Ignition timing control system for internal combustion engine

Claim 2

The ignition timing control system for an internal combustion engine comprising a circuit for generating a reference ignition signal in synchronism with the rotation of the engine, a circuit for generating a retard ignition signal at a point shifted by a selected shaft angle of the engine from the reference ignition signal, and an ignition circuit for controlling the ignition timing of the engine according to the retard ignition signal, wherein said retard ignition signal generator includes a capacitor circuit for charging and discharging, a first current circuit for always supplying a first current to the capacitor circuit, said first current circuit forming a first current mirror circuit including a first transistor coupled to said capacitor circuit, a second current circuit for supplying said capacitor circuit with a second current which has reverse polarity to the first current and which is equal to the sum of the first current and a discharge current from the capacitor circuit, said second current circuit forming a second current mirror circuit including a second transistor coupled to said capacitor circuit, a switching circuit which starts the flow of the second current in synchronism with the reference ignition signal and cuts off the second current when the terminal voltage across said capacitor circuit reaches a reference level, and an output circuit for generating the retard ignition signal when the terminal voltage across said capacitor circuit reaches the reference level, wherein each of said first and second current circuits comprises a series circuit of a resistor and a diode which is connected with an emitter-base path of each of said first and second transistors in parallel, so that the collector currents of said first and second transistors are equal to the first and second currents respectively.

Claim 3

The ignition timing control system as defined in claim 1, further comprising means for changing the ratio of said first current to said second current according to the operation condition of the engine.

Claim 4

The ignition timing control system for an internal combustion engine as defined in claim 2, wherein said ratio changing means includes means for generating a control signal according to an operation condition of the engine to control a base current of said first transistor.

Claim 5

The ignition timing control system for an internal combustion engine as defined in claim 2, wherein said ratio changing means includes means for generating a plural step control signal according to the operating condition of the engine to control a base current of the first transistor.

Claim 6

The ignition timing control system for an internal combustion engine as defined in claim 1 or 2, wherein said capacitor circuit includes at least two capacitors, and the capacitors are connected so that the total capacity of the capacitors becomes larger when the engine starts.

Claim 7

The ignition timing control system for an internal combustion engine as defined in claim 3, 4 or 2, including means for decreasing a base current of said second transistor when the engine starts.

Claim 8

The ignition timing control system for an internal combustion engine as defined in claim 5, including means for decreasing a base current of said second transistor when the engine starts.

Claim 9

The ignition timing control system for an internal combustion engine as defined in claim 1, wherein said retard ignition signal generator further includes a trigger circuit which generates a trigger signal in synchronism with said reference ignition signal, and means for making said second transistor operative by the trigger signal to start said second current.

Claim 10

The ignition timing control system for an internal combustion engine as defined in claim 8, wherein said trigger circuit includes a delay circuit for delaying said reference ignition signal and a circuit for generating a trigger signal which has a pulse width of the delay time interval of the delay circuit.

Claim 11

The ignition timing control system for an internal combustion engine as defined in claim 9, wherein said delay circuit is a Miller intergrator.

Claim 12

An ignition timing control system for an internal combustion engine comprising a circuit for generating a reference ignition pulse in synchronism with the engine, a circuit for generating a retard ignition pulse which has a leading edge in synchronism with a trailing edge of the reference ignition pulse and a trailing edge which appears at a point shifted by a selected shaft angle of the engine from the trailing edge of the reference ignition pulse, and an ignition circuit adapted to start the flow of current at a point of the leading edge of said reference ignition pulse in a primary winding of an ignition coil and to cut off the primary winding current at a point of the trailing edge of said retard ignition pulse, wherein said retard ignition pulse generator includes a capacitor circuit for charging and discharging, a first constant-current circuit for always supplying a first current to said capacitor circuit, a second constant-current circuit for supplying a second current which has reverse polarity to and a value larger than the first current, a switching circuit which starts the flow of the second current in synchronism with the trailing edge of the reference ignition pulse and cuts off the second current when the terminal voltage across said capacitor circuit reaches a reference level, and an output circuit for generating a retard ignition pulse which has a pulse width corresponding to the time interval during which said second current flows, and wherein said ignition timing control system further includes a a circuit for generating a delay pulse having a leading edge which is synchronized with the leading edge of said reference ignition pulse and a trailing edge which is delayed from the trailing edge of said reference ignition pulse, and a circuit for applying to said ignition circuit an ignition pulse which has a pulse width of the time interval from the leading edge of the reference ignition pulse to the trailing edge of the retard ignition pulse by combining said retard ignition pulse with said delay pulse.

Claim 13

An ignition timing control system for an internal combustion engine comprising a circuit for generating a reference ignition pulse in synchronism with the engine, a circuit for generating a retard ignition pulse which has a leading edge in synchronism with a trailing edge of the reference ignition pulse and a trailing edge which appears at a point shifted by a selected shaft angle of the engine from the trailing edge of the reference ignition pulse, and an ignition circuit adapted to start the flow of current at a point of the leading edge of said reference ignition pulse in a primary winding of an ignition coil and to cut off the primary winding current at a point of the trailing edge of said retard ignition pulse, wherein said retard ignition pulse generator includes a capacitor circuit for charging and discharging, a first constant-current circuit for always supplying a first current to said capacitor circuit, a second constant-current circuit for supplying a second current which has reverse polarity to and a value larger than the first current, a switching circuit which starts the flow of the second current in synchronism with the trailing edge of the reference ignition pulse and cuts off the second current when the terminal voltage across said capacitor circuit reaches a reference level, and an output circuit for generating a retard ignition pulse which has a pulse width corresponding to the time interval during which said second current flows, and wherein said ignition timing control system further includes a a circuit for generating a delay pulse having a leading edge which is synchronized with the leading edge of said reference ignition pulse and a trailing edge which is delayed from the trailing edge of said reference ignition pulse, and a circuit for applying to said ignition circuit an ignition pulse which has a pulse width of the time interval from the leading edge of the reference ignition pulse to the trailing edge of the retard ignition pulse by combining said retard ignition pulse with said delay pulse.

Claim 14

The ignition timing control system for an internal combustion engine as defined in claim 11, wherein said delay pulse generating circuit is a Miller intergrator.

Claim 15

The ignition timing control system for an internal combustion engine as defined in claim 11, further including a current limiting circuit for maintaining an output current from said ignition circuit within a selected level.

Claim 16

The ignition timing control system for an internal combustion engine as defined in claim 13, further including a current limit time reducing circuit for generating an output voltage in proportion to the time interval during which said current limiting circuit limits the output current of said ignition circuit, wherein said reference ignition pulse generator includes means for controlling by said output voltage a level for activating a switching circuit which generates said reference ignition pulse.

Claim 17

The ignition timing control system for an internal combustion engine as defined in claim 11, further comprising means for controlling a leading edge of said ignition pulse according to a current value in the primary winding of the ignition coil to obtain a required current in said primary winding, and means for controlling a trailing edge of said ignition pulse according to the operation condition of the engine.

Claim 18

An ignition timing control system for an internal combustion engine comprising a circuit for generating a reference ignition signal in synchronism with the engine, a circuit for generating a retard ignition signal at a point shifted by a selected shaft angle from the reference ignition signal, a circuit for selecting either of said reference ignition signal and said retard ignition signal, and an ignition circuit for controlling the ignition timing of the engine according to the ignition signal selected by said selecting circuit, wherein said retard ignition signal generator includes a capacitor circuit for charging and discharging, a first constant-current circuit for always supplying a first current to the capacitor circuit, a second constant-current circuit for supplying to said capacitor circuit a second current which has reverse polarity to and a value larger than said first current, a switching circuit which starts the flow of said second current in synchronism with said reference ignition signal and cuts off said second current when the terminal voltage across said capacitor circuit reaches the reference level, wherein when said reference ignition signal is selected, said selecting circuit operates to continue the flow of said second current through said switching circuit.

Claim 19

An ignition timing control system for an internal combustion engine comprising a circuit for generating a reference ignition signal in synchronism with the engine, a circuit for generating a retard ignition signal at a point shifted by a selected shaft angle from the reference ignition signal, a circuit for selecting either of said reference ignition signal and said retard ignition signal, and an ignition circuit for controlling the ignition timing of the engine according to the ignition signal selected by said selecting circuit, wherein said retard ignition signal generator includes a capacitor circuit for charging and discharging, a first constant-current circuit for always supplying a first current to the capacitor circuit, a second constant-current circuit for supplying to said capacitor circuit a second current which has reverse polarity to and a value larger than said first current, a switching circuit which starts the flow of said second current in synchronism with said reference ignition signal and cuts off said second current when the terminal voltage across said capacitor circuit reaches the reference level, wherein when said reference ignition signal is selected, said selecting circuit operates to continue the flow of said second current through said switching circuit.

Claim 20

The ignition timing control system for an internal combustion engine as defined in claim 16, wherein said retard ignition signal generator further includes a trigger circuit which generates a trigger signal in synchronism with said reference ignition signal, thereby to start the flow of said second current.

Claim 21

The ignition timing control system for an internal combustion engine as defined in claim 17, wherein when said reference ignition signal is selected, said selecting circuit inhibits a trigger signal from said trigger circuit.

Claim 22

The ignition timing control system for an internal combustion engine as defined in claim 18, wherein said selecting circuit further operates to maintain continuous flow of said second current through said switching circuit when said selecting circuit inhibits the trigger signal from said trigger circuit.