Thermal Flow Sensor

Patent metadata

Field	Value
Publication number	US-2016209255-A1
Application number	US-201414914709-A
Country	US
Kind code	A1
Filing date	Feb 3, 2014
Priority date	Sep 2, 2013
Publication date	Jul 21, 2016
Grant date	—

Abstract

A thermal flow sensor with improved measurement accuracy is provided. The thermal flow sensor includes: an air flow rate detection element with a diaphragm having a thin-film portion in a semiconductor substrate; at least one heat generating resistor on the diaphragm; at least one temperature measuring resistor that detects temperature on each of an upstream side and a downstream side of the heat generating resistor; and a correction circuit portion that processes an output signal of the air flow rate detection element on the basis of temperature difference information of at least the two temperature measuring resistors on the upstream side and the downstream side, wherein a waveform of the output signal processed by the correction circuit portion is a waveform obtained by cutting a part of a mountain part or a valley part constituting a peak value by outputting of an arbitrary predetermined value when the peak value of the waveform exceeds the arbitrary predetermined value.

First claim

1 . A thermal flow sensor, comprising:
an air flow rate detection element with a diaphragm having a thin-film portion in a semiconductor substrate; at least one heat generating resistor on the diaphragm; at least one temperature measuring resistor that detects temperature on each of an upstream side and a downstream side of the heat generating resistor; and a correction circuit portion that processes an output signal of the air flow rate detection element on the basis of temperature difference information of at least the two temperature measuring resistors on the upstream side and the downstream side, wherein a waveform of the output signal processed by the correction circuit portion is a waveform obtained by cutting a part of a mountain part or a valley part constituting a peak value by outputting of an arbitrary predetermined value when the peak value of the waveform exceeds the arbitrary predetermined value.

2 . The thermal flow sensor according to claim 1 , wherein the arbitrary predetermined value is determined from two parameters of an amplitude value and an average flow rate obtained from signals based on the output signal of the air flow rate detection element.

3 . The thermal flow sensor according to claim 2 , wherein the average flow rate and the amplitude value are obtained from signals based on the output signal of the air flow rate detection element using values detected from a circuit that detects a maximum value and a circuit that detects a minimum value.

4 . The thermal flow sensor according to claim 3 , wherein the signals based on the output signal of the air flow rate detection element is a signal corrected by a circuit that compensates response delay of the output signal of the air flow rate detection element.

5 . The thermal flow sensor according to claim 3 , wherein the output signal is subjected to a correcting process by a frequency response circuit.

6 . The thermal flow sensor according to claim 3 , wherein the signal input to the circuit that detects the maximum value and the circuit that detects the minimum value is the signal obtained by correcting the output signal in a linear direction based on a relation between a flow rate and an output.

Assignees

• Hitachi Automotive Systems Ltd

Inventors

• Doi Ryosuke
• Tashiro Shinobu
• Suzuki Kazunori
• Matsumoto Masahiro

Classifications

• G01F5/00

  Measuring a proportion of the volume flow · CPC title

• G01F1/696

  Circuits therefor, e.g. constant-current flow meters · CPC title

• G01F1/72

  Devices for measuring pulsing fluid flows · CPC title

• G01F1/692 Primary

  Thin-film arrangements · CPC title

• G01F1/68 Primary

  by using thermal effects · CPC title