METHOD FOR CONTROLLING CAMSHAFT ALIGNMENT FOR IMPROVED RESTARTING OF A START-STOP ENGINE

Abstract

Method for operating a variable valve timing mechanism that controls the phase setting of a camshaft (40, 42) in an engine (10), wherein the variable valve timing mechanism comprises an electric motor (64), the method comprising: Determining a value for an operating motor current limit; setting a value for a starting current limit equal to a predetermined value that is higher than the value of the operating motor current limit when a set of predetermined conditions is met, or otherwise substituting the value of the operating motor current limit as the value of the starting current limit; Determine that the operation of the motor (10) has been interrupted; operate the electric motor (64) of the variable valve timing mechanism with a current of a magnitude less than or equal to the starting current limit, after determining that the operation of the motor (10) has been interrupted; determine that the operation of the motor (10) has been resumed; and Operating the electric motor (64) of the variable valve control mechanism with a current of a magnitude less than or equal to the operating motor current limit, after it has been determined that the operation of the motor (10) has been resumed.

Description

AREA

[0001] The present disclosure relates to a method for controlling the camshaft alignment for improved restarting of an engine with start-stop capability. STATE OF THE ART

[0002] This section provides background information related to the present disclosure that does not necessarily belong to the prior art.

[0003] Modern automotive engines typically employ a variable valve timing (VVT) mechanism to alter the phase, or timing (relative to the crankshaft's rotational position), of the intake and / or exhaust valves opening. VVT mechanisms generally adjust the intake and / or exhaust valve opening phase by rotating a camshaft, which controls the valve opening and closing. It is common for such VVT mechanisms to drive the camshaft with an electric motor.

[0004] It is a known practice to employ a VVT mechanism in an engine with start-stop capabilities to prepare the engine for restarting. In such situations, the VVT ​​mechanism is used to pre-position the camshaft in an orientation more conducive to restarting the engine. Furthermore, the VVT ​​mechanism can be used to adjust the camshaft's phase (relative to the crankshaft) during an engine start sequence to improve the engine's starting ability, for example, by reducing the amount of torque required to initiate crankshaft rotation through delayed engine restart.When techniques for reducing the torque required to initiate crankshaft rotation and delaying engine timing are used together, there is a need to advance the camshaft phase adjustment gradually but rapidly. While known techniques for operating a VVT mechanism are suitable for the intended purpose, such techniques are nevertheless open to improvement.

[0005] DE 10 2013 205 929 A1 relates to a method for controlling an actuator for variable cam timing (VCT), wherein, during the shutdown of an engine, the camshaft position is adjusted to a target initial position by means of an electric VCT actuator.

[0006] The object of the present invention is to provide an improved method for operating a mechanism with variable valve control. SUMMARY

[0007] The present invention relates to a method for operating a mechanism with variable valve control according to claim 1, and to a method for operating a mechanism with variable valve control according to claim 11. The dependent claims describe preferred embodiments of the two methods. This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all of its features.

[0008] In one form, the present disclosure provides a method for operating a variable valve timing mechanism that controls the phase setting of a camshaft in an engine, wherein the variable valve timing mechanism comprises an electric motor. The method involves determining a value of an operating motor current limit and setting a value of a starting current limit equal to a predetermined value that is higher than the value of the operating motor current limit when a set of predetermined conditions is met, or otherwise setting the value of the operating motor current limit as the value of the starting current limit.The procedure involves determining that the operation of the motor has been interrupted, operating the electric motor of the variable valve timing mechanism with a current of a magnitude less than or equal to the starting current limit after determining that the operation of the motor has been interrupted, determining that the operation of the motor has been resumed, and operating the electric motor of the variable valve timing mechanism with a current of a magnitude less than or equal to the operating motor current limit after determining that the operation of the motor has been resumed.

[0009] In some forms, the set of predetermined conditions includes the requirement that the electric motor temperature is below a predetermined temperature threshold. In some forms, a predetermined value is based on the age of the electric motor. In some forms, a predetermined value is based on the temperature of the electric motor. In some forms, the operating motor current limit is based on the temperature of the electric motor. In some forms, the operating motor current limit is determined by a step function based on the temperature of the electric motor. In some forms, determining that the motor has resumed operation is based, at least in part, on a control signal provided by a motor control device. In some forms, determining that the motor has resumed operation is based on an algorithm that utilizes one or more parameters of the motor.In some forms, determining that the engine has restarted is based on one or more parameters of the variable valve timing mechanism. In other forms, determining that the engine has restarted is based on a timer value.

[0010] The present disclosure also provides a method for operating a variable valve timing mechanism that controls the phase setting of a camshaft in an engine, wherein the variable valve timing mechanism comprises an electric motor. The method includes determining that the engine operation has been interrupted and operating the electric motor in a restart mode to control the camshaft phase setting when it is determined that the engine operation has been interrupted. The method also includes determining, independently of a dedicated restart signal, that the engine operation has resumed and operating the electric motor in an engine operating mode to control the camshaft phase setting when it is determined that the engine operation has resumed.Determining whether the motor restarts involves determining if the electric motor's rotational speed exceeds a predetermined motor speed threshold. Alternatively or additionally, determining whether the motor restarts involves determining whether a power-up cycle, during which electrical power is supplied to the electric motor, is greater than or equal to a predetermined cycle threshold.

[0011] In some forms, determining that the motor's operation has been interrupted involves determining whether the electric motor's rotational speed is less than or equal to a predetermined motor speed threshold. In some forms, determining that the motor's operation has been interrupted involves determining that the electric motor's rotational speed has been less than or equal to the predetermined motor speed threshold for a duration greater than or equal to a predetermined time threshold. In some forms, determining that the motor's operation has been interrupted involves determining that the magnitude of a work cycle, during which electrical power is supplied to the electric motor, lies within a predetermined range.In some forms, determining that the motor's operation has been interrupted involves determining that a quantity of a work cycle, during which electrical power is supplied to the electric motor, is less than a predetermined work cycle threshold. In some forms, determining that the motor's operation has resumed involves determining that the electric motor's rotational speed has been greater than or equal to the predetermined motor speed threshold for a duration greater than or equal to a predetermined time threshold.

[0012] Further applications will become apparent from the description provided herein. The description and specific examples in this summary serve only for illustration and are not intended to limit the scope of the present disclosure. DRAWINGS

[0013] The drawings herein serve only to illustrate selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. Fig. Figure 1 is a schematic representation of an exemplary engine with a variable valve timing mechanism configured to perform a camshaft prepositioning function according to the teachings of the present disclosure; Fig. Figure 2 is a schematic representation of a part of the engine made of Fig. 1, which describes the variable valve timing mechanism in more detail; Fig. Figure 3 is a schematic representation in flowchart form of an exemplary procedure for performing a camshaft prepositioning function according to the teachings of the present disclosure; and Fig. Figure 4 is a schematic representation in flowchart form of an exemplary procedure for adjusting a current limit according to the teachings of the present disclosure.

[0014] Corresponding reference numbers indicate corresponding parts in the different views of the drawings. DETAILED DESCRIPTION

[0015] Exemplary embodiments are explained in more detail below with reference to the accompanying drawings.

[0016] With reference to Fig. Figure 1 of the drawings shows an exemplary internal combustion engine 10. The engine 10 is illustrated as having a V-configuration with a first and a second bank 12 and 14 respectively, each having one or more cylinders 16. However, it is understood that the teachings of the present disclosure are applicable to other engine configurations. Intake air flows through an air cleaner 18 and to a throttle valve 20, which regulates the flow of fresh air used by the internal combustion engine 10 for combustion. The air flowing past the throttle valve 20 enters an intake port 22 and is drawn into a cylinder 16 of the engine 10 during an intake stroke. Fuel can be injected into the intake air either in the section of the intake port 22 near the cylinder 16 before the movement of the air and fuel into the cylinder 16 (i.e.,The air-fuel mixture in the cylinder is ignited by a spark plug 28 and combusts, producing gases that push a piston down in the cylinder 16 to rotate a crankshaft 30. The gases produced during the combustion of the air-fuel mixture in the cylinder 16 are subsequently extracted from the cylinder 16.

[0017] Each cylinder 16 has one or more intake valves 34 and one or more exhaust valves 36 that can be opened to allow air to flow into or out of the cylinder 16. The opening and closing of the intake valve(s) 34 and the exhaust valve(s) 36 is controlled by one or more camshafts. In the example provided, each bank 12, 14 has an intake valve camshaft 40 and an exhaust valve camshaft 42. An endless drive is typically used to rotatably couple the camshaft(s) 40, 42 to the crankshaft 30. The endless drive usually includes gears that are coupled to the camshaft(s) 40, 42 and the crankshaft 30, and a chain or toothed belt fitted around the gears. Depending on the engine configuration, the endless drive can be configured to provide a desired speed reduction between the crankshaft 30 and the camshaft(s).In the example provided, the engine 10 is a four-stroke engine and as such the endless drive is configured such that the intake and exhaust valve camshafts 40 and 42 rotate at half the speed of the crankshaft 30.

[0018] The engine 10 further incorporates one or more variable valve timing (VVT) mechanisms that are selectively employed to change the phase setting of a camshaft (i.e., the timing relative to the rotational position of the crankshaft 30 of the opening and closing of an associated set of valves). In the example provided, each bank 12, 14 has an intake VVT ​​mechanism 50 and an exhaust VVT mechanism 52. The intake and exhaust VVT mechanisms 50 and 52 are generally similar and well known in the art. Accordingly, a discussion of the intake VVT ​​mechanism 50 is sufficient.

[0019] With further reference to Fig. 2 The intake VVT ​​mechanism 50 is operated by an actuator 60, which is controlled by an engine control module (ECU) 62. In short, the ECU 62 controls the actuator 60 as needed to advance or retard the timing of the camshaft 40 during the operation of the engine 10 according to a predetermined control methodology, generally to reduce the fuel consumption rate of the engine 10. The actuator 60 includes an electric motor 64, which can be operated to cause a relative rotation between the camshaft 40 and an element of the endless drive that provides rotational force to the camshaft 40 (i.e., the sprocket 68 in the specific example provided).

[0020] The engine 10 has start-stop capabilities, in which its operation (by the ECU 62) is stopped in a situation where a vehicle (not shown) powered by the engine 10 comes to a standstill for a predetermined time interval. The various VVT mechanisms on the engine 10 (i.e., the intake and exhaust VVT mechanisms 50 and 52) can be used to reposition the intake and exhaust valve camshafts 40 and 42, respectively, so that the engine 10 is in a state that is thought to be better suited to restarting at the end of a start-stop cycle, for example, to allow the engine 10 to restart faster and / or with lower emissions.In the provided example, each of the intake and exhaust VVT mechanisms 50 and 52 includes a mechanism control device 70 configured to monitor and operate the actuator 60. However, it is understood that some or all of the monitoring and control functions performed by the mechanism control device 70 could be performed by the ECU 62. Each mechanism control device 70 is configured to perform the routines shown schematically in the... Fig. 3 and Fig. Figure 4 illustrates this. In short, the mechanism control devices 70 are configured to operate the electric motors 64 of the actuators 60 at an increased current level under certain conditions until the engine 10 has been restarted. In this way, the electric motors 64 can be "overdriven" to allow the camshaft phase setting to change more quickly during the engine 10 restart, not only to improve starting performance but also to reduce emissions and improve fuel efficiency.

[0021] In Fig. The control process begins at bladder 100 and proceeds to decision block 102, where the control unit determines whether the mechanism control device 70 detects that the engine operation is stopped. Various criteria can be used by the mechanism control device 70 to determine that the engine operation is stopped, such as a signal generated by the ECU 62. In the example described herein, two exemplary criteria are used by the mechanism control device 70 to identify a situation in which the engine operation is stopped, although it is understood that any type of criteria can be used to determine whether the engine operation is stopped.

[0022] A first exemplary criterion that can be used by the mechanism control device 70 to identify a situation in which the engine operation is stopped relates to the rotational speed of the engine 10 and, in particular, whether the rotational speed of the engine 10 has fallen below a predetermined speed threshold for a period of time exceeding a predetermined time. It is understood that the rotational speed of other components (e.g., the camshaft 40, the crankshaft 30, the electric motor 64, etc.) can be used to determine whether the engine operation is stopped. Since the rotational speed of the electric motor 64 is proportional to the rotational speed of the engine 10, the mechanism control device 70 can use the rotational speed of the electric motor 64 to make the determination with respect to the rotational speed of the engine 10.The electric motor 64 includes a position sensor that detects the rotational position of the motor's rotor and generates a rotor position signal that is transmitted to the mechanism control device 70. The mechanism control device 70 can use the position sensor to control the commutation of the electric motor 64 and determine its rotational speed. Alternatively, the rotor speed can be determined by the mechanism control device 70 from the magnitude of the electromagnetic backforce (EMF) generated by the electric motor 64. The mechanism control device 70 can start a timer as soon as it determines that the rotor speed is below a speed that correlates with the predetermined speed threshold of the motor 64.Thus, the first criterion is fulfilled at a time when the rotational speed of the rotor is maintained at a speed below the speed that correlates with the predetermined speed threshold of motor 10 for a time equal to or exceeding the predetermined time.

[0023] A second exemplary criterion that can be used by the mechanism control device 70 to identify a situation in which motor operation is stopped concerns the size of a requested work cycle used to drive the electric motor 64. Without the need or desire to pre-position a camshaft, the electric motor 64 of the actuator 60 would not require any electrical power in a situation where the motor 62 has stopped operating. Thus, a requested work cycle with a size outside a predetermined work cycle range or zone indicates that the operation of the motor 10 should be stopped. Accordingly, the second criterion is met if the requested work cycle has a size that lies outside the predetermined work cycle range.

[0024] In the provided example, the controller determines that the motor's operation is stopped when both the first and second criteria are met. However, it is understood that the controller could use the fulfillment of the first criterion alone, the fulfillment of the second criterion alone, or the fulfillment of either the first or the second criterion to determine that the operation of motor 10 is stopped.

[0025] If, in decision block 102, the controller does not determine that the operation of motor 10 should be stopped, the controller returns to decision block 102. However, if the controller determines that the operation of motor 10 should be stopped, the controller proceeds to block 104.

[0026] In block 104, the control unit receives a desired camshaft shut-off position. As discussed above, the desired camshaft shut-off position is a position to which a camshaft is pre-positioned during the "stop" portion of a "start-stop" cycle when the engine 10 is not running, so that the engine 10 is in a state that is assumed to be more suitable for restarting at the end of a "start-stop" cycle. As an example, the mechanism control device 70 can receive the desired camshaft shut-off position from the ECU 62, which can either store the desired camshaft shut-off position or dynamically calculate it based on, for example, various electrical and mechanical characteristics of the electric motor 64.

[0027] In block 106, the controller adjusts a current limit to the magnitude of the electric current supplied to the electric motor 64 of the actuator 60. The current limit can be adjusted based on at least one of the current limit, a predetermined current limit, a current motor temperature, a predetermined temperature limit, and a motor temperature profile. Exemplary current adjustment controls performed by the mechanism control device 70 are described below with reference to Fig. 4 described in more detail.

[0028] In block 108, the control unit holds the camshaft at the desired camshaft pre-start phase setting. As an example, the mechanism control device 70 can supply current to the electric motor 64 with a magnitude less than or equal to the current limit determined at block 106 in order to hold the camshaft at the desired camshaft pre-start phase setting.

[0029] In decision block 110, the controller determines whether motor 10 is restarted. The decision to restart motor 10 can be triggered by the activation of a starter motor, the use of a flag or other control signal indicating that motor 10 should be restarted, or the occurrence of a situation in which one or all of the criteria used in decision block 110 to determine that motor operation should be stopped are no longer met. If the controller does not determine that motor 10 is restarted, it returns to block 110. If the controller determines that motor 10 is restarted, it proceeds to block 112.

[0030] In block 112, the control unit positions the camshaft from its current phase setting toward or into a desired camshaft phase setting. For example, the control unit retards a camshaft phase setting 40, 42 relative to the crankshaft phase setting 30 before / during an engine restart. Conversely, the control unit advances a camshaft phase setting 40, 42 relative to the crankshaft phase setting 30 before / during an engine restart. In one form, the mechanism control device 70 can supply current to the electric motor 64 at a magnitude less than or equal to the updated current limit.

[0031] In decision block 114, the controller determines whether the motor restart fulfills a motor restart condition. For example, fulfilling the motor restart condition could indicate that motor 10 has resumed operation and that various motor parameters are met, while failing to fulfill the motor restart condition could indicate that motor 10 has not resumed operation or that various motor parameters are not met during / after the motor restart. Determining whether various motor parameters are met can be based on a comparison of the crankshaft speed 30 with a threshold value, a comparison of the motor 10 speed with a threshold value, or whether the size of the operating cycle for driving the electric motor 64 is within the predetermined operating cycle range, among other motor parameters.

[0032] If the controller determines at block 114 that the engine restart does not meet the restart condition, the controller proceeds to block 116, where it determines whether predetermined operating parameters of engine 10 are met. For example, meeting the predetermined operating parameters may indicate that engine 10 continues to function properly (or functions according to a set of predefined criteria) when the engine restart condition is not met, and failing to meet the predetermined operating parameters may indicate that engine 10 is not functioning properly (e.g., ECU 62 and / or mechanism control device 70 detects an engine / mechanism fault) when the engine restart condition is not met.The control unit can determine whether the predetermined operating parameters of the motor 10 are met based on various motor parameters, such as the speed of the crankshaft, the speed of the motor 10, the size of the work cycle for driving the electric motor 64, the value of the timer and other motor parameters to determine the proper function of the motor 10.

[0033] Additionally or alternatively, the determination that the predetermined operating parameters are met can be based wholly or partly on a threshold time value and a value of a timer of the mechanism control device 70, which increments proportionally to the sequence of occurrences of one or more predetermined events, such as determining that the engine 10 is restarted or that the speed of the crankshaft 30 exceeds a predetermined threshold.

[0034] As an example, the predetermined operating parameters are met if the timer value indicates that the engine restart has been completed within a predetermined time period. Conversely, the predetermined operating parameters may not be met if the timer value indicates that the engine restart has not been completed within the predetermined time period. It is evident from the above that a determination that the engine 10 has been restarted involves a control mechanism that determines that all necessary conditions or parameters associated with the resumption of operation by the engine 10, including the expiration of timers, have been sufficiently met and do not relate to the ability of the engine 10 to operate in the absence of a rotational input from anything other than combustion within the engine 10.

[0035] As another example, the controller can determine that the predetermined operating parameters are met if the size of the work cycle for driving the electric motor 64 is within a predetermined work cycle range and the speed of the electric motor 64 is greater than or equal to a minimum predetermined threshold speed (e.g., 0). As yet another example, the controller can determine that the predetermined operating parameters are not met if the size of the work cycle for driving the electric motor 64 is outside a predetermined work cycle range and the speed of the electric motor 64 is less than or equal to a minimum predetermined threshold speed (e.g., 0).

[0036] If the control unit determines at block 116 that the predetermined operating parameters are met, it proceeds to block 112. However, if the control unit determines at block 116 that the predetermined operating parameters of motor 10 are not met, it proceeds to block 118.

[0037] When the controller determines that the motor restart meets the restart condition, it returns to block 114 and proceeds to block 118, where the controller adjusts the current limit. In one form, the current limit can be adjusted based on at least one of a predetermined current limit, a current motor temperature, a predetermined temperature limit, a motor temperature profile, or a motor temperature profile. As an example, the controller can reset the current limit used to drive the electric motors 64 to a lower level associated with the normal operation of motor 10.

[0038] In Fig. Figure 4 shows a current matching control, which is taken from the mechanism control device 70 at block 106. Fig.3. The current matching control begins at decision block 202, where the current matching control determines whether a current limit is greater than a predetermined current limit. The current limit is used by the mechanism control device 70 to limit the magnitude of the electric current supplied to the electric motor 64 of the actuator 60. If the current matching control determines that the current limit is not greater than the predetermined current limit in decision block 202, the control proceeds to block 208, where the current matching control uses a temperature of the electric motor 64 and a motor temperature profile to determine an updated current limit (e.g., a new value for the current limit).The motor temperature profile could include an algorithm, a lookup table, or a mapping of various parameters, including the temperature of the electric motor 64, that correlate the various parameters with a current limit for the electric motor 64.

[0039] If the current matching controller determines that the current limit is greater than the predetermined current limit, it proceeds to decision block 204. In decision block 204, the current matching controller determines whether the temperature of the electric motor 64 of the actuator 60 is greater than or equal to a predetermined motor temperature limit. If the temperature of the electric motor 64 is greater than or equal to the predetermined motor temperature limit in decision block 204, the current matching controller proceeds to block 208, where the updated current limit is determined in the manner described above.

[0040] Returning to decision block 204, if the controller determines that the electric motor temperature is not greater than or equal to the predetermined motor temperature limit, the current matching control moves to block 206, where it sets the updated current limit to a predetermined high current limit. This predetermined high current limit may be the same as or different from the predetermined current limit in decision block 202. The controller then moves to decision block 202.

[0041] It is understood that the set of predetermined conditions used to determine whether the predetermined high current limit is used could include other conditions, such as a parameter relating to the amount of time the electric motor 64 has been used. For example, if the electric motor 64 has been used at a point where a predetermined percentage, such as 80 percent, of its service life has been consumed, then the current adjustment control can be configured to prevent the use of the predetermined high current limit. Additionally or alternatively, the predetermined high current limit can be varied over the service life of the electric motor 64.

[0042] The foregoing description of the embodiments has been provided for illustrative and descriptive purposes. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment but are, where applicable, interchangeable and may be used in a selected embodiment even if it is not specifically shown or described. These may likewise be varied in many ways. Such variations are not to be considered a departure from the disclosure, and all such modifications are intended to be contained within the scope of the disclosure.

[0043] As used herein, the expression "at least one of A, B and C" should be interpreted as meaning a logical (A OR B OR C) using a non-exclusive logical OR, and should not be interpreted as meaning "at least one of A, at least one of B and at least one of C".

[0044] The description of the revelation is merely exemplary, and therefore variations that do not deviate from the content of the revelation are to be considered within its scope. Such variations are not to be regarded as a departure from the spirit and scope of the revelation.

[0045] In the figures, the direction of an arrow, as indicated by the arrowhead, generally illustrates the flow of information (such as data or instructions) that is relevant to the representation. For example, if Element A and Element B exchange a variety of information, but information transferred from Element A to Element B is relevant to the representation, the arrow may point from Element A to Element B. This unidirectional arrow does not mean that no other information is transferred from Element B to Element A. Furthermore, Element B may send requests or acknowledgments of information to Element A for information sent from Element A to Element B.

[0046] In this application, the term "controller" may refer to, be a part of, or include an application-specific integrated circuit (ASIC); a digital, analog, or mixed analog / digital discrete circuit; a digital, analog, or mixed analog / digital integrated circuit; a combinational logic circuit; a field-programmable gate array (FPGA); a processor circuit (shared, dedicated, or group) that executes code; a memory circuit (shared, dedicated, or group) that stores code executed by the processor circuit; other suitable hardware components that provide the described functionality; or a combination of some or all of the foregoing, as in a system-on-a-chip.

[0047] The term "memory" is a subset of the term "computer-readable medium." The term "computer-readable medium," as used herein, does not include transient electrical or electromagnetic signals propagating through a medium (such as on a carrier wave); the term "computer-readable medium" can therefore be considered tangible and non-volatile. Non-restrictive examples of a non-volatile, tangible computer-readable medium include non-volatile memory circuits (such as a flash memory circuit, an erasable programmable read-only memory circuit, or a mask read-only circuit), volatile memory circuits (such as a static random-access memory circuit or a dynamic random-access memory circuit), magnetic storage media (such as analog or digital magnetic tape or a hard disk), and optical storage media (such as a CD, a DVD, or a Blu-ray Disc).

[0048] The devices and procedures described in this application can be implemented in whole or in part by a specialized computer created by configuring a general-purpose computer to perform one or more specific functions embodied in computer programs. The functional blocks, flowchart components, and other elements described above serve as software specifications that can be translated into computer programs through the routine work of a person skilled in the art or a programmer.

Claims

[1] Method for operating a variable valve timing mechanism that controls the phase adjustment of a camshaft (40, 42) in an engine (10), wherein the variable valve timing mechanism comprises an electric motor (64), the method comprising: Determining a value for an operating motor current limit; setting a value for a starting current limit equal to a predetermined value that is higher than the value of the operating motor current limit when a set of predetermined conditions is met, or otherwise substituting the value of the operating motor current limit as the value of the starting current limit; Determine that the operation of the motor (10) has been interrupted; operate the electric motor (64) of the variable valve timing mechanism with a current of a magnitude less than or equal to the starting current limit, after determining that the operation of the motor (10) has been interrupted; determine that the operation of the motor (10) has resumed; and Operating the electric motor (64) of the variable valve control mechanism with a current of a magnitude less than or equal to the operating motor current limit, after it has been determined that the operation of the motor (10) has been resumed. [2] Method according to claim 1, wherein the set of predetermined conditions includes that the temperature of the electric motor (64) is below a predetermined temperature threshold. [3] Method according to claim 1, wherein one dimension of the predetermined value is based on an age of the electric motor (64). [4] Method according to claim 1, wherein one dimension of the predetermined value is based on a temperature of the electric motor (64). [5] Method according to claim 1, wherein the value of the operating motor current limit is based on a temperature of the electric motor (64). [6] Method according to claim 5, wherein the value of the operating motor current limit is determined by a step function based on the temperature of the electric motor (64). [7] Method according to claim 1, wherein determining that the operation of the motor (10) has been resumed is based at least partially on a control signal provided by a motor control device. [8] Method according to claim 1, wherein determining that the operation of the motor (10) has been resumed is based on an algorithm that uses one or more parameters of the motor (10). [9] Method according to claim 1, wherein determining that the operation of the engine (10) has been resumed is based on one or more parameters of the variable valve timing mechanism. [10] Method according to claim 1, wherein determining that the operation of the motor (10) has been resumed is based on a value of a timer. [11] Method for operating a variable valve timing mechanism that controls the phase adjustment of a camshaft (40, 42) in an engine (10), wherein the variable valve timing mechanism comprises an electric motor (64), the method comprising: Determine that the operation of the motor (10) has been interrupted; Operating the electric motor (64) in a restart mode to control the phase setting of the camshaft (40, 42) when it is determined that the operation of the motor (10) has been interrupted; Determine, independently of a dedicated restart signal, that the operation of the motor (10) has resumed; and Operating the electric motor (64) in a motor operating mode to control the phase setting of the camshaft (40, 42) when it is determined that the operation of the motor (10) has been resumed, where determining that the operation of the motor (10) is resumed, The following is included: Determining whether the rotational speed of the electric motor (64) is greater than a predetermined motor speed threshold, and / or Determining that a quantity of a work cycle, with which electrical power is supplied to the electric motor (64), is greater than or equal to a predetermined work cycle threshold. [12] Method according to claim 11, wherein determining that the operation of the motor (10) has been interrupted includes determining whether a speed of the electric motor (64) is less than or equal to a predetermined motor speed threshold. [13] Method according to claim 12, wherein determining that the operation of the motor (10) has been interrupted includes determining that the rotational speed of the electric motor (64) has been less than or equal to the predetermined motor speed threshold for a period of time greater than or equal to a predetermined time threshold. [14] Method according to claim 11, wherein determining that the operation of the motor (10) has been interrupted includes determining that a quantity of a work cycle with which electrical power is supplied to the electric motor (64) is within a predetermined quantity range. [15] Method according to claim 11, wherein determining that the operation of the motor (10) has been interrupted includes determining that a quantity of a work cycle with which electrical power is supplied to the electric motor (64) is less than a predetermined work cycle threshold. [16] Method according to claim 11, wherein determining that the operation of the motor (10) is resumed includes determining that the rotational speed of the electric motor (64) has been greater than or equal to the predetermined motor speed threshold for a period of time greater than or equal to a predetermined time threshold.

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