WO2023104789A1

WO2023104789A1 - Control of a vehicle engine under transient speed conditions

Info

Publication number: WO2023104789A1
Application number: PCT/EP2022/084583
Authority: WO
Inventors: Xavier Moine
Original assignee: Vitesco Technologies GmbH
Priority date: 2021-12-10
Filing date: 2022-12-06
Publication date: 2023-06-15
Also published as: FR3130325B1; FR3130325A1

Abstract

Method for controlling an internal combustion engine in a vehicle, an engine output shaft, a driven wheel that can be driven by the engine, and a transmission positioned between the engine output shaft and the driven wheel, the transmission offering a transmission ratio R which, under continuous-speed conditions, corresponds to the ratio between the rotational speed Ns of the driven wheel and the rotational speed of the engine output shaft Ne ( R=Ns/Ne), comprising: - detecting a transition corresponding to a changeover from a request for negative torque to a request for positive torque and then, prior to each combustion, performing the following steps: - estimating the rotational speed Ns_est of the driven wheel, - determining the difference GAP_cur in angular rotation between the engine output shaft and the driven wheel taking account of the transmission ratio, - estimating the number of combustions to be cut nb_cut to make the rotational speed Ne of the engine output shaft correspond substantially to (Ns_est/R), - estimating the difference GAP_pred in angular rotation between the engine output shaft and the driven wheel taking account of the transmission ratio corresponding to the difference GAP_cur increased by the difference in angular rotation between the engine output shaft and the driven wheel taking account of the transmission ratio with the forthcoming nb_cut number of combustions cut, and when GAP_pred exceeds a predetermined limit, the torque command for the forthcoming nb_cut number of combustions is substantially zero.

Description

Control of a vehicle engine in transient state

[0001] This disclosure relates to the control of an engine in transient state. More particularly it relates to a method for controlling an internal combustion engine in a vehicle comprising said engine, an engine output shaft, an electronic control unit of said engine, an engine torque control member entering a chain engine torque control, at least one wheel that can be driven by the engine, called drive wheel, and a transmission arranged between the engine output shaft and the at least one drive wheel, said transmission having a corresponding transmission ratio R in continuous operation to the ratio between the speed of rotation Ns of the at least one drive wheel and the speed of rotation of the motor output shaft Ne (ie R=Ns/Ne).

Technical area

[0002] This disclosure relates to the field of the management of an internal combustion engine. A vehicle is generally equipped with an engine which transmits a torque to at least one wheel. A transient regime here corresponds in particular to a transition from a negative torque - possibly zero - to a positive torque. It is considered that the torque is negative when a wheel in connection with the motor comes to drive the motor whereas the torque is positive - the most frequent situation - when the motor comes to drive the wheel. A negative torque is observed in particular during deceleration or when the vehicle is on a slope in the direction of descent. The transient state can also relate to the transition from a positive torque to a negative torque.

An engine torque control member entering an engine torque control chain is any device allowing the driver to act on the engine torque, for example a rotary engine torque control handle in the case of a vehicle with 2, 3, or 4 wheels whose direction is controlled with a handlebar type body. It can also be a foot accelerator. The engine torque control chain can be mechanical or electrical, and include for example a mechanical or motorized air inlet throttle control system.

The present disclosure relates more particularly to a vehicle in which the connection between the engine and at least one wheel has play. This is in particular a vehicle with a transmission comprising a chain. It is therefore more particularly a motorcycle or a four-wheeled all-terrain vehicle (also called a “quad”) or another vehicle with a chain transmission. [0005] The problem at the origin of the present disclosure is to avoid having a shock when the engine torque which is negative becomes positive. During this change in speed, the engine first takes up the play in the transmission and then drives the vehicle. The shock which can occur when the engine starts to drive the vehicle again subjects the transmission, in particular the chain if it is a chain transmission, to strong mechanical stresses which can be harmful for the transmission.

Prior technique

[0006] In a transient state, for example when the motor torque which is negative becomes positive, if no correction is made, when the torque becomes positive, the motor encounters practically no resisting torque during the crossing of the clearance of the transmission and the engine speed increases sharply and therefore the rotational speed of the motor shaft also increases. On the other hand, the speed of rotation on the wheel(s) side remains constant (or even decreases slightly). Due to the difference between these rotational speeds, a shock occurs because suddenly the entire transmission is put under stress.

[0007] To avoid such a shock, it is known to limit the torque during the transient state. In a vehicle fitted with an electrically controlled air intake throttle, the opening of this throttle can be controlled gradually to limit the impact. When there is no such electrically controlled throttle valve, it is also known to act on the ignition delay for a spark-ignition engine in order to limit the torque supplied by the engine.

[0008] These solutions make it possible to limit the jerk felt during a transient state but have the consequence of increasing the response time of the engine when the driver requests acceleration.

Summary

[0009] The purpose of the present disclosure is therefore to allow control of the engine in a transient state without jolts (or shocks) in the transmission of the vehicle while maintaining good reactivity of the engine.

[0010] A method for controlling an internal combustion engine in a vehicle is proposed, comprising said engine, an electronic control unit for said engine, an engine torque control member entering an engine torque control chain, a motor output shaft, at least one wheel able to be driven by the motor, called drive wheel, and a transmission arranged between the motor output shaft and the at least one drive wheel, said transmission having a corresponding transmission ratio R in continuous operation at the ratio between the speed of rotation Ns of the at least one drive wheel and the speed of rotation of the motor output shaft Ne (i.e. R=Ns/Ne), comprising the following steps: - detection of a transition corresponding to a transition from a negative torque request to a positive torque request, from the engine torque control member entering the engine torque control chain, then, before each combustion, carrying out of the following steps:

- estimation of the speed of rotation Ns_est of the at least one drive wheel, from a device for measuring the speed of rotation of the at least one drive wheel, or from a device for measuring the rotational speed of the motor output shaft N and of the transmission ratio R,

- determination of the difference GAP_cur of angular rotation between the motor output shaft and the at least one driving wheel by taking into account the transmission ratio, from the difference in rotational speed between the motor output shaft and said at least one driving wheel brought back to the level of the engine via the known transmission ratios, by means of a computer of the engine control unit,

- estimation of the number of combustions to be inhibited nb_cut so that the speed of rotation of the engine output shaft Ne substantially corresponds to (Ns_est / R), from the difference GAP_cur of determined angular rotation and the measured engine speed, by means of the engine control unit computer,

- estimation of the GAP_pred difference in angular rotation between the motor output shaft and the at least one drive wheel by taking into account the transmission ratio corresponding to the determined GAP_cur difference increased by the difference in angular rotation between the engine output and the at least one drive wheel taking into account the transmission ratio by inhibiting the nb_cut combustions to come, by means of the computer of the engine control unit, and when GAP_pred exceeds a predetermined limit, the unit of engine control transmits a torque command with zero or substantially zero value for the nb_cut combustions to come.

This method makes it possible to adapt the rotational speed of the motor output shaft during the transient phase to the rotational speed of the wheel, taking into account the transmission ratio so that at the end of the transient phase when the setpoint torque is applied, the transmission of the torque takes place smoothly. In the case of a system with mechanical throttle control, the torque transition detection can be done by reading the throttle position, for example a threshold map as a function of engine speed and temperature. The transition is detected when the throttle position changes from a value below the threshold to a value above the threshold. In the case of an application with motorized butterfly, the reading of the position of the handle is translated by the system into a torque request. This torque demand value can be used directly for transition detection. The electronic engine control unit comprises, in known manner, a computer which makes it possible to perform the calculations according to the method according to the invention as defined above. The substantially zero torque control can be obtained by inhibiting the combustions (zero torque control). It is also possible in the case of a controlled ignition engine to delay the ignition so as to degrade the combustion and to limit the torque. For example, it is possible to provide a torque which is negligible with respect to the positive setpoint torque command, for example less than 10% of the positive command torque requested.

[0012] This method relates in particular to a transient phase in which the control torque is negative and where it becomes positive. It is in this case that the strongest jolts are felt in the prior art. According to a similar principle, provision can be made in the method described to also take into account the transitional phases from a positive control torque to a negative control torque. In this case, there is then, for example, a control method as described above which also comprises the following steps:

- detection of a transition corresponding to a transition from a positive torque request to a negative torque request, from the engine torque control device entering the engine torque control chain,

- inhibition of a first combustion as soon as the change from a positive torque request to a negative torque request is detected, by means of the engine control unit, each time a combustion is inhibited, the following steps are carried out:

- estimation of the number of combustions to be carried out nb_comb so that the speed of rotation of the engine output shaft Ne substantially corresponds to (Ns_est/R), from the difference GAP_cur of determined angular rotation and the measured engine speed, by means of the engine control unit computer,

- estimation of the GAP_pred difference in angular rotation between the motor output shaft and the at least one driving wheel by taking into account the transmission ratio corresponding to the determined GAP_cur difference increased by the difference in rotation angular between the engine output shaft and the at least one drive wheel taking into account the transmission ratio by performing nb_comb combustions, by means of the engine control unit computer, and when GAP_pred exceeds a predetermined limit, the The engine control unit controls the nb_comb combustions and then stops the combustion in the vehicle engine according to the negative torque demand.

In a method as described above, the estimated rotational speed Ns_est of the at least one drive wheel can for example be determined by recurrence as follows: Ns_est_n = (Ns_est_n-1) - delta_Ns where delta_Ns is a function vehicle speed and gear ratio.

[0014] Provision can also be made for a method according to the present disclosure that the number of combustions to be inhibited can be determined as follows: nb_cut_n = ((Ne_n) - (Ns_est_n) / R) / delta_gap where Ne_n is the speed of rotation of the engine output shaft when the rotational speed of the at least one wheel is estimated at (Ns_est_n), and delta_gap is a function of engine speed, i.e. Ne, and engine temperature .

[0015] To adapt to the value of the transmission play over time, in order to detect and also correct a transmission play estimated to be greater than it really is, it can advantageously be provided that during a transition corresponding to a transition from a negative torque request to a positive torque request, the variation in speed of the vehicle proportional to the speed of the wheel shaft is analyzed during the transition period, and that if the speed gradient becomes greater than a predetermined acceleration then the predetermined limit for GAP_pred is decreased.

[0016] Similarly, to detect and correct a transmission clearance estimated to be smaller than it really is, it is advantageous to provide that during a transition corresponding to a transition from a negative torque request to a torque request positive, the variation in speed of the vehicle proportional to the speed of the wheel shaft is analyzed beyond the transition period for a predetermined duration, and that if the speed gradient becomes greater than a predetermined acceleration during said duration, then the predetermined limit for GAP_pred is increased.

[0017] For the variants of the method making it possible to adapt the value of the play of the transmission over time, it is also possible advantageously to provide that if the speed gradient becomes greater than a predetermined acceleration during the transition period, a first counter is incremented; that if the velocity gradient becomes greater than a predetermined acceleration beyond the transition period for the predetermined duration, a second counter is incremented.

[0018] In the variants of the method making it possible to adapt the value of the transmission clearance over time, if the predetermined limit for GAP_pred leaves a predefined interval and/or if the first counter exceeds a first value and/or if the second counter exceeds a second value, then an alert message can advantageously be generated.

[0019] According to another alternative embodiment of the method, it is proposed to adapt the torque just before passing the torque setpoint to substantially zero. It is assumed here that the predetermined limit for GAP_pred is called GAP_trans, and that GAP_pred is calculated iteratively and successively takes the values gap_pred_n. If then GAP_trans is between two successive iterative values gap_pred_n and gap_pred_(n+1) of GAP_pred, the torque setpoint for the nth combustion is advantageously adapted so that gap_pred_(n+1)=GAP_trans.

[0020] According to another aspect, a computer program is proposed comprising instructions for the implementation of all or part of a method as defined herein when this program is executed by a processor, in particular a control unit electronics of an internal combustion engine. In another aspect, there is provided a non-transitory, computer-readable recording medium on which such a program is recorded.

According to yet another aspect, an internal combustion engine is proposed, characterized in that it comprises an electronic control unit for the implementation of each of the steps of a method described above.

Brief description of the drawings

[0022] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the appended drawings, in which:

Fig. 1

[0023] [Fig. 1] shows a curve 1 of variation in speed of a vehicle as a function of time that can be obtained with a control method of the prior art during a transition phase in which one passes from a setpoint of negative torque to positive torque.

Fig. 2

[0024] [Fig. 2] is a curve 2 similar to that of FIG. 1 with implementation of a control method according to the present disclosure. Fig. 3a

[0025] [Fig. 3a] shows a control curve 31 as a function of time.

Fig. 3b

[0026] [Fig. 3b] shows a curve 32 of engine speed as a function of time.

Fig. 3c

[0027] [Fig. 3c] shows a curve 33 of speed as a function of time.

Fig. 3d

[0028] [Fig. 3d] shows a curve 34 illustrating transmission play for the present disclosure as a function of time.

Fig. 4a

[0029] [Fig. 4a] shows a curve 41 illustrating the torque command as a function of time, corresponding to a transition from a negative command torque to a positive command torque.

Fig. 4b

[0030] [Fig. 4b] shows, in abscissa correspondence with FIG. 4a, a curve 42 illustrating the engine speed as a function of time, corresponding to a transition from a negative control torque to a positive control torque.

Fig. 4c

[0031] [Fig. 4c] shows, in abscissa correspondence with FIGS. 4a and 4b, a curve 43 illustrating the acceleration of the vehicle as a function of time, corresponding to a transition from a negative control torque to a positive control torque.

Fig. 5a

[0032] [Fig. 5a] is a view similar to FIG. 4a, showing a curve 51 illustrating the torque command as a function of time, corresponding to a passage from a positive command torque to a negative command torque.

Fig. 5b

[0033] [Fig. 5b] is a view similar to FIG. 4b, showing a curve 52 illustrating the engine speed as a function of time, corresponding to a passage from a positive control torque to a negative control torque.

Fig. 5c [0034] [Fig. 5c] is a view similar to FIG. 4c showing a curve 53 illustrating the acceleration of the vehicle as a function of time, corresponding to a transition from a positive control torque to a negative control torque.

Fig. 6

[0035] [Fig. 6] shows a curve 6 similar to curves 1 and 2 showing the speed variation of a vehicle as a function of time when a transmission play is underestimated.

Fig. 7

[0036] [Fig. 7] shows a curve 7 similar to curves 1, 2 and 6 showing the speed variation of a vehicle as a function of time when a transmission clearance is overestimated.

Fig. 8

[0037] [Fig. 8] shows a flowchart for an adaptation of a method according to the present disclosure to an actual transmission game and/or an alert concerning a transmission game.

Fig. 9

[0038] [Fig. 9] shows a flowchart of an example of transient torque control.

Description of embodiments

Reference is now made to Figure 1. This figure shows a speed variation curve 1 of a vehicle in a transient state described below. On the abscissa we find the time in seconds (s) and on the ordinate the variation of the speed of the vehicle in meters per second per second (m/s/s).

Taken as an example in the present description a motorcycle, not shown, which comprises a frame on which are mounted a motor and two wheels, one of the two wheels being driven in rotation by the motor. The torque produced by the motor is supplied to a motor output shaft, hereinafter called motor shaft, which is coupled to a gearbox having a gearbox output shaft on which there is a toothed wheel. The motor-driven wheel, or rear wheel, also has a cogwheel and a chain connects the two cogwheels. In known manner, a clutch device, or clutch, is arranged between the gearbox and the engine. The assembly formed by the gearbox, the clutch, the cogwheels and the chain is subsequently called "transmission".

The motor rotates at a speed called engine speed which corresponds to the speed of rotation of the motor shaft. This regime, or speed of rotation, is subsequently called Ne. [0042] For example, the engine rotational speed or engine speed is given in a known manner by means of an engine position sensor, for example a sensor of known Hall effect type or other, consisting of a toothed wheel at the periphery and fixed to the crankshaft, whose teeth during the rotation of the crankshaft pass in front of a reader which generally detects the fronts of the teeth: the time passing between two successive fronts measured by the sensor makes it possible in a known way to know the instantaneous speed of rotation of the crankshaft and by extension its average speed of rotation.

The rear wheel turns for its part at a speed of rotation Ns. This speed Ns is representative of the (linear) speed of the motorcycle.

The speed of rotation of the wheel is given in known manner, for example by means of a variable reluctance sensor positioned opposite a ferromagnetic target mounted on the wheel and by measuring the frequency of the signal. It is also possible to estimate this rotational speed of the wheel from the engine speed and the known transmission ratio as indicated below.

[0045] In steady state, when the engine drives the rear wheel, without change at the level of the gearbox, the transmission has a constant ratio defined by:

[0046] R = Ns / Ne

[0047] For each gearbox ratio, a ratio R is thus associated. In the remainder of the description, it is assumed that the gearbox ratio does not change. In the various steps described, there is therefore always the same ratio R.

[0048] However, the transmission has a play. That is to say that if the motor shaft rotates slightly, then it does not necessarily drive the rear wheel. This is particularly the case if the motor shaft rotates in one direction while driving the rear wheel. If the motor and the rear wheel stop while keeping the transmission, in particular the chain, "under stress", and if the motor then begins to turn in the opposite direction, then it would have to rotate a few degrees to a few tens of degrees (depending on the R ratio) before driving the rear wheel in the opposite direction.

This game, in a motorcycle, is generally of the order of the length of a chain link, that is to say a few centimeters. In the rest of the description, the play of the transmission is expressed in degrees of rotation of the motor shaft. This angular value then depends on the gear engaged in the gearbox and the angular value corresponding to the clearance thus depends on R. By way of purely illustrative and non-limiting example, for a motorcycle, depending on the ratio R, the angular value can vary between 50 and 170°. In Figure 1, it is assumed that the motorcycle is in the deceleration phase, without braking. The motorcycle is for example on flat ground without any action by its driver on the acceleration control means. In this case, it is the rear wheel which exerts a torque on the motor. The inertia of the motorcycle makes it possible to maintain, with a slight deceleration, the engine speed. It is then considered that the motor torque command is negative. Figure 1 illustrates the change in speed (acceleration) of the motorcycle in meters per second per second (m/s/s) on the ordinate as a function of time in seconds (s) on the abscissa when the engine torque command becomes positive again , i.e. when the driver again wishes to increase the speed (or at the very least, slow down less, for example to be at constant speed). In this case, the motor exerts a positive torque on the rear wheel to drive the motorcycle.

There is thus on the left of Figure 1 a flat acceleration portion which corresponds to a constant deceleration reflecting in particular the effects of friction of the motorcycle on the road and the aerodynamic effects. When the torque command then becomes positive, the engine speed increases. Due to the play in the transmission, almost no resistive torque is exerted on the motor shaft. Indeed, the chain was stretched in the direction allowing a drive of the motor shaft and so that the motor shaft can drive the rear wheel, the tension of the chain must be done in the opposite direction. During this phase, the motor shaft picks up speed very quickly. Once the chain reaches the end of play to then drive the rear wheel, the speed of the motor shaft is much higher than Ns/R and therefore a shock occurs when the chain stretches in the direction allowing drive the rear wheel. This creates a jerk which results in a short acceleration followed by a short deceleration of the motorcycle until the speed of the motor shaft and the speed of the wheel again coincide with the ratio R. The peak acceleration visible in Figure 1 corresponds to the shock that occurs at the end of the chain tension. Then, the motorcycle has a constant acceleration corresponding to the torque command requested by the driver.

The idea behind this disclosure is to control the motor so that when the chain is stretched again in the opposite direction, there is no shock. This is achieved by ensuring that the rotational speed of the motor shaft corresponds to the rotational speed of the rear wheel divided by the ratio R. Thus the torque is applied to the rear wheel when the motor shaft and the rear wheel are “synchronous”.

Figures 3a to 3d illustrate the principle implemented to avoid the shock described above. Figures 3a, 3b, 3c, and 3d therefore respectively include four curves 31, 32, 33, and 34 as a function of time as shown. The four curves 31, 32, 33, and 34 are in correspondence with respect to the abscissa axis (time) as indicated by the lines aligned grid verticals for the four Figures 3a, 3b, 3c, and 3d. Curve 31 represents combustion cut-off demand, curve 32 represents engine speed, curve 33 represents speed, and curve 34 represents transmission play.

In Figure 3a, a slot on the curve 31 illustrates a combustion cut request. This request has no immediate effect, but there is a slight lag between the combustion cut-off request and the effect measured following this request.

In Figure 3b, the engine speed Ne has been illustrated with curve 32.

In FIG. 3c, curve 33 illustrates the image of the rotational speed of the wheel at the input of the transmission, engine side, that is to say Ns/R in revolutions per minute (tr /min). This variable is subsequently called Nveh=Ns/R.

The curve 34 in Figure 3d corresponds to the play of the calculated transmission, expressed in degrees at the engine. As will be explained below, the aim is to make this estimated clearance coincide with the transmission clearance.

The clearance actually corresponds to the area of the difference between curve 32 of engine speed (Ne) and curve 33 of the image of rotational speed of the rear wheel (Nveh). Indeed, this surface corresponds to an integral of the surface of the Ne-Nveh curve and corresponds to the difference in rotation between the motor shaft and the “virtual” wheel shaft.

We note in Figure 3b that the engine speed (Ne) represented by the curve 32 first increases: this corresponds to the setpoint for passing from negative torque to positive torque. Then it decreases because an electronic control device, known for example as the ECU, cuts off power to the engine leading to a drop in engine speed. Then, the engine speed increases again corresponding to the given positive torque setpoint.

The speed of rotation Nveh represented by the curve 33 in FIG. 3c, illustrating the speed of the vehicle first decreases slightly then increases when the engine speed increases again.

Here the two curves 32 and 33, respectively representing the engine speed Ne and the variable Nveh as described above, are shifted but the right-hand parts of these two curves (increasing slope) are substantially coincident.

The surface to be determined corresponds substantially to two triangles: a first corresponding to the increase in engine speed and the other to the decrease in engine speed. The right moment to lower the engine speed should be determined so that the area of these two triangles corresponds to the play of the transmission (expressed as explained above in degrees of motor shaft rotation. Curve 34 in FIG. 3d illustrates the estimated area of the two triangles as the calculations are made and explained below.

[0063] First of all, the electronic control device (ECU for example) detects a transient phase, that is to say the passage of an instruction from the driver of the vehicle from a negative torque to a positive torque or vice versa.

[0064] In the case of a system with mechanical throttle control, this detection can be carried out by reading the position of the throttle, for example by means of a threshold map as a function of engine speed and temperature. : the transition is detected when the throttle position changes from a value below the threshold to a value above the threshold. In the case of an application with motorized butterfly, the reading of the position of the handle is translated by the system into a torque request. This torque demand value can be used directly for the detection of the transition.

The case of a transient phase corresponding to the transition from a negative torque setpoint to a positive torque is treated first with reference to Figures 3a-3d while the transition from a positive torque setpoint to a negative torque is discussed second with reference to Figures 5a-5c. The control of these transients is similar but with small differences.

[0066] Several quantities relating to the clearance of the transmission are used. Each of these quantities corresponds to an angle of rotation of the motor shaft. As already indicated, slack can also be expressed in terms of a length, for example a chain link, that is to say in general a few centimeters (from 1 to 5 cm, most often of the order of 2 to 3cm). The movement of the chain of such a length corresponds to a rotation of a toothed wheel at the gearbox output. Thus, the angular displacement at the motor shaft depends on the gear engaged in the gearbox and therefore on R defined previously.

It is assumed during the description of the control method which follows that the gearbox ratio does not vary (therefore R is constant) and that the clutch remains in the engaged position (motor coupled to the gearbox) . If the clutch is actuated and/or the gear ratio is changed, the process which is about to be described is interrupted.

It is considered that the play of the transmission is known. This game is called gap_trans. This quantity depends on the ratio R. As explained below, this value will also depend on the engine speed Ne. [0069] During the transient phase, the motor shaft will rotate through the gap_trans angle without driving the rear wheel. The gap_cur variable corresponds to the angle by which the motor shaft has already turned without driving the rear wheel.

The difference in angular rotation gap_cur between the motor output shaft and the drive wheel can for example be determined by means of the integral of the difference in rotational speed between the motor and the wheel brought back to the level of the motor via known transmission ratios. The integral begins when the torque demand transition is detected as described above in paragraphs [0057] to [0058] and below.

To control the transient phase, an angle gap_est is calculated. It corresponds to the estimated angular offset between the motor shaft and the image of the wheel shaft (therefore taking account of the ratio R as explained above) at the end of the transient phase.

[0072] During an initialization phase, we carry out:

[0073] Gap_cur = 0

[0074] Gap_est = 0

[0075] Nveh = Ne

The idea here is to inhibit combustion in the engine from a moment to be determined so that the speed of rotation of the motor shaft corresponds to the speed Nveh when the motor returns to drive the rear wheel.

[0077] Calculations are then carried out at the same frequency as the combustions in the engine. Calculations are carried out between two successive combustions to determine from which moment combustion in the engine should be inhibited and the number of combustions to be inhibited.

When the torque setpoint becomes positive, the motor cannot immediately drive the wheel because of the play in the transmission. For a time, the speed of the vehicle decreases due in particular to friction with the roadway and with the air. The higher the speed, the greater the friction.

The calculations performed are recurring calculations.

For example, we first determine an estimate of the speed of the vehicle N_veh_n:

[0081] N_veh_n = N_veh_(n-1) - delta_N_veh(Ne, R)

[0082] where delta_N_veh is a function of the engine speed and of the gearbox ratio, that is to say of the speed of the vehicle. [0083] Next, we come to determine what offset between the motor shaft and the image of the wheel shaft occurs at each combustion. To simplify the calculations, it is assumed that the time between two combustions does not vary during the transient phase. For example, the time between two combustions is chosen as the unit of time for making the calculations (this time depends on the type of engine -2-stroke or 4-stroke-, the engine speed and the number of cylinders). Thus, the gap_trans value will be determined according to the regime at the start of the transient phase, i.e.

[0084] gap_trans function of Ne at the start of the transient phase and R.

The clearance variation between two combustions thus corresponds to the variation between the speed Ne and the speed of rotation N_veh. We thus have:

[0086] gap_cur_n = gap_cur_(n-1) + Ne_n - Nveh_n

The number of combustions to be inhibited is determined on the basis of the calculated angular rotation difference and the measured engine speed, as follows: the number of combustions to be inhibited is calculated in parallel so that the engine speed Ne coincides with Nveh. If combustion is inhibited, we know how to estimate the change in speed caused because no resisting torque is then exerted on the engine. The variation (slowing down) of the engine speed then essentially depends on the engine speed and the engine temperature and/or, if known, the oil temperature.

Let n_cut be the combustion number to be inhibited so that Ne coincides with Nveh. We have

[0089] n_cut = (Ne_n - Nveh_n) / delta_gap (Ne, T)

[0090] where delta_gap corresponds to a speed variation for a unit of time if there is no combustion.

It is then necessary to predict what angular shift between the motor shaft and the image of the wheel shaft will occur during the n_cut time units without combustion. We neglect here the rotational speed variations (motor side and wheel side) and we add the predicted value to the gap_cur value already calculated to have the prediction of the angular offset over the entire transient phase, i.e.:

[0092] gap_pred_n = gap_cur_n + [delta_gap (Ne, T) * nb_cut * (nb_cut +1) / 2]

[0093] As long as gap_pred_n remains lower than gap_trans, the engine continues to operate normally. As soon as gap_pred_n becomes greater than or equal to gap_trans, the engine control unit transmits a zero-value torque command for the following combustion and for the nb_cut combustions to come. This torque control at a zero value can be obtained for example by inhibiting the nb_cut combustions. This can be obtained for example by inhibiting the ignition command of the combustion to be inhibited or by delaying this command so that the indicated torque supplied by the engine is zero.

[0094] In this way, at the end of the stage where the combustions are inhibited, the transient phase ends and the motor then drives the chain and the wheel. The transient phase is illustrated in figure 2 with curve 2. This figure 2 is similar to figure 1 and therefore represents the variation in speed of a vehicle in meters per second per second (m/s/s) as a function of the time in second (s), but here the control of the motor is carried out as described above by adapting the speed of the motor shaft so as not to have a shock.

The solution which is proposed here can easily be implemented. Combustion inhibition is easier to manage in the engine than an ignition delay which aims to limit the torque exerted temporarily to have a lesser shock when the chain is powered up again.

The proposed control method is based on physical measurements, such as engine speed and does not make predictions of engine speed or other quantities.

[0097] With this method, even on the first report of the gearbox, a motorcycle, in particular of large displacement, can be driven without significant jerks.

The proposed method also makes it possible to improve the response time of a torque request compared to the methods of the prior art which make it possible to reduce the importance of the shock when the chain is tightened.

Finally, the proposed method makes it possible to avoid the use of accessories which can be costly, such as, for example, damping systems at the level of the chain.

[0100] This method can also be used advantageously during a transition phase when the torque command changes from a positive torque value to a negative torque value. In such a case, the shock observed is less significant (given that the torque to be exerted on the chain is less when the chain is tightened again) but exists.

[0101] In the case of a system with mechanical throttle control, this detection can be carried out by reading the position of the throttle, for example by means of a threshold map as a function of engine speed and temperature. : the transition is detected when the throttle position changes from a value above the threshold to a value below the threshold. In the case of an application with motorized butterfly, the reading of the position of the handle is translated by the system into a torque request. This torque demand value can be used directly for the detection of the transition. The same principle applies but in a different way. While in the case explained above it was necessary to prevent the engine speed from being too high, here it is necessary to prevent it from being too low when the angular offset between the driving shaft and the wheel shaft corresponding to the play of the transmission Have been realised.

As for the above method, first of all the torque setpoint is executed. On the other hand, here, this results in the inhibition of combustion. The engine speed then decreases more rapidly than the image of the wheel shaft (or Nveh). It is therefore necessary to initiate combustion so that the engine speed increases again and reaches the level of Nveh when the chain begins to tighten again.

Thus, the combustions are inhibited when the transient phase is detected. Before each top dead center corresponding to an end of compression, the calculation is carried out to know the “virtual” speed of rotation Nveh. We also measure the angular offset between the motor shaft and the image of the wheel shaft: gap_cur. The number of combustions required for the motor shaft to return to a value Nveh is calculated. Depending on the number of combustions (for example nb_comb equivalent to nb_cut) gap_pred is also calculated, which is the sum of the angular offset achieved and the angular offset that nb_comb combustions makes it possible to obtain. As soon as this gap_pred value is greater than the gap_trans value defined above, nb_comb combustions, corresponding to the last nb_comb calculated, are carried out.

Figures 4a, 4b, and 4c, on the one hand, and Figures 5a, 5b, and 5c on the other hand show the differences between the implementation in a negative to positive torque transition phase (Figures 4a, 4b, and 4c) with implementation in a positive-to-negative torque transition phase (Figures 5a, 5b, and 5c).

On the curves 41 and 51 of FIGS. 4a and 5a respectively, the torque command on the ordinate is represented in Newton-meters (N m), we see that in one case (FIG. 4a) we start from a command of negative torque, then the torque demand increases. The torque becomes negative again while combustion is inhibited and then takes the final setpoint value. In the other case (figure 5a) we start from a positive torque command. As soon as the negative torque command is detected, combustion is stopped and then resumed to match the shaft speeds taking into account the transmission ratio as shown.

The curves 42 and 52 respectively in FIGS. 4b and 5b illustrate the variation in engine speed in revolutions per minute (rpm). In the first case (FIG. 4b) the speed passes through a relative maximum and in the other case (FIG. 5b) it passes through a relative minimum as shown. The curves 43 and 53 respectively in FIGS. 4c and 5c show that in both cases the acceleration of the vehicle, represented in meters per second per second (m/s/s), no longer has a peak, this which means that the transition phase was carried out smoothly.

[0109] An improvement to the above method, in particular for switching from a negative torque command to a positive torque, is also proposed. We note on the one hand that the torque command usually in an engine is provided at each combustion and on the other hand that in the above process, gap_pred approaches gap_trans without necessarily equaling it.

It is then proposed to adapt the torque setpoint in order to achieve equality between gap_pred and gap_trans. It is assumed here that gap_pred_n is less than gap_trans but that gap_pred_(n+1) is greater than gap_trans, i.e.:

[0111] Gap_pred_n < gap_trans < gap_pred_(n+1)

[0112] We want to obtain a variation of rotation between the motor shaft and the wheels to just compensate for the play of the transmission. We then wish to have an engine speed variation Delta_Ne such that:

[0113] Delta_Ne = (gap_trans - gap_pred_n + Ne - N_veh) / (nb_cut_n + 1.5)

The torque setpoint for the combustion to come is then:

[0115] TQ_max_n = J * Delta_Ne * Ne

[0116] where J is the moment of inertia of the motor.

This torque value can then be entered as a command in a controlled torque system. It is also possible in another system, for example, to provide an ignition delay according to a map of the corresponding engine.

In the above method, the gap_trans value is determined from an initial clearance and is adapted according to the transmission ratio and the engine speed. However, during the life of a vehicle, in particular a motorcycle (not only, it can also be for example a quadricycle commonly called "quad"), the chain tension settings can vary and the chain itself -even can lengthen. These phenomena then have an influence on the play of the transmission.

It is then proposed to be able to adapt the gap_trans value to adapt to the life of the vehicle. FIGS. 6 and 7 illustrate by curves 6 and 7 respectively, the implementation of a method as described above when the gap_trans value is not adapted to the actual game of the vehicle. In FIG. 6, the chain is slack and the clearance is greater than the expected clearance corresponding to gap_trans stored in the vehicle's electronic control device. In the illustrated case, it is a transition corresponding to a passage from a negative torque command to a positive torque command. In this example, once the angular offset corresponding to gap_trans is achieved, the clearance is not yet absorbed. There is still play but the positive torque setpoint is applied. Thus when the chain starts to tighten again, a shock appears as represented by the acceleration peak on curve 6. It is reduced but still exists. This peak occurs after the phase transition, when the procedure described above has come to an end.

[0121] Figure 7 illustrates the case on the contrary where the clearance is less important than expected, still in the case of a transition for the passage from a negative torque to a positive torque. In this case, the game is caught up earlier than expected. The speeds of the motor shaft and the wheel shaft (taking into account the ratio R) are therefore not in agreement and an acceleration peak occurs before the end of the procedure described above as represented with the first peak which occurs on curve 7. The procedure, as described above, is in a step during which the combustions are inhibited. This procedure continues until the end of this step and when the positive torque comes to be exerted suddenly, a new jerk occurs as shown with the second peak which occurs on curve 7. Two jerks are thus observed. successive strokes, a first during the procedure corresponding to the transition phase and a second after this transition phase.

FIG. 8 is a flowchart corresponding to a procedure for adapting the gap_trans value which can advantageously be adopted in combination with the control procedure described above.

To limit the calculation load, the proposed procedure is not implemented systematically but in certain cases where the jerks are more sensitive and therefore also more easily detectable. Thus, provision is made to possibly carry out an adaptation only during a transition from a negative torque to a positive torque, for certain gearbox ratios and only within a given speed range.

A first step 100 consists in verifying whether the conditions stated in the preceding paragraph are fulfilled.

When these conditions are met, during the transition phase, the electronic control device monitors the speed gradient of the vehicle during a step 200. If this gradient exceeds a predetermined value, a jerk is then diagnosed. .

In the event of diagnosis of a jerk, the procedure passes through a step 300. During this step 300, a first counter is incremented and/or the value of gap_trans is modified, for example increased slightly, for example by a rate comprised between 0.5% and 5%, for example 2%. It is for example possible to modify the value of gap_trans only if several detections of too small a clearance are recorded by the first counter. This in fact avoids modifying the value of the clearance if the detection is due to a one-time error.

If no jerk is detected during the transition phase 200, monitoring of the vehicle speed is continued for a predetermined time (step 400). If the vehicle speed gradient exceeds a predetermined threshold, the procedure passes through a step 500. During this step, a second counter is incremented and/or the value of gap_trans is modified, for example decreased slightly, for example by a rate of between 0.5% and 5%, for example 2%. For example, the value of gap_trans can only be modified if several detections of too large a clearance are recorded by the second counter. This in fact avoids modifying the value of the clearance if the detection is due to a one-time error.

If no jerk is detected just at the end of phase 400, it is possible during a step 600 to decrement the first and/or the second counters.

The adaptation procedure can also advantageously be used to create an alert and warn the driver of the vehicle of a problem with its transmission. For this purpose, a step 700 is provided during which the first counter and the second counter are each read. If the value of either of these counters is above a predetermined threshold, an alert can be triggered. This alert can also give an indication of whether the chain is too tight or too loose. This alert is made during a step 800 as shown in Figure 8.

As a variant, to create an alert, it is also possible to compare the value of gap_trans which has been modified with the value of gap_trans initially programmed. If the variation of this value is too great, an alert can be created. A different alert threshold can be provided for a chain that is too tight from the alert threshold for a slack chain.

Figure 9 provides a flowchart summarizing the management of a transient regime presented above.

This flowchart shows at the top a negative torque command TQ < 0, at the bottom a positive torque command TQ > 0, on the left the passage from a negative torque to a positive torque and on the right a passage from positive torque to a negative pair.

When it is a negative torque command TQ < 0, a Req request is made to modify the torque so that it goes from negative to positive.

A first step NP_STP_1 is then proposed in which, depending on the transmission ratio and the speed, the gap_trans value is calculated then in a iterative the gap_pred_n values are calculated at each combustion. As indicated above, a limitation of the torque to adapt the final value of gap_pred to gap_trans can be provided.

When the value of gap_pred equals gap_trans (or is greater than gap_trans), a second step NP_STP_2 is triggered. As illustrated in FIG. 9, if the first step is too long for example or if a problem is detected such as for example a maneuver at the level of the clutch, a change of setpoint towards a negative torque again, etc., the procedure can be interrupted (CANCEL..) without then going through step NP_STP_2.

[0136] During step NP_STP_2, the torque setpoint is zero, or almost zero, during the time to perform a previously calculated number (nb_cut) of combustions. For example, provision can be made here to inhibit combustion (no fuel injection and/or no ignition).

Conversely, when the torque command corresponds to a positive torque TQ > 0, a negative torque Req request can be requested. In this case, a first step PN_STP_1 is implemented. During this step, the torque command is immediately cut off, the gap_trans value is determined according to the transmission ratio and the rpm. The number of cycles with a zero torque setpoint is also determined during this step as a function of the gap_trans value and a positive torque setpoint value for a future PN_STP_2 step.

Then, most often (here too the procedure can be interrupted -ANNUL..-), a second step PN_STP_2 is implemented during which the positive torque command (cf. first step) is implemented so as to adjust the speed of the engine to the speed of the vehicle.

The flowcharts of Figures 8 and 9, and more generally the control method described above will advantageously be implemented by software means installed in an engine control unit (not shown) which equips any vehicle in order to control and to control the motor. An engine control unit (ECU for Engine Control Unit) comprises in known manner a computer able to perform all the calculations described in the method. The method according to the invention essentially does not require any means other than those fitted in a known manner to a vehicle with a heat engine controlled and controlled by an electronic engine control unit.

Industrial application

[0140] The present technical solutions can be applied in particular to engine control for motorcycles or other vehicles with play in the transmission. This control makes it possible to pass from a tension of the chain in one direction to a tension of the chain in the opposite direction smoothly, smoothly.

An advantage of the proposed solution is that it also makes it possible to provide good reactivity, in particular during a transition from a negative torque to a positive torque. The proposed solution can be implemented without additional cost and can also find its place on a vehicle without an electric throttle valve. In addition, by eliminating jerks, it is no longer necessary to provide a chain damper type device on the vehicle.

The present disclosure is not limited to the embodiments described above, only by way of examples, and to the variants envisaged, but it encompasses all the variants that a person skilled in the art may consider in the context of the protection sought.

Claims

-22- Claims

[Claim 1] Method for controlling an internal combustion engine in a vehicle comprising said engine, an engine output shaft, an electronic control unit of said engine, an engine torque control member entering a engine torque, at least one wheel able to be driven by the engine, called drive wheel, and a transmission arranged between the engine output shaft and the at least one drive wheel, said transmission having a corresponding transmission ratio R in continuous operation the ratio between the speed of rotation Ns of the at least one drive wheel and the speed of rotation of the motor output shaft Ne (i.e. R = Ns / Ne), characterized in that it comprises the following steps:

- detection of a transition corresponding to a transition from a negative torque request to a positive torque request, from the engine torque control member entering the engine torque control chain, then, before each combustion, carrying out of the following steps:

[Claim 2] Control method according to claim 1, characterized in that it further comprises the following steps:

- estimation of the number of combustions to be carried out nb_comb so that the speed of rotation of the engine output shaft Ne substantially corresponds to the expression Ns_est / R, from the difference GAP_cur of determined angular rotation and the measured engine speed, at the means of the engine control unit calculator,

- estimation of the GAP_pred difference in angular rotation between the motor output shaft and the at least one drive wheel by taking into account the transmission ratio corresponding to the determined GAP_cur difference increased by the difference in angular rotation between the engine output and the at least one drive wheel taking into account the transmission ratio by performing nb_comb combustions, by means of the engine control unit calculator, and when GAP_pred exceeds a predetermined limit, the engine control unit commands the nb_comb combustions then stops the combustion in the vehicle engine according to the negative torque demand.

[Claim 3] Method according to one of Claims 1 or 2, characterized in that the estimated speed of rotation Ns_est of the at least one driving wheel is determined by recurrence as follows:

Ns_est_n = (Ns_est_n-1) - delta_Ns where delta_Ns is a function of vehicle speed and gear ratio.

[Claim 4] Method according to one of Claims 1 to 3, characterized in that the number of combustions to be inhibited is determined as follows: nb_cut_n = ((Ne_n) - (Ns_est_n) / R) / delta_gap where Ne_n is the speed of rotation of the engine output shaft when the rotational speed of the at least one wheel is estimated by the expression Ns_est_n, and delta_gap is a function of the engine speed, i.e. Ne, and of engine temperature.

[Claim 5] Method according to one of Claims 1 to 4, characterized in that during a transition corresponding to a transition from a negative torque request to a positive torque request, the variation in speed of the vehicle proportional to the speed of the wheel shaft is analyzed during the transition period, and in that if the speed gradient becomes greater than a predetermined acceleration then the predetermined limit for GAP_pred is decreased.

[Claim 6] Method according to one of Claims 1 to 5, characterized in that during a transition corresponding to a passage from a negative torque request to a positive torque request, the variation in speed of the vehicle proportional to the speed of the wheel shaft is analyzed beyond the transition period for a predetermined duration, and in that if the speed gradient becomes greater than a predetermined acceleration during said duration, then the predetermined limit for GAP_pred is increased.

[Claim 7] Method according to one of Claims 5 or 6, characterized in that if the speed gradient becomes greater than a predetermined acceleration during the transition period, a first counter is incremented, in that if the speed gradient becomes greater than a predetermined acceleration beyond the transition period for the predetermined duration, a second counter is incremented.

[Claim 8] Method according to one of Claims 5 to 7, characterized in that if the predetermined limit for GAP_pred leaves a predefined interval and/or if the first counter exceeds a first value and/or if the second counter exceeds a second value, then an alert message is generated.

[Claim 9] Method according to one of Claims 1 to 8, characterized in that the predetermined limit for GAP_pred is called GAP_trans, in that GAP_pred is calculated iteratively and successively takes the values gap_pred_n, in that if GAP_trans is between two successive iterative values gap_pred_n and gap_pred_(n+1) of GAP_pred, then the torque setpoint for the nth combustion is adapted such that gap_pred_(n+1)=GAP_trans. -25-

[Claim 10] Computer program comprising program code instructions for the execution of all the steps of a method according to one of claims 1 to 9 when said program is executed on a computer, in particular an electronic control unit of an internal combustion engine. [Claim 11] Internal combustion engine, characterized in that it comprises an electronic control unit for implementing each of the steps of a method according to one of Claims 1 to 9.