JPH0621576B2 - Control method of internal combustion engine having variable compression ratio mechanism - Google Patents

Description

The present invention relates to a method for controlling an internal combustion engine equipped with a variable compression ratio mechanism, and more particularly to controlling the compression ratio, ignition timing, and fuel injection amount according to the octane number of gasoline fuel. On how to do.

[Conventional technology]

Japanese Patent Application Laid-Open No. 58-38343 discloses a method of detecting a load and a rotation speed of a gasoline engine and controlling a compression ratio according to the load and the rotation speed. However, with this method, when the octane number of the gasoline fuel changes significantly, the compression ratio cannot be changed to match it, so there is a limit to improving engine efficiency.

[Problems to be solved by the invention]

The present invention is to improve the engine efficiency by selecting a compression ratio according to the octane number when gasoline fuels having different octane numbers are used and preventing the occurrence of knocking.

[Means for solving problems]

According to the present invention, it is determined whether the gasoline used is a high octane gasoline or a regular gasoline, and whether knocking has occurred, and when it is determined that the gasoline is a high octane gasoline or for high-octane gasoline. If it is determined to shift to the process, the compression ratio is set to a high compression ratio, and the ignition timing is set using the ignition timing map for high octave, and if knocking occurs at the set ignition timing, Ignition timing is retarded, and if knocking continues even if ignition timing is retarded, it is decided to shift to regular processing, and if it is determined to be regular gasoline or for regular gasoline If it is determined to shift to the process, set the compression ratio to a low compression ratio and use the regular ignition timing map to set the ignition timing. If the knocking does not occur at the set ignition timing, the ignition timing is advanced and if the knocking does not occur continuously even though the ignition timing is advanced, the process goes to high-octane processing. Thus, there is provided a method for controlling an internal combustion engine having a compression ratio variable mechanism, which comprises retarding the ignition timing when knocking occurs at the set ignition timing.

〔Example〕

FIG. 1 is a control flowchart of the present invention, FIG. 2 is an embodiment of a compression ratio variable mechanism used in the present invention and its control system, and FIG. 3 is a map for setting a compression ratio.

First, in FIG. 2, the piston pin 3 with the eccentric bearing 3a is inserted between the piston 1 and the connecting rod 2 of the engine, and the compression ratio is determined by whether the movement of the eccentric bearing 3a is locked by the lock pin 5 or not. It changes. The hydraulic pressure for driving the lock pin 5 is supplied from the oil reservoir 10 by the oil pump 11 and the control valve 12, and is introduced into the cylinder 4 via the passage 14 in the crankshaft 13 and the passage 6 in the connecting rod 2. As a result, the lock pin 5 is pushed toward the eccentric bearing 3a, and is fitted into the hole 3b of the eccentric bearing 3a to lock the eccentric bearing 3a. At this time, the distance between the crankshaft 13 and the piston pin 3 is constant, that is, the high compression a state is maintained. When the control valve 12 is closed, the cylinder 4
Then, the hydraulic pressure is not supplied, the lock pin 5 is pulled in from the hole 3b of the eccentric bearing 3a, and the eccentric bearing 3a is freely rotated. At this time, the eccentric bearing 3a rotates in accordance with the movement of the piston 1, and a low compression ratio is achieved. The oil on the opposite side of the cylinder 4 is returned to the oil reservoir 10 via the passage 7 in the connecting rod 2 and the passage 16 in the crankshaft 13. The control valve 12 is controlled to open and close by a command from the control device (CPU) 20. Further, signals from an intake pipe negative pressure sensor, an engine speed sensor, and a knocking sensor are input to the CPU 20, which outputs a command for controlling the ignition device and the fuel injection device. Known sensors can be used for these sensors, ignition timing, and fuel injection amount control device itself.

The flowchart of FIG. 1 is, for example, 90 ° BT of an ignition cylinder.
It represents the interrupt handling routine executed by the DC. First, at step 100, it is determined whether high-octane control (control when the fuel has a high octane number) is currently being performed or regular control is being performed.
This determination is made by _checking whether a specific flag F _SW is “1” or “0.” This flag F _SW is manually operated by the driver to operate an octane number changeover switch (not shown). Can also be reversed, and can also be automatically controlled from the CPU side.

When the control for high-octane is performed, the routine proceeds to step 101, where the compression ratio control map is set by the compression ratio setting map for high-octane.

The compression ratio setting map used here is predetermined, and as shown in FIG. 3, the solid line shows the compression ratio setting map for high octane, and the broken line shows the compression ratio setting map for regular. When performing control for high-octane, when the engine operating range, that is, the points on the map due to the intake pipe negative pressure and engine speed are above the solid line, the high compression ratio is set, and when it is below the solid line. Is a low compression ratio.

In the next step 102, the ignition timing calculation is performed using the ignition timing map for high-octane and at the current compression ratio, and the fuel injection amount calculation is performed using the fuel injection amount map. Although not shown, such an ignition timing map and a fuel injection amount map are predetermined based on the fuel octane number and compression ratio.

In step 103, it is determined whether or not knocking has occurred, based on the output from the knocking sensor. If knocking does not occur, this processing routine is ended as it is, but if knocking occurs, in step 104, it is determined whether or not knocking has occurred even when the previous processing routine was executed, that is, knocking occurs continuously. Determine whether there was. If knocking has not occurred last time, a process of retarding the ignition timing by a fixed angle is performed in step 105. This is to reduce the ignition advance correction amount θk by a constant value. On the other hand, if knocking occurs continuously, that is, if knocking occurs again this time despite the retard correction performed in step 105 last time, it is considered that the fuel octane number is unsuitable, and the flag F _SW is set in step 106. After reversing, control for regular is performed thereafter. And in step 107,
A signal is output to the display (not shown) to display that the regular control is being performed.

When it is determined from the flag F _SW that regular control is being performed in step 100, the _routine proceeds to step 108, where the compression ratio control is established according to the regular compression ratio setting map (FIG. 3). That is, in FIG. 3, when the point on the map by the intake pipe negative pressure and the engine speed is above the broken line, the high compression ratio is set, and when it is below the broken line, the low compression ratio is set.

Next, at step 109, the ignition timing calculation is performed using the ignition timing map for the regular and current compression ratio, and the fuel injection amount calculation is performed using the fuel injection map.

In step 110, it is determined whether or not knocking has occurred. If knocking has occurred, then in step 111 it is determined whether or not knocking has occurred during the previous execution. If knocking did not occur last time, step 112
To retard the ignition timing by a certain angle. This is to decrease the ignition advance correction amount θk by a constant value as described above. On the other hand, if knocking occurs continuously, that is, if knocking occurs again even though the ignition advance was retarded in step 112 the previous time, it is determined that a trouble has occurred and the compression ratio is fixed to a low compression ratio in step 113. At the same time, the ignition timing is fixed to a value at which knocking never occurs.

If it is determined in step 110 that knocking has not occurred, the routine proceeds to step 114, where it is checked whether knocking has occurred when the processing of step 110 was performed the previous time. If knocking has occurred last time, the routine proceeds to step 115, where the ignition timing is advanced by a fixed angle. This is achieved by increasing the ignition advance correction amount θk by a constant value. Next, at step 116, the count value n indicating how many times the advance angle correction has been performed is set to "1".

If it is determined in step 114 that knocking has not occurred the previous time, the process proceeds to step 117, where the ignition timing is advanced by a fixed angle as in step 115, and then the count value n is advanced by "1" in step 118. In the next step 119, it is judged whether or not the count value n becomes equal to or more than a constant value n _0, and when n ≧ n ₀ , the flag F _SW is inverted in step 120 and the control for high octave is performed thereafter. . Then, in step 121, a display indicating that high-octane control is performed is displayed on a display (not shown).

As described above, in the present embodiment, the compression ratio is controlled by using the compression ratio map for high octane (FIG. 3) and correspondingly controlled by using the ignition timing and the fuel injection amount map. If knocking still occurs after the ignition timing is retarded, it is automatically controlled by the regular compression ratio map and the corresponding ignition timing and fuel injection amount maps. Further, in the case where the control for regular is performed, if knocking does not occur even if the ignition advance is corrected n ₀ times, the control automatically shifts to high-octane control. Note that if control is performed for regular control and knocking still occurs even if the ignition timing is corrected, it is determined that some failure has occurred, the compression ratio is fixed to the low compression side, and the ignition timing is delayed so that knocking does not occur. The ignition timing is fixed. Therefore, even if the octane number of the fuel used changes, the map of compression ratio, ignition timing, fuel injection amount can be selected automatically or manually according to the octane number, and the best output and fuel consumption rate can always be obtained. be able to.

〔The invention's effect〕

By adopting the above configuration, the object of the present invention can be achieved and the ignition timing can be set according to the octane number of the fuel, so that knocking as disclosed in JP-A-59-188056 is detected. As a result, it is possible to obtain a unique effect that the frequency of knocking can be significantly reduced as compared with the method of controlling the compression ratio and the ignition timing.

[Brief description of drawings]

FIG. 1 is a flow chart showing a control method of the present invention, and FIG.
FIG. 3 is a sectional view of an embodiment of a variable compression ratio mechanism and a schematic view of its control system, and FIG. 3 is a view showing a compression ratio setting map. 1 ... Piston, 2 ... Connecting rod, 3 ... Piston pin with eccentric bearing, 5 ... Lock pin, 11 ... Oil pump, 12 ... Control valve, 20 ... CPU.

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Claims (1)

[Claims] 1. It is determined whether the gasoline used is a high octane gasoline or a regular gasoline, and whether knocking has occurred. A) When it is determined to be a high octane gasoline or a high octane gasoline If it is determined to shift to the ignition process, (a) set the compression ratio to a high compression ratio, and set the ignition timing using the ignition timing map for high octave, and (b) set the ignition timing. If the knocking occurs, the ignition timing is retarded, and if the knocking occurs continuously even though the ignition timing is retarded, it is determined that the process will shift to regular processing. B) With regular gasoline If it is determined that there is, or if it is determined to shift to regular processing, (a) set the compression ratio to a low compression ratio and use the regular ignition timing map. (B) If knocking does not occur at the set ignition timing, the ignition timing is advanced, and if knocking does not occur continuously even if the ignition timing is advanced, A method for controlling an internal combustion engine equipped with a compression ratio variable mechanism, characterized in that it is determined that the processing shifts to high-octane processing, and C) the ignition timing is retarded if knocking occurs at a set ignition timing. .