CN-122017688-A - Method and system for testing current carrying capacity matching of wire of automobile wire harness fuse

CN122017688ACN 122017688 ACN122017688 ACN 122017688ACN-122017688-A

Abstract

The invention belongs to the technical field of automobile electronics, and provides a method and a system for matching and testing the current carrying capacity of an automobile wire harness fuse wire, wherein the method comprises the steps of establishing a standardized pulse loading section, and expanding a constant current test into a composite dynamic test sequence covering peak thermal shock and average thermal accumulation; the method comprises the steps of collecting a fuse heat accumulation integral value and a wire insulation layer multipoint temperature, introducing a three-dimensional evaluation index, identifying a heat response asynchronous condition, adopting a pulse peak value and a duty ratio gradual increment mode to respectively approach a wire transient temperature rise limit and a fuse heat accumulation fusing boundary, determining a safe matching interval through cross comparison, dividing a matching level according to the safe matching interval, respectively optimizing selection aiming at asynchronous risk and overheat priority failure combination, and feeding back an optimization result to a selection specification. The problem of test distortion caused by asynchronous thermal response of a fuse and a wire under dynamic pulse current is solved, and the matching reliability and the test accuracy of an automobile electrical system are improved.

Inventors

HU XINHUA
ZHANG LINGCHAO
LIANG JIE

Assignees

南昌友星电子电器有限公司

Dates

Publication Date: 20260512
Application Date: 20260413

Claims (10)

1. A method for testing the current carrying capacity matching of an automobile wire harness fuse wire is characterized by comprising the following steps: Step S10, a standardized pulse loading section is established by extracting key parameters of current waveforms of typical loads of a real vehicle, and a constant current test is expanded into a composite dynamic test sequence covering peak thermal shock and average thermal accumulation; Step S20, under the loading of a composite dynamic test sequence, collecting a fuse heat accumulation integral value and a wire insulation layer multipoint real-time temperature, introducing a temperature-time-current three-dimensional evaluation index, and identifying a thermal response asynchronous condition when the wire temperature approaches a short-term temperature resistance limit of the insulation layer and the fuse integral value does not reach a fusing threshold value; Step S30, based on a thermal response asynchronous condition, adopting a mode of gradually increasing a pulse peak value and a duty ratio to respectively approach a transient temperature rise limit of a wire and a thermal accumulation fusing boundary of a fuse, and determining a safe matching section of the fuse before the wire reaches dangerous temperature rise by cross comparison of two groups of critical conditions; Step S40, identifying asynchronous risk and overheat priority failure level combinations in the fuse-wire combination according to the safety matching interval, optimizing and adjusting the fusing characteristics of the fuse and the current carrying capacity of the wire according to the asynchronous risk combinations, optimizing the rated current level and the model selection of the fuse according to the overheat priority failure combinations, leading the fusing action to be advanced until the insulation layer of the wire reaches the temperature resistance limit, and finally feeding back the optimized result to the model selection standard.
2. The method for testing the current carrying capacity matching of the wire of the automotive harness fuse of claim 1, wherein the method for establishing the standardized pulse loading profile in the step S10 is as follows: Based on the extracted key parameter statistics, the pulse shape, the proportional relation between the peak current and the average current, the typical value range of the duty ratio and the typical value of the pulse period are formed, and the constant current test is expanded into the combination of four tests, namely a single pulse impact test, a continuous pulse accumulation test, a variable duty ratio gradual change test and a working condition circulation test.
3. The method for testing the current carrying capacity matching of the wire of the automotive harness fuse according to claim 1, wherein the method for synchronously collecting the integrated value of the fuse heat accumulation and the multipoint real-time temperature of the wire insulation layer in the step S20 is as follows: the voltage probes are connected in parallel at the two ends of the fuse, the current probes are connected in series at the front end of the fuse, voltage and current are collected at a sampling rate not lower than 10kHz, a heat accumulation integral value is calculated in real time, and the multi-point temperature sensor is arranged on the insulating layer of the lead and comprises a conductor center point, an insulating layer junction and the outer surface of the insulating layer, and the temperature of each monitoring point is synchronously collected.
4. The method for testing the current carrying capacity match of an automotive harness fuse wire of claim 3, wherein the step of identifying a thermally responsive asynchronous condition in step S20 comprises the steps of: Constructing a temperature curve based on the temperature of each monitoring point, drawing the temperature curve and the heat accumulation integral curve in the same time axis coordinate system, respectively marking a time point T_temp when the temperature of a wire reaches the short-term temperature resistance limit of an insulating layer and a time point T_fuse when the heat accumulation integral of a fuse reaches a fusing threshold value, calculating a time difference delta t=T_temp-T_fuse, and judging that the thermal response is asynchronous when delta T is smaller than zero and exceeds a preset allowable deviation range; The temperature data of the monitoring points are subjected to filtering processing, the temperature values of the monitoring points are connected into continuous curves according to time axes, the point with the highest temperature in each section is selected as the representative temperature of the section, and the maximum value in the representative temperature curves of all the sections is extracted to form a temperature curve.
5. The method for testing the current carrying capacity matching of the wire of the automotive harness fuse according to claim 1, wherein the approaching process of the transient temperature rise limit of the wire in the step S30 is as follows: Taking a standardized pulse loading section as a reference, fixing the duty ratio, gradually increasing pulse peak values according to the fixed step length, recording instantaneous temperature rise peak values of all temperature measuring points of a wire insulation layer, recording the pulse peak values as the wire instantaneous temperature rise limit under the current duty ratio when the temperature rise of any temperature measuring point reaches the short-term temperature resistance limit of an insulation material for the first time, changing the duty ratio, repeating the processes, and obtaining a wire temperature rise limit curve.
6. The method for testing the current carrying capacity matching of the fuse wire of the automobile wire harness according to claim 1, wherein the approaching process of the fuse heat accumulation fusing boundary in the step S30 is as follows: And (3) fixing a pulse peak value, gradually increasing a duty ratio according to a fixed step length, applying a continuous pulse sequence after each increment, monitoring a fuse heat accumulation integral value in real time, recording the duty ratio as a fuse heat accumulation fusing boundary under the current pulse peak value when the integral value reaches a designed fusing threshold value for the first time and fusing occurs, changing the pulse peak value, and repeating the process to obtain a fuse fusing boundary curve.
7. The method for testing the current carrying capacity matching of the automotive harness fuse wire according to claim 6, wherein the step S30 is performed in a manner that the safe matching interval is determined by: Drawing a wire temperature rise limit curve and a fuse fusing boundary curve in the same coordinate system, wherein the wire temperature rise limit curve represents the maximum pulse peak value allowed by a wire under different duty ratios, the fuse fusing boundary curve represents the minimum duty ratio which leads to fuse fusing under different pulse peak values, and the coordinate system is divided into a fuse non-action area, a wire temperature rise overrun area and an intersection area between the two curves by the two curves, wherein the intersection area is a safe matching interval.
8. The method for matching current carrying capacity of automotive harness fuse wires according to claim 7, wherein the step S40 of identifying the combination of asynchronous risk and overheat priority failure levels is performed by: Substituting the actual working point of the fuse-wire combination into a coordinate system with the duty ratio as an abscissa and the pulse peak value as an ordinate, judging that the fuse-wire combination is completely matched if the working point is positioned in a safe matching interval, judging that the fuse-wire combination is asynchronous risk combination if the working point is positioned below a fuse-wire fusing boundary curve, and judging that the fuse-wire combination is overheat priority failure combination if the working point is positioned above a wire temperature rise limit curve.
9. The method for testing the current carrying capacity matching of the automotive harness fuse wire according to claim 1, wherein the optimization method for the asynchronous risk combination in the step S40 is as follows: Selecting a fuse with a rated current level reduced by one grade or selecting a fast-melting fuse to replace a slow-melting fuse, selecting a wire with a cross section area increased by one specification or selecting an insulating material with a higher temperature resistance level at the wire side, optimizing, and then re-performing boundary approximation test to verify that a working point enters a safe matching interval; The optimization method for the overheat priority failure combination in step S40 is as follows: And selecting fuses with rated current level reduced by one grade or two grades, or selecting fast-melting fuses to replace slow-melting fuses, carrying out boundary approximation test again after optimization, confirming that the fusing time of the fuses and the time of the wires reaching the temperature rise threshold meet the preset allowable deviation range, and incorporating the matched combination passing optimization verification into the model selection standard.
10. The automobile wire harness fuse wire current carrying capacity matching test system is characterized by comprising the following modules: The pulse load construction module is used for establishing a standardized pulse loading section by extracting key parameters of current waveforms of typical loads of the real vehicle and expanding a constant current test into a composite dynamic test sequence covering peak thermal shock and average thermal accumulation; the asynchronous monitoring and identifying module is used for collecting a fuse thermal accumulation integral value and the multipoint real-time temperature of the insulating layer of the wire under the loading of the composite dynamic test sequence, introducing a temperature-time-current three-dimensional evaluation index, and identifying a thermal response asynchronous condition when the wire temperature approaches the short-term temperature-resistant limit of the insulating layer and the fuse integral value does not reach the fusing threshold value; the matching interval definition module is used for respectively approaching the transient temperature rise limit of the wire and the thermal accumulation fusing boundary of the fuse by adopting a mode of gradually increasing the pulse peak value and the duty ratio based on the thermal response asynchronous condition, and determining the safe matching interval of the fuse reaching the dangerous temperature rise before the wire by cross comparison of two groups of critical conditions; The combination grading optimization module is used for identifying asynchronous risk and overheat priority failure level combinations in the fuse-wire combination according to the safety matching interval, optimizing and adjusting the fusing characteristics of the fuse and the current carrying capacity of the wire according to the asynchronous risk combinations, optimizing the rated current level and the type selection of the fuse according to the overheat priority failure combinations, leading the fusing action to be advanced until the insulation layer of the wire reaches the temperature resistance limit, and finally feeding back the optimized result to the selection standard.

Description

Method and system for testing current carrying capacity matching of wire of automobile wire harness fuse Technical Field The invention belongs to the technical field of automobile electronics, and particularly relates to a method and a system for matching and testing current carrying capacity of an automobile wire harness fuse wire. Background In the design of an automobile electrical system, the verification of the matching property of a fuse and a wire is a key link for guaranteeing the safe and reliable operation of a circuit. The conventional matching test method generally adopts a constant current loading mode, namely, the constant current is continuously electrified according to the equal proportion of 125 percent and 150 percent of the nominal current-carrying capacity of the wire, and the rationality of the matching of the fuse fusing time and the wire temperature rise change is evaluated by monitoring the fuse fusing time and the wire temperature rise change. The test mode assumes that the current in the actual working condition is a steady-state continuous load, however, the modern automobile electrical system presents remarkable dynamic characteristics, and pulse-type fluctuation current is generated under the working conditions such as starting and stopping of an air-conditioning compressor, peak current impact of a motor and the like. Such pulsed currents have a "peak-to-valley" alternating characteristic such that the fuse and wire exhibit an inherent asynchronism in the thermal response mechanism. Specifically, the action threshold of the fuse mainly depends on the heat accumulation effect determined by the average current, the fusing mechanism is based on the heat integration principle, the transient temperature rise of the lead is dominated by the transient joule heat of the peak current, and the two have obvious differences in thermal inertia and response time. Under constant current test conditions, the thermal coupling relationship between the fuse and the wire tends to be consistent, and the matching result usually shows normal performance. However, under the dynamic pulse current loading, the existing test method is difficult to truly reflect the actual failure risk, and is mainly characterized by two misjudgment situations, namely, firstly, the peak current causes the temperature of the wire to rise sharply and possibly exceeds the temperature-resistant limit of the insulating layer, and the fuse does not act because the average current does not reach the threshold value, so that the insulating layer is implicitly aged, secondly, the current in the pulse valley stage suddenly drops, the heat accumulation of the fuse is insufficient, and the fuse cannot be fused in time before the wire is overheated. Therefore, the invention provides a method and a system for testing the current carrying capacity matching of an automobile wire harness fuse wire. Disclosure of Invention In order to overcome the deficiencies of the prior art, at least one technical problem presented in the background art is solved. The technical scheme adopted for solving the technical problems is that the method for testing the current carrying capacity matching of the wire of the automobile wire harness fuse comprises the following steps: Step S10, a standardized pulse loading section is established by extracting key parameters of current waveforms of typical loads of a real vehicle, and a constant current test is expanded into a composite dynamic test sequence covering peak thermal shock and average thermal accumulation; Step S20, under the loading of a composite dynamic test sequence, collecting a fuse heat accumulation integral value and a wire insulation layer multipoint real-time temperature, introducing a temperature-time-current three-dimensional evaluation index, and identifying a thermal response asynchronous condition when the wire temperature approaches a short-term temperature resistance limit of the insulation layer and the fuse integral value does not reach a fusing threshold value; Step S30, based on a thermal response asynchronous condition, adopting a mode of gradually increasing a pulse peak value and a duty ratio to respectively approach a transient temperature rise limit of a wire and a thermal accumulation fusing boundary of a fuse, and determining a safe matching section of the fuse before the wire reaches dangerous temperature rise by cross comparison of two groups of critical conditions; Step S40, identifying asynchronous risk and overheat priority failure level combinations in the fuse-wire combination according to the safety matching interval, optimizing and adjusting the fusing characteristics of the fuse and the current carrying capacity of the wire according to the asynchronous risk combinations, optimizing the rated current level and the model selection of the fuse according to the overheat priority failure combinations, leading the fusing action to be advanced until the insulation layer o