JPH1037769A - Two-cycle engine of intra-cylinder injection type - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection type two-cycle engine which can prevent irregular combustion and can make O2 feedback control stably over the whole operating range. SOLUTION: A two-cycle engine concerned is equipped with an ignition plug 34 mounted on a cylinder head 5, a fuel injection valve 14 which supplies in injection a greater amount of fuel with increasing load before ignition by the plug 34 in compliance with the engine load set by an accelerator operating part in the suction path or a combustion chamber (a) bounded by the cylinder head 5, cylinder body 4 and a piston 6, an O2 concentration sensing means 53 to sense the O2 concentration in a sample gas taken from the combusted gas, and an operation control means which controls the engine operating condition so that the sensed O2 concentration or the air-fuel ratio decided by it becomes the target value. The exhaust passage 35 is equipped with an exhaust gas control valve 39 which can change the section area, and sampling of the combusted gas by the O2 concentration sensing means 53 is stabilized by setting the degree of opening of the exhaust gas control valve in the operating range with small engine load to a smaller value than the degree of opening in the operating range with a large engine load.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention is to relates to a fuel injection type 2-cycle engine so as to inject and supply fuel, the stabilized operation, especially over the entire operating range of the O ₂ feedback control to the combustion chamber or the intake path To improve the method of collecting burned gas so that it can be performed.

[0002]

2. Description of the Related Art Conventionally, fresh air is introduced into a crank chamber through an intake passage to perform primary compression, and the compressed fresh air scavenges the inside of a cylinder, while fuel is injected from a fuel injection valve disposed on a combustion chamber wall. During the scavenging and exhaust strokes, and during the compression stroke, the fuel is injected by the ignition plug through the compression stroke and burned, and the burned gas is discharged from the combustion chamber to the exhaust passage prior to the scavenging stroke. An in-cylinder injection two-stroke engine configured as described above has been proposed.

On the other hand, in a two-cycle engine, the burned gas in the cylinder before combustion and before exhaust is selectively sampled, and the O ₂ concentration in the sampled gas is measured to determine the air-fuel ratio (A / A / C) in the cylinder. F) is obtained, and the fuel supply amount is feedback-controlled so that the detected air-fuel ratio becomes a target value.

[0004]

In order to employ the above-described feedback control in a fuel injection type two-cycle engine, the combustion in each cycle must be stable, that is, the burned gas must be stably collected in each cycle. Although it is necessary to be able to do so, it is difficult to stably employ the feedback control in the entire operation range of a two-cycle engine because irregular combustion generally occurs in a low-speed low-load operation range.

That is, in the two-cycle engine, particularly in a low load operation range, fresh air entering the combustion chamber by scavenging is
A so-called blow-by that is discharged from the combustion chamber to the exhaust passage together with the burned gas occurs. At low load where the throttle valve opening is small, the fresh air amount for scavenging itself is small, and during the scavenging process or during the period from the end of the scavenging process until the exhaust hole closes, the pressure in the combustion chamber drops below atmospheric pressure. I will. During this period, the combustion chamber communicates with the exhaust passage, and the burned gas in the exhaust passage whose temperature has decreased flows back into the cylinder. When the amount of fresh air blow-through is large, even if the throttle valve is abolished, the pressure in the combustion chamber during the above-mentioned period becomes large at a low load with a small amount of burnt gas, and The burned gas whose temperature has been further reduced by the part of the air and the fresh air that has blown through flows back into the cylinder.

[0006] In the case of injecting and supplying fuel into the intake passage, the mixture in the combustion chamber deviates from the proper mixing state by the proportion of the burned gas whose temperature has decreased. Therefore, even if the air-fuel mixture in the combustion chamber is ignited, a misfire may occur. On the other hand, in the case of fuel injection into the combustion chamber, vaporization itself is not sufficiently performed, so that it is difficult to form a proper air-fuel mixture. Once a misfire occurs, in the next cycle, what flows back in the next cycle is not the burned gas but fresh air remaining due to the misfire, so the proportion of burned gas in the combustion chamber decreases and a proper mixture is formed. Even if the temperature is low, it will ignite if ignited with a spark plug. Irregular combustion occurs due to repetition of misfire or ignition.

In particular, the number of the above-mentioned misfire cycles increases in the lower load operation range, and the number of combustion cycles in which the gas for detecting the O ₂ concentration can be reduced decreases. Even if the air-fuel ratio can be detected and the fuel amount is changed based on the detected air-fuel ratio, it is not possible to stop the misfire in a cycle in which the temperature of the burned gas has a large residual ratio. That is, even if the O ₂ feedback control is performed, it is not possible to improve the exhaust gas properties and the fuel efficiency in the low load operation range.

The present invention has been made in view of the above circumstances, and provides a fuel injection type two-cycle engine capable of preventing irregular combustion and stably operating O ₂ feedback control in the entire operation range. That is the task.

[0009]

According to a first aspect of the present invention, an accelerator operating portion is set in a combustion chamber or an intake passage formed by a spark plug mounted on a cylinder head, a cylinder head, a cylinder body, and a piston. A fuel injection valve for injecting a larger amount of fuel before the ignition by the spark plug in accordance with the engine load to be loaded, and an O for detecting a burned gas and detecting an O ₂ concentration in the collected gas.
₂ concentration detecting means, and the detected O ₂ concentration or the O ₂ concentration
_And an operation control means for controlling an engine operation state so that an air-fuel ratio obtained from the concentration becomes a target value.
In a cycle engine, an exhaust control valve that makes a passage cross-sectional area variable is provided in an exhaust passage, and the opening of the exhaust control valve in an operating range where the engine load is small is set smaller than the opening of the exhaust control valve in an operating range where the engine load is large. O
_{(2) A} burned gas stabilizing means for stabilizing the sampling of burned gas by the concentration detecting means.

According to a second aspect of the present invention, in the first aspect, the operation control means opens the exhaust control valve when the detected O ₂ concentration or air-fuel ratio is richer or leaner than a target value. At least one of increasing or decreasing the degree, decreasing or increasing the fuel injection amount, advancing or retarding the fuel injection timing, and increasing or decreasing the throttle valve opening is performed.

According to a third aspect of the present invention, in the first or second aspect, the exhaust control valve changes the upper edge position of the exhaust port substantially in the cylinder axial direction, thereby delaying the exhaust start timing (exhaust timing). Thus, the present invention is also characterized in that it also serves as an exhaust start timing variable valve that increases the exhaust passage cross-sectional area by reducing the exhaust passage cross-sectional area and increasing the exhaust start timing.

According to a fourth aspect of the present invention, in any one of the first to third aspects, at least two exhaust ports are provided in the cylinder axial direction, and an exhaust passage is connected to each of the exhaust ports.
The exhaust control valve is disposed at least in an exhaust passage connected to an exhaust port closest to the cylinder head.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the fuel injection valve directs the injection flow directly in the vicinity of the ignition plug or in the vicinity of the ignition plug after collision with the combustion chamber wall. It is characterized by being arranged as follows.

According to a sixth aspect of the present invention, in the fifth aspect, a plurality of injection flows are generated by providing at least one of a plurality of fuel injection valves or a plurality of fuel injection valves having a plurality of injection holes, and at least one of the fuel injection valves is provided. The injection flow is directed toward the top of the piston.

According to a seventh aspect of the present invention, in the sixth aspect, at least one injection flow is directed directly near the spark plug.

According to an eighth aspect of the present invention, in any one of the first to seventh aspects, the fuel injection valve is disposed on a cylinder side wall.

According to a ninth aspect of the present invention, in any one of the first to eighth aspects, a sampling hole for sampling the burned gas is provided in a portion of the exhaust passage upstream of the exhaust control valve. .

[0018]

According to the first aspect of the present invention, the opening of the exhaust control valve in the operating range where the engine load is small is set smaller than the exhaust control opening in the operating range where the engine load is large. Exhaust passage resistance in the region increases, and the exhaustability of burned gas in the exhaust stroke decreases.

That is, the air-fuel mixture in the combustion chamber is deviated from the proper mixing state as in the case where the burned gas having a low temperature stays in the combustion chamber without the exhaust control valve. Since the opening degree is reduced, the temperature of the burned gas remaining in the combustion chamber is high, and the ignitability at the time of ignition is improved.

As a result, misfire can be prevented and irregular combustion can be prevented, the burned gas can be stably collected in any cycle, the air-fuel ratio can be detected quickly and reliably, and feedback can be performed in all operation ranges. There is an effect that the control can be operated stably.

According to the second aspect of the present invention, when the air-fuel ratio detected by the air-fuel ratio detecting means is richer or leaner than the target value, the degree of opening of the exhaust control valve is increased or decreased. Since at least one of decreasing or increasing the fuel injection amount, advancing or retarding the fuel injection timing, and increasing or decreasing the throttle valve opening is performed, the air-fuel ratio converges to the target value. Can be done.

That is, when the detected air-fuel ratio is, for example, on the rich side, if the exhaust control valve opening is increased, the passage resistance of the exhaust passage is reduced, the intake air amount is increased, and the throttle valve opening is increased. In this case, the passage resistance of the intake passage decreases and the intake air amount increases, and in any case, the air-fuel ratio is corrected to the target value. When the fuel injection amount is reduced, the fuel ratio is reduced, so that the air-fuel ratio is corrected to the target value. Further, when the fuel injection timing is advanced, the diffusion of the fuel proceeds and the blow-through amount increases, so that the air-fuel ratio is corrected to the target value side. When the detected air-fuel ratio is on the lean side, the operation is reversed. As described above, in any case, the air-fuel ratio can be made to converge to the target air-fuel ratio, and the control accuracy of the feedback control can be improved.

According to the third aspect of the present invention, since the exhaust control valve also functions as the exhaust start timing variable valve, in the low load operation range, the exhaust passage resistance increases and the exhaust start timing is delayed, so that the burned combustion has already started. Gas emission is further reduced,
Acceleration of fuel vaporization by raising the temperature of the combustion chamber, prevention of fuel diffusion by prevention of gas flow in the combustion chamber and backflow into the combustion are further ensured, irregular combustion can be reliably prevented, and the burned gas can be reliably reduced in any cycle. The air-fuel ratio can be extracted quickly, and the air-fuel ratio can be quickly detected, and the feedback control can be operated more stably in the entire operation range.

According to the fourth aspect of the present invention, at least two exhaust ports are provided in the cylinder axial direction, each exhaust port is connected to an exhaust passage, and the exhaust passage is connected to at least the exhaust passage closest to the cylinder head. Since the control valve is provided, the exhaust passage resistance increases in the low load operation range and the exhaust start timing is delayed in the low load operation range, so that the feedback control operates more stably in the entire operation range. There is an effect that can be made.

According to the fifth aspect of the present invention, since the injection flow is arranged so as to be directed directly to the vicinity of the ignition plug or to be directed to the vicinity of the ignition plug after the collision with the combustion chamber wall, the mixture is densely mixed in the vicinity of the ignition plug. This has the effect that the air can be more reliably formed and the ignitability can be further improved.

According to the sixth aspect of the present invention, since a plurality of injection flows are generated and at least one injection flow is directed to the top of the piston, the vaporization of fuel directed to the top of the piston can be further improved. is there.

According to the seventh aspect of the present invention, since at least one jet flow is directed directly to the vicinity of the ignition plug, a rich mixture cloud can be formed more reliably near the ignition plug, and the ignitability can be improved. There is.

According to the eighth aspect of the present invention, since the fuel injection valve is disposed on the side wall of the cylinder, the injection nozzle of the injection valve is covered by the piston skirt during a period in which the combustion gas temperature is the highest, and the fuel injection There is an effect that the durability of the valve can be improved.

According to the ninth aspect of the present invention, since the burned gas sampling hole is provided in the exhaust passage upstream of the position of the exhaust control valve, the pressure of the burned gas acting on the O ₂ concentration sensor in a cyclic manner can be reduced. And the durability of the O ₂ concentration sensor can be improved.

[0030]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 14 are views for explaining a direct injection two-cycle engine according to an embodiment of the present invention. FIG. 1 is an overall configuration diagram including a control device, FIG. 2 is a plan configuration diagram, FIG. 4 is a sectional side view and a sectional plan view around the combustion chamber, FIG. 5 is a sectional side view of a fuel injection valve, FIGS. 6 and 7 are sectional side views and a front view of an injection nozzle portion, and FIG. FIG. 9 is a block diagram of the operation control device, FIG. 10 is an explanatory diagram of the operation, FIG. 11 is a three-dimensional map, FIG. 12 is an exhaust control valve opening-engine load characteristic diagram, and FIG. FIG. 14 is a flowchart of the feedback control characteristic, and FIG.

In FIG. 1, reference numeral 1 denotes a water-cooled parallel three-cylinder in-cylinder injection two-cycle engine. The engine 1 is mounted on a body frame 2 of a motorcycle with a crankshaft 8 directed horizontally in a vehicle width direction. I have. In the engine 1, an independent cylinder body 4 and a cylinder head 5 are stacked and fastened to a front portion of a crankcase 3 having a built-in transmission so that the cylinder axis is vertically oriented for each cylinder, and a cylinder bore 4a of each cylinder body 4 is provided. The piston 6 is slidably inserted therein, and each of the pistons 6 is connected to a crank arm 8 a of a crankshaft 8 by a connecting rod 7. Further, a combustion recess 5a is provided on the mating surface of the cylinder head 5, and the electrode 34a of the ignition plug 34 is located in the recess 5a.

The engine 1 has an intake system A for introducing outside air into a space (combustion chamber a) surrounded by the combustion recess 5a, the cylinder bore 4a, and the top of the piston 6, and fuel is supplied into the combustion chamber a. A fuel supply system B for directly injecting and supplying, and an exhaust system C for discharging burned gas generated in the combustion chamber a to the outside
And

The intake system A includes the crank arm 8a
A lead valve assembly 9 for preventing backflow is inserted into an intake port 3b formed so as to communicate with the back of each cylinder-independent crank chamber 3a in which the cylinders are accommodated. Through the throttle body 11,
And an air cleaner 12 common to the three cylinders, and the inside of each of the crank chambers 3a is communicated with the inside of the cylinder bore 4a through a plurality of scavenging passages 13. Reference numeral 13a is a scavenging port that opens to the cylinder bore 4a.

The throttle body 11 has a throttle valve 29 for controlling the opening and closing of the intake passage area. The throttle valve 29 is driven to open and close by a throttle actuator 31 disposed at an end of a valve shaft 30. The actuator 31 is controlled by an ECU 70, which will be described later, based on a rotation angle of an accelerator grip 19, which is an accelerator operation unit mounted on the right end of the steering handle 33. In the present embodiment, the rotation angle of the accelerator grip 19 indicates the engine load θ.

The fuel supply system B supplies the fuel in the fuel tank 21 to the fuel cock 22, the fuel filter 23, and the fuel injection valve 14 for each cylinder mounted on the rear wall 4 b of the cylinder body 4. Supply pump 24, fuel delivery pipe 2
5 and the fuel supply pipe 26. In addition, 27 is a pressure regulator for adjusting the fuel pressure in the fuel distribution pipe 26 to a predetermined pressure, and 28 is a return pipe.

As shown in FIGS. 5 to 7, the fuel injection valve 14 has a substantially rod-shaped valve body 1 in a substantially cylindrical housing 15.
6 is inserted and arranged to be able to advance and retreat, and the valve element 16 is connected to the electromagnetic coil 1.
7, the injection port 15e is opened and closed by driving forward and backward.

The housing 15 has a structure in which an introduction pipe 15b having a fuel introduction hole 15d and a nozzle body 15c having the injection port 15e are inserted and fixed in a cylindrical housing body 15a having both ends opened. ing.

The valve body 16 comprises a valve member 16a for opening and closing the injection port 15e, and an armature 16b constituting a part of a magnetic circuit. The magnetic circuit includes the armature 16b and the housing body 15a,
And the introduction pipe 15b. A return spring 18 is provided between the armature 16b and the introduction pipe 15b to urge the valve body 16 in a direction to close the injection port 15e.

A flange 16c is integrally formed in the middle of the valve member 16a.
The opening degree of the injection port 15e is regulated by the contact of the stopper c with the stopper 15i sandwiched between the nozzle body 15c and the housing body 15a. And the valve member 1
A magnetic gap G is provided between the upper end surface of the armature 16b and the lower end surface of the introduction pipe 15b in a state where 6a is in close contact with the valve seat of the injection port 15e. Since the magnetic gap G divides the magnetic circuit, it is adjusted at the time of manufacture so that the magnetic gap G accurately matches a predetermined design value.

A guide nozzle 15f for regulating the injection direction and distribution ratio of the fuel injected from the injection port 15e is fixed to the tip of the nozzle body 15c. The guide nozzle 15f has an upward hole 15g for directing the jet flow toward the spark plug and a downward hole 15h for directing the piston top. This downward hole 1
The diameter D2 of 5h is set to be larger than the diameter D1 of the upward hole 15g, so that the fuel amount of the injection flow y directed to the top of the piston is larger than the injection flow x directed to the spark plug. The jet stream y spreads at a wider angle than the stream x and spreads uniformly (see FIG. 4). The amount of combustion injection per combustion cycle is proportional to the time during which the valve body 16 keeps the injection port 15e open. As the rotation angle of the accelerator grip 19 is set larger, that is, as the engine load increases, the opening of the throttle valve 29 is set larger, and the opening time is set longer, and the combustion injection amount is increased. .

The exhaust system C discharges the burned gas generated in the combustion chamber a into an exhaust port 35a opening at the front of the cylinder bore 4a, an exhaust passage 35, and an exhaust gas connected to an external opening 35b of the passage 35. The air is discharged to the outside air through a pipe 36, an exhaust muffler 36a, and an outlet 36b.

In each of the exhaust passages 35, a valve body 38 of an exhaust start timing variable valve 37 for variably controlling the exhaust start timing (exhaust timing) by changing the substantially upper edge position of each exhaust port 35a is provided. A valve body 40 of an exhaust control valve 39 for variably controlling the passage cross-sectional area is provided in each of the exhaust pipes 36.

The exhaust start timing variable valve 37 is formed by connecting three valve bodies 38 arranged in each exhaust passage 35 by a drive shaft 41, and the drive shaft 41 is driven by an actuator 42 such as a servo motor. Is done. Each of the valve bodies 38 has a valve portion 38a in which a part of a drum-shaped rod is cut out in accordance with the shape of the inner surface of the exhaust passage, and the valve portion 38a is flush with the top wall surface of the exhaust passage 35. The advanced position (see the solid line in FIG. 3) and the most retarded position (FIG. 3) where the valve portion 38a projects into the exhaust passage 35.
(See a two-dot chain line).

When the valve body 38 is located at the most advanced position, the edge 38b of the valve portion 38a on the cylinder bore side coincides with the upper edge of the exhaust port 35a, and the top of the piston 6 connects the upper edge. Exhaust is started at the time of passing. On the other hand, when the valve body 38 is located at the most retarded position, the valve portion 38
The edge 38b of a is located below the upper edge of the exhaust port 35a, and the exhaust starts when the piston top passes through the edge 38b. The exhaust port area (exhaust passage area) is maximum when the valve body 38 is at the most advanced position, and is minimum when the valve body 38 is at the most retarded position. Therefore, the exhaust start timing variable valve 37 also functions as a variable valve of the exhaust passage area.

The exhaust control valve 39 is formed by connecting a valve body 40 disposed in each exhaust pipe 36 by a drive shaft 43. The drive shaft 43 is connected to an actuator 4 such as a servomotor.
4 is driven. The valve body 40 has a valve plate 4 attached to a valve shaft 40a.
0b is fixed by bolting, and the passage area of the exhaust pipe 36 is arbitrarily changed between fully open and fully closed.

The positions of the exhaust port 35a and the scavenging port 13a in the cylinder axial direction are set so that the exhaust port 35a starts to open first with the lowering of the piston 6, and the scavenging port 13a starts to open slightly later. Have been. Therefore, when the exhaust stroke starts after the explosion stroke, the scavenging stroke starts slightly later. This relationship is maintained even when the valve body 38 of the exhaust start timing variable valve 37 is located at the most retarded position.

The engine 1 has a rotation speed sensor (pulse generator) 51 which also serves as a crank angle sensor and detects an engine rotation speed, and an accelerator opening which detects an accelerator opening as sensors for detecting various parameters indicating an engine operating state. O ₂ for detecting the degree sensor 52, O ₂ concentration
Sensor 53, other intake pipe pressure sensor 54, intake pipe temperature sensor 55, crank chamber pressure sensor 56, in-cylinder pressure sensor 57, engine temperature sensor 58, exhaust pipe pressure sensor 5
9. Various sensors such as an exhaust pipe temperature sensor 60 are provided.

Here, as shown in FIG. 3, the O ₂ concentration sensor 53 is adapted to sample the burned gas from a sampling hole 4b formed closer to the cylinder head 5 than the exhaust port 35a of the cylinder bore 4a. . When the piston 6 rises to near the top dead center, ignition is performed, and the piston 6
Is lowered to open the sampling hole 4b, the burned gas containing no fresh air is supplied to the O ₂ concentration sensor 53 through the sampling hole 4b. The O ₂ concentration sensor is denoted by 53 ′ in FIG.
The sampling hole 4 provided in the cylinder bore 4a
Instead of b, a sampling hole 4b 'may be provided at an intermediate position between the exhaust port 35a of the exhaust passage 35 and the exhaust control valve 39 to sample the burned gas. Even when the exhaust control valve 39 is closed, the burned gas can be collected, the pressure of the burned gas acting in a cyclic manner can be reduced, and the durability of the O ₂ concentration sensor can be improved. . Further, if the sampling hole 4b 'is provided on the wall which is the upper surface in the vertical direction of the exhaust passage 35, the oil transmitted through the inner wall of the exhaust passage 35 will not block the sampling hole 4b'.

An EC 70 controls the operating state of the engine.
U, and the ECU 70 determines the opening degree (intake air amount) of the throttle valve 29, the opening timing (fuel injection timing) of the fuel injection valve 14, and the opening time (fuel Injection amount), the ignition timing by the ignition circuit 45, the opening of the exhaust start timing variable valve 37 (exhaust start timing), and the opening of the exhaust control valve 39 (exhaust passage resistance) are controlled.

Next, the operation control in the engine 1 of this embodiment will be described in detail. FIG. 10 is a characteristic diagram for explaining the opening / closing timing of each port, the fuel injection timing, and the like by the crank angle. In the drawing, TDC and BDC are the top dead center and the bottom dead center, respectively, and S is the scavenging port 13a. , E and E 'indicate the open period of the exhaust port 35a, Q indicates the fuel injection possible period during which the injection hole is exposed into the combustion chamber a, and C indicates the ignition timing. The fuel injection period changes according to the engine load and the opening of the exhaust control valve 39. That is, the fuel injection period becomes longer as the engine load increases. When the engine load is a medium load or a predetermined load smaller than the medium load, the fuel injection start timing is the latest. At this time, the opening degree of the exhaust control valve 39 is fully open. Q2 indicates a fuel injection period when the engine load is the above-mentioned predetermined load. Then, as the engine load becomes smaller than the predetermined load, the opening degree of the exhaust control valve 39 is reduced, the fuel injection start timing is advanced, and the fuel injection period is shortened. Q3 indicates the fuel injection period when the engine load is at a minimum. On the other hand, as the engine load becomes larger than the predetermined load, the fuel injection period becomes longer and the fuel injection start timing is advanced. In this engine load region, the opening of the exhaust control valve 39 is kept fully open. Q1 indicates the fuel injection period when the engine load is at its maximum.

In the present embodiment, the exhaust start timing variable valve 37
The exhaust start timing (timing at which the exhaust port opens) and the exhaust port open period change depending on the rotation angle of. When the variable valve 37 is rotated, for example, to the position indicated by the solid line in FIG. 3, the exhaust start timing is the earliest, the compression start timing is the latest, and the exhaust port open period is the longest (see FIG. 10E). On the other hand, when the exhaust start timing variable valve 37 is rotated to the position indicated by the two-dot chain line in FIG. 3, the exhaust start timing is the latest, the compression start timing is the earliest, and the exhaust port open period is the shortest (E in FIG. 10). 'reference).

The ECU 70 sets the exhaust start timing variable valve 37 also serving as the compression start timing variable valve in the low speed rotation low load operation range set based on the engine speed N and the engine load (accelerator opening) θ. It is located at the most retarded position shown by the dashed-dotted line, is located at the most advanced position shown by the solid line in the high-speed rotation high-load operation range, and is appropriately changed in the operation range therebetween. As a result, an exhaust timing according to the operating state of the engine is obtained, and a sufficient intake air amount in a high-speed rotation high-load operation range is secured while preventing blow-by in a low-speed low-load operation range.

FIG. 12 is a characteristic diagram for explaining a map value setting image of the opening degree of the exhaust control valve 39. That is, in the low-speed rotation range, the opening degree of the exhaust control valve 39 is substantially fully closed at the minimum engine load, increases as the load increases, and is fully opened at the substantially maximum load. In the middle speed range, the exhaust control valve 3
The opening of No. 9 is set to approximately 1/2 at the minimum load and fully opened at approximately the middle load. In the high-speed rotation range, the exhaust control valve 39
Is almost fully opened in a substantially full load range. That is, the exhaust control valve 39 is closed in the low-speed rotation and low-load operation range.

As described above, the control of the exhaust start timing variable valve 37 and the exhaust control valve 39 is basically controlled based on the engine load and the engine speed, but the O ₂ concentration detected by the O ₂ sensor 53 is controlled. Is adjusted in feedback control to converge the target value to the target value. This feedback control will be described mainly with reference to FIG.

In the O ₂ feedback control, the ECU 70
, The engine speed N and the accelerator opening θ are read, and the ignition timing (IGN), fuel injection timing (INJ), exhaust control valve opening (EXV), throttle opening ( TH) and the fuel injection amount (DUR) are read from a built-in basic map, and the ignition circuit 45 and the actuator of each valve are driven based on these values (steps S1 to S4).

Then, the engine speed N and the accelerator opening θ are compared with the previous N and θ, and when it is determined that the steady operation is being performed because the change of both is within a predetermined value (step S5), O _{2 is determined.} The density is read, and the detected value and the target value (O
O ₂ density difference between XG), i.e. if the lean state or rich state is Me determined (step S6～8), based on the O ₂ concentration difference, the exhaust control valve opening (EXV), the fuel injection amount (D
UR), the fuel injection timing (INJ), and the throttle opening (TH) correction amounts ΔEXV, ΔDUR, ΔINJ, ΔT
H, are calculated (step S9).

FIG. 13 schematically shows how to obtain the various correction amounts. The correction amount ΔEXV of the exhaust control valve opening is set to the closing side as the detected O ₂ concentration is leaner than the target value, and is set to the opening side as the detected O ₂ concentration is richer than the target value (see FIG. 7A). For example the introduction of fresh air and exhaust control valve 39 opening is closed exhaust passage resistance is increased is reduced, the introduced amount of fresh air becomes small and open the exhaust passage resistance increases, O ₂ concentration target value Converges to

Although not shown, the opening correction in the feedback control of the exhaust start variable valve 37 has basically the same tendency as the exhaust control valve 39, and is added to the opening of the exhaust control valve 39. Is controlled as follows. That is, when the exhaust control valve 39 is corrected to the open side, the exhaust start timing variable valve 37 is also corrected to the open side.

The correction amount ΔDUR of the fuel injection amount increases as the detected O ₂ concentration becomes leaner than the target value.
The closer to the rich side, the lower the side is set (see FIG. 8B). The O ₂ concentration converges to the target value, for example, toward the rich side when the fuel injection amount is increased, and toward the lean side when the fuel injection amount is decreased.

The correction amount INJ of the fuel injection timing is such that the closer the detected O ₂ concentration is to the lean side of the target value, the more the retarded side becomes.
The more the position is on the rich side, the more the advance angle is set (see FIG. 3C). For example, when the fuel injection timing is retarded, the fuel does not diffuse in the combustion chamber and the blow-through amount decreases, and when the fuel injection timing is advanced, the fuel diffusion advances and the blow-through amount increases, and the O ₂ concentration converges to the target value. I will do it.

The correction amount ΔTH of the throttle opening is set to the closing side as the detected O ₂ concentration is leaner than the target value, and is set to the opening side as the detected O ₂ concentration is richer than the target value (FIG. 4D).
reference). For example, the introduction amount of fresh air and exhaust control valve opening is closed intake passage resistance becomes large decrease, introduction of fresh air intake passage resistance is reduced to be opened is increased, O ₂ concentration converges to the target value I will do it.

Based on the sum of the various basic map values and the correction values, the opening of the exhaust control valve 39, the opening timing and opening time of the fuel injection valve 14, and the opening of the throttle valve 29 are controlled ( In steps S10 and 11), the engine speed N and the accelerator opening θ are read again, and the process returns to step S5 to repeat the above control. Step S5
In step S13, if it is determined that the vehicle is not operating in a steady state due to sudden acceleration or the like because the difference from the previous values of N and θ is equal to or greater than the predetermined value, the above-described various map values are cleared in step S13 and the process proceeds to step S1. Return.

As described above, in the engine 1 of this embodiment, the exhaust control valve 39 and the exhaust start timing variable valve 37 are throttled in the low-speed rotation low-load operation range, so that the exhaust passage resistance increases in the operation range. The exhaustability of the burned gas in the exhaust stroke decreases. Therefore, the blow-by phenomenon of fresh air is suppressed, and the burned gas having a high temperature stays in the combustion chamber a, the inside of the combustion chamber a is kept at a high temperature, and the finely-granulated fuel injected into the combustion chamber a is atomized. Vaporization is promoted.

That is, as in the case where the burned gas having a low temperature stays in the combustion chamber a without the exhaust control valve 39, the air-fuel mixture in the combustion chamber a deviates from the proper mixing state. Since the opening of the control valve 39 is reduced, the combustion chamber a
The temperature of the burned gas that has accumulated in the spark plug 34 is high.
The ignitability of the electrode 34 at the time of ignition is improved.

As a result, misfire can be prevented and irregular combustion can be prevented, and the burned gas can be extracted in any cycle.
The air-fuel ratio can be detected quickly, and the feedback control can be operated stably in the entire operation range.

If the detected O ₂ concentration is richer or leaner than the target value, the exhaust control valve 39,
The opening degree of the exhaust start timing variable valve 37 is increased or decreased, the fuel injection amount is decreased or increased, the fuel injection timing is advanced or retarded, and the throttle valve opening degree is increased or decreased. _{2 The} concentration can be made to converge to the target value.

That is, when the detected O ₂ concentration is on the lean side, the openings of the exhaust control valve 39 and the exhaust start timing variable valve 37 are corrected to decrease, the passage resistance of the exhaust passage increases, and the intake air amount increases. Is decreased, the opening of the throttle valve 29 is corrected to decrease, the passage resistance of the intake passage increases, the intake air amount decreases, and the O ₂ concentration converges to the target value. Further, the fuel injection amount is increased, and the fuel injection timing is further retarded, so that the diffusion of the fuel is difficult to proceed, the blow-through amount decreases, and the O ₂ concentration converges to the target value side. Thus, the O ₂ concentration (air-fuel ratio) can be made to converge to the target value, and the control accuracy of the feedback control can be improved.

The exhaust start timing variable valve 3 of this embodiment
7 also has an exhaust passage area variable function. That is, in the low-speed rotation low-load operation range, the area of the exhaust port 35a is reduced, the exhaust passage resistance is increased, the exhaust start timing is delayed, and the exhaustability of the burned gas is further reduced.

Therefore, the promotion of fuel vaporization by raising the temperature of the combustion chamber, the prevention of gas diffusion in the combustion chamber and the prevention of fuel diffusion by preventing backflow into the combustion are further ensured, and irregular combustion can be reliably prevented. In addition, the burned gas can be stably collected, the air-fuel ratio can be quickly detected, and the feedback control can be operated more stably in the entire operation range.

In the fuel injection valve 14 of this embodiment, part of the injection flow x flows toward the electrode of the ignition plug 34 through the upward hole 15g, and most of the injection flow y flows downward and It flows toward the top of the piston 6 while spreading more widely. Therefore, most of the fuel strikes the top of the high-temperature piston and is reliably vaporized and uniformly distributed in the combustion chamber, and a dense mixture cloud easily ignited near the electrode 34a due to the upward jet flow, further improving ignitability. it can.

Further, in this embodiment, the fuel injection valve 1
Since the fuel injection valve 14 is disposed on the side wall of the cylinder, the tip of the injection valve 14 is covered by the piston 6 during the period in which the combustion gas temperature is the highest, and the durability of the fuel injection valve 14 can be improved accordingly.

In the above embodiment, the case where the number of exhaust ports is one has been described, but the number of exhaust ports according to the present invention is not limited to one.

FIG. 15 shows an embodiment of the fourth aspect of the present invention. In this example, two exhaust ports 35c and 35d are provided side by side in the cylinder axis direction, exhaust passages 35 'and 35 are communicated with the respective exhaust ports 35c and 35d, and an exhaust start timing is set in the exhaust passage 35' located on the cylinder head side. A variable valve 37 'is provided, and an exhaust control valve 39 is provided downstream of the junction of the two passages 35', 35.

In the present embodiment, in the low-speed rotation and low-load operation range, the exhaust start timing variable valve 37 'completely closes the exhaust passage 35', and the opening degree of the exhaust control valve 39 is set in FIGS.
The control is performed based on the characteristic diagram shown in FIG. Thus, as in the above-described embodiment, in the low-speed rotation low-load operation range,
The exhaust passage resistance increases and the exhaust start timing is delayed, so that the feedback control can be operated more stably in the entire operation range.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram including a control device of a direct injection two-stroke engine according to an embodiment of the present invention.

FIG. 2 is a plan view of the engine.

FIG. 3 is a sectional side view of the engine.

FIG. 4 is a sectional plan view of the engine.

FIG. 5 is a sectional side view of a fuel injection valve employed in the engine.

FIG. 6 is an enlarged sectional view of a tip portion of the fuel injection valve.

FIG. 7 is a front view of the tip.

FIG. 8 is a system diagram of an intake system, a fuel supply system, and an exhaust system of the engine.

FIG. 9 is a block diagram of the control device.

FIG. 10 is a characteristic diagram of an opening period of each port, a fuel injection period, and the like in the engine.

FIG. 11 is an image diagram showing three-dimensional map data for operation control of the engine.

FIG. 12 is an image diagram for setting a map value of an opening degree of the exhaust control valve.

FIG. 13 is a characteristic diagram of various correction values for O ₂ feedback control of the control device.

FIG. 14 is a flowchart illustrating a control operation of the control device.

FIG. 15 is a schematic view of an engine according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Engine 5 Cylinder head 34 Spark plug 4 Cylinder body 6 Piston a Combustion chamber 14 Fuel injection valve 53 O ₂ sensor (O ₂ concentration detecting means) 70 ECU (Operating control means) 36 Exhaust pipe (exhaust passage) 39 Exhaust control valve 39 , 70 Exhaust control valve, ECU (burned gas stabilizing means) 35, 35 'Exhaust passage 35a Exhaust port 37 Exhaust start timing variable valve 15g, 15h Injection hole

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location F02D 13/02 F02D 13/02 AG 35/00 368 35/00 368C 41/02 325 41/02 325B 41/04 305 41/04 305C 310 310C 335 335C 41/14 310 41/14 310A F02M 61/14 310 F02M 61/14 310S 310U 61/18 320 61/18 320C 69/04 69/04 P 69/10 69/10

Claims (9)

[Claims] 1. A load increases in accordance with an engine load set by an accelerator operation section in a combustion chamber or an intake passage formed by a spark plug mounted on a cylinder head, a cylinder head, a cylinder body, and a piston. extent and amount of fuel ignition plug injecting and supplying the fuel injection valve before ignition by, O ₂ in the gas collected by blood collection was collected the burnt gasses
And O ₂ concentration detection means for detecting the concentration, O ₂ issued該検
In a fuel injection type two-stroke engine provided with an operation control means for performing feedback control of an engine operation state so that an air-fuel ratio obtained from the concentration or the O ₂ concentration becomes a target value, an exhaust passage having a variable passage cross-sectional area in an exhaust passage. By providing a control valve and setting the degree of opening of the exhaust control valve in the operating range where the engine load is small to be smaller than the degree of opening of the exhaust control valve in the operating range where the engine load is large, sampling of the burned gas by the O ₂ concentration detecting means can be performed. A fuel-injected two-stroke engine comprising: a means for stabilizing burned gas. 2. The operation control means according to claim 1, wherein
Is the detected O _TwoThe concentration or air-fuel ratio is
If the exhaust side is rich or lean, open the exhaust control valve.
Decrease or increase the fuel injection amount, increase or decrease the degree
Throttle, to advance or retard the fuel injection timing
Increase or decrease the valve opening.
A fuel-injection two-stroke engine characterized by the above-mentioned. 3. The exhaust passage cutoff valve according to claim 1, wherein the exhaust control valve makes an upper edge position of the exhaust port substantially variable in an axial direction of the cylinder and delays an exhaust start timing (exhaust timing). A fuel injection type two-stroke engine characterized in that it also serves as an exhaust start timing variable valve that increases the exhaust passage cross-sectional area by reducing the area and making the exhaust start timing earlier. 4. The exhaust passage according to claim 1, wherein at least two exhaust ports are provided in the cylinder axial direction, and an exhaust passage is connected to each exhaust port, and at least an exhaust passage connected to the exhaust port closest to the cylinder head. A fuel injection type two-stroke engine, wherein the exhaust control valve is disposed on the engine. 5. The fuel injection valve according to claim 1, wherein the fuel injection valve is disposed so that the injection flow is directed directly to the vicinity of the ignition plug or to the vicinity of the ignition plug after collision with the combustion chamber wall. A fuel-injection two-stroke engine characterized by the above-mentioned. 6. The fuel injection system according to claim 5, wherein the plurality of fuel injection valves are provided.
Alternatively, a fuel injection type two-stroke engine characterized in that a plurality of injection flows are generated by providing at least one of a fuel injection valve having a plurality of injection holes, and at least one injection flow is directed toward a top of the piston. 7. The fuel injection type two-stroke engine according to claim 6, wherein at least one injection flow is directed directly near the spark plug. 8. The fuel injection type two-stroke engine according to claim 1, wherein the fuel injection valve is disposed on a cylinder side wall in any one of the holes 1 to 7. 9. The fuel injection type two-cycle according to claim 1, wherein a sampling hole for sampling the burned gas is provided at an upstream portion of the exhaust passage at a position where the exhaust control valve is disposed. engine.