DE102021132950B3 - Method for operating a drive device for a motor vehicle and corresponding drive device - Google Patents

Abstract

The invention relates to a method for operating a drive device for a motor vehicle, the drive device having a drive unit (1) with a valve drive (6) which is connected via a camshaft adjuster (12, 13) to a crankshaft (3) of the drive unit (1). drive-related coupled camshaft (9, 10) with at least one cam for periodically actuating a gas exchange valve (7, 8) of a cylinder (2) of the drive unit (3), wherein the camshaft adjuster (12, 13) at least temporarily for adjusting control times of the gas exchange valve (7, 8) is operated. It is provided that at least temporarily a valve actuation period (Δφ) used to determine an operating variable of the drive unit (1) is determined and corrected at least during the adjustment as a function of an adjustment speed (ωNWS) of the camshaft adjuster (12, 13). The invention also relates to a drive device for a motor vehicle.

Description

The invention relates to a method for operating a drive device for a motor vehicle, the drive device having a drive unit with a valve drive, which includes a camshaft, which is coupled to a crankshaft of the drive unit via a camshaft adjuster in terms of drive technology, and has at least one cam for periodically actuating a gas exchange valve of a cylinder of the drive unit , wherein the camshaft adjuster is operated at least temporarily to adjust control times of the gas exchange valve. The invention also relates to a drive device for a motor vehicle.

From the prior art, for example, the publication U.S. 7,467,611 B2 known. This describes a method for controlling two independent camshaft positioners in an internal combustion engine. The method involves three basic steps: a) first, determining whether adjustment rate balancing is required between the two adjusters; b) second, determining optimal rate compensation control instructions; and c) thirdly, applying the determined control instructions for adjusting rate compensation at the respective adjusters. When determining the control instructions for adjusting rate compensation, there are three possible adjusting options: the inlet adjuster requires prioritization; the outlet actuator requires prioritization; or neither of the two controllers requires prioritization. Tables of values for each option are stored in an engine control unit. If one of the two controllers requires prioritization, the respective other controller is actuated after a delay that depends on the positioning accuracy of the prioritized controller, generally at a lower positioning speed. If neither actuator requires prioritization, both actuators are actuated at a rate consistent with an engine's oil delivery capability.

The publication is also from the state of the art DE 10 2007 027 868 B4 known. This relates to a method for increasing the switching reliability of a switching component of a motor vehicle internal combustion engine, in that a control unit initiates the respective switching process of the switching component between a first switching state and a second switching state at an activation time which is brought forward by a lead time compared to a desired switching time window , in which the switching duration of the switching component and, in addition, any predicted shift in position of the targeted desired switching time window are taken into account, with the control unit performing an adjustment of the switching parameters of the switching component during the respective switching process if it is forecast that a determined completion time of the switchover will be outside of the respectively envisaged desired switching time window will come to rest.

It is the object of the invention to propose a method for operating an internal combustion engine which has advantages over known methods, in particular enabling a more precise determination of a valve actuation period.

According to the invention, this is achieved with a method for operating an internal combustion engine having the features of claim 1 . It is provided that at least temporarily a valve actuation period used to determine an operating variable of the drive unit is determined and corrected at least during the adjustment as a function of an adjustment speed of the camshaft adjuster.

Advantageous configurations with expedient developments of the invention are specified in the dependent claims.

The method for operating the drive device is preferably part of the motor vehicle. The drive device basically serves to provide a drive torque, which is directed, for example, at driving the motor vehicle. For this purpose, the drive device has the drive unit, which is preferably present as an internal combustion engine and in particular has the cylinder, the crankshaft and the valve train. A piston is displaceably arranged in the cylinder and is drivingly coupled to the crankshaft, in particular via at least one connecting rod. The piston encloses a combustion chamber with a cylinder wall of the cylinder and a cylinder roof of the cylinder.

The gas exchange valve is fluidically connected to the cylinder, in particular to the combustion chamber. The gas exchange valve can be configured either as an inlet valve or as an outlet valve. In any case, it is present in terms of flow between an external environment of the drive unit and the combustion chamber, with a flow connection being established when the gas exchange valve is partially open and being interrupted when the gas exchange valve is closed.

If the gas exchange valve is configured as an inlet valve, it serves to admit fresh gas into the combustion chamber. When the gas exchange valve is at least partially open, fresh gas can flow into the combustion chamber from a fresh gas tract of the drive assembly. When the gas exchange valve is closed, the flow is technical connection between the fresh gas tract and the combustion chamber is prevented.

If the gas exchange valve is designed as an outlet valve, it is arranged in terms of flow between the combustion chamber and an exhaust tract of the drive assembly. When the gas exchange valve is at least partially open, exhaust gas can flow out of the combustion chamber in the direction of the exhaust tract and can then be discharged from the drive unit. When the gas exchange valve is closed, the fluidic connection between the combustion chamber and the exhaust system is blocked.

The gas exchange valve is actuated by means of the valve train. The valve drive includes the camshaft, which has the at least one cam that actuates the gas exchange valve periodically when the camshaft rotates. As long as the cam acts on the gas exchange valve, this opens or remains open. If the cam is arranged away from the gas exchange valve, the gas exchange valve is closed. The cam is designed such that the gas exchange valve begins to open at a first angular position of the camshaft and is just closed at a second angular position of the camshaft following the first angular position. In this respect, the first rotational angle position of the camshaft can be assigned to a valve opening time and the second rotational angle position to a valve closing time.

The camshaft is driven by the crankshaft. For this purpose, the camshaft is drivingly connected to the crankshaft, namely via the camshaft adjuster. There is a fixed gear ratio between the crankshaft and the camshaft, typically 2:1. This means that the speed of the crankshaft is twice the speed of the camshaft. The phase position of the camshaft relative to the crankshaft can be adjusted or changed with the aid of the camshaft adjuster. With a given rotary angle position of the crankshaft, the rotary angle position of the camshaft can thus be adjusted within a specific rotary angle position range with the aid of the camshaft adjuster. During the adjustment of the camshaft phasing, the speed ratio between the speed of the crankshaft and the speed of the camshaft deviates temporarily from the fixed gear ratio.

The valve opening time and the valve closing time are also referred to as control times of the gas exchange valve. The gas exchange valve is just open at the valve opening time and just closed at the valve closing time. Between the valve opening time and the valve closing time, the gas exchange valve is continuously at least partially open. The valve actuation period extends from the valve opening time to the valve closing time, which insofar describes an opening time period over which the gas exchange valve is at least partially open. To this extent, the valve actuation period is largely dependent on the configuration and the speed of the camshaft.

The valve opening time, the valve closing time and the duration or length of the valve actuation period are usually given in relation to a rotational angle position of the crankshaft, ie in the unit °KW. In this respect, the rotational movement of the crankshaft serves as a time base for describing the control times of the valve train. A first rotational angle position of the crankshaft can thus be assigned to the valve opening time and a second rotational angle position of the crankshaft can be assigned to the valve closing time. The valve actuation period can be correspondingly expressed as a rotational angle position range, which is limited on the one hand by the first rotational angle position and on the other hand by the second rotational angle position. In this respect, the control times can be understood both as a measure of time and as a measure of degrees, or the measure of time can be converted into the measure of degrees and vice versa.

Within the scope of this description, the timing of the control times and the degrees of the rotational angle positions of the crankshaft are used as equivalent to one another, unless otherwise stated. In this respect, a variable specified in the unit °KW is to be understood both as designating a rotational angle position of the crankshaft and as a time specification equivalent to this rotational angle position. Correspondingly, a range that is also specified in the unit °KW is to be understood both as a rotational angle position range of the crankshaft and as an equivalent time period or as a duration.

As already explained above, the camshaft positioner can be used to adjust the phase position of the camshaft in relation to the crankshaft. The result of setting or changing the phase position is that the valve opening time and the first rotational angle position of the crankshaft change. The same applies to the valve closing time and the second angular position of the crankshaft. The control times of the camshaft are thus set or adjusted by adjusting the phase position.

In this case, however, there is only a shift in the control times. This means that the control times of the gas exchange valve are fixed when the drive unit is designed and can only be shifted together afterwards, namely by actuating the camshaft adjuster accordingly. Adjusting the valve opening time always entails an adjustment of the valve closing time as well, so that at a given speed of the crankshaft apart from the adjustment of the control times, the valve actuation period is the same or - in other words - at a constant speed of the crankshaft a length of the valve actuation period after the adjustment of the Control times is unchanged compared to a length present before the adjustment.

The camshaft adjuster is preferably designed for rapid adjustment of the phase position between the crankshaft and the camshaft. The camshaft adjuster is preferably operated electrically, ie it has, for example, an electric motor, in particular a servo motor, by means of which the phase position can be adjusted. Alternatively, the camshaft adjuster can also be in the form of a hydraulic camshaft adjuster. The control times are adjusted with the adjustment speed. This describes the speed at which the valve opening time or the valve closing time is adjusted in relation to the crankshaft. The camshaft adjuster thus adjusts the phase position of the camshaft at a specific angular speed with respect to the crankshaft, which is preferably small compared to the rotational speed of the crankshaft.

For example, the adjustment speed of the camshaft adjuster is at most 400 °CA/s, while an angular velocity of the crankshaft at a speed of 1,000 rpm already corresponds to 6,000 °CA/s and is correspondingly greater at higher speeds. For example, the idle speed of the drive unit is at least 600 rpm, corresponding to 3,600 °KW/s. Consequently, the adjustment speed of the camshaft actuator is no more than 1/9, no more than 10%, no more than 7.5% or no more than 5% of the speed of the power unit. This can lead to the gas exchange valve being actuated several times during the adjustment of the control times, ie the adjustment being made while the gas exchange valve is being actuated.

To adjust the control times, the rotational speed of the camshaft is at least temporarily increased or decreased by the adjustment speed by the camshaft adjuster. This results in the changed phase position of the camshaft in relation to the crankshaft and thus the adjustment of the control times. In this way, the control times can be advanced or retarded in relation to the rotational speed of the crankshaft. In other words, the camshaft precedes the crankshaft after the valve timing has been advanced. Conversely, the crankshaft runs ahead of the camshaft after the valve timing has been retarded.

However, it follows from this that the valve actuation time period during the adjustment of the control times deviates from the specified valve actuation time period, which is predetermined by the design of the camshaft or cam. For example, adjusting the control times in a first direction, for example from early to late, while the camshaft actuator is being actuated leads to a temporarily longer valve actuation period and thus to a longer opening of the gas exchange valve. Conversely, adjusting the control times in a second direction opposite to the first direction, for example from late to early, while the camshaft actuator is being actuated leads to a temporarily shorter valve actuation period and a shorter opening of the gas exchange valve.

The valve actuation period is used to determine the operational magnitude of the power plant. The operating variable is in particular a variable that is used to control the drive unit. For example, an actual value of the operating variable is determined from the valve actuation period. The drive unit is controlled as a function of a deviation of the actual value from a setpoint value of the operating variable. To this extent, when the drive assembly is activated, the operating variable is set to the desired value, in particular set in a controlling and/or regulating manner.

If only the valve actuation period of the gas exchange valve specified by the design of the camshaft is used to determine the operating variable, then the operating variable is affected by an error dependent on the adjustment speed due to the above-explained change in the valve actuation period during the adjustment of the camshaft adjuster. This error in the determined valve actuation period and thus also in the actual value of the operating variable is all the greater, the greater the adjustment speed with respect to the rotational speed of the crankshaft. This is particularly important when using a highly dynamic camshaft adjuster, which is designed for a particularly rapid adjustment of the camshaft.

The invention therefore provides that at least during the adjustment of the control times, the valve actuation period is corrected as a function of the adjustment speed. In particular, an uncorrected valve actuation period is first determined from the rotational speed of the crankshaft and this is adjusted as a function of the adjustment speed of the camshaft adjuster. For example, the uncorrected valve actuation period is lengthened or shortened by a specific amount of time that is dependent on the adjustment rate.

The corrected valve actuation period thus describes the actual opening duration of the gas exchange valve more precisely than the uncorrected valve actuation period. For example, an opening duration of the gas exchange valve over which the gas exchange valve is actually open during the adjustment of the control times, insofar as it is at least partially open, is referred to as the effective opening duration. Outside the valve actuation period, the gas exchange valve is preferably closed, in particular completely closed.

To determine the above-described operating variable of the drive assembly, the corrected valve actuation period is used instead of the uncorrected valve actuation period. Thus, especially during the adjustment of the control times, i.e. while the camshaft adjuster is actuated at the adjustment speed, a more precise determination of the operating variable and thus reliable operation of the drive device is possible, especially in connection with a highly dynamic camshaft adjuster for rapid adjustment of the camshaft.

A further development of the invention provides that a corrected valve closing time of the gas exchange valve is determined from the valve actuation period of the gas exchange valve. The corrected valve closing point in time is a point in time at which the gas exchange valve is regarded as closed, taking into account the adjustment speed. A corrected second rotational angle position of the crankshaft, which corresponds to the corrected valve closing time, is preferably determined on the basis of the corrected valve actuation period. In this respect, the point in time related to the rotational angle position of the crankshaft at which the gas exchange valve is just closed is determined more precisely.

The corrected valve closing time is preferably determined from the valve actuation period and the valve opening time or the first rotational angle position. In particular, when the first rotational angle position is present, the corrected second rotational angle position is calculated from the corrected valve actuation period. In other words, the time at which the gas exchange valve will actually be closed, taking into account the adjustment speed of the camshaft adjuster, is calculated at the valve opening time. In this respect, the corrected valve closing time is not only calculated after the gas exchange valve has closed, but already when it opens.

The valve closing time plays a decisive role in particular when using the so-called Miller method, in which the valve closing time of the intake valve is advanced in order to reduce the risk of knocking or nitrogen emissions. Determining the corrected valve closing point in time enables more precise control of the drive device, in particular using the Miller method.

A development of the invention provides that the gas exchange valve is an intake valve, a fresh gas quantity supplied to the cylinder during a working cycle of the drive unit via the intake valve being determined from the valve actuation period of the intake valve. The existence of the gas exchange valve as an inlet valve has already been pointed out above. The working cycle is to be understood as meaning one cycle of the thermodynamic cycle process taking place in the cylinder. The drive assembly is preferably present as a four-stroke engine, so that the rotational angle position of the crankshaft runs through a range from 0° CA to 720° CA during a working cycle.

The amount of fresh gas supplied via the intake valve during the working cycle can be determined from the valve actuation period. The fresh gas quantity is to be understood in particular as a fresh gas quantity present in the combustion chamber after the intake valve has closed. By using the corrected valve actuation period to determine the fresh gas quantity, a more precise control of the thermodynamic cycle process taking place in the cylinder becomes possible. This is particularly important when using the Miller method explained above, for the control of which precise knowledge of the fresh gas quantity and the valve closing time is required.

A development of the invention provides that the operating variable determined from the valve actuation period is used at least temporarily to control the drive unit, the operating variable being selected from: volumetric efficiency, cylinder charge, drive power, drive torque and combustion air ratio. On the Company size has already been mentioned above. In this respect, the valve actuation time period is used at least temporarily to control the drive unit, namely via the operating variable determined from it or the actual value of the operating variable determined from it. The operating variable or its actual value is preferably determined directly from the valve actuation period. Additionally or alternatively, the operating variable or its actual value is determined from the corrected valve closing time. In the latter case, the operating variable is determined only indirectly from the valve actuation period.

The degree of delivery describes a ratio of the amount of fresh gas present in the cylinder after the intake valve closes to a theoretically maximum possible amount of fresh gas. The cylinder charge is a quantity of mixture introduced into the cylinder, this containing the quantity of fresh gas, a quantity of fuel that is supplied and possibly recirculated exhaust gas. The degree of delivery and the cylinder filling are thus significantly influenced by the opening duration of the intake valve. The degree of delivery and the cylinder filling in turn have a direct influence on the combustion air ratio of the exhaust gas generated during the working cycle and on the drive power provided by the drive unit. The latter refers to the drive power that is generated by the drive unit. The same applies to the drive torque.

The operating variables explained above are dependent on the valve actuation period or the valve closing time. Provision is now made to calculate the actual value of at least one of the operating variables mentioned, preferably the actual values of all of these operating variables, using the corrected valve actuation period. Accordingly, the at least one actual value of the operating variable or the deviation of the at least one actual value of the operating variable from its target value is calculated with greater accuracy, which enables more reliable operation of the drive device.

A development of the invention provides that a fuel quantity to be supplied to the cylinder during the working cycle is adjusted as a function of the valve actuation period and/or the corrected valve closing time. Due to the temporarily reduced or increased valve actuation period, the above-explained operating variable or its actual value determined from the valve actuation period is subject to an error dependent on the adjustment speed during the adjustment of the control times. In order to compensate for this error, provision is now made to adapt the fuel quantity to be supplied to the cylinder as a function of the valve actuation period or the corrected valve closing time.

This preferably takes place immediately at the beginning of the work cycle. Here, immediately at the beginning of the work cycle, it is first determined whether the camshaft adjuster is being operated to adjust the control times. If this is the case, the corrected valve actuation period of the gas exchange valve is taken into account when calculating the fuel quantity to be supplied during this working cycle. For example, the amount of fuel to be supplied is adjusted in such a way that the operating variable is set to the desired value, taking into account the corrected valve actuation period. This enables a particularly reliable setting of the operating variable on the drive assembly, in particular when the operating variable is the combustion air ratio.

A further development of the invention provides that, in addition to the intake valve, there is an exhaust valve and an exhaust camshaft, which is coupled to the crankshaft via an exhaust camshaft actuator in terms of drive technology, with at least one exhaust cam for periodically actuating the exhaust valve, with the exhaust camshaft actuator being operated at least intermittently to adjust control times of the exhaust valve, wherein a valve actuation period is determined at least temporarily and corrected at least during the adjustment as a function of an adjustment speed of the exhaust camshaft adjuster.

The gas exchange valve is present as an inlet valve, the camshaft as an inlet camshaft and the camshaft adjuster as an inlet camshaft adjuster. In addition to the intake valve, there is the exhaust valve. Both the exhaust valve and the exhaust camshaft and the exhaust camshaft adjuster are designed analogously to the above statements with regard to the gas exchange valve, the camshaft and the camshaft adjuster. The advantages of such a configuration or such a procedure have already been pointed out. Both the outlet valve and the inlet valve as well as the corresponding components of the valve train for their actuation can be further developed according to the explanations within the scope of this description, so that reference is made to them in this respect.

In this respect, the valve drive is designed as a valve drive with at least two camshafts, namely the intake camshaft and the exhaust camshaft. It is now provided for both the intake valve and the exhaust valve the corri determined valve actuation period. The advantages of such an approach have already been pointed out.

A development of the invention provides that a corrected valve closing time of the exhaust valve is determined from the valve actuation period of the exhaust valve. The corresponding procedure for determining the corrected valve closing time of the gas exchange valve has already been pointed out above. An analogous procedure is provided for determining the corrected valve closing time of the exhaust valve.

The valve closing time of the exhaust valve particularly influences the volumetric efficiency and the cylinder filling. If, for example, the exhaust valve remains open at least temporarily when the intake valve opens, or if the intake valve is already opened before the exhaust valve is fully closed, the residual gas in the cylinder can flow out through the exhaust valve and fresh gas can flow in through the intake valve favor and in this way increase the cylinder filling or the degree of delivery. Determining the corrected valve closing time of the exhaust valve from the corrected valve actuation period thus enables a more precise calculation of the cylinder charge or the degree of delivery.

A development of the invention provides that the valve closing time of the exhaust valve is set at least temporarily to a time after the valve opening time of the intake valve, with a corrected valve overlap period being determined from the corrected valve closing time of the exhaust valve and the valve opening time of the intake valve. The inlet valve and the outlet valve are thus open at the same time at least temporarily. The valve overlap period describes the period of time or the period of time over which both the intake valve and the exhaust valve are at least partially open at the same time.

The simultaneous opening of the intake valve and the exhaust valve is used in particular in the context of internal exhaust gas recirculation. In this case, the exhaust valve remains open at least temporarily during the intake stroke, so that exhaust gas from the exhaust tract is fed back into the combustion chamber of the cylinder. The recirculated exhaust gas is mixed with the fresh gas fed in via the intake valve. In this respect, the cylinder filling consists of a mixture of fresh gas, fuel and recirculated exhaust gas. Provision is now made to adapt a quantity of the recirculated exhaust gas by setting the valve closing point in time of the exhaust valve to the point in time after the valve opening point in time of the intake valve.

The valve overlap period is determined from the valve closing time of the exhaust valve and the valve opening time of the intake valve, in particular in the form of a difference. The corrected valve closing time of the exhaust valve is used here, so that the corrected valve overlap period is determined in this respect. The corrected valve overlap period describes a period of time over which the intake valve and the exhaust valve are at least partially open, taking into account the adjustment speed of the exhaust camshaft actuator. The corrected valve overlap period enables more precise control of the internal exhaust gas recirculation.

A development of the invention provides that from the corrected valve overlap period, an exhaust gas quantity recirculated into the cylinder via the outlet valve and/or a residual gas rate present in the cylinder is determined. Reference has already been made above to the internal exhaust gas recirculation and the recirculated exhaust gas. The recirculated amount of exhaust gas depends on the valve overlap period. As such, using the corrected valve overlap period enables the amount of recirculated exhaust gas to be determined more accurately.

The residual gas rate describes a ratio present in the cylinder after a gas exchange between the fresh gas quantity supplied during the working cycle and a residual gas quantity which has remained in the combustion chamber from a working cycle immediately preceding the working cycle. The residual gas rate is affected by the valve overlap period. The connection of the corrected valve overlap period thus enables a more precise determination of the residual gas rate present in the cylinder and thus a more precise control of the drive unit.

The invention also relates to a drive device for a motor vehicle, for carrying out the method according to the statements made within the scope of this description, the drive device having a drive unit with a valve train which drives a camshaft coupled via a camshaft adjuster to a crankshaft of the drive unit and having at least one cam for periodic actuation of a gas exchange valve of a cylinder of the drive unit, the drive device being provided and designed to operate the camshaft adjuster at least at times to adjust control times of the gas exchange valve. It is provided that the drive unit device is also provided and designed to at least temporarily determine a valve actuation period and to correct it at least during the adjustment as a function of an adjustment speed of the camshaft adjuster.

The advantages of such a configuration of the drive device or such a procedure have already been pointed out. Both the drive device and the method for operating it can be further developed according to the statements made within the scope of this description, so that reference is made to them in this respect.

The features and feature combinations described in the description, in particular the features and feature combinations described in the following description of the figures and/or shown in the figures, can be used not only in the combination specified in each case, but also in other combinations or on their own, without going beyond the scope of the leave invention. The invention is therefore also to be regarded as encompassing embodiments which are not explicitly shown and explained in the description and/or the figures, but emerge from the explained embodiments or can be derived from them.

• 1 eine schematische Schnittdarstellung einer Brennkraftmaschine.

The invention is explained in more detail below with reference to the exemplary embodiments illustrated in the drawings, without the invention being restricted. It shows the only

• 1 a schematic sectional view of an internal combustion engine.

The 1 shows a schematic representation of a drive unit 1, which is part of a drive device for a motor vehicle, not shown in detail. The drive unit 1 is designed as an internal combustion engine which has a cylinder 2 and a crankshaft 3 . A piston 4 is arranged in the cylinder 2 so that it can move longitudinally and is drivingly coupled to the crankshaft 3 , in particular to a crank pin of the crankshaft 3 , via a connecting rod 5 . The crankshaft 3 converts a linear movement of the piston 4 into a rotary movement.

The drive unit 1 has a valve train 6 . The valve drive 6 serves to periodically actuate two gas exchange valves 7 and 8 , which are present, for example, as an inlet valve 7 and an outlet valve 8 . The gas exchange valves 7 and 8 are actuated by means of a camshaft 9 and 10. In the example shown, the camshafts 9 and 10 are present as an intake camshaft 9 and an exhaust camshaft 10, which serve to actuate the intake valve 7 and the exhaust valve 8, respectively.

The inlet valve 7 and the outlet valve 8 are fluidically connected to a combustion chamber 11 which is delimited jointly by cylinder walls and a cylinder roof of the cylinder 2 and the piston 4 . Combustion chamber 11 is fluidically connected via inlet valve 7 to an inlet tract and via outlet valve 8 to an outlet tract of the drive unit, which are not shown in detail here.

The intake camshaft 9 and the exhaust camshaft 10 are each drivingly connected to the crankshaft 3 and are driven by it. The intake camshaft 9 and the exhaust camshaft 10 are connected in drive terms to the crankshaft 3 via two camshaft adjusters 12 and 13, namely an intake camshaft adjuster 12 and an exhaust camshaft adjuster 13. The two camshafts 9 and 10 are connected to the crankshaft 3 with a fixed transmission ratio, usually with a transmission ratio of 2:1. This means that the crankshaft 3 has twice the speed of the camshafts 9 and 10 .

With the help of the camshaft positioners 12 and 13, a phase position between the intake camshaft 9 or the exhaust camshaft 10 on the one hand and the crankshaft 3 on the other hand is adjusted at least temporarily. This results in a relative adjustment of a valve opening time φ ₁ of the intake valve 7 or the exhaust valve 8 and/or a valve closing time φ ₂ of the intake valve 7 or the exhaust valve 8. The valve opening time φ ₁ and the valve closing time φ ₂ are also referred to as control times of the gas exchange valves 7 and 8 . The control times are usually given in degrees with respect to a rotational angle position φ of the crankshaft 3 and are accordingly in the unit °KW.

gilt. Der Ventilbetätigungszeitraum Δφ beschreibt eine Zeitspanne, über die das jeweilige Gaswechselventil 7 und 8 wenigstens teilweise geöffnet ist. Der Ventilbetätigungszeitraum Δφ wird vorzugsweise ebenfalls im Gradmaß bezüglich der Drehwinkelstellung φ der Kurbelwelle 3 angegeben, sodass dieser ebenfalls in der Einheit °KW vorliegt, und hängt üblicherweise lediglich von einer Nockengeometrie und einer entsprechenden Ausgestaltung der Nockenwelle 9 und 10 ab.When the control times are adjusted, valve opening time φ ₁ and valve closing time φ ₂ are always adjusted together. Thus, from the valve opening time φ ₁ and the valve closing time φ ₂ results in a valve actuation period Δcp, where $$\Delta \mathrm{\phi =}{\mathrm{\phi }}_2-{\mathrm{\phi }}_1$$

is applicable. The valve actuation period Δφ describes a period of time over which the respective gas exchange valve 7 and 8 is at least partially open. The valve actuation period Δφ is preferably also measured in degrees with respect to the rotation angle position Development φ of the crankshaft 3 specified, so that this is also in the unit °KW, and usually depends only on a cam geometry and a corresponding configuration of the camshaft 9 and 10 from.

However, the control times are adjusted at an adjustment speed ω _NWS of the respective camshaft adjusters 12 and 13. During the adjustment of the control times, an angular speed of the camshafts 9 and 10 is temporarily increased or reduced by the adjustment speed ω _NWS of the respective camshaft adjusters 12 and 13. The result of this is that the valve actuation period Δφ related to the rotational angle position φ of the crankshaft 3 is shortened or lengthened during the adjustment, depending on the direction of adjustment.

gilt und ω_KW eine Winkelgeschwindigkeit der Kurbelwelle 3 beschreibt. Die Verstellgeschwindigkeit ω_NWS und die Winkelgeschwindigkeit ω_KW der Kurbelwelle werden vorzugsweise ebenfalls im Gradmaß bezüglich der Drehwinkelstellung φ der Kurbelwelle 3 angegeben und liegen in der Einheit °KW/s vor.The invention therefore provides that during the adjustment, the valve actuation period Δφ determined from the control times is corrected as a function of the adjustment speed ω _NWS of the respective camshaft adjuster 12 and 13 . A corrected valve actuation period Δφ' is thus determined, where $$\Delta \mathrm{\phi }\text{'}=\Delta \mathrm{\phi }\cdot \left(1-\frac{{\omega }_{NWS}}{{\omega }_{KW}}\right)$$

applies and ω _KW describes an angular velocity of the crankshaft 3 . The adjusting speed ω _NWS and the angular speed ω _KW of the crankshaft are preferably also given in degrees with respect to the rotational angle position φ of the crankshaft 3 and are in the unit °KW/s.

From the corrected valve actuation period Δφ′ of the intake valve 7 , a quantity of fresh gas supplied to the combustion chamber 11 can be determined with greater accuracy than would be the case if the valve actuation period Δφ determined directly from the control times was used.

ermittelt. Der korrigierte Ventilschließzeitpunkt φ'₂ beschreibt somit einen Zeitpunkt bezüglich der Drehwinkelstellung φ der Kurbelwelle 3, zu dem das jeweilige Gaswechselventil 7 und 8 unter Berücksichtigung der Verstellgeschwindigkeit ω_NWS des jeweiligen Nockenwellenstellers 12 und 13 gerade geschlossen ist.From the valve opening time φ ₁ and the corrected valve actuation period Δφ′, there is also a corrected valve closing time $$\mathrm{\phi }{\text{'}}_2={\mathrm{\phi }}_1-\Delta \mathrm{\phi }\text{'}$$

determined. The corrected valve closing point in time φ′ ₂ thus describes a point in time with respect to the angular position φ of the crankshaft 3 at which the respective gas exchange valve 7 and 8 is just closed, taking into account the adjustment speed ω _NWS of the respective camshaft adjuster 12 and 13 .

bestimmen. Der korrigierte Ventilüberschneidungszeitraum Δφ_AE beschreibt einen im Gradmaß bezüglich der Drehwinkelstellung φ der Kurbelwelle 3 angegeben Zeitraum, über den das Einlassventil 7 und das Auslassventil 8 unter Berücksichtigung der Verstellgeschwindigkeit ω_NWS des Auslassnockenwellenstellers 13 gemeinsam zumindest teilsweise geöffnet sind. Mittels des korrigierten Ventilüberschneidungszeitraums Δφ_AE ist insbesondere ein genaueres Ermitteln einer durch eine interne Abgasrückführung in den Brennraum 11 des Zylinders 2 zurückgeführte Abgasmenge beziehungsweise eine in dem Zylinder 2 vorliegende Restgasrate möglich.The corrected valve closing time φ′ ₂ describes is determined in particular for the outlet valve 8 and is referred to below as the corrected valve closing time φ′ _2A . A corrected valve overlap period can be derived from these in conjunction with the valve opening time φ _1E of the intake valve 7 $$\Delta {\mathrm{\phi }}_{\text{AE}}=\mathrm{\phi }{\text{'}}_{2\text{A}}-{\mathrm{\phi }}_{1\text{E}}$$

determine. The corrected valve overlap period Δφ _AE describes a period of time specified in degrees with respect to the rotational angle position φ of the crankshaft 3, over which the intake valve 7 and the exhaust valve 8 are at least partially open together, taking into account the adjustment speed ω _NWS of the exhaust camshaft positioner 13. By means of the corrected valve overlap period Δφ _AE , a more precise determination of an exhaust gas quantity recirculated into the combustion chamber 11 of the cylinder 2 by an internal exhaust gas recirculation or a residual gas rate present in the cylinder 2 is possible.

Reference List

1

drive unit

2

cylinder

3

crankshaft

4

Pistons

5

connecting rod

6

valve train

7

intake valve

8th

outlet valve

9

intake camshaft

10

exhaust camshaft

11

combustion chamber

12

intake camshaft adjuster

13

exhaust camshaft positioner

φ1

valve opening timing

φ2

valve closing timing

Δφ

valve actuation period

ωNWS

adjustment speed

Δφ'

corrected valve actuation period

φ'2

corrected valve closing timing

ΔφAE

corrected valve overlap period

Claims (10)

Method for operating a drive device for a motor vehicle, the drive device having a drive unit (1) with a valve train (6) which has a camshaft ( 9,10) with at least one cam for periodically actuating a gas exchange valve (7,8) of a cylinder (2) of the drive unit (3), the camshaft adjuster (12,13) being used at least temporarily to adjust control times of the gas exchange valve (7,8 ) is operated, characterized in that a valve actuation period (Δφ) used to determine an operating variable of the drive unit (1) is determined at least temporarily and is corrected at least during the adjustment as a function of an adjustment speed (ω _NWS ) of the camshaft adjuster (12,13). procedure after claim 1 , characterized in that a corrected valve closing time (φ' ₂ ) of the gas exchange valve (7.8) is determined from the valve actuation period (Δφ) of the gas exchange valve (7.8). Method according to one of the preceding claims, characterized in that the gas exchange valve (7, 8) is an intake valve (7), wherein from the valve actuation period (Δφ) of the intake valve (7) one is assigned to the cylinder (2) during a working cycle of the drive assembly (1 ) is determined via the inlet valve (7) supplied fresh gas quantity. Method according to one of the preceding claims, characterized in that the operating variable determined from the valve actuation period (Δφ) is used at least temporarily to control the drive unit (1), the operating variable being selected from: delivery rate, cylinder filling, drive power, drive torque and combustion air ratio. Method according to one of the preceding claims, characterized in that a fuel quantity to be supplied to the cylinder during the working cycle is adjusted as a function of the valve actuation period (Δφ) and/or the corrected valve closing time (φ' ₂ ). Method according to one of the preceding claims, characterized in that in addition to the intake valve (7) an exhaust valve (8) and an exhaust camshaft (10) drivingly coupled to the crankshaft (3) via an exhaust camshaft adjuster (13) with at least one exhaust cam for periodic actuation of the exhaust valve (8), the exhaust camshaft adjuster (13) being operated at least intermittently to adjust control times of the exhaust valve (8), a valve actuation period (Δφ) being determined at least intermittently and at least during the adjustment as a function of an adjustment speed (ω _NWS ) of the exhaust camshaft adjuster (13) is corrected. Method according to one of the preceding claims, characterized in that a corrected valve closing time (φ' ₂ ) of the outlet valve (8) is determined from the valve actuation period (Δφ) of the outlet valve (8). Method according to one of the preceding claims, characterized in that the valve closing time (φ' ₂ ) of the outlet valve (8) is adjusted at least temporarily to a time after the valve opening time (φ ₁ ) of the inlet valve (7), the corrected valve closing time ( φ ' ₂ ) of the exhaust valve (8) and the valve opening time (φ ₁ ) of the intake valve (7) a corrected valve overlap period (Δφ _AE ) is determined. Method according to one of the preceding claims, characterized in that an exhaust gas quantity recirculated via the outlet valve (8) into the cylinder (2) and/or a residual gas rate present in the cylinder (2) is determined from the corrected valve overlap period (Δφ _AE ). Drive device for a motor vehicle for carrying out the method according to one or more of the preceding claims, wherein the drive device has a drive unit (1) with a valve train (6) which has a camshaft adjuster (12, 13) with a crankshaft (3) of the drive unit (1) drive-wise coupled camshaft (9,10) with at least one cam for periodically actuating a gas exchange valve (7,8) of a cylinder (2) of the drive unit (3), wherein the drive device is provided and designed for the camshaft adjuster (12, 13) at least temporarily to adjust control times of the gas exchange valve (7,8), characterized in that the drive device is also provided and designed to at least temporarily determine a valve actuation period (Δφ) used to determine an operating variable of the drive unit (1). and at least during the adjustment depending on to correct an adjusting speed (ω _NWS ) of the camshaft adjuster (12,13).

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