阅读说明：本技术 凸轮轴传感器的处理方法 (Processing method of camshaft sensor ) 是由 P·祖博夫 于 2019-07-11 设计创作，主要内容包括：本发明涉及一种用于凸轮轴传感器(1)的设备和处理方法,该类型的凸轮轴传感器包括带齿的凸轮轴轮(2)和能够检测齿沿的相对的感测元件(3),该处理方法包括以下步骤：通过所述感测元件检测新的齿沿(k)；为新的齿沿(k)计算凸轮轴轮(2)的转速(Wk)；与由所述感测元件检测的前一齿沿(k-1)的凸轮轴轮的转速(Wk-1)进行比较；如果凸轮轴轮(2)的转速(Wk)在新的齿沿(k)和前一齿沿(k-1)之间变化较小,则新的齿沿(k)被验证有效,否则新的齿沿(k)被拒绝。(The invention relates to a device and a processing method for a camshaft sensor (1) of the type comprising a toothed camshaft wheel (2) and an opposite sensing element (3) capable of detecting the tooth edges, the processing method comprising the steps of: detecting a new tooth edge (k) by the sensing element; calculating the rotational speed (Wk) of the camshaft wheel (2) for the new tooth flank (k); comparing the rotational speed (Wk-1) of the camshaft wheel with the previous tooth edge (k-1) detected by the sensing element; if the rotational speed (Wk) of the camshaft wheel (2) varies less between the new tooth flank (k) and the preceding tooth flank (k-1), the new tooth flank (k) is validated, otherwise the new tooth flank (k) is rejected.)

1. A processing method for a camshaft sensor (1) of the type comprising a toothed camshaft wheel (2) and an opposite sensing element (3) able to detect the tooth edges, characterized in that it comprises the following steps:

detecting a new tooth edge (k) by the sensing element;

calculating the rotational speed (Wk) of the camshaft wheel (2) for the new tooth flank (k);

comparing the rotational speed (Wk-1) of the camshaft wheel (3) of the preceding tooth flank (k-1) detected by the sensing element;

if the rotational speed (Wk) of the camshaft wheel (2) varies less between the new tooth flank (k) and the preceding tooth flank (k-1), the new tooth flank (k) is validated, otherwise the new tooth flank (k) is rejected.

2. Method according to claim 1, wherein the rotational speed (Wk) is calculated by means of the ratio of the angle (Ak) by which the new tooth flank (k) is separated from the preceding tooth flank (k-1) to the period (Tk) by which the new tooth flank (k) is separated from the preceding tooth flank (k-1).

3. Method according to claim 2, wherein the angle (Ak, Ak-1) is taken to be equal to its theoretical value.

4. Method according to any one of claims 1 or 3, wherein the variation of the rotation speed (Wk) is smaller if the ratio of the rotation speed (Wk) of the new tooth flank (k) to the rotation speed (Wk-1) of the previous tooth flank (k-1) is comprised between a first threshold (S1) and a second threshold (S2), preferably the first threshold (S1) and the second threshold (S2) are opposite to each other.

5. Method according to claim 4, wherein said second threshold (S2) is comprised between upper limits 1 and 10, preferably between 1 and 3, more preferably between 1 and 1.5, more preferably equal to 1.2.

6. Method according to any of claims 1 to 5, wherein the change in the rotational speed (Wk) is smaller if the absolute value of the difference between the rotational speed (Wk) of the new tooth flank (k) and the rotational speed (Wk-1) of the preceding tooth flank (k-1) is below a third threshold value (S3).

7. Method according to claim 6, wherein said third threshold (S3) is comprised between 200 and 1000 revolutions per minute of the crankshaft, preferably substantially equal to 500 revolutions per minute of the crankshaft.

8. A device (4) capable of implementing the method according to any one of the preceding claims.

Technical Field

The present invention relates to the field of measurement, and more particularly to the field of camshaft sensors. The invention relates in particular to processing the reliability of the measurement signal by confirming the validity of the tooth edges.

Background

In automobiles, it is known to use a camshaft sensor to accurately know the angular position of a camshaft, particularly to perform engine control.

As shown in fig. 1, such a camshaft sensor 1 generally includes a camshaft wheel 2 that is rotatably connected with a camshaft. The camshaft wheel 2 has a known specific profile. The profile typically includes a reduced number of teeth, typically four, which are irregular in their angular extent and spacing. The camshaft sensor 1 further comprises a sensing element 3 fixed relative to the engine block, which sensing element 3 is capable of detecting a specific profile and is for this purpose arranged opposite the periphery of the camshaft wheel 2. According to one embodiment, the camshaft wheel 2 is metallic and the sensing element 3 is able to detect the metal like a hall effect sensor. Thus, a rising tooth edge (beginning of tooth) or a falling tooth edge (end of tooth) can be detected. Because of the small number of teeth, both the rising and falling edges are utilized. Advantageously, the length of the teeth and the length of the interdental spaces are different. This makes it possible to identify the camshaft wheel in a known manner, typically by means of a shape identification method, over several camshaft revolutions. The identification includes determining which tooth is seen by the sensing element 3. This identification makes it possible to know to which tooth the tooth edge belongs when the sensing element 3 detects the tooth edge. This identification thus enables the angular position of the camshaft to be known accurately, at least during the detection of the tooth edges.

In order to maintain the angular setting provided by this identification, all the tooth flanks must be detected, and only the tooth flanks that would otherwise risk offsetting the angular viewing position of the camshaft are detected.

The sensing element 3 may be spoofed in at least two known situations. In the first case, the electrical interference may cause a peak in the measurement signal, which may be confused with the tooth edge. In the second case, the camshaft reverses direction of rotation at least once. Then, the sensing element 3 detects a tooth edge which is not the expected next tooth edge, but is detected again and is the opposite type of immediately preceding detected tooth edge (when the rotation is reversed, a tooth edge of the rising type in one direction of rotation is detected as a tooth edge of the falling type, and vice versa).

In order to discriminate such abnormal tooth edges, various methods of processing signals from the sensing element 3 are known.

The first method is to continue to use the method employed in the identification process to identify the camshaft wheel 2 in order to verify each tooth edge.

FR 2991720 proposes another method. It uses the tooth period history (the period between the rising and falling edges) to construct the time index and the angle index. If these two criteria are compared and found to be within a given tolerance, the tooth edge is verified to be valid.

Another method is to measure the angular position of the tooth edges of the camshaft wheel 2 by means of a crankshaft sensor. If the measured value corresponds to the theoretical value, possibly specifying a tolerance, the tooth edge is validated.

All of these methods based on time and/or angle indices have a common disadvantage. In order to tolerate large speed variations of the camshaft, it is necessary to greatly enlarge the acceptance tolerances. Furthermore, the criteria used must take into account short and long teeth or interdental spaces. The widened tolerance for accommodating short teeth or interdental gaps becomes a very wide tolerance for long teeth or interdental gaps.

To account for speed variations, a 200% tolerance is typically used. However, the length difference between the interference peak and the teeth in the range of 20 ° is only 33%. Therefore, it is possible to confuse the interference peak with the small tooth. In some configurations, subsequent tooth edges may be confused with the last tooth edge detected, which is also detected in the opposite direction. As a result, one or more of the methods lose their discrimination ability.

Disclosure of Invention

The object of the present invention is to propose a processing method that allows the camshaft sensor to verify that the detection of a tooth edge seen on its signal corresponds well to the subsequent tooth edge.

This object is achieved by using a new test that is applicable to each detection of a tooth edge and makes it possible to verify whether said tooth edge is valid. This test may be used instead of or in addition to the test described above.

The invention relates to a processing method for a camshaft sensor of the type comprising a toothed camshaft wheel and an opposite sensing element capable of detecting the tooth edges, comprising the following steps:

detecting a new tooth edge by the sensing element;

calculating the rotational speed of the camshaft wheel for the new tooth edge;

comparing with the rotational speed of the camshaft wheel of the previous tooth edge detected by the sensing element;

if the camshaft wheel speed variation between the new tooth flank and the previous tooth flank is small, the new tooth flank is validated, otherwise the new tooth flank is rejected.

According to another feature, the rotational speed is calculated by the ratio of the angle by which the new tooth edge is separated from the previous tooth edge to the period by which the new tooth edge is separated from the previous tooth edge.

According to another feature, the angle is taken to be equal to its theoretical value.

According to another feature, the variation of the rotation speed is small if the ratio of the rotation speed of the new tooth flank to the rotation speed of the preceding tooth flank is comprised between a first threshold and a second threshold, preferably opposite to each other.

According to another feature, the second threshold value is comprised between 1 and 10, preferably between 1 and 3, more preferably between 1 and 1.5, more preferably equal to 1.2.

According to another feature, the variation in the rotation speed is smaller if the absolute value of the difference between the rotation speed of the new tooth flank and the rotation speed of the preceding tooth flank is lower than a third threshold value.

According to another feature, the third threshold value is comprised between 200 and 1000 revolutions per minute of the crankshaft, preferably substantially equal to 500 revolutions per minute of the crankshaft.

The invention also relates to a device capable of implementing the method of any one of the preceding claims.

Drawings

Other characteristics and innovative advantages of the invention will become apparent from reading the following description, provided by way of non-limiting example and with reference to the accompanying drawings, in which:

figure 1 already described shows the principle of a camshaft sensor,

FIG. 2 shows a camshaft signal that is validated on the basis of time and tooth edge,

fig. 3 shows the same camshaft signal, which is based on time and on the validation of the tooth edges.

Detailed Description

For purposes of clarity, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

The method according to the invention enables the signal from the camshaft sensor 1 to be processed to determine whether a new tooth edge is valid, making the measurement more robust.

Fig. 2 and 3 show such a measurement signal from the camshaft sensor 1. This signal substantially reproduces the profile of the camshaft wheel 2. The presented signal includes 4 teeth D1-D4 based on time t. A disturbance P has been introduced that may be confused with a tooth edge.

In order to verify the tooth edges, the processing method comprises the following steps. In a first step, a new tooth edge is detected. This new tooth edge is labeled k in an opposite manner. The leading tooth edge is labeled k-1 and the trailing tooth edge is labeled k + 1. Also, various numbers are marked on the tooth edge. Wk is the rotational speed determined using information known when detecting the tooth edge k. Tk is the "tooth period" or time that elapses between the previous tooth edge k-1 and the new tooth edge k. Ak is the angle between the previous tooth edge k-1 and the new tooth edge k.

For a new tooth flank k, the rotational speed Wk of the camshaft wheel 2 is calculated in a second step.

In a third step, the rotational speed Wk of the camshaft wheel 2 is compared with the rotational speed Wk-1 of the camshaft wheel 2 calculated for the preceding tooth flank k-1 during the preceding verification of the preceding tooth flank k-1.

In particular, the rotational speed of the camshaft and the rotational speed of the camshaft wheel 2 have a certain regularity due to the limited acceleration. Thus, the time interval that elapses between the previous tooth edge k-1 and the new tooth edge k is very short, and the speed does not vary very much between the two tooth edges k-1, k. Thus, by analyzing the change in the rotational speed Wk of the camshaft wheel 2 between the previous tooth flank k-1 and the new tooth flank k, it can be verified whether this change is small enough to be reasonable, since this is possible in terms of mechanical constraints. A small change in the rotational speed Wk allows a new tooth flank k to be verified. In contrast, too large a change may cause a new tooth edge k to be verified invalid.

The tooth edge with too great a change in speed does not correspond to the effective tooth edge. What is involved is the interference or edge observed after reversal of the direction of rotation of the camshaft. It can therefore be ignored without any consequence.

The instantaneous velocity Wk of camshaft wheel 2 at new tooth flank k is calculated by correlating the angle Ak separating the previous tooth flank k-1 and the new tooth flank k with the period Tk separating the previous tooth flank k-1 and the new tooth flank k.

The period Tk or tooth period is usually extracted from the signal of the camshaft sensor 2 by measuring the time distance between the preceding tooth edge k-1 and the new tooth edge k.

The angle Ak is taken to be equal to its theoretical value. This theoretical value is known because the camshaft wheel 2 has been identified beforehand. Thus, as with the previous tooth edge k-1, the new tooth edge k is identified and therefore their angular distance.

This is an advantage of the method according to the invention, since it does not use a crankshaft sensor. Furthermore, the method according to the invention can be implemented in a degraded mode in the event of a failure of the crankshaft sensor.

It should be noted that time Tk is the time that the previous tooth edge k-1 is separated from the new tooth edge k that is effectively detected, whether or not this new tooth edge is effective. In contrast, angle Ak is the angle of the leading tooth edge k-1 from the theoretical trailing tooth edge. With a valid new tooth edge k, there is coincidence. However, in the case of an invalid new tooth flank k, occurring earlier or later than expected, the angle Ak is the angle of separation of the previous tooth flank k-1 from the normal expected tooth flank. In the case where a new tooth flank k occurs earlier, the tooth flank that is usually expected is the tooth flank k + 1. In the case of a later occurrence of a new tooth edge k, the normally expected tooth edge is not present in the measurement signal.

Referring now to fig. 2, the method is applied to the effective tooth edge. The new tooth edge k is the falling edge of tooth D3. The detection of a new tooth edge k by the camshaft sensor 1 enables the determination of the tooth period Tk, that is to say the period in which the new tooth edge k (here the falling edge of the tooth D3) is separated from the preceding tooth edge k-1 (here the rising edge of the tooth D3). The corresponding angle Ak is known: this is the angular length of tooth D3. The velocity Wk can then be calculated by correlating the angle Ak with the time Tk, possibly assigned a scaling factor F, that is to say according to the formula Wk = F.

The factor F advantageously allows the velocity Wk to be expressed in units of expression such as radians/sec-1 or revolutions/min-1. It can be said that the angles are represented by the crankshaft frame of reference. Such references are commonly used as references in automobiles to distinguish them from camshafts that rotate at half speed.

This velocity Wk may then be compared to the velocity Wk-1 previously determined for the previous tooth flank k-1. It is found here that the speed variation between the two teeth along k-1 and k is small. Thus, the falling edge of tooth D3 is verified to be valid.

It should be noted that the velocity Wk-1 previously determined for the preceding tooth edge k-1 refers to the velocity determined for the immediately preceding tooth edge, but in particular the velocity determined for the tooth edge that is verified to be valid. Throughout the method, when a tooth edge is verified to be invalid and rejected, it is considered to have never existed. The same applies to the values of time Tk and angle Ak.

Referring now to fig. 3, the method is applied to an invalid tooth edge, here an edge artificially induced by an electrical disturbance P. Alternatively, the ineffective tooth flank may be a tooth flank generated by a change in the rotational direction of the camshaft, and may be generated earlier or later than the intended tooth flank. The new tooth edge k is here the disturbance P. The detection of a new tooth flank k by the camshaft sensor 1 enables the tooth period Tk to be determined, that is to say the period in which the new tooth flank k (here the disturbance P) is separated from the preceding tooth flank k-1 (here the falling flank of the tooth D3). The corresponding angle Ak is known. However, the new theoretically expected tooth edge is the rising edge of tooth 4. Further, the angle Ak is the angle between the falling edge of tooth D3 and the rising edge of tooth D4. It does not correspond to the period Tk. The velocity Wk can then be calculated by correlating the angle Ak with the time Tk.

This new speed Wk may then be compared to the speed previously determined for the previous tooth edge. Here, the non-correspondence between the angle Ak and the tooth period Tk results in an excessive change in velocity between the two teeth along k-1 and k. Therefore, the interference P is not verified to be valid.

At least two different tests can determine whether the change in the rotational speed Wk is small enough to make such a change reasonable.

According to a first test, the ratio of the rotation speed Wk of the new tooth flank k to the rotation speed Wk-1 of the previous tooth flank k-1 is determined. If the ratio is comprised between the first threshold S1 and the second threshold S2, the change in speed is small, S1 < Wk/Wk-1 < S2. Preferably, the first threshold value S1 and the second threshold value S2 are opposite to each other. The formula then becomes 1/S2 < Wk/Wk-1 < S2.

The second threshold S2 is comprised between the upper limits 1 and 10. Preferably, it is comprised between 1 and 3. More preferably, it is comprised between 1 and 1.5. A value of 1.2 is preferred, that is to say a speed variation tolerance between the two edges of 20%.

According to the second test, in addition to or instead of the first test, if the absolute value of the difference between the rotation speed Wk of the new tooth flank k and the rotation speed Wk-1 of the previous tooth flank k-1 is lower than the third threshold value S3, that is, Abs (Wk-1) < S3, the change in the rotation speed Wk is small.

Advantageously, the third threshold value S3 is comprised between 200 and 1000 revolutions per minute of the crankshaft, preferably substantially equal to 500 revolutions per minute of the crankshaft. For the second test, the velocities Wk, Wk-1 are expressed in the same units as the third threshold S3.

It should be noted that the thresholds S1, S2, S3 may be modified according to the shape of the camshaft wheels and the relative distribution of the teeth and notches in order to increase or decrease the tolerance.

The invention also relates to a device 4 capable of implementing the method according to any one of the preceding embodiments. As shown in fig. 1, such a device 4 is connected to the sensing element 3 of the camshaft sensor 1. It performs the above-described method to process the signal from the camshaft sensor 1. It can therefore convey more robust camshaft information to the user 5 (e.g. engine control).

The invention has been described above by way of example. It is understood that a person skilled in the art is capable of implementing different variant embodiments of the invention, for example by combining various features described above, alone or in combination, without departing from the scope of the invention.