Internal-combustion engines – Engine speed regulator – Idle speed control
Patent
1993-07-29
1994-12-13
Wolfe, Willis R.
Internal-combustion engines
Engine speed regulator
Idle speed control
123361, F02D 1110, F02D 4116
Patent
active
053721101
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method and a device for closed-loop control of the power delivered by an internal combustion engine propelling a motor vehicle and, more particularly, to such a method and such a device offering improved resistance to random variations in the engine load.
When the engine is in a critical operating phase (idling speed for example), and if a consumer of power, such as an air conditioner, is switched on, a possible stalling of the engine is prevented, according to a known arrangement, by delaying the setting off of the consumer of power until after the end of the critical phase. Such a solution is not, however, applicable if it affects the safety of the vehicle (the case of the activation of an anti-wheel lock device) or if the disturbance causing the overload is not controllable (gust of wind, approach of a gradient, etc.).
Devices are also known for regulating the engine speed in the idling phase, through servocontrol of the rate of rotation of the engine to a predetermined minimum rate of rotation. This minimum rate must be high enough to enable the engine to overcome the friction and inertia of the rotating masses of this engine, whilst also permitting random load variations (switching on of headlights, engaging of a gear in the gearbox, etc.). The response time of such a servocontrol is relatively long because the speed is a slowly varying variable. Moreover, the actuators used in these servocontrols are either accurate but slow (throttle with idle speed position-regulating tappet), or fast but inaccurate (additional solenoid-controlled valve mounted in parallel with a mechanical throttle). It is also possible to criticise the known idle-regulation devices of the prior art, for the excessively long idle-speed entry times required to avoid speed discontinuities.
For all these reasons, the setpoint speeds used in the regulation of an idle phase are purposely set to an exaggeratedly high value, so as to protect the engine from the risks by stalling upon fluctuations in load. This results in exaggerated fuel consumption and pollution by the exhaust gases which it seems necessary to reduce.
EP-A-318467 discloses a method in which the control of idle-speed of an engine is able to withstand the addition of a load like engaging the "Drive" position of a gearbox without having a too high initial rpm count. With this method, a minimum value of the current to be applied to an idle speed control valve is calculated (Ifb), under specific conditions (idling, with no additional load applied to the engine), with a closed-loop control of the rotational speed. Upon detection of the gearbox being in the "drive" position, an additional term (Iat) is added to this minimum value to cope with the additional load exerted by the gearbox. In an other embodiment of this method, during idling phases under feedback mode, an average value (Ixref) of the integral term of the above minimum value is memorised and used, when the system is not in feedback mode, to keep the idle speed control valve to a minimum opening. However, the method disclosed in EP-A-318467 has some major drawbacks: First, it requires that an information about the added load, i.e. the status (D/N) of the gearbox, is provided to the electronic control unit, which will not be possible if the load to be considered is an external one, and second, as many of the known regulation devices, it is only operational during the idle phase, and outside of this phase it is replaced by open-loop controls which do not permit compensation for load variations.
It will also be noted that those of the idle-regulation devices of the prior art which make use of the additional valve mentioned above, mounted in parallel with the inlet duct conventionally fitted with a throttle for regulating the admission of air, thus comprise two actuators which create complicated problems of matching of control laws when leaving an idle-regulation phase.
The subject of the present invention is therefore to provide a method and a device for controlling the power of an in
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Barreau Christian
Bidan Pierre
Boverie Serge
Greenberg Laurence A.
Lerner Herbert L.
Siemens Automotive S.A.
Wolfe Willis R.
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