JPH05280407A - Two-cycle engine controller - Google Patents

Abstract

(57) [Abstract] [Purpose] When the operating condition of the engine changes, it is possible to secure combustion stability and obtain good responsiveness, and also obtain favorable results in terms of emission performance. A controller for a two-cycle engine is provided. [Structure] In the case of slow acceleration, when the slow acceleration is detected, the supercharging pressure is first reduced, and the engine operating condition is from the lean limit line Ll of the combustible region A to the rich limit line Lr. Can be changed. Next, the fuel and the boost pressure are increased so that the operating condition changes along the rich limit line Lr. As a result, the supercharging pressure is set as low as possible when passing through the air-fuel ratio that is the maximum value of NOx, so that N
The generation amount of Ox can be reduced. After that, the fuel and the supercharging pressure are controlled so as to be increased, so that it is possible to meet the request for the gentle acceleration. In the case of sudden acceleration, the fuel amount is increased without lowering the boost pressure, so quick response can be secured.

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-stroke engines have been proposed. (For example, JP-A-59-49316 and JP-A-59-790.
40, JP-A-62-113820, JP-A-63-2
48915, JP-A-64-63617, and JP-A-62.
-135655 gazette etc.).

In particular, Japanese Unexamined Patent Publication No. 62-113820 discloses a two-stroke engine equipped with a supercharger. The 2-cycle engine has an advantage that the engine can be made compact because the output ratio is large, but it is difficult to secure stable combustibility as compared with the 4-cycle engine, and it is also disadvantageous in terms of emission performance. There is a problem that becomes.

Even when the operating state changes during acceleration or deceleration, it is necessary to control the characteristics of the two-cycle engine as described above. The present invention is configured in view of such circumstances, and when the operating state of the engine changes, it is possible to secure the stability of combustion and obtain good responsiveness, and also in terms of emission performance. It is an object of the present invention to provide a control system for a two-cycle engine that can obtain favorable results.

[0005]

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 unit that controls a supercharging pressure according to an operating state, and a fuel control unit that controls a fuel supply amount according to an operating state. Equipped with the first
Output control means for giving different control to the supercharging pressure control means or the fuel control means according to the changing speed of the operating state when the operating state changes from the operating state of No. 2 to the second operating state. And

Further, in a preferred aspect of the present invention, acceleration detecting means is provided, and during sudden acceleration, the output control means causes the supercharging pressure control means to perform control for holding the supercharging pressure constant. The fuel control means is controlled to increase the fuel supply amount from near the lean limit value to near the rich limit in the combustible range. Further, during the gradual acceleration, the previous period output control means causes the fuel control means to keep the fuel supply amount substantially constant, while the supercharging pressure control means causes the supercharging pressure control means to maintain the supercharging pressure in the combustible region. Is controlled from near the lean limit value to near the rich limit value, and then the fuel supply amount and the supercharging pressure are increased along the rich limit line of the combustible region. During deceleration, the previous period output control means maintains the fuel supply amount to the fuel control means substantially constant, while the supercharging pressure control means lean-limits the supercharging pressure in the combustible region. The fuel supply amount is reduced after the value is controlled to near the rich limit value.

[0007]

When the engine operating state accelerates from one steady operating state to another steady operating state, if the fuel amount is increased while maintaining the boost pressure, the air-fuel mixture continuously changes from lean to rich. Changes to. In this case, NOx is
In the air-fuel ratio region near the lean limit value, the generated amount becomes maximum. In addition, the higher the combustion temperature, the greater the amount generated. Therefore, if the fuel amount is increased as described above according to the change in the operating state, the fuel gas will inevitably pass through the air-fuel ratio region in which the NOx generation amount becomes the maximum, so that there is a problem that the emission performance deteriorates. Occurs. The present invention is
In view of this problem, even when acceleration is detected, if the acceleration request is relatively weak, the supercharging pressure is once lowered to control the combustion temperature to be low, thereby reducing NOx. After reducing the occurrence of the fuel, control is performed to increase the fuel amount and the boost pressure. Further, when there is a strong demand for acceleration, control is performed so as to ensure good responsiveness and meet the demand. That is, in the present invention, the first
Depending on the speed of transition from the operating state of to the second operating state,
The fuel and supercharging pressure are controlled differently to meet the respective requirements. Further, even during deceleration, the supercharging pressure is reduced to control near the rich limit value, and then the fuel is reduced to the lean side.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. Referring to FIG. 1, 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. Inside the engine 1, there is a cylinder bore 2
And a piston 3 is formed in the cylinder bore 2.
Are slidably arranged. Piston 3 is connecting rod 4
It is provided in the crank chamber 5 via the and is connected to a crank shaft 6 for taking out 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. Although not specifically shown, 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 2 for detecting an engine rotation signal from the distributor 24 and a pressure in the intake passage 18 provided downstream of the throttle valve 14.
5 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 boost pressure downstream of the throttle valve 14, that is, the intake pressure can be controlled. The amount of intake air introduced into the combustion chamber 7 is known from this intake pressure. The intake amount and intake pressure to the combustion chamber 7 are the performance of the engine, that is, the combustion state,
It seriously affects the engine output performance and emission performance.

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 control of this example will be described below. FIG. 2 shows a flowchart of output control performed by the controller 23. The controller 23 first detects the engine speed, the supercharging pressure downstream of the throttle valve 14, and the depression amount of the accelerator pedal 26, that is, the accelerator opening degree by inputting signals from various sensors.

Next, the controller 23 calculates the rate of change of the engine speed and the accelerator opening, and based on this, determines whether the degree of change of the operating state is slow acceleration or rapid acceleration. In this case, when the change in the engine speed and the change in the accelerator opening are equal to or larger than a predetermined value, it is determined that the acceleration is slow, and when the change is larger than a second predetermined value that is larger than that, it is determined that the acceleration is rapid. ..

When it is determined that the acceleration is slow, the controller 23 then sets the target boost pressure and the target fuel injection pulse according to the operating condition. Then, the bypass valve 17 is controlled in the opening direction to reduce the supercharging pressure, and the engine 1 is controlled to near the rich limit value in the combustible region. When the operating state near the rich limit value of the engine is obtained by reducing the supercharging pressure, the controller 23 then
Increase fuel and boost pressure.

In this case, the controller 23 has a map as shown in FIG. 3 showing the relationship between the engine speed change rate, the supercharging pressure and the generated torque, and calculates the engine speed change rate. While controlling the boost pressure. As a result, it is possible to secure a smooth change in the generated torque and prevent the occurrence of torque shock. In this case, the fuel injection amount is also increased according to the control of the supercharging pressure. This operation is continued until the target supercharging pressure and the target fuel supply amount in the target operating state are achieved. In another example, a map as shown in FIG. 4 is used to ensure a smooth increase in engine speed and prevent a shock. In other words,
It has a map that shows the relationship between the rate of change of accelerator opening or time, and the boost pressure and engine speed. Try to set it.

By controlling the supercharging pressure and the fuel supply as described above, in the case of gentle acceleration, the operating state changes along the line a as shown in FIG. That is, when the gentle acceleration is detected, the supercharging pressure is first reduced, and the operating condition of the engine is changed from near the lean limit line Ll of the combustible region A to near the rich limit line Lr. Next, the fuel and the boost pressure are increased so that the operating condition changes along the rich limit line Lr. As a result, the supercharging pressure is set as low as possible when passing through the air-fuel ratio that is the maximum value of NOx, so that the amount of NOx generated can be reduced. Further, thereafter, the fuel and the supercharging pressure are controlled so as to be increased, so that it is possible to meet the request for the gentle acceleration.

Further, in the case of sudden acceleration, as shown by the line b, the fuel is increased and the torque is secured without lowering the supercharging pressure, so that quick response can be secured. Further, in the case of deceleration, as shown in FIG. 6, the deceleration state is detected based on the change in the accelerator opening and the engine speed, and in the case of deceleration, the supercharging pressure is first reduced, Controls engine operating conditions near the rich limit. Next, the fuel supply is reduced to near the lean limit to obtain the target operating condition. By controlling in this way, the generation of NOx can be reduced as much as possible.

[0018]

According to the above configuration of the present invention, the operating conditions, that is, the fuel supply and the supercharging pressure are controlled according to the degree of change of the operating state, so that it is possible to meet the output request while reducing the generation of NOx as much as possible. it can. Therefore, a smooth output change at the time of acceleration and a smooth speed change at the time of deceleration can be achieved, and a preferable result can be obtained also in the emission performance.

[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 flowchart of supercharging pressure control according to the present invention,

FIG. 3 is a graph showing the relationship between supercharging pressure, engine speed change, and generated torque;

FIG. 4 is a graph showing the relationship between supercharging pressure, accelerator opening change, and engine speed torque;

FIG. 5 is a graph showing the relationship between supercharging pressure and average effective pressure,

FIG. 6 is a flowchart showing control of operating conditions during deceleration according to the first embodiment of the present invention.

[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

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location F02D 41/12 330 A 9039-3G 43/00 301 R 7536-3G

Claims (4)

[Claims] 1. A first operation comprising a supercharger, a supercharging pressure control means for controlling a supercharging pressure according to an operating state, and a fuel control means for controlling a fuel supply amount according to an operating state. And an output control means for giving different control to the supercharging pressure control means or the fuel control means according to the changing speed of the operating state when the operating state changes from the state to the second operating state. Two-cycle engine controller. 2. An acceleration detecting means is further provided, and during sudden acceleration, the output control means causes the supercharging pressure control means to keep the supercharging pressure constant while the fuel control means is controlled. 2. The control device for a two-cycle engine according to claim 1, wherein the control is performed such that the fuel supply amount is increased from near the lean limit value to near the rich limit in the combustible range. 3. The acceleration detecting means is further provided, and during the slow acceleration, the output control means causes the fuel control means to maintain the fuel supply amount substantially constant while the supercharging pressure control means is controlled. And controlling the supercharging pressure in the combustible region from near the lean limit value to near the rich limit value, and then increasing the fuel supply amount and the supercharging pressure along the rich limit line in the combustible region. Item 2. A control device for a two-cycle engine according to item 1. 4. A deceleration detecting means is further provided, and during deceleration, the first-term output control means is provided with respect to the fuel control means.
While maintaining the fuel supply amount substantially constant, the supercharging pressure control means controls the supercharging pressure in the combustible region from near the lean limit value to near the rich limit value, and then reduces the fuel supply amount. The control device for a two-cycle engine according to claim 1.