Abstract An ignition timing control device for a turbo-charged internal combustion engine which retards or advances the ignition timing in accordance with the load condition on the engine. The control device acts on a timing adjustment mechanism attached to the distributor to control the ignition timing as a function of the intake manifold pressure. The control device has a housing and a yieldable wall, such as a diaphragm, in the housing forming a pressure chamber on one side thereof. A pressure line is connected to the pressure chamber and opens into the intake manifold at a point swept by the throttle. The manifold pressure, which at that point varies with changes in engine load, is transmitted through the line to the pressure chamber to act on the diaphragm. The diaphragm is coupled to the ignition timing adjustment mechanism so that the timing is advanced or retarded in response to the displacement of the diaphragm. The diaphragm is movable between a neutral position and a retarding position in response to increased pressure in the intake manifold and thereby the pressure chamber to retard the ignition timing, but only when the intake manifold pressure is above a predetermined minimum representing the onset of engine knocking. Preferably, the diaphragm is also movable towards an advancing position in response to negative manifold pressures, representing higher engine speeds and part-load or no-load conditions of the engine, to advance the ignition timing during those operating states.
In a turbo-charged internal combustion engine having an ignition distributor, a throttle valve pivotally contained within the intake manifold of the engine, and an adjustment device acting on the distributor for advancing or retarding the ignition timing, the improvement comprising control means for adjusting the ignition timing as a function of the intake manifold pressure, said control means including a pressure housing, a yieldable wall in said housing forming a pressure chamber on one side thereof, a pressure line connected between said pressure chamber and said intake manifold and opening into said manifold at a point swept by the throttle, wherein changes in manifold pressure are transmitted through said line to said pressure chamber to act on said wall, at least a portion of said wall movable from a neutral position to a retarding position in response to increased pressure in said pressure chamber and to a timing advance position in response to negative pressures in said intake manifold and thereby said pressure chamber, coupling means between said wall and said adjustment device for retarding the ignition timing in response to displacement of said wall from said neutral position toward said retarding position and for advancing the ignition timing in response to displacement of said wall toward said advancing position, biasing means acting on said wall for permitting said wall to be moved toward said retarding position only when the pressure in the intake manifold, and thereby the pressure chamber, exceeds a predetermined minimum corresponding to the onset of engine knocking, wherein said biasing means comprises a first spring, and said housing includes stop means arranged so that said first spring engages the stop means when said wall is in the neutral position or the timing advance position, and said first spring engages said wall to act in opposition to the movement of said wall only when said wall is moved from said neutral position toward the retarding position, and further comprising a second spring acting on said wall in opposition to movement of said wall toward said timing advance position.
Claim 2
Dependent Claim
341 words
In a turbo-charged internal combustion engine having an ignition distributor, a throttle valve pivotally contained within the intake manifold of the engine, and an adjustment device acting on the distributor for advancing or retarding the ignition timing, the improvement comprising control means for adjusting the ignition timing as a function of the intake manifold pressure, said control means including a pressure housing, a yieldable wall in said housing forming a pressure chamber on one side thereof, a pressure line connected between said pressure chamber and said intake manifold and opening into said manifold at a point swept by the throttle, wherein changes in manifold pressure are transmitted through said line to said pressure chamber to act on said wall, at least a portion of said wall movable from a neutral position to a retarding position in response to increased pressure in said pressure chamber and to a timing advance position in response to negative pressures in said intake manifold and thereby said pressure chamber, coupling means between said wall and said adjustment device for retarding the ignition timing in response to displacement of said wall from said neutral position toward said retarding position and for advancing the ignition timing in response to displacement of said wall toward said advancing position, biasing means acting on said wall for permitting said wall to be moved toward said retarding position only when the pressure in the intake manifold, and thereby the pressure chamber, exceeds a predetermined minimum corresponding to the onset of engine knocking, wherein said biasing means comprises a first spring, and said housing includes stop means arranged so that said first spring engages the stop means when said wall is in the neutral position or the timing advance position, and said first spring engages said wall to act in opposition to the movement of said wall only when said wall is moved from said neutral position toward the retarding position, and further comprising a second spring acting on said wall in opposition to movement of said wall toward said timing advance position.