EP2225449A2

EP2225449A2 - Method for determining the torque available on the crankshaft of an internal combustion engine in a motor vehicle

Info

Publication number: EP2225449A2
Application number: EP08860067A
Authority: EP
Inventors: Matthias Winkel
Original assignee: ZF Friedrichshafen AG
Current assignee: ZF Friedrichshafen AG
Priority date: 2007-12-11
Filing date: 2008-12-01
Publication date: 2010-09-08
Also published as: DE102007055757A1; WO2009074474A2; US20110172933A1; WO2009074474A9; WO2009074474A3

Abstract

The invention relates to a method for determining the torque available on the crankshaft of an internal combustion engine in a motor vehicle, according to which an adaptation of the motor torque is carried out.

Description

Method for determining the torque of the internal combustion engine of a motor vehicle available at the crankshaft

The present invention relates to a method for determining the torque available at the crankshaft of the internal combustion engine of a motor vehicle according to the preamble of patent claim 1.

In order to realize modern driving strategies in automatic transmissions, according to the state of the art, the engine torque is required for a great variety of calculations. Here it is known to derive the engine torque from the injection quantity, but this disadvantageously results in a high degree of inaccuracy.

Furthermore, for the transmission control, the torque available at the crankshaft of the internal combustion engine, and thus at the clutch of the vehicle, is needed to optimize the calculations underlying the control. In the engine torque derived from the injection quantity according to the prior art, the engine friction and loss torques and the required drive torques of the auxiliary drives or other consumers such as, for example, the alternator etc. are disadvantageously included.

From EP 1365129 A2 a method for controlling an internal combustion engine is known, in the context of which the torque available at the crankshaft of the internal combustion engine is calculated by detecting the combustion chamber pressure occurring in a combustion chamber of the engine as a function of the crank angle, from which the indexed Engine torque is derived in the combustion chamber. From the indexed engine torque and the angular velocity of the crankshaft is then the loss of the torque Internal combustion engine and derived from the crankshaft of the engine torque derived.

The present invention has for its object to provide a method for determining the torque available at the crankshaft of the internal combustion engine of a motor vehicle, by the implementation of which the accuracy of the determination of the available torque is increased.

This object is solved by the features of patent claim 1. Further embodiments and advantages of the invention will become apparent from the dependent claims.

Accordingly, a method for determining the torque available at the crankshaft of the internal combustion engine of a motor vehicle is proposed, in the context of which an adaptation of the engine torque is performed.

As a result, the production-related tolerances of the internal combustion engines as well as the equipment of the vehicle with different auxiliary units can be taken into account. Furthermore, the engine characteristics can be compensated over the lifetime.

As part of a variant of the method according to the invention, it is proposed to carry out an adaptation of the engine torque based on the idling torque of the internal combustion engine. In this case, in defined, suitable states of the internal combustion engine, the current engine torque is detected and stored based on the injection quantity on the basis of a CAN signal; the detected torque is according to the invention for the further calculations in the operation of the vehicle of the on the injection quantity deducted engine torque, whereby a correction value is formed and a higher calculation accuracy is achieved.

For example, in idle, where the moment of the internal combustion engine available at the crankshaft is zero, the engine torque determined via the injection amount is 5% of the maximum possible torque, it is assumed that this 5% the engine friction and torque losses and the required drive torque the power take-offs or other consumers correspond, so that for the determination of the torque available on the crankshaft, the 5% of the engine torque determined via the injection quantity are subtracted.

Suitable or defined states for detecting the current engine torque are states with open powertrain and stable engine speed near / equal to the idling speed without specifications (eg, by pressing the accelerator pedal) to the engine control unit.

Preferably, the engine temperature is taken into account, for which purpose the detection of the current engine torque is performed either only when the engine is warm or at different temperature values, in which case n correction values are generated (n is the number of states at different temperatures) a corresponding characteristic are stored.

According to the invention, information about other consumers, for example via the air conditioning system, which influence the engine torque available at the crankshaft, can be included in the correction value formation / storage. The determined correction value or the correction characteristic can be filtered, limited and subjected to further algorithms; it is stored in a non-volatile memory. In the event that the detection of the current engine torque at speeds not equal to the idle speed durch- is performed, an interpolation is performed to determine the current engine torque at idle speed.

According to a further variant of the method according to the invention, in the context of the adaptation, the torque of the internal combustion engine available at the crankshaft can be determined by a comparison between the currently calculated driving resistance and the real driving resistance.

One of the most important parameters of a shift strategy in an automatic transmission is the topography or the associated driving resistance. If the topography is known, the ratio between the torque available at the crankshaft and the engine torque determined via the injection quantity can be calculated by a comparison between currently calculated driving resistance and real driving resistance.

The driving resistance f_fw is calculated as follows:

f_fw = ms ^* a_fzg-f_zs

with f_fw = driving resistance ms = vehicle mass including correction mass a_fzg = current vehicle acceleration f_zs = tractive force on a driven wheel

Furthermore, for a driven rear axle of a vehicle:

f_zs = m_mot ^* i_gg ^* iha ^* eta / r_dyn

with m_mot = engine torque i_gg = current gear ratio i_ha = rear axle ratio eta = efficiency (ie ratio between the torque available on the crankshaft and the engine torque) r_dyn = dynamic rolling radius of the tire

In the following, the known driving resistance is referred to as f_fw_org, wherein the calculated driving resistance is referred to as f_fw_rech. Ideally, f_fw_org = f_fw_rech

For the following calculations, it is assumed that the vehicle mass including correction mass ms is not subject to a change over time and that the acceleration a_fzg is measured and correct. It is known that the measured engine torque compared to the measured acceleration can have the much larger error.

According to the invention, the known driving resistance f_fw_org is detected during a shift with the drive train open, whereby the known tractive force on the wheel f_zs_org is zero and thus independent of the relationship between the torque available at the crankshaft and the engine torque. Accordingly:

f_fw_org = f_fw_rech f_fw_org = ms ^* a_fzg-f_zs f_zs = ms ^* a_fwz-f_fw_org eta = (ms ^* a_fzg-f_fw_org) / (m_mot ^* igg ^* i_ha / r_dyn)

Since, according to the invention, the absolute value of the ratio eta between the torque available at the crankshaft and the engine torque is not to be calculated, but only a correction value eta_kor to a stored characteristic map, the following formula results:

eta_kor = (ms ^* a_fzg-f_fw_org) / (m_mot ^* igg ^* i_ha ^* eta / r_dyn) and eta_kor = (ms ^* a_fzg-f_fw_org) / f_zs

The correction value eta_kor determined in this way is stored according to the invention in a correction map which is added to an existing map via the rotational speed and the moment of the ratio eta between the moment available on the crankshaft and the engine torque, as illustrated by FIG ,

In the map of the ratio eta between the moment available on the crankshaft and the engine torque, the value of eta is expressed in% expressed as a function of the engine speed and also expressed in% torque. Analogously, the correction value eta_kor is entered in the correction map as a function of the engine speed and the engine torque.

According to the invention, the maximum permissible deviation can be limited, the resolution resulting from the data width used. In FIG. 1, by way of example, a 6 ^* 6 correction map and a 6 ^* 6 map of the ratio eta between the torque available at the crankshaft and the engine torque are shown, with other quantities up to a 1 ^* 1 correction field, which a correction parameter corresponds, are possible.

In the example shown in FIG. 1, the interpolation points of the correction characteristic field are identical to the interpolation points of the characteristic diagram of the ratio eta between the moment (eta-map) available at the crankshaft and the engine torque and are adopted from there. With ignition_off, the determined correction map is stored in the EE-Prom, ie in an electrically erasable, programmable read-only memory. If the correction map can not be read because it has not yet been determined, for example, the correction map must be pre-assigned with zero deviation. Before the driving resistance calculation accesses the eta map, the stored map and the determined correction map are added point by point. It is proposed to perform this addition only when the correction map is updated.

According to the invention, when accessing the correction map between the nodes is interpolated. When describing a map, the same process would generate a lot of effort. For this reason, the fields of the map are classified and all values that lie within a range are assigned to this position; there is no influence on adjacent fields. In this case, the value range of a class always goes from the middle between two support points to the next center of the next pair of support points, with the edge positions of the characteristic field forming exceptions. In the event that the interpolation points are determined from the "Engine Configuration", changing them will also update the class limits for the correction map, examples of the interpolation points for the speed and torque, as well as for the corresponding correction ranges or value ranges of a class are shown in FIG.

For the determination of the correction factor, it is necessary to know the current topography, which may not change over the period of the determination.

During a shift, the current driving resistance can be determined very accurately in the traction-free phase. If only a short distance has been traveled between two circuits, which must not exceed a predetermined threshold and if during the circuits the same running resistance or a driving resistance within a predetermined Tolerance band, it can be assumed that the topography has not changed during this period.

The driving resistance itself is formed from the mean value of all unfiltered values within the traction-free phase, for which purpose all values are accumulated and temporarily stored as an average during the transition to determining the correction factor. According to the invention, a displacement detection is started at the same time with this transition. The end of the average value binding or the transition to the determination of the correction factor can take place, for example, with the end of the circuit.

If the number of unfiltered values for the driving resistances is too small or less than a predetermined number, then according to an embodiment of the invention, the values are discarded and the algorithm waits for the next circuit, which then counts as the first circuit. If a new circuit is performed, an averaging over the unfiltered driving resistances is carried out again in the traction-free phase, as already described.

When the second circuit is completed, the two averages (i.e., the first circuit average and the second circuit average) are compared. If they lie within a tolerance band and the distance covered is small, then the determined correction values can be taken over. If a small number of values are detected, the values are discarded and the algorithm waits for the next circuit.

According to the invention, after the second circuit, the last determined travel resistance is re-stored as the basis for the next determination and a reset of the position detection if sufficient values are present. At the next switching, the next correction factor determination takes place, etc. The following formula is used to determine the correction factor eta_tmp:

eta_tmp = (ms ^* a_fzg-f_fw_org) / f_zs,

where f_fw_org is the previously determined mean value of the unfiltered driving resistance during the shift. Averaging occurs within the traction free phase of the circuit by adding and counting the number of values. The values for eta_tmp are stored in the fields of a temporary eta map.

Only when a transfer of the values is permitted after the second shift, the averages are determined and added to the values of the correction map. The addition can be done in accordance with an embodiment of the invention by a simple PT1 filtering. Where:

eta_kor (n, m) = eta_kor (m, n) ^* k + eta_tmp (n, m) ^* (1 -k)

With

eta_kor (n, m) = the correction map via speed and torque eta_tmp (n, m) = the temporary correction map via speed and torque; and k = filter factor with a value range between 0 and 1.

The map eta_kor (n, m) is, as already explained, added to an existing map eta (n, m) of the ratio eta between the torque available at the crankshaft and the engine torque on the speed and the moment. The fields of the correction map eta_tmp (n, m) which are not described, or the fields which have too few values, are not transmitted. After completion of the value transfer, the temporary map eta_tmp (n, m) is reset and zeroed for the next determination.

According to the invention, no correction factor eta_tmp is calculated when, when the running resistances of the first and second circuits are too large in deviation from each other, when the running resistances are outside an allowable range or when the running resistances could not be detected, e.g. may be caused by too few values or by a brake intervention.

Furthermore, no correction factor eta_tmp is calculated when the vehicle speed has exceeded a predetermined threshold in a shift or when the distance traveled between two circuits is too long. Further, a correction factor eta_tmp is not calculated when the interval between two circuits is too large or exceeds a predetermined threshold when the number of determined correction values per field is too small, when the correction values are implausible, when the mass calculation of the vehicle is incomplete, if a reinitialization has taken place if the adaptation has been switched off, if the engine temperature is not within the desired range or if additional consumers are active for which the correction factor should not be determined.

According to an advantageous development of the invention, the engine drag torque can be determined analogously to the described procedure with known topography. For example, a 1 ^* 6 map can be used for this purpose, since only the speed dependence is given. In this case, the method can be extended such that an activated engine brake can be taken into account. Analogous to the described procedure That is, no engine drag torque correction value is determined when a torque change of the engine-side brakes or a torque change of the lift-off-side brakes (for example, a retarder) is performed or when the service brake of the vehicle is operated.

According to a further advantageous embodiment of the invention, the calculation of the torque available at the crankshaft of the internal combustion engine of a motor vehicle can not only be carried out permanently online in a control unit. This calculation can also be performed on a specific system on known routes; For example, the calculation can be carried out with a suitable computer on a test track, the values thus determined being stored in the ROM memory of the control unit. Furthermore, it can be provided that the existing functions in the control unit are activated only by a special call, which can be done for example by a diagnostic tool.

According to the invention, the adaptation can advantageously be accelerated by the fact that the topography is fixed or determined before the start of the calculations.

Claims

Patent Attorney

1. A method for determining the torque available at the crankshaft of the internal combustion engine of a motor vehicle, characterized Porsche Style n zei ch et et that for determining the torque available on the crankshaft, an adaptation of the engine torque is performed.

2. A method for determining the available at the crankshaft torque of the internal combustion engine of a motor vehicle, according to claim 1, characterized Porsche Style zei ch et et, that an adaptation of the engine torque based on the idling torque of the internal combustion engine is performed, wherein in defined states of the internal combustion engine the current engine torque determined via the injection quantity is detected and stored using a CAN signal, wherein the detected torque is subtracted from the engine torque determined during operation of the vehicle via the injection quantity, whereby a correction value is formed and a higher calculation accuracy is achieved.

3. A method for determining the available at the crankshaft torque of the internal combustion engine of a motor vehicle, according to claim 2, characterized Porsche Group et ze nich that the defined states for detecting the current engine torque states with open powertrain and stable engine speed near / equal to Idle speed without specifications to the engine control unit are.

4. A method for determining the torque available at the crankshaft of the internal combustion engine of a motor vehicle, according to claim 2 or 3, characterized Porsche Style n zei ch et et that the detection of the current engine torque carried out either only when the engine is warm engine. In the latter case, n correction values are generated, where n is the number of states at different temperatures and the n correction values are stored in a characteristic curve.

5. A method for determining the available at the crankshaft torque of the internal combustion engine of a motor vehicle, according to claim 2, 3 or 4, characterized Porsche Style n zei ch et that information about other consumers affect the available at the crankshaft engine torque, with influence in the correction value formation.

6. A method for determining the available at the crankshaft torque of the internal combustion engine of a motor vehicle, according to claim 2, 3, 4 or 5, characterized Porsche Group n zei ch et, that in the event that the detection of the current engine torque at speeds unequal the idling speed is performed, an interpolation is performed to determine the current engine torque at the idling speed.

7. A method for determining the available at the crankshaft torque of the internal combustion engine of a motor vehicle, according to claim 1, characterized Porsche Style n zei ch et et, that the available torque on the crankshaft of the internal combustion engine by comparing the currently calculated driving resistance and the real driving resistance is determined.

8. Method for determining the torque of the internal combustion engine of a motor vehicle available on the crankshaft, according to claim 7, characterized in that a correction factor eta_kor is calculated, which is stored in a correction map eta_kor (n, m), which is available to an existing map eta (n, m) on the speed and moment of the ratio eta between the available at the crankshaft- the moment and the engine torque is added over the speed and the moment, whereby the following formula is used to calculate the correction factor eta_kor:

eta_kor = (ms ^* a_fzg-f_fw_org) / f_zs, with f_fw_org = known driving resistance ms = vehicle mass a_fzg = current vehicle acceleration f_zs = tractive force on a driven wheel, whereby the known driving resistance f_fw_org is detected during an open powertrain shift and the determined mean value of the Unfiltered driving resistance during the circuit, the current topography must not change over the period of determination.

9. A method for determining the available at the crankshaft torque of the internal combustion engine of a motor vehicle, according to claim 8, characterized in that when two circuits only a short distance was covered, which must not exceed a predetermined threshold and if between the two Circuits a driving resistance was calculated within a predetermined tolerance band, it is assumed that the topography has not changed during this period, the driving resistance is formed from the average of all unfiltered values within the zugkraftfreien phase of the circuits, for which purpose the values of a circuit and accumulated at the transition to determining the correction factor as an average value, wherein a temporary correction factor eta_tmp is formed from the mean values, with eta_tmp = (ms ^* a_fzg-f_fw_org) / f_zs, wherein the values for eta_tmp in the fields a s temp map eta_tmp (n, m) are stored and where, when the second circuit is completed, the two mean values are compared, wherein if they are within a tolerance band and the distance traveled Distance does not exceed a threshold value, the determined correction values are adopted.

10. Method for determining the torque of the internal combustion engine of a motor vehicle available on the crankshaft, according to claim 9, characterized in that after the second circuit, if the values can be accepted, the temporary map eta_tmp (n, m) is added to the values of the correction map eta_kor (n, m).

11. Method for determining the torque of the internal combustion engine of a motor vehicle available on the crankshaft, according to claim 10, characterized in that the addition takes place by a simple PT1 filtering, in which case:

eta_kor (n, m) = eta_kor (m, n) ^* k + eta_tmp (n, m) ^* (1-k)

With

eta_kor (n, m) = correction map via speed and torque eta_tmp (n, m) = temporary correction map via speed and torque; and k = filter factor with a value range between 0 and 1.

12. A method for determining the torque available at the crankshaft of the internal combustion engine of a motor vehicle, according to claim 10 or 11, characterized Porsche Style n zei ch et, that the non-described fields of the correction map eta_tmp (n, m), or the fields , which have too small a number of values are not transmitted, after completion of the value transfer the temporary map eta_tmp (n, m) is reset.

13. Method for determining the torque of the internal combustion engine of a motor vehicle available on the crankshaft, according to claim 9, 10, 11 or 12, characterized in that no correction factor eta_tmp is calculated if the driving resistances are outside an admissible range lie when the number of values for the driving resistance falls below a predetermined number when a braking intervention is performed between the circuits, when in a circuit, the vehicle speed has exceeded a predetermined threshold, if the interval between two circuits is too large or a predetermined threshold exceeds, if the number of correction values determined per field is too small, if the correction values are implausible, if the mass calculation of the vehicle is not completed, if a reinitialization has taken place, if the engine temperature is not within the desired range or if additional consumers are active for which the correction factor should not be determined.

14. A method for determining the torque available at the crankshaft of the internal combustion engine of a motor vehicle, according to claim 9, 10, 11, 12 or 13, characterized Porsche Style n zei ch et, that when in the first and the second circuit, the number the unfiltered values of the driving resistances fall below a predetermined number, the values are discarded, with the next circuit being regarded as the first or second circuit.

15. A method for determining the available at the crankshaft torque of the internal combustion engine of a motor vehicle, according to claim 8, 9, 10, 11, 12, 13 or 14, characterized Porsche Style n zei ch et that the topography fixed or before the Start of the calculations is determined so that the adaptation for determining the torque of the internal combustion engine is accelerated on the crankshaft.