The deceleration mechanism plays a crucial role in the key components of the starter motor, and its performance directly affects whether the starter motor can operate efficiently. Planetary gear reduction mechanisms and external meshing gear reduction mechanisms are two common types, each with its own advantages. This article will compare their advantages and disadvantages in depth, and explore reasonable selection and design strategies for reduction mechanisms based on key factors such as power, torque requirements, and installation space of the starter motor.
Planetary gear reduction mechanism
Structural principle
The planetary gear reduction mechanism mainly consists of a sun gear, planet gears, planet carriers, and ring gears. The sun gear is located at the center, and multiple planetary gears revolve around it. At the same time, the planetary gears themselves are also rotating, and the planetary carrier supports the planetary gears. The ring gear meshes with the planetary gears. Power is input from the sun gear, transmitted through the planetary gears, and ultimately output by the planetary carrier or ring gear. This unique structure allows multiple planetary gears to jointly bear the load, achieving even distribution of power.
advantage
High transmission efficiency: The meshing method between planetary gears is scientific, with less sliding friction and low energy loss. The transmission efficiency can usually reach 90% -95%, which has obvious advantages in energy utilization.
Compact structure: Multiple planetary gears are evenly distributed, effectively utilizing space and achieving a larger transmission ratio in a smaller volume, suitable for starters with limited installation space.
Strong load-bearing capacity: Multiple planetary gears share the load together, and each planetary gear bears a relatively small load. Therefore, the planetary gear reduction mechanism can withstand a large torque and is suitable for high-power starters.
shortcoming
The manufacturing process is complex: the planetary gear reduction mechanism has many components, high precision requirements, and difficult manufacturing and assembly, leading to an increase in production costs.
Difficulty in maintenance: The internal structure is complex, and once a malfunction occurs, it is difficult for maintenance personnel to troubleshoot and repair the problem, resulting in increased maintenance time and cost.
External gear reduction mechanism
Structural principle
The external gear reduction mechanism consists of a driving gear and a driven gear, which achieve reduction through direct meshing of the two gears. The driving gear is connected to the input shaft, and the driven gear is connected to the output shaft. Power is transmitted from the driving gear to the driven gear, and due to the different number of teeth between the two gears, the speed is reduced and the torque is increased.
advantage
Simple structure: With only two gears meshing with each other, the structure is clear and easy to manufacture and assemble, and the cost is relatively low.
Convenient maintenance: Due to its simple structure, the fault points are easy to locate, and the maintenance operation is relatively simple, which can effectively reduce maintenance costs and time.
shortcoming
Relatively low transmission efficiency: During the meshing process of external gears, there is significant sliding friction between the tooth surfaces, resulting in high energy loss. The transmission efficiency is generally around 80% -85%.
Large space occupation: In order to achieve a larger transmission ratio, the gear size needs to be increased, which will cause the external gear reduction mechanism to occupy a large installation space and is not suitable for starter motors with limited space.
Limited bearing capacity: Only one pair of gears mesh to transmit power, and a single gear can bear a large load, limiting its application in high-power starters.
Selection and design strategy of deceleration mechanism
Select based on power requirements
For low-power starters, such as those for some small cars or motorcycles, the external gear reduction mechanism can meet basic needs due to its simple structure and low cost. High power starters, such as those used in large trucks and construction machinery, require the transmission of significant torque, and the high load-bearing capacity and efficiency of planetary gear reduction mechanisms are more suitable.
Design based on torque requirements
When the starter needs to output a large torque, a planetary gear reduction mechanism is a better choice. The torque output can be optimized by adjusting the number of planetary gears and the gear ratio between the sun gear and the ring gear. For starters with low torque requirements, the external gear reduction mechanism can meet the torque demand by designing the gear module and number of teeth reasonably.
Combined with installation space design
If the installation space of the starter motor is limited, the compact structure advantage of the planetary gear reduction mechanism is prominent, and the volume can be further reduced by optimizing the internal layout. For situations where there is ample installation space, the external gear reduction mechanism can increase the gear size appropriately to improve reliability while meeting the reduction requirements.
The planetary gear reduction mechanism and the external meshing gear reduction mechanism each have their own length. In the selection and design of starter reduction mechanisms, it is necessary to comprehensively consider factors such as power, torque requirements, and installation space, weigh the pros and cons, and choose the most suitable reduction mechanism to ensure efficient and reliable operation of the starter, providing strong guarantees for stable starting of the equipment.
