METHOD FOR OPERATING A VEHICLE COOLING SYSTEM

Description

[0001] The invention relates to a method for operating a vehicle cooling system, which comprises a first fan unit for generating a main cooling flow acting on a first cooler arrangement, and a second fan unit adjacent to the main cooling flow for generating a secondary cooling flow acting on a second cooler arrangement, wherein the secondary cooling flow is branched off from the main cooling flow by means of the second fan unit, and wherein the ambient air sucked in for generating the cooling flows passes a filter element for particle filtration located upstream of the fan units and the cooler arrangements.

[0002] Such a vehicle cooling system is used, among other things, in R-series agricultural tractors from the manufacturer John Deere. The vehicle cooling system, housed in an engine compartment, has a first radiator assembly and a spatially separate second radiator assembly. The first radiator assembly includes, among other things, a high-temperature heat exchanger for cooling a diesel engine, an oil cooler and an air conditioning condenser. The respective radiator components are arranged in series and / or parallel in a common main cooling flow, which is generated by an axial fan by sucking in ambient air. The second radiator assembly has a charge air cooler, which is mounted upstream within the engine compartment and extends essentially horizontally above the main cooling flow.To enable the intercooler to operate independently of the primary cooling system, an additional axial fan driven by a hydraulic motor is installed upstream. This allows a secondary cooling stream to be branched off from the main cooling stream, passing through the intercooler. The heated secondary cooling stream then exits the engine compartment via an air outlet opening located on the top of the hood.

[0003] To protect the radiator assemblies of the vehicle cooling system from dust deposits and the associated degradation of cooling performance, ambient air is drawn in via a filter element. This takes the form of a fine-mesh metal sieve designed as a particle filter, which is located directly behind a front radiator grille in the hood of the agricultural tractor. Since the surface of the metal sieve becomes clogged over time as it passes through dusty ambient air, it is necessary to clean the filter element at regular intervals. For this purpose, a corresponding driver instruction can be issued based on a timer via a user interface located in the driver's cab. The cleaning process itself is usually carried out manually using a blow gun powered by compressed air from a compressor.However, some vehicle cooling systems also offer the option of putting the axial fan of the first cooling arrangement into reversing operation by pivoting the associated fan blades, in which the direction of the main cooling flow is reversed so that the filter element can be blown out towards the outside environment and thus cleaned.

[0004] To account for the dust deposits that accumulate on the filter element between successive cleaning cycles, as well as the fact that compliance with cleaning intervals ultimately depends on the operator's diligence, the maximum cooling capacity of the vehicle cooling system must be oversized accordingly to ensure sufficient "safety reserves." This applies especially to the second cooler assembly, which is adjacent to or extends into the main cooling stream and should be as compact as possible, not only to avoid undesirable impairment of the cooling of the first cooler assembly.

[0005] Document FR3093303A1 discloses a method for operating a vehicle cooling system according to the preamble of claim 1.

[0006] Against this background, it is the object of the present invention to further develop a method for operating a vehicle cooling system of the type mentioned at the outset with regard to installation space optimization.

[0007] This object is achieved by a method having the features of patent claim 1.

[0008] In the method for operating a vehicle cooling system, the vehicle cooling system comprises a first fan unit for generating a main cooling flow acting on a first cooler arrangement and a second fan unit adjacent to the main cooling flow for generating a secondary cooling flow acting on a second cooler arrangement, wherein the secondary cooling flow is branched off from the main cooling flow by means of the second fan unit, and wherein the ambient air sucked in for generating the cooling flows passes a filter element for particle filtration located upstream of the fan units and the cooler arrangements.A control unit compares an actual value of a speed variable determined by sensors and / or calculations, which represents a speed occurring at the second fan unit depending on the cooling requirement, with a setpoint value specified for a cleaned state of the filter element, wherein, in the event that the comparison result lies outside a predetermined speed tolerance range, a trigger signal is generated by the control unit to initiate reversing operation of the first fan unit in order to blow out the filter element by means of the first fan unit by reversing the direction of the main cooling flow.

[0009] In other words, an excessive increase in the cooling requirement of the second cooler assembly derived from an observed speed discrepancy is used as an indicator for the need to perform a filter element cleaning process. This approach takes into account the actual particle load of the intake ambient air, which is naturally not the case with a pure time-sequence control or similar. The required oversizing of the second cooler assembly, including the associated second fan unit, is determined by the safety margin provided by the permissible speed tolerance range, and can therefore be structurally compact accordingly.

[0010] The cooling requirement dependency of the speed of the second fan unit results from the fact that in common vehicle cooling systems, a reduced cooling capacity detected due to a temperature increase is compensated by a successive increase in speed.

[0011] The second cooling arrangement is typically a charge air cooler for a diesel engine. This serves to cool the combustion air, which is heated by a turbocharger during compression and fed into the intake tract of the diesel engine. The second fan unit is designed as a hydraulically or electrically driven axial fan.

[0012] To implement reversible operation, the first fan unit, also designed as an axial fan, can have a plurality of fan blades projecting radially from a fan hub, the angle of which can be pivoted by means of an adjusting device. This allows the flow direction to be reversed without changing the direction of rotation of the axial fan. The latter is set in rotation via a belt drive connected to the diesel engine.

[0013] Advantageous further developments of the method according to the invention emerge from the subclaims.

[0014] Preferably, the actual value of the speed variable is determined by the control unit using a sensor by detecting the speed of a fan wheel included in the second fan unit. This can be achieved by using an inductive speed sensor of conventional design, which non-contactingly detects the revolutions of a drive shaft running between the fan drive and the fan wheel and transmits a corresponding speed signal to the control unit.

[0015] On the other hand, it is also conceivable for the actual value of the speed to be calculated by the control unit based on a control variable provided for the operation of the second fan unit. If the fan impeller is driven hydraulically, the control variables can represent a volume flow and / or a pressure of a hydraulic supply provided for operating an associated hydraulic motor. These can be indirectly derived, for example, from an electrical signal that is used to actuate a valve provided for specifying the volume flow and / or pressure. In the case of an electrical drive of the fan impeller, however, the control variables result from the voltage and / or current of a power supply provided for operating an associated electric motor. The variables in question can be easily detected by sensors and, if the control behavior of the hydraulic or hydraulic system is known, can be calculated.Electric motor provides a clear statement about the speed occurring at the fan wheel.

[0016] Furthermore, it is possible for the specified speed value for a cleaned filter element to be fixed for simplicity. The setpoint is specified in such a way that the maximum expected cooling requirement of an operating device or operating medium to be cooled by the second cooler arrangement is reliably covered. The setpoint specified for the speed value is stored, for example, in a memory unit that communicates with the control unit.

[0017] Alternatively, it is also conceivable that the target speed value specified for a cleaned filter element is not fixedly based on the maximum cooling requirement of the operating device or the operating medium to be cooled by the second cooler arrangement, but is variably specified by the control unit depending on a determined actual cooling requirement. If the second cooler arrangement is a charge air cooler, the actual cooling requirement of the charge air can be derived from, among other things, information regarding the engine speed or power of the diesel engine, the outside temperature, the air humidity, the charge air pressure, and / or the position of adjustable turbocharger blades.

[0018] To initiate the cleaning process, the trigger signal can be used to control a user interface to output an operator message informing the operator of the need to perform reversing operation. The user interface comprises, for example, a touch-sensitive display located in the driver's cab of a commercial vehicle equipped with the vehicle cooling system or as part of a mobile device that communicates with the control unit via a wireless interface. The operator information is output visually via the touch-sensitive display, but may also be audible via an acoustic signal generator included in the user interface.

[0019] Furthermore, it is possible for the trigger signal to control an actuating device included in the first fan unit to automatically execute reversing operation. For this purpose, the actuating device comprises an electrically, hydraulically, or pneumatically actuated arrangement integrated into a fan hub of the fan wheel for changing the angle of attack of the fan blades. The electrical, hydraulic, or pneumatic actuation of the arrangement is carried out by means of a control unit connected to the control unit.

[0020] Since performing the cleaning process requires a temporary interruption of operation of a commercial vehicle equipped with the vehicle cooling system, it is advantageous if the control unit only automatically executes the reversing operation after prior operator approval. The touch-sensitive display included in the user interface can be used, in particular, for the purposes of operator approval. In this case, the driver of the commercial vehicle has the opportunity to first find a suitable parking space, thus preventing unwanted blowing out of the filter element in enclosed buildings such as barns or workshops.

[0021] The method according to the invention for operating a vehicle cooling system is described in more detail below with reference to the accompanying drawings. Identical reference numerals refer to identical or functionally comparable components. They show: Fig. 1a schematically illustrated vehicle cooling system of a commercial vehicle designed as an agricultural tractor, Fig. 2which in Fig. 1 vehicle cooling system shown during the execution of a reversing operation, and Fig. 3 shows an embodiment of the method according to the invention for operating the Fig. 1 vehicle cooling system shown.

[0022] Fig. 1 shows a schematically illustrated vehicle cooling system 10, which is a component of a commercial vehicle designed as an agricultural tractor 12.

[0023] The depiction of an agricultural tractor 12 is merely exemplary in nature; rather, it may also be any other commercial vehicle from the agricultural or forestry sector as well as a construction vehicle.

[0024] The vehicle cooling system 10, housed in an engine compartment 14 of the agricultural tractor 12, has a first cooler assembly 16 and a second cooler assembly 18 spatially separated therefrom. The first cooler assembly 16 includes, among other things, a high-temperature heat exchanger 20 for cooling a diesel engine 22, an oil cooler 24, and an air conditioning condenser 26. The respective cooler components are arranged in series and / or parallel in a common main cooling flow 28, which is generated by a first fan unit 32 designed as an axial fan 30. The axial fan 30 is rotated by a belt drive 34 connected to the diesel engine 22.

[0025] Furthermore, the second cooler arrangement 18 is a charge air cooler 36, which is mounted within the engine compartment 14 upstream and essentially horizontally above the main cooling flow 28. The charge air cooler 36 serves to cool the combustion air, which is heated by a turbocharger 38 during compression and is to be supplied to an intake tract 40 of the diesel engine 22 (the hose connections present in this respect are shown in Fig. 1 (only indicated for the sake of clarity). In order to enable operation of the charge air cooler 36 independent of the first cooler arrangement 16, a second fan unit 42 in the form of a further axial fan 44 is connected upstream, which is driven by a hydraulic motor 46. Instead of such a hydraulic drive, however, an electric drive in the form of an electric motor can also be provided. In this way, a secondary cooling flow 48 passing through the charge air cooler 36 is branched off from the main cooling flow 28. The heated secondary cooling flow 48 then leaves the engine compartment 14 via an air outlet opening 52 formed on an upper side of a hood 50 (indicated by dashed lines).

[0026] To protect the cooler assemblies 16, 18 of the vehicle cooling system 10 from dust deposits and the associated degradation of cooling performance, the ambient air 54 required to generate the main and secondary cooling streams 28, 48 is drawn in via a filter element 56 located upstream of the fan units 32, 42 and the cooler assemblies 16, 18. The filter element 56 is in the form of a fine-mesh metal sieve 58 designed as a particle filter, which is located directly behind a front radiator grille 60 in the hood 50 of the agricultural tractor 12. Alternatively, the filter element 56 can also be structurally integrated directly into the front radiator grille 60.

[0027] Since the surface of the metal screen 58 becomes clogged over time as dusty ambient air 54 passes through it, it is necessary to clean the filter element 56 at regular intervals. For this purpose, the vehicle cooling system 10 offers the option of setting the axial fan 30 of the first cooling arrangement 16 into reversing mode, in which the direction of the main cooling flow 28 is reversed, allowing the filter element 56 to be blown out toward the outside environment and thus cleaned.

[0028] More precisely, the axial fan 30 comprised by the first fan unit 32 has a plurality of fan blades 64 projecting radially from a fan hub 62 for reversing operation, which blades can be pivoted with respect to their angle of attack α by means of an adjusting device 66. In this way, a reversal of the flow direction is possible without changing the direction of rotation of the axial fan 30. This operating state is shown in Fig. 2 reproduced.

[0029] For the sake of completeness, it should be noted that the Fig. 1 The spatial arrangement of the fan units 32, 42 or cooler units 16, 18 shown represents only one of several possibilities. In the present case, the second cooler unit 18 is located between the filter element 56 and the first cooler unit 16 with respect to the path of the main cooling flow 28; however, it can also be located between the first cooler unit 16 and the first fan unit 32.

[0030] The function of the Fig. 1 The additional components shown below will be described in conjunction with the Fig. 3 The procedure described above will be explained.

[0031] Fig. 3shows an exemplary embodiment of the method according to the invention for operating the vehicle system 10, illustrated as a flowchart. Accordingly, the method is started in an initialization step 100, whereupon, in a first step 102, a control unit 68 determines an actual value n ist of a rotational speed variable that represents a rotational speed occurring at the second fan unit 42 as a function of the cooling demand. The cooling demand dependency of the rotational speed of the second fan unit 42 results in this case from the fact that a reduced cooling capacity detected due to a temperature increase is compensated by means of a successive increase in the rotational speed.

[0032] The actual value n of the speed variable is determined in the first step 102 by the control unit 68 by sensing the speed of a fan wheel 70 included in the second fan unit 42. This is done by an inductive speed sensor 72 of conventional design, which non-contactingly detects the revolutions of a drive shaft 74 extending between the hydraulic motor 46 and the fan wheel 70 and transmits a corresponding speed signal to the control unit 68.

[0033] Alternatively, the actual value n ist of the rotational speed variable is calculated by the control unit 68 in the first step 102 based on control variables provided for the operation of the second fan unit 42. The control variables present on a CAN data bus 76 of the agricultural tractor 12 are detected by sensors and, given a known control behavior of the hydraulic motor 46, allow a clear statement about the rotational speed occurring at the fan wheel 70. In this case, the control variables represent a volume flow and / or pressure of a hydraulic supply provided for operating the hydraulic motor 46. In this case, these are indirectly derived by the control unit 68 from an electrical signal that serves to actuate a valve (not shown) provided for specifying the volume flow and / or pressure.In the case of using an electric motor, however, the control variables result from the voltage and / or current of a power supply intended for its operation.

[0034] In a second step 104, the control unit 68 compares the actual value n actual of the speed variable determined in the first step 102 with a setpoint value n setpoint specified for a cleaned state of the filter element 56.

[0035] If the control unit 68 detects in a third step 106 that the comparison result lies outside a predetermined speed tolerance range Δn, it generates a trigger signal in a fourth step 108 to initiate reversing operation of the first fan unit 32 in order to blow out the filter element 56 by means of the first fan unit 32 by reversing the direction of the main cooling flow 28. Otherwise, the method returns to the third step 106.

[0036] In other words, an excessive increase in the cooling requirement of the second cooler arrangement 18 derived from a speed discrepancy observed in the fourth step 108 is used as an indicator of the need to carry out a cleaning operation of the filter element 56.

[0037] According to a first option, the setpoint n soll specified for a cleaned state of the filter element 56 is fixedly predefined for the speed variable. The setpoint n soll is specified in such a way that the maximum expected cooling requirement of the charge air to be cooled by the second cooler arrangement 18 is reliably covered. The setpoint n soll specified for the speed variable is stored in a memory unit 78 that communicates with the control unit 68.

[0038] Deviating from this, a second option provides that the target value n soll of the speed variable specified for a cleaned state of the filter element 56 is not fixedly based on the maximum cooling requirement of the charge air to be cooled by the second cooler arrangement 18, but is variably specified by the control unit 68 depending on a determined actual cooling requirement. The actual cooling requirement of the charge air is derived by the control unit 68 from, among other things, information available via the CAN data bus 76 regarding an engine speed or power of the diesel engine 22, the outside temperature, the air humidity, the charge air pressure, and / or the position of adjustable turbocharger blades.

[0039] To initiate the cleaning process, a fifth step 110 provides for the trigger signal to control a user interface 80 to output an operator message informing the operator of the necessity of reversing. The user interface 80 comprises a touch-sensitive display 82, which is housed in a driver's cab of the agricultural tractor 12 or is part of a mobile terminal 84 that communicates with the control unit 68 via a wireless interface 86. The operator information is output visually via the touch-sensitive display 82, but also audibly via an acoustic signal generator 88 included in the user interface 80.

[0040] In a seventh step 114, following operator approval in a preceding sixth step 112, the actuating device 66 comprised by the first fan unit 32 is activated by means of the trigger signal to automatically execute reversing operation. For this purpose, the actuating device 66 comprises an electrically, hydraulically, or pneumatically actuated arrangement 90 integrated into the fan hub 62 of the fan wheel 70 for changing the angle of attack α of the fan blades 64. The electrical, hydraulic, or pneumatic actuation of the arrangement 90 is effected by means of a control unit 92 connected to the control unit 68. If operator approval is not given in the sixth step 112, the method is immediately terminated in a final step 116.

[0041] The touch-sensitive display 82 included in the user interface 80 is used for the purposes of operator release in the sixth step 112. In this case, the driver of the agricultural tractor 12 is given the opportunity to first find a suitable parking space so that unwanted blowing out of the filter element 56 in closed buildings such as barns or workshops can be ruled out.

[0042] The method according to the invention is then terminated in the final step 116.

Claims

1. Method for operating a vehicle cooling system which comprises a first fan assembly (32) for generating a main cooling flow (28) acting upon a first cooler arrangement (16), and a second fan assembly (42) which is adjacent to the main cooling flow (28) for generating a secondary cooling flow (48) acting upon a second cooler arrangement (18), the secondary cooling flow (48) being branched off from the main cooling flow (28) by means of the second fan assembly (42), and the ambient air (54) taken in for generating the cooling flows (28, 48) passing through a filter element (56) which is located upstream of the fan assemblies (32, 42) and of the cooler arrangements (16, 18) for filtering particles, characterized in that an actual value (nact) of a rotational speed variable which is determined by sensor and / or computer and which reproduces a rotational speed occurring at the second fan assembly (42) depending on the cooling requirement is compared by a control unit (68) with a desired value (ndes) specified for a cleaned state of the filter element (56), wherein, in the event that the comparison result lies outside a predetermined rotational speed tolerance range (Δn), a trigger signal is generated by the control unit (68) to initiate a reversing operation of the first fan assembly (32) in order to blow out the filter element (56) by means of the first fan assembly (32) by reversing the direction of the main cooling flow (28).

2. Method according to Claim 1, characterized in that the actual value (nact) of the rotational speed variable is determined by the control unit (68) by sensor by detecting a rotational speed of a fan wheel (70) included by the second fan assembly (42).

3. Method according to Claim 1 or 2, characterized in that the actual value (nact) of the rotational speed variable is determined by the control unit (68) by computer in accordance with a control variable provided for operating the second fan assembly (42).

4. Method according to at least one of Claims 1 to 3, characterized in that the desired value (ndes) of the rotational speed variable that is specified for a cleaned state of the filter element (56) is fixedly predetermined.

5. Method according to at least one of Claims 1 to 3, characterized in that the desired value (ndes) of the rotational speed variable that is specified for a cleaned state of the filter element (56) is variably predetermined by the control unit (68) depending on a determined actual cooling requirement.

6. Method according to at least one of Claims 1 to 5, characterized in that a user interface (80) for outputting operator information informing of the necessity of carrying out a reversing operation is activated by means of the trigger signal.

7. Method according to at least one of Claims 1 to 6, characterized in that an actuating device (66) included by the first fan assembly (32) and intended for automatically carrying out the reversing operation is activated by means of the trigger signal.

8. Method according to Claim 7, characterized in that the reversing operation is automatically carried out by the control unit (68) only after previous enabling by the operator.