JP3004323B2 - In-cylinder injection two-stroke engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an in-cylinder injection two-cycle engine in which fuel is directly injected into a cylinder.

[Conventional technology]

Recently, an in-cylinder injection two-stroke engine in which fuel is directly injected into a cylinder has attracted attention. In this engine, exhaust gas is exhausted from an exhaust port in a piston descending stroke, and air temporarily compressed in a crank chamber is supplied into a cylinder from a scavenging port, and fuel is directly injected into a cylinder by a fuel injection valve in a piston ascent stroke. The fuel injection is performed in a state where the exhaust port and the scavenging port are closed particularly in the constant speed rotation region. Therefore, there is no fuel blow-through, and the exhaust gas countermeasures, the fuel consumption rate, etc. It is advantageous.

[Problems to be solved by the invention]

However, in the above-described in-cylinder injection two-cycle engine, the required fuel injection amount increases in the high-speed rotation region, and the required injection time (crank angle) increases accordingly, so that before the exhaust port and the scavenging port are closed. The fuel injection is started, and the fuel blow-through also occurs.
Therefore, it is demanded that even in this high-speed rotation region, exhaust gas purification can be reliably performed by suppressing fuel blow-through, and fuel efficiency can be improved.

Further, in the above-described in-cylinder injection engine, since the fuel is injected toward the upper surface of the piston, there is a concern that the injected fuel adheres to the upper surface of the piston and the atomization and vaporization of the fuel deteriorate.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems. A fuel injection type two-stroke engine capable of suppressing blow-through of injected fuel even in a high-speed rotation region and suppressing the amount of fuel adhering to the upper surface of a piston. It is intended to provide.

[Means for solving the problem]

The invention according to the first aspect of the present invention includes a fuel injection valve for directly injecting fuel into a cylinder, and an exhaust valve for exhaust timing control provided in an exhaust passage connected to the exhaust port, wherein the exhaust port is opened and closed by a piston. The in-cylinder injection two-cycle engine described above is characterized in that a compressed air injection mechanism for injecting compressed air into the cylinder from the gap between the exhaust passage and the exhaust valve is provided.

According to a second aspect of the present invention, there is provided an in-cylinder injection type two-stroke engine having a fuel injection valve for directly injecting fuel into a cylinder. It is characterized in that a compressed air injection mechanism for injecting along the upper surface of the piston located near the middle of the dead center is provided.

[Action]

According to the fuel injection type two-stroke engine according to the first aspect of the present invention, since compressed air is injected into the cylinder from between the exhaust valve and the exhaust passage, an air curtain is formed near the exhaust port. As a result, the effect of pushing the injected fuel back into the cylinder is obtained, and the blow-through of the fuel is suppressed accordingly.

According to the second aspect of the invention, the fuel injected toward the upper surface of the piston is pushed back before adhering to the upper surface of the piston with the compressed air injected along the upper surface of the piston, and the amount of the fuel is suppressed. , Vaporization and atomization are promoted. Also, the adhering fuel is easily separated from the piston surface by the compressed air, which promotes vaporization and atomization.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIGS. 1 to 3 are views for explaining a fuel injection type two-stroke engine according to an embodiment of the invention of the first aspect of the present invention. FIG. 1 is a sectional side view, and FIGS. 3A is a cross-sectional side view and a cross-sectional plan view of an exhaust valve portion.

In the drawing, reference numeral 1 denotes an in-cylinder injection two-cycle engine. In the engine 1, a cylinder body 3 and a cylinder head 4 are stacked and fastened on a crankcase 2, and an air fuel injection device 13 is mounted on the cylinder head 4. It is of the structure that was done.

The air fuel injection device 13 includes a main body 14 having a valve body 14c for opening and closing the injection nozzle 14b, and a fuel injection valve 15 attached to the main body 14. In addition, 14a is an air rail connected to an air pump as a compressed air source, and 15a is a fuel rail connected to a fuel pump as a fuel source.

A piston 6 to be described later is provided on the lower surface of the cylinder head 4.
A combustion recess 4a that forms the combustion chamber 12 is recessed with the upper surface of the combustion chamber 12. The injection nozzle 14b of the air fuel injection device 13 faces the center of the combustion chamber 12. Further, an ignition plug 16 is mounted on the cylinder head 4 on the front side of the air fuel injection device 13.

A piston 6 is slidably inserted into a cylinder liner 5 fixedly inserted into the cylinder body 3.
A small end 7a of a connecting rod 7 is connected to the piston 6 by a piston pin 8. A large end 7b of the connecting rod 7 is connected to a crank arm 9a of a crank shaft 9 by a crank pin 10. The crank arm 9a is accommodated in a crank chamber 2a of the crank case 2, and the crank chamber 2a is provided in a scavenging passage formed in the cylinder body 3.
The cylinder liner 5 communicates with the scavenging port 5a which is opened in the middle of the cylinder liner 5 via 3a.

The crankcase 2 is formed with an intake port 2b communicating with the crank chamber 2a, and a reed valve 18 is mounted on the intake port 2b together with a joint 19. The reed valve 18 has a V-shaped cross section, a valve seat 20 having an inlet 20a formed on each inclined surface thereof, a valve plate 21 made of a spring steel plate for opening and closing the inlet 20a, and a valve plate 21. And a stopper 22 for regulating the opening. The joint 19 has a throttle body 23 having a throttle valve 23a.
Is connected.

An exhaust port 5b is formed in the cylinder liner 5 at a position facing the scavenging port 5a.
Is led out to the front wall of the cylinder body 3 by an exhaust passage 3b. A valve insertion hole 3e is recessed in the vicinity of the exhaust port 5b on the upper surface of the exhaust passage 3b, and exhaust timing is controlled by changing the upper edge position of the exhaust port 5b in the insertion hole 3e. An exhaust valve 11 is rotatably arranged. One end of the exhaust valve 11 has a drive pulley 24
The pulley 24 is connected to a servomotor by a drive wire 25.

Above the exhaust valve 11 of the cylinder body 3, an air passage 3c of the compressed air injection mechanism 17 is formed. The air passage 3c is substantially the same length as the valve insertion hole 3e, and is a concave groove formed to open into the insertion hole 3e.
A groove 11a is formed at a position corresponding to the groove 3d on the upper surface of the exhaust valve 11 so as to communicate with the groove 3d. Further, a gap a is provided between the valve insertion hole 3e and the exhaust valve 11 in a portion closer to the exhaust port 5b than the concave grooves 3d and 11a, and the gap a allows the concave grooves 3d and 11a to be formed in the exhaust port. It communicates with the cylinder via 5b. The air passage 3c is connected to an air pump 28 driven by a crankshaft by an air passage 27. In addition, this air pump
Numeral 28 is also used to supply compressed air to the air fuel injection device 13. In the middle of the air passage 27, an on-off valve 29 for opening and closing the passage 27 in response to a signal from the control device 30 is provided. Here, 32 is a changeover switch, and 31 is a battery.

 Next, the operation and effect of this embodiment will be described.

In the engine 1 of this embodiment, when the exhaust port 5b starts to open due to the lowering of the piston 6, exhaust gas starts to be discharged from the exhaust passage 3b, and when the scavenging port 5a starts to open, the crank chamber 2a
The air temporarily compressed in the cylinder is supplied into the cylinder via the scavenging passage 3a. In the low-speed rotation region, the fuel is directly injected into the cylinder by the air fuel injection device 13 near the timing when the scavenging port 5a starts to open in the late stage of the rising stroke of the piston 6 in the high-speed rotation region. And in this embodiment,
During the fuel injection period, the on-off valve 29 is
The compressed air is thereby supplied to the concave grooves 3d and 11a, and injected and supplied into the cylinder from the exhaust port 5b through the gap a between the valve insertion hole 3e and the exhaust valve 11, and the compressed air is supplied to the exhaust port 5b. An air curtain is formed. Immediately before the top dead center of the piston 6, it is ignited by the ignition plug 16 and combustion takes place.

As described above, according to the present embodiment, during the period in which the fuel injection is being performed, the compressed air is injected from the gap a of the exhaust valve 11, so that an air curtain is formed in the exhaust port 5b. The fuel injected by the exhaust port
Suppress from blowing through 5b. Here, the compressed air is set to 5 kg / cm ² or more at the supply source, and the injection pressure is much higher than the pressure near the exhaust port of the injected fuel, so that blow-through is reliably prevented. it can.
As a result, unburned components in the exhaust gas are reduced, which is advantageous in purifying the exhaust gas, and the fuel efficiency is improved.

FIG. 4 is a view for explaining an embodiment of the invention of the second aspect of the present application, and the same reference numerals as those in FIG. 1 indicate the same or corresponding parts.

In the drawing, reference numeral 33 denotes a compressed air injection mechanism, which mainly includes an injection body 34 having an injection nozzle 34a, a valve element 33a for opening and closing the injection nozzle 34a, and an electromagnetic coil 33b for driving the valve element 33a forward and backward. It is composed of The injection nozzle 34a is disposed on the side facing the ignition plug 16 and has an injection port 5d formed in the cylinder liner 5.
And is oriented in the radial direction of the cylinder. The injection port 5d is formed near the upper surface of the piston 6 that has risen to a position where the exhaust port 5b has been closed.

In the present embodiment, during the period in which the fuel injection from the air fuel injection device 13 is being performed, the air injection mechanism 33 retreats the valve body 33a to open the injection nozzle 34a, whereby the compressed air is injected and supplied in the radial direction. Is done. Therefore, the injected fuel is
The fuel is pushed back before adhering to the upper surface of the piston 6, and the adhering fuel is also blown off by the compressed air, so that atomization and vaporization of the fuel are promoted. Further, since the fuel is pushed to the electrode side of the ignition plug 16 by the compressed air, the ignition can be reliably performed from this point even when the amount of injected fuel is small in the low-speed rotation region.

In each of the above embodiments, the injection period of the compressed air is controlled to match the injection period of the fuel. However, the injection period of the compressed air does not necessarily need to be controlled in the above-described period. Injection may be performed during the ascent stroke, and may be performed at all times.

〔The invention's effect〕

As described above, according to the first aspect of the present invention, since the compressed air is injected from the gap of the exhaust valve, it is possible to suppress the blow-through of the injected fuel, and to achieve the effect of purifying the exhaust gas and improving the fuel efficiency. According to the second aspect of the present invention, the compressed air is injected along the upper surface of the piston, so that the vaporization and atomization of the fuel can be promoted to improve the combustion efficiency, so that the exhaust gas purification and the fuel efficiency can be improved. There is an effect that can be achieved.

[Brief description of the drawings]

1 to 3 are views for explaining a direct injection two-stroke engine according to an embodiment of the invention of the first aspect of the present invention. FIG. 1 is a sectional side view thereof, and FIGS. FIG. 4 is a cross-sectional side view and a cross-sectional plan view of an exhaust valve portion, and FIG. In the drawing, 1 is a direct injection two-cycle engine, 3b is an exhaust passage, 5 is a cylinder liner (cylinder wall), 5b is an exhaust port, 5d is an air injection port, 6 is a piston, 11 is an exhaust valve, and 15 is fuel. Injection valves, 17 and 33 are compressed air injection mechanisms, and a is a gap.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02B 17/00-25/20 F02B 29/06

Claims (2)

(57) [Claims] A cylinder having a fuel injection valve for directly injecting fuel into a cylinder and an exhaust valve for exhaust timing control provided in an exhaust passage connected to an exhaust port, wherein the exhaust port is opened and closed by a piston. An in-cylinder injection two-cycle engine, comprising a compressed air injection mechanism for injecting compressed air into a cylinder from a gap between the exhaust passage and the exhaust valve. 2. A cylinder injection type two-stroke engine having a fuel injection valve for directly injecting fuel into a cylinder, wherein compressed air is supplied from an air injection port formed in a cylinder wall to a top dead center and a bottom dead center. An in-cylinder injection two-stroke engine, comprising a compressed air injection mechanism for injecting air along an upper surface of a piston located near the middle.