WO2011036361A1

WO2011036361A1 - Method for predicting the rotation speed of an engine crankshaft in the end phase of the rotation, and use of said method to predict the stop cylinder

Info

Publication number: WO2011036361A1
Application number: PCT/FR2010/051734
Authority: WO
Inventors: Julien Tisseau; Christophe Blind
Original assignee: Peugeot Citroën Automobiles SA
Priority date: 2009-09-23
Filing date: 2010-08-19
Publication date: 2011-03-31
Also published as: BR112012005586A2; BR112012005586B1; FR2950388A1; CN102510941B; EP2480776A1; CN102510941A; FR2950388B1; EP2480776B1

Abstract

The invention relates to a method for predicting the rotation speed of a crankshaft (2) of an engine (1) in the end phase of the rotation, for which: the actual rotation speed (N) of the crankshaft is determined and recorded for an angular position range (T) of the crankshaft (2), said range being defined by a first and second angular position; a constant (C_o) is determined on the basis of actual speeds determined for the first and second angular positions; and a predicted rotation speed (Ñ) is determined for a third angular position, which is not included in the range (T), on the basis of the constant and the actual speed (N) that is determined in a fourth angular position included in said range and such that the spacing between the third and fourth angular positions is a multiple greater than or equal to said range. The invention also relates to the use of the method for predicting the stop cylinder.

Description

Method for predicting the rotational speed of an engine crankshaft in end of rotation phase and application of the method to the prediction of the stopping cylinder

Technical field of the invention

The present invention claims the priority of the French application 0956536 filed on September 23, 2009 whose content (text, drawings and claims) is hereby incorporated by reference.

The present invention relates to the field of internal combustion engines, and more particularly to the anticipated determination of the rotational speed in the stopping phase of the engine.

Technological background

In order to know and follow the position of each of the cylinders in a cycle, the electronic computers mainly have information provided by two sensors, which respectively characterize the rotation of the crankshaft of the engine (it is called a speed sensor), and potentially the rotation of at least one camshaft (this is called a position sensor AAC or camshaft). During a cycle of a 4-stroke engine, the crankshaft performs 2 turns, a rotation of 720 °. For the sake of clarity, in accordance with the usual practice, we ask that a cycle starts at 0 ° crankshaft angle at the beginning of a compression phase of a given cylinder and ends at 720 ° at the end of the intake phase of this same cylinder. The flywheel, secured to the crankshaft of the engine, is provided on its periphery with a set of teeth, called target, opposite which is positioned the speed sensor. It delivers an alternating voltage in crenels, presenting rising electric fronts and descending electric fronts, and whose frequency varies with the engine speed. Typically, the flywheel may have, for example, 58 teeth and two gaps (that is to say, a toothing of 60 teeth including 2 missing). The sensor will detect these gaps thus providing information on the position of the crankshaft and the speed of rotation or engine speed.

It is known to determine the instantaneous engine speed from the measurement of an inter-tooth duration, in other words, the time separating two rising fronts or two descending fronts. The knowledge of the engine speed can be used advantageously in various controls or engine commands such as improving the restart of the engine internal combustion engine for example to control the stopping cylinder, in particular in motor vehicles equipped with an automatic on / off.

However, the command or control in question obviously can not be implemented without knowing the engine speed, which can be embarrassing to respond to problems of motor vehicles equipped with an automatic on / off using a starter.

The invention aims to solve one or more of these disadvantages. The invention thus relates to a method for predicting the rotational speed of an internal combustion engine crankshaft in an end-of-rotation phase, characterized in that:

- The actual rotational speed of the crankshaft is determined and recorded at angular positions of said crankshaft for a range of angular positions of the crankshaft delimited by a first angular position and a second angular position corresponding to angular periodic oscillations of decreasing the speed of the crankshaft. rotation of the crankshaft.

A constant is determined as a function of the difference of squares of the real regimes determined for the first and second angular positions,

A predicted crankshaft rotation speed is determined for a third angular position of the crankshaft, not included in the range of angular positions of the crankshaft, as a function of the constant and the actual speed determined at a fourth angular position included in said range and such that the difference between the third and fourth angular positions is equal to or is a multiple of said range.

The actual speed measurement measured over a given range of angular position is thus used to predict at a future angular position of the crankshaft. In addition, the invention may include one or more of the following features:

- Preferably, the second angular position corresponds to the position at the present moment of the crankshaft which is the last angular position for which one can determine a real regime.

In a variant where the engine comprises four cylinders, the range of angular positions of the crankshaft is advantageously 180 °, 360 ° or 720 ° which corresponds to respectively to a motor phase, a motor revolution, a motor cycle. The range is representative of the periodicity of the loss couples of the phases of admission, compression, expansion and exhaust of the engine and the phase shift of the cylinders. Preferably the range of angular positions of the crankshaft is 360 ° to have a better precision of the prediction of the regime.

- In a variant where the engine comprises three cylinders, the range is 240 ° or 720 °, because of the phase shift of the cylinders - In a variant where the engine comprises six cylinders, the range is 120 °, 240 ° or 720 °, because of the phase shift of the cylinders.

- The crankshaft being rotatably connected to a toothed wheel comprising teeth for determining the angular position of said crankshaft, the angular width between each tooth being 6 °, the predicted crankshaft rotation speed for the third angular position of the crankshaft is determined according to the actual regime by applying the following relation:

in which :

A and B are variables such as:

n is the index of the tooth locating the second angular position of the crankshaft,

n + d is the index of the tooth identifying the third angular position of the crankshaft, n - + B is the index of the tooth identifying the fourth angular position of the crankshaft, 6

and INT is the whole fraction function.

There is thus a general formulation in the case of a conventional toothed wheel of 58 teeth and two gaps, that is to say, a toothing of 60 teeth, 2 missing, or a tooth to identify 6 ° rotation of the crankshaft.

The method further comprises the following steps:

the predicted diet is determined for the tooth of index n + 1,

from the predicted diet at the tooth of index n + 1, an inter-tooth time is calculated, a time counter of the calculated inter-tooth time is incremented,

the preceding steps are reiterated on the teeth of subsequent indices as long as the value of the time counter is less than a fixed time,

a predicted regime is determined for the fixed time, by interpolation between the predicted regimes for the last two indices.

This makes it possible to know in advance the regime to come after a fixed time and can make it possible to anticipate actions of motor control. Furthermore, the invention also relates to an application of the method of the invention to the prediction of the stopping cylinder of an internal combustion engine, characterized in that the third angular position of the crankshaft corresponds to a top dead center. combustion. The estimation of the speed for angular positions of the crankshaft corresponding to a top dead center, also called PMH combustion, makes it possible to determine the last PMH for which the estimated speed will be non-zero and to deduce the cylinder in corresponding compression that is designated as the stop cylinder.

Brief description of the drawings

Other features and advantages will appear on reading the following description of a particular embodiment, not limiting of the invention, with reference to the figures in which:

- Figure 1 is a schematic representation of an internal combustion engine 1.

- Figure 2 is a diagram showing the end of rotation phase of the crankshaft.

- Figure 3 illustrates the procedure of predicting the engine speed on a fixed angle.

- Figure 4 illustrates the procedure of predicting the engine speed over a fixed time.

FIG. 5 illustrates the procedure for predicting the stop cylinder.

detailed description

FIG. 1 schematically shows an internal combustion engine 1 comprising a crankshaft 2. The internal combustion engine is equipped with a device 3 for determining the rotational position of the crankshaft 2. This device comprises a toothed wheel 4, a sensor 5 of regime connected to an electronic control unit 6 also called ECU. The toothed wheel 4 is integrally connected in rotation to the crankshaft 2 so that when the internal combustion engine 1 operates, the toothed wheel 4 rotates relative to the to the engine 1. The periphery of the toothed wheel 4 comprises teeth 7 corresponding to an angular width of 3 ° and two teeth are separated by a recess 8 with an angular width of 3 °. In one part of the periphery, two adjacent teeth 7 have been removed to have an enlarged tooth gap called spacing 9. At each passage between a tooth 7 and a recess 8 or at the spacing 9, there is a tooth flank 10 The ECU 6 comprises the calculation and storage means necessary for determining the actual engine speed and the predicted engine speed according to the invention.

We define as the inter-tooth duration, t _id , the time separating two successive identical fronts. The fronts can be 12 or downs 13. A so-called instantaneous or real N regime expressed in degree / second can then be estimated by the following relation:

N = (1)

The sensor 5 is a Hall effect sensor mounted in a fixed manner with respect to the internal combustion engine 1. The sensor 5 captures the succession of teeth 7 and tooth gaps 8 or the spacing 9 which passes in front of it and generates a crenelelectric signal January 1, having rising electrical fronts 12 and descending electric fronts 13, whose Frequency varies with the N rotation speed of the motor.

According to the invention, during an end-of-rotation phase of the crankshaft of an internal combustion engine, the engine speed can be predicted using information based on the difference between a current instantaneous squared regime and the engine speeds. snapshot prior to squared. The term "end of rotation phase" is understood to mean the period following a stopping of the operation of the internal combustion engine 1 due to a cut by the ECU 6 of the injection and ignition.

FIG. 2 shows the end-of-rotation phase of the crankshaft 2 of the internal combustion engine 1 in the form of a diagram giving the variation of the speed N as a function of the angle Θ of the crankshaft 2. FIG. the end phase rotation speed N of the crankshaft 2 decreases. Indeed, the internal combustion engine 1 does not provide energy and loss of torque due to the friction forces, but not only, oppose the rotation of the crankshaft 2 of the engine 1 and slow the speed of rotation N Crankshaft 2. Figure 2 further shows that the decrease in the speed of rotation N of the crankshaft is not monotonous but presents oscillations periodically angularly, in other words on a range T of angular positions. Indeed, these oscillations are due to the fact that certain loss pairs such as those generated by the efforts of admission, compression, expansion and exhaust which are periodic phase shift between the engine cycles of each cylinder of the engine.

The invention will be better understood following the following demonstration:

The fundamental principle of the dynamics applied to rotations gives us:

With:

J: the moment of inertia of the motor elements connected to the toothed wheel 4,

θ (ΐ) the angle of the crankshaft 2 as a function of time,

^ C (0 (t)): in phase of end of motor rotation, the sum of the loss couples responsible for the stop in rotation of the motor.

Multiplying each term of the relation (2) by the regime N also determined by the following relation:

dt he comes:

c (e (t)) (4) dt dt dt

By integrating the relation (4) between a first instant ti and a second instant t ₂ , with θι the crank angle taken at time ti, such that:

And θ ₂ , the crankshaft angle raised to a second instant t ₂ , as Θ (1 ₂ ) = Θ ₂ (6)

He comes then

Or

Either, using the relation (3):

It is then noted judiciously that the relation (9) is particularly advantageous when the difference between θι and θ ₂ corresponds to a range T of angular positions.

Thus, preferably, for an engine comprising four cylinders, the range T of angular positions of the crankshaft 2 is 180 °, 360 ° or 720 °.

More preferably, the range T is 360 °, to have a better precision of the prediction of the regime.

Thus, because of the angular periodicity of the loss pairs, the second term of the relation (9) is advantageously a constant C ₀ and can therefore be written: + _T - N; = R¾_ -r¾ _T = c ₀ (io)

If we consider that the angular width between each tooth 7 of the toothed wheel 4 is 6 °, we can therefore index the relation (10) as a function of a number j of teeth:

where j is the index of any tooth. It is then possible to predict in a first manner the engine speed at a given angle of the crankshaft 2 or in a second manner at a fixed time.

The procedure for predicting an engine speed at a given angle of the crankshaft 2, in other words for a given number of teeth d of the toothed wheel 4 is as follows: the actual rotational speed of the crankshaft is determined and recorded at angular positions said crankshaft for a range T of angular positions of the crankshaft 2 delimited by a first angular position and a second angular position. To do this, a recording of the inter-tooth durations, t _id , for the period T considered, the number of records is in our example, the last thirty inter-tooth durations, t _id, or a record on a range of 180 °. Preferably, here the second angular position corresponds to the position at the present moment of the crankshaft 2.

FIG. 3 shows in full line the recorded angular period T and indicates in dashed line the variation of the rotational speed to come. For each inter-tooth time, t _id , the real rotational speed is determined by the relation (1). The actual speed values are stored in the ECU 6 for their future use in the rest of the procedure.

The constant C ₀ is determined as a function of the difference of squares of the real regimes determined for the first and second angular positions, in other words by the difference between the instantaneous squared regime of the first recording and the instantaneous squared regime of the last recording. .

- A predicted N rotation of the crankshaft 2 is determined for a third angular position of the crankshaft 2, not included in the range T of angular positions of the crankshaft 2, as a function of the constant C ₀ and the real speed N determined at a fourth angular position in said range T and such that the difference between the third and fourth angular positions is a multiple greater than or equal to said range (T). Indeed, the predicted diet N is determined on the basis of a general formula whose expression is now demonstrated: For the purposes of the demonstration and as illustrated in FIG. 3, the last record is assigned the index n. The first record therefore has the index (nT / 6).

In order to predict the tooth regime after the last recording, we can write:

(12) n- + d

6

In the rest of the demonstration, in order to distinguish the values of the regime determined from the inter-teeth times of that not known and therefore to predict, note N the first and N seconds.

Thus for 0 <d <T / 6, for example for d = 20 (see figure 3), the relation (12) becomes:

N ² , - N ² _{+ 20} = C ₀ (13) n + 20

6

Is :

N ² _{+ 20} = N ² _T - C (14) n + 20

6

For T / 6 <d <2T / 6, we have for example d = 50 (see figure 3), the relation (12) becomes:

'n + 50 - N - 2C ₀ (15)

For 2T / 6 <d <3T / 6, we have for example for d = 80 (see figure 3), the relation (12) becomes:

'n + 80 - N - 3C ₀ (16)

From these three examples, it can be seen that one can thus obtain a general expression of the predicted regime N _n + d, d teeth after the n acquisitions. Indeed, by posing:

6d

A = IN ^" (17) And

B = d - A (18) 6

It comes, for an internal combustion engine comprising four cylinders, equipped with a toothed wheel of 58 teeth (that is to say a toothing of 60 teeth including 2 missing), the following general formula:

We now describe the complementary procedure for predicting engine speed at a fixed time tp during the end of rotation phase.

The steps described above are repeated, that is to say: the step of recording inter-tooth durations, t _id , for the period T considered,

the step of determining the instantaneous diets, based on the inter-tooth durations, t _ids recorded.

the step of determining the constant C ₀ . Then proceed step by step, as shown in Figure 4:

As the regimes are known up to the tooth of index n, the value of a time counter S is initialized to 0 for the tooth of index n.

the predicted regime at the next tooth, of index n + 1, referenced N _{n + 1} in FIG. 4, is determined using the general relation (19),

from the predicted regime at the tooth of index n + 1, an inter-tooth time, t _id , corresponding from the relation (1), referenced t _{n +} i, is calculated in FIG. 4, - it is incremented the time counter S of the inter-tooth time calculated.

the preceding steps are reiterated on the teeth of subsequent indices as long as the value of the time counter S is less than the set time tp. Thus, as shown in FIG. 4, at the index n + 2, the cumulative cumulative inter-tooth time from index n is less than fixed time tp while at the next iteration, at the index n + 3, the cumulation of inter-teeth times, tid, is greater than the set time tp. We then continue the procedure as follows:

a predicted regime is determined for the fixed time tp, by interpolation between the predicted speeds for the last two indices, referenced respectively N _{N + 2} - N _{N + 3} in the figure

4. This gives a predicted regime N _p at the set time t _p .

Advantageously, this procedure can make it possible to determine the stop cylinder. Stop cylinder means the cylinder which is in the compression phase of the engine cycle.

To do this, we proceed as follows:

We repeat the steps described above, that is to say:

the step of recording inter-tooth durations, t _id , for the period T considered,

the step of determining the real diets, from the inter-tooth durations, t _ids recorded, using the relation (1).

the step of determining the constant C ₀ .

the actual top dead center (or TDC) combustion regime, named N _PM H, is calculated from the recording of the corresponding inter-tooth time.

Then, as follows, with a range T angular position: -One predicted gradually the regime for angular positions corresponding to the next PMH combustion, as shown in Figure 5 the estimation of the regime in k PMH combustion given by the following relation:

This until the moment when we will not be able to cross the PMH combustion, which corresponds to the minimum value of k such that:

N ² _PMH - kC ₀ <0 (22)

Is

With INT (x) the whole part function.

In this case it is concluded that the motor will go to PMH combustion before stopping, which allows to deduce the stopping cylinder.

The invention is not limited to a particular type of combustion engine. In the case of an internal combustion engine comprising three cylinders, the range T of angular positions of the crankshaft 2 is preferably 240 ° or 720 °, due to the phase shift of the engine cycles of the various cylinders.

In the case of an internal combustion engine comprising six cylinders, the range T of angular positions of the crankshaft 2 is preferably 120 °, 240 ° or 720 °, due to the phase shift of the engine cycles of the various cylinders.

The invention has the advantage of being simple to set up as a computer routine programmed in the ECU and does not require any particular calibration.

Claims

claims

1. Method for predicting the rotational speed of a crankshaft (2) of internal combustion engine (1) in an end-of-rotation phase, characterized in that:

- The actual rotational speed (N) of the crankshaft (2) is determined and recorded at angular positions of said crankshaft for a range (T) of angular positions of the crankshaft (2) delimited by a first angular position and a second angular position. corresponding to periodic oscillations angularly decreasing the speed of rotation (N) of the crankshaft (2).

A constant (C ₀ ) is determined as a function of the difference of squares of the real speeds determined for the first and second angular positions,

A predetermined crankshaft rotation speed (N) is determined for a third angular position of the crankshaft (2), not included in the range (T) of angular positions of the crankshaft (2), as a function of the constant ( C ₀ ) and the actual speed (N) determined at a fourth angular position in said range (T) and such that the difference between the third and fourth angular positions is equal to said range (T) or is a multiple of that -this.

2. Method according to claim 1, characterized in that the second angular position corresponds to the position at the present moment of the crankshaft (2) which is the last angular position for which one can determine a real regime.

3. Method according to claim 1 or claim 2, characterized in that, the engine comprising four cylinders, the range (T) of angular positions of the crankshaft (2) is 180 °, 360 ° or 720 °.

4. Method according to claim 3, characterized in that the range (T) is 360 °.

5. Method according to claim 1 or claim 2, characterized in that, the engine comprising three cylinders, the range (T) is 240 ° or 720 °.

6. Method according to claim 1 or claim 2, characterized in that, engine comprising six cylinders, the range (T) is 120 °, 240 ^° or 720 °.

7. Method according to any one of the preceding claims, the crankshaft (2) being integral in rotation with a toothed wheel (4) comprising teeth (7) for determining the angular position of said crankshaft (2), the angular width. between each tooth (7) being 6 °, characterized in that, the predicted regime (N) of rotation of the crankshaft (2) for the third angular position of the crankshaft (2) is determined according to the actual speed (N) by applying the following relation:

in which :

A and B are variables such as:

n is the index of the tooth (7) identifying the second angular position of the crankshaft (2), n + d is the index of the tooth (7) identifying the third angular position of the crankshaft (2), n - + B is the index of the tooth (7) identifying the fourth angular position of the 6

crankshaft (2),

and INT is the whole fraction function.

8. Method according to claim 7, characterized in that it further comprises the following steps:

the predicted diet (N) is determined at tooth (7) of index n + 1,

from the predicted diet (N) to the tooth of index n + 1, an inter-tooth time is calculated

a time counter (S) of the inter-tooth time (t _id ) calculated is incremented,

the preceding steps are reiterated on the teeth (7) of subsequent indices as long as the value of the time counter (S) is less than a fixed time (tp),

a predicted regime is determined for the fixed time (tp), by interpolation between the predicted speeds for the last two indices.

9. Application of the method according to any one of claims 1 to 7 to the prediction of the stop cylinder of an internal combustion engine, characterized in that the third angular position of the crankshaft (2) corresponds to a top dead center. combustion.