Automotive sensors and development trend analysis

I. Introduction

As a key source of information for automotive electronic control systems, automotive sensors provide real-time, accurate measurement and control of a variety of information including temperature, pressure, position, speed, acceleration and vibration. The key to measuring the level of a modern limousine control system is the number and level of its sensors. Currently, there are about one hundred sensors installed in a domestic general household car, while the number of sensors in a luxury sedan is as many as 200. The future of automotive sensor technology is the overall trend of miniaturization, multi-functional and intelligent.

Miniature sensors using micro- mechanical processing techniques micron sensitive element, the signal processor, the data processing device package on a single chip, because of its small size, cheap, easy integration, etc., can significantly improve the accuracy of the test system. At present, the technology is gradually mature, you can make a variety of micro-sensors such as detection mechanics, magnetism, heat and so on. Multi-function refers to a sensor capable of detecting two or more characteristic parameters or chemical parameters, thereby reducing the number of automotive sensors to improve system reliability. Intelligent is the combination of sensors and LSI, with a smart role.

Due to the important role of automotive sensors in automotive electronic control systems and the rapidly growing market demand, various countries in the world attach great importance to their theoretical research, new material applications and new product development. Here are some new products in this area.

Second, the ion detection system

Mitsubishi (Mitsubishi Electronics) is developing a car ion detection system. This system monitors the combustion of each cylinder in the engine by detecting ions. When the combustible mixture continues to burn, ionization occurs near the combustion peak. By placing a biased probe in the cylinder, the ion flow associated with ionization conditions can be measured.

The information control system that reflects various combustion conditions of the engine consists of a spark plug with a probe, an ignition coil with a test accessory, and an electronic module that processes the ion current signal, which discriminates the ignition, combustion and explosion of each cylinder Shock situation. A further function would be to monitor the condition of the engine's mixture, which controls the air-fuel ratio of each cylinder based on the combustion conditions shown by the ion flow.

Third, the rapid start of the oxygen sensor

The CO and HC emitted by the engine in cold running are the most, which requires the oxygen sensor to start into the closed-loop control state as soon as possible. NGK Spark Plug Co., Ltd. has developed a new type of oxygen sensor, which can achieve closed-loop control within 15s. By reducing the heating area and reducing the impedance, the sensor heating device is improved. Due to the new materials and new temperature control system, the heater life is similar to the existing type, improving the low temperature characteristics.

Four, sliding sensor

Bosch develops a bi-directional sensor that is a combination of linear accelerometers using piezo-electric crystals. This combination is more conducive to the sensor settings, signal processing and packaging. The sensor has two micromachined signal generators and each correspond to a reference plane for the direction of the measured acceleration. Corresponding forces can be measured for independent signals corresponding to a reference plane. The high quality factor Q value allows the sensor package can be carried out under atmospheric pressure.

Fifth, the piezoelectric resonant angular velocity sensor

The sensor developed by Mitsubishi Electric Corp. is a glass-silicon-glass structure whose resonant part is a silicon beam made by etching. Excited by an external oscillator, the resonant frequency of about 4KHz. Beam thickness and the same silicon, its width and length by etching process to decide. The connection of the silicon beam to the glass support uses an anodic welding process under vacuum to ensure that the natural frequency does not change much.

The change of angular velocity can be measured according to the change of capacitance between the metal electrodes on the glass supports on both sides of the beam caused by the change of vibration frequency of the silicon beam. The sensor circuit consists of a capacitor voltage (C-V) converter and a synchronous demodulator. The C-V converter is a conversion capacitor comparator (ASIC). The non-linearity is ± 1% when the measurement range is ± 200 ° / s.

Sixth, high-pressure sensor

Denso develops an immersed high-pressure sensor. These sensors can be used to detect oil, hydraulic, gasoline, and air conditioning refrigerant pressures such as brake hydraulic controls, air conditioner compressors and power steering pumps at idle, fuel control systems, suspension control systems, and automatic transmissions Hydraulic shift system. The pressure changes in these systems at 2 ~ 20MPa, and the sensor can withstand 38MPa.

This sensor uses a resin glue instead of the commonly used metal and glass to package, to form a large enough oil molecular channels, to achieve an optimized design of the shape and the components of the sealing size. All components, including pressure sensing components and amplification circuitry, are grouped together on a single chip.

Seven, direct thermal detection sensor

The GM R & D Center is experimenting with a direct-on-the-go test system to suppress the deployment of a side airbag at the rear rear seat (RFIS). The passenger seat surface temperature and driver seat performance temperature comparison, if the difference between the two and the predetermined value, the airbag deployment will be suppressed. The temperature of the occupant's seat is measured by a thermistor mounted on the seat surface. Direct or indirect thermal resistance can be used. In fact, the suppression system can adopt a variety of detection methods. When the direct thermal detector is not reliable enough, other methods may be adopted to improve the reliability of the system. It has been suggested to configure other sensors, such as measuring body weight, capacitance, vibration, the use of ultrasound, microwave, optics and infrared. Others have suggested configuring multiple detection devices for a suppression system to make their work more reliable.

Eight, oil viscosity sensor

When to replace the oil is generally based on the time or mileage specified by the manufacturer. A few manufacturers have adopted a more advanced way to calculate oil change intervals by recording engine speed and temperature. Lucas Varity is developing a piezoelectric vibratory viscometer that works in close proximity to a vibrating viscometer - vibrators (ball, flake or rod) decay in vibration frequency when viscous damping is applied. Therefore, depending on the shape of the oscillator, you can measure the viscosity and density of some of the parameters. A vibratory viscometer vibrator is a quartz rod that can be excited to torsional vibrations. By measuring the amplitude and resonant bandwidth corresponding to the viscosity of the liquid, the viscosity can be determined (to be exact, the viscosity