Abstract: A venting device for a hydraulic control unit, designed as a diaphragm in a bore in the control unit, so that collected air can escape, via the diaphragm, to outside the housing. A membrane, which is permeable to air and oil when under pressure, closes the diaphragm bore with respect to the outside. The housing bore and the diaphragm form an inside space that can be vented, via the membrane. The inside space being delimited, during operation, by the diaphragm and an oil column which passes from the control unit into the housing bore and is continually maintained at a defined pressure at which oil, in the housing bore, either does not pass through the membrane or only a minute amount passes therethrough. The oil column remains in the housing bore so that only air, contained in the oil, is vented to the outside without any air being drawn into the control unit from outside.

Abstract: A venting device for a hydraulic control unit, designed as a diaphragm in a bore in the control unit, so that collected air can escape, via the diaphragm, to outside the housing. A membrane, which is permeable to air and oil when under pressure, closes the diaphragm bore with respect to the outside. The housing bore and the diaphragm form an inside space that can be vented, via the membrane. The inside space being delimited, during operation, by the diaphragm and an oil column which passes from the control unit into the housing bore and is continually maintained at a defined pressure at which oil, in the housing bore, either does not pass through the membrane or only a minute amount passes therethrough. The oil column remains in the housing bore so that only air, contained in the oil, is vented to the outside without any air being drawn into the control unit from outside.