In the 1960s, there were only oil pressure sensors, oil sensors and water temperature sensors on the car, which were connected to meters or indicators. In the 1970s, in order to control emissions, some sensors were added to help control the car's powertrain, as the catalytic converters, electronic ignition and fuel injection devices that occurred during the same period required these sensors to maintain a certain air-fuel ratio to control emissions. In the 1980s, anti-lock brakes and airbags improved car safety. Today, sensors are everywhere. In the power system, there are sensors for measuring various fluid temperatures and pressures (such as intake air temperature, airway pressure, cooling water temperature, and fuel injection pressure); sensors for determining the speed and position of each part (such as speed, section) Valve opening, camshaft, crankshaft, transmission angle and speed, position of exhaust recirculation valve (EGR), etc.; and sensors for measuring engine load, knock, misfire, and oxygen content in exhaust gas; Sensor for seat position; sensor for measuring wheel speed, road height difference and tire pressure in anti-lock brake system and suspension control device; protecting the airbag of front passengers, not only requires more collision sensors and acceleration sensors, Sensors such as occupant position and weight are also required to ensure timely and accurate work. Sensors are added in the face of side-loading, overhead airbags and more sophisticated side-head airbags from manufacturers. As the researchers use anti-collision sensors (ranging radar or other ranging sensors) to determine and control the lateral acceleration of the car, the instantaneous speed of each wheel and the required torque, the brake system becomes the vehicle stability control. An integral part of the system. In short, the old-fashioned oil pressure sensor and water temperature sensor are independent of each other. Due to the limited maximum or minimum value, some of the actual functions of the sensor are equivalent to the switch. As sensors move toward electronics and digitization, their output values will be more relevant. To this end, manufacturers are developing and producing better sensors. Here are some of the new products in this area.

Ion detection system

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

This information control system, which 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 for processing the ion current signal. It can distinguish the ignition, combustion and explosion of each cylinder. Earthquake situation. A further function would be to monitor the engine's air-fuel condition by controlling the air-fuel ratio of each cylinder based on the combustion conditions exhibited by the ion current.

Quick start oxygen sensor

The CO and HC emissions from the engine during 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 that achieves closed loop control within 15 seconds. The heating device of the sensor is improved by reducing the heating zone and reducing the impedance. Due to the use of new materials and a new temperature control system, the life of the heater is similar to the existing type, improving the low temperature characteristics.

Side slip sensor

Bosch developed a two-way sensor that is a combination of linear accelerometers with piezoelectric crystals. Such a combination is more conducive to sensor setup, signal processing and packaging. The sensor has two micromachined signal generators that each correspond to a reference plane of the measured acceleration direction, and an independent signal corresponding to a certain reference plane can measure the corresponding force. The high quality factor Q value allows the sensor package to be operated under normal pressure.

Piezoelectric resonant angular velocity sensor

The sensor developed by Mitsubishi Electric Corporation is a glass-silicon-glass structure, and its resonating part is a silicon beam made by etching. Excited by an external oscillator, the resonant frequency is about 4KHz. The thickness of the beam is the same as that of the silicon wafer, and its width and length are determined by etching. The connection between the silicon beam and the glass support uses an anodic welding process under vacuum to ensure that the natural frequency variation is small.

The change of the angular velocity can be measured according to the change of the capacitance between the metal electrodes on the glass supports on both sides of the beam caused by the variation of the 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). When the measurement range is ¡À200¡ã/s, the nonlinearity is ¡À1%.

High pressure sensor

Denso develops an immersed high pressure sensor. These sensors can be used to detect oil, hydraulics, gasoline, and air conditioning refrigerant pressures, such as hydraulic control systems for brakes, air compressor compressors and power steering pumps at idle speeds, fuel control systems, suspension control systems, and automatic transmissions. Hydraulic shifting system. The pressure of these systems varies from 2 to 20 MPa, while the sensor can withstand pressures of 38 MPa. This sensor is encapsulated with a resin glue instead of the commonly used metal and glass to form a sufficiently large oil molecular channel to achieve the appearance and Optimized design of the dimensions of the components. All components including the pressure sensing element and the amplifying circuit are concentrated on one chip.

The direct thermal detection device GM R&D Center is experimenting with a direct thermal detection system to suppress the deployment of side airbags at the rear adult seat (RFIS). The temperature of the passenger's seat surface is compared with the driver's seat performance temperature. If the two are different and the difference from the predetermined value is large, the deployment of the airbag is suppressed. The temperature of the passenger seat is measured by a thermistor placed on the surface of the seat, and a direct thermal or non-direct thermal thermistor can be used.

In fact, the suppression system can adopt various detection methods. When the operation of the direct thermal detector is not reliable enough, other methods can be used to improve the reliability of the system. It has been suggested to configure other sensors, such as measuring weight, capacitance, vibration, using ultrasound, microwave, optical and infrared. It has also been suggested to configure a variety of detection devices for a suppression system to make its work more reliable.

Oil viscosity sensor

When to change the oil is generally based on the time or mileage specified by the manufacturer. A few manufacturers have adopted a more advanced approach to calculate the oil change interval by recording engine speed and temperature. Lucas Varity is developing a piezoelectric vibrating viscosity sensor that works like a vibrating viscometer¡ªthe vibrator (ball, sheet, or rod) decays when it is subjected to viscous damping. Therefore, depending on the vibrator of different shapes, some parameters of viscosity and density can be measured. The vibrator of a vibrating viscometer is a quartz rod that can be excited to torsional vibration. By measuring the amplitude and resonance bandwidth corresponding to the viscosity of the liquid, the viscosity can be determined (accurately, the combined value of viscosity and density). . It can be seen that a vibrating viscometer is a device for determining the viscosity by measuring the shear waveform transmitted by the liquid. However, the shear waveform of the contact between the sensing element and the liquid is distorted, resulting in a poor correspondence between the test value and the liquid.

The viscosity sensor provides an interface to improve the contact between the sensing element and the liquid, similar to the well-known ultrasonic transducers used in biomedical and marine vessels.

At the heart of the sensor is a piezoelectric transducer that produces tangential motion when voltage is applied across it. The electrodes are arranged on the surface of the piezoelectric crystal by metal evaporation deposition and then entirely coated with an insulating layer.

A frequency sweeper determines the resonant frequency of the sensing element by the alternating voltage generated by the oscillator. Because the resistance of the sensing element reaches a maximum at resonance, this bee value changes correspondingly as the viscosity of the liquid changes, and is converted into a voltage signal by the peak detecting circuit.

The thickness of the insulating layer is determined according to the range of the measured viscosity, since the shear wave reflected from the liquid interface must be completely absorbed by the insulating layer, so the thickness of the insulating layer is about a quarter wavelength.

Magnetic sensitive speed sensor

SST Technologies has developed an integrated sensor that is a magnetically sensitive speed sensor that combines high magnetic reluctance (GMR) materials with semiconductor devices. High reluctance materials are characterized by changes in their resistance values as a function of the magnetic field. The semiconductor device is composed of a signal processor and a voltage regulator fabricated on the same BICMOS circuit board. The high magnetoresistive material is first sprayed on the BICMOS board base, and it is made into a resistor by a photolithography etching process, which is connected to the BICMOS circuit through an aluminum foil, and then coated with a layer of alloy to gaher the magnetic lines of force.

The sensor is a bipolar structure, and outputs a square waveform pulse signal through level conversion. The output frequency is the same as the rotation frequency of the soft magnetic signal teeth, and the excitation mechanism is a permanent magnet. Since the signal processing circuit of the sensor is DC-coupled, it can handle the zero speed state. And it has high sensitivity to work in a large air gap.

The ABS sensor adopting the above technology has a bipolar structure in which the speed is processed at zero speed and the output signal changes between two levels, and the pulse frequency is the same as the rotation frequency of the signal tooth or the magnetic pole. In the allowable temperature and operating frequency range, the bandwidth ratio is (50 ¡À 10)%, and the gear gap is 2.5, the air gap characteristic can reach 3mm.