JPS5830475A - Idle run stabilizing method for internal combustion engine - Google Patents

Abstract

PURPOSE:To stabilize the number of revolution of idling by retarding the ignition timing of each cylinder periodically during idling operation. CONSTITUTION:If ignition assumes to occur at time A, the time required for opening the exhaust valve will be prolonged, consequently increasing a combustion ratio, campared with the case R when ignition timing is delayed, thereby producing better combustion. However, the composition of inert gas is increased in the next cycle, resulting in deteriorated status of combustion. In the case of R where ignition timing is delayed, the composition of inert gas to be fed in the next cycle will be a little decreased due to lack of combustion time at the case R, thereby reducing the range of fluctuations in combustion.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of controlling ignition timing to stabilize combustion.

Generally, when the engine is idling, the proportion of residual exhaust gas remaining in the cylinder is very large. Inert gas in this residual exhaust gas (
For example, the proportion of CO2) changes depending on the combustion state of the previous cycle, so even if the ignition timing is kept constant, the combustion time changes, which appears as a fluctuation in the idle speed.

Conventionally, engine speed fluctuations were made less noticeable by setting the idle speed higher, but this was not desirable in terms of fuel efficiency and other factors.

An object of the present invention is to control inert gas by periodically retarding the ignition timing of each cylinder during idling, and to reduce idling speed by reducing combustion fluctuations. That is, advancing the ignition timing results in better combustion and increases the amount of inert gas. As the amount of inert gas increases, ignitability deteriorates. Conversely, if the ignition timing is delayed, ignitability improves, but the combustion time becomes insufficient, resulting in a decrease in output and a decrease in inert gas. Therefore, in the present invention, the idling state is detected, and in the idling state, the ignition timing is delayed every n+1 ignition cycles for the number n of cylinders of the internal combustion engine, thereby reducing combustion fluctuations.

The present invention will be explained below with reference to embodiments shown in the drawings.

Figure 1 shows its configuration; 2 is a throttle sensor that detects that the engine's throttle valve is in the fully closed position and outputs a high-level signal; 8 is a throttle sensor that detects the rotation of the speed meter cable; A rotation sensor that outputs a high level signal when the rotation speed is below a predetermined number, and a water wetness sensor 4 that detects the temperature of cooling water using volumetric expansion of a wax body and outputs a high level signal when the temperature is above a predetermined temperature. It is. Also, 1
is an AND circuit, and when each sensor 2, 3.4 is outputting a high level signal, the output becomes a low level and detects that the engine is in an idle state after warming up. b is a microcomputer, which includes a central processing unit (OPU) 50 that performs calculations such as ignition timing, and a random access memory (RAM) that temporarily stores calculation results, etc.
) 51, a read-only memory (ROM) 52 that stores calculation programs, ignition timing data, etc., and an input/output device (Ilo) 5a that exchanges input/output signals. 6 is a rotation sensor using an electromagnetic pickup that detects the rotational speed and rotational position of the engine crankshaft, and 7 is an intake air amount sensor that detects the intake air amount of the engine. 8 is an ignition device, which includes an igniter, an ignition coil,
It has a distributor and a spark plug, and receives an ignition timing signal from the microcomputer 5 to ignite the engine.

The operation of the apparatus configured as described above will be explained with reference to the flowchart shown in FIG. In the microcomputer 5, the program is advanced by a clock signal (not shown).
In the part shown in the figure for selecting the ignition timing, step 1
0, the idle state is determined based on the output of the AND circuit 1, and if it is the idle state, the process branches to step 1]. In step 11, the contents of the counter in the RAM 51 allocated under the name [ouNTJ are compared with a constant "n - 1-1" which is the number of cylinders n plus 1, and if they are equal or larger than the constant, the process branches to step 12. The ignition timing (θB
ET) as the effective ignition timing (θxxEaT). In the next step 13, a numerical value "00" is set in 0UNJ, and thereafter the ignition timing output timing is calculated by a program not shown and an ignition timing signal is output. Step 11
If the content of l'-0UNTJ is smaller than "n + 1", the process branches to step 15 and sets the ignition timing (θADV) that is advanced than θRET and allows good combustion as the effective ignition timing (θwxrraT). At step 16, add "1" to the contents of OUN TJ and reset it to 0UNTJ.If it is not idling at step 10, at step 14, set the rotation speed N and intake air amount per unit rotation Q/N. From this, the map is searched to calculate the optimal ignition timing.In this way, at idle, the ignition timing is retarded every n+1 ignition cycles, so the ignition timing for each cylinder is delayed once every n times. delayed.

Figure 2 explains the proportion of inert gas, the state of combustion, and the influence of ignition timing.

In an internal combustion engine, combustion gas from the previous cycle remains in the gap volume at compression top dead center, so inert gas is brought into the next cycle. This ratio represents the compression ratio as E and the pressure of the combustion gas as P.
ex, if the pressure of fresh air is FB, then (pex/PB*]l
i). Therefore, the smaller the value of FB, the larger the residual proportion and the longer the combustion time due to its specific heat capacity. Second
The middle part of the figure shows the relationship between the proportion of inert gas and the change in combustion rate over time.The proportion of inert gas is small when the pressure PB of fresh air is 760 to Hg (absolute pressure), which is equivalent to fully opening the throttle valve. It burns rapidly and completes a little later than the top dead center (TDa) position. FB is s6
ozmHg (absolute pressure), which is equivalent to idle, brings in about 8 times as much combustion gas from the previous cycle, so the combustion time becomes longer and the exhaust valve opening timing shown by the two-dot chain line (111X・0
), combustion is not completed, and the cylinder pressure does not rise much compared to the cylinder pressure a during non-combustion, as shown in the upper row of FIG. The unburned gas in the gas brought in from the previous cycle is equivalent to fresh air.The proportion of active gas varies depending on the combustion rate of the previous cycle, and even if the ignition timing is constant, it causes fluctuations in shaft output. I'll wake you up.

The lower part of Figure 2 explains the effect of ignition timing at the same inert gas ratio.If the ignition timing is advanced as shown in A, the time until the exhaust valve opens will be longer, so R
The combustion ratio is larger than when the ignition timing is delayed, resulting in better combustion, but in the next cycle, the ratio of inert gas increases and combustion becomes worse. In other words, the fluctuation becomes large.

When the ignition timing is delayed as shown by R, the proportion of inert gas carried into the next cycle is slightly reduced due to insufficient combustion time, and the fluctuation range of combustion becomes smaller.

Due to the causal relationship described above, in the present invention, the ignition timing is advanced during idling to obtain good combustion, and the ignition timing of each cylinder is periodically delayed to reduce the proportion of inert gas. Since fluctuations are kept small, it is possible to stably achieve a lower idle speed than before.

In the above embodiment, a retard mode is provided in which the ignition timing is delayed by n + 1 ignition cycles for the number of cylinders n.
A similar effect can be obtained by setting the period to -1, 2 n +1, or 2n-1, and a configuration may also be adopted in which the retard mode is supplied every other number of ignitions.

As described above, in the present invention, when an idling state is detected, ignition timing that is retarded than the ignition timing that achieves good combustion is periodically given to each cylinder, so the proportion of inert gas is reduced. This has the excellent effect of suppressing combustion fluctuations to a small level and stably achieving low idle speed.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing one embodiment of the present invention, FIG. 2 is a characteristic diagram for explaining the operation of the present invention, and FIG. 8 is a flowchart of main parts showing the arithmetic processing procedure in the microcomputer in FIG. 1. It is. l・-・AND circuit, 2・throttle sensor, 8・
... Rotation sensor, 4... Water temperature sensor, 5... Microcomputer, 8... Ignition device. Representative Patent Attorney Takashi Okabe

Claims (1)

[Claims] A method that determines whether or not a spark ignition internal combustion engine is in an idling state, ignites at an ignition timing that allows good combustion when the engine is in an idling state, and ignites at a predetermined amount retarded than this ignition timing. A method for stabilizing the idle of an internal combustion engine, characterized by controlling ignition timing so as to periodically apply ignition timing to each cylinder.