JP2001107795A - Fuel property determination device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely determine fuel property. SOLUTION: When a fuel property determination performing condition (intake air temperature is lower than a restart determination value, cooling water temperature is within a predetermined temperature range, idle operation is carried out) is satisfied (step 101 to step 103), a fuel injection amount calculated in accordance with an engine operation state is read and a combustion amount of the fuel is found by dividing an intake air amount by an air-fuel ratio (14.6×λ) of an exhaust gas (step 104 to step 107). Then, the injection mount is corrected using a learning value for correcting a system error (step 108), and the combustion amount is further corrected in accordance with an intake pipe pressure (step 109, step 110). Then, a fuel property parameter which estimates the fuel property is found from a rate of integrated value of the combustion amount with respect to an integrated value of the injection amount within a predetermined period (step 111), and a command value of the injection amount of a fuel injection valve is corrected in accordance with the fuel property parameter (step 112).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel property judging device for an internal combustion engine which judges the property of fuel supplied to the internal combustion engine.

[0002]

2. Description of the Related Art A general gasoline engine mounted on a vehicle often has a fuel injection valve mounted on an intake pipe to inject fuel (gasoline) into an intake port. In this intake port injection, part of the fuel injected from the fuel injection valve is
The air is directly sucked into the cylinder, but the rest adheres to the inner wall surface of the intake port or the surface of the intake valve, and then gradually evaporates and is sucked into the cylinder. Therefore, the amount of fuel sucked into the cylinder changes depending on the amount of fuel (wet) adhering to the inner wall surface or the like of the intake port. The amount of fuel evaporation (evaporation rate) varies depending on the fuel properties, but the fuel properties are not constant even for the same type of fuel, differ between manufacturers, and even for fuels of the same manufacturer, the fuel properties vary depending on the season and sales area. Be changed. Therefore, in order to perform accurate air-fuel ratio control (fuel injection control) in consideration of the evaporation amount of the fuel, it is necessary to detect the fuel property. Thus, as disclosed in Japanese Patent Application Laid-Open No. 9-203342, it has been proposed to determine the fuel property from the parameters of startability, rotation fluctuation, and rotation rise.

[0003]

However, since the startability, the rotation fluctuation, and the rotation start-up vary depending on various factors other than the fuel property, even if the fuel property is determined using these parameters, the fuel property is not improved. Under the influence of various factors other than the above, the fuel property cannot be accurately determined. For this reason, the correction accuracy of the fuel injection amount due to the fuel property is deteriorated, and the emission, drivability, and fuel efficiency may be deteriorated.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an apparatus for determining the fuel property of an internal combustion engine that can accurately determine the fuel property.

[0005]

According to a first aspect of the present invention, there is provided a fuel property determining apparatus for an internal combustion engine, comprising: an injection amount of a fuel injected from a fuel injection valve; A certain parameter
) Is obtained by the injection amount parameter calculation means, and the combustion amount of the fuel combusted in the cylinder or a parameter having a correlation with the combustion amount (hereinafter, referred to as “the combustion amount parameter”) is obtained by the combustion amount parameter calculation means. The fuel property is determined by the fuel property determining means based on the relationship between the injection quantity parameter and the combustion quantity parameter.

For example, the heavier the fuel property, the lower the volatility (evaporability) of the fuel, the more the amount of fuel (wet amount) attached to the inner wall surface of the intake port, etc. Since the ratio of the amount of combustion decreases, the relationship between the amount of fuel injected and the amount of combustion changes depending on the properties of the fuel. Therefore, if the fuel property is determined based on the relationship between the injection amount parameter and the combustion amount parameter, the fuel property can be accurately determined.

Here, when the fuel combustion amount is used as the combustion amount parameter, the intake air amount of the internal combustion engine is detected by the intake air amount detection means, and the air-fuel ratio of the exhaust gas is set to the air-fuel ratio. The fuel ratio may be detected by the fuel ratio detection means, and the combustion amount may be calculated using the detected values. That is, since the air-fuel ratio of the exhaust gas is determined from the intake air amount and the fuel combustion amount, the fuel combustion amount can be calculated using the intake air amount and the exhaust gas air-fuel ratio. In addition, since the detection of the intake air amount and the air-fuel ratio of the exhaust gas can be performed by using a sensor generally provided for air-fuel ratio control, it is not necessary to newly provide a sensor for detecting a combustion amount parameter, thereby reducing cost. Can be

According to a third aspect of the present invention, the excess fuel supply ratio, which is the reciprocal of the excess air ratio of the air-fuel mixture supplied to the internal combustion engine, is determined as an injection amount parameter, and the combustion which is the reciprocal of the excess air ratio of the exhaust gas. The excess fuel ratio may be obtained as a combustion amount parameter. For example, as the fuel property becomes heavier, the wet amount increases, and the ratio of the excess combustion fuel ratio to the excess fuel supply ratio decreases.Therefore, the relationship between the excess fuel supply ratio and the excess combustion fuel ratio depends on the fuel properties. Change. Therefore, if the fuel property is determined based on the relationship between the excess fuel supply rate and the excess fuel fuel rate, the fuel property can be accurately determined. When the invention according to claim 3 is applied to a system for controlling an air-fuel ratio by obtaining an excess fuel ratio from an output signal of an air-fuel ratio sensor, processing for obtaining a combustion amount parameter becomes extremely simple, and a process for determining a fuel property is performed. Arithmetic processing can be simplified.

The fuel property may be determined by comparing the integrated value of the combustion amount parameter and the integrated value of the injection amount parameter within a predetermined period. In this way, the influence of noise and the influence of fluctuations in the operating state can be reduced, and the accuracy of fuel property determination can be improved.

Alternatively, the fuel property is determined by comparing the integrated value of the difference between the injection amount parameter and the combustion amount parameter within a predetermined period with the integrated value of the injection amount parameter. Is also good. That is, the difference between the injection amount and the combustion amount is a parameter for evaluating the wet amount adhering to the inner wall surface or the like of the intake port. As the fuel property becomes heavier, the ratio of the wet amount to the injection amount increases. Therefore, if the integrated value of the difference (wet amount parameter) between the injection amount parameter and the combustion amount parameter within a predetermined period is compared with the integrated value of the injection amount parameter, the fuel property can be determined with high accuracy.

Also, in consideration of the fact that the wet amount changes in accordance with the operating state of the internal combustion engine, the relationship between at least one of the injection amount parameter and the combustion amount parameter or both or the fuel property determination criterion is provided. May be corrected by the operating state correction means according to the operating state of the internal combustion engine. With this configuration, the change in the wet amount due to the change in the operating state of the internal combustion engine can be corrected to determine the fuel property, so that the stable fuel property independent of the operating state of the internal combustion engine can be determined.

In this case, the wet amount varies depending on the intake pipe pressure, the intake air amount, the engine speed, the cooling water temperature, and the like. Among them, the wet amount is most strongly affected by the intake pipe pressure. Focusing on this point, the relationship between at least one or both of the injection amount parameter and the combustion amount parameter or the fuel property determination standard may be corrected according to the intake pipe pressure. This makes it possible to use the intake pipe pressure to perform stable fuel property determination that is not affected by the operating state of the internal combustion engine.

Further, since the wet amount is relatively strongly affected by the engine speed, the relationship between at least one of the injection amount parameter and the combustion amount parameter or both or the fuel property determination criterion is determined by the engine. The correction may be made according to the rotation speed. This makes it possible to make a stable determination of the fuel property irrespective of the operating state of the internal combustion engine using the engine speed.

Further, since the wet amount decreases as the temperature of the internal combustion engine increases, the change in the combustion amount due to the difference in the fuel property decreases as the temperature increases, and the accuracy of the fuel property determination decreases. Therefore, the internal combustion engine is restarted in a warmed-up state (hereinafter referred to as "warm-up restart").
It is preferable that the restart determination means determines whether or not the determination has been made, and at the time of warm-up restart, the fuel property determination by the fuel property determination means is prohibited by the fuel property determination prohibition means. In other words, when restarting the warm-up, since the temperature of the inner wall surface of the intake port is high and the wet amount is small from the beginning of the start,
The change in the amount of combustion due to the difference in the fuel property is small, and the accuracy of determining the fuel property is reduced. Therefore, if the determination of the fuel property is prohibited at the time of restarting the warm-up, a decrease in the determination accuracy of the fuel property can be prevented.

In both heavy fuel and light fuel, when the temperature of the internal combustion engine rises to a certain degree after starting, the amount of the injected fuel (the amount of wet generation) on the inner wall surface of the intake port and the wet amount are determined. The amount of evaporation is balanced, and the amount of fuel injection and the amount of combustion become substantially equal. Therefore, if there is a difference between the fuel injection amount and the combustion amount when the temperature rises to such a temperature, it is considered that the difference is due to an error of the system.

In consideration of this point, as in claim 10,
The temperature of the internal combustion engine is detected by the engine temperature detection means, and when the temperature of the internal combustion engine is equal to or higher than a predetermined temperature, the relationship between the injection amount parameter and the combustion amount parameter is learned by the learning means, and the fuel property is determined by the learning correction means. At this time, the relationship between at least one or both of the injection amount parameter and the combustion amount parameter or the fuel property determination criterion may be corrected using the learning value learned by the learning means. That is, by learning the relationship between the injection amount parameter and the combustion amount parameter when the temperature of the internal combustion engine is equal to or higher than a predetermined temperature at which the fuel injection amount and the combustion amount are substantially equal, the system error can be learned. By using the learning value, the fuel property can be determined by canceling the system error, and the determination accuracy of the fuel property can be improved.

The temperature of the internal combustion engine is considered to be equal to or higher than a predetermined temperature at which the fuel injection amount and the combustion amount become substantially equal after a predetermined period has elapsed from the start.
After a predetermined period has elapsed since the start of the internal combustion engine, the relationship between the injection amount parameter and the combustion amount parameter is learned, and the relationship between at least one or both of the injection amount parameter and the combustion amount parameter or the fuel property determination criterion is learned. The correction may be made using the learning value learned by the means. Also in this case, similarly to the tenth aspect, the accuracy of the fuel property can be improved by canceling the error of the system.

[0018]

[Embodiment (1)] An embodiment (1) of the present invention will be described below with reference to FIGS.

First, a schematic configuration of the entire engine control system will be described with reference to FIG. An air cleaner 13 is provided at the most upstream portion of an intake pipe 12 of an engine 11 which is an internal combustion engine, and an air flow meter 14 (intake air amount detection means) for detecting an intake air amount is provided downstream of the air cleaner 13. Have been. Downstream of the air flow meter 14, a throttle valve 15 and a throttle opening sensor 16 for detecting a throttle opening are provided.

Further, on the downstream side of the throttle valve 15, a surge tank 17 is provided.
7, an intake pipe pressure sensor 18 for detecting an intake pipe pressure is provided. The surge tank 17 is provided with an intake manifold 19 for introducing air into each cylinder of the engine 11, and a fuel injection valve 20 for injecting fuel is attached to a branch pipe of each cylinder of the intake manifold 19. ing.

On the other hand, a catalyst 22 such as a three-way catalyst for reducing harmful components (CO, HC, NOx, etc.) in exhaust gas is provided in the exhaust pipe 21 of the engine 11. An air-fuel ratio sensor 23 (air-fuel ratio detecting means) for detecting the air-fuel ratio of the exhaust gas is provided upstream of the catalyst 22. A cooling water temperature sensor 24 (engine temperature detecting means) for detecting a cooling water temperature is provided on a cylinder block of the engine 11.
A crank angle sensor 25 for detecting the engine speed NE is attached.

The outputs of these various sensors are input to an engine control circuit (hereinafter referred to as "ECU") 26. The ECU 26 is mainly configured by a microcomputer, and executes fuel injection control, ignition control, and the like according to the engine operating state detected based on various sensor outputs.

During the operation of the engine, part of the fuel injected from the fuel injection valve 20 is directly drawn into the cylinder.
The remainder adheres to the inner wall surface of the intake port 27 and the surface of the intake valve 28 and then gradually evaporates and is sucked into the cylinder. Accordingly, the amount of fuel (combustion amount) actually sucked into the cylinder changes depending on the fuel injection rate and the wet fuel evaporation rate on the inner wall surface of the intake port 27, but the fuel injection rate and the wet fuel evaporation rate. Since the rate changes depending on the fuel properties, the amount of fuel (combustion amount) actually sucked into the cylinder changes depending on the fuel properties.

Therefore, the ECU 26 determines the fuel property based on the following principle and corrects the injection amount according to the fuel property. For example, when the engine temperature is low immediately after the start of the engine, as the fuel property becomes heavier, the volatility of the fuel decreases, the rate of fuel adhesion to the inner wall surface of the intake port 27 increases, and the wet fuel evaporation rate increases. Rate will drop,
The ratio of the combustion amount to the fuel injection amount decreases [FIG.
(B)]. Therefore, the ratio of the combustion amount to the fuel injection amount changes according to the fuel property, and the ratio of the combustion amount to the fuel injection quantity is a parameter for evaluating the fuel property.

Utilizing this relationship, the ECU 26 executes the processing shown in FIG.
The fuel property parameter is calculated from the ratio of the combustion amount to the fuel injection amount by the fuel property determination program, and the injection quantity is corrected based on the fuel property parameter. Less than,
The processing content of the fuel property determination program of FIG. 2 will be described.

The fuel property determination program shown in FIG. 2 is started for each injection, and first, in steps 101 to 103, it is determined whether fuel property determination execution conditions are satisfied. The fuel property determination execution conditions are as follows. The intake air temperature is lower than the restart determination value (Step 10
1) Cooling water temperature is within a predetermined temperature range, that is, Tlow <cooling water temperature <Thigh (Step 102) Idle operation (Step 103)

In this case, (steps 101 and 10)
By 2), it is determined whether or not warm-up is restarted, or whether or not the engine temperature is within a predetermined temperature range. When restarting the warm-up or when the engine temperature is high, the intake port 27
Since the temperature of the inner wall surface and the like is high and the amount of fuel attached to the inner wall surface and the like (wet amount) is small, the change in the amount of combustion due to the difference in fuel properties is reduced, and the accuracy of fuel property determination is reduced. Therefore, when restarting the warm-up or when the engine temperature is high, the fuel property determination is prohibited. When the cooling water temperature is lower than the lower limit temperature Tlow (for example, −10 ° C.), the temperature is too low and the engine operating state is unstable, so that the calculation accuracy of the fuel property parameter decreases. Therefore, even when the cooling water temperature is lower than the lower limit temperature Tlow, the fuel property determination is prohibited.

When the operating state of the engine changes, the accuracy of the calculation of the amount of combustion decreases due to a delay in the behavior of the injected fuel. Therefore, the idling operation in which the engine operation state does not change is set as the fuel property determination execution condition (step 103). If there is a condition that does not satisfy any one of the conditions described above, the fuel property determination execution condition is not satisfied, and the present program ends without performing the subsequent processing.

On the other hand, if all of the conditions (1) to (4) are satisfied, the fuel property determination execution condition is satisfied, and the routine proceeds to step 104, where the fuel injection amount of the fuel injection valve 20 is read. The fuel injection amount is calculated by an injection amount calculation program (not shown) according to the engine operating state. This function plays a role as an injection amount parameter calculation means referred to in the claims.

In the next step 105, the intake air amount detected by the air flow meter 14 is read, and in the following step 106, the excess air ratio λ of the exhaust gas detected by the air-fuel ratio sensor 23 is read. Thereafter, step 107
, The combustion amount of the fuel, the intake air amount, the stoichiometric air-fuel ratio (14.
6) Using the excess air ratio λ of the exhaust gas, it is calculated by the following equation. Combustion amount = intake air amount / (14.6 × λ) Using the above equation, the combustion amount is determined by dividing the intake air amount by the air-fuel ratio of exhaust gas (14.6 × λ).

Thereafter, in step 108, in order to cancel the error of the system, the fuel injection amount is corrected by the following equation using a learning value calculated by a learning value calculation program shown in FIG. Injection amount = Injection amount x Learning value

Thereafter, in step 109, the intake pipe pressure detected by the intake pipe pressure sensor 18 is read, and in the next step 110, the combustion amount of fuel is corrected according to the following equation according to the intake pipe pressure. Combustion amount = Combustion amount x {1 + coefficient x (intake pipe pressure / reference pressure -1)}

In the above equation, the coefficient is a suitable value obtained through experiments and simulations, and the reference pressure is the reference intake pipe pressure during idling operation. Using the above equation, the combustion amount is calculated by correcting the change in the wet amount (combustion amount) due to the change in the intake pipe pressure. Since the wet amount also changes depending on the intake air amount, the rotation speed of the internal combustion engine, the cooling water temperature, and the like,
The combustion amount may be corrected according to the intake air amount, the engine speed, the cooling water temperature, or the like.

After the correction of the combustion amount, the process proceeds to step 111,
A fuel property parameter for evaluating the fuel property is obtained from the ratio of the integrated value of the combustion amount to the integrated value of the injection amount within a predetermined period. Fuel property parameter = combustion amount integration value / injection amount integration value Here, the combustion amount integration value and the injection amount integration value use, for example, an integration value from a predetermined number of calculations before the present to the present,
Alternatively, an integrated value from a predetermined time before the present to the present may be used.

After calculating the fuel property parameters, step 1
Proceeding to step 12 according to the fuel property parameters
The injection amount read in step 04 is corrected. The ECU 26 outputs an injection pulse corresponding to the corrected injection amount to the fuel injection valve 20, and executes the fuel injection with the corrected injection amount.

The processing in step 101 plays a role corresponding to the restart determination means and the fuel property determination prohibition means.
Further, the processing of step 107 corresponds to a combustion amount parameter calculating means, the processing of step 108 corresponds to a learning correction means, and the processing of step 110 corresponds to an operating state correction means. Further, the processing of step 111 plays a role corresponding to the fuel property determining means.

By the way, as shown in FIG. 4 (b), when the engine temperature rises to a certain extent after starting, in either case of heavy fuel or light fuel, the fuel injected to the inner wall surface of the intake port 27 and the like is increased. The amount of adhesion (the amount of wet generation) and the amount of wet evaporation are balanced, so that the amount of fuel injection and the amount of combustion become substantially equal (the amount of combustion / the amount of injection becomes approximately 1). Therefore, if there is a difference between the fuel injection amount and the combustion amount when the temperature rises to such a temperature, it is considered that the difference is due to an error of the system.

Then, the ECU 26 executes the learning value calculation program shown in FIG. 3 to learn the relationship between the combustion amount and the injection amount when the engine temperature is equal to or higher than the predetermined temperature.
A learning value for correcting a system error is calculated. FIG.
The learning value calculation program is started for each injection and plays a role as a learning means referred to in the claims. When this program is started, first, steps 201 and 202
Then, it is determined whether or not the following condition is satisfied as a learning value calculation condition. The cooling water temperature is equal to or higher than a predetermined temperature TZ (step 2).
01) During idle operation (step 202)

Here, the predetermined temperature TZ is a temperature at which the fuel injection amount and the combustion amount become substantially equal. After starting,
Since the fuel injection amount and the combustion amount become substantially equal before the warm-up is completed, the predetermined temperature TZ may be set to a temperature lower than the warm-up completion temperature. The reason why the learning value is calculated during the idling operation is to calculate the fuel property parameter during the idling operation. Any one of the above conditions
If at least one condition is not satisfied, the learning value calculation condition is not satisfied, and the program ends without performing the subsequent processing.

On the other hand, if all of the conditions are satisfied, the learning value calculation condition is satisfied, and the routine proceeds to step 203, where the fuel injection amount of the fuel injection valve 20 is read. After this, step 2
In step 04, the intake air amount is read, and the next step 205
Then, the excess air ratio λ of the exhaust gas is read. Thereafter, in step 206, the combustion amount of the fuel is calculated by the following equation using the intake air amount, the stoichiometric air-fuel ratio (14.6), and the excess air ratio λ of the exhaust gas. Combustion amount = intake air amount / (14.6 × λ)

Thereafter, at step 207, a learning value is obtained from the ratio of the integrated value of the combustion amount to the integrated value of the injection amount within a predetermined period. Learning value = integrated combustion amount / integrated injection amount Here, the integrated combustion amount and the integrated injection amount are, for example, an integrated value from a predetermined number of calculations before the present to the present,
Alternatively, an integrated value from a predetermined time before the present to the present may be used.

In the embodiment (1) described above, focusing on the fact that the ratio of the combustion amount to the fuel injection amount changes according to the fuel property, the ratio of the combustion amount to the fuel injection amount is expressed by Since the parameter is calculated as the fuel property parameter to be evaluated, the fuel property can be determined with high accuracy without using a fuel property sensor. As a result, the accuracy of correction of the fuel injection amount based on the fuel property can be improved, the air-fuel ratio control independent of the fuel property can be realized, the emission can be reduced, and the drivability and fuel efficiency can be improved.

Moreover, the fuel is calculated by using the intake air amount and the air-fuel ratio (excess air ratio) of the exhaust gas which can be detected by sensors (the air flow meter 14 and the air-fuel ratio sensor 23) generally provided for the air-fuel ratio control. Since the amount of combustion is calculated, it is not necessary to newly provide a sensor for detecting the amount of combustion, and it is possible to satisfy the demand for reduction in the number of parts and cost.

Further, in the present embodiment (1), the fuel property parameter is calculated from the ratio of the integrated value of the combustion amount to the integrated value of the injection amount within a predetermined period. Can be reduced, and the accuracy of fuel property determination can be improved. According to the test results of the inventor, the injection amount in a predetermined period (for example, 100 data) shown in FIG. 5B is compared with the behavior of the ratio of the combustion amount to the injection amount shown in FIG. It was confirmed that the behavior of the ratio of the combustion amount integrated value to the integrated value was extremely small with the influence of noise and the fluctuation of the engine operating state, and the heavy fuel and the light fuel could be clearly distinguished. However, in an area where the influence of noise or the fluctuation of the engine operating state does not matter much, the fuel property may be determined from the relationship between the injection amount and the combustion amount without using the integrated value. Alternatively, instead of the integrated value of the injection amount and the combustion amount, an average value and a smoothed value for a predetermined period may be used.

In this embodiment (1), attention is paid to the fact that the wet amount (combustion amount) changes with the intake pipe pressure, and the fuel combustion quantity is corrected in accordance with the intake pipe pressure. It is possible to perform stable fuel property determination independent of the intake pipe pressure.

Since the wet amount changes depending on the intake air amount, the engine speed, the cooling water temperature and the like in addition to the intake pipe pressure, the combustion amount is corrected based on the intake air amount, the engine speed, the cooling water temperature and the like. You may do it. Further, the injection amount may be corrected according to the engine operating state such as the intake pipe pressure, or the fuel property parameter (the relationship between the injection amount and the combustion amount) may be corrected, or the fuel property parameter calculation formula ( The fuel property determination standard) may be corrected.

In this embodiment (1), focusing on the fact that a system error can be learned from the relationship between the combustion amount and the injection amount when the engine temperature is equal to or higher than the predetermined temperature, Since the fuel injection amount is corrected using the learning value learned in step (1), highly accurate fuel property determination that excludes system errors can be performed.

Incidentally, the combustion amount may be corrected using the learning value, or the fuel property parameter (the relationship between the injection amount and the combustion amount) may be corrected or the fuel property parameter calculation formula (fuel property determination May be corrected.

[Embodiment (2)] In the embodiment (2) of the present invention, a learning value for correcting a system error is calculated by the learning value calculation program of FIG.

In the learning value calculation program of FIG. 3 of the embodiment (1), one of the learning value calculation conditions is that the cooling water temperature is equal to or higher than the predetermined temperature TZ (step 201). In 2), the learning value calculation program of FIG. 6 takes into account that the engine temperature becomes equal to or higher than a predetermined temperature TZ at which a fuel injection amount and a combustion amount become substantially equal after a predetermined period has elapsed from the start. It is one of the learning value calculation conditions that a predetermined time T has elapsed after the start (step 201a). The predetermined time T is a time required for the engine temperature to become equal to or higher than the predetermined temperature TZ. In this case, the predetermined time T may be a fixed value, or may be changed according to the engine temperature (cooling water temperature) at the time of starting. The process of calculating the learning value in step 202 and thereafter is the same as the above-described learning value calculation program in FIG.

In the embodiment (2) described above, similarly to the embodiment (1), it is possible to calculate a learning value for canceling a system error, cancel the system error, and accurately determine the fuel property. can do.

[Embodiment (3)] By the way, the heavier the fuel property, the greater the wet amount, and the excess fuel ratio (exhaust gas) with respect to the excess fuel ratio (the reciprocal of the excess air ratio of the supply air-fuel mixture). The ratio of the excess fuel ratio to the excess fuel ratio varies depending on the fuel properties. Therefore, the ratio of the excess combustion fuel ratio to the excess supply fuel ratio is a parameter for evaluating fuel properties.

Therefore, in the embodiment (3) of the present invention, the fuel property parameter is calculated from the ratio of the excess combustion fuel rate to the excess fuel supply rate by the fuel property determination program of FIG. 7, and the injection amount is determined by the fuel property parameter. to correct. The embodiment (3) is applied to a system for controlling the air-fuel ratio by calculating the excess fuel ratio from the output signal of the air-fuel ratio sensor 23.

In the fuel property determination program of FIG. 7, first, as in the first embodiment, steps 301 to 301 are executed.
At 303, it is determined whether or not the fuel property determination execution condition is satisfied. If the fuel property determination execution condition is satisfied, the process proceeds to step 204, where the fuel injection amount of the fuel injection valve 20 is read, and the next In step 205, the intake air amount is read.

Thereafter, in step 306, the excess fuel supply ratio is calculated by the following equation using the injection amount, the stoichiometric air-fuel ratio (14.6), and the intake air amount. Excess fuel supply rate = injection quantity x 14.6 / intake air quantity

After that, in step 307, the excess fuel combustion ratio 1 / λ of the exhaust gas detected by the air-fuel ratio sensor 23 is read, and in the next step 308, the fuel property parameter for evaluating the fuel property is set to a value within a predetermined period. It is determined from the ratio of the integrated value of the excess fuel ratio 1 / λ to the integrated value of the excess fuel ratio. Fuel property parameter = combusted fuel excess rate integrated value / supplied fuel excess rate integrated value After calculating the fuel property parameter, in step 309, the injection amount (injection pulse) read in step 304 is corrected according to the fuel property parameter.

In the embodiment (3) described above, the excess fuel ratio 1 / the excess fuel ratio relative to the excess fuel ratio is determined according to the fuel property.
Paying attention to the point where the ratio of λ changes, the ratio of the excess fuel ratio 1 / λ to the excess supply fuel ratio is calculated as a fuel property parameter for evaluating the fuel property, so a fuel property sensor is used. Without this, it is possible to accurately determine the fuel properties. Moreover, the air-fuel ratio sensor 23
Since the present invention is applied to a system for calculating the excess fuel ratio 1 / λ from the output signal of the above, the process for obtaining the excess fuel ratio 1 / λ is extremely simplified, and the calculation process of the fuel property determination program can be simplified.

In this embodiment (3), the excess fuel supply ratio and the combustion fuel ratio are also determined by using the intake pipe pressure or other operating state parameters (intake air amount, engine speed, cooling water temperature, etc.) and learning values. One of the excess ratios may be corrected, or
The fuel property parameter (the relationship between the injection amount and the combustion amount) may be corrected, or the calculation formula of the fuel property parameter (fuel property determination standard) may be corrected.

In each of the embodiments described above, the integrated value of the injection amount parameter (injection amount, excess supply fuel ratio) and the integrated value of the combustion amount parameter (combustion amount, excess combustion fuel ratio) within a predetermined period are compared. However, since the difference between the injection amount parameter and the combustion amount parameter is a parameter for evaluating the wet amount adhering to the inner wall surface or the like of the intake port 27, the injection amount parameter within a predetermined period is determined. The fuel property may be determined by comparing the integrated value of the difference between the fuel and the combustion amount parameter (wet amount parameter) with the integrated value of the injection amount parameter. Even in this case, the fuel property is determined with high accuracy. Can be.

Further, in each of the above embodiments, the fuel property determination processing is performed during the idling operation. However, the fuel property determination processing may be performed during the steady operation in which the engine operation state is stable. good. In addition, when the transient operation state occurs during the integration of the injection amount parameter and the combustion amount parameter, the integrated value is reset.
When returning to the steady operation state, the integration process may be restarted. Alternatively, it may be determined whether or not it is immediately after refueling, the fuel property may be determined only immediately after refueling, and the determination result may be maintained until the next refueling.

In addition, according to the present invention, the calculation formula of the fuel property parameter may be changed, or the fuel property parameter may be obtained from the map.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an entire engine control system showing an embodiment (1) of the present invention.

FIG. 2 is a flowchart showing a flow of processing of a fuel property determination program according to the embodiment (1).

FIG. 3 is a flowchart showing a flow of processing of a learning value calculation program according to the embodiment (1).

FIG. 4 is a time chart showing behaviors of an injection amount, an injection amount / combustion amount, an air-fuel ratio, an engine speed, and an intake pipe pressure immediately after engine start when using heavy fuel and light fuel.

FIG. 5A is a time chart showing a behavior of a ratio of a combustion amount to an injection amount, and FIG. 5B is a time chart showing a behavior of a ratio of a combustion amount integrated value to an injection amount integrated value in a predetermined period.

FIG. 6 is a flowchart showing the flow of processing of a learning value calculation program according to the embodiment (2) of the present invention;

FIG. 7 is a flowchart showing a processing flow of a fuel property determination program according to the embodiment (3) of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 14 ... Air flow meter 14 (intake air amount detection means), 18 ... Intake pipe pressure sensor, 19 ... Intake manifold, 20 ... Fuel injection valve, 21 ... Exhaust pipe, 22 ..., 23 ... air-fuel ratio sensor (air-fuel ratio detecting means), 24 ... cooling water temperature sensor (engine temperature detecting means), 26 ... ECU (injection amount parameter calculating means, combustion amount parameter calculating means, fuel property determining means, operating state correction) Means, restart determination means, fuel property determination prohibition means, learning means, learning correction means), 27 ... intake port, 2
8 ... intake valve.

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) F02D 45/00 340 F02D 45/00 340D 366 366 368 368F 41/04 330 41/04 330P 41/06 380 41/06 380B 41/18 41/18 D G01M 15/00 G01M 15/00 Z F term (reference) 2G087 AA19 BB21 BB25 CC13 CC21 CC23 CC28 CC29 FF21 3G084 BA13 CA01 DA04 DA13 DA20 DA27 EB12 EB20 EC04 FA02 FA07 FA11 FA13 FA14 FA20 FA29 3G301 HA01 JA09 JA20 KA04 MA11 ND03 ND04 ND25 PA01Z PA07Z PA10Z PB02Z PB03Z PD02Z PE08Z

Claims (11)

[Claims] 1. A fuel property determination device for determining the property of fuel supplied to an internal combustion engine, comprising: an injection amount of fuel injected from a fuel injection valve or a parameter having a correlation with the injection amount (hereinafter referred to as an “injection amount parameter”). Means for calculating an injection amount parameter for determining the amount of fuel to be burned in a cylinder or a parameter having a correlation with the amount of combustion (hereinafter, referred to as a "burning amount parameter")
A combustion property parameter calculating means, and a fuel property determining means for determining a fuel property based on a relationship between the injection quantity parameter obtained by the injection quantity parameter calculating means and the combustion quantity parameter obtained by the combustion quantity parameter calculating means. A fuel property determining device for an internal combustion engine, comprising: 2. An intake air amount detecting means for detecting an intake air amount of the internal combustion engine, and an air-fuel ratio detecting means for detecting an air-fuel ratio of exhaust gas, wherein the combustion amount parameter calculating means comprises: The fuel property determination device for an internal combustion engine according to claim 1, wherein the combustion amount is calculated by using the exhaust gas and the air-fuel ratio of the exhaust gas. 3. An injection amount parameter calculating unit obtains, as an injection amount parameter, an excess fuel ratio, which is a reciprocal of an excess air ratio of the air-fuel mixture supplied to the internal combustion engine, The fuel property judging device for an internal combustion engine according to claim 1, wherein a combustion excess fuel ratio, which is a reciprocal of the excess air ratio, is obtained as a combustion amount parameter. 4. The fuel property determination means according to claim 1, wherein the fuel property is determined by comparing an integrated value of the combustion amount parameter and an integrated value of the injection amount parameter within a predetermined period. 3. The fuel property determination device for an internal combustion engine according to any one of 3. 5. The fuel property determining means determines a fuel property by comparing an integrated value of a difference between the injection amount parameter and the combustion amount parameter within a predetermined period with an integrated value of the injection amount parameter. The fuel property determination device for an internal combustion engine according to any one of claims 1 to 3, wherein: 6. An operating condition correcting means for correcting a relationship between at least one or both of the injection amount parameter and the combustion amount parameter or a fuel property determination criterion according to an operating condition of the internal combustion engine. The fuel property judging device for an internal combustion engine according to claim 1. 7. The system according to claim 1, wherein the operating state correcting means corrects a relationship between at least one of the injection amount parameter and the combustion amount parameter or a fuel property determination criterion according to an intake pipe pressure. 7. The fuel property determination device for an internal combustion engine according to 6. 8. The system according to claim 1, wherein the operating state correcting means corrects a relationship between at least one of the injection amount parameter and the combustion amount parameter or both or a fuel property determination criterion according to an engine speed. 8. The fuel property determination device for an internal combustion engine according to 6 or 7. 9. A restart determining means for determining whether or not the internal combustion engine has been restarted in a warm-up state (hereinafter referred to as “warm-up restart”), and the restart determining means determines that warm-up has been restarted. 9. A fuel property determination for an internal combustion engine according to claim 1, further comprising fuel property determination prohibition means for prohibiting the fuel property determination by said fuel property determination means when the determination is made. apparatus. 10. An engine temperature detecting means for detecting a temperature of the internal combustion engine, and a relationship between the injection quantity parameter and the combustion quantity parameter when the temperature of the internal combustion engine detected by the engine temperature detecting means is equal to or higher than a predetermined temperature. Learning means for learning, and learning correction means for correcting the relationship between at least one of the injection amount parameter and the combustion amount parameter or a fuel property determination criterion using a learning value learned by the learning unit. The fuel property judging device for an internal combustion engine according to any one of claims 1 to 9, wherein: 11. A learning means for learning a relationship between the injection amount parameter and the combustion amount parameter after a predetermined period has elapsed from the start of the internal combustion engine; and at least one or both of the injection amount parameter and the combustion amount parameter. 10. A fuel property determination for an internal combustion engine according to claim 1, further comprising: learning correction means for correcting a relationship or a fuel property determination criterion using a learning value learned by the learning means. apparatus.