WO2014127818A1

WO2014127818A1 - Electrical female terminal

Info

Publication number: WO2014127818A1
Application number: PCT/EP2013/053414
Authority: WO
Inventors: Ould M.L. YAHYA; Dominique Rozet; Laurent Tristani; François CORMIER
Original assignee: Delphi International Operations Luxembourg S.À.R.L.
Priority date: 2013-02-21
Filing date: 2013-02-21
Publication date: 2014-08-28

Abstract

Electrical female terminal for automotive vehicle connectors. The female terminal 100) comprises a box-shaped cage (130) extending in aterminal insertion direction (D) between a front opening (132) and tail (120). The cage (130) comprises a bottomwall (136).The bottom wall (136) comprises an electrical contact area (170) whichis substantially flatover its width and substantially convex along its length(L).

Description

Electrical female terminal FIELD OF THE INVENTION

The invention relates to electrical terminals, and more particularly to electrical female terminals to be accommodated in connectors used for automotive vehicles. BACKGROUND OF THE INVENTION

For electrical connections in automotive vehicles, it is common to use male and female terminals made of metal such as copper, mounted in connector housings made of insulating material such as plastics.

These terminals are usually made of a folded and stamped sheet metal. In this document sheet metal means sheet of metal and such a sheet metal is not necessarily made of steel or any other iron alloy. It can be a copper alloy for instance.

The female terminal according to the invention is of the type comprising a rear tail for attaching (e.g. by crimping and/or soldering) an electrical lead and

a cage or plug-in portion for receiving and contacting the male terminal pin.

A male terminal pin can be inserted in the cage through a front opening. The rear tail is at the opposite longitudinal side of the cage, relatively to the front opening.

The cage extends in the insertion direction of the male terminal pin, between the front opening and the rear tail. The cage may have a box shape with a top wall, a bottom wall and two lateral walls. These walls extend substantially in the direction of insertion of the male terminal pin in the cage. In other words, the cage has a longitudinal direction corresponding to the insertion direction of the male terminal pin within it. Miniaturized female terminals have a cage adapted for receiving male pins having a cross-section less than 1 mm width, for instance 0.5mm width or even less than that.

It is known, for instance from the patent document EP2193577B1, to provide the top and bottom walls with electrical contacting areas through which the electrical contact with the male terminal pin is established. The electrical contacting area of a contact spring extending from the top wall and the electrical contacting area of the bottom wall lie directly opposite one another. Such electrical contacting areas take the form, for example, of an elevated portion: bump, bead, convex portion, rib or projection.

An aim of the invention consists in improving the electrical contact of female terminals, while keeping adapted insertion and retention forces.

This aim is at least partially achieved with a female terminal for automotive vehicle connectors, wherein the electrical contact area of the bottom wall is substantially flat over its width and substantially convex along its length.

Such a configuration is particularly adapted for male terminals having a pin with flat surfaces facing and contacting the electrical contacting areas of respectively the top and bottom walls. Indeed, for such male terminals, the flat width allows increasing the electrical contact surface, while the roundness of the electrical contact area perpendicularly to the insertion direction allows keeping an insertion force relatively low due to the fact that the friction surface between the pin and the contact area remains relatively limited along this direction. The best results, when using male terminal pins with a 0.25mm to 1mm width, are obtained when the curvature of the electrical contact area of the bottom wall is comprised between 0.6mm and 1.7mm, and more advantageously between 0.8mm and 1.3mm.

In terms of manufacturing, forming the round electrical contact area of the bottom wall is easier if an opening is cut out respectively on each side along its length.

The desired contact force is obtained thanks to a top wall comprising a double beam comprising two spring contact beams, one of these two spring beams extending longitudinally at least partially over the other. This can be obtained for example with two spring beams linked to the cage by a support portion and a joint which is folded over substantially 180 degrees and forms a latching tooth. This 180-degree-folded tooth extends from the edge of the support portion and is anchored in a lateral wall of the cage, so as to close and strengthen the cage. Advantageously, one of the two spring beams comprises a contact protrusion facing the electrical contact area of the bottom wall. This protrusion allows pressing about in the middle of the width of the male terminal pin. It provides a better control of the pressure on the male terminal pin over the electrical contact area of the bottom wall.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the invention appear from the following detailed description of one of its embodiments, given by way of non-limiting example, and with reference to the accompanying drawings.

In the drawings:

- Figure 1 represents schematically in perspective from above an embodiment of a terminal according to the invention;

- Figures 2 represents schematically in perspective from below the terminal of figure 1;

- Figure 3 represents is a front view of the terminal of figures 1 and 2;

- Figure 4 is a longitudinal cross section along the plane III-III of the terminal of figures 1, 2 and 3.

MORE DETAILED DESCRIPTION OF THE INVENTION

On the figures, the same references denote identical or similar elements.

Figure 1 shows an electrical female terminal 100. Such a terminal is intended to be accommodated in an electrical connector housing made of insulating material such as plastics (e.g. PBT, PA66, etc.).

The female terminal 100 is made of a single piece or sheet (blank) of an electrically conducting metal, such as copper, which is stamped, bent and folded.

The terminal 100 has a rear tail 120. On the figures the rear tail is only partially represented as its structure does not relate directly to the invention. The rear tail 120 has a crimping section for attaching an electrical lead. The terminal 100 also comprises a cage 130 for receiving a male terminal pin 200 (only the tip of this male terminal is represented on Fig. 1).

The cage 130 extends in the insertion direction D defined by the direction of mating or insertion of the male terminal pin 200 in the cage 130. Consequently, the cage 130 extends between a front end, here a front opening 132, through which the male terminal pin 200 is inserted, and the rear tail 120. The cage 130 has a box shape with a top wall 134, a bottom wall 136 and two lateral walls 138, 140 extending substantially in the insertion direction D of the male terminal pin 200 in the cage 130. The cage 130 is adapted for receiving male pins having a cross - section about 0.5mm width or less. For example, the external dimensions of the cage are 1mm width (from a lateral wall to the other) and 1.15mm height (from the top wall to the bottom wall). If the sheet metal is 0.15mm thick, the internal dimensions are about 0.7mm width and 0.85mm height. These are average values as the female terminals are manufactured within specified tolerance ranges.

As shown on Fig. 4, the top and bottom walls 134, 136 face each other and are essentially parallel to each other. The lateral walls 138, 140 also face each other and are essentially parallel to each other. The top and bottom walls 134, 136 are essentially perpendicular to the lateral walls 138, 140. The top wall 134 comprises at least a front portion having two layers of sheet metal.

One 138 of the lateral walls 138, 140 is continued above and bent over the top wall 134 for forming a reinforcement rib 142 extending longitudinally over at least a part of the cage 130. The rib 142 consequently lies on the top wall 134 of the cage 130. A locking lance 144 is cut out and bent upwardly so as to protrude from the rib 142. The locking lance 144 is intended to engage the connector housing for locking the terminal 100 in a housing cavity.

The other 140 lateral wall is bent for forming the top wall 134. A front portion of the top wall 134 corresponds to a support portion 154 comprising two layers 154a, 154b of sheet metal. The support portion 154 makes about a 90- degree angle with the lateral wall.

As shown on figure 3, the support portion 154 extends, in the front region of the cage, from the front opening 132 to two contact spring beams 150, 152. The support portion 154 of the two contact beams 150, 152 forms a portion of the top wall 134. Indeed, the cage comprises two contact spring beams 150, 152, which are linked to each other via the support portion 154. The contact spring beams 150, 152 extend from the support portion 154 to free ends. The support portion 154 is also folded at 180 degree, so that on the one hand, the support portion 154 comprises the two layers 154a, 154b, and on the other hand, one 150 of the spring beams 150, 152 partially covers the other one 152. The two layers of the support portion 154 are linked together by a 180-degree folded joint having a tooth-shape. This tooth 160 extends from the edge of the top wall 134 (see Fig. 1). The support portion 154 of the contact beams 150, 152 also comprises a window 156 which is cut out, in the support portion 154, substantially in front of the contact spring beam 150 (see Fig. 3). The window 156 opens on the top surface of the support portion 154. A rear tooth 164 also appears on the edge of the top wall 134 (see Fig. 1).

The rib 142 extends longitudinally over at least a part of the support portion 154. Another latch tooth 162 extends from the rib 142 (see Fig. 3). This latch tooth engages the window 156 for latching and closing the rib 142 over the cage 130.

The 180-degree-folded tooth 160 and the rear tooth 164, on the one hand, and the latch tooth 162 on the other hand, are inserted in respective cutouts (See also Figs. 1 and 4). With these two anchoring means (cutouts and teeth 147, 156, 160, 162), the cage 130 is securely closed and both the rib 142 and the locking lance 144 are strongly maintained on the cage 130.

The contact spring beams 150, 152 are also bent so as to protrude or bulge in the cage 130 (See Fig. 4). One 152 of these spring beams 150, 152 has a contact portion 158 designed to contact the male terminal pin 200 when inserted in the cage 130. The contact portion 158 comprises a bump 159 or protrusion pressing about in the middle of the width of the male terminal pin.

The double beam configuration is particularly advantageous when the sheet metal in which the female terminal is made is relatively thin (0.15mm). On the one hand, the two beams provide enough stiffness. But, on the other hand, the fact that they be linked to the cage only on one of their ends, prevents them from being too stiff. The configuration of the spring beams as described above allows achieving a normal force in a range of 1.5-3N, and more precisely about 2N. A contact force about 2N appears to be a good compromise for having a relatively low insertion force, but nevertheless keeping a pressure on the male terminal pin high enough (in the range of 250-400 MPa for copper terminals coated with a Tin layer in the range from 1 to 5μιη thick and preferably about 2μιη thick) for having a good electrical conduction. Facing the bump 159, the bottom wall has an electrical contact area 170 having substantially a partially cylindrical shape. This electrical contact area 170 is substantially plane over its width W and substantially convex along its length L.

The width W of the electrical contact area 170 is substantially the same as the contact beam one (see Fig. 4). The width W is slightly smaller than the internal width of the cage 130. There is a gap on both lateral sides of the electrical contact area 170, between the lateral walls 138, 140 of the cage 130 and the edges 171, 172 of the round contact area 170. As best seen on figure 2, these gaps correspond to openings 173, 174 cut out respectively on each side along the length L of the round contact area. These openings 173, 174 make easier the 90-degree folding of the lateral walls 138,140 relatively to the bottom wall 134.

The dimensions of the electrical contact area 170 are optimized in order, on the one hand, to decrease the electrical contact resistance between the pin 200 and the electrical contact area 170, and on the other hand, to have a contact pressure on the pin surface in the range from 250-400MPa, and preferentially equal to 300 MPa.

The width W of this electrical contact area 170 is substantially the same as the male terminal pin one. For male terminal pins 200 having a 0.5mm width, the width W is comprised between 0.3mm and 0.8 mm and more advantageously substantially equal to 0.6mm.

The length L of the electrical contact area is about 1.5mm. The height H is advantageously about 0.15mm.

As shown on Fig. 3, a circle can be inscribed over the major part of the convex rounded shape of the electrical contact area 170. This way a curvature r can be defined. Advantageously, the curvature r is comprised between 0.6 and 1,5 mm.

Figs. 5a and 5b show simulation results obtained for a male terminal pin made of copper C26000 (CuZn30) and a female terminal made of copper C70250 (K55). For this example, the pin 200 has a plane contact surface 0.5mm width. This contact surface is coated with an under-layer of Ni 1.5μιη thick, coated with a layer of Tin 3μιη thick. The female terminal 100 has a round contact surface 0.5mm width too. This contact surface is coated only with a layer of Tin 2μιη thick. Fig 5a diagram shows that if the curvature r increases above 1.5mm, the contact pressure between the electrical contact area 170 and the pin 200 falls below 250MPa, which is too low.

Fig 5b diagram shows that if the curvature r decreases below 0.6mm, the contact resistance between the electrical contact area 170 and the pin 200 is over 2mQ, which is too high.

These results show that the configuration of the terminal according to the invention allows obtaining a relatively low contact resistance (about 1.5mQ). This way the thermal performance of the female terminal is improved (more current can be conducted through the female terminal 100) and the risk of contact failure over time is decreased.

Claims

1. Female terminal for automotive vehicle connectors, comprising a box- shaped cage (130) made of a sheet of metal which is folded and stamped, the cage (130) extending in a terminal insertion direction (D) between a front opening (132) and a rear tail (120), the cage (130) having at least a top wall (134) and a bottom wall (136) facing each other between which a male terminal (200) inserted through the front opening (132) can be contacted, at least the bottom wall (136) having an electrical contact area (170) with a length (L) extending parallel to the insertion direction (D) and with a width (W) extending in a direction

perpendicular to the insertion direction (D),

characterized in that the electrical contact area (170) of the bottom wall (136) is substantially flat over its width (W) and substantially convex along its length (L).

2. Terminal according to claim 1, comprising an opening (173 or 174) respectively on each side (171, 172) along the length (L) of the electrical contact area (170) of the bottom wall (136).

3. Terminal according to claim 1 or claim 2, wherein the curvature (r) of the electrical contact area (170) of the bottom wall (136) is comprised between 0.6mm and 1.7mm, and more advantageously between 0.8mm and 1.3mm.

4. Terminal according to any preceding claim, comprising two spring contact beams (150, 152), one (150) of these two spring beams (150, 152) extending longitudinally at least partially over the other (152), the two spring beams (150, 152) being linked to the cage (130) by a support portion (154) and a joint which is folded over substantially 180 degrees.

5. Terminal according to claim 4, wherein the support portion (154) comprises a 180-degree-folded tooth (160) which is anchored in a lateral wall

6. Terminal according to claim 4 or 6, wherein one (152) of the two spring beams (150, 152) comprises a contact protrusion (159) facing the electrical contact area (170) of the bottom wall (136).

7. Electrical connector assembly comprising a female connector with at least one female terminal (170) having the technical features recited in at least one of the preceding claims and a male connector having at least one terminal with a pin (200) inserted in the female terminal cage (130) and comprising two flat surfaces contacting respectively the top wall (134) and the bottom wall (136).

8. Electrical connector assembly according to claim 7, wherein the width of the flat surfaces perpendicularly to the insertion direction (D) of the male terminal pin (200) in the female terminal cage (130) is substantially the same than the width (W) of the electrical contact area (170) of the bottom wall (136).