Fan drive device with proportional valve

A fan drive device, comprising:

• a hydraulic motor configured to be directly coupled to a fan, the hydraulic motor including a first working connection, a second working connection, and a constant displacement volume;
• and
• a hydraulic valve configured to be operably connected to a constant displacement volume hydraulic pump, the hydraulic valve having a pump connection and a tank connection, wherein
• the hydraulic valve includes two fluid connections, each of which is configured to be fluidically connected to the hydraulic motor,
• the hydraulic valve is designed as a proportional valve including a continuously adjustable control piston proportional to a control current of the hydraulic valve,
• the hydraulic valve is a sole hydraulic control mechanism within the fan drive device for controlling a speed of the fan,
• the control piston is axially movably mounted in a control cylinder and includes a first control edge which defines a first variable aperture, a second control edge which defines a second variable aperture, a third control edge which defines a third variable aperture, and a fourth control edge which defines a fourth variable aperture,
• the pump connection is configured to be connected to the first working connection only via the first variable aperture,
• the pump connection is configured to be connected to the second working connection only via the second variable aperture,
• a tank connection is permanently connected to a first auxiliary chamber of the control cylinder and a second auxiliary chamber of the control cylinder,
• the first working connection is configured to be connected to the first auxiliary chamber only via the third variable aperture,
• the second working connection is configured to be connected to the second auxiliary chamber only via the fourth variable aperture,
• the first variable aperture is associated with the fourth variable aperture such that the first variable aperture and the fourth variable aperture both move in respective closing directions in unison and both move in respective opening directions in unison,
• the second variable aperture is associated with the third variable aperture such that the second variable aperture and the third variable aperture both move in respective closing directions in unison and both move in respective opening directions in unison, and
• at a control piston position outside a first end position and a second end position, respective aperture cross-sections of the third variable aperture and the fourth variable aperture are greater than respective aperture cross-sections of the associated first variable aperture and second variable aperture.