Application of piezoelectric ceramics in automotive field

Piezoelectric ceramic materials exhibit both the forward and reverse piezoelectric effects and find extensive utilization in various devices, including piezoelectric sensors, actuators, transducers, and filters.

Piezoelectric Ceramic Materials

Their applications span numerous sectors such as aerospace, information electronics, industrial machinery, medical treatment, and automotive technology. According to statistical projections, the global market for piezoelectric materials and devices is anticipated to attain a value of US$35.4 billion by the year 2026.

Application of piezoelectric ceramics in the automotive sensing field

Automotive sensors serve as the primary information source for the electronic control systems in vehicles, making them pivotal components of these systems. As automobiles increasingly embrace electronics and automation, their dependence on sensors continues to grow. In fact, an ordinary family car can incorporate over 200 sensors. Among these, piezoelectric ceramic sensors include types such as detonation sensors, ultrasonic sensors, and acceleration sensors.

Piezoelectric ceramic detonation sensor

A piezoelectric ceramic detonation sensor comprises a piezoelectric ceramic oscillator, a metal sheet, a sealing gasket, a metal casing, and more. The charge generated by the piezoelectric oscillator is directly proportional to the engine cylinder's vibrations. The resulting voltage is transmitted to the electronic control unit via shielded wiring, allowing detection of the approximately 7kHz vibration-generated voltage. Based on the voltage's magnitude, the electronic control unit determines the occurrence of engine knocking.

Depending on the vibration intensity, the ignition timing is adjusted either promptly or with a delay, preventing knocking in advance. This ensures that the engine operates near the threshold of knocking during ignition, optimizing thermal efficiency and reducing fuel consumption. This approach achieves a knock-free operational state, enabling the engine to perform at its maximum potential in terms of power and economic efficiency.

Ultrasonic sensor

Ultrasonic sensors serve as car reverse collision avoidance and alarm systems. They consist of an aluminum alloy casing, a piezoelectric ceramic transducer, sound-absorbing materials, and lead electrodes. By applying an electrical signal to the piezoelectric ceramics, mechanical vibrations are generated, emitting ultrasonic waves. These waves bounce back upon encountering obstacles during air propagation. Upon reaching the piezoelectric ceramics, they generate an electrical signal.

Ultrasonic Sound Transducer

Through data processing involving time differences, the system calculates and displays the distance between the vehicle and obstacles. In case of an impending collision, the system triggers an alarm. This technology accurately detects small obstacles located behind the vehicle or within the driver's blind spots. Additionally, ultrasonic sensors are employed in electronically controlled suspension systems to directly monitor the distance between the vehicle's chassis and the road surface.

Piezoelectric ceramic acceleration sensor

Piezoelectric ceramic acceleration sensors find application in automotive airbag systems. These sensors consist of two piezoelectric ceramic sheets bonded together with a shared internal electrode, forming a diode structure. They are installed in the direction of vehicle motion, configured as cantilever beams, and integrated with the peripheral circuit using thick-film technology.

Housed within a casing, these sensors detect the instantaneous collision intensity of the vehicle, whether at low or high speeds and convert it into an electrical signal output. In high-intensity collisions, the airbag is deployed promptly and accurately, enhancing the vehicle's safety performance.

Application of piezoelectric ceramics in the automotive drive field

Piezoelectric ceramics harness the inverse piezoelectric effect to create piezoelectric actuators, widely employed in the automotive sector for tasks like controlling electric rearview mirrors, electric doors and windows, and electric seats. This form of actuation offers several advantages: it significantly reduces motor size, boasts precise control, remains immune to electromagnetic interference, operates silently, and can directly facilitate linear motion control without requiring a conversion mechanism to translate rotational motion into linear motion.

One noteworthy innovation in the automotive industry is the piezoelectric injector, a novel fuel injection system driven by piezoelectric ceramics. This technology enables precise control over injection volume and timing, leading to enhanced fuel efficiency and reduced exhaust emissions. Piezoelectric injectors have become a staple in advanced automobile electronic injection systems, outperforming traditional mechanical carburetors. They can boost engine power by 5% to 10% while simultaneously decreasing gasoline consumption by the same margin, resulting in a 20% reduction in exhaust emissions.

Most piezoelectric ceramic drivers utilized in piezoelectric injectors in the market rely on conventional PZT piezoelectric ceramics. These ceramics are favored for their elevated piezoelectric coefficient, dependable performance, and robust mechanical strength. Nevertheless, their Curie temperature (TC) hovers around 360°C, limiting their use to temperatures below 180°C. Consequently, there is an immediate need for the development of high-temperature piezoelectric materials that offer exceptional performance, cost-effectiveness, and temperature stability to expand their applicability in challenging environments.

Application of piezoelectric ceramics in the field of automobile sound insulation and noise reduction

Noise in cars has become a significant factor impacting the overall driving experience. When a car is driven at low speeds and the brake pads make contact with the rotor, it can result in vibrations, sometimes leading to unpleasant, harsh noises. While this noise doesn't affect the braking performance, it often necessitates the unnecessary replacement of brake pads and the addition of various components like gaskets and sound-absorbing materials to eliminate the noise.

One effective solution to mitigate this issue is to incorporate a straightforward piezoelectric ceramic brake mechanism into the car's brake piston. This mechanism introduces a controlled, periodic "jitter" to the support plate within the brake pad assembly. This controlled vibration effectively dampens the vibrations responsible for the sharp noises, allowing for adjustments based on factors such as temperature, humidity, and braking conditions. This solution operates seamlessly as part of the regular wear and tear of the vehicle's drive system.

Application of piezoelectric ceramics in tire pressure detection systems

In traffic accidents, tire failure is a significant contributing factor to sudden incidents, with tire blowouts accounting for a notable portion of such accidents. Consequently, maintaining proper tire pressure while driving and promptly detecting tire leaks are crucial measures for preventing tire blowouts.

Piezo Sensor for Wheel Balancing Machine

The prevailing solution for automated tire condition monitoring in vehicles is the Tire Pressure Monitoring System (TPMS). This system continuously and automatically monitors tire pressure in real-time while the vehicle is in motion, issuing alerts for both tire leakage and low air pressure to enhance road safety.

Presently, TPMS products rely on batteries for power, which unavoidably entails certain drawbacks, including bulkiness, the need for periodic battery replacement, performance degradation in extreme temperatures, and overall reduced battery lifespan. Consequently, there is growing interest in exploring passive TPMS solutions. Indeed, the unique properties of piezoelectric ceramics offer promising avenues for the development of passive TPMS technology.

Conclusion

In recent years, as the number of automobiles in our country has surged, people's expectations for vehicle safety and comfort have grown significantly. This trend is expected to continue as technologies like piezoelectric ceramic materials and structures, environmental conservation, composites, nanotechnology, and other innovations further drive the development and application of advanced piezoelectric ceramics in the automotive industry.