Abstract: A fuel injector inhibiting adhesion of deposits and simultaneously improving durability by a simple configuration is provided. A fuel injector having a valve body provided with a main space receiving fuel and an injection hole and a needle movably supported at the valve body and having a seal part at its front end, in which needle the movement causes the seal part to separate from or contact an inner surface of the valve body and thereby open or close a fuel passage communicating the main space and the injection hole of the valve body, the fuel injector characterized in that the injection hole of the valve body is covered by an injection hole coating comprised of a material with a lower adsorption and reactivity with oxygen compared with the material of the valve body itself, and the seal part of the needle is covered by a seal part coating comprised of a material higher in liquid-repellency compared with the material of the needle itself and not forming a metal surface.

Abstract: Melt-spun polyester fibers are taken up in the absence of heat at a speed of 5,000 to 6,000 m/min under conditions that satisfy the following relations (IX) and (X), subsequently heat-treating the fibers for a period of from 0.01 to 0.05 seconds with a heating roller while the length of the melt-spun fibers is held constant with no drawing step being provided between the taking up and heat treatment steps, and finally winding up the heated fibers0.04.ltoreq.L/(SSxd).ltoreq.0.08 (IX)1.0.ltoreq.To.ltoreq.1.5 (X)where L is the distance (cm) between the spinneret and the convergence point, SS is the speed (m/min) of a take up roller, To is the spinning tension (g/d) at a point immediately after the convergence point and D is the filament fineness (d) of the fiber wound up and is within the range of from 1 to 3 d.

Abstract: A polyester fiber and process embodiments for the production thereof are described, wherein the polyester fiber is produced by high-speed spinning and is characterized by a filament fineness of from 1 to 3 d, a strength of at least 4.0 g/d, an elongation of up to 40%, a crystallinity (X.rho.) of from 40 to 55%, a birefringence of from 140.times.10.sup.-3 to 165.times.10.sup.-3, an orientation function of from 0.36 to 0.45 in the amorphous portion, and a thermal shrinking stress that satisfies the relations1.1.ltoreq.ST.sub.200 /ST.sub.100 .ltoreq.2.0 (I)and50.ltoreq.ST.sub.max .ltoreq.180 (II),where ST.sub.100 is the shrinking stress (mg/d) at 100.degree. C., ST.sub.200 is the shrinking stress (mg/d) at 200.degree. C., and ST.sub.max is a peak stress (mg/d) on a thermal shrinking stress curve.