EP1544433B1 - Method for monitoring the cooling circuit of a motor vehicle - Google Patents

Abstract

The device has a memory in which abnormality conditions are stored, a pressure sensor (200), and a gas bubble detection sensor (300), where each condition has a specific combination of measurement results of pressure, temperature and rate of bubbles. A signal processing unit (400) compares the sensors` measurements with pre-recorded abnormality conditions to identify an appearance of a condition in a cooling system (50). An independent claim is also included for a process for monitoring a cooling system of a heat engine of a motor vehicle.

Description

The invention relates to cooling circuits and in particular the monitoring of the latter as to the appearance of any operating anomalies.

The importance of the cooling circuit in the operation of a motor vehicle engine is well known.

In the absence of cooling, the engine undergoes a temperature rise damaging to its essential organs that may require the standard change of the engine.

In addition to the usual temperature sensors coupled with visual warning devices on the dashboard, few solutions have been proposed for effective monitoring of the proper operation of the cooling system. For example, the document FR 2 673 244 A1 describes a device for monitoring the proper functioning of the cooling circuit of a heat engine comprising a temperature sensor and a pressure sensor.

The invention is part of such an approach, aimed at providing the driver or the mechanic more effective monitoring of the cooling circuit associated with the engine of a motor vehicle.

This object is achieved according to the invention by means of a device for monitoring the proper functioning of the cooling circuit of a motor vehicle engine, comprising a temperature sensor, a pressure sensor and a bubble presence sensor, a memory in which are stored anomaly scenarios each consisting of a specific combination of measurement results among the pressure, the temperature and the bubble ratio, and further means able to compare the measurements provided by the sensors with those of the scenarios of pre-recorded anomalies to identify the actual occurrence of one of these scenarios in the cooling circuit.

1. a) l'étape consistant à mesurer une pression dans le circuit de refroidissement et de capter une présence élevée de bulles dans le circuit de refroidissement,
2. b) l'étape consistant à comparer ces mesures avec celles de scénarios d'anomalies prédéfinis, chacun des scénarios en une combinaison spécifique de résultats de mesures parmi la température, la pression et la présence élevée de bulles,
3. c) l'étape consistant à identifier l'apparition effective d'un de ces scénarios d'anomalie dans le circuit de refroidissement en cas de similitude entre la combinaison de résultats des mesures effectives et la combinaison prédéfinie de résultats de mesures de ce scénario.

It is also proposed according to the invention a method for monitoring a motor vehicle heat engine cooling circuit comprising measuring the coolant temperature, characterized in that it comprises:

1. a) the step of measuring a pressure in the cooling circuit and sensing a high presence of bubbles in the cooling circuit,
2. b) the step of comparing these measurements with those of predefined anomaly scenarios, each of the scenarios in a specific combination of measurement results among temperature, pressure and the high presence of bubbles,
3. c) the step of identifying the actual occurrence of one of these abnormality scenarios in the cooling circuit in the event of a similarity between the combination of actual measurement results and the predefined combination of measurement results from that scenario.

• la figure 1 est un schéma de fonctionnement d'un dispositif de surveillance de circuit de refroidissement conforme à l'invention ;
• la figure 2 est un schéma de fonctionnement plus détaillé représentatif de ce même dispositif.

Other characteristics, objects and advantages of the invention will appear on reading the detailed description which follows, made with reference to the appended figures in which:

• the figure 1 is a circuit diagram of a cooling circuit monitoring device according to the invention;
• the figure 2 is a more detailed operating diagram representative of this same device.

The present device makes it possible to diagnose a cooling circuit 50 of a heat engine.

The device here comprises the following elements. It includes in particular three sensors 100, 200, 300 sensitive to different parameters. A processing unit 400 receives signals from these sensors 100, 200, 300, in which a diagnostic algorithm 500 is embedded. The device also includes a communication interface 600 with a client interface system (for example a visual interface under the shape of a dashboard).

One of the sensors is a temperature sensor 100, which may be, without excluding other technologies, a Negative Temperature Coefficient (NTC) resistance. A second sensor 200 senses the pressure in the cooling circuit. A third sensor is present for the detecting gas bubbles, preferably capable of providing a measurement of a bubble rate in the liquid.

The signal processing unit 400 is intended to verify that the cooling system 50 is functioning properly.

If it detects a malfunction, the cross-checking of the information from the three sensors 100, 200, 300 enables it to give indications of the origin of the malfunction that has occurred.

The table below presents a summary of the different cases of drift of measurement results that may appear in the cooling circuit.

Note by T Ok the case where the temperature 100 read by the temperature sensor 100 is normal.

Note by T ↗ the case where the temperature 100 read by the temperature sensor 100 is too high.

Note by T ↘ the case where the temperature 100 read by the temperature sensor is too low.

Note by P Ok the case where the pressure 200 read by the pressure sensor 200 is normal.

Note by P ↗ the case where the pressure 200 read by the pressure sensor 200 is too high.

Note by P ↘ the case where the pressure 200 read by the pressure sensor is too low.

Note by TB = 0 the case where the bubble level in the coolant is normal.

Note TB ↗ the case where the bubble ratio in the coolant 50 is too important.

The following table summarizes a series of pre-recorded anomaly scenarios in a memory of the processing unit 400. Each of the scenarios consists of a combination of three measurement states (temperature, pressure, bubble rate) and a indication of anomaly associated with the combination in the presence. 1 T Ok P OK TB = 0 The cooling circuit is working normally 2 T Ok P OK TB ↗ The circuit has an insufficient liquid level 3 T Ok P ↗ TB = 0 This circuit has a safety valve state in an abnormally blocked situation 4 T Ok P ↗ TB ↗ Engine has faulty cylinder head gasket 5 T Ok P ↘ TB = 0 The circuit shows a liquid leak 6 T Ok P ↘ TB ↗ The circuit has an expansion tank cap that is abnormally open 7 T ↗ P OK TB = 0 The circuit has a calorstat which is abnormally blocked closed 8 T ↗ P OK TB ↗ The circuit has a liquid level which is insufficient and / or has a calorstat which is abnormally blocked closed 9 T ↗ P ↗ TB = 0 The circuit has a safety valve which is abnormally blocked and also has a calorstat which is abnormally blocked closed 10 T ↗ P ↗ TB ↗ The circuit has a calorstat which is abnormally blocked closed. The circuit has a cylinder head gasket that is defective 11 T ↗ P ↘ TB = 0 The circuit has a calorstat which is blocked closed and the circuit also has a liquid leak 12 T ↗ P ↘ TB ↗ The circuit has an expansion tank cap that is abnormally open and the circuit has a heat sink that is abnormally blocked closed 13 T ↘ P OK TB = 0 The circuit has a calorstat that is abnormally blocked open 14 T ↘ P OK TB ↗ The circuit has a heat sink that is abnormally blocked open and the circuit also has an insufficient liquid level 15 T ↘ P ↗ TB = 0 The circuit has a heat sink that is abnormally blocked open and the circuit also has a safety valve that is abnormally blocked 16 T ↘ P ↗ TB ↗ The circuit has a heat sink that is abnormally blocked open and the circuit also has a cylinder head gasket that is defective 17 T↘ P ↘ TB = 0 The circuit has a heat sink that is abnormally blocked open and the circuit also has a liquid leak 18 T ↘ P ↘ TB ↗ The circuit has a heat sink that is abnormally blocked open and the circuit also has an expansion tank cap that is abnormally open

The table above is only a summary of the anomalies that may arise.

The processing unit 400 also analyzes here the behavior of the input variables (pressure, temperature and bubble rate) over time and continuously. This allows him to refine the diagnosis.

For example, in the case of anomalies due to a coolant level too low, it turns out, initially, the appearance of gas bubbles in the circuit and then an increase in temperature if the Bubble rate really gets too big (line 8 of the chart).

In this case the algorithm will identify the fact that the calorstat is working properly and that the overheating is rather due to the lack of liquid.

If now we are in a case of abnormality where the calorstat is abnormally blocked in closing, the algorithm sees first the increase of the temperature then the appearance of bubbles because the engine is too hot (line 8 of the table ).

He then recognizes that the level is correct but that it is rather the calorstat which is incriminated.

Thus, by comparing the actual history of the combinations of measurements with pre-stored histories, the processing unit 400 succeeds in distinguishing between the two cases of anomalies which could have caused the final situation, that is to say temperature too high and bubble rate high (line 8 of the table).

Thus, by comparing the actual history of the combinations of measurements with pre-stored histories, the processing unit 400 succeeds in distinguishing between the two cases of anomalies which could have caused the final situation, that is to say temperature too high and bubble rate high (line 8 of the table).

The information processing unit 400 preferably uses a microcontroller to provide this processing. However, the bubble sensor 300 already uses a microcontroller 400 as will be described hereinafter. It is advantageous to use this same microcontroller to perform both the bubble rate identification function too high and the diagnosis of the cooling system.

The client interface 400 can be of any type. However, it should be noted that the system that controls the operation of a heat engine needs to know the temperature of the coolant. It is advantageous, in this aspect, to use an interface 600 capable of returning both the diagnosis of the cooling circuit and the temperature of the liquid, or even, if necessary, the pressure. The interface 600 can be CAN, LIN, Asynchronous and without any limitation of technology.

The bubble presence sensor 300, which is advantageously recommended here, is a bubble detection bubble level sensor of the type comprising a light emitter 310 and a light receiver 320. It advantageously has processing means implementing an algorithm. 330 which calculates a variation of the light intensity between two successive measurements of the receiver. These means for measuring variations are in particular means for comparing a variation of the luminous intensity between two measurements with a predefined threshold, the crossing of the threshold initiating the incrementation of a counter which itself triggers an alert when another pre-defined threshold value is exceeded this time by this counter.

Such a too high bubble rate detector is exposed in the application FR 02 14 805 on behalf of the applicant.

Claims (24)

1. Device for monitoring the proper operation of the cooling circuit (50) of a motor vehicle internal combustion engine, comprising a temperature sensor (100) and a pressure sensor (200), characterized in that it also comprises a sensor (300) for detecting the presence of bubbles, a memory in which there are stored anomaly scenarios each consisting of a specific combination of results of measurements from among pressure, temperature and the presence of bubbles, and additionally means (400, 500) adapted to compare the measurements provided by the sensors with those of the prerecorded anomaly scenarios so as to identify the actual occurrence of one of these scenarios in the cooling circuit (50).
2. Monitoring device according to Claim 1, characterized in that each scenario includes data indicating the nature of an anomaly associated with this scenario.
3. Monitoring device according to either one of the preceding claims, characterized in that the device (100, 200, 300, 400, 500) comprises a prerecorded scenario which consists of a non-significant temperature, a non-significant pressure and an excessively high bubble level, this scenario including the indication of an inadequate fluid level.
4. Monitoring device according to either one of the preceding claims, characterized in that the device (100, 200, 300, 400, 500) includes a prerecorded scenario which consists of a non-significant temperature, an excessively high pressure and a non-significant bubble level, this scenario including the indication of a safety valve jam.
5. Monitoring device according to any one of the preceding claims, characterized in that the device (100, 200, 300, 400, 500) includes a prerecorded scenario which consists of a non-significant temperature, an excessively high pressure and an excessively high bubble level, this scenario including the indication of a cylinder head gasket malfunction.
6. Monitoring device according to any one of the preceding claims, characterized in that the device (100, 200, 300, 400, 500) includes a prerecorded scenario which consists of a non-significant temperature, an excessively low pressure and a non-significant bubble level, and this scenario includes the indication of a fluid leak.
7. Monitoring device according to any one of the preceding claims, characterized in that the device (100, 200, 300, 400, 500, 600) includes the prerecorded scenario which consists of a non-significant temperature, an excessively low pressure and an excessively high bubble level, and this scenario includes the indication of an abnormal situation of expansion tank cap opening.
8. Monitoring device according to any one of the preceding claims, characterized in that the device (100, 200, 300, 400, 500, 600) includes a prerecorded scenario which consists of an excessively high temperature, a non-significant pressure and a non-significant bubble level, and this scenario includes an indication of a thermostat being jammed shut.
9. Monitoring device according to any one of the preceding claims, characterized in that the device (100, 200, 300, 400, 500, 600) includes a prerecorded scenario which consists of an excessively high temperature, a non-significant pressure and an excessively high bubble level, and this scenario includes an indication of very inadequate fluid level and/or of the thermostat being in a jammed-shut situation.
10. Monitoring device according to any one of the preceding claims, characterized in that the device (100, 200, 300, 400, 500, 600) includes a prerecorded scenario which consists of an excessively high temperature, an excessively high pressure and a non-significant bubble level, and this scenario includes the indication of an abnormal safety valve jam situation and of an abnormal jammed-shut thermostat situation.
11. Monitoring device according to any one of the preceding claims, characterized in that the device (100, 200, 300, 400, 500, 600) includes a prerecorded scenario which consists of an excessively high temperature, an excessively high pressure and an excessively high bubble level, and this scenario includes the indication of an abnormally jammed-shut thermostat and of a defective cylinder head gasket.
12. Monitoring device according to any one of the preceding claims, characterized in that the device (100, 200, 300, 400, 500, 600) includes a prerecorded scenario which consists of an excessively high temperature, an excessively low pressure and a non-significant bubble level, and this scenario includes the indication of an abnormally jammed-shut thermostat and of a fluid leak.
13. Monitoring device according to any one of the preceding claims, characterized in that the device (100, 200, 300, 400, 500, 600) includes a prerecorded scenario which consists of an excessively high temperature, an excessively low pressure and an excessively high bubble level, and this scenario includes an indication of an abnormal opening of the expansion tank cap and of an abnormally jammed-shut thermostat.
14. Monitoring device according to any one of the preceding claims, characterized in that the device (100, 200, 300, 400, 500, 600) includes a prerecorded scenario which consists of an excessively low temperature, a non-significant pressure and a non-significant bubble level, and this scenario includes an indication of an abnormally jammed-open thermostat.
15. Monitoring device according to any one of the preceding claims, characterized in that the device (100, 200, 300, 400, 500, 600) includes a prerecorded scenario which consists of an excessively low temperature, a non-significant pressure and an excessively high bubble level, and this scenario includes the indication of an abnormally jammed-open thermostat and of an inadequate fluid level.
16. Monitoring device according to any one of the preceding claims, characterized in that the device (100, 200, 300, 400, 500, 600) includes a prerecorded scenario which consists of an excessively low temperature, an excessively high pressure and a non-significant bubble level, and this scenario includes the indication of an abnormally jammed-open thermostat and of a jammed safety valve.
17. Monitoring device according to any one of the preceding claims, characterized in that the device (100, 200, 300, 400, 500, 600) includes a prerecorded scenario which consists of an excessively low temperature, an excessively high pressure and an excessively high bubble level, and this scenario includes the indication of an abnormally jammed-open thermostat and of a defective cylinder head gasket.
18. Monitoring device according to any one of the preceding claims, characterized in that the device (100, 200, 300, 400, 500, 600) includes a prerecorded scenario which consists of an excessively low temperature, an excessively low pressure and a non-significant bubble level, and this scenario includes the indication of an abnormally jammed-open thermostat and of a fluid leak.
19. Monitoring device according to any one of the preceding claims, characterized in that the device (100, 200, 300, 400, 500, 600) includes a prerecorded scenario which consists of an excessively low temperature, an excessively low pressure and an excessively high bubble level, and this scenario includes the indication of an abnormally jammed-open thermostat and of an abnormally open expansion tank cap.
20. Monitoring device according to any one of the preceding claims, characterized in that the device (100, 200, 300, 400, 500, 600) includes at least one prerecorded anomaly scenario which consists of the occurrence of successive combinations of measurements from among temperature, pressure and the elevated presence of bubbles, the device additionally including means for taking into account a history of combinations of actual measurements provided by the three sensors, these means being adapted to compare this history with the said at least one scenario of successive combinations so as to identify the actual occurrence of this scenario of successive combinations in the cooling circuit.
21. Monitoring device according to the preceding claim, characterized in that it includes the prerecorded scenario consisting of the changeover between the following two combinations:

    • the occurrence of an excessively high bubble level and a non-significant temperature, then

    • an excessively high bubble level and an excessively high temperature,

    this scenario including an indication of an excessively low cooling fluid level.
22. Monitoring device according to any one of the preceding claims, characterized in that it includes the prerecorded scenario consisting of the changeover between the following two combinations:

    • excessively high temperature and non-significant bubble level, then

    • excessively high temperature and excessively high bubble level,

    this scenario including an indication whereby a thermostat of the circuit has a malfunction.
23. Monitoring device according to any one of the preceding claims, characterized in that the means for comparing measurement results with the combinations of prerecorded scenarios are formed by a microcontroller (400), this microcontroller (400) also carrying out a preprocessing of the input and output signals from a light source (310) and light detector (320) which form the bubble level sensor (300).
24. Method of monitoring the cooling circuit of a motor vehicle internal combustion engine, comprising the action of measuring the cooling fluid temperature and the pressure in the cooling circuit (50), characterized in that it comprises:

    a) the step consisting in additionally providing a measurement of the presence of bubbles in the cooling circuit (50),

    b) the step consisting in comparing these measurements with those of predefined anomaly scenarios, each of the scenarios consisting of a specific combination of results of measurements from among temperature, pressure and the presence of bubbles,

    c) the step consisting in identifying the actual occurrence of one of these anomaly scenarios in the cooling circuit in the event of similarity between the combination of actual measurement results and the predefined combination of measurement results of this scenario.

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