JP2009162138A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of accurately estimating a purge flow rate which is to be reflected to air/fuel ratio control. <P>SOLUTION: The weight of a canister 31 is measured. The purge flow rate of evaporation fuel during purging of the evaporation fuel is estimated according to increase amount of the obtained weight due to adsorption of the evaporation fuel of the canister 31 and intake pressure generating in an intake system of an engine during purging of the evaporation fuel. Therefore, the purge flow rate is accurately estimated. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine.

  The internal combustion engine is provided with an evaporative fuel processing mechanism in which the evaporative fuel generated in the fuel tank is prevented from being released into the atmosphere, and the evaporative fuel is collected by a canister. In this evaporative fuel processing mechanism, since the amount of evaporative fuel collected by the canister is limited, evaporative fuel is desorbed from the canister during engine operation and introduced into the intake passage through the purge passage and burned in the combustion chamber. A so-called purge process is performed. By performing such a purging process, the evaporative fuel collecting performance of the canister can be recovered.

  In order to adapt the air-fuel ratio control to the internal combustion engine having the evaporated fuel processing mechanism as described above, the fuel by the purge process is added to the original air-fuel mixture supplied to the combustion chamber. It is necessary to perform air-fuel ratio control in consideration of fuel. For example, Patent Document 1 discloses a technique for performing air-fuel ratio control in consideration of fuel by purge.

Japanese Patent Laid-Open No. 10-281022

By the way, the purge flow rate and the purge concentration are estimated, for example, by repeating addition and subtraction according to the behavior of the air-fuel ratio during the purge process, and reflected in the air-fuel ratio control.
However, if the accuracy of the estimated values of the purge flow rate and the purge concentration is low, an unintended air-fuel ratio disorder may occur during the purge process. Further, when the purge concentration is high, it takes a certain time until the calculated estimated value converges. Therefore, the purge flow rate cannot be increased until the estimated value is reached.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a control device for an internal combustion engine that can accurately estimate a purge flow rate to be reflected in air-fuel ratio control.

  An internal combustion engine control apparatus according to the present invention includes a canister for recovering evaporated fuel generated in a fuel tank, evaporation purge means for purging the evaporated fuel recovered in the canister to an intake system of the internal combustion engine, and supplying the internal combustion engine to the internal combustion engine An air-fuel ratio sensor for detecting the air-fuel ratio of the mixture of fuel and air to be measured, and the purge flow rate of the evaporated fuel by the evaporation purge means so that the air-fuel ratio detected by the air-fuel ratio sensor becomes the target air-fuel ratio. The air-fuel ratio control means for adjusting the fuel injection amount from the injector to the intake system of the internal combustion engine, the purge flow rate estimation means for estimating the purge flow rate considered by the air-fuel ratio control means, and the weight for measuring the weight of the canister And the purge flow rate estimating means is configured to increase the weight due to the adsorption of evaporated fuel in the canister obtained by the weight measuring means. And the evaporation purge according to the intake air pressure generated in the intake system of the internal combustion engine at the time of purging of fuel vapor by means estimates the purge flow of fuel vapor during the purge of the evaporative fuel, it is characterized.

  In the above configuration, the weight measuring unit measures the initial weight while the internal combustion engine is stopped, and the purge flow rate estimating unit estimates the purge flow rate using the initial state weight at the start of the purge, and performs the purge. Thereafter, a configuration using an estimated value obtained by subtracting the weight according to the discharged purge flow rate can be employed.

  In the above configuration, it is possible to employ a configuration having correction means for correcting the purge flow rate estimated by the purge flow rate estimation unit according to at least one of the intake air temperature and the fuel component.

  In the above configuration, the purge flow rate estimating means may employ a configuration in which a purge concentration is calculated from an increase in weight of the canister, and a purge flow rate is calculated from the purge concentration and the purge air amount.

  ADVANTAGE OF THE INVENTION According to this invention, the control apparatus of the internal combustion engine which can estimate the purge flow volume for reflecting in air-fuel ratio control with a sufficient precision is obtained.

Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic configuration diagram of an internal combustion engine to which the control device for an internal combustion engine according to the present embodiment is applied.

  As shown in FIG. 1, an internal combustion engine 10 includes a fuel injection valve 12 that injects fuel into a combustion chamber 11 through a fuel supply path connected to a fuel tank 21, and the injected fuel and intake air. And an ignition plug 13 for igniting an air-fuel mixture as a mixture. An intake passage 14 and an exhaust passage 15 are connected to the combustion chamber 11. A surge tank 16 is provided in the middle of the intake passage 14, and a throttle valve 17 for adjusting the intake air amount is further provided on the upstream side thereof.

  On the other hand, the internal combustion engine 10 is provided with an evaporated fuel processing mechanism 30. The evaporative fuel processing mechanism 30 includes a canister 31 connected to the fuel tank 21 via a vapor passage 32, a purge passage 33 connecting the canister 31 and the downstream side of the throttle valve 17 in the intake passage 14. An air introduction passage 34 for introducing air into the canister 31 and a purge valve 35 for opening and closing the purge passage 33 are provided. Further, the canister 31 is provided with a weight sensor 60 for measuring the weight of the canister 31, and a detection signal of the weight sensor 60 is input to an electronic control device 40 described later.

  Evaporated fuel (hereinafter referred to as vapor) generated in the fuel tank 21 is introduced from the fuel tank 21 through the vapor passage 32 into the canister 31 and is once adsorbed by an adsorbent provided therein. Then, the purge valve 35 is opened and the atmosphere is introduced into the canister 31 through the atmosphere introduction passage 34, whereby the vapor adsorbed in the canister 31 is introduced into the surge tank 16 through the purge passage 33. The fuel contained in the vapor is burned in the combustion chamber 11 together with the fuel injected from the fuel injection valve 12. Further, the fuel amount of the vapor purged into the intake passage 14 in this way is adjusted based on the opening degree of the purge valve 35. The purge valve 35 is an electromagnetic valve whose opening degree is adjusted based on an electrical signal, and the opening degree is controlled by receiving a duty signal.

  Such purge control for the internal combustion engine 10 and air-fuel ratio control for correcting the fuel injection amount of the fuel injection valve 12 are performed by the electronic control unit 40. The electronic control unit 40 includes a central processing unit 41 (CPU), a read only memory (ROM), a random access memory (RAM), a backup RAM, an external input circuit, an external output circuit, and the like. In order to execute the various controls as described above, various sensors for detecting the operating state of the internal combustion engine 10 are connected, and detection signals from these sensors are appropriately taken into the electronic control unit 40.

  The electronic control unit 40 is provided in the exhaust passage 15 and detects an air-fuel ratio sensor 52 for detecting the oxygen concentration in the exhaust gas (air-fuel ratio of the air-fuel mixture), and the pressure in the intake passage 14, that is, the intake pressure PM. Detection signals of the intake pressure sensor 51 are respectively input. A purge air amount at the time of a purge process described later can be calculated based on the intake pressure PM or the like. Further, the rotation angle of the crankshaft is detected, and the detection signal of the crank angle sensor 53 for detecting the engine rotational speed NE and the position of the crankshaft based on the detection signal and the detection signal of the throttle sensor 54 for detecting the opening degree of the throttle valve 17. Are also input to the electronic control unit 40, respectively.

  Each control such as purge control and air-fuel ratio control is executed by the electronic control unit 40 based on the operating state of the internal combustion engine 10 and the running state of the vehicle detected by the sensors 51 to 54 and the like. The vapor purged into the intake air affects the air-fuel ratio of the air-fuel mixture in the internal combustion engine 10. For example, when vapor fuel is introduced into the intake passage 14, the air-fuel ratio shifts to the rich side. Therefore, the electronic control unit 40 estimates the purge flow rate of the vapor introduced into the intake passage 14 based on the concentration of the purged vapor, the purge air amount passing through the purge valve 35, and the like, and the fuel injection is performed in accordance with the purge flow rate. By correcting the amount of fuel injected from the valve 12 to increase or decrease, the air-fuel ratio is maintained at the target air-fuel ratio.

Next, an example of the purge process by the electronic control unit 40 will be described with reference to the flowchart shown in FIG.
First, it is determined whether the engine is in operation (step S1). If the engine is not in operation, that is, when the engine is stopped, the weight of the canister 31 is measured from the detection signal of the weight sensor 60 (step S2). This is calculated as a reference increment for the canister 31 (step S3). That is, the weight of the canister 31 in the initial state is measured while the engine is stopped, and the difference between the measured weight and the weight of the known canister 31 in a state where the fuel is not adsorbed is set as a reference increment.

  In step S1, if the engine is operating, it is determined whether there is a purge processing start request (step S2). The purge process is periodically requested during engine operation, for example.

  When there is a purge processing start request, the purge concentration is calculated. The purge concentration is the concentration of the evaporated fuel in the canister 31. For example, as shown in FIG. 3, the purge concentration is calculated from a map or the like representing the relationship between the weight increase of the canister 31 and the purge concentration measured in advance by experiments or the like. At the start of purging, the purge concentration is calculated using the reference increment in the initial state calculated in step S3. After purging, the purge concentration is calculated according to the weight increase of the canister 31 obtained in step S10 described later.

  Next, the intake pressure of the intake system is acquired (step S6). The flow rate of the air that passes through the purge valve 35 and is supplied to the surge tank 16 side is substantially determined according to the magnitude of the intake pressure of the intake system (obtained from the intake pressure sensor 51).

  Next, the reference purge flow rate is determined from the purge concentration calculated in step S5 and the intake pressure acquired in step S6 (step S7). The reference purge flow rate is a flow rate of evaporated fuel determined by the flow rate of air supplied to the surge tank 16 through the purge valve 35 and the purge concentration, and is determined using, for example, a map as shown in FIG. Can do.

  Next, the calculated reference purge flow rate is corrected using conditions that affect the flow rate (supply amount) of the evaporated fuel to the intake system, such as the intake air temperature (atmospheric temperature) and the fuel component (alcohol concentration) (step S8). This is to improve the estimation accuracy of the reference purge flow rate estimated in step S7. The estimated purge flow rate is used in the above-described air-fuel ratio control and is reflected in the engine control.

  Next, the weight of the evaporated fuel corresponding to the purge flow rate calculated in step S8 is calculated as a canister reduction correction amount (step S9).

  Next, the weight increase of the canister 31 is updated using the canister reduction correction amount calculated in step S9. That is, the weight increase of the canister 31 after the purge process is performed is obtained by subtracting the weight (canister decrease correction amount) to be decreased by the current purge process from the weight increase of the canister 31 at the previous purge process. .

  Next, a purge process is executed (step S11). That is, the purge valve 35 is opened at a predetermined opening so that the estimated purge flow rate of evaporated fuel is supplied to the intake system. As a result, the difference between the estimated purge flow rate used for air-fuel ratio control and the purge flow rate actually supplied to the intake system can be reduced, so that the occurrence of air-fuel ratio disturbance can be suppressed.

  In the present embodiment, the estimation accuracy of the purge flow rate can be improved by estimating the purge flow rate using the weight change of the canister 31 and the intake pressure. In addition, since it is difficult to accurately measure the weight of the canister 31 during operation of the engine due to noise or the like, the weight of the canister 31 is measured only when the engine is stopped, and the weight of the canister 31 according to the purge flow rate during engine operation. Calculate the increment. Thereby, the calculation accuracy of the increase in the canister weight is increased, and the estimation accuracy of the purge flow rate can be further improved.

1 is a schematic configuration diagram of an internal combustion engine to which a control device for an internal combustion engine according to an embodiment of the present invention is applied. It is a flowchart which shows an example of a process of an electronic control apparatus. It is a graph which shows the relationship between the increase in weight of a canister and purge concentration. It is a graph which shows the relationship between the purge density | concentration for every intake pressure, and a purge flow rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine 11 ... Combustion chamber 12 ... Fuel injection valve
DESCRIPTION OF SYMBOLS 13 ... Spark plug 14 ... Intake passage 15 ... Exhaust passage 16 ... Surge tank 17 ... Throttle valve 21 ... Fuel tank 30 ... Evaporative fuel processing mechanism 31 ... Canister 32 ... Paper passage 33 ... Purge passage 34 ... Atmospheric introduction passage 35 ... Purge valve 40 ... Electronic control device 51 ... Intake pressure sensor 52 ... Air-fuel ratio sensor 53 ... Crank angle sensor 54 ... Throttle sensor

Claims (4)

A canister for recovering the evaporated fuel generated in the fuel tank;
An evaporation purge means for purging the evaporated fuel collected in the canister to the intake system of the internal combustion engine;
An air-fuel ratio sensor for detecting an air-fuel ratio of a mixture of fuel and air supplied to the internal combustion engine;
Air-fuel ratio control for adjusting the fuel injection amount from the injector to the intake system of the internal combustion engine in consideration of the purge flow rate of the evaporated fuel by the evaporation purge means so that the air-fuel ratio detected by the air-fuel ratio sensor becomes the target air-fuel ratio Means,
A purge flow rate estimating means for estimating a purge flow rate considered by the air-fuel ratio control means;
Weight measuring means for measuring the weight of the canister,
The purge flow rate estimating means is responsive to the increase in weight due to the adsorption of evaporated fuel by the canister obtained by the weight measuring means and the intake pressure generated in the intake system of the internal combustion engine when the evaporated fuel is purged by the evaporation purge means. , Estimate the purge flow rate of the evaporated fuel when purging the evaporated fuel,
A control device for an internal combustion engine. The weight measuring means measures an initial weight while the internal combustion engine is stopped,
The purge flow rate estimating means estimates the purge flow rate using the initial weight at the start of the purge, and uses an estimated value obtained by subtracting the weight according to the purged purge flow rate after performing the purge.
The control apparatus for an internal combustion engine according to claim 1.   3. The control device for an internal combustion engine according to claim 1, further comprising a correction unit that corrects the purge flow rate estimated by the purge flow rate estimation unit in accordance with at least one of an intake air temperature and a fuel component.   2. The control apparatus for an internal combustion engine according to claim 1, wherein the purge flow rate estimating means calculates a purge concentration from an increase in weight of the canister, and calculates a purge flow rate from the purge concentration and the intake pressure.

Images