JPH04365964A - Fuel steam detecting device of internal combustion engine - Google Patents

Abstract

PURPOSE:Toimprove detecting accuracy of fuel steam component when the flow amount of air fuel mixture of fuel steam and air suppoied from a camistor into an intake sytem is small. CONSTITUTION:An orifice 171, a pressure meter 20, and a passage 18 for bypassing an arifice 171 are provided on a page passage 17 for connecting a canistor 15 to an intake pipe 2. The bypass passage 18 is provided with an electromagnetic solenoid 25 for opening/closing the orifice 181 and the passage 18. An arifice 231 and a passage 24 for bypassing the orifice 231 are provided in an atmosphere passage 23 for supplying air into the canistor 15, and the bypass passage 24 is provided with an electromagneic solenoid 26 for opening/closing the orifice 241 and the passage 24. A pressure gauge 22 is provided on the upper part of the canistor 15. When a flow amount value calculated by output values of pressure gauges 20, 22 is a prescribed value or less, the electromagnetic solenoids 25, 26 are closed, and a flow amuont value is calculated by the output values of the pressure gauges 20, 22 under its condition. Fuel steam comonent is detected on the basis of the calculated flow amount value.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel vapor detection device for an internal combustion engine having a fuel vapor emission suppression device, and more particularly to a fuel vapor detection device for an internal combustion engine having a fuel vapor emission suppression device. The present invention relates to a device for detecting.

0002

2. Description of the Related Art As shown in FIG. 4, a canister 100 having an adsorbent 101, a passage 104 connecting the canister 100 and a fuel tank, a two-way valve 105 disposed in the middle of the passage 104, 100 and an engine intake system, and a purge control valve 108 disposed in the middle of the purge passage 106.
An atmospheric passage 102 and a purge passage 10 that communicate with the atmosphere.
6 are provided with orifices 103 and 107, and atmospheric pressure differential gauges 109 and 110 are provided so that fuel vapor components in the air-fuel mixture containing fuel vapor flowing through the purge passage 106 are detected based on the outputs of the differential pressure gauges 109 and 110. A fuel vapor detection device has already been proposed by the applicant (
(Patent Application No. 2-417320).

According to this device, differential pressure gauges 109 and 11
Based on the output difference of 0, the flow rate Q1 of the air-fuel mixture flowing through the purge passage 106 is detected, and the flow rate Q4 of the air flowing through the atmospheric passage 102 is detected based on the output of the differential pressure gauge 110. Therefore, by subtracting Q4 from Q1, the fuel vapor component (fuel vapor flow rate) VQ in the air-fuel mixture can be calculated.

0004

[Problems to be Solved by the Invention] The relationship between the output P of the differential pressure gauge 109 or 110 and the flow rate Q is generally as shown in FIG. small. In other words, the differential pressure gauge output P
A slight deviation in the flow rate Q changes greatly. On the other hand, since the output P of the differential pressure flow meter includes an inherent error, the effect of the error becomes large in a region where the flow rate Q is small, and there is a problem that fuel vapor components cannot be detected accurately.

The present invention has been made to solve this problem, and an object of the present invention is to provide a fuel vapor detection device that can improve detection accuracy particularly when the flow rate of the air-fuel mixture is small.

[0006]

[Means for Solving the Problems] In order to achieve the above objects, the present invention provides a canister for adsorbing fuel vapor generated in a fuel tank, and an air-fuel mixture containing the fuel vapor adsorbed in the canister to be introduced into an engine. In a fuel vapor detection device for detecting fuel vapor in the air-fuel mixture of an internal combustion engine, the system includes a purge passage that supplies air to the canister, and an atmospheric passage that supplies atmospheric air to the canister. a first flow path cross-sectional area variable means for changing; a first flow meter for detecting the flow rate of the air-fuel mixture flowing through the purge passage;
a second passage cross-sectional area variable means for changing the passage cross-sectional area of the atmospheric passage; a second flow meter that detects the flow rate of the atmosphere flowing through the atmospheric passage; and the first or second flow meter. and detecting means for detecting fuel vapor components based on the outputs of the first and second flowmeters when the cross-sectional areas of the purge passage and the atmospheric passage are changed according to the detected flow rate values. This is how it was done.

[0007]

[Operation] The cross-sectional area of the purge passage and the atmosphere passage is changed according to the flow rate value detected by the first or second flow meter, and based on the output of the first and second flow meter at the time of the change. fuel vapor components are detected.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is an overall configuration diagram of a fuel supply control device including a fuel vapor detection device for an internal combustion engine according to an embodiment of the present invention. Reference numeral 1 indicates, for example, a four-cylinder internal combustion engine; A throttle body 3 is provided in the middle of the intake pipe 2, and a throttle valve 301 is disposed inside the throttle body 3. A throttle valve opening (θTH) sensor 4 is connected to the throttle valve 301, and outputs an electric signal according to the opening of the throttle valve 301 and supplies it to an electronic control unit (hereinafter referred to as "ECU") 5. .

The fuel injection valve 6 is provided for each cylinder between the engine 1 and the throttle valve 301 and slightly upstream of the intake valve (not shown) in the intake pipe 2. Connected to fuel tank 8 and EC
The ECU 5 is electrically connected to the ECU 5, and the opening time of the fuel injection valve 6 is controlled by a signal from the ECU 5.

On the other hand, an intake pipe absolute pressure (PBA) sensor 10 is provided immediately downstream of the throttle valve 301 via a pipe 9, and the absolute pressure signal converted into an electric signal by this absolute pressure sensor 10 is It is supplied to the ECU5.

The engine rotational speed (NE) sensor 11 is installed around the camshaft or crankshaft (not shown) of the engine 1, and generates a signal pulse (hereinafter referred to as TDC signal pulse) is output, and this signal pulse is sent to the ECU.
5.

O2 sensor 1 as exhaust gas concentration detector
2 is attached to the exhaust pipe 13 of the engine 1, detects the oxygen concentration in the exhaust gas, outputs a signal according to the detected value, and supplies it to the ECU 5.

Between the upper part of the sealed fuel tank 8 and the intake pipe 2 downstream of the throttle body 3, there are a passage 14 constituting a fuel vapor emission suppressing device, a two-way valve 141, a canister 15 containing an adsorbent 151, purge passage 17,
A linear control valve (EPC) with a solenoid that drives the valve.
A purge control valve 16 is provided. The solenoid of the purge control valve 16 is connected to the ECU 5, and is controlled according to a signal from the ECU 5 to linearly change the valve opening amount. The canister 15 communicates with the atmosphere through an atmospheric passage 23 in which an orifice 231 is provided.
includes a bypass passage 2 that bypasses the orifice 231.
4 is provided. A solenoid valve 26 that opens and closes the orifice 241 and the bypass passage 24 is disposed in the bypass passage 24, and the solenoid valve 26 is controlled to open and close by the ECU 5. A pressure gauge (second flow meter) 22 is installed in the space above the adsorbent 151 of the canister 15 via a pipe 21 . The pressure gauge 22 is constituted by an atmospheric pressure differential pressure gauge, detects the relative pressure P2 inside the pipe 21 with respect to the atmospheric pressure, and supplies the detection signal to the ECU 5.

An orifice 171 is provided in the purge passage 17 between the purge control valve 16 and the canister 15;
Furthermore, a bypass passage 18 bypassing the orifice 171
is provided. A solenoid valve 25 that opens and closes the orifice 181 and the bypass passage 18 is disposed in the bypass passage 18, and the solenoid valve 25 is controlled to open and close by the ECU 5. Further, a pressure gauge (first flow meter) 20 is installed in the purge passage 17 via a pipe 19 . Pressure gauge 20
is composed of an atmospheric pressure differential pressure gauge, and the tube 1 relative to atmospheric pressure is
Detects the relative pressure P1 within 9 and sends the detection signal to the ECU 5.
supply to

According to this fuel vapor discharge suppression device, when the fuel vapor generated in the fuel tank 8 reaches a predetermined set pressure, it pushes open the positive pressure valve of the two-way valve 141, flows into the canister 15, and flows into the canister 15. Adsorbent 15 in 15
1 is adsorbed and stored. On the other hand, when the solenoid is not energized by the control signal from the ECU 5, the purge control valve 16 is closed, but when the solenoid is energized by the control signal, the valve opens only by the amount corresponding to the energization amount. The purge control valve 16 is opened, and the evaporated fuel temporarily stored in the canister 15 is transferred to the atmospheric passage 23 due to the negative pressure in the intake pipe 2.
It is sucked into the intake pipe 2 together with the air taken in from the air, and sent to the cylinder. Furthermore, if the fuel tank 8 is cooled due to the influence of outside air and the negative pressure inside the fuel tank increases, the two-way valve 14
The negative pressure valve is opened, and the fuel vapor temporarily stored in the canister 15 is returned to the fuel tank 8. In this way, the fuel vapor generated in the fuel tank 8 is prevented from being released into the atmosphere.

The ECU 5 includes an input circuit having functions such as shaping input signal waveforms from various sensors, correcting voltage levels to predetermined levels, and converting analog signal values into digital signal values, and a correction coefficient VQKO2 and a correction coefficient VQKO2 to be described later. Central processing circuit (hereinafter referred to as “C”) that executes the EPCV value calculation program etc.
PU"), various calculation programs executed by the CPU, storage means for storing Q1 and Q4 tables described later, Ti maps, calculation results, etc., the fuel injection valve 6, the purge control valve 16, and the solenoid valves 25, 26. It is composed of an output circuit that supplies drive signals, etc.

Based on the various engine parameter signals mentioned above, the CPU determines various engine operating states such as a feedback control operating range and an open loop control operating range depending on the oxygen concentration in the exhaust gas, and also determines various engine operating states depending on the engine operating state. , the fuel injection time Tout of the fuel injection valve 6 synchronized with the TDC signal pulse is calculated based on the following equation (1).

[0019] Tout=Ti×KO2×VQKO2×K1+K2
...(1) Here, Ti is the injection time Tou of the fuel injection valve 6
This is a reference value of t, and is read from a Ti map set according to the engine speed NE and the intake pipe absolute pressure PBA.

KO2 is an air-fuel ratio feedback correction coefficient, which is set according to the oxygen concentration in the exhaust gas detected by the O2 sensor 12 during feedback control; This is a coefficient set according to each driving region.

VQKO2 is a vapor amount correction coefficient, and is a value set according to the vapor amount detected when purging is being executed. The details will be described later with reference to FIG.

[0022] K1 and K2 are other correction coefficients and correction variables that are respectively calculated according to various engine parameter signals, and are used to optimize various characteristics such as fuel consumption characteristics and engine acceleration characteristics according to engine operating conditions. The predetermined value is determined as follows.

The CPU supplies the fuel injection valve 6 with a drive signal to open the fuel injection valve 6 via the output circuit based on the fuel injection time Tout determined as described above.

In this embodiment, the bypass passage 18 and the solenoid valve 25 constitute a first passage cross-sectional area variable means, and the bypass passage 24 and the solenoid valve 26 constitute a second passage cross-sectional area variable means. Ru. Further, the ECU 5 constitutes a detection means.

FIG. 2 shows a flowchart of a program that calculates the flow rate VQ of fuel vapor flowing through the purge passage 17, and also calculates the correction coefficient VQKO2 and EPCV value based on this VQ value.
Executed in PU. Note that the electromagnetic valves 25 and 26 are opened before starting the execution of this program.

First, in step S1, orifice 1
71,181 jet area (channel cross-sectional area) and pressure gauge 2
The total air vapor flow rate Q1, which is the flow rate of the mixture of air and fuel vapor passing through the orifices 171 and 181, is stored in the storage means of the ECU 5 based on the relative pressures P1 and P2 detected by the solenoid valves 25 and 22. Read from the Q1 table for large flow rate used when opening the valve. Since the relative pressures P1 and P2 indicate the pressure inside the pipe 17 and the pressure inside the canister 15 with respect to atmospheric pressure, the differential pressure P1-P2 is the pressure difference between the orifices 171 and 1.
This corresponds to the pressure difference on the outlet side with respect to the inlet side pressure of 81. Q1 table for large flow rate has two orifices 171,
This table was set based on the fact that the flow rate of gas passing through the orifices 171 and 181 is uniquely determined when the jet area of 181 and the differential pressure P1-P2 are determined.
A total air vapor flow rate Q1 corresponding to each value of 1-P2 is stored (see curve A in FIG. 3(a)). The total air vapor flow rate Q1 comes from the fuel tank 8 and flows into the canister 15.
This is the total flow rate of the vapor flow rate VQ due to the fuel vapor (vapor) adsorbed in the canister 15 and the air flow rate Q4 due to the air sucked from the atmospheric passage 23 (and bypass passage 24) of the canister 15. Note that the total air vapor flow rate Q1 includes vapor that passes directly from the fuel tank 8 through the orifices 171 and 181 without being adsorbed by the canister 15, but since this is highly concentrated fuel vapor, the vapor flow rate VQ
We will treat it by including it in

In step S2, the Q1 value read out in step S1 is set to a predetermined flow rate Q1C (for example, 10 [l/min]).
]) If the answer is negative (NO), that is, Q1>Q1C is established, and the flow rate of the mixture is large, the jet area of the two orifices 231 and 241 and the pressure gauge 22 have detected relative pressure P2 and from orifice 23
1,241 is read out from the Q4 table for large flow rate stored in the storage means of the ECU 5, and the process proceeds to step S7. Since the relative pressure P2 indicates the internal pressure of the canister 15 with respect to atmospheric pressure, the relative pressure P2 corresponds to the pressure difference between the pressure on the inlet side and the outlet side of the orifice 231. Q4 table for large flow rate has orifice 231
, 241 and the differential pressure P2 are determined, the flow rate of gas passing through the orifices 231 and 241 is uniquely determined. is stored (Figure 3 (
(see curve C in b)).

On the other hand, the answer to step S2 is affirmative (YES).
, that is, when Q1≦Q1C is established and the flow rate of the mixture is small, the solenoid valves 25 and 26 are closed (step S
4) Read the air vapor total flow rate Q1 from the Q1 table for small flow rates (step S5). The Q1 table for small flow rate is a table set similarly to the Q1 table for large flow rate corresponding to the jet area of only the orifice 171, and the Q1 value corresponding to each value of differential pressure P1-P2 is stored. (see curve B in Figure 3(a)).

In the following step S6, the air flow rate Q4 is read from the Q4 table for small flow rates. The Q4 table for small flow rate is a table set similarly to the Q4 table for large flow rate corresponding to the jet area of only the orifice 231, and stores Q4 values corresponding to each value of differential pressure P2. (See curve D in FIG. 3(b)).

In step S7, the vapor flow rate VQ due to the fuel vapor adsorbed in the canister 15 or the fuel vapor directly coming from the fuel tank 8 and the air sucked through the atmospheric passage 23 (and 24) of the canister 15 are determined. The vapor flow rate VQ (=Q1-Q4) is calculated by subtracting the air flow rate Q4 from the total flow rate Q1 including the air flow rate Q4.

According to steps S1 to S7 above, when the flow rate Q1 of the air-fuel mixture is small (Q1≦Q1C), the solenoid valves 25 and 26 are closed, and the Q1 table and Q4 table for small flow rates are used. While the Q1 value and Q4 value are calculated, when the flow rate Q1 of the air-fuel mixture is large (Q1>Q1C), the solenoid valves 25 and 26 remain open and the Q1 table and Q4 table for large flow rates are used. Q1 value and Q4 value are calculated. As a result, as stated below,
The detection accuracy of the Q1 value and the Q4 value when the air-fuel mixture flow rate Q1 is small can be improved, and therefore the accuracy of the vapor flow rate VQ calculated from these detected values can be improved.

FIG. 3(a) shows the relationship between the differential pressure P1-P2 and the Q1 value, and curves A and B in the figure correspond to the Q1 tables for large flow rate and small flow rate, respectively. Here, in curve A, when Q1=10 [l/min], P1-P2
= 187mmAq, and the error of the pressure gauge is ±10mmA
q, the error ratio is approximately ±5% (= ±10/1
87). On the other hand, for curve B, Q1=10 [
l/min], P1-P2 = 3000 mmAq, and the error ratio is approximately ±0.3% (= ±10/3000)
This greatly improves accuracy. That is, for example, 10 [l
/min], the detection accuracy can be greatly improved by closing the electromagnetic valve 25 and determining the Q1 value from the Q1 table for small flow rates.

FIG. 3(b) shows the relationship between the atmospheric pressure difference P2 and the Q4 value, and curves C and D in the figure correspond to the Q4 tables for large flow rates and small flow rates, respectively. In curve C,
When Q4 = 10 [l/min], P2 = 90 mmAq, and if the error of the pressure gauge is ±10 mmAq, the error ratio is approximately 11% (= ±10/90), whereas in curve D, When Q4=10 [l/min], P2=15
00mmAq, and the error ratio is approximately 0.7% (=±1
0/1500). Therefore, as in the case of the Q1 value, when the flow rate is small, the solenoid valve 26 is closed, and the Q4 value is obtained from the Q4 table for small flow rates, thereby greatly improving the detection accuracy.

By improving the accuracy of the mixture flow rate Q1 and the air flow rate Q4, the vapor flow rate VQ (=Q1-Q4
) accuracy can be improved.

Vapor flow rate V calculated as described above
Based on Q, the vapor amount correction coefficient VQK is determined in step S8.
Calculate O2. That is, first, based on the following equation (2), the vapor flow rate VQ is expressed as the liquid gasoline weight equivalent GVQ (g/
min).

[0036]

[Equation 1] KVQ is a coefficient indicating the ratio of gasoline vapor amount (l/min) included in vapor flow rate VQ (l/min),
It is 1/1.69. VMOL is 1 molar volume value,
It is represented by 22.4 l/MOL value at 0°C. Gasoline vapor molecular weight is approximately 64.

The gasoline weight equivalent amount GV thus obtained
A vapor amount correction coefficient VQKO2 is calculated based on the following equation (3) using Q (g/min).

[0038]

[Equation 2] The basic injection weight is calculated by subtracting the reference value Ti of the fuel injection time from the fuel weight (
g).

Vapor amount correction coefficient VQK thus obtained
O2 is 1.0 during purge cut when the purge control valve 16 is closed, and becomes a value of 1.0 or less when the purge control valve 16 is opened and purge is executed. Using this value, the fuel injection time Tout is calculated based on the above formula (1), and the fuel injection valve 6 supplies the engine 1 with an amount of fuel that suppresses fluctuations in the air-fuel ratio due to the size of the purge amount. be done.

Furthermore, in step S9, step S7
It is determined whether the vapor flow rate VQ calculated in is equal to or greater than a predetermined value. The predetermined value is set by another program as a function of the engine motion parameter, and is used to prevent the average value of the air-fuel ratio correction coefficient KO2 from deviating significantly from 1.0 and deteriorating the responsiveness of feedback control. This is a discrimination reference value that is set taking into consideration.

If the answer to step S9 is negative (NO), that is, if the calculated vapor flow rate VQ is smaller than the predetermined value, the purge control valve 16 is opened in order to increase the vapor amount and increase the fuel vapor emission suppressing ability. Controlled amount E corresponding to valve amount
The PCV value is increased by the value C from the current value (step S1
0) Exit this program. The value C is an update constant for the EPCV value. On the other hand, if the answer to step S9 is affirmative (YES),
That is, if the calculated vapor flow rate VQ is equal to or higher than the predetermined value, the vapor amount is decreased and the control amount EP of the purge control valve 16 is adjusted to prevent deterioration of the responsiveness of the feedback control.
The CV value is decreased by the value C from the current value (step S11
) Exit this program.

As described above, the actual vapor amount VQ is detected, and the fuel injection amount is corrected accordingly (step S8).
, prevents fluctuations in air-fuel ratio caused by purge, and
The opening amount of the purge control valve 16 is controlled in accordance with the detected purge amount (steps S10 and S11) to prevent the average value of the air-fuel ratio correction coefficient KO2 from deviating significantly from the value 1.0. As a result, when air-fuel ratio control shifts from open loop mode to feedback mode, air-fuel ratio correction coefficient KO2
It is possible to prevent deterioration in responsiveness of feedback control that would occur if the average value used as the initial value of deviates significantly from the value 1.0.

In the above embodiment, the solenoid valves 25 and 26 are closed when the air-fuel mixture flow rate Q1 is the predetermined value Q1C, but the present invention is not limited to this, and when the air flow rate Q4 is below the predetermined value The solenoid valves 25 and 26 may be closed.

[0044]

Effects of the Invention As detailed above, according to the present invention, the flow cross-sectional areas of the purge passage and the atmospheric passage are changed according to the flow rate value detected by the first or second flowmeter, and when the change is made, Since the fuel vapor component is detected based on the outputs of the first and second flowmeters, it is possible to improve the accuracy of detecting the fuel vapor component when the flow rate of the air-fuel mixture is small.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of a fuel supply control device including a fuel vapor detection device for an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a flowchart of a calculation program for an air-fuel ratio correction coefficient (VQKO2) and a control value for a purge control valve (EPCV value).

[Figure 3] Pressure gauge output values (P1, P2) and flow rate (Q1,
It is a figure showing the relationship with Q4).

FIG. 4 is a diagram showing the configuration of a conventional fuel vapor detection device.

FIG. 5 is a diagram showing the relationship between differential pressure gauge output (P) and flow rate (Q).

[Explanation of symbols]

1 Internal combustion engine 2 Intake pipe 5 Electronic control unit (ECU) 6 Fuel injection valve 8 Fuel tank 15 Canister 16 Purge control valve 17 Purge passage 18 Bypass passage 20 Pressure gauge 22 Pressure gauge 23 Atmospheric passage 24 Bypass passage 25 Solenoid valve 26 Solenoid valve

Claims (1)

[Claims] 1. A canister for adsorbing fuel vapor generated in a fuel tank, a purge passage for supplying a mixture containing the fuel vapor adsorbed in the canister to an engine intake system, and supplying atmospheric air to the canister. In the fuel vapor detection device for detecting fuel vapor in the air-fuel mixture of an internal combustion engine, the purge passage includes a first passage cross-sectional area variable means for changing a passage cross-sectional area of the purge passage; a first flow meter that detects the flow rate of the air-fuel mixture flowing through the purge passage; a second flow passage cross-sectional area variable means that changes the flow passage cross-sectional area of the atmospheric passage; and a second flow passage cross-sectional area variable means that detects the flow rate of the atmospheric air flowing through the atmospheric passage. the first and second flow meters when the flow path cross-sectional areas of the purge passage and the atmosphere passage are changed according to the flow rate value detected by the first or second flow meter; 1. A fuel vapor detection device for an internal combustion engine, comprising a detection means for detecting fuel vapor components based on the output of a flow meter.