Fluid flowmeter and engine control system using the same

Abstract

An air temperature sensor sensing an air temperature, supplied with a pulse signal as a driving signal from a pulse signal source, senses an air temperature based on the pulse signal. While the air temperature sensor is self-heated during an electrical current supplying time period by the pulse signal, it is cooled during an electrical current halting time period. Accordingly, the self-heating of the air temperature sensor by the driving signal is suppressed, and a thermal effect on air flow rate sensing elements disposed in an air flow downstream side of the air temperature sensor is also reduced.

1 . A fluid flowmeter for measuring a fluid flow rate by use of a flow rate sensing element, the fluid flowmeter comprising: 
 a temperature sensing element disposed on a first diaphragm formed in a substrate; and    a pulse signal source supplying a temperature sensing pulse signal to the temperature sensing element,    wherein the flow rate sensing element is disposed on a second diaphragm formed on the substrate.    
   
   
       2 . The fluid flowmeter according to  claim 1 , wherein the flow rate sensing element includes: a heating resistance element; a first temperature-sensitive resistance element disposed in a fluid upstream side of the heating resistance element; and a second temperature-sensitive resistance element disposed in a fluid downstream side of the heating resistance element, 
 wherein a fluid flow rate is measured based on the change of resistance of the first temperature-sensitive resistance element and second temperature-sensitive resistance element.    
   
   
       3 . The fluid flowmeter according to  claim 2 , wherein a heating pulse signal is supplied to the heating resistance element, and a control is performed so that the heating resistance element is heated at a constant temperature.  
   
   
       4 . The fluid flowmeter according to  claim 3 , wherein the cycle time of the temperature sensing pulse signal is longer than that of the heating resistance pulse signal.  
   
   
       5 . The fluid flowmeter according to  claim 3 , wherein, to the heating resistance element, there is supplied a pulse signal from the pulse signal source supplying a pulse signal to the temperature sensing element.  
   
   
       6 . The fluid flowmeter according to  claim 1 , wherein a duty ratio of the temperature sensing pulse signal is varied according to the measured fluid flow rate.  
   
   
       7 . A fluid flowmeter comprising: 
 a temperature sensing element disposed on a first diaphragm formed in a substrate,    and a flow rate sensing element disposed on a second diaphragm in the substrate,    wherein a fluid flow rate sensed by the flow rate sensing element is corrected using a fluid temperature sensed by the temperature sensing element so as to measure the fluid flow rate,    the fluid flowmeter further including a pulse signal source supplying a temperature sensing pulse signal to the temperature sensing element, wherein the fluid flow rate is corrected using sensing signal from the temperature sensing element, which is driven by the temperature sensing pulse signal.    
   
   
       8 . The fluid flowmeter according to  claim 7 , wherein the flow rate sensing element includes: a heating resistance element; a first temperature-sensitive resistance element disposed in a fluid upstream side of the heating resistance element; and a second temperature-sensitive resistance element disposed in a fluid downstream side of the heating resistance element, 
 wherein a fluid flow rate is measured based on the change of resistance of the first temperature-sensitive resistance element and second temperature-sensitive resistance element.    
   
   
       9 . The fluid flowmeter according to  claim 8 , wherein a heating pulse signal is supplied to the heating resistance element, and a control is performed so that the heating resistance element is heated at a constant temperature.  
   
   
       10 . The fluid flowmeter according to  claim 9 , wherein the cycle time of the temperature sensing pulse signal is longer than that of the heating resistance pulse signal.  
   
   
       11 . The fluid flowmeter according to  claim 9 , wherein, to the heating resistance element, there is supplied a pulse signal from the pulse signal source supplying a pulse signal to the temperature sensing element.  
   
   
       12 . The fluid flowmeter according to  claim 7 , wherein a duty ratio of the temperature sensing pulse signal is varied according to the measured fluid flow rate.  
   
   
       13 . The fluid flowmeter according to  claim 12 , wherein the duty ratio is varied between 50% or less and a minimum value determined from a temperature sensing sensitivity.  
   
   
       14 . An engine control system comprising: an air flowmeter for sensing a flow rate and temperature of air supplied to an automobile engine; and engine control means for controlling an air flow rate and fuel consumption supplied to the engine based on the air flow rate and air temperature measured by the air flowmeter, wherein: the air flowmeter includes: a temperature sensing element disposed on a first diaphragm formed on a substrate; a pulse signal source supplying a temperature sensing pulse signal to the temperature sensing element; and a flow rate sensing element disposed on a second diaphragm formed on the substrate; and 
 a fluid flow rate sensed by the flow rate sensing element or an ignition timing of the engine is corrected based on the temperature sensing signal from the temperature sensing element driven by the temperature sensing pulse signal.    
   
   
       15 . An engine control system comprising: an air flowmeter for sensing the flow rate and temperature of air supplied to an automobile engine; and engine control means for controlling the air flow rate and fuel consumption supplied to the engine based on the air flow rate and air temperature measured by the air flowmeter, wherein the air flowmeter includes: a temperature sensing element disposed on a first diaphragm formed on a substrate; a pulse signal source supplying a temperature sensing pulse signal to the temperature sensing element; a flow rate sensing element disposed on a second diaphragm formed on the substrate; and air flow rate adjusting means for correcting a fluid flow rate sensed by the flow rate sensing element based on the temperature sensing signal from the temperature sensing element driven by the temperature sensing pulse signal.  
   
   
       16 . The engine control system according to  claim 13 , wherein the duty ratio of the temperature sensing pulse signal is varied according to the measured air flow rate.