The present invention concerns a control method in the case of a fault in an internal combustion engine fitted with a servo-assisted butterfly valve.
The present invention finds useful application in the control of an internal combustion engine of a motor vehicle (or rather, a two-wheeled vehicle), to which the following description will make explicit reference, but without any loss in generality.
Electronics, both passive (sensors to detect control quantities) and active (actuators for directly operating mechanical components), are increasingly present in modern motor vehicles. For example, virtually all motor vehicles have electronic injection, namely fuel injectors that are operated by electric actuators piloted by an electronic control unit, and are fitted with a lambda sensor, or rather a probe able to detect the composition of the exhaust gas. Recently, the application of DBW (Drive By Wire) systems has been proposed, in which the accelerator is no longer mechanically connected to the engine throttle control, but is only connected to a position sensor that detects the position of the accelerator and, in consequence, pilots an actuator that mechanically operated the butterfly valve.
DBW (Drive By Wire) systems are provided with an electronic control unit, which receives readings from a position sensor that detects the position of the accelerator and operates an electric actuator that controls an electric drive that pilots the butterfly valve's actuator. A particularly dangerous fault that would normally impose immediate switching off of the engine (or rather the halting of the motor vehicle) is the disconnection of the cable that connects the electronic control unit to the electric drive that pilots the butterfly valve's actuator, as in this situation the electronic control unit is no longer able to control the position of the butterfly valve.
The object of the present invention is to provide a control method in the case of a fault in an internal combustion engine fitted with a servo-assisted butterfly valve, this control method being of easy and economic embodiment and allowing the vehicle to continue to be driven with reduced performance in order to autonomously reach a service centre.
In accordance with the present invention, a control method is provided in the case of a fault in an internal combustion engine fitted with a servo-assisted butterfly valve as claimed in the attached claims.
The present invention shall now be described with reference to the attached drawings, which illustrate a non-limitative example of embodiment, in which:
In
As shown in
The intake manifold 7 receives fresh air (or rather air coming from the outside environment) through a feed duct 11 regulated by a butterfly valve 12 and is connected to the cylinders 6 via respective intake ports 13 (only one of which is shown in
Each cylinder 6 includes a spark plug 16, which is positioned at the top the cylinder 6 and is cyclically piloted to ignite the mixture at the end of the compression phase (that is in correspondence to TDC—Top Dead Centre). According to the embodiment shown in
An electronic control unit 18 superintends the running of the internal combustion engine 5, piloting the injectors 17 and the spark plugs 16. In addition, the electronic control unit 18 implements a DBW (Drive By Wire) system; in consequence, the butterfly valve 12 is servo-controlled and is operated by an electric actuator 19 that is controlled by the electronic control unit 18 according to the signals received from a position sensor 20, which detects the position of an accelerator 21 of the motorcycle 1 in real time. For safety reasons, the position sensor 20 has at least two mutually redundant potentiometers, so that the reading provided by a potentiometer can always be confirmed by the reading provided by the other potentiometer.
According to the embodiment shown in
The electronic control unit 18 includes a plurality of diagnostic algorithms that are cyclically executed to determine the onset of possible faults in components of the motorcycle 1. Some faults do not involve the main components of the motorcycle 1 and are therefore just signalled to the rider of the motorcycle 1 by the turning on of a specially provided warning light on the instrument panel 27. Instead, other faults involve the main components of the motorcycle 1 and render driving at full performance dangerous for the rider and/or mechanics, whilst driving the motorcycle 1 with reduced performance is possible (or rather, fairly safe) in order to reach a service centre with the motorcycle 1.
In particular, the electronic control unit 18 and possibly the electric drive 24 as well, cyclically check the correct functioning of the connection between the electronic control unit 18 and the electric drive 24. If an interruption in the connection between the electronic control unit 18 and the electric drive 24 occurs, the electronic control unit 18 is no longer able to communicate the desired position for the butterfly valve 12 to the electric drive 24; in this situation, the electric drive 24 is switched off so that the butterfly valve 12 sets itself in a predefined limp-home position and the internal combustion engine 5 is piloted to keep the number of revs constant and equal to a predefined and calibratable emergency value (for example, between 2000 and 3000 rpm).
With respect to normal running, to keep the number of revs constant and equal to the predefined emergency value, the electronic control unit 18 normally cuts the injection of fuel (i.e. it acts on the injectors 17) and/or stops the ignition spark for the mixture inside the cylinder 6 (i.e. it acts on the spark plugs 16).
During the design phase of the internal combustion engine 5 the quantity of limp-home air that is made to pass through the butterfly valve 12 in the limp-home position is determined in advance and this quantity of limp-home air is stored in the electronic control unit 18; therefore, in the case of interruption of the connection between the electronic control unit 18 and the electric drive 24, the quantity of fuel to inject via the injectors 17 is determined in function of the effective number of revs (or rather, the difference between the effective number of revs and the desired number of revs, equal to the predefined emergency value) and in function of the quantity of limp-home air. In this way, it is possible to avoid feeding the cylinders 6 with an excessively rich mixture (i.e. with too much fuel in relation to the air present) or an excessively lean (i.e. with too little fuel in relation to the air present) mixture.
Normally, in the case of interruption of the connection between the electronic control unit 18 and the electric drive 24 (i.e. in the case of interruption of the CAN/BUS type electric cable 23), the electronic control unit 18 sends a switch-off command to the electric drive 24 using the electric cable 25 that controls the switching on and off of the electric drive 24. Obviously, in the case of interruption of the connection between the electronic control unit 18 and the electric drive 24 (i.e. in the case of interruption of the CAN/BUS type electric cable 23), the electric drive 24 could autonomously switch itself off without requiring and/or awaiting a special command from the electronic control unit 18; this possibility renders the system more robust, as it is unaffected by a possible break in the electric cable 25 as well. Alternatively, in order to remain on, the electric drive 24 could require a non-zero electrical voltage on the electric cable 25 and therefore, in the case of the electric cable 25 breaking, the electric drive 24 would autonomously and automatically switch itself off.
The above-described control method for the internal combustion engine 5 in the case of interruption of the connection between the electronic control unit 18 and the electric drive 24 offers numerous advantages, as it is simple and economic to produce, provides a high level of safety for the rider of the motorcycle 1 and allows the rider of the motorcycle 1 to ride the motorcycle 1 (obviously at reduced speed) to a service centre without needing to call a tow truck.
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07425324 | May 2007 | EP | regional |
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Number | Date | Country | |
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20090000594 A1 | Jan 2009 | US |