INDUSTRIAL TRUCK WITH IMPROVED MOTOR COOLING

Abstract

 An industrial truck includes a frame (11, 14), a lifting assembly (15) including a movable lifting element (13) for lifting a load (14), at least an electrical motor (17) for the traction of the wheels of the industrial truck, and an axle structure (16) connected to the frame (14) by flanges (52) and constituted by a left portion (22), a right portion (21) and a housing (31, 32, 33) of the motor joined together with each other, the housing (31, 32, 33) being interposed between the left and right portions, each of the left and right portions comprising supporting means (51) for supporting the lifting assembly (15), the housing of the electrical motor being configured to withstand a bending stress induced by the weight of the lifting assembly,
wherein the housing is thermally coupled with a stator (18) of the motor (17) and includes at least one cooling duct (41-43) in which a cooling liquid flows to cool the electrical motor,
wherein the housing includes an outer surface (34) on which a power electronic module (35) for the motor is mounted, and
wherein, in a region of the housing (33) between the outer surface (34) and a recess (70) of the housing configured to accommodate the electric motor (17), the housing (33) includes a motor cooling duct (42) close to the recess (70) and at least one power electronic module cooling duct (41) between the electric motor cooling duct (42) and the outer surface (34).

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The field of the present invention concerns an industrial truck, such as a forklift truck, including an improved cooling system for the wheel traction motor.

BACKGROUND OF THE INVENTION

[0002] Forklift trucks including a chassis (or frame), a mast pivotally mounted on the chassis and a fork slidably mounted on the mast are known in the art. The fork is used to lift a load, for example for transporting ware in a store. The mast can be tilted with respect to the chassis to facilitate loading and unloading of the ware.

[0003] It is also known to provide an electric motor for the traction of the wheels of the forklift truck. The electrical motor can be mounted e.g. on the front axle of the truck for the traction of the front wheels. In order to cool the electrical motor, a cooling system has been proposed in the prior art, wherein an air fan ventilates the outer surface of the electrical motor housing. However, in this configuration the cooling system can have failures due to the deposition of dust on the blades of the air ventilator and can produce disturbing noise for the driver of the truck. Furthermore, the air cooling system may not be capable of properly dissipating the heat generated by the power electronics module (such as an inverter) incorporated in the truck for the control of the currents to be fed to the electrical motor.

SUMMARY OF THE INVENTION

[0004] In view of the above, it is an object of the present invention to provide an industrial truck which ensures an efficient and improved cooling of the electrical traction motor.

[0005] It is a further object of the present invention to provide an industrial truck which ensures an improved cooling of the electrical traction motor and of the power electronics module associated to the electrical motor.

[0006] It is a further object of the present invention to provide an industrial truck which is less prone to failures of the cooling system compared to the conventional systems.

[0007] It is a further object of the present invention to provide an industrial truck which can ensure an improved cooling of the electrical motor while minimizing the complexity of the cooling system, in particular by minimizing the overall number of components to be foreseen in the combined system "axle structure/motor cooling system".

[0008] In view of the above object, the present invention proposes an industrial truck including:

• a frame,
• a lifting assembly including a movable lifting element for lifting a load,
• at least an electrical motor for the traction of wheels of the industrial truck, and
• an axle structure connected to the frame of the truck by means of flanges and constituted by a left portion, a right portion and a housing of the electrical motor, the housing being interposed between the left portion and the right portion, the housing being joined to each of the left portion and the right portion, wherein each of the left portion and the right portion comprises supporting means for supporting the lifting assembly, and the housing of the electrical motor is configured to withstand a bending stress induced in the housing by the weight of the lifting assembly,

wherein the housing of the electrical motor is thermally coupled with a stator of the electrical motor and includes at least one cooling duct in which a cooling liquid flows to cool the electrical motor during the operation of the industrial truck,

wherein the housing includes an outer surface on which a power electronic module for controlling the electric motor is mounted, and

wherein, in a region of the housing between the outer surface and a recess of the housing configured to accommodate the electric motor, the housing includes an electric motor cooling duct positioned close to the recess and at least one power electronic module cooling duct positioned between the electric motor cooling duct and the outer surface for cooling the power electronic module during the operation of the industrial truck.

[0009] The arrangement according to the invention allows to achieve a symmetrical distribution of the stress on the front axle structure, while obtaining a uniform and efficient dissipation of the heat generated by the electrical motor and by the power electronic module. Concentrated peaks of temperature can be avoided in the proximity of the power electronic module, thus enhancing reliability of the motor control. In addition, by using cooling ducts embedded in the front axle structure, the cooling system is less noisy and less prone to failure compared to conventional air cooling systems. Since the housing of the electrical motor includes cooling ducts for cooling both the electrical motor and the power electronic module, an efficient cooling of the heated components is ensured without the need of an additional cooling circuit. The heat generated in the axle structure can thus be efficiently removed while an advantageous distribution of the bending stress on the axle is achieved, since the supports of the lifting assembly are formed on the lateral left and right portions.

[0010] According to an embodiment, an outer cylindrical surface of the stator of the electrical motor adheres to an internal wall of the housing of the electrical motor. Hence, an optimal heat dissipation can be achieved as well as a compact design of the front axle structure.

[0011] According to an embodiment, the housing includes a plurality of cooling ducts surrounding the electrical motor. Hence, an efficient and uniform cooling can be achieved on the whole outer surface of the electrical motor.

[0012] According to an embodiment, the housing is formed by cast iron, preferably by ductile cast iron. This permits to properly obtain cooling ducts in the housing while achieving the necessary mechanical resistance to withstand the bending stress induced by the lifting assembly on the front axle structure.

[0013] According to an embodiment, the outer surface on which the power electronic module is mounted is formed by raw cast iron, wherein a layer of thermally conductive material is fixed to the outer surface and the power electronic module is fixed on the layer of conductive material, which is interposed between the power electronic module and the outer surface. Hence, an efficient cooling of the power electronic module can be achieved even if the housing is not machined. Thus, the manufacturing of the front axle structure and, especially, of the motor housing can be simplified.

[0014] According to an embodiment, the housing includes a longitudinally hollow body forming the recess for accommodating the electrical motor and two end pieces, the two end pieces being attached respectively to opposite longitudinal ends of the longitudinally hollow body, wherein the longitudinally hollow body includes a plurality of longitudinal cooling ducts that are in communication with a first manifold duct formed in one of the two end pieces and with a second manifold duct in the other of the two end pieces. Accordingly, the housing can be manufactured with an improved integrated cooling circuit in a simple manner in three pieces.

[0015] According to an embodiment, each of the left portion and the right portion comprises a flange for connecting to the frame of the industrial truck. Hence, the stresses induced on the front axle structure by the lifting assembly can be properly transmitted to the frame.

[0016] According to an embodiment, the industrial truck comprises a lifting assembly hydraulic circuit for feeding liquid to one or more hydraulic actuators configured to move the lifting element, wherein liquid circulating in the lifting assembly hydraulic circuit is the same as the cooling liquid. Accordingly, the same liquid used for the actuators of the lifting assembly can be used for cooling the axle structure, thereby simplifying the construction of the industrial truck.

[0017] According to an embodiment, the left portion and the right portion of the front axle structure are connected to the housing of the electrical motor by means of flanges. Hence, an optimal distribution of the stresses is achieved in the front axle structure.

[0018] According to an embodiment, the left portion of the axle structure is connected to one end piece of the housing and the right portion of the axle structure is connected to other end piece of the housing. This allows to achieve a simplified structure of the axle.

[0019] According to an embodiment, the manifold ducts in the first and second end pieces of the housing are formed with an annular groove open towards the hollow body of the housing. Hence, a proper distribution of the cooling liquid can be ensured in a plurality of cooling ducts in the housing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and other advantages of the present invention will be illustrated with reference to an example embodiment of the invention, described with reference to the appended drawings listed as follows.

Fig. 1 shows a lateral schematic view of an industrial truck according to the invention;

Fig. 2 shows the frame of the industrial truck and the lifting assembly detached from the frame;

Fig. 3 shows an embodiment of front axle structure according to the invention;

Fig. 4 shows the front axle structure with a part of the housing removed;

Fig. 5 shows the front axle structure with another part of the housing removed;

Fig. 6 shows a cross section of the front axle structure along a vertical plane containing an axis of the front axle structure;

Fig. 7 shows a view of a component of the electric motor housing;

Fig. 8 shows a scheme of the hydraulic circuit of the cooling system and of the actuators of the lifting assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Figure 1 shows a schematic representation of an industrial truck 10 according to an embodiment of the present invention, e.g. a forklift truck. The industrial truck 10 includes a frame 11, a mast 12 pivotally mounted on the frame 11 and lifting element 13 (e.g. a fork) for lifting a load 14; the lifting element 13 is mounted on the mast 12 in a slidable manner along the mast 12; in figure 1 the lifting element 13 is shown in a lowered position. The mast 12 is pivotally mounted on the chassis 11 around a pivot, which is preferably located close to the front axle of the truck 10; however, the mast 12 and the lifting assembly could be positioned also closed to the rear axle of the truck. The mast 12 may be tilted over a range of directions encompassing a vertical direction. The mast 12 forms part of a lifting assembly 15, which is configured to lift the lifting element 13 to lift a load. The lifting assembly 15 includes actuating means (not shown) for causing the lifting element 13 to slide along the mast 12; the actuating means can be implemented according any known configuration in the art. The industrial truck 10 is electrically driven. Further, the industrial truck 10 might include two wheels on the front axle and one or two wheels on the rear axle, as well as steering wheels for steering the truck while driving.

[0022] The truck 10 includes a lifting actuator (not shown) configured to move the lifting element 13 along the mast 12 and a tilting actuator (not shown) configured to tilt the mast 12 with respect to the frame 11 around a horizontal axis. The truck further includes a control unit 40 (schematically represented in dashed lines in fig. 1) configured to control the lifting actuator and the tilting actuator. The control unit 40 may control also further actuators of the truck, i.e. a wheel drive system. The wheel drive system may include one or more motors for driving the wheels of the truck and a braking system. The motor can be an electrical motor such as a reluctance, induction or permanent magnet motor, or the like.

[0023] Figure 2 shows the frame 11, 14 of the industrial truck and the front axle structure 16 connected to the frame, wherein the wheels are removed in the drawing and the lifting assembly 15 is shown detached from the frame 11, 14. The front axle structure 16 includes a housing 33 for receiving the electrical motor for the traction of the front wheels, and a left portion 22 on which supporting means 51 are formed to support the lifting assembly 15 (a right portion of the front axle structure is described later). The left portion 22 is also connected to the frame 14 and supports the wheel carrier element 22b.

[0024] Figure 3 shows the front axle structure 16 according to an embodiment of the invention. The front axle structure 16 is connected to the frame 14 of the truck by means of flanges 52. The front axle structure is constituted by a left portion 22, a right portion 21 and a housing 31, 32, 33 of the electrical motor joined together with each other. The housing 31, 32, 33 is interposed between the left portion 22 and the right portion 21. The left portion 22 and the right portion 21 may be directly joined to the housing 31, 32, 33, i.e. without the interposition of other elements, although other arrangement may be possible. Each of the left portion 22 and the right portion 21 comprises supporting means 51 (e.g. flanges) for supporting the lifting assembly 15. Furthermore, preferably each of the left portion 22 and the right portion 21 includes a flange 52 for the connection to the frame 14, preferably a vertical flange formed on the upper part of the front axle structure 16. The left portion 22 and the right portion 21 are each formed preferably as a single integral piece, e.g. made of cast iron.

[0025] The housing 31, 32, 33 of the electrical motor includes cooling ducts (described later more in details) and is configured to withstand a bending stress induced in the housing by the weight of the lifting assembly 15.

[0026] In one embodiment, the right portion 21 includes a circular flange 80 for connection to the housing 31-33 by means of a plurality of fastening means 90. The left portion 22 include a similar flange for the connection the housing of the motor.

[0027] Preferably, opposite to the housing 31-33, the left portion 22 is connected to a further element 22a which supports the wheel carrier element 22b in a rotatable manner. Similarly, the right portion 21 is connected to a further element 21a which supports the wheel carrier element 21b.

[0028] The housing of the electrical motor includes, preferably, a longitudinally hollow body 33 forming the recess for accommodating the electrical motor and two end pieces 31, 32. Each of the longitudinally hollow body 33 and two end pieces 31, 32 are each formed as a single integral piece. The two end pieces 31, 32 are attached respectively to opposite longitudinal open ends of the longitudinally hollow body 33. The longitudinal hollow body 33 is preferably substantially cylindrical. The two end pieces 31, 32 have the shape of a circular plate. The two end pieces 31, 32 are connected to the longitudinally hollow body 33 by means of a plurality of fastening means 91 distributed along the outer circumference of the end pieces 31, 32.

[0029] The housing includes an outer surface 34 on which a power electronic module 35 (e.g. an inverter for feeding the currents to the electrical motor) for controlling the electric motor is mounted. Preferably, the outer surface 34 for mounting the power electronic module is formed on the hollow body 33 of the housing, most preferably on the upper part of the front axle structure 16, i.e. the power electronic module 35 is placed above the front axle structure 16. Preferably, the outer surface 34 is planar.

[0030] In one preferred embodiment, the components of the housing 31, 32, 33 are formed by cast iron, most preferably by ductile cast iron. Ductile cast iron is preferred to achieve a desired mechanical resistance, e.g. resistance in case of collisions. However, although cast iron is the preferred material, the components forming the housing 31-33 could be also formed with aluminium, in case of very low nominal loads of the industrial truck. The outer surface 34 can be formed with raw cast iron to avoid an expensive machining process after casting. In this case, a layer 36 of thermally conductive material is applied to the outer surface 34 and the power electronic module 35 is mounted on the layer of conductive material 36, which is interposed between the power electronic module 35 and the outer surface 34. Preferably, the layer of conductive material 36 is made of graphite and is formed with a Pyrolytic Graphite Sheet, PGS. This allows to ensure a proper thermal conduction from the power electronic module 35 to the housing 31-33 even if the outer surface 34 is not machined after casting. In the figure, the layer of conductive material 36 and the power electronic module 35 are shown in exploded schematic view. Preferably, the outer surface 34 has a rectangular elongated shape extending along a longitudinal direction of the axle. The power electronic module 35 has advantageously a planar shape and covers at least 80% of the outer surface 34 when mounted on the housing 31-33. The layer 36 occupies the whole space between the power electronic module 35 and the outer surface 34.

[0031] Alternatively, the planar outer surface 34 could be processed by machining to obtain a smooth surface; in this case, the layer 36 could be omitted and sufficient thermal conduction may be achieved via a smooth machined surface 34.

[0032] Figure 4 shows the front axle structure of figure 3 in which the hollow body 33 is removed and the electrical motor is not shown. Figure 5 shows the front axle structure of figure 3 in which the end piece 32 is not shown. Figure 6 is a cross section of the housing 31-33, in which the motor 17 is shown. Figure 7 shows the hollow body 33 taken alone.

[0033] As well illustrated at figures 4, 5, 6 and 7, the longitudinally hollow body 33 includes a plurality of longitudinal cooling ducts 41-43 that are in communication with a first manifold duct 45 formed in the end piece 31 and with a second manifold duct 46 in the end piece 32. In the present disclosure, with "longitudinal" it is intended in a direction parallel to the longitudinal extension of the front axle structure 16. The first manifold duct 45 and the second manifold duct 46 may have an annular shape; the annular shape may be closed (i.e. without interruption as shown in fig. 4) or may be open (i.e. with an interruption). For example, the first manifold duct 45 and the second manifold duct 46 may be formed as a groove in the end pieces 31 and 32, respectively. The groove may be open in the direction facing the hollow body 33 to allow supply and collection of the coolant to/from the cooling ducts in the hollow body 33.

[0034] As shown in figure 4, in one embodiment, the manifold duct 45 has a circular shape. Preferably, the manifold duct 45 is arranged close to the outer rim of the end piece 31. The manifold duct 46 in the end piece 32 (shown in figure 6) has a similar shape and arrangement. The end pieces 31 and 32 includes a hole in a central position to allow the shaft 81 connected to the rotor 19 of the motor 17 to pass through the end pieces 31, 32 and transmit the wheel traction motion. The end piece 31 includes a plurality of longitudinal holes 82 formed between the outer rim of the end piece 31 and the manifold duct 45 for receiving fastening means for connecting the end piece 31 to the hollow body 33. The end piece 32 includes a similar arrangement of longitudinal holes for connection to the hollow body 33. The end piece 31 includes an inlet 83 for feeding cooling liquid into the manifold 45. The end piece 32 includes an outlet 84 for the collection of liquid exiting the housing through the manifold 46. The inlet 83 and the outlet 84 are preferably formed on the upper part of the front axle structure. The inlet 83 and the outlet 84 are preferably formed adjacent to the outer surface 34. The manifold ducts 45, 46 are in communication with the ducts in the hollow body 33, in particular with the ducts 42, 43. The ducts 41 arranged close to the outer surface 34 for cooling the power electronic module may be in communication with respective ducts 83a, 84a in the end pieces 31, 32 that connect the inlet/outlet 83, 84 with the respective manifold ducts 45, 46. The ducts 83a and 84a extend advantageously along a substantially vertical direction. The inlet 83 and the outlet 84 are connected to an external hydraulic circuit (not shown in fig. 4) configured for the circulation of the cooling liquid inside the manifolds 45 and 46 and the cooling ducts in the hollow body 33. The cooling liquid circulates in the front axle structure only in the motor housing 31, 32 and 33. The cooling liquid does not circulate in the left and right parts 21, 22 of the front axle structure 16.

[0035] The housing 31-33 of the electrical motor is thermally coupled with a stator 18 of the electrical motor 17, whereby in the cooling ducts 41-43 a cooling liquid flows to cool the electrical motor during the operation of the industrial truck. Specifically, as well shown in figure 6, the stator 18 of the motor is formed with resin cast so as to adhere to the inner wall 44 of the hollow body 33 of the housing. The stator 18 is formed by casting resin in the housing to incorporate the stator windings.

[0036] The rotor 19 is fixed on the hollow shaft 81 which passes through the central holes in the end pieces 31 and 32. The shaft 81 is supported by bearings carried by the left and right portions 21, 22 of the front axle structure 16.

[0037] As well shown in figures 6 and 7, in a region of the housing 31-33 between the outer surface 34 and a recess 70 configured to accommodate the electric motor 17, the housing 31-33 (and specifically the hollow body 33 of the housing in the embodiment shown in the figures) includes an electric motor cooling duct 42 positioned close to the recess 70 and at least one power electronic module cooling duct 41 positioned between the electric motor cooling duct 42 and the outer surface 34 for cooling the power electronic module during the operation of the industrial truck. Preferably, the electric motor cooling duct 42 has an elongated cross section. The elongated cross section preferably has the shape of a segment of circumference with a constant distance from the recess 70. The power electronic module cooling ducts 41 are preferably more than one, most preferably three as shown in the figure 7. All the power electronic module cooling ducts 41 are positioned between the electric motor cooling duct 42 and the outer surface 34. The hollow body 33 has a substantially cylindrical shape and the ducts 41, 42 extend along a longitudinal direction of the hollow body 33, which in turn corresponds to the direction of the longitudinal axis of the front axle structure.

[0038] Preferably, the housing (and in particular the hollow body 33 in the embodiments shown in the figures) includes a plurality of cooling ducts 42, 43 surrounding the electrical motor. Specifically, in addition to the above described motor cooling duct 42, the hollow body includes three additional motor cooling ducts 43 which surrounds the motor 18. The shape of the ducts 43 is similar to the shape of the cooling duct 42. The four ducts 42, 43 are arranged symmetrically around the recess 70. Preferably, the thickness of a lateral wall of the hollow body 33 in a region between the electrical motor 17 and the power electronic module 35 is larger than a second region other than the first region. This allows to arrange more cooling ducts 41, 42 in the thicker region, so as to improve the cooling effect and avoid peaks of temperature in the structure.

[0039] The cooling liquid enters the from the inlet 83 into the manifold duct 45 in the end piece 31, which distributes the cooling liquid to all ducts 41, 42 and 43 in the hollow body 33. However, as above discussed, the cooling duct 41 may be fed by a separate duct 83a. The cooling liquid is then collected by the manifold duct 46 in the end piece 32 and exits the housing of the electrical motor via the outlet 84. As above discussed, the liquid from the cooling ducts 41 may be collected by a duct 84a separate from the manifold 46.

[0040] The industrial truck according to the invention further comprises a lifting assembly hydraulic circuit 60 for feeding liquid (e.g. oil) to one or more hydraulic actuators configured to move the lifting element 13 of the lifting assembly 15. Advantageously, the liquid circulating in the lifting assembly hydraulic circuit 60 is the same as the cooling liquid. According to one embodiment, the hydraulic circuit includes a first main pump 61 for pumping the oil to the oil control valves of the actuators of the lifting assembly 15 and a second pump 62 to send oil to the cooling circuit including the ducts formed in housing 31-33 of the electric motor in the front axle structure 16. Both pumps 61 and 62 may be driven by the same motor. Furthermore, both pumps 61, 62 draw oil from a common oil tank 64 via a suction filter 63. Before reaching the ducts in the housing 31-33 of the motor in the front axle structure, the oil pumped by the pump 62 circulates in an oil cooler 65 for cooling the liquid. After circulating in the circuit of the lifting assembly actuators and in the cooling circuit of the front axle structure, the oil is collected into the common oil tank 64.

[0041] The above description of embodiments applying the innovative principles of the invention is provided solely for the purpose of illustrating said principles and must thus not be considered as limiting the scope of the invention claimed herein.

[0042] For example, although a preferred embodiment involves the use of the oil circulating in the hydraulic circuit of the lifting assembly as refrigerant, also another liquid could be used. For example, also water could be used as refrigerant. In this case, an independent hydraulic circuit would be included in the industrial truck, separate from the hydraulic circuit for operating the actuators of the lifting assembly.

[0043] Furthermore, although in the above embodiments the front axle structure has been described, the same axle structure could also be implemented in the rear axle structure.

Claims

1. An industrial truck including:

- a frame (11, 14),

- a lifting assembly (15) including a movable lifting element (13) for lifting a load (14),

- at least an electrical motor (17) for the traction of wheels of the industrial truck, and

- an axle structure (16) connected to the frame (14) of the truck by means of flanges (52) and constituted by a left portion (22), a right portion (21) and a housing (31, 32, 33) of the electrical motor, the housing (31, 32, 33) being interposed between the left portion (22) and the right portion (21), the housing (31, 32, 33) being joined to each of the left portion (22) and the right portion (21), wherein each of the left portion (22) and the right portion (21) comprises supporting means (51) for supporting the lifting assembly (15), and the housing of the electrical motor is configured to withstand a bending stress induced in the housing by the weight of the lifting assembly,

wherein the housing of the electrical motor is thermally coupled with a stator (18) of the electrical motor (17) and includes at least one cooling duct (41-43) in which a cooling liquid flows to cool the electrical motor during the operation of the industrial truck,

wherein the housing includes an outer surface (34) on which a power electronic module (35) for controlling the electric motor is mounted, and

wherein, in a region of the housing (33) between the outer surface (34) and a recess (70) of the housing configured to accommodate the electric motor (17), the housing (33) includes an electric motor cooling duct (42) positioned close to the recess (70) and at least one power electronic module cooling duct (41) positioned between the electric motor cooling duct (42) and the outer surface (34) for cooling the power electronic module during the operation of the industrial truck.

2. An industrial truck according any of the preceding claims, wherein the housing (33) includes a plurality of cooling ducts (42, 43) surrounding the electrical motor (17).

3. An industrial truck according any of the preceding claims, wherein the housing (31, 32, 33) includes a longitudinally hollow body (33) forming the recess (70) for accommodating the electrical motor (17) and two end pieces (31, 32), the two end pieces (31, 32) being attached respectively to opposite longitudinal ends of the longitudinally hollow body (33), wherein the longitudinally hollow body (33) includes a plurality of longitudinal cooling ducts (41-43) that are in communication with a first manifold duct (45) formed in one of the two end pieces (31) and with a second manifold duct (46) in the other of the two end pieces (32).

4. An industrial truck according claim 3, wherein the left portion (22) is directly connected to one end piece (32) of the housing and the right portion (21) is directly connected to other end piece (31) of the housing.

5. An industrial truck according claim 3, wherein the manifold ducts (45, 46) in the first and second end pieces (31, 32) of the housing are formed with an annular groove that is open towards the hollow body (33) of the housing for communicating with the at least one cooling duct in the hollow body (33).

6. An industrial truck according any of the preceding claims, wherein the left portion (22) and the right portion (21) are connected to the housing (31-33) by means of flanges (80).

7. An industrial truck according any of the preceding claims, wherein each of the left portion (22) and the right portion (21) comprises a flange (52) for connecting to the frame (14) of the industrial truck.

8. An industrial truck according any of the preceding claims, wherein the housing (31, 32, 33) is formed by cast iron, preferably by ductile cast iron.

9. An industrial truck according to claim 8, wherein the outer surface (34) of the housing is formed by raw cast iron, wherein a layer (36) of thermally conductive material is fixed to the outer surface (34) and the power electronic module (35) is fixed on the layer of conductive material (36), wherein the layer (36) of thermally conductive material is preferably formed with a Pyrolytic Graphite Sheet, PGS.

10. An industrial truck according any of the preceding claims, further comprising a lifting assembly hydraulic circuit (60) for feeding liquid to one or more hydraulic actuators configured to move the lifting element, wherein liquid circulating in the lifting assembly hydraulic circuit is the same as the cooling liquid.

Drawing