DE102014112543A1 - Method for determining the position of a camshaft of an internal combustion engine and internal combustion engine for carrying out such a method - Google Patents

Abstract

The invention relates to a method for determining the position of a camshaft of an internal combustion engine, in particular an internal combustion engine used in a motor vehicle. Furthermore, the invention relates to an internal combustion engine for carrying out such a method. The invention has for its object to provide a method for determining the position of a camshaft of an internal combustion engine and an internal combustion engine for performing such a method available, which are simple and inexpensive to implement and as precise as possible determination of the camshaft position at least in a motion portion of the Enable camshaft movement. According to a method according to the invention for determining the position of a camshaft of an internal combustion engine, the distance to a first cam (34) of the camshaft is measured with the aid of at least one first sensor (32) arranged at a first position and determined on the basis of the first sensor (32) Distance the absolute position of the camshaft is determined. The method is particularly suitable for internal combustion engines with camshaft used as a valve train, the cam usually have a continuous outer contour with a circular arc Nullhubabschnitt (36) and a deviating from the zero stroke section (36) Arbeitshubabschnitt (38). By measuring the distance from a first sensor (32) to the cam, with exactly two measurements, the exact position can be determined at least in the motion subregion in which the distance from the first sensor (32) to the working stroke section (38) is measured the camshaft can be determined.

Description

The invention relates to a method for determining the position of a camshaft of an internal combustion engine, in particular an internal combustion engine used in a motor vehicle. Furthermore, the invention relates to an internal combustion engine for carrying out such a method.

To model the combustion chamber filling of an internal combustion engine, the knowledge of the exact angular position of the cams of the gas exchange valves is of great importance. This applies in particular to internal combustion engines in which the phase of at least one camshaft relative to the crankshaft is adjustable. In most internal combustion engines donor wheels are rotatably connected to the camshaft or crankshaft of the internal combustion engine and detects the position of the encoder wheel via at least one sensor. Frequently encountered camshaft sensor wheels (so-called quick-start sensor wheels) have a limited number of teeth distributed over the circumference, usually four teeth with four gaps between the teeth.

Out DE 103 16 126 A1 it is also known in a body rotatable about an axis, such. As the encoder wheel of a camshaft to increase the resolution for detecting the angular position of the body in that the distance between a distance sensor and the rotatable body for each predetermined angular segment of the rotatable body is different.

Out DE 10 2005 021 300 B4 a rotary encoder with at least one rotatable object and at least one sensor element is known, wherein the sensor element outputs an analog signal in dependence on the rotational position of the rotatable object relative to the sensor element. In this case, a conductivity, a dielectric constant, a magnetizability, a magnetic moment and / or a distance between the sensor element and a circumferential surface of the rotatable object, via which a magnetic, inductive and / or capacitive interaction with the sensor element, angle-dependent with respect to continuously changing an axis of rotation of the rotatable object between 0 ° and 360 ° such that the sensor element outputs the signal having a desired waveform as the rotatable object rotates relative to the sensor element, the sensor element including a transducer element and an exciter system.

The invention has for its object to provide a method for determining the position of a camshaft of an internal combustion engine and an internal combustion engine for performing such a method available, which are simple and inexpensive to implement and as precise as possible determination of the camshaft position at least in a motion portion of the Enable camshaft movement.

The object is achieved according to the invention with the features of the independent claims. Further practical embodiments of the invention are described in the subclaims.

In accordance with a method according to the invention for determining the position of a camshaft of an internal combustion engine, the distance to a first cam of the camshaft is measured with the aid of at least one first sensor arranged at a first position, and the absolute position of the camshaft is determined on the basis of the distance determined with the first sensor. By the term cams are meant exclusively cams for actuating gas exchange valves of the internal combustion engine. The method is particularly suitable for internal combustion engines with camshaft used as a valve train, the cam usually have a continuous outer contour with a circular arc Nullhubabschnitt and deviating from the Nullhubabschnitt Arbeitshubabschnitt. By measuring the distance from a first sensor to the cam, the exact position of the camshaft can be determined at least in the motion subregion in which the distance from the first sensor to the working stroke section is measured with exactly two measurements. An advantage of the method according to the invention is in particular that the measurement takes place on a cam itself and thus is very accurate, in particular with respect to this cam. The measurement is thus independent of any manufacturing tolerances and / or mounting tolerances of a separately manufactured or formed on the camshaft camshaft sensor wheel. In most camshafts, the working stroke portion of a cam extends over about 60 ° to 150 ° of the circumference of the cam, more preferably over 80 ° to 120 °. As a result, with the method described above at least 1/6 (at 60 °) of the circumference within a very short time the position of the camshaft is very accurately determined. The use of only one sensor and the associated exact position determination and continuous tracking of the position of the camshaft in a motion portion of the camshaft can be sufficient with a suitable arrangement of the sensor, in particular for 1-cylinder internal combustion engines.

The calculation of the combustion chamber filling takes place in the engine control units of many internal combustion engines usually in an angle-synchronized manner before the charge-exchange TDC, ie once per engine revolution. If at an internal combustion engine For each cylinder, a sensor directed to a cam of the cylinder is used, this sensor can be arranged geometrically so that the current camshaft position can be determined for each cylinder shortly before the calculation of the filling. With such an arrangement and a corresponding method, a precise modeling of the combustion chamber filling can be carried out in a simple and cost-effective manner. Since the exact position of the charge cycle gas exchange valve is known, the combustion chamber filling can be modeled each cylinder individually.

In a practical further development of the method according to the invention, the distance to the first cam or to a second cam is measured with the aid of a second sensor arranged at a second position, and the absolute position of the distance is determined on the basis of the distances determined with the first sensor and / or with the second sensor Camshaft determined. In this respect, the arrangement of a second sensor must be distinguished on the one hand such that the distance to the first cam can also be measured or, on the other hand, such that the distance to a second cam can be measured. In both cases, it is preferable if the first sensor and the second sensor are positioned such that the motion subregions in which the distance to working stroke sections is measured are different motion subregions, so that overall a large, resulting movement range is achieved. Subarea results in which measured the distance to a working stroke and the position of the camshaft therefore on the basis of this measurement (and possibly a temporally very short distance following measurement) can be determined very accurately. An advantage of a measurement with two sensors on two different cams is that the position of the sensors selected similarly or even selected identical and the attachment of the sensors can be done so far analog. Another advantage is that it is sufficient if the first cam and the second cam are accessible only in a limited area.

In a further practical embodiment of the method according to the invention, the distance to the first cam, to a second cam or to a third cam is measured with the aid of a third sensor arranged at a third position and due to the distance with the first sensor, with the second sensor and with the third sensor detected distances determines the absolute position of the camshaft. The foregoing regarding the second sensor applies to the third sensor accordingly. In addition, it should be noted that with the use of three sensors, a working stroke range of at least 120 ° (with respect to the camshaft) and a suitable arrangement of the sensors, a continuous, exact position detection of the camshaft is possible.

If at least three sensors are used in the method according to the invention, the absolute position of the camshaft in the complete range of movement of the camshaft movement can be determined continuously or quasi-continuously. With a quasi-continuous determination, in particular, a determination of the position at equally spaced intervals (eg every 10 ms) or in distances predetermined by the position of the crankshaft or camshaft (eg every 5 ° CA or every 5 ° NW ) meant. By reducing the time intervals to a few milliseconds (ms) or less, an approximately continuous determination of the position of the crankshaft can take place.

By using a fourth sensor, a fifth sensor or other sensors, a quasi-continuous or continuous determination of the position of the camshaft can take place even if space constrained only sensors in a very limited range and / or if the working stroke is less than 120 ° (relative to the circumference of the camshaft).

In a further practical embodiment of the method according to the invention, the absolute position of the camshaft and / or the relative rotation of the camshaft with respect to a crankshaft of the internal combustion engine is determined with additional consideration of the position of the crankshaft of the internal combustion engine and / or evaluation of other signals of other motorsynchron driven elements. In order to detect the position of a crankshaft, in particular a signal of a sensor wheel sensor directed at a crankshaft sensor wheel is evaluated. As crankshaft-donor wheels usually relatively high-resolution wheels are used, which are rotatably connected to the crankshaft and formed on this. Conventional donor wheels have about 60 teeth distributed over the circumference and a gap (usually generated by one or two "missing" teeth), so that the position of the camshaft on the teeth can always be specified relatively accurately. A particular advantage of the method according to the invention is that taking into account the position of the crankshaft, in particular with the aid of a crankshaft sensor wheel, and taking into account the absolute position of the camshaft, in particular by means of one of the methods described above, also the relative position of the camshaft determined is. This is known in particular for internal combustion engines with phase-adjustable camshafts. With regard to the evaluation of other signals of other motor-driven elements, reference is made in particular to the following possibilities:

Possibility Number 1

Currently, in some internal combustion engines, especially in Otto turbo engines, the high-pressure fuel pump is driven by the camshaft. This can be done for example in 4-cylinder internal combustion engines via a 4-fold cam. The position of this 4-way cam can be used as a supplemental, continuous signal to determine the absolute position of the camshaft and / or the relative rotation of the camshaft relative to a crankshaft of the internal combustion engine. In combination with the distance signal detected via one or more sensors to one or more cams of the gas exchange valves, a particularly high accuracy and a larger range can be achieved, in which the absolute and / or relative position of the camshaft can be determined. The method can also be used to determine if a cylinder is currently in the charge cycle OT (LOT) or in the ignition TDC (ZOT). A determination of the position of the camshaft can be possible in this case even when the engine is stationary, but not only on the 4-speed cam.

Option 2

Camshafts are sometimes manufactured as built-up camshafts as splines with deferred cam pieces. Such a spline can be used to detect supplemental signals. In this case, no continuous, additional signal is available, but further, additional individual signals per camshaft revolution. A determination of the position of the camshaft with the engine stopped is possible in this case in individual positions.

The invention also relates to an internal combustion engine having at least one camshaft, wherein at least one first sensor is arranged at a first position such that the distance from the first sensor to a first cam of the camshaft is measurable, wherein the sensor is functionally connected to an evaluation unit and the evaluation unit is designed to determine the position of the camshaft on the basis of at least one distance measured with the first sensor relative to the first cam. The evaluation unit is preferably an engine control unit.

In a further practical embodiment of an internal combustion engine according to the invention, a second sensor is arranged at a second position such that the distance from the second sensor to the first cam or to a second cam is measurable, and the evaluation unit for determining the position of the camshaft on the basis at least one measured with the first sensor distance and / or at least one measured with the second sensor distance is formed.

In a further practical embodiment of an internal combustion engine according to the invention, a third sensor is arranged at a third position such that the distance from the third sensor to the first cam or to the second cam or to a third cam is measurable, and the evaluation unit for determining the position the camshaft is formed on the basis of at least one distance measured with the first sensor and / or at least one distance measured with the second sensor and / or a distance measured with the third sensor.

In general, it can be said that internal combustion engines according to the invention are preferred for simple and precise modeling of the combustion chamber filling, in which there is at least one sensor for each cylinder, which is arranged in such a way that immediately before calculation of the combustion chamber filling, especially with angle-synchronous calculation of the combustion chamber filling Cylinder, the position of the camshaft with the help of this sensor can be clearly determined. The number of sensors required for this depends, in particular, on the geometric design of the cams and on the possibility of phase adjustment of the camshaft relative to the crankshaft.

It is also preferred if, in an internal combustion engine according to the invention with at least one crankshaft, the evaluation unit is functionally connected to a device which detects the absolute position of the crankshaft. This can be, in particular, a crankshaft sensor wheel sensor directed at a crankshaft-transmitting wheel of the at least one crankshaft of the internal combustion engine. In this case, the evaluation unit is preferred for determining the absolute position of the camshaft and / or the relative position of the camshaft relative to the crankshaft on the basis of at least one distance measured with the first sensor and / or at least one distance measured with the second sensor and / or a measured distance with the third sensor and / or a signal measured by the crankshaft sensor wheel sensor.

Further practical embodiments and advantages of the invention are described below in conjunction with the drawings. Show it:

1 a schematic representation of a crankshaft transducer wheel and a quick-start camshaft sensor wheel a Internal combustion engine according to the prior art as well as with sensors directed at these sensor wheels determined pulse-time diagrams,

2 a crankshaft sensor wheel and an arrangement of a sensor of a first embodiment of an internal combustion engine according to the invention,

3 a crankshaft sensor wheel and an arrangement of two sensors according to a second embodiment of an internal combustion engine according to the invention,

4 a crankshaft sensor wheel and an arrangement of three sensors according to a third embodiment of an internal combustion engine according to the invention,

5 a crankshaft sensor wheel and an arrangement of three sensors according to a fourth embodiment of an internal combustion engine according to the invention,

6 a crankshaft sensor wheel and an arrangement of a sensor according to the first embodiment, together with the arrangement of a 4-way cam and

7 a crankshaft sensor wheel and an arrangement of a sensor according to the first embodiment, together with the arrangement of a spline shaft.

1 shows a schematic representation of a crankshaft sensor wheel 10 and a quick start camshaft sensor wheel 12 a not shown internal combustion engine according to the prior art. The direction of rotation of the crankshaft sensor wheel 10 is with the arrow 14 marked, the direction of rotation of the quick-start camshaft sensor wheel 12 is with the arrow 16 characterized. Left next to the donor wheels 10 . 12 are a pulse-time diagram 18 for the crankshaft sensor wheel 10 and a pulse-time diagram 20 for the quick-start camshaft sensor wheel 12 shown. These pulse-time diagrams 18 . 20 arise from on the donor wheels 10 . 12 directed sensors 22 . 24 , by means of which pulses during the rotation of the encoder wheels 10 . 12 measured and recorded in particular via an engine control unit (not shown).

With the specifications ZOT 4, ZOT 2, ZOT 1, ZOT 3 in the pulse-time diagram 18 of the crankshaft sensor wheel 10 Reference is made to ignition TDCs of four different cylinders of a four-cylinder gasoline engine.

The quick start camshaft sensor wheel 12 includes four teeth 28 and four gaps 30 , Like from a synopsis of the two pulse-time diagrams 18 . 20 and especially at the two gaps 26 of the crankshaft sensor wheel 10 can be seen, the crankshaft sensor wheel rotates 10 together with the crankshaft (not shown) twice as fast as the quick start camshaft sender wheel 12 together with the camshaft (not shown), ie two revolutions (720 °) of the crankshaft sensor wheel 10 correspond to one revolution (360 °) of the quick-start camshaft sender wheel 12 ,

By the name Δφ in 1 as well as in the 2 to 5 should be visualized that the camshaft is phase-adjustable relative to the crankshaft.

Due to the low number of teeth 28 on the quick start camshaft sender wheel 12 results in only a rough resolution of the quick-start camshaft sensor wheel 12 , resulting in low accuracy results. The absolute position of the camshaft and the relative position of the camshaft to the crankshaft is therefore accurately determined only at a few, certain times during a revolution of the crankshaft. Particularly large inaccuracies in the determination of the relative orientation of the camshaft to the crankshaft arise in particular during phase shifts at high speed.

The 2 to 5 show four different embodiments of a respective identical crankshaft sensor wheel 10 with various sensor arrangements of an internal combustion engine according to the invention. To identify the elements in the 2 to 5 For identical or at least functionally identical elements the same reference numerals as in 1 used. On the representation of one on the crankshaft sensor wheel 10 directed sensor (reference numeral 22 in 1 ) was in the 2 to 5 omitted in the context of a simplified representation.

2 shows an arrangement of a first sensor 32 , by means of which the distance to a first cam 34 the camshaft (not shown) is measured. The direction of rotation of the cam is with the arrow 16 characterized. The cam 34 has an arcuate Nullhubabschnitt 36 and one steplessly (and thus in the mathematical sense with a steady transition) to this Nullhubabschnitt 36 subsequent working stroke section 38 on. In the zero lift section 36 indicates the distance from the axis of rotation 40 the camshaft to the outer contour of the cam 34 constant value r _min on. In the working stroke section, the distance initially increases to a maximum value r _max and decreases then again in the same way to the value r _min from. The distance r measured by the sensor over time t is in a path-time diagram 42 in 2 shown. The resulting curves in the range from r _min to r _max and back to r _min 44 the path-time diagram 42 extend over a crankshaft angle of 240 °. This corresponds to a camshaft angle of 120 °. In the range extending over 240.degree. Crankshaft angle either the exact absolute position of the camshaft can be detected either by two measurements within a very short time, the two measurements being required to determine if the value measured first is in an "increasing" range. Value r or with "decreasing" value r. Alternatively, taking into account the with the crankshaft sensor wheel 10 can be determined absolute position of the crankshaft by measuring only one value r the absolute position of the camshaft, if a value r is determined during the measurement, which is greater than r _min and less than r _max and due to the usually limited relative Phasenverstellmöglichkeit between crankshaft and camshaft clearly indicates in which (of the two possible positions) the camshaft is currently located. When measuring the value r _max , the position of the camshaft is unique. When measuring the value r _min , the absolute position in the in 2 embodiment shown not clearly determined.

3 shows an improved embodiment, which differs from the in 2 described embodiment insofar as with the aid of a second sensor 46 also the distance to the first cam 34 the camshaft (not shown) is measured. Here are the sensors 32 . 46 on opposite sides of the cam 34 arranged. This results in 3 about areas 48 other curves, which in turn extend over 240 ° crankshaft angle. Thus, according to the in 2 shown embodiment already over a range of about 480 ° crankshaft angle (from a total of 720 ° crankshaft angle) within a very short time the absolute and relative position of the camshaft are determined without the camshaft to be provided with additional rotatable bodies such as donor wheels or the like.

In 4 a further improved embodiment compared to the embodiments described above is shown. This is different from the one in 3 illustrated embodiment insofar as using a third sensor 50 also the distance to the first cam 34 the camshaft (not shown) is measured and as the sensors 32 . 46 . 50 are offset by 120 ° to each other. This results in 4 in the fields of 52 again more curves, which in turn extend over 240 ° crankshaft angle. Due to the arrangement of the sensors 32 . 46 . 50 rows are lined up 44 . 48 . 52 continuously together and thus cover two crankshaft revolutions (720 ° CA) completely (corresponds to one camshaft revolution (360 ° NW)). Thus results during one camshaft revolution - apart from three points 54 , in which all measured values are r _min - at any time a different combination of measured values. With this arrangement, therefore, the absolute position of the camshaft can be determined at (nearly) every point in time by simple measurement and comparison of the measured values with a correlation table stored in an engine control unit or, alternatively, a calculation model.

At the in 5 The third embodiment shown has been the second sensor 46 arranged so that it is the distance to a second cam 56 measures. In the 5 The arrangement shown is chosen so that the same path-time diagram 42 as with the in 4 shown embodiment.

The evaluation described above with the first sensor 32 , the second sensor 46 and / or the third sensor 50 and possibly taking into account the absolute position of the crankshaft takes place in the in 2 to 5 shown embodiments of the engine control unit (not shown).

The 6 and 7 show two further embodiments of inventive internal combustion engines on the basis of in 2 shown, first embodiment.

At the in 6 In addition, as shown in the embodiment, the signal of a 4-fold cam 58 evaluated by means of a not shown, another sensor. The way-time signal 60 of the 4-way cam, which oscillates continuously between n _max and n _min , is in 6 shown to the left of the 4-way cam.

At the in 7 In addition, the signal of a splined shaft is additionally shown 62 evaluated by means of a not shown, another sensor. The way-time signal 64 the spline 62 , which is a step-shaped signal changing between k _max and k _min , is in 7 next to the splined shaft 62 shown.

The features of the invention disclosed in the present description, in the drawings and in the claims may be essential both individually and in any desired combinations for the realization of the invention in its various embodiments. The invention is not limited to the described embodiments limited. It can be varied within the scope of the claims and taking into account the knowledge of the person skilled in the art.

In this regard, particular reference is made to the possibilities of using fourth and / or further sensors directed at cams, measuring the distance to a third and / or further cam and / or selecting the distance of individual sensors to the zero-stroke range of the corresponding cam to be different ( eg in order to take account of a specific installation space situation, to vary the values and / or to make efficient use of installation space).

LIST OF REFERENCE NUMBERS

10

Crankshaft sensor wheel

12

Quick Start camshaft sensor wheel

14

Arrow (to indicate the direction of rotation of the KW encoder wheel)

16

Arrow (to indicate the direction of rotation of the NW quick-start sender wheel / cam)

18

Pulse-time diagram

20

Pulse-time diagram

22

sensor

24

sensor

26

Gaps

28

teeth

30

Gaps

32

first sensor

34

first cam

36

Nullhubabschnitt

38

working stroke

40

axis of rotation

42

Path-time diagram

44

Area

46

second sensor

48

Area

50

third sensor

52

Area

54

Points

56

second cam

58

4-Cam

60

Path-time diagram

62

splined shaft

64

Path-time diagram

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10316126 A1 [0003]
• DE 102005021300 B4 [0004]

Claims (10)

Method for determining the position of a camshaft of an internal combustion engine, characterized in that by means of at least one first sensor ( 32 ) the distance to a first cam ( 34 ) of the camshaft is measured and due to the with the sensor ( 32 ) determined distance, the absolute position of the camshaft is determined at least in a motion portion of the camshaft movement. Method according to the preceding claim, characterized in that by means of a second sensor arranged at a second position ( 46 ) the distance to the first cam ( 34 ) or to a second cam ( 56 ) and due to the first sensor ( 32 ) and / or with the second sensor ( 46 ) determined distances, the absolute position of the camshaft is determined at least in a motion portion of the camshaft movement. Method according to the preceding claim, characterized in that by means of a third sensor arranged at a third position ( 50 ) the distance to the first cam ( 34 ), to a second cam ( 56 ) or to a third cam and due to the first sensor ( 32 ), with the second sensor ( 46 ) and with the third sensor ( 50 ) determined distances, the absolute position of the camshaft is determined at least in a motion portion of the camshaft movement. Method according to the preceding claim, characterized in that the absolute position of the camshaft in the complete range of movement of the camshaft movement is determined continuously or quasi-continuously. Method according to one or more of the preceding claims, characterized in that determines the absolute position of the camshaft and / or the relative rotation of the camshaft relative to a crankshaft of the internal combustion engine with additional consideration of the position of a crankshaft and / or evaluation of other signals of other motor-synchronously driven elements becomes. Internal combustion engine with at least one camshaft, characterized in that at least one first sensor ( 32 ) is arranged at a first position such that the distance from the first sensor ( 32 ) to a first cam ( 34 ) of the camshaft is measurable, the sensor ( 32 ) is functionally connected to an evaluation unit and the evaluation unit for determining the position of the camshaft on the basis of at least one with the first sensor ( 32 ) measured distance to the first cam ( 34 ) is trained. Internal combustion engine according to the preceding claim, characterized in that a second sensor ( 46 ) is arranged at a second position such that the distance from the second sensor ( 46 ) to the first cam ( 34 ) or to a second cam ( 56 ) is measurable, and the evaluation unit for determining the position of the camshaft on the basis of at least one with the first sensor ( 32 ) measured distance and / or at least one with the second sensor ( 46 ) Measured distance is formed. Internal combustion engine according to the preceding claim, characterized in that a third sensor ( 50 ) is arranged at a third position such that the distance from the third sensor ( 50 ) to the first cam ( 34 ) or to the second cam ( 56 ) or to a third cam, and the evaluation unit for determining the position of the camshaft on the basis of at least one with the first sensor ( 32 ) measured distance and / or at least one with the second sensor ( 46 ) measured distance and / or one with the third sensor ( 50 ) Measured distance is formed. Internal combustion engine according to one or more of the preceding claims with at least one crankshaft, characterized in that the evaluation unit is functionally connected to a device which detects the absolute position of the crankshaft. Internal combustion engine according to the preceding claim, characterized in that the device has a crankshaft sensor wheel (2) connected non-rotatably to the crankshaft ( 10 ).

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