JPH0565710B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a canister purge device for an internal combustion engine that purges evaporated fuel from a canister that adsorbs and stores evaporated fuel generated in a fuel system to an intake system via a purge line.

[Prior art]

Conventionally, as such a purge device for evaporated fuel, an inlet pipe purge method (Japanese Patent Application Laid-Open No. 53-5317,
(see Japanese Utility Model Application Publication No. 55-41586 and Japanese Patent Application Publication No. 55-84846) are known. In this type of purge system, when purging evaporated fuel from the canister to the suction pipe via the purge line, the control valve that controls the amount of fuel purged to the purge line is placed on the carburetor side (upstream of the throttle valve) on the operating side. ) Many of them are designed to guide negative pressure from the Here, the control valve uses advanced negative pressure (-70 mmHg OFF), and is configured to be switched on and off at the predetermined pressure (-70 mmHg). On the other hand, from the point of view of exhaust gas purification regulations, purge is suppressed or shut off by controlling the temperature-sensitive valve to cut off the negative pressure brought to the operation side of the control valve until the catalyst temperature has not risen sufficiently to the activation temperature. However, after the catalyst temperature has risen sufficiently to the activation temperature, the control of the temperature-sensitive valve is released to apply negative pressure to the operating side of the control valve to perform purging (for example,
(Refer to Publication No. 57-132060).

[Problem to be solved by the invention]

By the way, when purging the evaporated fuel adsorbed on the canister into the intake system, a sufficient purge amount must be ensured from the viewpoint of exhaust gas treatment. To do this, the purge line must be opened from operating regions where the amount of intake air to the engine is small (for example, idling, low speed ranges, etc.), but in this case, the air-fuel ratio in the above region depends on the purge amount. This results in a large change, becoming lean at low temperatures and rich at high temperatures, which has a significant negative impact on driving performance. In reality, the air-fuel ratio in the above-mentioned range is corrected by the cartridge, but the reality is that it is quite difficult and the correction cannot be made sufficiently. The present invention has been proposed based on the above circumstances, and has an object to provide a canister purge device for an internal combustion engine that improves running performance by avoiding sudden changes in the air-fuel ratio while increasing the amount of purge. This is the purpose.

[Means to solve the problem]

To achieve this object, the device according to the present invention has a canister that adsorbs and stores vaporized fuel generated in the fuel system, and a control valve that opens and closes with negative pressure in the purge line leading from the canister to the intake system. The purge line is connected to a plurality of purge holes provided in the suction passage near the upstream and downstream sides of the throttle valve at the idling opening, and the purge line is connected to a plurality of purge holes provided in the intake passage near the throttle valve at the idling opening. A negative pressure detection passage leading to negative pressure is connected to the suction passage downstream of the throttle valve, and the negative pressure detection passage is equipped with a mechanism that opens the passage when the temperature of the engine system is above the set temperature and closes the passage when the temperature is below the set temperature. It is characterized by being equipped with a warm valve.

[Effect]

In such a configuration, when the temperature of the engine system is low, below the set temperature, the temperature-sensitive valve closes the negative pressure detection passage, cuts off the negative pressure to the control valve, and since the valve is closed, the vaporized fuel is No purge will occur. In addition, when the temperature of the engine system becomes higher than the set temperature, the temperature-sensitive valve opens the negative pressure detection passage, and at this time, the negative pressure detection passage brought to the operating part of the control valve is connected to the intake passage downstream of the throttle valve. Because of this communication, when the engine is under high temperature conditions, the control valve opens even in operating ranges where the amount of intake air is small, such as when idling or decelerating, and the purge line opens and the purge area expands. In addition, by expanding the purge area, the purge amount is also dispersed, and the influence of purge is made uniform over the entire operating range of the expanded purge area. As a result, it is possible to achieve both the objectives of increasing the amount of purge and improving running performance.

【Example】

An embodiment of the present invention will be specifically described below with reference to the drawings. In the figure, reference numeral 1 indicates a carburetor, a throttle valve 3 is disposed downstream of a bench lily 2, and an intake pipe 4
is connected to. On the other hand, a canister 5 communicating with the fuel system is filled with activated carbon 6 and is provided with a control valve 7 at the top. The canister 5 is connected to a fuel tank (not shown) via a line 8 and receives evaporated fuel generated in the fuel tank.
It also communicates with the float chamber of the carburetor 1 via a line 9, so as to receive the evaporated fuel generated in the float chamber. The control valve 7 is opened and closed by negative pressure, and has a negative pressure detection passage 11 in its operating section.
One end of the negative pressure detection passage 11 is connected to the intake passage 4 downstream of the throttle valve 3, and the other end of the negative pressure detection passage 11 is connected to the intake passage 4 downstream of the throttle valve 3.
A temperature-sensitive valve 10 is provided in the negative pressure detection passage 11 in the middle of the passage. This temperature sensitive valve 1
0 is controlled so that the passage is opened when the temperature of the engine system is higher than the set temperature, and closed when the temperature is lower than the set temperature (such as during warm-up operation). Further, the purge line 12, which is opened and closed under the control of the control valve 7, is led to the carburetor 1, and its tip is connected to the throttle valve 3 at the idling opening.
purge holes 13 that open near the upstream and downstream sides of the
It is connected to 14. In such an embodiment, since the temperature-sensitive valve 10 is provided in the negative pressure detection passage 11, under a low temperature condition such as during warm-up when the temperature of the engine system is below the set temperature, the negative pressure detection passage 11 is closed, the negative pressure to control valve 7 is cut off, and valve 7
Since the canister 5 is closed, vaporized fuel is not purged from the canister 5. Furthermore, when the temperature in the engine system rises above the set temperature, the temperature-sensitive valve 10 opens the negative pressure detection passage 11. At this time, the negative pressure detection passage 11 is communicated with the intake passage 4 downstream of the throttle valve 3, and the above-mentioned control valve 7 detects the purge line 12 by controlling the suction pipe negative pressure to a shallow negative pressure of −40 mmHg or less, for example.
Close purge line 1 at higher negative pressures.
Since the control valve 7 is configured to open 2, when the temperature of the engine system is higher than the set temperature, the control valve 7 opens even in operating regions where the amount of intake air is small, such as during idling or deceleration. The purge line 12 is kept open. This expands the purge period, especially during idling and deceleration, which usually accounts for about 30% of the total engine operation time, so purge in this area greatly increases the absolute amount of purge. However, the total purge amount increases. In addition, by extending the purge period, the amount of purge increases, the amount of purge is dispersed, and the degree of influence of purge can be made uniform. Moreover, during the purge period, the purge line 12 is communicated with the purge holes 13 and 14 provided in the suction passage 4 near the upstream and downstream sides of the throttle valve 3 at the idling opening degree, so that the purge can be carried out when the throttle valve 3 is opened. In other words, it is possible to purge in proportion to the amount of intake air, and by avoiding sudden changes in the air-fuel ratio, it is possible to improve driving performance. In the above embodiment, instead of the diaphragm device, the control valve 7 may be a check valve, a temperature-sensitive valve, a solenoid valve via a temperature switch, or the like. In addition, the number, hole diameter, size, etc. of the purge run openings, that is, the purge holes, are selected appropriately.
Can be adapted to design characteristics. The present invention can be applied not only to a carburetor but also to a system having a throttle valve such as a fuel injection type.

【Effect of the invention】

As described in detail above, the present invention connects the negative pressure detection passage that communicates with the operating part of the control valve to the intake passage downstream of the throttle valve, and also connects the negative pressure detection passage to the intake passage when the temperature of the engine system exceeds the set temperature. Since the configuration includes a temperature-sensitive valve that opens the passage and closes the passage when the temperature is below the set temperature, purging from the canister is not performed under the low temperature conditions of the engine where the catalyst temperature is low, avoiding deterioration of exhaust gas purification performance. can. In addition, under high-temperature engine conditions, the purge run-in is opened from operating regions with low intake air volume, such as during idling or deceleration, and the purge period is expanded, thereby increasing the purge volume while dispersing and uniformizing the purge volume. Moreover, in the purge region, the purge line is connected to multiple purge holes provided in the suction passages upstream and downstream of the throttle valve at the idling opening, making it possible to generate a purge amount proportional to the air amount. , it is possible to improve running performance by avoiding sudden changes in the air-fuel ratio. As a result, according to the present invention, it is possible to obtain a canister purge device that satisfies both an increase in the amount of purge and an improvement in running performance.

[Brief explanation of drawings]

The drawing is a system diagram showing one embodiment of the present invention. 1... Carburetor, 2... Bench lily, 3... Throttle valve, 4... Intake pipe, 5... Canister, 6... Activated carbon, 7... Control valve, 8, 9... Line, 10... Feeling Warm valve, 11... negative pressure detection passage, 12... purge line, 13, 14... purge hole.

Claims (1)

[Claims] 1. A canister that adsorbs and stores evaporated fuel generated in the fuel system, and a purge line leading from the canister to the suction system is equipped with a control valve that opens and closes under negative pressure to prevent the evaporated fuel from flowing into the suction system. In a device that purges fuel, the purge line is connected to a plurality of purge holes provided in the suction passage near the upstream and downstream of the throttle valve at the idling opening, and the control valve's operating section is connected to the purge hole downstream of the throttle valve. A negative pressure detection passage is connected to the intake passage of the engine, and a temperature-sensitive valve is provided in the negative pressure detection passage, which opens the passage when the temperature of the engine system is above the set temperature, and closes the passage when the temperature is below the set temperature. A canister purge device for an internal combustion engine, characterized by: