JPH05321772A - Evaporated fuel control device of internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent the air fuel ratio of an internal combustion engine when the purging is executed. CONSTITUTION:In an evaporated fuel control device of an internal combustion engine, a fuel concentration sensor 46 to detect the concentration of the fuel content in the evaporated fuel is provided between a canistor 37 and a control valve 40. On the other hand, the evaporated fuel flow rate is computed from the suction negative pressure of the internal combustion engine and the opening of the control valve 40. The fuel content weight in the evaporated fuel to be supplied in a surge tank 35 is computed from this evaporated fuel flow rate and the fuel content density to be computed by the detected signals of the fuel concentration sensor 46. The injection of the fuel injection valve 4 of the internal combustion engine is corrected for the loss. This arrangement prevents disturbance of the air fuel ratio of the internal combustion engine at the time of purging.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporative fuel control system for an internal combustion engine, and more particularly to calculating the weight of the fuel component in the evaporative fuel using a fuel concentration sensor or the like to prevent disturbance of the air-fuel ratio of the internal combustion engine during purging. Regarding what you do.

[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, JP-A-62-233 discloses that the fluctuation of the air-fuel ratio of the internal combustion engine is suppressed when the evaporated fuel is purged.
Japanese Patent Publication No. 466 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 the evaporated fuel is supplied to the internal combustion engine. Therefore, it is impossible to grasp the total amount of fuel supplied to the internal combustion engine. 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 concentration of the fuel component in the evaporated fuel, reduces the amount of fuel injected from the fuel injection valve by the weight, and purges. An object of the present invention is to provide an evaporated fuel control device for an internal combustion engine, which prevents the air-fuel ratio of the internal combustion engine from being disturbed at that time.

[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, the discharge passage 50 for opening and closing, the opening / closing means 51 for opening / closing the discharge passage 50 to adjust the flow rate of the evaporated fuel to the intake system, Fuel concentration detection means 52 for detecting the fuel component concentration in the evaporated fuel supplied to the intake system, and evaporated fuel flow rate calculation for calculating the flow rate of evaporated fuel from the opening degree of the opening / closing means 51 and the operating state of the internal combustion engine. Means 53, a fuel component density calculating means 54 for calculating the fuel component density in the evaporated fuel from the detection signal from the fuel concentration detecting means 53, and an evaporated fuel flow rate calculated by the evaporated fuel flow rate calculating means 53. A fuel component weight calculation means 55 for calculating the fuel component weight in the evaporated fuel from the fuel component density calculated by the fuel component density calculation means 54; and a 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 fuel injection valve of the internal combustion engine, and the evaporated fuel control device for the internal combustion engine.

A canister having an adsorbent for adsorbing the evaporated fuel may be provided in the discharge passage between the fuel tank and the fuel 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. A fuel concentration detecting means is provided between the opening / closing means and the fuel tank. The fuel concentration detecting means detects the concentration of the fuel component in the evaporated fuel supplied to the intake system of the internal combustion engine.

Then, from the detection signal detected by the fuel concentration detecting means, the fuel component density in the evaporated fuel from the fuel tank is calculated by the fuel density calculating means. on the other hand,
The evaporated fuel flow rate 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. Further, the exhaust pipe 3 for each cylinder is formed in one passage, and the passage is provided with a 0 ₂ sensor 6 as air-fuel ratio detecting means. 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.

A fuel concentration sensor 46 is provided in the discharge passage 36 extending from the canister 37 to the purge valve 40. The fuel concentration sensor 46 detects the concentration of the fuel component in the evaporated fuel passing through the discharge passage 36.

FIG. 2 shows a sectional view of the fuel concentration sensor 46. The fuel concentration sensor 46 has a sensor housing 47 whose both ends are connected to the discharge passage 36. The inside of the sensor housing 47 acts as a gas passage 48 through which the evaporated fuel from the canister 37 passes. A crystal oscillator 49, leads 51, a gas adsorption film 50, a base 52, a cover 53 and the like are provided in the gas passage 48. Gas adsorption film 50 in contact with evaporated fuel in the gas passage 48
Is provided on the crystal oscillator 49. Also, lead 5
1 is connected to a terminal 54, and this terminal 54 is connected to a frequency-voltage converter 55 containing an oscillation circuit. Further, a voltmeter 56 for detecting the voltage output from the frequency-voltage converter 55 is provided.

In the fuel concentration sensor 46 having the above structure, the crystal oscillator 49 always oscillates regardless of the presence or absence of fuel, and oscillates the fundamental frequency when the fuel component concentration is 0%. The frequency-voltage converter 55 is set to output 0 mV when the fundamental frequency of the crystal oscillator 49 is input (that is, when the fuel component concentration is 0%).

Here, when the fuel component in the vaporized fuel passing through the gas passage 48 is adsorbed by the gas adsorption film 50 on the crystal oscillator 49, the crystal oscillator 49 has a frequency corresponding to the concentration of the fuel component. To oscillate. Then, the frequency-voltage converter 55 outputs a voltage corresponding to the amount of frequency change from the fundamental frequency.

The control circuit 44 calculates the fuel component density in the vaporized fuel passing through the fuel concentration sensor 46 based on the output voltage of the fuel concentration sensor 46. The relationship between the fuel component density, the frequency change amount, and the output voltage is shown in the map of FIG. The control circuit 44 uses this map to control the fuel concentration sensor 46.
The fuel component density in the evaporated fuel can be calculated according to the output voltage from.

In FIG. 1, the control circuit 44 includes a throttle sensor (not shown) for detecting the opening of the throttle valve 5.
From a throttle opening signal from the engine, an engine speed signal from a speed sensor (not shown) that detects the speed of the engine 1, and an intake pipe internal pressure sensor (not shown) that detects the internal pressure of the intake pipe 2. The intake pipe internal pressure signal and the cooling water temperature signal from a water temperature sensor (not shown) that detects the temperature of the engine cooling water are 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 fuel 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 evaporated fuel flow rate when the negative pressure of the surge tank is −450 mmHg, for example. The control circuit 44 has a configuration shown in FIG.
The map shows the fuel vapor flow rate determined by the intake pipe internal pressure and the purge valve drive duty. When the intake pipe internal pressure signal and the purge valve drive duty signal are input, the control circuit 44 uses this map to calculate the fuel vapor flow rate during purging.

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 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.
So that the vaporized fuel of 1 reaches the fuel concentration sensor 46 sufficiently. Then, after a predetermined time has elapsed, 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 this step 104, the output voltage corresponding to the frequency change amount detected by the fuel concentration sensor 46 is read. Then, in step 105, the fuel component density corresponding to this output voltage is calculated 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, in step 107, the fuel component density Q _EVP is calculated by multiplying the fuel component density calculated in steps 105 and 106 by the vaporized 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 the fuel component density calculated in step 105 is less than a predetermined value β. When 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. Then, in order to prevent the air flowing in from the atmosphere opening hole 38 of the canister 37 from being unnecessarily sucked into the intake pipe 2, the purge valve 40 is set to α (% / se).
Close at the rate of c). 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 opened at a rate of α (% / sec). As a result, the amount of adsorbed fuel in the canister 37 can be reduced. It should be noted that this predetermined value β is still sufficient for the canister 37 even when the purge valve 40 is closed in step 111.
Is set so that there is a margin for the adsorption amount of. Here, for example, the predetermined value β may be a density when the air and fuel components in the evaporated fuel supplied from the canister 37 to the surge tank 35 have a 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 basic 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 fuel component weight per unit time in the evaporated fuel at the time of purging is determined by the fuel 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.

[0031]

The evaporative fuel control system for an internal combustion engine according to the present invention detects the fuel component concentration while calculating the evaporative fuel flow rate during purging, and determines the fuel component weight in the evaporative fuel supplied to the intake system. To calculate. 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 a fuel concentration sensor of this embodiment.

FIG. 3 is a map showing a relationship between a fuel component density, a frequency change amount, and an 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 fuel concentration sensor 50 release passage 51 opening / closing means 52 fuel 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 (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location F02M 25/08 301 U 7114-3G (72) Inventor Toshihiro Suzumura 1-chome 1 Showa-cho, Kariya city, Aichi prefecture Address: Nippon Denso Co., Ltd.

Claims (3)

[Claims] 1. A discharge passage communicating with a fuel tank for supplying the evaporated fuel of the fuel tank to an intake system of an internal combustion engine, and an opening / closing means for opening / closing the discharge passage to adjust a flow rate of the evaporated fuel to the intake system. And a fuel concentration detecting means provided in the discharge passage between the fuel tank and the opening / closing means for detecting a concentration of a fuel component in the evaporated fuel supplied to the intake system, and an opening degree of the opening / closing means. An evaporated fuel flow rate calculating means for calculating a flow rate of evaporated fuel from the operating state of the internal combustion engine; a fuel component density calculating means for calculating a fuel component density in the evaporated fuel from a detection signal from the fuel concentration detecting means; Fuel component weight calculation means for calculating the fuel component weight in the evaporated fuel from the evaporated fuel flow rate calculated by the fuel flow rate calculation means and the fuel component density calculated by the fuel component density calculation means; Evaporative fuel control of an internal combustion engine, comprising: a control unit that corrects the fuel injection amount injected from the fuel injection valve of the internal combustion engine from the fuel component weight calculated by the fuel component weight calculation unit. 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 fuel concentration detecting means, the canister including an adsorbent that adsorbs 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.