Method for monitoring the functioning of a compressor

Abstract

A method for monitoring the functioning of a compressor, which is switchable into a delivery mode and, when in the delivery mode, delivers compressed air via a dryer line of a compressed-air preparation unit into at least one main supply line, from which multiple supply lines of compressed-air consumer circuits branch off, wherein a pressure sensor is connected at each of at least some of the supply lines, is disclosed. The method results in outputting a warning message if a weighted pressure gradient grd_p.sub.V_W has not exceeded a gradient limiting value grd_p.sub.G_W within a predefined monitoring time period T.sub.M.

Claims

1. A method for monitoring the functioning of a compressor, which is switchable into a delivery mode, and which, in the delivery mode, delivers compressed air via a dryer line of a compressed-air preparation unit into a main supply line, from which multiple supply lines of compressed-air consumer circuits branch off, wherein a pressure sensor is connected to one of the multiple supply lines, wherein, in the delivery mode of the compressor, a supply pressure p.sub.V is detected with the aid of the pressure sensor, a pressure gradient grd_p.sub.V derived therefrom is compared to a predefined gradient limiting value grd_p.sub.G_W, and, depending on a result of the comparison, a warning message or a warning signal is output or not, including the following method steps: a) continuously detecting, with the aid of the pressure sensor, the supply pressure p.sub.V in the one of the multiple supply lines of at least one compressed-air consumer circuit provided with the pressure sensor, b) continuously calculating the pressure gradient grd_p.sub.V of the supply pressure p.sub.V from at least two consecutively detected pressure values p.sub.V_i, p.sub.V_i+1 and the time difference Δt between their detection at least during the delivery mode of the compressor, c) weighting the pressure gradient grd_p.sub.V by division by a current drive rotational speed n.sub.K of the compressor (grd_p.sub.V_W w=grd_p.sub.V/n.sub.K) or by a current rotational speed-dependent setpoint delivery rate Q.sub.soll of the compressor (grd_p.sub.V_W=grd_p.sub.V/Q.sub.soll), d) comparing the weighted pressure gradient grd_p.sub.V_W with the predefined gradient limiting value grd_p.sub.G_W, e) outputting the warning message or warning signal if the weighted pressure gradient grd_p.sub.V_W has not exceeded the predefined gradient limiting value grd_p.sub.G_W within a predefined monitoring time period T.sub.M.

2. The method as claimed in claim 1, wherein pressure fluctuation values of the supply pressure p.sub.V that are based on thermodynamic effects that arise in the compressed-air consumer circuits after consumption of compressed air are not taken into account when continuously calculating the pressure gradient grd_p.sub.V of the supply pressure p.sub.V.

3. The method as claimed in claim 1, wherein the values of the pressure gradient grd_p.sub.V and the weighted pressure gradient grd_p.sub.V_W are low-pass filtered.

4. The method as claimed in claim 3, wherein the values of the pressure gradient grd_p.sub.V and the weighted pressure gradient grd_p.sub.V_W are low-pass filtered for an established period of time T.sub.A.

5. The method as claimed in claim 3, wherein the values of the pressure gradient grd_p.sub.V and the weighted pressure gradient grd_p.sub.V_W are low-pass filtered for an established period of time T.sub.A after the occurrence of a drop of the supply pressure p.sub.V.

6. The method as claimed in claim 1, wherein the calculation of the pressure gradient grd_p.sub.V and the weighted pressure gradient grd_p.sub.V_W is suspended for an established period of time T.sub.A′ after the occurrence of a drop of the supply pressure p.sub.V.

7. The method as claimed in claim 1, wherein the predefined monitoring time period T.sub.M is defined as a cumulative operating time of a motor vehicle.

8. The method as claimed in claim 1, wherein the predefined monitoring time period T.sub.M is based on a cumulative distance traveled by a motor vehicle.

9. The method as claimed in claim 1, wherein the predefined monitoring time period T.sub.M is defined as the cumulative delivery mode duration of the compressor.

10. The method as claimed in claim 1, wherein multiple fault accounts are maintained in computer readable memory for various causes of a fault.

11. The method as claimed in claim 1, wherein the step of weighting the pressure gradient grd_p.sub.V is performed only in a limited range of the supply pressure p.sub.V in order to detect certain causes of a fault.

12. The method as claimed in claim 1, wherein the step of weighting the pressure gradient grd_p.sub.V is performed only in a limited range of the current drive rotational speed n.sub.K of the compressor in order to detect certain causes of a fault.

13. The method as claimed in claim 11, wherein the compressor includes a friction clutch, and wherein slipping of the friction clutch of the compressor is detected in that the weighted pressure gradient grd_p.sub.V_W in an upper range of the supply pressure p.sub.V has not exceeded the gradient limiting value grd_p.sub.G_W within the predefined monitoring time period T.sub.M.

14. The method as claimed in claim 11, wherein the compressor includes a friction clutch, and wherein slipping of the friction clutch of the compressor is detected in that the weighted pressure gradient grd_p.sub.V_W in an upper range of the drive rotational speed n.sub.K of the compressor has not exceeded the gradient limiting value grd_p.sub.G_W within the predefined monitoring time period T.sub.M.

15. A method for monitoring the functioning of a compressor, which is switchable into a delivery mode, and which, in the delivery mode, delivers compressed air via a dryer line of a compressed-air preparation unit into a main supply line, from which multiple supply lines of compressed-air consumer circuits branch off, wherein a pressure sensor is connected to one of the multiple supply lines, wherein, in the delivery mode of the compressor, a supply pressure p.sub.V is detected with the aid of the pressure sensor, a pressure gradient grd_p.sub.V derived therefrom is compared to a predefined gradient limiting value grd_p.sub.G, and, depending on a result of the comparison, a warning message or a warning signal is output or not, including the following method steps: a) continuously detecting, with the aid of the pressure sensor, the supply pressure p.sub.V in the one of the multiple supply lines of at least one compressed-air consumer circuit provided with the pressure sensor, b) continuously calculating the pressure gradient grd_p.sub.V of the supply pressure p.sub.V from at least two consecutively detected pressure values p.sub.V_i, p.sub.V_i+1 and the time difference Δt between their detection at least during the delivery mode of the compressor, c) comparing the pressure gradient grd_p.sub.V with a current, rotational speed-dependent, predefined gradient limiting value grd_p.sub.G, which does not take withdrawal of compressed air by consumers into account, d) outputting the warning message or warning signal if the pressure gradient grd_p.sub.V has not exceeded the predefined gradient limiting value grd_p.sub.G within a predefined monitoring time period T.sub.M.

16. The method as claimed in claim 15, wherein the predefined gradient limiting value grd_p.sub.G is defined as a fraction, determined by an adaptation factor f.sub.A<1, of a weighted pressure gradient grd_p.sub.C_W that is characteristic for the compressor and the connected compressed-air consumer circuits grd_p.sub.G=f.sub.A×grd_p.sub.C_W.

17. The method as claimed in claim 16, wherein the adaptation factor f.sub.A is a first adaptation factor f.sub.A1, wherein the weighted pressure gradient grd_p.sub.C_W is multiplied by a second adaptation factor f.sub.A2 less than the first adaptation factor f.sub.A1 when a permanent consumption of compressed air is present in one of the compressed-air consumer circuits.

18. The method as claimed in claim 16, wherein the weighted pressure gradient grd_p.sub.C_W is determined from a displacement V.sub.K of the compressor, a volumetric efficiency .sub.V of the compressor, and a storage volume V.sub.S of all compressed-air consumer circuits.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The foregoing aspects and many of the attendant advantages will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts throughout the various views, unless otherwise specified:

(2) FIG. 1 shows a diagram with the time profiles of various characteristic values of a compressed-air supply system, and

(3) FIG. 2 shows the schematic configuration of a typical compressed-air supply system of a motor vehicle.

DETAILED DESCRIPTION

(4) In FIG. 2, a compressor 2 and an electronically controlled compressed-air supply system 4 of a motor vehicle are shown in a schematic representation and in which the method according to the invention is applicable for monitoring the functioning of the compressor 2.

(5) The compressed-air supply system 4 comprises the assemblies of a compressed-air preparation unit 6, a multi-circuit protection valve unit 8, and an electronic control unit 10.

(6) The compressor 2 is connected, on the output side, at a delivery line 12 and comprises a control pressure input 14. Due to the application of a sufficiently high control pressure from a connected control pressure line 16 at the control pressure input 14, a friction clutch (not represented) is engaged, whereby the compressor 2 is drivingly connected to a drive engine (not represented) of the motor vehicle and, as a result, switched into the delivery mode. In the delivery mode, the compressor 2 draws in air from the surroundings and delivers it, as compressed air, into the delivery line 12.

(7) The compressed-air preparation unit 6 comprises a dryer line 18, in which a filter unit 20, a dryer unit 22, and a check valve 24 are arranged, one after the other, in a delivery direction indicated by the direction arrow 42. The dryer line 18 is connected, on the input side, at the delivery line 12 and, on the output side, branches into two main supply lines 26, 28. The second main supply line 28 is limited with respect to its maximum pressure via an installed pressure limiting valve 30. The pressure limiting valve 30 preferably has a hysteresis. Ahead of the filter unit 20, a vent line 32, in which a vent valve 34 is arranged, branches off from the dryer line 18 and leads into the surroundings via a muffler 36. The vent valve 34 is designed as a pressure-controlled 2/2-way switching valve, which is closed in the control-pressureless state and can be opened via the application of a sufficiently high control pressure at a control pressure line 38 connected at its control pressure input. Between the dryer unit 22 and the check valve 24, a regeneration line 40 is connected at the dryer line 18, through which already dried compressed air is returnable to the dryer unit 22.

(8) The multi-circuit protection valve unit 8 comprises five overflow valves 46, 50, 54, 58, 62 of a multi-circuit protection valve (not represented in greater detail), a regeneration control valve 74, a compressor control valve 70, and two throttle check valves 66, 78. In the multi-circuit protection valve unit 8, the first main supply line 26 branches into the three supply lines 44, 48, 52 of three compressed-air consumer circuits V21, V22, V25.

(9) The compressed-air consumer circuits V21, V22, V25 are, for example, a first service brake circuit V21 of the motor vehicle, a second service brake circuit V22 of the motor vehicle, and an air suspension circuit V25. The pressure-limited second main supply line 28 branches, in the multi-circuit protection valve unit 8, into the two supply lines 56, 60 of two further compressed-air consumer circuits V23, V24 and into a control pressure main line 68. The further compressed-air consumer circuits V23, V24 are, for example, a trailer and parking brake circuit V23 and an auxiliary consumer circuit V24. One of the overflow valves 46, 50, 54, 58, 62 of the multi-circuit protection valve is arranged in each of the supply lines 44, 48, 52, 56, 60, respectively, of the five compressed-air consumer circuits V21, V22, V23, V24, V25.

(10) On the output side of the relevant overflow valves 58, 50, a connection line 64 with the throttle check valve 66 opening in the direction of the supply line 48 of the second service brake circuit V22 is arranged between the supply line 56 of the trailer and parking brake circuit V23 and the supply line 48 of the second service brake circuit V22. Via this connection, at an appropriate pressure gradient, compressed air can flow out of the trailer and parking brake circuit V23 into the second service brake circuit V22 and drain the parking brake circuit V23.

(11) The compressor control valve 70 and the regeneration control valve 74 are connected, on the input side, at the control pressure main line 68. Each of the two control valves 70, 74 is designed as a 3/2-way solenoid switching valve, the input-side connections of which are blocked in the de-energized state and which are switchable via the energization of an associated electrical control line 72, 76, respectively.

(12) Due to an energization of the compressor control valve 70, the control pressure line 16 of the compressor 2 connected to the compressor control valve 70 on the output side is connected to the control pressure main line 68, whereby the friction clutch of the compressor 2 is disengaged and the compressor 2 is decoupled from the drive engine. When the control pressure input 14 of the compressor 2 is pressureless, the friction clutch of the compressor 2 is engaged, and so the compressor 2 is then in the delivery mode with the drive motor running. In the delivery mode, the compressor 2 delivers compressed air, according to the delivery direction indicated by the direction arrow 42, through the delivery line 12, the filter unit 20, the dryer line 18, the dryer unit 22, and the check valve 24 into the two main supply lines 26, 28 and, via the overflow valves 46, 50, 54, 58, 62 of the multi-circuit protection valve, further into the compressed-air consumer circuits V21, V22, V23, V24, V25.

(13) Due to an energization of the regeneration control valve 74, the regeneration line 40 connected thereto on the output side, in which the throttle check valve 78 opening in the direction of the dryer line 18 is arranged, is connected to the control pressure main line 68. As a result, the control pressure line 38 of the vent valve 34, which is connected at the regeneration line 40 between the regeneration control valve 74 and the throttle check valve 78, is also acted upon by the pressure prevailing in the control pressure main line 68, whereby the vent valve 34 is opened. As a result, already dried compressed air flows out of the second main supply line 28 via the control pressure main line 68 and the regeneration line 40 counter to the delivery direction 42 through the dryer unit 22 and the filter unit 20, via the vent line 32 and the muffler 36 into the surroundings, whereby the dryer unit 22 is regenerated and the filter unit 20 is cleaned.

(14) A pressure sensor 82, 88, 94 is connected, via a connection line 80, 86, 92, respectively, at the supply lines 44, 48, 56 of the first service brake circuit V21, of the second service brake circuit V22, and of the trailer and parking brake circuit V23. These pressure sensors 82, 88, 94 are connected via an electrical sensor line 84, 90, 96, respectively, to an electronic control unit 98 (ECU). Likewise, the compressor control valve 70 and the regeneration control valve 74 are connected, via their electrical control lines 72, 76, to the electronic control unit 98. The pressure sensors 82, 88, 94 and the electronic control unit 98 are combined in the assembly of the electronic control unit 10.

(15) The method according to the invention for monitoring the functioning of a compressor 2 is explained in greater detail in the following with reference to the above-described embodiment and arrangement of the compressor 2 and of the compressed-air supply system 4 on the basis of the diagram according to FIG. 1. In the diagram, the engine speed n.sub.M of the drive engine, which is identical to the drive rotational speed n.sub.K of the compressor 2 when the friction clutch is engaged, the delivery pressure p.sub.F effective in the delivery line 12 at the output of the compressor 2, and the supply pressure p.sub.V effective in one of the supply lines 44, 48 and detected with the aid of a pressure sensor 82, 88, respectively, are represented with respect to the time t. The delivery pressure p.sub.F of the compressor 2 is not detected with the aid of sensors, per se, and is contained in the diagram from FIG. 1 only for better understanding in the present case. Moreover, in the diagram according to FIG. 1, the time profiles of the pressure gradient grd_p.sub.V of the supply pressure p.sub.V, of the pressure gradient grd_p.sub.V_W weighted with the drive rotational speed n.sub.K of the compressor 2 and with the engine speed n.sub.M of the drive engine, and of a gradient limiting value grd_p.sub.G_W are represented.

(16) The monitoring method provides that the supply pressure p.sub.V in the supply line 44, 48 of at least one compressed-air consumer circuit V21, V22 provided with a pressure sensor 82, 88 is continuously detected with the aid of sensors in a predefined interval Δt. The pressure gradients grd_p.sub.V of the supply pressure p.sub.V are then continuously calculated, at least during the delivery mode (T.sub.F1, T.sub.F2, T.sub.F3) of the compressor 2, from at least two consecutively detected pressure values p.sub.V_i, p.sub.V_i+1 in each case and the time difference Δt between their detection. Thereafter, the pressure gradients grd_p.sub.V are weighted in order to determine the weighted pressure gradient grd_p.sub.V_W by division by the particular current drive rotational speed n.sub.K of the compressor (grd_p.sub.V_W=grd_p.sub.V/n.sub.K) and low-pass filtered.

(17) The pressure gradients grd_p.sub.V_W weighted in this way are compared with a predefined gradient limiting value grd_p.sub.G_W, which is represented as a straight line in FIG. 1 and which is defined as a fraction, taken into account by an adaptation factor f.sub.A<1, of a weighted pressure gradient grd_p.sub.C_W that is characteristic for the compressor 2, the compressed-air supply system 4, and the connected compressed-air consumer circuits V21, V22, V23, V24, V25 (grd_p.sub.W_G=f.sub.A×grd_p.sub.C_W).

(18) If the weighted pressure gradient grd_p.sub.V_W of the supply pressure p.sub.V has not exceeded the gradient limiting value grd_p.sub.G_W within a predefined monitoring time period T.sub.M, which can be considered, by way of example, as the time period represented in the diagram according to FIG. 1, a warning message or a warning signal is output. The warning signal or the warning message can take place or be given via the illumination of a warning light in the dashboard or in the instrument panel of the motor vehicle, via the illumination of an appropriate warning icon in the instrument panel, via the display of an appropriate warning text in a display of the instrument panel, and/or via the storage of an appropriate error message in a fault memory associated with the electronic control unit 10 of the compressed-air supply system 4.

(19) The time period T.sub.M indicated in the diagram according to FIG. 1 comprises three delivery modes T.sub.F1, T.sub.F2, T.sub.F3 of the compressor 2. Since the weighted pressure gradient grd_p.sub.V_W of the supply pressure p.sub.V has exceeded the predefined gradient limiting value grd_p.sub.G_W during the first two delivery modes T.sub.F1, T.sub.F2, a warning signal or a warning message is not output in the present case example. The electronic control unit 98 would output a warning signal or a warning message only for the case in which the weighted pressure gradient grd_p.sub.V_W of the supply pressure p.sub.V does not exceed the predefined gradient limiting value grd_p.sub.G_W in all three delivery modes T.sub.F1, T.sub.F2, T.sub.F3 of the compressor 2.

(20) Within the scope of the monitoring method according to the invention, multiple fault accounts can be maintained for various causes of a fault, for which the adaptation factor f.sub.A of the characteristic pressure gradient grd_p.sub.C_W and/or the type and length of the monitoring time period T.sub.M can be established in different ways. Likewise, in order to detect certain causes of a fault, the calculation of the weighted pressure gradient grd_p.sub.V_W can be performed only in a limited range of the supply pressure p.sub.V and/or in a limited range of the drive rotational speed n.sub.K of the compressor 2.

LIST OF REFERENCE NUMBERS (PART OF THE DESCRIPTION)

(21) 2 compressor 4 compressed-air supply system 6 compressed-air preparation unit (assembly) 8 multi-circuit protection valve, multi-circuit protection valve unit (assembly) 10 electronic control unit including sensors (assembly) 12 delivery line 14 control pressure input 16 control pressure line 18 dryer line 20 filter unit 22 dryer unit 24 check valve 26 first main supply line 28 second main supply line 30 pressure limiting valve 32 vent line 34 vent valve 36 muffler 38 control pressure line 40 regeneration line 42 direction arrow, delivery direction 44 supply line 46 overflow valve 48 supply line 50 overflow valve 52 supply line 54 overflow valve 56 supply line 58 overflow valve 60 supply line 62 overflow valve 64 connection line 66 throttle check valve 68 control pressure main line 70 compressor control valve 72 electrical control line 74 regeneration control valve 76 electrical control line 78 throttle check valve 80 connection line 82 pressure sensor 84 electrical sensor line 86 connection line 88 pressure sensor 90 electrical sensor line 92 connection line 94 pressure sensor 96 electrical sensor line 98 electronic control unit (ECU) ECU electronic control unit f.sub.A adaptation factor grd_p pressure gradient grd_p.sub.C characteristic pressure gradient (unweighted) grd_p.sub.C_W characteristic pressure gradient (weighted) grd_p.sub.G gradient limiting value (unweighted) grd_p.sub.C_W gradient limiting value (weighted) grd_p.sub.V pressure gradient of the supply pressure grd_p.sub.V_W weighted pressure gradient of the supply pressure grd_p.sub.W weighted pressure gradient i.sub.PTO ratio of a power take-off n rotational speed n.sub.K drive rotational speed of the compressor n.sub.K_m mean drive rotational speed of the compressor n.sub.M engine speed p pressure p.sub.F delivery pressure of the compressor p.sub.V supply pressure p.sub.V_i i.sup.th measured value of the supply pressure p.sub.V_i+1 (i+1).sup.th measured value of the supply pressure Q.sub.soll rotational speed-dependent setpoint delivery rate Q.sub.soll_m mean setpoint delivery rate t time T.sub.A period of time T.sub.A′ period of time T.sub.M monitoring time period T.sub.F1 first delivery mode duration T.sub.F2 second delivery mode duration T.sub.F3 third delivery mode duration V.sub.K displacement of the compressor V.sub.S storage volume V21 compressed-air consumer circuit, first service brake circuit V22 compressed-air consumer circuit, second service brake circuit V23 compressed-air consumer circuit, trailer and parking brake circuit V24 compressed-air consumer circuit, auxiliary consumer circuit V25 compressed-air consumer circuit, air suspension circuit Δt interval, time difference V volumetric efficiency

(22) The terms “comprising” or “comprise” are used herein in their broadest sense to mean and encompass the notions of “including,” “include,” “consist(ing) essentially of,” and “consist(ing) of. The use of “for example,” “e.g.,” “such as,” and “including” to list illustrative examples does not limit to only the listed examples. Thus, “for example” or “such as” means “for example, but not limited to” or “such as, but not limited to” and encompasses other similar or equivalent examples. The term “about” as used herein serves to reasonably encompass or describe minor variations in numerical values measured by instrumental analysis or as a result of sample handling. Such minor variations may be in the order of ±0-25, ±0-10, ±0-5, or ±0-2.5, % of the numerical values. Further, The term “about” applies to both numerical values when associated with a range of values. Moreover, the term “about” may apply to numerical values even when not explicitly stated.

(23) Generally, as used herein a hyphen “-” or dash “—” in a range of values is “to” or “through”; a “>” is “above” or “greater-than”; a “≥” is “at least” or “greater-than or equal to”; a “<” is “below” or “less-than”; and a “≤” is “at most” or “less-than or equal to.” On an individual basis, each of the aforementioned applications for patent, patents, and/or patent application publications, is expressly incorporated herein by reference in its entirety in one or more non-limiting embodiments.

(24) It is to be understood that the appended claims are not limited to express and particular compounds, compositions, or methods described in the detailed description, which may vary between particular embodiments which fall within the scope of the appended claims. With respect to any Markush groups relied upon herein for describing particular features or aspects of various embodiments, it is to be appreciated that different, special, and/or unexpected results may be obtained from each member of the respective Markush group independent from all other Markush members. Each member of a Markush group may be relied upon individually and or in combination and provides adequate support for specific embodiments within the scope of the appended claims.

(25) The present invention has been described herein in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings. The present invention may be practiced otherwise than as specifically described within the scope of the appended claims. The subject matter of all combinations of independent and dependent claims, both single and multiple dependent, is herein expressly contemplated.