JPH0756246B2 - Engine ignition timing control method - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to an engine ignition timing control method.

[Prior art]

In general, the ignition timing of the engine is controlled so that the maximum output is obtained according to the engine speed, and the ignition timing is advanced as the rotation speed increases.

Further, it is known that the output characteristics of the engine are greatly influenced by dynamic effects such as inertial effect and pulsating effect of the gas flow in the exhaust pipe. That is, there is a phenomenon that the pulsating wave of the exhaust gas discharged from the exhaust hole to the exhaust pipe is reflected at the end of the exhaust pipe and reaches the exhaust hole again, and one of the suppression or negative pressure of this pulsating reflected wave is opening. The output greatly depends on whether or not the exhaust hole is reached.

For example, in the case of a two-cycle engine, if a pulsating reflection wave of negative pressure is made to reach the exhaust hole when the scavenging hole is open, this negative pressure wave passes through the combustion chamber, the scavenging passage, and the crankcase to the intake hole. As it extends, more and more fresh air will be inhaled. Further, when a positive pressure reflected wave is applied to the exhaust hole immediately after that, the outflow of fresh air pushed into the combustion chamber is prevented. Therefore, due to these effects, the charging efficiency of fresh air is improved and the output can be increased.

Conventionally, such control of the pulsating reflected wave of the gas flow in the exhaust pipe has been performed according to the engine speed because the opening / closing timing of the exhaust hole is inversely proportional to the engine speed.
However, the propagation velocity of the reflected wave changes depending on the temperature, and has a characteristic that it is faster when the temperature is higher and slower as the temperature is lower. Therefore, if the pulsating reflection wave and the opening / closing timing of the exhaust hole are synchronized with each other only by the engine speed, the exhaust pipe is cooled by rain such as when driving in the rain, or when driving in the severe cold of winter. When the exhaust pipe is strongly cooled,
The propagation speed of the reflected wave becomes slower than in the steady state, and the output improvement due to the above dynamic effect is reduced.

However, since the exhaust pipe gas temperature can be changed by controlling the ignition timing, it is necessary to detect the temperature and control the ignition timing to correct the exhaust pipe gas temperature so that the maximum output is obtained. Good. However, as shown in FIG. 5, the gas temperature in the exhaust pipe is different from the supply air ratio (intake negative pressure).
The temperature may be the same when the value is small and when it is large.In such an engine, the best ignition timing cannot be determined only by the gas temperature in the exhaust pipe, and the dynamic effect for always maintaining the maximum output described above. You will not be able to get the tuning of.

[Object of the Invention]

An object of the present invention is to solve the above-mentioned problems and to appropriately control the ignition timing by the gas temperature in the exhaust pipe regardless of the intake negative pressure, and to always maintain the maximum output. To provide.

[Structure of Invention]

The present invention for achieving the above object is a method of detecting an engine speed, an exhaust gas temperature in an exhaust pipe, and an intake negative pressure, and controlling an ignition timing of the engine based on these signals. The negative angle and the positive pressure of the pulsating reflection wave of the exhaust gas are spread in this order to the exhaust hole at the time of opening to fill the exhaust hole at the time of opening by correcting the angle to the retard side as the temperature of the gas in the exhaust pipe becomes lower. The maximum output based on the increased efficiency is generated, and the ignition timing is corrected to the retard side as the intake negative pressure becomes larger, so that the pulsation reflection wave spread timing to the exhaust hole at the time of opening is substantially the same state. It is characterized by maintaining at.

In the present invention, "the intake negative pressure is large" means that the absolute value of the pressure in the negative direction with respect to the atmospheric pressure is large.

〔Example〕

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

FIG. 1 shows an engine for a motorcycle to which the present invention is applied, 1 is a two-cycle engine, 2 is a piston, 3 is a crankshaft, 4 is a spark plug, 5 is an intake hole, and 6 is an exhaust hole. , 7 are exhaust pipes connected to the exhaust holes 6.

The exhaust pipe 7 has a straight pipe portion 7f of the same diameter on the upstream side, a diameter expansion portion 7r is connected to the downstream thereof, and a muffling portion 7m (not shown) is connected at the end. The expanded diameter portion 7r is provided with a sensor 11 such as a thermocouple or thermistor that detects the temperature of the gas in the exhaust pipe. A sensor 12, which is a pickup such as an electromagnetic coil for detecting the engine speed, is provided opposite to the crankshaft 3, and a sensor 19 for detecting an intake negative pressure is provided in the intake passage 20. The sensor 19 may directly detect the intake negative pressure or may indirectly detect the intake negative pressure from the opening of the throttle valve.

The detection signals of these sensors 11, 12, 19 are input to a control unit 16 composed of a microcomputer, and the control unit 16 drives a drive unit 17 based on these signals and controls ignition of the spark plug 4 via an ignition coil 18. To do. By this ignition control,
The dynamic effect of the pulsating reflection of the exhaust gas flow is obtained. That is, by the above ignition control, a negative pressure pulsating reflected wave is made to reach the exhaust hole 6 when the scavenging hole is opened, and further it is made to reach the intake hole 5 via the combustion chamber, the scavenging passage, and the crankcase. Let's inhale more fresh air. Immediately after that, when the exhaust hole 6 is opened, a positive pressure pulsating reflected wave is exerted to prevent the fresh air pushed into the combustion chamber from flowing out. These effects improve the charging efficiency of fresh air, thereby improving the output and always maintaining the maximum output.

In the control described above, the optimum ignition timing (° BTDC ... angle before top dead center) that maximizes the output according to the engine speed (rpm) is, as shown in Fig. 2, the higher the engine speed becomes. Control to advance. This ignition timing is further corrected according to the gas temperature in the exhaust pipe detected by the sensor 11. That is, there is a characteristic that the propagation speed of the pulsating wave becomes slower as the temperature becomes lower, and this change makes it impossible to maintain the maximum output. Therefore, this is corrected by the exhaust pipe gas temperature detected by the sensor 11, and the ignition timing is set to the third value.
It is controlled as shown in the figure. That is, when the ignition timing is delayed, there is a characteristic that the exhaust pipe gas temperature rises, so when the exhaust pipe is cooled and the exhaust pipe gas temperature becomes low, such as when driving in the rain, the ignition timing is set to the top dead center direction. It is delayed so that the temperature of the exhaust gas is corrected to increase.

Further, in the normal combustion region, the ignition delay is longer and the combustion period is longer when the fresh air supply ratio is smaller than when it is large. Therefore, in order to obtain the maximum output according to the air supply ratio, in the present invention, the intake negative pressure corresponding to the air supply ratio is detected by the sensor 19, and the smaller the air supply ratio (intake negative pressure), as shown in FIG. The ignition timing is advanced and retarded as the ignition timing is increased.

On the other hand, between the air supply ratio and the above-mentioned exhaust pipe gas temperature used for ignition timing control in the present invention, a fifth
There is a relationship as shown in the figure, and there is a characteristic that the gas temperature in the exhaust pipe decreases again when the supply ratio becomes a certain value or more. Therefore, as described above, even if the gas temperature in the exhaust pipe is the same, there are two cases, that is, when the supply air ratio (intake negative pressure) is small and when it is large. This is because when the air supply ratio is large, the weight of fresh air in the combustion chamber is large and the thermal energy of the exhaust gas after combustion is also large, but on the other hand, the amount of fresh air that blows through is also large, so it is above a certain level. It is considered that the gas temperature in the exhaust pipe gradually decreases when the air supply ratio becomes. Therefore, the best ignition timing cannot be determined only by the gas temperature in the exhaust pipe, but in the case of the present invention, the ignition timing is controlled according to the intake negative pressure, so that the two cases are clearly distinguished. , Can be controlled accurately. Further, as a result, the output can be always improved by the dynamic effect of the pulsating reflected wave, and the maximum output can always be maintained.

〔The invention's effect〕

The ignition timing control method of the present invention is a method of detecting an engine speed, an exhaust gas temperature in an exhaust pipe, and an intake negative pressure, and controlling the engine ignition timing based on these signals. The negative angle and the positive pressure of the pulsating reflection wave of the exhaust gas are spread in this order to the exhaust hole at the time of opening to fill the exhaust hole at the time of opening by correcting the angle to the retard side as the temperature of the gas in the exhaust pipe becomes lower. The maximum output based on the increased efficiency is generated, and the ignition timing is corrected to the retard side as the intake negative pressure becomes larger, so that the pulsation reflection wave spread timing to the exhaust hole at the time of opening is substantially the same state. It is something to maintain. By such control, as described above, the ignition timing is appropriately controlled by the exhaust pipe gas temperature regardless of the intake negative pressure and the temperature environment during traveling, and the output is efficiently improved by the dynamic effect of the pulsating reflected wave. The maximum output can be maintained at all times.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a two-cycle engine to which the ignition timing control method of the present invention is applied, FIG. 2 is a relationship diagram between engine speed and optimum ignition timing, and FIG. 3 is a graph showing exhaust gas temperature in the exhaust pipe and optimum ignition timing. FIG. 4 is a relationship diagram between the air supply ratio (intake air negative pressure) and the optimum ignition timing, and FIG. 5 is a relationship diagram between the air supply ratio (intake air negative pressure) and the exhaust pipe gas temperature. 1 ... 2-cycle engine, 3 ... crankshaft, 4 ...
Spark plug, 5 ... intake hole, 6 ... exhaust hole, 7 ... exhaust pipe,
11 …… (exhaust pipe gas temperature) sensor, 12 …… (engine speed sensor), 16 …… control unit, 19 …… (intake negative pressure) sensor.

Claims (1)

[Claims] 1. A method for detecting an engine speed, a gas temperature in an exhaust pipe, an intake negative pressure, and controlling an ignition timing of the engine by these signals, wherein the ignition timing is advanced as the engine speed becomes faster. The negative pressure and positive pressure of the pulsating reflection wave of the exhaust gas are transmitted in this order to the exhaust hole at the time of opening by correcting the retard angle side as the temperature of the exhaust gas in the exhaust pipe becomes lower. The maximum output is generated, and the ignition timing is corrected to the retard side as the intake negative pressure becomes larger, so that the pulsation reflection wave propagation timing to the exhaust hole at the time of opening is maintained substantially in the same state. A method for controlling ignition timing of an engine, comprising: