JPH04252866A - Air-fuel injection engine - Google Patents

Abstract

PURPOSE:To decrease the discharge of NOx in full through a slight exhaust gas recirculation value as well as to stabilize a driving run at time of medium- high load driving by conducting a part of exhaust gas to an injector under the specified driving conditions, and spraying this exhaust gas to a combustion chamber together with air and fuel. CONSTITUTION:When a piston goes up and a scavenging stroke is over, an injector 48 opens and a mixture of air and fuel is sprayed into a combustion chamber 50. When the piston 16 is reached to a specified timing advance position short of a top dead center, this mixture is ignited by a spark plug 46, and the piston 16 goes down, and when an exhaust port is opened, exhaust is started. A mixture 60 feeds the injector 48 with air alone at time of low load, but if load grows larger, it mixes air and the exhaust gas together, feeding it to the injector 48. In brief, exhaust gas recirculation takes place at medium load. Therefore, a combustion temperature at this medium load is lowered, thus the discharge of NOx is reduced.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air/fuel injection engine in which air and fuel are injected into a combustion chamber from a common injector.

0002

[Prior Art] In order to reduce unburned gases such as HC and CO in exhaust gas, air and liquid fuel are injected into a combustion chamber into which fresh air consisting only of air is introduced, and the injected fuel is diffused. There are air/fuel injected engines that are ignited by a spark plug in the area.

In this case, during low-load operation with a small amount of fuel injected, the combustion temperature is also relatively low, making it possible to properly purify the exhaust gas, but during medium- to high-load operation, the combustion temperature increases and nitrogen oxides (NOx) are produced. increases. In order to reduce NOx, part of the exhaust gas is sucked into the combustion chamber together with fresh air during medium- to high-load operation, and is then returned to the combustion chamber through exhaust gas recirculation (EGR).
) method is widely used.

However, in the above-mentioned air/fuel injection system, if EGR is performed in which exhaust gas is mixed into the intake air as in the conventional system, the combustion temperature cannot be lowered sufficiently because the exhaust gas is not sufficiently mixed into the ignition region. For this reason, the amount of EGR must be increased, resulting in an excessive amount of exhaust gas being contained in the area around the combustion chamber, resulting in a problem that medium to high load operation becomes unstable.

[0005]

[Object of the Invention] Accordingly, the present invention has been developed to sufficiently reduce NOx emissions with a small amount of EGR in an air/fuel injection engine, and to stabilize operation during medium and high load operation. The purpose is to

[0006]

According to the invention, the object is to inject air and fuel into the combustion chamber from a common injector.
Achieved by an air/fuel injection engine characterized in that under predetermined operating conditions, a portion of the exhaust gas is guided into the injector and this exhaust gas is injected into the combustion chamber together with the air and fuel. .

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a partially sectional side view of a single-cylinder motorcycle engine according to an embodiment of the present invention, and FIG. 2 is a sectional view showing a mixer. In FIG. 1, numeral 10 is a crankcase, 12 is a cylinder body, 14 is a cylinder head,
16 is a piston, 18 is a crankshaft, and 20 is a connecting rod.

22 is an air cleaner, and 24 is an element provided therein. The air cleaner 22 is connected to a crank chamber 32 via a throttle body 26, an intake pipe 28, and a reed valve 30. 34 is a throttle valve. 36 is a scavenging passage, and 38 is an exhaust passage. A pincushion-shaped exhaust control valve 40 with a portion cut out is provided on the upper wall of the exhaust port, and the exhaust timing is changed by rotating this in accordance with changes in engine speed. 42 is a plunger type air pump, which is mechanically driven by the crankshaft 18 via a gear mechanism (not shown). This air pump 42 compresses the air led from the air cleaner 22 and discharges it to the discharge port 44 .

46 is a spark plug, and 48 is an electromagnetic injector. This injector 48 mixes air led from the discharge port 44 of the air pump 42 and fuel led from a fuel pump (not shown), such as a gear pump, and injects the mixture into the combustion chamber 50. During high-load operation, a small amount of exhaust gas enters the injector 48 here, and a small amount of exhaust gas enters the mixer 6 (described later).
Contaminated by 0. The injection timing of the injector 48 is managed by a control circuit (not shown) to vary depending on operating conditions, and is set to open from the end of the scavenging stroke to the compression stroke.

The air pressure and fuel pressure introduced into the injector 48 are controlled by a differential pressure regulator 52 so as to be constant. That is, the discharge pressure of the air pump 42 is kept constant by the differential pressure regulator 52, while the diaphragm valve balances the resultant force of this air pressure and the differential pressure setting spring force with the fuel pressure. Excess air that has passed through the differential pressure regulator 52 is returned to the air cleaner 22 through a pipe 54.

Next, the mixer 60 for performing EGR will be explained. This mixer 60 mixes exhaust gas into the air entering the injector 48 from the air pump 42 when the throttle valve 34 is at a medium opening.

In FIG. 2, 62 is a body, and a spool 64 is slidably mounted on this body 62. The spool 64 is formed into a cylindrical shape with an open lower end, and the opening at the lower end is connected to the air inlet of the injector 48 by a pipe 66 provided in the body 62. body 6
2, an air inflow port 68 and an exhaust gas inflow port 70 are formed at opposing positions with the spool 64 in between. Approximately 5 kg/cm of air is introduced into the air inlet port 68 by a pipe 72 from the outlet 44 of the air pump 42.
m of pressurized air is directed through check valve 74. Reference numeral 76 is a relief valve that returns surplus air that is not used by the injector 48 out of the air supplied from the air pump 42 to the air cleaner 22 through a pipe 78. The exhaust gas inflow port 70 is connected to the exhaust passage 3 by a pipe 80.
8 (Figure 1).

The spool 64 moves up and down as the throttle grip 82 opens and closes, and returns to the lowest position when the throttle grip 82 is in the idle position. A distributor 86 is interposed in the middle of the wire 84 connecting the throttle grip 82 and the spool 64, and the rotation of the throttle grip 82 is transmitted to the throttle valve 34 by the wire 88 to open and close it.

At low load positions, including idle of the spool 64, only the air inlet port 68 is open and the injector 4
8 is supplied with only air. throttle grip 82
When the spool 64 is rotated in the opening direction and the load increases, the baffle plate 64 formed on the spool 64 opens in front of the air inflow port 68.
a is opposed, while the exhaust gas inflow port 70 is opened. As a result, the air sent from the air pump 42 is depressurized by the throttling effect of the baffle plate 64a, and the spool 6
4, while exhaust gas flows into this spool 64. The air and exhaust gas are then mixed and guided to the injector 48.

When the throttle grip 82 is further turned and a high load is applied, the exhaust gas inflow port 70 is closed again and only the air inflow port 68 is opened. Therefore, only air is guided to the injector 48. This is preferable based on a comprehensive evaluation of the concentration of each component in the exhaust gas, including HC and CO, taking into account that the amount of air (fresh air) required increases due to the increase in fuel amount at high loads. This is for the purpose of Further, by supplying only air under high load, it is possible to prevent tar and carbon in the exhaust gas from adhering to the injector 48. However, the present invention enables E
Including those who perform GR. Note that in consideration of the control range of the injection amount of the injector 48, fuel may be added from another injector 90 into the scavenging passage 36 during high load. In this case, the scavenging passage 36 that injects fuel is the exhaust passage 3
8 is desirable.

Next, the operation of this embodiment will be explained. As the piston 16 rises, outside air is drawn into the crank chamber 32 through the element 24, throttle body 26, intake pipe 28, and reed valve 30. As the piston 16 descends,
When the inside of the crank chamber 32 is prepressurized and the piston 16 opens the scavenging port, the air inside the crank chamber 32 passes through the scavenging passage 36 and flows into the combustion chamber 50 from the scavenging port.

When the piston 16 rises and the scavenging stroke ends, the injector 48 opens and a mixture of air and fuel is injected into the combustion chamber 50. When the piston 16 reaches a predetermined advanced angle position before top dead center, the air-fuel mixture is ignited by the spark plug 46, and when the piston 16 descends and the exhaust port opens, exhaust begins.

The mixer 60 supplies only air to the injector 48 when the load is low, but when the load increases, the mixer 60 mixes air and exhaust gas and supplies the mixture to the injector 48. That is, EGR is performed under medium load. This lowers the combustion temperature under medium loads and reduces NOx emissions. Note that the present invention includes a four-stroke engine.

[0019]

[Effects of the Invention] As described above, since the present invention adds exhaust gas to the injector that injects air and fuel into the combustion chamber under predetermined operating conditions, there is no possibility that the exhaust gas will mix into the ignition area where the fuel has diffused. , the combustion temperature decreases, and NO.
Emissions of X will decrease. In particular, since the exhaust gas subjected to EGR directly enters the ignition region, it can directly contribute to lowering the combustion temperature in this region, making it possible to significantly reduce NOx with a small amount of EGR. Therefore, an excessive amount of exhaust gas is not contained in the area around the combustion chamber, and engine operation is stabilized.

[Brief explanation of the drawing]

[Fig. 1] A partially sectional side view of a single-cylinder motorcycle engine that is an embodiment of the present invention.

[Figure 2] Cross-sectional view showing the mixer

[Explanation of symbols]

48 Injector 50 Combustion chamber 60 Mixture

Claims (1)

[Claims] 1. An air/fuel injection engine in which air and fuel are injected into a combustion chamber from a common injector, in which a portion of exhaust gas is guided to the injector under predetermined operating conditions, and this exhaust gas is injected into the air and fuel. An air/fuel injection engine characterized by injecting fuel into the combustion chamber.