JPH0571430A - Evaporated fuel processor of internal combustion engine - Google Patents

Abstract

(57) [Summary] [Purpose] Evaporative fuel is supplied to the intake passage even if negative pressure is not generated in the intake passage. [Composition] During low engine load operation, the air-fuel mixture that occupies a part of the combustion chamber is burned under excess air, and when the engine load increases, a uniform air-fuel mixture is formed. The air intake 21 and the purge port 19 of the charcoal canister 12 are opened in the intake duct 4 where substantially the same static pressure is generated, and the direction of the opening of the air intake 21 is set to the upstream direction of the intake air flow. Air containing evaporated fuel is purged from the purge port 19 into the intake duct 4 by the differential pressure between the dynamic pressure of the intake air flow acting on the air intake port 21 and the static pressure acting on the purge port 19.

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.

[0002]

2. Description of the Related Art During low engine load operation, an air-fuel mixture is formed in a limited region of a combustion chamber, and the other region is filled with air, and the air-fuel mixture is ignited by a spark plug. A cylinder injection internal combustion engine is known in which the entire combustion chamber is filled with air-fuel mixture during operation (see Japanese Patent Laid-Open No. 2-169834). In this internal combustion engine, the throttle valve is fully opened in most operating states except during extremely low load operation, so that the drive loss of the engine due to the pumping action can be greatly reduced.

[0003]

In an ordinary internal combustion engine, for example, vaporized fuel generated in a fuel tank is once adsorbed by activated carbon in a charcoal canister, and air taken in from an air intake is supplied into the charcoal canister. Thus, the evaporated fuel adsorbed on the activated carbon is desorbed and the air containing the evaporated fuel is purged from the purge port into the engine intake passage. In this case, the air intake is normally open to the atmosphere, and the air containing evaporated fuel is purged from the purge port into the intake passage due to the pressure difference between the negative pressure in the intake passage acting on the purge port and the atmospheric pressure. It However, when the throttle valve is fully opened in most operating states as in the above-mentioned internal combustion engine, negative pressure does not occur in the intake passage in most operating states, and therefore, it occurs in the intake passage as described above. As long as the negative pressure is used to perform the purging action, there is a problem that the air containing the evaporated fuel cannot be purged into the intake passage in most operating conditions.

[0004]

In order to solve the above problems, according to the present invention, the air taken in from the air intake is supplied into the charcoal canister, and then the air containing the evaporated fuel is supplied from the purge port. In an internal combustion engine in which the engine intake passage is purged, the air intake port and the purge port are opened in the engine intake passage where almost the same static pressure is generated, and the direction of the opening of the air intake port It is set in the upstream direction so that the air containing evaporated fuel is purged from the purge port into the engine intake passage by the differential pressure between the dynamic pressure of the intake air flow acting on the air intake and the static pressure acting on the purge port. ing.

Further, according to the present invention, when the engine load is smaller than a predetermined set load, the internal combustion engine forms an air-fuel mixture in a limited region in the combustion chamber and uses the air-fuel mixture by the spark plug. When the engine is ignited and the engine load is larger than the set load, it consists of a cylinder injection internal combustion engine that fills the entire combustion chamber with air-fuel mixture.When the engine load is larger than the set load, when the engine load is smaller than the set load A large amount of air containing evaporated fuel is purged from the purge port into the engine intake passage as compared with the above.

[0006]

According to the first aspect of the invention, since the air containing the evaporated fuel is purged by the pressure difference between the dynamic pressure of the intake air flow acting on the air intake and the dynamic pressure acting on the purge port, the air in the intake passage is purged. Even if the negative pressure is not generated, the purging action is performed. On the other hand, in the invention described in claim 2, when the engine load is low, the air-fuel mixture is formed in a limited region in the combustion chamber. At this time, since the amount of intake air becomes small, the dynamic pressure acting on the air intake becomes low, and as a result, the amount of purge of air containing evaporated fuel into the intake passage decreases.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, an engine body 1 has four cylinders 1.
It has a. Each cylinder 1a has a corresponding intake branch pipe 2
Is connected to a common surge tank 3, and the surge tank 3 is connected to an air cleaner 5 via an intake duct 4. A throttle valve 7 driven by a step motor 6 is arranged in the intake duct 4. The throttle valve 7 is closed to some extent only when the engine load is extremely low, and is kept fully open when the engine load is slightly higher.
On the other hand, each cylinder 1a is connected to a common exhaust manifold 8, and this exhaust manifold 8 is connected to a three-way catalytic converter 9. A fuel injection valve 10 is attached to each cylinder 1a, and these fuel injection valves 10 are controlled based on the output signal of the electronic control unit 30.

As shown in FIG. 1, the intake duct 4 is provided with an evaporated fuel processing device 11 for supplying evaporated fuel into the intake duct 4. The vaporized fuel processing device 11 includes a charcoal canister 13 having an activated carbon layer 12, and vaporized fuel chambers 14 and air chambers 15 are formed in the canisters 13 on both sides of the activated carbon layer 12, respectively. Evaporative fuel chamber 1
4 is connected in parallel to the fuel tank 18 via a pair of check valves 16 and 17 which are arranged in parallel and can flow in opposite directions on the one hand, and on the other hand, a purge port 19 which opens into the intake duct 4 upstream of the throttle valve 7 To a purge conduit 20. On the other hand, the air chamber 15 is connected via an air conduit 22 to an air intake opening in the intake duct 4 upstream of the throttle valve 7. Purge port 1 as shown in FIG.
9 is formed on the side wall surface of the intake duct 4, and the opening of the air intake 21 is arranged in the central portion of the intake duct 4 so as to face upstream of the intake air flow.

When the pressure in the fuel tank 18 becomes higher than the valve opening pressure of the check valve 16, the evaporated fuel generated in the fuel tank 18 flows into the evaporated fuel chamber 14 via the check valve 16,
Next, this evaporated fuel is adsorbed by the activated carbon in the activated carbon layer 12. On the other hand, since both the purge port 19 and the air intake 21 are open in the intake duct 4 upstream of the throttle valve 7, almost the same static pressure acts on the purge port 19 and the air intake 21. However, since the opening of the air intake 21 is directed upstream of the intake air flow, the air intake 2
The dynamic pressure of the intake air flow acts on 1. On the other hand, no dynamic pressure acts on the purge port 19, and only static pressure acts on it. Therefore, due to the pressure difference between the dynamic pressure acting on the air intake port 21 and the static pressure acting on the purge port 19, air is directed from the air intake port 21 toward the purge port 19 through the air conduit 22, the activated carbon layer 12 and the purge conduit 20. Flowing. When this air passes through the activated carbon layer 12, it desorbs the evaporated fuel adsorbed by the activated carbon in the activated carbon layer 12, whereby the air containing the evaporated fuel is purged from the purge port 19. That is, even if the negative pressure is not generated in the intake duct 4, the air containing the vaporized fuel is not contained in the purge port 1.
9 will be purged into the intake duct 4. When the pressure in the fuel tank 18 becomes lower than the valve opening pressure of the check valve 17, the check valve 17 opens. Therefore, the check valve 17 prevents the fuel tank 19 from being deformed due to the pressure drop in the fuel tank 18.

The electronic control unit 30 is composed of a digital computer and has a RAM (random access memory) 32 and a ROM connected to each other via a bidirectional bus 31.
A (read only memory) 33, a CPU (microprocessor) 34, an input port 35 and an output port 36 are provided. The accelerator pedal 23 is connected to a load sensor 24 that generates an output voltage proportional to the depression amount of the accelerator pedal 23, and the output voltage of the load sensor 24 is an AD converter 37.
Is input to the input port 35 via. Further, the input port 35 is connected to a rotation speed sensor 25 that generates an output pulse representing the engine rotation speed. On the other hand, the output port 36 is connected to the step motor 6 and each fuel injection valve 10 via the corresponding drive circuit 38.

2 and 3 show the structure of the combustion chamber of each cylinder 1a. 2 and 3, 50 is a cylinder block, 51 is a piston that reciprocates in the cylinder block 50, 52 is a cylinder head fixed on the cylinder block 50, and 53 is between the piston 51 and the cylinder head 52. The combustion chambers formed are shown respectively. Although not shown in the drawing, an intake valve and an exhaust valve are arranged on the inner wall surface of the cylinder head 52, and the intake port is the combustion chamber 5
The air that has flowed into the inside of the cylinder 3 is configured to generate a swirling flow around the cylinder axis. As shown in FIG. 2, the spark plug 54 is arranged in the center of the inner wall surface of the cylinder head 52, and the fuel injection valve 10 is arranged in the peripheral portion of the inner wall surface of the cylinder head 52. As shown in FIGS. 2 and 3, on the top surface of the piston 51, a shallow dish portion 55 having a substantially circular contour shape extending from below the fuel injection valve 10 to below the spark plug 54 is formed. A basin portion 56 having a substantially hemispherical shape is formed at the center of 55. Also, the spark plug 54
A concave portion 57 having a substantially spherical shape is formed at a connecting portion between the lower shallow dish portion 55 and the deep dish portion 56.

FIG. 4 shows a combustion method during engine low load operation, FIG. 5 shows a combustion method during engine medium load operation, and FIG. 6 shows a fuel injection amount Q and engine load, for example, the accelerator pedal 23. It shows the relationship with the depression amount L of. 6, the depression amount L of the accelerator pedal 23 is L
_During engine low load operation smaller than ₁ , as shown in FIGS. 4 (A) and 4 (B), fuel injection F toward the peripheral wall surface of the basin portion 56 at the end of the compression stroke, gasoline injection in the embodiment shown in FIG. Done. The fuel injection amount Q at this time increases as the depression amount L of the accelerator pedal 23 increases as shown in FIG. The fuel injected toward the peripheral wall surface of the basin portion 56 is diffused while being vaporized by the swirling flow S, and as a result, as shown in FIG. Is formed. At this time, the inside of the combustion chamber 53 other than the recess 57 and the basin 56 is filled with air. Next, the air-fuel mixture G is ignited by the spark plug 54.

On the other hand, in FIG. 6, during the engine medium load operation in which the depression amount L of the accelerator pedal 23 is between L ₁ and L ₂ , the fuel injection is carried out separately at the initial stage of the intake stroke and the final stage of the compression stroke. That is, first, FIG. 5 (A) and (B)
As shown in, the fuel injection F is performed toward the shallow dish portion 55 in the early stage of the intake stroke, and the injected fuel forms a lean air-fuel mixture in the entire combustion chamber 53. Next, as shown in FIG. 5 (C), fuel injection F is performed toward the peripheral wall surface of the basin portion 56 at the end of the compression stroke, and as shown in FIG. An ignitable air-fuel mixture G is formed in the dish 56. The air-fuel mixture G is ignited by the spark plug 54, and the lean air-fuel mixture in the entire combustion chamber 53 is ignited by the ignition flame. In this case, it suffices if the fuel injected at the end of the compression stroke produces a spark, so as shown in FIG. 6, the fuel injection amount at the end of the compression stroke is irrespective of the depression amount L of the accelerator pedal 23 during engine medium load operation. Is kept constant.
On the other hand, the fuel injection amount at the beginning of the intake stroke increases as the depression amount L of the accelerator pedal 23 increases.

In FIG. 6, when the amount of depression L of the accelerator pedal 23 is larger than L _{2 and the} engine is under a high load operation, FIG.
As shown in (A) and (B), the fuel is injected toward the shallow dish portion 55 only once in the early stage of the intake stroke, whereby a uniform air-fuel mixture is formed in the combustion chamber 53. At this time, the fuel injection amount at the beginning of the intake stroke increases as the depression amount L of the accelerator pedal 23 increases as shown in FIG.

By the way, when the evaporated fuel is supplied into the intake duct 4 during the engine medium load operation or the engine high load operation, the evaporated fuel is injected into the combustion chamber 5 together with the fuel injected in the early stage of the intake stroke.
3 forms an air-fuel mixture that occupies the entire inside of the fuel cell 3, so that the evaporated fuel is burned in the combustion chamber 53 together with the injected fuel. On the other hand, as shown in FIG. 4, when the evaporated fuel is supplied into the intake duct 4 during engine low load operation in which the air-fuel mixture G is burned in the presence of a large amount of air, almost all the evaporated fuel burns. It diffuses into the air in the chamber 53. However, since the air in which the evaporated fuel is diffused is extremely lean, the ignition flame does not propagate, and thus the evaporated fuel diffused in the air is discharged into the exhaust manifold 8 without being burned. Even if the evaporated fuel is discharged into the exhaust manifold 8 as described above, the evaporated fuel is burned in the catalytic converter 9 so that the evaporated fuel is not released to the atmosphere as it is, but the evaporated fuel is discharged into the exhaust manifold 8. If this happens, this evaporated fuel will not contribute to combustion, and therefore this evaporated fuel will be wasted. However, when the evaporated fuel processing device 11 shown in FIG. 1 is used, the amount of evaporated fuel that is wasted can be extremely reduced.

That is, in FIG. 1, the dynamic pressure acting on the air intake 21 is proportional to the flow velocity of the intake air flowing in the intake duct 4, while the fuel injection amount Q increases as the depression amount L of the accelerator pedal 23 increases. As the intake air amount increases, the flow velocity of the intake air flowing through the intake duct 4 is proportional to the depression amount L of the accelerator pedal 23. Therefore, the dynamic pressure acting on the air intake port 21 is proportional to the depression amount of the accelerator pedal 23, and thus the purge amount of the air containing the evaporated fuel purged from the purge port 19 as shown in FIG. QE increases as the depression amount L of the accelerator pedal 23 increases. Therefore, the purge amount QE during the low load operation (L <L ₁ ) in which the compression stroke injection is performed is considerably small, and thus the amount of evaporated fuel that is wasted without contributing to combustion can be extremely reduced.

Next, a routine for controlling fuel injection will be described with reference to FIG. Note that this routine is repeatedly executed. Referring to FIG. 8, first, at step 60, the fuel injection amount Q is calculated. As shown in FIG. 9, the fuel injection amount Q is stored in advance in the ROM 33 as a function of the engine speed N and the depression amount L of the accelerator pedal 23.
It is stored in. Next, at step 61, it is judged if the depression amount L of the accelerator pedal 23 is smaller than L ₁ , that is, if it is during low load operation. When L <L _1, the routine proceeds to step 63, where the injection is performed at the end of the compression stroke. On the other hand, when L ≧ L ₁ , the routine proceeds to step 62, where L
It is determined whether or not <L _2, that is, during medium load operation. When L <L ₂ , the routine proceeds to step 64, where injection is performed at the beginning of the intake stroke and the end of the compression stroke. On the other hand, L ≧
At the time of L ₂ , that is, at the time of high load operation, the routine proceeds to step 65, where injection is performed at the beginning of the intake stroke.

Another embodiment is shown in FIGS. In FIG. 10, the same components as those in FIG. 1 are designated by the same reference numerals. Referring to FIG. 10, in this embodiment, the purge port 19 is opened on the inner wall surface of the intake duct 4 downstream of the throttle valve 7, and the solenoid valve 26 is arranged in the purge conduit 20. The solenoid valve 26 is controlled to open and close based on the output signal of the electronic control unit 30. Also in this embodiment, when the solenoid valve 26 is open, the air containing the evaporated fuel is sucked from the purge port 19 due to the pressure difference between the dynamic pressure acting on the air intake port 21 and the static pressure acting on the purge port 19. It is supplied into the duct 4.

FIG. 11 shows the relationship between the opening / closing operation of the solenoid valve 26 and the purge amount QE and the depression amount L of the accelerator pedal 23. As shown in FIG. 11, in this embodiment, when the engine load L is lower than L ₁ , that is, when the engine is operating at a low load, the solenoid valve 26 is closed, and when the engine load L becomes higher than L ₁ , the solenoid valve 26 is closed. Is opened. Therefore, in this embodiment, the purge action is completely stopped during engine low load operation, so that the evaporated fuel can be completely prevented from being wasted without contributing to combustion.

FIG. 12 shows a routine for controlling the fuel injection and the solenoid valve 26, and this routine is repeatedly executed. Referring to FIG. 12, first, at step 70, the fuel injection amount Q is calculated. The fuel injection amount Q is stored in advance in the ROM 33 as a function of the engine speed N and the depression amount L of the accelerator pedal 23 as shown in FIG. Next, at step 71, it is judged if the depression amount L of the accelerator pedal 23 is smaller than L ₁ , that is, if it is during low load operation. When L <L _1, the routine proceeds to step 73, where the injection is performed at the end of the compression stroke,
Then, it proceeds to step 76. In step 76, the solenoid valve 2
6 is closed. On the other hand, when L ≧ L _1, the routine proceeds to step 72, where it is judged if L <L ₂ or not, that is, if it is during medium load operation. When L <L _2, the routine proceeds to step 74, where injection is performed at the beginning of the intake stroke and the end of the compression stroke, and then the routine proceeds to step 77. On the other hand, when L ≧ L ₂ , that is, during high load operation, the routine proceeds to step 75, where the injection is performed at the beginning of the intake stroke, and then the routine proceeds to step 77. In step 77, the solenoid valve 26 is opened.

Also in the embodiment shown in FIG. 1, the purge port 19 can be opened in the intake duct 4 downstream of the throttle valve 7. However, in this case, a large amount of air containing evaporated fuel will be supplied from the purge port 19 into the intake duct 4 when the throttle valve 7 opens during extremely low load operation, so the purge port 19
Is the intake duct 4 upstream of the throttle valve 7 as shown in FIG.
It is preferable to open the inside. On the other hand, in the embodiment shown in FIG. 10, the purge port 19 may be opened in the intake duct 4 upstream of the throttle valve 7, and in this case no problem occurs.

[0022]

The evaporated fuel can be supplied into the intake passage even if a negative pressure is not generated in the intake passage.

[Brief description of drawings]

FIG. 1 is an overall view of an internal combustion engine.

FIG. 2 is a side sectional view of a combustion chamber.

FIG. 3 is a plan view of the top surface of the piston.

FIG. 4 is a diagram for explaining a combustion method during low load operation.

FIG. 5 is a diagram for explaining a combustion method during medium load operation.

FIG. 6 is a diagram showing a fuel injection amount.

FIG. 7 is a diagram showing a purge amount.

FIG. 8 is a flowchart for executing a main routine.

FIG. 9 is a diagram showing a fuel injection amount.

FIG. 10 is an overall view showing another embodiment of the internal combustion engine.

FIG. 11 is a diagram showing a purge amount and an opening / closing operation of a solenoid valve.

FIG. 12 is a flowchart for executing a main routine.

[Explanation of symbols]

 4 ... Intake duct 7 ... Throttle valve 12 ... Activated carbon layer 13 ... Charcoal canister 19 ... Purge port 21 ... Air intake

Claims (2)

[Claims] 1. An internal combustion engine in which air taken in from an air intake is supplied into a charcoal canister, and then air containing evaporated fuel is purged into an engine intake passage from a purge port. And the purge port are opened in the engine intake passage where almost the same static pressure is generated, and the direction of the opening of the air intake is set to the upstream direction of the intake air flow, and the intake air flow acting on the air intake is An evaporative fuel treatment apparatus for an internal combustion engine, wherein air containing evaporative fuel is purged from the purge port into the engine intake passage by a differential pressure between a dynamic pressure and a static pressure acting on the purge port. 2. The internal combustion engine, when the engine load is smaller than a preset set load, forms an air-fuel mixture in a limited region in the combustion chamber and ignites the air-fuel mixture with a spark plug, and the engine load Is greater than the set load, it consists of a cylinder injection type internal combustion engine in which the entire combustion chamber is filled with air-fuel mixture, and when the engine load is larger than the set load, the fuel vapor is higher than when the engine load is smaller than the set load. The evaporative fuel treatment system for an internal combustion engine according to claim 1, wherein a large amount of air containing air is purged from the purge port into the engine intake passage.