Ground milling machine having a cooling system, cooling system, and method for cooling a ground milling machine

Abstract

The present invention relates to a ground milling machine with two cooling ducts, which allow a mutually separated guidance of cooling air. The present invention further relates to such a cooling system and a method for cooling a ground milling machine.

Claims

1. A ground milling machine, comprising: an internal combustion engine arranged in an engine compartment; a hydraulic system with at least one hydraulic pump and travelling devices which are driven by individual hydraulic motors; a milling gear driven directly or indirectly by the internal combustion engine, the milling gear comprising a drive pulley, a driven pulley and a traction device as a part of a belt drive; a cooling system with an engine cooling device and a hydraulic fluid cooling device; the engine cooling device comprising a first fan and a cooling circuit with an engine heat exchanger; a first cooling air duct formed such that cooling air aspirated by the first fan from the ambient environment is guided to the engine heat exchanger and subsequently to a first cooling air outlet; wherein the hydraulic fluid cooling device comprises a second fan and a hydraulic fluid heat exchanger, wherein a second cooling air duct is implemented such that cooling air aspirated from the ambient environment by the second fan is guided to the hydraulic fluid heat exchanger and subsequently to a second cooling air outlet, wherein the first cooling air duct and the second cooling air duct are implemented so as to conduct the cooling air of the first cooling air duct and the cooling air of the second cooling air duct through the engine cooling device and the hydraulic fluid cooling device separately from each other and by circumventing the engine compartment, wherein the ground milling machine is configured to be operated in working operation and in travelling operation, the working operation designating an operating mode in which the ground milling machine travels at a substantially constant first speed and mills the ground surface with a rotating milling drum leading to a first load of the internal combustion engine and a second load of the hydraulic system, with the second load being less than the first load during the working operation, the travelling operation designating an operation mode in which the milling drum is idle and the ground milling machine travels at a second speed which is greater than the first speed leading to a third load of the internal combustion engine and a fourth load of the hydraulic system, with the third load being less than the fourth load during the travelling operation, so that a first heating of a cooling liquid of the internal combustion engine and a second heating of the hydraulic oil of the hydraulic system occurs in working operation, with the first heating being greater than the second heating during the working operation, and a third heating of the cooling liquid of the internal combustion engine and a fourth heating of the hydraulic oil of the hydraulic system occurs in travelling operation, with the third heating being less than the fourth heating during the travelling operation, and wherein the first fan is operated in working operation of the ground milling machine substantially under full load or at maximum speed, whereas the second fan is operated in travelling operation of the ground milling machine substantially under full load or at maximum speed so that the first and the second fans are alternatively or oppositely loaded to a lesser or greater extent with respect to each other, or their speeds are controlled in opposite directions with respect to each other, with the first and second fans being controlled individually and independently of each other.

2. The ground milling machine according to claim 1, wherein the cooling system is implemented such that the engine heat exchanger and the first fan are arranged adjacent to the hydraulic fluid heat exchanger with the second fan.

3. The ground milling machine according to claim 1, wherein the first cooling air duct and the second cooling air duct guide the cooling air aspirated by the respective first and second fan in parallel with respect to each other.

4. The ground milling machine according to claim 1, wherein the first cooling air duct or the second cooling air duct is arranged adjacent to the engine compartment, and is spatially separated from said compartment by a first separating wall.

5. The ground milling machine according to claim 4, wherein the first cooling air duct and the second cooling air duct are arranged directly adjacent to each other and are spatially separated from each other by a second separating wall.

6. The ground milling machine according to claim 5, wherein the second separating wall is arranged perpendicularly and directly adjacent to the first separating wall and is fixed to the first separating wall.

7. The ground milling machine according to claim 4, wherein for venting the engine compartment, at least one passage opening from the engine compartment to the second cooling air duct is provided through which heated engine air can flow from the engine compartment into the second cooling air duct.

8. The ground milling machine according to claim 1, wherein the first fan is arranged in the direction of flow of the cooling air behind the engine heat exchanger, or the second fan is arranged in the direction of flow of the cooling air behind the hydraulic fluid heat exchanger.

9. The ground milling machine according to claim 1, wherein the hydraulic fluid cooling device comprises a third fan in addition to the second fan, the second and third fan being controllable independently of each other.

10. The ground milling machine according to claim 1, wherein an additional heat exchanger is provided in the engine cooling device, which additional heat exchanger is connected to a cooling circuit for cooling the milling gear, the additional heat exchanger being arranged adjacent to the engine heat exchanger.

11. The ground milling machine according to claim 1, wherein an additional heat exchanger is provided in the hydraulic fluid cooling device, which additional heat exchanger is connected to a cooling circuit for cooling a pump transfer gear, the additional heat exchanger being arranged adjacent to the hydraulic fluid heat exchanger.

12. The ground milling machine according to claim 1, wherein a common retaining frame is provided, on which the engine cooling device, the hydraulic fluid cooling device, a first separating wall, and a second separating wall are mounted.

13. The ground milling machine according to claim 1, wherein the ground milling machine comprises at least one air intake opening to the first or second cooling air duct, which is arranged on the upper side of the ground milling machine in the working direction (a) behind an operator platform.

14. The ground milling machine according to claim 7, wherein a closure element is provided, which is implemented so as to be able to control the volumetric flow through the air intake opening to the second cooling air duct or the at least one passage opening between the engine compartment and the second cooling air duct in order to set the level of the engine compartment ventilation as needed.

15. The ground milling machine according to claim 1, wherein the first and second cooling air outlet open into a common exhaust air space, which comprises at least one air discharge opening to the ambient environment.

16. The ground milling machine according to claim 15, wherein the at least one air discharge opening of the first or second cooling air outlet is arranged in the rear of the ground milling machine, and that the exhaust air space or the at least one air discharge opening comprises an air guide device, which is implemented so as to guide the exhaust air in the working direction (a) to the rear and in an upwardly inclined manner to the ambient environment.

17. A cooling system for a ground milling machine according to claim 1.

18. A method for cooling the internal combustion engine arranged in an engine compartment and the hydraulic system of a ground milling machine according to claim 1, comprising the steps: suction of cooling air into a first cooling air duct by a first fan; conduction of the cooling air of the first cooling air duct through an engine heat exchanger; and ejection of the cooling air of the first cooling air duct through a cooling air outlet of the first cooling air duct; wherein aspiration of cooling air into a second cooling air duct by a second fan, conduction of the cooling air of the second cooling air duct through a hydraulic fluid heat exchanger and ejection of the cooling air from the second cooling air duct, wherein a conduction of the cooling air of the second cooling air duct through the hydraulic fluid cooling device occurs spatially separated from the conduction of the cooling air of the first cooling air duct through the engine cooling device, and wherein the cooling air of the first cooling air duct and the cooling air of the second cooling air duct are conducted so as to circumvent the engine compartment.

19. The method according to claim 18, wherein the cooling air of the first cooling air duct is conducted in the engine cooling device either through the engine heat exchanger or through an additional heat exchanger, which is connected to a cooling circuit for cooling the milling gear.

20. The method according to claim 18, wherein the cooling air of the second cooling air duct is conducted in the hydraulic fluid cooling device either through the hydraulic fluid heat exchanger or through an additional heat exchanger which is connected to a cooling circuit for cooling a pump transfer gear.

21. The method according to claim 18, wherein the respective volumetric flows of the aspirated cooling air of the first and second cooling air duct are controlled independently of each other by the first and the second fan.

22. The method according to claim 18, wherein engine air is co-aspirated into the second cooling air duct from the separate engine compartment through passage openings in the first separating wall which delimits the engine compartment.

23. The method according to claim 22, wherein the volumetric flow of the engine air which is co-aspirated into the second cooling air duct is controlled as needed via a closure element.

24. The method according to claim 18, wherein the cooling air is aspirated into the first and the second cooling air duct on the upper side of the ground milling machine in the working direction (a) behind an operator platform.

25. The method according to claim 18, wherein the cooling air is ejected in the rear of the ground milling machine in the working direction (a) to the rear and especially in an upwardly inclined manner.

26. The ground milling machine according to claim 1, wherein the ground milling machine comprises one of a cold milling machine, a stabilizer or a recycler.

27. The ground milling machine according to claim 2, wherein the cooling system is implemented such that the engine heat exchanger and the first fan are arranged adjacent to the hydraulic fluid heat exchanger with the second fan transversely to the working direction (a).

28. The ground milling machine according to claim 4, wherein the first cooling air duct or the second cooling air duct is arranged adjacent to, and in the working direction (a) directly behind, the engine compartment, and is spatially separated from said compartment by a first separating wall.

29. The ground milling machine according to claim 7, wherein the at least one passage opening is provided in a hydraulic cooler side of the first separating wall which delimits the second cooling air duct towards the engine compartment.

30. The ground milling machine according to claim 10, wherein the additional heat exchanger is arranged above the engine heat exchanger.

31. The ground milling machine according to claim 11, wherein the additional heat exchanger is located above the hydraulic fluid heat exchanger.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will be explained below in closer detail by reference to exemplary embodiments shown in the drawings. In the schematic Figures:

(2) FIG. 1a shows a side view of a ground milling machine, specifically a road cold milling machine;

(3) FIG. 1b shows a side view of a ground milling machine, specifically a stabiliser/recycler;

(4) FIG. 2a shows a drive train of the ground milling machine of FIG. 1a;

(5) FIG. 2b shows an alternative drive train of the ground milling machine of FIG. 1a;

(6) FIG. 3 shows a perspective side view of a first embodiment of a cooling system of a ground milling machine;

(7) FIG. 4 shows a top view of the cooling system according to FIG. 3;

(8) FIG. 5 shows a first separating wall;

(9) FIG. 6 shows a perspective side view of a further embodiment of a cooling system of a ground milling machine;

(10) FIG. 7 shows a heat exchanger and a fan of the cooling system according to FIG. 6; and

(11) FIG. 8 shows a flowchart of a method according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

(12) Like components are provided with like reference numerals. Repeated components are partly not designated individually in each drawing.

(13) FIG. 1a shows a ground milling machine 1 of the type of a road cold milling machine (center rotor milling machine), comprising an operator platform 2 and a machine frame or chassis 3. The ground milling machine 1 moves in the working direction a over the ground 7 to be processed by using the running gears 6. The ground milling machine 1 mills the ground 7 by means of a milling drum 9 which is mounted in a milling drum box 8 so as to rotate about the rotational axis 10. The removed milling material can be transferred in the working direction a via a discharge device 5, e.g., a discharge conveyor in a pivotable discharge arm, to a transport vehicle not shown here, and can be removed by said vehicle. The ground milling machine 1 further comprises a drive train 13 which is shown in closer detail in FIG. 2a or 2b. In order to cool components of said drive train 13, a cooling air supply is provided as a part of a cooling system among other things, which cooling air supply is implemented in such a manner that intake air 11 is sucked in on the upper side of the ground milling machine 1 via air intake openings 54 in the region 4 of the ground milling machine 1 situated in the working direction a behind the operator platform 2. The exhaust air 12 is ejected via the air discharge openings 55 in the rear of the ground milling machine 1 against the working direction a to the rear in an upwardly inclined manner (for example, by means of respective guide blades in the outlet region). The design of the region situated between the air intake opening 54 and the air discharge opening 55 will be explained below in closer detail.

(14) An alternative ground milling machine 1 is shown in FIG. 1b, which shows a stabiliser/recycler. The ground material is milled in these ground milling machines, however, as opposed to road cold milling machines, this material is not removed but crushed and/or mixed with additives. The essential elements such as the operator platform 2, the machine frame or chassis 3, the running gears 6, a milling drum 9 mounted in a milling box (cover) 8, and the drive train 13 are also present in these ground milling machines. Reference is thus made in these respects to the aforementioned disclosure.

(15) An exemplary drive train 13 of the ground milling machine 1, especially for a cold milling machine, is shown in a roughly schematic view in FIG. 2a. It comprises an internal combustion engine 14 such as a diesel engine, which is connected via a first shaft 15 to a pump transfer gear 16. The pump transfer gear 16 comprises several distributor shafts 17, via which multiple units 18 are driven, especially at least one hydraulic pump of a hydraulic system. The hydraulic system 18 is implemented in such a manner, for example, that hydraulic motors are driven via hydraulic pumps, which hydraulic motors are used for the travel drive of the running gears 6 of the ground milling machine 1. All required hydraulic pumps of the ground milling machine 1 can be coupled to the pump transfer gear 16 and can be supplied by said gear with power. A drive shaft 19 is further provided, via which a milling drum gear 56 can be driven, which will be explained below in closer detail.

(16) A milling gear 56 is further driven by means of the internal combustion engine 14, which in the specific embodiment comprises a drive pulley 20, a driven pulley 22 and a traction means 21 as a part of a belt drive in the manner known in the prior art. The drive pulley 20 transmits said power via the traction means 21 to the driven pulley 22, and from said pulley to a drum shaft 23. The drum shaft 23 drives the milling drum 9, usually via a respective reduction gear, which is not shown here, in working operation of the ground milling machine 1 for rotation about the rotational axis 10.

(17) In working operation of the ground milling machine 1, i.e., while the milling drum 9 mills ground material from the ground 7 during its rotation, the internal combustion engine 14 runs at a comparatively high speed over a longer period of time. A large amount of heat is thus developed by the internal combustion engine 14 in this operating stage. In travelling operation of the ground milling machine 1, i.e., when the milling drum 9 is idle and the running gears 6 are driven via the hydraulic system 18, the internal combustion engine 14 is loaded to a considerably lesser extent and runs in this operating range with comparatively low power. The heat development is accordingly low. In contrast, the hydraulic system 18 is heavily loaded in travelling operation of the ground milling machine 1 with respect to the operation of the hydraulic pumps for driving the respective hydraulic driving motors on the running gears 6. The hydraulic oil of the hydraulic system 18 thus heats up very strongly. This effect in turn occurs to a substantially lesser extent in working operation because the travelling speed of the ground milling machine 1 is then comparatively low. In order to achieve an energy-efficient cooling of the components of the ground milling machine 1, especially with respect to the cooling of the internal combustion engine and the hydraulic system, the present invention proposes a cooling system which enables in working operation mainly a cooling of the internal combustion engine 14 via a cooling circuit with cooling liquid which is connected thereto, and which in travelling operation of the ground milling machine 1 mainly allows effective cooling of the hydraulic oil of the hydraulic system 18 or at least parts thereof. Details of such a cooling system will be explained below in closer detail.

(18) FIG. 2b shows an alternative embodiment of the drive train 13, reference being hereby made to the preceding statements with respect to FIG. 2a concerning the general configuration. The essential difference here is that the connection of the milling drum gear or the shaft 19 occurs via the pump transfer gear. A shiftable clutch (not shown in closer detail in FIG. 2b) can further be provided at this point (between the pump transfer gear 16 and the drive pulley 20).

(19) A first embodiment of a cooling system 24 is shown in closer detail in FIGS. 3 and 4. The intake air 11 flows from above through the air intake opening 54 into the cooling system 24. The aspirated intake air flows proportionally either into a first cooling air duct 28 or into a second cooling air duct 30. The intake air 11 is thus divided into two air flows, which are conducted separately from each other either through the first cooling air duct 28 or the second cooling air duct 30. The first cooling air duct 28 conducts the cooling air 39 to the engine cooling device 50, which comprises the engine heat exchanger 32, the engine fan device 48 and a cooling circuit, which is not shown, with cooling liquid for the internal combustion engine 14. The cooling circuit for the internal combustion engine 14 is in fluidic connection with the engine heat exchanger 32. The second cooling air duct 30, on the other hand, conducts cooling air 41 separately from the cooling air 39 to the hydraulic fluid cooling device 51, which comprises the hydraulic fluid heat exchanger 35 and the hydraulic fan device 49. In the direction of flow of the cooling air 39, 41 behind the fan devices 48, 49, the two exhaust air flows 40, 42 of the engine cooling device 50 and the hydraulic fluid cooling device 51 are conducted together as exhaust air 12 back to the ambient environment of the ground milling machine 1. In the direction of flow of the cooling air, the first cooling air duct 28 extends from a duct inlet 68, via which the intake air is extracted by suction from above, to a duct outlet 70, which in the present embodiment corresponds to the outflow side of a first fan 34. The cooling air flows through the engine heat exchanger 32 between the duct inlet and the duct outlet, and/or, depending on the embodiment, through at least one supplementary heat exchanger arranged in the first cooling air duct 28. Correspondingly, the second cooling air duct 30 extends in the direction of flow of the cooling air from a duct inlet 69, via which the intake air 11 is extracted by suction from above, to a duct outlet 71, which in the present embodiment corresponds to the outflow side of a second fan 37 (in the present embodiment the second and third fan). The cooling air flows through the hydraulic fluid heat exchanger 35 between the duct inlet and the duct outlet, and/or, depending on the embodiment, at least one supplementary heat exchanger arranged in the second cooling air duct 30. The cooling air ducts 28 and 30 are thus defined by a mutually separate cooling air inlet, the mutually separate guidance of the cooling air, the arrangement of at least one respective heat exchanger and the at least one fan within the duct, and one respective cooling air outlet after the passage of the heat exchanger and the fan (in this sequence or in reverse sequence).

(20) The flow of the cooling air from the air intake openings 54 to the air discharge openings 55 is produced and maintained by the engine fan device 48 and the hydraulic fan device 49. The engine fan device 48 comprises a first fan cover or hood 33 in the direction of flow to the rear and an upstream first fan 34. The hydraulic fan device 49 correspondingly comprises a second fan cover or hood 36 and, in the shown embodiment, a second and third fan 37. The hoods 33 and 36 are used for channelling the path of flow of the cooling air 39, 41 and for ensuring that substantially the entire cooling air is sucked through the fans 34, 37. The fans 34, 37 allow the suction of cooling air from the ambient environment and the production and maintaining of the cooling air flow through the cooling air ducts. The first and the second cooling air ducts 28, 30 lie on the suction side of the fans 34, 37. From the suction side of the fans 34, 37, the air is conveyed in the direction of flow to the pressure side, on which a first cooling air outlet 52 adjoins the first duct outlet 70 and a second cooling air outlet 53 adjoins the second duct outlet 71 directly after the fans 34, 37. The two cooling air outlets 52, 53 are not separate from each other in the illustrated embodiment and jointly form a common exhaust air space 38. The exhaust air 12 flows through the exhaust air space 38 until it exits at the air discharge openings 55 from the ground milling machine 1 to the ambient environment. The first and the second cooling air ducts are further lined towards their duct sides with respective side walls, for example, to the base and to the sides, except for the regions of the duct inlet 68 and 69 and duct outlet 70 and 71, in order to enable a channelled guidance of cooling air along the longitudinal extension of the first and the second cooling air duct.

(21) The fans 34, 37 are, for example, fans with a fan wheel which comprises multiple blades arranged radially around the rotational axis of the fan wheel, which blades cause the air to move upon rotation of the fan wheel and produce the air flow from the suction to the pressure side of the fans 34, 37. The fans 34, 37 can be driven hydraulically or electrically.

(22) The first cooling air duct 28 and the second cooling air duct 30 lie directly adjacent to the engine compartment 25 in which the internal combustion engine 14 is arranged, or behind said compartment in the working direction a. They are spatially separated therefrom by a first separating wall 26, so that the intake air 11 which is conveyed in the direction of the fan devices 48, 49 circumvents the engine compartment 25. The first and the second cooling air duct 28, 30 are also arranged adjacent to each other and separated from each other by the second separating wall 31. The further side walls of the first and second cooling air duct 28, 30 are only shown transparently and in dots in FIGS. 3 and 4 for reasons of clarity of the illustration.

(23) A retaining frame 47 (indicated with the dot-dash line in FIG. 4) is further provided. The retaining frame 47 is a support structure which especially retains the fans 34, 37 and connects said fans to a machine frame of the ground milling machine 1. Essential elements of the first cooling air duct 28 and the second cooling air duct 30 can be premounted on the retaining frame 47 in form of a cooling assembly and can be subsequently installed as a unit in the ground milling machine 1. This facilitates mounting considerably.

(24) The first separating wall 26 shown in FIGS. 3 and 4 is also shown in detail in FIG. 5 in a top view against the direction of flow and in the direction of view as seen from the side of the heat exchangers 32, 35. The engine therefore lies into the sheet plane behind the first separating wall 26, whereas parts of the first and the second cooling air duct 28, 30 are situated out of the sheet plane before the separating wall 26. The first separating wall 26 is divided by the second separating wall 31 into an engine cooler side 27 and a hydraulic cooler side 29, the engine cooler side 27 being the portion of the first separating wall 26 which separates the first cooling air duct 28 from the engine compartment 25. The hydraulic cooler side 29 of the first separating wall 26, on the other hand, is the portion of the first separating wall 26 which separates the second cooling air duct 30 from the engine compartment 25. In the illustrated embodiment, a total of six passage openings 43 are provided in the hydraulic cooler side 29 of the first separating wall 26, which passage openings connect the engine compartment 25 to the air space of the second cooling air duct 30. In the space of the second cooling air duct 30 which is situated before the second and third fan 37, i.e., on the suction side of the second and third fan 37 of the hydraulic fluid cooling device 51, a vacuum is present in the second cooling air duct 30. This leads to the consequence that engine air 44 (i.e., air surrounding the internal combustion engine in the engine compartment) is extracted by suction through the passage openings 43 in the first separating wall 26 and reaches the second cooling air duct 30 and mixes there with the cooling air 11. The engine air 44 is conveyed from the second cooling air duct 30 together with the cooling air 41 of the hydraulic fluid cooling device 51 through the fan 37 into the exhaust air space 38. Efficient engine compartment ventilation is produced by removing the engine air 44 from the engine compartment 25. This is especially advantageous if the engine cooling device 50 is already operated at maximum power, for example, in travelling operation. Since, in this case, the cooling demand of the hydraulic fluid cooling device is comparatively low for the reasons mentioned above, the slight heating of the cooling air produced by the admixed engine air is not disadvantageous.

(25) FIG. 5 further illustrates an optional refinement, which enables a regulation of the opening area of the passage openings 43. A broad spectrum of potential alternatives can be used in this case, wherein it is essential that the flowable opening area of one or several passage openings 43 is adjustable via an adjusting movement. Apertures, closure flaps or even slides 57 can specifically be used in this case, for example, as is shown in FIG. 5, by way of example, at the two bottom passage openings 43. The left slide is in a position in which the passage opening 43 is closed and, therefore, an exchange of air through the passage opening is completely prevented. The right passage opening 43, on the other hand, is already nearly completely opened by the slide 57. Provision may be made, in this case, for example, for an actuating element not designated here in closer detail, for example, a motor or the like, via which the adjustment of the slide position can be automated. It is understood that manual adjustment is also possible. The passage openings 43 are dimensioned with respect to their size and number in such a way that both efficient cooling of the internal combustion engine 14 is ensured by the removal of the engine air 44, and also that sufficient fresh cooling air 41 is moved past the hydraulic fluid heat exchanger 35 in order to ensure efficient cooling of the hydraulic oil of the hydraulic system 18.

(26) The first fan 34 and the second and third fan 37 can be triggered and also controlled independently from each other as required by a control device 67 (FIG. 7). Said control device 67 controls the volumetric flow via the respective fans 34, 37 on the basis of the temperature of the cooling liquid of the cooling circuit of the internal combustion engine 14 or the hydraulic oil of the hydraulic system 18. Suitable temperature sensors are provided for this purpose. If the demand for the cooling air flow increases in the case of rising temperatures, the control device will raise the fan speed and vice versa. This ensures that the fan speed always is in the optimal range. It is further important here that the fans 34, 37 are all controllable by the control device 67 independently of each other. If the need for cooling only increases at the engine heat exchanger 32, the control device 67 will only turn up the first fan 34. This ensures individual fan control for the first and the second cooling air duct.

(27) FIGS. 6 and 7 show a further embodiment of the cooling system 24. As in the preceding embodiment, the fans 34, 37 are all controlled independently of each other by the control device 67. In contrast to the embodiment of FIGS. 3 and 4, the cooling system 24 of FIG. 6 comprises in addition to the engine heat exchanger 34 an additional heat exchanger 45 which is arranged directly above the heat exchanger 32. A cooling liquid flows through the heat exchanger 45, which cooling liquid is part of a cooling system for cooling the milling gear 56. The heat exchanger 45 is arranged in such a way that fresh cooling air 39 flows through said heat exchanger, which cooling air has not yet passed any further heat exchanger and which is extracted by suction by the first fan 34 from the first cooling air duct 28. In order to achieve this, the heat exchanger 45 is also located before the first hood 33 of the engine fan device 48 in the direction of flow of the cooling air 39. The exhaust air of the heat exchanger 45 therefore flows together with the exhaust air of the engine heat exchanger 32 into the common exhaust air space 38. The volumetric flow required for this purpose is generated by the first fan 34. The arrangement of the heat exchanger 45 for cooling the milling gear 56 directly adjacent to and especially above the engine heat exchanger 35, without the heat exchanger 45 and the engine heat exchanger 35 overlapping each other, is also shown in FIG. 7, which shows a view of the engine cooling device 50 and the hydraulic fluid cooling device 51 in the direction of flow of the cooling air 39, 41 from the side of the first and the second cooling air duct 28, 30.

(28) The two cooling devices 50, 51 are separated from each other with respect to space and air flow by the second separating wall 31, so that the cooling air 39 from the first cooling air duct 28 only passes through the heat exchangers 35, 45 and the first fan 34, and the cooling air 41 which is separated therefrom passes together with the engine air 44 through the heat exchanger 32, 46 and the second and third fan 37. The mixing of the air from the first of the second cooling air duct 28, 30 only occurs in a common exhaust air space 38, which adjoins the duct outlets 70 and 71 in the direction of flow of the cooling air.

(29) Furthermore, in contrast to the cooling system 24 of FIG. 3, a further heat exchanger 46 is arranged adjacent to, and especially directly above, the hydraulic fluid heat exchanger 35 in the embodiment of the cooling system 24 of FIG. 6. A cooling liquid flows through the further heat exchanger 46, which absorbs the waste heat of the pump transfer gear 16 via a cooling circuit arranged on said gear. A cooling fluid flows around the further heat exchanger 46, which absorbs the exhaust heat of the pump transfer gear 16 via a cooling circuit which is arranged thereon. The further heat exchanger 46 is connected to the second hood 36 in such a way that cooling air 41 of the second cooling air duct 30 is sucked by the second and/or third fan 37 through the further heat exchanger 46, which air previously has not passed any further heat exchanger. This ensures efficient cooling of the pump transfer gear 16 by the further heat exchanger 46. FIG. 7 also shows that the further heat exchanger 46 within the hydraulic fluid cooling device 51 is arranged adjacent to, especially above, the hydraulic fluid heat exchanger 32 in such a way that the heat exchanger 46 does not overlap with the hydraulic fluid heat exchanger 32. The air which is sucked through the second and/or third fan 37 through the further heat exchanger 46 or the hydraulic fluid heat exchanger 35 joins in the common exhaust air space 38 with the cooling air 39 which flows through the engine cooling device 50.

(30) FIG. 6 also shows a further closure element 57, which can seal the second cooling air duct 30 against the air intake openings 54. In contrast to the aforementioned closure element 57 of the passage openings 43, the closure element 57 thus controls the volumetric flow between the ambient environment and the second cooling air duct 30. The access to the second cooling air duct 30 can be sealed by the closure element 57, for example, as a result of which the volumetric flow of the engine air 44 from the engine compartment 25 through the passage openings 43 is increased in combination with the same power of the fans 37. The ventilation of the engine compartment is thus increased with increased volumetric flow through the passage openings 43. The engine air 44 is preheated by the combustion engine 14, so that the cooling efficiency at the hydraulic fluid heat exchanger 35 and the further heat exchanger 46 which cools the pump transfer gear 16 is reduced. However, since these components are loaded to a lesser extent in working operation of the ground milling machine 1, reduced cooling of these components is still adequate. The hydraulic fluid cooling device 51 can thus be used in working operation of the ground milling machine 1 for the support of the engine cooling device 50 for cooling the internal combustion engine 14 without any disadvantage.

(31) Furthermore, a closure element 57 is also present in this embodiment, which is arranged as a pivotable flap which rests on the passage openings 43 so as to close them all, and which can be pivoted away from the openings so as to open them. The closure element 57 can thus vary and also completely prevent a flow of engine air 44 from the engine compartment 25 into the second cooling air duct 30. It is thus possible, in travelling operation of the ground milling machine 1, for example, when the hydraulic system 18 is substantially maximally loaded, to prevent engine compartment ventilation by the passage openings 43 in order to utilise the entire cooling power of the hydraulic fluid cooling device 51 for cooling the hydraulic oil of the hydraulic system 18 and/or the cooling liquid of the pump transfer gear 16 in the additional heat exchanger 46. The provision of the closure elements 57, 57 thus ensures that both in working operation and also in travelling operation of the ground milling machine 1 the components that are respectively loaded to the greatest extent can be cooled efficiently.

(32) FIG. 6 further shows a guide blade 73, which is arranged in the air exit region on the ground milling machine 1, where the cooling air exits the ground milling machine 1 to the ambient environment. The guide blade 73 deflects the cooling air flow to the rear and in an upwardly inclined manner, so that it does not raise dust from the ground when leaving the machine.

(33) FIG. 8 finally illustrates the sequence of the method for cooling the internal combustion engine 14 arranged in an engine compartment 25 and the hydraulic system 18 of a ground milling machine 1. The start of the method is designated by reference numeral 58. It is a basic concept that the method is essentially carried out in the spatially separated compartments 63 and 64, which functionally correspond to the first and the second cooling air duct 28, 30. No air can be exchanged between the compartments 63, 64. The respective cooling air flows 39, 41 are thus separated from each other.

(34) The first step in the two compartments 63, 64 is the suction 59 of cooling air from the ambient environment. Said suction of air from the ambient environment is produced by the first fan 34 and a second and/or third fan 37. The volumetric flow of the aspirated air to the two compartments 63, 64 is subject to the control 66 by a control device 67. The control device 67 regulates the volumetric flow of the fans 34, 37 depending on the temperature of the cooling liquid of a cooling circuit for the internal combustion engine 14 or depending on the temperature of the hydraulic oil of the hydraulic system 18.

(35) The suction 59 of the cooling air 39, 41 is followed by the conduction 60 of the cooling air 39, 41 through the engine cooling device 50 and the hydraulic fluid cooling device 51. The cooling air 39 of the first compartment 63 thus either passes a heat exchanger 45 which is connected to a cooling circuit for cooling the milling gear, or the engine heat exchanger 35. In each case, the cooling air 35 then passes the first fan 34. Separated therefrom, the cooling air 41 of the second compartment 64 either passes the heat exchanger 46 which is connected to a cooling circuit for cooling the pump transfer gear 16, or the hydraulic fluid heat exchanger 32. In each case, the cooling air 41 then passes either the second or third fan 37. In the second compartment 64, a suction 65 of engine air 44 from the engine compartment 25 into the second compartment 64 can further occur. The engine air 44 flows in the second compartment 64 together with the cooling air 41 further through the hydraulic fluid cooling device 51 and thence into the exhaust air space 38.

(36) The ejection 61 of the air through the air discharge openings 55 occurs from the exhaust air space 38. The ejection 61 of the air may occur either separately from each other from the different compartments 63 and 64 or, as indicated by the dashed line between the step 60 in the second compartment 64 and step 61 in the first compartment 63, via a common exhaust air space 38 through the air discharge openings 55. The end 62 of the method is thus reached. The individual method steps are performed continuously and simultaneously during the operation of the ground milling machine 1 and are controlled by the control device 67.

(37) While the present invention has been illustrated by description of various embodiments and while those embodiments have been described in considerable detail, it is not the intention of Applicants to restrict or in any way limit the scope of the appended claims to such details. Additional advantages and modifications will readily appear to those skilled in the art. The present invention in its broader aspects is therefore not limited to the specific details and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of Applicants' invention.