Patent ID: 7472586

Claim:
A flow amount measuring device for measuring a flow amount of injection fluid injected by a fluid injection valve, comprising: a housing for defining an inner space connected with a fluid path for guiding the injection fluid from a source of the injection fluid to the fluid injection valve, the inner space being divided into a first fluid chamber and a second fluid chamber, wherein the first and second fluid chambers are operatively connected with each other so that when the injection fluid is supplied from the source of the injection fluid into the first fluid chamber, the injection fluid of the second fluid chamber is supplied to the fluid injection valve; a partitioning wall for dividing the inner space into the first and second fluid chambers; a movable member movably arranged in the partitioning wall for moving through the partitioning wall to both of the first and second fluid chambers according to pressure difference between the first and second fluid chambers; and a detector for detecting an amount of the movement of the movable member, wherein the movable member has a sealed cavity so that specific gravity of the movable member is substantially the same as that of the injection fluid.