Sensor unit and working cylinder with a sensor unit

An operating cylinder unit (50) comprising:

• a cylinder (51),
• a piston rod (52) axially supported in the cylinder which supports a piston (52a), wherein the piston (52a) or the piston rod (52) are axially moveable close to an inner surface of the cylinder (51) and wherein the piston divides an inner cavity of the cylinder (51) in two cylinder cavities (54, 55), which are typically loaded by an operating pressure and are therefore configured as high pressure cavities, wherein the cylinder (51) comprises a cylinder base (51) and a cylinder wall (51) connected to the cylinder base, wherein the cylinder wall has an inner circumferential surface (51b),
• characterized in that
• a sensor unit (1) is arranged in an end portion of the cylinder (51) completely within the cylinder (51), between the cylinder base and the piston and within the inner circumferential surface (51) of the cylinder wall and within one of the two cylinder cavities (54 55), wherein the sensor unit comprises:
• a) a flexible tension element (2),
• a winding drum (3) for the tension element (2),
• at least one encoder magnet (4) that is operatively connected with the winding drum (3),
• a spring (5) that preloads the winding drum (3) in a wind up direction,
• a magnetic field sensitive sensor (6) in a magnetic operating range of the encoder magnet (4),
• a pressure tight planar wall (7) between the encoder magnet (4) and the sensor (6) which separates a sensor cavity (15) in which the sensor (6) is arranged from a mechanical cavity (14),
• b) the sensor unit (1) includes a unit housing (9) which includes at least a sensor housing (9.15) about the sensor cavity (15) with the sensor (6) included therein and a mechanical housing (9.14) about the mechanical cavity (14) and about the winding drum (3), the encoder magnet (4) and the spring (5) being inside the mechanical cavity (3),
• c) the sensor housing (9.15) and the mechanical housing (9.14) are connectable or connected to each other to be handled together as the unit housing (9),
• e) wherein the wall (7) forms part of a wall of the sensor housing (9.15) and/or of the mechanical housing (9.14),
• d) the sensor unit (1) comprises a first seal (8) on an outer surface (9a1) of the sensor housing (9.15) and/or of the mechanical housing (9.14), wherein the first seal (8) is neither inside the sensor cavity (15) nor inside the mechanical cavity (14) and not arranged between the sensor housing (9.15) and the mechanical housing (9.14),
• wherein a diameter of the unit housing (9) is smaller than a diameter of the inner circumferential surface,
• the first seal (8) of the sensor unit (1) is arranged sealed tight at the inner circumferential surface (51b) as an inside of the cylinder wall and divides the corresponding cylinder cavity (54, 55) of the cylinder (51) in two spaces that are separated from each other pressure tight,
• wherein one space of the two spaces is a high pressure space and is connected with the mechanical cavity 14 of the sensor unit (1), and
• another space of the two spaces is a low pressure space that is advantageously connected with an ambient outside of the cylinder 51 is connected with the sensor cavity (15) in which the sensor (6) is arranged.