METHOD FOR DETECTING ELECTRICAL FAULTS IN A CURRENT SUPPLY OF A CONSUMER

Abstract

A method for detecting an electrical fault in a current supply of a consumer, where a transition resistance of the current supply allocated to the consumer is determined from a local voltage value allocated to the consumer, a local current value allocated to the consumer, and a global voltage value, and compared to a resistance threshold value allocated to the consumer, and an electrical fault in the current supply of the consumer is detected as a function of the comparison result.

Claims

1. A method for detecting an electrical fault in a current supply of a consumer, the method comprising: determining a transition resistance of the current supply allocated to the consumer from a local voltage value allocated to the consumer, a local current value allocated to the consumer, and a global voltage value; comparing the determined transition resistance to a resistance threshold value allocated to the consumer; and detecting an electrical fault in the current supply of the consumer as a function of the comparison result.

2. The method as recited in claim 1, wherein the local voltage value allocated to the consumer is ascertained in the consumer.

3. The method as recited in claim 1, wherein the local current value allocated to the consumer is ascertained in the consumer.

4. The method as recited in claim 1, wherein the global voltage value is ascertained from a plurality of local voltage values allocated to respective different consumers.

5. The method as recited in claim 4, wherein the global voltage value is ascertained from the plurality of local voltage values allocated to the respective different consumers through a calculation rule that includes at least one of a maximum-value formation, a mean-value formation, and a median-value formation.

6. The method as recited in claim 1, wherein the transition resistance allocated to the consumer is compared to the resistance threshold value allocated to the consumer in a computer unit that is separate from the consumer.

7. The method as recited in claim 6, wherein the transition resistance allocated to the consumer is determined in the computer unit that is separate from the consumer.

8. The method as recited in claim 1, wherein when an electrical defect is detected, at least one measure is initiated, from the group that includes: (i) an activation of a warning light, (ii) a setting of a fault-memory entry, (iii) a reduction of a permitted maximum current level, and (iv) a change in the operating mode of the consumer.

9. A computer unit for detecting an electrical fault in a current supply of a consumer, the computer unit designed to: determine a transition resistance of the current supply allocated to the consumer from a local voltage value allocated to the consumer, a local current value allocated to the consumer, and a global voltage value; compare the determined transition resistance to a resistance threshold value allocated to the consumer; and detect an electrical fault in the current supply of the consumer as a function of the comparison result.

10. A non-transitory machine-readable memory medium on which is stored a computer program for detecting an electrical fault in a current supply of a consumer, the computer program, when executed on a computing unit, causing the computing unit to perform: determining a transition resistance of the current supply allocated to the consumer from a local voltage value allocated to the consumer, a local current value allocated to the consumer, and a global voltage value; comparing the determined transition resistance to a resistance threshold value allocated to the consumer; and detecting an electrical fault in the current supply of the consumer as a function of the comparison result.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0015] FIG. 1 schematically shows a vehicle electrical system that has a multitude of control units.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0016] FIG. 1 shows a vehicle electrical system 100 as it may form the basis of the present invention, in the form of a wiring diagram. Vehicle electrical system 100 has an electrical current supply 10, which includes a generator and a battery, in particular. Current supply 10 is connected to a fuse box 20 having individual fuses F1, F2, . . . , which are meant to protect connected consumers from an overcurrent.

[0017] Different consumers such as control units 41-45 are connected via a cable harness 30. The control units may in particular involve what is known as an instrument cluster 41 for driver information, a vehicle control unit 42 (VCU) for specifying the driving and operating strategies, a gearbox control unit 43 (GCU) for the gear selection, an engine control unit 44 (ECU) for controlling the internal combustion engine, and a pump control unit 45 (PCU) for controlling a fuel pump. The control units are connected in a data-transmitting manner by way of a data bus 50, such as a CAN bus.

[0018] Preferably, at least one of the control units, e.g., vehicle control unit 42, is set up to execute a preferred specific embodiment of the present invention. At the same time, at least two, and preferably all, control units are developed to repeatedly, e.g., regularly, determine a local voltage value, especially through a measurement, as well as a local current value, especially through measurements, calculations or estimates, and to transmit the determined local voltage values and the local current values to vehicle control unit 42. As an alternative, it may also be the case that vehicle control unit 42 determines the local current values for one or more control unit(s) that are not designed to determine them on their own, for example, in particular via a calculation or estimate with the aid of characteristics maps, for example.

[0019] Vehicle control unit 42 then determines the transition resistance allocated to the consumer for each local voltage value/local current value pair and compares it to at least one resistance threshold value allocated to the consumer.

[0020] An advantageous component of the present invention is a software function, which compiles the available voltage values of the different control units and their current requirement (measured or calculated current requirement) via a network (CAN bus 50 in FIG. 1) (in FIG. 1, via five control units, for example). Systematic corrections, e.g., of offset voltages or ADC measuring errors, are advantageous in this context in order to improve the further calculations.

[0021] These values may be used for determining a global voltage value for a probable supply voltage, which is used as a reference for the vehicle, e.g., as a maximum value, a mean value, a median, a combination thereof, etc. A current-free voltage measurement would be advantageous but is not mandatory. The highest possible reliability of the value of the calculated reference voltage, in particular through the mentioned systematic corrections, is of importance.

[0022] The transition resistance for each supply line to the control units is able to be calculated via the deviation of the individual local voltage values from the global voltage value and the associated current consumption. If the transition resistance deviates considerably in the direction of a higher value, then a developing fault is able to be detected and allocated in a predictive manner, especially before the affected control unit executes a faulty function due to a voltage that is too low.

[0023] For example, the current connection of pump control unit 45 has a weak point 60 that is to be detected as an electrical fault within the framework of the present invention. Weak point 60, for example, is defined in that one core of a four-core current feed line is defective.

[0024] Each connection between the line and the control-unit connection has a transition resistance, which is defined by the plug connection and the copper resistance of the cable. The specific resistance of copper at 25 C. amounts to p=0.0173 mm.sup.2/m.

[0025] The following applies to the electrical resistance of a circular line:

[00001]$R_W=\frac{I.Math..Math.4}{D^2.Math.}$

at D=1 mm diameter, and 1=2*5 m10 m length, the result is R.sub.w=0.22 .

[0026] Together with the plug connection (depending on the manufacturer specifications, e.g. approx. R.sub.s=0.05 ), the following results as transition resistance R.sub.Ci=R.sub.W+R.sub.S for each core i and, accordingly, as total transition resistance R.sub.ges:

[00002]$R_{\mathrm{ges}}=\frac{1}{\frac{1}{R_{C.Math..Math.1}}+\frac{1}{R_{C.Math..Math.2}}+\frac{1}{R_{C.Math..Math.3}}+\frac{1}{R_{C.Math..Math.4}}}$

[0027] This total transition resistance would be 33% higher in case of a defect of a core. In this way an electrical fault is detectable by comparing a currently ascertained total transition resistance to a comparison value or a threshold value.

[0028] Particularly easy to measure is an increased total transition resistance at a high power consumption because a clearly measurable voltage drop then results in local voltage value U.sub.L in comparison with supply voltage U.sub.G as the global voltage value. The instantaneous global voltage value may be determined especially from the voltage values of the particular measuring devices 41-45 that have the lowest possible current consumption just then or, ideally, that have no current consumption at all.

[0029] Instantaneous local voltage value U.sub.L is determined, in particular measured, in pump control device 45, as is local current value I.sub.L. Together with global voltage value U.sub.L, the following results as instantaneous transition resistance R.sub.L:

[00003]$R_L=\frac{U_G-U_L}{I_L}$

[0030] Assuming a regular transition resistance of R.sub.Ci=0.27 per line (1 mm diameter, 2*5 m long, plug), for example, then a total transition resistance R.sub.ges=0.0675 results for four parallel lines. At I.sub.L=20 A current consumption, a regular voltage drop of 1.35V comes about.

[0031] In case of damage, with only three parallel lines, a total transition resistance R.sub.ges=0.09 results, and at a current consumption of 20 A, a voltage drop of now 1.8V. If there is even only one line left for active use, then the voltage drop already amounts to at least 5.4 V. Such voltage differences are easily measurable; conversely, the existing transition resistances are therefore able to be determined quite well and compared to reference values or threshold values.

[0032] For example, one or more resistance threshold value(s) may be stored in a characteristics map for each control unit. In the illustrated case, for instance, at a determined transition resistance of R.sub.L=0.0675, the absence of faults may be assumed; at a determined transition resistance of 0.0675 <R.sub.L<0.09, a developing fault of a core could be assumed, and at a determined transition resistance of R.sub.L>0.09 , an electrical fault, in particular in the form of a core defect seems likely, etc. It may also be useful to additionally provide even higher threshold values for characterizing additional electrical faults, such as a defect of two or three cores. For instance, the threshold values may be determined, such as measured, in a fault-free state, e.g., at the end of the line, for instance also across the whole category for a vehicle type.

[0033] When an electrical defect is detected, at least one measure will preferably be initiated from the group that includes the activation of a warning light, the setting of an error memory entry, a reduction in a permitted maximum current level, a change of the operating mode of the consumer. For instance, a pump power may be reduced.

[0034] The measure makes it possible to reach a vehicle-specific operating state that avoids damage and/or a risk. Such measures depend on the vehicle and are to be stored in a decision logic, for instance.

[0035] In case of faults in the vehicle, each segment of the current supply is able to be evaluated. Through a graphically processed representation on a diagnostic system, for example, the service technician is able to be assisted in searching for the search or in eliminating a fault through this function, or the effect may be viewed online (for instance in case of erratic contacts that lead to changes in the resistance).