METHOD FOR OPERATING A VEHICLE COOLING SYSTEM

Description

[0001] The invention relates to a method for operating a vehicle cooling system which has a main cooling path and a secondary cooling path branching off upstream from the main cooling path, wherein a main cooling unit for generating a main cooling airflow passing through a first heat exchanger arrangement is assigned to the main cooling path and a secondary cooling unit located upstream in the main cooling path for generating a secondary cooling airflow passing through a second heat exchanger arrangement is assigned to the secondary cooling path.

[0002] Such a vehicle cooling system, distributed across multiple cooling paths, is used, for example, in agricultural tractors manufactured by John Deere. This system includes an axial fan driven by a diesel engine via a belt drive. This fan draws in ambient air through a front grille in the hood to create a main cooling airflow that passes through a heat exchanger assembly. The heat exchanger assembly contains, among other components, an engine radiator, an oil cooler, and an air conditioning condenser, all arranged side-by-side or one behind the other within the main cooling airflow. Upstream, in the upper boundary region of the main cooling airflow, is another axial fan.The additional axial fan is driven by a separate hydraulic or electric motor, which independently generates a secondary cooling airflow branching off from the main cooling airflow at a virtually vertical angle. This secondary cooling airflow is then passed through the charge air cooler of the diesel engine and subsequently exits into the outside environment at the top of the agricultural tractor's engine hood.

[0003] The well-known vehicle cooling system has the characteristic that the operation of the two axial fans with separate drives is comparatively inefficient, especially when cooling requirements are moderate in the low-load range of the agricultural tractor.

[0004] Each of the applicant's publications DE102014208545 A1 and DE102019204468 A1 describes a method for operating a conventional vehicle cooling system.

[0005] The object of the present invention is therefore to optimize a method of the type mentioned at the outset with regard to energy-efficient operation of a vehicle cooling system distributed over several cooling paths.

[0006] This problem is solved by a method for operating a vehicle cooling system with the features of claim 1.

[0007] In a method for operating a vehicle cooling system, the vehicle cooling system has a main cooling path and a secondary cooling path branching off upstream from the main cooling path. A main cooling unit for generating a main cooling airflow passing through a first heat exchanger arrangement is associated with the main cooling path, and a secondary cooling unit located upstream in the main cooling path is associated with the secondary cooling path for generating a secondary cooling airflow passing through a second heat exchanger arrangement. In a first operating mode, a control unit operates both the main cooling unit and the secondary cooling unit to generate independent cooling airflows, whereas in a second operating mode, the control unit operates only the main cooling unit.The auxiliary cooling unit is placed in an idle operating state such that, due to the pressure conditions prevailing upstream in the main cooling airflow, a passive auxiliary cooling airflow is generated passing through the second heat exchanger arrangement.

[0008] The first operating mode corresponds to the conventional operation of both cooling units with active generation of both the main and secondary cooling airflows, whereas in the second operating mode, the secondary cooling unit is deliberately deactivated or in an idle state, so that power consumption is essentially limited to the operation of the main cooling unit. This takes into account situations in which the cooling demand of the second heat exchanger arrangement is so low that generating a passive secondary cooling airflow flowing through the second heat exchanger in the opposite direction is sufficient for adequate heat dissipation. By selecting the first or second operating mode as needed, the distributed vehicle cooling system can therefore be operated particularly energy-efficiently.

[0009] The cooling units typically each include an axial fan, which, in the case of the main cooling unit, is driven by a belt drive from the agricultural tractor's diesel engine, and in the case of the secondary cooling unit, by a separate hydraulic or electric motor. For the idling operation specified in the second operating mode, this means that a fan speed of typically 10 to 15 revolutions per minute is selected. Choosing such a low fan speed ensures that the passive secondary cooling airflow remains unaffected during idling. However, the rotating fan blades of the axial fan make it obvious that the vehicle's cooling system is in operation and therefore pose a potential risk of injury, especially when the hood is open.

[0010] For the sake of completeness, it should be noted that the term "cooling path" is used abstractly here and refers to the path intended or specified for the course of the respective cooling airflow, regardless of whether such a cooling airflow is actually present or not.

[0011] Advantageous further developments of the method according to the invention are set out in the dependent claims.

[0012] Preferably, the first or second operating mode is selected depending on a determination of the current cooling requirement of the second heat exchanger arrangement carried out by the control unit.

[0013] For energy efficiency reasons, the control unit always prioritizes the second operating mode. However, the first operating mode is selected if, based on the cooling demand calculation, the control unit determines that the cooling capacity achievable by generating the passive secondary cooling airflow is insufficient to reliably meet the cooling requirements of the second heat exchanger assembly. The same applies if the control unit determines that the full capacity of the main cooling unit is required to adequately cool the first heat exchanger assembly.

[0014] Therefore, when selecting the operating mode, the control unit takes into account the determined cooling requirement of the first heat exchanger arrangement.

[0015] To determine the current cooling requirement, the control unit can compare the temperature conditions measured by sensors in the respective cooling circuits of the heat exchanger arrangements with the outside temperature. A sufficient number of temperature sensors are used to measure the temperature conditions in the cooling circuits and the outside temperature. The sensor data from these sensors is transmitted to the control unit via an internal CAN data bus or a comparable data transmission interface.

[0016] Furthermore, in the second operating mode, the control unit can increase the intensity of the main cooling airflow by controlling the main cooling unit, particularly according to a cooling requirement determined for the first heat exchanger arrangement. By appropriately increasing the cooling capacity of the main cooling unit, it is possible, among other things, to prevent the cooling of the first heat exchanger arrangement from being impaired by the additional waste heat from the second heat exchanger arrangement entering the main cooling airflow via the passive secondary cooling airflow when the secondary cooling unit is switched off or running idle.

[0017] The inventive method for operating a vehicle cooling system is described in more detail below with reference to the drawings. Identical reference numerals refer to identical components or components comparable in function. The drawings show: Fig. 1 shows a schematic embodiment of a vehicle cooling system of an agricultural tractor distributed over several cooling paths in a first operating mode, and Fig. 2 shows the embodiment shown in Fig. 1 Vehicle cooling system reproduced in a second operating mode.

[0018] Fig. 1 Figure 1 shows a schematic representation of an exemplary embodiment of a vehicle cooling system distributed across multiple cooling paths.

[0019] The vehicle cooling system 12, housed in an agricultural tractor 10 (not shown in detail), has a main cooling path 14 and a secondary cooling path 16 branching off upstream from the main cooling path 14, wherein a main cooling unit 18 for generating a main cooling airflow 22 passing through a first heat exchanger arrangement 20 is assigned to the main cooling path 14 and a secondary cooling unit 24 located upstream in the main cooling path 14 for generating a secondary cooling airflow 28 passing through a second heat exchanger arrangement 26 is assigned to the secondary cooling path 16.

[0020] For example, the main cooling unit 18 comprises an axial fan 34, which is driven by a diesel engine 30 of the agricultural tractor 10 via a belt drive 32. Air from the outside environment 36 is drawn in through a front grille 38 of an engine hood 40 by means of this fan to generate the main cooling airflow 22 passing through the first heat exchanger assembly 20. The first heat exchanger assembly 20, designed as a heat exchanger package 42, includes, among other things, an engine radiator 44, an oil cooler 46, and an air conditioning condenser 48 of a vehicle air conditioning system, which are arranged side by side or one behind the other in the main cooling airflow 22.

[0021] For example, the axial fan 34 is located behind the heat exchanger package 42 with respect to the direction of the main cooling airflow 22, but it can also be located in front of it.

[0022] The auxiliary cooling unit 24 is a further axial fan 52 located upstream in an upper marginal region 50 of the main cooling airflow 22. A separate drive 54 in the form of a hydraulic or electric motor 56 is assigned to the further axial fan 52, which serves to independently generate the auxiliary cooling airflow 28 branching off essentially vertically upwards from the main cooling airflow 22. According to a Fig. 1 In the first operating mode of the vehicle cooling system 12, the secondary cooling airflow 28 generated by means of the additional axial fan 52 is directed through a charge air cooler 58 of the diesel engine 30 encompassed by the second heat exchanger arrangement 26 and then exits into the outside environment 36 at a top 60 of the engine hood 40 of the agricultural tractor 10.

[0023] In this case, the additional axial fan 52 is located in front of the heat exchanger package 26 with respect to the direction of the secondary cooling airflow 28, but it can also be located behind it.

[0024] More precisely, in the first operating mode, the axial fans 34, 52 of both the main cooling unit 18 and the secondary cooling unit 24 are operated in such a way that independent cooling airflows 22, 28 are generated, whereas in a Fig. 2 In the second operating mode shown, only the axial fan 34 of the main cooling unit 18 is in operation. The other axial fan 52 of the secondary cooling unit 24 is stationary in the second operating mode or is set to an idle operating state, in which it has only a low fan speed in the range of 10 to 15 revolutions per minute, so that, due to the pressure conditions prevailing upstream in the main cooling airflow 22 (which lead to the formation of a negative pressure), a passive secondary cooling airflow 62 is generated, passing through the second heat exchanger arrangement 26 in the opposite direction or being drawn in from the outside environment 36.

[0025] A control unit 64 coordinates the operation of the cooling units 18, 24 by switching between the two operating modes. The first or second operating mode is selected based on a determination by the control unit 64 of the current cooling demand of the two heat exchanger arrangements 20, 26, for which the temperature conditions detected by sensors in the respective cooling circuits of the heat exchanger arrangements 20, 26 are related to the outside temperature.

[0026] For the sensory detection of the temperature conditions prevailing in the cooling circuits as well as the outside temperature, a corresponding number of temperature sensors 66 are provided, the sensor data of which are supplied to the control unit 64 via a vehicle-internal CAN data bus 68.

[0027] For energy efficiency reasons, control unit 64 always prioritizes the [process / activity] in Fig. 2The second operating mode shown is used. However, the first operating mode is selected if the control unit 64, based on the cooling demand calculation, determines that the cooling capacity achievable by generating the passive secondary cooling airflow 62 is insufficient to reliably cover the cooling demand of the second heat exchanger arrangement 26. The same applies if the control unit 64 determines that the full capacity of the main cooling unit 18 is required to adequately cool the first heat exchanger arrangement 20. Therefore, the control unit 64 takes the determined cooling demand of the first heat exchanger arrangement 20 into account when selecting the operating mode.

[0028] If the system switches to the second operating mode, the intensity of the main cooling airflow 22 is increased by the control unit 64, if necessary by controlling the main cooling unit 18, according to the cooling requirement determined for the first heat exchanger arrangement 20. By appropriately increasing the cooling capacity of the main cooling unit 18, it is possible, among other things, to prevent the cooling of the first heat exchanger arrangement 20 from being impaired by the additional waste heat from the second heat exchanger arrangement 26 entering the main cooling airflow 22 via the passive secondary cooling airflow 62 when the auxiliary cooling unit 24 is switched off or in idle operation mode.

Claims

1. Method for operating a vehicle cooling system, comprising a main cooling path (14) and a secondary cooling path (16) branching off upstream in the main cooling path (14), a main cooling unit (18) for generating a main cooling air flow (22) passing through a first heat exchanger arrangement (20) being associated with the main cooling path (14) and a secondary cooling unit (24), located upstream in the main cooling path (14), for generating a secondary cooling air flow (28) passing through a second heat exchanger arrangement (26) being associated with the secondary cooling path (16), characterized in that, in a first operating mode, both the main cooling unit (18) and the secondary cooling unit (24) are operated by a control unit (64) in order to generate mutually independent cooling air flows (22, 28), whereas, in a second operating mode, only the main cooling unit (18) is operated by the control unit (64) or the secondary cooling unit (24) is set to an idle operating state so that, due to the pressure conditions prevailing upstream in the main cooling air flow (22), a passive secondary cooling air flow (62) passing through the second heat exchanger arrangement (26) is produced.

2. Method according to Claim 1, characterized in that the first or second operating mode is selected according to an ascertainment of the current cooling requirement of the second heat exchanger arrangement (26) which is carried out by the control unit (64).

3. Method according to Claim 2, characterized in that, during the selection of the operating mode by the control unit (64), an ascertained cooling requirement of the first heat exchanger arrangement (20) is also taken into account.

4. Method according to Claim 2 or 3, characterized in that, for the ascertainment of the current cooling requirement by the control unit (64), the temperature conditions recorded using sensors in respective cooling circuits of the heat exchanger arrangements (20, 26) are correlated with the external temperature.

5. Method according to at least one of the preceding claims, characterized in that, in the second operating mode, the intensity of the main cooling air flow (22) is increased via the control unit (64) by activating the main cooling unit (18).