickness (e.g. 1.5 mm), wherein a connecting tube portion23into which the tab13of the above male terminal10is to be at least partly inserted is formed before a wire connection portion to be connected to an unillustrated insulated wire, the wire connection portion comprising a barrel21to be crimped, bent or folded and connected to an end of a core of the insulated wire and the louver spring member30is at least partly housed or arranged in this connecting tube portion23. A locking hole or recess22used to retain the female terminal20housed in or arranged at a female housing (not shown) is formed in a lateral or bottom plate between the barrel21and the connecting tube portion23.

The connecting tube portion23particularly substantially is in the form of a flat rectangular tube having open front and/or rear ends, and an opening in the front surface serves as an entrance24through which the tab13is to be at least partly inserted. A louver insertion opening25through which the louver spring member30is to be at least partly inserted is formed in a lateral (e.g. right) wall of the connecting tube portion23when viewed from front.

The louver spring member30is formed by press-working a plate member made of a conductive material more resilient than the female terminal20such as copper beryllium. Roughly, the louver spring member30is such that front ends of two upper and lower contact plates31, which are arranged to substantially face each other while being spaced apart by a specified (predetermined or predeterminable) distance, in an inserting direction are connected by a coupling plate32and a receiving plate33for at least partly receiving the back end edge of the upper contact plate31is formed to stand up or project at an angle different from 0° or 180°, preferably substantially at a right angle from (particularly the back end edge of) the lower contact plate31, and/or particularly substantially has a flat rectangular or polygonal tube shape as a whole.

In each of the shown contact plates31, a plurality of (e.g. five) resilient contact pieces35(particularly supported at or near both ends) and substantially extending in a width direction, i.e. substantially an inserting direction ID of the tab13are formed at intervals. Accordingly, the both contact plates31particularly correspond to contact piece rows. Each resilient contact piece35particularly includes an inwardly projecting longitudinal central part, and a substantially flat part in a specified (predetermined or predeterminable) range of a projecting end serves as a contact portion36.

When viewed from front, the respective upper resilient contact pieces35are inclined toward right and, conversely, the respective lower resilient contact pieces35are inclined at the substantially same angle toward left. Vertical distances between the contact portions36of the upper and lower resilient contact pieces35are set to be shorter than the thickness of a flat portion14(whose upper and lower surfaces are parallel flat surfaces14A) of the tab13by a specified (predetermined or predeterminable) dimension.

One or more positioning pieces37are formed to project from opposite end portions of the back edge of the lower contact plate31, and one or more locking pieces38are formed to substantially extend obliquely outward respectively from (particularly substantially opposite end portions of) the front end edge(s) of the upper and/or lower contact plates31.

As shown inFIG. 5, one or more positioning holes or recesses26into which the respective positioning pieces37are to be at least partly inserted are formed at bottom end positions of the lateral (left) wall of the connecting tube portion23, and (particularly substantially opposite end portions of) the upper and/or lower opening edges of the louver insertion opening25particularly are hammered to project inwardly, thereby forming one or more locking portions27engageable with the one or more respective locking pieces38.

When the louver spring member30is at least partly inserted into the connecting tube portion23through the louver insertion hole25, the one or more positioning pieces37are located right before the one or more respective positioning holes26and the upper and/or lower locking pieces38are resiliently displaced at a final stage of insertion. When the louver spring member30is inserted to a proper position where the receiving plate33at the back side comes into contact with the lateral (e.g. left) wall, the positioning pieces37at least partly enter the positioning holes26and/or the locking pieces38pass the locking portions27to be engaged with the inner surfaces of the locking portions27while being at least partly restored. In this way, the louver spring member30is housed while being closely fitted into the connecting tube portion23of the female terminal20, positioned in a longitudinal direction of the connecting tube portion23, and retained in the inserting direction of the louver spring member30.

In a state where the louver spring member30is inserted at the proper position in this way, the contact portions36of the upper and lower resilient contact pieces35are located at positions substantially equidistant from the front edge of the connecting tube portion23and, as described above, the vertical distances between the upper and lower contact portions36are maintained to be shorter than the thickness of the flat portion14of the tab13by the specified (predetermined or predeterminable) dimension.

One or more, particularly a pair of (upper and/or lower) excessive deformation preventing portions28are formed at a position right before a housing space for the louver spring member30in the connecting tube portion23particularly by hammering upper and lower wall portions. Specifically, the upper and/or lower excessive deformation preventing portions28are respectively formed to be oblique over the substantially entire width particularly by hammering. A distance between the projecting edges of the upper and/or lower excessive deformation preventing portions28is slightly longer than the thickness of the flat portion14of the tab13to prevent the tab13from being obliquely inclined or twisted about an axis line, and surfaces of the both excessive deformation preventing portions28at the front side serve as guide surfaces28A, the spacing of which is widened toward the front.

One or more, particularly a pair of (upper and/or lower) excessive deformation preventing portions29are likewise formed at a position right behind the housing space for the louver spring member30in the connecting tube portion23particularly by hammering the upper and/or lower wall portions. Specifically, the upper excessive deformation preventing portion29is formed at a widthwise intermediate position, particularly by hammering a widthwise central part of the upper wall, to project downward or inward and the lower excessive deformation preventing portions29are formed at one or more positions, particularly by hammering the lower wall at two positions, i.e. at the opposite widthwise ends, to project upward or inward. Particularly, a total of three upper and lower excessive deformation preventing portions29cover substantially the entire width. A distance between the projecting ends of the upper and lower excessive deformation preventing portions29is likewise set to be slightly longer than the thickness of the flat portion14of the tab13to prevent shaking and twisting movements of the tab13.

In this embodiment, the shape of the tip portion of the tab13of the male terminal10is elaborated. In a specified (predetermined or predeterminable) area of the tip portion of the tab13, the width is gradually narrowed toward the tip (i.e. in inserting direction ID) and the upper and lower surfaces are formed into inclined surfaces15,16which gradually thin the tip portion toward the tip or distal end. Particularly, the upper and lower inclined surfaces15,16(as particular first and second inclined surfaces) are formed such that the positions of base end edges15A,16A connected to the substantially flat surfaces14A differ or are offset or displaced in forward and backward directions FBD (or along the inserting direction ID).

The both inclined surfaces15A,16A particularly are formed by being pressed and squashed between upper and lower molds of a press machine. Their shapes are specifically described with actual dimensions with reference toFIG. 4.

When thickness “a” of the tab13is more than about 1.2 mm (e.g. about 1.5 mm), the lower inclined surface16is formed to be inclined obliquely downwardly at an angle of less than about 10° (e.g. of “about 8°”) from a tip edge at a position spaced downwardly by a distance “b” (of less than about 0.5 mm, e.g. of about 0.4 mm) from a middle thickness position “o” on the tip surface (or distal end surface) of the tab13, and a horizontal distance “c” in forward and backward directions FBD from the tip edge to the base end edge16A connected to the flat surface14A is less than about 3 mm, e.g. about 2.5 mm at this time.

On the other hand, the upper inclined surface15is formed to be inclined obliquely upwardly likewise at an angle of less than about 10° (e.g. of “about 8°”) from a tip edge at a position spaced upwardly by a distance “d” (less than the distance “b” or of less than about 0.5 mm, e.g. of about 0.35 mm) from the middle thickness position “o” on the tip surface (or distal end surface) of the tab13, and a horizontal distance “e” in forward and backward directions FBD from the tip edge to the base end edge15A connected to the flat surface14A is more than the distance “c” or more than about 3 mm, e.g. 3.3 mm at this time. As a result, the base end edge15A of the upper inclined surface15particularly is at a position 0.8 mm behind the base end edge16A of the lower inclined surface16.

Further, the peripheral edge of the tip surface of the tab13particularly is rounded.

A design technique for making the positions of the base end edges15A,16A of the upper and lower inclined surfaces15,16described above different in forward and backward directions FBD is substantially the same as a design technique for forming the inclined surfaces15,16to be inclined obliquely upwardly and downwardly at the same angle of inclination from tip edges at positions spaced upwardly and downwardly by the same distance from a reference point displaced downwardly from the middle thickness position “o” on the tip surface of the tab13by a specified (predetermined or predeterminable) dimension as described below.

Particularly, in the case of forming the upper and lower inclined surfaces15,16when the tip of the tab13has a pointed shape with no thickness, the upper and lower inclined surfaces15,16are formed at the same angle of inclination to extend in obliquely upward and downward directions like from the tip edges at the above reference point.

As described in detail later, upon connecting the both terminal fittings10,20, the tab13of the male terminal10is at least partly inserted into the connecting tube portion23of the female terminal20and passes through or contacts the louver spring member30at least partly housed in the louver spring member30. When the tab13is at least partly inserted by a proper amount, an area17of the tip portion of the tab13where the inclined surfaces15,16are formed at least partly projects backward from the rear edge of the connecting tube portion23, i.e. the flat surfaces14A of the tab13face the excessive deformation preventing portions29on the rear edge of the connecting tube portion23as shown inFIG. 8(e).

In other words, the upper and lower inclined surfaces15,16are formed in the area17of the tip portion at least partly projecting from the rear edge of the connecting tube portion23of the female terminal20when the tab13of the male terminal10is inserted by the proper amount. This significance is as follows.

To reduce an overall level of the insertion force of the tab13, it is more effective if the inclination of the inclined surfaces15,16is more moderate and the lengths of the inclined surface15,16are longer. On the other hand, the length of the tip portion particularly projecting from the rear edge of the connecting tube portion23when the tab13is inserted by the proper amount is limited to avoid interference with the core of the wire connected to the wire connection portion, particularly to the barrel11by crimping. Here, if inclined surfaces are formed beyond the projecting area of the tip portion of the tab13, base end sides of the inclined surfaces are engaged with the excessive deformation preventing portions29provided on the rear edge of the connecting tube portion23, wherefore a function of preventing shaking and twisting movements of the tab13cannot be sufficiently fulfilled.

Accordingly, in this embodiment, the upper and lower inclined surfaces15,16particularly are formed only in the projecting area of the tip portion of the tab13while particularly being inclined as moderately as possible. Thus, the flat surfaces14of the tab13substantially face the excessive deformation preventing portions29at the rear side when the tab13is inserted by the proper amount, with the result that the function of preventing shaking and twisting movements of the tab13can be reliably fulfilled.

Next, functions of this embodiment are described.

The male terminal10and the female terminal20are respectively at least partly housed in the male and female housings after being connected to the ends of the wires (particularly by crimping), and the both terminal fittings10,20are connected as the two housings are connected. In other words, when being at least partly inserted into the connecting tube portion23of the female terminal20, the tab13of the male terminal10is guided into the louver spring member30at least partly housed in the connecting tube portion23and thrusts itself between the contact portions36at the opposite sides while resiliently displacing the upper and lower rows of the resilient contact pieces35. The tab13inserted by the proper amount is resiliently sandwiched between the contact portions36at the opposite sides, whereby the tab13and the louver spring member30, consequently the male and female terminal fittings10,20are electrically connected.

Here, a variation of the insertion force of the tab13of the male terminal10according to this embodiment is as follows. An experiment was conducted by inserting the tab13of the male terminal10into the connecting tube portion23of the female terminal20at a constant speed as shown inFIG. 7, measuring a load (insertion force) by a load cell in the process of further inserting the tab13after the tip of the tab13came into contact with the upper and lower contact portions36of the louver spring member30, and graphing (characteristic curve X) a relationship between an insertion amount (mm) of the tab13and an insertion force (N) as shown inFIG. 9.

A specific insertion process of the tab13of the male terminal10is described again with reference toFIG. 8. When being at least partly inserted into the connecting tube portion23, the tip of the tab13is inserted between the upper and lower rows of the resilient contact pieces35of the louver spring member30particularly while substantially being centered, so to speak, by being guided by the guide surfaces28A of the front excessive deformation preventing portions28. First, as shown inFIG. 8(a), the tip surface of the tab13comes into contact with the front edges of the contact portions36of the upper and lower resilient contact pieces35. As insertion is further continued from such a state, the both inclined surfaces15,16pass the contact portions36, whereby the tab13is pushed in while resiliently displacing the upper and lower resilient contact pieces35outwardly to gradually increase the insertion force.

Thereafter, as the base end edge16A of the lower inclined surface16passes the lower contact portions16earlier as shown inFIG. 8(b), a relatively small first peak P1(e.g. about 35 N) of the insertion force is reached. Subsequently, as the base end edge15A of the upper inclined surface15passes the upper contact portions36as shown inFIG. 8(c), a relatively small second peak P2(e.g. about 50 N) of the insertion force, though larger than the above first peak P1, is reached. Thereafter, as shown inFIG. 8(d), the upper and lower flat surfaces14A pass between the upper and lower contact portions36together, whereby the tab13is inserted with a lowered constant insertion force (e.g. about 25 N). The insertion is stopped when the tip area17of the tab13including the both inclined surfaces15,16particularly pass beyond the excessive deformation preventing portions29at the rear side as shown inFIG. 8(e).

Strictly speaking, the first and second peaks P1, P2are reached when the tab13is further inserted a predetermined distance after the contact of the base end edges16A,15A of both inclined surfaces16,15with the contact portions36. This is thought to be because the base end edges16A,15A pass the contact portions36at delayed timings due to a backward displacement of the louver spring member30or inclination of the resilient contact pieces35resulting from a housing tolerance of the louver spring member30.

As described above, according to this embodiment, the base end edges15A,16A of the respective inclined surfaces15,16connected to the substantially flat surfaces14A are formed at different positions in forward and backward directions FBD upon forming the inclined surfaces15,16on the upper and lower surfaces of the tip portion of the tab13of the male terminal10. Thus, upon inserting the tab13into the louver spring member30built in the female terminal20, the insertion force is distributed to have relatively small peaks (35N, 50N) at two positions. As compared with the case in the prior art where a large peak (70 N) is reached at one position, the insertion force is reduced. Therefore, the male and female terminal fittings10,20can be efficiently connected.

Further, a reduction of the insertion force is dealt with by a simple structural change of making the positions of the base end edges15A,16A of the respective upper and lower inclined surfaces15,16formed on the tip portion of the tab13different in forward and backward directions FBD and, hence, inexpensively dealt with.

Furthermore, since the both upper and lower inclined surfaces15,16particularly are formed only in the tip area17which particularly projects from the rear edge of the connecting tube portion23when the tab13is inserted by the proper amount, the flat surfaces14A of the tab13can substantially face the excessive deformation preventing portions29at the rear side when the tab13is inserted by the proper amount. Therefore, the function of preventing shaking and twisting movements of the tab13by the excessive deformation preventing portions29can be reliably fulfilled.

The invention is not limited to the above described and illustrated embodiment. For example, the following embodiments are also included in the technical scope of the present invention.

As the design technique for making the positions of the base end edges of the upper and lower inclined surfaces provided on the tip portion of the tab of the male terminal different in forward and backward directions, it may also possible to form the respective inclined surfaces to extend at different angles of inclination in obliquely upward and downward directions from tip edges at the middle thickness position of the tip surface of the tab or at positions spaced upwardly and downwardly from the middle thickness position by the same distance in addition to the above design technique illustrated in the above embodiment.

The positions of the respective base end edges of the upper and lower inclined surfaces of the tip portion of the tab may be set such that the lower base end edge is located behind the upper base end edge contrary to the above embodiment.

Numerical values indicating the positions of the tip edges of the respective inclined surfaces, the angle of inclination and the like illustrated in the above embodiment upon set the positions of the respective base end edges of the inclined surfaces of the tab are merely examples and suitable numerical values can be selected according to conditions such as the thickness of the tab.

Instead of housing the separate louver spring member in the connecting tube portion in the female terminal, each of the upper and lower wall portions of the connecting tube portion may be directly hammered to form a plurality of resilient contact pieces.

The numbers of the resilient contact pieces arranged on the respective upper and lower surfaces of the connecting tube portion are arbitrary, including one, and may differ between the upper and lower sides.

So long as the contact portions are located at substantially symmetrical positions at the upper and lower sides, the contact portions at either the upper or lower side may be fixed. Such a mode is also included in the technical range of the present invention.