Steering unit for a forklift truck

Abstract

Steering unit for a forklift truck with a steering motor designed as an electric motor and control electronics, wherein the electric motor is arranged in a motor housing and the control electronics in an electronics housing and the motor housing and the electronics housing form a single unit, characterized in that the electric motor (2) is arranged in a closed motor housing (6) and the control electronics (5) are arranged in a closed electronics housing (7), wherein the electronics housing (7) is attached to the motor housing (6) by means of a fastening device (8) and the electronics housing (7) is thermally decoupled from the motor housing (6), wherein an air gap is formed between the motor housing (6) and the electronics housing (7).wherein at least one feedthrough (11) for electrical and / or mechanical connections is arranged between the electronics housing (7) and the motor housing (6) and wherein the feedthrough (11) and / or the fastening device (8) is made of a material with low thermal conductivity.

Description

[0001] The invention relates to a steering unit for a forklift truck with a steering motor designed as an electric motor and control electronics, wherein the electric motor is arranged in a motor housing and the control electronics in an electronics housing and the motor housing with the electronics housing forms a single unit.

[0002] Steering units of this type, comprising a steering motor formed by an electric motor and control electronics that regulate the speed and position of the electric motor and are equipped with power electronics that supply the electric motor with the necessary energy, are used in industrial trucks with an electric drive system, which is usually supplied with electrical energy by a battery pack, a fuel cell or a hybrid unit.

[0003] In known steering units, the control electronics are located above the electric motor on an upper bearing plate of the electric motor. The control electronics are integrated into the electric motor housing. This results in the electric motor and the control electronics forming a single unit that requires little installation space, has compact dimensions, and can be easily installed in the industrial truck. Furthermore, the integration of the control electronics and the electric motor into a common housing, along with the design of the steering unit as a single unit, allows power connections and sensors to be connected internally between the electric motor and the control electronics, thus reducing overall construction effort.

[0004] In such steering units, a high power output from the electric motor is required during operation, which results in high heat losses for the electric motor during operation.

[0005] The steering units are cooled by natural convection via the common housing, thereby dissipating the heat losses generated during the operation of the steering unit to the environment.

[0006] However, integrating the control electronics and the electric motor into a single housing means that the electric motor's heat losses during steering unit operation are directly transferred to the control electronics. Since the electric motors used are typically capable of operating at a higher maximum temperature than the control electronics, the steering unit can experience unacceptably high operating temperatures for the control electronics, leading to thermal overload. Furthermore, high operating temperatures reduce the lifespan of the control electronics. These effects are exacerbated by the fact that, due to space constraints in industrial trucks, the steering unit and thus the electric motor are mounted vertically, placing the control electronics above the hot electric motor.

[0007] To prevent thermal problems in the steering unit's control electronics during operation, a cooling device, such as a fan, can be provided to generate a cooling airflow and increase heat dissipation from the electric motor and / or control electronics to the environment via forced convection. However, such a cooling device requires additional construction effort and installation space. Furthermore, a fan has a high risk of failure due to contamination and consumes additional electrical energy.

[0008] DE 103 12 432 A1 discloses a forklift truck with a frame and a steering unit of the generic type.

[0009] An electric motor for a power steering system with part number 1611951980 from Peugeot is known from https: / / www.der-ersatzteile-profi.de / artikel / elektromotor-fuer-servolenkunga3337569.html.

[0010] An electric motor for a power steering system with part number 1611951980 from Peugeot is also known from https: / / motopoland.com.ua / detail / 8764134701.

[0011] An electric power steering system for the Meriva model vehicle from the company Opel is known from https: / / edocks.de / BREMSEN--LENKUNG-Servomotor-Motor-Elektrische-Servolenkung-RHD-Steuergeraet-Meriva-A-Opel.html.

[0012] The present invention is based on the objective of providing a steering unit of the type mentioned at the outset in which thermal overload of the control electronics can be effectively avoided with low construction effort and low installation space requirements.

[0013] The problem is solved by a steering unit with the features of claim 1. Advantageous further developments result from the dependent claims.

[0014] The problem is solved according to the invention by arranging the electric motor in a sealed motor housing and the control electronics in a sealed electronics housing, wherein the electronics housing is attached to the motor housing by means of a fastening device and the electronics housing is thermally decoupled from the motor housing. Thus, according to the invention, the electric motor and the control electronics are arranged in separate sealed housings, wherein the two housings are connected to form a single unit by means of a fastening device and are thermally decoupled.This achieves, according to the invention, the advantages of designing the steering unit as a modular unit with regard to simple power connections and a simple connection of sensors between the electric motor and the control electronics, as well as a simple and compact arrangement of the steering unit in the industrial truck. Furthermore, thermal overload of the control electronics is effectively avoided with minimal additional construction effort and space requirements. The sealed housings and the thermal decoupling of the control electronics from the electric motor ensure that the maximum operating temperature of the control electronics is not exceeded during operation of the electric motor, thus allowing the electric motor to operate at a higher temperature than the maximum operating temperature of the control electronics.The drive power available from the electric motor can thus be optimally utilized without the risk of thermal overload of the control electronics. Overall, this results in a steering unit that, despite requiring little installation space and effort, offers high power density and effectively prevents thermal overload of the control electronics. Furthermore, the elimination of a cooling device in the form of a fan ensures high availability of the steering unit according to the invention.

[0015] According to the invention, an air gap, in particular a horizontally arranged air gap, is formed between the motor housing and the electronics housing. This insulating air gap between the motor housing and the electronics housing provides simple thermal decoupling, whereby the amount of heat from the electric motor, which is transferred via the air gap from the motor housing to the electronics housing of the control electronics, is less than the amount of heat that can be dissipated from the electronics housing to the environment. This effectively prevents thermal overload of the control electronics during operation of the electric motor, thus allowing the electric motor to be operated at a temperature higher than the maximum operating temperature of the control electronics.

[0016] According to the invention, at least one feedthrough for electrical and / or mechanical connections is provided between the electronics housing and the motor housing. By means of such a feedthrough, the power connections for the electric motor and connecting cables for sensor devices can be arranged easily and with minimal construction effort between the electric motor and the control electronics within the assembly formed by the motor housing and the electronics housing. Furthermore, it is possible to route a mechanical connection via the feedthrough for, for example, a speed sensor or rotary position sensor of the electric motor, which is arranged in the electronics housing and is in operative connection with the output shaft of the electric motor.

[0017] According to the invention, the feedthrough and / or the fastening device are made of a material with low thermal conductivity. This ensures that only a small amount of heat is transferred from the electric motor to the control electronics via the feedthrough or the fastening device.

[0018] According to a preferred embodiment of the invention, the fastening device is formed by fastening elements, in particular screw connections, which are arranged, in particular, evenly distributed on a partial circle. With such a fastening device, a mechanical connection between the motor housing and the electronics housing can be achieved as a single unit with minimal construction effort.

[0019] A particular advantage is that the control electronics are arranged horizontally above the electric motor. This easily provides a large radiating surface on the top of the electronics housing for heat dissipation from the control electronics to the environment and results in a compact design with a low overall height for the steering unit according to the invention.

[0020] The electric motor can be designed as a three-phase motor, in particular an asynchronous motor, which can be supplied with electrical energy by power electronics integrated into the control electronics.

[0021] It is also possible to design the electric motor as a direct current motor.

[0022] Further advantages and details of the invention will be explained in more detail with reference to the embodiment shown in the schematic figure.

[0023] The figure shows a steering unit 1 of a forklift truck according to the invention.

[0024] The vertically arranged steering unit 1 has an electric motor 2 which drives an output shaft 4 via a gearbox 3, for example a gearbox with a fixed reduction ratio. A control unit 5, which is arranged horizontally above the electric motor 2, is provided for controlling the electric motor 2 and supplying it with electrical energy.

[0025] According to the invention, the electric motor 2 is arranged in a sealed motor housing 6 and the control electronics 5 in a sealed electronics housing 7, which are mechanically connected to form a single unit by means of a fastening device 8. A horizontally arranged air gap 9 is created between the motor housing 6 and the electronics housing 7 by means of the fastening device 8, which thermally decouples the electric motor 2 from the control electronics 5.

[0026] The fastening device 8 has several fastening elements 10, for example designed as screw connections, which are arranged in particular on a pitch circle. This allows the electronics housing 7 to be easily attached to the top of the motor housing 6 and the motor housing 6 to be connected to the electronics housing 7 to form a single unit. The air gap 9 can be easily created and changed by means of spacers or spacer shoulders molded onto the underside of the electronics housing 7.

[0027] A feedthrough 11 is arranged between the electronics housing 7 and the motor housing 6, for example concentrically to the output shaft 4, in which electrical and / or mechanical connections between the control electronics 5 and the electric motor 2 can be routed. For example, power connections from the control electronics 5 to the electric motor 2 and connecting lines from sensor devices arranged in the motor housing 6, such as a temperature sensor and a speed sensor or a rotary position sensor, to the control electronics 7 are routed through the feedthrough 11.

[0028] The feedthrough 11 and the fastening device 8 are advantageously made of a material with low thermal conductivity, which reduces the transfer of heat losses from the electric motor 2 into the control electronics 5 via the feedthrough 11.

[0029] The electronic housing 7, for example, has at least one connection opening 12 for an electrical power connection and a plug connection 13 for a control line on one side surface.

[0030] The steering device 1 according to the invention, in which the electric motor 2 is arranged in a sealed motor housing 6 and the control electronics 5 in a sealed electronics housing 7, are connected to form a single unit by means of the fastening device 8. This results in compact dimensions for the steering unit 1 with a low overall height, which allows for easy installation of the steering unit in a forklift truck with minimal installation space requirements.

[0031] Via the feedthrough 11, a simple mechanical and electrical connection between the electric motor 2 and the control electronics 5 is possible within the assembly formed by the control electronics 5 and the electric motor 2.

[0032] The motor housing 6 is thermally decoupled from the electronics housing 7 by means of the air gap 9, thereby effectively preventing thermal overload of the control electronics 5 in a simple manner. This allows the electric motor 2 to be operated at a temperature higher than the maximum operating temperature of the control electronics 5. The drive power available from the electric motor 2 can thus be optimally utilized, resulting in a high power density of the steering unit 1 according to the invention.

Claims

[1] Steering unit for a forklift truck comprising a steering motor designed as an electric motor and control electronics, wherein the electric motor is arranged in a motor housing and the control electronics are arranged in an electronics housing and the motor housing and the electronics housing form a single unit, characterized by, that the electric motor (2) is arranged in a closed motor housing (6) and the control electronics (5) are arranged in a closed electronics housing (7), wherein the electronics housing (7) is attached to the motor housing (6) by means of a fastening device (8) and the electronics housing (7) is thermally decoupled from the motor housing (6), wherein an air gap is formed between the motor housing (6) and the electronics housing (7), wherein at least one feedthrough (11) for electrical and / or mechanical connections is arranged between the electronics housing (7) and the motor housing (6), and wherein the feedthrough (11) and / or the fastening device (8) is made of a material with low thermal conductivity. [2] Steering unit according to claim 1, characterized by , that the fastening device (8) is formed by fastening elements (9), in particular screw connections, which are arranged in particular evenly distributed on a partial circle. [3] Steering unit according to claim 1 or 2, characterized by , that the control electronics (5) are arranged horizontally above the electric motor (5). [4] Steering unit according to one of claims 1 to 3, characterized by , that the electric motor (5) is designed as a three-phase motor, in particular an asynchronous motor. [5] Steering unit according to any one of claims 1 to 3, characterized by , that the electric motor (5) is designed as a direct current motor.

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