Compressor or vacuum pump provided with a transmission

A vacuum pump comprising with a vacuum pump element with a driven shaft and a motor with a drive shaft to drive the vacuum pump element, said vacuum pump further being provided with a transmission between said drive shaft and said driven shaft, wherein said transmission comprises a housing and at least a driven gearwheel that is mounted on the driven shaft and a drive gearwheel that is mounted on the drive shaft, and wherein the housing comprises two separated chambers, a first chamber that is connected to the driven shaft and a second chamber which is separate from the first chamber, whereby the first chamber is connected via a channel with the second chamber, whereby around the drive gearwheel or driven gearwheel the second chamber is formed, whereby the form of the second chamber is such that when the gearwheel in question rotates a gas flow is created around this gearwheel which causes a negative pressure in the channel by a venturi effect;

• wherein a distance in a radial direction between a wall of the second chamber and the gearwheel in question gets bigger in a rotation direction of the gearwheel in question.