Claims:I claim:

1. An electronic control unit (ECU) (101), said ECU (101) adapted to:

identify a falling edge pulse of at least one missing tooth of a tone wheel (103) and a rising edge pulse of the missing tooth of the tone wheel (103) based on an output from a measuring element (102);

calculate a time difference between the rising edge pulse of the missing tooth and the falling edge pulse of the missing tooth; and

determine an engine stroke based on the calculated time difference.

2. The ECU (101) of claim 1, wherein said ECU (101) determines the engine stroke as a compression stroke when the calculated time difference is equal to greater than a threshold.

3. The ECU (101) of claim 1, wherein said ECU (101) determines the engine stroke as an exhaust stroke when the calculated time difference is lesser than a threshold.

4. The ECU (101) of claim 1, wherein said measuring element (102) is a speed sensor.

5. The ECU (101) of claim 1, wherein said measuring element (102) is mounted in proximity of said tone wheel (103).

6. The ECU (101) of claim 1, wherein said measuring element (102) measures an engine speed.

7. A method for determining an engine stroke of an internal combustion engine, said method comprising:

identifying a falling edge pulse of at least one missing tooth of a tone wheel (103) and a rising edge pulse of the missing tooth of the tone wheel (103) based on an output from a measuring element (102) by an ECU (101);

calculating a time difference between the rising edge pulse of the missing tooth and the falling edge pulse of the missing tooth by the ECU (101); and

determining an engine stroke based on the calculated time difference by the ECU (101).

8. The method as claimed in claim 7, wherein determining the engine stroke as a compression stroke when the calculated time difference is equal to greater than a threshold.

9. The method as claimed in claim 7, wherein determining the engine stroke as an exhaust stroke when the calculated time difference is lesser than a threshold.
, Description:Field of the invention

[0001] The invention relates to a method and a device for engine synchronization.

Background of the invention

[0002] Engine condition determination and sensing is of utmost importance for optimizing engine performance. In an internal combustion engine, various techniques are used for sensing position of crankshaft which is required for proper timing of fuel injection into the engine. In conventional systems, the cam wheel and the crank wheel are provided with sensors to determine different aspects of engine condition like engine speed, engine position and direction. In a four stroke engine, the piston completes four separate strokes to constitute a single engine cycle. A camshaft performs one revolution for every two revolutions of the crankshaft. The state or the stroke of the engine cycle is determined, for example, by detecting a rotational position of the camshaft. The state of the engine cycle is determined by using a camshaft sensor and a crankshaft sensor. The crankshaft sensor provides an angular position of the crankshaft. Since the engine turns two revolutions, the engine reaches top dead center (TDC) twice in each engine cycle. In the four stroke engine, a crank signal from the crankshaft sensor cannot differentiate between the intake stroke and the power stroke. Similarly the crankshaft sensor cannot differentiate between the compression stroke and the exhaust stroke. The result obtained by the crankshaft sensor regarding the stoke of the engine cycle is thus ambiguous. A camshaft sensor is relatively expensive and also has to be timed in to provide accurate results. Using two sensors, that is, a camshaft sensor and a crankshaft sensor increases the cost and also consumes more space reducing system consistence.

[0003] Using virtual cam sensor, the compression stroke is identified at the TDC following the compression stroke. That is, the compression stroke is identified at the end of the compression stroke as the engine speed gradient used to identify the compression stroke is calculated at the TDC following the compression stroke. Hence, synchronization of the internal combustion engine is established at the TDC following the compression stroke and the fuel can be released into the engine only during the next compression stroke. Hence, time required for injection release is more and the overall engine start-time is higher. A device with more flexibility to detect a compression stroke followed by the synchronization and fuel injection during the detected compression stroke is required to attain quick startability.

[0004] Korean patent application, 2005033365, discloses a method for discriminating the stroke of a single-cylinder four-stroke engine mounted with an electronic ignition system and a fuel injecting system. The method electronically controls fuel-injection and ignition time by discriminating the stroke with a crank shaft rotation sensor and to repress unburned gas emitted to the air and generated during igniting and injecting the fuel for every two-strokes.

Short description of the drawing

[0005] An exemplifying embodiment of the invention is explained in principle below with reference to the drawing. The drawing is,

[0006] FIG. 1 illustrates a system comprising an electronic circuit unit (ECU) to determine an engine stroke of an internal combustion engine in accordance with this invention; and

[0007] FIG. 2 illustrates a method for determining the engine stroke of the internal combustion engine in accordance with this invention.

Description of the invention

[0008] Figure 1 illustrates a system (1000) comprising an electronic circuit unit (ECU) (101) to determine an engine stroke of an internal combustion engine in accordance with this invention. The ECU (101) is adapted to identify a falling edge pulse of at least one missing tooth of a tone wheel (103) and a rising edge pulse of the missing tooth of the tone wheel (103) based on an output from a measuring element (102); calculate a time difference between the rising edge pulse of the missing tooth and the falling edge pulse of the missing tooth; and determine an engine stroke based on the calculated time difference.

[0009] For better understanding of the ECU (101) in accordance with this disclosure, the system (1000) comprising the ECU (101) can be disclosed in the following manner. Only few components of the system (1000) are shown in the Figure 1. The system (1000) comprises a piston and a crank shaft. A transmission mechanism connects the crank shaft and a cam shaft. The system (1000) comprises a tone wheel (103) and a measuring element (102). In an embodiment, the measuring element (102) is a speed sensor. The measuring element (102) is mounted in proximity to the tone wheel (103). The tone wheel (103) has at least one missing tooth. The missing tooth defines at least one position of the internal combustion engine. The measuring element (102) measures an engine speed. The output of the measuring element (102) represents the engine speed in the form of pulses. The pulses represents the teeth of the tone wheel (103). Each pulse represent a tooth of the tone wheel (103). The at least one missing teeth is represented as a gap in the pulses.

[00010] The ECU (101) receives the output of the measuring element (102) representing the engine speed. The ECU (101) identifies the falling edge pulse of the missing tooth of the tone wheel (103) and the rising edge pulse of the missing tooth of the tone wheel (103). That is, the ECU (101) identifies the gap in the pulses obtained from the measuring element (102). Since the missing tooth defines at least one position of the internal combustion engine, the gap defining the missing tooth of the tone wheel (103) is different for a compression stroke and an exhaust stroke.

[00011] The ECU (101) calculates the time difference between the rising edge pulse of the missing tooth and the falling edge pulse of the missing tooth. The ECU (101) determines the engine stroke based on the calculated time difference. Here, the engine stroke is either the compression stroke or the exhaust stroke. In other words, the ECU (101) distinguishes between the compression stroke and the exhaust stroke based on the calculated time difference.

[00012] During the compression stroke, air is trapped inside the cylinder since an inlet valve and an exhaust valve are in a closed state. This causes the movement of the piston to slow down. Thus, the gap in the pulses for the compression stroke obtained from the measuring element (102) is more. That is, the time difference between the rising edge pulse of the missing tooth and the falling edge pulse of the missing tooth is more. The ECU (101) determines the engine stroke as a compression stroke when the calculated time difference is equal to greater than a threshold. The threshold is defined via calibration to determine the engine stroke corresponding to the missing teeth gap.

[00013] During the exhaust stroke, the exhaust valve is in an open state and the inlet valve is in the closed state. This allows the air to escape out of the cylinder thereby facilitating free movement of the piston. Thus, the gap in the pulses for the exhaust stroke obtained from the measuring element (102) is less. That is, the time difference between the rising edge pulse of the missing tooth and the falling edge pulse of the missing tooth is less. The ECU (101) determines the engine stroke as the exhaust stroke when the calculated time difference is lesser than the threshold.

[00014] By using the calculated time difference, the ECU (101) identifies the compression stroke before a top dead center (TDC) position of the piston following the compression stroke. The ECU (101) can prepare for fuel injection release during the same identified compression stroke enabling quick startability. This also makes engine synchronization possible without a cam shaft and a cam sensor. The ECU (101) can be used in both single cylinder and multi cylinders internal combustion engine to determine the engine stroke.

[00015] FIG. 2 illustrates a method for determining the engine stroke of the internal combustion engine in accordance with this invention. At step S1, the ECU (101) identifies the falling edge pulse of the at least one missing tooth of the tone wheel (103) and the rising edge pulse of the missing tooth of the tone wheel (103) based on the output from the measuring element (102). The measuring element (102) is a speed sensor. At step S2, the ECU (101) calculates the time difference between the rising edge pulse of the missing tooth and the falling edge pulse of the missing tooth by the ECU (101). At step S3, the ECU (101) determines the engine stroke based on the calculated time difference. The ECU (101) determines the engine stroke as the compression stroke when the calculated time difference is equal to greater than the threshold. The ECU (101) determines the engine stroke as the exhaust stroke when the calculated time difference is lesser than the threshold.

[00016] It must be understood that the embodiments explained in the above detailed description is only illustrative and does not limit the scope of this invention. The scope of this invention is limited only by the scope of the claims. Many modification and changes in the embodiments aforementioned are envisaged and are within the scope of this invention.