EP1529936B1 - Cooling system for an internal combustion engine of a vehicle with a disconnectable water pump - Google Patents

Description

The present invention relates to a cooling system for an internal combustion engine of a vehicle according to the features of patent claim 1.

In conventional vehicles, the water pump is mechanically driven by a V-belt from the engine. The water pump thus runs continuously during engine operation. In some operating conditions of the engine, however, it is not necessary or desirable for the water pump to pump coolant through the cooling circuit. In particular, when the engine is cold, could be dispensed with the operation of the water pump.

Already known are cooling systems with water pumps, which are "separated" by an internal throttling in the cooling circuit, but which are permanently driven by a belt drive. Electric water pumps are also known. However, electric water pumps are relatively expensive, require a lot of space and fall out in the event of a power failure. In constantly running water pumps is generally considered problematic that unnecessary energy is consumed.

From the DE 100 23 508 A1 a cooling system with a shut-off water pump is known, wherein monitored during operation of the internal combustion engine, the load condition of the engine and the operating temperature of the internal combustion engine.

A cooling system with a shut-off water pump is also from the DE 40 32 701 A1 known.

From the DE 30 24 209 A is a liquid cooling for internal combustion engines is known in which an electronic control unit regulates a circulating pump. The setpoint for this control can be adjusted according to various external parameters and operating parameters of the motor.

The EP 0 323 210 A2 describes a system for controlling the cooling of an engine compartment of a motor vehicle. This should not only protect the engine from overheating, but also a turbocharger located in the engine compartment.

The EP 1 046 798 A2 claims a cooling system for an internal combustion engine with an emergency detection device by which a coolant pump, which is driven by an electric motor in normal operation, is mechanically connected to a rotating part of the internal combustion engine in case of failure of the electric motor.

The object of the invention is to provide a cooling system for an internal combustion engine with a shut-off water pump, which has an improved with regard to the energy consumption of the internal combustion engine, the life of the engine and reliability shutdown logic.

• mindestens ein thermischer Zustandsparameter,
• der Lastzustand des Verbrennungsmotors,
• ein "Betriebszustand" der Fahrgastraumheizung des Fahrzeugs,
• ein "Zeitparameter" und
• ein Fehlerspeicher, in dem für den Kühlkreislauf relevante Fehlerzustände speicherbar sind.

A cooling system according to the invention comprises a water pump, which is provided to pump coolant through a cooling circuit of the internal combustion engine, wherein a control device is provided, which shuts off the water pump during operation of the internal combustion engine, if this is considered "permissible". For the assessment of whether switching off the water pump is considered permissible with the internal combustion engine running are monitored:

• at least one thermal condition parameter,
• the load condition of the internal combustion engine,
• an "operating condition" of the passenger compartment heating of the vehicle,
• a "time parameter" and
• an error memory in which relevant for the cooling circuit error states can be stored.

During operation of the internal combustion engine, the water pump is only switched off when the at least one thermal condition parameter and the load condition and the operating state of the passenger compartment heating and the time parameters make the deactivation of the water pump permissible and if the fault memory is faultless. For checking whether the thermal state parameter and the load state and the operating state of the passenger compartment heating and the time parameters make it possible to switch off the water pump, a "valuation logic" is specified for each of these "queries", which will be explained in more detail later.

The water pump can be electrically driven. Preferably, however, a mechanically driven by the engine water pump is provided. The water pump can be mechanically driven by the internal combustion engine via a friction gear.

According to a development of the invention, the friction wheel drive is mechanically biased. By acting on the Reibradantrieb actuator, the water pump can be switched off. For safety reasons, it can be provided that whenever the actuator is "de-energized", the water pump is switched on. For this purpose, a mechanical spring may be provided, which in the event of a power failure, i. if the actuator is de-energized, the friction wheel drive "closes". In this way, a "fail-safe function" can be displayed in a simple manner, which ensures the drive of the water pump in case of failure.

It has already been mentioned that at least one thermal condition parameter is monitored for switching off the water pump. Alternatively, two or more thermal state parameters may be monitored.

According to a development of the invention, it is provided that a thermal state parameter is the engine temperature and that it is regarded as a necessary condition for the permissibility of switching off the water pump that the engine temperature is less than a predetermined value.

For example, the instantaneous coolant temperature can be queried at each engine start, which corresponds approximately to the engine temperature. Of course, the engine temperature can also be determined via separate sensors or by maps. If the engine temperature or the coolant temperature at engine start smaller than a predetermined value, so the water pump should be turned off, as in this case, a cooling of the engine is not required and energy can be saved by switching off the water pump. At higher engine or coolant temperature, however, there is no longer any potential savings, so that when a predetermined value for the engine or coolant temperature is exceeded, the water pump should remain switched on.

As a further thermal condition parameter, the temperature of the intake air from the engine can be monitored. As a further necessary condition for the permissibility of switching off the water pump can be considered that the temperature of the intake air from the engine air is less than a predetermined value. At an intake air temperature or at an ambient air temperature which is greater than a predetermined value, the water pump can be switched on when the engine is started, if there are no more potential savings. If, however, the temperature at engine start is below the specified value, then the water pump should remain switched off.

The engine temperature and the intake air temperature can be summarized in the control logic by an AND operation to a "start operation criterion" or - generally speaking - to a "thermal condition criterion". The thermal condition criterion only indicates a switch-off of the water pump when the engine temperature or the coolant temperature and at the same time the intake air temperature are lower than the respective predetermined temperature values. In other words, as a necessary condition for the permissibility of turning off the water pump, it is considered that the engine coolant temperature is smaller than the predetermined value and, in addition, that the intake air temperature is smaller than the predetermined value.

For the evaluation of the permissibility of switching off the water pump is monitored as a further necessary condition of the operating condition of the passenger compartment heating. When assessing whether or not the shutdown of the water pump is allowed during the starting phase of the engine, the heating power requested for the passenger compartment is important. For a reliable defrosting of the windscreen or to ensure adequate heating comfort, it may be necessary that the water pump is switched on already in the start phase of the engine. For example, it may be provided that in the starting phase of the engine, the water pump may only be switched off when the requested by the driver for the passenger compartment heating power is less than a predetermined value. The "operating state" of the passenger compartment heating can be monitored, for example, based on the passenger compartment set temperature set by the driver. When Another necessary criterion for the permissibility of switching off the water pump in the starting phase of the engine can therefore be considered that the set target temperature is less than a predetermined value or that the heating power, which depends on the set target temperature and the set air flow, smaller than a is predetermined value.

As already mentioned, the load state of the internal combustion engine is monitored for the assessment of the permissibility of switching off the water pump in the starting phase of the internal combustion engine. The load state of the internal combustion engine can be monitored on the basis of a load state parameter or on the basis of a plurality of load state parameters. It can be provided that, as a necessary prerequisite for the permissibility of switching off the water pump in the starting phase of the internal combustion engine, it is considered that at least one load state parameter is smaller than a predetermined value. As the load state representing signals, for example, the vehicle speed and / or the rotational speed of the internal combustion engine and / or the internal combustion engine supplied amount of fuel or the internal combustion engine supplied fuel mass flow can be considered.

As a necessary condition for the permissibility of switching off the water pump during the warm-up phase of the internal combustion engine can be provided that the load condition of the engine does not exceed a predetermined load condition. The vehicle speed, the engine speed and the fuel mass flow can be linked to each other, for example, by an OR operation. If the vehicle speed is less than a predetermined value or the engine speed is less than a predetermined value or the fuel mass flow supplied to the engine is less than a predetermined value, it is considered to be a necessary load state criterion for turning off the water pump.

As a further necessary criterion for the permissibility of the shutdown of the water pump, a time parameter is monitored. For this purpose, a "time counter" can be provided, which measures the duration of the operation of the internal combustion engine during which the water pump is switched off. As more necessary Prerequisite for the permissibility of switching off the water pump or for the permissibility of the shutdown of the water pump can be considered that the time measured by the timer is less than a predetermined value. It can be provided that the water pump should remain switched off for a predetermined period of time after a cold start of the engine. A necessary condition for switching off the water pump is therefore that the measured time duration is less than a predetermined period of time.

To avoid problems with short-haul trips, i. can be provided for repeated starts and stops of the internal combustion engine, it can be provided that the time counter at a shutdown and a subsequent restart of the internal combustion engine only to a starting value, e.g. Reset "zero seconds" if the water pump was switched on before the last shutdown of the internal combustion engine. Consequently, at each engine start, the "time routine" runs so that the timer counts on various repeat starts, namely until the water pump is switched on and the engine has been running for several seconds at idle speed or a higher speed. In a subsequent restart, the time counter is then reset.

Modern vehicles have onboard diagnostic electronics (OBD). In the onboard diagnostic electronics, various fault or fault states of the vehicle or individual vehicle components are stored. Of the monitored in a vehicle "error conditions" individual states are relevant for the cooling circuit, other error conditions are the function of the cooling circuit irrelevant. Switching off the water pump is only considered admissible if no relevant error conditions for the cooling circuit are stored in the fault memory. If, for example, it is detected that a sensor for sensing the engine or cooling water temperature is defective, this is stored in the fault memory. For safety reasons, the "shut-off logic" for the water pump is then bridged, with the result that the water pump runs along from the engine start, ie that it is not switched off. It makes sense to take into account all the parameters that can have a negative influence on the function of the engine when the water pump is switched off.

In summary, it can be stated that the water pump is switched off only when all the conditions deemed necessary for shutdown are present, i. if the at least one thermal condition parameter, the load condition of the internal combustion engine, the operating condition of the passenger compartment heater, the time parameter and the fault memory "indicate" that switching off the water pump is permissible. If only one of these "test criteria" is not correct, the water pump remains or is switched on for safety reasons.

In the following the invention will be explained in connection with the drawing. The only FIG. 1 shows an embodiment of a circuit logic of a cooling system according to the invention.

FIG. 1 schematically shows a logic diagram for switching off a water pump 1, which is driven by an internal combustion engine 2 via a friction gear 3. Furthermore, a control unit 4 is provided, which drives the Reibradgetriebene 3. The friction gear 3 is designed so that in the de-energized state of the control unit 4, the internal combustion engine 2 via the friction gear 3, the water pump 1 drives. By appropriate control of the friction gear 3 by the control unit 4, the drive of the water pump 1 can be switched off.

• ein Funktionsblock 5, in dem thermische Zustandsparameter überwacht werden,
• ein Funktionsblock 5, in dem der Betriebszustand der Fahrgastraumheizung überwacht wird,
• ein Funktionsblock 7, durch den der Lastzustand des Verbrennungsmotors 2 überwacht wird,
• ein Funktionsblock 8, durch den ein Zeitkriterium überwacht wird und
• ein Funktionsblock 9, der im Wesentlichen dem Speicherinhalt eines Fehlerspeichers entspricht.

A shutdown of the drive of the water pump 1 takes place only if certain criteria are met cumulatively. To assess whether turning off the water pump 1 is considered permissible or not, various function blocks are integrated into an electronic control unit, namely

• a functional block 5 in which thermal condition parameters are monitored,
• a functional block 5, in which the operating state of the passenger compartment heating is monitored,
• a function block 7, by which the load state of the internal combustion engine 2 is monitored,
• a function block 8, by which a time criterion is monitored and
• a functional block 9, which essentially corresponds to the memory content of a fault memory.

In function block 5, the engine temperature T _MOT and the temperature of the intake air T _A sucked by the internal combustion engine are monitored. A necessary condition for the permissibility of switching off the water pump 1 is that the engine temperature T _{MOT is} less than 80 ° C and that the intake air temperature T _{A is} less than 30 ° C. Schematically speaking, the engine temperature and the intake air temperature T _{A form} inputs 10, 11 of an AND operation 12.

In function block 6, the operating state of the passenger compartment heater is checked. For example, it may be provided that switching off the water pump is only considered permissible if the requested for the passenger compartment heating power is less than a predetermined value or if the heater is not turned on, which is schematically indicated here by a non-member 13 , which forms another input of the AND gate 12.

In the function block 7, the vehicle speed, the engine speed and the instantaneous fuel consumption of the internal combustion engine are monitored. If the vehicle speed is less than 80 km per hour, or if the engine speed is less than 4000 rpm or the fuel consumption is less than a predetermined value, an OR gate 14 provides a logical "1" which is another input 15 of the AND Gate 12 is supplied.

In function block 8, the time duration during which the water pump 1 is switched off during operation of the internal combustion engine is measured by means of a time counter. If the internal combustion engine is switched off after a run in which the water pump was switched on, the time counter is reset to zero. When the internal combustion engine starts, the timer begins to run. During the first 800 seconds after the start of the internal combustion engine, the function block 8 supplies a logical "1" to an input 16 of the AND gate 12, which allows the water pump to be shut off. If the predetermined time duration of, for example, 800 seconds is exceeded, the function block 8 delivers a logic zero, so that the water pump is automatically switched on. For short trips with several consecutive repeat starts the timer is not reset every time, but continues to count until the water pump was once switched on (X = 0), which is shown here schematically by a detection line 17.

In function block 9 is monitored whether at any time a relevant for the cooling system fault condition has been present or exists. Only if no relevant for the cooling system fault condition has been present or present, the function block 9 provides a logic "1" to the AND gate 12. The "no-relevant-error query" is indicated here schematically by a negation element 18.

Claims (13)

1. Cooling system for an internal combustion engine (2) of a vehicle having a water pump (1) for pumping coolant through a cooling circuit of the internal combustion engine (2), wherein the water pump (1) can be switched off by a control device (4) during operation of the internal combustion engine (2), wherein during operation of the internal combustion engine

   - at least one thermal state parameter (5) and

   - an operating state of the cabin heating system (6) and

   - the load state (7) of the internal combustion engine (2) and

   - a time parameter (8) and

   - an error memory (9), in which error states relevant to the cooling circuit can be stored, are monitored

   wherein the water pump (1) is switched off only when

   - the at least one thermal state parameter (5) and

   - the operating state (6) of the cabin heating system and

   - the load state (7) and

   - the time parameter (8) indicate that shutting off the water pump (1) is admissible and

   - the error memory is error-free,

   wherein the admissibility is checked in each case according to an evaluation logic which is preset for the individual criteria.
2. Cooling system as claimed in claim 1, wherein the water pump (1) is driven by the internal combustion engine (2) via a friction drive (3).
3. Cooling system as claimed in claim 2, wherein the friction drive (3) is mechanically pretensioned and the water pump (1) can be switched off by an actuator acting on the friction drive (3), wherein the water pump (1) is switched on whenever the actuator is non-energised.
4. Cooling system as claimed in any one of claims 1 to 3, wherein a thermal state parameter is the engine temperature (T_MOT), and the engine temperature (T_MOT) being lower than a preset value is regarded as a necessary prerequisite for the admissibility of switching off the water pump (1).
5. Cooling system as claimed in any one of claims 1 to 4, wherein a thermal state parameter is the temperature of the air (T_A) taken in by the internal combustion engine (2), and that the temperature (T_A) of the air taken in by the internal combustion engine (2) being lower than a preset value is regarded as a necessary prerequisite for the admissibility of switching off the water pump (1).
6. Cooling system as claimed in any one of claims 1 to 5, wherein the load state of the internal combustion engine (2) is monitored with the aid of at least one load state parameter, and the at least one load state parameter being lower than a preset value is regarded as a necessary prerequisite for the admissibility of switching off the water pump (1).
7. Cooling system as claimed in any one of claims 1 to 6, wherein the load state of the internal combustion engine (2) is monitored with the aid of a plurality of load state parameters, and that at least one of the load state parameters being lower than a preset value is regarded as a necessary prerequisite for the admissibility of switching off the water pump (1).
8. Cooling system as claimed in claim 6 or 7, wherein a load state parameter is the vehicle speed (v).
9. Cooling system as claimed in any one of claims 6 to 8, wherein a load state parameter is the engine speed of the internal combustion engine (n) of the internal combustion engine (2) [sic].
10. Cooling system as claimed in any one of claims 6 to 9, wherein a load state parameter is the current fuel consumption of the internal combustion engine (2).
11. Cooling system as claimed in any one of claims 1 to 10, wherein the operating state of the cabin heating system is monitored with the aid of the heating output requested for the cabin.
12. Cooling system as claimed in any one of claims 1 to 11, wherein a time counter is provided which, during operation of the internal combustion engine (2), measures the time duration during which the water pump (1) is switched off, wherein the time measured by the time counter being less than a preset value is regarded as a necessary prerequisite for the admissibility of switching off the water pump (1).
13. Cooling system as claimed in claim 12, wherein in the case where the internal combustion engine (2) is switched off and subsequently restarted, the time counter is reset to a start value and begins to count again only if the water pump (1) had been switched on before the internal combustion engine (2) was switched off.

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