JPH0444839Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention collects evaporated fuel generated in a fuel tank, etc., and supplies the collected evaporated fuel to the engine for combustion during engine operation. The present invention relates to an evaporative fuel processing device for an engine.

(Prior Art) Conventionally, as an evaporative fuel processing device for an engine as described above, there is one disclosed in, for example, Japanese Utility Model Publication No. 52-9454. This prior art communicates the intake passage of an engine with a fuel tank via a canister, and also interposes a purge valve between the canister and the intake passage of the engine. The fuel collected in the canister is combusted in such a way that the air-fuel ratio of the air-fuel mixture supplied to the engine is not significantly changed. Therefore, in this conventional technology, not only does the evaporated fuel theoretically contribute effectively to combustion in the engine, but also the injection of the evaporated fuel does not drastically change the air-fuel ratio of the air-fuel mixture supplied to the engine. This has the advantage of being able to dispose of evaporated fuel without causing problems in the operating state of the engine.

However, in the case of such a conventional configuration, in order to make the opening degree of the purge valve correspond to the opening degree of the throttle valve, for example, a negative pressure extraction hole (purge hole) is formed for extracting negative pressure into the intake passage. However, a configuration is adopted in which this negative pressure extraction hole is guided to the purge valve, but in this case, the vaporized fuel collected in the canister has the highest concentration at the beginning of the purge, and gradually decreases as the purge progresses. Since the concentration will decrease, even if the opening of the purge valve is simply varied by the intake negative pressure as described above, the opening of the purge valve itself will not necessarily match the purge amount of vaporized fuel, and the initial purge ( At the beginning of the purge valve opening, a relatively large amount of evaporated fuel (overrich) is supplied even if the purge valve opening is small, while at the end of the purge, only a relatively small amount of evaporated fuel is supplied, considering the purge valve opening. There is a tendency not to. Therefore, in reality, the air-fuel mixture often becomes overrich in the early stages of purging, and if the configuration of the prior art described above is adopted as is, it will be difficult to accurately control the air-fuel ratio.

(Purpose of the invention) The present invention has been made based on the above-mentioned circumstances, and includes an air supply means for supplying air to the evaporated fuel supply passage and a supply of the evaporated fuel from the canister only within a predetermined period of time after the purge valve starts opening. By providing an air mixing supply means for mixing and supplying a predetermined amount of air supplied by the air supply means to the vaporized fuel purged into the engine through the passage, the engine air-fuel mixture can be prevented from becoming overrich at the initial stage of purging. It is an object of the present invention to provide an evaporative fuel processing device for an engine that avoids this.

(Means for achieving the object) In order to achieve the above object, the present invention connects a canister for collecting evaporated fuel from a fuel tank, a vaporizer, etc. to an engine via a purge valve and an evaporative fuel supply passage. In the evaporated fuel processing device for an engine, the evaporated fuel is communicated with the intake passage of the canister, and the evaporated fuel collected in the canister is purged and combusted by the engine when the purge valve is opened. an air supply means for supplying air; and an air mixing supply means for mixing and supplying a predetermined amount of air supplied by the air supply means with the vaporized fuel only within a predetermined time after the purge valve starts opening. It is.

(Function) According to the above means, in the initial stage of purging of evaporated fuel, the predetermined amount of air supplied from the air supply means is mixed with the evaporated fuel supplied from the canister to the engine by the air mixing supply means. Become. Therefore, the highly concentrated evaporated fuel from the canister at the initial stage of purging is first diluted in the evaporated fuel supply passage to a predetermined concentration that does not cause A/F fluctuations, and then supplied to the engine. Therefore, the tendency of the air-fuel mixture to become overbalanced due to the start of purge of evaporated fuel as in the prior art is reliably avoided, making it possible to accurately control the air-fuel ratio.

(Embodiment) First, FIG. 1 shows an evaporative fuel processing device for an engine according to a first embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes an engine body, and an intake passage 3 is connected to this engine body 1 via an intake manifold 2. The intake passage 3 is also connected to an air cleaner 5 via a carburetor 4.
It is connected to the. The carburetor 4 mixes fuel supplied from the fuel tank 6 via the fuel supply system with clean air supplied from the air cleaner 5 to atomize it, and passes the atomized mixture through the intake passage 3. from intake manifold 2 to engine body 1
into each cylinder. On the other hand, the intake passage 3 is provided with a throttle valve 7 for regulating the amount of intake air supplied to the engine. Also,
A throttle opening sensor 8 is attached to one end of the rotating shaft of the throttle valve 7, and an electric signal (A/D
(Convert and use) Output θ ₁ . The output of the throttle opening sensor 8 is input to a control unit 10 having a CPU configuration via, for example, a multiplexer switch (MUX switch). This control unit 10 functions as a general engine control unit and also has a timer function to control the air supply valve 13, as will be described later.

On the other hand, reference numeral 11 denotes a canister for collecting evaporated fuel in the fuel tank 6, which is provided between the downstream side of the throttle valve 7 in the intake passage 3 of the engine and the upper part of the fuel tank 6. This canister 11 has a body 1, for example, as shown in FIG.
A charcoal filter 11b is provided inside the fuel tank 1a, and the evaporated fuel in the fuel tank 6 is introduced into the filter portion through the evaporated fuel inlet 11c and collected by adsorption. Further, a valve body 14a attached to the tip of an operating rod of a purge valve 14 having a diaphragm valve structure, for example, is brought into contact with the vaporized fuel supply port 11d of the canister 11 in a normally closed state. Further, the evaporated fuel supply port 11 can be communicated with the intake passage 3 through the evaporated fuel supply path 12a via the valve body 14a, and the negative pressure chamber 14b of the purge valve 14 can be communicated with the evaporated fuel supply port 11 through the negative pressure introduction path 12b. and communicates with the intake passage 3. Further, the intermediate portion of the vaporized fuel supply path 12a can communicate with the air cleaner 5 through an air introduction path 12c via an electromagnetic opening/closing air supply valve 13.

Next, the operation of the evaporative fuel processing device for the engine according to the first embodiment will be explained with reference to FIG.

FIG. 3 shows that the operating state of the engine is divided into five stages () to () based on the opening degree θ of the throttle valve 7, and the air supply valve 13,
The operational relationship of each part such as the purge valve 14 is shown in a sequence.

First, the throttle valve 7 is currently in the idling opening state θ ₀ (the throttle valve 7 is in the negative pressure introduction path 12b).
The same opening 12b is on the intake downstream side of the opening _12b1 .
b ₁ is in a positive pressure state), and at the stage () in which intake negative pressure is not supplied to the negative pressure chamber 14b of the purge valve 14, both the air supply valve 13 and the purge valve 14 are in a closed state.

Next, from the step () above, when the throttle valve 7 is opened by a minute opening (opening degree θ ₁ ), the throttle opening sensor 8 detects this opening degree θ ₁ and causes the control unit 10 to activate the timer. Command signal θ ₁
supply. As a result, the control signal G is supplied from the control unit 10 to the air supply valve 13, and the air supply valve 13 is opened (FIG. 3b). As a result, air from the air cleaner 5 is supplied to point P2 in the evaporated fuel supply path 12a (the opening position of the air introduction path 12c). On the other hand, the throttle valve opening degree θ ₁ in this state is a minute opening degree for detecting the throttle valve opening operation, and is
The purge valve 14 does not open because it is not large enough to generate an intake negative pressure at b, and the vaporized fuel is not yet supplied to the vaporized fuel supply path 12a [()
].

On the other hand, from this stage () to the stage () in which the throttle valve 7 is opened to θ ₂ (the throttle valve 7 is on the intake upstream side of the opening 12b ₁ of the negative pressure introduction path 12b, and the opening 12b ₁ is When the pressure reaches a negative pressure state, the purge valve 14 opens and starts purging the evaporated fuel F (FIG. 3c).
The concentration of evaporated fuel F at this time is high because it is just after the start of purge, but at this point, the air supply valve 13 is already open as described above, and the purge valve 14 is open at the point _P2 . Since air is supplied before the valve, the evaporated fuel F is
P ₁ point between P ₂ points and purge valve 14 (F=F ₁ )
Even if the concentration is high, at point _P3 (F= _F3 ) downstream of point _P2 , it becomes diluted due to the incorporation of air (Fig. 3d, e). This dilution of the purge fuel due to aeration is shown in dashed lines in FIG. 3e. This dilution effect of the evaporated fuel occurs during a predetermined period of time at the initial stage of purge, that is, during the period T (third
(see Figure b). This time T is set to a sufficient time in consideration of the time during which the air-fuel mixture conventionally tends to become overrich at the initial stage of purging.

Then, when the above-mentioned time T has elapsed and the vaporized fuel _F1 at the above-mentioned point _P1 becomes lean (point L in Fig. 3 d), the supply of the control signal G to the air supply valve 13 is stopped and the air supply is stopped. The valve 13 is closed (FIG. 3b), and the lean vaporized fuel F is directly supplied to the point _P3 [step ()]. Therefore, in this state, normal air-fuel ratio control can be performed.

Furthermore, when the throttle opening degree θ decreases from the above stage () to the stage ( ₂ ), the intake negative pressure also decreases below the operating set value of the purge valve 14, and the purge valve 14 The valve closes (Fig. 3c) to complete the purge operation.

Therefore, according to the above configuration, the highly concentrated evaporated fuel at the beginning of the purge is appropriately diluted with a predetermined amount of air before being supplied to the engine, which eliminates the problem of overriching the air-fuel mixture at the beginning of the purge as in the conventional case. This will ensure that the changes are prevented.

Next, FIG. 4 shows an evaporative fuel processing device for an engine according to a second embodiment of the present invention.

In FIG. 4, as in the case of FIG. 1, numeral 1 is the engine body, 2 is the intake manifold, 3 is the intake passage, 4 is the carburetor, 5 is the air cleaner, 6 is the fuel tank, 7 is the throttle valve, 11 1 and 2 respectively indicate canisters, and the configurations and functions of each of the above are completely the same as those of the first embodiment. In this second embodiment, the control unit 10 is not used as in the first embodiment, and instead of the electromagnetic opening/closing type air supply valve 13 in the first embodiment, an air supply valve having a diaphragm valve structure is used. A supply valve and a volume tank are used to dilute the highly concentrated evaporated fuel at the initial stage of purging with the air in the volume tank.

That is, in FIG. 4, the reference numeral 20 is an air supply valve used in the second embodiment, and the negative pressure chamber 2 is
0a is communicated with the negative pressure introduction passage 12b from the intake passage 3, while the valve chamber 20b side thereof is interposed between the evaporated fuel supply passage 12a from the canister 11 and the air introduction passage 12c from the air cleaner 5. When the valve body 20c is opened, the two are brought into communication and air is injected into the evaporated fuel supply path 12a. The air supply valve 20 normally maintains a state of communication between the air introduction path 12c and the fuel vapor supply path 12a (open state), and in this communication state, air is supplied into the fuel vapor supply path 12a. A predetermined amount of fuel is stored in a volume tank 23 provided in the middle of the vaporized fuel supply path 12a. When negative pressure is supplied from the intake passage 3 to the negative pressure chamber 20a via the negative pressure introduction path 12b, the valve body 20c is closed to cut off the communication state. When the negative pressure is supplied in this way, the purge valve 14 is opened and the evaporated fuel from the canister 11 is supplied into the volume tank 23 through the evaporated fuel supply path 12a. ,
Inside this volume tank 23, it is mixed with air and diluted.

On the other hand, reference numeral 24 indicates that the valve chamber 24b side is interposed in the middle of the vaporized fuel supply path 12a, and the negative pressure chamber 24
The a side is a diaphragm valve connected in communication with the negative pressure introduction path 12b through a one-way valve 25 having a small hole 25a and a lead 25b, and when negative pressure is supplied to the negative pressure introduction path 12b, i.e. At the time of purging, the valve body 24c is opened to allow the volume tank 23 to communicate with the engine side.

Next, the purge valve 14, the air supply valve 2
0, volume tank 23, diaphragm valve 2
4. The interaction between the one-way valve 25 and the like will be explained in detail with reference to FIG.

FIG. 5 shows that, as shown in FIG. 3, the operating state of the engine is divided into six stages () to () based on the opening degree θ of the throttle valve 7, and the air supply valve 13, The operational relationship of each part such as the purge valve 14 is shown in a sequence.

First, the throttle valve 7 is currently in the idling opening state θ ₀ (the throttle valve 7 is in the negative pressure introduction path 12
The same opening 1 is on the intake downstream side of opening 12b ₁ of b.
_2b1 is in a positive pressure state), and at the stage () when the intake negative pressure is not supplied to the purge valve 14 and the negative pressure chamber 14b, the purge valve 14 is closed (Fig. 5b), and the one-way valve 25 is in communication. Condition (Figure 5e)
However, since the inside thereof is in a positive pressure state, the diaphragm valve 24 does not open (FIG. 5d), and therefore, there is no evaporated fuel F in the evaporated fuel supply path 12a. On the other hand, in this state, the air supply valve 2
Since the negative pressure chamber 20a of No. 0 is in a positive pressure state, its valve chamber 20b is opened (FIG. 5c) to maintain communication between the air cleaner 5 and the volume tank 23, and there is no air cleaner in the volume tank 23. It is already filled with air from 5 (Fig. 5g).

Next, from the step () above, the throttle valve 7 further changes the opening degree θ ₁ (the throttle valve 7
When the air supply valve ₂₀ closes, the purge valve 14 opens and the evaporation occurs. The vaporized fuel F is about to be supplied to the fuel supply path 12a, but in this state, the diaphragm valve 24, which increases the negative pressure via the one-way valve ₂₅ with a delay of a predetermined time t1 _, The valve does not open and maintains the closed state until the time elapses (Fig. 5d). Therefore, at this point in time, the evaporative fuel F is not yet supplied to the evaporative fuel supply path 12a.

On the other hand, from the step () above, the one-way valve 25
When the specific delay time t ₁ has elapsed (), the diaphragm valve 24 also opens in conjunction with the opening of the purge valve 14, and the suction action of the intake negative pressure causes the inside of the canister 11 to be Evaporated fuel F (high concentration as it has just started purge)
is first supplied to point P ₁ (the upstream side of the volume tank 23 in the evaporative fuel supply path 12a), and then this highly concentrated evaporated fuel F (=F ₁ ) is supplied to the volume tank 23 (point P ₂ ). It is mixed and diluted with the supplied air that has been filled in advance, and this air-fuel mixture reaches point _P3 (the part downstream of the volume tank 23 in the evaporative fuel supply path 12a), where the diluted evaporative fuel (final purge fuel) F (=F ₃ ). The dilution effect of the evaporated fuel by the volume tank 23 is performed for a predetermined time t ₂ determined by the air capacity in the volume tank 23, and during this time t ₂ the concentration of the final purge fuel F ₃ is lower than that of the air. It is necessary at least to reach a lean concentration (point 1 in Fig. 5 h) where the air-fuel ratio of the engine does not become overbalanced even if it is not mixed. The state (state after ₂ hours t) is shown as the stage (). This stage () indicates, for example, a state in which a certain period of time has elapsed since the engine speed exceeded the idle range and entered the normal operating range. Therefore, in this state, the volume tank 23 contains almost only the evaporated fuel F (FIG. 5g).

Then, when the throttle valve 7 is closed from the stage () to a state where no intake negative pressure is generated in the negative pressure introduction path 12b (opening degree smaller than θ ₁ described above), the purge valve 14 is closed and the other air supply Valve 20 is opened. Moreover, at this time, the one-way valve 25 maintains the negative pressure chamber 24a of the diaphragm valve 24 at a predetermined negative pressure state for a predetermined time _t3 even after the throttle valve 7 is closed due to its delay function. During the delay time _t3 , the diaphragm valve 24 is open (see FIG. 5d).
Therefore, when the air supply valve 20 is newly opened in this state as described above, the volume tank 23
Air is again supplied into the volume tank 23, and the residual evaporated fuel F in the volume tank 23 is mixed with the air and significantly diluted, and further purged to the engine side by the air pressure [step ()].

As a result, when the diaphragm valve 24 closes () after the time _t3 has elapsed, the volume tank 23 returns to its original state (FIG. 5g), where only air is filled (Fig. 5g). Prepare for the start of vaporized fuel purge.

Therefore, even with the above configuration, the purge fuel having a high concentration at the initial stage of purge is appropriately diluted with a predetermined amount of air.

(Effects of the invention) As explained above, the evaporated fuel processing device for an engine of the present invention connects the canister for collecting evaporated fuel from the fuel tank, vaporizer, etc. via the purge valve and the evaporated fuel supply passage. In the evaporated fuel processing device for an engine, the evaporated fuel is communicated with the intake passage of the engine, and the evaporated fuel collected in the canister is purged and combusted by the engine when the purge valve is opened. and an air mixing supply means for mixing and supplying a predetermined amount of air supplied by the air supply means with the evaporated fuel only within a predetermined time after the purge valve starts opening. It is characterized by:

Therefore, according to the present invention, in the initial stage of purging of evaporated fuel, the predetermined amount of air supplied from the air supply means is mixed with the evaporated fuel supplied from the canister to the engine by the air mixing supply means. . Therefore, the highly concentrated evaporated fuel from the canister at the initial stage of purging is first diluted to a predetermined concentration that does not cause A/F fluctuations in the evaporated fuel supply passage, and then supplied to the engine.
As a result, the conventional tendency for the air-fuel mixture to become overbalanced due to the start of purge of evaporated fuel is reliably avoided, making it possible to accurately control the air-fuel ratio and achieving stable operating conditions. .

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an evaporative fuel processing device for an engine according to a first embodiment of the present invention, and FIG.
An enlarged sectional view of the canister part of the device shown in Fig. 1, Fig. 3
The figure shows a sequence showing the operational relationship of each part of the device shown in FIG. 1, FIG.
FIG. 5 is a sequence diagram showing the operational relationship of each part of the apparatus shown in FIG. 4 above. 1...Engine body, 2...Intake manifold, 3...Intake passage, 5...Air cleaner,
6... Fuel tank, 10... Control unit, 11... Canister, 12a... Evaporated fuel supply path, 12b... Negative pressure introduction path, 12c... Air introduction path, 13, 20... Air supply valve, 14 ...Purge valve.

Claims (1)

[Scope of utility model registration request] A canister for collecting evaporated fuel from a fuel tank, a carburetor, etc. is communicated with the intake passage of the engine via a purge valve and an evaporated fuel supply passage, and the evaporated fuel collected in the canister is removed when the purge valve is opened. An evaporated fuel processing device for an engine that purges and burns the engine at the time of valve operation, comprising an air supply means for supplying air to the evaporated fuel supply passage, and the air supply means only within a predetermined time after the purge valve starts opening. 1. An evaporative fuel processing device for an engine, comprising an air mixing supply means for mixing and supplying a predetermined amount of air supplied by the evaporative fuel with the evaporative fuel.