AT510327A1 - METHOD AND DEVICE FOR STATE ESTIMATION OF AN OIL SENSOR OIL - Google Patents

Description

HAON / l 3 / -SEP / 2010 17:16

WESTPHAL, MUSSGNUG & PA FAX No.: +49 89 54403080 S, 004

GUN004AT

description

Method and device for state-heating an oil for an oil sensor 5

The present invention relates to a method and an apparatus for determining the oil condition by means of a number of physical parameters, for example for determining the degree of soiling, aging, oxidation and viscosity.

Lubricating oils are among the most important technical lubricants. Essentially, a distinction is made between machine, engine, transmission, chain and hydraulic clamps as well as oils for precision-15 technical devices and cooling lubricants.

Engine oils are indispensable in internal combustion engines, for example, since they provide lubrication to all moving parts of the engine, thus reducing mechanical friction by forming a sliding film between moving surfaces. In addition, motor oils are responsible for ensuring the heat dissipation of thermally stressed moving parts that are not reached by the coolant. 25

The problem underlying the invention is that the condition of lubricating oils, especially when used in motors worsened over time. However, the invention is not limited to engine oils. As a natural product, oils react in an oxidation reaction with atmospheric oxygen, which is generally referred to as "natural aging". referred to as. As a result, for example, the viscosity of the oil changes, which can lead to a break in the lubricating film. 13/09 2010 MO 17:16 [SE / EM NR 5167] @ 004 MON / 13 / SEP / 201Ο 17:16

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Contaminants, for example, by atmospheric dust particles or microscopic metal chips resulting from mechanical abrasion, which reduce the lubricity, whereby the friction in an engine, for example, 2unimmt. 10

If the condition of a lubricating oil changes, for example due to natural aging or contamination with premodern particles, they can no longer reliably ensure lubrication and cooling, which is why an oil change must be carried out unconditionally. 15

It is an object of the present invention to provide a method and a device for the simplest possible monitoring and assessment of the oil condition, in particular to provide information about the need for an oil change in critical oil condition. 20

The invention achieves the object by a method according to independent claim 1. Illustrative exemplary embodiments are the subject of the dependent claims. 25

A method for determining the oil condition is disclosed. According to an example of the invention, (step A) is set a set of physical parameters (e.g., temperature, turbidity, water content, conductivity, relative permittivity, etc.) representing the oil condition. For each of these physical parameters, a reference value is determined which represents a setpoint for the respective physical parameter at a reference time (2.B., immediately after an oil change). A measure (step B) representing the oil state is initialized to a reference value (eg, zero). Further, (step C) is determined for each physical parameter at particular sampling times each time. *** " ] @ 005 MON / 13 / SEP / 2010 17:16

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* * 4 * * * «« i * * * * because a reading was taken. Depending on the corresponding measured value and the associated reference value (step D), an influencing variable determining the oil state is determined. The measure representing the oil state is incremented by 5 (step E) by the value of all the influencing variables and by an influencing quantity representative of the time (e.g., operating hours) so as to update the measure of the oil condition. Finally (step F), steps C, D and E are repeated after a predetermined time period (e.g., 10 one sample interval) has elapsed since the last sampling time.

Although it may be convenient to carry out steps A to F in the order indicated by the reference numerals, this is not absolutely necessary.

The measure for the oil condition is incremented after each pass of steps C, D, and E by the sum of the predictors calculated from the physical parameters so that the score increases with each pass through the loop, indicating a change in oil condition degradation matches over time. Thus, in a relatively simple and thus robust manner, a quantification of the oil state allows, which is an advantage over the conventional methods 25, which often only take snapshots of the oil condition for its assessment.

According to an exemplary embodiment of the method presented above, at least two threshold values can be defined for the measure 30 describing the oil condition. For example, the thresholds can be determined experimentally for different oil types and applications. If the figure reaches or exceeds a first (the lower) 13/09 2010 MO 17:16 [SE / EM NR 5167] 0006 0¾

EP / 2010 17:16 WESTTHAL, MUSSGNUG & PA GUN004AT FAX N °: +49 89 54403080 • · · * p. 007 4 • fr »* • · i · • fr ·« ·· »« threshold, sc this will open signaled suitable way. If a second (upper) threshold value is exceeded, this can also be signaled by a corresponding alarm signal. For example, when the second threshold is exceeded, the condition of the oil is so poor that the machine should no longer be operated without first performing an oil change.

The metric representing the oil condition may be determined at discrete times and each logged in a suitable memory, e.g., flash or EEPROM memory, prior to incrementing. The metric can be used together with the measured values for the physical parameters used and a corresponding " Time-15 pel " stored in a memory, so that later information about the change or deterioration of the oil condition over time can be queried and evaluated.

The measure is determined from physical parameters that represent the oil condition. At least one of the following parameters can be used: the temperature, the turbidity, the electrical conductivity, the relative permittivity or the water content b2W. the humidity as well as the dynamic and kinematic viscosity. 25

It is not mandatory to set two thresholds for the measure describing the oil condition. However, two thresholds offer the possibility to define three oil states, for example 30 - a first harmless oil state {measure is less than the first, lower threshold), 13/09 2010 MO 17:16 [SE / EM HR 51G7] @ 007 MON / 13 / SSP / 2010 17:16

WESTPHAL, MUSSGNUG & PA FAX No.: +49 89 54403080 mm ♦ · * ♦ • ♦ S, 008

GUN004AT - a second bad oil state (measure is greater than the first threshold, but less than the second, upper threshold), and - a third critical oil state (measure is greater than the second threshold) at which an oil change urgently.

It may in some cases be quite useful to define even more oil conditions, which requires additional thresholds. The present inventive method is not limited to two thresholds (and thus three oil states). Once the oil change has been carried out, the metric is reset to a reference value, the reference value usually being zero. 15

The dimensional state representing the oil state is determined via various influencing variables, which are calculated from corresponding physical parameters. Each influencing variable may e.g. are formed from a linear and an exponential term. As a result, a linear and an exponential contribution to the corresponding large influence of each physical parameter can be mapped. In addition, a weighting coefficient is assigned to the linear and exponential term of each influencing variable in order to be able to weight the contributions to the measure. The weighting coefficients for each factor are determined experimentally, for example, depending on the type of oil and the application.

For the realization of the oil sensor, a suitable device 30 is necessary, which has an evaluation unit, which is designed to carry out the method described, in particular the method according to the patent claim 1. 13/09 2010 KD 17:16 [SE / EM NR 5167] @ 008 MON / 13 / SEP / 2010 17:16

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In particular, the device has sensor units which are suitable and designed to measure the physical parameters dependent on the oil state and characterizing them, from which subsequently the corresponding flow variables and finally the dimension describing the oil state can be calculated. In addition, the device has a display unit which is adapted to indicate the oil condition, in particular signaling whether the oil is in a safe, still acceptable state or already in a critical state. The signaling can be done optically or acoustically or in both ways.

The oil sensor may be designed such that it can be fastened, for example, in the outlet opening of an oil container or an oil sump or an oil-carrying line. Frequently, the outlet openings are threaded, so that they can be closed with a screw plug. The device may be designed such that it closes the outlet opening of an oil pan instead of a closure screw. On the one hand, this offers the advantage that the oil sensor is easy to assemble and, on the other hand, that the condition of the lubricating oil can be queried at any time during operation of the machine, which is supplied with lubricating oil. 25

The present invention will be explained in more detail with reference to the embodiments illustrated in the figures. It shows

FIG. 1 shows an exemplary spatial representation of the oil sensor according to the invention;

Figure 2 is a schematic representation of the major components of the oil sensor, 13/09 2010 MO 17:16 [SE / EM NR 5167] @ 009 89 54403080 p. 013 * * 9 * * i «4 · ·» · 4 < X0N / 13 / SEF / 2G10 17:16 WESTPHAL, MUSSGNUG & PA FAX No.: +49

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3 shows a diagram of the method according to the invention for determining the oil condition, and FIG. 4 shows an exemplary circuit with a differential amplifier for measuring the electrical conductivity.

The drawings are intended to illustrate the present invention in its preferred embodiments, but are not to be taken in any limiting sense. In the figures, like reference numerals designate like or similar components of similar meaning.

In Figure 1, the oil sensor 100 is exemplified in a perspective view. FIG. 2 shows the most important components of the oil sensor 100 and their functional interaction in a schematic representation. The oil sensor 100 essentially has a sensor housing 110, a fastening means 130, a housing 140 for accommodating an evaluation unit 220 and a display unit 150. 20

In the sensor housing 110, sensor elements 210 are arranged, which are designed to detect physical parameters which depend on the oil state and therefore describe or represent it. Which physical parameters come into question will be explained in more detail below. The sensor housing 110 is immersed during operation in the oil, which is usually located in an oil pan. The sensor housing 110 is usually designed so that complete wetting is ensured with the oil to be measured in all 30 operating states. In order for the sensor elements 210 in the sensor housing 110 to come into contact with the oil, openings 120 are provided in the sensor housing through which the oil can pass. The openings 120 may be made in accordance with a 13/09/2010 MO 17:16 [SE / EM NR 5167] @ 010

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Execution be realized in the form of uniformly or non-uniformly distributed over the sensor housing 110 bores.

In a further embodiment of the invention, the sensor housing 110 may be designed as a sieve. An advantage of a sensor housing 110 designed as a sieve is, in particular, that on the one hand the formation of air bubbles is prevented and on the other hand particles that are too large are kept away from the sensors. It may also be expedient that the sensor housing 110 is cylindrically shaped. 10

The sensor housing 110 has a mounting side, on which a fastening means 130 is arranged. The attachment means 130 may be e.g. be cylindrical in shape and have an external thread. This allows the oil sensor to be screwed into the outlet port of an oil pan instead of a plug.

Furthermore, the oil sensor 100 has a housing 140, in which an evaluation unit 220 is housed. The housing 140, for example, also offers space for one or more energy stores, in particular at least one electrochemical energy store (battery), so that the oil sensor can operate autonomously, ie independently of an external power supply. 25 in the housing 140 is further housed an externally visible display unit 150, which serves to indicate the oil condition at any time. In the case of a battery supply, it is advantageous to save energy. Therefore, on the housing 140, a button can be arranged, which serves to turn on the on-display unit 150 on request or off. In particular, the pushbutton can only be provided for temporary switching on of the display unit 150 in order to ensure the longest possible service life in the event of a self-sufficient power supply. 13/09 2010 MO 17: 16 [SE / EMN 5197] @ 011 p

WESTPHAL, MUSSGNUG & PA FAX No.: +49 83 54403080

GUN004AT 9 10 15 20 25 nes or more energy storage. In addition, an interface 170 may be mounted on the housing 140, which is suitable for programming the evaluation unit 220 and / or for connecting it to an external power supply and / or to connect it to a bus system in order to make the quantitatively determined oil condition accessible to external devices. The interface 170 may also be a known RS485 signal transmission interface that allows for ongoing computerized monitoring of the oil condition, for example, for use in an SP $ (Programmable Logic Controller). The use of a wireless interface (e.g., a known GSM or 2igBee interface) is also conceivable. It should be noted at this point that any further suitable interface can be used. The Qizustand can be queried via the display unit 150. In general, a distinction is made between a harmless, a degraded (but still acceptable) and a critical oil condition. For signaling the oil condition, the display unit may be in the manner of a traffic light outlet. Accordingly, if the oil condition is safe, a green LED will illuminate an orange or yellow LED if the oil is in a degraded, still acceptable condition, but needs to be replaced shortly, and a red LED if the oil condition is critical and Oil must be changed immediately in any case.

FIG. 2 schematically shows that the sensor elements 210 and the display unit 150 are controlled, managed and evaluated by the evaluation unit 140. The e-nergy supply and other electronic components, such as 13/09 2010 MO 17:18 [SE / EM NR 5187] ®012 ιίΟΝ / 13 / SEP / 2010 17:17

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GUN004AT 10 • i «• * e. Amplifier circuits may be in the evaluation unit o-the outside angeord.net.

At least two of the following parameters can be used as physical parameters R for the mood of the oil state according to the invention; the temperature T, the turbidity E, the electrical conductivity p, the relative permittivity, the water content or the (relative) humidity rH of the lubricating oil, the dynamic viscosity μ and the kinematic viscosity. For each parameter used R = {T, E, p, ε £, rH, μ, v, ...} a suitable sensor is provided in each case. It should be noted that the formula symbol for the relative humidity is not fixed. The relevant literature also contains, for example, cp, f, U, 15 rH or rF. In the following, the relative humidity should be designated rH.

The permittivity number εΓ of the oil is essentially influenced by the water contained in the oil, so that the permittivity of the oil is representative of the amount of water contained in the oil. In one embodiment of the present invention, an additional (e.g., micromechanical) sensor may be provided to directly determine, in the oil, its relative humidity, RH, relative to the total volume of the moisture laden oil. This makes it possible to differentiate between the permittivity and the moisture measurement of the oil by means of two sensors, so that the measurement results obtained from the permittivity and the moisture measurement can also be weighted differently when determining the dimension Q. This can be advantageous in certain applications. 13/09 2010 MO 17:16 [SE / EM NR 5167] 0013

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WESTPHAL, MUSSGNUG & PA FAX Nos.: + 49 89 54403080 l 014 11> i 4 4 4 · · * 4 «* 4 • 4 t · · · · · * *« * * i * «4M« · > ·

The sensor for additional moisture measurement of the oil may be a known capacitive sensor. Such sensors can be integrated, for example, on silicon chips, whereby a design as a microsystem (English: microelectromechanical 5 system, short: MEMS) and thus the space-saving arrangement in the oil sensor according to the invention is possible.

FIG. 3 shows a block diagram 300 of the method according to the invention for oil state administration, 10

The oil sensor 100 according to the invention is immersed in fresh oil which is in a safe state. Then, reference parameters R0 = {To, S0, po, s ro, bHo, μο, v0,. .. > 3, step 3101 for fresh oil to the set of 15 physical parameters, R = {T, E, p, εΣ, rH, μ, v, ...} determined and in a suitable memory, for example is stored in the evaluation unit 220. Also stored are weighting coefficients pi, p2 with which the physical parameters R are weighted in the method 20 These weighting coefficients are essentially dependent on the type of oil and the respective application and are determined experimentally beforehand (cf. 3, step 320) It should be noted at this point that, in particular in the case of a large number of applications that remain the same, the reference parameters Ro can also be determined and made available in advance by reference measurements by the manufacturer of the oil.

Furthermore, a time step At fixed-30 is set via the evaluation unit, which determines the period of time which elapses between the measurement (see Fig. 3, step 330) of a set of physical parameters R. The measurement of the reference parameters R0 is performed only at the time to (or the reference 13/09 2010 MO 17:18 [SE / EM HR 51G7] @ 014

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• • • parameters R0 are known from the beginning). A first measurement (see Fig. 3, step 330) of the set of physical parameters R is made at time t "to + At, a second measurement for example at time t = to + 2 * At and so on. 5

From the weighting coefficients pi, p2, the reference parameters R0 for fresh oil and the measured physical parameters R are corresponding influencing variables ξκ the

Form 10 (1) pi- (R-Ro) tp2 * exp (R-Rq) is calculated (see Fig. 3, step 340), where pi is a linear contribution and P2 is an exponential contribution of each of the physical parameter R , Ro weighted. For each physical parameter from the set R, an influencing variable ξκ is calculated according to the above formula, wherein all influencing variables ξκ that are greater than zero are added to a measure Q representing the oil state (see FIG. 3, step 350). It should also be noted at this point that the weighting coefficients pi, p2 can be different for each of the physical parameters R used (temperature T, permittivity ε, etc.). In the above equation 1, R and Ro are each only placeholders for the respective physical parameter (T, 25 ε,...) Or for the respective reference parameter (T0, ε0,

The sought dimension Q representing the state of the oil is then calculated as follows: Q [t0 + (n + 1) * At] = Q [t0 + n-At] + (ξτ [t0 + (n + 1) * At] + (2) + ζε [to + (n + 1) At] + + ξε [to + (n + 1) · At] + 13/09 2010 Mon 17:16 [SE / EM MR 5167] @ 015 30 N / 13 /S.EP/201Ü 17:17

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GUN004AT * 13 * * «* 4 9 * * · · · * *« * · · · · * * ♦ · ·· * ·· * · »»! +. , , + ξϋΐηΐί)

In this case, the influencing variable ξΐίπιβ depends on the time At which has elapsed since the last measurement (that is, on the sampling time Δt). The measure Q at time t0 {e.g. Oil change) is initialized to a reference value, e.g., Q [to] = 0.

In the embodiment of the invention shown in Figure 3, there are two thresholds Q: and Cb, where Qi-] 0; Qz [, for the metric 10 Q and hence the oil states - harmless for Q <Q1, - degraded for Ql ^ Q <Q2 and - critical for Qa: Q2 15 (see Fig. 3, step 360). In the safe state a green LED lights up, in the bad one an orange and in the critical one a red one (see Fig. 3, step 370). It is also conceivable that when the critical state 20 is reached, an additional acoustic warning signal sounds. Like the physical reference parameters Ro, the thresholds for the measure Q are determined in advance for certain types of oil and applications. 25 If there is no oil change (see Fig. 3, step 380), then a new measurement (see Fig. 3, step 330) of the physical parameters R, temporally spaced by At from the previous measurement. The influencing variables ξκ are newly determined (cf. FIG. 3, step 340) and for. old value of the measure -30 number Q is added, so that the measure · Q is incremented by the sum of the influencing variables ξκ. Based on the measure Q and the threshold values Qi, Q2, the oil condition is displayed again. 13/09 2010 MO 17:18 [SE / EM NR 5187] @ 016 W13 / SEP / 2Ü10 17:17

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Referring to Figure 3, an iteration loop includes steps 330, 340, 350, 370, and 380 being run through until an oil change (step 380) must be performed because Q is the threshold Qz, which was a critical oil implied, reached or exceeded.

When an oil change is performed (see Figure 3, step 380), the metric Q is reset to zero (step 390) and, if necessary, the reference parameters Ro are redetermined. As long as no oil change (step 380) is necessary, the iteration loop, consisting of steps 330, 340, 350, 370 and 380, is traversed at time intervals Δt.

The method 15 shown in the block diagram 300 in FIG. 3 is implemented, for example, in the evaluation unit 220 with the aid of a signal processor or a microcontroller.

Another aspect of the present invention is schematically illustrated in FIG. FIG. 4 shows a measuring unit 400 for measuring the electrical conductivity p of the lubricating oil. The electrical conductivity is one of the physical influencing parameters R. The illustrated four-stage measuring unit 400 essentially has a first stage 410, via which an input signal 401 can be switched through, a second stage 420 which amplifies the through-connected input signal 401, a third stage 430 switching between two inputs of a fourth stage 440, the fourth stage being a differential amplifier. The input signal 401 is present before-30 as electrical voltage and is supplied for example by a sensor with a suitable measuring geometry 413. An output signal 402 of the measuring unit 400 represents the electrical conductivity p. 13/09 2010 «0 17:16 [SE / EM NR 5167] @ 017 .0N / 13 / .SEP / 2Q10 17:17

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The input signal 4D1 provided by the first stage 410 is applied to the second stage 420, especially when a first digitally controlled switch 5 412 in the first stage 410 is closed. In this case, the voltage provided by a voltage source 411 is applied to the measurement geometry 413. The measuring geometry of the conductivity sensor 413 may be listed, for example, as a capacitive conductivity sensor, is arranged at the measured 10 lubricating oil between two plates.

Each electronic circuit, including those arranged in the measuring unit 400, is subject to errors due to temperature fluctuations. An input signal 401 is affected by the temperature fluctuations 15 with a considerable thermal error, which would distort the output signal 401.

Therefore, in a first step, the input signal 401 is blocked by the first stage 410 of the circuit. The digi-20 tale switch 412 is open and the conductivity sensor 413 provides no input signal 401 to the second stage 420. At a first input of the differential amplifier 410 (the fourth stage) is based solely on the thermal error in a capacitor 403 parallel to the first 25 input is stored. A second digitally controlled

Switch 414 must be closed for this purpose. After the thermal fault is stored in the capacitor 403, the switch 414 opens. In a second step, the first stage 410 turns on the input signal 411, with the input 30 signal 401 in the measuring unit 400 having the thermal fault. The first switch 412 is closed. The switch stage 430 switches the input signal 401 to a second input of the differential amplifier 440, in which a 13/09 2010 MO 17:16 [SE / EM NR 5167] @ 018) Ν / ί 3 / & EP / 2010 17:17

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GUNQ04AT * * * * * * * * * «* * *« * ** «« «···· *« »* * * -j ^ g * * * * * *« ** »« third digital controlled switch 415 is closed.

The second switch 413 is open in the rule. At the differential amplifier 440 is thus at a first input of the capacitor stored in the capacitor 403 thermal error and at 5 a second input the input signal 401 afflicted with the thermal error, the erroneous input signal 401 are stored in a second capacitor 404 in parallel to the second input of the differential amplifier can. The differential amplifier 440 forms the difference between the signals present at its two inputs. As a result, the thermal error is eliminated and the output signal 402 maps the electrical conductivity p of the oil with sufficient accuracy and without errors due to temperature fluctuations in the electronics of the measuring unit 400. 15

The digitally controlled switches 412, 414 and 415 can, moreover, be controlled via the "microcontroller" arranged in the evaluation unit 140. The dynamic viscosity μ and the static viscosity v can be measured, for example, by known inductively excited membranes. The excitation frequency can be in a range of approximately f = 0.1 kHz to 5kKz.

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GUK004AT 17 *

In the following, the above-explained method for determining the state of an oil is summarized again: 5) determining a set of physical parameters / representing the oil state and measuring a reference value for each physical parameter; B) initializing a measure (Q) representing the oil condition to a reference value (Q = 0); C) taking a measured value for each physical parameter at specific sampling instants (t0, to + Δt, t0 + 2-ht, D) determining an influencing variable determining the oil condition rr.it for each measured physical parameter as a function of the corresponding measured value and the associated reference value; E) incrementing the measure (Q) by the added value of all the influencing variables and by the value of an influencing variable (ai * s) representing the time (i.e., the operating hours). 13/09 2010 MO 17:16 [SE / EM NR 5167] @ 020

Claims (29)

, 0N / 13 / SEP / 2010 17:17 WESTPHAL, MUSSGNUG & PA FAX no.: +49 89 54403080 p. 021 SUN004AT IS * f «· Patent Patent Patent claims 5 IC 15 20 25 l. A method of determining an oil condition comprising the steps of: (A) determining a set of physical parameters representing the oil condition and measuring a reference value for each physical parameter; (B) initializing a measure (Q) representing the oil state to a reference value (Q-0); (C) taking a measured value for each physical parameter at specific sampling times (t0, t0 + Att to + 2 * At (D) determining an influencing variable determining the oil state for each measured physical parameter as a function of the corresponding measured value and the associated reference value; (E) incrementing the measure (Q) by the added value of all the influencing variables as well as by the value of an influencing variable (ai'At) representing the time. A method according to claim 1, further comprising the step of: {F) repeating steps C, D and E after elapse of a predetermined period of time (At) since the last sampling time. 3. The method according to claim 1 or 2, further comprising the steps of: - comparing the current measure (Q) for the Ölzu- 30 stood with a first threshold (Qi); Signaling when the current oil level condition (Q) reaches or exceeds the first threshold (Qi). 13/09 2010 M0 17:16 [SE / EM NR 5167] @ 021 N / 13 / SSP / 20IQ 17:18 WESTPHAL, MUSSGNUC & PA FAX No.: +49 89 54403080 p. 022 * «· · · * * · GUN004AT • I t «· · ·« · · ·· * 19 · * 4. The method according to claim 3, further comprising the steps of: - comparing the current measure (0) for the oil supply with a second threshold (Ck); Signaling when the current oil condition metric (Q) reaches or exceeds the second threshold (Q2). 5. The method according to any one of claims 1 to 4, wherein the time-representing influencing variable (ai'At) depends on the time that has elapsed since the last measurement. 6. The method according to any one of claims 1 to 5, wherein the amount of the oil state influencing and characterizing physical. Parameters include at least one of the following: temperature (T), turbidity (E), electrical conductivity 20 (σ), relative permittivity (sr) or water content or relative humidity (rH), dynamic viscosity (μ), kinematic viscosity (v) , 25 7. The method according to any one of claims 1 to 6, wherein in an oil change, the current measure (Q) is set back to a reference value (Q = 0). 8. The method according to any one of claims 1 to 7, further comprising the step of: - Checking whether all factors are greater than or equal to zero. 13/09 2010 MO 17: 1G [SE / EM NO 51G7] @ 022 30 ION / 13 / SEP / 2010 17:18 WESTPHAL, MUSSGNUG & PA FAX No.: +49 8S 54403080 p. 023 GUN004AT ** 2σ * 9. Method according to one of claims 1 to 8, wherein the contribution of the individual parameters determined from the physical parameters to the measure (Q) is weighted by suitable empirical weighting coefficients. 10. The method according to any one of claims 1 to 9, wherein the physical parameters and / or the influencing variables and / or the measure (Q) as a function of the time 10 representing influencing variable (ai-ht) is logged in an appro Neten memory. 11. The method according to any one of the preceding claims, wherein in addition to the measurement of the relative permittivity (es) 15 an additional measurement of the water content or the relative humidity (rH) of the oil takes place, and wherein the additional measurement result, the relative humidity of the oil characterized in the determination of the measure (Q) is included. 20 12. An apparatus for determining an oil condition, comprising the following components: sensor elements 210 for detecting oil state determining physical parameters, which are adapted to 25 to provide measurement signals; an evaluation unit 140 with a microcontroller or signal processor, which is designed to evaluate and process the measurement signals from the measurement units and to carry out a method for determining the oil content, the method comprising at least the following steps: (A) setting a quantity of 13/09 2010 MQ 17:16 [SE / EM NR 5167] @ 023 OOK / 13 / SEP / 2010 17:18 WESTPHAL, MUSSGNUG & PA FAX No: +49 89 54403080 p. 024 GUN004AT • «« • · · · · · · · · «21 - 5 10 15 20 25 nes reference value for each physical parameter; (B) initializing a measure (Q) representing the oil state to a reference value (Q = O); (C) taking a measured value for each physical parameter at specific sampling instants (t0, t0 + Δtr to + 2-Δt, (D) determining an influencing quantity influencing the oil state for each measured physical parameter as a function of the corresponding measured value and the associated reference value; E) Incrementing the measure (Q) by the added value of all the influencing variables as well as by the value of an influencing variable (ai * At) representing the time. 13. The apparatus of claim 11, wherein the sensor elements 210 are configured to measure an amount of the oil state affecting and characterizing physical parameters, the amount of these parameters comprising at least one of the following: temperature (T), turbidity (E), electrical Conductivity (σ), relative permittivity (ε ^), water content or relative humidity (rH), dynamic viscosity (μ), kinematic viscosity (v). 14, device according to one of claims 11 or 12, wherein the evaluation unit 140 has a memory for logging the physical parameters and / or the influencing variables and / or the measure (Q) as a function of the time-representing influencing variable (ai'At) and wherein this memory is a flash and / or EEPROM memory. 13/09 2010 K0 17:16 [SE / EM NR 5167] ®024 30! 0Η / 13 / ΞΕΡ / 2010 17:18 WESTPHAL, MUSSGNUG & PA FAX No.: +49 89 54403080 p. 025 GUN004A? 2? 15. The device according to claim 12 with a sensor element for measuring the electrical conductivity (c), wherein said sensor element comprises a sensor 413 and an amplifier circuit 400, said amplifier circuit 5 device 400 holds at least one differential amplifier 440 ent and wherein the sensor an input signal 401 provides. 16. The device according to claim 15, wherein the differentiation device stronger 440 of the sensor element has at least two inputs and wherein parallel to a first input, a capacitor 403 is connected. 17. The device according to claim 16, wherein a second capacitor 404 is connected in parallel to a second input of the differential amplifier. 18. Device according to claim 15, 16 or 17 with a sensor element which is designed to measure the electrical conductivity (σ) in at least two claws, wherein in a first step the input signal 401 from the sensor element via a first digital controlled switch 412 is blocked, wherein the thermal error is applied via a second digitally controlled ter switch 414 to the first input of the differential amplifier and wherein the error in the capacitor 403 of the first input of the differential amplifier 440 is stored. 19. The apparatus according to claim 18, wherein in a second step, the input signal 401 from the sensor 413 to a second input of the differential amplifier 440 via a third digitally controlled switch 415 on 13/09 2010 MO 17:16 [SE / EM NR 5167] @ 025 £ OH / 13 / SEP / 2010 17:18 GUN004AT WESTPHAL, MUSSGNUG & PA FAX #: +49 89 54403080 ♦ · · · · · 2Γ3 the second capacitor 404 is turned on while the second digitally controlled switch 414 is open, wherein the differential amplifier 440 is adapted to form from the input signal 401 and the stored thermal error, which at the two at the inputs of the differential amplifier capacitors 403, 404, a difference representing the electrical conductivity (p), and wherein the first and the second step can also be carried out in the reverse order 10. 20. Device according to one of claims 15 to 19, wherein the sensor is a capacitive sensor. 21. Device according to one of claims 12 to 20, comprising a sensor housing, a housing for accommodating the evaluation unit and a fastening means, wherein the fastening means is adapted to fix the device in an outlet opening of an oil pan to 20. 22. Device according to one of claims 12 to 21, pointing to a display unit, wherein the display unit is controlled by the evaluation unit and wherein the display unit is adapted to visually and / or acoustically indicate the oil condition. 23. The device according to claim 22, wherein the evaluation unit further comprises a red, a yellow or orange and a green illuminant, wherein the red illuminant indicates a critical, the orange or yellow one deteriorates and the green indicates a safe oil condition. 13/09 2010 MO 17:10 [SE / EM NO 5107] @ 026 MOW / 13 / SEP / 2010 17:18 WESTPHAL, MUSSGNUG & PA FAX No.: +49 89 54403080 P. 027 | »Ft ····· * ··» »·» ft · * · ft * · GUN004AT. *: 24. The device according to claim 23, wherein the bulbs are light-emitting diodes. 25. The apparatus of claim 21, wherein the sensor housing has evenly or non-uniformly distributed over its circumference openings which are large enough to allow the oil to flow therethrough. 26. The device according to any one of claims 12 to 25 with egg nem electrical energy storage for self-sufficient energy supply. 27. The device according to any one of claims 11 or 12, wherein the sensor element 15 for measuring the dynamic Viskosi (μ) and kinematic viscosity (v) has a low-frequency, inductively excited membrane. 28. Device according to one of claims 12 or 13, wherein 20 in addition to the sensor for measuring the relative permittivity (sr) another sensor for additional measurement of the relative humidity of the oil in Sensoxgehäuse (110) is arranged. 29. The apparatus of claim 28, wherein the additional sensor for measuring the relative humidity of the oil is a capacitive sensor integrated on a silicon chip. 13/09 2010 NO 17:16 [SE / EM NR 5167] @ 027