JPS59173548A - Evaporated fuel discharge preventing device in internal- combustion engine - Google Patents

Abstract

PURPOSE:To enhance the efficiency of removal of evaporated fuel, by providing two main and auxiliary canisters so that evaporated fuel generated in a large amount after stopping of an engine is absorbed by the special purpose auxiliary canister for a predetermined time, and evaporated fuel generated during the time other than the above- mentioned time is absorbed by the other main canister. CONSTITUTION:When the temperature of an operating engine is above a predetermined temperature, a control valve 8 is changed over so that the inlet port 8a and the second outlet port 8c thereof are communicated together. In this condition, when vacuum downstream of a throttle valve 11a is introduced into a pressure chamber 4f through a vacuum port 11b to open a control valve 4, evaporated fuel in a fuel container 1 is guided through passages 5, 6, and is absorbed by a main canister 2. Then, when the engine stops and the control valve 4 is closed, evaporated fuel which is generated in a large amount in the fuel container 1 is guided through passages 5, 9, 13 and is absorbed by an auxiliary canister 3. Thereafter, the temperature of the engine becomes lower than the predetermined temperature due to cooling-down of the engine, the control valve 8 is changed over so that evaporated fuel which is generated in a small amount is absorbed by the main canister 2.

Description

[Detailed description of the invention] The present invention relates to an evaporative fuel emission prevention device for an internal combustion engine.

Such evaporative fuel emission prevention devices are equipped with one canister containing activated carbon that adsorbs fuel evaporated from a fuel container, such as a fuel tank or float chamber of a vaporizer, and its capacity is designed to be large enough to sufficiently adsorb evaporated fuel. ing. However, after using the canister for a certain period of time, when the canister is close to saturation, if you stop the engine and leave it for a while, most of the evaporated fuel will be released into the canister for several tens of minutes after the engine is stopped. cannot be absorbed completely,
It was discovered that there was a risk of overflowing from the canister. A possible cause of this is that the activated carbon in the canister deteriorates due to repeated adsorption of fuel. Figure 1 shows the deterioration rate (%) of canister efficiency with respect to the number of months of use from when a new car equipped with an internal combustion engine is put on the market until it is collected.
It shows. Here, ◯, △, and × indicate canisters with different adsorption levels and activated carbon components, and a tendency as shown by the solid line is obtained. Figure 2 shows the efficiency deterioration rate (%) and 5HED
The amount of evaporated fuel leaking from the canister according to the law DBL (g/
1est). Furthermore, in Figure 3,
The amount of air ff1(A) required for separation and the amount of fuel ′B separated (
g) is shown for new canisters and canisters that have already been used. It can be seen from these figures that the canister becomes less efficient as it is used.

The present invention has focused on these points, and the canister is divided into two parts, so that a large amount of evaporated fuel generated after stopping between the rows is adsorbed into a dedicated canister, and the deterioration of the canister is prevented by using the two canisters properly. This is to reduce the amount of fuel vapor and prevent the release of evaporated fuel into the atmosphere. The switching of fuel adsorption to both canisters is performed in relation to the intake negative pressure and the engine temperature, such as the engine cooling water temperature.

Therefore, according to the present invention, the main canister and the sub-canister, the first control valve that switches the flow path in response to the engine negative pressure, and the second control valve that switches the flow path in response to the engine temperature. The fuel evaporation space of the fuel container is communicated with the main canister through a first control valve which is provided and is in the first switching position when the engine is running, and when the engine is stopped and the interrow temperature is below a certain level, the second control valve is in communication with the main canister. The fuel evaporation space of the fuel container is communicated with the main canister through a first control valve in the switching position and a second control valve in the first switching position. , the fuel evaporation space of the fuel container is communicated with the secondary canister via the first control valve in the second switching position and the second control valve in the second switching position.

A detailed description of the invention with reference to the drawings shows that 1 is a fuel container of an internal combustion engine, such as a fuel tank or a float chamber of a carburetor, and 2 and 3 are a main canister and a sub-canister containing activated carbon. 4 is a control valve that switches the flow path in response to the engine negative pressure,
an inlet boat 4a leading to the fuel evaporation space of the main canister 2, and a first outlet boat 4b leading to the main canister 2 via the passage 6;
A second outlet boat 4C is connected via a passage 9 to an inlet boat 8a of a control valve 8 whose sensitive part is screwed into the cooling water jacket 7 of the engine and switches the flow path in response to the engine temperature. There is. A valve body 4d that switches the connection between the inlet port 1-4a of the control valve 4 and the outlet boat 4b or 4C.
is connected to the diaphragm 4e, and this diaphragm 4e
The operating pressure chamber 4f is defined by a part of the valve case.
Via the passage 10 the carburetor or throttle body 11
The throttle valve 11a is connected to an intake pressure take-off boat Ilb located downstream of the throttle valve 11a. The control valve 8 is adapted to connect the inlet boat 8a to the first outlet boat 8b below a certain interrow temperature, and to connect the inlet boat 8a to the second outlet boat 8C above this engine temperature. . The outlet boat 8b communicates with the main canister 2 via a passage 12, and the outlet port 8C communicates with the secondary canister 3 via a passage 13. The fuel removal passages of the main canister 2 and the secondary canister 3 and ]6 lead to a purge boat l]c located in the carburetor or thrower body 11. Note that the passage 16 is provided with a throttle 17.

Now, when the engine is operating and the temperature is above a certain temperature, zero pressure is generated downstream of the throttle valve 11a, and this is supplied to the operating pressure chamber 4f of the control valve 4, so that the diaphragm 4e is moved by the force of the spring. The inlet boat 4a is deflected upward against the flow, and the inlet boat 4a is communicated with the outlet boat 4b. Therefore, the evaporated fuel in the fuel container 1 is adsorbed into the main canister 2 via the passages 5 and 6.

At this time, the inlet boat 8a of the starvation valve 8 is the outlet boat 1-8c.
It is in communication with the exit boat 8b and is cut off from the exit boat 8b.

When the engine stops, the downstream side of the throttle valve 11a also becomes atmospheric pressure, so the diaphragm 4e is pushed downward by the spring.
The valve body 4d disconnects the inlet boat 4a from the outlet boat 1-4b and allows the inlet boat 4a to communicate with the outlet boat 4C. Since the engine temperature is still high, the inlet port 8a of the control valve 8
remains in communication with exit boat 8c. Therefore, a large amount of evaporated fuel generated in the fuel container 1 in this condition passes through the passage 5.9.13 and is adsorbed into the sub-canister. When the engine cools down to a certain temperature or lower, the control valve 8 switches and connects the inlet boat 8a to the outlet boat 8b, so that a small amount of evaporated fuel in the fuel container 1 is generated.
It passes through the passages 5, 9 and 12 and is attracted to the main canister 2.

During engine operation, the adsorbed fuel is removed from the main canister 2 via a passage 15 to the purge port llc, and the adsorbed fuel from the sub canister 3 is removed via a passage 16 by a throttle 17. This will be done with restrictions.

In this way, according to the present invention, two canisters are provided, and only for a predetermined period of time after the engine stops when a large amount of evaporated fuel is generated, the evaporated fuel is adsorbed in a dedicated sub-canister, and at other times, fuel is generated in the main canister. By adsorbing evaporated fuel, it is possible to reduce the deterioration of the efficiency of the canister and to prevent the release of evaporated fuel into the atmosphere even if a large amount of evaporated fuel is generated.

In this case, since the side canister 3 is used only under limited conditions, it can be of small size. Moreover, when the same volume of fuel is adsorbed into one canister and two canisters with the same total volume, the amount of detached fuel per unit volume increases in the case with two canisters. Therefore, the withdrawal efficiency is improved. Further, by improving the evaporation efficiency, there is also an advantage that the deterioration rate is further reduced.

[Brief explanation of drawings]

1 to 3 are diagrams for explaining deterioration of the canister, and FIG. 4 is a configuration and connection diagram of an embodiment of the present invention. l...Fuel container, 2...Main canister, 3...Sub-canister, 4, 8...Control valve, 4a, 8a...
Entrance boat, 4b+ 4c+ 8b+ 8c 7-
Outlet boat, 4f...Operating pressure chamber, 7...Cooling water tank, 11b...Intake pressure extraction port. II+J2J Figure 1 Figure 2 □ Deterioration rate (H) Figure 3 Air volume (A')

Claims (1)

[Claims] A fuel container, a main canister and a sub-canister containing activated carbon that adsorbs evaporated fuel, a first control valve that switches a flow path in response to engine negative pressure, and a first control valve that switches a flow path in response to engine negative pressure. a second/control valve for switching the flow path, the fuel evaporation space of the fuel container is communicated with the main canister via the first control valve which is in the first switching position when the engine is operating, and when the engine is stopped; Below a certain engine temperature, the fuel evaporation space of the fuel container is communicated with the main canister via the first control valve in the second switching position and the second control valve in the first switching position. When the engine is stopped and the engine temperature is above a certain temperature, the fuel evaporation space of the fuel container is communicated with the sub-canister through the first control valve in the second switching position and the second control valve in the second switching position. A vaporized fuel emission prevention device between internal combustion rows.