Hydraulic unit for a cylinder head of an internal combustion engine with hydraulic, variable valve train

1. Hydraulic unit for a cylinder head of an internal combustion engine with a hydraulic, variable valve train, comprising:

at least one drive-side master unit,

at least one driven-side slave unit activating a gas-exchange valve,

at least one controllable hydraulic valve,

at least one medium-pressure chamber,

at least one high-pressure chamber that is arranged in a transmission sense between an associated one of the at least one drive-side master unit and an associated one of the at least one driven-side slave unit and that can be connected to an associated one of the at least one medium-pressure chamber via an associated one of the at least one hydraulic valve, and

a hydraulic housing with a housing bottom part and a housing top part,

wherein at least the at least one master unit, the at least one slave unit, the at least one high-pressure chamber, the at least one hydraulic valve, and the at least one medium-pressure chamber in connection with the hydraulic housing belong to the hydraulic unit that can be mounted on the cylinder head, and a low-pressure chamber used as a hydraulic medium reservoir is formed in a housing top part, the low-pressure chamber communicates with the at least one medium-pressure chamber merely via at least one choke opening, and the choke opening passes through a separating wall extending between the at least one low-pressure chamber and the at least one medium-pressure chamber.

2. Hydraulic unit according to claim 1 , wherein the choke opening extends at a geodetic low point of the separating wall for the case that the hydraulic unit is installed at an angle to a force of gravity in or with the internal combustion engine.

3. Hydraulic unit according to claim 1 , wherein the housing top part is provided with at least one ventilation opening opening into the cylinder head for the low-pressure chamber.

4. Hydraulic unit according to claim 1 , wherein the at least one low-pressure chamber has a volume V L , the at least one medium-pressure chamber has a volume V M , and the at least one high-pressure chamber has a volume V H with a volume ratio (V L +V M )/V H ≧2.

5. Hydraulic unit according to claim 1 , wherein the separating wall is formed as a housing intermediate part of the hydraulic housing assembled with a sandwich construction from the housing bottom, intermediate and top parts.

6. Hydraulic unit according to claim 5 , wherein the housing top part is coated with a sealing medium made from an elastomeric material at least in a region of contact with the housing intermediate part.

7. Hydraulic unit according to claim 1 , wherein the housing top part is a deep drawn aluminum or steel part.

8. Hydraulic unit according to claim 1 , wherein the housing top part is an injection molded plastic part.