Ultrasonic liquid level sensor probe

An ultrasonic liquid level sensor probe, comprising:

• an insertion portion to be inserted into a liquid inside a container;
• and
• a connecting member attachable to the container,
• wherein the insertion portion has piezoelectric plate FPC modules on a wave-transmission side and a wave-reception side attached to an outer peripheral surface of an inner pipe of a double pipe in which an outer pipe and the inner pipe face each other across an arrangement space,
• wherein the arrangement space of the double pipe is closed so as to prevent entry of the liquid, thereby isolating the piezoelectric plate FPC modules on the wave-transmission side and the wave-reception side that are attached in the arrangement space from the liquid,
• wherein the inner pipe has an inner side serving as an entry space in which the liquid enters and rises when the insertion portion is inserted into the liquid,
• wherein the piezoelectric plate FPC modules on the wave-transmission side and the wave-reception side are each in a double-sided arrangement, in which FPCs are bonded to both-side surfaces that are a positive electrode surface and a negative electrode surface of each of two or more piezoelectric plates arranged at intervals,
• wherein each individual piezoelectric plate has a plate shape with one surface in a thickness direction being the positive electrode surface and an opposite-side surface being the negative electrode surface, the positive electrode surface being provided with a positive electrode, the negative electrode surface being provided with a negative electrode,
• wherein one of the FPCs is an FPC for individual electrodes, and another of the FPCs is an FPC for a common electrode,
• wherein the FPC for the individual electrodes has one surface serving as a bonding surface to be bonded to the piezoelectric plates, and has an opposite-side surface serving as an outer surface, the bonding surface being provided with a bonding surface wiring pattern, the outer surface being provided with an outer surface wiring pattern,
• wherein the FPC for the common electrode has one surface serving as a bonding surface to be bonded to the piezoelectric plates, and has an opposite-side surface serving as an outer surface, the bonding surface being provided with a bonding surface wiring pattern, the outer surface being provided with an outer surface wiring pattern,
• wherein the positive electrode of each individual piezoelectric plate, or a positive extraction electrode extracted from the positive electrode to one side surface of opposed side surfaces of the piezoelectric plate, is connected to the bonding surface wiring pattern of the FPC for the individual electrodes, and the bonding surface wiring pattern is connected to the outer surface wiring pattern of the FPC for the individual electrodes through intermediation of through-holes in an electrically conductive manner,
• wherein the negative electrode of each individual piezoelectric plate, or a negative extraction electrode extracted from the negative electrode to another side surface of the piezoelectric plate, is connected to the bonding surface wiring pattern of the FPC for the common electrode, and the bonding surface wiring pattern is connected to the outer surface wiring pattern of the FPC for the common electrode through intermediation of through-holes in an electrically conductive manner,
• wherein the piezoelectric plate FPC modules on the wave-transmission side and the wave-reception side that are fixed to the outer peripheral surface of the inner pipe of the double pipe are fixed in such orientations that ultrasonic waves emitted from the piezoelectric plate FPC module on the wave-transmission side propagate through the entry space to be received by the piezoelectric plate FPC module on the wave-reception side, and
• wherein the connecting member is attached to the double pipe, and is electrically connected to the FPCs of the piezoelectric plate FPC module on the wave-transmission side and the piezoelectric plate FPC module on the wave-reception side.