JPS6139107Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a fuel vapor release prevention device for an internal combustion engine such as an automobile gasoline engine.

In order to prevent fuel vapor that evaporates from the liquid level of a car's gasoline tank from being released into the atmosphere, the upper part of the fuel tank is connected to the engine's intake pipe, with a canister containing an adsorbent such as activated carbon interposed between them. A fuel vapor release prevention device is used in which fuel vapor once adsorbed by an adsorbent is desorbed by air taken in from an air intake port of a canister during engine operation and is sent to the engine intake side. This desorption effect is inert when the air temperature is low, so by heating the air sucked into the canister to ensure sufficient desorption, the performance of the canister can be fully demonstrated, and the size of the canister can be prevented. are doing. For example, as disclosed in Japanese Patent Application Laid-Open No. 56-121856, warm air near the exhaust manifold is guided to the canister, and in this case, engine cooling water is When the temperature rises, a switching valve operates to cut off warm air and introduce atmospheric air directly, while others introduce a portion of the engine intake air into the canister after passing through the air cleaner's automatic temperature control device.

In the conventional system as described above, the heating source is the outside temperature of the exhaust manifold of the engine, so there is a delay in heating. Moreover, it is difficult to adjust the air temperature to the appropriate temperature for supplying to the canister, and there is a high risk of fire due to overheating. Even when the temperature is low, the warm air side is cut off, making it difficult to maintain the appropriate temperature of the desorbing air.

This idea was made to solve the above problem, and a positive resistance thermistor heater (hereinafter abbreviated as DTC heater) is installed in the middle of the canister's atmosphere introduction pipe, and its ON/OFF is controlled by opening and closing of the canister's purge valve. To provide a fuel vapor release prevention device which uses the same negative pressure source, starts heating at the same time as the inflow of desorbed air starts, maintains an appropriate temperature, and prevents overheating. .

This idea will be explained with examples. In FIG. 1, an upper portion 2a in a fuel tank 2 that supplies fuel to an internal combustion engine 1 for an automobile is connected to a canister 4 through an evaporator tube 3, and communicates with an activated carbon layer 4a housed within the canister 4. The activated carbon layer 4a and the downstream side of the throttle valve 5a of the intake pipe 5 of the internal combustion engine 1 are connected through a delivery pipe 6. The purge valve 7 provided in the delivery pipe 6 is a throttle valve 5a.
It has a structure in which the valve is opened by negative pressure introduced from a small hole provided at the top through a negative pressure pipe 8. An air intake port 4b is provided at the bottom of the canister 4. The above configuration is the same as the conventional one, but this invention has the following features. That is, an air introduction pipe 10 is connected to the air intake port 4b at the bottom of the canister 4, and the other end is opened to the atmosphere in the engine room or the like. A plurality of thermistor elements are arranged in parallel in the middle of the air introduction pipe 10, and a PTC heater 11 (commonly called a harmonica type) is interposed therebetween with an air passage. An example of a PTC heater is shown in FIGS. 2 and 3. In the figure, 11a is a thermistor attached to an enlarged intermediate portion of the air introduction pipe 10, 11b is a support frame for the thermistor, and 12a and 12b are conductive wires forming a circuit with a power source 13. Conductor wires 12a, 12
One of the switches b, for example 12a, has an open/close switch 14 interposed therebetween. The open/close switch 14 is connected to an operating rod 15d fixed to the diaphragm 15c of a negative pressure motor 15, which is made up of an airtight container 15a and a diaphragm 15c urged outward by a spring 15b inside the container. Negative pressure chamber 15e
and the negative pressure pipe 8 are connected by a negative pressure branch pipe 16, and the switch 14 is set to open when the negative pressure chamber 15e has no negative pressure, and to close when the negative pressure chamber 15e has negative pressure.

Furthermore, a delay valve 17 is installed in the middle of the negative pressure branch pipe 16 if necessary. The delay valve 17 is a one-way valve that opens only from the negative pressure motor 15 side to the negative pressure pipe 8 direction, as shown in FIG. be.

The fuel vapor release prevention device of this invention constructed as described above operates as follows. Fuel vapor generated in the fuel tank 2 passes from the upper part 2a of the fuel tank 2 through the evaporation tube 3 to the activated carbon layer 4a of the canister 4, where it is adsorbed. When the engine is operated, a negative pressure is generated on the downstream side of the suction pipe 5 of the engine, but the negative pressure does not reach the negative pressure pipe 8 in an idling operating state when the throttle valve 5a is closed. When the throttle valve 5a is opened, the small hole becomes on the downstream side of the throttle valve 5a, and negative pressure is transmitted to the purge valve 7 via the negative pressure pipe 8 to open the purge valve 7. 5, the fuel vapor adsorbed by the air taken in from the air intake port 4b is desorbed and combined into an air-fuel mixture through the delivery pipe 6.

The above-mentioned functions are the same as those of the conventional one, but in the fuel vapor release prevention device according to this invention,
At the same time, the negative pressure in the negative pressure pipe 8 reaches the negative pressure chamber of the negative pressure motor 15 via the negative pressure branch pipe 16 forming the negative pressure pipe.
At the same time as the purge valve 7 opens and suction of desorption air into the canister begins, the switch 14 closes.
The PTC heater starts heating. PTC heater is 5
Since the set saturation temperature is reached in a very short time of about 15 seconds, there is almost no delay in heating the air.
Also, when the atmospheric temperature is low, the resistance is low, allowing a large current to flow and generating a large amount of heat, and when the atmospheric temperature is high, only a small current flows and the calorific value is small, and the system self-adjusts according to atmospheric temperature changes. Maintain a constant saturation temperature as shown in FIG. Therefore, by appropriately selecting the temperature characteristics and capacity of the PTC heater, it is possible to set an appropriate heater that is sufficient for heating and does not cause the canister to overheat. When the negative pressure in the negative pressure pipe 8 disappears and the purge valve 7 closes, the negative pressure from the negative pressure branch pipe 16 to the negative pressure motor 15 also stops, and the switch 14 is opened, so that the inflow of air for desorption of the canister and the start and stop of heating are performed. It is done in response.

Next, the case where the delay valve 17 is provided will be described. The negative pressure is transmitted from the suction pipe 5 through the one-way valve 17a, and there is no difference from the case described above. When the negative pressure from the suction pipe 5 disappears, the purge valve 7 closes and the flow of desorption air into the canister is stopped. However, since the one-way valve 17a does not open, the negative pressure in the negative pressure motor gradually flows through the orifice 17b. As a result, the switch 14 is kept closed for a considerable period of time, and the PTC heater continues to be heated.
As a result, even when the throttle valve is opened and closed in small increments and frequently to control engine operation, the PTC
Eliminates frequent turning on and off of the heater and eliminates unnecessary inrush current load on the power supply. Also, PTC
Since the heater has the above-mentioned characteristics, it will not overheat even if it is energized when there is no air inflow.

As mentioned above, the fuel vapor release prevention device according to this invention generates heat in response to the inflow of desorption air, and is equipped with a heater that heats it, and the temperature and heat generation characteristics of the heater are selected as desired. Moreover, since the upper temperature limit is saturated, there is no risk of overheating, and since a PTC heater with an extremely fast temperature increase rate is used, the desorption air can be heated safely and appropriately. Furthermore, by adding simple equipment as described above, there is an advantage that a conventional non-heating device can be converted into the fuel vapor release prevention device of this invention.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an embodiment of this invention, Figures 2 and 3 are side and front views of the PTC heater, Figure 4 is a sectional view of the delay valve, and Figure 5 is a temperature characteristic diagram of the PTC heater. . 2... Fuel tank, 4... Canister, 7...
Purge valve, 8... Negative pressure pipe, 11... PTC heater, 14... Switch, 15... Negative pressure motor,
16... Negative pressure branch pipe, 17... Delay valve.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. A fuel vapor release prevention device that temporarily adsorbs fuel vapor in the fuel tank to the adsorption layer of the canister, then sucks in the atmosphere during engine operation, desorbs the fuel vapor, and sends it to the engine side. In this circuit, an atmosphere inlet pipe with the other end open to the atmosphere is provided at the atmosphere inlet of the canister, a positive resistance thermistor heater is interposed in the middle of the atmosphere inlet pipe, and this is connected to a power source and a switch. The switch is connected to a negative pressure motor that communicates with the engine intake pipe directly above the throttle valve through a negative pressure line, and the switch is set to close when the negative pressure motor is in a negative pressure position. Fuel vapor release prevention device. 2. The fuel according to claim 1 of the utility model registration claim, in which a delay valve consisting of a one-way valve that opens only to the intake pipe side of the engine and an orifice arranged in parallel is interposed in the middle of the negative pressure pipe. Vapor release prevention device.