SE1650059A1

SE1650059A1 - A system and a method for monitoring a gearbox

Info

Publication number: SE1650059A1
Application number: SE1650059A
Authority: SE
Inventors: Birgersson Fredrik
Original assignee: Scania Cv Ab
Priority date: 2016-01-20
Filing date: 2016-01-20
Publication date: 2017-07-21
Also published as: SE541859C2; DE112017000245B4; WO2017127008A1; DE112017000245T5

Abstract

A system for monitoring a gearbox (1) in a vehicle, comprising a processing unit (12) and a set of sensors (13-16) configured to communicate signals to the processing unit, said set of sensors comprising: - a first accelerometer (13) configured to sense rigid body motion of the gearbox, positioned on a portion of the gearbox which is more rigid than an average outer wall of a gearbox housing (7), and - a first strain gauge (15) configured to sense a torque applied to the gearbox, said first strain gauge being positioned on the gearbox in a position where an output torque from the. gearbox is detectable,. wherein said processing unit is configured to receive said signals and, based thereon, generate health and performance information of the gearbox.(Fig. 1)

Description

A svstem and a method for monitorinq a qearbox TECHNICAL FIELD OF THE INVENTION The present invention relates to a system for monitoring a gearboxin a powertrain of a vehicle according to the preamble of claim 1.lt further relates to a motor vehicle comprising such a system andto a method for monitoring a gearbox according to the preamble ofclaim 14. The method and the system are not limited to any specifictype of gearbox, but can be applied to all sorts of gearboxes usedin motor vehicles, such as range-splitter gearboxes, range-changegearboxes, automatic gearboxes, automated gearboxes, manual gearboxes, etc.

The gearbox is arranged to be connected to an engine of the motorvehicle via a clutch or via a corresponding device, such as at least one electric machine.

BACKGROUND AND PRIOR ART Gearboxes in powertrains of motor vehicles are used to convertpower from an engine of the motor vehicle into power at a specifictorque and speed needed to drive the vehicle. As power isconverted in the gearbox, the applied torque affects the gearboxand the gearbox is consequently subjected to significant wearduring operation of the motor vehicle. The amount of wear on thegearbox, and thereby its component life expectancy, is to a largedegree impacted by the way in which the vehicle is driven. Drivingat high torques typically increases the wear on the gearbox and thereby reduces its component life expectancy. The health of the gearbox is also affected by sudden accelerations, occurring forexample when the vehicle travels over an uneven surface, such asat road bumps, kerbs, and railway crossings or similar. A furthercause for wear of the gearbox is deteriorated lubricating oilcontained in the gearbox, which results in poor lubrication of the components within the gearbox.

Due to the many different factors affecting the gearbox, it isdifficult to predict the component life expectancy of the gearbox.Failures of the gearbox or of components therein therefore oftenhappens unexpectedly, and reasons for harm caused to thegearbox are investigated only after encountering a problem.Evaluation of the factors having led to the problem or failure may also be both costly and time consuming.

SUMMARY OF THE INVENTION lt is a primary objective of the present invention to provide asolution to the above described problems and provide a solutionby means of which the health and performance of the gearbox canbe continuously assessed in order to enable identification ofproblems at an early stage. Another objective is to provide meansfor improving and shortening an evaluation process carried out once a problem related to the gearbox has been encountered.

At least the primary objective is achieved by means of the initially defined system, which is characterised in that the system comprises a processing unit and a set of sensors configured to communicate signals to the processing unit, said set of sensorscomprising: - a first accelerometer configured to sense rigid body motionof the gearbox in at least one direction, positioned on aportion of the gearbox which is more rigid than an averageouter wall of the gearbox housing, and - a first strain gauge configured to sense a torque applied tothe gearbox, said first strain gauge being positioned on thegearbox in a position where an output torque from thegearbox is detectable, wherein said processing unit is configured to receive said signalsand, based thereon, generate health and performance information of the gearbox.

By means of the strategically positioned accelerometer and strain gauge, applied torques affecting the gearbox and suddenaccelerations leading to rigid body motion of the gearbox can besensed and signals related thereto can be communicated to theprocessing unit, preferably placed on the gearbox in the vicinity ofthe sensors. The processing unit is configured to generate healthand performance information which can be communicatedwirelessly to a central service node or the like, and/or be stored inthe processing unit and read off a storage means comprisedtherein as the motor vehicle is being serviced, or as a problemrelated to the gearbox is encountered. The system according tothe invention thereby enables continuous assessment of theperformance and health of the gearbox, enabling identification ofproblems at an early stage. The system furthermore provides information that is useful when a failure of or a problem with the gearbox is evaluated. This information can significantly shorten the evaluation process.

The system according to the invention can be mounted externallyon the gearbox and can thereby easily be removed and replacedwhen needed. Individual sensors as well as the processing unititself can easily be exchanged, and it is easy to adapt the systemto the gearbox on which it is mounted by simply attaching thesensors, e.g. by gluing or taping, onto suitable positions on thegearbox.

The system can be made independent from other systems of themotor vehicle. All relevant signals to the processing unit are thuscommunicated from the sensors of the system. However, it is alsopossible to connect the system to other sensors or systems of thevehicle and thereby obtain signals that can be relevant forassessment of the performance and health of the gearbox. lf thegearbox already comprises an electronic control unit (ECU), theprocessing unit may of course be integrated with or attached tothe ECU.

The first accelerometer is positioned on a portion of the gearboxwhich is more rigid than an average outer wall of the gearboxhousing. This can be e.g. a seam between two parts of the gearboxhousing or another part of the gearbox housing which has a largerwall thickness than a front housing of the gearbox housing. ln thisway, the first accelerometer will be less affected by vibrations arising in the gearbox housing itself.

According to one embodiment, the processing unit is configuredto, based on said signals and/or on said health and performanceinformation of the gearbox, estimate a component life expectancyof the gearbox. To be able to accurately estimate life expectanciesof the entire gearbox as well as of individual components in theis useful gearbox and attached to it to avoid changing of components, as well as to prevent and foresee unexpectedbreakdowns of the gearbox or of components within or attached tothe gearbox _ According to one embodiment, the health and performanceinformation generated by the processing unit includes at least atorque applied to the gearbox and a rigid body motion of thegearbox. The torque can be determined based on the signal fromthe first strain gauge and gives valuable input for estimating acomponent life expectancy of the gearbox housing. Based on theoutput torque, an input torque can easily be calculated.Information relating to the rigid body motion of the housing isthe first accelerometer and gives input for estimating a component life determined based on at least the signal fromexpectancy of the gearbox and components therein. Appliedtorques as well as sudden accelerations and decelerations of thegearbox can be logged in a load history and a movement history, respectively, of the gearbox.

According to one embodiment, the processing unit is configured touse at least one data reduction algorithm in the generation ofhealth and performance information of the gearbox and whereinsaid processing unit comprises storage means for storing said information. The data reduction can be carried out by rainflow counting, cycle counting, or rearranging of data into matrices etc.This reduces the amount of data that needs to be storedsignificantly, making it possible to reduce storage capacity of theprocessing unit. lt also facilitates future evaluations of the storeddata.

According to one embodiment, the processing unit is configured togenerate and store health and performance information relating toat least one of a load history, a movement history, a gear history,a gear shifting history, and damage caused to a component withinthe gearbox. The load history can include for example forces andtorques applied to the gearbox, sudden accelerations,temperature, and oil particle concentrations, depending on whichsensors are included in the set of sensors. The movement historycan include rigid motion accelerations, vehicle speed, ageographical position of the gearbox, etc. The gear history caninclude information about an accumulated time per engaged gearand the gear shifting history can include occurrences of shiftsbetween individual gears. Damage is caused by e.g. appliedtorques, sudden accelerations, rattling gears, forces from gear-shifting and synchronisation, etc. By logging the occurrence ofdamage, it is possible to predict when components within or on thegearbox, or the gearbox housing, are expected to break down dueThe stored movement history, gear history, gear shifting history and damage to fatigue. information relating to load history,is useful in an evaluation process after failure of the gearbox aswell as to continuously evaluate the gearbox's health during usage.

According to one embodiment, the gearbox comprises a torqueabsorbing structure between the front end and the rear end, andsaid first strain gauge is positioned on or in front of the torqueabsorbing structure. ln the case where the gearbox is mountedusing a beam or similar as a torque absorbing structure, the straingauge should be positioned on or in front of this torque absorbingstructure to be able to detect an applied torque.

According to one embodiment, said first accelerometer ispositioned between the torque absorbing structure and the rearend. ln this position, there are less vibrations originating from theengine than in front of the torque absorbing structure. Thereby,less filtering of the signal from the sensor is needed to gain usefulinformation relating to the rigid body motion of the gearbox.According to one embodiment, said set of sensors furthercomprises a second accelerometer attached on the gearboxhousing between the front end and the torque absorbing structure.With the second accelerometer positioned in the vicinity of theengine, vibrations from the engine and resulting from gear shiftingand gear meshing can be sensed and identified. The health andperformance information generated by the processing unit in thisembodiment preferably includes gear shifting information and gearmeshing information generated at least partly based on a signalfrom the second accelerometer, so that it is possible to generatedetailed gear and gear shifting histories. For example, the gearhistory can include a total and an average time per engaged gearand the gear shifting history can include occurrences of shiftsbetween individual gears. Order analysis of the signal from the second accelerometer is preferably performed to generate the requested gear and gear shifting information. The order analysiscan also generate information relating to engine orders. Thus, thesecond accelerometer provides additional precision to thegenerated health and performance data which can be used whenpredicting component life of e.g. gear wheels, brackets andattached components, also including electrical units attached tothe gearbox. lt also makes it easy to identify broken or damagedgear wheels at an early stage. Furthermore, the detection ofengine orders makes it possible to identify problems arising from e.g. the clutch.

According to one embodiment, said first accelerometer is a triaxialaccelerometer. By using a triaxial accelerometer, rigid body motionin all three directions can be sensed and only one accelerometeris thus needed to sense three dimensional rigid body motion. Anseveral biaxial and/or uniaxial alternative is to have accelerometers mounted.According to one embodiment, said set of sensors furthercomprises at least one of a temperature sensor configured tosense a temperature of oil contained in the gearbox and a particlecounter configured to count particles present in said oil. Atemperature sensor and a particle counter can provide usefulinformation about the conditions in the gearbox that may be usedto reweight logged damage of components. For example, adamage caused at an elevated temperature may be given a higherweight than a damage caused at a lower temperature.

According to one embodiment, said set of sensors further comprises at least one tachometer configured to measure a The tachometer preferably measures the rotational speed of one of the rotational speed of a component within the gearbox.shafts within the gearbox. lt facilitates determination of a currentrotational speed of the engine and can also be used to identify rattle of the gearbox.

According to one embodiment, the processing unit is attached tothe gearbox. Preferably, at least one sensor from said set ofsensors is integrated with the processing unit. For example, theprocessing unit can be glued to the gearbox housing and atemperature sensor can be integrated therewith to sense atemperature of the housing. Also an accelerometer, a strain gaugeor another sensor can be integrated with the processing unit. Thismakes the system according to the invention easier to mount and reduces the amount of wiring needed.

According to one embodiment, the processing unit comprises aGPS receiver. The processing unit can thereby, based on datafrom the GPS receiver, generate and store e.g. a speed history and a geographical positioning history of the gearbox.

According to one embodiment, the processing unit is configured tocommunicate wirelessly with an external central node. Informationcan thereby be continually communicated and the health of the gearbox can be monitored from a distance.

According to another aspect of the invention, the invention relatesto a motor vehicle comprising a powertrain including a gearbox and the proposed system for monitoring said gearbox.

According to another aspect of the invention, the above mentionedprimary object is achieved by the initially defined method,characterised in that the method comprises the steps of: - providing the proposed system, - sensing rigid body motion of the gearbox in at least onedirection using said first accelerometer and sending signalsre|ating thereto to the processing unit, - sensing torques applied to the gearbox using said first straingauge and sending signals re|ating thereto to the processingunH,and - in the processing unit, receiving said signals and, basedthereon, generating health and performance information ofthe gearbox. Advantages and advantageous features of sucha method appear from the above description of the proposed system.

According to one embodiment of this aspect of the invention, themethod further comprises the step of: - based on said signals and/or said health and performance information of the gearbox, estimating a component life expectancy of the gearbox.

Other advantageous features as well as advantages of the present invention will appear from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will in the following be further described by means of example with reference to the appended drawings, wherein 11 Fig. 1 shows a schematic illustration of a system according toan embodiment of the invention mounted on a gearbox, Fig. 2 shows schematic diagrams of health and performanceinformation obtained using the system according to anembodiment of the invention, and Fig. 3 is a flow chart illustrating a method according to an embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THEINVENTION A gearbox 1 comprising a system for monitoring the gearboxaccording to an embodiment of the invention is schematicallyshown in fig. 1. The gearbox 1 forms part of a powertrain of a motorvehicle and has a front end 2 at which an input shaft 3 is connectedto an internal combustion engine via a clutch or a correspondingdevice, and a rear end 4 at which the gearbox 1 via an output shaft5 is connected to drive wheels. The gearbox is configured to bemounted on a chassis of the motor vehicle and has for this purposea mounting member 6 in the form of a beam that can be screwedor bolted onto the chassis, or onto mounting brackets provided onthe chassis. This mounting member 6 functions as a torqueabsorbing structure, absorbing torques applied to the gearbox. lfinstead the gearbox is mounted at a front flange attached to theengine, the entire gearbox will deform under torque. A gearboxhousing 7, here comprising a front housing 8, a rear housing 9,surrounds mechanical and a rearmost bearing housing 10, components, such as shafts, gear wheels and bearings, provided 12 within the gearbox 1. A control recess 11 is in the shown embodiment provided on the front housing 8.

The system for monitoring the gearbox comprises, on one hand, aprocessing unit 12 attached onto the gearbox housing 7 by meansof e.g. gluing, taping, screwing, or similar. ln the shownembodiment, the processing unit 12 is attached to the rear housing9, but it can of course be attached to any external part of thegearbox 1. On the other hand, the system comprises a set ofsensors connected to the processing unit 12, in the shown embodiment including a first accelerometer 13, a second accelerometer 14, a strain gauge 15, and an integratedtemperature sensor and tachometer 16. All sensors 13-16 areconfigured to collect and send data to the processing unit 12.Further strain gauges and/or accelerometers may also be providedon the gearbox for increased precision, as well as an oil particle counter and an external temperature sensor.

The first accelerometer 13 is in the shown embodiment a triaxialaccelerometer configured to sense rigid body motion of thegearbox 1 in three directions, predominantly at relatively lowfrequencies. For this purpose, it is externally positioned on aportion of the gearbox 1 which is relatively rigid in comparison withan average outer wall of the gearbox housing 7. ln this case, thefirst accelerometer 13 is positioned rear of the mounting member 6 on a rigid part of the bearing housing 10.

The strain gauge 15 is positioned on the mounting member 6, at aposition where an output torque from the gearbox 1 is detectable, such that it can be used to detect a torque applied to the gearbox. 13 Thus, the strain gauge 15 cannot be positioned rear of themounting member 6, since no torque is detectable at that position.lf desired, the sensed output torque can easily be converted to an input torque in the processing unit 12.

The second accelerometer 14 is positioned on the rear housing 9between the front end 2 and the mounting member 6, thus on amuch less rigid position than the first accelerometer 13 and closerto the engine. The second accelerometer 14 is configured to detectsignals giving rise to high frequency vibrations in the gearboxhousing 7. On one hand, such signals originate from the engine,related to e.g. engine order and rotational speed of the engine. Onthe other hand, the signals originate from the gearbox itself,related to e.g. gear shifts, gear meshing orders and bearingThe second accelerometer orders. 14 can alternatively be positioned on the front housing 8.

The integrated temperature sensor and tachometer 16 is mountedon the gearbox housing 7 in the vicinity of the processing unit 12.An opening is made in the gearbox housing 7 to accommodate thesensor 16, so that it can be used to measure the temperature oflubricating oil contained within the gearbox 1 and to monitor a rotational speed of a shaft or a gear wheel within the gearbox.

The processing unit 12 comprises a processor and an internalstorage means for data storage. The processing unit 12 isconfigured to receive signals sensed by and communicated by the13-16 and, performance sensors based thereon, generate health and Such health and performance information is related to loads affecting the gearbox, information of the gearbox. 14 such as applied torque, sudden accelerations, vibrations,temperature, etc. The processing unit 12 uses the input signalsfrom the sensors13-16 to determine those loads and to estimatea component life expectancy of the gearbox 1. Damage and loadand movement histories may be stored in the means for data storage.

Data from the first accelerometer 13 can be used to determine highfrequency and low frequency rigid body motion of the gearbox 1.Data from the strain gauge 15 can be used to determine an outputtorque from the gearbox, and thereby also to calculate an inputtorque. Data from the second accelerometer 14, possibly incombination with data from the first accelerometer 13 and withdata from the strain gauge 15, can be used to determine rotationalspeed and engine orders of the engine as well as to identify andlog gear shifts and to determine which gear is engaged. Data fromthe tachometer 16 simplifies an evaluation of the current rotationalspeed, and can also be used to detect rattle or noise from thegearbox. Temperature data from the integrated temperaturesensor and tachometer 16 can be used to determine at which temperature a certain gear shift or acceleration took place.

The processing unit 12 is preferably configured to use one or moredata reduction algorithm(s) to reduce the amount of data to bestored. For example, rainflow count and/or cycle count can be usedto log damage arising from applied torques, accelerations, orvibrations, and data can be arranged into matrices, etc. Orderanalysis and FFT (Fast Fourier Transform) signal analysis can alsobe used to determine relevant frequencies, e.g. gear meshing orders, bearing orders and engine orders.

Fig. 2 shows schematic diagrams of health and performance information obtained using the system according to anembodiment of the invention, wherein data reduction algorithms have been used to extract the relevant information. ln (a), the accumulated time that a specific torque has beenapplied to the gearbox is shown, based on the signal from thestrain gauge 15. From the diagram, it is possible to identifywhether a particular torque has been over-represented, forexample if the vehicle has been driven at unnecessarily high torques, which causes wear on the gearbox. ln (b), the number of cycles that the gearbox has been subjectedto a specific acceleration, leading to rigid body motion of thegearbox, is shown. The data is primarily obtained from the signal from the first accelerometer 13. ln (c), accumulated damage to a component (here a bracket fixingan electrical unit) is shown for acceleration of the gearbox as afunction of frequency. Any components attached to the gearbox 1are subjected to e.g. engine- and road-induced vibrations causingstructural fatigue. The processing unit 12 processes received vibration data and outputs calculated damage to the component. ln (d), the accumulated time that a particular gear has beenengaged is shown. Data relating to this are best derived from thesignals from the second accelerometer 14 in combination with thefirst accelerometer 13. Combined with input from e.g. the strain gauge 15 one can also log the above data as a function of torque. 16 This data helps to understand which bearings and gears in the gearbox1 are likely to fail. ln (e) and (f) respectively, the number of times that successful andunsuccessful gear shifts from and to particular gears have beenperformed is shown. The precision can be improved by alsologging the time that a gear shift takes for certain up- and down-shifts. retrieves axial position of manoeuvring axles of the gearbox may For high-precision evaluation, a specific sensor that be added to the system.

Similar diagrams can be obtained for accumulated time per amountof oil particles detected and/or temperature, angular accelerationas a function of engaged gear, etc. Furthermore, data relating todifferent parameters can be combined to get an overview of loadsand movements affecting the gearbox. ln a method according to an embodiment of the invention,illustrated in fig. 3, a system according to the invention asdescribed above is provided on a gearbox S1 in a first step S1. lna second step S2, rigid body motion of the gearbox 1 is sensedusing the first accelerometer 13, and torques applied to thegearbox are sensed using the strain gauge 15. Other mountedsensors sense in this step e.g. rotational speed, temperature, anumber of particles in the lubricating oil, vibrations, etc. Localstrain gauges attached close to critical positions may be used tosense torque locally. ln a third step S3, signals relating to thesensed physical quantities are sent to the processing unit 12. ln a fourth step S4, the signals are received in the processing unit. 17 Based thereon, in a fifth step S5, health and performanceinformation of the gearbox 1 is generated in the processing unit12. ln the fifth step, data processing is used to generate the requested information from the reduction algorithms and signal incoming signals.

The invention is of course not in any way restricted to the em-bodiments described above, but many possibilities to modifica-tions thereof would be apparent to a person with skill in the artwithout departing from the scope of the invention as defined in theappended claims. For example, further sensors can be added tothe system, such as additional strain gauges mounted at positionswhich have been found to be vulnerable, or additionalaccelerometers, e.g. an accelerometer positioned on the bearinghousing for obtaining information relating to bearing orders and tobe able to predict and prevent bearing failures. Also a GPSreceiver can be provided, depending on which information is desued.

Claims

1. A system for monitoring a gearbox (1) in a powertrain of avehicle, said gearbox having a front end (2) which via a clutch ora corresponding device is arranged to be connected to an engine,a rear end (4) arranged to be connected to drive wheels, and agearbox housing (7), characterised in that the system comprises a processing unit (12) and a set ofsensors (13, 14, 15, 16) configured to communicate signals to theprocessing unit, said set of sensors comprising: - a first accelerometer (13) configured to sense rigid bodymotion of the gearbox (1) in at least one direction, positionedon a portion of the gearbox which is more rigid than anaverage outer wall of the gearbox housing (7), and - a first strain gauge (15) configured to sense a torque appliedto the gearbox (1), said first strain gauge (15) beingpositioned on the gearbox (1) in a position where an outputtorque from the gearbox is detectable, wherein said processing unit (12) is configured to receive saidsignals and, based thereon, generate health and performance information of the gearbox (1).

2. The system according to claim 1, wherein the processing unit(12) is configured to, based on said signals and/or on said healthand performance information of the gearbox (1), estimate a component life expectancy of the gearbox (1).

3. The system according to claim 1 or 2, wherein the health and performance information generated by the processing unit (12) 19 includes at least a torque applied to the gearbox (1) and a rigid body motion of the gearbox (1).

4. The system according to any one of the preceding claims,wherein the processing unit (12) is configured to use at least onedata reduction algorithm in the generation of health andperformance information of the gearbox (1) and wherein saidprocessing unit (12) comprises storage means for storing said information.

5. The system according to claim 4, wherein the processing unit(12) is configured to generate and store health and performanceinformation relating to at least one of a load history, a movementhistory, a gear history, a gear shifting history, and damage caused to a component within the gearbox (1).

6. The system according to any one of the preceding claims,wherein the gearbox comprises a torque absorbing structure (6)between the front end (2) and the rear end (4), and wherein saidfirst strain gauge (15) is positioned on or in front of the torqueabsorbing structure (6).

7. The system according to claim 6, wherein said firstaccelerometer (13) is positioned between the torque absorbing structure (6) and the rear end (4).

8. The system according to claim 6 or 7, wherein said set ofsensors (13, 14, 15, 16) further comprises a second accelerometer(14) attached on the gearbox housing (7) between the front end (2) and the torque absorbing structure (6).

9. The system according to any one of the preceding claims, wherein said first accelerometer (13) is a triaxial accelerometer.

10. The system according to any one of the preceding claims,wherein said set of sensors (13, 14, 15, 16) further comprises atleast one of a temperature sensor (16) configured to sense atemperature of oil contained in the gearbox (1) and a particle counter configured to count particles present in said oil.

11. The system according to any one of the preceding claims,wherein said set of sensors (13, 14, 15, 16) further comprises atleast one tachometer (16) configured to measure a rotational speed of a component within the gearbox (1).

12. The system according to any one of the preceding claims,wherein the processing unit (12) is attached to the gearbox (1),preferably wherein at least one sensor from said set of sensors is integrated with the processing unit (12).

13. A motor vehicle comprising a powertrain including a gearbox(1) and a system for monitoring said gearbox (1) according to any one of claims 1-12.

14. A method for monitoring a gearbox (1) in a powertrain of avehicle, said gearbox (1) having a front end (2) which via a clutchor a corresponding device is arranged to be connected to anengine, a rear end (4) arranged to be connected to drive wheels,and a gearbox housing (7), characterised in 21 that the method comprising the steps of: providing a system according to any one of claims 1-12,sensing rigid body motion of the gearbox (1) in at least onedirection using said first accelerometer (13) and sendingsignals relating thereto to the processing unit (12), sensing torques applied to the gearbox (1) using said firststrain gauge (15) and sending signals relating thereto to theprocessing unit (12), and in the processing unit (12), receiving said signals and, basedthereon, generating health and performance information of the gearbox (1).

15. The method according to claim 14, further comprising the step of:15 - based on said signals and/or said health and performanceinformation of the gearbox (1), estimating a component life expectancy of the gearbox (1 ).