JP2006132438A - Control device for engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an engine capable of promptly determining that poor fuel is used and changing over to engine control for poor fuel without delay, thereby preventing deterioration of driveability due to improper engine control. <P>SOLUTION: By setting a property determination flag F1 when fuel is supplied, engine control at a cold start of the engine after that is conducted for normal fuel based on the setting of the property determination flag F1 (step S24), and then fuel property is determined based on the engine's rotating condition (step S28). Thereafter, engine control is conducted based on this determination result (steps S18-S22). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an engine control device, and more particularly to an engine control device that determines the properties of fuel used and executes engine control based on the determined fuel properties.

  As is well known, engine performance is greatly affected by the properties of the fuel used, so instead of appropriately volatile fuel (hereinafter referred to as normal fuel), fuel with insufficient volatility (hereinafter referred to as poor fuel) is used. In such a case, drivability deteriorates particularly during cold start where combustion is unstable. FIG. 6 is a time chart showing the cold start situation according to the fuel properties. By applying the same fuel injection amount, the air-fuel ratio changes to the lean side in the poor fuel shown by the thick line with respect to the normal fuel shown by the thin line. As a result, it can be seen that a decrease in rotation and a decrease in torque occur immediately after start-up, thereby deteriorating drivability. Note that this lean air-fuel ratio is caused by the fact that the fuel vaporization rate adhering to the intake port is less for poor fuel than for normal fuel.

As countermeasures, it may be possible to always perform fuel injection control and ignition timing control on the premise of poor fuel, but the drivability failure at the cold start is resolved, but transient or high when normal fuel is used. Another problem arises that the air-fuel ratio in the load region becomes rich and CO and HC increase. In view of this, measures are taken to determine the properties of the fuel used based on rotation fluctuations immediately after start-up and detection by a fuel property sensor, and to switch engine control in accordance with the determination results (see, for example, Patent Documents 1 and 2).
JP-A-3-233151 JP 2000-64878 A

  In the methods disclosed in Patent Documents 1 and 2, the engine is controlled until the next fuel property is determined based on the previously determined fuel property, so that the fuel is used during the trip (for example, when the engine is stopped). ) Is not assumed at all when the properties of the fuel used change. However, for example, when the engine control is based on the normal fuel property determination and poor fuel is supplied when the engine is stopped, or when the remaining fuel in the tank changes due to leaving the vehicle for a long time, etc. The phenomenon in which the properties of the fuel used change during the trip is not uncommon, and if these situations occur, the properties of Patent Documents 1 and 2 will be used for the next property determination despite the use of poor fuel. Until then, there was a problem that improper engine control corresponding to normal fuel was continued, causing drivability deterioration due to poor starting.

  The present invention has been made to solve such problems, and the object of the present invention is to quickly determine the use of bad fuel and quickly switch to engine control corresponding to bad fuel, Accordingly, an object of the present invention is to provide an engine control device that can prevent deterioration of drivability due to inappropriate engine control.

  In order to achieve the above object, the invention of claim 1 is directed to a fuel property determining means for determining whether the fuel property of the engine is normal fuel or poor fuel, and the possibility that the fuel property changes while the engine is stopped. Based on the previous determination result by the fuel property determination unit and the change condition determination unit that determines whether or not a certain condition is satisfied, the engine control at the time of the current engine start is performed, while the fuel condition is changed by the change condition determination unit If it is determined that a condition that may occur is satisfied, the engine control corresponding to the normal fuel is performed regardless of the previous determination result of the fuel property by the fuel property determination means at the time of the engine cold start immediately after And control means for causing the fuel property determination means to determine the fuel property.

  Therefore, based on the previous determination result by the fuel property determination means, the control means performs engine control at the time of the current engine start, while the change condition determination means determines that a condition that may change the fuel property is satisfied. In this case, the engine control corresponding to the normal fuel is performed at the time of the engine cold start immediately after that, regardless of the previous determination result of the fuel property, and the fuel property is determined by the fuel property determination means. By executing engine control corresponding to normal fuel, the engine rotation becomes unstable when bad fuel is used. Therefore, the fuel property can be determined based on the rotation state at this time.

When the fuel property is likely to change, the fuel property is determined at the time of the cold start immediately thereafter. Therefore, when the fuel property has changed to the worse side, only once at the time of the cold start immediately after Although the engine rotation becomes unstable, after that, the engine control is switched to the appropriate engine control corresponding to the poor fuel, and the situation where the engine control corresponding to the inappropriate normal fuel is continued is avoided.
The invention of claim 2 further comprises complete explosion determination means for determining the complete explosion of the engine at the time of cold start, and the control means is cranking of the engine before the complete explosion determination by the complete explosion determination means. The engine control corresponding to the inferior fuel is performed, and after the complete explosion determination, the engine control corresponding to the normal fuel is performed and the fuel property determination means determines the fuel property.

  Accordingly, when the engine is cranking before the complete explosion determination by the complete explosion determination means, the engine control corresponding to the bad fuel is performed. Therefore, even if the poor fuel is used, the engine is started well. The

  As described above, according to the engine control apparatus of the first aspect of the present invention, when the condition that the fuel property may change is satisfied, the engine control corresponding to the normal fuel is performed at the cold start immediately after. In addition, since the fuel properties are determined, it is possible to quickly determine the use of bad fuel and switch to engine control corresponding to the bad fuel at an early stage, thereby deteriorating drivability due to inappropriate engine control. Can be prevented in advance.

  According to the engine control apparatus of the second aspect of the present invention, in addition to the first aspect, the engine control corresponding to the poor fuel is performed during the cranking. Therefore, the engine control corresponding to the normal fuel is performed along with the determination of the fuel property. It is possible to prevent the engine startability from being deteriorated when the operation is performed.

[First Embodiment]
Hereinafter, a first embodiment in which the present invention is embodied in an engine control device that takes measures when poor fuel is supplied will be described.
FIG. 1 is an overall configuration diagram showing an engine control apparatus according to the present embodiment. The engine 1 of the present embodiment is configured as an in-line four-cylinder engine, and a spark plug 3 is provided in the combustion chamber 2 of each cylinder. An intake passage 5 is connected to each combustion chamber 2 via an intake valve 4, and a fuel injection valve 6 is provided in the intake passage 5. An exhaust passage 8 is connected to each combustion chamber 2 via an exhaust valve 7, and a catalyst and a silencer (not shown) are provided in the exhaust passage 8. The fuel injection valve 6 of each cylinder is connected to a fuel tank 10 via a fuel line 9, and fuel (gasoline) stored in the fuel tank 10 is pumped up by a fuel pump 11 and passed through the fuel line 9 at a predetermined pressure. It is supplied to the fuel injection valve 6 of the cylinder.

  During operation of the engine 1, intake air is introduced into the intake passage 5 via an air cleaner (not shown), and the intake air is flow-adjusted by a throttle valve and then distributed to each cylinder, together with fuel injected from the fuel injection valve 6. The air-fuel mixture is introduced into the combustion chamber 2 as the intake valve 4 is opened. In the combustion chamber 2 of each cylinder, the air-fuel mixture is ignited by a spark plug 3 in the vicinity of the compression top dead center, and a rotational force is applied to the crankshaft 13 through the piston 12 by combustion. Is opened to the outside through the exhaust passage 8 through the catalyst and the silencer.

  On the other hand, the vehicle includes an input / output device (not shown), a storage device (ROM, RAM, BURAM, etc.) used for storing control programs and control maps, a central processing unit (CPU), an ECU 21 (engine) provided with a timer counter, etc. Control unit) is installed. On the input side of the ECU 21, a crank angle sensor 22 that outputs a crank angle signal in synchronization with the rotation of the crankshaft 13 of the engine 1, a water temperature sensor 23 that detects a cooling water temperature THw of the engine 1, and a liquid level in the fuel tank 10 A fuel sensor 24 that detects the level, that is, the amount of fuel stored in the tank 10, a vehicle speed sensor 25 that detects the vehicle speed V, and other various switches and sensors are connected. The ignition plug 3, the fuel injection valve 6, the fuel pump 11, and other devices are connected to the output side of the ECU 21.

The ECU 21 executes fuel injection control for driving and controlling the fuel injection valve 6 and ignition timing control for driving and controlling the ignition plug 3 based on detection information from various sensors, thereby operating the internal combustion engine 1. The ECU 21 determines the property of the fuel used based on the rotation state of the engine 1 and switches between fuel injection control and ignition timing control according to the determined fuel property.
And while the techniques of Patent Documents 1 and 2 described above perform the fuel property determination process for each predetermined trip set in advance, in the present embodiment, as an example of a condition in which the fuel property may change as an example Fuel supply is set, and the fuel property is determined at the time of engine cold start immediately after the fuel supply. Hereinafter, the fuel property determination process will be described in detail. Here, the fuel property is defined by the volatility (fuel vapor pressure, refractive index, density, dielectric constant) of the fuel. For example, when the vapor pressure is used as a reference, the normal fuel having appropriate volatility is used. The vapor pressure is relatively high, and the vapor pressure of poor fuel with insufficient volatility is relatively low.

  The ECU 21 executes an oil supply determination routine shown in FIG. 2 at a predetermined control interval. This routine is executed even when the ignition key is turned off by refueling the vehicle. First, in step S2, it is determined whether or not the vehicle is stopped (that is, the vehicle speed V = 0). If (No), the routine is once terminated. When the determination in step S2 becomes Yes (positive) due to the stop of the vehicle, the fuel amount A in the fuel tank 10 detected by the fuel sensor 24 in step S4 is read every predetermined period, and the previous fuel amount A and the current fuel amount are read. A difference ΔA from the amount A is calculated.

  The predetermined period is set to be sufficiently longer than a general refueling time, and the calculated difference A is a value reflecting an increase in fuel when refueling is performed. Instead of reading the fuel amount A every predetermined period, the fuel amount A is read when the ignition key is turned off and on, and the difference ΔA is obtained as a change in the fuel amount A from the off operation to the on operation. The difference ΔA in this case is also a value reflecting the increase in fuel due to refueling.

  In subsequent step S6, it is determined whether or not the difference A is equal to or larger than a predetermined value ΔA0 set in advance. The processing in step S6 is to determine whether or not there is a possibility that the fuel property in the fuel tank 10 has changed due to refueling (change condition determining means). Here, for example, when the fuel stored in the tank 10 is low and the fuel is supplied to the vicinity of the full tank, the fuel supply fuel occupies a large proportion of the stored fuel. On the other hand, when the fuel is supplied in a state where the fuel in the tank 10 is hardly reduced, the ratio of the supplied fuel to the stored fuel is small. Even if it is done, it is unlikely to change the fuel properties. Therefore, the predetermined value ΔA0 is set in advance for each amount of fuel stored in the tank 10 as the minimum amount of fuel to be changed in fuel properties. In step S6, the predetermined value ΔA0 corresponding to the current amount of fuel stored in the tank 10 is set. A determination is made based on.

  In addition, without considering the ratio of the stored fuel and the refueling fuel in this way, it is considered that there is a possibility that the fuel property in the tank 10 may change when refueling is performed regardless of the amount of refueling fuel. May be. In this case, a value slightly larger than the detection error that can be generated by the fuel sensor 24 is set as the predetermined value ΔA0, and it is determined in step S6 whether the fuel has increased beyond the sensor detection error.

When refueling is not performed, and when refueling is performed and less than the predetermined value ΔA0, the ECU 21 determines No in step S6 and ends the routine. On the other hand, when refueling greater than the predetermined value ΔA0 is performed. In step S8, after setting the fuel property determination flag F1, the routine is terminated.
On the other hand, when the engine 1 is started by the start operation of the ignition key of the vehicle, the ECU 21 executes the property determination / control switching routine shown in FIG. 3 at a predetermined control interval. The ECU 21 stores a result of fuel property determination performed during the previous engine operation as a poor fuel flag F2.

The ECU 21 first determines in step S12 whether or not it is a cold start. This determination is made based on a predetermined value THw0 (for example, 40 ° C.) set as the cooling water temperature at the completion of warm-up. When the cooling water temperature THw detected by the water temperature sensor 23 is less than the predetermined value THw0, the determination of No is made. In step S14, the routine is terminated after the start control in the normal temperature state is performed.
Therefore, at the time when good startability is ensured by completion of warm-up in this way, the engine 1 is started by normal fuel injection control and ignition timing control regardless of the fuel properties.

  Further, when it is determined that the engine is cold start and the determination of Yes is made in step S12, it is determined in step S16 whether or not the fuel property determination flag F1 is set, and when the determination is No, that is, in the fuel tank 10 When refueling is not performed so as to change the fuel property, and it can be considered that the set poor fuel flag F2 reflects the property of the currently used fuel, the subsequent setting according to the setting of the bad fuel flag F2 Implement control.

  In this case, it is first determined in step S18 whether or not the poor fuel flag F2 is set. If the determination is Yes, engine control corresponding to the bad fuel (hereinafter referred to as bad fuel control) is performed in step S20. On the other hand, when the determination in step S18 is No, engine control corresponding to normal fuel (hereinafter referred to as normal fuel control) is performed in step S22, and engine start is performed under each control (control means). Specifically, the processing in steps S20 and S22 is dealt with by changing the fuel injection amount, the injection timing, the ignition timing, and the like. For example, when the poor fuel is used, the rate of vaporization of the fuel adhering to the intake port decreases. By increasing the amount, lean air-fuel ratio is suppressed. By controlling the engine in accordance with the fuel properties, a good drivability is realized by suppressing a decrease in rotation and a torque drop immediately after starting.

  On the other hand, when the determination in step S16 is Yes, that is, when the fuel property in the fuel tank 10 changes due to the refueling, and the poor fuel flag F2 may not reflect the current property of the fuel used. The process proceeds to step S24. In step S24, normal fuel control is executed (control means), and in step S26, complete explosion determination is performed (complete explosion determination means). For example, the ECU 21 determines a complete explosion when the engine speed Ne obtained from the crank angle signal of the crank angle sensor 22 exceeds a preset complete explosion determination value Ne0, and proceeds from step S26 to step S28.

Therefore, in this embodiment, the cranking of the engine 1 is performed under the normal fuel control, and the normal fuel control is continued even after the complete explosion determination. The control at the time of start-up is stopped at the end of the property determination / control switching routine after completing the property determination of the fuel used to be described below, and thereafter the engine operation is continued by normal control executed in another routine. .
When bad fuel control is performed at the cold start, not only bad fuel but also normal fuel is not used, and severe engine rotation is unlikely to occur, but conversely, when normal fuel control is performed, When using the engine, noticeable engine rotation disturbance occurs. The process of step S24 is to forcibly switch to the normal fuel control to generate an engine rotation state corresponding to the fuel properties. If bad fuel is used, the engine rotation state at this time is shown in FIG. As in the case of using the poor fuel of the prior art shown in FIG. 6, the air-fuel ratio changes to the lean side due to improper control, and the engine rotation becomes unstable due to the influence.

  In step S28, as the fuel property determination process, the engine speed Ne at the start is sampled over a predetermined period, and the sampling data is statistically processed. In the subsequent step S30, it is determined whether or not the used fuel is poor fuel from the statistical result. (Fuel property determination means). As a specific determination method, for example, the increase in rotation in the combustion stroke of the first idle after the complete explosion determination is obtained, and when there is a lot of data with a small increase in rotation, it is determined that the fuel is poor, or the rotation from the compression stroke to the combustion stroke A variation difference is obtained, and when there is a lot of data with a small rotation variation difference, it is determined that the fuel is poor, or a change in angular acceleration is obtained, and when there is a lot of data with a large change in angular acceleration, it is determined that the fuel is poor.

  When the determination in step S30 is Yes, after setting the poor fuel flag F2 in step S32, the fuel property determination flag F1 is reset in step S34 and the routine is ended. If the determination in step S30 is No, the poor fuel flag F2 is reset in step S36, then the fuel property determination flag F1 is reset in step S34, and the routine is terminated.

As a result, the poor fuel flag F2 enters a set state corresponding to the fuel used. When the property determination / control switching routine is executed at the time of cold start thereafter, the ECU 21 receives the set of the fuel property determination flag F1 and receives step S16. From step S18 to step S18, the control according to the setting of the poor fuel flag F2 is performed, and the engine 1 is started.
As described above, in the control device for the engine 1 according to the present embodiment, when refueling that may change the fuel property in the fuel tank 10 is performed, it is normally forced to be performed at the time of engine cold start immediately thereafter. After switching to the fuel control, the fuel property determination process is performed, and at the subsequent cold start, the engine control is performed based on the fuel property of the determination result. Therefore, when the fuel property in the tank 10 changes to the poor side due to the supply of the bad fuel, the engine rotation becomes unstable only once at the time of the cold start immediately after that, but after that, it corresponds to the bad fuel. Since the control is switched to an appropriate control, it is possible to avoid the situation in which the inappropriate normal fuel control is continued, and to prevent the drivability from being deteriorated.

In addition, in step S6, the fuel property determination process is performed only when fueling that may change the fuel property is performed based on the predetermined value ΔA0, and the fuel property is changed even if fueling is performed. If not, the fuel property determination process is not performed. Therefore, it is possible to obtain an effect of keeping the fuel property determination process that causes the deterioration of drivability to the minimum necessary.
[Second Embodiment]
Next, a second embodiment in which the present invention is embodied in another control device for the engine 1 will be described. The difference of this embodiment with respect to the first embodiment is that the first embodiment consistently continues the normal fuel control at the cold start when determining the fuel properties, whereas in this embodiment, the difference is The poor fuel control is performed during the ranking, and the normal fuel control is performed after the complete explosion determination. The overall configuration shown in FIG. 1 and the fuel supply determination routine shown in FIG. 2 are the same. Therefore, the parts having the same configuration are denoted by the same member numbers, the description thereof is omitted, and the differences are mainly described.

  The ECU 21 executes a property determination / control switching routine shown in FIG. 4 at predetermined control intervals when the engine is started. The processing in the case where it is not during the cold start (No in step S12) and in the case where the property determination flag F1 is not set and it is not necessary to determine the fuel property (No in step S16) is the same as in the first embodiment. On the other hand, if it is determined that the engine is in cold start, the determination of Yes is made in step S12, the determination of Yes is made in step S16 by setting the property determination flag F1, and the process proceeds to step S24, the ECU 21 executes the poor fuel control. (Control means) Then, in step S26, complete explosion determination is performed (complete explosion determination means). If the determination in step S26 is Yes due to the complete explosion determination, the process proceeds to step S52, and after switching to normal fuel control, fuel property determination processing is performed in steps S28 and S30 (control means, fuel property determination means).

  FIG. 5 is a time chart showing the cold start situation according to the present embodiment, and the cranking of the engine 1 is performed under poor fuel control by the processing of the ECU 21, and after the complete explosion determination (Ne> Ne0), it is normal. After switching to fuel control, the properties of the fuel used are determined. Therefore, for example, the fuel injection amount is switched from the poor fuel control line with a large injection amount to the normal fuel control line with a small injection amount, with the complete explosion determination as a boundary, as indicated by a thick line in the figure. Since the property judgment is performed based on the engine rotation status after the complete explosion, it is not always necessary to perform normal fuel control during cranking before the complete explosion, and cranking is performed in a situation where poor fuel is used. When the normal fuel control is performed, the rate of vaporization of the fuel adhering to the intake port is reduced, and the air-fuel ratio is made lean so that the startability is deteriorated.

  By performing poor fuel control during cranking, leaning of the air-fuel ratio caused by bad fuel is prevented, so that the engine 1 is started well and complete explosion determination is performed. By switching to the fuel control, it is possible to determine the fuel properties without any trouble. Therefore, in this embodiment, in addition to the effects described in the first embodiment, the effect that the deterioration of the engine startability when the normal fuel control is performed with the execution of the fuel property determination process can be prevented. Obtainable.

In FIG. 5, the injection amount corresponding to the poor fuel is switched stepwise from the injection amount corresponding to the normal fuel, and the fuel injection timing and the ignition timing are also switched stepwise in the same manner. As shown, the injection amount corresponding to the poor fuel may be gradually shifted from the injection amount corresponding to the normal fuel, and the fuel injection timing and the ignition timing may be gradually shifted as well.
On the other hand, in the above embodiment, it is determined whether there is a possibility that the fuel property has changed based on the increase in the fuel amount A in the fuel tank 10 detected by the fuel sensor 24, but the determination method is limited to this. For example, a switch is provided on the fuel lid of the vehicle or the cap of the fuel filler opening provided in the fuel lid, and when the opening of the fuel lid or the cap is detected by this switch, fueling is performed and the fuel property is changed. It may be determined that there is a possibility.

It is a whole lineblock diagram showing the control device of the engine of an embodiment. It is a flowchart which shows the oil supply determination routine which ECU performs. It is a flowchart which shows the property determination and control switching routine which ECU of 1st Embodiment performs. It is a flowchart which shows the property determination and control switching routine which ECU of 2nd Embodiment performs. It is a time chart which shows the cold start situation by the control device of the engine of a 2nd embodiment. It is a time chart which shows the cold start condition by the control apparatus of a prior art engine.

Explanation of symbols

1 engine 21 ECU (fuel property determination means, change condition determination means, control means, complete explosion determination means)

Claims (2)

Fuel property determining means for determining whether the fuel property of the engine is normal fuel or poor fuel;
Change condition determination means for determining whether or not a condition that may cause a change in fuel properties is satisfied while the engine is stopped;
When engine control is performed at the time of the current engine start based on the previous determination result by the fuel property determination means, and when it is determined by the change condition determination means that a condition that may change the fuel property is satisfied. In addition, the engine control corresponding to the normal fuel is performed regardless of the previous determination result of the fuel property by the fuel property determination unit immediately after the engine cold start, and the fuel property determination unit performs the fuel property determination. And an engine control device. A complete explosion determination means for determining the complete explosion of the engine at the time of cold start;
The control means performs engine control corresponding to inferior fuel during cranking of the engine before the complete explosion determination by the complete explosion determination means, and performs engine control corresponding to normal fuel after the complete explosion determination and the fuel. 2. The engine control device according to claim 1, wherein the property determining means is configured to determine the fuel property.

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