JPH06173745A - Fuel supply control method for multi-cylinder engine - Google Patents

Abstract

PURPOSE:To prevent unburned gas discharging due to misfire by stopping the fuel supply to cylinders wherein a misfire is detected when a misfire is detected when an engine is being warmed up. CONSTITUTION:An engine speed detector 9 for detecting engine speed NE and a water temperature detector 10 for detecting engine cooling water temperature TW are connected to a control means 8. An intake manifold 3 is provided with fuel injection valves 7 ... individually corresponding to cylinders C..., and fuel supply to each cylinder C is controlled by the control means 8. The control means 8 can individually detect a misfire in each cylinder C and controls the fuel injection valves 7... so as to stop the fuel supply to the cylinder C while detecting cylinders wherein misfire is detected when engine speed NE is less than set engine speed when an engine E is idling and engine cooling water temperature TW is at specified temperature or lower. Therefore, this constitution serves to prevent unburned gas from being discharged in the atmosphere with a catalyst inactivated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply control method for a multi-cylinder engine capable of individually detecting misfires in a plurality of cylinders and stopping the fuel supply to the cylinders in which misfires are detected.

[0002]

2. Description of the Related Art When unburned gas generated due to engine misfire flows into a catalytic converter in an exhaust system, the reaction of the unburned gas causes an excessive rise in the catalyst temperature, resulting in deterioration of the catalyst. As disclosed in Japanese Patent Laid-Open No. 30954, there is a system in which the fuel supply to the misfiring cylinder is stopped when the misfiring cylinder is detected.

[0003]

By the way, the above-mentioned conventional one is to stop the fuel supply in response to the detection of the misfiring cylinder regardless of the operating state of the engine, but in some cases the operability of the engine deteriorates. For example, if the fuel supply is stopped in response to detection of a misfiring cylinder when the engine speed is low, the engine may stop. Therefore, in the prior art disclosed in Japanese Patent Laying-Open No. 4-54254, the abnormal overheating region of the catalyst is set based on at least one of the engine load and the engine speed,
When the misfiring cylinder is detected, the fuel supply is stopped when the operating state of the engine is in the abnormal overheat region to avoid deterioration of the drivability of the engine.

However, when the catalyst is not activated, the unburned gas discharged from the misfiring cylinder may be released into the atmosphere as it is.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a fuel supply control method for a multi-cylinder engine which prevents the release of unburned gas due to the occurrence of misfire. To do.

[0006]

In order to achieve the above object, according to the invention of claim 1, in response to detection of a misfiring cylinder when the engine is in a warm-up process, the cylinder to which misfiring is detected is detected. Stop fuel supply.

According to the fourth aspect of the invention, when the misfire cylinder is detected, when the engine speed is equal to or higher than the set speed, the fuel supply to all the cylinders is stopped and the engine speed is lower than the set speed. When the engine is in the process of warming up under the condition, the fuel supply to the cylinder where misfire is detected is stopped.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

1 and 2 show an embodiment of the present invention. FIG. 1 is a schematic diagram showing an intake system and an exhaust system of a multi-cylinder engine, and FIG. 2 is a flow chart showing a control procedure.

First, in FIG. 1, in a multi-cylinder, for example, four-cylinder engine E, an intake pipe 2 having a throttle valve 1 is provided.
Are connected to each cylinder C ... through an intake manifold 3, and an exhaust pipe 5 having a catalytic converter 4 is connected to each cylinder C ... through an exhaust manifold 6. The intake manifold 3 is provided with fuel injection valves 7 ... Corresponding to the individual cylinders C. The operation of each fuel injection valve 7, that is, the fuel supply to each cylinder C is controlled by the control means 8. To be done.

The control means 8 is capable of individually detecting the misfire in each cylinder C, and responds to the misfiring cylinder detection when the engine E is in a predetermined operating state, to the cylinder C in which the misfire is detected. The operation of the fuel injection valves 7 ... Is controlled to stop the fuel supply. Thus, the control means 8 has the engine speed N
An engine speed detector 9 that detects _E and a water temperature detector 10 that detects the engine cooling water temperature T _W are connected.

In the control means 8, the control procedure for the fuel supply control at the time of detecting the misfiring cylinder is set as shown in FIG. 2. Next, the control procedure will be described.

In FIG. 2, in the first step S1, it is determined whether or not it is in the fuel supply stop region. That is, the fuel supply stop region corresponding to the vehicle deceleration determined by the opening degree of the throttle valve 1, the engine speed N _{E, the} intake pressure and the like is set in advance, and the operating state of the engine E is the fuel supply stop region. If it is determined that the vehicle is located at, the process proceeds to the second step S2.

In the second step S2, the feedback control for determining the fuel supply amount to all cylinders based on the O ₂ concentration in the exhaust gas is stopped, and then the fuel supply to all cylinders is stopped in the third step S3. To do.

When it is determined in the first step S1 that the operating state of the engine E is out of the fuel supply stop region, it is determined in the fourth step S4 whether or not a cylinder misfire has occurred. To detect this cylinder misfire,
For example, by looking at changes in the opening degree of the throttle valve 1, intake pressure, shift speed, vehicle speed, and the like, during steady-state operation in which fluctuations in the engine operating state are small, when the fluctuations in the engine speed N _E become large When the fluctuation occurs, it is determined that the cylinder C in the explosion stroke is in the misfire state, and such misfire detection is disclosed in JP-A-3-290044.
It is already known in Japanese Patent Laid-Open Publication No. 2005-242242, etc., and there is also known one that detects a misfiring cylinder by detecting pressure in the combustion chamber, detecting secondary voltage fluctuations in the ignition device, or detecting ion current generated in the combustion chamber. ing. Then, in the fourth step S4, when the misfire rate, that is, the number of misfires per predetermined rotation speed exceeds the first predetermined value, for example, 20%, it is determined that the cylinder misfire has occurred, and the cylinder misfire has occurred. If it is determined that there is no cylinder, normal fuel supply control is continued in the fifth step S5, and if it is determined that a cylinder misfire has occurred, the routine proceeds to a sixth step S6.

In the sixth step S6, it is determined whether or not the engine speed N _E is equal to or higher than the set speed N _E0 (for example, 3000 rpm). If N _E ≧ N _E0 , the second step S2 is executed. 7th when N _E <N _EO
Go to step S7.

In the seventh step S7, a misfire of a second predetermined value (for example, 50%) or more set to be larger than the first predetermined value (for example, 20%) used for determining whether or not the misfiring cylinder has occurred. If it is determined that the misfire rate is greater than or equal to the second predetermined value, the eighth step S8 is bypassed to the ninth step S9, and the misfire rate is less than the second predetermined value. If there is, proceed to the eighth step S8.

In the eighth step S8, the engine cooling water temperature is set.
T_WIs the predetermined temperature T_W0Below (T_W≤T _W0) Is
Is judged, T_W> T_WOIf it is, the fifth step S5
To T_W≤T_WOEngine E is warmed up
If it is in the process, the process proceeds to the ninth step S9.

Then, in the ninth step S9, the feedback control for determining the fuel supply amount to all the cylinders based on the O ₂ concentration in the exhaust gas is stopped, and in the following tenth step S10, the fuel to the misfiring cylinder is fueled. Stop the supply.

Next, the operation of this embodiment will be described. When the engine speed N _E is equal to or higher than the set speed N _E0 , the fuel supply to all cylinders is stopped in response to the misfiring cylinder detection. It is possible to prevent the unburned gas generated as a result from flowing into the catalytic converter 4 of the exhaust system, and to prevent the catalyst temperature from excessively rising due to the reaction of the unburned gas to thermally damage the catalyst.

Further, the engine speed N _E is the set speed N _E0
When the misfiring cylinder is detected when the temperature is less than 1, the fuel supply to the misfiring cylinder is stopped when the engine E is warming up and the engine cooling water temperature T _W is equal to or lower than the predetermined temperature T _W0. In the state where the catalyst in (1) is not activated, the unburned gas due to the cylinder misfire does not flow out of the catalytic converter 4 as it is and is discharged.

When the engine E finishes warming up and the engine cooling water temperature T _W exceeds the predetermined temperature T _W0 , the normal fuel supply control is continued, so that the engine E does not stop and is kept low. It is possible to avoid deterioration of the engine operating condition in the rotation range.

Moreover, when the misfire rate is equal to or higher than the second predetermined value, it is unlikely that normal combustion will be restored even if fuel is supplied to the misfire cylinder, and improvement in engine drivability cannot be expected. It is possible to prevent deterioration of exhaust gas properties by always stopping the fuel supply when the misfire rate is equal to or higher than a predetermined value.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the present invention described in the claims. It is possible to do.

[0025]

As described above, according to the invention of claim 1,
In response to the misfiring cylinder detection when the engine is in the warm-up process, the fuel supply to the cylinder where misfiring is detected is stopped.
It is possible to prevent the unburned gas from being released to the atmosphere while the catalyst is not activated.

According to the fourth aspect of the present invention, when the engine speed is equal to or higher than the set speed when the misfiring cylinder is detected, the fuel supply to all the cylinders is stopped, and the engine speed is lower than the set speed. When the engine is in the process of warming up in this state, the fuel supply to the cylinder that has detected the misfire is stopped, so that it is possible to prevent the heat damage to the catalyst and avoid the deterioration of the drivability of the engine. It is possible to prevent the unburned gas from being released into the atmosphere.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an intake system and an exhaust system of a multi-cylinder engine.

FIG. 2 is a flowchart showing a control procedure.

[Explanation of symbols]

C Cylinder E Multi-cylinder engine N _E Engine speed N _E0 Set speed T _W Engine cooling water temperature T _W0 Predetermined temperature

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical display location F02D 45/00 362 E 7536-3G 368 Z 7536-3G (72) Inventor Eri Kuroda Wako, Saitama Prefecture Chuo 1-4-1 Stock Company Honda Technical Research Institute

Claims (4)

[Claims] 1. A fuel supply control method for a multi-cylinder engine capable of individually detecting a misfire of a plurality of cylinders (C) and stopping the fuel supply to the cylinder (C) in which the misfire is detected. ) Is in the warm-up process, the fuel supply control method for a multi-cylinder engine is stopped in response to the misfiring cylinder detection. 2. The engine according to claim 1, wherein it is determined that the engine (E) is in the warm-up process by the engine cooling water temperature (T _W ) being equal to or lower than a predetermined temperature (T _W0 ). Fuel supply control method for cylinder engine. 3. A misfire rate, which is the number of misfires per predetermined number of revolutions, is detected for each cylinder, and when the misfire rate exceeds a predetermined value, it is determined that the cylinder has misfired. Item 3. A fuel supply control method for a multi-cylinder engine according to Item 1 or 2. 4. A misfiring cylinder detection in a fuel supply control method for a multi-cylinder engine capable of individually detecting misfiring of a plurality of cylinders (C) and stopping the fuel supply to the cylinder (C) in which misfiring is detected. sometimes, the rotational speed of the engine (E) when (N _E) is the set rotational speed (N _EO) or stops fuel supply to all cylinders, the rotational speed of the engine (E) (N
_In a multi-cylinder engine characterized by stopping fuel supply to a cylinder (C) that has detected a misfire when the engine (E) is in the warm-up process in a state in which E) is less than a set engine speed (N _EO ). Fuel supply control method.