EP3140526B1 - Method for monitoring the state of opening of a control valve of a coolant circuit of an internal combustion engine, and device for the same - Google Patents

Description

The present invention relates to a method for monitoring the opening state of a control valve of a coolant circuit of an internal combustion engine according to the preamble of claim 1. The invention also relates to a device for carrying out the method according to claim 11.

Internal combustion engines are usually operated with a coolant circuit which has a heat exchanger via which the waste heat produced during combustion and not required for the interior air conditioning of the vehicle operated with the internal combustion engine can be emitted to the environment. If the internal combustion engine or the engine is started, that is to say switched from the non-fired state to the fired state, the engine runs through a warm-up process which should be kept as short as possible.

The engine is started, for example, at a coolant temperature corresponding to the ambient temperature and then the temperature of the coolant flowing through the engine increases, which is measured, for example, at the coolant outlet area or at another measuring point of the engine by means of a sensor can, according to a heat-up curve which depends, for example, on the load required by the engine.

In the coolant circuit of the engine there is a control valve, usually referred to as a thermostat or thermostatic valve, which has a valve member in the form of a valve plate or the like and is intended to influence the flow of coolant in the coolant circuit through the heat exchanger. During the warm-up process, the valve member is intended to prevent the flow of coolant through the heat exchanger, i.e. to keep the so-called large cooling circuit, which includes the heat exchanger, closed so that only the so-called small cooling circuit is traversed, which uses the circulation channels of the engine for the flow of coolant through the engine block and cylinder head and one or more heat exchangers for interior theming of the vehicle.

It is the task of the heat management exercised by a control unit, for example the engine control unit, to influence the heat transport by means of the coolant regulation. On the one hand, heat management is intended to ensure sufficient interior air conditioning in the vehicle and, on the other hand, to ensure that the engine warms up quickly in order to reduce the pollutants emitted during the warm-up process during combustion and to keep the wear caused by the engine’s cold run as low as possible.

The control valve or thermostatic valve plays an important role in the warm-up process, the opening state of which is decisive for the time required for the warm-up process. The control valve should keep the large cooling circuit closed below its intended operating opening temperature, which varies from engine to engine, and thus avoid the emission-relevant dissipation of heat via the heat exchanger during the warm-up process. The pollutant emission of a vehicle type can be a relevant criterion for the type approval, which is why it can be required to monitor the intended functioning of the control valve during operation of the vehicle, for example using diagnostic devices present in the vehicle, i.e. devices for on-board diagnostics (OBD diagnostics).

With the diagnosis of the thermostat, the heating behavior of the coolant should be checked to see whether the engine reaches its operating temperature in a reasonable time. The correct function of the thermostatic valve or control valve must therefore be monitored and any malfunction detected.

A malfunction is present, among other things, if the temperature of the coolant has not reached a minimum temperature within a reasonable time, which is set for further vehicle-specific OBD diagnostics. There is also a malfunction if the coolant temperature determined does not reach the operating opening temperature of the control valve.

According to a method going back to one of the applicants, the function of the control valve in the cooling circuit is monitored by measuring the temperature of the coolant in the coolant outlet area of the engine using a coolant outlet sensor. The measured temperature T _Mot is compared with a modeled coolant engine temperature, which uses the air mass flow rate as a criterion for the engine load, the ambient temperature as a correction variable and the coolant outlet temperature measured when the engine is started as a starting value for an iteration and the current modeled coolant engine temperature. Plotted over time, the characteristic curve of the modeled coolant engine temperature runs at a small distance below the real temperature characteristic curve of the control valve for a control valve that is functioning as intended.

The known method begins after the internal combustion engine has been started, i.e. after the change in the operating state of the internal combustion engine from the non-fired state to the fired state, and determines the modeled temperature as a function of the measured air mass flow rate, among other things, and compares this temperature with the actual temperature in the coolant outlet area or a coolant temperature measured at another suitable sensor measuring point by calculating the difference. If the delta between the measured and the modeled temperature is greater than a predetermined threshold value, an error bit is set, since the actually measured temperature deviates significantly from the modeled temperature and this is an indication that the control valve is not at the time when the coolant is only supposed to flow through the small cooling circuit is completely closed, i.e. the situation of an open-jammed control valve is present.

Due to the dissipation of heat via the heat exchanger to the vehicle environment, such an open-jammed control valve ensures that the time required for the warm-up process is significantly longer than the time required for a control valve that is functioning as intended, and the emission of pollutants is greater than that of a control valve that is functioning as intended resulting pollutant emissions. The error is noted in the vehicle's on-board diagnostics system (OBD system) and the driver of the vehicle can be informed by means of a visual indication as a maintenance instruction that the cause of the error, the open-jammed control valve, can be eliminated after the vehicle's own error memory has been read out.

Although this method has already proven itself in practice, it shows room for improvement. This known method requires the engine to be started up to measure the air mass flow rate and a minimum energy input into the engine's coolant to measure the actual coolant temperature during the warm-up phase, which is limited by an upper coolant temperature threshold value of 80° C., for example.

Based on DE 199 60 190 A1 a control valve for a control circuit has become known, which can be a cooling circuit of an internal combustion engine. The control valve has a valve element which can be adjusted via an electric DC motor or a proportionally acting electromagnet. The position of the control valve can be detected using a position measuring device that has the option of inductive, capacitive or magnetic displacement measurement.

Based on DE 10 2012 018 255 A1 a thermostatic valve has become known which has a non-contact monitoring device for the position of the main valve, which has a sensor element which is contained in a valve housing part and has at least one associated permanent magnet for generating a magnetic field to which the sensor element is exposed. The sensor element is connected to an evaluation device, for example to an engine controller. The engine control can thus detect the closed position of the main valve or an open position in the event of a signal change.

Based on WO 03 042 514 A1 a proportional valve is provided which is intended for controlling volume flows in the heating and/or cooling system of a motor vehicle and has a valve housing with at least one valve member which interacts with at least one valve seat of a valve chamber, the volume flow through the valve being essentially proportional to the Manipulated variable of the valve member is.

Proceeding from the known method described above, the object of the present invention is to improve the method for monitoring the control valve and to enable the direct detection of the opening state of the control valve. A device for carrying out the method is also to be provided.

In order to solve this problem, the invention has the features specified in claim 1 with regard to the method. Advantageous configurations of the method are described in the further claims. In addition, the invention has the features specified in claim 11 in order to solve the object with regard to the device.

The invention provides a method for monitoring the opening status of a control valve of a coolant circuit of an internal combustion engine, the control valve being actuatable by an actuator valve member for releasing and/or blocking a coolant flow in the coolant circuit having a heat exchanger and has a device for detecting the position of the valve member, wherein, according to the method, a first actual value representing the position of the valve member is detected by the device before the internal combustion engine is started and the actual value is compared with a reference value which corresponds to a blocked position of the valve member.

In other words, the invention creates a method for diagnosing the opening state of a control valve of a cooling circuit of an internal combustion engine, the control valve having, for example, a valve disk as a blocking element for the coolant flow. The actuator can be a wax cartridge or the like that actuates the valve member, which can also be electrically heated in order to be able to influence the position of the valve member independently of the coolant temperature. If a wax cartridge is used as the actuator, this wax cartridge has an adjusting pin or the like, which can actuate the valve member in the form of the valve disk directly or indirectly when the wax expands due to heating by the coolant. It is therefore possible to use an actuator which can actively release the blocked position of the valve member but cannot actively produce a blocked position, in which case the actuator then actuates the valve member, for example against the force of a return spring. It is also possible to configure the actuator to act bidirectionally, so that it can actively both cancel and bring about the blocked position. The position of the valve member can be determined by means of a device for detecting its position and a first actual value representing the position of the valve member is detected according to the method according to the invention before the internal combustion engine is started and compared with a reference value which corresponds to a blocked position of the valve member. The comparison operation may be performed by the device or another device such as the engine controller.

A reference value for the blocked position of the valve member is stored in the engine control unit, which is only to be mentioned as an example, and is compared with the actual value of the position of the valve member, which is detected before the internal combustion engine is started. This reference value can be a voltage value, for example, which is output by a sensor. A changing position of the valve member corresponds then a changing voltage value. Before the internal combustion engine is started, the sensor then outputs a voltage value which corresponds to the actual value of the position and is compared with the voltage value which corresponds to the blocked position of the valve member. By forming the difference between the actual value and the reference value, it can then be determined before the internal combustion engine is started whether the valve disk is in its blocked position.

The starting of the internal combustion engine corresponds to the state or point in time at which the internal combustion engine is transferred from the non-fired state to the fired state, ie it is started to run automatically by means of an electric starter motor, for example. The actual value of the position of the valve member before the internal combustion engine is started is therefore compared with a reference value which corresponds to a blocked position of the valve member, i.e. a position in which the valve member forms a flow branch for the coolant from the internal combustion engine in the direction of the heat exchanger or from the heat exchanger in the direction blocked to the internal combustion engine, so a flow movement of coolant through the heat exchanger is prevented.

If the valve member were not blocking, such a flow movement would be brought about by the coolant pump usually present in the coolant circuit, which would result in an undesirable release of heat through the heat exchanger during the warm-up phase, which would make the warm-up process take much longer.

The method according to the invention thus enables the monitoring of the opening state of the control valve or thermostat valve or thermostat in the coolant circuit of an internal combustion engine at a point in time before the engine is even started; the method according to the invention therefore offers the advantage of emission-free monitoring of the opening state of the control valve. The method thus enables the position of the valve member to be diagnosed even before the engine is started and before pollutant emissions occur.

According to a development of the invention, it is provided that if the actual value deviates from the reference value, an error entry is entered in an error memory; the method according to the invention is therefore designed for on-board diagnosis of vehicles. In addition to the entry of a fault in the vehicle's fault memory, a clearly legible notice can also be output on a vehicle's display device for the user of the vehicle. Since the reference value corresponds to the closed position of the valve member, a difference between the reference value and the actual value is an indication of an open-jammed thermostatic valve, which can be determined using the method according to the invention without pollutant emissions occurring during the diagnostic method.

According to a further development of the method according to the invention, it is also provided that the valve member is actuated before the internal combustion engine is started to change the position of the valve member which can be detected by the device. In other words, this means that the invention also provides for the actuator to be controlled to change the relative position of the valve member relative to the sensor, even before the engine is fired. A change in the position of the valve member by a distance that corresponds to the resolution accuracy of the device or the sensor that detects the position of the valve member is sufficient. A minimal deflection of the valve member is therefore sufficient to establish that the valve member is free to move, ie can be moved by the actuator.

This development of the method according to the invention has the advantage that not only can it be determined that the valve member is in a blocked position before the internal combustion engine is started, i.e. it is not the case that the valve member is jammed open and it is also not the case that the valve member is although it is in its locked position, it cannot be released from the locked position. The freedom of movement of the valve member can thus be diagnosed via a short displacement movement of the valve member, which is within the range of the resolution accuracy of the detecting device. This movement can be so small that an elastomeric component provided on the valve member and resting against a passage of the thermostatic valve for the coolant still closes the passage holds and in this way both the intended blocking position of the valve member can be verified and it can be verified that the valve member is not in a closed, jammed position. In this way, the intended function of the valve member can be verified both with regard to its blocking position and with regard to its passage function, ie the risk of the internal combustion engine overheating due to a closed, jamming position of the valve member can also be avoided.

According to a development of the method according to the invention, it is also provided that a setpoint value corresponding to the changed position of the valve member is compared with the changed actual value detected by the device and, if the setpoint value deviates from the actual value, an error entry is entered in an error memory. With this further development, the advantage of a dual functionality can be achieved. On the one hand, it can be used to check the function of the actuator that was activated to change the actual position of the valve member and, on the other hand, the path measurement on the valve element can also be referenced by comparing the position setpoint with the actual value measured by the path measuring device and using the path measurement for as OK is diagnosed if the actual value is within a tolerance window that includes the setpoint.

According to a development of the invention, it is also provided that the temperature of the coolant is recorded and the first actual value is recorded at least until the temperature has reached a predetermined temperature threshold value. If the actuator controls the valve member to open depending on the temperature of the coolant and the valve member is in an open position as intended at a temperature above the predetermined temperature threshold value, this corresponds to an intended function of the valve member and the first actual value no longer needs to be measured.

The method according to the invention also undergoes an advantageous development in that the valve member is actuated by the actuator when a coolant temperature detected in the coolant circuit is below a predetermined threshold value. The threshold value can be a value less than or equal to a tolerance field intended operating opening temperature of the valve member act. So as long as the measured coolant temperature is below the operating opening temperature of, for example, 105 degrees Celsius of the valve member, which is subject to a tolerance zone of 5 degrees Celsius, for example, a blocked position of the valve member can be detected even when the coolant circuit is almost at the operating opening temperature, and the pulsing of the actuator to bring about a minimal change in path of the Valve member are carried out. With the method according to the invention, the blocked position of the valve member can be verified, for example during a red light phase, even in vehicles that work with a start-stop system, and it can also be determined that the actuator is working as intended and the position measuring system of the device can be referenced.

The method according to the invention can thus still be used when the internal combustion engine has already almost completed the actual warm-up process, but coolant flows around the valve member at a temperature that is still below the intended operating opening temperature of the valve member. In this way, the position measuring system, with which the position of a control element of the actuator that actuates the valve member is determined, can also be referenced during, for example, a short start-stop phase.

According to an advantageous development of the method according to the invention, it is also provided that the operating state of a coolant pump delivering coolant to a charging device of the internal combustion engine is detected and the valve member is actuated by the actuator depending on the detected operating state to bring about an open position of the valve member. The charging device can be, for example, an exhaust gas turbocharger whose bearing block is actively cooled with coolant from the coolant circuit. If the engine is switched off when it is warm, there is a risk that the engine oil in the bearing block will coke. In order to avoid coking, the bearing block is actively supplied and cooled by the coolant pump with coolant from the coolant circuit, which makes it necessary for the coolant to release the heat thus absorbed from the bearing block back to the environment via the heat exchanger.

If the temperature in the coolant circuit falls below the operating opening temperature of the valve member, the valve member assumes its blocked position again, for example preloaded by a return spring Coolant circuit can be released. To prevent this, the operating state of the coolant pump delivering coolant to the charging device is monitored and the valve member is kept in the open state by means of the actuator when the coolant pump is in delivery mode.

According to the method according to the invention, the operating state of the coolant pump, which is controlled, for example, by a thermal switch in the area of the bearing bracket of the charging device, is recorded and then, if this is in operation, the actuator of the control valve is also controlled to open the valve member below the operating opening temperature, so that the control valve in remains in an open position guiding the flow of coolant through the heat exchanger, so that the bearing block can also continue to be actively cooled when the temperature of the coolant in the coolant circuit has fallen below the operating opening temperature of the control valve.

In addition to detecting the operating state of the coolant pump for the bearing block, a development of the invention also provides for the valve member to be actuated by the actuator when the open position of the valve member is less than or equal to a predetermined threshold value of the open position. In other words, this means that the open position of the valve member is also monitored during operation of the coolant pump and the actuator actuates the valve member to open the valve member when the determined open position has fallen below a predetermined open position, since the return spring moves the valve member back in the direction pressed to its locked position. Such actuation of the actuator to increase the opening passage of the valve member does not only take place when the valve member has assumed its blocking position, but rather when the valve member moves in the direction of the blocking position, but this has not yet taken. This ensures that the coolant flow through the heat exchanger is not interrupted when the coolant pump is delivering. A corresponding activation of the actuator for keeping the valve member open can therefore already take place when the flow cross section in the thermostatic valve has not yet been completely closed again by the return spring, for example, in order to prevent heat build-up in the coolant circuit.

The method according to the invention for monitoring the opening state of the control valve is characterized in that the actual value of the position of the valve member is detected before the internal combustion engine is started and is compared with the setpoint value. The term starting the internal combustion engine is understood very generally to mean a change in the operating state of the internal combustion engine, in which it changes from the non-fired state to the fired state. A trigger signal for carrying out the method according to the invention can be, for example, a release signal for the activation of an electric starter motor of the internal combustion engine or such a release signal for a fuel feed pump of the internal combustion engine or also quite generally a trigger signal derived from the activation of the on-board voltage system of the vehicle.

The invention also provides a device for carrying out the method with a thermostatic valve with a valve plate that can be displaced by means of a spring-loaded actuating element in the coolant passage to or from a heat exchanger of a coolant circuit of an internal combustion engine and a wax element that can be subjected to heat by means of an electrically actuatable heating element and actuates the actuating element, as well as a den Travel path of the valve disk and/or actuating element without contact and a device for comparing an actual value of the travel path with a target value of the travel path.

The thermostatic valve therefore has a spring-loaded actuating element for moving the valve disk and is arranged upstream in the coolant circuit, i.e. in the flow direction of the coolant circuit in the inlet to the heat exchanger, or downstream, i.e. in the flow direction of the coolant circuit in the return of the heat exchanger. With the valve disc, the coolant flow to or be influenced away from the heat exchanger in that the displacement movement of the valve disk completely blocks or completely opens a passage in a housing of the thermostatic valve or assumes a position between these two extreme positions. The adjusting element can be a sleeve which receives the wax element and is filled with the wax as the expansion medium, which is supported against the heating element. If the wax expands, the result is that the wax is supported against the end face of the heating element, which remains stationary, which causes a reaction force that displaces the sleeve together with the valve disk. The setting pin can also be arranged to be displaceable together with the valve disk, so that the expanding wax displaces the setting pin together with the valve disk.

In both cases, the wax element is subjected to heat from the coolant and expands when heat is supplied, so that the expansion movement of the wax element causes a displacement movement that moves the valve disk in the housing of the thermostatic valve against the action of a return spring to change the flow cross-section of the passage. If the wax element is subjected to heat by means of the electrically actuable heating element, this leads to an opening movement of the valve disk, counter to the action of the restoring spring, independently of the temperature of the coolant. By supplying the electrical heating element with short current pulses, a displacement movement of the actuating pin and thus of the valve disk can be triggered, which is detected by the sensor that detects the position of the valve disk without contact and is detected by the device for comparing an actual value of the travel path with a setpoint value of the travel path .

It can thus be ensured that the valve disk of the thermostatic valve does not jam in a blocked position, which would entail the risk of the internal combustion engine overheating. A zero path measurement of the travel of the valve disk can also be used to determine that the valve disk is in the blocked position and therefore not in an open, jammed position, which would lead to undesirable heat dissipation via the heat exchanger of the coolant circuit during the warm-up process of the internal combustion engine.

• Fig. 1 eine schematische Darstellung eines Kühlmittelkreislaufs einer Brennkraftmaschine mit Wärmetauscher und Kühlmittelpumpe;
• Fig. 2 eine Schnittdarstellung eines Thermostatventils mit geschlossenem Ventilteller in der Stellung zum Warmlaufen der Brennkraftmaschine;
• Fig. 3 eine Darstellung ähnlich Fig. 2 mit zur Freigabe einer Kühlmittelströmung vom Wärmetauscher vollständig verlagertem Ventilteller;
• Fig. 4 eine Schnittdarstellung eines im Gehäuse der Kühlmittelpumpe angeordneten kennfeldgesteuerten und beheizbaren Thermostatventils;
• Fig. 5 eine vergrößerte Darstellung eines Ausschnitts des Thermostatventils nach Fig. 4; und
• Fig. 6 ein Ablaufdiagramm zur Erläuterung des erfindungsgemäßen Verfahrens.

The invention is explained in more detail below with reference to the drawing. This shows in:

• 1 a schematic representation of a coolant circuit of an internal combustion engine with heat exchanger and coolant pump;
• 2 a sectional view of a thermostatic valve with the valve plate closed in the position for warming up the internal combustion engine;
• 3 a representation similar 2 with the valve disc fully displaced to allow a flow of coolant from the heat exchanger;
• 4 a sectional view of a map-controlled and heatable thermostatic valve arranged in the housing of the coolant pump;
• figure 5 an enlarged view of a section of the thermostatic valve 4 ; and
• 6 a flowchart to explain the method according to the invention.

1 The drawing shows a schematic representation of a coolant circuit 1 of an internal combustion engine 2, which is an eight-cylinder engine in a V arrangement.

The coolant circuit 1 comprises a heat exchanger 3, through which ambient air can flow in order to release heat to the environment, with a sucking electric fan 4 also being provided for this purpose. In the coolant circuit 1 there is also a heat exchanger 5 for cooling transmission oil, which for this purpose can give off heat to a heat exchanger 6 through which coolant flows, which is coupled to the heat exchanger 3 for fluid exchange, so that the heat from the transmission oil circuit is released to the environment can be dissipated.

A surge tank 32 serves as a surge tank for the expanding heated coolant.

A mechanically or electrically actuated coolant pump 7 ensures that the coolant flows through coolant channels 8 of the internal combustion engine 2 and circulates in the circuit. A housing 9 of the coolant pump 7 has a connecting flange 10 which is designed to accommodate a control valve or thermostatic valve 11 which can be seen in more detail with reference to the further figures.

At the in 1 In the illustrated embodiment of the thermostatic valve 11, a valve disk 12 is in the blocked position, i.e. a return flow of coolant from the heat exchanger 3 via the coolant return line 20 into a mixing chamber 13 formed in the housing 9 of the coolant pump 7 is not possible and the coolant is in the illustrated position of the thermostatic valve 11 is conveyed in the warm-up phase only through the so-called small cooling circuit, which comprises the internal combustion engine 2 and an air-conditioning circuit 15 operated by a coolant pump 14 for the vehicle air-conditioning.

In this warm-up position, the electric coolant pump 7 is operated at approximately 10% of its delivery rate in order to avoid hot spots forming in the coolant channels 8 of the internal combustion engine 2 . A so-called short-circuit plate 16 of the thermostatic valve 11 is in an open position so that coolant can circulate within the small cooling circuit.

The temperature T _Mot of the coolant exiting the internal combustion engine 2 is measured by means of a sensor 17 .

2 The drawing shows a sectional view of the thermostatic valve or control valve 11 in the short-circuit mode position in the warm-up phase. In this operating position, the coolant exiting the internal combustion engine 2 is routed via the open short-circuit plate 16 into the mixing chamber 13 of the control valve 11 and from the mixing chamber 13 back to the in 1 the drawing Apparent flow 18 is supplied in order to get back into the coolant channels 8 of the internal combustion engine 2, so that the internal combustion engine 2 reaches its operating temperature as quickly as possible. How it based on 2 As can be seen from the drawing, coolant that has already been heated by the internal combustion engine 2 can be routed into the air conditioning circuit 15 and flows back to the mixing chamber 13 in the return flow 19 .

The thermostatic valve 11 has the valve plate 12 already mentioned, which is held in the blocked position by a return spring 21 . The control valve or thermostatic valve 11 has an actuator 22, with which the valve member in the form of the valve disk 12 can be transferred from its closed position to an open position, which in 3 shown in the drawing.

The actuator 22 is a wax element 23, which contains a wax that liquefies and expands when heat is applied expanding wax is acted upon and so the sleeve 24 is displaced when the wax expands against the action of the return spring 21 and the valve disk 12 coupled to the sleeve 24 is actuated from the blocked position to the open position. In the embodiment shown in the drawing, the adjusting pin performs the function of both the heating element and the function of the adjusting element.

in the in 3 In the open position shown in the drawing, the coolant can return from the heat exchanger 3 via the coolant return line 20 into the mixing chamber 13 and from there again via the feed 18 into the coolant channels 8 of the internal combustion engine 2.

The thermostatic valve 11 has an electrically actuable heating element 26 ( 3 ), which can be supplied with voltage from the on-board voltage system of a vehicle via an electrical plug connection 27 in order to use the heat input into the wax element 23 for a temperature independent of the coolant temperature taking place displacement movement of the valve disk 12 against the action of the return spring 21 to ensure. In this way, the application of heat to the wax element 23 can be carried out in a map-controlled manner via a control operation carried out, for example, by an electronic control device of the internal combustion engine 2 (not shown in detail), in order, for example, in the event of a high load requirement on the internal combustion engine 2, to increase the opening cross section that can be released by the valve disk 12 and thus to meet the increased cooling requirement the internal combustion engine 2 to meet.

4 The drawing shows a sectional view of the thermostatic valve 11. Coolant from the return of a bearing block of an exhaust gas turbocharger of the internal combustion engine 2, not shown in detail, can also be introduced into the mixing chamber 13 via an inlet line 28. In the illustrated position of the thermostatic valve 11, the valve disk 12 is in the blocked position, i.e. in the position that is assumed during the warm-up phase of the internal combustion engine 2, in which the entry of coolant from the heat exchanger 2 via the coolant return line 20 is prevented. The resistance heating element 26 can be energized via the electrical plug connection 27 in order to ensure an expansion of the expansion material in the form of thermal wax contained in the sleeve 24 .

figure 5 the drawing shows an enlarged representation of a detail according to 4 of the drawing with the thermostatic valve 11. As is readily apparent, a sealing cap 32 is provided at the upper end region of the wax element 23, which closes the sleeve 24 filled with wax. A permanent magnet 29 is located above the closure cap 33, the distance from a sensor 30 in the form of a Hall sensor provided in the illustrated embodiment and thus its position relative to the sensor 30 can be determined without contact by detecting the field strength of the permanent magnet 29. The permanent magnet 29 has an inner recess into which an O-ring 35 can be inserted, which fixes the magnet 29 by means of a locking ring 36 . Electronic circuit components 37 for recording the resulting change in the position of the permanent magnet 29 relative to the sensor 30 and depending on the stroke movement of the sleeve 24 and thus the valve disk 12 changing sensor voltage can be integrated into the housing 34 of the connector 27.

The distance between the permanent magnet 29 and the sensor 30 is known when the valve disk 12 is in the blocking position, based on the design data. The method according to the invention can be used to determine whether valve disk 12 is in the blocked position by comparing the actual value of the distance between valve disk 12 and sensor 30, which corresponds to the position of valve disk 12 and is measured by sensor 30, with the distance value corresponding to the blocked position of valve disk 12 as a reference value is compared. If the actual value measured by sensor 30 is within a tolerance range of the measurement around the reference value, valve disk 12 is in the desired locked position, so that an undesirable dissipation of heat during the warm-up process of internal combustion engine 2 via heat exchanger 3 can be avoided.

In this way, before the internal combustion engine 2 is started, ie before it is fired and thus even begins to produce pollutant emissions, it can be determined whether the valve disk 12 is in the desired locked position or not. The check according to the known method described above during the warm-up process of the internal combustion engine 2 and thus a period of several minutes to determine whether the valve disk 12 is in the desired locked position or not is already carried out according to the method according to the invention before the internal combustion engine is fired without having to release pollutant emissions.

In addition, according to an advantageous development of the method according to the invention, it can be determined before the internal combustion engine is started whether the valve disk 12 is in a “stuck closed” position, which would entail the risk of the internal combustion engine 2 overheating.

For this purpose, provision is made for the actuator in the form of the electrically heatable wax element 23 to be energized for a change in the position of the valve disk 12 that can be detected by the sensor 30, so that the valve disk 12 is just that far is shifted, so from the passage of coolant through the flow cross section 31 ( 3 ) blocking position is moved towards a position releasing the flow cross section 31 so that the sensor 30 can detect the change in position of the valve disk 12 within the scope of its measurement resolution. If this minimally detectable change in position is so small that an elastomer component (not shown) that is molded onto valve disk 12 and is pretensioned in the direction of the blocking position still closes flow cross section 31 even after the slight change in position of valve disk 12 has been carried out, this check leads to the freedom of movement of valve disk 12 even when the internal combustion engine is started immediately afterwards, does not lead to an undesired dissipation of heat via the heat exchanger 3.

In addition, a displacement of the valve disk 12 in the direction of the "open" position of the flow cross section 31 by pulsing the heating element 26 during this checking process does not lead to a loss of heat via the heat exchanger 3 that is relevant in terms of amount, since after the pulsing of the heating element 26 the valve disk 12 is immediately relocated by the return spring 21 in the direction of the locked position.

The method according to the invention thus makes it possible to prevent both the position of the valve disk 12 in the "jammed open" position, which enables an undesired dissipation of heat via the heat exchanger 3 during the warm-up process of the internal combustion engine 2, and the likewise undesired state of the valve disk 12 "jammed closed". to detect the locked position before the internal combustion engine 2 is even started.

According to a further development of the method according to the invention that is also provided, it is also possible to monitor the opening state of the thermostatic valve 11 when the thermostatic valve 11 is in the blocked position as intended, if the internal combustion engine 2 has already almost completed the warm-up process and the thermostatic valve 11 has not yet reached the operating opening temperature or the Temperature of the coolant and thus the thermostatic valve 11 due to a non-fired downtime of the internal combustion engine 2 again has dropped below the operating opening temperature of the thermostatic valve 11. Such a situation can occur, for example, in vehicles with start-stop systems, in which the internal combustion engine 2 is switched from the fired state to the non-fired state before the operating opening temperature of the thermostatic valve 11 is reached, i.e. before a red light showing signal system, for example.

The check as to whether the valve disk 12 can be displaced or is jammed in the intended blocking position can also be carried out as a function of an action triggered by the user of a vehicle. The pulsing of the heating element 26 and thus the checking of the valve disk 12 can be triggered if the user selects a sports driving program provided by the vehicle at a coolant temperature below the operating opening temperature of the thermostatic valve 11, i.e. selects, for example, shifting characteristics of the vehicle transmission with shifting points at high engine speeds. In such a case, with an expected high load requirement on the internal combustion engine 2, the intended function of the valve disk 12 to be opened can be verified even before the coolant temperature rises due to the high load requirement.

The method according to the invention for monitoring the open position of valve disk 12 in the blocked position can then be triggered, for example, by a release signal for the electric starter motor of internal combustion engine 2, and it can then be checked whether valve disk 12 is below the operating opening temperature of thermostatic valve 11 in the intended blocked position located.

Briefly energizing the heating element 26 can also be used to check whether the thermostatic valve 11 in the blocking position can be opened as intended, i.e. whether the valve disk 12 can be shifted from the blocking position in the direction of a position that releases the flow cross section 31, thereby preventing overheating of the internal combustion engine 2 can be prevented.

In the event that the check reveals in all of the cases mentioned that the valve disk 12 is in a “jammed open” position, a fault entry can be entered in the vehicle’s fault memory, from which a corresponding need for maintenance on the thermostatic valve 11 results. An error entry “Thermostatic valve jammed closed” specifically specifying the need for maintenance can also be entered in the error memory if the valve disk 12 cannot be moved to a position change that can be detected by the sensor 30 by pulsing the heating element 26 as intended.

6 the drawing shows the flow chart for explaining the method according to the invention. Depending on the measured field strength, the sensor 30 emits a voltage signal which indicates the distance between the permanent magnet 29 and the sensor 30 and thus the position of the valve member in the form of the valve disk 12 relative to the sensor 30 . In this embodiment, the implementation of the method according to the invention is controlled by a control device of the internal combustion engine 2 .

In a step S1, triggered by a signal indicating the energization of the electric starter motor of the internal combustion engine 2, the distance between the permanent magnet 29 and the sensor 30 is measured by means of the sensor 30 and then in a step S2 a reference value corresponding to the blocked position of the valve disk 12 is taken from a vehicle memory read.

In a next step S3, the actual value of the position of the valve disk 12 measured in this way is compared with the reference value. If it is determined in this way that the valve disk 12 is in its intended blocking position, in a next step S4 an entry "okay" is entered in the vehicle memory.

If, on the other hand, it is determined in step S3 that the valve disk 12 is not in its intended blocking position, a corresponding fault entry is made in the vehicle's fault memory in a step S5 and a Maintenance notice issued on an on-board display device for the user of the vehicle.

In a next step S6 according to a further development of the method according to the invention, after the condition "OK" has been determined as present according to step S4, the engine control unit outputs a signal for brief heating of the wax element 23 to a control device for energizing the heating element 26 and then in In a next step S7, the actual value of the position of the valve disk 12 is determined and then, in a next step S8, the actual value measured in this way is compared with the reference value already known from step S2.

If it is established that the actual value of the position of the valve disk 12 differs from the reference value, an entry "okay" is entered in the vehicle memory in a next step S9. If, on the other hand, it is determined in step S8 that the actual value of valve disk 12 still corresponds to the reference value, in step S10 a corresponding fault entry is entered in the vehicle's fault memory and a maintenance notice is issued to the user of the vehicle.

With regard to features of the invention not explained in detail above, reference is expressly made to the patent claims and the drawing. Reference List 1. coolant circuit 32 surge tank 2. internal combustion engine 33 cap 3. heat exchanger 34 Housing 4. Fan 35 o ring 5. heat exchanger 36 locking ring 6. heat exchanger 37 circuit components 7. coolant pump 8th. coolant channels 9. Housing 10 connection flange 11. Control valve, thermostatic valve 12. valve disk, valve member 13. mixing chamber 14 Coolant pump for vehicle air conditioning 15 air conditioning circuit 16 short circuit plate 17 sensor 18 leader 19 return 20 coolant return line 21 return spring 22 actuator 23 wax element 24 sleeve 25 actuator 26 heating element 27 connector 28 inlet line 29 permanent magnet 30 sensor 31 flow cross-section

Claims (11)

1. Method for monitoring the opening state of a control valve (11) of a coolant circuit (1) of an internal combustion engine (2), wherein the control valve (11) has a valve member (12) that can be actuated by an actuator (22) for releasing and/or blocking a coolant flow in the coolant circuit (1) having a heat exchanger (3) and a device for recording the position of the valve member (12), characterised in that a first actual value representing the position of the valve member (12) is recorded by the device before starting the internal combustion engine (2), and the actual value is compared to a reference value which corresponds to a blocking position of the valve member (12).
2. Method according to claim 1, characterised in that an error entry is registered in an error memory when the actual value deviates from the reference value.
3. Method according to claim 1 or 2, characterised in that the valve member (12) is actuated by the actuator (22) before starting the internal combustion engine (2) to form a change of the position of the valve member (12) that can be detected by the device.
4. Method according to claim 3, characterised in that a target value corresponding to the changed position of the valve member (12) is compared to the changed actual value detected by the device and, if the target value deviates from the actual value, an error entry is registered in an error memory.
5. Method according to one of the preceding claims, characterised in that the temperature of the coolant is recorded, and the actual value is recorded at least until the temperature has reached a predetermined temperature threshold value.
6. Method according to one of claims 3 to 5, characterised in that the valve member (12) is actuated by the actuator (22) when a coolant temperature recorded in the coolant circuit (1) lies below a predetermined threshold value.
7. Method according to claim 6, characterised in that the threshold value is less than or equal to an intended operating opening temperature of the valve member (12) afflicted by a tolerance field.
8. Method according to one of the preceding claims, characterised in that the operating state of a coolant pump conveying coolant to a charging device of the internal combustion engine (2) is recorded, and the valve member is actuated by the actuator (22) depending on the operating state for causing an opening position of the valve member (12).
9. Method according to claim 8, characterised in that the coolant is conveyed at least to a storage device of the charging device, and the valve member is actuated by the actuator (22) when the opening position is less than or equal to a predetermined threshold value of the opening position.
10. Method according to one of the predetermined claims, characterised in that the monitoring is triggered by a triggering signal introducing the start of the internal combustion engine (2).
11. Device for carrying out the method according to one of the preceding claims, characterised by a thermostat valve (11) having a valve plate (12) that can be shifted by means of a spring-loaded actuating element in the coolant passage to or from a heat exchanger (3) of a coolant circuit (1) of an internal combustion engine (2) and a wax element (23) that can be supplied with heat by means of an electrically actuatable heating element (26) and actuates the actuating element and a sensor (30) recording the shifting path of the valve plate (12) and/or actuating element without contact and a device for comparing an actual value of the shifting path to a target value of the shifting path, wherein the device has apparatus, which is designed to compare the actual value to the target value in a state of the internal combustion engine before starting the internal combustion engine.

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