Eaton Corporation

Jerry A Olson

Hermann Kaiser

Robert S Migrin

Richard A Nellums

James Matthew Brown

A low pressure drop hot film/swirl air flowmeter (10) for an automotive engine is disclosed. The flowmeter includes a main air flow passage (18), a relatively small venturi (20) disposed within the passage for receiving a portion of the air flow, a constant temperature thermal anemometer (48) positioned to sense the air flowing in the throat (44) of the venturi, and a set of swirl vanes (22) operative to impart a swirl to the remainder of the air in the main passage, thereby creating a reduced pressure at the venturi outlet for forced aspiration therethrough without appreciably increasing the pressure drop across the flowmeter. The anemometer includes a bridge circuit (114), one leg of which comprises a resistive sensor (70) within the throat of the venturi. In the preferred embodiment of the invention, an ambient air temperature sensor (72) is included as another of the legs of the bridge to provide temperature compensation for the flowmeter. The anemometer generates an output signal representative of total mass air flow through the flowmeter.

Hot film/swirl fluid flowmeter

A low pressure drop air flowmeter (10) for an automotive engine is disclosed. The meter includes a main air flow passage (26), a relatively small venturi tube (28) receiving a portion of the air flow, a pressure port (74) for sensing stagnation pressure in the main passage, a pressure port (70) for sensing static pressure in the throat of the venturi, and a complimentary pair of sets of stationary swirl vanes (30 & 32) disposed adjacent the outlet of the venturi and operative to jointly impart a swirl through the remainder of the air in the main passage, thereby creating a reduced pressure at the venturi outlet for amplifying the pressure difference between the stagnation and static pressures without appreciably increasing the pressure drop across the flowmeter. The sets of swirl vanes are rotationally displaceable with respect to one another, allowing some of the air to bypass the effect of the swirl vanes without being diverted to a separate passageway. This arrangement results in a fluid flowmeter having a characteristic pressure drop which is less than that for a conventional device, particularly at high flow rates, and which can be easily reconfigured to suit a specific application. Also disclosed is a solenoid valve (54) operative to selectively sample stagnation pressure in the main flow passage and signal pressure in the throat of the venturi and generate an electrical output signal as a function of the difference between these two pressure signals.

Single path adjustable flowmeter

A low pressure drop air flowmeter (10) for an automobile engine is disclosed. The meter contains a main air flow passage (24), a relatively small venturi (20) to receive a portion of the air flow, pressure ports (98a and 120) for sensing stagnation and static pressure and a set of swirl vanes (22) disposed adjacent the outlet of the venturi and operative to impart a swirl to the remainder of the air in the main passage, thereby creating a reduced pressure at the venturi outlet for amplifying the pressure difference between the stagnation and static pressure without appreciably increasing the pressure drop across the flowmeter. A tertiary passage (28) provides a path of fluid communication between points upstream and downstream of the swirl vanes. This passage includes a flow restricting throat (29) which is manually calibrated during or after assembly. Air exiting the tertiary passage impinges upon the swirl to modulate the vortex velocities. This arrangement results in a fluid flowmeter having a characteristic pressure drop which is less than that of a conventional device, particularly at high flow rates. Also disclosed is a solenoid valve (48) operative in the auto-referencing mode to selectively sample stagnation pressure in the tertiary passage or alternatively upstream of the venturi inlet and signal pressure in the throat of the venturi and generate an electrical output signal as a function of the diffrence between these two pressure signals.

Fluid flowmeter

A low pressure drop air flowmeter for an automobile engine is disclosed. The meter contains a main air flow passage, a relatively small venturi to receive a portion of the air flow, pressure ports for sensing stagnation and static pressure and a set of swirl vanes disposed adjacent the outlet of the venturi and operative to impart a swirl to the remainder of the air in the main passage, thereby creating a reduced pressure at the venturi outlet for amplifying the pressure difference between the stagnation and static pressure without appreciably increasing the pressure drop across the flowmeter. A tertiary passage provides a path of fluid communication between points upstream and downstream of the swirl vanes. This passage can be selectively opened or restricted by a valve which, in the preferred embodiment of the invention, opens the tertiary passage with increasing overall flow rate. This arrangement results in a fluid flowmeter having a characteristic pressure drop which is less than that of a conventional device, particularly at high flow rates. Also disclosed is a solenoid valve operative to selectively sample stagnation pressure in the tertiary passage and signal pressure in the throat of the venturi and generate an electrical output signal as a function of the difference between these two pressure signals.

Two stage flowmeter

A low pressure drop air flowmeter for an automotive engine is disclosed. The meter includes a main air flow passage, a relatively small venturi tube receiving a portion of the air flow, a pressure port for sensing stagnation pressure in the main passage, a pressure port for sensing static pressure in the throat of the venturi, and a set of stationary swirl vanes disposed adjacent the outlet of the venturi and operative to impart a swirl to the remainder of the air in the main passage, thereby creating a reduced pressure at the venturi outlet for amplifying the pressure difference between the stagnation and static pressures without appreciably increasing the pressure drop across the flowmeter. Also disclosed is a solenoid valve having a single valving member operative in one position to communicate the stagnation pressure to an absolute pressure transducer and operative in another position to communicate the static pressure to the transducer.

A low pressure drop air flowmeter for an automotive engine is disclosed. The meter includes a main air flow passage, a relatively small venturi to receive a portion of the air flow, a pressure port for sensing stagnation pressure in the main passage, a pressure port for sensing static pressure in the throat of the venturi, and a set of swirl vanes disposed adjacent the outlet of the venturi and operative to impart a swirl to the remainder of the air in the main passage, thereby creating a reduced pressure at the venturi outlet for amplifying the pressure difference between the stagnation and static pressure without appreciably increasing the pressure drop across the flowmeter. A geometrically reconfigurable element is included in the main passage resulting in a swirl rate which increases with increasing air flow but at a decreasing rate. This characteristic results in an output pressure differential signal which varies substantially linearly with flow rate over a relatively large range of operation. The reconfigurable element can be of the iris type which varies the effective tip radius of the swirl vanes, or alternatively, can comprise flexible swirl vanes which present a variable pitch to the remainder of the air flowing in the main passage. Also disclosed is a solenoid valve having a multiple valving arrangement operative to communicate the stagnation pressure to an absolute pressure transducer in one position, to communicate the static pressure with the transducer in another position, and to communicate engine manifold vacuum pressure with the transducer in a third position. Finally, pressure relief means are disclosed which provide a path for fluid communication between the main passage and the atmosphere at a point downstream of the swirl vanes when the direction of the air flow through the meter is reversed, such as when the engine backfires.

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Dearborn, MI, United States of America

Jerry A Olson