BERTSCH RICHARD (DE)
RUPPMANN CLAUS (DE)
| DE3119211C2 | 1984-03-15 | |||
| US3826237A | 1974-07-30 |
| 1. | l. |
| 2. | injected internal combustion engine, the apparatus comprising a tank venting valve (12) for purging the fuel tank at temperatures above a first threshold temperature, characterised by additional fuel input means (10) for feeding additional fuel to the engine at temperatures below a second threshold temperature which is lower than said first threshold temperature. |
| 3. | Apparatus as claimed in claim 1, wherein the tank venting valve and second additional fuel input means (10, 12) are connected to a common output stage (18), and are connected in parallel with each other. |
| 4. | Apparatus as claimed in claim 1 or claim 2, wherein the first additional fuel input means comprises a tank venting valve (12). |
| 5. | Apparatus as claimed in any of claims 1 to 3, wherein the second additional fuel input means comprises a coldstarting valve (10) for increasing the amount of fuel delivered at temperatures below the second threshold temperature. |
| 6. | Apparatus as claimed in claim 4, further comprising a temperaturedependent switch (14) connected in series with the coldstarting valve (10). |
| 7. | Apparatus as claimed in any of the preceding claims, wherein the tank venting valve and the additional fuel input means (12, 10) are connected to a control means (18) which determines when the additional fuel input means (10) is actuated. |
| 8. | Apparatus as claimed in claiπrδ, wherein the control means (18) also determines the quantity of fuel or purging rate to be fed to the engine. |
State of the Art
The present invention relates to an apparatus for use in cold-starting a fuel-injected internal combustion engine, in accordance with the precharacterising clause of claim 1.
In fuel-injected internal combustion engines, the amount of fuel to be injected is calculated by a control device which receives and interprets the signals relating to one or more engine parameters (e.g. load, engine speed etc.), and actuates the injection valve or valves accordingly. However, at low temperatures, the amount of fuel to be injected, as calculated by the control device, is often insufficient for satisfactory operation of the engine. This is due to a number of reasons, primarily the fact that at low temperatures some of the fuel injected condenses in the inlet manifold, reducing the amount of fuel fed to the cylinders, and some fuel condenses in the cylinder itself, leading to incomplete combustion of the fuel actually drawn into the cylinder. This results in a weak mixture in the engine.
It is thus necessary to increase the amount of fuel fed to the engine at low temperatures. It is known to do this firstly by triggering a cold-starting valve independently of the control device, but this involves additional hardware for the connections between the cold-starting valve and the fuel injectors, increasing the cost of such a system. The second way of achieving cold-starting is to connect a cold-starting valve to the
control device via a separate output stage. Again, this has the disadvantage of increased hardware and thus increased cost.
It is an object of the present invention to provide a cold-starting apparatus which does not involve an increase in hardware expenditure, yet which provides satisfactory cold-starting. Advantages of the Invention
The above object is achieved by adopting the features set forth in claim 1. In this way, when one of the first and second fuel regulating means is increasing the supply of fuel, the other of the fuel regulating means is not, and thus the two fuel regulating means cannot act against one another. Another way of viewing it would be that each of the first and second fuel regulating means influences the supply of fuel in that range of temperature where the regulation of the respective regulating means is most accurate and effective. For example, it is more necessary at very low temperatures to ensure that the fuel supply is increased during cranking, rather than being concerned with achieving a theoretically stoichiometric air/fuel mixture.
Further advantages are obtained by the features of claims 2 to 4. Drawings
By way of example only, a specific embodiment of the present invention will now be described, with reference to the accompanying drawing, which is a diagrammatic representation of an apparatus for use in cold-starting a fuel-injection internal combustion engine, in accordance with the present invention. Description of Exemplary Embodiment
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Referring to the figure, the apparatus comprises a cold-starting valve 10, a tank venting valve 12 and a temperature-dependent switch 14 connected to the output of the cold-starting valve 10. The two valves 10, 12 are connected in parallel between a battery connection 16 and earth E, and .an electronic engine fuel injection control device 18 (illustrated schematically as a transitor) is also connected between the battery connection 16 and earth E, in series with each of the cold-starting valve 10 and the tank venting valve 12.
The tank venting valve is used to control the purging rate of fuel from an intermediate storage reservoir which is connected to a vent of the vehicle fuel tank and in which vaporised fuel is collected and condensed.
Each of the cold starting valve 10 and tank venting valve 12 are connected to the control device 18. When the control device 18 determines that the engine is cold and that consequently extra fuel in cranking is required, the control device 18 completes the circuit, and the switch 14 is then closed, and the control device 18 can actuate one of the cold starting valve 10 and the tank venting valve 12.
The tank venting valve can only be effective when the engine temperature is greater than or equal to +10°C, since below this temperature an insignificant amount of fuel is vaporised from the fuel tank for it to be fed into the engine.
Conversely, the temperature-dependent switch 14 is arranged to close when the engine temperature is less than or equal to -5°C. Thus, at temperatures where the tank venting valve 12 is in operation, the temperature- dependent switch 14 ensures that no temperature
compensation for the fuel is effected by the cold- starting valve 10. Conversely, at the temperatures of operation of the cold-starting valve 10, any adjustments made by the control device 18 to the tank venting valve 12 is ineffective, due to the minimal amount of fuel which is vaporised from the fuel tank. Thus, effectively, at temperatures at or below the operational threshold of the cold-starting valve 10, the tank venting valve 12 has no effect.
At low temperatures, the power stage 18 is only actuated in cranking. It is switched off when the engine reaches a speed threshold of, for example, 700 r.p.m.
The operating ranges of the two valves do not overlap. Consequently, any previous adjustment to one of the valves is not impaired by the operation of the other, and each valve effectively operates independently.
The invention, by modification of software in the control device 18 allows an existing control device to perform an additional function without additional expenditure of hardware. The control device can thus optimally activate other cold-starting parameters, since it triggers the cold-starting valve 10 itself.