JPH0776532B2 - Engine output control method - Google Patents

Description

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

[Prior art]

In general, the ignition timing of the engine is controlled so as to advance as the rotation speed becomes higher in order to maximize the output according to the engine speed.

Further, it is known that the output characteristic of the engine is largely influenced by the dynamic effect of the gas flow in the exhaust pipe, which is generally called the inertial effect or the pulsating effect. That is, there is a phenomenon that the pulsating wave of the exhaust gas discharged from the exhaust hole of the engine to the exhaust pipe is reflected from the end of the exhaust pipe or the like and reaches the exhaust hole again, and either positive pressure or negative pressure of this pulsating reflected wave is generated. It is known that the output greatly depends on whether the exhaust hole is reached during the opening period.

For example, in the case of a two-cycle engine, if the negative pressure reflected wave is controlled so as to reach the exhaust hole during the opening period of the scavenging hole, this negative pressure wave will reach the intake hole through the combustion chamber, the scavenging passage, and the crankcase, and a larger amount. If the positive pressure reflected wave can be made to reach the exhaust hole immediately after that, it will prevent the fresh air pushed into the combustion chamber from flowing out. Therefore, the filling efficiency is improved and the output can be increased by the action of these negative pressure and positive pressure pulsating reflected waves.

Conventionally, such control of the pulsating reflected wave of the gas flow in the exhaust pipe has been performed by controlling exhaust specifications such as exhaust timing according to the engine speed. However, the propagation speed of the reflected wave changes depending on the temperature, and has a characteristic that it is faster when the temperature is high and slower when the temperature is lower. For this reason, as described above, only by controlling the exhaust timing according to the engine speed, the exhaust pipe is exhausted such as when the exhaust pipe is cooled by rain like running in rain or when running in a severe winter. When the tube is strongly cooled, etc., the propagation speed of the reflected wave becomes slower than in the steady state, so that the output improvement due to the above dynamic effect is reduced.

[Object of the Invention]

An object of the present invention is to solve the above problems, to prevent the output characteristics due to the dynamic effect of the exhaust gas flow from being affected by the difference in temperature around the exhaust pipe, and to always achieve a high output. It is to provide an output control method.

[Structure of Invention]

The present invention that achieves the above object is provided with a reciprocating piston in a cylinder, and the piston outputs exhaust gas from an exhaust hole to an exhaust pipe while the piston progresses an expansion stroke from top dead center. In the control method, a means for detecting the number of revolutions of the engine and a means for detecting the gas temperature in the exhaust pipe are provided in the expanded diameter portion of the exhaust pipe, and the exhaust start timing of the exhaust gas increases as the engine speed increases. As soon as the ignition timing is advanced and the gas temperature in the exhaust pipe becomes lower, the exhaust start timing determined by the engine speed is advanced and the ignition timing determined by the engine speed is delayed. By doing so, during the opening period of the exhaust hole, the pulsating reflected wave of the exhaust gas can be controlled in order of negative pressure and positive pressure to maximize the engine output. It is a feature.

〔Example〕

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

FIG. 1 shows a motorcycle engine to which the present invention is applied, and 1 is a two-cycle engine. In this 2-cycle engine 1, 2 is a piston, 3 is a crankshaft,
Reference numeral 4 is a spark plug, 5 is an intake hole, 6 is an exhaust hole, and 7 is an exhaust pipe connected to the exhaust hole 6.

A rotary valve 8 for changing the opening degree of the upper opening of the exhaust hole 6 is provided above the exhaust hole 6. This rotary valve 8
When the piston 2 closes the exhaust hole 6 by controlling the opening degree of the upper opening portion of the exhaust hole 6 by controlling the actuator 14 according to the engine speed and the exhaust gas temperature in the exhaust pipe as described later. The exhaust timing of is adjusted.

The exhaust pipe 7 has a straight pipe portion 7f having the same diameter in the front portion, a widened enlarged portion 7r is connected to the rear portion thereof, and a muffling portion 7m is connected to the rearmost portion. At the front end of the straight pipe portion 7f, a resonance chamber 9 is provided so as to branch, and a butterfly-shaped on-off valve 10 is provided at the inlet thereof. The opening / closing valve 10 is controlled via an actuator 15 in accordance with the engine speed and the exhaust gas temperature in the exhaust pipe, as will be described later, and the opening thereof is adjusted.

That is, the resonance chamber 9 constitutes a part of the exhaust pipe 7 downstream from the exhaust hole 6, and the shape of the exhaust pipe 7 is substantially changed by the rotation of the opening / closing valve 10, whereby the pulsating reflected wave to the exhaust hole 6 is changed. Change the return time. The resonance chamber 9 and the on-off valve 10 are exhaust pipe shape changing means.

Further, a sensor 11 such as a thermocouple or thermistor for detecting the exhaust gas temperature is provided in the expanded diameter portion 7r of the exhaust pipe 7.
Since the flow velocity of the exhaust gas is slower and the temperature change is smaller in the expanded diameter portion 7r than in the straight pipe portion 7f, it is possible to detect a nearly average value as the exhaust gas temperature in the exhaust pipe.
If the exhaust gas temperature inside is controlled, the accuracy of control of ignition timing and the like described later can be increased. Furthermore, the expanded part
In 7r, the temperature is lowered as a whole by the amount of expansion of the exhaust gas, and the heat load of the sensor 11 for detecting the exhaust gas temperature is decreased. Further, a sensor 12 composed of a pickup such as an electromagnetic coil for detecting the engine speed is provided on the crankshaft 3 in a pair.

The detection signals of both sensors 11 and 12 are input to the control unit 16 including a microcomputer, and the control unit 16 drives the drive unit 17 based on these signals. The ignition system unit 17a of the drive unit 17 controls the ignition timing of the spark plug 4 via the ignition coil 18, and the exhaust system unit 17b of the drive unit 17 drives the rotary valve 8 via the actuator 14, which will be described later. The exhaust timing is controlled so as to obtain the output improvement due to the dynamic effect of the exhaust gas flow. Further, the exhaust system unit 17c changes the pressure waveform of the exhaust gas by driving the opening / closing valve 10 via the actuator 15, so that the output can be easily improved by the dynamic effect of the exhaust gas flow. If necessary, other exhaust system specifications may be added to the exhaust system unit of the drive unit 17, as shown in FIG.

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. 4, the higher the engine speed is. Controlled to advance. Controlled.

Although the arrival of the pulsating reflected wave is delayed in response to the increase in the engine speed, it is corrected by adjusting the exhaust start timing and the opening / closing valve of the resonance chamber. Optimal exhaust timing (° ATDC… angle after top dead center) and optimal on-off valve angle θ (°… opening based on closed state-see Fig. 1) that maximizes output according to engine speed (rpm) Are carried out as shown in FIGS. 5 and 6, respectively.

The control of the optimum exhaust timing in FIG. 5 is intended to accelerate the arrival time of the pulsating reflected wave to the exhaust hole 6 by correcting the exhaust start timing so as to correspond to the increase in the engine speed. When the pores are open, a negative pressure pulsating reflected wave is made to reach the exhaust hole 6, and it is made to reach the intake hole 5 through the combustion chamber, the scavenging passage, and the crankcase, so that a larger amount of fresh air is sucked in. Then, when the exhaust hole 6 immediately after that is opened, a positive pressure pulsating reflected wave is exerted to prevent the fresh air pushed into the combustion chamber from flowing out. As a result, the charging efficiency of fresh air is improved and the output is improved.

Further, by advancing the exhaust start timing, the gas in the early expansion stroke, that is, the gas with a high temperature, flows into the exhaust pipe 7, so that the temperature decrease of the gas in the exhaust pipe due to the external environment such as rain is weakened. , Pulsating reflected wave exhaust hole 6
Correct so that the return time to is shortened.

Further, the optimum opening / closing valve rotation angle θ (opening degree) in FIG.
The pressure waveform is changed by controlling the rotation angle of 10, and the return time of the pulsating reflected wave to the exhaust hole 6 is changed. That is, in response to an increase in the engine speed, the opening / closing valve rotation angle θ (opening) is reduced with the increase in the engine speed to control the inflow of exhaust gas into the resonance chamber 9 and reduce the pulsation reflection wave. The filling efficiency can be improved by correcting the arrival time to the exhaust hole 6 so as to be shorter.

In the present invention, the control of the optimum ignition timing, the optimum exhaust timing, and the optimum opening / closing valve rotation angle by the control unit 16 is not performed only by the engine speed, but is corrected according to the exhaust pipe gas temperature detected by the sensor 11. To be done. That is, the propagation speed of the pulsating wave changes depending on the temperature, and as shown in FIG. 3, the exhaust gas pressure at the outlet P of the exhaust hole 6 is equal to that of the exhaust pipe 7.
When A is weakly cooled, it becomes like a curve A, but when it is strongly cooled, it becomes a delayed state like a curve B. For this reason, the output improvement characteristic due to the dynamic effect of the exhaust gas flow also changes depending on the exhaust gas temperature, so by correcting this based on the gas temperature in the exhaust pipe, the output improvement due to the dynamic effect is maximized and It enables high output. Thus, the optimum ignition timing, the optimum exhaust timing, and the optimum opening / closing valve rotation angle corrected based on the gas temperature in the exhaust pipe are performed as shown in FIGS. 7, 8 and 9.

That is, in the case of the ignition timing, since there is a characteristic that the exhaust gas temperature rises when the ignition timing is delayed, for example, when the exhaust pipe is cooled and the exhaust pipe gas temperature becomes low when the vehicle travels in the rain, As shown in FIG. 7, as the temperature of the gas in the exhaust pipe becomes lower, the ignition timing determined by the engine speed is delayed with respect to the direction of the top dead center to raise the temperature of the gas in the exhaust pipe, so that the pulsating reflection wave returns to the exhaust hole 6. Correct so that the arrival time is shortened.

Further, in the case of the exhaust start timing, when the exhaust start timing is advanced, the gas having a high temperature in the combustion chamber flows into the exhaust pipe 7 and the exhaust pipe internal gas temperature rises. As shown in FIG. 8, when the exhaust gas becomes low, the exhaust start time determined by the engine speed is advanced and the exhaust pipe gas temperature is raised as the exhaust pipe gas temperature becomes lower. Therefore, the pulsating reflected wave can be effectively used.

However, if the exhaust start timing is too early, the work period given by the piston 2 after top dead center will be shortened and the effect of the pulsating reflected wave will be diminished. However, in the present invention, the ignition timing is delayed. Since the temperature of the gas in the exhaust pipe is increased by the correction, the return arrival time of the pulsating reflected wave is shortened, the exhaust start time is not too early, and the decrease in work by the piston 2 is unlikely to occur. The maximum output of the engine 1 is always obtained.

Further, in the case of the opening / closing valve rotation angle, when the gas temperature in the exhaust pipe becomes low, the optimum opening / closing valve rotation angle θ is made smaller as the gas temperature in the exhaust pipe becomes lower as shown in FIG.
The exhaust gas is prevented from flowing into the exhaust hole 6, and the return arrival time of the pulsating reflected wave to the exhaust hole 6 is corrected to be shortened to improve the charging efficiency.

〔The invention's effect〕

As described above, in the output control method of the present invention, the reciprocating piston is provided in the cylinder, and the exhaust gas is exhausted from the exhaust hole to the exhaust pipe while the piston progresses the expansion stroke from the top dead center. In the engine output control method, a means for detecting the engine speed and a means for detecting the gas temperature in the exhaust pipe are provided in the enlarged diameter portion of the exhaust pipe, and the exhaust gas is exhausted as the engine speed increases. As the start timing is advanced, the ignition timing is advanced, and as the gas temperature in the exhaust pipe becomes lower, the exhaust start timing determined by the engine speed is advanced and the ignition timing determined by the engine speed is delayed. By performing the correction as described above, the pulsating reflected wave of the exhaust gas is exerted in the order of negative pressure and positive pressure during the opening period of the exhaust hole, and control is performed to maximize the engine output. Therefore, by correcting the exhaust start timing and ignition timing, which are determined to maximize the intake charging efficiency by the engine speed, according to the change in the exhaust gas pipe gas temperature, errors may occur due to changes in the environment, etc. By correcting the return arrival time of the pulsating reflected wave and controlling so as to surely improve the filling efficiency, it is possible to always exhibit the high output of the engine.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a motorcycle engine to which the output control method of the present invention is applied, FIG. 2 is a conceptual diagram of the method, FIG. 3 is a fluctuation diagram of exhaust gas pressure at an outlet of an exhaust hole, and FIG. Fig. 5 shows the relationship between engine speed and optimum ignition timing. Fig. 5 shows the relationship between engine speed and optimum exhaust timing. Fig. 6 shows the relationship between engine speed and optimum on-off valve rotation angle. Fig. 7 shows exhaust gas. FIG. 8 is a relationship diagram between the gas temperature in the pipe and the optimum ignition timing, FIG. 8 is a relationship diagram between the gas temperature in the exhaust pipe and the optimum exhaust timing, and FIG. 9 is a relationship diagram between the gas temperature in the exhaust pipe and the optimum opening / closing valve rotation angle. 1 ... Engine, 3 ... Crankshaft, 4 ... Spark plug, 5
...... Intake hole, 6 ... Exhaust hole, 7 ... Exhaust pipe, 7f ... Straight pipe part, 7r ... Expanding part, 8 ... Rotary valve, 9 ... Resonance chamber, 10 ...
… Open / close valve, 11 …… (exhaust pipe gas temperature) sensor, 12…
… (Engine speed) sensor, 14,15 …… Actuator, 16 …… Control unit, 17 …… Drive unit, 18 …… Ignition system unit.

Claims (3)

[Claims] 1. A reciprocating piston is provided in a cylinder,
In an engine output control method in which exhaust gas is exhausted from an exhaust hole to an exhaust pipe while the piston progresses an expansion stroke from top dead center, a means for detecting the engine speed and an expansion of the exhaust pipe. A means for detecting the gas temperature in the exhaust pipe is provided in the diameter portion, and the exhaust start timing of the exhaust gas is advanced as the engine speed increases, and the ignition timing is advanced and the gas temperature in the exhaust pipe becomes lower. The pulsation reflection wave of the exhaust gas during the opening period of the exhaust hole is corrected by advancing the exhaust start timing determined by the engine speed and correcting the ignition timing determined by the engine speed. A method for controlling the output of an engine, wherein the control is performed so as to maximize the engine output by exerting a negative pressure and a positive pressure in this order. 2. The exhaust pipe, together with the engine speed,
By means for changing the return time of the pulsating reflected wave to the exhaust hole according to the temperature of the gas in the exhaust pipe, the return time is shortened as the engine speed increases,
2. The engine output control method according to claim 1, wherein the return time determined according to the engine speed is corrected so as to be earlier as the gas temperature in the exhaust pipe becomes lower. 3. A means for changing the return time of the pulsating reflected wave to the exhaust hole is composed of a resonance chamber branched in the middle of the exhaust pipe via an opening / closing valve, and the opening degree of the opening / closing valve is reduced. The engine output control method according to claim 2, wherein the return time is shortened by performing the above.