Terminal crimped state testing method

Details Terminal crimped state testing method Terminal crimped state testing method

2002-02-22

2004-11-16

Deb, Anjan (Department: 2858)

Electricity: measuring and testing

Fault detecting in electric circuits and of electric components

Of individual circuit component or element

C072S021400, C029S748000, C029S861000

Reexamination Certificate

active

06819116

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a terminal crimping device for making a terminal-equipped wire which constitutes a wire harness, and more particularly to a terminal crimped state testing method for testing the crimped state of the terminal crimped by the terminal crimping device.
2. Description of the Related Art
In order to attach a terminal to an electric wire, a terminal crimping device has been used traditionally. As regards the electric wire, before the terminal is attached to it, the coated portion such as its end is removed to expose the core at the end. Namely, the electric wire is subjected to a scraping operation. The above terminal is provided with a core caulking leg for caulking the exposed core and an electric wire caulking leg for caulking the electric wire for each coated portion.
Traditionally, the terminal has been crimped on the electric wire in such a way that the core caulking leg and the electric wire caulking legs are caulked by the terminal crimping device. As the case may be, during the crimping step, poor crimping occurs. In order to detect the poor crimping of the crimped terminal, a poor crimping detecting device is employed.
This device tests the terminal-equipped wire whether or not it is poor by comparing the characteristic waveform obtained by sampling the characteristic values during the crimping step in time sequence with a reference waveform which is the characteristic waveform previously acquired for a good terminal-equipped wire. This is based on the fact that the characteristic value (load) during the abnormal crimping varies in a different manner from that during the normal crimping, i.e. the acquired characteristic curve is different from the reference waveform.
An example of the poor crimping detecting device is disclosed in JP-A-185457. This poor crimping detecting device tests the terminal-equipped wire whether it is good or not by comparing the integrated value over the time of sampling the characteristic curve with the integrated value of the reference waveform when the terminal-equipped wire is obtained from the normal crimping.
However, there is the degree of a difference in a waveform between the reference waveform and the characteristic waveform according to the degree of poorness. For example, if the electric wire is not scraped at a required position and the coated portion is caulked by the core caulking leg, the acquired characteristic waveform is much different from the reference waveform. Further, also where the core cut at a scraping position is caulked by the core caulking leg, the acquired characteristic waveform is much different from the reference waveform. In these cases where the degree of poorness is high, whether or not the crimped state of the crimping terminal is good or not can be easily decided. However, if there is a small difference between the reference waveform and the characteristic waveform, it is difficult to decide whether the crimped wire is good or not.
In the poor crimping detecting method-disclosed in JP-A-185457, severe poorness, which provides a large difference in the integrated value, can be easily detected. However, the poorness, which provides the characteristic waveform which is higher than the reference waveform at an initial time of the crimping and lower at a terminating time thereof, is difficult to create a difference in the integrated value. This makes it difficult to decide whether or not the crimped electric wire is good or not.
The decision whether or not the crimped state of the terminal is good is made during the step of crimping the terminal on the wire. This requires the time taken for the operation to be shortened.
As described above, the terminal is provided with the core caulking leg and the electric wire caulking leg. These legs are caulked simultaneously by the terminal crimping device. Therefore, if poor crimping occurs, it was difficult to identify a singular point.
SUMMARY OF THE INVENTION
An object of this invention is to provide a terminal crimped state detecting device which can stably decide whether or not the crimped state is good, surely detect slight poorness and shorten the time required for the decision.
In accordance with this invention, there is provided a method for testing the crimped state of a terminal on the basis of a waveform of the characteristic values obtained in the process of crimping the terminal on a core of an electric wire, comprising the steps of: acquiring a reference waveform from the characteristic waveform when the terminal has been crimped normally, and dividing the reference waveform into first plural reference waveform segments; dividing a characteristic waveform obtained when a terminal to be tested is crimped on the electric wire into a plural segments corresponding to those of the reference waveform; and deciding whether or not the crimped state of the terminal is good on the basis of the first reference waveform segments of the reference waveform and the waveform segments of the characteristic waveform.
In accordance with the method as described above, since the crimped state of the terminal is tested on the basis of a part of the characteristic waveform divided into waveform segments, whether or not the crimped state of the terminal is good is stably decided, thereby detecting the poor crimping precisely. Incidentally, a part of the characteristic waveform used for decision is preferably a region where a difference in the characteristic value is shown remarkably according to whether or not the crimped state is good.
On the basis of a part of the divided waveform segments of the characteristic waveform, whether or not the crimped state is good is decided. This shortens the time required for decision. Incidentally, the characteristic waveform preferably exhibits the load applied to the terminal when it is deformed during the crimping operation or the displacement of a crimping apparatus which is used for crimping. The reference waveform segment and sample waveform segment which are used for decision on whether or not the crimped state is good are preferably selected according to the terminal and electric wire.
In the method as described above, preferably, singular points of the reference waveform are previously acquired on the basis of increments of the reference waveform; and the first reference waveform segments contain the singular points.
In accordance with the method described above, since a part of the reference waveform segments which is used for decision contains singular points, in the case of the terminal in which the load value at a singular point and its vicinity varies according to whether or not the crimped state is good, the poor crimping can be detected more precisely. Incidentally, a part of the characteristic waveform used for decision is preferably a region where the characteristic value greatly varies according to whether or not the crimped state is good.
The singular points are preferably points where the pair of caulking legs of the crimping terminal are brought into contact with each other in the course during which they are deformed in the process of crimping by the terminal crimping device, where the pair of caulking legs of the crimping terminal start to come in contact with the core, and the load starts to rise, where in the course of caulking the core, the load turns from “rise” into “fall”, where the load reaches the peak and hence is not still applied.
In the method described above, preferably, singular points of the reference waveform are previously acquired on the basis of increments of the reference waveform; and the first reference waveform segments are located between the singular points.
In accordance with the method described above, since a part of the reference waveform segments used for decision is located between the singular points, in the case of the terminal where the easiness (or difficulty) of deformation, i.e. load value varies between the singular points according to whether the crimping state is good or not, the poor crimping can be surely

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