Current collector with interruption monitoring

Abstract

The invention relates to a current collector (4) for an electrically driven vehicle for feeding-in electrical energy from an overhead line system (3). The current collector comprises a contact strip (7) for electrically contacting a contact wire (2), the contact strip having a sliding piece (9) supported by a sliding piece holder (8). A compressed-air duct (13) is at least partially bounded by the sliding piece (9) and connected to a compressed-air supply (11). According to the invention, a pneumatic restrictor (14) is arranged between the compressed-air supply (11) and the sliding piece (9). A test-pressure sensor (16) cyclically measures an actual test pressure (PDist) prevailing downstream of the restrictor (14) and a feed-pressure sensor (15) cyclically measures an actual feed pressure (SDist) prevailing upstream of the restrictor (14). An evaluation device (17) is designed to cyclically calculate a setpoint test pressure (PDsoll) prevailing downstream of the restrictor (14) in a test volume depending on the measured actual feed pressure (SDist) from the difference between a feed-air mass flow (Qzu) flowing in through the restrictor (14) and a discharge-air mass flow (Qab) flowing out due to a leak (L), present downstream of the restrictor (14) in the pressure channel (13), into the surrounding area (U). The evaluation device cyclically determines a test-pressure deviation (ΔPD) between the actual test pressure (PDist) and the setpoint test pressure (PDsoll) and generates a fault message (E1) when a first threshold value (S1) is exceeded by the determined test-pressure deviation (ΔPD). As a result, fewer incorrect fault messages are generated during the interruption monitoring.

Description

[0001] Description

[0002] Pantograph with breakage monitoring

[0003] The invention relates to a current collector according to the preamble of patent claim 1.

[0004] Such a pantograph is designed and provided for an electrically or hybrid-electrically powered vehicle for feeding electrical energy from an overhead line system having at least one contact wire. It comprises at least one contact strip for electrically contacting the at least one contact wire, which contact strip has a contact piece carried by a contact piece holder. Furthermore, the pantograph comprises a compressed air duct at least partially delimited by the contact piece and a compressed air supply connected to the compressed air duct for feeding in compressed air. Furthermore, it comprises a test pressure sensor for measuring an actual test pressure prevailing in the compressed air duct.

[0005] Such a current collector is known from the published patent application DE 39 14 675 A1, which discloses a contact strip with a breakage detector device. For this purpose, the contact strip has a gas-tight channel which is connected to a device for generating increased air or gas pressure in the channel and to a detector which signals a drop in pressure. If the contact strip breaks or becomes excessively worn, the channel becomes leaky, and the break or wear is indicated by the drop in pressure. The supports on the contact horns provided according to the invention are also included in this breakage monitoring system. These also have a corresponding channel which is connected to the channel of the carbon strip via an inserted piece of hose. The connection to the gas supply and the monitoring device can be made via a connection nipple in the area of ​​one of the contact horns.The supports of the runners can also be made in one piece with the grinding strip.

[0006] From the publication EP 3 147 152 A1, a non-rail-bound, electrically or hybrid-electrically powered vehicle with a pantograph for feeding in electrical traction energy from an overhead line system is known. The pantograph has a contact strip arrangement that can be raised and lowered and brought into sliding contact with a contact wire of the overhead line system running above a lane. The contact strip arrangement has laterally projecting insulating horns with a predetermined breaking point. The contact strip arrangement further has a detection device that is designed to detect when an insulating horn breaks off and to trigger automatic lowering of the contact strip arrangement. For this purpose, the air duct of the automatic emergency lowering can be connected to the emergency lowering up to the predetermined breaking point, and the emergency lowering can thus be initiated via the safety relay.

[0007] Known monitoring devices rely on detecting a pressure drop in the pressure channel as an indication of a major leak, such as a broken grinding piece or a broken horn. However, the monitoring device can also mistakenly interpret a drop in the supply pressure from the compressed air supply as a detection event.

[0008] The invention is therefore based on the object of providing a current collector of the type mentioned at the beginning, the breakage monitoring of which generates fewer false error messages.

[0009] The object is achieved according to the invention by a generic current collector with the features specified in the characterizing part of patent claim 1.

[0010] The pantograph is designed for an electrically or hybrid-electrically powered vehicle, such as a road vehicle or a rail vehicle, for example as a bar-type pantograph. It is used to feed in electrical energy from a single- or two-pole overhead line system, which has one contact wire for rail vehicles and two contact wires designed as forward and return conductors for road vehicles. The pantograph comprises at least one contact strip for each contact pole for making electrical contact with the respective contact wire, but can also comprise two contact strips per contact pole arranged one behind the other in the direction of travel. Each contact strip has a contact piece carried by a contact piece holder, which is preferably made of carbon.The one or more contact strips of a contact pole can each be mounted on a rocker arrangement which can be carried by a pantograph-like support frame. The current collector comprises a compressed air duct which is at least partially delimited by the contact strip and to which a compressed air supply for feeding in compressed air is connected. The compressed air duct extends from the compressed air supply into each of the at least one contact strip and is there at least partially delimited by the respective contact strip. The current collector further comprises a test pressure sensor for measuring an actual test pressure prevailing in the compressed air duct.

[0011] According to the invention, the current collector comprises a pneumatic throttle arranged in the compressed air duct between the compressed air supply and the contact piece, wherein the test pressure sensor cyclically measures an actual test pressure prevailing in the compressed air duct downstream of the throttle. It also comprises a feed pressure sensor for cyclically measuring an actual feed pressure prevailing in the compressed air duct upstream of the throttle. Furthermore, the current collector comprises an evaluation device which is designed to cyclically calculate a target test pressure prevailing in the compressed air duct downstream of the throttle as a function of the measured actual feed pressure from the difference between a supply air mass flow flowing in through the throttle and an exhaust air mass flow flowing out into the environment through a leak present in the pressure duct downstream of the throttle.The evaluation device is further designed to cyclically determine a test pressure deviation of the actual test pressure from the target test pressure and to generate an error message if a first threshold value is exceeded by the determined test pressure deviation.

[0012] In this context, "cyclical" means continuously at discrete, fixed time intervals, for example, every 5 ms. The time intervals can also be determined by a clock pulse of a control device of the pantograph, which controls the compressed air supply and a lifting device for raising and lowering the at least one contact strip.

[0013] The evaluation device comprises known means for electronic data processing, such as a computer unit and data memory with stored calculation algorithms for calculating the target test pressure in the test volume, i.e. the volume of the compressed air duct downstream of the throttle.

[0014] The essential variable used to calculate the target test pressure is the difference between the supply air mass flow flowing in through the throttle and the exhaust air mass flow flowing out through a leak. The supply air mass flow is determined by the current actual feed pressure upstream of the throttle, by the throttle's passage cross-section, and by the actual test pressure prevailing in the test volume. The exhaust air mass flow is determined by the actual test pressure in the test volume, by the size of the leak in the test volume, and by the ambient air pressure prevailing in the environment.

[0015] The calculation of the mass flows of the compressed air is based on a flow model of the throttle and the leak in which a distinction is made between subcritical and supercritical flow depending on the pressure conditions upstream and downstream of the throttle or the leak. Even with an intact grinding piece, a small leak can be assumed due to a lack of tightness in a practical implementation of the compressed air duct. From the size of the test pressure deviation, the evaluation unit recognizes a crack or break in the grinding piece with a gap width that is equivalent to a passage cross-section of, for example, 2 mm. Since the flow model continually calculates the behavior of the target test pressure in the test volume as a function of the measured actual feed pressure upstream of the throttle, the determined test pressure deviation is insensitive to pressure fluctuations in the feed pressure.Such pressure fluctuations occur, for example, when additional consumers, such as a pneumatic lifting device for the pantograph, are connected to the compressed air supply. By taking the actual supply pressure into account, pressure drops in the pressure channel, which are due to a reduction in the supply pressure from the compressed air supply or to temperature fluctuations, can be prevented from being incorrectly interpreted as break detections in the contact piece. This reduces the number of false error messages.

[0016] In an advantageous embodiment of the current collector according to the invention, the evaluation device is designed to cyclically calculate an actual rate of change of the actual test pressure from chronologically successive measurements of the actual test pressure, to calculate a target rate of change of the calculated target test pressure from chronologically successive calculations of the target test pressure, to determine a rate of change deviation of the actual rate of change from the target rate of change, and to generate an error message if a second threshold value is exceeded by the determined rate of change deviation. The respective rate of change indicates how quickly the target test pressure or the actual test pressure changes, which mathematically corresponds to the first derivative of the test pressure with respect to time.By monitoring the rate of change deviation with respect to an exceedance of the second threshold, critical behavior of the test pressure in the test volume is detected much earlier than with known solutions that merely compare the static pressure in the pressure channel with a fixed target value. With the described embodiment, response times in the range of 10 ms to 40 ms can be achieved. This can be crucial if, due to the generated error message, a pantograph control device must react quickly to break the contact between the contact strip and the contact wire of the overhead line system.

[0017] In a further advantageous embodiment of the current collector according to the invention, the evaluation device is designed to calculate the supply air mass flow from the measured actual feed pressure, the measured actual test pressure and a flow coefficient of the throttle, and to calculate the exhaust air mass flow from the measured actual test pressure, an ambient air pressure and a flow coefficient of the leak. The flow model stored in the evaluation device is based on the mass flow Q = dm / dt of the compressed air through a nozzle, which is determined by the respective upstream inlet pressure, the downstream counter pressure and the narrowest cross section of the nozzle. For this purpose, determination equations for the mass flow with different approximation assumptions to simplify the equations are known, for example from https: / / de.wikipedia.org / wiki / Düsenströmung. A concrete simplified form is, for example, given by the equations

[0018] Q = 257 • KV • PI • [ pN • T ] -1 / 2 , for P2 < 1 / 2 - P1, where :

[0019] Q : mass flow in kg / h,

[0020] PI : Inlet pressure upstream of the nozzle in bar, P2 : Back pressure downstream of the nozzle in bar, KV : Flow coefficient in kg / h, pN : Density in kg / m 3 , and T : temperature in K For the temperature can be 297 K, for the density 1 , 2 kg / m 3 be used. The flow coefficients K v The values ​​for the throttle and leak are determined empirically for a pantograph model and are then fixed. For the throttle, the actual feed pressure is used as the inlet pressure and the actual test pressure as the back pressure. For the leak, the actual test pressure is used as the inlet pressure and the ambient air pressure as the back pressure.

[0021] In a further advantageous embodiment, the current collector according to the invention further comprises a pneumatic lifting device for raising and lowering the at least one contact strip and a control device connected to the evaluation device for controlling the lifting device. The evaluation device is designed to transmit a generated error message to the control device and, upon transmission of an error message, to trigger a lowering of the at least one contact strip and / or to generate a driver message. The lifting device can have a pantograph-like frame carrying the contact strips, which frame can be raised by an air bellows. The air bellows can be supplied with compressed air from the compressed air supply. The lifting device is electrically controlled by means of the control device of the current collector in order to put it into or out of operation and to trigger a raising or lowering of the contact strips.If the evaluation device transmits a generated error message to the control device, the control device can block the lifting of the contact strips or lower the contact strips that contact the contact wire in order to prevent defective pantographs with a cracked or broken contact piece from contacting the contact wire.

[0022] In a further advantageous embodiment of the current collector according to the invention, the evaluation device is designed to recognize an exceedance of the first threshold value due to the test pressure deviation and / or the second threshold value due to the change rate deviation occurring during the ramp-up of the feed pressure from an ambient pressure to a nominal feed pressure as a blockage in the pressure channel and to generate a corresponding error message. Such blockages in the pressure channel can be caused by production or assembly errors and would prevent correct determination of a test pressure deviation and / or a change rate deviation and thus error detection "compressed air escaping through a break or crack, for example in the contact piece". Such a blockage reduces the test volume in the pressure channel, which is why the measured actual test pressure rises faster than the calculated target test pressure.This is even more true for the rate of change of the test pressure. Thus, the evaluation device can quickly indicate a failure—for example, when the feed pressure is increased to the nominal feed pressure—and, by means of an error message, instruct the control device to prevent the grinding bars from being raised. This can detect a fault, such as a blockage in the pressure channel, which prevents the actual purpose—for example, the detection of a crack in or breakage of the grinding piece—from being fulfilled.

[0023] Failure to detect the fault will result in safety risks, such as damage to the vehicle and / or overhead line system due to contact between a contact wire and a defective contact strip, which, according to the invention, must be compensated for in another way, such as by automatically preventing the contact strips from being raised or by issuing a corresponding warning to the vehicle driver.

[0024] In a further advantageous embodiment of the current collector according to the invention, the evaluation device is designed to recognize, after the nominal feed pressure has been reached, an exceedance of the first threshold value due to the test pressure deviation and / or the second threshold value due to the change rate deviation as a crack or break in the contact piece and to generate a corresponding error message. If a crack in a contact piece or a break in a contact piece occurs during operation of the vehicle, which can occur, for example, with a heavily worn contact piece with no remaining wear reserve, the actual test pressure drops from its nominal value more sharply than the calculated target test pressure.This drop is detected early on by the corresponding exceedance of the second threshold value due to the rate of change deviation, so that only a very short reaction time elapses from the occurrence of the error until the control system triggers an intervention. This allows potential consequential damage caused by a defective contact strip to be avoided or reduced by interrupting contact between the contact strip and the contact wire by lowering the pantograph.

[0025] The invention also relates to an electrically or hybrid-electrically powered vehicle, in particular a road vehicle, which is equipped with a current collector according to one of the claims described above.

[0026] Further features and advantages of the invention will become apparent from the following description of an embodiment with reference to the drawings, in which

[0027] FIG 1 a road vehicle with a pantograph according to the invention in front view,

[0028] FIG 2 a time diagram of target and actual test pressure during the error-free ramp-up of the feed pressure to nominal value,

[0029] FIG 3 is a time diagram of the desired and actual rate of change of the test pressure corresponding to FIG 2,

[0030] FIG 4 is a time diagram of the test pressure deviation corresponding to FIG 2,

[0031] FIG 5 is a time diagram of the change rate deviation corresponding to FIG 4,

[0032] FIG 6 a time diagram of target and actual test pressure during the ramp-up of the feed pressure in the presence of a blockage in the pressure channel,

[0033] FIG 7 is a time diagram of the desired and actual change rates corresponding to FIG 6, and FIG 8 is a time diagram of the actual test pressure and the actual change rate of the test pressure starting from the nominal feed pressure in the event of a sudden crack in a grinding piece.

[0034] According to FIG 1, an electrically or hybrid-electrically powered road vehicle 1, designed for example as a heavy commercial vehicle, uses an electrified lane of a roadway, for example a multi-lane motorway, above which two contact wires 2, designed as forward and return conductors, of a two-pole overhead line system 3. To feed in electrical energy from the overhead line system 3, the road vehicle 1 has a current collector 4, which has two contact strips 4 for each contact pole, arranged one behind the other in the longitudinal direction of the vehicle, for electrically contacting the respective contact wire 2. The current collector 4 comprises a pantograph-like support frame 5, for example with a lower arm and two upper arms, which are articulated to one another and to the vehicle. Each upper arm carries a rocker 6 which can be rotated about a transverse axis of the vehicle and on which a pair of contact strips 7 are spring-mounted.Each of the grinding strips 7 has an elongated grinding piece 9 made of graphite and carried by a grinding piece holder 8. Downwardly bent over horns are arranged at the lateral ends of the grinding strips. The support frame 5 is coupled to a lifting device 10 designed as an air bellows for raising and lowering the grinding strips 7. The lifting device 10 is fed with compressed air from a compressed air supply 11. For this purpose, the current collector 4 comprises a control device 12 which electrically controls valves in order to connect the lifting device 10 to the compressed air supply 11 for erecting the support frame 5 or to shut off the lifting device 10 from the compressed air supply 11 for gravity-driven lowering of the support frame 5. The current collector 4 comprises a compressed air duct 13 which is connected to the compressed air supply 11. The compressed air duct 13 can be partially closed by separate, if necessary.Compressed air lines can be formed that can be flexibly laid along the support frame 5, branch out and extend into each of the grinding strips 7. In the grinding strips 7, the compressed air channel 13 is at least partially delimited by the respective grinding piece 9.

[0035] Further, according to FIG. 1, the current collector 4 comprises a pneumatic throttle 14 arranged in the compressed air duct 13 between the compressed air supply 11 and the contact piece 9. A feed pressure sensor 15 is connected to the compressed air duct 13 for the cyclical measurement of an actual feed pressure SDist prevailing upstream of the throttle 14. Furthermore, a test pressure sensor 16 is connected to the compressed air duct 13 for the cyclical measurement of an actual test pressure PDist prevailing in the test volume downstream of the throttle 14.

[0036] 1, the current collector 4 further comprises an evaluation device 17 which is designed to cyclically calculate a desired test pressure PDsoll prevailing in the compressed air duct 13 downstream of the throttle 14 as a function of the measured actual feed pressure SDist from the difference between a supply air mass flow Qzu flowing in through the throttle 14 and an exhaust air mass flow Qab flowing out into the environment U through a leak L present in the pressure duct 13 downstream of the throttle 14. The evaluation device 17 is also designed to cyclically determine a test pressure deviation APD of the actual test pressure PDist from the desired test pressure PDsoll and to generate an error message E1 if a first threshold value S1 is exceeded by the determined test pressure deviation APD. In this context, cyclical means continuously at fixed time intervals, for example every 5 ms.The time intervals can also be determined by a clock pulse of the control device 12 of the pantograph 4. For this purpose, the evaluation device 17 comprises known means for electronic data processing, such as computer units (not shown in detail) and data memories with stored calculation algorithms for calculating the desired test pressure PDsoll in the test volume.

[0037] The difference between the supply air mass flow Qzu flowing in through the throttle 14 and the exhaust air mass flow Qab of the compressed air flowing out through the leak L is used as a parameter essential to the invention in calculating the target test pressure PDsoll. The supply air mass flow Qzu is determined by the currently applied actual feed pressure SDist upstream of the throttle 14, by a passage cross-section of the throttle 14, and by the actual test pressure PDist prevailing in the test volume. The exhaust air mass flow Qab is determined by the actual test pressure PDist in the test volume, by the size of the leak L in the test volume, and by the ambient pressure UD prevailing in the environment U. For the calculation of the mass flows Qin and Qab of the compressed air, a flow model of the throttle 14 and the leak L is used, in which a distinction is made between subcritical and supercritical flow depending on the pressure conditions upstream and downstream of the throttle 14 or the leak L.Preferably, the evaluation device 17 is designed to calculate the supply air mass flow Qzu from the measured actual feed pressure SDist, the measured actual test pressure PDist, and a flow coefficient KV14 of the throttle 14, and the exhaust air mass flow Qab from the measured actual test pressure PDist, an ambient pressure DU, and a flow coefficient KVL of the leak L. The flow model stored in the evaluation device 17 is based on the approximate equation for the mass flow Q = dm / dt of the compressed air through a nozzle. This is determined by the respective upstream pressure, the downstream counterpressure, and the narrowest cross-section of the nozzle to a good approximation by:

[0038] Q = 514-KV- [ (P1 - P2) • P2 / pN- T] R2, for P2 > 1 / 2-P1

[0039] Q = 257 -KV- PI • [pN- T] “ 1 / 2 for P2 < 1 / 2 • PI

[0040] Where: Q : mass flow in kg / h,

[0041] Pl : inlet pressure upstream of the nozzle in bar, P2 : back pressure downstream of the nozzle in bar, KV : flow coefficient in kg / h, pN : standard density in kg / m3 , and T : temperature in K .

[0042] 297 K can be used for the temperature and 1.2 kg / m3 for the density. The flow coefficients KV for throttle 14 and leak L are determined empirically for a model of the pantograph 4 and are then fixed. For the supply air mass flow Qzu through the throttle 14, the actual feed pressure SDist is used as the inlet pressure PI and the actual test pressure PDist as the back pressure P2, and for the exhaust air mass flow Qab through the leak L, the actual test pressure PDist is used as the inlet pressure PI and the ambient pressure UD as the back pressure P2.

[0043] Even with intact grinding pieces 9, a small leak L can be assumed due to a leak in a practical implementation of the compressed air duct 13. The evaluation unit 17 recognizes from the size of the test pressure deviation APD a crack or break in a grinding piece 9 with a gap width that is equivalent to a passage cross-section of, for example, 2 mm. Since the flow model continuously calculates the behavior of the target test pressure PDsoll in the test volume as a function of the measured actual feed pressure SDist upstream of the throttle 14, the determined test pressure deviation APD is insensitive to pressure fluctuations in the feed pressure SD. Such pressure fluctuations occur, for example, when additional consumers, such as the pneumatic lifting device 10, are connected to the compressed air supply 11.By taking the actual feed pressure SDist into account, pressure drops in the pressure channel 13, which are due to a reduction in the feed pressure on the part of the compressed air supply 11 or to temperature fluctuations, can be prevented from being incorrectly interpreted as break detections in a grinding piece 9. This reduces the number of false error messages.The evaluation device 17 is also designed to cyclically calculate an actual change rate PD ' ist of the actual test pressure PDist from successive measurements of the actual test pressure PDist, to calculate a target change rate PD ' soll of the calculated target test pressure PDsoll from successive calculations of the target test pressure PDsoll, to determine a change rate deviation APD ' of the actual change rate PD ' ist from the target change rate PD ' soll, and to generate an error message E2 if a second threshold value S2 is exceeded by the determined change rate deviation APD '. The respective change rate indicates how quickly the target test pressure PDsoll or . the actual test pressure PDist changes, which mathematically corresponds to the first derivative of the test pressure with respect to time.By monitoring the rate of change deviation APD' with regard to whether the second threshold value S2 is exceeded, critical behavior of the actual test pressure PDist in the test volume is detected much earlier than with known solutions that merely compare the static pressure in the pressure channel with a fixed target value. This enables response times in the range of 10 ms to 40 ms to be achieved. This can be crucial if, due to the generated error message E2, the control device 12 of the pantograph 4 must react quickly to break the contact between the contact strip 9 and the contact wire 2 of the overhead line system 3.

[0044] The lifting device 10 is electrically controlled by the control device 12 of the pantograph 4 in order to put it into operation or out of operation and to trigger a raising or lowering of the contact strips 7. If the evaluation device 17 transmits a generated error message E1 or E2 to the control device 12, the control device 12 can block a raising of the contact strips 7 or lower the contact strips 7 contacting the contact wire 2 in order to prevent a defective pantograph 4 with a cracked or broken contact piece 9 from contacting the contact wire 2.The evaluation device 17 is further designed to recognize an exceeding of the first threshold value S 1 by the test pressure deviation APD and / or the second threshold value S2 by the change rate deviation APD ' as a blockage in the pressure channel 13 during the ramp-up of the feed pressure SD from an ambient pressure UD to a nominal feed pressure SDnenn and to generate a corresponding error message E3. Such blockages in the pressure channel 13 can be caused by production or assembly errors and would prevent a correct determination of a test pressure deviation APD and / or a change rate deviation APD ' and thus an error detection "compressed air is escaping through a break or crack, for example in the grinding piece". Such a blockage reduces the test volume in the pressure channel 13, which is why the measured actual test pressure PDist rises faster than the calculated target test pressure PDsoll.This applies even more to the rate of change PD ' of the test pressure PD . Thus, the evaluation device 17—for example, when the feed pressure SD is ramped up to the nominal feed pressure SD nominal—can quickly indicate a failure and, by means of an error message E3, instruct the control device 12 to prevent the grinding bars 7 from being raised. This can detect a fault, such as a blockage in the pressure channel 14, which prevents the actual purpose, such as the detection of a crack in or breakage of a grinding piece 9, from being fulfilled.Failure to detect the fault results in safety risks, such as damage to vehicle 1 and / or overhead line system 3 due to contact between a contact wire 2 and a defective contact strip 9, which, according to the invention, are to be compensated for in another way, such as by automatically preventing the contact strips 7 from being raised or by issuing a corresponding warning W to the vehicle driver.

[0045] The evaluation device is designed in particular to recognize an exceedance of the first threshold value S 1 by the test pressure deviation APD and / or the second threshold value S2 by the change rate deviation APD ' as a crack or break in a grinding piece 9 after the nominal feed pressure SDnenn has been reached and to generate a corresponding error message E1 or E2. If a crack in a grinding piece 9 or a break in a grinding piece 9 occurs during operation of the vehicle 1, which can occur, for example, with a heavily worn grinding piece 9 with no remaining wear reserve, the actual test pressure PDist drops more sharply from its nominal value than the calculated target test pressure PDsoll.This drop is detected early on by the corresponding exceedance of the second threshold value S2 by the rate of change deviation APD ', so that only a very short reaction time elapses from the occurrence of the error until the triggering of an intervention by the control device 12. As a result, possible consequential damage that a defective contact piece 9 can cause can be avoided or reduced by interrupting contact between the contact piece 9 and the contact wire 2 by lowering the pantograph 4.

[0046] In the following described FIGS. 2 to 8, the operation of the evaluation device 17 according to the invention is explained using time diagrams of cyclically recorded measured values ​​and cyclically calculated comparison variables.

[0047] FIG 2 shows how, when the feed pressure SD is increased by means of the compressed air supply 11 in the test volume downstream of the throttle 14, the measured actual test pressure PDist and the calculated nominal test pressure PDsoll develop over time t. The measured actual test pressure PDist is initially at the level of the ambient pressure UD and increases from the system start at around t = 16.7 s until the nominal feed pressure SDnenn is reached in the test volume at around t = 19.0 s. The pressure in the test volume is maintained at this level during operation of the pantograph 4, although it can fluctuate slightly, for example at t = 20.4 s. FIG 2 shows that when the pressure channel 13 is unblocked, the measured actual test pressure PDist follows the calculated target test pressure PDsoll almost identically - even during the increase by t = 20.4 s, which is caused by a fluctuation in the actual feed pressure SDist.This is also shown in FIG. 4, which shows the test pressure deviation APD between the actual test pressure PDact and the target test pressure PDset, which does not exceed a predetermined first threshold value S1. Likewise, according to FIG. 3, the measured actual change rate PD'act of the actual test pressure PDact follows the calculated target change rate PD'set of the target test pressure PDset, with the actual change rate PD'act scattering around the curve of the calculated target change rate PD'set approximately every 5 ms due to the discrete measurements. Nevertheless, according to FIG. 5, with the pressure channel 13 unblocked, the change rate deviation APD' between the actual change rate PD'act and the target change rate PD'set does not exceed the predetermined second threshold value S2. The case is different in the case of a blockage in the pressure channel 13, in which, according to FIG 6, the actual test pressure PDist rises faster than the target test pressure PDsoll and at the time shown the test pressure deviation APD exceeds the first threshold value Sl.Considering the corresponding change rate curve shown in FIG. 7, the change rate deviation APD' between the actual change rate PD'actual and the target change rate PD'target already exceeds the second threshold value S2 at an earlier time, also shown. A failure of the break detection due to a blockage in the pressure channel 13 can thus be revealed earlier by monitoring the second threshold value S2.

[0048] Starting from regular operation, in which the nominal feed pressure SDom prevails in the test volume, FIG 8 shows how the actual test pressure PDist (upper curve in FIG 8) and even faster the actual change rate PD'ist of the actual test pressure PDist drops when a leak occurs in the pressure channel 13, for example a break in a contact piece 9. Due to the faster drop in the change rates PD'ist and PD'soll compared to the test pressures PDist and PDsoll, the change rate deviation APD' will exceed the second threshold value S2 earlier than the test pressure deviation APD exceeds the first threshold value S1. By monitoring the second threshold value S2, the reaction time for a control intervention is shortened.

Claims

Patent claims 1. A current collector (4) for an electrically or hybrid-electrically driven vehicle, in particular a road vehicle (1), for feeding electrical energy from an overhead line system (3) having at least one contact wire (2), comprising - at least one contact strip (7) for electrically contacting the at least one contact wire (2), which has a contact strip (9) carried by a contact strip holder (8), - a compressed air channel (13) at least partially delimited by the contact piece (9), - a compressed air supply (11) connected to the compressed air duct (13) for supplying compressed air, and - a test pressure sensor (16) for measuring an actual test pressure (PDist) prevailing in the compressed air duct (13), characterized by - a pneumatic throttle (14) arranged in the compressed air duct (13) between the compressed air supply (11) and the contact piece (9), wherein the test pressure sensor (16) cyclically measures an actual test pressure (PDist) prevailing in the compressed air duct (13) downstream of the throttle (14), - a feed pressure sensor (15) for cyclical measurement of an actual feed pressure (SDist) prevailing in the compressed air duct (13) upstream of the throttle (14), and - an evaluation device (17) which is designed to - to cyclically calculate a target test pressure (PDsoll) prevailing in the compressed air duct (13) downstream of the throttle (14) as a function of the measured actual feed pressure (SDist) from the difference between a supply air mass flow (Qzu) flowing in through the throttle (14) and an exhaust air mass flow (Qab) flowing out into the environment (U) through a leak (L) present in the pressure duct (13) downstream of the throttle (14), - to cyclically determine a test pressure deviation (APD) of the actual test pressure (PDact) from the target test pressure (PDsoll), and - to generate an error message (El) if a first threshold value (Sl) is exceeded by the determined test pressure deviation (APD).

2. Current collector (4) according to claim 1, wherein the evaluation device (17) is designed to - to cyclically calculate an actual change rate (PD'ist) of the actual test pressure (PDist) from successive measurements of the actual test pressure (PDist), - to calculate a target change rate (PD'soll) of the calculated target test pressure (PDsoll) from successive calculations of the target test pressure (PDsoll), - to determine a change rate deviation (APD') of the actual change rate (PD'actual) from the target change rate (PD'target), and - to generate an error message (E2) if a second threshold value (S2) is exceeded by the determined rate of change deviation (APD').

3. Current collector (4) according to claim 1 or 2, wherein the evaluation device () is designed to - to calculate the supply air mass flow (Qzu) from the measured actual feed pressure (SDist), the measured actual test pressure (PDist) and a flow coefficient (KV14) of the throttle (14), and - to calculate the exhaust air mass flow (Qab) from the measured actual test pressure (PDist), an ambient pressure (UD) and a flow coefficient (KVL) of the leak (L).

4. Current collector (4) according to one of the preceding claims, further comprising - a pneumatic lifting device (10) for raising and lowering the at least one contact strip (7) and - a control device (12) connected to the evaluation device (17) for controlling the lifting device (10), - wherein the evaluation device (17) is designed to transmit a generated error message (E1, E2) to the control device (12), and - wherein the control device (12) is designed to trigger a lowering of the at least one contact strip (7) and / or to generate a driver message (W) upon transmission of an error message (El, E2).

5. Current collector (4) according to one of the preceding claims, wherein the evaluation device (17) is designed to detect an exceedance of the first threshold value (S1) by the test pressure deviation (APD) and / or the second threshold value (S2) by the change rate deviation (APD') as a blockage in the pressure channel (13) during the ramp-up of the feed pressure (SDist) from an ambient pressure (UD) to a nominal feed pressure (SDnenn) and to generate a corresponding error message (E3).

6. Current collector (4) according to one of the preceding claims, wherein the evaluation device (17) is designed to detect an exceedance of the first threshold value (S1) by the test pressure deviation (APD) and / or the second threshold value (S2) by the change rate deviation (APD') as a crack or break in the contact piece (9) after the nominal feed pressure (SDnenn) has been reached and to generate a corresponding error message (E1, E2).

7. Electrically or hybrid-electrically powered vehicle, in particular a road vehicle (1), with a current collector (4) according to one of the preceding claims.

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