Exhaust gas recirculation system

Claim 2

In an internal combustion engine, the combination comprising: means including an intake passage through which ambient air is drawn into the engine from the surrounding atmosphere; means including an exhaust passage through which exhaust gases are forced from the engine into the surrounding atmosphere; means responsive to the operation of the engine for developing an input signal pressure which differs from the atmospheric pressure by more than a first predetermined amount when the recirculation of exhaust gases from the exhaust passage to the intake passage is desired and which differs from the atmospheric pressure by less than the first predetermined amount when the recirculation of exhaust gases from the exhaust passage to the intake passage is not desired; means including a recirculation valve responsive to the input signal pressure and coupled between the exhaust passage and the intake passage for opening to permit the recirculation of exhaust gases from the exhaust passage to the intake passage through the valve when the input signal pressure differs from the atmospheric pressure by more than the first predetermined amount and for closing to prohibit the recirculation of exhaust gases from the exhaust passage to the intake passage through the valve when the input signal pressure differs from the atmospheric pressure by less than the first predetermined amount; means responsive to operation of the recirculation valve for developing an output signal pressure which differs from the atmospheric pressure by more than a second predetermined amount when the recirculation valve is closed and which differs from the atmospheric pressure by less than the second predetermined amount when the recirculation valve is open; and means responsive to the input and output signal pressures for indicating that the recirculation valve is stuck closed when the input signal pressure differs from the atmospheric pressure by more than the first predetermined amount and the output signal pressure differs from the atmospheric pressure by more than the second predetermined amount or for indicating that the recirculation valve is stuck open when the input signal pressure differs from the atmospheric pressure by less than the first predetermined amount and the output signal pressure differs from the atmospheric pressure by less than the second predetermined amount.

Claim 3

In an internal combustion engine, the combination comprising: means including an intake passage through which ambient air is drawn into the engine from the surrounding atmosphere due to the difference between the atmospheric pressure outside of the passage and an intake pressure inside of the passage which is substantially less than the atmospheric pressure, the intake passage including a recirculation outlet port located within the passage such that the outlet port is exposed to the intake pressure and including an input signal port located within the passage such that the signal port is exposed to an input signal pressure; means including an exhaust passage through which exhaust gases are forced from the engine into the surrounding atmosphere due to the difference between the atmospheric pressure outside of the passage and an exhaust pressure inside the passage which is substantially greater than the atmospheric pressure, the exhaust passage including a recirculation inlet port located within the passage such that the inlet port is exposed to the exhaust pressure; a throttle mounted within the intake passage for movement between a fully closed position and a fully open position to regulate the flow of air through the passage, the throttle located relative to the input signal port such that the input signal pressure is below the atmospheric pressure by at least a first predetermined amount when the throttle is between the fully closed position and the fully open position in which event exhaust gas recirculation is desIred and such that the input signal pressure is not below the atmospheric pressure by at least the first predetermined amount when the throttle is in either the fully closed position or the fully open position in which event exhaust gas recirculation is not desired; means including a recirculation passage connected between the recirculation inlet port of the exhaust passage and the recirculation outlet port of the intake passage for conducting the recirculation of exhaust gases from the exhaust passage to the intake passage due to the difference between the exhaust pressure and the intake pressure, the recirculation passage including an output signal port located within the passage such that the signal port is exposed to an output signal pressure; means including a recirculation valve disposed within the recirculation passage for permitting the recirculation of exhaust gases when the valve is open and for prohibiting the recirculation of exhaust gases when the valve is closed, the recirculation valve located relative to the output signal port such that the output signal pressure is below the atmospheric pressure by at least a second predetermined amount when the valve is closed and is not below the atmospheric pressure by at least the second predetermined amount when the valve is open; means including a valve actuator connected to the recirculation valve and coupled to the input signal port of the intake passage for opening the recirculation valve when the input signal pressure is below the atmospheric pressure by at least the first predetermined amount and for closing the recirculation valve when the input signal pressure is not below the atmospheric pressure by at least the first predetermined amount; means including a first switch actuator connected to the first switching device and coupled to the input signal port of the intake passage for shifting the first switching device from the first state to the second state when the input signal pressure is below the atmospheric pressure by at least the first predetermined amount and for shifting the first switching device from the second state to the first state when the input signal pressure is not below the atmospheric pressure by at least the first predetermined amount; means including a second switch actuator connected to the second switching device and coupled to the output signal port of the recirculation passage for shifting the second switching device from the second state to the first state when the output signal pressure is below the atmospheric pressure by at least the second predetermined amount and for shifting the second switching device from the first state to the second state when the output signal pressure is not below the atmospheric pressure by at least the second predetermined amount; and means for providing a perceptible indication when the first switching device is in the second state and the second switching device is in the first state in which event the recirculation valve is stuck closed or when the first switching device is in the first state and the second switching device is in the second state in which event the recirculation valve is stuck open.

Claim 4

In an internal combustion engine, the combination comprising: means including an intake passage through which ambient air is drawn into the engine from the surrounding atmosphere due to the difference between the atmospheric pressure outside of the passage and an intake pressure inside of the passage which is substantially less than the atmospheric pressure, the intake passage including a recirculation outlet port located within the passage such that the outlet port is exposed to the intake pressure and including an input signal port located within the passage such that the signal port is exposed to an input signal pressure; means including an exhaust passage through which exhaust gases are forced from the engine into the surrounding atmosphere due to the difference between the atmospheric pressure outside of the passage and an exhaust pressure inside the passage which is substantially greater than the atmospheric pressure, the exhaust passage including a recirculation inlet port located within the passage such that the inlet port is exposed to the exhaust pressure; a throttle mounted within the intake passage for movement between a fully closed position and a fully open position to regulate the flow of air through the passage, the throttle located relative to the input signal port such that the input signal pressure is below the atmospheric pressure by at least a first predetermined amount when the throttle is between the fully closed position and the fully open position in which event exhaust gas recirculation is desIred and such that the input signal pressure is not below the atmospheric pressure by at least the first predetermined amount when the throttle is in either the fully closed position or the fully open position in which event exhaust gas recirculation is not desired; means including a recirculation passage connected between the recirculation inlet port of the exhaust passage and the recirculation outlet port of the intake passage for conducting the recirculation of exhaust gases from the exhaust passage to the intake passage due to the difference between the exhaust pressure and the intake pressure, the recirculation passage including an output signal port located within the passage such that the signal port is exposed to an output signal pressure; means including a recirculation valve disposed within the recirculation passage for permitting the recirculation of exhaust gases when the valve is open and for prohibiting the recirculation of exhaust gases when the valve is closed, the recirculation valve located relative to the output signal port such that the output signal pressure is below the atmospheric pressure by at least a second predetermined amount when the valve is closed and is not below the atmospheric pressure by at least the second predetermined amount when the valve is open; means including a valve actuator connected to the recirculation valve and coupled to the input signal port of the intake passage for opening the recirculation valve when the input signal pressure is below the atmospheric pressure by at least the first predetermined amount and for closing the recirculation valve when the input signal pressure is not below the atmospheric pressure by at least the first predetermined amount; means including a first switch actuator connected to the first switching device and coupled to the input signal port of the intake passage for shifting the first switching device from the first state to the second state when the input signal pressure is below the atmospheric pressure by at least the first predetermined amount and for shifting the first switching device from the second state to the first state when the input signal pressure is not below the atmospheric pressure by at least the first predetermined amount; means including a second switch actuator connected to the second switching device and coupled to the output signal port of the recirculation passage for shifting the second switching device from the second state to the first state when the output signal pressure is below the atmospheric pressure by at least the second predetermined amount and for shifting the second switching device from the first state to the second state when the output signal pressure is not below the atmospheric pressure by at least the second predetermined amount; and means for providing a perceptible indication when the first switching device is in the second state and the second switching device is in the first state in which event the recirculation valve is stuck closed or when the first switching device is in the first state and the second switching device is in the second state in which event the recirculation valve is stuck open.