A method for designing automobile fuse capacity

Abstract

The present invention discloses a method for designing the capacity of an automotive fuse used in a circuit containing several automotive electrical appliances. The method comprises: classifying the automotive electrical appliances according to their operating time; obtaining operating current data for each automotive electrical appliance; calculating the root mean square (RMS) current of each automotive electrical appliance within a time interval sequence; summing the RMS currents of each automotive electrical appliance at the same time interval to obtain the total RMS current of the automotive electrical appliances; obtaining the theoretical minimum breaking current of the automotive fuse based on the total RMS current, and selecting an automotive fuse based on the theoretical breaking current. The fuse design method of the present invention simultaneously considers the effects of both long-term and short-term operating currents on the fuse, making fuse capacity design more precise. Compared to existing design methods, it can improve the accuracy of at least one specification level and facilitate the design of electronic fuse protection strategies for currents at different time intervals.

Description

Technical Field

[0001] The present invention relates to the technical field of automobile fuse capacity design, and in particular to an automobile fuse capacity design method. Background Art

[0002] The function of automotive fuses is to protect wiring, preventing wiring harness burnout or even fire in the event of a short circuit or overload. Fuses are categorized as primary, secondary, or tertiary, depending on their position in the power distribution topology. Generally, primary fuses protect the wiring of the entire vehicle's electrical appliances, secondary fuses protect lower-level fuse boxes or single high-current appliances, and tertiary fuses protect single appliances or multiple appliances connected in parallel. Therefore, each fuse level has design requirements for fuse capacity to accommodate multiple appliances connected in parallel.

[0003] The existing fuse capacity design for multiple parallel electrical appliances generally adds the electrical currents directly, or uses vehicle test data and engineer experience, or uses a method based on scenario analysis and weighting coefficients as described in Publication No. CN 113283087A, Invention Name: A Method for Designing the Capacity of Main Fuse for Automotive Wiring Harness Based on Scenario Analysis. The method based on directly adding the currents of all electrical appliances can easily lead to the selected fuse capacity being too large, requiring the use of wires with larger diameters, which is wasteful. If it is based on vehicle test data and engineer experience, the design may be too dependent on later test results, and it will be difficult to unify the design standards. The method based on scenario analysis and weighting coefficients may underestimate the impact of high-current electrical appliances that work for a short time. With the increasing development of trends such as intelligent driving, intelligent cockpits, and vehicle networking, the functions of automobiles are increasing, the analysis of working scenarios is more difficult, and the confirmation rules of weighting coefficients are difficult to unify. All of these will cause large deviations in design results. In addition, electronic fuses are being used more and more for functional safety reasons. The protection function of electronic fuses depends on more detailed current characteristics of electrical appliances. Traditional fuse capacity design methods for multi-channel parallel electrical appliances lack this data. Summary of the Invention

[0004] It is to be understood that both the foregoing general description and the following detailed description of the present disclosure are exemplary and explanatory and are intended to provide further explanation of the disclosure.

[0005] In response to the defects of the above-mentioned existing technologies and the latest technical requirements, the present application discloses a method for fuse capacity design based on the analysis of the operating current characteristics of electrical appliances and the time-current characteristic curve of the fuse. The method can reasonably design the primary, secondary, and tertiary fuse capacities of automobiles containing multiple electrical appliances, taking into account the influence of steady-state current and transient current, and is suitable for electronic fuses.

[0006] To achieve the above-mentioned object, the present invention provides a method for designing the capacity of an automotive fuse, wherein the fuse is used in a circuit including a plurality of automotive electrical appliances, and wherein the method comprises:

[0007] Step S1, classifying the plurality of automotive electrical appliances according to working hours;

[0008] Step S2, obtaining the operating current data of each of the automotive electrical appliances;

[0009] Step S3, calculating the root mean square current of each of the automotive electrical appliances within a time interval sequence:

[0010]

[0011] Among them, I i is the i-th continuous current value of the automotive electrical appliance in the time interval, and n is the number of current data collection points in the time interval;

[0012] Step S4, adding the root mean square current of each of the automotive electrical appliances at the same time interval to obtain the total root mean square current of the automotive electrical appliances;

[0013] Step S5: obtaining a theoretical minimum breaking current of the automobile fuse according to the total RMS current, and selecting an automobile fuse according to the theoretical breaking current.

[0014] Preferably, the present invention further provides a method for designing automobile fuse capacity, characterized in that step S5 further comprises:

[0015] A safety margin is added to the total root mean square current to obtain a safety fusing current of the plurality of automotive electrical appliances, and an automotive fuse having a current greater than the safety fusing current is selected from a fuse fusing time-current characteristic curve.

[0016] Preferably, the present invention further provides a method for designing the capacity of an automobile fuse, characterized in that for a total RMS current I within a time interval of 0.1s or less, sum for:

[0017]

[0018] The safety fuse current I after adding the safety margin 熔断 for:

[0019] I 熔断 ≥I sum *2

[0020] For the total RMS current within a time interval of 0.1s or more, the safety fuse current I after adding the safety margin is 熔断for:

[0021] I 熔断 ≥I sum / 80%.

[0022] Preferably, the present invention further provides a method for designing the capacity of an automobile fuse, characterized in that, in step S1, the long-time working electrical appliances include automobile electrical appliances that need to work continuously for at least 100 seconds; the short-time working electrical appliances include automobile electrical appliances with a single working time of less than 100 seconds.

[0023] Preferably, the present invention further provides a method for designing automobile fuse capacity, characterized in that, for the long-time working electrical appliance, the working current data in step S2 is obtained by the supplier;

[0024] For short-time working electrical appliances, the working current data in step S2 is current data collected for a single operation or a single cycle operation.

[0025] Preferably, the present invention further provides a method for designing automobile fuse capacity, characterized in that the time interval between the current data of the long-time working electrical appliance and the short-time working electrical appliance is within 1 ms.

[0026] Preferably, the present invention further provides a method for designing automobile fuse capacity, characterized in that the maximum time interval of the time series of the short-time working electrical appliances should not exceed the time span of the collected current data by one order of magnitude.

[0027] Preferably, the present invention further provides a method for designing automobile fuse capacity, wherein the smaller the time interval, the more accurate the design of the fuse capacity.

[0028] The fuse design method of the present invention simultaneously considers the effects of both long-duration and short-duration operating currents on the fuse, making fuse capacity design more precise. Compared with existing design methods, it can improve the accuracy of at least one specification level and facilitate the design of electronic fuse protection strategies for currents at different time intervals. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Reference will now be made in detail to the preferred embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings to represent the same or similar parts. Furthermore, although the terminology used in this disclosure is selected from commonly known and commonly used terms, some of the terms mentioned in this disclosure may have been selected at the applicant's discretion, the detailed meanings of which are explained in the relevant sections of the description herein. Furthermore, it is required that this disclosure be understood not only by the actual terms used, but also by the meaning connoted by each term.

[0030] The above and other objects, features and advantages of the present invention will become apparent to those skilled in the art from the detailed description of the present invention with reference to the accompanying drawings below.

[0031] Figure 1 This is a fuse blowing time-current characteristic curve diagram in a preferred embodiment;

[0032] Figure 2 It is the working current curve of electrical appliances;

[0033] Figure 3 is an example of a time-current characteristic curve in one embodiment;

[0034] Figure 4 It is a design flow chart of the present invention. DETAILED DESCRIPTION

[0035] To more clearly illustrate the technical solutions of the embodiments of this application, the following is a brief introduction to the drawings required for describing the embodiments. Obviously, the drawings described below are merely examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios based on these drawings without inventive effort. Unless otherwise apparent from the context or otherwise noted, the same reference numerals in the figures represent the same structure or operation.

[0036] As used in this application and the claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" are not intended to refer to the singular but may include the plural. Generally speaking, the terms "comprises" and "include" only indicate the inclusion of the steps and elements specifically identified, and these steps and elements do not constitute an exclusive list. A method or apparatus may also include other steps or elements.

[0037] Unless otherwise specifically stated, the relative arrangement of the parts and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the drawings are not drawn according to actual proportional relationships. The techniques, methods and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the techniques, methods and equipment should be considered as part of the authorization specification. In all examples shown and discussed here, any specific values ​​should be interpreted as being merely exemplary and not as limitations. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that similar numbers and letters represent similar items in the following figures, and therefore, once an item is defined in one figure, it does not need to be further discussed in subsequent figures.

[0038] In the description of this application, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "horizontal, vertical, vertical, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of this application; the directional words "inside and outside" refer to the inside and outside relative to the outline of each component itself.

[0039] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used herein to describe the spatial positional relationship of a device or feature to other devices or features as shown in the figures. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figures. For example, if the device in the drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0040] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is solely for the purpose of distinguishing the corresponding components. Unless otherwise stated, these terms have no special meaning and therefore should not be construed as limiting the scope of protection of this application. Furthermore, while the terms used in this application are selected from commonly known and commonly used terms, some terms mentioned in this specification may have been selected by the applicant at his or her discretion, and their detailed meanings are explained in the relevant sections of this description. Furthermore, this application should be understood not only by the actual terms used, but also by the meaning implied by each term.

[0041] Figure 4 The design steps of the automobile fuse capacity of the present invention are given, and the following is a detailed description of each step of the method:

[0042] Step S1: Classify all electrical appliances according to their working current characteristics;

[0043] According to the working time, the electrical appliances in the designed car are classified into long-time working appliances and short-time working appliances.

[0044] Generally speaking, long-duration electrical appliances need to work continuously for at least 100 seconds, such as lighting systems, cooling fans, audio systems, air-conditioning blowers, etc.; short-duration loads have a single working time of less than 100 seconds, such as horns, window regulators, electric power steering, door locks, etc.

[0045] Step S2: Collecting operating current data of different electrical appliances under typical working conditions;

[0046] For electrical appliances that work for a long time, the operating current data of the electrical appliances under the typical working conditions can be obtained from the electrical appliance supplier.

[0047] For long-duration electrical appliances, Figure 1 An example of a fuse melting time-current characteristic curve is shown. The vertical axis represents time, with a maximum scale of 1000 seconds. Current data for long-duration electrical appliances operating continuously for more than 1000 seconds is collected.

[0048] For electrical appliances that work for a short time, the operating current under typical working conditions is collected by collecting current data for a single or single cycle of operation, such as honking the horn once, raising or lowering the door or window glass once, turning 1 to 2 times, unlocking and locking once each, etc.

[0049] Preferably, the sampling interval of the current data of both the long-time working electrical appliances and the short-time working electrical appliances is within 1 ms.

[0050] Step S3: Calculate the root mean square current of each electrical appliance in the time interval in sequence according to the electrical appliance category and the corresponding time interval sequence;

[0051] Preferably, the time interval sequence in this step needs to be as follows Figure 1 Select from the range of fuse melting current-time curves provided in the example.

[0052] The vertical axis time scale of the curve is a logarithmic scale. A better way is to select the main scale, that is, [0.01s, 0.1s, 1s, 10s, 100s, 1000s]. This way, the amount of calculation is small, but the final curve will be rougher. Another way is to select all scales, that is, [0.01s, 0.02s,…; 0.1s, 0.2s,…; 1s, 2s,…; 10s, 20s,…; 100s, 200s,…; 1000s], which requires a lot of calculation, but the final curve will be smoother).

[0053] For electrical appliances that work for a long time, the time interval sequence can be defined as [0.01s, 0.1s, 1s, 10s, 100s, 1000s] or [0.01s, 0.02s,…; 0.1s, 0.2s,…; 1s, 2s,…; 10s, 20s,…; 100s, 200s,…; 1000s] to make the final time-current curve smoother and the design result of the fuse capacity more accurate.

[0054] For electrical appliances that work for a short time, the maximum time interval of the time series should not exceed one order of magnitude of the time span of the collected current data. For example, if the time span of the current data of a speaker is 10s, the time series can be defined as [0.01s, 0.1s, 1s, 10s].

[0055] Calculate the RMS current I at each time interval RMS The formula is:

[0056]

[0057] In formula (1),

[0058] I i is the i-th continuous current value of the electrical appliance within a specific time interval;

[0059] n is the number of current data collection points within a specific time interval. For example, if the current sampling interval is 1 ms, then when calculating the RMS current value within a 1 s time interval, n is 1000.

[0060] The above method calculates the RMS current at each time interval in sequence. For example, if the time interval sequence is [0.01s, 0.1s, 1s, 10s, 100s, 1000s], the current at the time interval of 0.01s can be calculated first. At this time, any continuous current data with a time interval of 0.01s can be selected from the sampled data and substituted into the above formula to obtain the RMS current of each electrical appliance.

[0061] If the current data spans a longer time interval than the time interval being calculated, you can use this method to calculate multiple RMS current values ​​for the same time interval. The maximum of these RMS currents is selected as the RMS current for the time interval and used in the next calculation.

[0062] For example, if the time span of the collected current data is 10 seconds and the data sampling interval is 0.1 seconds, when calculating the RMS current with a time interval of 1 second, the RMS current values ​​with multiple time intervals of 1 second, such as 0 to 1 second, 0.1 to 1.1 seconds, ..., 8.9 to 9.9 seconds, and 9 to 10 seconds, can be calculated.

[0063] The data sampling interval is the sampling accuracy when testing the working current of an electrical appliance, indicating how often the current data is taken.

[0064] by Figure 2 Looking at the working current curve of an electrical appliance, the data sampling interval is 0.001s. The sampling time span is the total time length of the electrical appliance current sampling data, indicating how long the current data of the electrical appliance continuously works. In the figure, this value is 1000s. The time interval for calculating the root mean square current comes from the value in the time interval sequence, in the example, it is 0.01s.

[0065] Step S4: adding the root mean square currents of all electrical appliances at the same time interval to obtain a total time-current data sequence of the electrical appliances;

[0066] The sum of the root mean square currents in each time interval in this step is the maximum value of the root mean square current in each time interval.

[0067] The formula for calculating the sum of the RMS current in each time interval is:

[0068]

[0069] In formula (2),

[0070] I i is the maximum RMS current of the i-th electrical appliance in the corresponding time interval, and n is the number of all electrical appliances protected by the fuse.

[0071] Furthermore, for corresponding time intervals, that is, the maximum RMS currents of all electrical appliances within 0.01 s are added together, the maximum RMS currents within 0.1 s are added together, and so on.

[0072] Step S5: Select the fuse capacity based on the safety margin.

[0073] Preferably, in order to consider the safety margin, the total RMS current I in the time interval of 0.1s and below is sum , select the safety factor 0.5, then the safety fuse current is:

[0074] I 熔断 ≥I sum *twenty three)

[0075] For the total RMS current in a time interval of more than 0.1s, a safety factor of 0.8 is selected, and the safe fuse current is:

[0076] I 熔断 ≥I sum / 80% (4)

[0077] The safe melting point current I considering the margin is obtained by the above formula 熔断 As the minimum required value, in the fuse melting time-current curve, select the time interval in which the fuse's melting current is greater than the safe melting point current I 熔断 The final fuse capacity is determined accordingly.

[0078] Example:

[0079] Assume that the electrical appliances protected by a fuse include headlights, taillights, blower, navigation, instrument, fuel pump, wiper motor, ignition coil, rear window heating, power steering, horn, window motor and sunroof motor.

[0080] According to step S1 of the method of the present invention, electrical appliances are first divided into two categories: long-duration and short-duration. For details, please refer to Table 1.

[0081] Then refer to step S3, according to the collected current curve, the time interval sequence

[0082] [0.01s, 0.1s, 1s, 10s, 100s, 1000s] Calculate the RMS current value and add up the RMS current of each appliance at the same time interval to obtain the total RMS current of the appliances at different time intervals, as shown in the following table.

[0083]

[0084] Table 1 Example of calculating the RMS current of electrical appliances

[0085] According to Table 1, the current and total current of each electrical appliance in each time interval are obtained by formulas (1) and (2), and the current of the safety margin is finally obtained according to formulas (3) and (4). Threshold corresponds to the safety fuse current I 熔断 The minimum required value.

[0086] By consulting the manufacturer's fuse manual, we can obtain the corresponding fusing current of different specifications of fuses at different time intervals. Together with the total RMS current of the electrical appliances at different time intervals obtained in the above table, we can plot the points on the same logarithmic scale chart and connect them smoothly to obtain Figure 3 .

[0087] In this figure, “Load” represents the total current of the electrical appliances, which corresponds to I in the above formula (2). sum The "Fuse-xxA" curve is the fuse's melting curve. Furthermore, for safety reasons, a certain design margin must be left for the fuse. The "Threshold" curve includes this safety margin.

[0088] The figure also shows that if 100A and 80A fuses are selected, although the fusing current at the 100s and 1000s intervals exceeds the total RMS current of the appliance and the total current after taking into account the safety factor, the fusing current at the 1s and 10s intervals cannot meet the total current requirement of the appliance. This can cause the fuse to blow abnormally during normal operation in some cases, causing vehicle failure or even an accident. If a larger fuse is selected, such as a 150A fuse, while it will ensure that the fuse will not blow during normal operation, the wire diameter must match the fuse capacity. Larger fuses require thicker wire, which wastes material and unnecessarily increases the weight and volume of the wiring harness. It may also prevent the fuse from operating in time to provide protection when the appliance current is abnormal. In summary, a 125A fuse is more appropriate.

[0089] In summary, compared with the prior art, the advantages of the fuse design method of the present invention are:

[0090] This method features easy-to-standardize design standards, is simple to operate, and can be conveniently ported into software algorithms. It simultaneously accounts for the effects of both long-duration and short-duration operating currents on fuses, making fuse capacity design more precise and improving accuracy by at least one specification level compared to existing design methods. Furthermore, it can meet the more precise requirements of electronic fuses for electrical currents, facilitating the design of electronic fuse protection strategies for currents at different time intervals.

[0091] The basic concepts have been described above. It will be apparent to those skilled in the art that the above disclosures are merely illustrative and do not constitute limitations on this application. Although not explicitly stated herein, those skilled in the art may make various modifications, improvements, and amendments to this application. Such modifications, improvements, and amendments are suggested in this application and remain within the spirit and scope of the exemplary embodiments of this application.

[0092] At the same time, this application uses specific terms to describe the embodiments of this application. For example, "one embodiment," "an embodiment," and / or "some embodiments" refer to a certain feature, structure, or characteristic related to at least one embodiment of this application. Therefore, it should be emphasized and noted that "one embodiment," "an embodiment," or "an alternative embodiment" mentioned twice or multiple times in different locations in this specification does not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of this application may be appropriately combined.

[0093] Similarly, it should be noted that, in order to simplify the presentation of this application and thus facilitate understanding of one or more embodiments of the invention, the foregoing descriptions of the embodiments of this application sometimes combine multiple features into a single embodiment, figure, or description thereof. However, this disclosure method does not mean that the subject matter of this application requires more features than those recited in the claims. In fact, an embodiment may have fewer features than all of the features of a single embodiment disclosed above.

[0094] In some embodiments, numbers are used to describe the quantity of components and attributes. It should be understood that such numbers used in the description of the embodiments are modified by the modifiers "about", "approximately" or "substantially" in some examples. Unless otherwise stated, "about", "approximately" or "substantially" indicate that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the description and claims are approximate values, which may change according to the required features of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the general method of retaining digits. Although the numerical domains and parameters used to confirm the breadth of their range in some embodiments of the present application are approximate values, in specific embodiments, the settings of such numerical values ​​are as accurate as possible within the feasible range.

[0095] Although the present application has been described with reference to the current specific embodiments, ordinary technicians in this technical field should recognize that the above embodiments are only used to illustrate the present application, and various equivalent changes or substitutions can be made without departing from the spirit of the present application. Therefore, as long as the changes and modifications to the above embodiments are within the scope of the essential spirit of the present application, they will fall within the scope of the claims of the present application.

Claims

1. A method for designing the capacity of an automobile fuse, wherein the fuse is used in a circuit containing several automobile electrical appliances, characterized in that: The method comprises: Step S1, classifying the plurality of automotive electrical appliances according to their working time into long-time working appliances and short-time working appliances; the long-time working appliances include automotive appliances that need to work continuously for more than 100 seconds; the short-time working appliances include automotive appliances with a single working time of less than 100 seconds; Step S2, obtaining the operating current data of each of the automotive electrical appliances; Step S3, calculating the root mean square current of each of the automotive electrical appliances in each time interval within a time interval sequence: Among them, I i is the i-th continuous current value of the automotive electrical appliance in the time interval, and n is the number of current data collection points in the time interval. When the time span of the current data is greater than the time interval to be calculated, multiple RMS current values ​​are obtained by rolling calculation for the same time interval, and the maximum value of these RMS current values ​​is selected as the RMS current of the time interval. Step S4, summing the root mean square current of each of the automotive electrical appliances at the same time interval to obtain the total root mean square current of the automotive electrical appliances; the total root mean square current I sum for: ； in, For the The maximum value of the RMS current of each electrical appliance in the corresponding time interval, The number of all electrical appliances protected by the fuse; Step S5, obtaining the theoretical minimum fusing current of the automobile fuse according to the total RMS current, and selecting an automobile fuse according to the theoretical minimum fusing current; The method further includes adding a safety margin to the total root mean square current to obtain a safety fusing current of the plurality of automotive electrical appliances, and selecting an automotive fuse having a current greater than the safety fusing current from a fuse fusing time-current characteristic curve; For the total RMS current within a time interval of 0.1s or less, the safety fuse current I after adding the safety margin is 熔断 for: For the total RMS current within a time interval greater than 0.1s, the safety fuse current I after adding the safety margin is 熔断 for:

2. The method for designing automobile fuse capacity according to claim 1, characterized in that: For the long-duration electrical appliance, the operating current data in step S2 is obtained by the supplier; For short-time working electrical appliances, the working current data in step S2 is current data collected for a single operation or a single cycle operation.

3. The method for designing automobile fuse capacity according to claim 2, characterized in that: The time interval between the current data of the long-time working electrical appliance and the short-time working electrical appliance is within 1 ms.

4. The method for designing automobile fuse capacity according to claim 3, characterized in that: The maximum time interval of the time interval sequence for the short-time operating electrical load should not exceed the time span of the collected current data by an order of magnitude.

5. The method for designing automobile fuse capacity according to claim 1, characterized in that: The smaller the time interval, the more accurately the fuse capacity is designed.

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