JPH08121236A - Misfire detecting method and its device - Google Patents

Abstract

PURPOSE: To provide a method that detects misfire states via an analysis of the acceleration of an engine crankshaft. CONSTITUTION: A first engine crankshaft acceleration 405 is measured in proximity to a first preset engine crankshaft angle, and a first measured value 407 indicative of the first engine crankshaft acceleration 405 is read in. A second engine crankshaft acceleration 417 is measured near a second present engine crankshaft angle, and a second measured value 419 indicative of the second engine crankshaft acceleration 417 is read in. The first and second measured values 407 and 419 are synthesized in S421 that offers an acceleration factor 423 indicative of the synthesized measured value. Unless the acceleration factor 423 exceeds a preset limit value, a misfire display is made by S427.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to the field of misfire detection in internal combustion engines, and more particularly, by analyzing the acceleration of the crankshaft of an engine to detect misfire during an internal combustion event in the engine. Ignition (m
isfire) detection method and its device.

[0002]

BACKGROUND OF THE INVENTION Electronic engines employ systems for detecting misfires in combustion events. When a cylinder repeatedly misfires, fuel to that cylinder is shut off in the next engine cycle. This prevents large amounts of unburned fuel from passing to the exhaust catalyst. This is done to prevent degradation of catalyst performance and useful life, thereby minimizing emissions.

[0003]

Some misfire detection schemes utilize a rotational speed sensor mounted on the crankshaft of the engine to convert engine rotation to an electrical signal. These methods monitor the average angular velocity and use a sign analysis of this average engine crankshaft velocity.
Others attempt to predict misfire based on reanalysis). Other schemes rely on measuring the average engine crankshaft acceleration. Both of these approaches rely on averaging multiple combustion cycles,
Inaccuracies arise. This is problematic because these schemes are inaccurate and uncertain under transient operating conditions and other conditions related to combustion instability, including engine-crankshaft variations in cylinder-to-cylinder ignition.

Further, the misfire component of the detected signal is
The size and frequency vary considerably over the entire operating range of the engine. Since the averaging scheme relies on predicting changes from steady state, it inherently loses accuracy under these transient operating conditions. In addition, the impact on non-combustion is considerable. These effects are generally due to changes in engine load torque, friction torque and inertial torque.

Other schemes built into the ignition system can only detect ignition-related misfires that are only part of the possible misfire conditions, and thus the complete misfire required for accurate misfire detection. Lack of functionality.

Therefore, there is a need for an improved system for detecting misfires in internal combustion engines that is more reliable and accurate, requires minimal calibration, and is easily adaptable to a variety of engine types.

[0007]

A method and apparatus for detecting a misfire condition by analyzing the acceleration of an engine crankshaft will be described. The method measures a first engine crankshaft acceleration in proximity to a first predetermined engine crankshaft angle, provides a first measured value representative of the first engine crankshaft acceleration, and provides a second predetermined value. Measurement of the second engine / crankshaft acceleration close to the engine / crankshaft angle is performed, a second measurement value representing the second engine / crankshaft acceleration is given, and the first measurement value and the second measurement value are combined. And the acceleration coefficient that represents this composite measurement
Gives (acceleration coefficient). Therefore, if the acceleration coefficient does not exceed the predetermined limit, misfire is displayed.

[0008]

The preferred embodiment describes a method for detecting misfire conditions by analyzing engine crankshaft acceleration within a single combustion cycle. The method measures a first engine crankshaft acceleration in proximity to a first predetermined engine crankshaft angle, provides a first measured value representative of the first engine crankshaft acceleration, and provides a second predetermined value. Measurement of the second engine / crankshaft acceleration close to the engine / crankshaft angle is performed, a second measurement value representing the second engine / crankshaft acceleration is given, and the first measurement value and the second measurement value are combined. Then, an acceleration coefficient representing this combined measurement value is given. Therefore, if the acceleration coefficient does not exceed the predetermined limit, misfire display is performed. In addition, the measurement of the third engine crankshaft acceleration close to the cylinder TDC is done by normalization coefficie measurement.
nt), which, when combined with the acceleration coefficient, is used to substantially eliminate the effects of non-combustion-related behavior of engine crankshaft acceleration.

The improvements described in the preferred embodiments include, for example, diesel engines, stratified combustion engines (stratif).
ied charge engine) or spark ignition engine (spark ign)
itionengine). The preferred embodiment describes application to a spark ignition engine.

The chart of FIG. 1 (1) shows a signal 101 derived from a sensor that measures the angular acceleration of the engine crankshaft during a single combustion cycle. In this case, the illustrated acceleration signal 101 is a signal obtained from a non-misfire or proper combustion cycle.

A horizontal axis 103 is a cylinder BDC compression 105.
That is, the bottom dead center and the cylinder TD
It is represented by the angle of engine crankshaft angular rotation with respect to C107 or the top dead center.
The vertical axis 109 is represented as engine crankshaft acceleration. Note that from cylinder BDC 105, the acceleration signal is substantially equal to zero. In this engine angular position, the piston is in the compression part of the cycle. As the engine crankshaft rotates, the engine crankshaft, or acceleration signal 101, will decelerate, or have a negative acceleration. 30 ° B
TDC113, that is, before top dead cen
ter), this negative acceleration reverses and goes to the positive side. This positive acceleration tendency is substantially zero in the cylinder TDC1.
After passing 07, it reaches the next angular position of 30 ° ATDC 117, where the acceleration tendency is reversed. In general, the individual cylinder combustion will depend on the operating conditions, depending on the operating conditions, before the cylinder TDC 20.
Between 40 ° and 40 ° after cylinder TDC. At 30 ° ATDC 117, ie after top dead center, the absolute value of engine crankshaft acceleration is higher than at 30 ° BTDC. This is because proper combustion occurs, which causes this difference. This difference in engine crankshaft acceleration is used to detect the difference between proper ignition and misfire conditions.

The chart in FIG. 1 (2) shows the signals that represent misfire or an improper combustion cycle.
The same horizontal axis and vertical axis as in (1) are used. This signal is shown in Figure 1.
Compared to the signal of (1), the engine crankshaft acceleration is 30 ° BTDC201 and the cylinder TD.
It can be seen that C203 is substantially the same. However, at 30 ° ATDC 205, the absolute value of engine crankshaft acceleration is substantially lower than at 30 ° ATDC in FIG. 1 (1). This 30 ° BTD
The relationship between C and engine crankshaft acceleration at 30 ° ATDC is important in detecting misfire conditions.

FIG. 2 is a system block diagram of a misfire detection system that overcomes the deficiencies of the prior art. The preferred embodiment describes how to build this system. Of course, it will be appreciated by those skilled in the art that corresponding devices can be constructed to achieve the same advantages.

In the preferred embodiment, the Motorola MC68H
The C11E9 microcontroller 300 performs the method implemented in firmware. This firmware will be described with reference to the flowchart of FIG. MC68
It is advantageous to use the HC11E9 microcontroller 300 because it has a built-in counter that is convenient for processing the acceleration signals described below. Many other substantially equivalent hardware platforms for implementing this method will be understood by those skilled in the art.

The flywheel 301 is connected to the engine crankshaft and has lobes or teeth 303 on its outer end. In the preferred embodiment, they are spaced 10 ° apart for convenience of the described method.
Of course, it will be understood by those skilled in the art that other tooth spacings will give the same effective results. These teeth 303 are inductive transducers when the flywheel 301 is driven by the engine crankshaft.
ducer) 305. Inductive transducer 305 provides a signal 313 representing the angular position or velocity of flywheel 301.

Another single tooth 307 is located on the engine TDC and is detected by another inductive transducer 309. Inductive transducer 309 provides a signal 311 representing the TDC of flywheel 301. These signals 311 and 313 are processed by the MC68H for further processing.
It is applied to the counter input of C11E9 and is used to detect the individual cylinder TDCs needed to implement the misfire detection method. Of course, flywheel teeth 30
3, 307 and the corresponding sensors 305, 309, instead of Hall-Effect, light and RF,
Other detection techniques are also available. Those skilled in the art will also contemplate other methods of measuring acceleration, or torque output, from the combustion process, which is advantageous with this method. It includes, for example, an in-line torque sensor. The method described herein, regardless of its detection method, depends only on the torque output of the engine measured as engine crankshaft acceleration information and the corresponding absolute position information or engine TDC information.

The element 315 is connected to the signal 313 and the signal 31.
Given a 1, represents a firmware routine that determines the engine crankshaft position as an angular displacement. As described above, the flywheel teeth 303 are arranged at 10 ° intervals. This routine is synchronized by the unique teeth 307 on the flywheel TDC and simply counts the teeth to determine the absolute engine crankshaft position as an angular displacement. In the preferred embodiment, a 4-stroke, 6-cylinder engine is used.
The firing order is 1, 4, 2, 5, 3, 6. Cylinder T
DC is scheduled every 720 ° / 6, or 120 °. Therefore, the TDC of cylinder 1 is in the 0 ° flywheel position, the TDC of cylinder 4 is in the 120 ° flywheel position, the TDC of cylinder 2 is in the 240 ° flywheel position, and the TDC of cylinder 5 is in the 360 ° flywheel position. Position, cylinder 3 has a TDC of 480
At the flywheel position, the cylinder 6 has a TDC of 6
At the 00 ° flywheel position. Of course, other engines with different firing order and cylinder TDC
Other flywheel tooth arrangements and minor modifications to routine 315 can be easily measured. If you are a person skilled in the art,
Many other equivalent means and methods for determining absolute engine crankshaft position are understood.

The angular position or velocity signal 313 is also provided to an element 317 which determines engine crankshaft acceleration. Also, those skilled in the art will appreciate many ways to extract this information from the velocity signal 313. In the preferred embodiment, the counter embodied in the MC68HC11E9 microcontroller 300 is a flywheel tooth 3
Count the time between 03. The result is used to calculate engine crankshaft acceleration by comparing successive values of the measured time. Preferably, to remove the part of the information about non-combustion torque,
Filtered. This is the torsional vibration (torsional
vibrations) or very low frequency acceleration effects. After being processed by element 317, the engine crankshaft acceleration 319 is determined by the crankshaft angle 323 provided by element 315 as detailed below.
Together with this, it is given to the element 321.

Element 321 is the heart of the method,
This will be described in detail with reference to the flowchart of FIG. When a misfire condition is detected, a misfire indication is provided at the output 325 of element 321. This misfire indication 325 is provided to element 327 which, together with the crankshaft angle 323 provided by element 315, identifies the misfiring cylinder and the fuel for that particular cylinder in the next fueling cycle. Cut off. This is MC68HC11
It is assumed that the E9 microcontroller 300 has a wider range of functions as an engine controller having a function of controlling fuel supply. These details are not described here because those skilled in the art are familiar with various devices and methods that provide this functionality.
The method and apparatus described herein can be conveniently incorporated into a larger system or utilized as a standalone function.

FIG. 3 is a flow chart for explaining the operation of the misfire detection method. As mentioned above, this is MC68
5 represents firmware programmed into the HC11E9 microcontroller 300. This firmware is
Substantially recognize the behavior difference between the engine and crankshaft acceleration signals shown in FIGS. 1 (1) and 1 (2). The routine also describes an additional step to eliminate the effects of engine crankshaft acceleration on unfiltered non-combustion. This provides a highly effective alternative to conventional misfire detection systems due to the improved accuracy and reliability of misfire detection. This improved accuracy and reliability is due to the inherent non-averaged nature of the method and, in the absence of the possibility of combustion-related torque, to its own powerful notion of normalizing the measurement at cylinder TDC. To do.

The engine / crankshaft acceleration signal consists of torque related information and non-combustion related information.
To remove the torque related information, this information must be subtracted from both torque related measurements. This will be described in detail below.

In step 401, the routine is entered each time the cylinder combustion cycle begins. Note that this routine shows that the method directly measures the acceleration at the target crankshaft angle by waiting until it detects this angle. This is just one of many ways to make this measurement. Of course, one of ordinary skill in the art will appreciate other equivalent methods, such as capturing engine crankshaft acceleration in another routine and processing it here.

In the next step 403, the routine waits until the measured engine crankshaft angle approaches the first predetermined engine crankshaft angle, in this case 30 ° before cylinder TDC. As mentioned above, 30 ° before cylinder TDC is within the compression stroke. Once equal to 30 ° before cylinder TDC, the routine in step 405 fetches and stores the engine crankshaft acceleration measurement as a variable named A30BTDC407, which represents the engine crankshaft angle at 30 ° before cylinder TDC.

This same capture process is repeated for another predetermined engine crankshaft angle step 409,
Also at 411. In step 409,
The routine waits until the measured engine crankshaft angle approaches another predetermined engine crankshaft angle, in this case the cylinder TDC, also referred to as the third predetermined engine crankshaft angle. Upon proximity, in step 411, the routine retrieves and stores the engine crankshaft acceleration measurement as a variable named ATDC 413, which represents engine crankshaft acceleration in cylinder TDC. This variable ATDC
413 is also called a normalization coefficient. This is used to substantially eliminate the effects of non-combustion related behavior of engine crankshaft acceleration 319.

In the next step 415, the measured engine
The routine waits until the crankshaft angle approaches the second predetermined engine crankshaft angle, in this case 30 ° after cylinder TDC. As mentioned above, the cylinder T
30 ° after DC is within the expansion stroke. If this equals 30 ° after cylinder TDC, then in step 417 the routine retrieves and stores the engine crankshaft acceleration as a variable named A30ATDC419, which represents the engine crankshaft acceleration at 30 ° after cylinder TDC.

Next, in step 421, the three stored measurements or variables are recalled, preferably A
The 30BTDC407 measured value is added to the A30ATDC419 measured value, and the double of the ATDC413 measured value is subtracted to synthesize. This gives NADC 423, the normalized acceleration coefficient. Preferably, twice the variable ATDC 413 is subtracted, as the non-combustion related acceleration must be subtracted from both compression cycle and expansion cycle measurements, as described above. This same combustion cycle normalization, i.e. the elimination of non-combustion related effects, is a great accuracy advantage over the prior art. This allows accurate torque-related acceleration to be used to detect misfire conditions, without allowing the non-combustion related effects over time or averaged to be removed from the real-time measurements as in conventional systems, Therefore, a reliable result is obtained.

In step 425, NADC variable 4
23 is compared to a predetermined limit. During a normal combustion or ignition event, variable A30ATDC419 is set to variable A3.
It is expected to be much larger than 0BTDC407.
Since these acceleration measurements have opposite signs, for example, the acceleration due to combustion, shown at 117 in FIG. 1 (1), produces a substantially positive result. However, if misfire is in progress for a particular cylinder, the measurements will substantially cancel. Normal ignition exceeds this limit, but not misfire, as compared to a predetermined limit. If a misfire occurs, a misfire indication is provided at step 427 and the routine repeats from step 401. When normal ignition occurs, the routine repeats from step 401.

In the preferred embodiment, angles close to 30 ° BTDC and 30 ° ATDC are used to measure engine crankshaft acceleration during compression and subsequent expansion strokes, although other angular positions are 30 °. It can be used as long as it is within ± 10 ° of the ° position. This is because the peak combustion torque occurs in this range in the general slider crank mechanism used in the present internal combustion engine.

Thus far, a method of detecting a misfire condition by analyzing the acceleration of the engine crankshaft within a single combustion cycle has been described which substantially overcomes the shortcomings of the prior art. The misfire condition is detected by combining several measurements within a single combustion cycle. Multi-cycle averaging schemes with inherent inaccuracies are avoided. Also, by measuring another engine crankshaft acceleration close to the cylinder TDC,
A normalization factor is obtained, which is combined with other measurements and is used to substantially eliminate the effects of non-combustion related behavior of engine crankshaft acceleration, providing a more accurate representation of misfire conditions. And display surely.

[Brief description of drawings]

FIG. 1 is a chart of signals derived from a sensor that measures angular acceleration of an engine crankshaft, showing the acceleration distribution of the engine crankshaft during a non-ignition or proper combustion cycle.

FIG. 2 is a system of a misfire detection system according to the present invention.
It is a block diagram.

FIG. 3 is a flowchart illustrating an operation of a misfire detection method.

[Explanation of symbols]

 101 Acceleration signal 103 Horizontal axis 105 Cylinder BDC 107 Cylinder TDC 109 Vertical axis 113 30 ° BTDC 117 30 ° ATDC 201 30 ° BTDC 203 Cylinder TDC 205 30 ° ATDC 300 Micro controller 301 Flywheel 303 Teeth (lobe) 305 Induction transducer 307 teeth 309 Induction transducer 311 Signal 313 Angular position (speed) signal 315 Firmware routine 317 Element 319 Engine crankshaft acceleration 321 Element 323 Crankshaft angle 325 Output (misfire indication) 327 element

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Donald James Lenboski, Zunia Oakman Boulevard, Dearborn, Michigan, USA 7447 (72) Inventor Marvin Lester Lynch, Rosslyn Road 19555, Detroit, Michigan, USA

Claims (19)

[Claims] 1. A method for detecting a misfire condition by analyzing engine crankshaft acceleration, comprising: measuring a first engine crankshaft acceleration proximate a first predetermined engine crankshaft angle. ,
A first representing the first engine crankshaft acceleration
Providing a measured value; measuring a second engine crankshaft acceleration proximate to a second predetermined engine crankshaft angle, and providing a second measured value representative of the second engine crankshaft acceleration; Combining one measurement value and a second measurement value and providing an acceleration coefficient representing the combined measurement value; and providing a misfire indication when the acceleration coefficient does not exceed a predetermined limit. A method characterized by. 2. The step of measuring a first engine crankshaft acceleration proximate to a first predetermined engine crankshaft angle includes the step of proximate a first predetermined engine crankshaft angle within a compression stroke. The method of claim 1, wherein the first engine crankshaft acceleration is measured. 3. The step of measuring a second engine crankshaft acceleration proximate to a second predetermined engine crankshaft angle comprises the second predetermined engine crank being within an expansion stroke following the compression stroke. The method of claim 2, wherein the second engine crankshaft acceleration proximate the shaft angle is measured. 4. The first engine crankshaft acceleration proximate to 30 ° before top dead center of the cylinder is measured by measuring the first engine crankshaft acceleration proximate to a first predetermined engine crankshaft angle. The method according to claim 2, characterized in that 5. The second engine crankshaft acceleration proximate to 30 ° after top dead center of the cylinder comprises measuring the second engine crankshaft acceleration proximate to a second predetermined engine crankshaft angle. The method according to claim 4, characterized in that 6. The step of measuring the first engine crankshaft acceleration proximate to a first predetermined engine crankshaft angle includes: within ± 10 ° about 30 ° before top dead center of the cylinder. The step of measuring the first engine crankshaft acceleration and measuring the second engine crankshaft acceleration close to the second predetermined engine crankshaft angle is ± 10 ° around 30 ° after top dead center. The method of claim 1, wherein the second engine crankshaft acceleration within the range is measured. 7. The method of claim 1, wherein the step of comparing adds the first measurement value to the second measurement value. 8. Measuring a third engine crankshaft acceleration proximate to the cylinder TDC and providing a normalization coefficient; combining the normalization coefficient and the acceleration coefficient to provide a normalized acceleration coefficient; The method of claim 1, further comprising: and providing a misfire indication when the normalized acceleration coefficient does not exceed a predetermined limit. 9. The step of combining comprises subtracting the normalization factor from the acceleration factor.
The described method. 10. The method of claim 8, wherein the step of synthesizing subtracts twice the normalization factor from the acceleration factor. 11. A device for detecting a misfire condition by analyzing engine crankshaft acceleration: measuring a first engine crankshaft acceleration proximate to a first predetermined engine crankshaft angle. ,
A first representing the first engine crankshaft acceleration
Means for providing a measured value; means for measuring a second engine / crankshaft acceleration in proximity to a second predetermined engine / crankshaft angle and means for providing a second measured value representative of the second engine / crankshaft acceleration; Apparatus for combining the first measurement value and the second measurement value to give an acceleration coefficient; and means for giving a misfire indication when the acceleration coefficient does not exceed a predetermined limit. . 12. The means for measuring a first engine crankshaft acceleration proximate a first predetermined engine crankshaft angle, wherein the means for measuring a first engine crankshaft acceleration is within a compression stroke.
First near a given engine crankshaft angle
12. The apparatus of claim 11 comprising means for measuring engine crankshaft acceleration. 13. A means for measuring a second engine crankshaft acceleration proximate to a second predetermined engine crankshaft angle, said means for determining a second predetermined engine crankshaft within said expansion stroke following said compression stroke. 13. The apparatus of claim 12 comprising means for measuring a second engine crankshaft acceleration near the shaft angle. 14. The means for measuring the first engine crankshaft acceleration proximate to a first predetermined engine crankshaft angle is within ± 10 ° about 30 ° before top dead center of the cylinder. The means for measuring the first engine / crankshaft acceleration and the means for measuring the second engine / crankshaft acceleration close to a second predetermined engine / crankshaft angle are centered around 30 ° after top dead center. 12. The apparatus of claim 11, comprising means for measuring a second engine crankshaft acceleration within a range of ± 10 °. 15. Means for measuring a third engine crankshaft acceleration in the vicinity of the cylinder TDC and providing a normalization coefficient; combining the normalization coefficient and the acceleration coefficient to provide a normalized acceleration coefficient, The apparatus of claim 11, further comprising: means for providing a misfire indication when the normalized acceleration coefficient does not exceed a predetermined limit. 16. The apparatus of claim 15, wherein the means for combining comprises means for subtracting the normalization factor from the acceleration factor. 17. The apparatus of claim 15, wherein the means for combining comprises means for subtracting twice the normalization coefficient from the acceleration coefficient. 18. A system for detecting a misfire condition by analyzing the acceleration of an engine crankshaft, the angle measuring means providing an indication of the instantaneous position of the engine crankshaft of the engine; the engine of the engine. Cylinder TDC measuring means for giving an indication of the top dead center position of the crankshaft; in front of the cylinder TDC in response to the angle measuring means and the cylinder TDC measuring means.
Means for measuring a first engine crankshaft acceleration in the vicinity of 0 ° and providing a first measured value representative of said first engine crankshaft acceleration; a cylinder in response to said angle measuring means and said cylinder TDC measuring means TD
Means for measuring a second engine crankshaft acceleration near 30 ° after C and providing a second measured value representative of the second engine crankshaft acceleration; combining the first measured value with the second measured value And means for providing an acceleration coefficient; and means for providing a misfire indication when said acceleration coefficient does not exceed a predetermined limit. 19. Means for measuring a third engine crankshaft acceleration in the vicinity of the cylinder TDC and providing a normalization coefficient; combining the normalization coefficient and the acceleration coefficient,
Means for providing a normalized acceleration coefficient; means for providing a misfire indication when the normalized acceleration coefficient does not exceed a predetermined limit; and means for shutting off fuel in response to the misfire indication; 19. The system of claim 18, further comprising: