Case Study of Development Project of Silent Hair Cup Motor for Miniature Medical Automatic Injection Device

Development basis and background

 

In the field of micro medical injection devices, there have been changes from needle mechanical syringes to needle-free mechanical syringes. In recent years, many medical device companies have begun to develop and adopt electric injection devices. However, such electric devices are generally large in size, which is not conducive to carrying. On the other hand, professional medical personnel are required to assist in operation. There are limitations in the use of certain fields, such as insulin auto-injectors in the field of diabetes. As the heart drive motor of this type of device, large torque, high speed and large volume are no longer the focus of consideration. On the contrary, the structure is small in size, capable of rapid drive response, low noise, long life, high power density, and excellent comprehensive stability. It is the factor that needs to be considered.

 

At present, a large medical equipment company is actively contacting with our company, preparing to fully cooperate with our company to develop a miniature silent hollow cup motor for automatic insulin injection. This motor is driven by battery DC and is expected to be installed on an ultra-small portable device with internal insulin automatic detection device and reserved syringe and other accessories. The device is placed in a certain part of the human body and can automatically inject according to the insulin level of the human body, it greatly reduces the unforeseen risks and treatment difficulties of patients with such chronic diseases.

 

Main R & D contents and results

 

R & D content:

1. Development and design of motor contact shrapnel

1) The original development and research of a phosphor bronze material L-shaped structure contact shrapnel to replace the electronic wire, the thickness of the shrapnel is 0.15mm, the bottom layer is tin-plated, and the surface layer is gold-plated to increase the conductivity of the contact shrapnel;

2) The positive and negative shrapnel is designed to match the rear cover closely with the convex point structure in seconds, and a new type of rear cover is developed and designed at the same time, so that the vertical arm of the shrapnel and the groove of the rear cover are matched in shape to ensure the strength of the combination to the maximum extent;

3) The vertical arm of the L-shaped contact shrapnel and the horizontal arm are at a 95 degree angle, so as to ensure a certain amount of preloading during assembly; At the same time, considering that the shrapnel itself is easy to deform, the positive and negative cross arms are falsely connected in the structure to avoid deviation of angle and consistency caused by deformation during subsequent production and testing.

 

2. Mute matching optimization design.

Through the optimization design of motor assembly and structural process, including tolerance and precision analysis of bearings, rotor components, commutator and brushes, the optimization analysis of assembly production process, the use of new materials and motor noise reduction materials, so as to design and develop a new type of motor noise reduction.8500±10% RPMNoise level up42dBAThe following silent hollow cup motor.

 

3. Realization of rotor winding optimization technology based on integrated rotor structure and high power density requirements

The power and power density of ultra-miniature air-core cup motors at low rotating speed often fail to meet the requirements. The traditional manual coil wiring method is not neat and unreasonable, which often leads to large changes in phase resistance, large changes in rotating speed, increased imbalance in motor operation, decreased stability of motor performance, short circuit between wires and other defects. Through the research on multi-objective function optimization design technology of hollow cup winding structure, we calculated the total number of turns, pitch and groups, at the same time, using the structural characteristics, external performance requirements and spatial position of the motor, the high-precision manufacturing mold and tooling fixture of the hollow cup rotor are optimized and designed, and the automatic production equipment of the hollow cup rotor coil is introduced, so that the plane coil is wound on the forming core rod and flattened, then crimped and formed into the laminated winding cup shape, the head and tail are overlapped and bonded to form the rotor cup, through the optimization design, the rotor can effectively reduce the magnetic circuit air gap, greatly increase the effective length of the coil cutting magnetic field, improve the utilization rate of permanent magnets, and under the same effective cutting magnetic field line state, the resistance is small, which can greatly reduce the copper loss and improve the power density.

 

 

 

R & D Results:

The project has carried out a more comprehensive analysis and research on the structure, process and automation of the motor, and has achieved good results in all stages. At least has been developed.3Series models more20A kind of miniature medical automatic injection device with silent hollow cup motor. The product structure and process of the project are original, the development and development of equipment and tooling are in the forefront of domestic research, the overall size of the product is small, high efficiency and energy density, high technology and assembly technology content, high cost performance, focusing on the miniaturization of motors, integration and permanent magnetization. It can be said that the current research on such motors in China is still in the initial stage. Even if it is involved, it is only a small part of the research on small hollow cup micromotors. It is the first case to study systematically, comprehensively and scientifically like the project. The development and research of hollow cup micromotors involving the main characteristics of this project have not been reported in the literature. The technical level of the products is in the leading domestic level and can completely replace imported products. The product developed by the project is very suitable for miniature medical drive pump body, and has obtained municipal achievement appraisal and an invention patent.

 

Legend of developed motor

 

 

Application Legend