JP2007239523A - Evaporated fuel supply device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To supply a sufficient amount of evaporated fuel to an intake system in engine start. <P>SOLUTION: A sub-tank 7 with a smaller capacity than a fuel tank 6 is provided besides the fuel tank 6. In engine operation or engine stop, fuel in the sub tank 7 is heated and evaporated by a heating and evaporating device 15, and the evaporated fuel is adsorbed by a canister 12. The evaporated fuel in the canister 12 is taken into the intake system 2 by opening a purge valve 13, at the start of the engine. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an evaporated fuel supply device for an internal combustion engine for improving emission at start-up.

In the internal combustion engine, the evaporated fuel generated in the fuel tank while the engine is stopped is guided to the canister and temporarily adsorbed, and the evaporated fuel adsorbed on the canister is supplied to the engine intake system at the time of starting the engine and thereafter. .
Further, in the apparatus described in Patent Document 1, a tank heater for heating is provided below the fuel tank so that the evaporated fuel can be used positively even when there is almost no evaporated fuel in the canister when the engine is started. The evaporative fuel can be used by actively generating the evaporative fuel by operating the tank heater at the start.
JP-A-9-242619

The above device is a device that intentionally and actively generates a readily volatile fuel component. However, in the configuration in which the fuel tank is directly heated, it takes a considerable amount of power and time to generate the evaporated fuel. In addition to being economical, the fuel supply is delayed at the time of starting, and the supply of the evaporated fuel is delayed.
The present invention has been made in view of such a situation, and an object of the present invention is to be able to supply a necessary and sufficient amount of evaporated fuel when starting an engine.

  Therefore, in the present invention, a sub-tank having a smaller capacity is provided separately from the fuel tank, and the fuel in the sub-tank is evaporated and adsorbed to the canister when the engine is operating or when the engine is stopped.

  According to the present invention, the provision of the dedicated sub tank makes it easy and quick to generate the evaporated fuel. By generating the evaporated fuel and adsorbing it to the canister by the time of starting the engine, a sufficient amount can be obtained at the time of starting the engine. Therefore, it is possible to obtain a desired start-up emission improvement effect.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a system diagram showing a first embodiment of the present invention.
An intake system (intake pipe) 2 of an engine (internal combustion engine) 1 is provided with a throttle valve 3 at an upstream collecting portion, and a fuel injection valve 4 for each cylinder in a branch pipe to each cylinder on the downstream side. Is provided. Reference numeral 5 denotes an exhaust system (exhaust pipe).

  The fuel injection valve 4 is opened by an injection pulse signal output in synchronization with engine rotation from an engine control unit (ECU) (not shown), and injects and supplies fuel adjusted to a predetermined pressure. The fuel in the fuel tank 6 is supplied to the fuel injection valve 4 by being pumped by a fuel pump (not shown) and regulated by a pressure regulator (not shown).

Here, separately from the fuel tank 6, a sub-tank (vaporization fuel tank) 7 having a smaller capacity is provided. The capacity of the sub-tank 7 is set to a size capable of storing an amount of fuel necessary and sufficient to generate evaporated fuel to be used at start-up.
The fuel tank 6 and the sub tank 7 are connected by a fuel passage 8, and a part of the fuel in the fuel tank 6 is supplied to the sub tank 7 by a fuel pump 9 provided in the fuel passage 8. The fuel pump 9 is driven so that a certain amount of fuel is held in the sub tank 7.

A fuel passage 11 is led out from the sub tank 7 via a supply valve (check valve) 10. This fuel passage 11 is connected to a canister 12.
The canister 12 is filled with an HC adsorbent such as activated carbon, and can temporarily adsorb evaporated fuel introduced from the fuel passage 11.
A purge passage 14 is led out from the canister 12 via a purge valve (check valve) 13. The purge passage 14 opens into the intake pipe 2 downstream of the throttle valve 3. Note that the diameter of the purge passage 14 is set so that mixing of the intake air and the evaporated fuel becomes a startable ratio. If necessary, a fresh air inlet (atmospheric opening) is formed in the canister 12.

The fuel passage 11 between the sub tank 7 and the canister 12 is provided with a heating evaporator 15 so as to cover it.
The heating evaporation device 15 is constituted by, for example, a device that circulates engine cooling water around the fuel passage 11 (heat exchanger with cooling water). The fuel inside is heated to produce evaporated fuel. Alternatively, it is configured by an electric heater and energized at an appropriate timing during engine operation or when the engine is stopped, thereby heating the fuel in the fuel passage 11 and generating evaporated fuel.

Next, the operation will be described.
The fuel pump 9 is driven so that a certain amount of fuel is held in the sub tank 7.
At an appropriate timing during engine operation (after warm-up) or when the engine is stopped, the supply valve 10 is opened, and the fuel in the sub tank 7 is led to the fuel passage 11.
A heating evaporator 15 is disposed in the fuel passage 11, and evaporative fuel is generated by receiving heat exchange with engine cooling water or electric heating by a heater.

The produced evaporated fuel reaches the canister 12 and is adsorbed therein.
Therefore, a necessary and sufficient amount of evaporated fuel can be adsorbed to the canister 12 in preparation for the next start of the engine during engine operation and / or when the engine is stopped. The supply valve 10 is closed when a desired amount of evaporated fuel is generated and adsorbed by the canister 12.
When starting the engine, the purge valve 13 is opened. Then, as a result of the negative suction pressure of the engine 1 acting on the canister 12, the evaporated fuel adsorbed on the canister 12 is desorbed, and the desorbed evaporated fuel is sucked into the intake pipe 2 through the purge passage 14. The Therefore, it can start using evaporative fuel, can improve startability, and can obtain the emission improvement effect at the time of start. Depending on the setting, for example, when there is little evaporated fuel, fuel is injected from the fuel injection valve 4.

  According to the present embodiment, the sub-tank 7 having a smaller capacity is provided separately from the fuel tank 6 and the fuel in the sub-tank 7 is evaporated and adsorbed to the canister 12 when the engine is operating or when the engine is stopped. Is easily and quickly generated, and by generating evaporated fuel and adsorbing it to the canister 12 before starting the engine, a sufficient amount of evaporated fuel can be used when starting the engine. Obtainable.

Further, according to the present embodiment, by providing the heating evaporation device 15 that heats and evaporates the fuel in the sub-tank 7, the evaporated fuel can be generated more actively, and even when the operation time is short, the starting evaporation Fuel can be obtained reliably.
When the heating evaporator 15 is one that is heated by engine cooling water, it can be economically implemented without power consumption.

When the heating evaporator 15 is one that is heated by an electric heater, the heating time can be set freely and management is facilitated.
Further, according to the present embodiment, by providing the heating and evaporation device 15 in the fuel passage 11 from the sub tank 7 to the canister 12, it is possible to efficiently heat and evaporate the evaporated fuel compared to the case where the entire sub tank 7 is heated. 12 can be adsorbed immediately.

Further, according to the present embodiment, the sub tank 7 is configured such that the fuel in the fuel tank 6 is supplied by the fuel pump 9 so that a fixed amount of fuel is held, so that the sub tank 7 always evaporates. The fuel for use can be secured.
FIG. 2 shows a second embodiment of the present invention, which will be described.
In the second embodiment, the heating evaporator 16 is provided so as to heat the sub tank 7 directly.

  The heating evaporation device 16 is constituted by, for example, a device that circulates engine cooling water around the sub tank 7 (heat exchanger with cooling water). The fuel is heated to produce evaporative fuel. Alternatively, it is configured by an electric heater and energized at an appropriate timing during engine operation or when the engine is stopped, thereby heating the fuel in the sub tank 7 and generating evaporated fuel.

  Therefore, in the case of the second embodiment, during the engine operation (after warming up) and / or when the engine is stopped, the sub-tank receives heat exchange with the engine cooling water or electric heating by the heater by the heating evaporation device 16. Evaporated fuel is generated in the fuel tank 7. The produced fuel vapor is introduced into the canister 12 through the fuel passage 11 and adsorbed thereto by opening the supply valve 10 at an appropriate timing.

In particular, according to the second embodiment, since the heating evaporation device 16 is provided so as to directly heat the sub tank 7, the generation of the evaporated fuel is ensured and can be sent to the canister 12 side after the generation.
FIG. 3 shows a third embodiment of the present invention, which will be described.
In the third embodiment, the opening of the purge passage 14 to the intake pipe 2 has a venturi structure. That is, a venturi portion 17 is formed upstream of the throttle valve 3 of the intake system 2 and a purge passage 14 is opened here.

In particular, according to the third embodiment, the mixing ratio of the intake air and the evaporated fuel can be kept constant. Moreover, in 3rd Embodiment, although the purge valve (13) was abbreviate | omitted, you may make it attach.
In the first to third embodiments described above, the heating evaporators 15 and 16 are provided for the sub-tank 7. However, the sub-tank 7 has a small capacity and easily rises in temperature due to the heat of the engine. When evaporative fuel is generated inside during operation, the heating and evaporating devices 15 and 16 can be omitted.

  Further, a pressure sensor, a temperature sensor, or the like may be attached to the canister 12 to manage the fuel concentration and control the supply amount to the intake system.

1 is a system diagram showing a first embodiment of the present invention. System diagram showing a second embodiment of the present invention System diagram showing a third embodiment of the present invention.

Explanation of symbols

1 Engine 2 Intake system (intake pipe)
3 Throttle valve 4 Fuel injection valve 5 Exhaust system (exhaust pipe)
6 Fuel tank 7 Sub tank (Vaporization fuel tank)
8 Fuel Passage 9 Fuel Pump 10 Supply Valve 11 Fuel Passage 12 Canister 13 Purge Valve 14 Purge Passage 15 Heating Evaporator (Heat Exchanger with Cooling Water or Electric Heater)
16 Heating evaporator (heat exchanger with cooling water or electric heater)
17 Venturi Club

Claims (7)

In an evaporative fuel supply apparatus for an internal combustion engine that includes a canister that adsorbs evaporative fuel and supplies the evaporative fuel adsorbed on the canister to the engine intake system at least when the engine is started.
An evaporative fuel supply device for an internal combustion engine, characterized in that a sub-tank having a smaller capacity is provided separately from the fuel tank, and the fuel in the sub-tank is evaporated and adsorbed to the canister when the engine is operating or stopped. .   2. An evaporative fuel supply apparatus for an internal combustion engine according to claim 1, further comprising a heating evaporating device for heating and evaporating the fuel in the sub tank.   3. The evaporative fuel supply apparatus for an internal combustion engine according to claim 2, wherein the heating and evaporating apparatus is heated by engine cooling water.   The evaporative fuel supply device for an internal combustion engine according to claim 2, wherein the heating evaporation device is heated by an electric heater.   5. The evaporated fuel supply device for an internal combustion engine according to claim 2, wherein the heating evaporation device is provided in a fuel passage from the sub tank to the canister. 6.   The evaporative fuel supply apparatus for an internal combustion engine according to any one of claims 2 to 4, wherein the heating and evaporating apparatus is provided so as to directly heat the sub tank.   The internal combustion engine according to any one of claims 1 to 6, wherein the fuel in the fuel tank is supplied to the sub tank by a fuel pump so that a fixed amount of fuel is held. Evaporative fuel supply device.

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