JP3141544B2 - Evaporative fuel processor for internal combustion engines - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel vapor treatment system for an internal combustion engine for treating fuel vapor generated from a fuel tank.

[0002]

2. Description of the Related Art Conventionally, an evaporative fuel processing apparatus for an internal combustion engine for suppressing the emission of evaporative fuel generated in a fuel tank to the atmosphere has conventionally been provided by converting evaporative fuel generated in a fuel tank into activated carbon in a canister. There has been known a method of temporarily adsorbing and purging (discharging) this into an intake system.

In this type of evaporative fuel processing apparatus for an internal combustion engine, since the purge flow rate from the canister and the fuel injection quantity injected from the fuel injection valve flow into the engine, the evaporative fuel is purged to the intake system. In this case, a technique has been proposed to maintain the air-fuel ratio of the air-fuel mixture at a predetermined air-fuel ratio by making the fuel injection amount variable according to the purge flow rate (US Pat. No. 4,641,623).
issue).

Further, in the above-mentioned prior art, there is also disclosed a technique of controlling a purge flow rate purged to an intake system to a predetermined amount when evaporated fuel is adsorbed to a canister by a predetermined amount or more.

[0005]

It is known that it is desirable to supply a large amount of vaporized fuel to the engine at a low temperature start or the like in order to improve the startability of the engine.

However, in the above-mentioned conventional evaporative fuel processing apparatus, since the amount of evaporative fuel adsorbed on the canister is not quantitatively detected, a predetermined amount of evaporative fuel is always secured and purged into the intake system. There was a problem that it was difficult.

The present invention has been made in view of such problems, and provide always the necessary amount of evaporated fuel to ensure the desired required evaporative fuel amount in the engine, thereby especially
An object of the present invention is to provide an evaporative fuel processing apparatus for an internal combustion engine, which can improve the exhaust characteristics at the time of a low temperature start .

[0008]

To achieve the above object, the present invention provides an internal combustion engine having a fuel tank, a canister for adsorbing and storing evaporated fuel, and a purge passage connecting the canister to an intake system. A flow meter interposed in the purge passage immediately downstream of the canister, wherein a detection result of the flow meter is equal to or less than a predetermined flow rate.
To increase the amount of fuel vapor generated from the fuel tank.
Air supply increasing means for increasing the amount of air supplied to the fuel tank
And a fuel tank heating means .

Further, the present invention provides a fuel tank,
Canister for adsorbing and storing a charge, and the canister and intake system
Of an internal combustion engine with a purge passage connecting
In the fuel processor, the pump immediately downstream of the canister is provided.
The flow meter interposed in the storage passage and the detection result of the flow meter
If the flow rate is less than the predetermined flow rate, the steam generated from inside the fuel tank
Evaporative fuel increasing means for increasing the amount of generated fuel, water temperature detecting means for detecting engine cooling water temperature, evaporative fuel supplied to the engine from the canister via the purge passage, and directly from the fuel tank to the engine. Gas-liquid ratio determining means for determining the gas-liquid ratio with the supplied liquid fuel according to the engine cooling water temperature, a purge control valve controlling a purge flow rate passing through the purge passage according to the gas-liquid ratio, Fuel injection amount setting means for setting a fuel injection amount according to the gas-liquid ratio.

[0010]

According to the above construction, the vaporized fuel discharged from the canister is measured by the flow meter, and the measured vaporized fuel is measured.
When the fuel flow is below the specified flow rate, the air supply
An increased amount of air is supplied into the fuel tank and the fuel tank
The heating means heats the fuel tank, which evaporates
Fuel increase is promoted.

Further, the gas-liquid ratio of the fuel supplied to the engine is determined according to the engine cooling water temperature, and the fuel injection amount is set based on the gas-liquid ratio.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is an overall configuration diagram showing an embodiment of an evaporative fuel processing apparatus for an internal combustion engine according to the present invention.

In FIG. 1, reference numeral 1 denotes an internal combustion engine having, for example, four cylinders (hereinafter simply referred to as an "engine"), and an engine speed (NE) sensor around a camshaft or a crankshaft (not shown) of the engine 1 is shown. 2 are installed.

The NE sensor 2 outputs a signal pulse (hereinafter referred to as a "TDC signal pulse") at a predetermined crank angle position every time the crankshaft of the engine 1 rotates 180 degrees.
The DC signal pulse is sent to the electronic control unit
(Referred to as “ECU”) 3.

An engine water temperature (TW) sensor 4 composed of a thermistor or the like is mounted on the cylinder wall of the cylinder block of the engine 1 which is filled with cooling water.
Is converted into an electric signal and supplied to the ECU 3.

An air cleaner 6 is attached to a tip of an intake pipe 5 of the engine 1, a throttle body 7 is provided in the middle of the intake pipe 5, and a throttle valve 7 'is provided therein. . Further, a throttle valve opening (θTH) sensor 8 is connected to the throttle valve 7 ′, and outputs an electric signal corresponding to the opening of the throttle valve 7 ′ and supplies it to the ECU 3.

An air supply pipe 9 and a purge pipe 10 are provided between the air cleaner 6 and the throttle body 7 and between the throttle body 7 and the engine 1, respectively. The pipe 10 is connected to an evaporated fuel processing system 50 described later.

Further, a branch pipe 11 is provided on the downstream side of the purge pipe 10, and an absolute pressure (PBA) sensor 12 is provided at a tip of the branch pipe 11. Also, PBA
The sensor 12 is electrically connected to the ECU 3, and the absolute pressure PBA in the intake pipe 5 detected by the PBA sensor 12 is converted into an electric signal and supplied to the ECU 3.

The fuel injection valve 13 is provided for each cylinder between the engine 1 and the throttle body 7 and slightly upstream of an intake valve (not shown) of the intake pipe 5. Each fuel injection valve 1
3 is connected to a fuel pump 15 via a first fuel supply pipe 14 and is electrically connected to the ECU 3.
The valve opening time of the fuel injection is controlled by the signal from 3.

An exhaust gas concentration sensor (hereinafter referred to as "O2 sensor") 41 is provided in the middle of an exhaust pipe 40 of the engine 1. The O2 sensor 41 detects the oxygen concentration in the exhaust gas and outputs an electric signal thereof to the ECU 3. To supply.

The fuel vapor processing system 50 includes a first fuel tank 17 having a filler cap 16 which is opened when fuel is supplied, and a second fuel tank 17 branched from the first fuel supply pipe 14. A second fuel tank 19 into which the fuel in the first fuel tank 17 is introduced via a supply pipe 18
And a canister 22 in which activated carbon 20 as an adsorbent is built in and a heat retaining section 21 made of a heat storage agent such as zeolite or charcoal trap is provided around the canister 22.
A purge control valve 24 interposed in the middle of the purge pipe 10 connected to the fuel cell, a vaporized fuel flow meter 25 disposed upstream of the purge control valve 24 (immediately downstream of the canister 22), and one end of a purge control valve. A connection pipe 26 branched from between the valve 24 and the vaporized fuel flow meter 25 and having the other end connected to the second fuel tank 19, and a fan 2 interposed in the connection pipe 26.
7 and a first switching valve 28 arranged upstream of the fan 27 for switching the communication path with the air supply pipe 9.
Reference numeral 29 denotes a return pipe, and the first fuel tank 17
The fuel introduced into the second fuel tank 19 through the return pipe 29 is returned to the first fuel tank 17 through the return pipe 29 by overflowing the return pipe 29. Reference numeral 30 denotes a check valve.

Further, the vaporized fuel flow meter 25 has an EC
An output signal is electrically connected to U3, and an output signal detected by the vaporized fuel flow meter 25 is supplied to the ECU3. The purge control valve 24, the fan 27, and the first switching valve 28 are each ECU
3 and is electrically operated, and its operation state is controlled by a signal from the ECU 3. In addition, a heater 31 is provided below the second fuel tank 19, and the heater 31 is electrically connected to the ECU 3, and its operation is controlled by a signal from the ECU 3. Further, a water passage 32 is formed in the heater 31, so that cooling water from a water flow pump (not shown) circulates. 33 is the second
, And is configured to prevent the cooling water from flowing into the heater 31 when the heater 31 is in a non-operating state.

The ECU 3 corrects the voltage level to a predetermined level by shaping the input signal waveforms from the various sensors described above.
An input circuit having a function of converting an analog signal value to a digital signal value, and a central processing circuit (hereinafter, “CPU”)
Storage means for storing a calculation program executed by the CPU, calculation results, and the like, and an output circuit for supplying drive signals to the fuel injection valve 13, the purge control valve 24, the fan 27, and the like. ing.

Further, the ECU 3 (CPU) determines various engine operation states such as a feedback control operation area and an open loop control operation area based on the above-mentioned various engine parameter signals. Based on 1), a fuel injection time TOUT of the fuel injection valve 6 synchronized with the TDC signal pulse is calculated.

TOUT = TiM × KCMDM × KO2 × K1 + K2 (1) where TiM is a basic fuel injection time set according to the engine speed NE and the intake pipe absolute pressure PBA. The TiM map to determine is EC
It is stored in the storage means (ROM) of U3.

KCMDM is a corrected target air-fuel ratio coefficient, which is calculated by multiplying a target air-fuel ratio coefficient KCMD set according to the operating state of the engine by a fuel cooling correction coefficient KETV. Further, the fuel cooling correction coefficient KE
TV is a coefficient for correcting the fuel injection amount in advance in consideration of a change in the intake air amount due to a cooling effect by actually injecting the fuel, and is a target air-fuel ratio coefficient KCM.
It is set according to the value of D.

KO2 is an air-fuel ratio correction coefficient, which is set so that the air-fuel ratio detected by the O2 sensor 41 matches the target air-fuel ratio during the air-fuel ratio feedback control, and corresponds to the engine operating state during the open-loop control. It is set to a predetermined value.

K1 and K2 are correction coefficients and correction variables calculated in accordance with various engine parameter signals, respectively, and optimize various characteristics such as fuel consumption characteristics and acceleration characteristics according to the operating state of the engine for each cylinder. Is set to a predetermined value as shown in FIG.

In the evaporative fuel processing apparatus for an internal combustion engine, when the evaporative fuel detected by the vaporized fuel flow meter 25 is equal to or less than a predetermined value, the second fuel tank 19 is heated by the heater 31, and By driving the fan 27 to supply air to the second fuel tank 19, the increase in the amount of evaporated fuel is promoted.

FIG. 2 is a flowchart showing a control procedure of the evaporative fuel increasing means. This program is executed in synchronism with the ON input of an ignition switch (not shown).

First, in step S1, it is determined whether or not the evaporated fuel amount QV detected by the vaporized fuel flow meter 25 is equal to or less than a predetermined value QVL. If the answer to step S1 is affirmative (YES), an "ON command" is issued to the fan 27 to promote the increase in the amount of fuel vapor (step S2). Further, the heater 31 is operated and the second switching valve is operated. 33 to supply the cooling water into the heater 31 (step S
3). That is, the second fuel tank 19 is heated by the heater 31, and the air is pressure-fed from the intake pipe 5 to the second fuel tank 19 via the air supply pipe 9 and the connection pipe 26,
An increase in the amount of evaporated fuel in the second fuel tank 19 is promoted.

Thereafter, the flow returns to step S1 again, where QV <
It is determined whether or not QVL is established. If the answer is affirmative (YES), steps S2 and S3 described above are repeated, while if the answer to step S1 is negative (NO), steps S4 and S5 are executed and the program ends. I do. That is, when the answer to step S1 is negative (NO), the purge flow rate flowing into the intake pipe 5 via the purge pipe 10 is relatively large, and a desired vaporized fuel can be supplied to the engine even at a low temperature start. Judge,
The fan 27 is turned off (step S21), the heater 31 is turned off, and the switching valve 33 is operated to shut off the flow of the cooling water into the heater 31, thereby ending the program.

FIG. 3 is a flowchart of a fuel injection amount control routine. This program is executed in synchronization with generation of a TDC signal pulse.

First, at step S11, the engine speed NE, the intake pipe absolute pressure PBA and the engine cooling water temperature T are set.
W is detected.

Next, in step S12, equation (1)
The fuel injection time TOUT is calculated based on Next, in step S13, it is determined whether or not the engine is in a complete explosion state. Here, whether the engine is in a complete explosion state is determined by the engine speed N.
Judgment is made based on whether or not E has continued at or above the predetermined rotation speed for a predetermined time or more. If the answer is negative (NO), the process returns to step S11, while the answer is positive (YE
In the case of S), the process proceeds to step S14, in which the V / L map is searched to determine the gas-liquid ratio V / L.

As shown in FIG. 4, the V / L map specifically shows engine cooling water temperatures TW0 to TW6 (for example, 25
C. to 90 ° C.), map values V / L0 to V / L6 (where V / L = 100) are given, and the gas-liquid ratio V / L
L is read out by searching this V / L map or calculated by an interpolation method. In addition, this V / L
Need more evaporative fuel during cold start
Therefore, as the engine cooling water temperature TW decreases,
The gas-liquid ratio V / L is set to be large.

Next, in step S15, the required purge flow rate QP is calculated based on the equation (2).

QP = Q × (V / L) (2) Here, Q is a fuel injection flow rate obtained by converting the fuel injection time TOUT into a flow rate.

Next, in step S16, a corrected fuel injection time TOUTM is calculated based on equation (3).

TOUTM = TOUT−TP (3) where TP is a fuel injection time when the required purge flow rate QP is injected from the fuel injection valve 13.

Next, in step S17, the duty of the purge control valve 24 is controlled based on the required purge flow rate QP.
Further, in step S18, a command to execute a predetermined air-fuel ratio feedback control is issued, and the present program ends.

As described above, in the above-described embodiment, the required amount of vaporized fuel supplied to the engine can always be ensured in accordance with the detection result of the vaporized fuel flow meter, and is determined in accordance with the engine cooling water temperature TW. The purge flow rate and the fuel injection amount are determined according to the gas-liquid ratio.

[0044]

As described above in detail, the present invention relates to an evaporative fuel processing system for an internal combustion engine including a fuel tank, a canister for adsorbing and storing evaporative fuel, and a purge passage connecting the canister and an intake system. And a flow meter interposed in the purge passage immediately downstream of the canister , and air to a fuel tank for increasing the amount of evaporative fuel generated in the fuel tank when a detection result of the flow meter is equal to or less than a predetermined flow rate. Offering
Air supply increasing means for increasing the supply amount, and a fuel tank heating means
Because it has a stage, feel measured by the flow meter
When the converted fuel is below the predetermined flow rate, the air supply
Air is supplied to the fuel tank in
The fuel tank is heated by the heating means,
Increased fuel generation is promoted, so
Supply a large amount of fuel to the engine.
As a result, the exhaust characteristics can be improved.

Also, the present invention provides a fuel tank,
A canister that adsorbs and stores the canister, and the canister and the intake system.
Fuel in an internal combustion engine with a purge passage connecting the
In the material processing apparatus, the par
The flow meter installed in the passage and the detection result of the flow meter
If the flow rate is below a certain level, the evaporation generated from inside the fuel tank
Evaporative fuel increasing means for increasing fuel, a water temperature detecting means for detecting an engine cooling water temperature, evaporative fuel supplied to the engine from the canister via the purge passage, and direct supply to the engine from the fuel tank Gas-liquid ratio determining means for determining a gas-liquid ratio with the liquid fuel to be performed according to the engine cooling water temperature; a purge control valve controlling a purge flow rate passing through the purge passage according to the gas-liquid ratio; The fuel injection amount setting means for setting the fuel injection amount according to the gas-liquid ratio is provided, so that the desired vaporized fuel and the fuel injection from the purge passage are set according to the gas-liquid ratio set according to the desired water temperature. The desired liquid fuel from the valve is supplied to the engine, and high-precision fuel injection
Control can be performed, and the exhaust efficiency at the time of low temperature starting can be improved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing one embodiment of an evaporative fuel processing apparatus for an internal combustion engine according to the present invention.

FIG. 2 is a flowchart showing a control procedure of an evaporative fuel increasing means.

FIG. 3 is a flowchart of a fuel injection amount control routine.

FIG. 4 is a V / L map.

[Explanation of symbols]

Reference Signs List 1 internal combustion engine 3 ECU (evaporative fuel increasing means) 5 intake pipe 17 first fuel tank 19 second fuel tank 22 canister 25 flow meter 27 fan (air supply increasing means)

Claims (2)

(57) [Claims] 1. An evaporative fuel processing apparatus for an internal combustion engine comprising a fuel tank, a canister for adsorbing and storing evaporative fuel, and a purge passage connecting the canister and an intake system, wherein the purge passage immediately downstream of the canister. fuel performing a flow meter which is interposed, the increase of the fuel vapor detection result of the flow meter is generated from the previous <br/> Symbol fuel tank in the case of less than the predetermined flow rate
Means for increasing the amount of air supplied to the tank,
An evaporative fuel processing apparatus for an internal combustion engine, comprising: a fuel tank heating unit . 2. A fuel tank for adsorbing and storing fuel vapor.
A canister and a part connecting the canister and an intake system;
Fuel passage for an internal combustion engine with
And a flow interposed in the purge passage immediately downstream of the canister.
The flow meter and the detection result of the flow meter is less than a predetermined flow rate,
Evaporation to increase the amount of fuel vapor generated from the fuel tank
A fuel temperature increasing means for detecting an engine cooling water temperature ; and a fuel temperature estimating means for evaporating fuel supplied from the canister to the engine via the purge passage and a liquid fuel supplied directly to the engine from the fuel tank. Gas-liquid ratio determining means for determining a gas-liquid ratio according to the engine cooling water temperature, a purge control valve for controlling a purge flow rate passing through the purge passage according to the gas-liquid ratio, and it characterized by comprising a fuel injection quantity setting means for setting a fuel injection amount
Evaporative fuel processing apparatus of internal combustion engine.