Drive unit for a forklift truck

Abstract

The invention relates to a drive unit for a forklift truck, comprising a steerable wheel (1) which is pivotably mounted on a vehicle frame about a vertical pivot axis. A drive motor 14, 14' with a drive shaft 13, 13' is arranged coaxially to the pivot axis, the drive shaft being connected to the wheel 1 via a gearbox. A releaseable parking brake 10, 10' is attached to the drive shaft 13, 13'. A brake shaft 9, 9' of the parking brake 10, 10' is rotatably driven from the drive shaft 13, 13' of the drive motor 14, 14' via a reduction gearbox 12, 12', which reduces the rotational speed of the drive shaft 13, 13' of the drive motor. The wheel 1 is rotatably driven from the brake shaft 9, 9' via the gearbox.

Description

[0001] The invention relates to a drive unit for a forklift truck, with a steerable wheel which is pivotably mounted on a vehicle frame about a vertical pivot axis, wherein a drive motor with a drive shaft is arranged coaxially to the pivot axis, which in turn is connected to the wheel via a gearbox, and with a releaseable parking brake acting on the drive shaft, wherein a brake shaft of the parking brake can be rotatably driven from the drive shaft of the drive motor via a reduction gearbox which reduces the speed of the drive shaft of the drive motor, and from which the wheel can in turn be rotatably driven via the gearbox.

[0002] From DE 10 2005 035 312 A1 a drive unit for a forklift truck of the type mentioned above is known.

[0003] In such a drive unit, it is known that the parking brake can be used to brake the drive shaft of the drive motor. The drive motor can accelerate or decelerate the vehicle. Since the size of the drive motor, which is primarily designed as an electric machine, depends essentially on its torque, it is advantageous to aim for the highest possible speed for the drive motor and, consequently, a lower torque. However, conventional parking brakes cannot be operated at arbitrarily high speeds. The size of the parking brake is determined by the required braking torque and the maximum kinetic energy of the vehicle. In an emergency braking situation, the parking brake should be able to dissipate the entire kinetic energy of the vehicle without overheating.

[0004] The object of the invention is to create a drive unit for a forklift truck of the type mentioned above, which avoids these disadvantages, has a simple design of small size and allows the use of a drive motor of the highest possible speed when the parking brake is not overloaded.

[0005] This problem is solved in a first solution according to the invention by arranging the auxiliary gearbox above the drive motor and the parking brake above the auxiliary gearbox.

[0006] This design makes it possible for the drive motors, which are preferably electric machines, to achieve high speeds of, for example, between 7000 rpm and 15000 rpm, while being smaller and less expensive. The reduction gearbox reduces the speed of the drive motor's shaft and correspondingly increases the torque.

[0007] During a braking maneuver, when the parking brake is used as an emergency brake, the power flow is reversed.

[0008] Furthermore, the first solution allows easy access to the parking brake in case of servicing.

[0009] The problem is solved according to the invention in a second solution by the fact that the transmission is a transmission that reduces the speed of the brake shaft.

[0010] This further reduces the rotational speed and increases the torque to drive the impeller.

[0011] If the drive motor and / or the auxiliary gearbox and / or the parking brake are designed as modular units, then in the event of a defect in one of these modules, this module can be easily replaced.

[0012] A small installation space requirement is achieved when the drive shaft of the drive motor and the brake shaft of the parking brake are arranged coaxially to each other.

[0013] The auxiliary gearbox can be located below the drive motor and the parking brake below the auxiliary gearbox.

[0014] If the auxiliary gearbox is a single-stage planetary gearbox, this has the space-saving advantage that the drive and the output of the auxiliary gearbox are arranged coaxially to each other.

[0015] The transmission can be any suitable drive transmission such as a gear, friction wheel or traction transmission, or a combination thereof.

[0016] The parking brake can be an electrically released spring-applied brake.

[0017] To save installation space, the gearbox can be a spur gear-bevel gear or a spur gear-planetary gear.

[0018] Exemplary embodiments of the invention are shown in the drawing and are described in more detail below. The drawing shows: Fig. 1 a perspective view of a first embodiment of a drive unit Fig. 2 a longitudinal section of the drive unit according to Fig. 1 Fig. 3 an enlarged partial longitudinal section according to Fig. 2 Fig. 4 a perspective view of a second embodiment of a drive unit Fig. 5 a longitudinal section of the drive unit according to Fig. 4 Fig. 6 an enlarged partial longitudinal section according to Fig. 5.

[0019] The drive units for a forklift truck shown in the figures have a wheel 1 that is fixedly mounted on a horizontal wheel axle 2. The wheel axle 2 can be rotatably driven by a spur gear / bevel gear transmission 3.

[0020] For this purpose, a first spur gear 5 is fixedly arranged at the upper end of a vertically arranged transmission shaft 4, and a bevel pinion 6 is fixedly arranged at the lower end. The bevel pinion 6 engages with a bevel gear 7, which is fixedly arranged on the impeller axle 2.

[0021] The first spur gear 5 is rotatably driven by a second spur gear 8, which is fixedly arranged on the lower end of a vertical brake shaft 9.

[0022] The brake shaft 9 is part of a parking brake 10 designed as an electrically released spring-applied brake with a brake rotor 11 fixedly mounted on the brake shaft 9, which can also be used as an emergency brake in an emergency. In normal driving operation, the parking brake is released and only applies the brakes when the vehicle is stationary.

[0023] The components described above are arranged in a housing 15, in which the wheel axle 2 is also rotatably mounted and which is attached to a frame plate 16 of a vehicle frame 16 of the industrial truck.

[0024] The housing 15 has at its upper end a steering spur gear 17 coaxial with the brake shaft 9, 9', into which a steering pinion (not shown) of a steering drive 18 arranged on the frame plate 16 engages. This allows the housing 15 and with it the wheel to pivot about a vertical axis for steering the industrial truck.

[0025] In the exemplary embodiment of the Fig. 1 to 3 the upper end of the brake shaft 9 can be rotatably driven via the output of a pre-assembled gearbox 12 designed as a planetary gearbox, the pre-assembled gearbox 12 being arranged coaxially above the parking brake 10.

[0026] On the input side, the auxiliary gearbox 12 can be rotatably driven by the rotor shaft 13, which is coaxial to the brake shaft 9, of a drive motor 14 designed as an electric machine and arranged above the auxiliary gearbox 12.

[0027] In the exemplary embodiment of the Fig. From bottom to top, 4 to 6 are arranged first a drive motor 14', then a pre-gearbox designed as a planetary gear 12' and at the top a parking brake 10'.

[0028] The drive motor 14', auxiliary gearbox 12' and parking brake 10' largely correspond in design to the corresponding components of the exemplary embodiment of the Fig. 1 to 3.

[0029] The only difference is that the rotor shaft 13' of the drive motor 14' is designed as a hollow shaft, through which the brake shaft 9' is guided downwards and carries the second spur gear 8 at its lower end.

[0030] The drive motor 14, 14', auxiliary gearbox 12, 12' and parking brake 10 10' are designed as modular units that can be assembled in both embodiments.

[0031] If the industrial truck is to be driven, the drive motor 14, 14' can provide torque and rotational speed to the rotor shaft 13, 13'. The rotor shaft 13, 13' drives the auxiliary gearbox 12, 12', which reduces the rotational speed and increases the torque accordingly. In these examples, the auxiliary gearbox 12, 12' is designed as a single-stage planetary gearbox. This has the advantage that the input and output of the auxiliary gearbox 12, 12' are coaxial. The output of the auxiliary gearbox 12, 12' drives the brake shaft 9, 9', which in turn drives the spur-bevel gearbox 3. The spur-bevel gearbox 3 further reduces the rotational speed and increases the torque to drive the impeller 1. During a service braking operation, the power flow is reversed.

[0032] The brake shaft 9, 9' is non-rotatably connected to the brake rotor 11 of the parking brake 10, 10', which is designed as an electrically released spring-applied brake. The brake shaft 9, 9' and the brake rotor 11 rotate at a lower speed than the drive motor 14, 14'. The speed ratio depends on the gear ratio of the auxiliary gearbox 12, 12'. The gear ratio of the auxiliary gearbox 12, 12' can be selected such that the permissible maximum speed of the brake rotor 11 is never exceeded under any operating condition, while still allowing the drive motor 14, 14' to operate at a high speed. The size, and therefore the cost, of a drive motor 14, 14' depends significantly on the required torque. A high speed of the drive motor 14, 14' allows for a smaller size because the required torque is lower for the same power output than at a lower speed.Both when the industrial truck is being driven and when it is being braked, the electric parking brake 10, 10' is released. This means that the parking brake 10, 10' does not apply any braking torque to the brake shaft 9, 9'.

[0033] The parking brake 10, 10' is normally engaged (i.e., not released) when the forklift truck is stationary and needs to be held in place (parking brake function). The parking brake 10, 10' can then transmit a braking torque to the brake rotor 11 via the brake shaft 9, 9' into the drive unit, thus preventing the forklift truck from moving, for example, by rolling on an inclined plane. Since the speed of the forklift truck is zero in this operating state, the brake rotor 11 has a rotational speed of zero. Therefore, no power is dissipated in the parking brake 10, 10'. Typically (e.g., according to ISO 6292), the forklift truck should be able to be held on an inclined plane with a gradient of at least 15%.

[0034] Furthermore, the parking brake 10, 10' can be engaged while the forklift is in motion, for example, by activating an emergency stop switch on the forklift. This initiates an emergency braking procedure. The kinetic energy of the forklift is transferred from the wheel 1, in the form of torque and rotational speed, to the spur gear-bevel gear 3. There, the torque and rotational speed are converted and transmitted to the brake shaft 9, 9' and the brake rotor 11 of the parking brake 10, 10'. During the emergency braking procedure, the parking brake 10, 10' converts the torque and rotational speed into heat and dissipates it into the environment. Since the emergency braking procedure takes only a short time, the parking brake 10, 10' must be able to absorb almost all of the forklift's kinetic energy as heat, as it can only dissipate a large portion of the heat to the environment after the braking process. Reference sign 1 wheel 2 wheel axle 3 spur gear-bevel gear units 4 Gear shaft 5 first spur gear 6 conical pinions 7 bevel gear 8 second spur gear 9 Brake shaft 9' brake shaft 10 Parking brake 10' Parking brake 11 Brake rotor 12 auxiliary gearboxes 12' auxiliary gearbox 13 Rotor shaft 13' Rotor shaft 14 Drive motor 14' drive motor 15 cases 16 frame plate 17 Steering spur gear 18 Steering drive

Claims

[1] Drive unit for a forklift truck, comprising a steerable wheel (1) which is pivotably mounted on a vehicle frame about a vertical pivot axis, wherein a drive motor (14, 14') with a drive shaft (13, 13') is arranged coaxially to the pivot axis, which in turn is connected to the wheel (1) via a gearbox, and with a releaseable parking brake (10, 10') acting on the drive shaft (13, 13'), wherein a brake shaft (9, 9') of the parking brake (10, 10') can be rotatably driven from the drive shaft (13, 13') of the drive motor (14, 14') via a reduction gearbox (12, 12') which reduces the rotational speed of the drive shaft (13, 13') of the drive motor, and from which the wheel (1) can in turn be rotatably driven via the gearbox, characterized by , that the auxiliary gearbox (12') is located above the drive motor (14') and the parking brake (10') is located above the auxiliary gearbox (12'). [2] Drive unit for a forklift truck, comprising a steerable wheel (1) which is pivotably mounted on a vehicle frame about a vertical pivot axis, wherein a drive motor (14, 14') with a drive shaft (13, 13') is arranged coaxially to the pivot axis, which in turn is connected to the wheel (1) via a gearbox, and with a releaseable parking brake (10, 10') acting on the drive shaft (13, 13'), wherein a brake shaft (9, 9') of the parking brake (10, 10') can be rotatably driven from the drive shaft (13, 13') of the drive motor (14, 14') via a reduction gearbox (12, 12') which reduces the rotational speed of the drive shaft (13, 13') of the drive motor, and from which the wheel (1) can in turn be rotatably driven via the gearbox, characterized by , that the gearbox (3) is a gearbox reducing the speed of the brake shaft (9, 9'). [3] Drive unit according to one of the preceding claims, characterized by, that the drive motor (14, 14') and / or the auxiliary gearbox (12, 12') and / or the parking brake (10, 10') are designed as modular units that can be assembled. [4] Drive unit according to one of the preceding claims, characterized by , that the drive shaft (13, 13') of the drive motor (14, 14') and the brake shaft (9, 9') of the parking brake (10, 10') are arranged coaxially to each other. [5] Drive unit according to claim 2, characterized by , that the auxiliary gearbox (12) is located below the drive motor (14) and the parking brake (10) is located below the auxiliary gearbox (12). [6] Drive unit according to claim 1, characterized by , that the drive shaft of the drive motor (14') is designed as a hollow shaft through which the brake shaft (9') of the parking brake (10') is led to the gearbox (3). [7] Drive unit according to one of the preceding claims, characterized by , that the pre-assembly gear (12, 12') is a single-stage planetary gear. [8] Drive unit according to one of the preceding claims, characterized by , that the parking brake (10, 10') is an electrically released spring pressure brake. [9] Drive unit according to any one of the preceding claims, characterized by , that the transmission is a spur gear-bevel gear (3).

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