JPH08177503A - Exhaust pulsation regulating device of two-cycle engine - Google Patents

Abstract

PURPOSE: To optimize the return timing of an exhaust reflected wave, and enhance engine performance by detecting the air-fuel ratio by introducing burnt gas from an introducing port only in a period until a scavenging flow reaches the introducing port of an auxiliary exhaust passage after ignition. CONSTITUTION: An ECU 15 calculates the target air-fuel ratio optimal for its operation condition on the basis of throttle opening and rotating speed of a two-cycle engine 1 detected by a throttle valve driving actuator 12 also serving as a sensor. On the other hand, an exhaust pipe length variable device 50 arranged in an exhaust pipe 8 is composed of a longitudinally movable variable convergence 51. Then, the ECU 15 finds the air-fuel ratio of burnt gas on the basis of a detecting value of an O2 sensor 30 arranged in an auxiliary exhaust passage 29, and controls the exhaust pipe length variable device 50 on the basis of a difference between this detecting air-fuel ratio and the target air-fuel ratio. Therefore, an exhaust reflected wave reflected by an end part of the exhaust pipe 8 is regulated so as to return to a main exhaust port as a negative pressure wave just before an exhaust stroke of the next cycle, and exhaust efficiency of an engine 1 is enhanced, and performance can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects the air-fuel ratio of an air-fuel mixture from the O ₂ concentration of burnt gas and compares the detected value with a target air-fuel ratio. The present invention relates to an exhaust pulsation adjusting device for a two-cycle engine that adjusts the return timing of reflected waves.

[0002]

2. Description of the Related Art In an engine, detecting the air-fuel ratio of an air-fuel mixture and adjusting the operating condition of the engine to the optimum state based on the detected value is to improve engine performance, improve fuel efficiency, take measures for exhaust gas, etc. Is desirable from the point of.

For example, in an engine, it is known that the exhaust pulsation effect is utilized to enhance the exhaust efficiency and thereby improve the engine performance. That is, in the exhaust stroke, the pressure wave propagating in the exhaust pipe at the speed of sound is reflected at the pipe end, and the pressure wave returns as a reflected wave toward the cylinder in the exhaust pipe,
If the timing is adjusted so that this exhaust reflected wave returns to the exhaust port as a negative pressure wave immediately before the exhaust stroke of the next cycle, the exhaust gas will flow out into the exhaust pipe vigorously and the exhaust efficiency will be improved.

By the way, as a method of detecting the air-fuel ratio of the air-fuel mixture, an O ₂ sensor is arranged in the exhaust passage, and the O ₂ in the exhaust gas (burnt gas) detected by the O ₂ sensor is detected.
_The method of calculating the air-fuel ratio of the air-fuel mixture based on the ₂ concentration has been conventionally implemented in a 4-cycle engine.

Thus, even in a two-cycle engine,
A method of detecting the air-fuel ratio of the air-fuel mixture by the above method can be considered.

[0006]

However, in the two-cycle engine, since both the scavenging port and the exhaust port are opened during the scavenging / exhaust stroke, fresh air containing unvaporized fuel to be scavenged from the combustion chamber. The so-called blow-by phenomenon that flows out into the exhaust passage occurs, and the exhaust gas contains fresh air containing nearly 20% oxygen, and the O ₂ sensor installed in the exhaust passage detects the O ₂ concentration of the exhaust gas flowing therethrough. However, the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber cannot be detected accurately. For this reason, in the 2-cycle engine, the return timing of the reflected exhaust wave in the exhaust pipe cannot be accurately adjusted as in the 4-cycle engine.

The present invention has been made in view of the above problems, and its object is to accurately detect the air-fuel ratio of the air-fuel mixture and set the return timing of the exhaust reflected wave in the exhaust pipe to the operating state of the engine. An object of the present invention is to provide an exhaust pulsation adjusting device for a two-cycle engine that can be optimally adjusted accordingly.

[0008]

In order to achieve the above-mentioned object, the invention according to claim 1 separates burned gas and fresh air by scavenging introduced into the cylinder from the scavenging port when the exhaust port is opened. An exhaust pulsation adjusting device provided in a two-cycle engine for gas exchange is provided with an exhaust pulsation adjusting means, an O ₂ sensor provided in the middle of an auxiliary exhaust passage for guiding a burnt gas from a combustion chamber to the outside, and the O ₂ sensor. The air-fuel ratio detecting means for obtaining the air-fuel ratio of the air-fuel mixture on the basis of the signal of the An air-fuel ratio detection device capable of introducing fuel gas is compared with a target air-fuel ratio set based on the engine speed or / and throttle opening and an air-fuel ratio detection value detected by the air-fuel ratio detection device. The difference between the two Control means for adjusting the return timing of the exhaust reflected wave in the exhaust pipe by controlling the exhaust pulsation adjusting means on the basis of the above.

Further, the invention according to claim 2 has at least two cylinders having a phase difference in sliding of pistons, and the scavenging air introduced into the cylinder from the scavenging opening when the exhaust port is opened in each cylinder. An exhaust pulsation adjusting device provided in a two-cycle engine for exchanging burnt gas with fresh air by means of an O ₂ sensor provided in the middle of a communication passage communicating exhaust pulsation adjusting means and two adjacent cylinders. And an air-fuel ratio detecting means for obtaining the air-fuel ratio of the air-fuel mixture based on the signal from the O ₂ sensor, and the scavenging port opens from the ignition of one of the two adjacent cylinders in the expansion stroke. Up to a period of up to only the air-fuel ratio detection device capable of opening both ends of the communication passage, and a target air-fuel ratio set based on the engine speed or / and throttle opening and the air-fuel ratio detection device And a control means for adjusting the return timing of the exhaust reflected wave in the exhaust pipe by controlling the ignition timing adjusting means based on the difference between the detected air-fuel ratio detected value and the detected value. Characterize.

[0010]

According to the first aspect of the present invention, the O ₂ concentration of burnt gas containing no fresh air is accurately detected by the air-fuel ratio detection device. That is, since the burned gas is introduced into the auxiliary exhaust passage only during the period from ignition to when the scavenging airflow reaches the inlet of the auxiliary exhaust passage, the unburned fuel flowing through the auxiliary exhaust passage is not vaporized. does not contain the fresh air containing, O ₂ by the O ₂ concentration in the burnt gas is detected by O ₂ sensor, air-fuel ratio is the air-fuel ratio detecting means of the mixture supplied to the combustion chamber
It can be accurately obtained based on the detected value of the concentration. Therefore, 2
In a cycle engine as well as in a four-cycle engine, the air-fuel ratio of the air-fuel mixture is accurately detected, and the return timing of the exhaust reflected wave in the exhaust pipe is set based on the difference between the detected air-fuel ratio value and the target air-fuel ratio. It can be optimally adjusted according to the operating state, and exhaust efficiency can be improved to improve engine performance.

According to the second aspect of the invention, as in the first aspect of the invention, the burnt gas O ₂ containing no fresh air is added.
The concentration is accurately detected by the air-fuel ratio detection device. That is, the burnt gas of one cylinder in the expansion stroke flows through the communication passage to the other cylinder in the compression stroke, and in this case, the scavenging port of the cylinder in the expansion stroke is closed, and therefore flows through the communication passage. The burned gas does not include fresh air containing unvaporized fuel, and therefore the O ₂ concentration of this burned gas is detected by the O ₂ sensor, and the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber of each cylinder is empty. It is accurately obtained by the fuel ratio detection means based on the detected value of the O ₂ concentration. Therefore, also in the 2-cycle engine, it is possible to accurately detect the air-fuel ratio of the air-fuel mixture and optimally adjust the return timing of the exhaust reflected wave in the exhaust pipe according to the operating state of the engine, as in the 4-cycle engine. As a result, exhaust efficiency can be improved and engine performance can be improved.

[0012]

【Example】

[First invention] An embodiment of the first invention will be described below with reference to the accompanying drawings.

<First Embodiment> FIG. 1 is a cutaway side view of an essential part of a motorcycle showing a two-cycle engine equipped with an exhaust pulsation adjusting device according to the present invention, and FIG. 2 is an enlarged sectional view of the essential part of the two-cycle engine. 3 is a cross-sectional view of an exhaust pipe showing an exhaust pipe length varying device, FIG. 4 is a diagram showing control characteristics of the exhaust pipe length varying device, FIG. 5 is a timing chart of ignition and opening / closing of a sweep / exhaust port and a sub-exhaust passage, FIG. 6 is a block diagram showing the configuration of the control system, and FIG. 7 is a diagram showing a target air-fuel ratio map.

The exhaust pulsation adjusting device for a two-cycle engine (type 1) according to the present invention comprises an exhaust pulsation adjusting means, an O ₂ sensor for detecting the O ₂ concentration of burnt gas not containing scavenging gas, and the O ₂ sensor. An air-fuel ratio detection device comprising an air-fuel ratio detection means for obtaining the air-fuel ratio of the air-fuel mixture based on the signal of
The target air-fuel ratio set based on the engine speed or / and the throttle opening is compared with the air-fuel ratio detection value detected by the air-fuel ratio detection device, and the exhaust pulsation adjusting means is controlled based on the difference between them. By doing so, a control means for adjusting the return timing of the reflected exhaust wave in the exhaust pipe is included.

A two-cycle engine 1 shown in FIG. 1 is a water-cooled single-cylinder engine, which is arranged in a space surrounded by a main frame 51 and a down tube 52 of a motorcycle and is formed in a cylinder body 2 of the same. Further, an intake pipe 4, a carburetor 5 and an air cleaner 6 connected to the rear of the vehicle body (right side in FIG. 1) are connected to the intake passage 3, and an exhaust pipe 8 is connected to a main exhaust passage 7 formed in the cylinder body 2 as well. It is connected. The intake passage 3 is provided with a reed valve 9, and the exhaust pipe 8 is provided with an exhaust valve 11 which is opened / closed by an exhaust valve opening / closing actuator 10. The carburetor 5 has a valve provided therein. A throttle main valve drive actuator 12 for opening and closing the throttle valve shown in the figure and for detecting the opening of the throttle valve, a variable main jet drive actuator 13 including a solenoid for driving a main jet (not shown), and an air jet (not shown) Variable air jet drive actuators 14 each of which is composed of a driving solenoid are provided.

Thus, the exhaust valve opening / closing actuator 1
0, sensor and throttle valve drive actuator 12,
The variable main jet drive actuator 13 and the variable air jet drive actuator 14 are electrically connected to an engine control device (hereinafter referred to as ECU) 15. In FIG. 1, 53 is a rear arm, 54 is a chain sprocket, and 55 is a drive chain.

Here, the structure of the two-cycle engine 1 will be described.

A piston 16 is slidably fitted in a cylinder 2a formed in the cylinder body 2 of the two-cycle engine 1, and the piston 16 is rotatably housed in a crank chamber 17a in a crankcase 17. The crankshaft 18 is connected via a connecting rod 19. A rotation sensor 20 for detecting the engine speed is attached to the bottom of the crankcase 17, and the rotation sensor 20 is electrically connected to the ECU 15.

The cylinder head 21 attached to the upper portion of the cylinder body 2 is provided with a recess 21a which forms a combustion chamber S between the cylinder head 21 and the top surface of the piston 16.
An ignition plug 22 is screwed to the center of the cylinder head 21. The spark plug 22 is the ignition control circuit 23.
The ignition timing is controlled by, and the ignition control circuit 23 is electrically connected to the ECU 15.

Further, as shown in FIG. 2, a main scavenging passage 24 and a sub-scavenging passage 25 are formed in the cylinder body 2 in addition to the intake passage 3 and the main exhaust passage 7. The main exhaust passage 7 is communicated with the inside of the crank chamber 17a via the intake port 3a, and the main exhaust passage 7 is connected to the cylinder 2a via the main exhaust port 7a.
It has an opening inside. Further, one end of the main scavenging passage 24 opens into the cylinder 2a through the main scavenging port 24a,
The other end is connected to the crank chamber 17a through the main scavenging passage inlet 24b.
It has an opening inside. The auxiliary scavenging passage 25 connected to the intake passage 3 opens into the cylinder 2a via the auxiliary scavenging port 25a. As shown in the figure, the upper edge of the main exhaust port 7a is located above the main scavenging port 24a and the sub-scavenging port 25a.

By the way, in the exhaust pipe 8, as shown in FIG. 3, an exhaust pipe length varying device 5 which is an exhaust pulsation adjusting means.
0 is provided, and the exhaust pipe length varying device 50 is configured by a variable convergent 51 that is movable back and forth within the range of the solid line position and the chain line position in the figure.

Now, the air-fuel ratio detecting device will be described.

As shown in detail in FIG. 2, a chamber 26 is formed above the main exhaust passage 7 of the cylinder body 2, and the chamber 26 is connected to the inside of the cylinder 2 a through a first passage 27. , Communicates with the main exhaust passage 7 through the second passage 28. Therefore, the cylinder body 2
An auxiliary exhaust passage 29 is formed by the first passage 27, the chamber 26, and the second passage 28.

An O ₂ sensor 30 is attached to the chamber 26, and the first passage 27 has a first
The check valve 31 has the second check valve 3 in the second passage 28.
2 are provided.

The O ₂ sensor 30 is the ECU 1
5 is electrically connected. The first check valve 31 permits the flow of burnt gas from the cylinder 2a toward the chamber 26. It does not open at the compression pressure after the sweeping / exhaust stroke, but the combustion after the ignition combustion is completed. Its spring load is set to open under pressure. On the other hand, the second check valve 32 permits the flow of burnt gas from the chamber 26 toward the main exhaust passage 7, and opens at a pressure lower than the opening pressure of the first check valve 31. The spring load is set so that the main exhaust passage 7 is not opened by the negative pressure generated in the main exhaust passage 7.

Further, the inlet 27a of the first passage 27
Is above the main exhaust port 7a, and the combustion chamber S
During combustion of the air-fuel mixture, the piston 16 closes it, and opens at a position where it opens after the timing when the air-fuel mixture combustion is completed.

Thus, the air-fuel ratio detecting apparatus according to the present embodiment includes the auxiliary exhaust passage 29, the O ₂ sensor 30 provided in the middle of the auxiliary exhaust passage 29 (the chamber 26), the first and second check valves. The ECU 15 is configured to include 31, 32 and the ECU 15 that also functions as an air-fuel ratio detecting means. Next, the operation thereof will be described below with reference to FIG.

In the compression stroke in which the piston 16 moves upward in the cylinder 2a, the negative pressure generated in the crank chamber 17a pulls the fresh air from the air cleaner 6, and the carburetor 5 mixes the fuel with the fresh air. A mixture is formed, and this mixture is introduced from the intake passage 3 into the crank chamber 17a through the intake pipe 4 and the reed valve 9. The air-fuel mixture introduced into the crank chamber 17a is primarily compressed by the piston 16 moving downward in the expansion stroke.

On the other hand, when the main scavenging port 24a, the sub scavenging port 25a, and the main exhaust port 7a are closed by the piston 16 in the compression stroke, the air-fuel mixture supplied into the cylinder 2a is compressed by the piston 16 and the piston 16 moves upward. Immediately before reaching the dead center (TDC), the air-fuel mixture in the combustion chamber S is ignited by the ignition plug 22 and ignited and burned (see FIG. 5). Since the first check valve 31 of the first passage 27 is not opened by the compression pressure as described above, the unburned air-fuel mixture does not flow to the auxiliary exhaust passage 29 side.

Then, when the piston 16 moves to the expansion stroke in which the piston 16 moves downward due to the high combustion pressure generated by the combustion of the air-fuel mixture in the combustion chamber S, first, the first passage 27 which constitutes the sub exhaust passage 29 is introduced. The opening 27a opens after the completion of the combustion of the air-fuel mixture (see FIG. 5), and the first check valve 31 of the first passage 27 is pushed open by the combustion pressure. Then, the burned gas generated by the combustion of the air-fuel mixture flows into the chamber 26 from the first passage 27, and the burned gas pushes the second check valve 32 open by the pressure of the burned gas from the second passage 28 to the main exhaust passage. 7, the O ₂ sensor 30 detects the O ₂ concentration of the burnt gas flowing through the auxiliary exhaust passage 29 (chamber 26).

After that, when the piston 16 further moves downward,
Next, the main exhaust port 7a is opened, and the burnt gas is blown from the main exhaust port 7a to the main exhaust passage 7 and discharged into the atmosphere through the exhaust pipe 8. After that, the main scavenging port 24a and the sub scavenging port are discharged. 25
When a is opened (see FIG. 5), the air-fuel mixture in the crank chamber 17a that has been primarily compressed in the previous cycle has the main scavenging passage 24.
Through the sub-scavenging passage 25 and the main scavenging port 24a and the sub-scavenging port 2
There is a scavenging action that pushes out the burned gas remaining in the cylinder 2a into the main exhaust passage 7 from 5a into the cylinder 2a, and a part of the scavenging gas blows into the main exhaust passage 7.

Thus, the main scavenging port 24a and the sub-scavenging port 25a
From the inside of the cylinder 2a until it reaches the inlet 27a of the first passage 27.
The pressure of the burnt gas remaining in a is sufficiently reduced, and the pressure of the air-fuel mixture flowing into the cylinder 2a is low, so that the burned gas and the air-fuel mixture are opened by the time the first check valve 31 of the first passage 27 is opened. Therefore, at least before the mixture reaches the inlet 27a of the first passage 27, the detection of the O ₂ concentration of the burnt gas by the O ₂ sensor 30 ends. Therefore, the burnt gas flowing through the auxiliary exhaust passage 29 does not include the air-fuel mixture (fresh air), and the O ₂ sensor 30 detects the O ₂ concentration of the burned gas that does not include the air-fuel mixture (fresh air).

In FIG. 5, A3 is a period from the completion of the combustion of the air-fuel mixture to the arrival of the scavenging air flow in the introduction passage 27a of the auxiliary exhaust passage 29, and the introduction port 27 is included in this period A3.
When a is opened and the burnt gas is guided to the O ₂ sensor 30, it is possible to detect the O ₂ concentration of the burned gas that does not include the air-fuel mixture (fresh air).

In this embodiment, the crank angle at which the inlet 27a formed on the side surface of the cylinder 2a is opened by the piston 16 is in the period A3, and the valve opening pressure P1 of the first check valve 31 is equal to the inlet pressure. piston 16 is set larger than the internal pressure of the cylinder 2a p ₂ when closing the inlet opening 27a in the internal pressure p ₁ and the compression stroke of the cylinder 2a when the scavenging flow to the mouth 27a reaches.

Then, in the engine in which p ₁ ≧ p ₂ , by setting P1 = p ₁ , it becomes possible to introduce the burnt gas into the auxiliary exhaust passage 29 during the period of a ₁ shown in FIG. . If the P1> p _1, which during termination of the introduction period of a ₁ has been advanced is the introduction period of the burnt gas. Also, p
_In an engine with ₁ > p ₂ , it is necessary to satisfy P1 ≧ p _3, and similarly, the advanced period of the introduction period of a ₁ is the burned gas introduction period. The main exhaust port 7a
Since the internal pressure p ₃ of the cylinder 2a when the valve starts opening is usually higher than p ₁ and p ₂ , a method of introducing burnt gas during the period of a ₂ by setting P1 = p ₃ is used. It will be possible. The longer the introduction period is, the longer the period for the O ₂ sensor 30 to detect the O ₂ concentration of the burnt gas is, which is desirable. However, by increasing the detection performance of the O ₂ sensor 30, P1> p ₃ is set, and more reliably. Burned gas containing no air-fuel mixture (fresh air) can be guided to the auxiliary exhaust passage 29. Here, the valve opening pressure P1 of the first check valve 31 is always set higher than the valve opening pressure P2 of the second check valve 32 (P1> P2).

When the O ₂ concentration of the burnt gas is detected by the O ₂ sensor 30 as described above, the signal is EC
Inputted to U15, the ECU 15 obtains the air-fuel ratio of the air-fuel mixture from the detected value of the O ₂ concentration. Therefore, in this embodiment, EC
U15 functions as the air-fuel ratio detecting means.

Further, in this embodiment, the rotation sensor 20
The engine speed and the throttle opening (engine load) detected by the sensor and throttle valve drive actuator 12 (see FIGS. 1 and 6) are the ECU
15 are input respectively.

Further, in this embodiment, the target air-fuel ratio setting means and the control means are constituted by the ECU 15,
The ECU 15 calculates the optimum target air-fuel ratio for the operating state based on the rotation speed of the two-cycle engine 1 and the throttle opening (engine load) detected by the rotation sensor 20 and the sensor / throttle valve drive actuator 12, or Reads a predetermined target air-fuel ratio from the map shown in FIG. 7 stored in the memory.

Then, the ECU 15 compares the air-fuel ratio detection value detected by the air-fuel ratio detecting device with the target air-fuel ratio, and based on the difference between them, the exhaust pipe length varying device 50.
By optimizing the return timing of the reflected exhaust wave in the exhaust pipe 8 (that is, the reflected exhaust wave reflected at the end of the exhaust pipe 8 is a negative pressure wave immediately before the exhaust stroke of the next cycle as the main exhaust port). Adjust to return to 7a). Specifically, for example, when the air-fuel ratio of the air-fuel mixture shifts in the direction matching the low speed range (that is, the exhaust pulsation effect is obtained in the low speed range), the exhaust pipe length is changed as shown by the broken line in FIG. The variable convergent 51 of the variable device 50 is moved forward (in the direction) at an earlier timing with respect to the engine speed. In FIG. 4, the horizontal axis represents the engine speed and the vertical axis represents the position of the variable convergent 51.

Therefore, according to this embodiment, in the air-fuel ratio detecting device, the O ₂ concentration of the burnt gas which does not contain the air-fuel mixture (fresh air) is detected by the O ₂ sensor 30 and is supplied to the combustion chamber S. Since the air-fuel ratio of air is accurately obtained by the ECU 15 based on the detected value of the O ₂ concentration, also in the 2-cycle engine 1, the air-fuel ratio of the air-fuel mixture is accurately detected in the same manner as in the 4-cycle engine to detect the exhaust reflected wave. The return timing can be optimally corrected according to the operating state (rotational speed) of the engine 1, and the exhaust efficiency of the two-cycle engine 1 can be improved to improve the performance.

In this embodiment, the target air-fuel ratio is calculated based on both the engine speed and the throttle opening (engine load), but the target air-fuel ratio may be calculated based on only one of them. Although the exhaust pipe length varying device 50 is controlled by the engine speed in this embodiment, it may be controlled by the engine speed or / and the throttle opening (engine load).

Further, in this embodiment, since the introduction port 27a of the first passage 27 is closed by the piston 16 during combustion of the air-fuel mixture, the heat load on the O ₂ sensor 30 can be suppressed to a small level.

By the way, the piston 16 moves to the bottom dead center (BD
When it passes through C) and moves upward, as shown in FIG.
By the piston 16, the main scavenging port 24a and the sub scavenging port 2
5a is first closed, and subsequently, the main exhaust port 7a and the inlet port 27a of the auxiliary exhaust passage 29 (first passage 27) are closed. When the main exhaust port 7a is closed, the cylinder 2
The air-fuel mixture supplied to the inside of a is compressed by the piston 16, and thereafter, the same operation as described above is repeated to continuously operate the two-cycle engine 1.

In FIG. 5, A1 is a period from ignition until the main / sub scavenging ports 24a and 25a start to open, A2 is a period from ignition to scavenging air flow reaching the inlet 27a,
B is the opening period of the main exhaust port 7a, C1 is the main / sub scavenging port 24
The open periods of a and 25a, D is the open period of the inlet 27a, and if the burned gas can be introduced from the inlet 27 only during the period of A2, the air-fuel ratio of the air-fuel mixture can be accurately detected.

By the way, when the operating state of the two-cycle engine 1 changes, the time from the opening of the main / sub scavenging ports 24a, 25a to the arrival of the scavenging air at the inlet 27a changes, but A1 shown in FIG. Only during the period 27
If it is possible to introduce burnt gas from a, the main and auxiliary scavenging ports 24
Since the introduction of the burnt gas from the inlet 27a is completed before the openings a and 25a are opened, the air-fuel ratio of the air-fuel mixture can always be detected reliably.

It is also possible to dispose the inlet port 27a of the first passage 27 between the position where the main exhaust port 7 is open and the position where the main / sub scavenging ports 24a and 25a are open. By doing so, the combustion of the air-fuel mixture is almost completely completed by the time the inlet 27a is opened, and the internal pressure of the combustion chamber S decreases, so that the opening pressure of the first check valve 31 can be set low.
Also, when the inlet 27a is opened, the main / sub scavenging port 24
Since a and 25a are closed, the air-fuel mixture (fresh air) is not mixed with the burnt gas being measured.

Here, another embodiment of the air-fuel ratio detecting device is shown in FIG.
It will be described based on. 8 is a schematic cross-sectional view of a main part of a two-cycle engine (type 2) equipped with the air-fuel ratio detection device according to this embodiment. In this figure, the same elements as those shown in FIG. are doing.

In this embodiment, the main exhaust passage 7 and the auxiliary exhaust passage 29 are formed in the cylinder head 21, and the auxiliary exhaust passage 29 has the inlet 29a always opened in the combustion chamber S. The main exhaust port 7a of the main exhaust passage 7 is configured to be opened / closed by an exhaust valve 34 operated by a cam 33, and an opening / closing control valve 35 controlled to be opened / closed by the ECU 15 is provided in the middle of the sub exhaust passage 29. .

A scavenging valve 36 and a roots type supercharger 37 are provided in the scavenging passage 24. The auxiliary exhaust passage 29
The outlet of is connected to the middle of the downstream side of the main exhaust passage 7,
You may open directly to the atmosphere.

As a result, as shown in FIG. 5, the main exhaust port 7
The opening period of a can be asymmetrical with respect to the bottom dead center (BDC) like B2. In this embodiment, the main scavenging port 24a is opened on the side surface of the cylinder 2a, and the opening period of the main scavenging port 24a is the bottom dead center (BDC) like C1.
It becomes symmetric with respect to. If scavenging is possible even after the exhaust valve 34 is closed in this way, the efficiency of filling the air-fuel mixture (fresh air) can be increased. In the engine where the main exhaust port is provided on the side surface of the cylinder, the scavenging port is provided on the cylinder head, and the scavenging valve that opens and closes by a cam drive is provided on the scavenging port, the main exhaust port opening period and the scavenging port opening period are The setting can be made as shown in B and C2 of FIG. 5, and the charging efficiency of the air-fuel mixture (fresh air) can be increased in the same manner as described above.

Thus, according to this embodiment, the opening / closing control valve 3
5 can be arbitrarily set during the A3 period in FIG. For example, if the burned gas introduction period is set as a ₄ , even if the time when the scavenging air reaches the introduction port 29a changes depending on the operating state, the mixture that does not always contain the air-fuel mixture (fresh air) is reliably generated. The combustion gas can be guided to the O ₂ sensor 30.

By increasing the detection performance of the O ₂ sensor 30, the burned gas introduction period can be set as shown by a ₃ . As a result, even if the operation state changes and the time at which the air-fuel mixture completes combustion varies, the main exhaust passage 7
Even if a backflow of burnt gas due to exhaust pulsation occurs at
The O ₂ sensor 30 can always be made to detect the O ₂ concentration in the burnt gas.

Further, A1 in FIG. 5 (from ignition to main scavenging port 24a
O ₂ during the period from the ignition to the time when the scavenging flow reaches the inlet 29a), that is, during the combustion stroke.
It is also possible to guide the gas in the combustion chamber S to the sensor 30. In this case, because it contains unburned gas in addition to the burned gas, in order to obtain an accurate air-fuel ratio is to be corrected according to the O ₂ concentration value detected by the O ₂ sensor 30 to the operating state There is. Since at least after ignition, there is no unvaporized fuel, and the desired air-fuel ratio can be easily obtained by correction. By setting the introduction period as shown by a ₅ in FIG. 5, even if the unburned gas ratio at each crank angle changes according to the operating state, correction can be relatively easily performed.

Next, another embodiment of the exhaust pulsation adjusting means is shown in FIG.
21 to 21 respectively.

FIG. 9 is a schematic sectional view of a two-cycle engine showing an example in which the exhaust pulsation adjusting means is constituted by the exhaust timing varying device 52. The exhaust timing varying device 52 is a rotary type provided in the exhaust passage 7. It is composed of an exhaust timing adjusting valve 53. In FIG. 9, 16 is a piston and S is a combustion chamber.

Thus, for example, when the air-fuel ratio of the air-fuel mixture shifts in the direction matching the low speed range, the exhaust timing adjusting valve 53 is set faster than the engine speed as shown by the broken line in FIG. Open at the timing. In FIG. 10, the horizontal axis represents the engine speed and the vertical axis represents the opening degree of the exhaust timing adjustment valve 53.

FIG. 11 is a schematic plan sectional view of a two-cycle engine showing an example in which the exhaust pulsation adjusting means is constituted by an auxiliary exhaust passage sectional area varying device 54. The auxiliary exhaust passage sectional area varying device 54 has two auxiliary portions. It is configured by an auxiliary exhaust valve 56 provided in each of the exhaust passages 55. still,
In FIG. 11, 2a is a cylinder and 7 is a main exhaust passage.

Thus, for example, when the air-fuel ratio of the air-fuel mixture deviates in a direction matching the low speed range, the auxiliary exhaust valve 56 is set at a timing earlier than the engine speed as shown by the broken line in FIG. Open with. In FIG. 12, the horizontal axis represents the engine speed and the vertical axis represents the opening degree of the auxiliary exhaust valve 56.

FIG. 13 is a schematic side view of a two-cycle engine showing an example in which the exhaust pulsation adjusting means is constituted by an exhaust branch inlet opening degree varying device 57, and the exhaust branch inlet opening degree varying device 57 is installed in the exhaust pipe 8. It is composed of an exhaust branch 58 formed in part and an opening / closing valve 59 provided at the inlet of the exhaust branch 58. In FIG. 13, 2 is a cylinder body and 21 is a cylinder head.

Thus, for example, when the air-fuel ratio of the air-fuel mixture deviates in a direction matching the low speed range, the on-off valve 59 is set at an early timing relative to the engine speed as shown by the broken line in FIG. close. In FIG. 14, the horizontal axis represents the engine speed and the vertical axis represents the opening degree of the opening / closing valve 59.

FIG. 15 is a schematic side view of a two-cycle engine showing an example in which the exhaust pulsation adjusting means is constituted by the exhaust branch volume varying device 60. The exhaust branch volume varying device 60 is formed in a part of the exhaust pipe 8. The exhaust branch 61 and the piston 62 slidably fitted in the exhaust branch 61. In FIG. 15, 2 is a cylinder body and 21 is a cylinder head.

Thus, for example, when the air-fuel ratio of the air-fuel mixture shifts in the direction matching the low speed range, the piston 62 is slid to move the exhaust branch 6 as shown by the broken line in FIG.
The volume of 1 is reduced by the timing that is faster than the engine speed. In FIG. 16, the horizontal axis represents the engine speed and the vertical axis represents the volume of the exhaust branch 61.

FIG. 17 is a sectional view of the exhaust pipe 8 showing an example in which the exhaust pulsation adjusting means is constituted by the back pressure varying device 63. The back pressure varying device 63 is provided in the exhaust pipe 8 and the back pressure regulating valve is provided. It is composed of 64.

Thus, for example, when the air-fuel ratio of the air-fuel mixture deviates in the direction matching the low speed range, the back pressure adjusting valve 64 is set to a faster timing with respect to the engine speed as shown by the broken line in FIG. To close. In FIG. 18, the horizontal axis represents the engine speed and the vertical axis represents the opening degree of the back pressure adjusting valve 64.

FIG. 19 is a sectional view of the exhaust pipe 8 and the silencer 66 showing an example in which the exhaust pulsation adjusting means is constituted by the back pressure varying device 65. The back pressure varying device 65 is provided in the vicinity of the outlet of the silencer 66. And a back pressure adjusting valve 67.

Thus, for example, when the air-fuel ratio of the air-fuel mixture deviates in the direction matching the low speed range, the back pressure adjusting valve 67 is set to a timing which is faster than the engine speed as shown by the broken line in FIG. To close.

FIG. 20 is a sectional view of the exhaust pipe 8 showing an example in which the exhaust pulsation adjusting means is constituted by the exhaust pipe heating device 68. The exhaust pipe heating device 68 is wound around the outer periphery of the front end portion of the exhaust pipe 8. It is composed of a heater 69 and a battery 70 that supplies a current to the heater 69. By energizing the heater 69 from the battery 70 to heat the exhaust pipe 8,
The temperature of the exhaust gas flowing through the exhaust pipe 8 is increased, and the propagation speed (sonic velocity) of the exhaust pressure wave is increased.

FIG. 21 is a schematic sectional view of a two-cycle engine showing an example in which the exhaust pulsation adjusting means is constituted by a compression ratio varying device 71. The compression ratio varying device 71 is a combustion chamber S.
And a piston 73 slidably fitted in the cylinder 72.

In the above, an example in which each exhaust pulsation adjusting means is controlled by using the engine speed as a parameter has been described, but each exhaust pulsating adjusting means is controlled by using the engine speed or / and the throttle opening (engine load) as a parameter. It may be done. [Second Invention] An embodiment of the second invention will be described below with reference to the accompanying drawings.

Since the second invention is applied to a multi-cylinder two-cycle engine, and only the air-fuel ratio detecting device is structurally different from the first invention, only the air-fuel ratio detecting device will be described below.

<First Embodiment> FIG. 22 is a schematic sectional view of a main part of a two-cycle two-cylinder engine equipped with an air-fuel ratio detecting device according to a first embodiment of the second invention. FIG. 23 is an ignition and sweep / exhaust port. 22 is a timing chart of opening and closing of the communication passage and FIG.
In FIG. 2, the same elements as those shown in FIG. 2 are designated by the same reference numerals.

In the two-cycle two-cylinder engine according to the present embodiment, the sliding (crank angle) of the piston 16 has a phase difference between the cylinders, and the first cylinder 2A and the second cylinder 2B have a continuous cylinder 2a. The passages 38 communicate with each other. The inlets 38a and 38b at both ends of the communication passage 38 are connected to the exhaust port 7
An O ₂ sensor 30 is installed in the chamber 26 provided in the middle of the communication passage 38, which is open above a.
The O ₂ sensor 30 is electrically connected to the ECU 15.

Then, as shown in FIG. 23, the first cylinder 2
For A, the exhaust port 7a, the scavenging port 24a, and the inlet port 38a are opened during the periods B1, C1, and E1. Therefore, the period E1 in which the inlet 38a of the first cylinder 2A is opened and the second cylinder 2
In the periods e ₁ and e ₂ in which the introduction port 38b of B overlaps the period E2, both the introduction ports 38a and 38b are opened and the inside of the cylinder 2a of both cylinders 2A and 2B is connected to the communication passage 3
8 to communicate with each other. At this time, the timing of closing the inlet 38b for the second cylinder 2B is the first cylinder 2A.
Since it is earlier than the opening timing of the scavenging port 24a, the residual pressure in the cylinder 2a of the first cylinder 2A in the expansion stroke becomes higher than the compression pressure of the second cylinder 2B in the compression stroke, and during the period e ₁ , The burnt gas flows from the first cylinder 2A to the communication passage 3
8 to the second cylinder 2B. And in this case,
Since the scavenging port 24a of the first cylinder 2A is closed, the burnt gas flowing through the communication passage 38 does not include fresh air (or air-fuel mixture) as scavenging gas, and therefore the O ₂ concentration of this burned gas is O _2.
2 Detected by the sensor 30.

Further, the timing for closing the scavenging port 24a for the first cylinder 2A is the introduction port 38b for the second cylinder 2B.
Since it is earlier than the timing at which the
The first residual pressure in the cylinder 2a of the cylinder 2B is in the compression stroke.
It becomes higher than the compression pressure of the cylinder 2A, and burned gas flows from the second cylinder 2B to the first cylinder 2A during the period e ₂ , and in this case, since the scavenging port 24a of the second cylinder 2B is closed, The burnt gas flowing through the passage 38 does not include fresh air (or air-fuel mixture) as scavenging gas, so the O ₂ concentration of this burned gas is detected by the O ₂ sensor 30.

It should be noted that both of the inlets 38a and 38b are located farther from the top dead center (TDC) so that the combustion in each cylinder is completed at the respective start timings of the periods E1 and E2. It is arranged. In FIG. 23, G1 and G2 are periods from ignition to combustion completion in each cylinder.

Both inlets 38a and 38b have a top dead center (T
Since both of the inlets 38a and 38b are opened before the combustion in each cylinder is completed, the detected O
₂ Calculate the air-fuel ratio based on the corrected concentration value.

Therefore, also in this embodiment, as in the first aspect of the invention, the O ₂ sensor 30 detects the O ₂ concentration of the burnt gas which does not include the air-fuel ratio (fresh air) in the air-fuel ratio detecting device, and the combustion chamber The air-fuel ratio of the air-fuel mixture supplied to S is ECU
Since it is accurately obtained by 15 based on the detected value of the O ₂ concentration, even in the multi-cylinder two-cycle engine 1,
As with the 4-cycle engine, the air-fuel ratio of the air-fuel mixture can be accurately detected, and the return timing of the reflected exhaust wave in the exhaust pipe can be optimally adjusted according to the operating state of the engine 1. It is possible to improve the exhaust efficiency and improve the performance.

<Second Embodiment> Next, a second embodiment of the second invention will be described with reference to FIGS. 23 and 24. Incidentally, FIG.
Is a 2-cycle 2 equipped with the air-fuel ratio detection device according to the present embodiment.
FIG. 23 is a schematic cross-sectional view of a main part of a cylinder engine, in which the same elements as those shown in FIG. 22 are designated by the same reference numerals.

In this embodiment, the tops of the cylinders 2a of the respective cylinders are communicated with each other by the communication passage 38, and the communication passage 38 is formed.
A chamber 26 is provided in the middle of the chamber 26, an O ₂ sensor 30 is installed in the chamber 26, and the ECU 15 is provided between the chamber 26 of the communication passage 38 and each cylinder 2A, 2B.
An opening / closing control valve 35, whose opening / closing is controlled by the above, is provided.

Thus, the periods e ₁ and e ₂ shown in FIG.
By opening the open / close control valve 35, the air-fuel ratio can be accurately obtained based on the detected value of the O ₂ concentration.

Incidentally, one cylinder 2A (2
(B) Ignition to opening of the scavenging port 24a (Fig. 23)
If both open / close control valves 35 are simultaneously opened by the ECU 15 during a period indicated by F), the burnt gas of one cylinder 2A (2B) in the expansion stroke passes through the communication passage 38 and the other in the compression stroke. Cylinder 2B (2A), in this case,
Since the scavenging port 24a of the cylinder 2A (2B) in the expansion stroke is closed, the burnt gas containing unvaporized fuel flowing through the communication passage 38 does not include fresh air (or air-fuel mixture) as scavenging,
Therefore, the O ₂ concentration of the burned gas is detected by the O ₂ sensor 30, and the air-fuel ratio can be accurately detected by the correction according to the operating state.

Therefore, also in this embodiment, since the air-fuel ratio of the air-fuel mixture is accurately obtained by the air-fuel ratio detecting device,
Also in the multi-cylinder two-cycle engine 1, similarly to the four-cycle engine, the air-fuel ratio of the air-fuel mixture is accurately detected and the return timing of the exhaust reflected wave in the exhaust pipe is optimally adjusted according to the operating state of the engine 1. Therefore, the exhaust efficiency of the multi-cylinder two-cycle engine 1 can be increased to improve the performance.

In the above embodiment, an example in which the second invention is applied to a two-cylinder engine has been described.
It goes without saying that the second invention is similarly applicable to a multi-cylinder engine having three or more cylinders.

[0084]

As is apparent from the above description, claim 1
According to the invention described above, the O ₂ concentration of the burnt gas containing no fresh air is accurately detected by the air-fuel ratio detection device (that is, the period from ignition to when the scavenging airflow reaches the inlet of the auxiliary exhaust passage). Since the burnt gas is introduced into the auxiliary exhaust passage only within the inside, fresh air is not included in the burnt gas flowing through the auxiliary exhaust passage, and the O ₂ concentration in this burned gas is detected by the O ₂ sensor. , The air-fuel ratio of the air-fuel mixture supplied to the combustion chamber is accurately obtained by the air-fuel ratio detection means on the basis of the detected value of the O ₂ concentration. Therefore, in the 2-cycle engine as well as in the 4-cycle engine, The return timing of the reflected exhaust wave can be optimally adjusted according to the operating state of the engine, and the effect that the exhaust efficiency of the two-cycle engine 1 can be improved to improve the performance and the like can be obtained.

According to the second aspect of the invention, as in the first aspect of the invention, the burnt gas O ₂ containing no fresh air is added.
The concentration is accurately detected by the air-fuel ratio detection device (that is, the burnt gas of one cylinder in the expansion stroke flows through the communication passage to the other cylinder in the compression stroke, and in this case, the cylinder in the expansion stroke). Since the scavenging port of is closed, the burnt gas flowing through the communication passage does not contain fresh air. Therefore, the O ₂ concentration of this burnt gas is detected by the O ₂ sensor and supplied to the combustion chamber of each cylinder. Since the air-fuel ratio of the air-fuel mixture is accurately obtained by the air-fuel ratio detection means based on the detected value of the O ₂ concentration), the return timing of the exhaust reflected wave in the exhaust pipe in the two-cycle engine as well as in the four-cycle engine Can be optimally adjusted according to the operating state of the engine, and the effect that the exhaust efficiency of the two-cycle engine 1 can be improved to improve the performance and the like can be obtained.

[Brief description of drawings]

FIG. 1 is a cutaway side view of a main part of a motorcycle showing a two-cycle engine including an exhaust pulsation adjusting device according to a first aspect of the present invention.

FIG. 2 is an enlarged cross-sectional view of a main part of a two-cycle engine including the exhaust pulsation adjusting device according to the first invention.

FIG. 3 is a sectional view of an exhaust pipe showing an exhaust pipe length varying device.

FIG. 4 is a diagram showing control characteristics of an exhaust pipe length varying device.

FIG. 5 is a timing chart of ignition and opening / closing of a sweep / exhaust port and a sub-exhaust passage.

FIG. 6 is a block diagram showing a configuration of a control system.

FIG. 7 is a diagram showing a target air-fuel ratio map.

FIG. 8 is a schematic cross-sectional view of a main part of a two-cycle engine according to another embodiment of the first invention.

FIG. 9 is a schematic cross-sectional view of a two-cycle engine showing an example in which the exhaust pulsation adjusting means is configured by an exhaust timing varying device.

FIG. 10 is a control characteristic diagram of an exhaust timing adjustment valve of an exhaust timing variable device.

FIG. 11 is a schematic plan sectional view of a two-cycle engine showing an example in which the exhaust pulsation adjusting means is constituted by an auxiliary exhaust passage sectional area varying device.

FIG. 12 is a control characteristic diagram of an auxiliary exhaust valve of the auxiliary exhaust passage sectional area varying device.

FIG. 13 is a schematic side view of a two-cycle engine showing an example in which the exhaust pulsation adjusting means is configured by an exhaust branch inlet opening degree varying device.

FIG. 14 is a control characteristic diagram of an opening / closing valve of the exhaust branch inlet opening degree varying device.

FIG. 15 is a schematic side view of a two-cycle engine showing an example in which the exhaust pulsation adjusting means is constituted by an exhaust branch volume varying device.

FIG. 16 is a control characteristic diagram of the exhaust branch volume of the exhaust branch volume varying device.

FIG. 17 is a cross-sectional view of an exhaust pipe showing an example in which the exhaust pulsation adjusting means is configured by a back pressure varying device.

FIG. 18 is a control characteristic diagram of a back pressure adjusting valve of the back pressure varying device.

FIG. 19 is a cross-sectional view of an exhaust pipe and a silencer showing an example in which the exhaust pulsation adjusting means is configured by a back pressure varying device.

FIG. 20 is a sectional view of an exhaust pipe showing an example in which the exhaust pulsation adjusting means is configured by an exhaust pipe heating device.

FIG. 21 is a schematic cross-sectional view of a two-cycle engine showing an example in which the exhaust pulsation adjusting means is constituted by a compression ratio variable device.

FIG. 22 is a schematic cross-sectional view of a main part of a two-cycle two-cylinder engine according to the first embodiment of the second invention.

FIG. 23 is a timing chart of ignition and opening / closing of a sweep / exhaust port and a communication passage of a two-cycle engine according to a second aspect of the present invention.

FIG. 24 is a schematic cross-sectional view of a main part of a two-cycle two-cylinder engine according to a second embodiment of the second invention.

[Explanation of symbols]

1 2 cycle engine 2a Cylinder 7 Main exhaust passage 7a Main exhaust outlet 12 Sensor and throttle valve drive actuator 15 ECU (mixing ratio detection means, control means) 16 Piston 20 Rotation sensor 24 Scavenging passage 24a Main scavenging opening 25 Sub scavenging passage 25a Sub auxiliary Scavenging port 27 First passage 27a Inlet port 28 Second passage 29 Sub-exhaust passage 30 O ₂ sensor 38 Communication passages 38a, 38b Inlet port 50 Exhaust pipe length varying device (exhaust pulsation adjusting means) 52 Exhaust timing varying device (exhaust pulsation adjusting means) ) 54 auxiliary exhaust passage cross-sectional area varying device (exhaust pulsation adjusting means) 57 exhaust branch inlet opening degree varying device (exhaust pulsation adjusting means) 60 exhaust branch volume varying device (exhaust pulsation adjusting means) 63, 65 back pressure varying device (exhaust Pulsation adjusting means) 68 Exhaust pipe heating device (exhaust pulsation adjusting means) 1 compression ratio varying device (exhaust pulsation adjusting means) S combustion chamber

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location F02B 25/20 D F02D 9/04 H 15/04 F 35/00 368 B 45/00 368 F

Claims (2)

[Claims] 1. A device provided in a two-cycle engine for exchanging burned gas and fresh air by scavenging gas introduced into a cylinder from a scavenging port when the exhaust port is opened, the device comprising exhaust pulsation adjusting means. And an O ₂ sensor provided in the middle of the auxiliary exhaust passage for guiding the burnt gas from the combustion chamber to the outside, and an air-fuel ratio detecting means for obtaining the air-fuel ratio of the air-fuel mixture based on the signal from the O ₂ sensor. And an air-fuel ratio detection device capable of introducing burned gas from the inlet of the auxiliary exhaust passage only during a period from ignition to the introduction of scavenging air to the inlet of the auxiliary exhaust passage, and an engine speed or / and By comparing the target air-fuel ratio set based on the throttle opening and the air-fuel ratio detection value detected by the air-fuel ratio detection device, and controlling the exhaust pulsation adjusting means based on the difference between the two, the exhaust pipe of Exhaust pulse adjuster of a two-stroke engine, characterized in that it is configured to include a control means for adjusting the return timing of the air reflected wave, the. 2. A burned gas and a fresh air are provided by scavenging introduced into the cylinder from the scavenging port when the exhaust port is opened in each cylinder, which has at least two cylinders having a phase difference in sliding of the piston. A device provided in a two-cycle engine for exchanging gas, the exhaust pulsation adjusting means, an O ₂ sensor provided in the middle of a communication passage communicating between two adjacent cylinders, and a signal from the O ₂ sensor. The air-fuel ratio detecting means for obtaining the air-fuel ratio of the air-fuel mixture based on the above is included, and both ends of the communication passage are provided only during a period from ignition of one cylinder in the expansion stroke of two adjacent cylinders to opening of the scavenging port. And an air-fuel ratio detection device capable of opening the engine, and a target air-fuel ratio set based on the engine speed or / and the throttle opening and an air-fuel ratio detection value detected by the air-fuel ratio detection device are compared. Control means for adjusting the return timing of the reflected exhaust wave in the exhaust pipe by controlling the ignition timing adjusting means based on the difference between the exhaust pulsation adjustment of the two-cycle engine. apparatus.