Determine angular position by x+1 tooth camshaft sensor

Abstract

The invention relates to a method for determining the angular position of a shaft by means of a sensor (1) comprising a toothed wheel (2) comprising p teeth (d1-d p ) distributed at equal angles and an additional tooth (d + ) and a sensitive element (3) capable of detecting the teeth (d1-d p , d + ), the method comprising the following steps: - receiving the tooth signal and its date, - shifting the preceding time interval: T n‑3 ←T n‑2 , T n‑2 ←T n‑1 , T n‑1 ←T n , - determining the current time interval according to the formula T n =t n -t n‑1 , - calculating the ratio (Rn) according to the formula R n =(T n *T n‑3 ) / (T n‑1 *T n‑2 ), - comparing the ratio (R n ) with a threshold value (G), if the ratio (R n ) is greater than the threshold value (G), the current tooth signal (S n ) corresponds to the second tooth (d2) immediately following the first tooth (d1), the first tooth (d1) itself immediately following the additional tooth (d + ).

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of measuring the angular position of a rotating shaft, such as a camshaft, for an internal combustion engine. BACKGROUND

[0002] It is known to use, for determining the angular position of a rotating shaft, such as a camshaft, a sensor comprising a toothed wheel fixed to the shaft and comprising teeth, and a sensitive element fixedly arranged facing the toothed wheel and able to detect the teeth. The sensor is able to provide a signal for each detected tooth.

[0003] According to the prior art, the toothed wheel of a camshaft sensor comprises a small number of teeth, generally between 3 and 16. These teeth are irregular in their respective positions and in their respective angular ranges. To determine the angular position of the toothed wheel and thus of the associated shaft, various methods exist, which mostly take advantage of this irregularity.

[0004] However, camshaft sensors have recently been developed, the toothed wheel of which is called X+1 differential toothed wheel, because it comprises X+1 teeth having generally small angular ranges, which are generally equal from one tooth to another, these X teeth being angularly equidistant or all set at 360° / X, and an additional tooth set between two of these X teeth, preferably in the middle of these two teeth (hence the denomination X+1 teeth). The profile of this new toothed wheel makes the methods designed for the old toothed wheels obsolete, mainly because of the lower irregularity and asymmetry of the teeth. SUMMARY

[0005] The present invention thus proposes a new paradigm for determining the angular position of an X+1 toothed wheel.

[0006] To this end, the subject of the invention is a method for determining the angular position of a shaft by means of a sensor comprising a toothed wheel fixed to the shaft, the toothed wheel comprising p teeth distributed at equal angles and an additional tooth set between the last tooth and the first tooth, preferably in the middle of the last tooth and the first tooth, and a sensitive element fixedly arranged facing the toothed wheel and able to detect the teeth, the method comprising the steps of:

[0007] - receiving a tooth signal and its date,

[0008] - shifting the preceding time interval: T n-3 ← T n-2 , T n-2 ← T n-1 , T n-1 ← Tn ,

[0009] - determining, via a date difference, a current time interval separating the current tooth signal from a preceding tooth signal, according to the formula T n = t n -t n-1 , where T n is the current time interval and t n is the date of the current tooth signal, t n-1 is the date of the preceding tooth signal,

[0010] - calculating a ratio according to the formula R n = (T n *T n-3 ) / (T n-1 *T n-2 ), where R n is the ratio for the current tooth signal, T n is the current time interval for the current tooth signal, T n-1 is the time interval for the preceding first-order (preceding in order 1) tooth signal, T n-2 is the time interval for the preceding second-order tooth signal, and T n-3 is the time interval for the preceding third-order tooth signal,

[0011] - comparing the ratio to a threshold value, if the ratio is greater than the threshold value, the current tooth signal corresponds to a second tooth immediately following a first tooth, the first tooth itself immediately following an additional tooth.

[0012] Particular features or embodiments, which can be used alone or in combination, are:

[0013] - determining the threshold value according to the following formula:

[0014] G = k.max i＝1..p +[((Ang i -Ang i-1 )*(Ang i-4 -Ang i-3 )) / ((Ang i-2 -Ang i-1 )*(Ang i-3 -Ang i-2 ))], where:

[0015] - G is the threshold value,

[0016] - max is the maximum function,

[0017] - k is a non-circulation factor,

[0018] - Angi It represents the angle position of the i-th tooth, where i is the angle position of all p+1 teeth, including additional teeth.

[0019] - The non-cyclic factor k equals 0.53.

[0020] - This method is applied to camshafts.

[0021] A second aspect of the invention relates to an engine controller comprising a processing unit having means for implementing the method.

[0022] A third aspect of the invention relates to a motor vehicle including such an engine controller. Attached Figure Description

[0023] The invention will be better understood by referring to the following description, which is given by way of example only, in conjunction with the accompanying drawings, in which:

[0024] [ Figure 1 The angular position sensor is shown.

[0025] [ Figure 2 The image shows the measurement output from this sensor.

[0026] [ Figure 3 The figure illustrates the ratio R. n A table of values. Detailed Implementation

[0027] Figure 1 The figure shows sensor 1, which is capable of determining the angular position of a rotating axis.

[0028] The sensor 1 includes a differential toothed wheel 2, which rotates integrally with the shaft whose angular position is to be measured. The toothed wheel 2 is of type X+1, comprising X+1 teeth, where X teeth are d1-d... p (where p = X) are distributed at equal angles around the periphery of the toothed wheel 2; and additional teeth d + X can be any quantity.

[0029] The toothed wheel 2 shown in the diagram has 8+1 teeth. The spacing between these teeth d1-d8 is 360 / 8 = 45°, and the additional tooth d... + It is positioned at a distance of 22.5° from each of its two adjacent teeth.

[0030] Additional tooth d + Set in X teeth d1-d p The two are preferably located in the middle between them. In the following text, by convention, it is assumed that the additional tooth d... + Set on the last tooth d p Between and the first tooth d1.

[0031] Sensor 1 also includes a sensing element 3, which is fixedly disposed facing the toothed wheel 2. The sensing element 3 is capable of detecting teeth d1-d2. p d + In a known manner, via sensing element 3, sensor 1 produces an all-or-nothing measurement result when it detects a substance (i.e., when sensing element 3 faces the teeth d1-d). p d + When it detects no substance (i.e., when the sensing element 3 faces the space between the two teeth), it has a high state (or a corresponding low state), and when it does not detect any substance (i.e., when the sensing element 3 faces the space between the two teeth), it has the opposite state, i.e., a low state (or a corresponding high state).

[0032] Therefore, for each mechanical tooth passing through sensing element 3, sensing element 3 will generate two edges: a first edge at the beginning of the tooth and a second edge at the end of the tooth, the second edge being on the opposite side of the first edge. For example, the first edge is a rising edge and the second edge is a falling edge, or vice versa. As shown above, these teeth are identical, and the information related to tooth length or the duration of time / angle between the two edges is almost irrelevant. Furthermore, only one of the two edges is retained and is referred to as the valid edge or tooth signal S. n .

[0033] Therefore, as Figure 2 As shown, the measurement result output by sensor 1 indicates the tooth d1-d p d + The existence of, and including each tooth d1-d p d + tooth signal S n Tooth signal S n For example, it could be the start or rising edge of the tooth edge, or the end or falling edge of the tooth edge, as illustrated. The measurement result is a function of time. Furthermore, the tooth signal S can be extracted from the measurement output of sensor 1. n The date t was generated n And thus extract teeth d1-d p d + The date t that precedes sensitive element 3 n .

[0034] The method for determining angular position uses this sensor 1 and includes the following recursive and iterative steps. The processing unit 4, responsible for executing the method, receives the measurement output from the sensor 1 and extracts the tooth signal S from it for each tooth pass. n and the date of its occurrence t n .

[0035] This method introduces a third order récurrence. This means that the first processing needs to exist of four tooth signals S n and thus of five associated dates t n in order to determine four time intervals T n . Furthermore, during initialization, the first date t n is saved until there are five successive occurrences.

[0036] The current time interval T n is determined from the current date t n and the preceding date t n-1 .

[0037] Each time a new tooth signal S n is received, one iteration is performed and the indices change. The preceding third order quantity with index n-3 is no longer useful, the preceding second order quantity with index n-2 becomes the new preceding third order quantity, the preceding first order quantity with index n-1 becomes the new preceding second order quantity, and the current quantity with index n becomes the new preceding first order quantity. The new current quantity with index n is determined as a function of the received new tooth signal S n .

[0038] Thus, the first step consists in shifting the preceding time intervals T i according to an ordered and stepwise allocation for the values of i between n-2 and 2: T n-3 ← T n-2 , T n-2 ← T n-1 , T n-1 ← T n , with the arrow ← indicating the allocation.

[0039] During a second step, the new current time interval T n is determined. The time interval T n is the duration between the current tooth signal S n or the last received tooth signal and the preceding tooth signal S n-1 . The time interval T n is determined by calculating the difference between the corresponding date t n of the current tooth signal S n-1 and the corresponding date t n of the preceding tooth signal S n according to the formula T n-1 = t n-1 - t n .

[0040] The principle of the invention is to propose a test which makes it possible to distinguish a particular angular position, i.e. a position associated with a particular identifiable tooth. To this end, each time a new time interval T n is determined, a ratio R n is calculated as a function of the current time interval T n and of each preceding time interval.

[0041] Once the particular tooth has been identified, each time a tooth signal S n is received, the angular position of the toothed wheel 2, and therefore of the shaft to which it is fixed, is precisely known, both for the future and retroactively to the past. This makes it possible to precisely measure the angular position of the shaft of the camshaft, for example.

[0042] The angular position of the camshaft is useful for the sequencing of the engine controller 4 and, for example, for determining the date of injection.

[0043] It is also generally used to specify the angular position of the crankshaft. In particular, the camshaft sensor measures modulo 360°, whereas the engine cycle occurs over 720°. The angular position of the camshaft which performs a complete rotation in each engine cycle thus makes it possible to obtain a crankshaft angular measurement modulo 720°.

[0044] If the crankshaft sensor fails, the angular position of the camshaft also makes it possible to determine a measurement of the backup crankshaft angular position. To this end, as advantageously proposed by the invention, the method for determining the angular position of the camshaft must be autonomous and generally does not require a measurement from the crankshaft sensor.

[0045] According to one feature, the ratio Rn is calculated according to the following formula:

[0046] R n = (T n * T n-3 ) / (T n-1 * T n-2 ), where:

[0047] - R n is the ratio for the current tooth signal S n ,

[0048] - T n is the current time interval corresponding to the current tooth signal S n , T n-1 is the preceding first-order time interval for the preceding first-order tooth signal S n-1 , T n-2 is the preceding second-order time interval for the preceding second-order tooth signal S n-2 , T n-3 is the preceding third-order time interval for the preceding third-order tooth signal Sn-3 The preceding three time intervals.

[0049] Ratio R n This allows for the effective differentiation of specific teeth, namely the second tooth d2 immediately following the first tooth d1, and the first tooth d1 itself being followed by an additional tooth d+.

[0050] refer to Figure 3 The table in the table, with values ​​in the rows related to the positional and angular deviations between the crankshafts, reports the values ​​in crankshaft degrees, meaning they are obtained by measuring the positional and angular deviations of the crankshaft. The corresponding values ​​used to measure the positional and angular deviations of the camshaft, and therefore wheel 2, should be divided by 2.

[0051] Therefore, refer to Figure 3 The table below shows the ratio R calculated for an 8+1 toothed wheel, assuming a constant rotational speed. n For tooth d2, the value is 4, while for all other teeth, the value is less than or equal to 1: for d+ and d4, the value is 0.5, and for other teeth d1, d3, d5, d6, d7 and d8, the value is 1.

[0052] This significant 4-fold difference makes it easy to separate a specific tooth d2 from the others by choosing a threshold G between 1 and 4.

[0053] This significant difference also makes it possible to make a reliable distinction, including when incorporating a non-cyclic factor, taking into account possible variations in shaft speed, such as during the start-up phase. Therefore, by considering a non-cyclic factor of 1.9 or 1 / 1.9 = 0.53, the rotational speed is considered capable of varying in this relationship, affecting the time / angle conversion, and thus the ratio R. n By applying this acyclic factor to the preceding value, for tooth d... + The intervals [0.26; 0.95] were obtained for d4, [0.53; 1.9] for d1, d3, d5, d6, d7, and d8, and [2.11; 7.6] for d2, which are clearly separated from the two preceding intervals. This last, unique and clearly distinguishable interval allows for the definitive determination of the angular position.

[0054] Furthermore, by empirically selecting a threshold G between 1.9 (=1*1.9) and 2.11 (=4 / 1.9), the ratio R is... n By comparing with the threshold G, the tooth signal S can be determined. n Is the current tooth a specific tooth d2 that immediately follows tooth d1, and is tooth d1 itself immediately followed by an additional tooth d? + If the ratio R n If the value is greater than the threshold G, then the current tooth is a specific tooth d2. Conversely, if the ratio R... nIf the current tooth is less than the threshold G, then the current tooth is any other tooth d1 or d3-d. p d + One of them. Once a specific tooth d2 has been identified, the next tooth signal S... n It can be associated with the next tooth with a high degree of certainty.

[0055] The fact that a specific tooth d2 is identified on each revolution of the toothed wheel 2 allows the angular position of the toothed wheel 2 and the associated angular position of the shaft to be known. This certainty is advantageous because it allows for readjustment on each revolution, including via the tooth signal S. n The same applies in cases of loss (e.g. due to interference) or increase (e.g. due to parasitism), or when the rotational direction of the toothed wheel 2 changes.

[0056] According to another feature, the threshold G is determined by the following formula: G = k * max i＝1..p +[((Ang i -Ang i-1 )*(Ang i-4 -Ang i-3 )) / ((Ang i-2 -Ang i-1 )*(Ang i-3 -Ang i-2 In this formula, k is a non-cyclic factor, Ang i It is the angle position of the i-th tooth, where i is the angle position of all p+1 teeth d1-d. p d + (including additional teeth) + ), and max is the maximum value function.

[0057] For the exemplary 8+1 toothed wheel 2, the threshold G calculated by the aforementioned formula falls completely within the aforementioned interval [1.9; 2.11].

[0058] According to another characteristic, the non-cyclic factor k equals 0.53, which is 1 / 1.9.

[0059] According to another feature, this method can be advantageously applied to camshafts.

[0060] The present invention also relates to an engine controller that relates to this method.

[0061] The present invention also relates to a motor vehicle including such an engine controller.

[0062] The present invention has been described and illustrated in detail in the accompanying drawings and the foregoing description. The latter should be considered illustrative and given by way of example, and not intended to limit the invention merely to the description. Many variations of the embodiments are possible.

[0063] List of reference numerals

[0064] 1: Sensor,

[0065] 2: A toothed wheel,

[0066] 3: Sensitive components,

[0067] 4: Engine controller,

[0068] d1-d8, d p d + :tooth.

Claims

1. A method for determining the angular position of an shaft by means of a sensor (1), said sensor comprising a toothed wheel (2) and a sensing element (3), said toothed wheel (2) being fixed to said shaft, said toothed wheel comprising p teeth (d1 - d) distributed at equal angles. p ) and set on the last tooth (d p The additional tooth (d) between the first tooth (d1) and the second tooth (d2) + The sensitive element (3) is fixedly positioned facing the toothed wheel (2) and is capable of detecting the teeth (d1 - d). p d + ), characterized in that, The method includes the following steps: - Receive tooth signal (S) n ) and its date, - Shift the preceding time interval: T n-3 ←T n-2 T n-2 ←T n-1 T n-1 ←T n , - According to formula T n = t n - t n-1 The current tooth signal (S) is determined by the date difference. n ) and the preceding tooth signal (S) n-1 The current time interval separated by T, where T n It is the current time interval, t n It is the current tooth signal (S) n The date of ), and t n-1 It is the tooth signal (S) mentioned above. n-1 (date) - According to formula R n = (T n * T n-3 ) / (T n-1 * T n-2 ) Calculate the ratio, where R n It is used for the current tooth signal (S) n The ratio of T n It is used for the current tooth signal (S) n The current time interval, T n-1 It is used for the first-order tooth signal (S) in front. n-1 The time interval T n-2 It is used for the preceding second-order tooth signal (S) n-2 The time interval T) n-3 It is used for the preceding third-order tooth signal (S) n-3 The time interval, - Compare the ratio to a threshold; if the ratio is greater than the threshold, then the current tooth signal (S) n The first tooth (d1) corresponds to the second tooth (d2) immediately following the first tooth (d1), and the first tooth (d1) itself is immediately following the additional tooth (d2). + ).

2. The method according to the preceding claim, wherein the threshold is determined according to the following formula: Where G is the threshold, max is the maximum value function, k is the non-cyclic factor, and Ang i It represents the angle position of the i-th tooth, where i is the angle position of all p+1 teeth (d1 - d). p d + ), including additional teeth (d + ).

3. The method according to the preceding claim, wherein the non-cyclic factor k is equal to 0.

53.

4. The method according to any one of the preceding claims, applied to a camshaft.

5. The method according to claim 1, wherein, The additional tooth (d) + ) set on the last tooth (d p The middle part between the first tooth (d1) and the first tooth (d2).

6. An engine controller (4), characterized in that, The engine controller includes a processing unit, which is provided with means for implementing the method as described in any one of the preceding claims.

7. A motor vehicle, characterized in that, The motor vehicle includes an engine controller as described in the preceding claim.

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