JPH05321711A - Evaporation fuel control device of internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent turbulence of the air fuel ratio of an internal combustion engine when purge is carried out. CONSTITUTION:In the evaporation fuel control device of an internal combustion engine, an oxygen concentration sensor 46 is provided between a canister 37 and a control valve 40 to detect concentration of oxygen in evaporation fuel. The fuel component density in evaporation fuel is calculated from concentration of oxygen detected by the sensor 46. On the other hand, an evaporation fuel flow amount is calculated from intake negative pressure of the internal combustion engine and the opening degree of the control valve. The fuel component weight in evaporation fuel supplied into a surge tank 35 is calculated from the fuel component density and the evaporation fuel flow amount. The injection amount of the fuel injection valve 4 of the internal combustion engine is corrected in reducing direction for the fuel component weight. It is thus possible to prevent turbulence of the air fuel ratio of an internal combustion engine when purge is carried out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporated fuel control device for an internal combustion engine, and more particularly to a device for calculating a fuel component weight in evaporated fuel by an oxygen concentration sensor or the like so that the air-fuel ratio of the internal combustion engine during purging is not disturbed.

[0002]

2. Description of the Related Art Conventionally, vaporized fuel generated in a fuel tank is temporarily stored in a canister, and when the internal combustion engine is operating,
There is known an evaporated fuel control device that performs so-called purging, in which an intake negative pressure is appropriately supplied from a canister to an intake system of an internal combustion engine. With this device, the evaporated fuel in the fuel tank is burned and prevented from being released into the atmosphere. Here, in order to prevent the air-fuel ratio of the internal combustion engine from fluctuating when the evaporated fuel is purged, JP-A-62-23346.
No. 6 publication is disclosed.

According to this publication, the evaporated fuel is first purged in a small amount, and the air-fuel ratio which changes depending on the evaporated fuel supplied to the intake system is detected by an air-fuel ratio sensor provided in the exhaust system. Then, this value is fed back to the air-fuel ratio control means that adjusts the intake air amount and the supplied fuel amount of the intake system to obtain the air-fuel ratio deviation due to the purge. At this time,
If the air-fuel ratio deviation is within a predetermined value, a large amount purge is performed, and if the air-fuel ratio deviation exceeds a predetermined value, a purge amount control that prohibits the transition to a large amount purge is performed. This prevents a sudden change in the air-fuel ratio due to the purge.

[0004]

However, in the above publication, the weight of the fuel component in the evaporated fuel to be purged cannot be grasped before it is supplied to the internal combustion engine, so that the total amount of fuel supplied to the internal combustion engine cannot be calculated. I cannot grasp the amount. Therefore, the evaporated fuel added to the intake air causes the overall air-fuel ratio of the intake air to change to some extent. As a result, there is a problem in that it is difficult to purge the evaporated fuel into the intake air while always operating the engine stably in the best condition.

In view of the above problems, the present invention calculates the weight of fuel in the evaporated fuel from the oxygen concentration in the evaporated fuel and reduces the amount of fuel injected from the fuel injection valve by the weight,
An object of the present invention is to provide an evaporated fuel control device for an internal combustion engine that prevents the air-fuel ratio of the internal combustion engine at the time of purging from being disturbed.

[0006]

In order to achieve the above object, the present invention communicates with a fuel tank and supplies the evaporated fuel of the fuel tank to an intake system of an internal combustion engine, as shown in the claim correspondence diagram of FIG. Is provided in the discharge passage 50 between the fuel tank and the opening / closing means 51, and the opening / closing means 51 for opening / closing the discharging passage 50 to adjust the flow rate of evaporated fuel to the intake system. Oxygen concentration detecting means 52 for detecting the oxygen concentration in the evaporated fuel supplied to the intake system
And the evaporated fuel flow rate calculation means 53 for calculating the evaporated fuel flow rate from the opening degree of the opening / closing means 51 and the operating state of the internal combustion engine.
A fuel component density calculating means 54 for calculating the fuel component density in the evaporated fuel from the oxygen concentration detected by the oxygen concentration detecting means 52; the evaporated fuel flow rate calculated by the evaporated fuel flow rate calculating means 52; Fuel component density calculation means 54
The fuel component weight calculation means 55 for calculating the fuel component weight in the evaporated fuel from the fuel component density calculated by the above, and the fuel injection valve of the internal combustion engine by the fuel component weight calculated by the fuel component weight calculation means 55. The control means 56 for reducing and correcting the fuel injection amount injected from the engine is provided, and a technical means called an evaporated fuel control device for an internal combustion engine is adopted.

Further, a canister having an adsorbent for adsorbing the evaporated fuel may be provided in the discharge passage between the fuel tank and the oxygen concentration detecting means. Further, the opening degree of the opening / closing means may be controlled according to whether or not the fuel component density calculated by the fuel component density calculating means is less than a predetermined value.

[0008]

In the evaporated fuel control apparatus for an internal combustion engine according to the present invention, there is provided a discharge passage communicating with the fuel tank for supplying the evaporated fuel from the fuel tank to the intake system of the internal combustion engine, and an opening / closing means for opening and closing the discharge passage. Is equipped with. An oxygen concentration detecting means is provided between the opening / closing means and the fuel tank. The oxygen concentration detecting means detects the oxygen concentration in the evaporated fuel supplied to the intake system of the internal combustion engine.

Then, from the oxygen concentration detected by the oxygen concentration detecting means, the fuel component density in the evaporated fuel from the fuel tank is calculated by the fuel component density calculating means. On the other hand, the flow rate of evaporated fuel supplied to the intake system is calculated by the evaporated fuel flow rate calculation means from the operating state of the internal combustion engine such as the intake pipe internal pressure and the control amount of the opening / closing means. The fuel component weight in the vaporized fuel is calculated by the fuel component weight calculating means from the fuel component density and the vaporized fuel flow rate. Then, by the control means, the fuel injection amount injected from the fuel injection valve of the internal combustion engine is reduced and corrected by this fuel component weight.

Therefore, the air-fuel ratio of the internal combustion engine is optimally controlled, and the air-fuel ratio of the internal combustion engine at the time of purging is prevented from being disturbed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of an evaporated fuel control system for an internal combustion engine to which the present invention is applied will be described. FIG. 1 is an overall configuration diagram of an evaporated fuel control device of this embodiment.

As shown in FIG. 1, an intake pipe 2 and an exhaust pipe 3 are connected to each cylinder of a multi-cylinder engine 1 of an internal combustion engine. An electromagnetic fuel injection valve 4 is provided in each intake pipe 2 which is the intake system of the internal combustion engine.
Each of these intake pipes 2 is assembled in a surge tank 35. Then, a passage for introducing intake air into the surge tank 35 is formed, and a throttle valve 5 for adjusting the amount of intake air taken into the engine 1 is provided in this passage. On the other hand, the exhaust pipes 3, which are the exhaust system of the internal combustion engine provided for each cylinder, gather in one passage. A 0 ₂ sensor 6 as an air-fuel ratio detecting means is provided in this passage. The 0 ₂ sensor 6 outputs a voltage signal corresponding to the oxygen concentration in the exhaust gas.

The fuel supply system for supplying fuel to the fuel injection valve 4 has a fuel tank 7, a fuel pump 8, a fuel filter 9 and a pressure regulating valve 10. Then, the fuel (gasoline) in the fuel tank 7 is transferred to the fuel filter 9 by the fuel pump 8.
The fuel is pressure-fed to each fuel injection valve 4 via and the fuel supplied to each fuel injection valve 4 is adjusted to a predetermined pressure by the pressure regulating valve 10.

The discharge passage 3 extending from the upper portion of the fuel tank 7.
6 is a canister 37 containing activated carbon as an adsorbent.
It is connected to the surge tank 35 via. The canister 37 is provided with an atmosphere opening hole 38 for introducing outside air. Further, in the discharge passage 36 from the canister 37 to the surge tank 35 side, a purge solenoid valve (hereinafter referred to as a purge valve) 40 as an opening / closing means is provided. The purge valve 40 includes a spring (not shown), a valve body 41, a seat portion 42, a coil 43 and the like. The valve body 41 is always biased by a spring (not shown) in a direction in which the valve body 41 comes into contact with the seat portion 42. In addition, the valve body 41
Exciting the coil 43 separates it from the seat portion 42 against the biasing force of the spring. As a result, the discharge passage 36 is opened by exciting the coil 43 of the purge valve 40, and the discharge passage 36 is closed by demagnetizing the coil 43. The opening degree of the purge valve 40 is controlled by duty control based on pulse width modulation.

An oxygen concentration sensor 46 is provided in the discharge passage 36 extending from the canister 37 to the purge valve 40. The oxygen concentration sensor 46 detects the oxygen concentration in the vaporized fuel passing through the discharge passage 36.

FIG. 2 shows a sectional view of a diaphragm galvanic cell type oxygen concentration sensor 46. This oxygen concentration sensor 46
Is a sensor housing 4 whose both ends are connected to the discharge passage 36.
Equipped with 7. The inside of the sensor housing 47 acts as a gas passage 48 through which the evaporated fuel from the canister 37 passes. In addition, the sensor housing 47
Noble metal electrode (Pt) 49 and base metal electrode (Pb) 5
0 and an electrolytic solution 51 are provided. The noble metal electrode 49 is in contact with the evaporated fuel in the gas passage 48 via the Teflon film 52. A load resistor 53 is connected between the two electrodes 49 and 50. The potential difference of the load resistor 53 is detected by the voltmeter 54.

At the noble metal electrode 49, the reaction represented by the following chemical formula 1 is in progress.

[0018]

Embedded image O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻ On the other hand, in the base metal electrode 50, the reaction represented by the following chemical formula 2 is in progress.

[0019]

2Pb → 2Pb ²⁺ + 4e ⁻ According to the chemical formulas 1 and 2, a current proportional to the oxygen concentration in the air flows.

Here, when the fuel component is not contained in the evaporated fuel passing through the gas passage 48, the oxygen concentration is 21%.
Becomes At this time, the voltage output to the voltmeter 54 becomes maximum. When the evaporated fuel is completely filled with the fuel component, the oxygen concentration becomes 0%, and the fuel component density at that time is, for example, 2.32 g / l. At this time,
The voltage output to the voltmeter 54 becomes the minimum.

FIG. 3 shows a map showing the relationship between the fuel component density, the oxygen concentration and the output voltage. As in this map, the relationship between the voltage proportional to the oxygen concentration and the fuel component density can be obtained. That is, the voltage output to the voltmeter 54 of the oxygen concentration sensor 46 corresponds to the fuel component density.

In FIG. 1, a control circuit 44 composed of a microcomputer detects a throttle opening signal from a throttle sensor (not shown) for detecting the opening of the throttle valve 5 and the rotational speed of the engine 1. An engine speed signal from a speed sensor (not shown), an intake pipe internal pressure signal from an intake pipe internal pressure sensor (not shown) that detects the internal pressure of the intake pipe 2, and a water temperature that detects the temperature of engine cooling water. A cooling water temperature signal from a sensor (not shown) is input. From these signals, the control circuit 44 detects the opening of the throttle valve 5, the engine speed, the intake pipe internal pressure, and the engine cooling water temperature.

Further, the control circuit 44 inputs the detection signal (voltage value) from the oxygen concentration sensor 46 as described above, and calculates the fuel component density using the map of FIG. Also,
The control circuit 44 is connected to the purge valve 40, and the purge valve 4
0 is duty controlled.

Next, from the canister 37 to the surge tank 3
A method of calculating the flow rate of the evaporated fuel supplied to No. 5 and the weight of the fuel component will be described. In general, the flow rate of evaporated fuel from the canister 37 to the surge tank 35 is determined by the negative pressure of the surge tank 35, which is the intake pipe internal pressure, and the opening degree of the purge valve 40 by duty control. FIG. 4 shows a map showing the relationship between the purge valve drive duty that determines the opening degree of the purge valve 40 and the vaporized fuel flow rate when the surge tank negative pressure is −450 mmHg. The control circuit 44 stores the vaporized fuel flow rate determined by the intake pipe internal pressure and the purge valve drive duty as shown in the map of FIG. Control circuit 4
When the intake pipe internal pressure signal and the purge valve drive duty signal are input, 4 calculates the fuel vapor flow rate during purging using this map.

Next, the weight of the fuel component in the vaporized fuel is obtained by multiplying the vaporized fuel flow rate by the fuel component density. Therefore, based on the fuel component density and the evaporated fuel flow rate calculated by the control circuit 44 as described above, the weight of the fuel component supplied from the canister 37 to the surge tank 35 is
It is calculated within 4.

Purge control by the control circuit 44 which performs the above calculation will be described. FIG. 5 is a purge control routine executed by the control circuit 44 at predetermined time intervals.

The control circuit 44 determines in step 100 whether or not the purge control execution condition is satisfied. The execution condition is satisfied, for example, when the engine is not idling and when the fuel is not cut. When the execution condition is satisfied, the routine proceeds to step 101, where it is determined whether or not the flag F = 1. The flag F is reset to F = 0 when a key switch (not shown) is turned on. When the flag F = 1 is not satisfied, that is, when the purge is performed for the first time after the engine 1 is started, the routine proceeds to step 102. In step 102, the fully closed purge valve 40 is opened at a rate of α (% / sec).
This α indicates the ratio of the purge valve drive duty (%) to the time (sec). For example, α may be 0.2. Then, in step 103, the canister 37 waits until a predetermined time elapses after the purge valve starts to open.
The vaporized fuel of 1 reaches the oxygen concentration sensor 46 sufficiently.

After a lapse of a predetermined time, the process proceeds to step 104. Further, if the flag F = 1 in step 101, it is determined that the purge control has been executed from the previous time, the processing of steps 102 and 103 is skipped, and the process proceeds to step 104. In step 104, the oxygen concentration in the evaporated fuel detected by the oxygen concentration sensor 46 is read. From the oxygen concentration read in step 104, the fuel component density is calculated in step 105 from the map of FIG. Further, in step 106, the evaporated fuel flow rate is calculated from the drive duty of the purge valve 40 and the intake pipe internal pressure which are input to the control circuit 44, using the map of FIG. Next, the process proceeds to step 107 and steps 105 and 106.
The fuel component weight Q _EVP is calculated by multiplying the fuel component density calculated in (1) and the evaporated fuel flow rate.

Next, at step 108, correction is performed to reduce the fuel component weight Q _EVP calculated at step 107 from the fuel injection amount Q _FUEL injected from the fuel injection valve 4.
Then, the reduction correction value (Q _FUEL −Q _EVP ) is set as the fuel injection amount newly injected from the fuel injection valve 4, and the fuel injection valve 4 injects the corrected fuel amount. Next, in step 109, the flag F = 1 is set.

In step 110, it is determined whether or not the fuel component density calculated in step 105 is less than the predetermined value β. If the fuel component density is less than the predetermined value β, the routine proceeds to step 111, where it is determined that the amount of fuel adsorbed in the canister 37 is small, and the air flowing in from the atmosphere opening hole 38 of the canister 37 is unnecessarily intake pipe. The purge valve 40 is closed at a rate of α (% / sec) in order to prevent it from being sucked in. On the other hand, if the fuel component density is greater than or equal to the predetermined value β, the routine proceeds to step 112, where it is determined that the amount of fuel adsorbed in the canister 37 is large, and the purge valve 40 is set to α.
Open at a rate of (% / sec). As a result, the amount of adsorbed fuel in the canister 37 can be reduced. The predetermined value β is set so that the adsorption amount of the canister 37 still has a sufficient margin even when the purge valve 40 is closed in step 111. Here, for example, the predetermined value β may be the density when the air in the evaporated fuel supplied from the canister 37 to the surge tank 35 and the evaporated fuel component have the stoichiometric air-fuel ratio.

When it is determined in step 100 that the execution condition is not satisfied, the process proceeds to step 111 and the purge valve 40 is closed. When the purge valve 40 is fully closed, the closing of the purge valve 40 in step 111 is stopped. On the other hand, even when the purge valve 40 is opened and fully opened in steps 102 and 112,
The opening of the purge valve 40 is stopped.

The fuel injection amount of the fuel injection valve 4 is determined by the intake pipe internal pressure signal and the engine speed signal input to the control circuit 44, and the basic injection amount is determined by the throttle opening signal and the cooling water temperature signal. The basic injection amount is determined by being corrected. Detailed description of the control for determining the fuel injection amount is omitted in this embodiment.

From the above, the weight of the fuel component per unit time in the evaporated fuel when purged is determined by the oxygen concentration sensor 4
It can be calculated from the detected value from 6. Then, when the fuel is purged, the fuel injection amount of the fuel injection valve 4 is controlled so as to be excluded by the calculated fuel component weight. This can prevent the air-fuel ratio of the internal combustion engine at the time of purging from being disturbed.

In the above embodiment, the fuel component density at an arbitrary oxygen concentration is calculated from the characteristic that the fuel component density is 2.32 g / l when the oxygen concentration is 0%. However, when this characteristic may change from the value in the above-mentioned embodiment due to the difference in the outside air temperature (especially the difference in the volatility of the fuel), the oxygen concentration of 0% depending on the value.
The fuel component density at that time may be calculated to calculate the fuel component density at an arbitrary oxygen concentration.

In the above embodiment, the noble metal electrode 49 is Pt, but it may be Ag.

[0036]

The evaporated fuel control apparatus for an internal combustion engine according to the present invention calculates the flow rate of the evaporated fuel and detects the oxygen concentration of the evaporated fuel when purged, and calculates the fuel component density from this oxygen concentration. .. From the fuel component density and the vaporized fuel flow rate, the weight of the fuel component in the vaporized fuel supplied to the intake system is calculated. Then, the injection amount of the fuel injection valve of the internal combustion engine is reduced and corrected by this fuel component weight. As a result, the air-fuel ratio of the internal combustion engine is optimally controlled, and it is possible to prevent the air-fuel ratio of the internal combustion engine at the time of purging from being disturbed.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an evaporated fuel control device of the present embodiment.

FIG. 2 is a cross-sectional view of an oxygen concentration sensor of this embodiment.

FIG. 3 is a characteristic diagram showing the relationship between fuel component density, oxygen concentration, and output voltage.

FIG. 4 is a characteristic diagram showing a relationship between an opening of a purge valve and an evaporated fuel flow rate.

FIG. 5 is a flowchart showing a purge control routine of this embodiment.

FIG. 6 is a claim correspondence diagram.

[Explanation of symbols]

 1 engine 2 intake pipe 4 fuel injection valve 5 throttle valve 7 fuel tank 35 surge tank 36 release passage 37 canister 40 purge valve 44 control circuit 46 oxygen concentration sensor 50 release passage 51 opening / closing means 52 oxygen concentration detecting means 53 evaporative fuel flow rate calculating means 54 Fuel Component Density Calculating Means 55 Fuel Component Weight Calculating Means 56 Control Means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigenori Isomura 1-1-1, Showa-cho, Kariya city, Aichi Nihon Denso Co., Ltd.

Claims (3)

[Claims] 1. A discharge passage communicating with a fuel tank for supplying evaporated fuel from the fuel tank to an intake system of an internal combustion engine; and opening / closing means for opening / closing the discharge passage to adjust a flow rate of evaporated fuel to the intake system. An oxygen concentration detecting means provided in the discharge passage between the fuel tank and the opening / closing means for detecting the oxygen concentration in the evaporated fuel supplied to the intake system; an opening degree of the opening / closing means and an internal combustion engine The evaporated fuel flow rate calculating means for calculating the evaporated fuel flow rate from the operating state of the fuel, the fuel component density calculating means for calculating the fuel component density in the evaporated fuel from the oxygen concentration detected by the oxygen concentration detecting means, and the evaporated fuel A fuel component weight calculation means for calculating the fuel component weight in the evaporated fuel from the evaporated fuel flow rate calculated by the flow rate calculation means and the fuel component density calculated by the fuel component density calculation means; Control means for reducing and correcting the fuel injection amount injected from the fuel injection valve of the internal combustion engine by the fuel component weight calculated by the fuel component weight calculation means; apparatus. 2. The internal combustion engine according to claim 1, further comprising a canister provided in the discharge passage between the fuel tank and the oxygen concentration detecting means, the canister including an adsorbent for adsorbing the evaporated fuel. Evaporative fuel control device. 3. The opening degree of the opening / closing means is controlled according to whether or not the fuel component density calculated by the fuel component density calculating means is less than a predetermined value. An evaporative fuel control device for an internal combustion engine as described above.