JPH02245458A - Internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent the over-rich condition of an air-fuel mixture suctioned into an engine cylinder by increasing the air intake of the engine upon the start of purging when the air intake per engine revolution is less than the predetermined level. CONSTITUTION:In the predetermined engine operation mode, fuel vapor is purged into an engine intake system A with a purge means 100. Also, an air intake amount per engine revolution is detected with an intake amount detecting means 101. Furthermore, when an air intake amount per engine revolution detected with the means 101 is equal to or less than the predetermined amount, the intake amount of an internal combustion engine B per unit hour is increased with an intake increase means 102, upon the start of purging with the means 100. According to the aforesaid construction, it is possible to prevent an air-fuel mixture suctioned into an engine cylinder from being thickened due to fuel vapor contained in purges gas, thereby preventing an over-rich condition.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an internal combustion engine having a purge device.

It is equipped with a purge device that discharges the fuel vapor stored in the canister into the intake system during engine operating conditions (hereinafter referred to as "purge"), and the basic fuel injection amount calculated according to the engine operating conditions is output from a 0□ sensor. 2. Description of the Related Art An internal combustion engine is known that controls the air-fuel mixture supplied into an engine cylinder to have a stoichiometric air-fuel ratio by correcting it using a feedback correction coefficient FAF that is changed based on a signal.

On the other hand, JP-A-63-186955 discloses that the control center value of the feedback correction coefficient FAF is calculated during engine idling operation and during low load operation, and the fuel concentration of the purge gas is determined based on the difference between each control center value. An internal combustion engine is disclosed which includes a detection means and which corrects the amount of fuel injected from a fuel injection valve by reducing the amount of fuel injected from a fuel injection valve when the fuel concentration of purge gas is equal to or higher than a predetermined fuel concentration.

[Conventional technology]
[Problem to be Solved by the Invention] Conventionally, when the fuel vapor generated in the fuel tank is not purged, it is stored in the canister and stored near the top of the canister at a predetermined concentration level. Since a high concentration of purge gas is accumulated, this high concentration purge gas is introduced into the engine cylinder for several seconds immediately after the start of purge. Therefore, in operating conditions where the amount of intake air per revolution of the engine is small, such as idling, the high concentration of purge gas has a large effect on the air-fuel ratio, causing the air-fuel mixture sucked into the engine cylinders to temporarily become extremely oversaturated. There is a problem that it becomes dark (rich).

This problem cannot be resolved by any of the aforementioned agencies. In other words, in any of the above-mentioned engines, it is not possible to control the air-fuel ratio by following the transient change in the air-fuel ratio toward the rich side at the start of purge, and the air-fuel mixture sucked into the engine cylinder temporarily become extremely rich. As a result, the air-fuel ratio falls below the combustible air-fuel ratio, resulting in rough idling, engine stalling, and deterioration of vehicle drivability.

[Means to solve the problem]

In order to solve the above-mentioned problems, according to the present invention, as shown in the block diagram of the invention in FIG. Intake air amount detection means 101 that detects the amount of intake air per rotation, and intake air amount detection means 101
When the amount of intake air per rotation of the engine detected by the purge means 100 starts purging when the amount of intake air per rotation of the engine is less than the predetermined amount of intake air per rotation of the engine, the amount of intake air per unit time is increased. The engine intake air amount increasing means 102 is also provided.

[For production]

When the purge is started when the amount of intake air per engine revolution is less than a predetermined amount of intake air per engine revolution, the amount of air taken into the engine per unit time is increased. Therefore, the degree to which the air-fuel mixture sucked into the cylinder is enriched by the fuel vapor contained in the purge gas can be reduced.

[Embodiment] Referring to FIG. 2, 1 is a cylinder block, 2 is a piston, 3 is a cylinder head, 4 is a combustion chamber, 5 is an intake manifold, and 6 is an exhaust manifold. The intake manifold 5 is connected to an air cleaner 10 via a surge tank 7, an intake duct 8, and an air flow meter 9. A throttle valve 11 is disposed in the intake duct 8, and a fuel injection valve 12 is disposed in the intake manifold 5 facing an intake boat 13. An exhaust pipe 14 is connected to the exhaust manifold 6, and a three-way catalyst 15 is disposed in the middle of the exhaust pipe 14. A cylinder 16 filled with activated carbon is connected to the upper space of a fuel tank 18 via a fuel vapor introduction passage 17. Further, the canister 16 is connected to the inside of the surge tank 7 via a purge passage 19, and the purge passage 19 is provided with a constriction portion 20. The degree of constriction (flow path resistance) of this constricted portion 20 is relatively small. Further, a purge control valve 21 is provided in the purge passage 19 between the canister 16 and the throttle 20. This purge control valve 21 allows the purge passage 19 to communicate when turned on, and blocks the purge passage 19 when turned off. Since the opening of the purge passage 19 into the surge tank 7 is always located downstream of the throttle valve 11, purging is possible even during idling operation.

A bypass passage 22 is provided that connects the surge tank 7 and the intake duct 8 by bypassing the throttle valve 11, and an intake air amount adjusting throttle 23 is disposed in the middle of the bypass passage 22. Further, an idle-up control valve 24 is provided in the bypass passage 22 between the connection part with the intake duct 8 and the throttle 23. The idle-up control valve 24 allows the bypass passage 22 to communicate when turned on, and blocks the bypass passage 22 when turned off.

The electronic control unit 40 consists of a digital computer with ROMs interconnected by a bidirectional bus 41.
(read-only memory) 42, RAM (random access memory) 43, CPU (microprocessor) 4
4, an input port 45 and an output port 46.

An intake air temperature sensor 30 disposed within the air flow meter 9 detects the intake air temperature, and this output signal is sent to an AD converter 47.
The data is input to the input port 45 via the input port 45. The air flow meter 9 generates an output voltage proportional to the amount of intake air, and this output voltage is input to the input port 45 via the AD converter 48. 0! arranged inside the exhaust manifold 6! sensor 3
1 detects the oxygen concentration in the exhaust gas, and this output signal is input to the input boat 45 via the AD converter 49. An idle switch 32 disposed near the throttle valve 11 is turned on when the throttle valve 11 is at the idle opening, and this output signal is manually input to the input boat 45. A crank angle sensor 33 built into the distributor 25 generates an output pulse representing the engine speed, and this output pulse is input to the input port 45.

On the other hand, the output boat 46 has corresponding drive circuits 50 and 51.
It is connected to the purge control valve 21, the fuel injection valve 12, and the idle up control valve 24 via the valve 52.

FIG. 3 shows a routine for calculating the fuel injection time TAU. This routine is executed by an interrupt at every fixed crank angle. Referring to FIG. 3, first, in step 60, the intake air amount Q and the engine speed NE are read. Next, in step 61, Q/NE is calculated. This Q/NE indicates the amount of intake air per engine revolution, and corresponds to the engine load. In step 62, the basic fuel injection time TP is calculated from the two-dimensional map of the engine speed NE and Q/NE. In step 63, the fuel injection time TAU is calculated using the following equation.

TAU=TP -FAF -K Here, FAF is a feedback correction coefficient that is changed based on the output signal of the Ot sensor 31, and corrects TP so that the air-fuel ratio becomes the stoichiometric air-fuel ratio. however,
FAF is set to 1 when feedback control is not executed. K is another correction coefficient.

Next, the operation of this embodiment will be explained with reference to FIG. Referring to FIG. 4, the engine is being operated at idle, and when the purge execution conditions are satisfied at the first point in time, the purge control valve 21 is turned on and the purge is started. At the start of purge, a highly concentrated purge gas containing a large amount of fuel is introduced into the surge tank 7 from the canister 16 .

During idling operation, the engine speed is low and the amount of intake air is low, so it is greatly affected by the purge gas with high fuel concentration, and thus in conventional engines, the air-fuel ratio decreases significantly, as shown by the dotted line in Figure 4. become richer. The air-fuel mixture sucked into the engine cylinder is feedback-controlled to maintain the stoichiometric air-fuel ratio as described above, but when purge gas containing a large amount of fuel is supplied as at the start of purge,
The above-mentioned feedback control is unable to keep up with the situation, resulting in a significant transitional richness. As a result, the engine speed during idling becomes unstable or the engine stalls. In this embodiment, when purge is started during idle operation, the idle up control valve 24 is opened simultaneously with the start of purge, thereby executing idle up. For example, the idle speed is 650 rpm + m, and the idle up speed is 750 rpm.
rpm. By increasing the idle, the amount of intake air is increased compared to normal idling operation, which reduces the degree to which the air-fuel ratio becomes rich due to the large amount of fuel contained in the purge gas, and also increases the engine speed. Therefore, the influence of purge gas per engine revolution can be reduced. Therefore, by increasing the idle, it is possible to prevent the air-fuel ratio from becoming significantly richer due to an increase in the amount of intake air and an increase in the engine speed. In this way, even if purge is started during idling operation, the air-fuel ratio will not become significantly rich, thus preventing the idling speed from becoming unstable, engine stalling, and deterioration of vehicle drivability. can do. Also at time 2, when a predetermined period of time has elapsed since tl, the idle up control valve H valve 24 is turned off to end the idle up.

At L2, the amount of fuel in the purge gas is considerably reduced compared to the initial stage of purge initiation, so the air-fuel ratio will not become significantly richer even if the normal idle speed is restored.

FIG. 5 shows a routine for controlling purge and idle up. This routine is executed by interrupt at regular intervals. Referring to FIG. 5, first step 70
In step 71, it is determined whether air-fuel ratio feedback control is being executed, and in step 71, the intake air temperature TA is 5.
It is determined whether the temperature is 0°C or higher. In steps 70 and 71, it is determined whether the purge execution conditions are satisfied. If a negative determination is made in either step 70 or step 71, that is, if it is determined that the purge execution conditions are not satisfied, the process proceeds to step 72 and the purge control valve 21 is turned off. This causes the purge passage 19 to be blocked, so that no purge is performed. Next, in step 73, the flag F is set to 0, and in the stellar block 74, the timer counter TC is set to 0. In addition,
When the electronic control unit 40 is activated, both the flag F and the timer counter TC are initialized to zero. In step 75, the idle up control valve 24 is turned off, the bypass passage 22 is cut off, and this routine ends.

If an affirmative determination is made in step 70 and step 71, that is, if the purge execution condition is satisfied, the process proceeds to step 76 and the purge control valve 21 is turned on. As a result, the purge passage 19 is brought into communication, and the purge is thus started.

Since the purge gas with high fuel concentration is accumulated near the upper part of the canister 16, when the purge is started, the purge gas with high fuel concentration is introduced into the surge tank 7, and this state continues for several seconds. In step 77, flag F is 0.
Since F is initially O, the process advances to step 78. In step 78, it is determined whether the idle switch 32 is on or not. When the idle switch 32 is off,
That is, if the engine is not in idle operation, the process proceeds to step 79 and flag F is set to 1. Next, in step 74, TC is set to O, and in step 75, the idle up control valve 24 is maintained in the off state. In this case, since the engine is not running at idle, the amount of intake air is higher than when running at idle, and the engine speed is also higher than when running at idle, so the air-fuel mixture supplied into the engine cylinder becomes significantly richer due to the influence of the purge gas. Never. In the next processing cycle, since F is set to l, a negative determination is made in step 77, and this routine ends.

This maintains the idle up control valve 24 in the off state. Therefore, if idle operation occurs after purge has started, idle up will not be executed.
This is because the richest purge gas is purged at the start of purge, so even if the engine starts idling after the start of purge, the degree to which the air-fuel ratio becomes rich is small, so there is no need to idle up.

If the engine is in idle operation at the start of purge, an affirmative determination is made in step 78 and the process proceeds to step 80. In step 80, it is determined whether or not the timer counter TC is equal to or less than a predetermined count value A. If TC≦A, the process proceeds to step 81 where TC is incremented by 1, and the process proceeds to step 82 where the idle up control valve 24 is turned on.

As a result, the bypass passage 22 is brought into communication and idle up is performed. In step 80, T.C.
>A, the process proceeds to step 75, where the idle-up control valve 24 is turned off, and the idle-up is ended.

In this embodiment, there is no need to increase the degree of restriction (increase flow path resistance) of the throttle 20 (see Figure 2) in consideration of the influence of purge gas with high fuel concentration at the start of purge, so the amount of purge gas can be reduced. It is not limited by the aperture 20. Furthermore, since purge can be started even during idle operation, the capacity of the canister can be reduced.

In this embodiment, a case has been described in which the purge is started during idle operation, but the present invention is not limited to the idle operation, but can also be applied to a case where the purge is started during low load.

〔Effect of the invention〕

When the purge is started when the amount of intake air per engine rotation is less than the predetermined amount of intake air per engine rotation, the amount of intake air to the engine is increased, so that the amount of air sucked into the cylinder is increased. It is possible to prevent the air-fuel mixture from becoming overrich due to the influence of the purge gas.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the invention, Fig. 2 is an overall block diagram of an internal combustion engine, Fig. 3 is a flowchart for calculating fuel injection time, Fig. 4 is an explanatory diagram of the operation of an embodiment of the present invention, FIG. 5 is a flowchart for controlling purge and idle up. 9... Air flow meter, 21... Purge control valve, 24... Idle up control valve, 33... Crank angle sensor, 40... Electronic control unit. Diagram

Claims (1)

[Claims] a purge means for purging fuel vapor into the engine intake system in a predetermined engine operating state; an intake air amount detection means for detecting the intake air amount per engine revolution; and an engine detected by the intake air amount detection means. Increasing the amount of engine intake air to increase the amount of engine intake air per unit time when purging is started by the purge means when the amount of intake air per revolution is less than a predetermined amount of intake air per revolution of the engine. An internal combustion engine with means.