APPARATUS FOR MONITORING AN OIL THERMOSTAT

Abstract

The invention relates to an apparatus for monitoring an oil thermostat arranged in an oil circuit of an internal combustion engine. The apparatus comprises a sensor unit (4, 14b; 15) which is designed to determine at least one first parameter, by means of which a current setpoint operation of the oil thermostat (10) can be derived, and to determine at least one second parameter, by means of which a current actual operation of the oil thermostat (10) can be derived. The apparatus further comprises an evaluation device (40), which is designed to detect an onset of an error function of the oil thermostat (10) as a function of the first parameter and the second parameter.

Claims

1. An apparatus for monitoring an oil thermostat arranged in an oil circuit of an internal combustion engine, wherein the oil thermostat is designed to supply an oil flow to a first flow branch in which an oil cooler is arranged or to a bypass flow branch depending on an admission temperature (T2) of the oil flow supplied to the oil thermostat, wherein a first outlet of the oil thermostat, which outlet is assigned to the first flow branch, is closed when the admission temperature (T2) lies below a first temperature threshold value (T1), wherein the apparatus comprises: (a) a sensor device which is designed to determine at least one first parameter by means of which a current desired operation of the oil thermostat can be derived, and to determine at least one second parameter by means of which a current actual operation of the oil thermostat can be derived; and (b) an evaluation device which is designed, depending on the first parameter and the second parameter, to identify an occurrence of a malfunction of the oil thermostat.

2. The apparatus as claimed in claim 1, wherein the sensor device is designed to measure the admission temperature (T2) of the oil as the first parameter, and wherein preferably the oil sump temperature is measured as the admission temperature (T2).

3. The apparatus as claimed in claim 2, wherein (a) the sensor device is designed to measure a second oil temperature (T3) downstream of the oil cooler and upstream of the internal combustion engine and to determine a temperature difference (ΔT) from the admission temperature (T2) minus the second oil temperature (T3) as the second parameter; and (b) the evaluation device identifies the occurrence of a malfunction of the oil thermostat, (b1) when the admission temperature (T2) lies below the first temperature threshold value (T1), at least one predetermined reaction period (Z1) has elapsed since the admission temperature (T2) has been below the first temperature threshold value (T1), and the temperature difference (ΔT) is greater than a first threshold value (ΔT1); or (b2) when the admission temperature (T2) is above the first temperature threshold value (T1) at least one predetermined reaction period (Z1) has elapsed since the admission temperature (T2) has been above the first temperature threshold value (T1), and the temperature difference (ΔT) is smaller than a second threshold value (ΔT2); or (c) when, after the first temperature threshold value (T1) is exceeded by the admission temperature (T2), an increase of the temperature difference (ΔT) proceeds more slowly than a predetermined desired increase of the temperature difference (ΔT).

4. The apparatus as claimed in claim 3, further comprising a temperature sensor for measuring the second oil temperature (T3), (a) which is arranged upstream of a junction of the first flow branch and of the bypass flow branch or downstream of an oil filter arranged before the internal combustion engine; or (b) which is designed as a combined pressure and temperature sensor; or (c) which is integrated in an oil filter head.

5. The apparatus as claimed in claim 2, wherein (a) the sensor device is designed to measure, as the second parameter, an oil pressure progression (P) at a pressure measurement point which is arranged downstream of the first outlet of the oil thermostat and upstream with respect to the internal combustion engine; and (b) the evaluation device identifies a malfunction of the oil thermostat when the measured progression of the oil pressure (P) does not indicate any pressure swing (ΔP) within a range of the admission temperature (T2) that lies between the first oil temperature threshold value (T1) and a second temperature threshold value (T1*), wherein the second temperature threshold value (T1*) lies above the first temperature threshold value (T1) and specifies a temperature threshold above which a second outlet of the oil thermostat, which outlet is assigned to the bypass flow branch, is completely closed.

6. The apparatus as claimed in claim 5, wherein (a) the pressure measurement point is arranged in the first flow branch between the first outlet of the oil thermostat and the oil cooler, and the pressure swing (ΔP) is a negative peak; or (b) the pressure measurement point is arranged downstream of the oil cooler and after a junction of the first flow branch and of the bypass flow branch, and the pressure swing is a positive peak.

7. The apparatus as claimed in claim 1, wherein the following is established as the first parameter: (a) the admission temperature (T2) of the oil, wherein preferably the oil sump temperature is measured as the admission temperature (T2); (b) a cooling water temperature; or (c) an operating state of the vehicle, in particular whether a cold start or whether a journey at full load is carried out.

8. The apparatus as claimed in claim 1, wherein (a) a gradient of an admission temperature (T2) of the oil, preferably a gradient of the oil sump temperature, is determined as the second parameter; and (b) the evaluation device establishes, depending on the determined value of the first parameter, a predetermined and stored desired characteristic curve of the gradient of the admission temperature (T2) and identifies a malfunction of the oil thermostat when the measured gradient of the admission temperature does not correspond to the desired characteristic curve.

9. The apparatus as claimed in claim 1, wherein (a) as the second parameter, an oil temperature is measured at a measurement point which is arranged in the first flow branch upstream with respect to the oil cooler; and (b) the evaluation device identifies a malfunction of the oil thermostat when the measured oil temperature in accordance with the second parameter remains substantially unchanged since, in accordance with the determined first parameter, the first outlet would have had to be opened or closed.

10. The apparatus as claimed in claim 1, wherein (a) the sensor device is designed to detect a position or a movement of a final control element of the oil thermostat as the second parameter; and (b) the evaluation device is designed to identify the malfunction of the oil thermostat with reference to the detected position or movement of the final control element.

11. The apparatus as claimed in claim 10, wherein the malfunction of the oil thermostat is identified (a) when no movement of the final control element is detected within a predetermined oil temperature range or cooling water temperature range; or (b) when, during a cold start, the final control element is in a position in which the first outlet is opened; or (c) when, during a driving mode at full load, the final control element is in a position in which the first outlet is closed.

12. The apparatus as claimed in claim 10, wherein the sensor device comprises a displacement sensor which is mechanically coupled in terms of movement to the final control element.

13. The apparatus as claimed in claim 10, wherein (a) the sensor device is designed as an electric oscillating circuit with a coil, wherein the coil is arranged from the outside on or in the vicinity of the oil thermostat in such a manner that a movement of the final control element of the oil thermostat changes the inductance of the coil and therefore an oscillation frequency of the oscillating circuit; or (b) the sensor device has a transmitter coil and a receiver coil which are each arranged on opposite sides from the outside on or in the vicinity of the oil thermostat, and therefore a movement of the final control element of the oil thermostat changes a signal induced in the receiver coil by the transmitter coil.

14. The apparatus as claimed in claim 13, wherein the apparatus is designed as a mobile test apparatus for workshop use, comprising fastening means in order to arrange the sensor device from the outside on the oil thermostat temporarily for a measurement operation.

15. The apparatus as claimed in claim 10, wherein the sensor device is designed as a switching circuit which is integrated in the oil thermostat and is designed (a) to detect a position or movement of the final control element of the oil thermostat by means of integrated switching contacts; (b) to extract its supply energy from the oil heat by means of an energy-harvesting switching circuit; and (c) to transmit a measurement signal wirelessly, preferably by means of a close range radio transmission, to the evaluation device.

16. The apparatus as claimed in claim 1, wherein the oil thermostat is a sleeve valve oil thermostat or an expansion element oil thermostat, in particular a wax expansion oil thermostat.

17. A vehicle, in particular commercial vehicle, comprising an apparatus for monitoring an oil thermostat arranged in an oil circuit of an internal combustion engine, wherein the oil thermostat is designed to supply an oil flow to a first flow branch in which an oil cooler is arranged or to a bypass flow branch depending on an admission temperature (T2) of the oil flow supplied to the oil thermostat, wherein a first outlet of the oil thermostat, which outlet is assigned to the first flow branch, is closed when the admission temperature (T2) lies below a first temperature threshold value (T1), wherein the apparatus includes: (a) a sensor device which is designed to determine at least one first parameter by means of which a current desired operation of the oil thermostat can be derived, and to determine at least one second parameter by means of which a current actual operation of the oil thermostat can be derived; and (b) an evaluation device which is designed, depending on the first parameter and the second parameter, to identify an occurrence of a malfunction of the oil thermostat.

Description

[0041] A further aspect of the invention relates to a vehicle, in particular a commercial vehicle, with an apparatus as disclosed herein. The previously described preferred embodiments, variants and features of the invention can be combined with one another as desired. Further details and advantages of the invention are described below with reference to the attached drawings, in which:

[0042] FIG. 1 shows a schematic illustration of an oil circuit of an internal combustion engine for illustrating various embodiments;

[0043] FIG. 2 shows a characteristic temperature progression in the event of a malfunction of the oil thermostat;

[0044] FIG. 3 shows a characteristic temperature progression in the event of a malfunction of the oil thermostat;

[0045] FIG. 4 shows a temperature increase in the event of a functioning oil thermostat and in the event of a defective oil thermostat;

[0046] FIG. 5 shows an oil pressure progression depending on the oil temperature;

[0047] FIG. 6 shows variant embodiments for determining the position and/or movement of the final control element of the oil thermostat; and

[0048] FIG. 7 shows further variant embodiments for determining the position and/or movement of the final control element of the oil thermostat.

[0049] FIG. 1 shows schematically the parts of an oil circuit 1, wherein only that part of the oil circuit which is arranged in the flow progression between oil sump and internal combustion engine is illustrated.

[0050] Arranged in the oil circuit 1 is an oil pan 2 in which the oil sump 2a is arranged, the filling level of which is monitored with an oil level probe 3. The oil from the oil sump 2a is supplied to the throughflow inlet 11 of an oil thermostat 10 via an admission line 5. An oil pump 6, a pressure control valve 7 and a non-return valve 8 are arranged in the admission line 5.

[0051] The oil thermostat 10 is designed, for example, as a sleeve valve oil thermostat or wax expansion oil thermostat and contains a final control element which moves into a determined position depending on the oil temperature (admission temperature T2) prevailing at the inlet 11 of the oil thermostat 10. Via the line 9, the oil supplied to the oil thermostat lies against a control inlet of the oil thermostat valve 10 and, for example, in the case of a wax expansion thermostat, leads, depending on the oil temperature, to heating and therefore expansion or to cooling and contraction of the final control element of the oil thermostat, and therefore the valve disks of the final control element are moved in order to open or to close a first outlet 12 of the oil thermostat 10 and to close or to open the second outlet 13 of the oil thermostat 10.

[0052] If the admission temperature T2 of the oil is lower than a first temperature threshold value T1, that outlet 12 of the oil thermostat 10 which connects the admission line 5 to a first flow branch 17 in which an oil cooler 16 is arranged is closed. The oil is instead supplied via the second outlet 13 of the oil thermostat 10 to a second bypass flow branch 18 which circumvents the oil cooler 16. If, by contrast, the admission temperature T2 is greater than a second temperature threshold value T1* which lies above the value T1, the second outlet 13 is completely closed and the first outlet 12 opened, and therefore the oil flows exclusively via the oil cooler 16. In the region between T1 and T1*, the first outlet is opened and the second outlet is only partially closed.

[0053] The first flow branch 17 and the second flow branch 18 are brought together after the oil cooler 16 to form a common flow portion 19. The oil then flows through an oil filter 20 which furthermore has a filter service valve 21 and a filter-circumventing valve 22. The oil filter 20 is followed downstream by a syphon 23 in the oil filter head and an oil pressure sensor 25 integrated in the oil filter head. The oil is subsequently supplied to the internal combustion engine (not illustrated) via the line portion 26.

[0054] The above-described components of the oil circuit 1 are known per se from the prior art and do not have to be described in further detail here.

[0055] According to the invention, an apparatus for monitoring the oil thermostat is furthermore provided in order to be able to identify a malfunction of the oil thermostat. The apparatus comprises a sensor device which is designed to determine at least one first parameter by means of which or from which a current operation of the oil thermostat 10 can be deduced.

[0056] For this purpose, the sensor device can comprise, for example, a temperature sensor 4 which determines the oil sump temperature as the first parameter. The oil sump temperature T2 substantially corresponds to the oil temperature which prevails at the oil thermostat 10 and which, in the desired operation, determines the position of the final control element. The oil sump temperature sensor 4 can be integrated in the oil level sensor 3 and can be provided as what is referred to as a combination sensor. As already mentioned above, the desired operation state of the oil thermostat 10 can be deduced directly from the determined oil sump temperature. As already explained above, the first outlet 12 to the first flow branch 17 having the oil cooler 16 is closed at oil sump temperatures of T2<T1. At a temperature of T2≧T1 and T2≦T1*, the throughflow through the first flow branch 17 is open, and the bypass flow branch 18 is likewise also partially open. Within a range of the oil sump temperature of T2>T1* the throughflow through the first flow branch 17 is completely opened and the second outlet 13 and therefore the bypass flow branch 18 are completely closed. Exemplary values for T1 lie within the range of 95 degrees to 105 degrees and approx. 120 degrees for T1*.

[0057] The sensor device of the apparatus for monitoring the oil thermostat is furthermore designed to determine a second parameter by means of which a current actual operation of the oil thermostat can be deduced. For this purpose, for example use can be made of the temperature sensor 14b which is arranged downstream of the oil cooler 16 in the first flow branch 17 before the latter is brought together with the bypass flow branch 18. A second oil temperature T3 downstream of the oil cooler 16 can be measured with this temperature sensor 14b. From said second oil temperature T3, a temperature difference ΔT can then be determined from the admission temperature T2 minus the second oil temperature T3, on the basis of which temperature difference it can then be ascertained whether the actual operation of the oil thermostat 10 corresponds to the anticipated desired operation.

[0058] This is illustrated, for example, in FIG. 2. FIG. 2 shows a progression of the admission temperature T2, which has been determined by means of the sensor 4, over time, and a progression of the second oil temperature T3, which has been measured with the sensor 14b downstream of the oil cooler 16, over time. The dashed line T1 indicates the threshold value of the opening temperature T1.

[0059] In the illustrated case, the admission temperature T2 is lower than the opening temperature T1 of the first outlet 12 of the oil thermostat 10. During the desired operation, oil would therefore not be permitted to flow through the first flow branch since the first outlet 12 would have to be closed in this case. However, FIG. 2 shows a temperature progression which occurs in the event of a malfunction of the oil thermostat 10, for example in the event of a defect of the final control element, wherein oil flows through the oil cooler 16 even at admission temperatures of T2<T1. As a result, the oil is cooled down by the oil cooler 16 by the amount ΔT.

[0060] An evaluation unit 40 connected to the sensor device 4, 14b via a signal input line 41 then checks on the basis of the established measurement values whether the determined temperature difference ΔT has a value which is anticipated according to a desired operation, or whether there is a malfunction of the oil thermostat 10. The evaluation unit 40 checks whether the temperature difference ΔT from the admission temperature T2 minus the second oil temperature T3 is smaller than a predetermined first temperature threshold value ΔT1.

[0061] A malfunction of the oil thermostat is identified when the admission temperature lies below the first temperature threshold value, at least one predetermined reaction period Z1 has elapsed since the admission temperature has been below the first temperature threshold value T1, and the temperature difference ΔT from the admission temperature minus the second oil temperature is greater than a first threshold value ΔT1.

[0062] If, however, the temperature difference ΔT is greater than a first threshold value ΔT1 it can be concluded therefrom that oil cooling takes place and therefore the oil has to be run through the flow branch 17 with the cooler 16, and therefore there is a malfunction of the thermostat 10.

[0063] The first threshold value ΔT1 is defined depending on the reduction of the oil temperature (cooling power of the oil cooler) which reduction is produced by the oil cooler. The first threshold value should be, for example, greater than customary oil temperature fluctuations, which are not caused by the oil cooler, in the region between oil sump and internal combustion engine, but somewhat smaller than the average cooling power of the oil cooler. The predefined reaction period Z1 takes into account a time-delaying behavior of the oil thermostat and constitutes a period up to which, after a change of the switching behavior of the oil thermostat, the temperature difference ΔT resulting therefrom downstream of the oil thermostat would have to be adjusted. The reaction period depends on the type of oil thermostat and on the position of the measurement point for the second temperature and can be defined, for example, experimentally.

[0064] If the evaluation device 40 identifies a malfunction of the oil thermostat 10, it outputs a warning signal via the output line 42, said warning signal being output, for example, via a display apparatus in the cockpit of the vehicle.

[0065] FIG. 3 shows the temperature progression in the event of a malfunction of the oil thermostat 10, in the event of which the oil thermostat 10 despite an admission temperature T1 which is greater than the first temperature threshold value T1 does not pass into a position in which the first outlet 12 is opened and oil flows through the oil cooler 16. This can be seen in FIG. 3 by the fact that the temperature difference ΔT from admission temperature minus the second temperature T3, which is measured by means of the temperature sensor 14b is smaller than a predetermined second temperature threshold value ΔT2. Depending on the cooling power of the oil cooler 16, the threshold value ΔT2, is selected in such a manner that a temperature difference ΔT is always greater than the threshold value ΔT2 when the oil flows through the oil cooler 16. The small distance of the temperature T3 from the admission temperature T2 indicates on the contrary that a defective oil thermostat has to be present. The fact that the temperature progression T3 lies somewhat below the temperature profile T2 results from the fact that the bypass flow branch 18 is arranged spatially in the vicinity of the oil cooler 16 and thereby radiates cooling power somewhat from the oil cooler 16 and also slightly cools the oil in the bypass flow branch 18. In order to avoid erroneous measurements, the evaluation of the differential temperature ΔT is in turn carried out only after a predetermined reaction period of time Z1 has elapsed.

[0066] FIG. 4 illustrates a further possibility, according to a variant embodiment, of identifying a malfunction. In FIG. 4, in turn, the dashed line T1 denotes the first temperature threshold value below which the first outlet is closed and above which the first outlet 12 is opened. The progression of the admission temperature T2 over time is measured in turn with the temperature sensor 4 in the oil sump of the oil circuit 1.

[0067] FIG. 4 illustrates the progression of the admission temperature T2 over time, starting from a cold start of the motor vehicle. The cold starting range is illustrated by the range indicated by K. During the cold start, the admission temperature greatly increases since the cold engine oil is heated by the driving mode. The temperature range Z2 indicates the thermostat opening range which begins after the admission temperature T2 exceeds the opening temperature T1. The following range B indicates a range of operationally hot inertia.

[0068] The dashed line which is indicated by the reference sign T3 indicates the progression of the oil temperature which is measured before the internal combustion engine, but downstream of the oil cooler 16, for example with the temperature sensor 24.

[0069] During the cold starting range K below the temperature threshold value T1, the oil cooler is, as expected, closed, and therefore the temperature T3 follows the progression of the admission temperature T2 and lies only minimally below the value thereof, because of the abovementioned radiating effects of the cooler 16.

[0070] When the temperature threshold value T1 is reached and exceeded, the final control element of the oil thermostat 10 should progressively open the first outlet 12. In the event of a normally functioning oil thermostat, the progression which is indicated by the chain-dotted line T3.2 would arise. In this case, the temperature difference ΔT=T2−T3.2 increases gradually.

[0071] FIG. 4 furthermore shows a temperature progression over time, which is indicated by the dashed line T3.1 and which can be measured at the sensor 24 in the event of a slightly defective oil thermostat 10. The temperature difference between admission temperature T2 and temperature T3.1 after the oil cooler does not diverge too rapidly here, as according to the progression T3.2, although the temperature difference ΔT after the point B1 is in turn identical for both temperature progressions.

[0072] However, it has been ascertained within the scope of the invention that, in the case of an oil thermostat 10, the final control element of which is already displaying the onset of a jamming behavior or slight sticking, the temperature progression T3.1 can be observed, and therefore the final control element initially “jams” in the range Z2 and only at a later time “tears loose” and jumps abruptly into the complete open position. Such a jamming behavior is an indication of a future complete jamming of the oil thermostat 10.

[0073] According to this variant, the evaluation device 40 identifies such an erroneous behavior in the increase of the temperature difference ΔT, when the increase of the temperature difference proceeds more slowly than a predefined desired increase of the temperature difference. In other words, the progression of the temperature difference over time is detected. If said progression is less pronounced than a predefined desired increase which is stored in the evaluation device 40 in the form of an experimentally determined characteristic curve, a malfunction of the oil thermostat 10 is detected. One possibility for ascertaining a malfunction here is to predefine a minimum value for the temperature difference from T2 and T3 that has to be reached after a predefined reaction period has elapsed after the opening temperature T1 is exceeded. If the measured temperature difference after expiry of the predefined reaction period is smaller than the minimum value for the temperature difference, a malfunction is present.

[0074] If the evaluation device 40 therefore identifies one of the temperature progressions illustrated in FIGS. 2 to 4, a defective behavior of the oil thermostat 10 is diagnosed.

[0075] It should furthermore be pointed out that industrialized thermostats may already be subject in the new state to a control temperature tolerance. This can basically be taken into consideration in the evaluation unit; for example, in the event of a continuous increase in wear of the thermostat, the defined temperature limit T1 and T1*, which lead to a movement of the control mechanism are increasingly more frequently broken or displaced. In the evaluation unit, calculation sequences can therefore be active and characteristic fields can be stored, which adapt the defined temperature limits T1 and T1* and/or the threshold limits ΔT1 and ΔT2 for the monitoring variants of FIGS. 2 to 4 due to wear in order thus to signal the exchange or defect of the thermostat only if the correct operation of the engine would beyond doubt no longer be ensured.

[0076] FIG. 5 illustrates a further possibility according to the invention for identifying whether the oil thermostat 10 is defective. In this case, the sensor device is designed to measure a pressure progression over time by means of a pressure sensor 15 which is arranged in the first flow branch 17 between the first outlet 12 of the oil thermostat 10 and the oil cooler 16. Furthermore, the sensor device in turn determines the progression of the admission temperature T2 over time, for example by means of the temperature sensor 4.

[0077] In FIG. 1, the range between the two temperature threshold values T1 and T1* of the oil thermostat is indicated by the dashed lines. As already mentioned above, in the case of a normally functioning oil thermostat, the first outlet 12 is closed when the admission temperature T2 lies below the value T1. Above the temperature T1* the first outlet is completely opened and a second outlet 13 is completely closed. Within the temperature transition range 50 between T1 and T1* the first outlet 12 is opened and the second outlet 13 is only partially closed, and therefore oil flows both through the first flow branch 17 and also through the second flow branch 18.

[0078] The pressure progression over time, as measured by the pressure sensor 15, is depicted by the curve P. The pressure progression P describes the progression of a normally functioning oil thermostat 10. Within the temperature ranges of the admission temperature T2 below T1, the pressure progression substantially has the value P1 and, within the ranges in which the admission temperature lies above the value T1*, the value P2. P2 here is essentially somewhat higher than P1 since the oil cooler 16 has a higher flow resistance than the bypass line 18 and therefore leads to increased pressure values P2. However, within the transition range between T1 and T1*, the two lines are at least partially opened, and therefore the flow resistance is lowest within this range. This leads to a negative pressure peak ΔP within the range of the pressure progression over time between T1 and T1*.

[0079] If a pressure peak ΔP of this type within the range of the pressure progression over time is measured within the temperature transition range 50 between T1 and T1*, it can be concluded therefrom that the thermostat value 10 operates correctly. However, if the evaluation device 40 identifies on the basis of the measured pressure progression P that no such pressure swing ΔP occurs within the temperature transition range 50, it can be concluded therefrom that the final control element of the oil thermostat 10 has not moved as expected and therefore there is a malfunction.

[0080] Instead of the pressure sensor 15 which is arranged between the oil thermostat and oil cooler 16, the pressure progression can also be measured, for example, with the pressure sensor 25 which is arranged after the oil filter. In this case, the desired pressure progression differs from that illustrated in FIG. 5 by the fact that a positive peak is measured within the transition ranges between T1 and T1* since the oil throughflow quantity is at the greatest at the measurement point of the pressure sensor 25 within this range. If, in turn, and analogously to FIG. 5, within the transition range, a positive peak is not measured within said range, it can again be concluded that there is a malfunction.

[0081] The temperature sensors 4, 14a, 14b and 24 and the pressure sensors 15 and 25 have all been illustrated simultaneously in FIG. 1 to simplify the illustration. However, it is emphasized that, depending on the variant embodiment of the sensor apparatus, only some of said sensors have to be present in the oil circuit 1, for example it may be sufficient, depending on the variant embodiment, to use the temperature sensor 4 for determining the admission temperature and additionally also to use the sensor 14b or 24 for determining the differential temperature. Instead of the temperature sensors 14b and 24, it may also be possible, for example, to provide only one pressure sensor 15 or 25 if a defect is identified on the basis of the pressure progression P and not on the basis of the differential temperature ΔT. In the present case, the oil thermostat 10, the oil cooler 16, the oil filter 20, the filter service valve 21, the filter circumventing valve 22, the oil syphon 23 and also the sensors 14a, 15, 23 and 24 are structurally integrated in an oil module which is illustrated with the chain-dotted line 27.

[0082] Further embodiments of the invention are illustrated below with FIGS. 6 and 7. FIG. 6 first of all in turn illustrates part of an oil circuit, now in a schematized structural illustration. The reference sign 2 refers in turn to the oil pan and the reference sign 6 to the oil pump which conveys oil out of the oil pan 2 and supplies the oil to the oil thermostat 10. The reference sign 12 in turn refers to the first outlet of the oil thermostat 10 which supplies oil to the oil cooler 16 via the first flow branch 17. The reference sign 13 in turn refers to the second outlet of the oil thermostat 10, via which oil can be supplied to the bypass flow branch 18. In addition, FIG. 7 illustrates part of the cooling water circuit with a cooling water supply line 70, a region 71 which forms part of the oil cooler functionality and in which the cooling water flows around the meandering oil line of the oil cooler 16, and a line portion 72 via which the cooling water heated in the oil cooler 16 is removed. The reference sign 73 indicates merely in greatly schematized form the return of the oil back to the oil pan 2 after passing through the region of the internal combustion engine.

[0083] The reference signs 14a and 15 in turn denote the temperature and pressure sensors which have already been illustrated in FIG. 1 and are arranged in the first flow branch 17 after the first outlet 12 of the oil thermostat 10. Said temperature and pressure sensors are designed here in a structural unit as a combination sensor unit 14a, 15 which can be used both for measuring pressure and measuring temperature.

[0084] Instead of the combined oil pressure and temperature sensor 14a, 15 the function of the oil thermostat can also be monitored directly by means of a displacement sensor 81 in which a coupling rod 82 is directly mechanically coupled in terms of movement to the final control element 10b of the oil thermostat 10. According to this variant embodiment, the movement of the final control element 10b of the oil thermostat 10 is therefore directly detected by the displacement sensor 81 and output by the displacement sensor 81 to the evaluation device 40 via an output line 83. According to this variant embodiment, the evaluation device 40 is designed to diagnose a malfunction when the final control element 10b does not move when the opening temperature T1 is exceeded or in general when the temperature range between T1 and T1* is reached.

[0085] FIG. 6 illustrates yet another variant embodiment as an alternative to the use of the displacement sensor 81. Instead, an integrated switching circuit 80 can be provided in the interior of the oil thermostat 10, said switching circuit being designed to detect a position and/or movement of the final control element 10b of the oil thermostat 10 by means of integrated switching contacts.

[0086] In this connection, a switching contact of the switching circuit 80 is arranged at one end of the final control element 10b and detects a movement of a valve disk 10c of the final control element 10b when the latter moves in order to close or to open an outlet of the oil thermostat 10 and, in the process, comes into contact or out of contact with the switching contact.

[0087] Furthermore, the integrated switching circuit 80 is designed to extract its supply energy from the oil heat by means of what is referred to as an energy-harvesting switching circuit. Energy-harvesting switching circuits of this type are known per se from the prior art. Furthermore, the switching circuit 80 is designed to transmit its measurement signals wirelessly to the evaluation device 40 by means of a close range radio transmission. As a result, the integrated switching circuit can be completely encapsulated by the oil thermostat 10, and therefore no additional sealing elements, signal lines or energy supply lines have to be provided.

[0088] FIG. 7 illustrates two further variant embodiments of the invention which are in turn illustrated simultaneously in FIG. 7, but can each be used separately.

[0089] In contrast to the variants of FIG. 6, the movement of the final control element 10b of the oil thermostat 10 is now determined inductively either by means of an oscillating circuit with one coil 76 or by means of two coils 74 and 75.

[0090] According to a first variant, the sensor device comprises an electric oscillating circuit with a coil 76, wherein the coil 76 is arranged from the outside on the housing 10a of the oil thermostat 10. The coil here is arranged in such a manner that a movement of the final control element 10b of the oil thermostat 10, which final control element is designed magnetically, changes the inductance of the coil 76 and therefore an oscillation frequency of the oscillating circuit. The measurement signal of the oscillating circuit with the coil 76 is transmitted to the evaluation device 40 via a signal line 76a.

[0091] The evaluation device 40 can therefore in turn monitor the function of the oil thermostat 10 by determining on the basis of one of the aforementioned possibilities for determining a first parameter, from which the desired operation of the oil thermostat can be deduced, when a final control element of the oil thermostat 10 would have to move. On the basis of the detected frequency of the oscillating circuit, the evaluation device 40 can furthermore establish whether an anticipated movement of the final control element 10b is actually taking place at the anticipated time or whether, for example, the final control element is jamming and therefore no change of the oscillation frequency can be measured.

[0092] A further possibility for the contactless identification of the movement of the final control element 10b of the oil thermostat 10 is to design the sensor device in such a manner that a transmitter coil 74 and a receiver coil 75 are arranged on respectively opposite sides from the outside on the oil thermostat housing 10b or in the vicinity thereof. A movement of the magnetic final control element 10b of the oil thermostat 10 then changes a signal which is induced in the receiver coil 75 by the transmitter coil 74 and is transmitted to the evaluation device 40 via a signal line 75a. This change can in turn be diagnosed by the evaluation device 40, and therefore the presence of such a change of the signal received with the receiver coil correspondingly indicates a normal function of the oil thermostat. If, at the anticipated time according to the desired operation, no such change of the signal received by the receiver coil is measured, a malfunction of the oil thermostat 10 is present.

[0093] The invention is not restricted to the preferred exemplary embodiments described above. On the contrary, a multiplicity of variants and modifications are possible which likewise make use of the inventive concept and therefore fall within the scope of protection. In particular, the invention also claims protection for the subject matter and the features of the dependent claims independently of the claims referred back to.

LIST OF REFERENCE SIGNS

[0094] 1 Oil circuit [0095] 2 Oil pan [0096] 2a Oil sump [0097] 3 Oil level probe [0098] 4 Oil sump temperature sensor [0099] 5 Admission line [0100] 6 Oil pump [0101] 7 Pressure control valve [0102] 8 Non-return valve [0103] 9 Oil control line [0104] 10 Oil thermostat valve [0105] 10a Oil thermostat valve housing [0106] 10b Final control element [0107] 10c Valve disk [0108] 11 Inlet [0109] 12 First outlet [0110] 13 Second outlet [0111] 14a Oil temperature sensor [0112] 14b Oil temperature sensor [0113] 15 Oil pressure sensor [0114] 16 Oil cooler [0115] 17 First flow branch [0116] 18 Bypass flow branch [0117] 19 Oil line [0118] 20 Oil filter [0119] 21 Filter service valve [0120] 22 Filter circumventing valve [0121] 23 Syphon in the oil filter head [0122] 24 Oil temperature sensor [0123] 25 Oil supply to the internal combustion engine [0124] 26 Oil line [0125] 27 Oil module [0126] 40 Evaluation device [0127] 41 Signal input line [0128] 42 Signal output line [0129] 50 Temperature transition range [0130] 70 Cooling water supply line [0131] 71 Cooling water flow-around region [0132] 72 Cooling water removal line [0133] 73 Oil return [0134] 74 Transmitter coil [0135] 75 Receiver coil [0136] 75a Receiver coil signal lines [0137] 76 Oscillating circuit [0138] 76a Oscillating circuit signal lines [0139] 80 Integrated switching circuit [0140] 81 Displacement sensor [0141] 82 Coupling rod [0142] 83 Signal lines [0143] B Range of operationally hot inertia [0144] K Cold starting phase [0145] P Pressure progression [0146] ΔP Pressure swing (Peak) [0147] T1 First temperature threshold value [0148] T1* Second temperature threshold value [0149] T2 Admission temperature [0150] T3 Second oil temperature [0151] T3.1 Temperature gradient in the event of defective behaviour [0152] T3.2 Temperature gradient in the event of normal behaviour [0153] ΔT Temperature difference [0154] ΔT1 First threshold value [0155] ΔT2 Second threshold value [0156] Z1 Reaction period [0157] Z2 Thermostat opening range