JPH062620A - Evaporative fuel processing unit of internal combustion engine - Google Patents

Abstract

PURPOSE:To make a large quantity of carbureted fuel generable by interposing a second fuel tank between a canister and a first fuel tank, and increasing the quantity of evaporative fuel being produced out of the second fuel tank. CONSTITUTION:This processing unit is provided with a first fuel tank 17 storing fuel to be fed to an internal combustion engine 1, and a canister 22 being made connectible to this first fuel tank 17 and adsorptively storing evaporative fuel. In addition, it is provided with a throttle valve 7' installed in the midway of an intake pipe 5 connected to an engine 1, and a purge passage 10 connecting this intake pipe 5 at the downstream side of this throttle valve 7' and the canister 22. Moreover, a second fuel tank 19 is interposed between the canister 22 and the first fuel tank 17, while there is provided a evaporative fuel increment means 3 which increases the quantity of evaporative fuel to be generated out of the second fuel tank 19. With this constitution, a large quantity of carbureted fuel, namely, evaporative fuel is made possible to be adsorbed to the canister 22.

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, at the time of cold start, it is desirable to supply a large amount of vaporized fuel to the engine in order to improve the startability of the engine, and the fuel adsorbed in the canister is heated to accelerate vaporization of the fuel. Techniques have already been proposed (for example, Japanese Utility Model Laid-Open No. 3-97560).

[0004]

However, in the above-mentioned conventional technique, since only the fuel amount corresponding to the evaporated fuel generated from the fuel tank is heated, a large amount of vaporized fuel (evaporated fuel) can be generated. Therefore, there is a problem in that the desired vaporized fuel required at the time of cold start or the like cannot be supplied to the engine.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an evaporated fuel processing apparatus for an internal combustion engine capable of producing a large amount of vaporized fuel.

[0006]

To achieve the above object, the present invention provides a first fuel tank for storing fuel supplied to an internal combustion engine, and a first fuel tank which is communicable with the first fuel tank and evaporates. Internal combustion engine including a canister for adsorbing and storing fuel, a throttle valve interposed in the middle of an intake pipe connected to the engine, and a purge passage connecting the intake pipe downstream of the throttle valve and the canister In the evaporative fuel treatment apparatus, the second fuel tank is interposed between the canister and the first fuel tank, and the evaporative fuel increasing means for increasing the evaporative fuel generated from the second fuel tank. It is characterized by having.

Specifically, a flow meter interposed in the purge passage, a connecting pipe branched from the purge passage on the downstream side of the flow meter and connected to the second fuel tank, and the throttle. An air supply pipe connecting the intake pipe on the valve upstream side and the connection pipe, and a fan interposed in the connection pipe on the downstream side of the air supply pipe, wherein the vaporized fuel increasing means includes the flowmeter. An air supply unit that drives the fan when the detected purge flow rate is less than or equal to a predetermined value and supplies air to the second fuel tank through the air supply pipe and the connection pipe. It has a feature.

An air supply pipe is provided which allows the upstream side of the throttle valve and the second fuel tank to communicate with each other,
It is also preferable that the evaporated fuel amount increasing means includes an air supply means for supplying air to the second fuel tank according to a pressure difference between the upstream side and the downstream side of the throttle valve.

Further preferably, the evaporative fuel increasing means has a heating means for heating the second fuel tank.

[0010]

According to the above structure, the evaporated fuel increased by the evaporated fuel increasing means is conveyed from the second fuel tank and adsorbed and stored in the canister, and a large amount of evaporated fuel can be purged from the canister to the intake pipe. Becomes

Further, specifically, the promotion of increasing the amount of evaporated fuel is executed when the purge flow rate is below a predetermined value. Alternatively, the supply of air to the second fuel tank according to the pressure difference between the upstream side and the downstream side of the throttle valve promotes the increase in the amount of evaporated fuel.

Further, by heating the second fuel tank, the amount of evaporated fuel can be increased.

[0013]

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 a "TDC signal pulse") at a predetermined crank angle position every 180 ° 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 including a thermistor or the like is attached to the cylinder peripheral wall filled with 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.

Further, 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.

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.

In the vaporized fuel processing apparatus for the internal combustion engine, however, 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 equal to or less than 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.

After that, 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.

As described above, in the above embodiment, the second fuel tank 19 is detected according to the detection result of the vaporized fuel flow meter 25.
Since the amount of the evaporated fuel generated from the fuel injection valve 13 is increased, the increase of the evaporated fuel can be promoted without adversely affecting the amount of fuel injected from the fuel injection valve 13.

FIG. 3 is a diagram showing another embodiment,
Instead of forcibly sending air to the second fuel tank with a fan, air is supplied to the second fuel tank 19 in accordance with the pressure difference between the upstream side and the downstream side of the throttle valve 7 '. is there. That is, at the time of starting when a large amount of vaporized fuel is required, the throttle valve opening θTH is small, and a large amount of air is introduced into the second fuel tank 19 to promote the generation of evaporated fuel. The amount of air introduced into the second fuel tank 19 is reduced, and the generation of excess evaporated fuel is suppressed.

[0031]

As described above in detail, the present invention includes the first fuel tank for storing the fuel supplied to the internal combustion engine,
A canister that is capable of communicating with the first fuel tank to adsorb and store evaporated fuel, a throttle valve that is interposed in the middle of an intake pipe connected to the engine, an intake pipe downstream of the throttle valve, and In a fuel vapor treatment system for an internal combustion engine, comprising: a purge passage connecting with a canister; a second fuel tank is interposed between the canister and the first fuel tank; Since the evaporated fuel increasing means for increasing the amount of evaporated fuel generated from the tank is provided, a large amount of vaporized fuel (evaporated fuel) can be adsorbed to the canister.

Specifically, a flow meter interposed in the purge passage, a connecting pipe branched from the purge passage on the downstream side of the flow meter and connected to the second fuel tank, and the throttle. An air supply pipe connecting the intake pipe on the valve upstream side and the connection pipe, and a fan interposed in the connection pipe on the downstream side of the air supply pipe, wherein the vaporized fuel increasing means includes the flowmeter. Since the fan is driven when the detected purge flow rate is less than or equal to a predetermined value, and the air supply means for supplying air to the second fuel tank via the air supply pipe and the connection pipe is provided. A large amount of vaporized fuel is generated from the second fuel tank and is adsorbed and stored in the canister, so that the desired vaporized fuel can be stored in the canister even at low temperature starting or restarting the engine, which requires a large amount of vaporized fuel. To secure Can, it is possible to improve the exhaust efficiency of HC in the exhaust gas after the start.

An air supply pipe is provided which allows the upstream side of the throttle valve and the second fuel tank to communicate with each other,
The throttle valve opening is also small because the vaporized fuel amount increasing means includes air supplying means for supplying air to the second fuel tank according to the pressure difference between the upstream side and the downstream side of the throttle valve. Large amount of air during cold start
Is supplied to the fuel tank of
Since the amount of vaporized fuel adsorbed on the canister increases, it becomes possible to improve the exhaust efficiency of HC in the exhaust gas after starting.

Further, the evaporated fuel increasing means is the second
Since it has the heating means for heating the fuel tank, the fuel supplied to the fuel supply system is not directly warmed and the fuel injection amount does not fluctuate with respect to the desired value.

[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 an overall configuration diagram of another embodiment.

[Explanation of symbols]

 1 Internal Combustion Engine 3 ECU (Evaporative Fuel Increasing Means, Air Supply Means) 5 Intake Pipe 7'Throttle Valve 17 First Fuel Tank 19 Second Fuel Tank 22 Canister 25 Flow Meter 27 Fan 31 Heater (Heating Means)

Claims (4)

[Claims] 1. A first fuel tank for storing fuel to be supplied to an internal combustion engine, a canister capable of communicating with the first fuel tank to adsorb and store evaporated fuel, and an intake air connected to the engine. In a vaporized fuel processing apparatus for an internal combustion engine, comprising: a throttle valve provided in the middle of a pipe; and a purge passage connecting an intake pipe downstream of the throttle valve and the canister, a second fuel tank is provided with the canister. And the first fuel tank, and an evaporative fuel increasing means for increasing the amount of evaporative fuel generated from the second fuel tank is provided. apparatus. 2. A flow meter provided in the purge passage,
A connecting pipe branched from the purge passage downstream of the flow meter and connected to the second fuel tank; an air supply pipe connecting the intake pipe upstream of the throttle valve and the connecting pipe; A fan provided in the connection pipe on the downstream side of the air supply pipe, the evaporated fuel increasing means drives the fan when the purge flow rate detected by the flow meter is equal to or less than a predetermined value,
2. The evaporated fuel processing apparatus for an internal combustion engine according to claim 1, further comprising air supply means for supplying air to the second fuel tank via the air supply pipe and the connection pipe. 3. An air supply pipe is provided which allows the upstream side of the throttle valve and the second fuel tank to communicate with each other, and the vaporized fuel amount increasing means is provided with a differential pressure between the upstream side and the downstream side of the throttle valve. 2. An evaporative fuel treatment system for an internal combustion engine according to claim 1, further comprising air supply means for supplying air to the second fuel tank in accordance with the above. 4. The evaporation of an internal combustion engine according to claim 1, wherein the evaporative fuel increasing means has a heating means for heating the second fuel tank. Fuel processor.