DE102022106230B3 - Method for determining the aging of an oil and for indicating that an oil change is due - Google Patents

Abstract

The invention relates to a method for determining the aging of an oil in an oil circuit, taking into account the thermal load, using the Arrhenius approach. It is characterized in that the temperature is determined in at least two different sections of the oil circuit, after which the thermal load on the oil in the respective section is calculated based on the determined temperature, after which the values of the thermal load are calculated based on the volumes of the respective associated section of the oil circuit are summed up weighted. The invention also relates to a method for indicating that an oil change is due, for which purpose oil aging is determined according to the invention, with a warning being issued when a first limit value is reached and an estimated remaining running time until a second limit value is reached, and with a request for the Oil change is issued.

Description

The invention relates to a method for determining the aging of an oil in an oil circuit, taking into account the thermal load, using the Arrhenius approach. The invention also relates to a method for indicating that an oil change is due.

The invention relates to an oil in an oil circuit, in particular the oil in a retarder. In practice, it is usually the case that this retarder oil is replaced after the retarder has run for a fixed period of time, which is typically estimated based on the kilometers driven by the vehicle equipped with the retarder. For refinement, it can also be provided that this oil change interval is carried out depending on different quality classes of the oil and an assessment by the person using the vehicle with regard to the load on the vehicle during operation. All of this is imprecise and leads either to an oil change that is too early, which causes a waste of resources, or to an oil change that is too late, which can lead to damage to the components used in the oil circuit, in particular a retarder.

Also describes the EP 1 217 261 A2 an apparatus and a method for optimizing the time intervals for the oil change in a transmission. A physical variable of the oil or a variable linked to such a physical variable is used for this. This is measured accordingly. For example, the temperature can be used as a variable for estimating the aging of the oil. The scientific basis for this is the so-called Arrhenius approach, in which the aging of the oil can be estimated quite reliably using a corresponding formula based on the temperature.

Also describes the WO 2020/114 622 A1 a method for determining oil change intervals in an internal combustion engine, which essentially estimates the oil change based on learned curves.

For hydraulic media containing water is also from the DE 10 2017 124 099 A1 a method for determining a maintenance interval is known, in which the aging of the water-containing medium is estimated using a pH value, this pH value being predicted using temperature values, the calculation also being based on the Arrhenius model here.

From the DE10 2011 082 674 A1 a method is known for determining a point in time when an operating medium of a unit, in particular a hydraulic fluid of a transmission device, is changed. Depending on the current temperature (T_G, T_H, T_B) of the equipment determined at a defined point in time, a damage time (t_G, t_H, t_B) of the equipment that corresponds to the current temperature is determined by which a maximum period of time (t_max) up to a theoretical time of changing the equipment is reduced.

From the DE 10 2006 015 678 A1 a similar method for determining the point in time when a change is required for the operating media of a drive unit is known. The amount of damage is compared with the limit amount of damage and a necessary change of equipment is signaled at least when the limit amount of damage is reached for a specific temperature.

Furthermore, from the DE 10 2015 215 465 A1 a device for detecting an oil temperature of a transmission is known, the device being set up to store the oil temperature of the transmission measured by at least one temperature sensor together with a respective dwell time at the measured oil temperature on at least one memory element.

The object of the present invention is now to specify an improved method for determining the aging of an oil in an oil circuit, which allows a simple but relatively exact estimation of the oil aging. Furthermore, it is the object of the present invention to specify a method based thereon for indicating that an oil change is due.

According to the invention, this object is achieved by a method having the features in claim 1, and here in particular in the characterizing part of claim 1. With regard to the display of a due oil change, the solution is specified in claim 15.

The method according to the invention now uses the Arrhenius approach in order to determine the aging of the oil based on the thermal stress on the oil. Unlike in the prior art, no single measurement of an oil temperature is used here, but the temperature is determined within the oil circuit in at least two different sections. Then, based on the determined temperature, the thermal load on the oil in the respective section is calculated. The calculated values of the thermal load are then weighted and added up based on the volumes of the respective associated section of the oil circuit.

The method according to the invention therefore takes into account the temperature of the oil in various sections together with the oil volume present in this section within the oil circuit. If individual sections are exposed to very high temperatures but the oil temperature is significantly lower in other sections of the oil circuit that are much larger in terms of volume, this is taken into account in the method according to the invention and reduces the calculated oil aging. This makes the method for determining the aging of the oil much more precise, which leads to both economic and ecological advantages.

The volumes should preferably be known for each section at any point in time when the temperature is measured and can then be included directly. As an alternative to this, average volume distributions can also be assumed for at least some of the sections, or the volume can be assumed to be constant over time in at least one of the sections.

In principle, the oil temperature can be measured in the at least two different sections of the oil circuit using at least two temperature sensors. However, it can also be determined differently. Therefore, according to a very advantageous development of the invention, it can be provided that the temperature is measured at at least one point in the oil circuit and is determined in at least one of the sections using the measured value. This measured value can now lie within the sections and the oil circuit or can in principle also be a measured value outside of the oil circuit, for example in a cooling oil circuit a measured value from the area of the cooling medium cooling the oil, which flows through a cooling heat exchanger. The temperature in at least one of the sections, preferably in the area of all of the sections, can now be determined on the basis of this measured value, in order to minimize the effort with regard to the number of sensors as much as possible.

A further advantageous refinement of the method can also provide for the temperature in at least one of the sections to be determined from operating states of the oil circuit. For example, a pressure value, a speed value, a torque value or the like in the oil circuit or a unit that can be operated in the oil circuit, for example a feed pump, a retarder or the like, can be used for this.

Both based on a measured value and based on the operating state, it can now be provided, according to an extremely favorable development of the method according to the invention, that the temperature is determined either from the measured value and/or the operating state using characteristic curves, characteristic diagrams, a mathematical substitute model and/or by means a neural network, i.e. using artificial intelligence. For this purpose, for example, empirical values can flow into the characteristic diagrams or the mathematical substitute model, or self-learning systems in the form of neural networks that react to corresponding parameters in the environment can be set up in order to use operating states and/or measured values in the oil circuit or in the environment of the oil circuit to determine the temperatures in the at least two different sections of the oil circuit if they are not measured directly. In particular, this can be done in combination with a temperature sensor in the area of the oil circuit, so that there is a direct measured value for one of the sections and for the other sections the temperature values for the other sections can be reliably determined from this measured value and preferably supplemented from the operating states .

According to a very advantageous development of this idea, it can be provided that the determined temperature value is filtered using a low-pass filter in order to take into account the inertia of the system or the oil with regard to a temperature change and thus enable an even more reliable determination.

A further advantageous embodiment of the method according to the invention can now also provide that the volume of the respective section is based on design data. If it is known which line lengths with which line diameter are used and what volume any intermediate elements, aggregates or the like used hold, then the volumes of the individual sections can be calculated fundamentally, so that the values of the volumes used for weighting can be based on such design data.

According to an extraordinarily favorable further development, provision can additionally be made for the volume of the respective section to be adapted on the basis of the operating state of the oil circuit using at least one correction value dependent on this operating state. Such an operating state could be the pressure in the oil circuit, for example. Depending on the pressure distribution in the oil circuit, different amounts of oil will accumulate in the individual sections. These differences in the volumes in the respective area therefore depend on the operating state. Alternative to the pressure For example, the operating state can also include the speed of an oil pump or a retarder, a corresponding torque or the like. The operating state of a retarder, for example, between idling and full braking power, which can preferably be recorded as a continuous value, can also be used to determine how much oil is currently in which areas of the lines in the oil circuit and how much is stored in a collection container or oil sump is. This allows the oil quantity and thus the volume of the respective section that is relevant for the weighting of the oil aging to be reliably determined. For this purpose, too, a characteristic map can be used in particular, which takes into account at least the speed and/or torque of the retarder in the oil circuit.

According to a further extraordinarily favorable embodiment of the method according to the invention, it can also be provided that the calculation of the oil aging takes into account not only the thermal load but also a used oil portion remaining in the oil circuit when the oil is changed. In the case of typically structured oil circuits, it is always the case that these can never be completely emptied during an oil change. In general, a volume fraction of up to five percent, for example, which is known from the design of the oil circuit, is designed in such a way that it cannot be emptied when the oil is changed. After an oil change, a certain volume fraction of the oil then present in the oil circuit consists of used oil. This proportion can now be taken into account when calculating oil aging.

According to an extraordinarily favorable embodiment of this variant of the method according to the invention, it can be provided that the value of the oil aging present during the oil change with the volume proportion of the used oil remaining in the oil circuit in the total oil volume is used. Oil aging after the oil change can be adjusted using a factor based on these input variables.

Another very favorable embodiment of the method according to the invention can also provide that the content of catalysts, such as copper or iron particles, in the oil of the oil circuit is included in the oil aging. Such a content of catalysts, which can accumulate in the oil in the course of operation, can also have a certain influence on the aging of the oil, so that this content is also taken into account according to the advantageous embodiment of the method.

Furthermore, according to a very advantageous development of the method according to the invention, it can also be provided that the shearing forces that have occurred on the oil in the oil circuit also flow into the oil aging. Such shear forces, which can occur in an oil pump or a retarder, for example, can be estimated at least indirectly from the operating conditions such as the braking torque applied by the retarder in connection with pressures and/or speeds and also have an influence on oil aging.

The method is particularly suitable for oil that is free of water. For the purposes of the invention, oil which is free of water means that the oil has a volume fraction of less than 1% water, preferably less than 0.2% water. Typically, such an oil is then referred to as anhydrous. It can preferably be in an oil circuit which has at least one collecting volume, a retarder and an oil heat exchanger. The method is therefore particularly suitable for determining the oil aging of retarder oil, but can also be used analogously for other oils.

The method according to the invention for indicating that an oil change is due now uses this oil aging determined in one of the variants described above and adds this up during the operation of the oil circuit. As soon as the oil aging determined in this way reaches a first limit value, a pre-warning is issued together with an estimated remaining time until a second limit value is reached. If the second limit value is then reached by the accumulated oil aging, a request for an oil change is issued. The method according to the invention for determining oil aging can therefore preferably be used to optimize oil change intervals and accordingly indicate when an oil change is due or how much time is left for the oil circuit until an oil change is due.

Further advantageous refinements of the method according to the invention also result from the exemplary embodiments, which explain the methods in more detail below with reference to the figures.

• 1 eine schematische Ansicht eines Ölkreislaufs zur Erläuterung einer ersten möglichen Ausführungsform des erfindungsgemäßen Verfahrens;
• 2 eine Darstellung analog zu der in 1 zur Erläuterung einer weiteren Ausgestaltung des erfindungsgemäßen Verfahrens;
• 3 eine Darstellung zur Erläuterung der mittelbaren Bestimmung von Messwerten für das erfindungsgemäße Verfahren; und
• 4 eine schematische Darstellung einer Vorrichtung zum Errechnen eines fälligen Ölwechsels.

show:

• 1 a schematic view of an oil circuit to explain a first possible embodiment of the method according to the invention;
• 2 a representation analogous to that in 1 to explain a further embodiment of the method according to the invention;
• 3 a representation to explain the indirect determination of measured values for the method according to the invention; and
• 4 a schematic representation of a device for calculating a due oil change.

In the representation of 1 an oil circuit 1 is indicated schematically. In the exemplary embodiment shown here, this comprises a retarder 2, an oil cooler 3 and a collection container or oil sump 4. This oil sump 4 is connected to the retarder via a first line 5 and to a lubricating oil pump 7 via a second line 6, which has a bearing 8 of the Retarders 2 supplied with lubricating oil. This lubricating oil pump 7 is also used to circulate the idling mass flow, then via the retarder 2. The retarder 2 itself is then connected via a first return line 9 with a throttle point 10 and a check valve 11 as well as a bypass line 12 for this purpose to the oil heat exchanger 3, from which the oil returns via a line designated 13 to the retarder 2 and/or into the Oil sump 4 arrives. This structure is intended to symbolize the oil circuit 1 with a retarder 2 purely by way of example. The oil is an oil, also referred to as retarder oil, which is free of water within the meaning of the invention, i.e. in particular a water content of less than 0.2%, typically less than 0.05%, based on the total volume of the oil, having.

The retarder 2 is now used to brake a vehicle, not shown here, in particular a commercial vehicle. It can be continuously controlled between idling operation and a maximum braking power that can be applied by the retarder 2 . Depending on the braking power or braking torque in the area of the retarder 2, the oil heats up to different degrees in different sections of the oil circuit 1.

For the first variant of the method according to the invention, the oil circuit 1 shown here is intended to 1 now essentially be divided into two sections A, B, in which the oil will have different temperatures. The first section, labeled A, is shown in the illustration 1 surrounded by a dot-dash line and includes the cooler half of the oil heat exchanger 3, the lines 5, 6 and 13, the oil sump 4 and the area of the lubricating oil pump 7. In this area, the oil is relatively cooler compared to the other section B surrounded by a broken line , i.e. the retarder 2, the lines 9 and 12 and the warmer half of the oil heat exchanger 3.

ermittelt werden.In order to record the thermal load on the oil as precisely as possible and thus to determine the aging of the oil as precisely as possible, two different temperatures T _n are now determined, once in section A and once in section B of the oil circuit 1 . The thermal load on the oil in the respective section A, B is then calculated for both temperatures T _n for each determination time section Δt. A suitable formula can be based, for example, on what is known as the Arrhenius approach, which very generally describes a quantitative temperature dependency in physical and chemical processes and is therefore suitable for determining a temperature-related damage number for the oil. In addition, the volume of sections A, B is determined for the same determination time segment Δt. These thermal loads are then weighted for the same determination period Δt with the volume fraction of section A on the one hand and the volume fraction of section B on the other hand and added up. The sum of all determination time intervals Δt gives the damage number for the oil is referred to as C-Oil and can be calculated, for example, according to the formula $$\text{C}-\text{Oil}={\displaystyle {\sum }_{\text{i}}\left[\mathrm{\Delta }{\text{t}}_{\text{i}\text{, i}-1}*{\displaystyle {\sum }_{\text{n}}\left(\left({\text{V}}_{\text{n/i}}{\text{/v}}_{\text{total}}\right)*{\text{b}}^{\left(\left(\text{margin}\text{, i}\left[{}^{\circ }C\right]-\text{TRef}\right)/10\right)}\right)}\right]}$$

be determined.

• C-Oil: Schädigungszahl/Ölalterung
• Δt: Bestimmungszeitabschnitt
• V_n,i: Volumen des jeweiligen Abschnitts n und der jeweiligen Bestimmung i V_ges: Gesamtvolumen des Ölkreislaufs
• T_n,i: Temperatur des Öls in dem jeweilgen Abschnitt n und der jeweiligen Bestimmung i
• T_Ref: Referenztemperatur, hier z.B. 85°C
• b: Arrehnius Basis, z.B. 2i: Index der jeweiligen Bestimmung

mean:

• C-Oil: damage number/oil aging
• Δt: determination period
• V _n,i : volume of the respective section n and the respective determination i V _ges : total volume of the oil circuit
• T _n,i : temperature of the oil in the respective section n and the respective destination i
• T _Ref : Reference temperature, here for example 85°C
• b: Arrehnius basis, eg 2i: index of the respective determination

This makes it possible to determine the thermal load over the temperature and volume distribution at virtually any point in time in the oil circuit 1 via the determination in each of sections A, B and the summation weighted over the volumes. This enables a very precise determination of the aging of the oil by thermal effects.

In the representation of 2 essentially the same figure with the same components and reference numbers of the oil circuit 1 can be seen again. The only difference is here in that instead of the two sections A, B, a significantly larger number of sections is used here. For example, the cooler area of the cooling heat exchanger together with the lines 5, 6 and 13 and the lubricating oil pump 7 form the first area A. The oil sump 4 forms the second area B, the retarder together with the line 9 forms a third section C and the bypass line 12 on its own forms a section D. In this case, the method described above is refined in such a way that sections A, B, C, D are now taken into account accordingly and thus four individual sections of the oil circuit 1, in order to achieve that the "resolution" of the detection of the continuous thermal load is increased, i.e. it takes place in as many of the sections A, B, C, D as possible and thus the measured value is improved even further.

In addition to the thermal load, which is summed up via the volumes V _n of the individual sections A, B, C, D, including in particular the structural volume of the respective section A, B. C, D offset with a correction value based on the operating parameters of the retarder 2 for can be used.

In addition, it is the case that the temperatures T _n in the individual sections A, B, C, D do not necessarily have to be measured. Like a correction value for the corresponding volumes V _n of sections A, B, C, D, they can also be calculated using operating parameters. In particular, the operating parameter of the braking torque M can be continuously detected by the retarder 2 for this purpose. In addition to the braking torque M, the braking power, the pressure p in one or more specific sections A, B, C, D of the oil circuit 1 or a speed n can also be taken into account. These values then allow, for example, as shown in the representation of the 3 is shown based on the speed n and the pressure p, to determine the required values, such as temperatures T or volume V in the respective, desired sections via a characteristic map 14 or alternatively also via mathematical models or artificial intelligence in the form of a neural network. These values are then preferably each filtered by a low-pass filter 15 shown here, in order to take into account the inertia of the system or the oil with regard to a temperature change.

To determine the intervals until the next oil change, you can now display the 4 indicated oil maintenance computer 17 are used. This is connected via a CAN bus designated 18 to a block designated 19, which provides input signals at the time of the oil change. Oil aging can be reset here and potentially relevant parameters of the new oil, such as the exact type of oil, can be entered here. This is indicated purely by way of example by two data blocks labeled 20 and 21 within box 19 .

Further input signals indicated via the box 22 can be made available during operation. In particular, these can be relevant operating variables such as the braking torque M, speeds n, pressures p and temperatures T. The relevant temperatures T _n can thus be determined for the at least two sections A, B, C, D and the volumes V _n of the oil present at the same partial point t within these sections A, B, C, D can be taken into account via the operating variables.

If the oil type is now entered via box 19 and the oil aging is reset when the oil is changed, the oil aging or stress can be calculated based on this data in the oil maintenance computer 17 continuously or from time to time using the temporarily stored measured values. Corresponding values can then be output via the CAN bus 18 via the output unit 23, for example the oil damage in percent in the box labeled 24 and a forecast of the mileage until the next oil change in the box labeled 25. Corresponding limit values can be stored for this in the oil maintenance computer 17, which on the one hand can output a warning for an oil change required shortly via a first limit value and also a request for this oil change via a second limit value. In between, a remaining mileage of the vehicle up to this oil change can be estimated and displayed, so that a person using the vehicle is correspondingly well informed, can estimate the oil aging well and can schedule the oil change at exactly the right time.

As already mentioned, other oil aging factors such as the influence of residual oil or used oil, which cannot be completely removed during an oil change, can be taken into account, as can the influence of catalysts, such as copper or iron particles, or the influence of the shearing forces acting on the oil in the oil circuit 1, particularly in the area of the retarder 2.

The influence of the used oil remaining in the oil circuit 1 during the oil change can be taken into account by a proportion of used oil after the oil change, which is due to the design, since the oil circuit 1 typically can never be completely emptied. and the aging of this waste oil dependent factor is formed and taken into account.

The influences of shearing can preferably be estimated via the load within the retarder 2, ie ultimately indirectly via the braking torque applied by the retarder 2. The proportion of catalytic converters in the oil can be measured or, preferably, estimated based on empirical values, for example via characteristic curves, characteristic maps.

Claims (10)

Method for determining the aging of an oil in an oil circuit (1) taking into account the thermal load using the Arrhenius approach, characterized in that the temperature (T _n ) in at least two different sections (A, B, C, D) of the oil circuit (1) is determined, after which the thermal load of the oil in the respective section (A, B, C, D) is calculated based on the determined temperature (T _n ), after which the values of the thermal load are calculated based on the volumes of the respective associated section ( A, B, C, D) of the oil circuit (1) are summed up in a weighted manner, the temperature (T _n ) being measured at at least one point in the oil circuit (1) and in at least one of the sections (A, B, C, D) is determined on the basis of the measured value, and that the temperature (T _n ) is determined from the measured value and/or the operating states using characteristic curves, characteristic diagrams (14), a mathematical substitute model and/or by means of a neural network, with the esp timmte temperature value (T _n ) is filtered via a low-pass filter (15). procedure after claim 1 , characterized in that the volume of the respective section (A, B, C, D) is based on design data. procedure after claim 2 , characterized in that the volume of the respective section (A, B, C, D) is adjusted based on the operating state of the oil circuit (1) by means of at least one correction value (kv) dependent on this operating state. Procedure according to one of Claims 1 until 3 , characterized in that at least one variable operating state of the oil circuit (1) is detected and, via a characteristic map (14), which takes into account at least the speed (n) and/or the torque (M) of an oil pump or a retarder (2), in which Determination of temperature (T _n ) and volume is used. Procedure according to one of Claims 1 until 4 , characterized in that in the calculation of the oil aging, in addition to the thermal load, a used oil portion remaining in the oil circuit (1) during an oil change is taken into account. Procedure according to one of Claims 1 until 5 , characterized in that the content of catalysts in the oil of the oil circuit (1) is included in the oil aging. Procedure according to one of Claims 1 until 6 , characterized in that the shear forces occurring on the oil of the oil circuit (1) flow into the oil aging. Procedure according to one of Claims 1 until 7 , characterized in that the oil is free of water. Procedure according to one of Claims 1 until 8th , characterized in that the oil circuit (1) comprises at least one collecting volume (4), a retarder (2) and an oil heat exchanger (3). Method for indicating that an oil change is due, including oil aging according to one of Claims 1 until 9 is determined, wherein when a first limit value is reached, a warning and an estimated remaining time until a second limit value is reached is output, and when a second limit value is reached, a request to change the oil is output.

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