Hot wire flow meter

Claim 2

A hot wire flow meter for generating a signal indicative of the flow rate of a pulsating fluid flow comprising: (a) a wire element positioned in a fluid flow path of said fluid, said wire element having an electrical resistance indicative of the temperature thereof; (b) temperature sensor means positioned in said fluid flow path for generating a temperature signal indicative of the temperature of said fluid; (c) first circuit means for passing an electric current through said wire element and generating a flow rate signal corresponding to said pulsating fluid flow, said first circuit means responsive to the temperature signal for maintaining the magnitude of said flow rate signal substantially independent of the temperature of said fluid; and (d) second circuit means responsive to the flow rate signal generated by said first circuit means for correcting a flow rate signal error by producing an error signal corresponding in value to the difference between the pulsating fluid flow rate and a hypothetical steady state fluid flow rate, and combining the fluid flow rate signal with the error signal to generate a corrected flow rate signal indicative of the actual flow rate of said pulsating fluid.

Claim 3

A hot wire flow apparatus as recited in claim 1 wherein said second circuit means comprises a peak holding means and means for producing said error signal in response to a peak value of said flow rate signal.

Claim 4

A hot wire flow meter as recited in claim 2 wherein said peak holding means comprises an upper peak holding circuit providing an upper peak value of said flow rate signal.

Claim 5

A hot wire flow meter as recited in claim 3 wherein said peak holding means comprises a lower peak holding circuit providing a lower peak value of said flow rate signal.

Claim 6

A hot wire flow meter as recited in claim 1 further including a filter circuit connected between said first and second circuit means for removing noise components from said flow rate signal.

Claim 7

A hot wire flow meter for generating a signal indicative of the flow rate of a pulsating fluid flow comprising: (a) a wire element positioned in a fluid flow path of said fluid, said wire element having an electrical resistance indicative of the temperature thereof; (b) temperature sensor means positioned in said fluid flow path for generating a temperature signal indicative of the temperature of said fluid; (c) first circuit means for passing an electric current through said wire element and generating a flow rate signal corresponding to said pulsating fluid flow, said first circuit means responsive to the temperature signal for maintaining the magnitude of said flow rate signal substantially independent of the temperature of said fluid; and (d) second circuit means responsive to said first circuit means to receive said flow rate signal for generating a corrected flow rate signal indicative of the actual flow rate of said pulsating fluid, said second circuit means having a peak holding means including an upper peak holding circuit providing an upper peak value of said flow rate signal and a lower peak holding circuit providing a lower peak value of said flow rate signal, said second circuit means being responsive to the magnitude of the difference between said upper and lower peak values.

Claim 8

A hot wire flow meter for generating a signal indicative of the flow rate of a pulsating fluid flow comprising: (a) a wire element positioned in a fluid flow path of said fluid, said wire element having an electrical resistance indicative of the temperature thereof; (b) temperature sensor means positioned in said fluid flow path for generating a temperature signal indicative of the temperature of said fluid; (c) first circuit means for passing an electric current through said wire element and generating a flow rate signal corresponding to said pulsating fluid flow, said first circuit means responsive to the temperature signal for maintaining the magnitude of said flow rate signal substantially independent of the temperature of said fluid; and (d) second circuit means responsive to said first circuit means to receive said flow rate signal for generating a corrected flow rate signal indicative of the actual flow rate of said pulsating fluid, said second circuit means having a peak holding means including an upper peak holding circuit providing an upper peak value of said flow rate signal and a lower peak holding circuit providing a lower peak value of said flow rate signal, said second circuit means being responsive to the magnitude of the difference between said upper and lower peak values.

Claim 9

A control system for an internal combusion engine having a hot wire flow meter for generating a signal indicative of the flow rate of a pulsating air flow to said engine, said system comprising: (a) a wire element positioned in an air flow path of said engine, said wire element having an electrical resistance indicative of the temperature thereof, (b) temperature sensor means positioned in said air flow path for generating a temperature signal indicative of the temperature of said fluid, (c) first circuit means for passing an electric current through said wire element and generating a flow rate signal corresponding to said pulsating air flow, said first circuit means including temperature compensating means responsive to the temperature signal for maintaining the magnitude of said flow rate signal substantially independent of the temperature of fluid, (d) second circuit means responsive to said flow rate signal for generating a corrected flow rate signal indicative of the actual flow rate of said pulsating air flow, said second circuit means including a peak holding means for correcting said flow rate signal in response to a peak value of said flow rate signal, and (e) fuel control means connected to receive said corrected flow rate signal for controlling the quantity of fuel injected into said engine.

Claim 10

A control system for an internal combusion engine having a hot wire flow meter for generating a signal indicative of the flow rate of a pulsating air flow to said engine, said system comprising: (a) a wire element positioned in an air flow path of said engine, said wire element having an electrical resistance indicative of the temperature thereof, (b) temperature sensor means positioned in said air flow path for generating a temperature signal indicative of the temperature of said fluid, (c) first circuit means for passing an electric current through said wire element and generating a flow rate signal corresponding to said pulsating air flow, said first circuit means including temperature compensating means responsive to the temperature signal for maintaining the magnitude of said flow rate signal substantially independent of the temperature of fluid, (d) second circuit means responsive to said flow rate signal for generating a corrected flow rate signal indicative of the actual flow rate of said pulsating air flow, said second circuit means including a peak holding means for correcting said flow rate signal in response to a peak value of said flow rate signal, and (e) fuel control means connected to receive said corrected flow rate signal for controlling the quantity of fuel injected into said engine.

Claim 11

A hot wire flow meter as recited in claim 7 wherein said peak holding means comprises an upper peak holding circuit providing an upper peak value of said flow rate signal.

Claim 12

A hot wire flow meter as recited in claim 8 wherein said peak holding means comprises a lower peak holding circuit providing a lower peak value of said flow rate signal.

Claim 13

A hot wire flow meter as recited in claim 9 wherein said second circuit means is responsive to the magnitude of the difference between said upper and lower peak values.

Claim 14

A hot wire flow meter as recited in claim 7 further including a filter circuit connected between said first and second circuit means for removing noise components from said flow rate signal.

Claim 15

A hot wire flow meter for generating a signal indicative of the flow rate of a pulsating fluid flow, comprising: a wire element positioned in a fluid flow path of said fluid, said wire element having an electrical resistance indicative of the temperature thereof; temperature sensor means positioned in said fluid flow path for generating a temperature signal indicative of the temperature of said fluid; first circuit means for passing an electric current through said wire element and generating a flow rate signal corresponding to said pulsating fluid flow, said first circuit means responsive to the temperature signal for maintaining the magnitude of said flow rate signal substantially independent of the temperature of said fluid; and second circuit means connected to receive the flow rate signal for generating a corrected flow rate signal, said second circuit means including means for detecting upper and lower peak values of the flow rate signal and responsive to the difference between said upper and lower peak values to correct said flow rate signal.

Claim 16

A hot wire flow meter for generating a signal indicative of the flow rate of a pulsating fluid flow, comprising: a wire element positioned in a fluid flow path of said fluid, said wire element having an electrical resistance indicative of the temperature thereof; temperature sensor means positioned in said fluid flow path for generating a temperature signal indicative of the temperature of said fluid; first circuit means for passing an electric current through said wire element and generating a flow rate signal corresponding to said pulsating fluid flow, said first circuit means responsive to the temperature signal for maintaining the magnitude of said flow rate signal substantially independent of the temperature of said fluid; and second circuit means connected to receive the flow rate signal for generating a corrected flow rate signal, said second circuit means including means for detecting upper and lower peak values of the flow rate signal and responsive to the difference between said upper and lower peak values to correct said flow rate signal.

Claim 17

A hot wire flow meter for generating a signal indicative of the flow rate of a pulsating fluid flow, comprising: a wire element positioned in a fluid flow path of said fluid, said wire element having an electrical resistance indicative of the temperature thereof; temperature sensor means positioned in said fluid flow path for generating a temperature signal indicative of the temperature of said fluid; first circuit means for passing an electric current through said wire element and generating a flow rate signal corresponding to said pulsating fluid flow, said first circuit means responsive to the temperature signal for maintaining the magnitude of said flow rate signal substantially independent of the temperature of said fluid; and second circuit means connected to receive the flow rate signal for generating a corrected flow rate signal, wherein said second circuit means comprises a peak holding means for correcting said flow rate signal in response to a peak value of said flow rate signal.

Claim 18

A hot wire flow meter for generating a signal indicative of the flow rate of a pulsating fluid flow, comprising: a wire element positioned in a fluid flow path of said fluid, said wire element having an electrical resistance indicative of the temperature thereof; temperature sensor means positioned in said fluid flow path for generating a temperature signal indicative of the temperature of said fluid; first circuit means for passing an electric current through said wire element and generating a flow rate signal corresponding to said pulsating fluid flow, said first circuit means responsive to the temperature signal for maintaining the magnitude of said flow rate signal substantially independent of the temperature of said fluid; and second circuit means connected to receive the flow rate signal for generating a corrected flow rate signal, wherein said second circuit means comprises a peak holding means for correcting said flow rate signal in response to a peak value of said flow rate signal.

Claim 19

A hot wire flow meter as recited in claim 13, wherein said peak holding means comprises an upper peak holding circuit providing an upper peak value of said flow rate signal, and a lower peak holding circuit providing a lower peak value of said flow rate signal.