Method for starting an internal combustion engine comprising a camshaft associated with an electrical variable valve timing device

Abstract

A method for starting an internal combustion engine (M) comprising a camshaft (A) equipped with an electrically operated variable valve timing (eVVT) device, comprising: / a / a step of applying maximum voltage to the electric actuator, then / b1 / a step of initiating a time delay Ts during which maximum voltage continues to be applied to said actuator and, in parallel, / b2 / a step of initiating synchronization of the internal combustion engine, then / c / if the time delay expires before the end of the synchronization of the internal combustion engine, a step of incrementing the value of the failure counter and a repetition of steps / a / to / c / if the value of the failure counter is less than a predetermined number Nmax, otherwise stopping the application of voltage to said actuator, the internal combustion engine being synchronized. Figure for publication: Figure 1

Description

Title of the invention: Method for starting an internal combustion engine comprising a camshaft associated with an electrical variable valve timing device. Field of the invention

[0001] The present invention relates to a method for starting an internal combustion heat engine comprising at least one camshaft associated with an electrical continuously variable timing distribution device. Previous art

[0002] In the operating cycle of a four-stroke internal combustion engine, it is necessary to know the precise position of the crankshaft in order to synchronize various actions such as fuel injection, spark plug control, valve timing, etc. This allows for the optimization of combustion efficiency and the reduction of fuel consumption and harmful emissions. In other words, an internal combustion engine must be synchronized (phased) in order to determine and optimize the best time to burn the fuel in the cylinder with a view to optimizing emissions, fuel consumption, etc.

[0003] Engine synchronization or phasing is generally achieved by combining information from a crankshaft position sensor and a camshaft position sensor which detect targets such as teeth on gears.

[0004] To achieve this, a crankshaft typically includes a gear, or crankshaft target, which usually comprises a set of teeth evenly distributed along its circumference (for example, from 36 to 120 teeth), and whose teeth are detected by a sensor called a CRK sensor. The gear attached to the crankshaft has a reference portion, also called a singularity or signature, devoid of teeth in the form of a groove or a long tooth, also called a GAP (a term used hereafter). By detecting the passage of the teeth past the sensor and counting the number of teeth from the GAP during engine rotation, it is possible to determine the crankshaft position over one 360° crankshaft revolution, in other words, 360°CRK, the crankshaft rotation angle being expressed in °CRK.

[0005] The crankshaft target equipped with teeth thus presents a singularity that makes it possible to know the engine position to within 360°CRK. However, an engine cycle (for a so-called 4-stroke engine) takes place over two complete rotations of the crankshaft, and knowledge of the crankshaft's angular position is therefore insufficient to determine the engine's position relative to an engine cycle.

[0006] It is known to combine the information obtained from the crankshaft rotation with angular position information corresponding to a camshaft, which is driven in rotation by the crankshaft with a reduction ratio of 2, such that the camshaft completes one full rotation for every two rotations of the crankshaft. Thus, the additional information from the camshaft makes it possible to determine the correct phasing. Since the camshaft rotation angle is expressed in °CAM, it is noted that a revolution of 360°CAM is equivalent to 720°CRK. By then positioning a toothed wheel on the camshaft, which also exhibits a rotational asymmetry, the corresponding information, combined with the information on the crankshaft position, makes it possible to accurately deduce the state of the engine cycle.

[0007] Furthermore, variable valve timing is a technique that allows several parameters to be varied in an internal combustion engine: the timing, the duration of opening and / or the lift of the intake and exhaust valves.

[0008] In particular, a continuously variable valve timing system can be implemented by varying, in either direction, the angular position of an intake or exhaust camshaft relative to the angular position of an engine crankshaft. This changes the camshaft phase angle and modifies the valve overlap, the period during which the intake and exhaust valves are open simultaneously. By modifying the valve overlap, the continuously variable valve timing system can improve engine breathing, reduce pumping losses, increase volumetric efficiency, and control the residual gas fraction.

[0009] Many internal combustion engines feature a camshaft associated with a variable (continuous) valve timing system, one acronym of which is VVT (cWT), for variable valve timing.

[0010] In a known manner, a continuously variable valve timing device includes an actuator for changing the position of the camshaft.

[0011] The control of the variable valve timing device is carried out from the position of the faces of a camshaft target and therefore cannot be properly controlled before the engine is synchronized.

[0012] A mechanical actuator conventionally includes a return spring which, when the associated internal combustion engine is stopped, places the camshaft in a reference angular position relative to the crankshaft. The internal combustion engine can then be started by synchronizing it with the reference angular position of the camshaft relative to the crankshaft.

[0013] There are also electric actuators. In the absence of a return mechanism, the angular position of the camshaft is unknown after the engine is stopped.

[0014] It is then no longer possible to synchronize the internal combustion engine from a crankshaft and a camshaft equipped with such an electric actuator as previously explained.

[0015] Also, when an engine has only electrical type devices on its camshafts, there is a need to determine the angular position of the camshafts equipped with such devices.

[0016] More generally, there is a need to determine the angular position of such an electrical device when the angular position of a camshaft equipped with a mechanical device is no longer known, for example because an angular position sensor associated with the device is faulty.

[0017] There is therefore a need to improve the starting of an internal combustion heat engine comprising at least one camshaft equipped with an electrical device for variable valve timing with continuous variable timing. Description of the invention

[0018] An idea which is at the basis of the invention is to have noticed that when a predetermined voltage, called maximum, is applied to such an electrical device for a predetermined duration, the electrical device then presents a configuration called stop associated with a predetermined angular position, called stop.

[0019] According to a first aspect of the invention, a method for starting an internal combustion heat engine is proposed, comprising a camshaft equipped with an electrical device for variable valve timing with continuous variable timing.

[0020] The electrical device includes an electric actuator configured to modify the angular position of the camshaft, the camshaft having a so-called stop configuration associated with a predetermined angular position, called stop, when a predetermined voltage, called maximum, is applied to said actuator for a predetermined duration Tb.

[0021] The process comprising: • / a / a step of applying the maximum voltage to said actuator electric for a period longer than the predetermined period, then • / b 1 / a step (Ed) of triggering a time delay Ts, called a safety time delay, of a duration Tmax during which a maximum voltage continues to be applied to said actuator and, in parallel, • / b2 / a step (Es) of starting an engine synchronization thermal analysis based on position data associated with the angular position of the stop, then • / c / if the timer expires before the end of the motor synchronization thermal, a step of incrementing the value of the failure counter and a repetition of steps / a / to / c / if the value of the failure counter is less than a predetermined number Nmax, otherwise the motor is synchronized and we stop (Estop) applying the so-called stop voltage on said actuator.

[0022] Preferably, the duration of application of the maximum voltage is determined from an angular speed of rotation of the actuator and a maximum angular deviation to reach the angular stop position.

[0023] Advantageously, the method includes, prior to step / a / , a step of determining the availability of only electrical type actuators for motor synchronization.

[0024] According to a second aspect of the invention, a computer program product is proposed comprising program code instructions recorded on a medium readable by a computer such as a processor, a controller or a microcontroller for the implementation of the steps of the process according to any one of the preceding claims when said program is implemented by said computer such as a processor, a controller or a microcontroller.

[0025] According to a third aspect of the invention, an electronic starting module for an internal combustion heat engine is proposed, comprising a camshaft equipped with an electrical device for variable valve timing with continuous variable timing.

[0026] As before, the electrical device includes an electric actuator configured to change the angular position of the camshaft, the camshaft having a so-called stop configuration associated with a predetermined angular position, called stop, when a predetermined voltage, called maximum, is applied to said actuator for a predetermined time Tb.

[0027] The electronic module is configured to: • / a / apply maximum voltage to said electrical actuator for a period exceeding the predetermined duration, then • / b 1 / trigger a time delay Ts, called a safety time delay, of a duration Tmax during which a maximum voltage continues to be applied to said actuator and, in parallel, • / b2 / start a synchronization of the internal combustion engine from a position data associated with the angular position of the stop, then • / c / if the timer expires before the end of the motor synchronization thermal, increment the value of the failure counter and repeat steps / a / to / c / if the value of the failure counter is less than a predetermined number Nmax, • otherwise stop applying a so-called stop voltage on said actuator, the internal combustion engine being synchronized.

[0028] According to another aspect of the invention, a heat engine comprising an electronic module according to the invention is proposed.

[0029] According to yet another aspect of the invention, a vehicle comprising a thermal engine according to the invention is proposed. Brief description of the figures

[0030] Other features and advantages of the invention will become apparent upon reading the detailed description that follows, for an understanding of which reference should be made to the accompanying drawings, in which: • [Fig. 1] is a schematic view of an embodiment of an electronic device according to the invention, • [Fig.2] illustrates a method according to the invention implemented in the device shown in [Fig.1], • [Fig.3] illustrates an implementation of the process of [Fig.2]. Detailed description of the invention

[0031] With reference to [Fig.1] and [Fig.2], a heat engine M mounted in a vehicle V with wheels R driven by the heat engine M mounted on said vehicle is illustrated.

[0032] The heat engine M is an internal combustion heat engine, for example a four-stroke engine, comprising an intake camshaft and an exhaust camshaft.

[0033] One of the two camshafts, referenced A, is equipped with an eVVT (electrical continuously variable valve timing) device. The other camshaft can, for example, also be equipped with an eVVT device. The invention also applies if the other camshaft is equipped with a mechanical continuously variable valve timing device and the sensor associated with the other camshaft is faulty.

[0034] The eVVT electrical device includes an electric actuator configured to change the angular position of the camshaft, the camshaft having a so-called stop configuration associated with a predetermined angular position, called stop, when a predetermined voltage, called maximum, is applied to said electrical device for a predetermined time.

[0035] For example, the predetermined angular position is 160° CRK.

[0036] The internal combustion engine M is controlled by an engine control unit (ECU).

[0037] The engine control unit ECU comprises an electronic module D according to the invention.

[0038] The electronic module D is configured to: • / a / apply Ea a maximum voltage on the electric actuator during a duration exceeding the predetermined duration, then • / b 1 / a step Ed of triggering a time delay Ts, called a safety time delay, of a duration Tmax, during which a maximum voltage continues to be applied to said actuator and, in parallel, • / b2 / a step Es of starting a synchronization of the internal combustion engine starting from a position value associated with the angular position of the stop, and then, • If the timer expires before the end of the internal combustion engine synchronization, a step increments the value of the failure counter and steps / a / to / c / are repeated if the value of the failure counter is less than a predetermined number (Nmax). • otherwise, the motor is synchronized and we stop (Estop) applying the stop voltage on said actuator.

[0039] The synchronization of the internal combustion engine is achieved by using the position of the singularity of the crankshaft target and the position of the theoretical fronts generated by a sensor associated with the camshaft target in the stop position.

[0040] The electronic module D can be implemented in the form of a computer program product, comprising program code instructions recorded on a medium readable by a computer such as a processor, a controller or a microcontroller for the implementation of the steps of the process P when said program is implemented by said computer such as a processor, a controller or a microcontroller.

[0041] The step of synchronizing the internal combustion engine from a position data associated with a known position of a camshaft is known to a person skilled in the art.

[0042] The duration of application of the maximum voltage can be determined from knowledge of the angular speed of rotation of the actuator and the maximum angular deviation to reach the angular stop position.

[0043] The maximum number Nmax prevents damage to the continuously variable valve timing (CVT) control device by repeatedly moving the electric actuator to a camshaft stop position. For example, Nmax=3 could be chosen.

[0044] Figure 3 illustrates a possible implementation of a method according to the invention.

[0045] It is illustrated in [Fig.3] two state machines, REQ and ACK.

[0046] The two state machines REQ and ACK can for example be implemented within the electronic control unit.

[0047] State machines can read the state of a variable SE indicating motor synchronization, equal to 1 when the motor is synchronized and to 0 otherwise.

[0048] The REQ state machine has three states: • an initial state REQ=0 indicating that there is no need to implement the process according to the invention; • a REQ=1 state indicating that there is a need to modify the angular position of the camshaft; • a REQ=2 state indicating that the Es synchronization step has begun, the transition to the REQ=2 state resulting in an Es start of a synchronization of the thermal engine from a position data associated with the angular position of the stop, the synchronization of said engine ending with an assignment of the value 1 to the variable. • a REQ=3 state indicating that a synchronization state has been reached.

[0049] The ACK state machine has three states: • an initial state ACQ=0 indicating that there is no need to implement the process according to the invention; • an ACK=1 state indicating that a request to move the camshaft into a stop configuration has been received, the transition to the ACK=1 state beginning with the start of a timer Ta as an input action and the application Ea of the maximum voltage on said electrical actuator for the predetermined duration Tb; • a state ACQ=2 indicating that the camshaft is in a stop configuration, the transition to state ACK=2 resulting in the start of a timer Ts as an input action, and the application of the maximum voltage on said electrical actuator.

[0050] The REQ state machine has access to a variable T, equal to 1 when only electric actuators are available for synchronization and equal to 0 otherwise.

[0051] The REQ state machine can read a counter C and compare it with a predetermined maximum number Nmax.

[0052] The REQ state machine can determine the synchronization state of the internal combustion engine. When a variable SE is equal to 1, this indicates a synchronization state of the internal combustion engine.

[0053] State machine transitions REQ: • from state REQ=0 to state REQ=1: the variable T is equal to 1 and the counter C is strictly less than Nmax; • from state REQ=1 to state REQ=2: when the ACK state machine changes to state ACK=2; • from state REQ=2 to state REQ=3: when the variable SE is equal to 1; • from state REQ=3 to state REQ=0: when the ACK state machine transitions to the state ACK=0.

[0054] ACK state machine transitions: • from state ACQ=0 to state ACK=1: when the state machine REQ goes to state REQ=1 and the counter C is strictly less than Nmax; • from state ACQ=1 to state ACK=2: when the time delay Ta reaches a predetermined value Tb; • from state ACQ=2 to state ACK=0: when the state machine REQ goes to state REQ=3, in which case the counter C is reset, or the timer Ts reaches a predetermined value Tmax in which case the counter C is incremented.

[0055] Of course, the invention is not limited to the examples just described, and many modifications can be made to these examples without departing from the scope of the invention. Furthermore, the various features, forms, variants, and embodiments of the invention can be combined in various ways, provided they are not incompatible or mutually exclusive.

Claims

Demands

1. A method (P) for starting an internal combustion heat engine (M) comprising a camshaft (A) equipped with an electrical device (eVVT) for continuously variable valve timing, the electrical device comprising an electric actuator configured to modify the angular position of the camshaft, the camshaft having a so-called stop configuration associated with a predetermined angular position, called the stop, when a predetermined voltage, called the maximum voltage, is applied to said actuator for a predetermined duration Tb, the method comprising: / a / a step (Ea) of applying the maximum voltage to said electric actuator for a duration greater than the predetermined duration, then / b 1 / a step (Ed) of triggering a time delay Ts, called the safety time delay, of a duration Tmax during which a maximum voltage continues to be applied to said actuator and, in parallel, / b2 / a step (Es) of starting a synchronization of the internal combustion engine from a position data associated with the angular position of the stop, then / c / if the timer expires before the end of the synchronization of the internal combustion engine, a step of incrementing the value of the failure counter and a repetition of steps / a / to / c / if the value of the failure counter is less than a predetermined number Nmax, otherwise the engine is synchronized and the application of the stop voltage on said actuator is stopped (Estop).

2. A method according to the preceding claim, wherein the duration of application of the maximum voltage is determined from an angular speed of rotation of the actuator and a maximum angular deviation to reach the angular stop position.

3. A method according to any one of the preceding claims, comprising, prior to step / a / , a determination step (Ei) of the sole availability of electric type actuators for motor synchronization.

4. Product: computer program comprising program code instructions recorded on a machine-readable medium such as a processor, controller or microcontroller for implementing the steps of the process according to any of the preceding claims when said program is implemented by said computer such as a processor, controller or microcontroller.

5. Electronic starting module (D) for an internal combustion engine (M) comprising a camshaft (A) equipped with an electrically controlled variable valve timing device (eVVT), the electrically controlled device having an electric actuator configured to change the angular position of the camshaft, the camshaft having a so-called stop configuration associated with a predetermined angular position, called the stop, when a predetermined voltage, called the maximum voltage, is applied to said actuator for a predetermined time Tb, the electronic module being configured to: / a / apply the maximum voltage to said electric actuator for a time exceeding the predetermined time, then / b 1 / trigger a time delay Ts, called the safety time delay, of a duration Tmax during which a maximum voltage continues to be applied to said actuator and, in parallel, / b2 / start a synchronization of the internal combustion engine from a position data associated with the angular position of the stop, then / c / if the timer expires before the end of the synchronization of the internal combustion engine, increment the value of a failure counter and repeat steps / a / to / c / if the value of the failure counter is less than a predetermined number Nmax, otherwise stop applying a voltage to said actuator, the internal combustion engine being synchronized.

6. Internal combustion engine, characterized in that it comprises an electronic module according to the preceding claim.

7. Vehicle comprising a heat engine according to the preceding claim.

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