Gear unit

1. A gear unit comprising:

a gear unit housing with at least one drive-side shaft, at least one output-side shaft, and at least one gear ratio stage having intermeshing toothed wheels;

a toothing space in the gear unit housing configured to receive the intermeshing toothed wheels and configured to be operated in one or more of: a partial vacuum, under atmospheric pressure, or at atmospheric pressure;

a bearing space in the gear unit housing which is separated from the toothing space and in which shaft bearings are arranged and configured to be operated permanently in atmospheric operation under atmospheric pressure;

lubricating oil configured to lubricate the toothing and the shaft bearings and to be collected in the toothing space

and the bearing space;

an oil collecting receptacle external to the gear unit, configured to collect the bearing lubricating oil guided from the bearing space;

a delivery pump configured to convey the toothing lubricating oil from the toothing space into the oil collecting receptacle during partial vacuum operation;

a check valve configured to convey the toothing lubricating oil from the toothing space into the oil collecting receptacle external to the gear unit during atmospheric operation;

a first oil line that leads from the toothing space in direction of the oil collecting receptacle external to the gear unit, wherein the check valve is arranged in the first oil line;

a second oil line that leads from the toothing space in direction of the oil collecting receptacle external to the gear unit, wherein the delivery pump is arranged in the second oil line; and

a third oil line that leads from the bearing space in direction of the oil collecting receptacle external to the gear unit.

2. The gear unit according to claim 1 , wherein in atmospheric operation, the toothing lubricating oil is conveyed from the toothing space into the oil collecting receptacle external to the gear unit via the check valve to be additionally supported via the delivery pump.

3. The gear unit according to claim 1 , further comprising a further check valve arranged in the second oil line downstream of the delivery pump.

4. The gear unit according to claim 3 , wherein the second oil line leads into one of the first oil line or the third oil line.

5. The gear unit according to claim 1 , wherein the second oil line leads into one of the first oil line or the third oil line.

6. The gear unit according to claim 5 , wherein one of:

the first oil line leads into the third oil line or

the third oil line leads into the first oil line.

7. The gear unit according to claim 1 , wherein one of:

the first oil line leads into the third oil line or

the third oil line leads into the first oil line.

8. The gear unit according to claim 7 , further comprising a vacuum pump coupled to the toothing space, wherein exhaust air from the vacuum pump is discharged into a region of the gear unit that is under atmospheric pressure while providing a closed oil circuit.

9. The gear unit according to claim 1 , further comprising a vacuum pump coupled to the toothing space, wherein exhaust air from the vacuum pump is discharged into a region of the gear unit that is under atmospheric pressure while providing a closed oil circuit.

10. The gear unit according to claim 9 , further comprising a coupling device between the toothing space and a region of the gear unit under atmospheric pressure, the atmospheric pressure being applied to the toothing space in partial vacuum operation via this region of the gear unit during at least outage of the vacuum pump and the delivery pump.

11. The gear unit according to claim 9 , further comprising a valve cooperating with the vacuum pump, wherein the valve can be opened when the partial vacuum pressure in the toothing space drops below a limit value to keep the partial vacuum pressure at the limit value.

12. The gear unit according to claim 11 , wherein the valve is coupled with a region of the gear unit under atmospheric pressure while providing a closed oil circuit.