JPH07220771A - Pressure contact terminal - Google Patents

Abstract

PURPOSE:To cope with requirement of high reliability such as a signal wire branch of a multiplex transmission system by setting ratio of a slit sectional area to an electric wire conductor contact area in a prescribed range. CONSTITUTION:In a pressure contact terminal 3, a width W' of a slit 3a and a thickness (t) of the pressure contact terminal 3 are set so that area ratio Ac (contact area of electric wire conductor)/Ast (sectional area of slit) is obtained 1.3 to 2.8. Here, when the area ratio Ac/Ast is less than 1.3, thermal stress applied to an electric wire conductor can not be sufficiently reduced, and durability of a connector connecting part is not sufficient in a complex environment test. On the other hand, when the area ratio exceeds 2.8, the slit width is narrowed, to make manufacture difficult, and to also provide apprehension of cutting the electric wire conductor than electric wire is press fitted to the slit. Accordingly, the area ratio is set to 1.3 to 2.8. Further in the case that the area ratio is 2.0 or more, since durability of the connector connecting part is remarkably improved in the complex environment test, the area ratio is preferably set to 2.0 to 2.8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure contact terminal of a pressure contact connector used for branching a wire harness or the like.

[0002]

2. Description of the Related Art FIG. 5 is a perspective view showing an example of a pressure contact connector used for branching a wire harness, FIG. 6 is its assembly drawing, FIG. 7 is a sectional view of the pressure contact connector, and FIG. 8 is a conventional pressure contact terminal. It is a schematic diagram which shows the connection state of an electric wire. The housing 1 is formed of, for example, an insulating material such as nylon, and the housing 1 is provided with a pressure contact terminal attachment portion 1b into which one or a plurality (two in the figure) of pressure contact terminals 3 are press-fitted. . The pressure contact terminal 3 is a flat plate-shaped member formed of a conductor such as brass. The pressure contact terminal 3 has two slits 3a whose width is set to be slightly smaller than the diameter of the electric wire 4 and are separated from each other. It is provided. Further, lock holes 1a for fixing the connector cover 2 are provided on both sides of the housing 1 in the longitudinal direction.

Like the housing 1, the connector cover 2 is made of an insulating material such as nylon, and has lock levers 2a extending downwards on both sides in the longitudinal direction thereof. The connector cover 2 is fixed to the housing 1 by inserting the lock lever 2a into the lock hole 1a of the housing 1 and engaging the tip projection of the lock lever 2a with the end of the lock hole 1a. In addition,
The cover 2 is provided with a protrusion 2b at a portion aligned with each slit 3a of the press contact terminal 3.

Next, a method for pressure-connecting the electric wire and the pressure-contact terminal in the conventional pressure-contact connector thus constructed will be described. First, the electric wire 4 is placed on the upper portion of each slit 3a of the pressure contact terminal 3 attached to the housing 1. Then, the lock lever 2a of the cover 2 is inserted into the lock hole 1a of the housing 1, and the cover 2 is pressed against the housing 1 so that the tip protrusion of the lock lever 2a is locked to the end of the lock hole 1a. Fix 2 and.
In the process of attaching the cover, as shown in FIG. 8, the protrusion 2b of the cover 2 presses the electric wire 4, whereby the electric wire 4 is press-fitted into the slit 3a of the press contact terminal 3, and the wall of the slit 3a insulates the electric wire 4. A cut is provided in the coating layer,
Through this notch, the pressure contact terminal 3 and the conductor wire 5 of the electric wire 4
And are electrically connected. That is, 2 via the pressure contact terminal 3.
The electric wires 4 of the book are electrically connected to each other. In this way, the wire harness can be easily branched.

[0005]

However, the pressure contact connector incorporating the above-described conventional pressure contact terminal has a problem that the durability of the connector connecting portion in the composite environment test is low. The composite environmental test is to apply a current to the electric wire connected to the pressure contact connector, simultaneously apply vibration and heat cycle to the pressure contact connector, and measure the time until the voltage drop reaches a predetermined value (hereinafter referred to as life). It is something to measure. The frequency of vibration in this composite environment test is 11.7 to 200 Hz (sweep), and the acceleration is 2
The heat cycle was 1.6 m / sec ² , and the heat cycle was held at a temperature of 80 ° C. for 16 hours, then lowered to −30 ° C. over 2 hours, and held at this temperature for 4 hours, as shown in FIG. Then, the temperature is raised to 80 ° C. over 2 hours, and this is repeated as one heat cycle. Although the pressure contact connector used for general applications does not require so much durability of the connector connection part in the composite environment test,
For example, a pressure contact connector used for branching a signal line of a multiplex transmission system is required to have high reliability, and it is necessary that a connector connection portion in a composite environment test has a long life of 2000 hours or more. The multiplex transmission system
Instead of wiring a large number of electric wires to transmit a plurality of information, for example, a large amount of information is transmitted only by two electric wires (twisted pair wires). For example, its impact is widespread. Therefore, the pressure contact terminal of the connector used for branching the signal line of the multiplex communication system is required to have higher reliability than the pressure contact terminal of the connector used for branching the normal wiring.

The present invention has been made in view of the above problems, and is suitable for a pressure-welded connector used in applications where the connector connection portion in a composite environment test has high durability and particularly high reliability is required. It is intended to provide a pressure contact terminal.

[0007]

A pressure contact terminal according to the present invention is a pressure contact terminal provided with a slit into which an electric wire is press-fitted, in the depth direction of the slit when the electric wire is press-fitted into the slit. the cross-sectional area of the slit in the orthogonal plane a _SL, the contact area between the conductor of the electric wire as a _C, and characterized in that the area ratio a _C / a _SL is set to 1.3 to 2.8 To do.

[0008]

In the composite environment test, the pressure contact terminal and the electric wire conductor are thermally expanded and contracted by the heat cycle, and the thermal stress is repeatedly applied to the electric wire conductor. It is considered that thermal fatigue of the electric wire conductor due to the repetition of this thermal stress causes a voltage drop. Therefore, by reducing the thermal stress applied to the wire conductor, it is possible to improve the durability of the connector connecting portion in the composite environment test. The thermal stress applied to the wire conductor is, as will be described later, the contact area A _C between the wire conductor and the pressure contact terminal and the cross-sectional area A _{SL of the} slit.
It becomes a function of the area ratio A _C / A _SL . Therefore, the area ratio A
By setting the slit width or the like so that _C / A _SL becomes a predetermined value or more, the thermal stress applied to the electric wire conductor can be reduced, and the durability in the composite environment test can be improved.

In the present invention, the area ratio A _C / A _{SL is set} to 1.3 to 2.8. When the area ratio A _C / A _SL is less than 1.3, the thermal stress applied to the electric wire conductor cannot be sufficiently reduced, and the durability of the connector connection portion in the composite environment test is not sufficient. On the other hand, if the area ratio A _C / A _SL exceeds 2.8, the slit width becomes narrow, manufacturing becomes difficult, and the wire conductor may be cut when the wire is pressed into the slit. Therefore, the area ratio A _C / A
_SL should be 1.3 to 2.8. The area ratio A _C / A _SL
When the value is 2.0 or more, the durability of the connector connecting portion in the composite environment test is significantly improved. Therefore, the area ratio A _C
Even more preferably, / A _SL is from 2.0 to 2.8.

[0010]

The present invention will be described in more detail below. As shown in FIG. 1 (a), the slit 3a of the pressure contact terminal 3 is formed.
When considering the thermal stress applied to the wire conductor 5 press-fitted into the wire conductor, 1/2 of the interval between the slits 3a is l _1a , 1/2 of the interval h between the slit 3a and the terminal end is l _1b , and the wire conductor is 5
And when the distance between the slit 3a bottom and l _b, FIG. 1 (b) the connection between the wire conductor 5 and the press-connecting terminal 3, replaced by simple calculation model of the joint between the rod and the beam, as shown in (c) be able to. Calculation of the thermal stress σ caused by the temperature difference ΔT in the heat cycle of the composite environment test in this calculation model gives the following Expression 1.

[0011]

## EQU1 ## σ = {k _b · k ₁ · k ₂ (δl ₁ + δl ₂ )} / {(k ₁ · k ₂ + k _b · k ₂ + k _b · k ₁ ) A} where k ₁ = A · E ₁ / l ₁ ; spring constant of rod 1 k ₂ = A · E ₂ / l ₂ ; spring constant of rod 2 k _b = E ₁ · t · h ³ / (4l _b ³ ); spring constant of beam δl ₁ = Α ₁ · ΔT · l ₁ ; Elongation of rod 1 δl ₂ = α ₂ · ΔT · l ₂ ; Elongation of rod 2 E ₁ , α ₁ ; Young's modulus and linear expansion coefficient of terminal material E ₂ , α ₂ ; Electric wire Young's modulus and linear expansion coefficient of the conductor l ₁ ; length of the rod 1 (terminal) (l ₁ = l _1a + l _1b ) l ₂ ; length of the rod 2 (electric wire conductor) (l ₂ = W ′) t; beam width (thickness of the terminal) h of; beam height l _b; beam length W; slit width of the press prior to the terminal W '; slit width of the terminal after pressure [Delta] T; temperature rise a; bar 1 and bar 2 of cross-sectional area _{(a = a C / 2)} a C; contact surface between the terminal and the wire conductors Transforming this equation 1, as shown in Equation 2 below.

[0012]

## EQU2 ## σ = {k _b · k ₁ (δl ₁ / W ′ + α ₂ · ΔT)} / {(1/2) βt (k ₁ + k _b ) + (k _b · k ₁ ) /
E ₂ } However, β = A _C / A _{SL From} this equation 2, it is understood that the thermal stress σ can be expressed as a function of β (that is, A _C / A _SL ).

On the other hand, it has been known experimentally that the relationship between the number N of heat cycles until reaching the end of life and the thermal stress σ can be expressed as shown in the following mathematical formula 3 (Langer's formula).

[0014]

## EQU3 ## σ = {E ₂ / (4N ^1/2 )} · ln {1 / (1-
φ)} + σ _w where σ _{w is} the tensile / compressive fatigue limit of the wire conductor φ is the static tensile breakage of the wire conductor

The heat cycle in the composite environment test is
Since one cycle is 24 hours, the average life μ of the connector connection portion in the composite environment test can be expressed by the following formula 4.

[0016]

(4) μ = 24 × N

From these equations 2, 3 and 4, it can be seen that the average life μ of the connector connecting portion is a function of the area ratio A _C / A _SL . Therefore, by setting the slit width and the like so that the area ratio A _C / A _SL becomes a predetermined value or more, the average life of the connector connecting portion in the composite environment test can be made a predetermined time or more. In the present invention, the area ratio A
_C / A _SL should be 1.3 or more. Thereby, the average life of the connector connecting portion in the composite environment test can be 2000 hours or more. Further, the area ratio A _C / A _SL is 2.
By setting it to 0 or more, the average life of the connector connecting portion can be 3000 hours or more. The area ratio A
_{When C} / A _SL exceeds 2.8, the width of the slit becomes narrow, making it difficult to form the slit, and the electric wire conductor is easily cut when the electric wire is press-fitted into the slit.
Therefore, the area ratio A _C / A _SL needs to be 2.8 or less.

Next, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 2 is a perspective view showing a press contact terminal according to an embodiment of the present invention. Pressure contact terminal 3 according to the present embodiment
The width and thickness of the slit 3a are set so that the area ratio A _C / A _SL is 1.3 to 2.8. In this case, A _SL has the width of the slit a after press fitting the electric wire 4 in the slit 3a as W ′ and the thickness of the press contact terminal 3 as t.
A _SL = W ′ × t. In addition, the contact area A _C between the wire conductor and the terminal is, as shown in FIG.
Of the contact length L ₁ , L ₂ , L ₃ , L ₄ of the pressure contact terminal 3 and the thickness t of the pressure contact terminal 3, that is, A _C = (L ₁ +
L ₂ + L ₃ + L ₄ ) × t.

The results of actually manufacturing the press contact terminal according to the present embodiment and examining the average life of the connector connecting portion in the composite environment test will be described below in comparison with the conventional example. The pressure contact terminals having the materials, plate thicknesses and slit widths shown in Table 1 below were manufactured, and these pressure contact terminals were mounted in the housing 1 as shown in FIG. Then, the width of the slit after the wire pressure contact and the contact area between the pressure contact terminal and the wire conductor were examined. As a conventional example, the plate thickness, slit width, and contact area between the pressure contact terminal and the wire conductor of the conventional pressure contact terminal were examined. The results are also shown in Table 1.

A pressure-bonded connector incorporating these pressure-bonded terminals was subjected to a composite environment test to examine the average life of the connector connection portion. The results are shown in Table 2 below together with the area ratio A _C / A _SL . The composite environment test was conducted under the above-mentioned conditions (Fig. 9).
In the heat cycle shown in, the vibration frequency is 11.7 to 2
It was carried out at 00 Hz and an acceleration of 21.6 m / sec ² ). Further, the number of samples was set to 20 for each terminal.

[0021]

[Table 1]

[0022]

[Table 2]

As is clear from Table 2, in the conventional pressure contact terminals, the area ratio A _C / A _SL is 1.2 or less, and the average life of the connector connecting portion in the composite environment test is 1452 hours or less. And short. In the case of a pressure contact connector used for general purposes, use of these pressure contact terminals does not cause any problem, but reliability is not satisfactory as the pressure contact terminal of the pressure contact connector used in a multiplex transmission system or the like. On the other hand, all the press-connecting connectors incorporating the press-connecting terminals of Examples 1 to 5 have an average life of 2023 hours or more, and particularly, the area ratio A _C / A _SL is 2.13 or more. Each has an extremely good durability with an average life of 3425 hours or more.

Next, pressure contact terminals having different area ratios A _C / A _SL from each other were further manufactured, and a composite environment test was conducted on the pressure contact connectors incorporating these pressure contact terminals. FIG. 4 is a graph showing the relationship between the two, with the horizontal axis representing the area ratio _AC / _ASL and the vertical axis representing the average life of the connector connection portion in the composite environment test. As is apparent from FIG. 4, by setting the area ratio A _C / A _SL to be 1.3 or more, the average life can be 2000 hours or more, and the area ratio A _C / A
By setting A _SL to 2.0 or more, the average life is 300
It can be 0 hours or more.

[0025]

As described above, in the press contact terminal according to the present invention, the area ratio A _C / A _SL is set within a predetermined range, so that the life of the connector connecting portion in the composite environment test can be improved. it can. Therefore, the pressure contact terminal according to the present invention is extremely suitable as a pressure contact terminal for a pressure contact connector used in applications requiring high reliability such as branching of signal lines in a multiplex transmission system.

[Brief description of drawings]

FIG. 1 (a) is a schematic diagram showing a connection between a pressure contact terminal and an electric wire conductor, and FIG. 1 (b) is a schematic diagram showing a joint between a bar and a beam showing a thermal stress equivalent to the thermal stress at the connection portion. (C)
FIG. 3 is a schematic diagram showing a calculation model of the thermal stress.

FIG. 2 is a perspective view showing a press contact terminal according to an embodiment of the present invention.

FIG. 3 is a schematic diagram showing a contact length between a conductor wire and a press contact terminal.

FIG. 4 is a graph showing a relationship between an area ratio A _C / A _SL and an average life of a connector connecting portion in a composite environment test.

FIG. 5 is a perspective view showing an example of a press-connecting connector used for branching a wire harness.

FIG. 6 is an assembly drawing of the same.

FIG. 7 is a sectional view of the same.

FIG. 8 is a schematic diagram showing a connection state between a pressure contact terminal and an electric wire.

FIG. 9 is a diagram showing a heat cycle in a composite environment test.

[Explanation of symbols]

 1; housing 2; connector cover 2a; lock lever 2b; protrusion 3; pressure contact terminal 3a; slit 4; electric wire 5; conductor wire

Claims (2)

[Claims] 1. A press-contact terminal provided with a slit into which an electric wire is press-fitted, wherein a cross-sectional area of the slit in a plane orthogonal to a depth direction of the slit is A _{SL when the} electric wire is press-fitted into the slit. , press contact terminals, characterized in that the contact area between the conductor of the electric wire as a _C, the area ratio a _C / a _SL is set to 1.3 to 2.8. 2. The area ratio A _C / A _SL is 2.0 to 2.
The pressure contact terminal according to claim 1, wherein the pressure contact terminal is set to 8.