JPH04325742A - Intake device for engine - Google Patents

Abstract

PURPOSE:To prevent misfire at the time of shifting from deceleration to idling so as to secure stable combustion in an engine performing lean combustion while making the security of a decelerating feeling at the time of deceleration compatible with stratification at the idling time or scavenging in the case of a two-cycle engine. CONSTITUTION:Deceleration is judged (S4) by whether engine speed N is over the specified speed N1 and an accelerator switch is on. In the case of judging deceleration, a deceleration control flag is set up (S5), and a throttle is totally closed (S6) to cut off fuel (S7). In the case of judging non-deceleration, whether idling or not is judged (S8), and when idling is judged and the flag is still up, the throttle opening theta is gradually enlarged (S10) and fixed to the specified opening K upon exceeding the specified opening K. Fuel return is then performed (S13), and the flag is cleared (S14).

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake system for a lean-burn engine.

0002

[Prior Art] In a two-stroke engine, two strokes, an expansion stroke and a compression stroke, are repeated, during which the exhaust port first opens on the bottom dead center side, then the scavenging port opens, and pressurization is applied during the overlap period of both ports. Gas exchange (scavenging) of the combustion chamber by intake air takes place, and then the exhaust port is closed and filling with intake air takes place. In this way, a two-stroke engine exchanges gas in the combustion chamber by pushing out exhaust gas with pressurized intake air, so there is essentially a large amount of residual gas, especially at idle or in a light load range. If the ratio becomes high, combustion tends to become unstable. therefore,
At idle and in light load ranges, it is necessary to gather fresh air and fuel near the spark plug to ensure reliable combustion through stratification.

[0003] As a means for achieving stratification during idle or light load in a two-stroke engine, a method such as that described in, for example, Japanese Patent Laid-Open No. 63-201311 has been known. In the two-stroke engine described in the above publication, the intake passage is divided into two systems, one for high load and one for low load, downstream of the throttle valve, and when the load is low, the control valve provided in the intake passage for high load is opened to reduce the Stratification is achieved by allowing intake air to flow in only from the load intake port, and by swirling it using a separate means and placing fresh air on top of the re-inflowing exhaust gas.

[0004] Also, in the case of a four-cycle engine, stratification of the air-fuel mixture is often used because it is necessary to improve fuel efficiency through lean combustion. And, regardless of whether it is a 2-stroke engine or a 4-stroke engine,
In order to achieve stratified charge combustion in the light load range, including when idling, the throttle valve must be opened to a certain extent to ensure air flow even when the accelerator is fully closed. However, if the throttle valve is simply kept open to a certain extent even when the accelerator is fully closed, the throttle valve will remain open to a certain extent even during deceleration, resulting in less pumping loss and a feeling of deceleration (so-called engine braking).
becomes worse. Therefore, in engines that perform stratified combustion, it has been proposed to keep the throttle valve open by a predetermined amount during normal idling, but to stop the fuel supply and completely close the throttle valve during deceleration. There is.

[0005]

[Problem to be Solved by the Invention] As described above, if control is performed such that the throttle valve is opened by a predetermined amount during idling, and the fuel supply is stopped and the throttle valve is closed during deceleration, the engine engine vibration feeling during deceleration will be reduced. It is possible to improve fuel efficiency by achieving lean combustion through stratification during idling while maintaining the fuel efficiency. However, if such control is performed, when transitioning from deceleration to idling, fuel is suddenly returned while intake air is suppressed or stopped, making misfires due to overrich more likely to occur. In addition, especially in the case of a two-stroke engine, scavenging is performed even during deceleration to completely expel combustion gas from the combustion chamber, preventing misfires when the deceleration state is exited and the engine enters a normal idle state, or when acceleration begins. However, if the throttle valve is closed during deceleration as described above, scavenging air will not be carried out during deceleration, and fuel will remain in the combustion chamber when the fuel is returned. The amount of combustion gas increases, causing misfires and deteriorating combustion stability.

The present invention has been made in view of the above-mentioned problems, and is aimed at ensuring a sense of deceleration during deceleration and improving stratification during idling in an engine that performs lean combustion by stratifying the air-fuel mixture. The objective is to prevent misfires and improve combustion stability when transitioning from deceleration to idling, while also achieving scavenging.

[0007]

[Means for Solving the Problems] The present invention makes it possible to restore fuel when transitioning from deceleration to idling after sufficiently increasing the air density in the combustion chamber or after sufficiently scavenging air. Its configuration is as shown in FIG. That is, the engine intake device according to the present invention has the following features:
an operating state detecting means for detecting the operating state of the engine; an idle determining means for determining the idle state of the engine based on the output of the operating state detecting means; idling air amount control means that controls the intake air amount adjustment means to make the intake air amount equal to the set idling air amount; and deceleration determination that determines a predetermined deceleration state of the engine based on the output of the operating state detection means. and deceleration fuel stop means that receives the output of the deceleration determining means, controls the fuel supply means to stop the fuel supply when entering a predetermined deceleration state, and resumes the fuel supply when the deceleration state is exited. , an engine comprising deceleration air amount reducing means that receives the output of the deceleration determining means and makes the intake air amount of the engine smaller than the set air amount at idle when the predetermined deceleration state is determined. The intake system is characterized in that, when the fuel is restored by the deceleration fuel stop means, a pre-fuel return reduction canceling means is provided for canceling the operation of the deceleration air amount reduction means prior to fuel restoration.

[0008]

[Operation] When it is determined that the engine is in a predetermined deceleration state, fuel supply is stopped and the amount of intake air is made smaller than the amount of air at idle. Therefore, during deceleration, pumping loss increases and the feeling of deceleration improves. Also,
When transitioning from deceleration to idling, the reduction in intake air amount is canceled prior to fuel return, and fuel supply is resumed once the air amount has returned to a predetermined level. Therefore, fuel is supplied in a state where the air density in the combustion chamber is sufficiently increased or scavenging is sufficiently performed, and misfires due to overrichness or poor scavenging are prevented.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings.

FIG. 2 is an overall system diagram of one embodiment of the present invention. In this embodiment, the engine 1 is a uniflow two-stroke engine with in-cylinder direct injection, and the cylinder 2
A scavenging port 3 is formed at the bottom of the cylinder 2, and an exhaust port 4 is formed at the head of the cylinder 2. The head of the cylinder 2 is provided with an exhaust valve 5 that is driven by a valve mechanism (not shown) in synchronization with the rotation of the crankshaft to open and close the exhaust port 4. An injector 7 is arranged.

The scavenging port 3 begins to open at a predetermined crank angle after the exhaust valve 5 opens, and is opened and closed by the piston 8 so as to close at a predetermined crank angle after the exhaust valve 5 closes. An intake passage 10 extending from the air cleaner 9
is connected to the scavenging port 3, and an air flow meter 11 for detecting the amount of intake air is provided immediately downstream of the air cleaner 9 in the intake passage 10. A mechanical supercharger 13 is provided at the . Further, the intake passage 10 is provided with a bypass passage 14 that bypasses the mechanical supercharger 13, and a bypass control valve 1 is provided in the bypass passage 14.
5 is provided.

A catalyst device 17 is provided in the exhaust passage 16 connected to the exhaust port 4, and an air-fuel ratio sensor 18 is provided downstream of the exhaust port 4 and upstream of the catalyst device 17.

The throttle valve 12 is electrically driven by a throttle motor 19. A control unit 20 consisting of a microcomputer is provided, and the control unit 20 receives the intake air amount signal from the air flow meter 11, the air-fuel ratio signal from the air-fuel ratio sensor 18, and the amount by which the accelerator pedal 21 is pressed to zero. Various signals such as an accelerator switch signal and an engine rotation signal, which are turned on when the engine speed is reached, are input as information. The control unit 20 calculates the ignition timing, fuel injection amount, throttle opening, and bypass control amount based on this information, and calculates the igniter 22, injector 7, and throttle motor 1 connected to the spark plug 6.
Control signals are output to the bypass control valve 9 and the bypass control valve 15, respectively.

[0014] The ignition timing is controlled by a map value depending on the engine speed (N) and load (Q/N). The basic amount of fuel injection is the value calculated based on the intake air amount (Q) and the engine speed (N) multiplied by the map value of the blow-through correction, and this is added to the value calculated based on the intake air amount (Q) and the engine speed (N).
It is obtained by multiplying the feedback correction value according to the output of . Then, an injection signal having a pulse width corresponding to the calculated fuel injection amount is output to the injector 7. Further, the throttle opening degree is controlled according to the accelerator opening degree signal, and the bypass control amount is controlled according to the engine rotation speed (N) and the load (Q/N).

Furthermore, in this embodiment, the engine speed (
An idle determination is made based on the fact that the accelerator switch is on when N) is below a predetermined rotation speed, and when the throttle valve 12 is idle, the throttle valve 12 is controlled to a predetermined opening slightly more than fully closed. On the other hand, if the accelerator switch is on and the engine speed (N) is above a predetermined speed, it is determined that deceleration is occurring, and during deceleration, fuel is cut and the throttle valve 12 is completely closed. Then, when the deceleration progresses and the rotation drops to a predetermined number of revolutions, the fuel is restored. At this time, the throttle valve 12 is gradually opened before the fuel is restored, and fuel injection is restarted when the throttle opening reaches the predetermined opening. do.

FIG. 3 is a flowchart for executing the control during idling and deceleration in this embodiment. Note that S1 to S16 indicate each step.

In the above flowchart, when started, first, the rotation period is determined from the engine rotation signal in S1, the engine rotation speed N is calculated in S2, and then, in S3
Read the accelerator switch signal.

[0018] In S4, it is determined whether or not deceleration is occurring depending on whether or not the engine speed N is greater than a predetermined speed N1 and the accelerator switch is on. When it is determined that deceleration is occurring, the process proceeds to S5 to decelerate. Set flag α (α=
1). Then, in S6, the throttle is fully closed (throttle opening θ=0), and in S7, the fuel is cut.

[0019] If the result in S4 is NO, it means that either the engine speed N has become lower than the predetermined speed N1 or the accelerator has been depressed, so the process goes to S8 and first it is determined whether or not the engine is idling. . That is, in S8,
Check whether N<N1 and the accelerator switch is on. If YES, it is determined to be idle, and the process goes to S9 to check whether flag α is 1 or not.

If the flag α is still 1 in S9, then S10
Go to and increase the throttle opening θ by a predetermined amount C.
Gradually open the throttle valve. And S11
θ is determined, and if θ is equal to or greater than K (map value for control during deceleration), θ is fixed at K in S12. Then, in S13, the fuel is restored, and in S14, the flag α
Clear.

If the flag α is not 1 in S9, it means that the engine is in a normal idle state, and the process goes to S15, where the throttle opening degree θ is controlled using the map value K during idle.

Further, if the answer in S8 is NO, it means that the engine has left the idle state, and in this case, the process goes to S16, and the throttle opening degree θ is controlled using the map value K during the non-idling state (during running).

In the above embodiment, the amount of intake air during deceleration is reduced by controlling the throttle valve itself, but a shutter valve is provided in the intake passage separately from the throttle valve, and the shutter valve is operated during deceleration. It can also be configured to close or open prior to fuel return. Further, these throttle valves or shutter valves do not necessarily need to be completely closed during deceleration, and their opening degree can be set as appropriate within a range that ensures a feeling of deceleration.

Furthermore, the present invention can be applied not only to two-stroke engines but also to four-stroke engines that perform lean combustion.

[0025]

Effects of the Invention Since the present invention is constructed as described above, it is possible to improve the feeling of deceleration due to an increase in pumping loss during deceleration in a lean-burn engine, and to improve the feeling of deceleration due to the increase in pumping loss during deceleration. In addition, it is possible to achieve both scavenging and ensure combustion stability by preventing misfires when transitioning from deceleration to idling.

[Brief explanation of drawings]

[Figure 1] Overall configuration diagram of the present invention

[Figure 2] Overall system diagram of one embodiment of the present invention

[Figure 3] Flowchart for executing control in the same embodiment

[Explanation of symbols]

1 Engine 7 Injector (fuel supply means) 12 Throttle valve (intake air amount adjustment means) 19
Throttle motor 20 control unit

Claims (1)

[Claims] 1. An operating state detecting means for detecting an operating state of an engine, an idle determining means for determining an idle state of the engine based on an output of the operating state detecting means, and an output of the idle determining means, idling air amount control means that controls an intake air amount adjusting means of the engine during idling to adjust the intake air amount to a set air amount during idling; and a predetermined deceleration state of the engine based on the output of the operating state detection means. a deceleration determination means for determining a deceleration determination means; receiving an output of the deceleration determination means and controlling a fuel supply means of the engine to stop fuel supply when the engine enters a predetermined deceleration state;
a deceleration fuel stop means for restoring fuel supply when the deceleration state is exited; and a deceleration determining means that receives the output of the deceleration determining means and sets the intake air amount of the engine to the idle setting air amount when the predetermined deceleration state is determined. In an engine intake system equipped with a means for reducing air amount during deceleration to reduce an air amount smaller than , when the fuel is restored by the fuel stopping means during deceleration, the operation of the air amount reducing means during deceleration is canceled prior to the return of fuel. An intake system for an engine, characterized in that it is equipped with means for canceling the weight loss before fuel return.