DE102019206968B3 - Method for recognizing a loss of coolant based on increased knocking - Google Patents

Abstract

Disclosed is a method for controlling a display unit 114 of an internal combustion engine 102, comprising the steps: Detecting knocking, i.e. ignitions that were not initiated by the spark plug 115, and generating knock signals, Checking whether the knocking signals are caused by others on the internal combustion engine 102 existing conditions can be explained, and output of a warning signal indicating a loss of coolant to the display unit 114 if the check reveals that only cylinders 108 that are too hot are the possible cause of the knocking signals.

Description

Technical area

The disclosure relates to a method with which a cooling water level in an internal combustion engine can be determined indirectly. Almost all motor vehicles currently have liquid coolant circuits. If there is a leak, the coolant can escape unnoticed. Usually only one temperature sensor is provided for monitoring the cooling circuit. This is usually not suitable for detecting a loss of coolant. Sometimes sensors are provided in the coolant circuit, in particular in an expansion tank, to detect when the cooling water level is too low. However, this sensor only detects a low level of cooling water in the expansion tank.

Are known from the prior art DE 42 42 124 A1 , the JP S63 263 242 A and the US 5,458,380 A1 .

description

The disclosure relates to a method for controlling a display unit for an internal combustion engine of a motor vehicle. A low cooling water level in the expansion tank does not yet provide any information about the cooling water level in the rest of the cooling system. Against this background, there is a need to reliably detect the cooling water level using means which are already provided in the motor vehicle.

The need is eliminated with the features of claim 1. Further refinements are the subject of the dependent claims, which can be combined with one another in a technologically meaningful manner. The description, in particular in connection with the figures, additionally characterizes and specifies the disclosure.

• • Erfassen von Klopfen, also von Zündungen, die nicht von der Zündkerze initiiert wurden, und Generieren von Klopfsignalen,
• • Überprüfen, ob die Klopfsignale durch andere am Verbrennungsmotor vorliegenden Bedingungen erklärbar sind, und
• • Ausgabe eines auf einen Kühlmittelverlust hinweisenden Warnsignals an die Anzeigeeinheit, wenn die Überprüfung ergibt, dass nur zu heiße Zylinder als Ursache für die Klopfsignale infrage kommen.

Accordingly, a method for controlling a display unit of an internal combustion engine is provided, comprising the steps:

• • Detecting knocking, i.e. ignitions that were not initiated by the spark plug, and generating knocking signals,
• • Check whether the knock signals can be explained by other conditions present in the combustion engine, and
• • Output of a warning signal to the display unit indicating a loss of coolant if the check shows that only cylinders that are too hot are the possible cause of the knocking signals.

In the case of a knocking combustion, an actual ignition of an air-fuel mixture is initiated by a spark plug using a regular ignition spark. As a result of the resulting combustion pressure and an induced temperature, an unwanted further ignition of the air-fuel mixture takes place at another point in the combustion chamber of the cylinder. The result is a second, almost parallel combustion in the cylinder. When both flame friends meet, an intense pressure wave with a high frequency is created. This pressure wave can be detected by the knock sensor.

A knocking combustion can lead to pre-ignition due to the high combustion temperature. Knock detection detects knocking and emits a knock signal, for example via knock sensors, is a standard function in modern gasoline engines - almost all current combustion engines have this function. Instead of hardware-based actual knock sensors, methods for detecting knock, for example knock detection via an ion stream on the spark plug, are also possible. Apparently, signals that are already present on the internal combustion engine are now used to detect a cooling water level. A mechanical coolant level sensor described at the beginning (mostly designed as a float with an electrical contact that is interrupted or closed when the coolant level falls below a certain level) can be omitted, especially since it can only be used to determine the coolant level outside and not in the internal combustion engine itself.

One embodiment provides for a number of cylinders to be detected on which knock signals are detected, and a state “cooling water level with high probability in order” to be set if knock signals are detected on less than half of the total number of cylinders. In other words, the condition “coolant level is very likely to be OK” if an implausible number of cylinders for a coolant loss is affected.

This is based on the idea that knocking in a heated internal combustion engine should occur at the same time on all or at least most of the cylinders due to insufficient cooling. If not, there could be other causes for the knocking. Sometimes knocking only starts on one cylinder due to a so-called hot spot. Hot spots can be caused by a lack of coolant. If knocking occurs on all cylinders and there are no hot spots, this can be attributed, for example, to inferior fuel with an at least reduced fuel quality or octane number. A partial or Complete loss of coolant leads to sudden overheating of the cylinder head, which has an immediate effect. There is strong knocking on all cylinders. A method described in this disclosure enables the coolant level to be monitored via an already available knock signal. A coolant level sensor described in the introduction can therefore be omitted. The internal combustion engine can be protected by issuing a warning signal to the driver. This can deactivate the combustion engine in order to avoid further heating and possible consequential damage.

In a further embodiment, the setting of a "cooling water level with a high degree of probability in order" is provided if the check of the knock signals showed that the knock signals can be explained by other conditions present in the internal combustion engine, in particular an aging of spark plugs, a known worn injection nozzle, a calcified cylinder cooling or if knocking signals occur constantly on a certain cylinder.

In a further embodiment, a check is carried out to determine when a last refueling process was completed and a status “cooling water level with high probability in order” is set if the last refueling process was only a short time ago, in particular less than 0.5 to 10 operating minutes, and therefore the knock signals can be explained by a reduced fuel quality.

If the motor vehicle is not used for a long time, poor quality fuel can still be responsible for knocking. Therefore, the operating minutes in which the internal combustion engine is actually running and drawing fuel from the fuel tank are counted and not its idle time. A refueling detection recognizes a refueling process is also a standard function which is already available in numerous internal combustion engines. This function or corresponding information can be used for the presently disclosed method. The result of the refueling detection is checked accordingly. If you have been refueling a short time ago, there is a high probability that the knock is due to the fuel you have filled up.

In one embodiment, as mentioned, knocking is detected and a knock signal is generated via a knock sensor, which is designed to detect vibrations on the cylinders and to generate a knock signal based on them.

In an alternative or supplementary embodiment, knocking is detected via an ion current measurement on the spark plug.

This is a method in which a voltage and / or a current is measured on the spark plug. The voltage and / or the current provide information about the conditions in the cylinder, including whether knocking occurs. The detection of knocking via an ion current measurement on the spark plug can supplement the detection of knocking via the knock sensor in order to ensure that knocking actually occurs in the cylinder.

A combination of these functions makes it possible to make an assumption about a cooling capacity that is currently enabled by the cooling system.

Means for controlling a display unit of an internal combustion engine can also be provided, having means for detecting knocking, i.e. ignitions that were not initiated by the spark plug, and generating knock signals, means for checking whether the knocking signals can be explained by other conditions present in the internal combustion engine are, and means for outputting a warning signal indicating a loss of coolant to the display unit if the check in step shows that only cylinders that are too hot come into question as the cause of the knocking signals.

In a further development, means can be provided that detect a number of cylinders on which knock signals are detected and means for checking whether knock signals are detected on more than half of the cylinders and means that set a state of "cooling water level in order with high probability", if knock signals are detected on less than half of the cylinders.

Means can also be provided which set a state of “cooling water level with high probability in order” if the check of the knock signals showed that the knock signals can be explained by other conditions present on the internal combustion engine, in particular an aging of spark plugs, a known worn injection nozzle, a Calcified cylinder cooling or if knocking signals occur constantly on a certain cylinder.

Furthermore, the following can be provided: Means for checking when a last refueling process was completed and setting a status “cooling water level with high probability in order” if the last refueling process was only a short time ago and the knocking signals can therefore be explained by a reduced fuel quality.

Means for detecting knocking and generating a knocking signal can be formed by a knocking sensor which is designed to detect vibrations on the cylinders and which has means for generating a knocking signal based on the detected vibrations.

As an alternative or in addition, means are provided which detect knocking by means of means for performing an ion current measurement on the spark plug and means for outputting a knock signal when a progression of the ion current measurement indicates knocking.

A means within the meaning of the present disclosure can be designed in terms of hardware and / or software and in particular have a control device with microprocessors (CPU) that is preferably connected to a memory and / or bus system with data or signals. The control device can have one or more programs or program modules. The CPU can be designed to process commands that are implemented as a program stored in a memory system, it can acquire input signals from a data bus and / or output signals to a data bus. A storage system can have one or more, in particular different, storage media, in particular optical, magnetic, solid and / or other non-volatile media. The program can be designed in such a way that it embodies or is capable of executing the methods described here, so that the control device can execute the steps of such methods.

In one embodiment, one or more, in particular all, steps of the method can be carried out completely or partially in an automated manner. In particular, the steps can be carried out automatically by the controller or its means.

Figure list

• 1: schematisch in einer Draufsicht ein Kraftfahrzeug mit einem Verbrennungsmotor und einer Steuereinrichtung, und
• 2: schematisch ein Flussdiagramm, welches ein Verfahren darstellt, das in der Steuereinrichtung entsprechend 1 implementiert sein kann, um ein Anzeigeelement zu steuern.

The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way. Show it:

• 1 : schematically in a plan view a motor vehicle with an internal combustion engine and a control device, and
• 2 : schematically, a flowchart which represents a method that is carried out in the control device 1 can be implemented to control a display element.

The following description is merely illustrative in nature. For the sake of clarity, the same reference numbers have been used in the drawings to identify similar elements. It should be noted that steps within a method can be performed out of order without changing the principles of the present disclosure. Steps of the method can be multiplications, summations and selections as well as assignments, for example assignment of output values to input values in characteristic diagrams.

1 shows schematically a motor vehicle from above 101 with an internal combustion engine 102 . Elements of the internal combustion engine 102 can have a control device 103 controlled and regulated. The internal combustion engine 102 has an intake duct 104 and an exhaust tract 105 on. Furthermore, there are injection nozzles 106 provided with those fuel that was previously from a fuel tank 107 was fed to the injectors, in cylinders 108 or the intake tract 104 immediately in front of the cylinder 108 can be injected.
There is also a knock sensor 109 intended. The knock sensor 109 In one embodiment, for example, vibrations directly on the internal combustion engine 102 measure and detect knocking. Further possibilities for detecting knocking are known, for example knocking detection via an ion stream on a spark plug 115 . When knocking, an air-fuel mixture ignites not as a result of intended ignition, but rather on hot components in the cylinder, for example 108 by itself. If the cylinder 108 So if the inside gets too hot, knocking can occur. Since gasoline engines often have a high degree of efficiency precisely at the knock limit, today's internal combustion engines have knock sensors. All parameters such as valve opening times, ignition times and injection times are set so that the internal combustion engine 102 just not knocking. Occasional knocking phenomena are therefore not always avoidable. If knocking is detected, parameters are shifted in such a way that the knocking stops.

There is also a cooling system 110 provided with an internal cooling circuit 111 , which is designed to be the internal combustion engine 102 and especially the cylinders 108 to cool. Via a heat exchanger 112 becomes a heat flow Q to an environment 113 submitted. The cooling circuit 111 and the heat exchanger 112 are fluidly connected to one another and filled with cooling liquid.

If the coolant is missing, for example because there is a leak, the cylinders will 108 no longer cooled and the knocking will continue until the internal combustion engine fails 102 amplify. Usually have internal combustion engines 102 only one temperature sensor for coolant. This is usually arranged relatively high up. If there is a loss of coolant, it is no longer wetted with liquid coolant. A Heat transfer from hot, in the internal combustion engine 102 remaining coolant to the temperature sensor does not take place. As a result, a sharp rise in temperature due to a lack of coolant cannot be detected by the temperature sensor.

For reliable detection of a loss of coolant, in 2 schematically a method for controlling a display unit 114 of an internal combustion engine 102 shown. In step 201 a knock is detected first. This is done via in 1 knock sensors shown only schematically 109 or via knock detection by measuring ion currents. Normally, after a detected knock, an ignition point and / or an injection point and, if necessary, a valve opening time are adjusted so that the knocking stops.

Apparently, the conventional measures are also carried out in one step 202 queried whether the knocking on more than half of the cylinders 108 occurs. In the in 1 The example shown is four cylinders 108 intended.

So it will be on three or four cylinders 108 a knock is detected, the step is 203 initiated. Are only two cylinders 108 concerned so will in step 206 status information (e.g. a flag or logic bit) "cooling water level is most likely OK" in the control device 103 set.

In step 204 it is checked whether the knock signals from others on the combustion engine 102 present conditions can be explained.

The status “cooling water level with a high degree of probability OK” is set, according to step 206 if the check of the knock signals showed that the knock signals were caused by others on the internal combustion engine 102 Existing conditions can be explained, in particular an aging of spark plugs 115 , a known worn out injector 106 , calcified cylinder cooling or when knocking signals on a certain cylinder 108 occur constantly. For the internal combustion engine 102 relevant information about an aged spark plug 115 , a worn injection nozzle, 106 , etc., are in an engine diagnostic function in the control device 103 implemented.

In step 204 a check is made as to when a refueling process was last completed. A status “cooling water level with a high probability in order” is also set, according to step 206 if the last refueling process was only for a short time, in particular 0.5 to 10 minutes of operation, in which the internal combustion engine was operating 102 took place, lies back. Accordingly, the knocking signals are more likely to be explained by poor quality fuel if the last refueling process was only a short time ago, in particular 0.5 to 10 minutes ago. This is based on the idea that a reduction in an octane number (a measure of the knock resistance of petrol) can lead to knocking. If the tank has just filled up, the knocking symptoms are more likely to be caused by an insufficient octane number. If the last refueling was a long time ago, it takes place in one step 205 an output of a warning signal “coolant level critical” or the like on a display unit 114 . Furthermore, status information (flag or logic bit) corresponding to the low coolant level can be stored in the control device 103 be set. If namely the internal combustion engine 102 has been running on fresh fuel for a long time without knocking, a lower octane number is no longer an option as a cause of knocking.

The process starts when knocking is detected 201 again. When the controller 103 the knocking is not eliminated by eliminating certain operating parameters, the steps are initiated or processed again 201 , 202 , 203 and 204 . It cannot therefore happen that an actual loss of coolant is not detected simply because the tank has just been refueled. In the second run, for example, an octane number that is too low can be ruled out and the message "cooling water level critical" according to step 205 respectively.

In addition, misfire detection can be used to validate the detected knock signals. The misfire detection is software-based as a method in the control device 103 implemented. Misfire detection is usually performed by monitoring a fluctuation in the crankshaft speed n . The crankshaft speed n is recorded several times per revolution. With each intended ignition by the spark plugs 115 would need an acceleration of the crankshaft speed n can be detected. What remains is the expected acceleration of the crankshaft speed n if it fails or if it is significantly less than would be the case with a complete combustion, this could indicate both a misfire from as well as knocking combustion. The cylinder causing the absent or reduced acceleration 108 is recorded on the basis of a crankshaft angle at which the acceleration failed to take place. It may be that the lack of or decreased acceleration was caused by knocking. This allows a knock signal (generated by a knock sensor 109 or an ion current measurement on the spark plug 115 ) validated and clearly a knocking cylinder 108 be assigned. According to this embodiment, a knock signal is generated after a detected knock. Furthermore, there is an absent or reduced acceleration of the crankshaft speed n detected. Is there a lack of acceleration or a reduced acceleration and a knock signal for the same cylinder 108 before, a knocking burn is as good as certain. The method continues in the manner disclosed and assigns the knock to a loss of coolant if further conditions are met.

Although at least one exemplary embodiment was shown in the preceding description and the description of the figures, it should be recognized that there are a large number of variations. Furthermore, it should be recognized that the exemplary embodiment or the exemplary embodiments are only examples and that they do not serve to limit the scope of protection, the applicability or the precise configuration in any way. Rather, the description and the description of the figures provide a person skilled in the art with useful instructions for implementing at least one embodiment; it should be clear that various changes in the form and function of the features described can be made without departing from the scope of protection of the claims and their equivalents .

List of reference symbols

101

Motor vehicle

102

Internal combustion engine

103

Control device

104

Intake tract

105

Exhaust tract

106

Injectors

107

Fuel tank

108

cylinder

109

Knock sensor

110

Cooling system

111

internal cooling circuit

112

Heat exchanger

113

Surroundings

114

Display unit

115

Spark plugs

116

Cylinder wall

201

step

202

step

203

step

204

step

205

step

206

step

n

Crankshaft speed

Q

Heat flow

Claims (8)

A method for controlling a display unit (114) of an internal combustion engine (102) in which knocking, i.e. ignitions that were not initiated by the spark plug (115), and the generation of knocking signals are detected, characterized by checking whether the knocking signals are caused by others the conditions prevailing on the internal combustion engine (102) can be explained, and • output of a warning signal indicating a loss of coolant to the display unit (114) if the check reveals that only cylinders (108) that are too hot are the possible cause of the knocking signals. Procedure according to Claim 1 , comprising the step of detecting a number of cylinders (108) on which knocking signals are detected and checking whether knocking signals are detected on more than half of the cylinders (108), and setting a status “cooling water level with high probability in order” if knock signals are detected on less than half of the total number of cylinders (108). Method according to one of the Claims 1 and / or 2, comprising the step: setting a state “cooling water level with high probability in order” if the checking of the knocking signals revealed that the knocking signals can be explained by other conditions present on the internal combustion engine (102). Procedure according to Claim 3 , in which an aging of spark plugs (115), a known worn-out injection nozzle (106), calcified cylinder cooling or the fact that knocking signals constantly occur at a certain cylinder (108) are selected as other conditions present in the internal combustion engine. Method according to one of the Claims 1 to 4th , having the step: Checking when a last refueling process was completed and setting a status “cooling water level with high probability OK” if the last refueling process was only a short time ago and therefore the knocking signals can be explained by a reduced fuel quality. Procedure according to Claim 5 when the last refueling was less than 0.5 to 10 minutes ago. Method according to one of the preceding claims, wherein the detection of knocking and the generation of a knock signal take place via a knock sensor (109) which is configured to detect vibrations on the cylinders (108) and to generate a knock signal based thereon. Method according to one of the preceding claims, wherein the detection of knocking and the generation of a knock signal take place via an ion current measurement on the spark plug (115).

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