Ignition timing adjusting system for spark-ignition internal combustion engines

Claim 2

In an ignition timing adjusting system for a spark-ignition internal combustion engine having an ignition timer element, an intake tube for delivering a mixture of fuel and air to the engine, and a throttle valve located in the intake tube, the system including a first vacuum actuator having a first air-tight diaphragm chamber, the first actuator being connected to the ignition timer element of the internal combustion engine for advancing the timing of the engine in response to increasing vacuum in the first chamber, a first vacuum line leading from the first actuator chamber and connected to a first vacuum port located in the intake tube downstream of the throttle valve, and an atmospheric pressure line leading from the first actuator chamber to the atmosphere, wherein the improvement comprises: first valve means for opening and closing said first vacuum line when the absolute value of the vacuum in the intake tube at the first intake port is greater and less, respectively, than the absolute value of the vacuum in the first actuator chamber; a second vacuum actuator having a second air-tight diaphragm chamber, the second actuator being connected to the ignition timer element to advance the timing of a spark-ignition internal combustion engine in response to increasing vacuum in the second chamber independently of said first actuator; a second vacuum line leading from the second chamber and connected to a second vacuum port in the inlet tube of the engine; and second valve means for opening and closing the atmospheric pressure line when the pressure of the atmosphere is greater and less, respectively, than a predetermined pressure corresponding to a preselected altitude, the first actuator being adjusted to provide a maximum ignition timing advance greater than the maximum advance provided by the second actuator, so that whenever the atmospheric pressure is less than said predetermined pressure, the first and second valve means will maintain the vacuum in the first actuator chamber at the maximum value of vacuum at the first vacuum port, whereby the first actuator will provide said maximum ignition timing advance for all engine operating conditions whenever the atmospheric pressure is less than said predetermined pressure, and whenever the first actuator chamber is exposed to atmospheric pressure, the second actuator will provide ignition advance according to engine load.

Claim 3

An ignition timing adjusting apparatus according to claim 1 wherein the second vacuum port is located closely upstream of the closed position of the throtte valve for producing a vacuum level in the second vacuum line corresponding to the opening condition of the throttle valve.

Claim 4

An ignition timing adjusting apparatus according to claim 1 further comprising air flow restricting means arranged along said first vacuum line for restricting air flow through the first vacuum port into the intake tube when the second valve means is open to assure that the actuator chamber is subjected to atmospheric pressure.

Claim 5

An ignition timing adjusting apparatus according to claim 1 wherein said first valve means comprises a one-way valve arranged in the first vacuum line so as to allow air flow therethrough from the first actuator chamber but to prevent flow in the reverse direction.

Claim 6

An ignition timing adjusting apparatus according to claim 1 wherein the second valve means comprises an atmospheric pressure responsive valve arranged in the atmospheric pressure line so as to permit air flow therethrough only when the atmospheric pressure is greater than said predetermined pressure.

Claim 7

An ignition timing adjusting apparatus according to claim 1 wherein the first and second actuators are mounted coaxially in tandem.

Claim 8

In an ignition timing adjusting system for a spark-ignition internal combustion engine having an ignition timer element, an intake tube for delivering a mixture of fuel and air to the engine, and a throttle valve located in the intake tube, the system including a first vacuum actuator having a first air-tight diaphragm chamber, the first actuator being connected to the ignition timer element of the internal combustion engine for advancing the timing of the engine in response to increasing vacuum in the first chamber, a first vacuum line leading from the first actuator chamber and connected to a first vacuum port located downstream relative to the throttle valve in the intake tube, and an atmospheric pressure line leading from the first actuator chamber to the atmosphere, wherein the improvement comprises: a first one-way valve arranged in the first vacuum line so as to allow air flow therethrough from the first actuator chamber but to prevent flow in the reverse direction for opening said first vacuum line only when the absolute valve of the vacuum in the intake tube at the first intake port is greater than the absolute value of the vacuum in the first actuator chamber, a second vacuum actuator having a second air-tight diaphragm chamber, the second actuator being mounted coaxially in tandem with the first vacuum actuator and connected to the ignition timer element to advance the timing of a spark-ignition internal combustion engine in response to increasing vacuum in the second chamber independently of said first actuator; and a second vacuum line leading from the second chamber and connected to a second vacuum port located closely upstream of the closed position of the throttle valve in the inlet tube of the engine, a second atmospheric pressure responsive valve arranged in the atmospheric pressure line so as to permit air flow therethrough only when the atmospheric pressure is greater than a predetermined pressure corresponding to a preselected altitude; and air flow restricting means arranged along said first vacuum line for restricting air flow through the first vacuum port into the intake tube when the second valve means is open, to assure that the actuator chamber is subjected to atmospheric pressure, the first actuator being adjusted to provide a maximum ignition timing advance greater than the maximum advance provided by the second actuator, so that whenever the atmospheric pressure is less than said predetermined pressure, the first and second valve means will maintain the vacuum in the first actuator chamber at the maximum value of vacuum at the first vacuum port, whereby the first actuator will provide said maximum ignition timing advance for all engine operating conditions whenever the atmospheric pressure is less than said predetermined pressure, and whenever the first actuator chamber is exposed to atmospheric pressure, the second actuator will provide ignition advance according to engine load.

Claim 9

In an ignition timing adjusting system for a spark-ignition internal combustion engine having an ignition timer element, an intake tube for delivering a mixture of fuel and air to the engine, and a throttle valve located in the intake tube, the system including a first vacuum actuator having a first air-tight diaphragm chamber, the first actuator being connected to the ignition timer element of the internal combustion engine for advancing the timing of the engine in response to increasing vacuum in the first chamber, a first vacuum line leading from the first actuator chamber and connected to a first vacuum port located downstream relative to the throttle valve in the intake tube, and an atmospheric pressure line leading from the first actuator chamber to the atmosphere, wherein the improvement comprises: a first one-way valve arranged in the first vacuum line so as to allow air flow therethrough from the first actuator chamber but to prevent flow in the reverse direction for opening said first vacuum line only when the absolute valve of the vacuum in the intake tube at the first intake port is greater than the absolute value of the vacuum in the first actuator chamber, a second vacuum actuator having a second air-tight diaphragm chamber, the second actuator being mounted coaxially in tandem with the first vacuum actuator and connected to the ignition timer element to advance the timing of a spark-ignition internal combustion engine in response to increasing vacuum in the second chamber independently of said first actuator; and a second vacuum line leading from the second chamber and connected to a second vacuum port located closely upstream of the closed position of the throttle valve in the inlet tube of the engine, a second atmospheric pressure responsive valve arranged in the atmospheric pressure line so as to permit air flow therethrough only when the atmospheric pressure is greater than a predetermined pressure corresponding to a preselected altitude; and air flow restricting means arranged along said first vacuum line for restricting air flow through the first vacuum port into the intake tube when the second valve means is open, to assure that the actuator chamber is subjected to atmospheric pressure, the first actuator being adjusted to provide a maximum ignition timing advance greater than the maximum advance provided by the second actuator, so that whenever the atmospheric pressure is less than said predetermined pressure, the first and second valve means will maintain the vacuum in the first actuator chamber at the maximum value of vacuum at the first vacuum port, whereby the first actuator will provide said maximum ignition timing advance for all engine operating conditions whenever the atmospheric pressure is less than said predetermined pressure, and whenever the first actuator chamber is exposed to atmospheric pressure, the second actuator will provide ignition advance according to engine load.