Technology for Increasing the Torque of Hybrid Stepper Motors Using the Radial Flux Method
This information is current as of June 9, 2023.
Conventional hybrid stepper motors have a structure in which an axially magnetized magnet is sandwiched between gear-shaped laminated cores and induces magnetic flux in small teeth to form magnetic poles. In contrast, we have developed a method of inducing magnetic flux and forming magnetic poles by placing radially-magnetized magnets between the small teeth of the gear-shaped iron cores. The new design method allows for a larger magnet cross-sectional area on the magnetic path than conventional hybrid-type stepper motors. The increased magnet cross-sectional area increases the interlinkage magnetic flux that contributes to torque, thus enabling higher torque compared to conventional hybrid types. The commercialized PKP Series High-Torque Type is expected to not only contribute to the downsizing and weight reduction of equipment and shortening of takt time in repetitive operations, but also to reduce losses, increase permissible radial load, and reduce magnetic flux leakage. This report describes the principles and features of high-torque technology using radial flux method.
Contents
- 1. Introduction
- 2. Transition of Increasing Torque for Stepper Motors
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3. Stepper Motor Using the Radial Flux Method
- 3.1. Classification of Stepper Motors
- 3.2. Motor Structure
- 3.3. Magnetic Circuit
- 3.4. Flow of Magnetic Flux
- 3.5. Experimental Results
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4. Features of PKP Series High-Torque Type
- 4.1. Takt Time Reduction
- 4.2. Loss Reduction
- 4.3. Reduction in Size and Weight of Equipment
- 4.4. Improvement of Permissible Radial Load
- 4.5. Influence to the Outside due to Leakage Magnetic Flux
- 5. Summary
To read more, download and refer to the PDF file below.
1. Introduction
A stepper motor is a motor that allows position control in an open-loop system. There are three typical structures: PM type (permanent magnet type), VR type (variable reluctance type), and HB type (hybrid type).
The PM type rotor has a structure with magnets arranged on the surface, and its advantage lies in its high torque from utilizing magnets, but its resolution is low because of the difficulty of producing ultra-small magnets. The VR type rotor consists of an iron core with small gear-shaped teeth. The advantage of this type of rotor is that the resolution can be increased by reducing the distance between the small teeth, but the torque is reduced because no magnets are used. The rotor of the HB type consists of a disk-shaped magnet sandwiched between gear-shaped iron cores (see Figure 4), and this simultaneously achieves high resolution, which is difficult with the PM type, and high torque, which is difficult with the VR type.
Today, HB type stepper motors are used as industrial motors in a variety of applications, including semiconductor manufacturing equipment and precision stages. When improving and developing facilities and equipment, there is a need to shorten takt time and reduce size and weight. To do this, a high-torque motor is necessary.
After explaining the transition to high-torque stepper motors at Oriental Motor, this report describes the structure and magnetic circuit of a stepper motor using the radial induction method, and finally, it explains its features with experimental results.
The full text on this topic can be downloaded as a PDF.
