Exhaust back pressure control

In a motor vehicle having a fuel-burning engine with an exhaust system, including components having variable resistance flow, an exhaust pressure control to automatically maintain a scheduled back pressure on the engine over a normal operating speed and load range despite changes in the flow resistance of the other exhaust components, comprising:

• a pivotal throttling valve located downstream from the engine and upstream from the variable resistance exhaust components;
• positioning means connected to said throttling valve for pivotal control of said throttling valve between open and a more closed operative position;
• an exhaust back pressure sensor including enclosure means with a flexible diaphragm for producing a force in one direction on the diaphragm corresponding to the exhaust pressure upstream from said throttling valve;
• a fluid pump operably connected to said engine for fluid pressurization corresponding to the operation of the engine;
• controller means including an enclosure with an inlet connected to said fluid pump and a reciprocable member supported therein movable in a direction opposite to said one direction of said diaphragm force and in response to the pressure level of said enclosure;
• metering means associated with said enclosure inlet for controlling the pressure transmitted to said enclsoure and being responsive to the engine throttle position so that low throttle positioning produces decreased pressure levels in said enclosure;
• a fluid valve with a movable valving member therein connected to said diaphragm member and said reciprocable controller member and positioned in response to the pressure balance on said member to transmit a pressure to said throttle valve positioning means to maintain a substantially scheduled back pressure over the normal engine speed and load range, whereby said metering means decreases the pressure in said control enclosure when the engine throttle is in a low speed and light load position so as to cause said exhaust throttling valve to move toward a more open position during this low speed and light load operating range.

In a motor vehicle having a fuel-burning engine witn an exhaust system, including components with variable flow resistance, an exhaust pressure control to automatically maintain a scheduled back pressure on the engine over a normal operating speed and load range despite changes in the flow resistance of the other exhaust components, comprising:

• a pivotal throttling valve located downstream from the engine and upstream from the variable resistance components;
• positioning means connected to said throttling valve for controlled pivotal movement of said throttling valve between open and more closed operative positions;
• said positioning means including a housing with a reciprocal member therein moved in response to fluid pressurization of the housing interior, said reciprocal positioning member being operably connected to said exhaust system throttling valve to pivot said throttling valve between open and more closed positions thereby changing the total flow restrictive effect of the exhaust system including said variable flow resistive components;
• a back pressure sensor defining an enclosure with a flexible diaphragm exposed to exhaust system pressure existing upstream from said exhaust throttling valve to produce a diaphragm force in a first direction corresponding to the back pressure on said engine;
• an engine-driven fluid pump for pressurizing fluid in response to operation of the engine;
• a controller assembly including a housing and a movable piston member therein forming enclosures on either side which are fluidly connected to said engine-driven fluid pump to exert forces on said movable piston;
• said pressurized fluid first entering one enclosure on one side of said piston and then flowing past a restrictor to recuce pressure into the other enclosure on a second side of said piston, whereby the net force on the piston member is in a direction opposite to the direction of said diaphragm force and proportional to the pressure level at the inlet of said enclosures;
• means including a tapered metering member at the inlet of said enclosure which is operably connected to the engine fuel control mechanism for regulating fluid pressure within said enclosures so that a low setting of said engine fuel control decreases the pressurization of said first and second enclosures;
• valve means including a reciprocal valving member connected to said diaphragm and said reciprocal piston member of said controller to regulate fluid pressure transmitted to said exhaust throttling valve positioner in response to the force balance of forces on said diaphragm and said movable piston member, thereby establishing a position of said exhaust throttling valve to produce a substantially scheduled exhaust back pressure on said engine in combination with the other variable restriction exhaust components.