Physical quantity detector

Patent metadata

Field	Value
Publication number	US-2016349132-A1
Application number	US-201515112714-A
Country	US
Kind code	A1
Filing date	Mar 3, 2015
Priority date	Mar 5, 2014
Publication date	Dec 1, 2016
Grant date	—

Abstract

A physical quantity detector includes: a bridge circuit portion that includes a bridge circuit including a first, second, third, and fourth strain gauges each having a resistance value that changes in response to an application of a physical quantity and to temperature, the bridge circuit portion outputting, as a first detection signal, a first voltage, and outputting, as a second detection signal, a second voltage; a temperature characteristic adjustment portion that is connected in parallel to the bridge circuit portion, and outputs, as a third detection signal, a third voltage corresponding to the input voltage; a first signal processing circuit portion that receives the first and second detection signals, and outputs a first differential voltage; and a second signal processing circuit portion that receives the second and third detection signals, and outputs a second differential voltage.

First claim

1 . A physical quantity detector, comprising:
a bridge circuit portion that includes a bridge circuit including a first strain gauge, a second strain gauge, a third strain gauge, and a fourth strain gauge each having a resistance value that changes in response to an application of a physical quantity and changes in response to temperature, the bridge circuit portion outputting, as a first detection signal, a first voltage obtained at a first middle point between the first strain gauge and the second strain gauge based on an input voltage applied to the bridge circuit, and outputting, as a second detection signal, a second voltage obtained at a second middle point between the third strain gauge and the fourth strain gauge; a temperature characteristic adjustment portion that is connected in parallel to the bridge circuit portion, the temperature characteristic adjustment portion having a resistance value change smaller than a resistance value change of the first strain gauge, the second strain gauge, the third strain gauge, and the fourth strain gauge in response to application of the physical quantity and to the temperature and outputting, as a third detection signal, a third voltage corresponding to the input voltage applied to the bridge circuit portion; a first signal processing circuit portion that receives the first detection signal and the second detection signal, and outputs, as a first differential voltage signal, a first differential voltage obtained by amplifying a differential voltage between the first voltage and the second voltage by a first amplification factor; and a second signal processing circuit portion that receives the second detection signal and the third detection signal, and outputs, as a second differential voltage signal, a second differential voltage obtained by amplifying a differential voltage between the second voltage and the third voltage by a second amplification factor, which is different from the first amplification factor.

2 . The physical quantity detector according to claim 1 , further comprising:
a determination circuit portion that determines an abnormality in the bridge circuit portion by receiving the first differential voltage signal and the second differential voltage signal and by determining whether the first differential voltage and the second differential voltage are within a predetermined normal range.

3 . The physical quantity detector according to claim 2 , further comprising:
a cut-off circuit portion that cuts off an output of a signal which has been determined to be abnormal by the determination circuit portion of the first differential voltage signal output from the first signal processing circuit portion and the second differential voltage signal output from the second signal processing circuit portion, the signal being.

4 . The physical quantity detector according to claim 1 , wherein:
in the bridge circuit portion, respective resistance values of the first strain gauge, the second strain gauges, the third strain gauges, and the fourth strain gauge are set, and the first strain gauge, the second strain gauges, the third strain gauges, and the fourth strain gauge do not satisfy an equilibrium condition, and the bridge circuit portion outputs signals each including an offset component as the first detection signal and the second detection signal; the first signal processing circuit portion has a first offset correction value correcting the offset component, and corrects the first differential voltage by the first offset correction value; and the second signal processing circuit portion has a second offset correction value correcting the offset component, and corrects the second differential voltage by the second offset correction value, the physical quantity detector further comprising:
a constant current circuit portion that supplies a constant current to each of the bridge circuit portion and the temperature characteristic adjustment portion; and
a determination circuit portion that determines an abnormality in the constant current circuit portion by receiving the first differential voltage signal and the second differential voltage signal and by determining whether a sum of the first differential voltage and the second differential voltage is within a predetermined normal range.

5 . The physical quantity detector according to claim 1 , wherein:
the temperature characteristic adjustment portion includes a first resistor and a second resistor having an resistance value identical with the first resistor connected in series, provides a voltage, as the third voltage, obtained at a third middle point between the first resistor and the second resistor, and outputs the third voltage as the third detection signal.

6 . The physical quantity detector according to claim 1 , wherein:
the temperature characteristic adjustment portion includes a single resistor having a LOW side electrically connected to a ground, uses a LOW-side voltage of the single resistor as the third voltage, and outputs the third voltage as the third detection signal.

7 . The physical quantity detector according to claim 1 , wherein:
the temperature characteristic adjustment portion includes a single resistor having a HIGH side to which the input voltage is applied, uses the input voltage of the HIGH side to the single resistor as the third voltage, and outputs the third voltage as the third detection signal.

Assignees

• Denso Corp

Inventors

• Hasegawa Naoki
• Oono Kazuyuki

Classifications

• G01L9/045 Primary

  with electric temperature compensating means (non electric temperature compensating means G01L19/04) · CPC title