DE102021102520A1 - Method for detecting contamination of a cooling air path for a traction battery and control unit - Google Patents

Abstract

The present invention relates to a method (400) for detecting contamination of a cooling air path (3) for a traction battery of an electric vehicle (100), the cooling taking place with a fan (7). The method (400) includes determining a reference profile (201, 202) of a fan parameter and detecting an actual profile (203, 204) of the fan parameter. A progression difference between the reference progression (201, 202) and the actual progression (203, 204) is also determined. It is determined that there is contamination based on the course difference. The invention also relates to a control unit (9) for carrying out the method (400) according to the invention.

Description

The invention relates to a method for detecting contamination of a cooling air path for a traction battery and a control unit for carrying out the method.

An electric vehicle generally requires a temperature control device for cooling and/or heating up a traction battery in order to release energy that has been lost (e.g. drive, battery, etc.) to the environment or to extract energy from the environment (heat pump). Cooling is necessary in order to operate components and systems safely over their service life and to implement operating characteristics (e.g. continuous output of an (electric) motor, charging capacity, etc.). As a rule, energy is exchanged via coolers and air-conditioning condensers through which air flows. A cooling air path is integrated into the front part of the vehicle, which allows cooling air to flow over a cooler package (comprising several coolers). To increase the cooling performance when stationary and when driving slowly, a fan is installed that supports the flow of cooling air. The fan is driven electrically. The operation of the fan affects the range of the electric vehicle, since the fan can be supplied with energy from the traction battery.

Over the period of use, a pressure loss across the cooling air path can increase due to a wide variety of circumstances and circumstances. Thus, an electric vehicle is operated in different climatic conditions (e.g. rain, snow, heat, etc.) and road conditions (e.g. dirt, leaves, blossoms, etc.). As a result, impurities can be introduced into the cooling air path. A cooler network provided on the inlet side of the cooling air path acts like a sieve through fins and tubes. Most contaminants pass through the radiator network and flow out of the vehicle again through the cooling air path. However, larger dirt and foreign objects (e.g. leaves, snow or similar) can get caught on the radiator core. As a result, the radiator network can be blocked temporarily (e.g. due to ice and snow) or for a comparatively long period of time. As a result, there may be a reduction in a flow of cooling air and accordingly a reduction in cooling capacity.

the DE 10 2012 218 190 A1 discloses a method for monitoring a cooling or heating device which is provided for controlling the temperature of a device with an electronic circuit, the cooling or heating device comprising a fan which generates an air flow passing through the device and the electronic circuit. In this case, the electronic circuit is transferred from a first to a second activity state or such a change is detected. A temperature of the electronic circuit in the second activity state is detected and a check is made to determine whether the temperature is outside a predefinable target range. Furthermore, the check can detect a detection of a parameter that characterizes the performance of the blower and can also check whether the parameter is outside a predefinable target range. The parameter can be at least one of a voltage applied to the drive motor of the blower, a current consumed by the drive motor, an electrical power consumed by the drive motor, an actual speed of the drive motor and a target speed of the drive motor.

The object of the present invention is to provide a method and a control device that improve the detection of contamination of a cooling air path for a traction battery of an electric vehicle.

This object is achieved by the method according to claim 1 and the control unit according to claim 10.

Further advantageous refinements of the invention result from the dependent claims and the following description of preferred exemplary embodiments of the present invention.

• - Ermitteln eines Soll-Verlaufs einer Lüfterkenngröße;
• - Erfassen eines Ist-Verlaufs der Lüfterkenngröße;
• - Ermitteln eines Verlaufsunterschieds zwischen dem Soll-Verlauf und dem Ist-Verlauf; und
• - Feststellen, dass eine Verschmutzung vorliegt anhand des Verlaufsunterschieds.

A first aspect of the invention relates to a method for detecting contamination of a cooling air path for a traction battery of an electric vehicle, the cooling taking place with a fan and the method comprising:

• - Determining a target course of a fan parameter;
• - detecting an actual course of the fan parameter;
• - Determining a progression difference between the desired progression and the actual progression; and
• - Determining that there is contamination based on the course difference.

The electric vehicle (also battery electric vehicle or battery electric vehicle, BEV) can be designed as a purely electric vehicle or as a hybrid vehicle.

Contamination within the cooling air path increases the pressure loss along the cooling air path and can reduce the performance of a cooling device of which the fan and the cooling air path are part. In this case, a lack of cooling air mass flow can be compensated for by actuating the fan. The fan requires electrical energy gie. The consumption of additional electrical energy can reduce the range of the electric vehicle and increase costs for a customer (e.g. increased charging of the traction battery and additional cooling of the charger during the charging process require operation of the fan and thus consumption of electrical energy). An increase in noise emissions through fan operation is also possible.

Therefore, in order to improve the cooling, it is necessary to detect the contamination of the cooling air path.

For this purpose, the reference course of a fan parameter is determined. The fan characteristic is a characteristic of the fan that is indicative of a performance of the fan. The fan parameter can include a current consumed by a motor of the fan (fan motor) and/or a voltage applied to the fan motor. The reference curve can be a predeterminable curve that is determined, for example, from models, simulations and/or tests. The reference course is determined for a case in which there is no contamination of the cooling air path. The reference curve is used to convert a predeterminable cooling capacity of the fan to cool the traction battery. In other words, the reference profile is the profile of the fan parameter to be expected while the traction battery is kept in a predetermined temperature range by means of the cooling device or the fan.

The actual course of the fan parameter is also recorded. This can be done using the appropriate measuring device. The current consumed by the fan motor can be recorded using an ammeter, and the voltage applied to the fan motor can be recorded using a voltmeter.

The actual course of the fan parameter can result from controlling the fan. The regulation is designed in such a way that the traction battery is kept in the predeterminable temperature range. For this purpose, the regulation can include a control circuit.

To determine that there is contamination, the actual course is compared with the reference course. In the process, it is determined whether there is a progression difference between the reference progression and the actual progression. Here, the history difference may consider at least one of: a duty cycle, a duration, and a maximum value.

If the cooling air path is soiled, the fan must be operated with a higher power in order to provide the same cooling air mass flow as in the case of an unpolluted cooling air path. Accordingly, the actual curve differs from the reference curve. If there is now a course difference, it can be determined that the cooling air path is contaminated.

Since the corresponding measuring devices for detecting the fan parameter are usually already present in the cooling device, contamination of the cooling air path can be determined without major modifications to the cooling device. Furthermore, the method can also be subsequently implemented in existing electric vehicles. A robust and reliable determination of contamination of the cooling air path can thus be made possible without significant additional effort, in particular since the reference profile and the actual profile of the fan parameter are used to determine the contamination.

In some embodiments, the history difference may account for at least one of the following: duty cycle, duration, and maximum value. The history difference may refer to a difference in the duty cycles, durations, and maximum values between the reference history and the actual history of the fan characteristic. As a rule, the fan or the fan motor is controlled by means of a pulse width modulated voltage (an example for the fan parameter), hereinafter "PWM control signal" (PWM pulse width modulation). The PWM control signal can be described, among other things, by the (signal) duration and the duty cycle.

The PWM drive signal can control/adjust the current drawn by the fan motor (another example of the fan characteristic). The maximum value of the waveform of the consumed current (current waveform) can be derived from the PWM drive signal considering the duty cycle of the PWM drive signal. Depending on which fan parameter is considered, either the maximum value (for the current curve) or the duty cycle (for the PWM control signal curve) can be used to describe the curve of the fan parameter.

By comparing at least one of the duty cycle, the duration and the maximum value of the reference curve with those of the actual curve, the curve difference can be determined in a particularly simple manner.

In other embodiments, the reference history and the actual history may be indicative of a pulse width modulated control signal for the fan. The curves can therefore use the pulse width mo be modulated control signal, ie the PWM drive signal, or the current waveform. As a result, the curve difference can be determined particularly easily by comparing at least one of the duty cycles, the durations and the maximum values of the curves with one another.

In further embodiments, it can be determined that there is contamination when the difference in the course exceeds a predeterminable limit value.

For example, contamination can be detected if a duty cycle ratio between an actual duty cycle (of the PWM control signal), which can be derived from the actual curve, and a reference duty cycle, which can be derived from the reference curve, exceeds a predeterminable duty cycle limit ratio. The predeterminable duty cycle limit ratio can be, for example, from 1.1 to 1.4, in particular from 1.2 to 1.3. The actual duty cycle can, for example, be an average actual duty cycle over a predeterminable time window (eg 60 minutes). Correspondingly, the reference duty cycle can be, for example, an average reference duty cycle over the predeterminable time window.

Additionally or alternatively, contamination can be determined if the duration of the actual history exceeds the duration of the reference history by a predeterminable duration limit value (e.g. 30 minutes).

Furthermore, additionally or alternatively, contamination can be determined if an actual maximum value, which can be derived from the actual curve, is greater than a predeterminable maximum limit value (amount) (e.g. from 10 to 20 amperes, in particular 15 amperes). a reference maximum value that can be derived from the reference history. The actual maximum value can, for example, be an average actual maximum value over the predeterminable time window. Correspondingly, the reference maximum value can be, for example, an average reference maximum value over the predeterminable time window.

The limit values mentioned above are determined in such a way that false-positive determinations can largely be avoided. The specified limit values are examples and can vary greatly depending on the system and vehicle.

In some embodiments, the method can be performed during a stationary operating state of the electric vehicle. A stationary operating state includes those operating states in which the electric vehicle and in particular the traction battery is operated or is under essentially constant operating parameters. Interactions due to external influences such as (opposite) wind, rain, etc., which affect the detection of the actual course of the fan parameter, can thus be reduced as far as possible and the method becomes more precise. Interactions can be caused, for example, by a relative wind, varying ambient temperatures, etc.

In other embodiments, the steady-state operating condition may include charging the electric vehicle. During a charging process, the traction battery of the electric vehicle is charged. In such a case, the actual curve and the reference curve of the fan parameter can be determined for the entire duration of the charging process or for a time section of the charging process. During the charging process, the electric vehicle is stationary and the environmental conditions are essentially constant. The influences on the recording of the actual course are thereby reduced as far as possible and the method becomes more precise.

In further specific embodiments, the course difference can be determined for a predeterminable time segment of the reference course and the actual course. The predeterminable time segment is between a start time and the end time of the curves. For example, the predeterminable period of time can have a duration of 30 to 60 minutes. The reference history and the actual history are compared with one another within the predeterminable time period. By only considering and evaluating a predeterminable time segment, the method can be carried out in a control unit in a particularly resource-efficient manner.

• Erhöhen eines Feststellungszählers, wenn festgestellt wird, dass eine Verschmutzung vorliegt; und
• Ausgeben eines Warnsignals, wenn der Feststellungszähler einen vorbestimmbaren Zählergrenzwert überschreitet.

In some embodiments, the method may further include:

• incrementing a detection counter when it is determined that contamination is present; and
• issuing a warning signal when the detection counter exceeds a predeterminable counter limit.

The detection counter can be stored in a control unit. The detection counter can be used to track how often contamination of the cooling air path is detected.

In some examples, the detection counter may be incremented only when a predeterminable minimum charge time is exceeded. This serves to debounce the detection of contamination, making the method more robust.

If the detection counter exceeds the predeterminable counter limit, the warning signal is issued to a driver of the electric vehicle. In some examples, the predeterminable counter limit may be three detections of contamination.

The warning signal is used to notify the driver that the cooling air path needs to be cleaned. The warning signal can be output via an infotainment system of the electric vehicle, for example. The warning signal can include at least one of acoustic, visual and haptic signals. By the warning signal being output, it can be ensured that the driver initiates suitable measures to clean the cooling air path and thus enable optimized cooling again.

In other specific embodiments, the reference curve can be dependent on an operating state, in particular an aging state, of the traction battery. There can therefore be a large number of different reference curves that can be used depending on the operating state of the traction battery. The operating state of the battery can include a battery temperature, an age of the battery (or the state of aging), a charge capacity of the battery, etc. This makes it possible to determine more precisely whether contamination is present.

A second aspect of the invention relates to a control unit that is set up to carry out one of the methods described above.

• 1 schematisch einen Aufbau einer Kühlvorrichtung;
• 2 schematisch einen Referenz-Verlauf und einen Ist-Verlauf eines PWM-Ansteuerungssignals und eines Stroms;
• 3 schematisch einen Referenz-Verlauf und einen Ist-Verlauf eines Stroms über einen Ladevorgang; und
• 4 ein Verfahren zum Feststellen einer Verschmutzung gemäß einer Ausführungsform.

Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings. It shows:

• 1 schematically a structure of a cooling device;
• 2 schematically a reference course and an actual course of a PWM control signal and a current;
• 3 schematically a reference course and an actual course of a current over a charging process; and
• 4 a method for detecting contamination according to an embodiment.

In 1 an electric vehicle 100 is shown schematically and partially. The electric vehicle 100 has a radiator core 1 (radiator grille) on the front. The cooling system 1 is arranged on the inlet side on a cooling air path 3 and includes air inlets in order to introduce an air mass flow A from the surroundings of the electric vehicle 100 into the cooling air path 3 . A cooler 5 for cooling the air mass flow A is also provided in the cooling air path 3 . A fan 7 is arranged downstream of the radiator 5 in order to support the air mass flow A. The fan 7 is driven by a fan motor (not shown). The fan motor is connected to a control unit 9 of the electric vehicle 100 and is controlled and/or regulated by it. Downstream of the fan 7, the air mass flow A passes a traction battery (not shown) for cooling the same.

Over the period of use of the electric vehicle 100, the cooling system 1 may become soiled. This leads to an at least partial blocking of the air mass flow A at the cooling network 1 when it is introduced into the cooling air path 3 . Furthermore, impurities can also be introduced into the cooling air path 3 . In both cases, to put it another way, the cooling air path 3 becomes contaminated. This leads to a reduced air mass flow A, which is routed to the traction battery if the fan is controlled with a PWM control signal with a reference profile 201 . The reference course 201 is determined for a case in which there is no contamination of the cooling air path 3 .

In 2 two diagrams are shown in which a voltage U applied to the fan motor and a current I consumed by the fan motor are shown over time t. In particular, the reference profile 201 and an actual profile 203 of the PWM control signal (voltage) are shown. Furthermore, a reference profile 202 and an actual profile 204 of the current, which can be determined/derived from the reference profile 201 and the actual profile 203 of the PWM control signal, are shown schematically and qualitatively.

The actual profile 203 of the PWM control signal corresponds to an exemplary profile of the PWM control signal in a case in which the cooling air path 3 is contaminated. The same applies to the actual profile 204 of the current.

A period duration (switching period) T ₀ and a switch-on duration t ₀ are entered in the reference curve 201 of the PWM control signal. The period duration T ₀ in the reference profile 201 and the actual profile 203 is constant and can be 40 Hz, for example. The period duration T ₀ and a switch-on duration t ₁ of the actual profile 203 of the PWM control signal are entered accordingly. The ratio of duty cycle to period corresponds to a duty cycle of the PWM drive signal.

In the present case, the on-time t ₀ is constant for the reference curve 201 of the PWM control signal. The same applies to the on-time t ₁ of the actual curve 203 of the PWM control signal. In other examples, the duty cycles t ₀ , t ₁ may vary.

In the case of the actual curve 203 of the PWM control signal, there is contamination in the cooling air path 3, which is why the fan 3 is operated with a larger PWM control signal or with a larger duty cycle compared to the reference curve 201 of the PWM control signal, in order to Provide cooling capacity for cooling the traction battery. Therefore, t ₁ > t ₀ . This is because, based on contamination of the cooling air path 3, the air mass flow A would drop when the fan 7 is controlled with the reference curve 201 of the PWM control signal. The cooling capacity would also decrease accordingly. The fan 7 must therefore be controlled with the larger PWM control signal according to the actual curve 203 of the PWM control signal than in the reference curve 201 of the PWM control signal. Therefore, the duty cycle of the actual waveform 203 (actual duty cycle) is larger than the duty cycle of the reference waveform 201 (reference duty cycle) of the PWM drive signal. Furthermore, the actual curves 203, 204 have a longer signal/curve duration than the reference curves 201, 202 in order to allow longer operation of the fan 7, as a result of which cooling takes longer.

The duty cycle of the PWM drive signal affects the current drawn. A maximum value of the reference curve 202 (reference maximum value) is smaller than the maximum value of the actual curve 204 of the current (actual maximum value), since a duty cycle of the reference curve 201 of the PWM control signal is smaller than a duty cycle of the actual - Course 203 of the PWM control signal. The maximum value is the current value at the maxima or peaks of the current curves 202, 204.

In 3 a diagram is shown in which a reference curve 301 and an actual curve 303 of the current (consumed by the fan motor) are shown as an example and qualitatively over a charging process of the traction battery. 3 shows a different example than in 2 . The current I is plotted against time t in the diagram. Out of 3 it can be seen that the actual profile 303 of the current has a higher maximum value and a longer duration in comparison to the reference profile 301 .

4 FIG. 4 shows a method 400 for determining contamination of the cooling air path 3 according to an embodiment. S and E represent a start and an end, respectively, of the method 400.

In 401 a charging process for charging the traction battery is started.

In 402 it is determined or checked whether operation of the fan 7 (fan operation) is required to cool the traction battery. This can be done, for example, via a temperature control that sets the battery temperature within a predetermined target range. If the check in 402 shows that fan operation is necessary, the fan motor is activated in 403a with a corresponding PWM activation signal. If the check in 402 shows that no fan operation is necessary, the method 400 jumps to 406. In 406 it is checked whether the traction battery has reached a predeterminable state of charge (for example fully charged).

In 404, the actual profile 203 of the PWM control signal (via the charging process) is recorded.

In 405, the reference profile 201 of the PWM control signal (for the charging process) is determined. The reference profile 201 can be retrieved from a database stored in the control unit 9, for example. The order of 404 and 405 can be swapped.

Then, in 406, the above-mentioned check is carried out as to whether the predeterminable state of charge has been reached. If the result of the check is negative, the method 400 jumps back to 402. If the result is positive, the method 400 continues to 407.

In 407 a profile difference between the reference profile 201 and the actual profile 203 of the PWM control signal is determined.

In 408 it is checked whether the difference in the course exceeds a corresponding predeterminable limit value. For example, it can be checked whether a difference in terms of a duty cycle, in particular an average duty cycle (e.g. over a predeterminable time window), between the reference profile 201 and the actual profile 203 exceeds a predefinable duty cycle limit ratio. Additionally or alternatively, it can be checked whether a difference in terms of an activation duration (signal duration) between the curves 201, 203 exceeds a predeterminable duration limit value.

If the result of check 408 is negative, i.e. the curve difference is less than the predeterminable limit value, then method 400 is ended. In other words, no contamination of the cooling air path 3 is detected.

If the result of test 408 is positive, method 400 proceeds to 409 . In 409 it is determined that the cooling air path 3 is contaminated. Also in 409, a determination counter may be incremented by one. In some examples, the determination counter may be incremented only when a predeterminable minimum charge time to reach the predeterminable state of charge is met or exceeded.

In 410 it is checked whether the detection counter exceeds a (further) predeterminable counter limit value. If no, the method 400 ends. If so, in 411 the determination counter can be read out by customer service, for example in a workshop.

In 412 it is checked whether the detection counter exceeds a predeterminable counter limit value. If no, the method 400 ends.

If the result of the check in 412 is positive, a warning signal is output to the driver in 413 to draw his attention to the fact that the cooling air path 3 needs to be cleaned.

In an alternative embodiment to the method 400, the reference profile 202 and the actual profile 204 of the current can also be used instead of the reference profile 201 and the actual profile 203 of the PWM control signal. Correspondingly, in 408 the reference profile 202 and the actual profile 204 of the current are compared with one another with regard to the maximum value instead of the duty cycle.

Reference List

1

radiator mesh

3

cooling air path

5

cooler

7

Fan

9

control unit

100

vehicle

201

Reference course of the PWM control signal

202

Reference history of the current drawn by the fan motor

203

Actual progression of the PWM control signal

204

Actual history of the current consumed by the fan motor

301

Reference history of the current drawn by the fan motor

303

Actual history of the current consumed by the fan motor

400

Method for detecting contamination of the cooling air path

A

air mass flow

t0

Switch-on time in the reference history

T0

Period length in the reference history

t1

Switch-on time in the actual history

T1

Period duration in the actual history

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102012218190 A1 [0004]

Claims (10)

Method (400) for determining contamination of a cooling air path (3) for a traction battery of an electric vehicle (100), the cooling taking place with a fan (7) and the method (400) comprising: determining a reference profile (201, 202) of a fan parameter; detecting an actual course of the (203, 204) fan parameter; determining a history difference between the reference history (201, 202) and the actual history (203, 204); and Determining that there is contamination based on the course difference. Method (400) according to claim 1 , wherein the history difference takes into account at least one of: a duty cycle, a duration, and a maximum value. Method (400) according to claim 1 or 2 , wherein the reference course (201, 202) and the actual course (203, 204) are indicative of a pulse width modulated control signal for the fan (7). Method (400) according to one of the preceding claims, it being determined that there is contamination if the difference in the course exceeds a predeterminable limit value. Method (400) according to Claim one of the preceding claims, the method (400) being carried out during a stationary operating state of the electric vehicle (100). Method (400) according to claim 5 , wherein the stationary operating state comprises a charging process of the electric vehicle (100). Method (400) according to one of the preceding claims, in which the course difference is determined for a predeterminable time segment of the reference course (201, 202) and the actual course (203, 204). The method (400) of claim any one of the claims, further comprising: incrementing a detection counter when it is determined that contamination is present; and issuing a warning signal when the detection counter exceeds a predeterminable counter limit. Method (400) according to Claim one of the preceding claims, in which the reference curve (201, 202) is dependent on an operating state, in particular an aging state, of the traction battery. Control unit (9), which is set up to the method (400) according to one of Claims 1 until 9 to perform.

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