JPH062621A - Evaporative fuel processing unit of internal combustion engine - Google Patents

Abstract

PURPOSE:To feed an intake system with a required evaporative fuel quantity by securing the desired quantity of this evaporative fuel at all times. CONSTITUTION:A flow meter 25 is installed in just the downstream of a canister 22, and when evaporative fuel detected by this flow meter 25 is less than the specified value, increment promotion for this evaporative fuel is always performed. In addition, when the evaporative fuel is purged to an intake system, a purge flow rate is controlled according to a specified gas-liquid ratio.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an evaporated fuel processing apparatus for an internal combustion engine which processes evaporated fuel generated from a fuel tank.

[0002]

2. Description of the Related Art Conventionally, as an evaporated fuel processing apparatus for an internal combustion engine in which the evaporated fuel generated in a fuel tank is restrained from being discharged into the atmosphere, the evaporated fuel generated in the fuel tank is converted into activated carbon in a canister. There is known a system of once adsorbing and then purging (releasing) this to the intake system.

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

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

[0005]

By the way, it is known that it is desirable to supply a large amount of vaporized fuel to the engine in order to improve the startability of the engine at the time of low temperature starting and the like.

However, in the above-described conventional evaporated fuel processing apparatus, since the amount of evaporated fuel adsorbed in the canister is not quantitatively detected, a predetermined amount of evaporated 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 the above problems, and it is possible to always secure a desired required amount of evaporated fuel and supply the required amount of evaporated fuel to the engine. An object is to provide a processing device.

[0008]

To achieve the above object, the present invention provides an internal combustion engine including a fuel tank, a canister that adsorbs and stores evaporated fuel, and a purge passage that connects the canister and an intake system. In the evaporative fuel processing apparatus, the flowmeter installed in the purge passage immediately downstream of the canister, and evaporative fuel increasing means for increasing the amount of evaporative fuel generated in the fuel tank according to the detection result of the flowmeter. It is characterized by having and.

Further, according to the present invention, a water temperature detecting means for detecting an engine cooling water temperature, an evaporated fuel supplied from the canister to the engine through the purge passage, and a liquid fuel directly supplied to the engine from the fuel tank are provided. Gas-liquid ratio determining means for determining the gas-liquid ratio according to the engine cooling water temperature, a purge control valve for controlling the purge flow rate passing through the purge passage according to the gas-liquid ratio, and a gas-liquid ratio And a fuel injection amount setting means for setting a fuel injection amount.

[0010]

According to the above construction, the vaporized fuel discharged from the canister is measured by the flow meter, and the increase of the vaporized fuel is controlled according to the vaporized fuel.

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 in detail below with reference to the drawings.

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

In the figure, reference numeral 1 denotes an internal combustion engine having four cylinders (hereinafter, simply referred to as "engine"), and an engine speed (NE) sensor is provided around a cam shaft or crank shaft (not shown) of the engine 1. 2 is attached.

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

An engine water temperature (TW) sensor 4 composed of a thermistor or the like is attached to the cylinder peripheral wall filled with the cooling water of the cylinder block of the engine 1, and the TW sensor 4 is attached.
The engine cooling water temperature TW detected by is converted into an electric signal and supplied to the ECU 3.

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

An air supply pipe 9 and a purge pipe 10 are provided so as to branch 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 arranged at the 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 the intake valve (not shown) in the intake pipe 5. Each fuel injection valve 1
3 is connected to the fuel pump 15 via the first fuel supply pipe 14 and is electrically connected to the ECU 3.
The valve opening time of fuel injection is controlled by the signal from 3.

An exhaust gas concentration sensor (hereinafter referred to as "O2 sensor") 41 is arranged in the middle of the exhaust pipe 40 of the engine 1, and the O2 sensor 41 detects the oxygen concentration in the exhaust gas and outputs its electric signal to the ECU3. Supply to.

Thus, the fuel vapor processing system 50 includes the first fuel tank 17 having the filler cap 16 that is opened when the fuel is supplied, and the second fuel 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.
A canister 22 having a built-in activated carbon 20 as an adsorbent and a heat-retaining portion 21 made of a heat storage agent such as zeolite or a charcoal trap, and 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 (directly downstream of the canister 22), and one end of purge control A connecting pipe 26 branched from between the valve 24 and the vaporized fuel flowmeter 25 and having the other end connected to the second fuel tank 19, and a fan 2 interposed in the connecting pipe 26.
7 and a first switching valve 28 which is arranged on the upstream side of the fan 27 and switches the communication path with the air supply pipe 9.
Reference numeral 29 is a return pipe, and the first fuel tank 17
The fuel introduced from the above into the second fuel tank 19 is returned to the first fuel tank 17 through the return pipe 29 by overflowing the return pipe 29. 30 is a check valve.

Further, the vaporized fuel flow meter 25 is an EC
The output signal electrically connected to U3 and detected by the vaporized fuel flow meter 25 is supplied to the ECU 3. The purge control valve 24, the fan 27, and the first switching valve 28 are ECUs, respectively.
3 is electrically connected to the ECU 3, and its operating state is controlled by a signal from the ECU 3. Further, a heater 31 is arranged below the second fuel tank 19, 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
The switching valve is configured to prevent cooling water from flowing into the heater 31 when the heater 31 is in a non-operating state.

The ECU 3 shapes the input signal waveforms from the various sensors described above to correct the voltage level to a predetermined level,
An input circuit having a function of converting an analog signal value into a digital signal value, and a central processing circuit (hereinafter referred to as "CPU").
And a storage means for storing a calculation program executed by the CPU, a calculation result and the like, and an output circuit for supplying a drive signal to the fuel injection valve 13, the purge control valve 24, the fan 27 and the like. ing.

Further, the ECU 3 (CPU) discriminates various engine operating states such as a feedback control operating region and an open loop control operating region based on the above-mentioned various engine parameter signals, and an equation ( Based on 1), the 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) Here, TiM is a basic fuel injection time set according to the engine speed NE and the intake pipe absolute pressure PBA. EC is the TiM map for determining
It is stored in the storage means (ROM) of U3.

KCMDM is a corrected target air-fuel ratio coefficient, and is calculated by multiplying the target air-fuel ratio coefficient KCMD set according to the operating state of the engine by the 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 the fact that the intake air amount changes due to the cooling effect by actually injecting the fuel, and the 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 coincides with 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 according to 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.

In the vaporized fuel processing apparatus for an internal combustion engine, when the vaporized fuel detected by the vaporized fuel flow meter 25 is below a predetermined value, the heater 31 heats the second fuel tank 19 and By driving the fan 27 to supply air to the second fuel tank 19, the amount of evaporated fuel can be increased.

FIG. 2 is a flow chart showing the control procedure of the evaporated fuel increasing means, and this program is executed in synchronization with the on-input of an ignition switch (not shown).

First, in step S1, it is determined whether the vaporized fuel amount QV detected by the vaporized fuel flow meter 25 is less than or equal to a predetermined value QVL. Then, when the answer to step S1 is affirmative (YES), an "ON command" is issued to the fan 27 to promote the increase of the evaporated fuel (step S2), and the heater 31 is operated and the second switching valve is activated. 33 is operated to supply the cooling water into the heater 31 (step S
3). That is, the heater 31 heats the second fuel tank 19, and air is pressure-fed from the intake pipe 5 to the second fuel tank 19 through the air supply pipe 9 and the connecting pipe 26.
The increase in the amount of evaporated fuel in the second fuel tank 19 is promoted.

Then, the process returns to step S1 again, and QV <
It is determined whether QVL is established. When the answer is affirmative (YES), the steps S2 and S3 described above are repeated, while when the answer at step S1 is negative (NO), the steps S4 and S5 are executed to end the program. To 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 the desired vaporized fuel can be supplied to the engine even at low temperature startup. Judge,
The fan 27 is set to the "off state" (step S21), the heater 31 is further set to the off state, and the switching valve 33 is operated to block the inflow of the cooling water into the heater 31, and the present program is terminated.

FIG. 3 is a flow chart of the fuel injection amount control routine, and this program is executed in synchronization with the generation of the TDC signal pulse.

First, at step S11, the engine speed NE, the absolute pressure PBA in the intake pipe, and the engine cooling water temperature T
Detect W.

Then, 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 the complete explosion state. Here, whether or not the engine is in a complete explosion state depends on the engine speed N.
It is determined by whether or not E has continued to be at a predetermined rotation speed or more for a predetermined time or more. If the answer is negative (NO), the process returns to step S11, while the answer is affirmative (YE).
In the case of S), the process proceeds to step S14, and the V / L map is searched to determine the gas-liquid ratio V / L.

Specifically, the V / L map is, as shown in FIG. 4, engine cooling water temperatures TW0 to TW6 (for example, 25).
Map value V / L0 to V / L6 (provided that V / L = 100) is given for (C to 90 ° C.)
L is read by searching this V / L map, or is calculated by an interpolation method.

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 the fuel injection flow rate obtained by converting the fuel injection time TOUT into the flow rate.

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

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

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

As described above, in the above embodiment, the required amount of the vaporized fuel supplied to the engine can be always ensured according to the detection result of the vaporized fuel flow meter, and it is determined according to 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 provides an evaporated fuel processing apparatus for an internal combustion engine, which includes a fuel tank, a canister for adsorbing and storing evaporated fuel, and a purge passage connecting the canister and an intake system. In the above, there is provided a flow meter installed in the purge passage immediately downstream of the canister, and an evaporated fuel increasing means for increasing the amount of evaporated fuel generated in the fuel tank according to a detection result of the flow meter. Therefore, it becomes possible to always supply the required evaporated fuel to the intake system according to the detection result of the flow meter, and it is possible to supply a large amount of evaporated fuel to the engine at the time of low temperature starting and the like.

Further, the gas-liquid ratio of the water temperature detecting means for detecting the engine cooling water temperature, the vaporized fuel supplied from the canister to the engine through the purge passage, and the liquid fuel directly supplied from the fuel tank to the engine is determined. A gas-liquid ratio determining unit that determines according to the engine cooling water temperature,
Since a purge control valve for controlling a purge flow rate passing through the purge passage according to the gas-liquid ratio and a fuel injection amount setting means for setting a fuel injection amount according to the gas-liquid ratio are provided, a desired amount can be obtained. The desired vaporized fuel from the purge passage and the desired liquid fuel from the fuel injection valve are supplied to the engine in accordance with the gas-liquid ratio set according to the water temperature, and the exhaust efficiency at the time of cold start can be improved. it can.

[Brief description of drawings]

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

FIG. 2 is a flowchart showing a control procedure of an evaporated 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]

 1 Internal Combustion Engine 3 ECU (Evaporative Fuel Increasing Means) 5 Intake Pipe 17 Fuel Tank 22 Canister 25 Flow Meter

Claims (2)

[Claims] 1. An evaporative fuel treatment apparatus for an internal combustion engine comprising a fuel tank, a canister for adsorbing and storing evaporated fuel, and a purge passage connecting the canister and an intake system, wherein the purge passage immediately downstream of the canister. And an evaporative fuel increasing means for increasing the amount of evaporative fuel generated from the inside of the fuel tank according to the detection result of the flow meter. Fuel processor. 2. A gas-liquid ratio of a water temperature detecting means for detecting an engine cooling water temperature, an evaporated fuel supplied from the canister to the engine through the purge passage, and a liquid fuel directly supplied to the engine from the fuel tank. Is determined 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 a fuel injection amount according to the gas-liquid ratio. 2. An evaporative fuel treatment system for an internal combustion engine according to claim 1, further comprising a fuel injection amount setting means for setting.