JPH0626390A - Control device for 2-cycle engine - Google Patents

Abstract

PURPOSE:To promote the atomization of fuel at low load area in an cylinder inner side injection type 2-cycle engine. CONSTITUTION:In an area at low load of a 2-cycle engine 1 where any blow-by is not produced, an injection pressure is lowered, an injection start time is advanced, and an injection interval is increased to prolong the lapse of time after an injector is energized for use of an area (B) where atomized particle size becomes small. Because a injection pressure is lowered at low load area, an engine load is reduced to increase rotational stability and also, because the injection interval is increased, an area where the atomized particle size becomes small can be used to promote the atomization of fuel.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for improving combustibility in a two-stroke engine by atomizing fuel.

[0002]

2. Description of the Related Art In a two-cycle engine for a vehicle or the like, for example, as described in JP-A-2-49939, fuel is directly injected into a cylinder by an in-cylinder injector in order to prevent the fuel from passing through. It is normal to jet. When the fuel is directly injected into the cylinder in this way, the atomization of the fuel is deteriorated.Therefore, it is preferable to use an air brass valve to inject the fuel together with the compressed air, or to increase the injection pressure of the fuel to atomize the fuel. It is being promoted. Further, the two-cycle engine described in JP-A-3-105059 is provided with an injector that directly injects fuel into the cylinder and an injector that injects fuel into the intake passage, and has a fuel injection amount. When the injection amount is small, only the in-cylinder injection is performed, and when the injection amount is large, a part of the injection is performed in the intake passage with a good atomization to improve the atomization of the fuel.

Separately from this, a diesel engine or the like using an injector capable of adjusting the injection pressure is conventionally known.

The injector shown in FIG. 6 is an example of a cylinder injection type injector whose injection pressure can be adjusted. The injector 100 shown in the figure holds a tubular movable element 102 and a solenoid coil 103 for driving the movable element 102 in a main body casing 101, and a cap 104 connected to one end side of the main body casing 101 with respect to in-cylinder pressure. It holds the needle 105 (valve member) that opens outward and functions as a check valve. In addition, the fuel inlet pipe 10 is attached to the socket 106 attached to the other end of the main body casing 101.
7 are connected. A connecting element 108 forming a seat surface with which the lower end of the movable element 102 can abut is fixed to the head of the needle 105, and the needle 105 is urged toward the closing side between the connecting element 108 and the cap 104. The first spring 109 is installed. A movable plate 110 is fixed to the head of the movable element 102, and a second spring 111 that urges the movable element 102 toward the needle 105 is installed between the movable plate and the socket 106.

When the solenoid coil 103 of the injector 100 is energized, the movable element 102 is lifted upward in the figure, the movable element 102 and the connecting element 108 are opened, and the high-pressure fuel supplied from the fuel inlet pipe 107 is released. It flows around the needle 105 through a groove on the outer circumference of the connecting element 108. Then, the needle 105 is pressed and opened by the fuel pressure against the biasing force of the first spring 109, and the fuel is injected.

[0006]

When the injection pressure is set high in order to prevent deterioration of fuel atomization due to in-cylinder injection in a two-cycle engine, the work load of the fuel pump increases and the engine load increases, As a result, engine rotation in the low load region where rotation is originally unstable becomes more unstable. Further, for example, in the injector shown in FIG. 6, the valve member biased by the elastic member opens the valve against the biasing force of the elastic member by the fuel pressure and injects the fuel, and the initial injection pressure is An elastic member for urging the valve member (first part of FIG. 6)
Since it is determined by the set load of the spring 109), the injection pressure is low at the initial stage of energization and the spray particle size is large as shown in FIG. Therefore, if the injection pressure is set high in such an injector, the energization time to the injector becomes shorter in a region where the required fuel injection amount is small, such as in the low load region, and as a result, In the characteristic diagram of FIG. 2, the injection ends only in the region where the spray particle size is large, which is indicated by A.
Atomization of fuel cannot be achieved.

Further, in the case of the one in which a part of the fuel is injected into the intake passage as in the two-cycle engine described in Japanese Patent Laid-Open No. 3-105059, only a part of the atomization of the fuel can be achieved, and There is also a stairwell. Also,
In the case of using an air blast valve to atomize fuel,
The engine load is also increased due to the compressed air injection.

The present invention has been made in view of the above problems, and in a two-cycle engine, promotes atomization of fuel and promotes combustibility in a low load region without causing rotational instability due to an increase in engine load. Intended to improve.

[0009]

DISCLOSURE OF THE INVENTION The present invention is directed to in-cylinder injection in which a valve member whose injection pressure is adjustable and biased by an elastic member is opened by a fuel pressure against the biasing force of the elastic member to inject fuel. Type injector is used in a two-cycle engine, the injection pressure is reduced in the low load region of the engine, and the injection period is extended by that amount, so that the spray particle size is small even in the low load region where the required fuel injection amount is small (Fig. It has been found that it is possible to utilize the region indicated by B in the characteristic diagram of 2), thereby promoting the atomization of the fuel without increasing the engine load, and the configuration thereof is as follows.
This is as shown in FIG. That is, the control device for a two-cycle engine according to the present invention receives an output of the in-cylinder injector capable of adjusting the injection pressure, an operating state detecting means for detecting the operating state of the engine, and an output of the operating state detecting means. , A required fuel injection amount calculation means for calculating a required fuel injection amount according to an operating state of the engine, and an output from the required fuel injection amount calculation means, and by setting an injection period corresponding to the required fuel injection amount, the injection Injector driving means for driving the injector from a predetermined injection start timing so as to obtain a period, low load area detecting means for detecting that the operating state of the engine is in a predetermined low load area, and output of the low load area detecting means In response to the output of the injection pressure reducing means for reducing the injection pressure of the injector in the low load area and the output of the low load area detecting means, the injection pressure is reduced in the low load area. Characterized by a decrease in the injection rate that an injection period enlarging means for enlarging the injection period to inject a required fuel injection quantity compensated by the injection period by.

In order to obtain the longest possible injection period while preventing the fuel from passing through in the low load region, the fuel injection start timing by the injector should always be set after at least one of the intake port and the exhaust port is closed. Of the non-blowing area detecting means for detecting that the operating state of the engine is in the non-blowing area where the scavenging efficiency and the air supply ratio are proportional, and the output of this non-blowing area detecting means, In the non-blowing region, it is preferable to provide injection start timing changing means for changing the injection start timing so as to start fuel injection during scavenging in which both the intake port and the exhaust port are open.

[0011]

When the engine is in the predetermined low load range, the injection pressure of the in-cylinder injector is set lower, and the injection period is extended so as to obtain the required fuel injection amount. As a result, the injector energization area (area indicated by B in the characteristic diagram of FIG. 2) where the spray particle size becomes small can be used,
As a result, atomization of the fuel in the low load region is achieved.
Further, by reducing the injection pressure, an increase in engine load can be prevented.

Further, since fuel injection is started during scavenging in which both the intake port and the exhaust port are open in the non-blowing region where the scavenging efficiency and the supply ratio are proportional, the injection period is prevented while preventing blow-through of fuel. It is possible to expand to the maximum.

[0013]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 3 is an overall system diagram of the first embodiment of the present invention. In the figure, reference numeral 1 is a uniflow type two-cycle engine, in which a cylinder chamber 3 is formed inside a cylinder block 2, and a cylinder head 4 is connected to the upper portion thereof. A combustion chamber recess 5 is formed on the inner surface of the cylinder head 4. An intake port 7 is formed in the lower portion of the cylinder block 2 so as to be opened and closed at a predetermined timing as the piston 6 moves up and down. On the other hand, the combustion chamber recess 5 of the cylinder head 4 is provided with an exhaust port 8 and an exhaust valve 9 that opens and closes the exhaust port 8. In the combustion chamber recess 5, an injector 10 for fuel injection whose injection pressure can be adjusted is also installed, and an ignition plug 11 is also installed. As the injector 10, for example, the one shown in FIG. 6 described above is used.

A surge tank 12 is formed in the cylinder block 2 upstream of the intake port 7. In the intake passage 13 connected to the inlet of the surge tank 12, a throttle valve 14, a mechanical supercharger 15 and an intercooler 16 are installed in this order from the upstream. Further, a bypass passage 17 that branches from the intake passage 13 downstream of the throttle body 14 and bypasses the mechanical supercharger 15 and the intercooler 16 is provided, and a bypass control valve 18 is installed in the bypass passage 17.

A control unit 19 is mounted on the engine 1, and a crank angle sensor 21 for detecting a rotation angle of a crankshaft 20 and a surge tank 12 are installed.
A boost sensor 22 for detecting the upstream boost pressure is provided, and an exhaust temperature sensor is set in an exhaust passage (not shown) downstream of the exhaust port 8.

The exhaust port 8 is opened at a predetermined crank angle in the latter half of the expansion stroke and closed at a predetermined crank angle in the early stage of the compression stroke. Further, the intake port 7 is opened at a crank angle after a predetermined period after the exhaust port 8 is closed in the expansion stroke,
In the compression stroke, the exhaust port 8 is closed at a crank angle after a predetermined period.

The control unit 19 receives a crank angle signal and an engine rotation signal from the crank angle sensor 21, a boost pressure signal from a boost sensor 22, and an exhaust temperature signal from an exhaust temperature sensor (not shown). To be done. Then, the control unit 19 determines the required fuel injection amount of the engine based on the engine speed and the boost pressure calculated from the output of the crank angle sensor 21. Then, a predetermined low load region is detected from the boost pressure, and a region in which the scavenging efficiency and the air supply ratio are proportional is detected from a preset map of engine speed and load (boost pressure).

FIG. 4 shows the relationship between the scavenging efficiency and the air supply ratio. The scavenging efficiency, that is, the ratio of the fresh air amount to the total amount of gas in the cylinder after completion of the scavenging, and the supply air ratio, that is, the ratio of the total supplied air amount to the supply amount that occupies the stroke volume in the standard state, are shown in the solid line in the figure. The relationship is as shown in. As you can see from this figure, in the low charge ratio region, all the fresh air supplied stays in the cylinder, so the scavenging efficiency and the charge ratio are proportional,
In the high air supply ratio region, the scavenging blow-through increases, so that the scavenging efficiency and the air supply ratio are not proportional. In the figure, the alternate long and short dash line shows the relationship between the scavenging efficiency and the air supply ratio in the ideal state.

The region where the scavenging efficiency and the air supply ratio are proportional is a region where all the fresh air supplied as described above stays in the cylinder, and here the fuel supplied together with the fresh air blows out to the exhaust side. There is no such thing. Therefore, in the low load region and in the region of C in FIG. 4 where the scavenging efficiency and the air supply ratio are proportional, the injection start timing, which is usually after the exhaust port 8 is closed, is the exhaust port 8 Is controlled before closing, and at the same time, the injection pressure of the injector 10 is controlled to the low pressure side. However, even in the low load region, in the region where the blow-by occurs, the fuel is injected after the exhaust port 8 is closed, and at that time, the injection pressure is set to the maximum because the injection period cannot be taken long. The injection pressure is controlled by controlling the fuel pressure supplied to the injector 10. In the figure, the fuel pressure control signal is included in the injector control signal.

Further, in the high load region of the engine, the injection start timing is set so that the fuel is injected after the exhaust port 8 is closed, and the injection pressure is based on the map of the engine speed and the boost pressure. Controlled. Further, when the exhaust temperature rises excessively in the high load range, control is performed so that fuel is injected at the maximum injection pressure during scavenging in order to cool the fuel.

FIG. 5 is a flow chart for executing the fuel injection control of the above embodiment, and S1 to S13 show respective steps thereof.

In the flowchart of FIG. 5, when starting, the engine speed Ne, boost pressure, crank angle and exhaust temperature are read in S1. Then, in S2, the required fuel injection amount is determined from the engine speed and the boost pressure.

Next, in S3, it is judged from the boost pressure whether the engine is in a predetermined low load range. And
If it is in the low load region, the process proceeds to S4, and it is determined from the map of the engine speed and the load (boost pressure) whether it is in the blow-through region. If it is in the blow-through region, the injection timing is set to after exhaust closing in S5, and S6 is set. To maximize the injection pressure.

If it is not in the blow-through region in S4, the process proceeds to S7, in which the injection start timing is set so that fuel injection is started during scavenging, and in S8 the injection pressure setting is lowered.

When it is determined in S3 that the load is not in the low load range, it is determined in S9 whether the exhaust temperature exceeds 900 ° C. When the temperature exceeds 900 ° C, the process proceeds to S10, the injection timing is set to inject the fuel into the scavenging,
In S11, the injection pressure is maximized. Also, the exhaust temperature is 900
When the temperature is less than or equal to ° C, the routine proceeds to S12, where the fuel injection timing is after exhaust closing, and the injection pressure is controlled at S13 based on the map of the engine speed Ne and the boost pressure.

In the above embodiment, the uniflow type two-cycle engine having the valve opening / closing type exhaust port has been described, but the present invention can also be applied to other types of two-cycle engines. Is.

[0028]

EFFECTS OF THE INVENTION Since the present invention is configured as described above, in the low load region of a two-cycle engine, fuel atomization is promoted without causing rotational instability due to an increase in engine load, and good combustibility is achieved. You can get

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of the present invention.

FIG. 2 is an injection characteristic diagram for explaining the problems and actions of the present invention.

FIG. 3 is a system diagram of an embodiment of the present invention.

FIG. 4 is an explanatory view of a blow-through area according to an embodiment of the present invention.

FIG. 5 is a flowchart for executing control according to an embodiment of the present invention.

FIG. 6 is a structural diagram showing an example of a cylinder injection type injector.

[Explanation of symbols]

 1 Uniflow type 2-cycle engine 7 Intake port 8 Exhaust port 10 Injector 19 Control unit 21 Crank angle sensor 22 Boost sensor

Front page continuation (72) Inventor Shigeru Sakurai 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Motor Corporation

Claims (2)

[Claims] 1. An in-cylinder injector in which the injection pressure is adjustable and a valve member biased by an elastic member opens the valve against the biasing force of the elastic member by fuel pressure to inject fuel.
An operating state detecting means for detecting an operating state of the engine, a required fuel injection amount calculating means for receiving an output of the operating state detecting means, and calculating a required fuel injection amount according to the operating state of the engine, and the required fuel injection. An injector driving means for driving the injector from a predetermined injection start timing so as to set an injection period corresponding to the required fuel injection amount and obtain the injection period by receiving the output of the amount calculation means; A low load range detecting means for detecting that the vehicle is in a predetermined low load range; an injection pressure reducing means for receiving the output of the low load range detecting means and reducing the injection pressure of the injector in the low load range; In response to the output of the load range detection means, the injection period is set so that the required fuel injection amount is injected by compensating for the decrease in the injection rate due to the decrease in injection pressure with the injection period in the low load range. Control device of a two-stroke engine, characterized in that a injection period enlarging means for enlarging the. 2. The injection start timing is normally set to a predetermined timing after at least one of the intake port and the exhaust port is closed, and the operating state of the engine is a non-blowing region in which the scavenging efficiency and the air supply ratio are proportional. In the non-blowing area, both the intake port and the exhaust port are opened in the non-blowing area to start the fuel injection during the scavenging. The control device for a two-cycle engine according to claim 1, further comprising injection start timing changing means for changing the timing.