JPH0776531B2 - Engine output control method - Google Patents

Description

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

[Prior art]

Generally, the ignition timing of the engine is controlled 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 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 reflection wave of the gas flow in the exhaust pipe has been performed by controlling exhaust system 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. Therefore, as described above, only by controlling the exhaust timing according to the engine speed, the exhaust gas is exhausted when the exhaust pipe is cooled by rain, such as when running in the rain, or when the vehicle runs during the 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 provides a reciprocating piston in a cylinder, wherein the piston exhausts exhaust gas from an exhaust hole to an exhaust pipe while the piston progresses an expansion stroke from top dead center. A means for detecting the number of revolutions of the engine and a plurality of means for detecting the average temperature of the gas temperature in the exhaust pipe of the exhaust pipe are provided dispersed in the length direction, and the exhaust gas starts to be exhausted as the engine speed increases. As the timing is advanced, the ignition timing is advanced, and as the average temperature of 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. By delaying the correction, the pulsating reflected wave of the exhaust gas is applied in the order of negative pressure and positive pressure during the opening period of the exhaust hole to maximize the engine output. It is characterized by controlling as much as possible.

〔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 that opens and closes an upper opening of the exhaust hole 6 is provided above the exhaust hole 6. This rotary valve 8 is controlled via an actuator 14 in accordance with the engine speed and the gas temperature in the exhaust pipe, as will be described later, and by changing the opening degree of the upper opening portion of the exhaust hole 6, the piston 2 is exhausted. The exhaust timing when closing 6 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 the actuator 15 according to 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, in the exhaust pipe 7, there are two sensors 11 such as a thermocouple or thermistor for detecting the exhaust gas temperature in the straight pipe portion 7f and an expanded portion.
There are 4 on each 7r, 2 for each. On the other hand, a sensor 12 including 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 these sensors 11, ..., 11 and the detection signals of the sensor 12 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. . At this time, the exhaust gas temperature detected by the plurality of sensors 11, ..., 11 is used after being calculated in advance by the control unit 16 to the average temperature thereof.

Of the drive unit 17, the ignition system unit 17a 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, The output timing is controlled so that the output of the engine is maximized at all times by a simple method using only the exhaust pipe and the sensor. Further, the exhaust system unit 17c drives the on-off valve 10 via the actuator 15, changes the pressure waveform of the exhaust gas according to the opening degree, and also controls so as to maximize the output improvement by the dynamic effect of the exhaust gas flow. To do.
As shown in FIG. 2, the exhaust system units of these drive units 17 may be added so as to control other exhaust system specifications, if necessary.

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.

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 via 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. Is done. That is, the propagation velocity of the pulsating wave changes depending on the temperature, and as shown in FIG. 3, the change of the exhaust gas pressure at the outlet P of the exhaust hole 6 becomes like the curve A when the exhaust pipe 7 is slightly cooled. However, when it is strongly cooled, it is delayed as shown by the curve B. For this reason, the output improvement characteristics due to the dynamic effect of the exhaust gas flow also change 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 maintained and a high output is always displayed. To do so. In this way, 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
This is carried out as shown in FIGS. 7, 8 and 9.

That is, in the case of the ignition timing, there is a characteristic that the exhaust gas temperature rises when the ignition timing is delayed. Therefore, for example, when the exhaust pipe is cooled and the exhaust gas temperature decreases when the vehicle travels in the rain, the seventh As shown in the figure, as the gas temperature in the exhaust pipe becomes lower, the ignition timing determined by the engine speed is delayed with respect to the top dead center direction to raise the gas temperature in the exhaust pipe. Correct to make the time earlier.

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, the lower the temperature of the exhaust pipe, the earlier the exhaust start timing determined by the engine speed and the higher the temperature of the exhaust pipe gas, the higher the temperature of the exhaust pipe gas becomes. The time can be shortened and the pulsating reflected wave can be effectively used.

However, if the exhaust start time is too early, the work time 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 gas temperature 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 exhaust gas temperature becomes low, the optimum opening / closing valve rotation angle θ becomes smaller as the gas temperature in the exhaust pipe becomes lower as shown in FIG. The gas inflow is suppressed, and the return time of the pulsating reflected wave to the exhaust hole 6 is corrected so as to be shortened, so that the charging efficiency is improved.

Moreover, in the present invention, since the average value of the plurality of sensors 11, ..., 11 arranged in the length direction of the exhaust pipe 7 is used as the gas temperature in the exhaust pipe used for control, the control with extremely high accuracy is performed. Can be done. That is, the exhaust gas temperature in the exhaust pipe 7 is high in the straight pipe portion 7f close to the exhaust hole 6 of the engine 1 as shown by the temperature curve E in FIG. Since the diameter portion 7r is gradually lowered and the cooling is not always uniform in the length direction, the accuracy of the correction control may be impaired depending on the measurement location, but as described above, the exhaust pipe 7 By using the average value of the detected temperatures at a plurality of points along the longitudinal direction as the control factor, it is possible to reduce the error due to external factors and recognize the accurate velocity of the pulsating reflected wave.

Further, it is desirable that a plurality of sensors 11 for detecting the exhaust gas temperature are arranged along the longitudinal direction of the exhaust pipe 7 as much as possible.
It is preferable to dispose not on 7f but only on the enlarged diameter portion 7r. As is clear from the temperature curve E in FIG. 10, the temperature distribution in the exhaust pipe 7 is such that in the straight pipe portion 7f having a small cross-sectional area, the flow velocity of the exhaust gas is fast and the temperature change in the longitudinal direction is large. This is because the error due to the measurement position becomes large due to the large size, whereas the flow velocity of the exhaust gas is slow in the expanded diameter portion 7r and the temperature change in the length direction is small, so that the error due to the measurement position is small.

〔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 unit for detecting the engine speed and a plurality of units for detecting the average temperature of the exhaust pipe gas temperature of the exhaust pipe are provided dispersed in the length direction to increase the engine speed. The earlier the exhaust start timing of the exhaust gas is advanced, the more advanced the ignition timing is, and the lower the average temperature of the exhaust pipe gas temperature is, the earlier the exhaust start timing determined by the engine speed is By correcting the ignition timing determined by the rotational speed so as to be delayed, the pulsating reflected wave of the exhaust gas is applied in the order of negative pressure and positive pressure during the opening period of the exhaust hole. Since it is controlled to maximize the engine output, the exhaust start timing and ignition timing determined to maximize the intake charging efficiency by the engine speed are corrected according to changes in the exhaust gas pipe gas temperature. As a result, the return arrival time of the pulsating reflected wave in which an error has occurred due to a change in the environment or the like is corrected, and control is performed so as to reliably improve the charging efficiency, so that the high output of the engine can be always exhibited.

Moreover, since the average value of the temperatures detected by the plurality of sensors installed in the length direction of the exhaust pipe is used as the gas temperature in the exhaust pipe, even if the long exhaust pipe is locally cooled or heated. There is no error due to the measurement location, the accurate velocity of the pulsating reflected wave can be recognized, and accurate control can be performed.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a motorcycle engine to which the control method of the present invention is applied, FIG. 2 is a conceptual diagram of the control method, FIG. 3 is a fluctuation diagram of exhaust gas pressure at an exhaust hole outlet, 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 shows the relationship between the gas temperature in the pipe and the optimum ignition timing. Fig. 8 shows the relationship between the gas temperature in the exhaust pipe and the optimum exhaust timing. Fig. 9 shows the relationship between the gas temperature in the exhaust pipe and the optimum opening / closing valve rotation angle. It is a relationship diagram between the gas temperature in the pipe and the position of the exhaust pipe. 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 (2)

[Claims] 1. A reciprocating piston is provided in a cylinder,
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 exhaust gas of the exhaust pipe. A plurality of means for detecting the average temperature of the gas temperature in the pipe are provided in a dispersed manner in the longitudinal direction, the exhaust start timing of the exhaust gas is advanced as the engine speed increases, and the ignition timing is advanced, and As the average temperature of the gas 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 corrected to be delayed, thereby opening the exhaust hole. An engine output control method characterized in that the pulsating reflected wave of the exhaust gas is applied in the order of negative pressure and positive pressure during a period to control the engine output to be maximum. Law. 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 average temperature of the gas temperature in the exhaust pipe,
A method of correcting the return time as the engine speed increases, and correcting the return time determined according to the engine speed so that the average temperature of the gas temperature in the exhaust pipe becomes lower. The engine output control method according to item 1.