METHOD FOR DETERMINING A DEGREE OF LOADING OF A FILTER

Abstract

A method for determining a degree of loading on a filter medium of a filter device on a vehicle through which a fluid flows includes determining an operating characteristic of the filter device based on at least one operating quantity of the vehicle and comparing a predefined reference characteristic of the filter device with the operating characteristic. The degree of loading is derived from a result of the comparing step.

Claims

1. A method for determining a degree of loading on a filter medium of a filter device on a vehicle through which a fluid flows, the method comprising: determining an operating characteristic of the filter device based on at least one operating quantity of the vehicle; comparing a predefined reference characteristic of the filter device with the operating characteristic; and deriving the degree of loading from a result of the comparing step.

2. The method of claim 1, further comprising providing the reference characteristic with a reference filter constant at a predefined limit value of the loading, or providing the operating characteristic with an operating filter constant representing an operating state of the filter medium.

3. The method of claim 1, further comprising providing the reference characteristic with a pressure loss representing the filter medium based on a load, or determining the operating characteristic having a pressure loss of the filter medium during the vehicle operation.

4. The method of claim 1, further comprising determining the operating characteristic based on at least one of a temperature of the fluid and a rotary speed of a drive motor of the vehicle.

5. The method of claim 4, further comprising determining the operating characteristic based on at least one of a temperature-dependent density of the fluid, a temperature-dependent viscosity of the fluid, and a volume flow of the fluid that is dependent on the rotary speed of the drive motor of the vehicle or the temperature of the fluid.

6. The method of claim 1, further comprising: positioning the filter medium in a filter housing of the filter device with a filter inlet and a filter outlet; and determining the operating characteristic based on at least one of a pressure loss of the filter housing and a pressure loss of the filter device between the filter inlet and the filter outlet.

7. The method of claim 6, further comprising determining the pressure loss of the filter device between the filter inlet and the filter outlet by means of at least one differential pressure sensor or a pressure sensor.

8. The method of claim 6, wherein: the pressure loss of the filter device between the filter inlet and the filter outlet corresponds to a differential pressure of a differential pressure switch at its switching point, and the operating characteristic is determined based on at least one operating quantity during the switching point of the differential pressure switch.

9. The method of claim 8, wherein: the differential pressure switch has, before the determination of the operating characteristic, a switching state of at least two switching states, and the switching point at which the differential pressure switch is switched to a different switching state is reached during a change of a rotary speed of a drive motor of the vehicle.

10. The method of claim 9, wherein: detecting if the differential pressure switch has a target switching state before the change of the rotary speed of the drive motor; and if a deviating switching state is detected, changing an operating quantity of the vehicle at least until the target switching state of the differential pressure switch is established.

11. The method of claim 10, further comprising increasing a temperature of the fluid at least until the target switching state of the differential pressure switch is established.

12. The method of claim 1, wherein the fluid comprises an oil.

13. The method of claim 1, further comprising transmitting data representing the degree of loading to a receiving unit located external to the vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The above-mentioned aspects of the present disclosure and the manner of obtaining them will become more apparent and the disclosure itself will be better understood by reference to the following description of the embodiments of the disclosure, taken in conjunction with the accompanying drawings, wherein:

[0038] FIG. 1 shows a block circuit diagram with schematic representation of means for determination of the current degree of loading of a filter medium on a vehicle;

[0039] FIG. 2 shows a flow diagram with representation of the steps of the method for determination of the current degree of loading of the filter medium; and

[0040] FIG. 3 shows a reference curve for representation of the pressure loss of a filter medium in dependence on loading.

DETAILED DESCRIPTION

[0041] FIG. 1 schematically shows a utility vehicle 10 such as an agricultural vehicle (for example, a tractor), with means for determining a current degree of loading B.sub.F of a filter medium 12 of a filter device 14, which is disposed on utility vehicle 10 and through which a fluid, in particular an oil, flows. The filter device 14 has a filter inlet 18 and a filter outlet 20 on its filter housing 16.

[0042] A differential pressure switch 22 for detection of a differential pressure dp.sub.Diff is connected between the filter inlet 18 and the filter outlet 20 on the filter device 14. The differential pressure switch 22 can assume, away from its switching point, two different switching states, for example, a first switching state (e.g., with the switch electrically closed) and a second switching state (e.g., with the switch electrically open). The first switching state corresponds to a status signal S.sub.1, while the second switching state corresponds to a status symbol S.sub.2. These status signals are registered by a data processing unit 24.

[0043] In the embodiment shown in FIG. 2, the differential pressure dp.sub.Diff, which is present at the time point of switching (switching point) of the differential pressure switch 22 from the second switching state S.sub.2 to the first switching state S.sub.1, is relevant for the determination of a current degree of loading B.sub.F of the filter medium 12. It is advantageous when using the differential pressure switch 22 or, alternatively, a valve with a pressure switch, that the switching take place at a pre-established pressure difference, thus, the differential pressure dp.sub.Diff at the time of switching is known.

[0044] The temperature T of the fluid and the rotary speed n of a drive motor of the utility vehicle 10 during the vehicle operation are detected or monitored as operating quantities of the utility vehicle 10. For this a temperature sensor 26 and a rotary speed sensor 28 are present on utility vehicle 10. The signals of these sensors 26 and 28 are received by the data processing unit 24.

[0045] The signals of the sensors 26, 28 and the status signals S.sub.A, S.sub.NA and, optionally, the differential pressure dp.sub.Diff are processed in the data processing unit 24. In addition, the data processing unit 24 determines additional operating quantities or operating parameters such as, for example, a density p(T) of the fluid that is dependent on the fluid temperature T, a dynamic viscosity (T) of the fluid that is dependent on the fluid temperature T, a volume flow Q(n, T) of the fluid that is dependent on the rotary speed n of the drive motor of the utility vehicle 10 and on the fluid temperature T, a pressure loss dp.sub.G of the filter housing 16, a pressure loss dp.sub.F of the filter medium 12, an operating filter constant c.sub.F, and a reference filter constant, c.sub.F,ref. The degree of loading B.sub.F of the filter medium 12 is derived from these data and, optionally, additional data. The degree of loading B.sub.F is put into signal form in the utility vehicle 10 by means of a visual or acoustic display unit 30. The degree of loading B.sub.F is indicated, for example, as a percent indication of 0%-100%, as an indication of amount (for example in grams), or as a multistep visual bar representation. Through this, the vehicle operator or another user of the utility vehicle 10 can be regularly informed about the current degree of loading B.sub.F.

[0046] The degree of loading B.sub.F can also be transmitted from the data processing unit 24 to an external receiving unit 32, which is present outside of the utility vehicle 10, for example, at the vehicle manufacturer. The transmission and external evaluation of the degree of loading B.sub.F or even some of the other said data can contribute to dimensioning the filter device 14 or its individual components more accurately.

[0047] In accordance with FIG. 2, the start of the method takes place with the drive motor running, i.e., at a rotary speed n>0 (step S1).

[0048] In step S2 of the method, a test is made to see if the differential pressure switch 22 is in a state that deviates from the target state, i.e., if status S corresponds to the status signal S.sub.1. If this is the case (i.e., the differential pressure switch 22 is not in the target state), initially the fluid temperature T is increased during vehicle operation (step S3) until the differential pressure switch 22 enters its target state, i.e., the status S corresponds to the status signal S.sub.2. In this state an increase of the rotary speed n of the drive motor, for example, upon an acceleration of the utility vehicle 10 (step S4), causes, at a specific rotary speed level, the switching point of the differential pressure switch 22 to be detected, at which it again takes on a state with the status S=S.sub.1 (step S5). The values of the rotary speed n and the fluid temperature T at the time of the switching point are registered (step S6) and processed in the data processing unit 24 in order to determine an operating characteristic (step S7) and to compare said characteristic with a predefined reference characteristic, in order to derive a current degree of loading B.sub.F from the comparison result.

[0049] As an alternative to the said increase of the rotary speed n, in step S4 it is also possible to use a reduction of the rotary speed n to detect a switching point of the differential pressure switch 22.

[0050] When carrying out the method in step S4, a change of the rotary speed n during the ordinary working operation of the utility vehicle 10 is used, so that no separate process steps are necessary for the required change of rotary speed.

[0051] As an alternative to the differential pressure switch 22, a differential pressure sensor 23 or two pressure sensors can be used, as indicated in FIG. 1 by the dashed lines. In this case a change of the rotary speed n during the process sequence is not necessary. Rather, the current differential pressure dp.sub.Diff is continuously available by means of the differential pressure sensor 23 or the pressure sensors, so that the operating characteristic and, from it, the current degree of loading B.sub.F can be determined at different, or any, operating points of the differential pressure sensor 23 or the pressure sensors.

[0052] To determine a suitable operating characteristic, one can proceed from the following relationships:

[0053] The differential pressure dp.sub.Diff of the differential pressure switch 22 is approximately the sum of the pressure loss dp.sub.F of the filter medium 12 and the pressure loss dp.sub.G of the filter housing 16 according to

dp.sub.Diff=dp.sub.F+dp.sub.G (1).

[0054] The pressure loss of the filter housing dp.sub.G during flow through the filter housing 16 can approximately be considered to be the sum of a turbulent flow share c.sub.turb.Math.p(T).Math.Q.sup.2 and a laminar flow share c.sub.lam.Math.(T).Math.Q, according to

dg.sub.s(p,, Q)=c.sub.turb.Math.p(T).Math.Q.sup.2+c.sub.lam.Math.(T).Math.Q (2),

[0055] where c.sub.turb and c.sub.lam are specific constants for the filter housing 16 and Q is the volume flow (for example in liters/minutes) of the fluid.

[0056] The pressure loss dp.sub.F of the filter medium 12 can be described by a linear relationship between the volume flow Q and the pressure loss dp.sub.F according to

dp.sub.F(, Q)=c.sub.F.Math.(T).Math.Q (3).

[0057] Solving equation (3) with the operating filter constant c.sub.F and taking into account equation (1) gives

c.sub.F=1/(T).Math.1/Q.Math.(dp.sub.Diffdp.sub.G) (4).

[0058] For the temperature-dependent density p(T) of the fluid, one can assume a linear relationship according to

p(T)=p(15 C.)a.Math.(T15 C.) (5)

[0059] where the fluid density p (15 C.) at 15 C. and the correction value a can be taken from characteristic maps or tables. The temperature-dependent fluid density p(T) can be determined in this way.

[0060] A linear relationship can be assumed for the temperature-dependent dynamic viscosity (T) of the fluid according to

(T)=p(T).Math.v(T) (6),

[0061] where v(T) is a kinematic viscosity of the fluid that is dependent on the fluid temperature and is known for the relevant fluid from the corresponding characteristic map or table values or even taking into account the Ubbelohde equation.

[0062] The current volume flow Q or Q(n, T) of the fluid in dependence on the rotary speed of the engine n and the fluid temperature T can likewise be taken from a characteristic map or the like. For example, an efficiency map (volumetric efficiency) of the relevant fluid pump at the existing back pressure of the fluid pump can be created in dependence on the fluid temperature T and the engine speed n. In the case of a highly varying back pressure and a pronounced dependence of the volumetric efficiency on the back pressure of the fluid pump, the use of the said sensors or the differential pressure sensor 23 instead of the differential pressure switch 22 is advantageous in order to improve the accuracy in the determination of the degree of loading B.sub.F.

[0063] Thus, all of the operating quantities or operating parameters in the above equations can be determined if the processing unit 24 receives and appropriately processes the registered or monitored fluid temperature T and engine speed n and the differential pressure dp.sub.Diff at the switching point of the differential pressure switch 22.

[0064] From that the operating filter constant c.sub.F can be determined as an operating characteristic according to equation (4). The operating filter constant c.sub.F can be compared with a predefined reference filter constant c.sub.F,ref as reference characteristic. A current percent degree of loading B.sub.F of the filter medium 12 can be derived from the ratio c.sub.F/c.sub.F,ref. Here the reference filter constant c.sub.F,ref can be determined, for example, by analogy with equation (3) as

c.sub.F,ref=dp.sub.F,ref/(.sub.ref.Math.Q.sub.ref) (7)

[0065] where dp.sub.F,ref is a predefined pressure loss of the filter medium 12 at a predefined load limit B.sub.GR (corresponds to a predefined degree of loading of 100%) at a predefined volume flow Q.sub.ref (for example 48 L/min) and at a predefined dynamic viscosity .sub.ref. These values can be established, for example, by the filter manufacturer as standard values or the corresponding data can be taken from characteristic curves or tables (FIG. 3). The load limit or the load limit value B.sub.GR can therefore be predefined under the preset reference conditions.

[0066] In another embodiment, a preset characteristic curve or function of the filter medium 12, can serve as reference characteristic, which gives a pressure loss dp.sub.F,ref of the filter medium 12 in dependence on the load B (for example amount in grams). This reference characteristic can then be compared with a pressure loss dp.sub.F of the filter medium 12 that is determined during vehicle operation as operating characteristic in order to determine a current load amount. The current load amount can, as an operating characteristic, be compared, for example, with a predefined maximum load amount B.sub.MAX as reference characteristic to derive a current percent degree of loading B.sub.F of the filter medium 12 from the ratio of the two values.

[0067] While embodiments incorporating the principles of the present disclosure have been described hereinabove, the present disclosure is not limited to the described embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of the disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this disclosure pertains and which fall within the limits of the appended claims.