US 4,359,987 AGranted

Digital timing system

AssigneeRobert Bosch GmbH

InventorsJurgen Wesemeyer, Georg Haubner

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Abstract

In an ignition system for internal combustion engines, reference mark signals are furnished during the rotation of a shaft of an engine. These signals are also used to compute engine speed. The microcomputer contains a storage (ROM) in which the constants required to approximate one or at the most two characteristic curves of ignition timing advance angle v. engine speed are stored. Interpolation between the one stored curve and a fixed ignition timing angle or by interpolation between the two stored characteristic curves, a family of other characteristic curves can be generated without requiring any further storage locations. The values required for the other characteristic curves are arrived at by interpolation and, preferably, by division or multiplication by factors of 2 which are accomplished by shifting numbers in a register. After the required values have been computed, they are counted down in a counter which, when it reaches a reference value causes the ignition timing signal to be generated.

Claims6

Dependent claims

In an internal combustion engine having a shaft, means rotating with said shaft for furnishing a first signal when said shaft rotates through a predetermined reference position, means (13) for measuring a predetermined operating parameter or said engine and furnishing an input signal corresponding to the so-measured value, and means (11) for furnishing speed signals in response to said first signal:

apparatus for approximating a plurality of curves of ignition timing advance angle v. engine speed for different values of said parameter, comprising
storage means (15) having a plurality of addressable storage locations for storing all timing advance angle values with reference to a constant timing advance angle required to approximate one of said curves;
means connected to said speed signal furnishing means and said storage means for reading out a timing advance value from a storage location addressed by said speed signal;
computer means (12, 16, 17, 18, 19) connected to said read out means and said measuring means for
translating said input signal value into a designation of one of a plurality of steps of input signal value to each of which a predetermined proportionality factor is assigned, the proportionality factor 1 being assigned to the input value step corresponding to the value of said parameter for which the timing advance values are stored with reference to said one of said curves in said storage means (15), and
multiplying the timing advance angle signal read out by said read out means by the proportionality factor assigned said input value step designated by said input signal as translated by the computing means, to obtain a proportionalized timing advance angle signal, and means for producing an ignition timing signal timed to correspond to said proportionalized timing advance angle signal.

3 more elements

In an internal combustion engine having a shaft, means rotating with said shaft while furnishing a first signal when said shaft rotates to a predetermined reference position, means for measuring a predetermined operating parameter of said engine and furnishing an input signal corresponding to the so-measured value, and means for furnishing speed signals in response to said first signal:

apparatus for interpolatively approximating a plurality of curves of ignition timing advance angle v. engine speed for different values of said parameter, comprising
storage means (15) having a plurality of addressable storage locations for storing all timing advance angle values required to approximate that one of said curves having the lowest timing advance angle values and that one of said curves having the highest timing advance angle values;
means connected to said speed signal furnishing means and said storage means for reading out pairs of timing advance values, one relating to each one of said two curves for which timing advance angle values are stored in said storage means, from storage locations addressed by said speed signal;
computer means connected to said read-out means and said measuring means for
translating said input signal value into a designation of one of a plurality of steps of input signal value lying between the input signal values corresponding to the two curves for which timing angle values are stored in said storage means, a proportionality factor less than unity being assigned to each of said steps;
determining the difference between the pair of timing advance values read out by said read-out means;
multiplying the difference found between said pair of timing advance values by the proportionality factor assigned to said input value step designated by said input signal as translated by the computing means and adding the result algebraically to one of said timing advance values of said pair of values read out by said read-out means, to obtain an interpolated timing advance angle signal, and means for producing an ignition timing signal timed to correspond to said interpolated timing advance signal.

4 more elements

Dependencies are inferred from the claim text.