Combustion pressure sensor with built-in charge amplifier

Patent metadata

Field	Value
Publication number	US-10247633-B2
Application number	US-201515103032-A
Country	US
Kind code	B2
Filing date	Jan 12, 2015
Priority date	Jan 22, 2014
Publication date	Apr 2, 2019
Grant date	Apr 2, 2019

Abstract

In a combustion pressure sensor having built-in charge amplifier, signal line overheating and deterioration of detection accuracy is restricted. The combustion pressure sensor includes a sensor body that includes a piezoelectric element having one end connected to chassis ground through a housing and detects pressure in a combustion chamber of engine, and a charge amplifier that includes at least a voltage converting unit converting output of the sensor body into voltage signal and a reference voltage generating unit generating reference voltage supplied to the voltage converting unit and operates on power supplied from a signal processing unit disposed outside. The reference voltage generating unit includes a voltage generating circuit having a constant current circuit and a resistor connected in series. The voltage generating circuit has one end connected to power line extending from the signal processing unit, and the other end connected to the end of the piezoelectric element.

First claim

The invention claimed is:

1. A combustion pressure sensor comprising:
a sensor body including a piezoelectric element having a ground side end connected to a chassis ground through a housing, and detecting a pressure in a combustion chamber of an engine; and
a charge amplifier including at least a voltage converting unit that converts an output of the sensor body into a voltage signal and a reference voltage generating unit that generates a reference voltage for being supplied to the voltage converting unit, and operating on a power supplied from a signal processing unit disposed outside of the charge amplifier, wherein
the reference voltage generating unit includes a voltage generating circuit having a constant current circuit and a resistor connected in series with each other,
one end of the voltage generating circuit is connected to a power supply line extending from the signal processing unit,
the other end of the voltage generating circuit is connected to the ground side end of the piezoelectric element, and
the ground side end of the piezoelectric element and a ground line employed for power supplying from the signal processing unit are connected through a ground separating capacitor.

2. The combustion pressure sensor according to claim 1 , wherein
a ground of the voltage converting unit is connected to the ground side end of the piezoelectric element.

3. The combustion pressure sensor according to claim 2 , wherein
the charge amplifier further includes an amplifying unit that differentially amplifies the voltage signal outputted from the voltage converting unit and the reference voltage generated in the reference voltage generating unit to generate a detection signal indicative of a detected combustion pressure in the combustion chamber.

4. The combustion pressure sensor according to claim 1 , wherein
the reference voltage generating unit supplies the reference voltage generated in the voltage generating circuit through a voltage follower circuit.

5. The combustion pressure sensor according to claim 3 , further comprising:
an engine control unit configured to receive and process the detection signal.

6. The combustion pressure sensor according to claim 1 , wherein
an end of the ground separating capacitor connected to the ground side end of the piezoelectric element is connected to the other end of the voltage generating circuit connected to the ground side end of the piezoelectric element.

Assignees

• Denso Corp

Inventors

• Shibata Takayuki
• Ooya Kouji

Classifications

• G01L23/22

  for detecting or indicating knocks in internal-combustion engines; Units comprising pressure-sensitive members combined with ignitors for firing internal-combustion engines · CPC title

• G01L23/10 Primary

  by pressure-sensitive members of the piezoelectric type · CPC title

• G01L19/0681

  Protection against excessive heat · CPC title