Method and device for detecting intrusion of liquid into a housing of a control unit and vehicle equipped with such a device

Abstract

The present invention detects the ingress of liquid, such as water, into the housing of a control unit, particularly a control unit of a steer-by-wire steering system. [Solution] The method includes detecting 102 a first characteristic quantity 202 characterizing the temperature within the housing, detecting 104 a second characteristic quantity characterizing the relative air humidity within the housing, storing 108 values ​​of the first and second characteristic quantities characterizing the temperature and relative air humidity within the housing, respectively, existing at at least one early point in time, particularly at predetermined time intervals, determining 106 an operating state of the control unit depending on the power consumption and / or the first characteristic quantity of the control unit, wherein the control unit includes a first operating state and a second operating state, the first operating state having less power consumption than the second operating state, and detecting 110 liquid intrusion depending on the determined operating state, the first characteristic quantity and the second characteristic quantity.

Description

[Technical Field]

[0001] The present invention relates to a method and device for detecting the ingress of a liquid, particularly a liquid containing water, for example water, into a housing of a control unit, and to a vehicle equipped with such a device. [Background technology]

[0002] Water ingress into the control unit, caused for example by a housing defect, such as a leak, can result in damage or malfunction of the electronics of the control unit. This malfunction jeopardizes the safe operation of the vehicle equipped with the control unit. To increase the safety of use of electronic devices, humidity sensors are used in various electronic devices in the vehicle. Direct limits of relative air humidity are useful for identifying condensation. The relative air humidity is evaluated locally at a single location of the humidity sensor. Temperatures within the housing of the electronic device are not uniform, resulting in localized condensation, for example, on cooling bodies whose temperatures are below the dew point. Accordingly, the occurrence of condensation does not necessarily mean that the housing of the electronic device is damaged. Summary of the Invention [Problem to be solved by the invention]

[0003] It is therefore desirable to be able to reliably detect the intrusion of liquid into the control unit. [Means for solving the problem]

[0004] Disclosure of the Invention This is achieved by the method, the device and the vehicle equipped with said device according to the independent claims.

[0005] A method for detecting the intrusion of a liquid, in particular a liquid containing water, into a housing of a control unit, in particular a control unit of a steer-by-wire steering system, comprises: detecting a first characteristic quantity characterizing a temperature in the housing; detecting a second characteristic quantity characterizing a relative air humidity in the housing; storing at least one value of the first characteristic quantity and the second characteristic quantity characterizing the temperature and the relative air humidity in the housing, respectively, existing at least at one earlier point in time, in particular for a predetermined time interval; identifying an operating state of the control unit as a function of the power consumption and / or the first characteristic quantity, the control unit including a first operating state and a second operating state, the first operating state having a lower power consumption than the second operating state; and detecting the intrusion of the liquid as a function of the identified operating state, the first characteristic quantity, and the second characteristic quantity. The first operating state is, for example, a standby operating state, and the second operating state is characterized as a working state, a power-on state, or a loaded state. The first operating state is characterized, for example, by the control unit's power consumption or current consumption being less than 200 μA, particularly less than 100 μA. In the first operating state, the control unit, for example, does not substantially exhibit self-heating, whereas in the second operating state, the increased power consumption results in increased power losses, which in turn leads to an increase in the temperature inside the housing. Detection depending on the operating state allows for more reliable identification of liquid intrusion into the housing, since the relative air humidity and temperature inside the housing behave differently depending on the operating state.

[0006] In a first operating state, the method includes determining a first parameter characterizing the dynamics of the relative air humidity inside the housing, particularly the duration during which the relative air humidity inside the housing changes by a predetermined value, in response to the second characteristic quantity and at least one stored value of the detected second characteristic quantity, and comparing the first parameter with a predetermined first threshold value. Liquid intrusion is detected when the first parameter exceeds the first threshold value, particularly when the first parameter falls below the first threshold value. The first parameter may be determined when the first characteristic quantity exhibits a behavior, e.g., a constant behavior, characterizing equilibrium between the temperature outside the housing and the temperature inside the housing. Equilibrium between the temperature outside the housing and the temperature inside the housing is thermal equilibrium. In the second operating state, a temperature fluctuation of 10°C may occur within, for example, two minutes. For example, the first characteristic quantity is considered to exhibit constant behavior when the temperature inside the housing changes by less than 2-3°C / min, particularly less than 1°C / min. The first parameter can be described as the rise time during which the relative air humidity increases by a predetermined value, e.g., 10%. At a constant temperature, the relative air humidity inside the housing and the relative air humidity outside the housing are compensated over time. This behavior is similar to the behavior of gas exchange. In an undamaged control unit, this compensation occurs via the pressure compensation element and the interface of the connecting wiring. If the housing is damaged, for example, by a leak, this compensation is achieved in a shorter time than in an undamaged housing. Furthermore, if liquid enters the housing, the relative air humidity inside the housing increases more quickly, especially at a constant temperature. Therefore, liquid intrusion can be detected using the first parameter and the first threshold value. The threshold value can be determined, for example, by testing a control unit housing that is not infiltrated with liquid. The first parameter can be efficiently determined using stored values. Furthermore, comparing the first parameter with the predetermined first threshold value enables computationally efficient and reliable detection of liquid intrusion in a first operating state in which the temperature inside the housing is substantially constant.

[0007] In a second operating state, the method may include determining a second threshold value for a second characteristic quantity as a function of a power dissipation of the control unit, the second threshold value characterizing a identifiable increase in temperature within the housing, and comparing the second characteristic quantity with the determined second threshold value, wherein liquid intrusion is detected when the second characteristic quantity exceeds the second threshold value. The power dissipation characterizes the difference between the power supplied to the control unit and the power dissipated by the control unit. The power dissipation causes the control unit to dissipate heat and generate heat. In the second operating state, the heat dissipation causes an increase in the temperature within the housing, which results in a corresponding dynamic behavior of the relative air humidity within the housing. By comparing the second characteristic quantity with the second threshold value, which varies depending on the power dissipation of the control unit, liquid intrusion into the housing can be reliably and efficiently detected at various operating points of the control unit.

[0008] The temperature outside the housing may be estimated in response to the temperature rise inside the housing and the detected first characteristic quantity, and the maximum possible relative air humidity inside the housing in the absence of liquid intrusion into the housing may be determined in response to the estimated temperature outside the housing, and a second threshold value may characterize this maximum relative air humidity inside the housing, thereby accurately detecting liquid intrusion into the housing with a high probability.

[0009] To determine the second threshold, the August-Roche-Magnus model may be used, which allows for efficient determination of the second threshold.

[0010] In a second operating state, the method may include determining a second parameter characterizing a variation of a second characteristic quantity relative to a variation of the first characteristic quantity, in particular a change in relative air humidity within the housing due to a change in temperature within the housing; detecting a value of the second characteristic quantity after a predetermined period of time from the sudden positive change in temperature within the housing when the second parameter assumes a positive value and the first characteristic quantity characterizes a sudden positive change in temperature within the housing; and comparing the detected second characteristic quantity before the sudden positive change in temperature with the detected value of the second characteristic quantity after the predetermined period of time, whereby intrusion of liquid into the housing is detected if the detected second characteristic quantity before the sudden positive change in temperature characterizes a relative air humidity lower than or equal to the value of the second characteristic quantity after the predetermined period of time. As a result, the method makes it possible to distinguish a short-term increase in relative air humidity caused by a humidity retention effect of components of the control unit from actual intrusion of liquid into the control unit housing. The predetermined period of time can be determined, for example, by testing the control unit without intrusion of liquid. Components of the control unit, for example plastic parts of the housing, semiconductors or epoxy layers of printed circuit boards, can absorb and release moisture.

[0011] In a second operating state, the method may include determining a third parameter characterizing the absolute air humidity in the housing as a function of the first and second characteristic quantities, particularly using the Auguste-Roche-Magnus model, when the second parameter assumes a positive value; determining a fourth parameter characterizing a variation of the third parameter in response to a variation of the first characteristic quantity, particularly a variation of the absolute air humidity due to a change in temperature in the housing, as a function of the third parameter and the first characteristic quantity; and comparing the fourth parameter with a predetermined third threshold value, detecting intrusion of liquid into the housing if the fourth parameter exceeds the third threshold value. The use of the absolute air humidity improves the method in terms of reliably detecting intrusion of liquid into the housing. The third threshold value characterizes, for example, the amount of moisture that can be absorbed by components of the control unit and released accordingly. The third threshold value can be determined, for example, by testing the control unit in the absence of intrusion of liquid. This allows the method to better distinguish between the actual intrusion of liquid into the housing and the dynamics of the air humidity inside the housing caused by humidity retention effects.

[0012] An apparatus for detecting the intrusion of a liquid, in particular a liquid containing water, e.g. water, into a housing of a control unit, in particular a control unit of a steer-by-wire steering system, comprises a first sensor device configured to sense a first characteristic quantity characterizing the temperature inside the housing and a second sensor device configured to sense a second characteristic quantity characterizing the relative air humidity inside the housing, the apparatus being configured to perform a method according to the above description.

[0013] The first sensor device and the second sensor device may be configured as a composite sensor device.

[0014] The vehicle comprises a control unit having a housing and an apparatus according to the above description.

[0015] Further embodiments will be apparent from the drawings and the description that follows. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 10 shows a flowchart of a method for detecting the intrusion of liquid into a housing of a control unit. [Figure 2] FIG. 1 illustrates a portion of a flowchart of a method embodiment. [Figure 3] FIG. 1 illustrates a portion of a flowchart of a method embodiment. [Figure 4] FIG. 1 illustrates a portion of a flowchart of a method embodiment. [Figure 5] FIG. 10 is a diagram showing the change in temperature and relative air humidity inside the housing over time. [Figure 6] FIG. 10 is a diagram showing the change in temperature and relative air humidity inside the housing over time. [Figure 7] FIG. 1 illustrates a portion of a flowchart of a method embodiment. [Figure 8] 1 is a schematic diagram of an apparatus for detecting the intrusion of liquid into a housing of a control unit. [Figure 9] FIG. 1 shows a flowchart of a method embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] 1 shows a flow chart of a method 100 for detecting intrusion 2 of a liquid, particularly a liquid containing water, e.g., water, into a housing 302 of a control unit 300, particularly a control unit 300 of a steer-by-wire steering system (FIG. 8). The method 100 includes detecting 102 a first characteristic quantity 202 characterizing a temperature 4 within the housing 302 (FIG. 8). The first characteristic quantity 202 may be, for example, the temperature 4 within the housing 302. The method 100 further includes detecting 104 a second characteristic quantity 204 characterizing a relative air humidity 6 within the housing 302 (FIG. 8). The second characteristic quantity 204 may be the relative air humidity 6 within the housing 302. The relative air humidity is the ratio, expressed as a percentage, between the air humidity present and the amount that would be present if the air were saturated.

[0018] The method 100 includes determining 106 an operating state of the control unit 300 in response to a power consumption and / or a first characteristic quantity 202 of the control unit 300, the control unit 300 including a first operating state 206 and a second operating state 208, the first operating state 206 having a lower power consumption than the second operating state 208. For example, if the control unit is a control unit of a steer-by-wire steering system provided in a vehicle, the second operating state 208 is, for example, an operating state in which the vehicle is in motion and the control unit is being used to control an actuator of the steer-by-wire steering system. In this example, the first operating state 206 exists, for example, when the vehicle is stationary and not ready to move.

[0019] The method 100 includes storing 108 at least one value 202a, 204a of a first characteristic quantity 202 and a second characteristic quantity 204, respectively, characterizing the temperature 4 and relative air humidity 6 within the housing 302, respectively, existing at at least one earlier point in time, in particular for a predetermined time interval. A number of values ​​202a, 204b may be stored in a table, or simply one value 202a, 204b each from an earlier point in time. The time interval may be fixed or variable. The time interval may be preset, for example, depending on the processor and / or storage capacity of the computing device implementing the method.

[0020] The method 100 includes detecting 110 a liquid intrusion 2 as a function of the determined operating conditions 206, 208, the first characteristic 202 and the second characteristic 204.

[0021] 2 illustrates a portion of an embodiment of the method 100. This portion relates to a procedure for detecting 110 a liquid intrusion 2. In a first operating state 206, the method 100 may include determining 112 a first parameter 210 characterizing a dynamic characteristic of the relative air humidity 6 in the housing 302, in particular the duration over which the relative air humidity 6 in the housing 302 changes by a predetermined value, as a function of the second characteristic quantity 204 and at least one stored value 204a of the sensed second characteristic quantity 204, respectively. The first parameter may be referred to, for example, as a rise time. The predetermined amount may be, for example, 2-10% relative air humidity (rH).

[0022] The embodiment of the method 100 further comprises comparing 114 the first parameter 210 with a predetermined first threshold 212, whereby a liquid intrusion 2 is detected if the first parameter 210 exceeds the first threshold 212, in particular if the duration is less than the first threshold 212. The first threshold 212 can be determined, for example, by testing at a constant temperature with a control unit that has not been infiltrated with liquid. These control units are referred to below as "control units with good housings" or "good control units." If the test is performed using a test chamber in which the relative air humidity can be adjusted, the dynamics or rise time of the test chamber can be determined by the relationship

number

[0023] The first parameter 210 is determined 112 when the first characteristic quantity 202 exhibits a behavior, e.g., a constant behavior, that characterizes an equilibrium between the temperature 8 outside the housing 302 (FIG. 8) and the temperature 4 inside the housing 302. When the temperature 4 inside the housing is constant, in a good housing, the relative air humidity changes slowly even when the temperature 8 outside the housing changes. If liquid enters the housing, the relative air humidity 6 inside the housing 302 changes more quickly. This phenomenon is detected by the comparison 114. This phenomenon is particularly noticeable when the relative air humidity 6 inside the housing 302 increases.

[0024] 3 illustrates a flow chart of a portion of an embodiment of the method 100, which relates to a procedure for detecting 110 liquid intrusion 2. In a second operating state 208, the method 100 may include determining 116 a second threshold value 214 for the second characteristic quantity 204 as a function of the power dissipation of the control unit 300, which characterizes an identifiable increase in temperature 4 within the housing 302. The method 100 in this embodiment further includes comparing 118 the second characteristic quantity 204 with the determined second threshold value 214, whereby liquid intrusion 2 is detected when the second characteristic quantity 204 exceeds the second threshold value 214. The second threshold value 214 and the second characteristic quantity 204 may be expressed, for example, as relative air humidity rH (percent).

[0025] The power loss can be determined, for example, from the difference between the power supplied and the power emitted by the control unit 300, for example via a shunt resistor. The power loss characterizes the heat generation or temperature rise in the housing.

[0026] Depending on the increase in temperature 4 inside the housing 302 and the detected first characteristic quantity 202, a temperature 8 outside the housing 302 may be estimated, and depending on the estimated temperature 8 outside the housing 302, a maximum possible relative air humidity inside the housing 302 may be determined in the absence of liquid penetration 2 into the housing 302, with a second threshold value 214 characterizing this maximum relative air humidity inside the housing 302. For a specific temperature 8 outside the housing 302 and a specific increase in temperature 4 inside the housing, assuming an air humidity outside the housing 302 of 100% rH, if a good housing 302 is present, the relative air humidity 6 inside the housing 302 will only reach a limited value, since the temperature 4 inside the housing 302 will increase by the amount of the increase in temperature 4 inside the housing 302. Starting from the determined rise in temperature 4 inside the housing 302 and the detected temperature 4 inside the housing 302, the temperature outside the housing 302 is estimated and a second threshold 214 is determined by assuming a relative air humidity outside the housing of 100% rH.

[0027] The Auguste-Roche-Magnus model may be used to determine 116 the second threshold 214. This model describes the relationship between different temperatures and relative air humidity in an adiabatic system:

number

[0028] Here, rH1 represents a first relative air humidity that can be used, for example, to determine the second threshold 214. The variable rH2 represents a second relative air humidity that can be set, for example, to 100%, to determine the second threshold 214. The variable T1 represents a first temperature at which the first relative air humidity exists. T1 represents, for example, the detected temperature inside the housing 302 in the example of determining the second threshold 214. The variable T2 represents a second temperature at which the second relative air humidity exists. T2 represents, for example, the temperature outside the housing 302 estimated depending on the power loss in the example of determining the second threshold 214.

[0029] The parameters a, b and c can, for example, parameterize the table based on the following tabular format:

[0030] [Table 1]

[0031] FIG. 4 illustrates a flow chart of a portion of an embodiment of the method 100. This portion relates to a procedure for detecting 110 liquid intrusion 2. In a second operating state 208, the method 100 may include determining 120 a second parameter 216 that characterizes a variation in the second characteristic 204 relative to a variation in the first characteristic 202, specifically, a change in relative air humidity 6 within the housing 302 due to a change in temperature 4 within the housing 302. The second parameter 216 may be expressed as a derivative drH / dT. Furthermore, the method 100 according to this embodiment includes detecting 122 a value 219 of the second characteristic 204 after a predetermined period 218 from a positive abrupt change 12 ( FIG. 8 ) in the temperature 4 within the housing 302, and comparing 123 the detected value 219 of the second characteristic 204 before the positive abrupt change 12 in the temperature 4 with the detected value 219 of the second characteristic 204 after the predetermined period 218. Detecting 122 and comparing 123 are performed when the second parameter 216 assumes a positive value and the first characteristic quantity 202 characterizes a positive abrupt change 12 in the temperature 4 within the housing 302. In this case, a liquid intrusion 2 into the housing 302 is detected when the detected second characteristic quantity 204 before the positive abrupt change 12 in the temperature 4 characterizes a relative air humidity rH that is lower than or equal to a value 219 of the second characteristic quantity 204 after the predetermined period 218.

[0032] FIG. 5 shows an exemplary time-dependent change in the temperature 4 and the relative air humidity 6 within the housing 302. Here, the parameter T represents temperature, rH represents relative air humidity, and t represents time. In this example, the housing 302 is a healthy housing 302, free of liquid intrusion 2. As the temperature increases, the humidity saturation limit also increases. For a constant absolute amount of humidity, as the temperature increases, the relative air humidity decreases, and vice versa. Thus, for example, a negative value of the derivative drH / dT or the second parameter 216 indicates that liquid has not infiltrated 2 into the housing 302. If the derivative drH / dT or the parameter 216 is positive or greater than zero, there may be liquid intrusion 2 into the housing 302. Due to the humidity-retaining effect of the components of the control unit 300, an increase in the temperature 4 within the housing 302 may release this absorbed moisture, resulting in a corresponding increase in absolute air humidity, which may cause a brief increase in the relative air humidity 6 within the housing 302.

[0033] 6 illustrates an exemplary change over time in the temperature 4 and the relative air humidity 6 within the housing 302. The temperature 4 within the housing 302 undergoes a positive jump 12. The change in the relative air humidity 6 within the housing indicates a brief rise in relative air humidity caused by a humidity retention effect. In a good housing 302, this brief rise will drop over a period of time after the positive jump 12. A predetermined period of time 218 characterizes this period of time. The predetermined period of time 218 can be determined, for example, by testing using a good control unit 300.

[0034] To distinguish an actual liquid intrusion 2 from a brief increase in the relative air humidity 6 within the housing 302, the detected second characteristic 204 before the sudden positive change 12 in the temperature 4 is compared 123 with the detected value 219 of the second characteristic 204 after a predetermined period 218. If the relative air humidity 6 within the housing 302 does not decrease after the predetermined period 218, then there is a high probability that a liquid intrusion 2 exists within the control unit 300 or within the housing 302 of the control unit 300.

[0035] FIG. 7 shows a flow chart of a portion of an embodiment of the method 100, which relates to a procedure for detecting 110 a liquid intrusion 2. In a second operating state 208, the method 100 may include determining 124 a third parameter 220 characterizing the absolute air humidity 10 in the housing 302 as a function of the first characteristic quantity 202 and the second characteristic quantity 204, in particular using the Auguste-Roche-Magnus model, if the second parameter 216 assumes a positive value. The third parameter 220 may, for example, be the absolute air humidity aH. The absolute air humidity is expressed, for example, in grams of water vapor per cubic meter of air volume and is a measure of the actual amount of water vapor (humidity) in the air, independent of the air temperature. The greater the amount of water vapor, the higher the absolute air humidity. The following relationship is used:

[0036]

number

[0037] where ρ ν represents absolute air humidity aH, e.g., third parameter 220. rH is relative air humidity, e.g., relative air humidity 6 in housing 302 or second characteristic quantity 204. T represents temperature, e.g., temperature 4 in housing 302 or first characteristic quantity 202. T0 is a parameter whose value represents absolute zero, e.g., 273.15°C. Parameters a, b, and c can be parameterized in the tabular form above.

[0038] Furthermore, the method 100 in this embodiment includes determining 126 a fourth parameter 222 characterizing a variation of the third parameter 220 with respect to a variation of the first characteristic quantity 202, in particular a variation of the absolute air humidity 10 with a change in temperature 4 within the housing 302, as a function of the third parameter 220 and the first characteristic quantity 202. The fourth parameter 222 can be expressed as a derivative daH / dT.

[0039] Furthermore, the method 100 in this embodiment includes comparing 128 the fourth parameter 222 with a predetermined third threshold 224, detecting liquid intrusion 2 into the housing 302 when the fourth parameter 222 exceeds the third threshold 224. Due to the humidity retention effect, when the temperature 4 inside the housing increases, the absolute air humidity 10 inside the housing increases, and accordingly, the derivative daH / dT, e.g., the fourth parameter 222, exhibits a positive value. If liquid is present in the control unit or liquid intrusion 2 into the control unit 300 occurs, the absolute air humidity 10 inside the housing 302 increases more rapidly as the temperature 4 inside the housing increases. This means that the derivative daH / dT, e.g., the fourth parameter 222, assumes a larger value. Testing with a good control unit 300 can identify the humidity retention effect and determine the third threshold 224 for the fourth parameter 222 or the derivative daH / dT.

[0040] The above-described embodiments of detection 110 may be included in any combination individually or in parallel in method 100, where if any of these procedures detects liquid intrusion 2, then liquid intrusion 2 into control unit 300 or housing 302 may be detected. In short, the procedures in method 100 may be logically ORed together during detection 110.

[0041] 8 shows schematically a control unit 300, in particular a control unit 300 for a steer-by-wire steering system, and an apparatus 400 for detecting the intrusion 2 of a liquid, in particular a liquid containing water, into a housing 302 of the control unit 300. The apparatus 400 comprises a first sensor device 402 configured to sense 102 a first characteristic quantity 202 characterizing a temperature 4 within the housing 302, and a second sensor device 404 configured to sense a second characteristic quantity 204 characterizing a relative air humidity 6 within the housing 306.

[0042] The apparatus 400 may include a computing device 406 configured to perform the method 100. The computing device 406 may be, for example, an externally located control unit or a computational unit integrated into the control unit 300.

[0043] In the illustrated example, the control unit 300 includes a defect 304 in its housing 302, through which a liquid, e.g., water, may ingress 2. When the housing 302 is intact, air and humidity are exchanged between the interior and exterior of the housing, e.g., via the piping and connection interface 308 and / or the pressure compensation valve 306. This exchange is affected by the defect 304, and in particular the liquid ingress 2. This effect is analyzed by the apparatus 400 and method 100, so that the liquid ingress 2 can be detected.

[0044] The first sensor device 402 and the second sensor device 404 may be configured as a composite sensor device.

[0045] 9 shows a flowchart of an embodiment of method 100 that combines the above steps of detection 110. For illustrative purposes, the individual method steps are labeled using logical comparison operators, where the comparison operators "<" mean "less than," ">" mean "greater than," "<=" mean "less than or equal to," and ">=" mean "greater than or equal to." The results of these comparisons are labeled with the abbreviations "T" for true and "F" for false. Reference numeral 2 indicates that liquid intrusion 2 into housing 302 has been detected, while reference numeral 1 indicates that no liquid has intruded into housing 302 or control unit 300.

[0046] To determine the second threshold 214 and / or the third parameter 220, an alternative model approach to the Auguste-Roche-Magnus model may be used, which allows for determining the second threshold 214 and / or the third parameter 220.

Claims

1. A method (100) for detecting the intrusion (2) of a liquid, in particular a liquid containing water, e.g. water, into a housing (302) of a control unit (300), in particular of a steer-by-wire steering system, comprising: - sensing (102) a first characteristic quantity (202) characterizing the temperature (4) inside said housing (302); - detecting (104) a second characteristic quantity (204) characterizing the relative air humidity (6) inside said housing (302); - storing (108) at least one value (202a, 204a) of said first characteristic quantity (202) and said second characteristic quantity (204), respectively, characterizing the temperature (4) and the relative air humidity (6) in said housing (302) present at at least one early point in time, in particular for a predetermined time interval; - determining (106) an operating state of the control unit (300) depending on the power consumption of the control unit (300) and / or the first characteristic quantity (202), the control unit (300) comprising a first operating state (206) and a second operating state (208), the first operating state (206) having a lower power consumption than the second operating state (208); - detecting (110) said intrusion of liquid (2) depending on said determined operating state (206, 208), said first characteristic quantity (202) and said second characteristic quantity (204); A method (100) comprising:

2. In the first operating state (206), the method (100) comprises: - determining (112) a first parameter (210) characterizing the dynamics of the relative air humidity (6) in the housing (302), in particular the duration of a change of the relative air humidity (6) in the housing (302) by a predetermined value, as a function of the second characteristic quantity (20a) and of the at least one stored value (204a) of the sensed second characteristic quantity (204), respectively; - comparing (114) said first parameter (210) with a predetermined first threshold (212), in which a liquid intrusion (2) is detected (114) if said first parameter (210) exceeds said first threshold (212), in particular if it falls below said duration; Including, The first parameter (210) is determined (112) when the first characteristic quantity (202) exhibits a behavior, e.g., a constant behavior, that characterizes the equilibrium between the temperature (8) outside the housing (302) and the temperature (6) inside the housing (302); The method (100) of claim 1.

3. In the second operating state (208), the method (100) comprises: determining (116) a second threshold value (214) for said second characteristic quantity (204) as a function of the power dissipation of said control unit (300) characterizing an identifiable increase in said temperature (4) in said housing (302); - comparing (118) said second characteristic quantity (204) with said determined second threshold value (214), wherein a liquid intrusion (2) is detected (118) if said second characteristic quantity (204) exceeds said second threshold value (214); Including, 3. The method (100) of claim 1 or 2.

4. a temperature (8) outside the housing (302) is estimated depending on the increase in the temperature (4) inside the housing (302) and the detected first characteristic quantity (202); and a maximum possible relative air humidity inside the housing (302) is determined depending on the estimated temperature (8) outside the housing (302) in the absence of a liquid intrusion (2) into the housing (302), the second threshold (214) characterizing the maximum relative air humidity inside the housing (302). The method (100) of claim 3.

5. an August-Roche-Magnus model is used to determine (116) the second threshold (214); The method (100) of claim 4.

6. In the second operating state (208), the method (100) comprises: - determining (120) a second parameter (216) characterizing the variation of said second characteristic quantity (204) with respect to the variation of said first characteristic quantity (202), in particular the variation of said relative air humidity (6) in said housing (302) with respect to the variation of said temperature (4) in said housing (302); - detecting (122) a value (219) of the second characteristic quantity (204) after a predetermined period (218) from the positive abrupt change (12) of the temperature (4) in the housing (302) when the second parameter (216) is positive and the first characteristic quantity (202) characterizes the positive abrupt change (12) of the temperature (4) in the housing (302), and detecting (122) a value (219) of the second characteristic quantity (204) detected before the positive abrupt change (12) of the temperature (4). ) with the detected value (219) of the second characteristic quantity (204) after the predetermined period (218), wherein a liquid intrusion (2) into the housing (302) is detected (123) if the detected second characteristic quantity (204) before the positive abrupt change (12) of the temperature (4) characterizes a relative air humidity (rH) that is lower than or equal to the value (219) of the second characteristic quantity (204) after the predetermined period (218); Including, The method (100) of any one of claims 1 to 5.

7. In the second operating state (208), the method (100) comprises: - determining (124) a third parameter (220) characterizing the absolute air humidity (10) inside the housing (302) as a function of the first characteristic quantity (202) and the second characteristic quantity (204), in particular using the Auguste-Roche-Magnus model, if the second parameter (216) takes a positive value; - determining (126) a fourth parameter (222) characterizing the variation of the third parameter (220) with respect to the variation of the first characteristic quantity (202), in particular the variation of the absolute air humidity (10) due to a change in the temperature (4) inside the housing (302), as a function of the third parameter (220) and the first characteristic quantity (202); - comparing (128) said fourth parameter (222) with a predetermined third threshold (224), detecting (128) an intrusion (2) of liquid into said housing (302) if said fourth parameter (222) exceeds said third threshold (224); Including, The method (100) of claim 6.

8. A device (400) for detecting the intrusion (2) of a liquid, in particular a liquid containing water, e.g. water, into a housing (302) of a control unit (300), in particular of a steer-by-wire steering system, comprising: a first sensor device (402) configured to sense (102) a first characteristic quantity (202) characterizing a temperature (4) within the housing (302); a second sensor device (404) configured to sense a second characteristic quantity (204) characterizing the relative air humidity (6) within the housing (306); Equipped with The apparatus (400) is configured to perform the method (100) of any one of claims 1 to 7.

9. The first sensor device (402) and the second sensor device (404) are configured as a composite sensor device.

9. The apparatus (400) of claim 8.

10. a control unit (300) having a housing (302); An apparatus (400) according to claim 8 or 9, A vehicle equipped with:

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