Abstract: A fluid pressure shock absorber includes a piston connected to an end of a piston rod and slidably moving inside a cylinder tube and dividing the cylinder tube into a piston-side chamber and a rod-side chamber, a rod internal space formed inside the piston rod, a first communication passage communicating the rod-side chamber with the rod internal space, a second communication passage formed in the piston and communicating the piston-side chamber with the rod internal space, and a restrictor provided in the second communication passage to apply a resistance to a flow of a working fluid passing through the second communication passage.

Abstract: An operation state detection system of a work machine includes a recognition portion provided on a work portion, an image pickup device provided on a work machine body portion and configured to pick up an image of the work portion, a calculation portion configured to calculate change amounts when the shapes of the recognition portions in the image picked up by the image pickup device change with the operation of the work portion, and a detection portion configured to the operation state of the work portion on the basis of the change amounts calculated by the calculation portion.