Wheel drive

A wheel drive has one first prime mover (1), one brake (19) and one second prime mover (8) which are co-axially disposed. Via a reduction gear (4), the first prime mover (1) drives a drive wheel (7) for the traction gear, the second prime mover (8), via a planetary transmission (11), drive the prime mover in direction of a steering motion.

This application is a national stage completion of PCT/EP2005/000486 filed Jan. 19, 2005 which claims priority from German Application Serial No. 10 2004 006 722.8 filed Feb. 11, 2004.

FIELD OF THE INVENTION

According to the kind defined in detail in the preamble of claim1, the invention relates to a wheel drive.

BACKGROUND OF THE INVENTION

Wheel drives, particularly one-wheel power packs for industrial lift trucks, generically have one prime mover which, via a reduction gear, drives the drive wheel and a steering motor by way of a drive wheel that can turn a steering axle around to perform a steering motion. The installation space for the wheel drive and the steering mechanism is extremely limited here.

DE 34 20 146 A1 discloses a wheel drive for an industrial lift truck where one drive wheel is actuated via a reduction gear by a prime mover and a steering motor, via a chain, can turn the drive wheel around a steering axis of rotation so as to perform a steering motion. The steering motor is separately placed here next to the traction motor whereby a large installation space is needed.

The problem on which this invention is based is to provide a wheel drive, in particular for a n industrial lift truck, in which the traction motor actuates the vehicle wheel and the wheel drive is rotatably actuatable via a steering motor around a steering axis of rotation and which is compactly and economically constructed.

SUMMARY OF THE INVENTION

According to the invention, the traction motor, the steering motor and the brake, which brakes the wheel drive, are co-axially disposed. The brake is preferably between the traction motor and the steering motor. By using a steering gear, which preferably is likewise situated co-axially relative to the steering motor, it is possible to use a compact steering motor.

In another development of the invention, the traction motor, the brake and the steering motor are located in a common housing whereby a further reduction of installation space needed is possible and an economical solution is obtained.

In one other development of the invention, the brake is designed as so-called negative brake whereby the brake is actuatable by spring tension in closing direction and by hydraulic pressure or electric actuation of a magnetic coil, it can be actuated in opening direction. The brake can be designed as friction disc brake, it being possible to place the friction linings either in one space filled with lubricant, or also to design it as dry-operating disc brake without lubricant.

In another development, the drive shaft of the traction motor is connected via engaging gears with a part, the so-called brake hub, which is connected with the rotating parts of the brake. The engaging gears can also be designed via a fitting key.

In one other development of the invention, the brake designed as a negative brake is actuatable in closing direction via cylindrical pressure springs or via a plate spring.

In another development of the invention, the drive shaft of the steering motor is connected with an inner central wheel of a planetary transmission or is designed integrally therewith which is in operative connection with planetary gears. The planetary gears are in operative connection with a first hollow gear and a second hollow gear, one of the hollow gears being non-rotatably connected with the vehicle chassis and the other hollow gear with the output wheel. Both hollow gears having different number of teeth, the planetary transmission is designed as a Wolfrom drive whereby, upon rotation of the inner central wheel, the drive wheel rotates around its steering axis thus performing a steering motion.

DETAILED DESCRIPTION OF THE INVENTION

One prime mover1preferably designed as electric motor drives via an (first) drive shaft2, a first spur gear3of a reduction gear4. The first spur gear3drives a second spur gear5which, via a bevel gear (not shown) drives an output6of the wheel drive which is connected with a drive wheel7. A second prime mover8drives, via a (second) drive shaft9, an inner central gear10of a4planetary gear11, which is designed as a Wolfram transmission. Planets12mesh with a first hollow gear13and a second hollow gear14, the first hollow gear13being non-rotatably supported in a cover15non-rotatably connected with a part of the vehicle chassis. The second hollow gear14is non-rotatably connected with a cover16non-rotatably connected with a housing17whereby the rotation of the second hollow gear14turns the housing17in direction of a steering motion. A steering gear18is located between the reduction gear4and the second prime mover8. A brake19is situated between the first prime mover1and second prime mover8. The first prime mover1, the second prime mover8, the brake19and the steering gear18are co-axially disposed. The drive shaft2is connected with rotating parts20of the brake19.

The drive shaft2of the first prime mover1is non-rotatably connected with a hub21, which is non-rotatably connected with the rotating parts20of the brake19. A pressure plate22is pressed by the tension of springs23on the rotating parts20whereby the brake is actuated in an engaging direction. By electric actuation of electric magnets24, the pressure plate22is detached from the rotating parts20whereby the brake is actuated in a disengaging direction.

The drive shaft2of the first prime mover1is connected via a fitting spring25with the hub21. The hub21is connected with the rotating part20of the brake19. Due to the tension of a plate spring26, the pressure plate22is pressed on the rotating part20whereby the brake is actuated in an engaging direction. By pressurization of a piston27, via an inlet28, the pressure plate22is detached, via a tappet29, from the rotating part20whereby the brake is actuated in the disengaging direction.

The drive shaft2of the first prime mover1has engaging gears30by way of which rotating parts20, the so-called brake discs, are non-rotatably connected. The brake, like the brake inFIG. 3, is actuated via the plate spring26in the engaging direction and by hydraulic pressurization via the inlet28in the disengaging direction.

The brake, according toFIG. 5, corresponds to the brake, according toFIG. 2, the rotating part20being non-rotatably connected via engaging gears30with the drive shaft2.

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