Abstract: In a joint structure for joining an insertion shaft that is driven to rotate to a reception side shaft having an insertion groove into which the insertion shaft is inserted so that a rotation of the insertion shaft is transmitted to the reception side shaft, a plurality of pairs of opposing side face portions are formed on an outer periphery of the insertion shaft, the insertion groove includes an axial hole that is formed to open onto an end surface of the reception side shaft and coincides with a pair of first side face portions of the side face portions, and a radial hole that is formed to penetrate the reception side shaft in a radial direction and coincides with a pair of second side face portions of the side face portions, and the axial hole and the radial hole are formed such that respective parts thereof intersect.

Abstract: A displaceable spring seat (2) supporting one end of a vehicle suspension spring (S) is supported by a fluid pressure of an operation chamber (J). A screw pump (P) supplying a working fluid to the operation chamber (J) includes a pump chamber (L) defined within a cylinder (10) by a piston (11, a nut (13) formed integrally with the piston (11), and a screw shaft (14) screwed into the nut (13). A guide member (16) fixed to the cylinder (10) is fitted onto an outer circumference of the nut (13) or the piston (11) such that when the screw shaft (14) is driven to rotate, the piston (11) is fed via the nut (13). The guide member (16) formed from a non-metallic, low-friction material, reduces a driving resistance of the piston (11) and improves a durability of a screw portion between the nut (13) and the screw shaft (14).

Abstract: In a front fork which is capable of adjusting a spring force of a suspension spring housed in a fork main body by driving a jack mechanism housed in the fork main body to raise and lower an upper end position of the suspension spring, the jack mechanism defines a pressure chamber by means of a cap member that closes an upper end opening of a vehicle body side tube and a piston member. By supplying and discharging a pressure oil to and from the pressure chamber, the piston member ascends and descends, thereby raising and lowering the upper end position of the suspension spring.