抄録
In this paper, a relation between the limit value of thrust constant and size of a linear DC motor (LDM) that is moving coil type with unipolar is described. It is deduced the relation between the limit value of the thrust constant of the LDM and the dimension of the yokes. Its relation is defined as a relational equation. To maximize the rate of thrust to the volume of LDM, the magnetic flux density in the yoke is adjusted to the value of magnetic saturation. Then, the equation consists. It means that the thrust constant is in inverse proportion to the stroke and proportional to the sectional area of the center yoke. By measurement of the thrust of the LDM and result of the magnetic field analysis (finite element method), the validity of the equation is confirmed. The equation qualitatively agrees with the measurement result, and its maximum error is 26.0 percent. Then two type LDMs are designed to verify the accuracy of the relational equation. One LDM is thin (maximum thickness is 14mm) with long stroke (100mm) for pen recorder. Another LDM is for high response positioning system with strong thrust (20 N). The relational equation agrees well with measured thrust constants of these LDMs, its error is about 14 percent.
