EP2173015B1 - Method for calculating the quality of a crimp connection between a conductor and a contact - Google Patents

Description

Technical area

The invention relates to a method for determining the quality of a crimp connection between a conductor and a contact, wherein a crimping device generates a crimping force by means of which the contact with the conductor are electrically and mechanically non-detachably connectable.

The term "crimping" has been introduced internationally and defined in terms of standardization. In practice, however, terms such as pressing, squeezing, striking or piecing are used. Crimping is the production of a non-releasable electrical and mechanical connection between a conductor and a contact. During crimping, the material to be joined of the crimp contact and the conductor is plastically, permanently deformed. In this case, if present, poorly conducting surface layers are broken, which favors the electrical conductivities. Correct crimping also prevents the penetration of corrosive media even under difficult operating conditions such as temperature changes or vibration.

The aim of the crimping is to produce a good mechanical and electrical connection, which remains qualitatively unchanged in the long run.

For crimping, contact specific crimp tools are used with a fixed crimp anvil down and vertically displaceable crimp punches above (see FIG. 1 to FIG. 3 ). In the crimping tool, the crimping die for the conductor crimp and the crimping die for the insulation crimp are mounted, which can usually be adjusted independently of one another in the vertical direction on the conductor diameter or insulation diameter by means of raster disks with different height cams. These settings directly affect the quality of the crimp connection.

For open crimp contacts (see FIG. 4 and FIG. 5 ), the cable feed takes place above the contact. The previously stripped conductor is usually positioned by machines simultaneously in the radial and axial direction relative to the contact correctly for the crimping process. Due to the downward movement of the crimping die, the conductor is first lowered via a mechanism into the upwardly opened conductor and insulation crimping claws, after which the actual crimping operation begins with forming the flaps corresponding to the crimping die shapes. After the stroke of the crimping die, the crimp has the desired compression molding (see FIG. 5 ), which in turn depends on the contact plate used, the conductor cross-section, the copper of the conductor and the stripping. When the contacts are closed, the conductor must be moved axially into the crimped area of the contact after the radial alignment.

A sectional view of a faultless crimp connection shows the original single round Strands of the conductor compact to polygons pressed against each other. The inner surface in the crimp area of the contact shows deformations of the contact points of the individual strands.

An important parameter for the degree of crimping of the conductor crimp is the crimp compression ratio CCR, defined as the ratio of the cross-sectional area of the crimped conductor crimp CCS to the sum of the cross-sectional areas of the conductor WCS and the contact portion TCS before deformation. $$\mathit{CCR}=\frac{\mathit{CCS}}{\mathit{WCS}+\mathit{TCS}}\cdot \mathit{100}\%$$

A quality goal is to comply with a specific Crimp Compression Ratio CCR, regardless of which wire cross section is processed. This is achieved by specifying the appropriate crimp height for each conductor cross-section.

For conductor crimp, all individual strands must be included. At the front end of the conductor crimps, the individual strands have to protrude about 0.5 mm depending on the cross section and must not disappear in the crimp. The conductor and conductor insulation must be visible in the window between the conductor crimp and the insulation crimp. The insulation crimp must enclose the insulation without penetrating it.

Important criteria for the assessment of a crimp connection are the crimp shape, the crimp height as Measure of crimp compression ratio and conductor pull-out strength. However, these criteria are only suitable when setting up the crimping machine and during sampling production. In order to meet today's quality requirements for all crimp connections, means must be available which can record, evaluate and store crimp data via each crimp connection during the crimping process and can influence machine data in a results-oriented manner. To evaluate the crimp connection (without mechanical destruction of the crimped connection), the crimping force is set in relation to the crimping path or the crimping time. With appropriate evaluation of the crimp data, the quality of a crimp connection can be reliably assessed.

A method or device for assessing the quality of a crimped connection must detect crimped errors such as false insulation crimp height, wrong conductor crimp height, untreated strands in the conductor crimp, incorrect or no stripping length, incorrect insertion depth or strands cut off during stripping and generate corresponding error messages.

State of the art

First, from the prior art EP 0 902 509 B1 a crimping device with a crimping die is known, with which a contact with a conductor can be connected. The crimping device comprises a force sensor arranged above the crimping die in order to determine the crimping force.

To determine the quality of the crimp connection, the crimp force curve is recorded and divided into several zones. To determine the width of the first and second zones, the fourth zone width is multiplied by a factor between 0 and 2. The highest point on the reference crimp curve is normalized to 100%. The third zone width is then determined by the two 90% points on the reference crimp curve.

From the registration EP 0 460 441 For example, a method for detecting missing strands or crimped conductor insulation in a crimp connection has become known from the crimp force characteristic. During a crimping process value pairs consisting of crimping force and position of the crimping die are measured and stored. The during the production of a crimped connection measured value pairs result in the crimp force curve of the crimping process with the crimping force as a function of the position of the crimping die. The curve section with a strong increase in force is linearized and a point determined from the average of the minimum and maximum crimping force. The point is compared to a reference value. If the point is within a predetermined deviation from the reference value, the crimp connection is of acceptable quality. When evaluating the Crimpkraftverlaufes the crimping and the maximum crimping force is also taken into account. If the maximum crimp force deviates excessively from a reference value, the crimped connection is rejected as unusable. The point in the curve section with a strong increase in force and the maximum crimping force provide information about missing strands or about crimped conductor insulation in the crimped connection.

In a standard crimping press, a force sensor detects the force during the crimping process, which is stored in digital form as a force-dependent curve. This is compared with a reference curve. Depending on the size of the deviation from the reference, the type of crimping error is determined.

A disadvantage of this method is that despite a large computer, memory and computational effort no differentiated statement about the quality of the crimp connection is possible.

Presentation of the invention

The invention aims to remedy this situation. An object of the invention is to provide a method and a device in which the abovementioned disadvantages are avoided and which lead to improved quality assurance.

The object is achieved according to a first aspect of the invention by a method having the features according to claim 1.

In addition, the object is achieved according to a second aspect of the invention by a device having the features according to the patent claim 11.

According to the first aspect, there is provided a method of determining the quality of a crimp connection between a conductor and a contact. In this method, a crimping force is applied to the conductor and the contact by means of a crimping device, the crimping force curve resulting during the crimping is determined, and a compression area lying below a reference crimping force curve is determined.

According to the invention, in the method further, the crimping force curve and the reference crimping force curve are divided into a plurality of zones, the division being made taking into consideration the size of the compression area, and at least one further area under the crimping force curve is determined, the area being a measure of the quality of the crimping connection is.

According to the second aspect, a crimping device for crimping a conductor and a contact is provided. The crimping means comprises a crimping die, a linear sensor for detecting the position of the crimping die, a force sensor for detecting the crimping force, and an evaluation unit connected to the linear sensor and the force sensor.

According to the invention, the evaluation unit is designed and operable such that the quality of a crimped connection can be determined by means of the method according to the first aspect of the invention.

The advantages achieved by the invention are essentially to be seen in the fact that with the better resolution of the error an increase in quality is possible that with the more sensitive fault diagnosis less rejects and that subsequent error, for example a breakdown of a passenger car due to loose contact in a plug connection can be avoided.

Advantageous developments of the invention will become apparent from the features indicated in the dependent claims.

Brief description of the drawings

Figur 1

zeigt ein Kabel und einen Kontakt vor dem Crimpen.

Figur 2

zeigt das Kabel und den Kontakt während des Crimpens.

Figur 3

zeigt das Kabel und den Kontakt nach dem Crimpen.

Figur 4

zeigt eine Crimpverbindung zwischen dem Leiter und einem Kontakt.

Figur 5

zeigt die Crimpverbindung im Querschnitt.

Figur 6a

zeigt einen Kontakt und einen Leiter vor dem Crimpen im Querschnitt.

Figur 6b

zeigt den Kontakt und den Leiter nach dem Crimpen im Querschnitt.

Figur 7

zeigt eine Crimppresse in einer dreidimensionalen Ansicht.

Figur 8

zeigt ein Blockdiagramm einer ersten Ausführungsform einer Steuerung zusammen mit einem Teil der Crimppresse.

Figur 9

zeigt ein Blockdiagramm einer zweiten Ausführungsform der Steuerung zusammen mit einem Teil der Crimppresse.

Figur 10a

zeigt eine Kraft-Winkel-Kurve, die mit der Steuerung gemäss Figur 9 aufgenommen wurde.

Figur 10b

zeigt eine aus der Kraft-Winkel-Kurve gemäss Figur 10 a) transformierte Kraft-Weg-Kurve.

Figur 11

zeigt ein Diagramm, in dem der Verlauf der auf 1 normalisierten Crimpkraft in Abhängigkeit vom Weg dargestellt ist mit einem Parameter csiA, der den Beginn der Kompressionsphase kennzeichnet.

Figur 12

zeigt den gleichen Verlauf der Crimpkraft wie in Figur 11, allerdings mit einem Parameter csiB, der die Breite der Dekompressionsphase kennzeichnet.

Figur 13

zeigt den gleichen Verlauf der Crimpkraft wie in Figur 11, allerdings mit einem Parameter csiC, der die Fläche der Kompression kennzeichnet.

Figur 14

zeigt einen Verlauf der Crimpkraft, welcher in zwei Auswertezonen Ziso und Zmc unterteilt ist.

Figur 15

zeigt den Kraft-Weg-Verlauf für einen fehlerlosen Referenzcrimp R, einen fehlerhaften Crimp C1 mit 10% fehlenden Litzen und einen fehlerhaften Crimp C2 mit eingecrimpter Isolation.

Figur 16a

zeigt eine Verteilungsdichtefunktion für den Fall, dass die Gewichtungsfaktoren S1, S2 und S3 gleich gross sind.

Figur 16b

zeigt eine Verteilungsdichtefunktion für den Fall, dass die Gewichtungsfaktoren S1, S2 und S3 optimal gewählt wurden, so dass die Streuung der Rmc Werte minimal ist.

In the following the invention with several non-limiting embodiments will be explained with reference to several figures.

FIG. 1

shows a cable and a contact before crimping.

FIG. 2

shows the cable and contact during crimping.

FIG. 3

shows the cable and contact after crimping.

FIG. 4

shows a crimp connection between the conductor and a contact.

FIG. 5

shows the crimp in cross section.

FIG. 6a

shows a contact and a conductor before crimping in cross-section.

FIG. 6b

shows the contact and the conductor after crimping in cross section.

FIG. 7

shows a crimping press in a three-dimensional view.

FIG. 8

shows a block diagram of a first embodiment of a controller together with a part of the crimping press.

FIG. 9

shows a block diagram of a second embodiment of the controller together with a part of the crimping press.

FIG. 10a

shows a force-angle curve with the controller according to FIG. 9 has been recorded.

FIG. 10b

shows one from the force-angle curve according to FIG. 10 a) transformed force-displacement curve.

FIG. 11

shows a diagram in which the course of the normalized to 1 crimping force as a function of the path is shown with a parameter csiA, which marks the beginning of the compression phase.

FIG. 12

shows the same course of the crimping force as in FIG. 11 , but with a parameter csiB that indicates the width of the decompression phase.

FIG. 13

shows the same course of the crimping force as in FIG. 11 , but with a parameter csiC, which identifies the area of the compression.

FIG. 14

shows a course of the crimping force, which is divided into two evaluation zones Ziso and Zmc.

FIG. 15

shows the force-displacement curve for a faultless reference crimp R, a faulty crimp C1 with 10% missing strands and a faulty crimp C2 with crimped insulation.

FIG. 16a

shows a distribution density function in the case that the weighting factors S1, S2 and S3 are equal.

FIG. 16b

shows a distribution density function in the case that the weighting factors S1, S2 and S3 have been optimally selected, so that the dispersion of the Rmc values is minimal.

Ways to carry out the invention

The FIGS. 1 to 3 show a crimping process in which one end of a cable 1, from which protrudes a piece of conductor, is connected to a contact 2. An open crimping zone 3 of the contact 2 has a first double lug 4 for the insulation crimp 5 and a second double lug 6 for a conductor crimp 7. FIG. 1 shows Crimpstempel 8, 9 in the top dead center. The end of the conductor insulation lies in the first double lug 4 and the stripped cable piece lies in the second double lug 6. As in FIG. 2 will be shown at Lowering the crimping dies 8, 9, the double flaps 4, 6 by means of wedge-shaped r recesses 10, which are located in the Crimpstempeln 8, 9, pressed against each other. The edition is an anvil 9.1. A dome-shaped upper end of the recess 10 gives the double lug 4, 6 together with the conductor insulation 11 and the conductor the final shape. FIG. 3 shows the finished crimp connection with the insulation crimp 5, in which the first double lug 4 is pressed around the conductor insulation 11, and with the conductor crimp 7, in which the second double lug 6 is pressed around the conductor.

FIG. 4 shows a faultless crimped connection, in which in a window 13, the insulation 11 of the cable 1 and the individual strands of the conductor 12 are visible. At the contact-side end of the conductor crimps 7, the individual strands are visible again.

FIG. 5 shows a good crimp connection 7 in cross section. After the stroke of the crimping dies 8, 9, the crimp 7 has the desired compression molding.

FIG. 6a shows a contact and a conductor before crimping in cross-section.

FIG. 6b shows the contact and the conductor after crimping in cross section.

FIG. 7 shows a possible embodiment of a crimping press in a three-dimensional view. The crimping press comprises a stand 14 which is in FIG. 7 partly broken up. On the stator 14, a motor 15 is arranged with a gear 16. In addition are arranged on the stand 14 first guides 17 on which a ram 18 is guided. A driven by the gear 16 shaft 19 has at one end an eccentric pin. The ram 18 comprises a guided in the first guides 17 slider 22 and a tool holder 23 with force sensor 23.1. The slider 22 is in loose connection with the eccentric pin, wherein the rotational movement of the eccentric pin is converted into a linear movement of the slider 22. The position of the slider 22 and thus the ram 18 is detected with a linear sensor 20. The maximum stroke of the slider 22 is determined by the top dead center and the bottom dead center of the eccentric pin 21 (FIGS. 8 and 9 ) certainly. The tool holder 23 usually actuates the crimping tool 8, 9 (FIG. Fig. 1 ), which produces the crimped connection together with an anvil 9.1 belonging to the crimping tool.

FIG. 8 shows in a block diagram a first embodiment of a controller 28 together with parts of in FIG. 7 shown crimping press. The controller 28 is designed as a control loop and is used to control the crimping press. The control loop includes a motor controller 40, the motor 15, and an angle sensor 45 for detecting the rotational angle of the motor shaft. The crimping movement for a stroke is regulated by the motor controller 40 according to a predetermined speed-angle profile. The rotational movement is transmitted from the motor 15 to the gear 16 and then to the shaft 19, at one end of the eccentric pin 21 is arranged. The eccentric pin 21 puts the slider 22 of the ram 18 in a linear movement.

The position of the slider 22 of the ram 18 is detected by the linear sensor 20. The linear sensor 20 comprises a scale with equidistant (distance .DELTA.s) arranged position markings, which are attached to the slider 22 of the ram 18. In addition, the linear sensor 20 includes a stationary read head. The linear sensor 20 generates an electrical voltage pulse 48 each time one of the position markers passes the read head.

wobei g der Verstärkungsfaktor des Spannungsverstärkers 46 ist.
Zudem ist ein Entladeschalter 44 vorgesehen, der die Ladung des Kondensators 43 vor jedem Crimpzyklus entlädt. Ein dem Ladungsverstärker nachgeschalteter Analog-Digitalwandler 47 digitalisiert die Ausgangsspannung u, welche die aufgewendete Kraft F repräsentiert, synchron zu den vom Linearsensor 20 gelieferten Positionsimpulsen 48. Aus der digitalisierten Kraft F und den Positionsimpulsen 48 wird die Kraft-Weg-Kurve des Crimpvorganges gebildet. Eine Steuereinheit 42 übernimmt die Speicherung und Auswertung der Kraft-Weg-Kurve.The force sensor 23.1 measures the force F. applied during the crimping process. The force sensor 23.1 is based on the piezoelectric effect and generates a charge q proportional to the force F. The proportionality factor is the charge constant k. A capacitor 43 with the capacitance C is connected in parallel with the force sensor 23.1 and forms a charge amplifier with a subsequent voltage amplifier 46. The output voltage u at the output of the charge amplifier is: $$u=\frac{k\cdot G}{C}\cdot F$$

where g is the gain of the voltage amplifier 46.
In addition, a discharge switch 44 is provided which discharges the charge of the capacitor 43 before each crimping cycle. A charge-amplifier downstream analog-to-digital converter 47 digitizes the output voltage u, which represents the applied force F, in synchronism with the position pulses 48 delivered by the linear sensor 20. From the digitized force F and the position pulses 48, the force-displacement curve of FIG Crimping process formed. A control unit 42 takes over the storage and evaluation of the force-displacement curve.

FIG. 9 shows an alternative embodiment of the controller 28. This differs from the embodiment according to FIG. 8 on the one hand by the fact that the angle sensor 45 detects the angle of rotation ε of the shaft 19 and for this purpose is in communication with the shaft 19. On the other hand, it differs from the embodiment according to FIG. 8 in that the position of the slider 22 is not offset by the linear sensor 20 (FIG. Fig. 8 ), but is detected by the angle sensor 45. With the aid of a corresponding transducer 50, the angle ε delivered by the angle sensor 45 is transformed into a path s. The force-displacement curve of the crimping process is then formed from the digitized force F and the path s determined in this way.

wird der Crimpweg s aus dem Winkel ε berechnet. Dabei ist r der Abstand zwischen dem Exzenterzapfen 21 und dem Zentrum der Welle 19. FIG. 10a shows the force-angle curve, which was sampled with constant angular steps Δε. The 180 ° point on the abscissa with the angle ε forms the bottom dead center of the ram 18. At this point, the force is maximum. With the formula: $$s=r\cdot \left(\mathit{1}+\cos \left(\mathrm{\epsilon }\right)\right)$$

the crimping path s is calculated from the angle ε. In this case, r is the distance between the eccentric pin 21 and the center of the shaft 19th

FIG. 10b shows the with this formula from the measured force-angle curve ( Fig. 10a ) derived force-displacement curve. The force-displacement curve is in a compression phase K and a decompression phase DK split. In the in the FIGS. 10b to 15 diagrams shown, the zero point is right on the x-axis.

Crimp

FIG. 11 shows a diagram in which the course of the crimping force is shown depending on the way. This course is also called Crimpsignatur. In this case, on the x-axis of the Crimpweg, the slider 22 of the ram 18 travels. The Crimpweg is also called Stroke. On the y-axis, the force normalized to 1 (English: "normalized force") is plotted. The force axis is normalized because the force sensor 23.1 (FIG. Fig. 7 ) does not have to be calibrated. Thus, it is sufficient if the force sensor 23.1 supplies a signal which, although proportional to the applied force F, is not absolutely scaled. The normalization of the force axis allows the use of a cost-effective, non-calibrated force sensor 23.1.

The crimping path can be derived from the position signal 48 generated by the linear sensor 20.

If the crimping press does not have a linear sensor 20, the crimping path can be derived from the rotational angle ε of the shaft (eccentric axis) 19. For this purpose, the rotation angle ε is measured with the angle sensor 45 and transformed with the transducer 50 into a path.

lässt sich ein Kennwert csiA bestimmen, der als Mass für den Beginn der Kompressionsphase K dient. Die Kompressionsphase beginnt dort, wo die Laschen 6 den Leiter 12 berühren. Der Kennwert csiA wird im Folgenden auch als Crimpsignatur-Index csiA bezeichnet.With the help of the formula: $$\mathit{csiA}=\frac{2A}{{\mathrm{<figure-callout\; id="2"\; label="\gamma "\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">\gamma </figure-callout>}}^2}$$

can be a characteristic value csiA determine that serves as a measure of the beginning of the compression phase K. The compression phase begins where the tabs 6 touch the conductor 12. The characteristic value csiA is also referred to below as the crimp signature index csiA.

Here, A is an area which is below the crimp force curve in the compression phase, starts at a normalized force of 1 - γ, and extends to the peak force Fp = 1. The area A is also referred to below as the compression area. γ is a constant which is chosen in an advantageous manner, so that its value is in the range of the constant increase in force. In the present example, γ = 0.5.

FIG. 12 shows the same course of the crimping force as in FIG. 11 , but with a parameter csiB that indicates the width of the decompression phase.

lässt sich ein Kennwert csiB als Mass für die Breite der Dekompressionsphase DK bestimmen. Die Dekompressionsphase DK beginnt, nachdem der Exzenterzapfen 21 den unteren Totpunkt erreicht hat und endet, wenn der Crimpstempel 8,9 vom Kontakt 2 entfernt wird. Der Kennwert oder Wert csiB wird im Folgenden auch als Crimpsignatur-Index csiB bezeichnet.With the help of the formula: $$\mathit{csiB}=\frac{2B}{{\gamma }^2}$$

a parameter csiB can be determined as a measure of the width of the decompression phase DK. The decompression phase DK begins after the eccentric pin 21 has reached the bottom dead center and ends when the crimping die 8,9 is removed from the contact 2. The characteristic value or value csiB is also referred to below as crimpsignature index csiB.

Here, B is the size of the area which is below the crimp force curve in the decompression phase DK. The area B is also referred to below as the decompression area. The value of the constant γ is advantageously in the range of the constant force descent and in the present example 0.8.

wobei k eine Konstante ist.
Da der Crimpsignatur-Index csiB proportional zur Spitzenkraft Fp ist, gilt: $$\mathrm{csiB}\sim \mathrm{Fp}$$

Aus den Werten csiA und csiB berechnet sich ein weiterer Crimpsignatur-Index csiC: $$\mathit{csiC}=\frac{\mathit{csiA}-\mathit{csiB}}{2}$$

For example, if the constant γ is chosen to be γ = 0.8, the surface B starts at a normalized force of 1-γ = 0.2 and extends to the peak force Fp = 1.
The following applies: $$\mathrm{fp}\left[\mathrm{N}\right]=\mathrm{csiB}\left[\mathrm{m}\right]\cdot \mathrm{k}\left[\mathrm{N}/\mathrm{m}\right]$$

where k is a constant.
Since the crimp signature index csiB is proportional to the peak force Fp, the following applies: $$\mathrm{csiB}~\mathrm{fp}$$

From the values csiA and csiB another crimpsignature index csiC is calculated: $$\mathit{csiC}=\frac{\mathit{csiA}-\mathit{<figure-callout\; id="2"\; label="csiB"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">csiB</figure-callout>}}{2}$$

As in FIG. 13 shown, the crimpsignature index csiC corresponds to the area of the triangle with the baseline csiA - csiB and height 1. This area corresponds to the compression area of the crimp signature.

The crimp signature index csiC can be used to monitor the crimp height CH. A small change ΔCH in the crimp height CH causes an equal change ΔcsiC of the crimpsignature index csiC with the opposite sign. It therefore applies: $$\mathrm{\Delta csiC}=-\mathrm{\Delta CH}$$

The crimpsignature indices csiC and csiB are used to calculate another crimpsignature index csiD: $$\mathit{csiD}=\frac{\mathit{csiC}}{\mathit{csiB}}$$

The crimp signature index csiD can be used to detect an error in setting up the crimping device. In particular, it can be detected with the crimp signature index csiD whether the conductor has been sufficiently stripped.

From the values csiB and csiC, another crimpsignature index csiE is calculated: $$\mathit{csiE}=\mathit{csiB}\cdot \mathit{csiC}$$

The crimp signature index csiE is proportional to the compression work of the crimping operation, and thus is also proportional to the crimp compression ratio CCR: $$\mathit{csiE}~\mathit{CCR}$$

The crimp signature index csiE can also be used to detect an error in setting up the crimping device. In particular, the crimpsignature index csiE can be used to check whether the crimp height CH set and the cable cross-section configured comply with the specifications.

Determination of the evaluation zones

The following is with reference to FIG. 14 described how the crimp force curve Ziso and Zmc are determined. The evaluation zone Zmc is further subdivided into N subzones Z1, Z2,..., Zi,..., ZN, for N> 2. N is set equal to 3 in the following statements. FIG. 14 shows a first Crimpkraftkurve R at a Referenzcrimp, which is also referred to below as Referenzimpimpkraftkurve R. FIG. 14 also shows a second crimp force curve E whose course is typical for a Leercrimp. Both crimp force curves R and E have the same evaluation zones Ziso and Zmc. The evaluation zone Zmc is additionally divided into three subzones Z1, Z2 and Z3.

The Ziso evaluation zone is used to detect the crimping error "insulation in the crimp". By contrast, the evaluation zone Zmc is used to detect the crimped error "Missing strands".

In order to detect the crimping error "missing strands", it is advantageous if the evaluation zone Zmc covers as far as possible that section of the crimping force curve in which the compression of the strands takes place. However, the beginning of the evaluation zone Zmc should not lie before this compression range, because otherwise unnecessary noise components are evaluated. Therefore, the determination of the zone widths with the crimp signature index csiA, which, as mentioned above, marks the beginning of the compression phase.

wobei W ein Parameter ist, der im Bereich von W = 0,5 bis 2,0 liegt und für den standardmässig W = 1 gilt.The evaluation zone Zmc is calculated as follows: $$\mathrm{Zmc}=\mathrm{0}.\mathrm{8th}\cdot \mathrm{W}\cdot \mathrm{csiA}=\mathrm{<figure-callout\; id="1"\; label="Z"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">Z</figure-callout>}\mathrm{1}+\mathrm{<figure-callout\; id="2"\; label="Z"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">Z</figure-callout>}\mathrm{2}+\mathrm{Z}\mathrm{3}$$

where W is a parameter that is in the range of W = 0.5 to 2.0 and for which W = 1 by default.

Subzones Z1, Z2 and Z3 are determined as follows: $$\mathrm{<figure-callout\; id="1"\; label="Z"\; filenames="imgf0001.png,imgf0004.png"\; state="\{\{state\}\}">Z</figure-callout>}\mathrm{1}=\mathrm{<figure-callout\; id="2"\; label="Z"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">Z</figure-callout>}\mathrm{2}=\mathrm{Z}\mathrm{3}=\mathrm{Zmc}/\mathrm{3}$$

The evaluation zone Ziso is determined as follows: $$\mathrm{Ziso}=\mathrm{Zmc}/3$$

Monitoring the crimp height during ongoing production

The crimp height is monitored with the crimp signature index csiC. For this purpose, the crimp signature index csiC is determined during a crimping process and compared with a tolerance value chTol.

In the event that the crimp height and thus the crimp signature index csiC of the currently to be inspected crimps deviates too much from the reference crimp height, that is, exceeds the tolerance value chTol, the production is switched off, that is no further crimping is performed.

Crimping error "Missing strands"

With the solution according to the invention it can be recognized whether and also how many strands of a conductor 12 (FIG. Fig. 4 ) were not crimped during crimping. FIG. 15 shows a typical force-displacement curve R for a faultless crimp and a typical force-displacement curve C1 for a faulty crimp with 10% missing strands.

wobei gilt:

• ScaleFactorRmc ist ein Skalierungsfaktor,
• Si ist der Gewichtungsfaktor für die Teilzone Zi und
• Ri ist die relative Flächendifferenz für die Teilzone Zi.

For error detection, a value Rmc, which indicates the relative proportion of missing strands and is also referred to below as the result, is first calculated as follows: $$\mathit{Rmc}=\mathit{ScaleFactorRmc}\cdot {\displaystyle \underset{i=1}{\overset{N}{\Sigma }}}\mathit{Si}\cdot \mathit{Ri}$$

where:

• ScaleFactorRmc is a scaling factor
• Si is the weighting factor for subzone Zi and
• Ri is the relative area difference for subzone Zi.

Subsequently, the value Rmc is compared with an error limit BLMC. The error limit BLMC is also referred to as the error limit.

wobei

• f die Fläche ist, die unter der Crimpkraftkurve in der Teilzone Zi liegt, und
• fRef die Referenzfläche ist, die unter der Referenzcrimpkraftkurve in der Teilzone Zi liegt.

The relative area difference Ri of a subzone Zi is calculated according to the following formula: $$\mathit{Ri}=\frac{{\displaystyle \underset{\mathit{Zi}}{\Sigma }}f-{\displaystyle \underset{\mathit{Zi}}{\Sigma }}\mathit{f\; Ref}}{{\displaystyle \underset{\mathit{Zi}}{\Sigma }}\mathit{f\; Ref}}.i=\mathit{1}...N$$

in which

• f is the area which lies below the crimp force curve in the subzone Zi, and
• fRef is the reference area that is below the reference crimp curve in subzone Zi.

The relative area difference Ri is thus the difference between the area f, which lies below the crimp force curve in the subzone Zi, and the reference area fref, which lies below the reference crimp force curve in the subzone Zi, divided by this reference area fref.

wobei

• Ri(ec) die relative Flächendifferenz der Teilzone Zi für einen Leercrimp ec und
• std(Ri) die Standardabweichung von Ri, ermittelt über eine grössere Anzahl von fehlerlosen Crimps, ist.

The variance of the value Rmc is reduced and thus the discriminatory power for the detection of crimped errors is improved when the weighting factors Si are determined according to the relevance of the respective relative area difference Ri. The weighting factors Si are calculated according to the following formula: $$\mathit{Si}={\left(\frac{\mathit{Ri}\left(\mathit{<figure-callout\; id="2"\; label="ec\; Hours\; Ri"\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">ec\; </figure-callout>},\right)}{\mathit{Hours}\left(\mathit{Ri}\right)}\right)}^2.i=\mathit{1}...N$$

in which

• Ri (ec) is the relative area difference of subzone Zi for an empty crimp ec and
• std (Ri) is the standard deviation of Ri, determined over a larger number of faultless crimps.

The scaling factor ScaleFactorRmc is used to scale the value Rmc, so that Rmc corresponds to the relative share of missing strands.

To determine the scaling factor ScaleFacorRmc, a false crimp is performed with a defined percentage mc% of missing strands. If, for example, 2 of 19 strands are missing, the value mc becomes mc = 2/19 * 100 = 10.5%. If, for example, an empty crimp is performed, ie if a contact is crimped without a conductor, the value mc becomes mc = 1/1 * 100 = 100%. The scaling factor ScaleFactorRmc is now determined so that the result of this error crimps Rmc = -mc%.

In the event that the result Rmc falls below the error limit -BLMC for the crimp to be checked, for example, the production is switched off, that is, no further crimping is performed. Instead, however, the crimp can also be marked as broke without production being stopped.

wobei der Faktor a zum Beispiel den Wert 3 hat.To determine the error limit BLMC, multiple crimping is performed. Then the standard deviation std (Rmc) of the Rmc results is calculated from the good crimps. Furthermore, the required percentage of missing strands is specified in percent with the value MCL. For example, if MCL is set to MCL = 10%, that means the system will have 10% missing Should identify strands safely. The error limit BLMC is now calculated as: $$\mathrm{BLMC}=\mathrm{MCL}-\mathrm{a}\cdot \mathrm{Hours}\left(\mathrm{Rmc}\right)\mathrm{,}$$

for example, the factor a has the value 3.

FIG. 16 clarifies these relationships. The value MCL specifies the percentage of missing strands that should be reliably detected. In FIG. 16a a first distribution density function of the value of Rmc is shown. FIG. 16b shows a second distribution density function of Rmc. In the in the FIGS. 16a and 16b shown distribution density functions is plotted on the x-axis, the variable Rmc. On the y-axis, the relative frequency p (Rmc) is specified, with which the variable Rmc has a certain value. The distribution density function of Rmc has the maximum at the mean of Rmc. The width of the distribution density function is defined by the variance of Rmc expressed by the standard deviation std (Rmc). In the FIGS. 16a and 16b the distribution density function of the Rmc values of the faultless crimps is designated pc.a and pc.b, respectively. The distribution density function of Rmc values with MCL% mc missing strands is in the FIGS. 16a and 16b denoted by fc.a or fc.b.

In the distribution density functions fc.a and pc.a according to FIG. 16a the weighting factors Si are equal. It can be seen that the selectivity - expressed by the error limit BLMC - is insufficient for error detection due to the wide spread of the Rmc values is. Although the Rmc values of the faulty crimps (see distribution density function fc.a) are all smaller than the error limit -BLMC, the faulty crimps are recognized, but some of the Rmc values of the faultless crimps (see distribution density function pc.a) are also smaller than the error limit -BLMC and are thus erroneously classified as faulty.

FIG. 16b shows the case where the weighting factors were determined as described above according to the relevance of the relative area differences Ri. The scattering of the Rmc values is smaller and the two distribution densities pc.b and fc.b do not overlap. Thus, a sufficient selectivity is given. The faulty crimps are classified as bad and the flawless crimps as good.

Crimping error "insulation in crimp"

Another possible error in crimping may be that between the contact 2 ( Fig. 4 ) and the conductor 1 more or less insulating material 11 is located. In FIG. 15 In addition to the typical force-displacement curve for a faultless crimp R, a typical force-displacement curve for a faulty crimp with crimped insulation C2 is also shown.

In order to be able to recognize a crimp with crimped insulation as faulty, the relative area difference Riso from the zone Ziso with a limit value BLISO compared. The limit value BLISO is also referred to as the error limit.

The relative area difference Riso is calculated as follows: $$\mathrm{Riso}=\frac{\mathrm{fiso}-\mathrm{f\; re\; fiso}}{\mathrm{f\; re\; fiso}}=\frac{\mathrm{\Delta fiso}}{\mathrm{f\; re\; fiso}}$$

The relative area difference Riso is thus the difference between the area fiso, which lies below the crimping force curve C2 in the evaluation zone ziso, and the reference area frefiso, which lies below the reference crimping force curve R in the zone ziso, divided by this reference area frefiso.

For example, if the relative area difference Riso in the crimp to be checked exceeds the area limit BLISO, the crimp is marked as scrap.

To determine the error limit BLISO, several crimps are performed. Then the error limit BLISO is statistically calculated from the good crimpings.

Determination of the process parameters

• Die Crimpsignatur-Indizes csiA₀, csiB₀, csiC₀, csiD₀ und csiE₀.
• Die Fehlergrenzen BLMC und BLISO.
• Die Gewichtungsfaktoren S1, S2 und S3.
• Der Skalierungsfaktor ScaleFactorRmc.

Before a crimp connection can be processed for the first time, the process parameters must first be determined once. These are then stored in a database and can each be used in the production of the corresponding Crimpverbindung be retrieved. Process parameters include:

• The Crimpsignatur indices csiA ₀ , csiB ₀ , csiC ₀ , csiD ₀ and csiE ₀ .
• The error limits BLMC and BLISO.
• The weighting factors S1, S2 and S3.
• The scaling factor ScaleFactorRmc.

Set up the crimping process

When setting up the crimping process on the crimping machine, make sure that the crimping connection meets the specifications. In particular, it must be checked whether the prescribed cable cross-section is processed and whether the crimp connection has the specified crimp height CH.

The setup with the subsequent automatic check can, for example, proceed as follows. In a first step, the specified crimp height CH is set as follows. After a first crimp has been produced, an operator measures the crimp height CH and adjusts the crimping tool accordingly. This is repeated until the crimp height CH is within the tolerance. In a second step, the setup is automatically checked. For this purpose, the current crimpsignature index csiE is compared with the process parameter csiE ₀ stored in the database. If the difference between csiE and csiE ₀ lies within the tolerance, ie the crimp height CH and the Conductor cross-section are OK, the production is released.

The foregoing description of the embodiments according to the present invention is for illustrative purposes only, and not for the purpose of limiting the invention. Within the scope of the invention, various changes, combinations of the embodiments and modifications are possible without departing from the scope of the invention as defined by the following claims and their equivalents.

LIST OF REFERENCE NUMBERS

1

electric wire

2

Contact

3

crimp

4

double strap

5

insulation crimp

6

double strap

7

conductor crimp

8th

crimping dies

9

crimping dies

9.1

anvil

10

recess

11

insulation

12

ladder

13

window

14

stand

15

engine

16

transmission

17

guide

18

ram

19

wave

20

Linear measuring system

21

eccentric

22

slide

23

toolholder

23.1

force sensor

28

control

40

motor controller

41

control unit

42

External computer

43

capacitor

44

discharge switch

45

angle sensor

46

Voltage amplifier

47

Analog - digital converter

48

Pulse train of the path increments

49

Pulse train of angular increments

50

Angle to path transformation unit

TCS

Cross-sectional area of the contact

WCS

Cross sectional area of the conductor

CCS

Cross sectional area of the conductor crimp

CH

crimp height

Ziso

evaluation zone

Zmc

evaluation zone

Z1

subzone

Z2

subzone

Z3

subzone

K

compression phase

DK

decompression

R

Referenzcrimpkurve

F

crimping force

C1

crimping curve

C2

crimping curve

e

crimping curve

Claims (11)

1. A method for determining the quality of a crimped connection between a conductor and a contact,

   - wherein by means of a crimping device a crimping force (F) is exerted on the conductor (1) and the contact (2),

   - wherein the crimping force curve (C1; C2; E; R) that occurs during the crimping is determined,

   - wherein a compression surface (A) that lies under a reference crimping force curve (R) is determined, characterized in that

   - the crimping force curve (C1; C2; E) and the reference crimping force curve (R) are subdivided into several zones (Ziso, Zmc, Z1 - Z3), wherein the subdivision takes place in consideration of the size of the compression surface (A), and

   - at least one further area (f; fiso) that lies under the crimping force curve (C1; C2; E) is determined, wherein the area is a measure of the quality of the crimping connection.
2. The method according to patent claim 1,
   wherein the compression area (A) is determined under a section (K) of the reference crimping force curve (R) in which the crimping force (F) increases.
3. The method according to patent claim 2,
   wherein the upper end of the section (K) is defined by the maximum crimping force (Fp).
4. The method according to one of patent claims 1 to 3, wherein a first Crimp Signature Index (csiA) is determined in consideration of the compression surface (A).
5. The method according to patent claim 4,
   wherein the zones (Z1 - Z3) are individually weighted.
6. The method according to patent claim 4 or 5, wherein

   - a reference area (fRef) is determined from the reference crimping force curve (R) for each of the zones (Z1, Z2, Z3),

   - an area (f) is determined from the crimping force curve (E) for each of the zones (Z1, Z2, Z3),

   - area differences (R1, R2, R3) and, in turn, a total area difference (Rmc) are determined therefrom and

   - it is determined, based on the total area difference (Rmc), whether one or more strands of the conductor (12) are missing.
7. The method according to one of patent claims 4 or 5,

   - wherein the size of the reference area (fRefiso) which lies in one of the zones (Ziso) under the reference crimping force curve (R) is determined from a reference crimping force curve (R),

   - wherein the area (fiso) which lies in the zone (Ziso) under the crimping force curve (C2) is determined from the crimping force curve (C2),

   - wherein the area difference (Riso) is determined from the reference area (fRefiso)and the area (fiso) and

   - wherein the area difference (Riso) is used to determine whether insulation material (11) is present in the crimp between the conductor (12) and the contact (1).
8. The method according to one of patent claims 1 to 7, wherein a decompression area (B) that lies under the reference crimping force curve (R) is determined, wherein the decompression area (B) is determined under the section (DK) of the reference crimping force curve (R) in which the crimping force (F) declines.
9. The method according to one of patent claims 1 to 8, wherein a further Crimp Signature Index (csiB) is determined in consideration of the decompression area (B).
10. The method according to patent claim 9,
    wherein the Crimp Signature Index (csiA) and the Crimp Signature Index (csiB) are used to infer a crimp height.
11. A crimping device for crimping a conductor and a contact,

    - having a crimping stamp (8; 9);

    - having a linear sensor (20) for registering the position of the crimping stamp (8; 9);

    - having a force sensor (23.1) for registering the crimping force (F) and

    - having an analyser unit (41, 42) connected to the linear sensor (2) and the force sensor (23.1),

    characterized in that the analyser unit (41, 42) is configured and operable in such a manner that it can be used to determine the quality of a crimped connection by means of the method according to one of patent claims 1 to 10.

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