Robert Boschgmbh

Pierburg Gmbh & Co Kg

Wolfgang Misch

Manfred Henning

Hans Kubach

Adolf Freytag

A first error signal produced by comparison of actual engine speed value with a reference speed value is modified by blocking out of it a component corresponding to speed deviation within a dead zone speed range. The modified signal is then processed separately by proportional and integrating amplifiers of a PI controller each having a characteristic unsymmetrical with respect to the sign of the error signal. Before processing by the integrating amplifier, the modified error signal is further altered by a contribution from a signal proportional to engine speed to compensate for drifts caused by gradual temperature or atmospheric pressure changes. When the engine is not in idling operation, a fedback contribution is supplied at the same place for preloading the integrator for the next idling operation. The separately processed signals are added together to produce a position reference signal for a displaceable idling speed stop for the engine throttle. A final error signal for control of the displaceable stop is obtained by comparing the position of the reference signal with a signal representing actual stop position. When the throttle is actuated by the driver and engine speed rises out of the drive range, the proportional amplifier is blocked and also the stop displacing mechanism, but an addition is made to the stop position reference signal by which the stop controller causes the stop to set a gap between it and the throttle preventing the throttle switch from returning to idling position until another speed comparison showing exit from the drive condition releases the idling speed control.

Idling speed control for internal combustion engines

Regulation of idling speed involves the production of a first error signal by comparing engine speed with a reference idling speed, and then deriving from the first error signal in an amplifying PI controller, proportional and integral components that are added together, for use of the PI sum signal as a reference value signal for the displaceable stop position. The latter is compared to the actual stop position to provide a second error signal for control of electro-pneumatic valves of a positioning device that displaces the stop. Both the proportional and integral components produced in the controller vary assymetrically about the reference idling speed, so that regulation operates more strongly when the engine speed is too low than when it is too high, except for a dead zone on either side of the reference idling speed. When the driver actuates the throttle, a switch signal designates that the idling condition is no longer present and a lower engine speed threshold defines a starting mode of operation at lower speeds and a higher engine speed threshold distinguishes the 'drive' mode from the partial load mode. Suitable operations of the displaceable stop during mode transitions and during operations in non-idling modes are provided. The controller output at the end of the last idling interval is stored for use when the engine returns to the idling mode.

A digital or analogue regulator circuit for activating a pump or pressure reducing valve, whose action respectively raises and lowers the body of a vehicle relative to the rear axle, each operating with a time delay so that temporary level changes will not initiate a regulatory process. Feedback circuits provide hysteresis. In both embodiments, level changes are represented by changes in the collector potential of a transistor and positive and negative feedback are provided to the base of the transistor to create the hysteresis or dead zone. In the digital embodiment, a counter generates the delay and the negative feedback.

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Wiehl, Germany

Wolfgang Misch