JPH03286167A - Misfire detecting device for two-cycle internal combustion engine - Google Patents

Abstract

PURPOSE:To detect misfire by using a pressure sensor permitting the easy designing and manufacture by comparing a standard value determined from the operation state of an internal combustion engine with a crank chamber pressure and detecting the misfire of the internal combustion engine when the crank chamber pressure is less than the standard value. CONSTITUTION:The signal supplied from a crank chamber pressure sensor 6 is inputted into a peak hold circuit 9, and the peak value PC of the pressure in a crank chamber is calculated. Then, in order to detect the operation state of an engine, the engine revolution speed is calculated by the signal of a crank angle sensor 11, and the throttle opening degree is detected by a throttle sensor 3. An ECU 13 calculates the peak pressure PCmap in a standard crank chamber in the normal ignition which corresponds to the engine revolution speed and throttle opening degree from the data map of a memory 14. When the crank chamber peak pressure PC is below the standard value PCmap, the misfire of the pertinent cylinder is judged. In this case, the correction coefficient K for correcting the fundamental fuel injection quantity is calculated so that the misfire in the pertinent cylinder is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to misfire detection in a two-stroke internal combustion engine and fuel injection amount control at the time of misfire detection.

[Conventional technology]

Some conventional two-stroke internal combustion engines detect the presence or absence of a misfire by detecting the presence or absence of a peak in exhaust gas pressure, and if a misfire is detected, the ignition timing is controlled in a direction that reduces the misfire. . (For example, JP-A-63-20867
Publication No. 4).

[Problem to be solved by the invention]

However, when detecting a misfire by detecting exhaust pressure, the exhaust gas becomes high temperature and high pressure, so the pressure sensor that detects the exhaust pressure is exposed to high temperature and high pressure. Therefore, there is a problem in that it is difficult to design and manufacture a pressure sensor that can withstand these conditions.

An object of the present invention is to perform misfire detection using a pressure sensor that is easy to design and manufacture.

[Means to solve the problem]

As shown in Fig. 1, a means for solving the above problems includes: an operating state detection means for detecting the operating state of the internal combustion engine; a crank chamber pressure detection means for detecting the crank chamber pressure of the internal combustion engine; a reference value creation means for creating a determined reference value; and a reference value created by the reference value creation means and the crank chamber pressure detected by the crank chamber pressure detection means, and the crank chamber pressure is determined to be the reference value. A misfire detection device for a two-cycle internal combustion engine is provided, comprising: a misfire detection means for detecting that the internal combustion engine has misfired when the misfire is smaller than the above.

Further, it is preferable to further include fuel injection amount correction means for correcting the fuel injection amount when a misfire is detected by the misfire detection means.

[Effect]

Accordingly, the pressure sensor is provided at a position directly connected to the crank chamber, which has a lower temperature than the exhaust gas salt, and a misfire is detected based on the presence or absence of a peak in the pressure sensor. Furthermore, when a misfire is detected, the fuel injection amount can be controlled so as to correct the injection amount in accordance with the operating state of the engine at that time to reduce the misfire.

〔Example〕

Embodiments of the present invention will be described based on the drawings.

FIGS. 2 and 3 are schematic diagrams of a two-stroke, two-cylinder internal combustion engine that is an embodiment of the present invention.

Reference numeral 1 denotes an engine body, which includes two cylinders, a first cylinder 1a and a second cylinder 1b. 2.2a is an intake pipe,
4.4a is a throttle valve that increases or decreases the amount of air flowing into the intake pipe 2.2a. 3 is a throttle sensor that detects the opening degree of this throttle valve 4.4a, and 7 is an air cleaner that purifies air from the outside. The purified air is then supplied to the intake pipe 2.2a. 5.5a is an injector that injects fuel into the purified air in the intake pipe 2.2a to form an air-fuel mixture. This air-fuel mixture is then supplied to the cylinders 1a and lb of the engine 1. A crank chamber pressure sensor 6 is connected to the crank chambers IA of the cylinders 1a and 1b via thin pipes 6a and 6b. Here, the first cylinder 1a
Since the crank chambers of the second cylinder 1b and the second cylinder 1b are independent, the crank chamber pressure sensor 6 detects the crank chamber pressure on the high pressure side of each cylinder. 9 is a peak hold circuit, which takes out the peak value of the pressure signal from the crank chamber pressure sensor 6; 8 is an exhaust manifold, which discharges exhaust gas produced after combustion in the engine 1 to the outside. 12 is a magnet of a magnet generator, which rotates in synchronization with the rotation of the engine. Reference numeral 10 indicates a cylinder discrimination sensor that discriminates between cylinders, and reference numeral 11 indicates a crank angle sensor that detects a crank angle. 13 is an ECU (electronic control unit) consisting of a microcomputer, which calculates the engine speed based on the crank angle signal, and also includes a crank angle sensor 11, a cylinder discrimination sensor 10, and a crank chamber pressure sensor 6.
The signals from the throttle opening sensor 3 are input manually, and the fuel injection amount is controlled based on these signals. Reference numeral 14 denotes a memory within the ECU 13, in which data maps of a reference fuel injection amount, a crank chamber peak pressure, and a fuel injection amount correction coefficient corresponding to the engine speed and throttle opening are stored. 15 is a spark plug arranged in each cylinder of the engine 1, and 16 is a piston that reciprocates within each cylinder 1a, lb.

Next, the operation of the apparatus of the present invention constructed as described above will be explained based on the flowchart shown in FIG.

In step 10, it is determined whether or not to calculate the injection amount.

When the ignition switch is on, it is determined that the injection amount is to be calculated, and the process proceeds to step 20.

When the ignition switch is off, this routine is bypassed without calculating the injection amount. In step 20, the signal from the crank chamber pressure sensor 6 is transferred to the peak hold circuit 9.
The peak value PC of the crank chamber pressure is calculated from the signal obtained manually. Next, in order to detect the operating state of the engine, in step 3o, the engine speed is calculated based on the signal from the crank angle sensor 11, and in step 40, the throttle opening degree is calculated based on the signal from the throttle sensor 3.

In step 50, from the data map of the basic fuel injection amount for the combination of engine speed and throttle opening stored in the memory 14 of the ECU 13,
A basic fuel injection amount TAU corresponding to the engine speed and throttle opening calculated using 0.40 is calculated.

In step 60, from the data map of the crank chamber peak pressure for the combination of engine rotation speed and throttle hlK stored in the memory 14 of the ECU 13, the data map corresponding to the engine rotation speed and throttle opening calculated in step 30.40 is determined. Calculate the reference crank chamber peak pressure PCmap at the time of normal ignition. Next, proceed to step 70,
In order to detect a misfire, the crank chamber peak pressure calculated in step 20 is compared with the reference crank chamber peak pressure at the time of normal ignition calculated in step 60. If the crank chamber peak pressure PC is larger than the reference crank chamber peak value PCmap, it is determined that there is no misfire in the relevant cylinder, and in step 7 step 90, the fuel injection amount correction coefficient for the relevant cylinder is set to =1.
In step 100, the fuel injection amount after correction is =1.
Therefore, the basic fuel injection amount TA calculated in step 50
Let it be U.

If the crank chamber peak pressure PC is less than or equal to the reference crank chamber peak value PCmaP in step 70, it is determined that the relevant cylinder has misfired. At this time, the process proceeds to step 80, where a correction coefficient K is calculated for correcting the basic fuel injection amount TAU so as to reduce misfires in the relevant cylinder. Here, from the data map stored in the memory 14 of the ECU 13, which is a correction coefficient for the combination of engine speed and throttle opening,
K corresponding to the engine speed and throttle opening calculated in step 30.40 is calculated. The value in item 20 is obtained by experimentally determining a correction fuel coefficient for each combination of engine speed and throttle opening that will reduce misfires when they occur, and storing them in the map. For example, K<1 is set in the high rotation range in order to compensate for excess fuel due to a decrease in intake air flow rate due to deterioration of exhaust efficiency that tends to occur at high rotation speeds.

Next, proceeding to step 100, the basic injection amount TAU calculated in step 50 is multiplied by the correction value K calculated in step 80. The result of this multiplication (TAUXK) is set as the next fuel injection amount for the corresponding cylinder.

Further, the correction coefficient obtained in step 80 is a coefficient that determines the next fuel injection amount for the misfired cylinder, which is determined in the misfire cylinder determination described later.

Here, determination of a misfiring cylinder when a misfire occurs will be explained based on a time course diagram of the crank signal, crank chamber pressure, etc. shown in FIG. The crank signal is sent from the crank angle sensor 11 to the cylinder 1a.
, 1b is at the top dead center, that is, every 180'' CA.The cylinder discrimination signal is output from the cylinder discrimination sensor 10.
Only when cylinder 1a is at top dead center, that is, 360″C
Output for each A. When the cylinder discrimination signal is not output while the crank signal is output, that is, cylinder 1
When a (#1) is at the bottom dead center, the sampling timing signal for cylinder 1a (#1) is output, and when the cylinder discrimination signal is also output when the crank signal is output, that is, cylinder 2 (#2) is output. ) outputs a sampling signal for cylinder 2 (#2) when it is at bottom dead center. With the reciprocation of the piston 16, the crank chamber pressure PC has the minimum volume when the piston 16 is at the bottom dead center.
When each cylinder is at the bottom dead center, PC takes a peak value. When a misfire occurs, the downward force of the piston 16 due to the combustion explosive force becomes smaller, and the peak pressure of the PC also becomes smaller. Third
The dotted line in the figure indicates that a misfire has occurred in the cylinder 1b, and the solid line indicates that it is normal.

When a misfire occurs and the pressure (peak value) at the bottom dead center of each cylinder becomes small, and the ECU 13 determines that a misfire has occurred, the misfiring cylinder is determined based on the sampling timing. When a misfire is determined, if the sampling timing signal (#1) is output, it is determined that the cylinder 1a is misfiring, and if the sampling timing signal (#2) is being output, it is determined that the cylinder 1b is misfiring. The corrected fuel injection amount is injected into the cylinder in which a misfire has been determined.

After detecting a misfire as described above, control is performed to reduce the misfire by correcting the basic fuel injection amount for the misfire cylinder.

Also, when calculating the basic fuel injection amount, instead of using a data map of the basic fuel injection amount for the combination of engine speed and throttle opening, a data map of the basic fuel injection amount for the combination of engine speed and crankcase peak pressure is used. It may also be used (as shown in Figure 4).

In addition, when a misfire occurs, in this embodiment, the fuel injection amount is corrected using a correction value determined by a data master knob that is a combination of engine speed and throttle opening. The fuel injection amount may be corrected every revolution of the engine or every predetermined period of time depending on the value (constant value) until there is no misfire.

Although this embodiment uses a 2-stroke, 2-cylinder engine, it is not limited to 2 cylinders and may be implemented with any number of cylinders.

[Effects of the Invention] As described above, according to the present invention, a misfire can be detected based on the presence or absence of a peak value of a signal from a crank chamber pressure sensor. Furthermore, there is an excellent effect that misfires can be reduced by correcting the fuel injection amount when misfires are detected.

[Brief Description of the Drawings] Fig. 1 is a diagram corresponding to claims, Fig. 2 is a schematic configuration diagram of a fuel injection control device for a two-stroke, two-cylinder internal combustion engine according to an embodiment of the present invention, and Fig. 3 is a diagram corresponding to a second embodiment of the present invention. FIG. 4 is a flowchart showing the operation of an embodiment of the present invention; FIG. 5 is a time course diagram of crank signals, cylinder-specific signals, crank chamber pressure, and sampling timing; FIG. The figure is a flowchart showing the operation of the fuel injection control device using a basic injection amount data map for combinations of engine speed and crank chamber peak pressure. 2... Crank chamber pressure sensor, 4... Throttle sensor, 11... Crank angle sensor, 13... ECt
J. 14...Memory. 1 Figure 1

Claims (2)

[Claims] (1) Operating state detection means for detecting the operating state of the internal combustion engine, crank chamber pressure detection means for detecting the crank chamber pressure of the internal combustion engine, and reference value creation means for creating a reference value determined from the operating state of the internal combustion engine. , Compare the reference value created by the reference value creation means with the crank chamber pressure detected by the crank chamber pressure detection means, and when the crank chamber pressure is smaller than the reference value, it is determined that the internal combustion engine has misfired. A misfire detection device for a two-stroke internal combustion engine, comprising: a misfire detection means for detecting a misfire. (2) The misfire detection device for a two-cycle internal combustion engine according to claim 1, further comprising fuel injection amount correction means for correcting the fuel injection amount when a misfire in the internal combustion engine is detected by the misfire detection means.