Method for diagnosing faults in an electric motor, in particular in a camshaft adjuster, and corresponding control device and computer program

Abstract

The invention relates to a method for diagnosing faults in an electric motor (100), wherein the electric motor (100) is coupled to a camshaft (121) of an internal combustion engine (120), wherein the electric motor (100) comprises three control lines (101, 103, 105) which, for operation of the electric motor (100), are sequentially activated and deactivated. The method comprises the following steps: (a) stopping the internal combustion engine (120); (b) energising the electric motor (100); (c) receiving a movement signal which is indicative of a movement of the camshaft (121) in response to the energisation; and (d) assessing whether there is a fault in the electric motor (100) on the basis of the movement signal. The invention also relates to a corresponding control unit (150) and to a computer program.

Description

[0001] 202301554

[0002] 1

[0003] DESCRIPTION

[0004] DESIGNATION

[0005] Method for fault diagnosis of an electric motor, in particular a camshaft adjuster, as well as corresponding control unit and computer program

[0006] TECHNICAL AREA

[0007] The present disclosure relates to methods for fault diagnosis of an electric motor operated as a camshaft adjuster, as well as corresponding control units and computer programs.

[0008] BACKGROUND OF THE INVENTION

[0009] In automotive electronic control units (ECUs), electrical control outputs are typically monitored electrically. This means the outputs are continuously checked for short circuits to the supply voltage (short to battery) and short circuits to ground. To do this, a voltage measured at a point in the ECU that, when the circuit is closed, exhibits a voltage difference relative to the supply voltage or ground is compared to the supply voltage or ground voltage, respectively. If the measured difference is too small, a diagnostic function in the ECU software indicates a short circuit to the supply voltage or ground.

[0010] Similarly, this voltage comparison also yields a difference that is too small relative to the supply voltage or ground when the line is open (OC), depending on the hardware design. This is also referred to as OC diagnostics. OC diagnostics are performed, for example, to detect damaged control lines of an electric motor. However, in the case of the control lines to a BLDC motor, this diagnosis can only be performed when the BLDC motor is stationary, because rotation of the rotor due to an externally applied torque can induce a voltage despite an open control line. Induced voltages can distort the diagnostic result. 202301554

[0011] 2

[0012] When a BLDC motor is used as a camshaft adjuster in a vehicle, this type of diagnostic check is therefore performed in many control units after the combustion engine has been switched off and the BLDC motor has come to a complete stop. This ensures that a break in the wiring at the camshaft adjuster can always be reliably detected during the engine's standstill phase following the occurrence of the break.

[0013] However, diagnosing the control lines of an electric motor based on a voltage comparison against ground or supply voltage has the disadvantage that a change in the camshaft position during the diagnostic procedure cannot be reliably detected. Typically, a software driver that interfaces with the BLDC motor must be switched to a sleep mode during the diagnostic process. In such a sleep mode, position detection of the electric motor's rotor, and therefore the camshaft, is not possible, for example, if only a simultaneous deactivation of the power stage for motor control and current measurement is possible. This means that the camshaft position cannot be reliably determined when the motor is subsequently started.Accordingly, an unfavorable position of the camshaft must be assumed; the engine start must be performed under worst-case assumptions regarding the camshaft position and is less comfortable.

[0014] BRIEF DESCRIPTION AND FORMS OF EXECUTION

[0015] It is therefore an objective of the present disclosure to provide an alternative method for fault diagnosis of an electric motor operated as a camshaft adjuster, which is particularly feasible with simultaneous position detection of the camshaft.

[0016] This problem is solved by a method for fault diagnosis of an electric motor, by a control unit, and by a computer program according to the independent patent claims. Advantageous embodiments and further developments are described in the respective dependent claims, the following description, and the drawings. 202301554

[0017] 3

[0018] Thus, according to a first aspect, a method for fault diagnosis of an electric motor is provided, wherein the electric motor has three control lines and is coupled to a camshaft of an internal combustion engine. The method comprises the following steps: (a) stopping or switching off the internal combustion engine; (b) energizing the electric motor; (c) receiving a motion signal indicative of movement of the camshaft and / or the electric motor in response to the energizing; and (d) assessing whether a fault of the electric motor exists based on the motion signal.

[0019] According to another aspect, a control unit, in particular a control unit for a motor vehicle, is provided, wherein the control unit is configured to carry out the procedure described above.

[0020] According to another aspect, a computer program is provided which includes instructions that, when executed by a computer, cause it to carry out the previously described procedure. In the context of the present disclosure, a computer is defined, for example, as a device that processes data using programmable computational instructions. Computers can be embedded in everyday devices, such as the control units of motor vehicles.

[0021] According to another aspect, a storage medium is provided with a computer program, wherein the computer program includes instructions which, when the computer program is executed by a computer, cause it to carry out the procedure described above.

[0022] According to another aspect, a system is provided which includes the control unit and the electric motor.

[0023] In the context of this disclosure, the term "control line" means, for example, a line used to control the electric motor. The control line may include one or more switching elements that control an electric current through the control line. According to one embodiment, the control line, in particular all control lines of the electric motor, is sequentially connected to the supply voltage or ground for operation of the electric motor. According to another embodiment, the control line, in particular all control lines of the electric motor, is sequentially activated and deactivated. A control line can be activated when corresponding switching elements 202301554

[0024] The control line is deactivated if at least one or both of these conditions are not met. The electric motor can have exactly three control lines, but it can also have more than three.

[0025] According to one embodiment, the three control lines, or in particular all control lines, are electrically connected to each other at one of their ends, especially in the area of ​​the rotor and / or the stator of the electric motor. At their respective opposite ends, the control lines may have a switching element, in particular a branch into two electrical lines, each containing a switching element. One of these switching elements may be connected to a positive voltage pole, the other to a negative voltage pole. The switching elements may, but do not have to, be part of the respective control line. In other words, the control lines are connected in a star configuration.

[0026] According to one embodiment, the three control lines, or in particular all of them, are each connected at one end to another of the control lines, with at least one coil of the other control line arranged between the end of the first control line and the end of the second control line. At their respective opposite ends, the control lines can have a switching element, in particular a branch into two electrical lines, each containing a switching element. One of these switching elements can be connected to a positive voltage pole, the other to a negative voltage pole. The switching elements can, but do not have to, be part of the respective control line. In other words, the control lines are connected in a ring or delta configuration.

[0027] According to one embodiment, the switching elements are transistors, in particular MOSFETs. They can be configured to be controlled by a pulse-width modulated signal.

[0028] According to one embodiment, the electric motor is a brushless DC motor (BLDC).

[0029] In the context of the present disclosure, the term “camshaft” can mean a rod-shaped element on which at least one projection is arranged, 202301554

[0030] 5. In particular, a rounded projection. Each projection can be configured to open and / or close an associated valve of the internal combustion engine when the rod-shaped element rotates, for example, an intake valve for a combustion mixture or an exhaust valve of the internal combustion engine. The projection can be configured to exert force against a return element of the valve, for example, against a return spring. The camshaft can be driven by a crankshaft, for example, via a timing belt or a timing chain with a gear ratio of one to two.

[0031] In the context of this disclosure, the term "crankshaft" means, for example, a shaft which carries at least one crank. Each crank can be configured to move an associated piston within a cylinder when the shaft rotates.

[0032] In the context of the present disclosure, the expression "coupling the electric motor with the camshaft" can mean that a connection, for example mechanical or electrical, is established between the electric motor and the camshaft, such that a rotation of a rotor of the electric motor correlates with a rotation of the camshaft. The ratio of the rotational movements can be determined by a transmission, such as a so-called harmonic drive transmission or three-shaft transmission. The transmission can have a high gear ratio, for example greater than fifty to one.

[0033] According to one embodiment, the phase of a camshaft rotation can be adjusted by means of the electric motor, particularly in relation to a rotation of the crankshaft. The phase angle can be adjustable within a predetermined angular range. This angular range can be limited by mechanical stops. The phase adjustment can be achieved by deviating a target rotational speed of the electric motor's rotor from the rotational speed of the camshaft, particularly by means of targeted, short-term deviations. Such an embodiment can be advantageous for achieving favorable valve timing for different operating conditions, for example, for idle or maximum power.An electromechanical camshaft adjuster can offer faster response times compared to conventional approaches, such as those based on oil chambers in a vane-type adjuster, especially at low engine temperatures, and allows for a more compact design. 202301554.

[0034] 6

[0035] In the context of the disclosure, the term "energizing" can be defined as controlling the electric motor, whereby current flows through the control lines and / or corresponding coils of the electric motor. The associated control profile can be suitable for setting a rotor of the electric motor into rotational motion, at least when the electric motor is intact. The rotational motion corresponding to the control profile can comprise at least one complete rotation of the electric motor, and in particular, several rotations.

[0036] In the context of the disclosure, the term "motion signal" can be defined as any signal indicating movement of the camshaft and / or rotor of the electric motor. The motion signal can also indicate slight movement or the absence of movement. The motion signal can be detected by a motion sensor and / or a position sensor. The motion sensor can be configured to measure movement of the camshaft and / or rotor of the electric motor. The position sensor can be configured to measure the position of the camshaft and / or rotor of the electric motor. By comparing positions measured at different times, movement or the absence of movement can be deduced, particularly at times before, during, and after the electric motor is energized.

[0037] The described method and the corresponding control unit can be advantageous for enabling reliable diagnostics of the electric motor, particularly its control lines, when the combustion engine is stopped. The simple, mechanical diagnostic principle is based on the possibility that even with the crankshaft stationary, a limited movement of the camshaft is possible, for example, a fraction of a complete rotation, especially up to thirty degrees. The method described above utilizes this by energizing the electric motor with the combustion engine switched off to move the camshaft. Fault diagnosis can then be based, for example, on the extent of the resulting camshaft movement.

[0038] Due to this simple, mechanical method for fault diagnosis, the position of the camshaft can be continuously monitored during the diagnostic procedure. 202301554

[0039] 7. In particular, the diagnostic procedure can be carried out without having to switch the electric motor's software driver into sleep mode. The acquisition of the camshaft position is not interrupted during the diagnosis, thus preventing any loss of starting comfort due to an uncertain camshaft position after all engine standby phases.

[0040] A properly functioning camshaft adjuster with three working control lines and three working circuits, when appropriately designed, is capable of generating a rotating electromagnetic field in the stator and significantly rotating a camshaft from a rest position, even with the combustion engine off, provided it receives a suitable current. Conversely, a faulty camshaft adjuster with only two working control lines and only one working circuit is incapable of generating a rotating electromagnetic field in the stator and significantly rotating a camshaft from a rest position, regardless of the current applied when the combustion engine is off.

[0041] For the diagnostic procedure, after the combustion engine has been switched off and the camshaft and camshaft adjuster have safely come to rest, the camshaft adjuster is selectively energized again to move the camshaft from its rest position. The position of the camshaft is continuously monitored by the engine control unit using a position sensor, specifically an incremental position sensor.

[0042] If, during testing, significant camshaft movement is measured with a current known to be sufficient for a fault-free system, this can be sufficient proof of the functionality of all three control lines, and the system can be considered fault-free. Conversely, if no significant camshaft movement is measured with a current known to be sufficient for a fault-free system, this could be due to an interruption in a control line, and the system can be considered faulty with an interrupted control line.

[0043] According to one embodiment, a magnetic field in the electric motor is controlled by means of the control lines, in particular via switching elements arranged in the control lines. This magnetic field can be configured to control a 202301554

[0044] 8

[0045] to drive the rotor of the electric motor. The magnetic field can be generated by coils of the rotor and / or stator of the electric motor.

[0046] In one embodiment, the control lines are electrically conductive and supply current to coils of the electric motor, which at least partially generate the magnetic field. For example, the coils are wire coils. The control lines can encompass the coils, particularly the wire coils.

[0047] According to one embodiment, when corresponding switching elements are closed, a current flows through two of the control lines, but not through the third. The direction of the current through the control lines can be determined by selecting which switching elements are to be closed.

[0048] According to one embodiment, a fault is assumed to exist if the motion signal indicates less than one complete revolution of the electric motor's rotor, particularly less than two-thirds of a revolution, and especially less than half a revolution. According to one further embodiment, a power limitation of the electric motor is implemented when a fault is present. Such an embodiment can be advantageous because, with the camshaft and electric motor stationary, starting the electric motor from a standstill is not possible if one of the control lines and / or corresponding circuits is faulty.

[0049] According to one embodiment, it is assumed that no fault exists if the movement signal indicates more than half a revolution of the electric motor's rotor, in particular more than one full revolution of the rotor, and especially more than two revolutions of the rotor. Such an embodiment can be advantageous because, with the camshaft and electric motor stationary, starting the electric motor from a standstill is only possible if all control lines and / or all corresponding circuits are intact.

[0050] According to one embodiment, the motion signal is determined by means of a position sensor for the rotor of the electric motor. The position sensor can be configured to detect, and in particular directly measure, a rotation of the rotor. Such an embodiment can be advantageous because the position sensor for the rotor is typically more accurate than a position sensor that directly measures the rotation of the camshaft. For example, a 202301554

[0051] 9

[0052] The camshaft position sensor is located on the camshaft's trigger wheel and can distinguish between four and twelve flanks. The engine position sensor, on the other hand, may be configured to measure with an angular resolution of less than twenty degrees, particularly less than ten degrees. Consequently, some camshaft movements may not be detectable by the camshaft position sensor at all. Alternatively or additionally, the movement signal can be determined using a camshaft position sensor.

[0053] According to one embodiment, the electric motor is coupled to the camshaft by means of a gearbox, wherein the gearbox ratio, which indicates the ratio of revolutions of the electric motor to revolutions of the camshaft, is greater than 10, and in particular greater than 50. The gearbox ratio can be 73 or greater. The gearbox can be a so-called Harmony Drive, which is designed to be particularly compact. Such an embodiment can be advantageous, especially if the motion signal is determined by the position sensor for the rotor of the electric motor, because the movement of the camshaft can be determined with high accuracy due to the gearbox ratio. This is especially true if the position sensor for the rotor of the electric motor already has a higher angular resolution than the position sensor for the camshaft.In other words, a large gear ratio of the rotor position sensor of the electric motor can enable a particularly precise determination of the camshaft position.

[0054] According to one embodiment, the method further comprises: after the combustion engine has stopped and before the electric motor has been energized, a check is performed using a position sensor to determine whether the camshaft and / or the rotor of the electric motor are at rest. The position sensor can be a position sensor for the camshaft and / or, preferably, a position sensor for the rotor of the electric motor. In particular, signals from both sensors can also be considered for the check. As described in connection with the two previous embodiments, the position sensor for the rotor of the electric motor can have a higher accuracy compared to the position sensor of the camshaft. In this respect, a rest position can be determined more accurately based on signals from the position sensor of the electric motor. 202301554

[0055] 10

[0056] According to one embodiment, the position of the electric motor rotor and / or the camshaft adjuster is continuously determined during the process. Such an embodiment can be advantageous because, as already described, the camshaft position is reliably known at the next engine start. The mechanical fault diagnosis method described in this disclosure can enable continuous detection of the camshaft position, for example, because the electric motor's software driver does not need to be switched to a sleep mode for diagnosing the electric motor.

[0057] According to one embodiment, the fault comprises at least one of a broken connection in one of the control lines and a malfunction in one of the switching elements. Such an embodiment can be advantageous because all these faults, especially the broken connection, can lead to damage to the electric motor and / or the control unit if they remain undetected.

[0058] According to one embodiment, the fault indicates a damaged control line and / or a damaged electrical circuit of the electric motor. Such an embodiment can be advantageous because, as already explained, damaged control lines can lead to an overload of the electric motor.

[0059] According to one embodiment, the procedure is carried out during a start-stop operation of the combustion engine. Such an embodiment can be advantageous because the combustion engine is stopped several times during start-stop operation, thus allowing the diagnostic procedure to be performed more frequently, particularly several times during a driving cycle, for example, when the vehicle is stopped at a traffic light or in a traffic jam.

[0060] According to one embodiment, the method further comprises: positioning the camshaft in a predetermined rest position after energizing the electric motor and / or after completion of the diagnostic procedure, for example, in a position that the camshaft had assumed before the start of the diagnostic procedure. The predetermined rest position can be a position in which a convenient engine start is possible.

[0061] According to one aspect, a procedure for fault diagnosis of an electric motor has the following steps: (a) Checking whether a fault suspicion variable is set, wherein the fault suspicion variable represents a previously determined fault suspicion 202301554

[0062] 11 indicates, in particular a suspected fault identified during the operation of the internal combustion engine; (b) performing a procedure as previously described in this disclosure when the suspected fault variable is set, in particular only when the suspected fault variable is set.

[0063] For a method by which such a fault suspicion variable is set, the method disclosed in patent application DE 10 2023 206 485 can be used, for example, the content of which is incorporated into the present disclosure. The method disclosed therein can be advantageous because it can also be carried out during the operation of the internal combustion engine, i.e., even with the engine running. However, it is subject to greater uncertainty.

[0064] Therefore, the procedure described here can be more reliable and consequently used to confirm or refute a previously identified suspected fault during a subsequent motor idle phase. If the suspected fault is refuted, any power limitation of the electric motor imposed due to the suspected fault can be lifted. If the suspected fault is confirmed, the power limitation can be retained. Such an embodiment can be advantageous, for example, if the diagnostic procedure is only performed during the subsequent motor idle phase when a suspected fault variable is set. It therefore does not need to be performed during all motor idle phases.

[0065] Within the framework of power limitation, the current to the electric motor can be reduced to such an extent that, at the cost of reduced dynamic performance, overheating is prevented. Reducing the current can be advantageous to prevent the electric motor from being impaired or damaged by a fault. This can occur, for example, due to excessive heat generation if only two of the three control lines are intact and / or activated, resulting in higher currents in the control lines, switching elements, and motor coils within the remaining circuit than would be the case if all three control lines were intact and / or activated.

[0066] The aforementioned patent application DE 10 2023 206 485 describes, among other things, a method by which, based on a histogram of the sum phase currents of the camshaft adjuster during operation of the 202301554

[0067] 12

[0068] A test for a short circuit can be performed on the combustion engine – i.e., not during an engine idle phase. If a suspected fault is detected, the current to the BLDC motor is limited for the remainder of the current combustion engine driving cycle to prevent overheating, even with the additional heating caused by a short circuit as described above.

[0069] In summary, the diagnostic procedure described here can be used either to confirm a suspected fault in the subsequent engine standby phase or independently of the fault suspicion procedure described above in any engine standby phase.

[0070] BRIEF DESCRIPTION OF THE DRAWINGS

[0071] Further advantages and beneficial designs and further developments of the method, the control unit and the computer program result from the following exemplary embodiments shown in connection with the figures.

[0072] They show:

[0073] Figure 1 shows an electric motor for control by a control unit according to an embodiment of the present disclosure; and

[0074] Figure 2 shows an electric motor coupled to a camshaft of an internal combustion engine, which is suitable for carrying out a method according to an embodiment of the present disclosure.

[0075] Identical, similar, or similarly effective elements are marked with the same reference symbols in the figures. In some figures, individual reference symbols have been omitted for clarity. The figures and the relative sizes of the elements depicted within them are not to be considered to scale. Rather, individual elements may be exaggerated for better representation and / or comprehensibility. 202301554

[0076] 13

[0077] DETAILED DESCRIPTION OF EXAMPLES OF EXECUTION

[0078] Figure 1 shows an electric motor 100 with six switching elements 108-113 for control by a control unit according to an embodiment of the present disclosure. The control unit is configured to perform a method for fault diagnosis of an electric motor 100, here a BLDC motor.

[0079] The electric motor 100 has three control lines 101, 103, 105, which are sequentially activated and deactivated for operation of the electric motor 100. For this purpose, the switching elements 108, 109, 110, 111, 112, 113, which can be implemented as transistors, for example, are switched sequentially such that one of the control lines 101, 103, 105 is connected to a negative terminal of a voltage source and another of the control lines 101, 103, 105 is connected to a positive terminal of the voltage source. Thus, two switching elements 108, 109, 110, 111, 112, 113 are connected to each control line.

[0080] 109, 110, 111, 112, 113 closed and all other switching elements 108, 109,

[0081] Control lines 110, 111, 112, and 113 are opened. Accordingly, a current flows through each of the two control lines 101, 103, and 105, and through two of the coils 102, 104, and 106 assigned to those two control lines. This generates a magnetic field that depends on the direction of the current through the control lines 101, 103, and 105. This magnetic field drives a rotor of the electric motor 100. The total current through all control lines 101, 103, and 105 can be measured using the current meter 107.

[0082] Brushless DC (BLDC) motors are used in a variety of applications, including automotive engineering. One example is the drive of an electromechanical camshaft adjuster to regulate the rotational speed of a camshaft in an internal combustion engine.

[0083] BLDC motors 100 are controlled by a control unit via three control lines 101, 103, 105. In the stator of the BLDC motor 100, the lines connected to the control lines 101, 103, 105 are electrically connected and mechanically arranged such that alternating electrical currents, caused by the control unit through variations in the control voltage, induce a rotating magnetic field in the stator. This rotating field rotates the rotor of the BLDC motor 100. The change in the rotor's position is measured by the control unit using an incremental position sensor, for example, an integrated Hall sensor. The BLDC motor 100 is thus controlled in a closed-loop system.

[0084] 14 the rotor speed as a controlled variable and the phase currents are controlled via the control lines 101 , 103 , 105 as manipulated variables.

[0085] The control unit generates the phase currents by means of pulse width modulation (PWM) of a control voltage on the control lines 101, 103, 105 of the BLDC motor.

[0086] 100. Any desired current profile can be generated, e.g., in the form of a sine or square wave, the shape of which can be described by the parameters frequency, amplitude, and phase. For the desired operation of the BLDC motor 100, a current with the desired current intensity must be supplied in the desired direction at any given time through any two of the three control lines.

[0087] Power flows to lines 101, 103, and 105. The third control line in each case, 101, 103, and 105, is not powered by the control unit.

[0088] A key requirement for the full functionality of this drive system is a reliable electrical connection between the control unit and the BLDC motor 100 via the three control lines 101, 103, and 105. A temporary or permanent interruption of one of these control lines can prevent the BLDC motor 100 from operating. However, this is not always the case.

[0089] At any given time during motor operation, current flows alternately through one of the three circuits formed by the control unit, any two of the three control lines 101, 103, 105, and the BLDC motor 100. Three phase-shifted alternating currents flow in the three control lines 101, 103, and 105. If one control line 101, 103, or 105 is interrupted, then two of these three circuits are interrupted. An alternating current in the remaining circuit can only generate an oscillating, but not a rotating, magnetic field in the stator of the BLDC motor 100. Without a rotating magnetic field, the BLDC motor 100 cannot start from a standstill under its own power.However, if (i) the BLDC motor 100 is already rotating at the time the control line is interrupted, or (ii) the BLDC motor 100 is set in motion by an external torque acting on its rotor, then, with a low torque tapped from the rotor shaft, it is possible for the closed-loop control unit to maintain the rotation of the BLDC motor 100 permanently by increasing the current in the remaining circuit to minimize the speed control deviation.

[0090] However, such continued operation with an interrupted control line 101, 103, 105 represents a completely different situation for the BLDC motor 100 and for the control unit 202301554

[0091] 15

[0092] The operating point is represented as fault-free operation with three control lines 101, 103, 105. After the interruption of one control line 101, 103, 105, the control unit must increase the current in the circuit via the remaining two control lines 101, 103, 105 sufficiently so that the BLDC motor 100 generates the same torque as in fault-free operation using all three circuits, in order to achieve the desired target speed of the BLDC motor 100. The critical components of the BLDC motor 100 (the active motor coils) and the control unit (the transistors of the remaining circuit) then carry a larger current and heat up more than in fault-free operation. The current I contributes quadratically to the heating power P across a resistor R, P = R * I 2A doubling of the current, for example, quadruples the heating power. Since, for cost reasons, it is common practice to operate the fault-free overall system at least at certain operating points close to the limits of its thermal load capacity, an additional heating event resulting from an interruption of a control line 101, 103, 105 threatens overheating and thermal destruction of the system.

[0093] This necessitates, for example, the reliable detection of an interruption in a control line 101, 103, 105 using the method described above, in order to prevent overheating through active countermeasures. Upon detection of a fault, the current to the BLDC motor 100 can be reduced for the subsequent operation of the combustion engine 120 to such an extent that, even with a reduced dynamic performance of the BLDC motor 100, overheating is not a risk.

[0094] With reference to Figure 2, the use of an electric motor 100, as shown in Figure 1, as a camshaft actuator will now be explained. For this purpose, the electric motor 100 is rigidly supported against the vehicle via the mechanical connection 130 and coupled to a camshaft 121 of an internal combustion engine 120, for example by means of a transmission 122. The camshaft 121 is configured to open and close corresponding valves 123 of the internal combustion engine 120 by means of the cams, for example, intake valves for intake or exhaust valves for exhaust gases. The camshaft 121 is coupled to a crankshaft 124 of the internal combustion engine 120, for example by means of a timing chain 125. The crankshaft 124 is configured to move pistons in corresponding cylinders of the internal combustion engine 120 in order to compress the combustion mixture in the cylinder.

[0095] 16

[0096] The rotor of the BLDC motor 100 usually rotates synchronously with the camshaft 121 of the internal combustion engine 120. The phase position of the camshaft 121 is adjusted by means of brief, controlled deviations between the target rotational speed of the BLDC motor 100's rotor and the rotational speed of the camshaft 121. The angular adjustment range of the BLDC motor 100's rotor relative to the camshaft 121 is limited by mechanical stops. With the electromechanical camshaft adjuster, both scenarios of continued operation despite an interrupted control line are possible: (a) The control line 101, 103, 105 can be interrupted by vibrations during the operation of the internal combustion engine 120, while the rotor of the BLDC motor 100 is rotating at approximately the camshaft speed, (b) Before the internal combustion engine 120 is started, the BLDC motor 100 is also stationary.If the BLDC motor 100 does not start to rotate as intended when the internal combustion engine 120 is started due to an interrupted control line 101, 103, 105, then it will be set in motion by the rotating camshaft 121.

[0097] If the position detection of the camshaft 121 is not possible without interruption, then either the line drop diagnosis during engine standstill phases can only be carried out if the camshaft is in a randomly non-critical shut-off position, or, after line drop diagnoses even in critical shut-off positions of the camshaft, a lower starting comfort must be accepted in fault-free systems.

[0098] Such disadvantages can be avoided if a fault diagnosis procedure for the electric motor 100 is carried out with the following steps: (i) stopping the internal combustion engine; (ii) checking whether the camshaft is at rest; (iii) energizing the electric motor; (iv) receiving a motion signal that is representative of camshaft movement in response to energizing; and (v) assessing whether there is a fault in the electric motor based on the motion signal.

[0099] This method has the advantage that, unlike a voltage comparison against ground or supply voltage, a software driver forming the interface to the BLDC motor does not need to be switched to a sleep mode. Consequently, the position of the camshaft 121 can be continuously monitored. With active position monitoring of the rotor using the incremental position sensor, the engine control unit can correctly map the rotation of the camshaft 121 even after the combustion engine 120 has been switched off. The camshaft position 202301554

[0100] 17 is already available at the start of the subsequent start of the combustion engine 120, and the engine start can take place normally without jerking.

[0101] The invention is not limited to the exemplary embodiments described therein. Rather, the invention encompasses every new feature as well as every combination of features, which in particular includes every combination of features in the exemplary embodiments and claims.

[0102] 202301554

[0103] 18

[0104] REFERENCE MARK

[0105] 100 electric motor

[0106] 101 first control line

[0107] 102 first coil

[0108] 103 second control line

[0109] 104 second coil

[0110] 105 third control line

[0111] 106 third coil

[0112] 107 Current measuring device

[0113] 108 first switching element

[0114] 109 second switching element

[0115] 110 third switching element

[0116] 111 fourth switching element

[0117] 112 fifth switching element

[0118] 113 sixth switching element

[0119] 120 internal combustion engine

[0120] 121 Camshaft

[0121] 122 gearbox

[0122] 123 Valve

[0123] 124 Crankshaft

[0124] 125 timing chain

[0125] 130 mechanical connection to the vehicle

Claims

202301554 19 PATENT CLAIMS 1. Method for fault diagnosis of an electric motor (100), wherein the electric motor (100) has three control lines (101, 103, 105) and is coupled to a camshaft (121) of an internal combustion engine (120), the method comprising the following steps: - Stopping the internal combustion engine (120); - Powering on the electric motor (100); - Receiving a motion signal indicative of movement of the camshaft (121) in response to energizing; and - Assess whether there is a fault in the electric motor (100) based on the movement signal.

2. Method according to the preceding claim, wherein the presence of a fault is assumed if the motion signal indicates less than one complete revolution of a rotor of the electric motor (100).

3. Method according to one of the preceding claims, wherein it is assumed that there is no fault if the motion signal indicates more than one complete revolution of the rotor of the electric motor (100).

4. Method according to one of the preceding claims, wherein the motion signal is determined by means of a position sensor for the rotor of the electric motor (100).

5. Method according to the preceding claim, wherein the electric motor (100) is coupled to the camshaft (121) by means of a transmission (122), wherein a transmission ratio of the transmission (122), which indicates the ratio of revolutions of the electric motor (100) to revolutions of the camshaft (121), is greater than 10, in particular greater than 50.

6. Method according to one of the preceding claims, further comprising checking, after stopping the internal combustion engine (120) and before energizing the electric motor (100), whether the camshaft (121) is at rest by means of a position sensor. 202301554 20 7. Method according to one of the preceding claims, wherein a position of the rotor of the electric motor (100) is continuously determined during the method.

8. Method according to one of the preceding claims, wherein the fault indicates a damaged control line (101 , 103, 105).

9. Method according to one of the preceding claims, wherein the method is carried out during a start-stop operation of the internal combustion engine (120).

10. Method according to one of the preceding claims, further comprising: placing the camshaft (121) into a predetermined rest position after energizing the electric motor.

11. Method for fault diagnosis of an electric motor (100), comprising the following steps: - Check if a fault suspicion variable is set, where the fault suspicion variable indicates a previously determined fault suspicion; - Performing the procedure according to one of the preceding claims when the fault suspicion variable is set.

12. Control unit configured to perform a method according to any of the preceding claims.

13. Computer program comprising instructions which, when executed by a computer, cause the computer to perform a method according to any one of claims 1 to 11.

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