Hydraulically controlled clutch release bearing for a diaphragm clutch, notably for a motor vehicle, having a guide sleeve

A hydraulically controlled clutch release bearing for a clutch (1) with a diaphragm spring (13), said clutch release bearing having a fixed portion (5, 6) comprising an inner support tube (6) and an outer body (5) concentric with the inner support tube (6), the inner support tube (6) and the outer body (5) defining a blind annular cavity (50) of axial orientation for receiving fluid and inside which is mounted, so as to be axially movable, a tubular piston (4) having a drive member (3) for acting on the diaphragm spring (13) of the clutch (1), wherein the inner support tube (6) projects axially, at a front end thereof, beyond the outer body (5), wherein the front end of the inner support tube (6) is surrounded by a guide sleeve (9) that offers a guide area for the piston (4), wherein said guide sleeve (9) constitutes a barrier blocking access of contaminants to the inner support tube (6) and the annular cavity (50), wherein a rear end (91) of the guide sleeve (9) forms a stop limiting axial travel of the piston (4) and the piston (4) is internally stepped so as to form a shoulder (43), on an inside portion thereof, for cooperating with the rear end (91) of the guide sleeve (9), and wherein said guide sleeve (9) contacts and is supported by the inner support tube (6).