JPH0374562A - Evapotranspirated gas purging device - Google Patents

Abstract

PURPOSE:To keep a purge air ratio constant regardless of the operating condition of an engine by providing a throttle part on the upstream side of a throttle valve in an intake passage and connecting a purge air passage communicated with a canister between the throttle part and a throttle valve. CONSTITUTION:An evapotranspirated gas purging device scavenges the evapotranspirated gas generated in a fuel tank 1 by leading it into a canister 3 through a vapor pipe 2. When an engine is operated, this evapotranspirated gas is sucked into an intake passage 13 by the negative pressure generated on the downstream side of a throttle valve 6 through a purge air pipe 4 and sent into a combustion chamber 8. A throttle 14 is provided at the intake passage 13, on the upstream side of the throttle valve 6, and the purge air pipe 4 from the canister 3 is connectedly opened between the throttle 14 and the throttle valve 6. The purge quantity of purge air can be automatically adjusted approximately in proportion to the intake air quantity by the action of the throttle 14.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is directed to the use of evaporated gas (
This invention relates to an evaporative gas purge device that sucks evaporated fuel gas into the intake system of an engine.

<Conventional technology> Evaporated gas generated in the fuel tank of an automobile would cause pollution if released directly into the atmosphere, so it is collected in a canister and sucked into the engine's suction system as purge air. I try to burn it.

An example of a conventional evaporative gas purge device of this kind is schematically shown in FIG. This device is designed to suck par share to the downstream side of the throttle valve in the intake system. A connection opening is provided on the downstream side of 6. Note that the canister 3 communicates with the atmosphere. Further, in FIG. 5, 7 is an engine, 8 is a combustion chamber thereof, 9 is a fuel injector, 10 is an intake manifold, 11 is a surge tank, and 12 is an air cleaner.

The evaporated gas generated in the fuel tank 1 passes through a vapor tube 2 and is collected in a canister 3.

When the engine 7 is operated, the evaporated gas is sucked into the intake passage together with the intake air absorbed by the canister 3, that is, as purge air, due to the negative pressure generated downstream of the throttle valve 6, and is sent to the combustion chamber 8. It will be done.

<Problems to be Solved by the Invention> As described above, the conventional transpiration gas purge device sucks purge air to the intake side using the intake negative pressure.

However, since automobile engines are normally used in a wide rotational speed range and a wide negative pressure range of 1fX, the intake negative pressure changes greatly and the purge amount (the amount of purge air sucked) changes over a wide range. Further, since the amount of intake air changes greatly, even if the intake negative pressure is constant (the amount of purge is constant), the amount of purge (purge air ratio) relative to the amount of intake air will also change greatly.

As a result, the air-fuel ratio learning system becomes complicated as operating conditions change, and there are many restrictions on learning conditions and the like.

In addition, in conventional transpiration gas purge devices, the intake negative pressure is large in the low load range, so the diameter of the bar share pipe 4 is determined to prevent deterioration of drivability due to enrichment (excessive concentration) due to excessive purge. There is. Therefore, on the contrary, there was a problem that sufficient purging could not be performed in a high load range, that is, the purge rate was low and the efficiency was poor.

Means for Solving the Problems> In order to solve the above problem, the present invention provides an evaporative gas purge device that collects evaporated gas of fuel generated in a fuel tank in a canister and sends it to the intake side of the engine as purge air. A constriction part is provided upstream of the throttle valve provided in the intake passage of the engine, and a purge air passage is connected between the constriction part and the throttle valve.

Embodiment FIG. 1 schematically shows a transpiration gas purge device according to an embodiment of the present invention.

Throttle valve 6 in intake passage 13 of engine 7
A throttle (subthrottle) 14 is provided on the upstream side of the throttle. A purge air pipe 4 from the canister 3 is connected and opened between the throttle 14 and the throttle valve 6.

Note that the canister 3 and other configurations are similar to those shown in FIG. 5.

In the transpiration gas purge device having this structure, a negative pressure is generated downstream of the throttle 14, and the negative pressure increases as the amount of intake air increases. 3 and throttle valve 6 increases. Therefore, the amount of purge air also increases.

In this way, the purge amount of purge air is automatically adjusted approximately in proportion to the intake air amount.

The relationship between the pressure of the restrictor 14 and the throttle valve 6191 and the amount of purge air is as follows.

The atmospheric pressure is Pl, the pressure between the throttle 14 and the throttle valve 6 is P1, the equivalent area of the throttle 14 is A2, the equivalent area of the purge air pipe 4 is A2, the amount of air flowing through the throttle 14 is 01, and the amount of purge air is 02. Then, G1=Aik, 4ρ (P, -P) However, ρ is the air density, G2-J, A2Qρ (P, -P) '・
'A2 (expressed as a constant. Therefore, if the purge air rate is G2/G1, it is expressed as G/G=JA/JA. In other words, once A and A are determined, it becomes constant.

Furthermore, the air-fuel ratio of purge air A/F ii! If a, the intake air-fuel ratio A/F is expressed by the following formula.

(A/F) to,,, = ((α+1.) G,
+ a G2' / G2 = ((α+1) J, A,
+aJ2A2)/J2A2 where α is approximately 1.4~o
o, but the movement is slow, so by slowly controlling A1 or A2 according to α (A/F
) is controlled to be constant. In other words, (A/F)tot, remains constant regardless of changes in engine operating conditions.

Note that the air-fuel ratio a of the purge air is about 1.4 or more when the amount of fuel on the intake air from the canister 3 is O, and it becomes approximately 1.4 when the amount of fuel is very large. by. In addition, in the above embodiment device, A,...
Since it is not variable like A21, by controlling the fuel injection amount by the injector 9 (A/F). t.

control.

According to the above-mentioned transpiration gas purge device, when the throttle opening is small and the amount of intake air is small, a small amount of purge air is sucked in, so that enrichment does not occur, and the throttle opening is increased and the amount of intake air is increased. Accordingly, the amount of purge air sucked increases, so the purge rate in the high load range improves, and a large amount of purge air can be purged.

FIG. 2 schematically shows a transpiration gas purge device according to another embodiment.

In this case, the throttle on the upstream side of the throttle valve 6 is made variable as a sub-throttle valve 15. The sub-throttle 15 is opened and closed by a vacuum actuator 16 which uses intake negative pressure as a driving source.

The reason why the sub-throttle 15 is made variable in this way is to prevent the intake air from being throttled by the sub-throttle 15 when the throttle valve 6 is fully opened. In other words, during high-load operation, the sub-throttle is fully opened to 15re.
This was done to ensure a large amount of air.

Therefore, the amount of purge air decreases to some extent during high-load operation, but since it rarely occurs during full-throttle operation, there is no problem in increasing the amount of purge air as a whole.

The device shown in FIG. 3 is the same as the embodiment shown in FIG. 2, except that the purge air pipe 4 is provided with a solenoid valve 17 as a variable throttle. This is to avoid instability in (A/F) totel control caused by an increase in evaporated gas during startup or refueling.

At the time of starting or refueling, a large amount of evaporated gas is sucked into the vapor pipe 2, and purge gas with a high A/F is purged into the intake passage. On the other hand, (A/F). , l are normally controlled by learning control, but there may be a situation where the learning control of A and /F on the intake side cannot catch up, albeit momentarily, during startup or the like.

In order to avoid such a situation, the purge amount is gradually increased during startup and the like, and the purge amount is controlled by opening and closing the solenoid valve 17.

A schematic control flow is shown in FIG.

The duty rate (α, β) is calculated from the elapsed time after startup or the elapsed time after refueling, and the smaller duty rate is selected to control the opening and closing of the solenoid valve 17 to control the amount of purge air. With this control, the purge rate is controlled at a slower speed than the A/F learning control, and during this time the learning control catches up and is established.

Note that the valve provided in the purge air pipe 4 may be of a variable throttle type instead of an ON-OFF type like the solenoid valve 17.

<Effects of the Invention> According to the evaporative gas purge device according to the present invention, the par shear rate is kept constant regardless of the engine operating conditions.
Control accuracy is improved without complicating A/F control due to load fluctuations during purge introduction.

Furthermore, since the amount of purge air is increased, the processing capacity for evaporated gas is improved.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a transpiration gas purge device according to one embodiment of the present invention, FIGS. 2 and 3 are schematic diagrams of other embodiments, and FIG. 4 is a schematic diagram of the embodiment shown in FIG. 3. #Schematic flowchart of control, FIG. 5t is a schematic diagram of an example of a conventional control. In the drawing, 1 is a fuel tank, 3 is a canister, 4 is a purge air pipe, 6 is a throttle valve, 7 is an engine, 13 is an intake passage, 14 is a throttle, 15 is a sub-throttle valve, 16 is a hub actuator, 17 is a solenoid valve. Patent applicant Mitsubishi Motors Corporation Agent

Claims (1)

[Claims] This is a transpiration gas purge device that collects evaporated fuel gas generated in a fuel tank in a canister and sends it out as purge air to the intake side of the engine, and has a constriction part on the upstream side of the throttle valve installed in the intake passage of the engine. A transpiration gas purge device comprising: a purge air passage connected between the constriction portion and the throttle valve.