What Advanced Technologies Enable Cixi Qihang's E-bike Motors to Have Low Noise Operation?

In the pursuit of green travel, electric bicycles (E-bikes) are becoming the preferred mode of transportation for more and more people, and as the core component of electric bicycles, the noise level during operation directly affects the user's riding experience. Cixi Qihang Motor Technology Co., Ltd. has demonstrated outstanding performance in the low-noise operation technology of E-bike Motors. With a series of advanced technologies, it has successfully reduced the motor operation noise to an extremely low level, bringing users a quiet and comfortable riding experience.

In the field of mechanical structure design, Cixi Qihang adopts precision gear design and manufacturing technology. The company uses finite element analysis (FEA) method to deeply optimize the gear tooth profile. Finite element analysis can decompose the mechanical properties of gears in detail through computer simulation, accurately calculate the force situation of each part during operation, and design the most reasonable tooth profile shape, effectively reducing the impact force and vibration of gears during mutual meshing. With the help of CNC machining centers for ultra precision gear cutting, the machining accuracy is extremely high, and the tolerance can be controlled within ≤ 0.005mm, ensuring smooth transmission between gears. In order to further improve the durability of gears and reduce friction noise, surface hardening treatment is also carried out on gears, such as carburizing, nitriding and other processes, to form a hard and wear-resistant protective layer on the gear surface. In practical applications of motors, such as in wheel hub motors, using helical gears instead of spur gears can effectively disperse the stress when gears come into contact, greatly reducing the buzzing noise and making the motor run quieter.

Cixi Qihang also has unique technological applications in the core of electric motors - magnetic field control. The company uses non sinusoidal waveform control algorithms, which can accurately adjust the current waveform based on the operating status of the motor, making the motor run more smoothly. Paired with high-performance neodymium iron boron (NdFeB) permanent magnets, the residual magnetic flux density is ≥ 1.2T, and the strong magnetism provides stable power for the motor. In addition, by adopting stator slot groove design and optimizing the pole arc coefficient, the cogging torque, that is, the "lagging" phenomenon generated by the motor during rotation, is effectively suppressed. After technological improvement, the cogging torque is controlled below 5% of the rated torque, which makes the motor almost free from significant vibration and noise during start-up and low-speed operation, achieving ultra quiet operation.

In order to isolate the vibration and noise generated during the operation of the motor from being transmitted to the frame, Cixi Qihang has integrated vibration damping technology into the structural design of the motor. The company has designed a double-layer motor casing and embedded shock-absorbing rubber or aluminum alloy honeycomb structure between the two layers. These special materials and structures are like tiny "buffers" that can absorb the vibration energy generated by the motor during operation and prevent it from propagating to the frame. At the same time, a high-precision dynamic balancing machine is used to dynamically balance the rotor, controlling the residual unbalance within ≤ 5g · mm/kg to ensure the stability of the rotor during high-speed rotation. And low modulus ceramic hybrid bearings are used to further reduce radial and axial vibrations, effectively reducing noise such as "clicking" and "beating" caused by vibration during motor operation. Taking the mid mounted motor as an example, a flexible coupling system is used to separate the motor from the crankshaft assembly, so that the motor vibration will not be transmitted to the parts that the rider directly contacts, greatly improving the quietness of the ride.

In the field of intelligent control, Cixi Qihang innovatively introduces active noise reduction technology into E-bike Motors. A controller based on DSP (Digital Signal Processor) is embedded inside the motor, which can collect real-time vibration data during the operation of the motor. Through the adaptive feedforward active noise reduction algorithm, the controller will analyze the frequency and intensity of the noise based on the collected data, and then generate an opposite noise reduction signal in reverse. It will be released through the magnetic field of the motor to actively cancel out periodic noise, such as harmonic noise generated by gear meshing. In a specific frequency range, such as 200-500Hz, this active noise reduction technology can achieve a noise reduction effect of 5-8dB, further optimizing the noise performance of motor operation.

In the design of the motor's cooling system, Cixi Qihang also fully considers noise control. The company adopts optimized radiator geometry and designs the most favorable shape and layout of heat dissipation fins for air circulation through extensive fluid dynamics simulations and experiments. At the same time, low-noise axial fans are selected, with a speed controlled at ≤ 2500RPM, to ensure efficient heat dissipation while controlling the airflow noise generated by the fan to ≤ 40dB. For high-power motors, natural convection cooling channel design is adopted to avoid noise problems caused by forced air cooling, achieving a perfect balance between efficient heat dissipation and low noise.

As a key component of motor operation, the performance of bearings also has a significant impact on noise control. Cixi Qihang uses preloaded angular contact ball bearings or magnetic levitation bearings, which can greatly reduce frictional resistance. At the same time, a diamond-like carbon (DLC) coating is coated on the surface of the bearing, which has an extremely low friction coefficient and good wear resistance, effectively reducing wear and noise during bearing operation. The bearing noise is controlled below 35dB at full load, making the motor run smoother and quieter.

In terms of motor winding technology, Cixi Qihang adopts multi strand Leeds wire winding. Compared with single strand copper wire, Leeds wire can effectively reduce skin effect and eddy current loss, and improve the electrical performance of the motor. And through the vacuum pressure impregnation (VPI) process, low viscosity epoxy resin is used to fix the winding, enhance the mechanical stability of the winding, suppress the winding vibration caused by electromagnetic force, and thus reduce the electromagnetic "buzzing" sound.

In terms of motor speed control, Cixi Qihang utilizes advanced control algorithms such as Field Oriented Control (FOC) and Sliding Mode Control. These algorithms can accurately adjust the motor speed based on the load situation of the motor and the rider's operating instructions. At the same time, by collecting real-time data from torque sensors, it ensures that the motor remains stable during acceleration and deceleration, avoiding noise caused by sudden speed changes and making the riding process smoother and quieter.

In terms of material application, Cixi Qihang uses a viscoelastic polymer coating with sound absorption properties, which is coated on the inner surface of the motor. This material can effectively absorb high-frequency noise above 1000Hz. The motor core is made of laminated silicon steel sheets with a thickness of ≤ 0.35mm, which has the characteristics of low iron loss and high magnetic permeability, reducing hysteresis and eddy current losses, and reducing the vibration and noise energy generated during motor operation from the source.