Method for monitoring a compressor in a railway braking system - Patents.com

Abstract

A method for monitoring a compressor of a railway braking system is provided, the railway braking system comprising an air generating and processing module (AGTU) (100) comprising a compressor (101) and a main tank (104) adapted to supply compressed air to a main pipe (105) configured to distribute the compressed air to at least one braking subsystem (106) comprising an auxiliary tank (116) adapted to supply compressed air to a brake control system (118). The monitoring method according to the invention comprises the steps of monitoring the behavior of at least one pressure value (P(t)) measured downstream of the main tank (104) or at the outlet of the auxiliary tank (116), and calculating a state of use and / or health of the compressor (101) based solely on the temporal behavior of the measured pressure value (P(t)).

Description

[Technical field]

[0001] The present invention generally relates to the field of railway braking systems, and more specifically to a method for monitoring a compressor of a railway braking system. [Background technology]

[0002] In rail transport systems, known braking systems use compressed air, preferably blown into the interior of brake cylinders, to generate braking force. The compressed air is generated by one or more compressors.

[0003] An example of a known railway braking system is shown in Figure 1. This example is highly simplified and is used only as an illustrative embodiment.

[0004] An air generation and treatment module (AGTU) 100 typically includes a compressor 101 and a dryer assembly 102 disposed downstream of the compressor 101. The dryer assembly 102 has the purpose of separating moisture present in the compressed air in liquid and gaseous states from the compressed air. The dryer assembly 102 includes one or more cyclone separators to remove the moisture in liquid state and a salt or aluminum drying system to remove the moisture in gaseous state.

[0005] Compressed air produced by the AGTU group 100 is collected in a main tank 104 via a non-return valve 103 .

[0006] The main tank 104 then supplies compressed air to a main pipe 105 which distributes the compressed air via non-return valves 109, 110 to one or more braking subsystems 106, 107, ... located along the train. The main pipe 105 also distributes compressed air via non-return valves 111 to one or more pneumatic suspension systems 108, not shown, located between the bogies and the body of the train.

[0007] The pneumatic suspension system 108 typically comprises an auxiliary tank 112, a levelling valve 113, bellows 114 and pressure sensor means 115. The bellows 114 is mechanically arranged between the associated bogie and the body, not shown, so as to act as a suspension. The distance between the body and the bogie depends on the pressure inside the bellows 114. In order to keep the distance between the body and the bogie at a constant value when the weight of the body changes, due to the change in the weight of the passengers, the levelling valve 113 operates as follows: The levelling valve 113, which is sensitive to the distance between the associated bogie and the body, operates to increase the pressure in the bellows 114 when the distance between the associated bogie and the body tends to decrease as a result of an increase in weight. The levelling valve 113 also operates to partially vent the pressure in the bellows 114 to atmosphere, reducing the pressure in the bellows 114 when the distance between the associated bogie and the body tends to increase as a result of a reduction in weight.

[0008] The brake subsystem 106, 107, . . . typically includes auxiliary tanks 116, 117, . . . which supply compressed air to the brake control systems 118, 119, .

[0009] The brake control systems 118, 119, . . . in turn each comprise an electronic unit 120, 121, . . . and a pneumatic panel 122, 123, .

[0010] The pressure sensor means 124, 125 send electrical signals 126, 127 indicative of the instantaneous pressure value of the pressure inside the auxiliary tanks 116, 117 to the electronic units 120, 121, .... The one or more pressure sensor means 115 measure the pressure in the bellows 114 and send electrical signals 135 to inputs 128, 129, ... of the electronic units 120, 121, ....

[0011] In modern braking systems, the pressure sensor means 124, 125, . . . are usually integrated inside the pneumatic panels 122, 123, .

[0012] Furthermore, modern brake control systems 118, 119, as shown for example in EP3328698, consist of highly integrated devices, in which the pressure sensor means 9a is equivalent to the pressure sensor means 124, 125 in FIG.

[0013] A hysteresis pressure switch 130 measures the pressure at the outlet of the main tank 104. If the measured pressure is below a lower hysteresis value, the hysteresis pressure switch 130 energizes a remote control switch 131 which supplies power to the compressor 101. When the pressure reaches and exceeds an upper hysteresis value, the hysteresis pressure switch 130 de-energizes the remote control switch 131, cutting off the power supply to the compressor 101. Hysteresis values ​​used in railway applications typically assume values ​​between 2 bar (200 kPa) and 3 bar (300 kPa), with maximum pressure values ​​typically between 9 bar (900 kPa) and 10 bar (1000 kPa).

[0014] The maximum pressure reached inside the auxiliary tanks 116, 117, ..., 112 always corresponds to the maximum pressure reached in the main tank 104, i.e. the upper hysteresis value of the hysteresis pressure switch 130 minus the pressure drop caused by the non-return valves 109, 110, ..., 111. However, this pressure drop is considered negligible for the purposes of the present invention.

[0015] The minimum pressure reached inside the auxiliary tanks 116, 117, ..., 112 is expected to be different between the individual auxiliary tanks 116, 117, ..., 112 due to the different air consumption of the individual braking subsystems 106, 107, ... and the pneumatic suspension system 108. Usually, only one of the auxiliary tanks 116, 117, ..., 112 will reach a minimum pressure corresponding to the minimum pressure inside the main tank 104 and activate the hysteresis pressure switch 130, which results in the energization of the remote control switch 131 with the subsequent ignition of the compressor 101. Summary of the Invention [Problem to be solved by the invention]

[0016] In the prior art, maintenance of a compressor is performed according to a maintenance cycle that is determined in advance at the design stage based on predicted usage, and the maintenance cycle remains the same throughout the compressor's lifetime.

[0017] Known concepts (such as CBM (condition based maintenance)), i.e. maintenance of compressors based on the actual functional condition of the compressor, which is checked periodically during the compressor's entire service life, are increasingly required on the market.

[0018] Flow measurement is a method to check the state of health of a compressor. The fill time is an indicator of whether the compression sealing members of the compressor are functioning properly or are malfunctioning. If the fill time is greater than the nominal value, it is an indication that the compression sealing members are worn. If the compression sealing members are worn, this will lead to losses in the compression stage, and the compression sealing members must be replaced to avoid any potential serious damage to the compressor itself. In this case, a prompt replacement of the sealing members is required to avoid any potential serious damage to the compressor itself.

[0019] One method of flow measurement that can be applied to the compressor 101 during its life on board a rail vehicle is to measure the time it takes for the compressor to go from a first initial value to a second final value. This measurement is made with respect to a reference value that is constant over time, for example with respect to the volume represented by the entire pneumatic system, including the main tank 104, the main pipe 105 and the auxiliary tanks 116, 117, ..., 112. If the initial and final pressure values ​​are not repeated from one measurement to another, an accurate measurement is to measure a ratio with, in the numerator of the fraction, the difference between the values ​​of the final and the initial pressure, and, in the denominator of the fraction, the difference between the time when the final pressure was measured and the time when the initial pressure was measured. This ratio is known as the flow rate and is directly proportional to the compressor flow. A flow rate below the nominal value is an indication of worn compression members. Wear of the compression members leads to losses in the compression stage of the compressor and the compression members must be replaced.

[0020] Another fundamental parameter indicating the remaining useful life of a compressor is the cumulative time it has spent supplying compressed air to the pneumatic system. This cumulative time can be measured as the total time the compressor is firing. The cumulative time, which is analyzed at the same time when the charging time exceeds a threshold limit value, can indicate whether the prediction of the maintenance cycle was optimistic, accurate or conservative. The information obtained from said measurements can therefore help to revise the estimates of the maintenance cycle by adapting it to the actual use and, as a consequence, optimizing as far as possible the known "life cycle cost", i.e. the cost over the compressor's entire useful life.

[0021] Finally, the parameter "duty cycle", i.e. the ratio between the cumulative time the compressor spends supplying compressed air to the pneumatic system and the cumulative running time of the train, is an important parameter for evaluating the use of the compressor. The cumulative running time of the train is understood to mean the total time that the train is on (running). This value is usually provided by the customer, i.e. the manufacturer of the railway train, to the provider of the railway system, to calculate the maintenance cycles and to agree the warranty periods. An accurate measurement of the "duty cycle" allows an accurate evaluation of the data initially provided by the manufacturer to the provider of the braking system, and thus allows an accurate evaluation of any customer complaints during the warranty period.

[0022] In the prior art, information regarding the state of the hysteresis pressure switch 130, i.e. the state of the remote control switch 131, is not known to the electronic units 120, 121, ..., as it is not considered to have any influence on the behavior of the braking subsystems 106, 107. Thus, the electronic units 120, 121 lack direct information regarding the firing or stopping state of the compressor 101. [Brief description of the drawings]

[0023] The functional and structural features of some preferred embodiments of an electronic system for controlling emergency and service braking according to the present invention will now be described in detail with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 shows a complete system of a braking system for a rail vehicle. [Diagram 2] FIG. 2 shows a first example of a fill and drain cycle for a brake system. [Diagram 3] FIG. 3 shows a second embodiment of a fill and drain cycle for a brake system. [Figure 4] FIG. 4 shows a third embodiment of a brake system fill and drain cycle. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Before describing several embodiments of the invention in detail, it should be noted that the invention is not limited in its application to the structural details and arrangement of components present in the following specification or illustrated in the figures. The invention can take other embodiments and can be practiced or substantially realized in various ways. It should also be understood that the phraseology and terminology are for the purpose of description and should not be construed as limiting. The words "include," "comprise," or variations thereof mean to include the elements described below and their equivalents, as well as additional elements and their equivalents.

[0025] Reference is first made to Fig. 2, which shows how the auxiliary tanks 116, 117, ..., 112 simultaneously reach a pressure value P corresponding to a lower hysteresis value during the discharge phase in order to switch the hysteresis pressure switch 130. ON , 112. In this case, the compressor 101 simultaneously fills the main tank 104 and the auxiliary tanks 116, 117, ..., 112 with compressed air via the main pipe 105.

[0026] Compressor 101 may typically be a positive displacement compressor, or a compressor having a flow rate directly proportional to the rotational speed.

[0027] In the railway sector, compressors are often driven by asynchronous motors powered at a fixed frequency, typically 50Hz or 60Hz. In this case, a constant flow rate can be assumed, taking into account that the speed slip characteristic of asynchronous motors is negligible. In this case, the pressure is expected to have an approximately constant gradient.

[0028] By observing the pressure P(t), the moment when the slope of the pressure P(t) changes from a negative value to a positive value can be identified as the ignition instant T1. In other words, the electronic unit samples the pressure P(t) signal with a sampling period T and is able to perform the calculation of the discrete derivative described below. (P(nT+1)-P(nT)) / T Thus, the time at which the discrete differential derivative above transitions from a negative sign to a positive sign is identified as the ignition time T1.

[0029] Furthermore, by observing the pressure P(t), the time when the gradient of the pressure P(t) transitions from a positive value to zero or a negative value can be determined as the shutdown time T2. In other words, the electronic units 120, 121 sample the pressure P(t) signal with a sampling period T, and further calculate the discrete derivative (P(nT+1)-P(nT)) / T, thereby determining the time when the discrete derivative transitions from a negative sign to a positive sign as the shutdown time T2.

[0030] In order to prevent noise present in the electrical signal from causing excessive local signal variations, digital filtering techniques for removing noise known to those skilled in the art of digital processing may be applied, such as, but not limited to, a simple moving average FIR (finite impulse filter) algorithm.

[0031] In view of the above, a method for monitoring a compressor of a railway braking system according to the present invention is detailed below.

[0032] The railway braking system includes an air generating and processing module AGTU 100 with a compressor 101 and a main tank 104 arranged to supply compressed air to a main pipe 105. The main pipe 105 is configured to distribute the compressed air to at least one brake subsystem 106 including an auxiliary tank 116 arranged to supply compressed air to a brake control system 118.

[0033] A method for monitoring a compressor of a railway braking system includes monitoring the behavior of at least one pressure value P(t) measured downstream of the main tank 104 or at the outlet of the auxiliary tank 116.

[0034] The pressure value P(t) may be measured by a pressure sensor means 132 located downstream of the main tank 104 or may be measured by a pressure sensor means 124 located at the outlet of the auxiliary tank 116.

[0035] Additionally, the method of monitoring the compressor includes deriving a usage and / or health status of the compressor 101 based solely on the time behavior of the measured pressure values ​​P(t).

[0036] During the braking phase, the air consumption of the brake systems 118, 119, ... may be different. For example, the support of different weights on the different bogies results in different brake pressures and therefore different discharges in the auxiliary tanks 116, 117, .... In practice, this situation is therefore frequent. In addition, the suspension system consumes air at different times for the brake systems. In particular, the suspension consumes air with the change of the weight supported on the bogies (typically at stations where passengers board and disembark).

[0037] The individual auxiliary tanks 116, 117, . . . , 112 cannot function to complement each other due to the function of the check valves 109, 110, .

[0038] In this case, only one of the auxiliary tanks 116, 117, ..., 112 has a pressure value P ON and restart the compressor.

[0039] 3 illustrates the above-mentioned filling phase. By way of example, at the ignition time T1, the three auxiliary tanks 116, 117, 112 each have a pressure value P ON , P1, P2, and assuming a constant flow rate of the compressor 101, there is a first phase between the ignition time T1 and the time T3. In this first phase, only the main tank 104 and the auxiliary tank 116 are filled. At time T3, when the pressure value reaches P1, the auxiliary tank 117 is added to the volume to be filled. This event increases the overall volume and, as a result, causes a decrease in the slope of the line graph P(t). Furthermore, at time T4, when the pressure value reaches P2, the auxiliary tank 112 is added to the volume to be filled. Thereby, the overall volume increases and the slope of the line graph P(t) further decreases. It is clear that the slope to be taken into account for calculating the filling time of the entire system must be the slope belonging to the graph interval that includes the interval between time T4 and the shutdown time T2, i.e., the period after the last change in slope.

[0040] The method for monitoring the compressor may also preferably include determining that a shutdown time T2 of the compressor 101 corresponds to a time when the derivative of the pressure P(t) changes from a positive value to a nominally null value or a negative value. The shutdown time T2 may be determined by the electronic control unit 120 of the brake control system 118.

[0041] The method for monitoring the compressor may also preferably further include determining that the firing time T1 of the compressor 101 coincides with the time at which the derivative of the pressure P(t) is detected to change from a negative value or a nominal zero value to a positive value.

[0042] The ignition time T 1 may be determined by the electronic control unit 120 of the brake control system 118 .

[0043] Alternatively, if further braking systems 119, ... are present, the method for monitoring a compressor according to the invention may comprise determining that the firing time (T1) of the compressor 101 corresponds to the smaller value among the times T1, T3, T4, where the times T1, T3, T4 correspond to the times at which the respective pressure values ​​P3, P2, P1 of the pressure P(t) are detected and where the change of the derivative of the pressure P(t) from a negative value or a nominal zero value to a positive value is detected. The pressures P1, P2, P3, ... are measured downstream of a number of auxiliary tanks 116, 117, ....

[0044] One or more of times T1, T3, T4 may be detected by a number of electronic units 120, 121, .... The electronic units 120, 121 may be interconnected by a communication means 133 and may communicate their respective detected times T1, T3, T4, ... to each other.

[0045] Further relative pressures P2, P3, . . . may be measured by further pressure sensor means 125, .

[0046] The further ignition times T1, T3, T4 may be specified by further electronic control units 121, ... of further brake control systems 119, .... Furthermore, the further ignition times T1, T3, T4 may be communicated from the electronic control unit 120 and the further electronic control units 121, ... by means of communication means 133.

[0047] The method for monitoring a compressor according to the present invention may preferably further comprise the step of calculating a filling ratio, which is calculated by multiplying the numerator of the fraction by the shutdown pressure value P(t) of the pressure P(t) at the shutdown time T2. OFF and the first pressure value P1 of pressure P(t) at a negative change time T4 which corresponds to the time when the last negative change of the derivative of pressure P(t) occurred, with the denominator of the fraction being the difference between the shutdown time T2 and the negative change time T4.

[0048] The electronic units 120, 121, ... calculate the pressure value P(t) calculated as the value of P(t) when the sign of the discrete derivative (P(nT+1)-P(nT)) / T goes from positive to zero or negative. OFF The electronic units 120, 121, ... may also determine the pressure value P OFF may be compared to the nominal value of the hysteresis pressure switch 130, which is a nominal value preloaded in the non-volatile memory of the electronic units 120, 121, . . .

[0049] “filing rate” ratio (P OFF -P ON By comparing (T2-T1) / (T2-T1) with tolerances preloaded in the non-volatile memory of the electronic units 120, 121, ..., the electronic units 120, 121, ... may establish the state of health of the compressor, and optionally, the electronic units 120, 121, ... may activate a request for maintenance signal if said ratio is lower than a nominal threshold value.

[0050] Furthermore, the method for monitoring a compressor according to the present invention may include the step of issuing anomaly information when the fill ratio is lower than a predefined threshold. The anomaly information may be issued by at least one or each of the electronic control units 120, 121.

[0051] At least as design data, P ON is known to all electronic units, P OFF If T4-T2 is the pressure value measured in real time, then the nominal "fill rate" ratio of the system is calculated by each electronic unit as (T4-T2) / (P OFF -P2).

[0052] In yet a further embodiment, the method for monitoring the compressor may further include a step of periodically calculating, by the electronic control unit 120, 121, an ignition period, which is the difference between the shutdown time T2 and the ignition time T1 or time Tm.

[0053] The electronic units 120, 121, ... may accumulate the actual firing time of the compressor by subsequently summing (T2-T1).

[0054] The electronic units 120, 121, ... count the total time that the brake system is on, i.e. active. In this way, by dividing the actual time of compressor use by the total time that the brake system is on, the electronic units 120, 121, ... continuously calculate the "duty cycle" of the compressor. Furthermore, the electronic units 120, 121, ... store this duty cycle in a non-volatile memory of the electronic units 120, 121, ... and provide it to the rail train manufacturer's maintenance staff for potentially future evaluation of correct use.

[0055] Therefore, the method for monitoring a compressor according to the present invention may further include the steps of calculating a total operating time of the compressor 101 as the sum of the calculated ignition periods during the useful life of the compressor 101, and storing this total operating time.

[0056] The total run time of the compressor 101 may be calculated by the electronic control units 120, 121, . . .

[0057] Figure 4 shows that during the filling phase, there may occur further repeated events that consume air, such as braking events or changes in the weight of the vehicle, which may require the suspension bellows to be filled. This possible event will result in a decrease in the slope over the duration of the event, as shown between TA and TB in Figure 4. In this case, the electronic unit simply uses the measured value of time T2-T1 to calculate the cumulative usage time and duty cycle, discarding the estimate of the filling time that may have been distorted by the events that occurred between TA and TB.

[0058] If further pressure sensor means 132 are present to directly measure the pressure in the main pipe 105 and a corresponding signal is available in at least one of the electronic units 120, 121, ..., this at least one electronic unit can derive information regarding the filling time, the cumulative time and the duty cycle by using the same criteria as in the conditions described so far, without the need to specify further times Tm between T1, T2, ...

[0059] If the communication means 133 are available for communication between the control units 120, 121, ..., the control units 120, 121, ... may use the P ON , P1, P2, ..., P OFF The two parties then send each other the exact value of , as well as the "fill rate" ratio, which will be calculated later.

[0060] It is also possible to transmit at least one of the values ​​of the fill ratio, the total operating time, or the operating duty cycle from the central unit 134. Alternatively or additionally, it is also possible to transmit at least one of the values ​​of the fill ratio, the total operating time, or the operating duty cycle from within the train to the ground using a wireless system.

[0061] Furthermore, the method for monitoring a compressor according to the present invention may further comprise the step of emitting an information signal when at least one of the ignition time T1 or the shutdown time T2 exceeds an associated threshold value. Also, the method for monitoring a compressor may further comprise the step of emitting an information signal when at least one of the ignition time T1 or the shutdown time T2 exceeds an associated threshold value. OFF and the ignition pressure value P(t) ON fall outside their respective tolerance ranges and / or if at least one fill time exceeds a predetermined limit.

[0062] The information signal may be emitted by at least one or each of the electronic control units 120, 121, . . .

[0063] Although methods based on observing the profile of P(t) cannot take into account the gradual increase in the volume to be filled, they are advantageously more accurate and obviously more reliable with respect to measuring the nominal filling time, which is performed by simply measuring the time that the hysteresis pressure switch 130 or the remote control switch 131 remains activated.

[0064] Various aspects and embodiments of the method for monitoring the usage and health status of a compressor of a railway braking system according to the present invention have been detailed. It is understood that each embodiment can be combined with any other embodiment. Moreover, the invention is not limited to the detailed embodiments, but may be modified within the scope defined by the appended claims.

Claims

1. 1. A method for monitoring a compressor of a railway braking system, comprising: The railway braking system comprises: an air generating and processing module (AGTU) (100) comprising a compressor (101); a main tank (104) arranged to supply compressed air to a main pipe (105) configured to distribute the compressed air to at least one brake subsystem (106) comprising an auxiliary tank (116) arranged to supply compressed air to a brake control system (118), The method for monitoring comprises: monitoring the behavior of at least one pressure value (P(t)) measured downstream of the main tank (104) or at the outlet of the auxiliary tank (116); determining that a shutdown time (T2) of the compressor (101) corresponds to a time at which a change in the derivative of the pressure value (P(t)) from a positive value to a nominal zero value or a negative value is detected in order to derive a usage and / or health status of the compressor (101) based on the behavior over time of the measured pressure value (P(t)); 1. A method for monitoring a compressor of a railway braking system, comprising:

2. A step of determining that a start-up time (T1) of the compressor (101) coincides with a time at which a change in the derivative of the pressure value (P(t)) from a negative value or a nominal zero value to a positive value is detected in order to derive a state of use and / or health of the compressor (101); 10. The method for monitoring a compressor of a railway braking system according to claim 1, further comprising:

3. A process for determining that a start-up time (T1) of the compressor (101) corresponds to the smaller of the times (T1, T3, T4) at which a change in the derivative of the pressure value (P(t)) from a negative value or a rated zero value to a positive value is detected and each pressure value (P1, P2, P3, ...) of the pressure value (P(t)) is detected, in order to derive a state of use and / or health of the compressor (101); Including, 2. Method for monitoring a compressor of a railway braking system according to claim 1, wherein said pressure values ​​(P1, P2, P3, . . .) are measured downstream of a number of auxiliary tanks (116, 117, . . .).

4. 4. The method for monitoring a compressor of a railway braking system according to claim 2 or 3, further comprising the step of periodically calculating the difference between the shutdown time (T2) and the start-up time (T1) as a start-up period.

5. Calculating the sum of the start-up periods calculated within the useful life of the compressor (101) as the total operating time of the compressor (101); 5. The method for monitoring a compressor of a railway braking system according to claim 4, further comprising the step of: storing said total operating hours within said useful life of said compressor (101).

6. 6. The method for monitoring a compressor of a railway brake system according to claim 5, further comprising the step of calculating a ratio of the calculated total operating time to an operating time of the railway vehicle as an operating duty cycle of the compressor (101).

7. 7. The method for monitoring a compressor of a railway brake system as claimed in claim 6, further comprising the step of transmitting at least one value of the total operating time or the operating duty cycle from within the train to the ground using a wireless system.

8. The shutdown pressure value (P(t)) at the shutdown time (T2) ＯＦＦ ) and the starting pressure value (P(t)) at the starting time (T1) ＯＮ 8. The method for monitoring a compressor of a railway braking system according to any of claims 2 to 7, further comprising the step of emitting an information signal if at least one of the following is outside its respective tolerance range:

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