Method for Operating a Cooling System of an Internal Combustion Engine and Protection System in a Cooling System

Abstract

A method is provided for operating a cooling system of an internal combustion engine, which cooling system has a controllable rotary slide valve with at least one switched inlet or outlet. The movement of the rotary slide valve into a plurality of switching positions, which each correspond with a cooling system state, is monitored. In accordance with an improper functional state of the rotary slide valve and a current switching position of the rotary slide valve, an operating state of the internal combustion engine is changed to an emergency operation state. A protection system in the cooling system carries out the method and includes a thermal management system, which receives and processes coolant temperatures, and a control unit of a controllable rotary slide valve having a position detector, which can detect a current switching position of the switchable rotary slide valve, wherein the thermal management system is connected to the control unit of the rotary slide valve.

Claims

1. A method for operating a cooling system of an internal combustion engine, in which a controllable rotary slide valve having at least one switched inlet or outlet is provided, the method comprising the acts of: monitoring movement of the rotary slide valve into multiple switching positions which correspond to, in each case, one cooling system state, and in a manner dependent on an improper functional state of the rotary slide valve and a present switching position of the rotary slide valve, changing an operating state of the internal combustion engine to an emergency operation state.

2. The method according to claim 1, wherein the emergency operation state comprises a limitation of a rotational speed and/or a torque of the internal combustion engine to a predetermined maximum emergency operation value.

3. The method according to claim 1, wherein the improper functional state of the rotary slide valve is defined by a movement stiffness of the rotary slide valve, a jamming of the rotary slide valve, a failure of an actuation unit of the rotary slide valve or a failure of a position detector of the rotary slide valve.

4. The method according to claim 3, wherein the present switching position of the rotary slide valve corresponds to a state of the cooling system in which a vehicle cooler is at least substantially not traversed by flow.

5. The method according to claim 4, wherein the present switching position of the rotary slide valve corresponds to a state of the cooling system in which a flow through coolant lines in the internal combustion engine is at least partially throttled.

6. The method according to claim 1, wherein the present switching position of the rotary slide valve corresponds to a state of the cooling system in which a vehicle cooler is at least substantially not traversed by flow.

7. The method according to claim 6, wherein the present switching position of the rotary slide valve corresponds to a state of the cooling system in which a flow through coolant lines in the internal combustion engine is at least partially throttled.

8. The method according to claim 1, wherein a coolant temperature is detected, and the operating state of the internal combustion engine is changed to the emergency operation state only above a threshold value temperature of the coolant temperature.

9. The method according to claim 8, wherein the emergency operation state limits one or more of a rotational speed or a torque of the internal combustion engine to a predetermined emergency operation value.

10. The method according to claim 8, wherein in the case of an unthrottled or only partially throttled coolant flow through a vehicle cooler, the emergency operation state is withdrawn again if the coolant temperature falls below the threshold value temperature.

11. The method according to claim 8, wherein the emergency operation state is not implemented if, in the present cooling system state, at least a minimum flow through a vehicle cooler is realized, even if the rotary slide valve is in an improper state, as long as the coolant temperature lies below the threshold value temperature.

12. The method according to claim 10, wherein the emergency operation state is not implemented if, in the present cooling system state, at least a minimum flow through the vehicle cooler is realized, even if the rotary slide valve is in an improper state, as long as the coolant temperature lies below the threshold value temperature.

13. The method according to claim 3, wherein in the case of an improper functional state of the rotary slide valve which is defined by a failure of the position detector of the rotary slide valve, the rotary slide valve is moved into a predetermined switching position in which coolant lines in the internal combustion engine are traversed by a flow of coolant.

14. The method according to claim 1, wherein in a functional state of the rotary slide valve in which a movement to a second predetermined switching position from a first predetermined switching position exceeds a setpoint time, a shaking-free step is performed, in which the rotary slide valve is moved quickly between different switching positions multiple times.

15. The method according to claim 1, wherein in the improper functional states of the rotary slide valve and in the case of the emergency operation state of the internal combustion engine being implemented, a fault message is stored in a fault memory and/or a fault display is triggered.

16. A protection system in a cooling system of an internal combustion engine, comprising: a thermal management system that receives and processes coolant temperatures; an actuation unit for a controllable rotary slide valve having at least one switched inlet or outlet; a position detector that detects a present switching position of the controllable rotary slide valve, wherein the thermal management system is connected to the actuation unit of the controllable rotary slide valve, the protection system being configured to: monitor movement of the rotary slide valve into multiple switching positions which correspond to, in each case, one cooling system state, and in a manner dependent on an improper functional state of the rotary slide valve and a present switching position of the rotary slide valve, change an operating state of the internal combustion engine to an emergency operation state.

17. The protection system according to claim 16, wherein the emergency operation state comprises a limitation of a rotational speed and/or a torque of the internal combustion engine to a predetermined maximum emergency operation value.

18. The protection system according to claim 16, wherein the improper functional state of the rotary slide valve is defined by a movement stiffness of the rotary slide valve, a jamming of the rotary slide valve, a failure of an actuation unit of the rotary slide valve or a failure of a position detector of the rotary slide valve.

19. The protection system according to claim 18, wherein the present switching position of the rotary slide valve corresponds to a state of the cooling system in which a vehicle cooler is at least substantially not traversed by flow.

20. The protection system according to claim 16, wherein the present switching position of the rotary slide valve corresponds to a state of the cooling system in which a flow through coolant lines in the internal combustion engine is at least partially throttled.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] FIG. 1 is a schematic detail of a cooling system of an internal combustion engine having a protection system according to an embodiment of the invention for carrying out a method according to an embodiment of the invention.

[0043] FIG. 2 is a flow diagram of an exemplary method according to the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0044] FIG. 1 shows a protection system 10 in a cooling system 11 of an internal combustion engine 12, in this case in a passenger motor vehicle. The cooling system 11 is monitored and controlled by a thermal management system 14. The cooling system 11 is illustrated only as a detail, and in schematic form, in the figure, and shows only the elements essential to the invention in a detail of one of the cooling circuits of said cooling system. The cooling system 11 may be of arbitrarily complex design, and may have additional subcircuits, which may be interconnected at the discretion of a person skilled in the art.

[0045] The coolant flow in the cooling circuits is controlled substantially by way of a controllable rotary slide valve 16 which has at least one switched inlet 18 or one switched outlet 20. In the example illustrated here, all of the inlets 18 with the exception of one are switchable, and the outlet 20 is not switched. It would however also be possible for a suitable rotary slide valve of some other design to be used.

[0046] The different switching position of the rotary slide valve 16 define different states of the cooling system 11.

[0047] In a first cooling system state, the rotary slide valve 16 is switched such that a vehicle cooler (not illustrated) and coolant lines in the internal combustion engine 12 are traversed by a maximum coolant flow or by an only slightly throttled coolant flow. The inlet 18, which is connected to the cooler return line 22, of the rotary slide valve 16 is at least partially open, such that the so-called large cooling circuit is traversed by flow, in which the coolant flows through the vehicle cooler and through the internal combustion engine 12, in particular the cylinder head. A bypass line 24 from the internal combustion engine 12 to a second switched inlet 18 of the rotary slide valve 16 is, in this case, closed.

[0048] In said first state, with the cooler return line 22 fully open, the maximum cooling power of the cooling system 11 is available to the internal combustion engine 12.

[0049] In a second state of the cooling system 11, the inlet 18, which is connected to the cooler return line 22, is partially open, as is the inlet 18, which is connected to the bypass line 24, resulting in a partially reduced cooling power.

[0050] In a third cooling system state, the vehicle cooler is fully throttled, such that it is no longer traversed by flow. For this purpose, the inlet 18, which is connected to the cooler return line 22, of the rotary slide valve 16 is closed. The inlet 18, which is connected to the bypass line 24, is, by contrast, fully open, such that the full flow cross section of the bypass line 24 is traversed by flow. In this case, the so-called small cooling circuit through the internal combustion engine 12, but not through the vehicle cooler, is traversed by a flow of coolant. The cooling power is further reduced in relation to the second cooling system state.

[0051] In a fourth possible cooling system state, the inlet 18 connected to the cooler return line 22 is fully closed, whereas the inlet 18, which is connected to the bypass line 24, of the rotary slide valve 16 is partially open, such that a part of the flow cross section of the bypass line 24 is closed. The cooling power is therefore further reduced in relation to the third cooling system state.

[0052] In a fifth cooling system state, both the inlet connected to the cooler return line 22 and that connected to the bypass line 24 are fully closed, such that neither the vehicle cooler nor the cylinder head are traversed by a flow of coolant. In this case, the cooling system 11 provides only the minimum cooling power.

[0053] The individual cooling system states may transition into one another in continuous fashion. Further cooling states are self-evidently likewise possible, in which for example further subcircuits (not described here) of the cooling system 11 are activated or deactivated.

[0054] The rotary slide valve 16 is equipped with a position detector which detects the present switching position of the rotary slide valve 16 and which is connected to an actuation unit 28 which actuates an electric control motor 30 which moves the rotary slide valve 16 into the respectably desired switching position. The actuation unit 28 communicates with the thermal management system 14, and the thermal management system 14 predefines a setpoint state for the switching positions of the rotary slide valve 16 in accordance with the respective requirements.

[0055] In this example, the thermal management system 14 has access to control electronics (not illustrated) of the internal combustion engine 12, and can, in the event of faults, restrict torque and rotational speed to an emergency operation state, for example a fixedly predefined low torque, in order to reduce the heat generated by the internal combustion engine 12.

[0056] Furthermore, in the embodiment described, the actuation unit 28 of the rotary slide valve 16 communicates with an emergency operation management system 34. The emergency operation management system 34 serves for the direct protection of the internal combustion engine 12 against overloading, and for this purpose, likewise has access to the control electronics of the internal combustion engine 12, and in the event of faults can restrict torque and rotational speed to an emergency operation state. In this example, the emergency operation management system 34 also communicates with the thermal management system 14.

[0057] Furthermore, in the example shown here, a general monitoring system 36 is provided which, for example, performs general fault management of the vehicle. Inter alia, the general monitoring system 36 in this case monitors coolant temperatures at various locations in the cooling system 11.

[0058] Here, multiple temperature sensors 38, 40 are provided in the cooling system 11, which temperature sensors detect a coolant temperature, wherein one temperature sensor 38 is arranged directly in the cylinder head, and one temperature sensor 40 is positioned downstream of the cylinder head in the feed line to the vehicle cooler. It is also possible for further temperature sensors to be provided. The temperature sensors 38, 40 are in this case connected to the thermal management system 14, such that the present coolant temperatures are available to the latter at all times.

[0059] The thermal management system 14, the actuation unit 28 of the rotary slide valve 16 including the position detector 26, the temperature sensors 38, 40, the emergency operation management system 34 and the general monitoring system 36 are in this case part of the protection system 10.

[0060] The above-described cooling system states are, in the case of default-free functioning, in proper functional states of the rotary slide valve 16, assumed by virtue of the actuation unit 28 moving the rotary slide valve 16 in accordance with the commands from the thermal management system 14. However, if the rotary slide valve 16 is operating in a faulty manner, improper functional states may arise. These are detected by the thermal management system 14 and/or by the emergency operation management system 34, and are evaluated with regard to their influence on the behavior of the cooling system 11, whereupon corresponding measures adapted to the fault state are implemented.

[0061] A first improper functional state of the rotary slide valve 16 arises for example if the latter functions with movement stiffness. In this example, movement stiffness is detected through monitoring of the time taken for the rotary slide valve 16 to pass from one switching position into another switching position. If the time actually required exceeds a predefined value, the fault state movement stiffness is identified.

[0062] In this case, the actuation unit 28 triggers the implementation of a shaking-free routine, in which the rotary slide valve 16 is for example moved as rapidly and abruptly as possible between different predefined positions in both directions of rotation multiple times in order to release the rotary slide of the valve again. This shaking-free routine may possibly be performed multiple times, wherein the execution and evaluation are controlled for example by programs stored in the actuation unit 28.

[0063] If the shaking-free routine is successful, it is thereafter possible for the thermal management system 14 to operate the cooling system 11 normally again.

[0064] However, if the shaking-free routine is not successful, a second improper functional state jamming is identified, in which it is assumed that the rotary slide valve 16 can no longer be moved correctly, and in the extreme case, remains permanently in the present switching position.

[0065] A third possible improper functional state relates to the failure of a position sensor or of another part of the position detector 26. In this case, the rotary slide valve 16 can duly still be actuated and moved, but feedback regarding the present switching position is no longer available.

[0066] In this example, not only a position sensor but also further means for detecting at least the end positions of the rotary slide of the rotary slide valve 16 are provided in the position detector 26. For example, a power consumption of the control motor 30 that adjusts the rotary slide is monitored in order to conclude, from an increase in power consumption, that an end stop has been reached. Furthermore, the time for which the control motor 30 is in operation is predefined.

[0067] A fourth improper functional state arises if other faults in the electronics or in the actuator arise which no longer permit normal operation of the rotary slide valve 16. This may for example involve an electrical failure or an electronics fault, and likewise includes a failure of the control motor 30.

[0068] In this example, any detected improper functional state of the rotary slide valve 16 is stored in a fault memory. In this example, permanent faults (jamming, a failure of the position detector 26 or other faults in the electronics or in the actuator) is displayed in the cockpit by way of one or more warning lamps and/or warning indicators.

[0069] Depending on the improper functional state of the rotary slide valve that has occurred and depending on the present cooling system state, different measures are implemented. A possible decision diagram in the event of the occurrence of the described improper functional states is illustrated in FIG. 2.

[0070] Referring to FIG. 2, in the event of a movement stiffness being detected (first improper functional state), it is basically the case in this example that a shaking-free routine is implemented.

[0071] Depending on the cooling system state, this may be preceded by a waiting period. In this case, this is performed if the vehicle cooler is fully traversed by flow or is only partially traversed by flow in a throttled manner, because the provided cooling power is, in principle, adequate for all operating states of the internal combustion engine.

[0072] If the vehicle cooler is traversed by flow in a throttled manner, the coolant temperature detected by way of the sensors 38, 40 is incorporated. If said coolant temperature lies above a predefined threshold value temperature, the internal combustion engine 12 is placed into an emergency operation state.

[0073] In the emergency operation state, in the embodiment described here, the rotational speed and/or the torque of the internal combustion engine 12 are restricted to a predefined emergency operation value, which is dependent on the vehicle and at which the internal combustion engine 12 can be reliably operated even with a reduced coolant throughflow.

[0074] The initiation of the emergency operation state, and the monitoring and possibly the ending thereof, may in this case be performed both by the thermal management system 14 and by the emergency operation management system 34 of the vehicle, possibly in cooperation with the general monitoring system 36.

[0075] If movement stiffness of the rotary slide valve 16 is identified and the cooling system is in the first or second state, the internal combustion engine 12 is placed into the emergency operation state by the thermal management system 14 only if the threshold value temperature is exceeded. The thermal management system 14 re-enables the operation of the internal combustion engine 12 over the entire power range when the coolant threshold value temperature is undershot again, or if the shaking-free routine is successful.

[0076] If the rotary slide valve 16 is detected as exhibiting movement stiffness in a cooling system state in which the maximum cooling power is provided, it is also possible, initially without intervention by the thermal management system 14, to await a temperature-controlled reaction of the general monitoring system 36 before the emergency operation state is initiated.

[0077] However, if movement stiffness is identified when the cooling system 11 is in a state in which a flow through the vehicle cooler is prevented (third to fifth cooling system state), then in a manner dependent on the present coolant temperature, the emergency operation state is triggered in the event of an exceedance of the coolant threshold value temperature. Depending on the temperature, this is maintained for the duration of the shaking-free routine, because in these cooling system states, the cooling system 11 reacts sensitively to intense changes in power of the internal combustion engine 12, and during the shaking-free routine, it is not ensured that adequate cooling power can be provided.

[0078] If the shaking-free routine is successful, then in this example the thermal management system 14 transmits an enable signal to the controller of the internal combustion engine, which re-enables all operating states of the internal combustion engine 12.

[0079] However, if the shaking-free routine is not successful, the state jamming (second improper functional state) is identified.

[0080] If the cooling system as in the first state in which the maximum cooling power is available, that is to say the rotary slide valve 16 is jammed in the position in which the inlet 18 that is connected to the cooler return line 22 is fully open, then in this example, the coolant temperature is monitored by the thermal management system 14 and/or by the general monitoring system 36, and the emergency operation state is initiated only in the event of an exceedance of the coolant temperature threshold. The thermal management system 14 withdraws the emergency operation state again in the event of the coolant temperature threshold being undershot again.

[0081] If the vehicle cooler is partially throttled (second cooling system state), the coolant temperature is monitored by the thermal management system 14, and the emergency operation state is temporarily initiated in the event of an exceedance of the coolant threshold value temperature.

[0082] However, if jamming is detected when the cooling system is in a state in which the flow through the vehicle cooler is prevented (third to fifth cooling system state), the fault is handled by the emergency operation management system 34, which in this example places the internal combustion engine 12 permanently into the emergency operation state regardless of the coolant temperature. The emergency operation state may be maintained permanently until the fault is withdrawn, or until a restart of the vehicle.

[0083] It is possible, after a restart of the vehicle, for the function of the rotary slide valve 16 to be checked again, and for the emergency operation state to be withdrawn again in the event of proper functioning. Otherwise, the operating state of the internal combustion engine 12 is re-enabled only after the fault has been eliminated in a workshop, and the fault memory has been reset.

[0084] In the event of a failure of the position detector 26, in particular in the event of failure of a position sensor which provides feedback regarding the present switching position of the rotary slide valve 16 (third improper functional state), the thermal management system 14 monitors the present coolant temperature and initiates the emergency operation state in the event of an exceedance of the threshold value temperature. If multiple improper functional states arise simultaneously, a failure of the position detector 26 is assigned the highest priority.

[0085] In this case, the emergency operation state may be handled either by the thermal management system 14 or by the emergency operation management system 34.

[0086] Furthermore, the rotary slide valve 16 is moved into a switching position in which the greatest possible cooling power is available. This is achieved for example by virtue of the rotary slide valve 16 being moved in the presently set rotational direction as far as a stop, wherein the rotary slide valve 16 is self-evidently designed such that the stop coincides with a switching position which yields adequate cooling power (cooler return line 22 fully or partially open). It may either be assumed in a time-controlled manner that the stop has been reached, or it may be detected that the stop has been reached through monitoring of the power consumption of the control motor 30.

[0087] After the predefined position has been reached, the rotary slide valve 16 is deactivated. If the rotary slide valve 16 can be moved into a switching position in which the maximum cooling power, or an only slightly reduced cooling power, is available, the initiation of the emergency operation state may be made dependent on the exceedance of the threshold value temperature.

[0088] If another fault arises in the electronics or in the actuator of the rotary slide valve 16 (fourth improper functional state), then in this example, with maximum cooling power (first cooling system state), it is merely the case that a fault is output, and possibly a warning lamp and/or a warning indicator is activated, but otherwise the thermal management system 14 and/or the general monitoring system 36 performs the monitoring of the coolant temperature.

[0089] In the case of reduced cooling power (in the second cooling system state, in which the cooler return line 22 is only partially open), the fault is handled by the thermal management system 14. Here, said thermal management system initiates the emergency operation state in a temperature-dependent manner. The emergency operation state may be maintained permanently until the withdrawal of the fault, or until a restart of the vehicle.

[0090] In all other cooling system states, in which the cooler return line 22 is closed, in this example, the emergency operation state is initiated and the control of the emergency operation state is performed by the emergency operation management system 34. The driver is notified of this state in this case by way of a further warning lamp and a prompt to have the fault repaired.

[0091] The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.