JPH09303144A - Spark ignition type two-cycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress temporary generation of exhaust white smoke and exhaust mist, by providing a heat insulating means in the upstream of an exhaust pipe, in a transition combustion operation region performing spark ignition earlier than spark ignition timing in an ordinary combustion operation region to advance combustion start timing. SOLUTION: In a CPU in a spark ignition type two-cycle engine E mounted in a motorcycle, based on an input value from a throttle valve opening sensor 45, engine speed sensor 46, intake negative pressure sensor 47, pressure sensor 49, etc., an operating condition of the engine E is judged, an opening of an exhaust control valve V is determined by an engine speed and a throttle valve opening. In a transition combustion operation region by spark ignition, spark ignition is performed earlier than spark ignition timing of an ordinary combustion operation region, combustion start timing is advanced. Here, in the upstream of an exhaust pipe, a heat insulating means formed by a heat resistant protector, with a heat resistant heat insulating material layered in an internal surface, is provided, in this way, the decreasing of a temperature of exhaust gas, flowing in the upstream part of the exhaust pipe, is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spark ignition type two-cycle system in which an air-fuel mixture is compressed and self-ignited for compression ignition combustion at least in a low load operation range by controlling an exhaust system. It is about the engine.

[0002]

2. Description of the Related Art In a conventional spark ignition type two-cycle engine, the air-fuel mixture in the combustion chamber is reduced by the thermal energy of the residual gas in the previous cycle by reducing the passage area of the exhaust system at least in a low load operation range. Compression ignition combustion is performed to perform compression ignition combustion (hereinafter, referred to as AR combustion), and spark ignition is performed in a transition combustion operation area between the compression ignition combustion operation area (hereinafter, AR combustion operation area) and a normal spark ignition combustion operation area. Control is performed so that the spark ignition timing in the transition combustion operation region is advanced from the spark ignition timing in the normal spark ignition combustion operation region to stabilize the combustion state of the two-cycle engine in all operation regions, Technical means for avoiding combustion noise and heat damage are known (see Japanese Patent Laid-Open No. 7-174064).

[0003]

By the way, in such a two-cycle engine, since the spark ignition timing is advanced in the transition combustion operation region, compared with a normal two-cycle engine in which the spark ignition combustion operation is performed over the entire operation region. In the transitional combustion operation region, the amount of exhaust gas is also small, and it is unavoidable that the temperature of exhaust gas in the exhaust pipe temporarily drops.In particular, in the exhaust pipe of a motorcycle engine, its front side is exposed to running wind. Or, since the front wheel splashes and splashes and is cooled, the temperature of the exhaust gas in the exhaust pipe tends to decrease, and as a result, the exhaust gas white smoke concentration temporarily increases.
There is a problem in that exhaust gas mist may be generated and the driving performance, fuel efficiency, and emission may not be improved to some extent.

Therefore, a means for secondarily heating the exhaust system by a separate heating means such as a heater is conceivable. However, in such means, it is difficult to control the heating because the heating timing is deviated and the above problems cannot be solved. However, there is another problem that the cost is increased.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a novel spark ignition type two-cycle engine that solves all the above problems.

[0006]

In order to achieve the above object, according to the invention as set forth in claim 1, the exhaust system is provided with a variable adjusting means for the opening ratio of the exhaust passage, and a normal combustion operation region by spark ignition, compression A compression ignition combustion operation region (AR combustion region) by self-ignition and a transition combustion operation region by spark ignition between the both operation regions are included, and the transition combustion operation region is earlier than the spark ignition timing of the normal combustion operation region. In a spark ignition type two-cycle engine in which spark ignition is performed to accelerate the combustion start timing, the temperature distribution in the exhaust pipe of the two-cycle engine shows normal combustion operation by spark ignition over the entire operating range. A heat insulating means is provided upstream of the exhaust pipe so that the temperature distribution in the exhaust pipe of a normal spark ignition two-cycle engine is substantially the same. It is characterized in.

To achieve the above object, according to the invention of claim 2, in the engine according to claim 1, the two-cycle engine is suspended on a body frame of a motorcycle, and an exhaust pipe of the engine is suspended. It is characterized in that a heat retaining means is provided on the front side in the vehicle traveling direction.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on embodiments of the present invention shown in the accompanying drawings.

FIG. 1 is a side view of a motorcycle equipped with a spark ignition type two-cycle engine according to the present invention, FIG. 2 is a longitudinal side view of a main part of the two-cycle engine, and FIG.
4 is a cross-sectional plan view taken along the line, FIG. 4 is a partial side view taken along line 4 of FIG. 3, FIG. 5 is a schematic side view showing the control system of the two-cycle engine, and FIG. 6 is a line 6-6 in FIG. 6 is an enlarged horizontal cross-sectional view of the exhaust pipe along FIG. 7, FIG. 7 is a developed vertical cross-sectional view of the exhaust pipe along line 7-7 of FIG. 6, and FIG. 8 is a vehicle speed of the motorcycle and a temperature near the center of the exhaust pipe. It is a graph which shows the relationship of.

In FIG. 1, a spark ignition type two-cycle engine E is suspended on a body frame F of a motorcycle, and the output of this engine E is transmitted to a rear wheel through a chain transmission mechanism as usual. To be done.

Next, this spark ignition type two-cycle engine E is used.
2 to 5, the engine main body 1 of this engine E has a cylinder head 3 integrally coupled to the upper surface of a cylinder block 2 via a gasket, and a lower surface thereof. The crankcase 4 is integrally connected via a packing. A piston 6 is slidably fitted in a cylinder bore 5 formed in the cylinder block 2, and a piston pin 7 of the piston 6 has a connecting rod 9 attached to a crankshaft 8 rotatably mounted on a crankcase 4. Are connected through.
A combustion chamber 10 is formed by the upper surface of the piston 6 and the recess formed in the lower surface of the cylinder head 3.
0, a spark plug 11 screwed to the ceiling of the cylinder head 3
Of the electrode 12 of the spark plug 11, the air-fuel mixture in the combustion chamber 10 is explosively burned by the electric spark of the electrode 12 of the spark plug 11, and the crankshaft 8 is rotationally driven by the ascending and descending drive of the piston 6. The spark ignition two-cycle engine E is operated.

On the rear surface of the crankcase 4 of the engine body 1 (with respect to the traveling direction of the motorcycle), the crank chamber 1
3, an intake port 14 communicating with 3 is opened, and an intake passage 15 whose outer end is open to the atmosphere is connected to the intake port 14. The intake passage 15 is directed from the upstream side to the downstream side. A carburetor 16 and a reed valve 17 are interposed in series. The carburetor 16 has a piston-type throttle valve 18 which faces the intake passage 15.
Is normally connected to a throttle drum 21 via a link 19 and a lever 20, and the throttle drum 21 is connected via a wire to a throttle grip provided on a handle of a motorcycle. Throttle valve 1 by twisting in the direction
8 can be raised against the urging force in the closing direction to adjust the opening degree. Further, the reed valve 17 is
The fresh air-fuel mixture generated by the carburetor 16 is opened by the intake negative pressure in the crank chamber 13, and the fresh air-fuel mixture is introduced into the intake passage 1.
5 is allowed to flow into the crank chamber 13 and its backflow is blocked.

Several scavenging ports 24 and one exhaust port 26 are opened in the inner peripheral surface of the cylinder bore 5, and the scavenging port 24 is provided with a scavenging passage 25 formed in the cylinder block 2. And the exhaust port 26 communicates with the exhaust passage 27. The scavenging port 24 and the exhaust port 26 are controlled to be opened and closed by raising and lowering the piston 6.
That is, in the ascending stroke of the piston 6, the ports 24 and 26 are closed by the piston 6, the crank chamber 13 becomes a negative pressure, and the fresh air-fuel mixture produced by the carburetor 16 is taken into the intake air. It is sucked into the crank chamber 13 through the passage 15. Further, in the descending stroke of the piston 6, the scavenging port 24 is opened by the piston 6, and the compressed fresh air-fuel mixture in the crank chamber 13 becomes
A part of the burnt gas that is supplied from the scavenging passage 25 to the combustion chamber 10 on the piston 6 through the scavenging port 24 and that remains in the combustion chamber 10 is exhausted from the exhaust port 26 through the exhaust port 26 due to the entry of this compressed new mixture. It is discharged to 27. When the scavenging port 24 and then the exhaust port 26 are closed due to the rise of the piston 6, the air-fuel mixture in the combustion chamber 10 is compressed, and when the piston 6 reaches near the top dead center, the spark plug 11
The combustion chamber 10 is ignited by spark ignition by the engine
The compressed air-fuel mixture therein is combusted to operate the two-cycle engine.

On the upstream side of the exhaust passage 27, that is, in the vicinity of the exhaust port 26, exhaust passage opening ratio adjusting means, that is, an exhaust control valve V for variably adjusting the opening ratio of the exhaust passage 27 is provided.

Next, the exhaust control valve V and its mounting structure will be described. On the front wall surface (with respect to the traveling direction of the motorcycle) of the cylinder block 2, a recess 28 communicating with the exhaust port 26 is formed. An arcuate concave surface 28 ₁ is formed on the inner surface of the concave portion 28. The recess 2
An exhaust passage block 29 is fixed to the front wall surface of the cylinder block 2 by a plurality of bolts 33 so as to cover the cylinder block 8. The inner wall surface of the exhaust passage block 29 has a vertical cross-section in the vertical direction so that a part of the inner wall surface fits the arcuate concave surface 28 ₁ of the exhaust port 26.
The curved surface 30 has the same arc shape as 8 ₁ and the cross section of which is the same curvature as the cylinder bore 5. Further, inside the exhaust passage block 29, the exhaust passage 27 communicating with the exhaust port 26 of the cylinder bore 5 and the valve accommodating space 31 communicating therewith are formed. In the valve housing space 31, the exhaust control valve V, which is formed in a fan shape in the vertical cross section and which can variably adjust the opening area of the exhaust port 26, is housed. In the exhaust passage block 29, a valve shaft 32 having a central axis line l-l in a direction substantially orthogonal to the cylinder axis line L-L of the cylinder bore 5 is rotatably mounted, and the exhaust control is performed on the valve shaft 32. The base of the valve V is rotatably supported, and the exhaust control valve V is swingable up and down around the valve shaft 32, and is a bottom for smoothing the flow of exhaust gas flowing through the exhaust passage 27. The wall 34 and the left and right side walls 35 that stand up from the left and right sides of the bottom wall 34 at substantially right angles.
And a front wall 36 including the curved surface 30 having an arc shape centered on the central axis line l-l of the valve shaft 32.
Reference numeral 6 is in sliding contact with the exhaust port 26 formed on the wall surface of the cylinder block 2, and the vertical swing of the exhaust control valve V causes an arc-shaped concave surface 28 ₁ of the cylinder block 2.
Slidingly adjusts the opening area of the exhaust port 26 variably. Further, in the central portion of the bottom wall 34 of the exhaust control valve V,
A through hole 37 is formed to prevent the residue such as carbon contained in the exhaust gas from staying. As shown in FIGS. 3 and 4, a seal member 38 for suppressing leakage of exhaust gas is interposed between the outer end portion of the valve shaft 32 and the exhaust passage block 29. Outer valve stem 3
A drive lever 39 is fixed to the outer end of 2, and the drive lever 39 is connected to a pulley 42 of an exhaust control servomotor 41 via a drive cable 40. According to the operation of the exhaust control servomotor 41, The exhaust control valve V is
The exhaust port 26 is swingably driven up and down to control the opening and closing of the exhaust port 26 from fully closed to fully open, and the opening ratio θe can be set from 0 to 100%.

Next, the operation control system of the two-cycle engine will be described mainly with reference to FIG. 5. The throttle opening degree θth of the manually operated piston type throttle valve 18 is the throttle opening degree including a potentiometer or the like. The engine speed Ne is measured by the sensor 45, the engine speed sensor 46 is measured, the intake negative pressure Pb is measured by the intake negative pressure sensor 47, and the cooling water temperature Tw is measured by the water temperature gauge 48. The ignition pressure, the compression start pressure, etc. are respectively detected by the pressure sensor 49 and are detected by the central processing unit CP.
U is input to the central processing unit CPU, and the clutch engagement / disengagement, transmission gear shift position, and the like are also input to the central processing unit CPU. Then, the central processing unit CPU calculates and determines the operating state of the spark ignition type two-cycle engine based on these input values, and initiates various control signals, for example, by the engine speed Ne and the throttle valve opening θth. The exhaust control servomotor 41 is drive-controlled to determine the opening degree of the exhaust control valve V so that the exhaust passage opening ratio θe is set in advance by a map. The exhaust passage opening ratio θe is set to a value that allows the air-fuel mixture in the cylinder to self-ignite at the most preferable timing for the operation of the engine E.

Further, in this two-cycle engine, the spark plug 11 blows an electric spark to air-fuel in the combustion chamber 10 at 10 ° (crank angle) before the top dead center of the piston 6 in a normal combustion operation region. Control is performed so as to ignite the air-fuel mixture, and based on a preset map from the engine speed Ne and the average effective pressure detected by the engine speed sensor 46 and the pressure sensor 49, a normal combustion operation region When the central processing unit CPU determines that the engine is operated in the transition combustion operation region, the ignition timing of the spark plug 11 is advanced to 20 ° before the top dead center of the piston 6 (crank angle). It is designed to control electric sparks.

As shown in FIG. 1, the exhaust passage block 29 arranged in the front portion of the engine body 1 (with respect to the traveling direction of the motorcycle) has an upstream connecting end of the exhaust pipe Ex, that is, an exhaust pipe portion 50. The connection end faces are integrally connected by a connecting tool such as a bolt.

As shown expanded in FIG. 7, this exhaust pipe E
x is composed of an exhaust pipe portion 50, a divergent cone portion 51, a straight portion 52, a convergent cone portion 53, and a tail pipe portion 54, which are sequentially joined integrally from the upstream side to the downstream side. There is. A temperature sensor 55 is attached to the straight portion 52 corresponding to the central portion in the longitudinal direction of the exhaust pipe Ex.

As shown in FIG. 1, the exhaust pipe Ex has its divergent cone portion 51 curved from the front to the rear so as to bypass the front portion of the engine body 1. The tail pipe portion 54 at the rear portion is extended rearward along one side of the vehicle body frame F toward the rear of the motorcycle, and its outer end is opened to the outside air via the muffler M.

By the way, when the motorcycle is traveling, traveling wind and splashes of the front wheels directly hit the front side of the divergent cone portion 51, thereby cooling the divergent portion 51. Therefore, as shown in FIGS. 6 and 7, the heat retaining means 56 is provided on one front side of the divergent cone portion 51, that is, on the front half of the cross section thereof.
Is applied. That is, the divergent cone portion 5
A heat-resistant protector 58 having a heat-resistant and heat-insulating material 57 such as glass wool laminated on the inner surface is integrally fixed to the front half of the semicircular cross-section of 1 (with respect to the traveling direction of the motorcycle) by a fixing means such as welding. It As a result, the upstream front portion of the exhaust pipe Ex is prevented from being cooled by the traveling wind and splashes on the splashes.

Next, the operation mode of the spark ignition type two-cycle engine will be described.

In an operating region in which the rotation speed Ne of the engine E is high, the rotation speed Ne of the engine E is high, and the throttle valve opening θth is large, the exhaust control valve V is controlled to swing upward and is in a substantially fully open state. And the exhaust passage opening ratio θe is approximately 100%.
Is set at 10 ° (crank angle) before the top dead center of the piston 6, spark ignition is performed by electric spark of the spark plug 11, and normal spark ignition combustion operation is performed.

Further, as the engine speed Ne of the engine E decreases and the engine speed Ne of the engine E and the throttle valve opening θth both decrease, the exhaust control valve V is swung downward and the exhaust port 26 is throttled. If the exhaust passage opening ratio θe decreases as a result, the engine E shifts to the transition combustion operation region between the normal combustion operation region and the AR combustion operation region. In this transition combustion operation region, the ignition timing of the spark plug 11 changes. , Faster than the normal operating range. That is, about 20 before the top dead center of the piston 6.
At (crank angle), the spark ignition is performed by the electric spark from the spark plug 11, so that in this transition combustion operation region, the combustion start timing is substantially equalized in the vicinity of the top dead center of the piston 6 and the pressure fluctuation and The maximum pressure is reduced, combustion noise is reduced, and abnormal combustion is prevented to reduce heat damage. By the way, in this case, if the exhaust pipe Ex is not provided with the above-mentioned heat retaining means 56, the ignition timing is advanced and the amount of exhaust gas flowing through the exhaust pipe Ex is comparatively small, so that the exhaust pipe Ex is exhausted. The temperature of the exhaust gas flowing through the exhaust pipe Ex lowers, and in particular, traveling wind and splashes of the front wheels hit the front side, whereby the upstream side of the exhaust pipe Ex is cooled, and as a result, the temperature of the exhaust gas flowing through the exhaust pipe Ex is further increased. However, there is a possibility that the exhaust gas white smoke concentration and the exhaust gas mist tend to increase, which temporarily causes a decrease in the driver driver performance of the engine, fuel consumption, and poor emission improvement. According to the present invention, the upstream portion of the exhaust pipe Ex, particularly the front half of the exhaust pipe Ex, which is easily cooled, is kept warm by the warming means 56, so that the exhaust gas is exhausted. The temperature drop of the exhaust gas flowing in the upstream portion of Ex is suppressed, and as a result, the temperature of the exhaust gas flowing in the exhaust pipe Ex can be maintained at an appropriate temperature over almost the entire region, and the temperature distribution in the exhaust pipe Ex in the transition combustion operation region can be reduced. The temperature distribution can be made substantially the same as that in the normal combustion operation region, and the temporary inconvenience does not occur.

Further, if the engine speed Ne of the engine E further decreases, or if the engine speed Ne of the engine E and the throttle valve opening θth further decrease, the exhaust control valve V is further swung downward. The exhaust port 26 is throttled, the exhaust passage opening ratio θe further decreases, and the thermal energy of the burned gas in the combustion chamber 10 causes the most preferable ignition timing of the engine E.
The fresh air-fuel mixture in the combustion chamber 10 is compression-ignited by compression and the AR combustion operation is performed.

In the transition combustion operation region between the AR combustion operation region and the irregular combustion operation region, the ignition timing by the spark plug 11 is advanced by 10 ° (crank angle) from the ignition timing in the normal combustion operation region. The irregular combustion is alleviated by being carried out, and the generation of unburned components such as HC is suppressed to improve the emission.

FIG. 8 shows the relationship between the vehicle speed (Km / h) of the motorcycle and the temperature (C °) near the center of the exhaust pipe Ex measured by the temperature sensor 55.
(1) is a temperature characteristic when the spark ignition type two-cycle engine performs a normal spark ignition combustion operation over the entire operation range thereof, and (2) shows a temperature characteristic when the engine is a normal spark ignition operation, AR It is a temperature characteristic in the case of performing a combustion operation and a transition combustion operation in which spark ignition is performed (as in Japanese Patent Publication No. 7-174064), and (3) is the above (2).
In the above, the temperature characteristics when the heat retaining means 56 is applied to the exhaust pipe Ex as described above, and as can be seen from these characteristics, (2) indicates that the exhaust pipe Ex inside the exhaust pipe Ex is at a lower vehicle speed than (1). However, the temperature characteristics of (3) can be made to have substantially the same temperature characteristics as (1), which means that in the transition combustion operation region, as described above, It is possible to improve the driving performance of the two-cycle engine and to improve the fuel consumption and the emission without lowering the temperature in the exhaust pipe Ex even if the speed is increased.

Although one embodiment of the present invention has been described above, the present invention is not limited to the embodiment, and various embodiments are possible within the scope of the present invention. For example, in the above-described embodiment, the case where the two-cycle engine of the present invention is applied to a motorcycle has been described, but it goes without saying that the two-cycle engine can be used as a drive source for other vehicles and devices, and the exhaust pipe and the heat insulating means are However, it is possible to use the other known structure.

[0029]

As described above, according to the invention of claim 1, the normal spark ignition combustion operation, the AR combustion operation and the transition combustion operation are performed, and the normal spark ignition combustion operation is performed in the transition combustion operation region. In the spark ignition type two-cycle engine, which is designed to ignite the spark earlier than the spark ignition timing of the region, by providing the heat insulating means on the upstream side of the exhaust pipe, the temperature distribution in the exhaust pipe of the two-cycle engine can be completely reduced. The temperature distribution in the exhaust pipe of a normal two-cycle engine, in which spark ignition combustion operation is performed by spark ignition over the operating range, can be made approximately the same, and as a result, temporary generation of white smoke in exhaust gas and exhaust mist It is possible to achieve the effect of suppressing the occurrence of fuel consumption and improving the driver's ability and improving fuel efficiency and emissions.

According to a second aspect of the present invention, according to the first aspect of the present invention, the two-cycle engine is for a motorcycle, and a heat retaining means is provided on a front side of an exhaust pipe of the engine in a vehicle traveling direction. As a result, even if the front side of the exhaust pipe is cooled by running wind or splashed splashes, the exhaust gas flowing through the exhaust pipe is kept at an appropriate temperature by the heat retaining means, and the above-mentioned effect is achieved without any hindrance. .

[Brief description of drawings]

FIG. 1 is a side view of a motorcycle equipped with a spark ignition type two-cycle engine.

FIG. 2 is a vertical sectional side view of a main part of a two-cycle engine.

FIG. 3 is a cross-sectional plan view taken along line 3-3 of FIG.

FIG. 4 is a partial side view taken along the line 4 of FIG.

FIG. 5 is a schematic side view showing a control system of a two-cycle engine.

6 is an enlarged cross-sectional view of the exhaust pipe taken along line 6-6 of FIG.

FIG. 7 is a developed horizontal cross-sectional view of an exhaust pipe.

FIG. 8 is a graph showing the relationship between the vehicle speed of the motorcycle and the temperature near the center of the exhaust pipe.

[Explanation of symbols]

 Ex ... Exhaust pipe F ... Body frame 56 ... ..... Insulating means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshinobu Tateshima 1-4-1 Chuo, Wako City, Saitama Prefecture Honda R & D Co., Ltd.

Claims (2)

[Claims] 1. An exhaust system is provided with means for adjusting an opening ratio of an exhaust passage, and a normal combustion operation region by spark ignition, a compression ignition combustion operation region by compression self-ignition, and a transition combustion operation region by spark ignition between these both operation regions. In the transitional combustion operation region, the spark ignition two-cycle engine is configured so that the ignition is performed earlier than the spark ignition timing of the normal combustion operation region to advance the combustion start time, The temperature distribution in the exhaust pipe (Ex) of the two-cycle engine is substantially the same as the temperature distribution in the exhaust pipe of a normal spark-ignition two-cycle engine in which normal combustion operation is performed by spark ignition over the entire operating region. The exhaust pipe (E
A spark ignition type two-cycle engine characterized in that a heat insulating means (56) is provided on the upstream side of (x). 2. The two-cycle engine is suspended on a vehicle body frame (F) of a motorcycle, and a heat insulation means (56) is provided on a front side of an exhaust pipe (Ex) of the engine in a vehicle traveling direction. The spark ignition type two-cycle engine according to claim 1.