Measuring element, mass air flow meter therewith and compensating method for accurately measuring air flow

• US 6,209,402 B1
• Filed: 01/16/1998
• Issued: 04/03/2001
• Est. Priority Date: 01/16/1997
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Yamada, Masamichi
• Primary Examiner(s): Fuller, Benjamin R.
• Assistant Examiner(s): THOMPSON, JEWEL VERGIE
• Application Number:
  US09/008,331
• Time in Patent Office: 1,173 Days
• Field of Search: 73/204.14, 73/204, 73/861.26, 73/204.18, 374/40, 364/571.01
• US Class Current: 73/861.26
• CPC Class Codes: G01F 1/684 Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
• CPC Class Codes: G01F 1/6845 Micromachined devices
• CPC Class Codes: G01F 1/698 Feedback or rebalancing circuits, e.g. self heated constant temperature flowmeters
• CPC Class Codes: G01F 1/699 by control of a separate heating or cooling element

Abstract

An improved measuring element for a mass air flow meter is provided with a temperature sensor for detecting a typical temperature indicative of the impact of heat on a heating resistor. The element is formed on a heat transfer pass from a configuration member supporting a substrate on which the heating resistor for measuring an air flow rate is formed, and an air temperature sensor for detecting air temperature, formed on the substrate and out of the air flow impinging the heating resistor.

Claims

1. A measuring element for a mass air flow meter, comprising:

a substrate;

an air temperature sensor configured for measuring an air temperature of an air stream and arranged on the substrate;

a heating resistor for measuring an air flow rate of the air flow arranged on the substrate;

a housing for supporting the substrate, with the air temperature sensor and the heating resistor being located in the air stream; and

a temperature sensor configured for detecting a substrate temperature operatively arranged on the substrate, wherein the temperature sensor is located inside of the housing and outside of the air stream, and the substrate temperature is used for correcting the detected air stream.

2. The measuring element according to claim 1, wherein the temperature sensor is configured to detect heat emitted from at least one of an internal combustion engine and an evaluation circuit and transferred to the heating resistor.

3. The measuring element according to claim 1, wherein the temperature sensor and the air temperature sensor are comprised of the same material as the heating resistor.

4. The measuring element according to claim 1, wherein the temperature sensor and the air temperature sensor comprise semiconductors.

5. The measuring element according to claim 4, wherein the semiconductors are one of a thermistor, a diode and a transistor.

6. A mass air flow meter, comprising:

a measuring element including a heating resistor on a substrate for measuring an air stream;

an operating circuit for supplying a current to the measuring element and for detecting a signal indicative of the air flow;

a control circuit for calculating the air flow based on a representative signal;

a temperature sensor configured for detecting a substrate temperature arranged on the substrate; and

a memory configured for storing compensation data for an air flow rate-substrate temperature characteristic, wherein the control circuit is operative to compensate the air flow by using the compensation data and the temperature obtained from the temperature sensor.

7. The mass air flow meter according to claim 6, wherein a housing covers the temperature sensor to prevent a direct contact with the air flow.

8. The mass air flow meter according to claim 6, wherein an air temperature sensor configured for detecting an air temperature, which is formed at the substrate outside of the air flow, is in operative contact with the heating resistor.