JPH0240041A - Fuel injection control device for 2-cycle direct injection engine - Google Patents

Abstract

PURPOSE:To perform accurate control of an air-fuel ratio by a method wherein an air amount in a cylinder is calculated from a blow-by factor during scavenging, determined by an accel opening, the number of revolutions, and an intake air amount by an airflow meter, and a fuel injection amount is decided by means of the number of revolutions of an engine and an air amount in a cylinder. CONSTITUTION:A control unit 45 decides a running condition by a deciding part 46 by means of the numbers of revolutions of an engine from sensors 42 and 43 and an accel opening. Based on the running condition, the map of a set part 48 is retrieved, and a blow-by factor during scavenging is decided by a deciding part 47. By means of the blow-by factor and an intake air amount measured by an airflow meter 44, an air amount Q' in a cylinder is calculated by a calculating part 49. A deciding part 50 retrieves the map of a set part 51 from the air amount Q' in a cylinder and a number N of revolutions of an engine to decide a fuel injection amount Ti, and an injector 10 is driven through a drive part 52. A fuel-air mixture-air ratio in a cylinder as well as a fuel injection amount can be controlled accurately.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a fuel injection control device for a two-stroke direct injection engine in which fuel is directly injected into a cylinder by an injector, and more particularly to a method of determining a fuel injection amount by taking into account air blow-through during scavenging.

[Conventional technology]

In a two-stroke engine, when air is supplied from the scavenging port for scavenging, some fresh air blows through. At this time,
If the fresh air is an air-fuel mixture containing fuel, this is undesirable because it causes fuel to blow through. Therefore, in order to prevent such fuel from blowing through, a method has been proposed in which only air is used for scavenging, and then fuel is supplied by an injector. Conventionally, regarding the above-mentioned two-stroke engine with an injector, there is a prior art, for example, disclosed in Japanese Patent Application Laid-open No. 11.3819/1983. Here, the air supply system has a thread path for only air and a thread path for the mixture injected by the injector, and after scavenging with air only, the fuel is calculated based on the engine rotation speed and the value detected by the air flow meter. is supplied from the injector to generate a mixture, and this mixture is shown to flow into the cylinder.

[Problem M that the invention attempts to solve]

By the way, the prior art described above has two types of scavenging system paths and is configured to supply air from these two paths during short-time scavenging, which makes the structure complicated and the air supply control complicated. In this respect, the in-cylinder direct injection type is preferable. Furthermore, since the detected value of the air flow meter is directly used to calculate the amount of fuel from the injector, there are the following problems. In other words, some of the air detected by the air flow meter blows through during scavenging and does not contribute to mixture formation, so if fuel is calculated without taking this blow-through into account, it is inevitable that the air-fuel ratio of the cylinder mixture will be accurately controlled. Can not. The present invention has been made in view of the above points, and its object is to provide fuel for a two-stroke direct injection engine that can accurately control the amount of fuel injected by an injector by taking into account air blow-through in a direct-in-cylinder injection type. An object of the present invention is to provide an injection control device.

[Means to solve the problem]

In order to achieve the above object, the fuel injection control device of the present invention is provided with an injector that injects fuel into the combustion chamber of a two-stroke engine main body, and a scavenging pump that supplies only air to the Schilling scavenging port. Seikle direct injection engines have a blow-through determination section that determines the blow-through rate of air during scavenging under various operating conditions based on the accelerator opening degree and engine speed, and a blow-through determining section that determines the amount of air in the cylinder based on the blow-through rate and the amount of intake air determined by the air flow meter. The cylinder air calculation unit includes a cylinder air calculation unit that calculates the cylinder air amount, and a fuel injection amount determination unit that determines the fuel injection amount based on the cylinder air amount and the engine rotation speed.

[For production]

Based on the above configuration, by setting the air blow-through rate during scavenging under each operating condition, the actual amount of air in the cylinder is calculated, and the amount of fuel injection is determined according to this amount of air in the cylinder and the engine speed. is determined accurately, and the air-fuel ratio of the in-cylinder mixture is i&
You will be able to control your subordinates appropriately.

【Example】

Hereinafter, one embodiment of the present invention will be described based on the drawings. In FIG. 1, the overall structure of the two-stroke engine is described. Reference numeral 1 is the main body of the two-stroke engine, and a piston 3 is inserted into a sill 2 so as to be able to reciprocate.
The piston 3 is connected to the crank chamber 4 by a connecting rod 6 eccentric to the crankshaft 5, and a balancer 7 is provided on the crankshaft 5 so as to offset the reciprocating inertia of the piston 3. A spark plug 9 and an in-cylinder direct injection type injector 10 are attached to the top of the combustion chamber 8. An exhaust port 11 is opened in the cylinder 2 and is opened and closed at a predetermined timing by a piston 3.
An exhaust pipe 12 communicating with the catalytic device 13 and the exhaust chamber 14. 15 mufflers are installed. In addition, a scavenging port 16 that opens and closes at a predetermined timing by the piston 3 is opened at a position approximately 90 degrees away from the exhaust port 11 of the cylinder 2 (or a position facing the exhaust port 11). A scavenging system is provided at 16. The injector 10 is of a two-fluid type, which stores a predetermined amount of fuel and then presses it with pressurized air to directly inject the fuel and air in a mixed state. Therefore, the fuel passage 20 of the injector 10 or the filter 2
1. communicates with the fuel tank 23 via the fuel pump 22;
A pressure regulating valve 24 is provided in the middle of the fuel passage 20 to always produce a constant low fuel pressure (slightly higher pressure than the pressurized air). In addition, a pressure regulating valve 2 is provided in the air passage 25 of the injector 10.
6. Accumulator 27. The compressor 28 is connected,
It is designed to produce pressurized air. Then, a predetermined amount of fuel is stored in the injector 10 in advance by a fuel pulse, and after the exhaust port 11 is closed, pressurized air is applied to the fuel by an air pulse and the fuel is injected. Next, the scavenging system of the scavenging port 16 will be described. A scavenging pipe 30 that communicates with the scavenging port 16 is connected to a displacement type via a scavenging chamber 31 that absorbs scavenging pressure waves when the scavenging port 16 is opened and closed, and an intercooler 32 that cools the scavenging air. A scavenging pump 33 is installed in series. Further, a bypass passage 35 communicates between the air cleaner 34 side upstream of the scavenging pump 33 and the downstream side of the intercooler 32.
A control valve 36 for load control is provided. The scavenging pump 33 is connected to the crankshaft 5 by a transmission means 37, and the engine output constantly drives the pump to generate scavenging pressure. Regarding the control system, the accelerator pedal 40 is connected to the control valve 36 via the opening degree changing means 41 so that the opening degree of the control valve 36 is opened and closed in inverse proportion to the accelerator opening degree.
Ru. Also, an engine rotation speed sensor 42 that measures the engine rotation speed N and accelerator opening degree φ that determines each operating condition. An air flow meter 44 for measuring the amount of intake air Q is attached immediately downstream of the accelerator opener 34. The signals from the engine speed sensor 42, accelerator opening sensor 43, and air flow meter 44 are input to the control unit 45 and processed, and the control unit 45 sends fuel and air pulse signals to the injector 10 and ignition signals to the spark plug 9. It is designed to output . The control unit 45 will be described in FIG. First, there is a driving condition determining section 46 which inputs the engine speed N of the engine speed sensor 42, the accelerator opening φ of the accelerator opening sensor 43, and the signals of these driving conditions are input to the blow-through determining section 47. Here, the map setting section 48 stores a map of the blow-through rate e of the increasing function with respect to the accelerator opening φ, as shown in FIG. Determine the air blow-through rate C during scavenging with reference to the map. This blow-through rate e and the intake air amount Q of the air flow meter 4
is input to the cylinder air amount calculating section 49, and the cylinder air amount Q' is calculated as Q
Calculated by '-e-Q. The cylinder air amount Q' and the engine speed N are input to the fuel injection amount determination section 50, and the fuel injection amount T1 is determined by using the coefficient α according to the target air-fuel ratio of the map setting section 51, TQ'/N. α, and the driving unit 52 is configured to output fuel and air pulse signals to the injector according to the fuel injection amount Ti. Next, the operation of the two-stroke direct injection engine configured as described above will be described. First, the scavenging air is discharged from the scavenging pump 33 and sent to the intercooler 32.
The supply air cooled by the exhaust gas is always circulated back to the intake side through the bypass passage 35, and the amount of scavenged air is introduced into the cylinder 2 side by limiting this return amount with the control valve 36. Here, the opening degree θ of the control valve 36 is set in inverse proportion to the accelerator opening degree φ, and when the accelerator opening degree φ is small, more is returned to the opening degree of the control valve 36 and the amount of scavenging air decreases. In this way, the scavenging amount is adjusted to correspond to the accelerator opening degree φ without causing pump loss. Therefore, when the piston 3 is located near the bottom dead center and the scavenging port 16 is opened together with the exhaust port 11 as shown in FIG. The scavenging air is cooled by the scavenging port 16.
It flows into the inside of the cylinder 2. This scavenging air pushes out residual gas from the exhaust port 11 to perform a scavenging action, and in this way, fresh air consisting only of air is introduced into the cylinder 2 in a short period of time. Then, when the piston 3 rises, the scavenging port 16 and the exhaust port 11 close, thereby completing the scavenging and moving to the compression stroke. Further, after the exhaust port 11 is closed, a predetermined fuel stored in the injector 10 in advance by a fuel pulse is injected with pressurized air by an air pulse to generate an air-fuel mixture. Then, it is ignited by the ignition plaque 9 just before top dead center and combusted, or in this case, it is injected from the injector 10 at the top of the combustion chamber 8 into the scavenging air flow flowing in from the scavenging port 16 at appropriate timing and time. When the fuel is introduced and guided to the appropriately placed spark plug position, a rich air-fuel mixture is created near the spark plug 9, resulting in stratified combustion. After the explosion caused by this combustion,
descends and moves to the fat expansion stroke, the exhaust port 11 is opened and exhaust is performed to the extent that the cylinder internal pressure is used, and then near the bottom dead center the cylinder returns to the scavenging stroke where the scavenging action is performed as described above. Run the engine. On the other hand, when the engine is operating, as shown in the flowchart of FIG. 4, the engine rotation speed sensor 42 is activated. The engine speed N, accelerator opening φ, and intake air amount Q are detected by the accelerator opening sensor 43 and air flow meter 44, and the blow-through determining unit 47 determines the air blow-through rate e during scavenging under each operating condition by referring to a map. It is determined as follows. Then, the cylinder air amount calculating section 49 calculates the actual cylinder air amount Q' after scavenging from the blow-through rate e and the intake air amount Q, and the fuel injection determining section 50 calculates the cylinder air amount Q' and the engine rotation speed. N,
The fuel injection amount Ti is determined by the factor of the coefficient α of the target air-fuel ratio, and the fuel is injected from the injector 10 based on this. Therefore, the air-fuel ratio of the in-cylinder air-fuel mixture always remains at a constant target value, and the load is controlled by increasing or decreasing the air-fuel ratio of the air-fuel mixture. Note that the intake air amount measured by the air flow meter may be used instead of the accelerator opening degree as the load element for determining the operating conditions. Furthermore, the fuel injection amount may be determined using either a map or an arithmetic expression. The injector may be of a high-pressure single fluid type.

【Effect of the invention】

As described above, according to the present invention, the amount of fuel injected from the injector of a two-stroke direct injection engine is determined based on the amount of air in the cylinder, which is obtained by taking into account the air blow-through during scavenging. Therefore, it is possible to accurately control the in-cylinder mixture air-fuel ratio as well as the fuel injection amount, and it is possible to always maintain good fuel efficiency, emissions, and running performance. Furthermore, since the air blow-through rate is determined, calculation of the amount of air in the cylinder is facilitated.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing an embodiment of the fuel injection control device for a two-stroke direct injection engine of the present invention, FIG. 2 is a block diagram of the control system, FIG. 3 is a diagram showing a map of the air blow-through rate, and FIG. Figure 4 shows the flowchart 1 to 1 of the operation. DESCRIPTION OF SYMBOLS 1... Engine body, 2... Cylinder, 8... Combustion chamber, 10... Injector, 16... Scavenging port, 33... Scavenging pump, 42... Engine speed sensor, 43 ... Accelerator opening sensor, 44... Air flow meter, 45... Control unit, 47... Air blow-through determining section, 49... Cylinder air flow calculation section, 50
...Fuel Injection Decision Department Patent Applicant Fuji Heavy Industries Co., Ltd. Agent Patent Attorney Makoto Kobashi Ukasa Patent Attorney Susumu Murai

Claims (1)

[Claims] In a 2-stroke direct injection engine in which an injector for injecting fuel is attached to the combustion chamber of the 2-stroke engine body, and a scavenging pump for supplying only air is connected to the scavenging port of the cylinder, a blow-through determination unit that determines an air blow-through rate during scavenging under various operating conditions according to the rotation speed;
A cylinder air calculation section that calculates the cylinder air amount based on the blow-through rate and the intake air amount measured by the air flow meter, and a fuel injection amount determination section that determines the fuel injection amount based on the cylinder air amount and the engine rotation speed. A fuel injection control device for a two-stroke direct injection engine, comprising: