JPH10281021A - Evaporated fuel disposal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain evaporated fuel reserved in a canister from being discharged to the atmosphere. SOLUTION: An engine 1 has a direct injection structure in which fuel is directly injected into a combustion chamber 8. An evaporated fuel treating device reserves, in a canister 16, evaporated fuel generated inside a fuel tank 12, and then, introduces the reserved fuel into an intake pipe 2 while adjusting a flow rate by a purge control valve 23 interposed between purge pipelines 22, 24. A projecting pipeline 31 projecting to substantially the center of the intake pipe 2 is connected to an opening formed at the tip of the purge pipeline 24. A throttle 32 is formed at the tip of the projecting pipeline 31. Consequently, the evaporated fuel reserved in the canister 16 can be discharged into the intake pipe 2 owing to a drop in pressure of the throttle 32.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel tank having a canister for temporarily storing fuel vapor generated in a fuel tank and discharging the fuel vapor stored in the canister together with air to an intake passage of an engine. The present invention relates to a processing device.

[0002]

2. Description of the Related Art Conventionally, an automobile engine is provided with a canister for temporarily storing fuel vapor generated in a fuel tank, and the canister is connected to an intake passage (downstream of a throttle valve) of the engine through a purge pipe. Side). Then, the evaporated fuel stored in the canister is discharged to the intake passage of the engine together with the air via the purge pipe according to the differential pressure between the intake negative pressure downstream of the throttle valve and the atmospheric pressure introduced into the canister. Further, a flow control valve formed of, for example, an electromagnetic valve is provided in the middle of the purge pipe, and the purge flow rate is controlled according to the opening degree of the flow control valve.

[0003] As a prior art document of this kind, there is known a "fuel evaporative gas emission suppression device" disclosed in Japanese Patent Publication No. 7-3211. In the device of this publication,
A residual oxygen concentration in the exhaust gas is detected, and a feedback correction amount for correcting the air-fuel ratio is calculated from the detection result. Then, when the deviation amount of the feedback correction amount caused by the evaporated fuel discharged to the engine becomes equal to or more than a predetermined value, the purge flow rate of the evaporated fuel and the air (evaporated gas) from the canister is reduced, and the dense evaporated gas is introduced. This also makes it possible to control the air-fuel ratio to a predetermined value.

[0004]

However, in recent years,
A so-called direct injection engine that directly injects fuel into an engine combustion chamber is embodied. In such a direct injection engine, when realizing stratified combustion in the combustion chamber, a throttle valve (intake throttle valve) is fully opened. . Therefore, under such an operation state, no negative pressure is generated in the intake passage, and no differential pressure is generated between the intake passage and the canister. As a result, the evaporated fuel stored in the canister is not released into the intake passage of the engine, and the evaporated fuel may leak from the canister into the atmosphere. In such a case, even if an attempt is made to perform the purge control of the evaporative gas as described in the above-mentioned publication, there is a possibility that appropriate control cannot be performed. In such a direct injection engine, it is conceivable to control the flow rate control valve to the maximum opening in order to compensate for the shortage of the purge amount, but it is not possible to perform a sufficient fuel purge.

The present invention has been made in view of the above-mentioned problem, and an object of the present invention is to provide an evaporative fuel processing apparatus capable of suppressing the emission of evaporative fuel stored in a canister into the atmosphere. That is.

[0006]

In order to achieve the above object, in the fuel vapor treatment apparatus according to the first aspect, a throttle provided in the intake passage is connected to an opening of the purge pipe to the intake passage. I am trying to do it. In short, during the operation of the engine in a state where the intake negative pressure does not occur in the intake passage, the purge amount of the evaporated fuel due to the intake negative pressure decreases. However, according to the present invention, even when the intake negative pressure does not occur as described above, a pressure drop occurs due to the throttle section, and the evaporated fuel is discharged into the intake passage via the purge pipe. As a result, the emission of evaporated fuel stored in the canister to the atmosphere can be suppressed.

In particular, in the case of the direct injection engine described in claim 2, when realizing stratified combustion in the combustion chamber, the throttle valve is fully opened or the throttle valve is not provided from the beginning. Therefore, there has been a demand for a configuration for increasing the purge amount of the evaporated fuel due to the intake negative pressure. On the other hand, in the present configuration, even for the direct injection engine as described above, the purge of the evaporated fuel can be promoted by the pressure drop by the throttle.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention embodied in a fuel injection control system will be described below with reference to the drawings. In the present embodiment, a gasoline engine (internal combustion engine) mounted on a vehicle is configured as a so-called “direct injection engine” that directly injects fuel into a combustion chamber. The engine is equipped with an evaporative fuel processor, and the evaporative fuel in the fuel tank is temporarily adsorbed to the canister of the evaporative fuel processor, and the adsorbed fuel is discharged to the engine intake system via a purge passage or the like. You. In addition, the present control system is provided with an electronic control unit (hereinafter, referred to as an ECU) that performs fuel injection control, evaporative fuel purge control, and the like.

FIG. 1 is a configuration diagram showing an outline of a fuel injection control system according to the present embodiment. As shown in FIG. 1, an intake pipe 2 and an exhaust pipe 3 are connected to the engine 1. An air cleaner 4 for filtering air is disposed upstream of the intake pipe 2, and air is sucked into the intake pipe 2 via the air cleaner 4. A throttle valve 5 is provided in the intake pipe 2, and the opening of the throttle valve 5 is adjusted by a throttle actuator 6 electronically controlled by the ECU 40. The sucked air is supplied to the combustion chamber 8 above the piston 10 via the throttle valve 5 and the intake valve 7. Then, the exhaust gas burned in the combustion chamber 8 is discharged to the exhaust pipe 3 via the exhaust valve 9.

On the other hand, a fuel pump 13 is connected to a fuel tank 12 containing liquid fuel (gasoline).
The fuel stored in the fuel tank 12 is supplied to the fuel injection valve 14 while being pressurized by the fuel pump 13, and injected into the intake pipe 2 with the opening operation of the fuel injection valve 14. Supplied. Here, the fuel injection valve 14 is disposed on the cylinder head 11 of the engine 1 and has an injection hole 14a.
Project into the combustion chamber 8. That is, the injected fuel is mixed with the intake air in the combustion chamber 8 and burned.

The fuel tank 12 is also connected to a canister 16 through a communication pipe 15. In addition, each part described below, including the fuel tank 12 and the communication pipe 15, constitutes an evaporated fuel processing device of the engine.

That is, in the evaporative fuel processing apparatus, an adsorber 18 made of, for example, activated carbon for adsorbing the evaporative fuel generated in the fuel tank 12 is accommodated in a canister main body 17 which is a main body of the canister 16. I have. With this configuration as the device, the evaporated fuel generated in the fuel tank 12 is taken into the canister body 17 through the communication pipe 15 and is adsorbed by the adsorbent 18 in the canister body 17. Become.

The canister body 17 has an air hole 19 open to the atmosphere. The canister body 17 can take in external air into the canister body 17 through the air hole 19. I have. The air holes 19
Is provided with a canister closing valve 20, which can be closed if necessary. The valve structure of the canister closing valve 20 is shown in FIG. 2 for reference.

In the canister closing valve 20 shown in FIG. 2, when a predetermined voltage (for example, 6 volts or more) is not applied to the coil 20a, the valve body 20b is urged (sucked) by a spring 20c, and Atmospheric hole 19
The conduit 20d that communicates with the opening is in an open state. On the other hand, when a predetermined voltage is applied to the coil 20a, the valve body 20b
Due to the exciting force, the spring 20c moves rightward in the figure against the biasing force of the spring 20c, and the conduit 20d, that is, the air hole 19 is closed. The coil 20
a of the predetermined voltage is applied to the ECU 4 described later.
Controlled through 0.

In the fuel vapor processing apparatus shown in FIG. 1, a hose connecting portion 21 is formed on the other surface of the canister body 17. A purge pipe 22 is attached to the hose connection section 21, and a purge control valve (flow control valve) 23 is connected to the other end of the purge pipe 22. The other end of the purge control valve 23 is further connected to the intake pipe 2 downstream of the throttle valve 5 via a purge pipe 24.

Here, a protruding pipe 31 protruding to a substantially central portion of the intake pipe 2 is connected to an opening of a tip end of the purge pipe 24. At the tip of the protruding pipe 31, that is, substantially at the center of the intake pipe 2, there is formed a throttle part 32 formed in the flow direction of the intake air. FIG. 5 is an enlarged view showing the projecting pipe 31 and the throttle section 32. As shown in the figure, the throttle section 32 gives a sufficient intake resistance in the intake pipe 2 by its throttle shape.

According to such a structure of the fuel vapor treatment apparatus, when the purge control valve 23 is opened, the intake pipe 2 and the canister 16 communicate with each other, and conversely, the control valve 23 is closed. As a result, the intake pipe 2 and the canister 16 are closed. The vaporized fuel adsorbed by the adsorbent 18 in the canister 16 enters the intake pipe 2 based on the negative pressure generated in the intake pipe 2 in the communication state based on the opening of the purge control valve 23. Will be introduced. FIG. 3 shows the valve structure of the purge control valve 23 for reference.

In the purge control valve 23 shown in FIG. 3, a port 23a is a port on the canister side to which the purge pipe 22 is connected, and a port 23b is a port on the intake pipe side to which the purge pipe 24 is connected. Also, the passage 23c
Is a passage connecting these ports 23a and 23b, and its opening degree, that is, the purge flow rate is determined according to the position of the valve body 23d. The valve element 23d is
Normally, the spring 23e is in a position to close the passage 23c as shown in the figure by the urging of the spring 23e.
It moves to the left in the figure against the bias by 3e. The coil 23f is energized by a duty-controlled pulse signal, and the purge flow rate determined based on the position of the valve element 23d is also determined based on the duty ratio of the pulse signal, for example, as shown in FIG. It changes continuously in such a manner as to be performed. Such a purge flow duty control is also executed through the ECU 40 described later.

In the evaporative fuel processing apparatus shown in FIG.
The purge pipe 22 connected to the purge control valve 23
And 24 are formed of a flexible material such as a rubber hose or a nylon hose. The fuel tank 1
The communication pipe 15 connecting the canister 16 and the canister 16 is also partially formed by a rubber hose or the like.

On the other hand, the fuel tank 12 is provided with a relief valve 12a for releasing the pressure in the fuel tank 12 when the pressure exceeds, for example, -40 to 150 mmHg. Therefore, even when a pressure fluctuation occurs in a section from the fuel tank 12 to the canister 16, the fluctuation is always suppressed to be equal to or less than the relief pressure range.

The fuel tank 12 is further provided with a pressure sensor 25 for detecting the pressure in the tank 12. The output of the pressure sensor 25 is used as a monitor signal when adjusting the pressure in the evaporated fuel processing device. It is sufficient that the pressure sensor 25 has a structure capable of withstanding the above-described relief pressure range. In the apparatus of the embodiment, a differential pressure sensor that detects a differential pressure (relative pressure) between the tank internal pressure and the atmospheric pressure is used as the pressure sensor 25.

In addition, in the same system, as shown in FIG. 1, a throttle opening sensor 26 for detecting the opening of the throttle valve 5, a rotation speed sensor 29 for detecting the rotation speed of the engine 1, An intake pipe pressure sensor 30 for detecting the pressure in the intake pipe 2 is provided.
The output of each of these sensors is taken into the ECU 40.

The ECU 40 includes a well-known CPU 41, a ROM 42 in which arithmetic programs for control and the like and data are stored in advance, and a RAM in which control data and the like are temporarily stored.
An input / output circuit 43 connected to the various sensors and actuators is connected to each other via a common bus 45. The ECU 40 drives the fuel injection valve 14 based on the detection signals from the various sensors, and also controls the purge control valve 23 and the canister closing valve 20.
, And collectively executes canister purge control and the like, including fuel injection control.

Here, an outline of the present control system by the ECU 40 will be briefly described. That is, the ECU 40 calculates the basic fuel injection amount to the engine 1 based on the output (rotation speed) NE of the rotation speed sensor 29 and the output (intake pressure) PM of the intake pipe pressure sensor 30, and also calculates the basic fuel injection amount. Then, various corrections such as air-fuel ratio correction are performed on the fuel injection amount to calculate a final fuel injection amount. Then, the fuel injection valve 14 is driven for a time indicated by the final fuel injection amount in synchronization with the intake stroke of the engine 1.

Further, the ECU 40 determines, for example, the vaporized fuel gas concentration (evaporation concentration) in the vaporized fuel processing apparatus based on the feedback correction coefficient FAF based on the air-fuel ratio deviation amount.
And the opening degree information of the purge control valve 23 corresponding to the detected evaporation concentration, that is, the purge flow rate is set.
In executing the purge control, the opening degree of the purge control valve 23 is determined with reference to the opening degree information, and the opening degree of the purge control valve 23 is duty-controlled to match the determined opening degree. Further, in order to control the pressure in the evaporative fuel processing device (in the canister 17) to a predetermined value, the canister closing valve 2
Adjust the opening and closing of 0.

On the other hand, in the direct-injection engine 1, the fuel sucked into the combustion chamber 8 via the intake valve 7 during the steady running operation is subjected to stratified combustion. At this time, since the throttle valve 5 is controlled to be almost fully opened by the throttle actuator 6, the intake negative pressure generated downstream of the throttle valve 5 in the intake pipe 2 becomes very small. However, the throttle section 32
Causes a pressure drop, and this pressure drop causes the canister 1
The vaporized fuel stored in 6 is discharged into the intake pipe 2 via the purge pipes 22 and 24 and the purge control valve 23.

According to the embodiment described above, the following effects can be obtained. In the present embodiment, a projecting pipe 31 projecting into the intake pipe 2
, And a throttle portion 32 is provided in the protruding pipe 31. Therefore, the canister 1
The fuel vapor stored in the fuel tank 6 is released into the intake pipe 2, so that the release of fuel vapor into the atmosphere can be suppressed.

Particularly, in the case of the direct injection engine 1 as in the present embodiment, when realizing stratified combustion in the combustion chamber 8, the throttle valve 5 is fully opened and the intake negative pressure becomes very small. However, even in such a case, the purge of the evaporated fuel can be promoted by the pressure drop.

The embodiment of the present invention can be realized in the following modes other than the above. FIG. 6 is a diagram showing another embodiment in which a throttle section is provided on the downstream side of the throttle valve 5 of the intake pipe 2. In the figure, the tip of the purge pipe 24 is open to the intake pipe 2. The opening is provided with a swash plate 33 that forms an angle θ with the wall surface of the intake pipe 2. In this case, a throttle portion can be formed between the swash plate 33 and the intake pipe wall surface, and when the intake air passes through the throttle portion, the pressure of the intake air drops. Therefore, this pressure drop causes the canister 1
6 can be discharged into the intake pipe 2. Further, if the angle θ of the swash plate 33 can be variably adjusted, the negative pressure of the intake air passing through the throttle unit by the swash plate 33 can be controlled, and the purge flow rate can be adjusted.

In the apparatus according to the above-described embodiment, the canister 16 is controlled when the throttle is fully opened in the direct injection engine.
The fuel vapor stored in the fuel cell is purged, but the fuel vapor may be changed as follows. For example, the invention may be applied to a control system of a direct injection engine in which a throttle valve is omitted. In other words, in the case of a direct injection engine, air-fuel ratio control in the extremely lean region can be realized, and the air-fuel ratio is controlled by the injection amount by the fuel injection valve, so that the adjustment of the intake air amount by the throttle valve and the throttle valve itself are omitted. It is possible to do. Accordingly, although the intake negative pressure naturally becomes very small, the provision of the above-described throttle portion allows the fuel vapor to be properly purged. The control of the intake air amount may be applied to a system in which a VVT device (variable valve timing adjusting device) is used instead of the throttle valve. Also in this case, by omitting the throttle valve,
Although the negative pressure of the intake air is not generated, the purge of the evaporated fuel can be appropriately performed by providing the throttle portion and reducing the pressure of the intake air. Also, when the present invention is applied to an intake port injection type engine that does not have the fuel direct injection structure or the VVT device described above, the purge of the evaporated fuel can be performed properly.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an outline of a fuel injection control system according to an embodiment of the invention.

FIG. 2 is a sectional view showing a valve structure of a canister closing valve.

FIG. 3 is a sectional view showing a valve structure of a purge control valve.

FIG. 4 is a graph showing a duty drive mode of a purge control valve.

FIG. 5 is a diagram showing a configuration of a throttle unit in the intake pipe.

FIG. 6 is a diagram showing a configuration of a throttle unit in an intake pipe according to another embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Intake pipe, 8 ... Combustion chamber, 12 ... Fuel tank, 16 ... Canister, 24 ... Purge piping, 31 ... Projection piping, 32 ... Throttle part, 33 ... Swash plate which comprises a throttle part.

Claims (2)

[Claims] An evaporative fuel processing apparatus for storing evaporative fuel generated in a fuel tank in a canister and discharging the evaporative fuel stored in the canister together with air to an intake passage of the engine through a purge pipe. An evaporative fuel processing apparatus, wherein a throttle provided in the intake passage is connected to an opening of the purge pipe to the intake passage. 2. The evaporative fuel treatment apparatus according to claim 1, wherein the apparatus is applied to a direct injection engine that directly injects fuel into an engine combustion chamber.