23 Sensor Denso Technichal
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Transcript of 23 Sensor Denso Technichal
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Making Sense!
1
In ThIs Issue ■ Outline ■ Construction ■ Operation
nexT Issue ■ Wheel Speed Sensor
Outline
There are many types of pressure sensors to detect the pressure placed upon liquids and gasses. In this session the H1 type refrigerant pressure sensor will be used as an
example to explain sensor construction, and detection principles.
■ Pressure Sensor Examples
Pressure Sensor
Construction
The H1 type pressure sensor is constructed primarily from a housing, O-ring, and sensor chip. The sensor chip measures 3 mm on each side, with a sensor element located in
the center.
■ Sensor Construction
2009sensor Fundamentals #009
SensorName/Type
ApplicationExample
• Rail Pressure (Diesel Vehicles Use)
• Fuel Tank Internal Pressure
• Engine Intake Manifold Pressure • Atmospheric Pressure (EMS Use)
• A/C Refrigerant Pressure• Engine Oil Pressure• Power Steering Oil Pressure• Continuously Variable Transmission (CVT) Oil Pressure• Compressed Natural Gas (CNG) Fuel Pressure
• Direct-Injection Engine Fuel Pressure• Suspension Oil Pressure• Brake Oil Pressure (Master Cylinder, Accumulator)
Pressure Range
5 MPa
H1
H1-20
H3
180 MPa
H2
100 kPa
MAPS
BAPS
10 kPa
TAPS
20 MPa
3 mm
Sensor Chip
Sensor Element
Encased Oil
Metal DiaphragmHousing
O-Ring
Connector Case
Sensor Chip
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LA990009-2390
© 2009 DENSO Sales California, Inc. All rights reserved. This document may not be reproduced or copied, in whole or in part, without the written permission of the publisher. DENSO Sales California, Inc. reserves the right to make changes without prior notice. 9/2009
■ Sensor Element ConstructionThe sensor element is made from single-crystal silicon with a thickness of 300 μm, forming a diaphragm shape. In addition, a bridge circuit is created on the sensor element from four diffusion resistors.
Pedestal
Diffusion Resistors(Bridge Circuit)Diaphragm
Vacuum Chamber
Pressure
300 µm
Operation
If pressure is applied to the inside of the sensor, a metal diaphragm depresses, transmitting the pressure through
the enclosed oil to the sensor element on the chip. When the sensor element diaphragm changes shape due to the applied pressure, the value of the diffusion resistors forming the element also changes due to the Piezoelectric resistance effect*. As a result, the sensor outputs the pressure change as a change in voltage.
* The Piezoelectric resistance effect is a phenomenon under which electric resistance changes due to an applied stress.
■ Pressure sensor usage example in a car A/C cycleThe pressure sensor used in car A/C cycles is known as a refrigerant pressure sensor, and is positioned in the piping between the condenser and the expansion valve. The refrigerant pressure sensor detects refrigerant pressure, and then outputs the value to the A/C ECU as a voltage change. The A/C ECU uses the pressure information to control items such as the discharge volume for variable capacity compressors, and electric fan rotational speed.
Sensor Chip
Output
PressurePressure
Encased Oil
Metal Diaphragm
High
Low
Low HighRefrigerant Pressure
Voltage
Sensor Output Characteristics (Example: Refrigerant Pressure Sensor)
Expansion Valve
Compressor
Condenser
Evaporator
RefrigerantPressure Sensor