JPH05280408A - Controller of two-cycle engine - Google Patents

Abstract

PURPOSE:To enable smooth output control without generation of shock suppressing supercharging pressure to a low level in response to a condition when fuel cut is stopped. CONSTITUTION:Fuel cut control is performed by a controller 23 in the case when acceleration opening is decreased, or a pedal 26 is not stepped in so that vehicle speed may be decreasing to some or all of cylinders according to either one of the above-mentioned grades. A control signal is outputted by the controller 23 to a bypass valve 17 so as to achieve a target supercharging pressure after correction by correcting the target supercharging pressure low when a deceleration condition is finished. Simultaneously with stopping the fuel cut, fuel pulse is corrected, and the control signal is outputted to an injector 21 so as to supply a specified amount of fuel. Thus, since the pressure value is set lower than the supercharging pressure of a constant operational condition by a specified value and operation is transferred smootly from deceleration to acceleration just after it is changed from the deceleration state to the acceleration state, any excessive output generation shock at the time of changing the state can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control system for a two-cycle engine.

[0002]

2. Description of the Related Art Conventionally, various types of two-cycle engines have been proposed. (For example, JP-A-59-493
16, JP-A-59-79040, JP-A-62-11
3820, JP-A-63-248915, JP-A-64
-63617, JP-A-62-135655, etc.).

The two-cycle engine has an advantage that the engine can be made compact because the output ratio is large.

[0004]

However, the two-cycle engine has a problem that it is more difficult to secure stable combustion properties than the four-cycle engine and is disadvantageous in terms of emission performance. Further, in the two-cycle engine, since the intake air and the exhaust gas are simultaneously scavenged, the exhaust efficiency greatly affects the combustibility. In a normal continuous operation state, that is, in a steady operation state, fuel is supplied in anticipation of a certain amount of exhaust gas remaining in the combustion chamber. However, when starting from a stopped state or in an engine that has been configured to cut fuel during deceleration, when the fuel supply is restored, the amount of residual exhaust gas in the combustion chamber is extremely small. Therefore, in such a situation, if the engine is controlled in the same manner as in the steady operation state, the output of the engine cannot be controlled properly.

The present invention has been constructed in view of the above circumstances, and provides a control device for a two-cycle engine capable of performing desired engine output control in an engine having a mechanism for cutting fuel during deceleration. The purpose is to do.

[0006]

In order to solve the above problems, the present invention is configured as follows. A control device for a two-cycle engine according to the present invention includes a supercharger, a supercharging pressure control means for controlling supercharging pressure according to an operating state of an engine, and a fuel for controlling a fuel supply amount according to the operating state. The control means, the fuel cut means for cutting the fuel at the time of deceleration, and the output limiting means for limiting the output at the time of returning the fuel supply from the fuel cut state are provided, and the output limiting means has a limit at the time of the returning. The supply pressure is controlled to a value lower than the supercharging pressure in the same steady operating state as the operation state at the time of the restoration, and the fuel control means is controlled so that the fuel supply amount corresponds to the low supercharging pressure value. It is characterized by doing.

[0007] Preferably, the output limiting means sets the supercharging pressure at the time of returning the fuel supply to be lower as the time in the fuel cut state is longer. Further, when the fuel supply is restored, the output limiting means sets the boost pressure to be lower as the engine speed at the start of fuel cut is higher. Further, when the fuel supply is restored from the fuel cut state, the output limiting means lowers the boost pressure as the engine load is smaller.

[0008]

When the amount of fresh air remaining in the combustion chamber increases, the combustion state becomes good, and a high output is produced as compared with the steady operation state. According to the present invention, when the amount of fresh air in the combustion chamber is large, for example, when the fuel supply is restored after the fuel cut, the boost pressure is kept low and the output is limited.

The amount of fresh air remaining in the combustion chamber varies depending on the fuel cut time or the engine speed. In the present invention, focusing on the factors that affect the amount of fresh air in these combustion chambers, the supercharging pressure is controlled and the output is limited. The amount of fuel is controlled according to the boost pressure. Therefore, the supercharging pressure of the intake air introduced into the combustion chamber corresponds to the output of the engine.

By performing such control, it is possible to prevent the occurrence of a shock due to an excessive output being exerted at the time of returning the fuel supply, and it is possible to smoothly control the output.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. Referring to FIGS. 1 and 2, there is shown a schematic configuration of a two-cycle engine to which the present invention can be applied. The two-cycle engine 1 of this example has a uniflow type structure. A cylinder bore 2 is formed inside the engine 1, and a piston 3 is slidably arranged in the cylinder bore 2. The piston 3 is provided in the crank chamber 5 via a connecting rod 4, and is connected to a crankshaft 6 that extracts combustion energy as rotational power.

The upper space defined by the upper portion of the cylinder bore 2 of the engine 1 and the upper surface of the piston 3 constitutes a combustion chamber 7. An intake passage 8 is connected so as to communicate with the combustion chamber 7. Specifically, as shown in FIG. 2, the cylinder bore 2
A plurality of intake ports 9 are provided so as to be spaced apart from each other on the peripheral wall, and the intake air is introduced into the combustion chamber 7 substantially uniformly over the entire circumference. An air cleaner 10 is arranged at the tip of the intake passage 8, that is, at the most upstream side, and an air flow meter 11 for detecting the amount of intake air is provided downstream thereof. A supercharger 12 that supercharges intake air is provided further downstream. An intercooler 13 that cools the supercharged air is arranged downstream of the supercharger 12, a throttle valve 14 is provided downstream thereof, and a surge tank 15 is provided further downstream to form an intake system. .. Further, in the configuration of this example, the return passage 16 for returning the excess supercharged air to the upstream side of the supercharger 12 is provided. The take-out portion of the return passage 16 includes an intercooler 13 and a throttle valve 14.
It is provided in the area between and. The return passage 16 is provided with a bypass valve 17 for adjusting the return amount of supercharged air.

An exhaust passage 18 is provided above the combustion chamber 7.
Is connected to the opening, that is, the exhaust port 19,
An exhaust valve 20 is attached. The engine 1 of this example is of a cylinder injection type, and an injector 21 for injecting fuel is attached near the exhaust passage 18. Further, a spark plug 22 is attached to the upper part of the combustion chamber 7. To control the engine 1 of this example, a controller 23 preferably including a microcomputer is provided. The controller 23 includes an intake pressure sensor 25 for detecting the engine rotation signal from the distributor 24 and the pressure in the intake passage 8 provided downstream of the throttle valve 14.
And a signal from an accelerator position sensor 27 that detects the amount of depression of the accelerator pedal 26 are input. The controller 23 performs a predetermined calculation based on these signals, and outputs a throttle opening signal to the actuator 28 of the throttle valve 14, a bypass opening signal to the actuator 29 of the bypass valve 17, and an ignition to the spark plug 22. Output a signal.

As described above, by controlling the opening degree of the throttle valve 14 and the opening degree of the bypass valve 17 by the controller 23, the supercharging pressure downstream of the throttle valve 14, that is, the intake pressure can be controlled. This intake pressure is applied to the combustion chamber 7
The amount of intake air introduced into is known. The amount of intake air into the combustion chamber 7 and the intake pressure have a significant influence on the engine performance, that is, the combustion state, the engine output performance, the emission performance, and the like.

In this example, in view of the fact that the required performance of the engine 1 changes in accordance with the operating state of the engine, the supercharging pressure downstream of the throttle valve, that is, the combustion chamber 7 is introduced in accordance with the change in the engine load. It controls the intake pressure. The intake pressure control of this example will be described with reference to FIG. FIG. 3 shows a flowchart of the intake pressure control by the controller 23. Controller 23
First, the engine speed, the amount of depression of the accelerator pedal 26, that is, the accelerator opening degree, and the vehicle speed are detected by inputting signals from various sensors.

Next, the controller 23 calculates the respective change rates from the detected values of the engine speed and the accelerator opening. Further, the target supercharging pressure is set according to the engine speed and the accelerator opening. In this case, controller 2
Reference numeral 3 is provided with a map created in advance corresponding to the engine speed and the accelerator opening, and the target supercharging pressure is set in light of this map.

Then, the controller 23 determines the fuel pulse width corresponding to the set target boost pressure. In this case, when the accelerator opening is reduced or not depressed and the vehicle speed is reduced, it is determined that the vehicle is in the decelerated state. When the vehicle is in the deceleration state, the fuel cut control is performed for some or all of the cylinders according to the degree.

Next, the controller 23 determines whether or not the deceleration has ended based on the change in the accelerator opening. When the deceleration state ends, the controller 23 outputs a control signal to the bypass valve 17 so as to correct the target boost pressure low and achieve the corrected target boost pressure. Also,
The fuel cut is stopped, the fuel pulse is corrected, and a control signal for outputting a predetermined fuel to the injector 21 is output.

By controlling in this way, the supercharging pressure changes as shown in FIG. That is, the supercharging pressure gradually decreases during deceleration until time t1. in this case,
Fuel cut control is performed. When the accelerator pedal 26 is operated at the time t1 to enter the acceleration state, the fuel cut is stopped and the fuel supply is restored. But,
Exhaust gas hardly remains in the cylinder where fuel cut was performed during deceleration.Therefore, if supercharging pressure is introduced as in steady operation, an excessive output occurs because the combustion state is good.
A torque shock may occur immediately after switching from fuel cut to reacceleration.

As shown by the broken line in FIG. 4, when the normal operation is changed to the acceleration state, the supercharging pressure changes in accordance with the change of the operation state. That is, when the supercharging pressure P1 is maintained during the steady operation, the supercharging pressure does not decrease even if it is converted to acceleration and increases in response to the acceleration operation. However, immediately after the deceleration state is changed to the acceleration state, a value P2 lower than the supercharging pressure P1 in the steady operation state by a predetermined value is set to smoothly shift from deceleration to acceleration.

In the control of this example, the supercharging pressure P2 is maintained for a predetermined period, and is controlled to continuously increase in response to the acceleration request at the time t2. By controlling in this way, it is possible to prevent an excessive shock of output when the fuel cut is changed to the re-acceleration. In this case, FIG. 4 shows a change in the operating state and a change in the supercharging pressure on the assumption that the throttle opening and the engine speed are the same.

Referring to FIG. 5, there is shown the relationship between the boost pressure and the deceleration period when the fuel supply is restored. The longer the deceleration period, the greater the amount of fresh air existing in the combustion chamber. In this example, the longer the deceleration period, the lower the boost pressure when the fuel supply is restored. As a result, it is possible to prevent a torque shock when the fuel supply is restored and to ensure a smooth output change.

On the other hand, as shown in FIG. 6, the engine speed and the supercharging pressure at the time of fuel cut are set to be smaller as the engine speed at the time of fuel cut is higher. This is because as the engine speed increases, the scavenging effect increases and the amount of fresh air in the combustion chamber increases. Referring to FIG. 7, there is shown a schematic configuration diagram of a two-cycle engine according to another embodiment of the present invention.

In the structure of this example, a shutter valve 30 for restricting the exhaust gas is provided in the exhaust passage of the engine. The shutter valve 30 is controlled by the controller 23 via the actuator 31. Referring to FIG. 8, the control contents of the exhaust throttle of this example are shown in the form of a flowchart.

The controller 23 detects the accelerator opening and the engine speed and sets the combustion pulse based on the detected values. Next, it is determined whether or not the vehicle is in the decelerating state. When the vehicle is in the decelerating state, a signal is sent to the actuator 31 to close the shutter valve 30. On the other hand, fuel cut control is performed. Then, the controller 23 determines from the accelerator opening degree whether or not it is re-acceleration. When it is determined that the acceleration is re-acceleration, the fuel supply is restored and the shutter valve 30 is controlled to open. Referring to FIG. 9, time t
When it enters the deceleration state at 1, fuel cut is performed. Along with this, the output also decreases. At time t2 on the way, the controller 23 closes the shutter valve 30 to limit the flow of exhaust gas. This also reduces the amount of fresh air introduced into the combustion chamber. When the deceleration state is canceled at time t3, the controller 23 stops the fuel cut. However, at this time, the shutter valve is kept closed. As a result, the output is maintained substantially constant, and the output gradually starts to increase at time t4. Then, at a time t5 when a certain time has elapsed after that, the actuator 31
Is controlled to open the shutter valve 30 to release the restriction of exhaust gas.

After this, at time t6, the output is restored to the state before it is almost decelerated.

[0027]

According to the above configuration of the present invention, the engine output is controlled according to the state when the fuel cut is stopped. Therefore, the deceleration state is stopped or the deceleration state is smoothly changed to the re-acceleration. Let You can Also,
Since the output is controlled according to the degree of deceleration or the degree of acceleration after deceleration, the responsiveness can be improved and, on the other hand, the torque shock can be eliminated.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a two-cycle engine according to one embodiment of the present invention,

FIG. 2 is a structural diagram of an engine according to one embodiment of the present invention,

FIG. 3 is a flowchart of supercharging pressure control according to one embodiment of the present invention,

FIG. 4 is a graph showing the supercharging pressure that changes according to the control according to the embodiment of the present invention;

FIG. 5 is a graph showing the relationship between supercharging pressure and deceleration period,

FIG. 6 is a graph showing the relationship between supercharging pressure and throttle opening,

FIG. 7 is a schematic configuration diagram of a two-cycle engine according to another embodiment of the present invention,

8 is a flowchart showing the contents of control according to one embodiment of the present invention with respect to the engine of FIG.

9 is a graph showing an example of output changes in the control of the engine of FIG.

[Explanation of symbols]

 1 Engine 2 Cylinder Bore 3 Piston 4 Connecting Rod 5 Crank Chamber 6 Crank Shaft 7 Combustion Chamber 8 Intake Passage 9 Intake Port 10 Air Cleaner 11 Air Flow Meter 12 Supercharger 13 Intercooler 14 Throttle Valve 15 Surge Tank 16 Return Passage 17 Bypass Valve 18 Exhaust Passage 19 Exhaust port 20 Exhaust valve 21 Injector 22 Spark plug 23 Controller 24 Distributor 25 Intake pressure sensor 26 Accelerator pedal 27 Accelerator position sensor 28 Throttle actuator 29 Bypass valve actuator 30 Shutter valve

Claims (4)

[Claims] 1. A supercharger, a supercharging pressure control means for controlling a supercharging pressure according to an operating state of an engine, a fuel control means for controlling a fuel supply amount according to the operating state, and a fuel during deceleration. And a fuel cut means for cutting the fuel supply from the fuel cut state, and an output limiting means for limiting the output at the time of returning the fuel supply from the fuel cut state. It is characterized in that the fuel pressure is controlled to a value lower than the supercharging pressure in the same steady operating state as the operating state, and the fuel control means controls the fuel supply amount to correspond to the low value of the supercharging pressure. Cycle engine controller. 2. The control device for a two-cycle engine according to claim 1, wherein the output limiting means sets the supercharging pressure at the time of returning the fuel supply to be lower as the fuel cut state is longer. 3. The method according to claim 1, wherein when the fuel supply is restored, the output limiting means sets the boost pressure to be lower as the engine speed at the start of fuel cut is higher.
Cycle engine controller. 4. The control system for a two-cycle engine according to claim 1, wherein, when the fuel supply is restored from the fuel cut state, the output limiting means lowers the boost pressure as the engine load is smaller.