Drive device for construction machine

A drive device for a construction machine, the drive device driving a driven portion in the construction machine, the drive device comprising:

• a motor serving as a drive source, and having a motor shaft for outputting a rotational force at a given rotational speed;
• and
• a speed reduction unit for reducing the rotational speed of the rotational force output from said motor, and transmitting the rotational force at a reduced rotational speed to said driven portion, wherein said speed reduction unit has
• a casing having an inner wall surface defining an inner space for containing an amount of lubricant oil,
• a gear mechanism disposed in the inner space of the casing for reducing the rotational speed of the rotational force output from said motor, the gear mechanism being submersed in the lubricant oil contained in the inner space of the casing,
• a speed reduction output shaft connected with the gear mechanism for outputting the rotational force at the reduced rotational speed to said driven portion, the speed reduction output shaft axially aligning with the motor shaft in a vertical direction, the speed reduction output shaft being disposed below the motor shaft so that a driven member attached to the speed reduction output shaft and constituting the gear mechanism lies deeper in the lubricant oil contained in the inner space than a driver member attached to the motor shaft and constituting the gear mechanism,
• a hollow cylindrical body arranged in the inner space and above said gear mechanism and having an inner diameter larger than an outer diameter of the motor shaft to thereby define a gap between the entire inner surface of the hollow cylindrical body and the outer surface of the motor shaft to keep the hollow cylindrical body from imparting a mechanical force to the motor shaft,
• an oil receiver arranged in the inner space and above said gear mechanism, and mounted on the outer surface of said cylindrical body, said oil receiver having a main storage portion extending in a radially outward direction of the motor shaft, and formed with an oil drain opening for discharging a given amount of lubricant oil from the main storage portion to said gear mechanism, the main storage portion having an outer end radially spaced away from the inner wall surface of the casing, whereby said oil receiver can receive, store and discharge a given amount of lubricant oil,
• a support member arranged above said oil receiver and mounted on the outer surface of the cylindrical body and said casing to support said cylindrical body, and
• an oil passage formed between the inner wall surface of the casing and the outer end of the oil receiver for guiding a given amount of lubricant oil rising through said oil passage to the main storage portion.