SE541859C2

SE541859C2 - A system and a method for monitoring a gearbox

Info

Publication number: SE541859C2
Application number: SE1650059A
Authority: SE
Inventors: Fredrik Birgersson
Original assignee: Scania Cv Ab
Priority date: 2016-01-20
Filing date: 2016-01-20
Publication date: 2019-12-27
Also published as: DE112017000245T5; DE112017000245B4; WO2017127008A1; SE1650059A1

Description

A system and a method for monitoring a gearbox TECHNICAL FIELD OF THE INVENTION The present invention relates to a system for monitoring a gearbox in a powertrain of a vehicle according to the preamble of claim 1. It further relates to a motor vehicle comprising such a system and to a method for monitoring a gearbox according to the preamble of claim 14. The method and the system are not limited to any specific type of gearbox, but can be applied to all sorts of gearboxes used in motor vehicles, such as range-splitter gearboxes, range-change gearboxes, automatic gearboxes, automated gearboxes, manual gearboxes, etc.

The gearbox is arranged to be connected to an engine of the motor vehicle 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 convert power from an engine of the motor vehicle into power at a specific torque and speed needed to drive the vehicle. As power is converted in the gearbox, the applied torque affects the gearbox and the gearbox is consequently subjected to significant wear during operation of the motor vehicle. The amount of wear on the gearbox, and thereby its component life expectancy, is to a large degree impacted by the way in which the vehicle is driven. Driving at 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 for example when the vehicle travels over an uneven surface, such as at road bumps, kerbs, and railway crossings or similar. A further cause for wear of the gearbox is deteriorated lubricating oil contained in the gearbox, which results in poor lubrication of the components within the gearbox.

Due to the many different factors affecting the gearbox, it is difficult to predict the component life expectancy of the gearbox. Failures of the gearbox or of components therein therefore often happens unexpectedly, and reasons for harm caused to the gearbox 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 It is a primary objective of the present invention to provide a solution to the above described problems and provide a solution by means of which the health and performance of the gearbox can be continuously assessed in order to enable identification of problems at an early stage. Another objective is to provide means for 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, wherein the system comprises a processing unit and a set of sensors configured to communicate signals to the processing unit, said set of sensors comprising: - a first accelerometer configured to sense rigid body motion of the gearbox in at least one direction, positioned on a portion of the gearbox which is more rigid than an average outer wall of the gearbox housing, and - a first strain gauge 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.

By means of the strategically positioned accelerometer and strain gauge, applied torques affecting the gearbox and sudden accelerations leading to rigid body motion of the gearbox can be sensed and signals related thereto can be communicated to the processing unit, preferably placed on the gearbox in the vicinity of the sensors. The processing unit is configured to generate health and performance information which can be communicated wirelessly to a central service node or the like, and/or be stored in the processing unit and read off a storage means comprised therein as the motor vehicle is being serviced, or as a problem related to the gearbox is encountered. The system according to the invention thereby enables continuous assessment of the performance and health of the gearbox, enabling identification of problems 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.

According to the invention, the health and performance information generated by the processing unit includes at least a torque applied to the gearbox and a rigid body motion of the gearbox. The torque can be determined based on the signal from the first strain gauge and gives valuable input for estimating a component life expectancy of the gearbox housing. Based on the output torque, an input torque can easily be calculated. Information relating to the rigid body motion of the housing is determined based on at least the signal from the first accelerometer and gives input for estimating a component life expectancy of the gearbox and components therein. Applied torques as well as sudden accelerations and decelerations of the gearbox can be logged in a load history and a movement history, respectively, of the gearbox.

According to the invention, the gearbox comprises a torque absorbing structure between the front end and the rear end, and said first strain gauge is positioned on or in front of the torque absorbing structure. In the case where the gearbox is mounted using a beam or similar as a torque absorbing structure, the strain gauge should be positioned on or in front of this torque absorbing structure to be able to detect an applied torque.

The system according to the invention can be mounted externally on the gearbox and can thereby easily be removed and replaced when needed. Individual sensors as well as the processing unit itself can easily be exchanged, and it is easy to adapt the system to the gearbox on which it is mounted by simply attaching the sensors, e.g. by gluing or taping, onto suitable positions on the gearbox.

The system can be made independent from other systems of the motor vehicle. All relevant signals to the processing unit are thus communicated from the sensors of the system. However, it is also possible to connect the system to other sensors or systems of the vehicle and thereby obtain signals that can be relevant for assessment of the performance and health of the gearbox. If the gearbox already comprises an electronic control unit (ECU), the processing unit may of course be integrated with or attached to the ECU.

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

According to one embodiment, the processing unit is configured to, based on said signals and/or on said health and performance information of the gearbox, estimate a component life expectancy of the gearbox. To be able to accurately estimate life expectancies of the entire gearbox as well as of individual components in the gearbox and attached to it is useful to avoid changing of components, as well as to prevent and foresee unexpected breakdowns of the gearbox or of components within or attached to the gearbox.

According to one embodiment, the processing unit is configured to use at least one data reduction algorithm in the generation of health and performance information of the gearbox and wherein said 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 stored significantly, making it possible to reduce storage capacity of the processing unit. It also facilitates future evaluations of the stored data.

According to one embodiment, the processing unit is configured to generate and store health and performance information relating to at least one of a load history, a movement history, a gear history, a gear shifting history, and damage caused to a component within the gearbox. The load history can include for example forces and torques applied to the gearbox, sudden accelerations, temperature, and oil particle concentrations, depending on which sensors are included in the set of sensors. The movement history can include rigid motion accelerations, vehicle speed, a geographical position of the gearbox, etc. The gear history can include information about an accumulated time per engaged gear and the gear shifting history can include occurrences of shifts between individual gears. Damage is caused by e.g. applied torques, sudden accelerations, rattling gears, forces from gearshifting and synchronisation, etc. By logging the occurrence of damage, it is possible to predict when components within or on the gearbox, or the gearbox housing, are expected to break down due to fatigue. The stored information relating to load history, movement history, gear history, gear shifting history and damage is useful in an evaluation process after failure of the gearbox as well as to continuously evaluate the gearbox’s health during usage.

According to one embodiment, said first accelerometer is positioned between the torque absorbing structure and the rear end. In this position, there are less vibrations originating from the engine than in front of the torque absorbing structure. Thereby, less filtering of the signal from the sensor is needed to gain useful information relating to the rigid body motion of the gearbox.

According to one embodiment, said set of sensors further comprises a second accelerometer attached on the gearbox housing between the front end and the torque absorbing structure. With the second accelerometer positioned in the vicinity of the engine, vibrations from the engine and resulting from gear shifting and gear meshing can be sensed and identified. The health and performance information generated by the processing unit in this embodiment preferably includes gear shifting information and gear meshing information generated at least partly based on a signal from the second accelerometer, so that it is possible to generate detailed gear and gear shifting histories. For example, the gear history can include a total and an average time per engaged gear and the gear shifting history can include occurrences of shifts between 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 analysis can also generate information relating to engine orders. Thus, the second accelerometer provides additional precision to the generated health and performance data which can be used when predicting component life of e.g. gear wheels, brackets and attached components, also including electrical units attached to the gearbox. It also makes it easy to identify broken or damaged gear wheels at an early stage. Furthermore, the detection of engine orders makes it possible to identify problems arising from e.g. the clutch.

According to one embodiment, said first accelerometer is a triaxial accelerometer. By using a triaxial accelerometer, rigid body motion in all three directions can be sensed and only one accelerometer is thus needed to sense three dimensional rigid body motion. An alternative is to have several biaxial and/or uniaxial accelerometers mounted.

According to one embodiment, said set of sensors further comprises at least one of a temperature sensor configured to sense a temperature of oil contained in the gearbox and a particle counter configured to count particles present in said oil. A temperature sensor and a particle counter can provide useful information about the conditions in the gearbox that may be used to reweight logged damage of components. For example, a damage caused at an elevated temperature may be given a higher weight 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 rotational speed of a component within the gearbox. The tachometer preferably measures the rotational speed of one of the shafts within the gearbox. It facilitates determination of a current rotational speed of the engine and can also be used to identify rattle of the gearbox.

According to one embodiment, the processing unit is attached to the gearbox. Preferably, at least one sensor from said set of sensors is integrated with the processing unit. For example, the processing unit can be glued to the gearbox housing and a temperature sensor can be integrated therewith to sense a temperature of the housing. Also an accelerometer, a strain gauge or another sensor can be integrated with the processing unit. This makes the system according to the invention easier to mount and reduces the amount of wiring needed.

According to one embodiment, the processing unit comprises a GPS receiver. The processing unit can thereby, based on data from 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 to communicate wirelessly with an external central node. Information can 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 relates to 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 mentioned primary 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 one direction using said first accelerometer and sending signals relating thereto to the processing unit, - sensing torques applied to the gearbox using said first strain gauge and sending signals relating thereto to the processing unit, and - in the processing unit, receiving said signals and, based thereon, generating health and performance information of the gearbox. Advantages and advantageous features of such a method appear from the above description of the proposed system.

According to one embodiment of this aspect of the invention, the method 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 Fig. 1 shows a schematic illustration of a system according to an embodiment of the invention mounted on a gearbox, Fig. 2 shows schematic diagrams of health and performance information obtained using the system according to an embodiment 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 THE INVENTION A gearbox 1 comprising a system for monitoring the gearbox according to an embodiment of the invention is schematically shown in fig. 1. The gearbox 1 forms part of a powertrain of a motor vehicle and has a front end 2 at which an input shaft 3 is connected to an internal combustion engine via a clutch or a corresponding device, and a rear end 4 at which the gearbox 1 via an output shaft 5 is connected to drive wheels. The gearbox is configured to be mounted on a chassis of the motor vehicle and has for this purpose a mounting member 6 in the form of a beam that can be screwed or bolted onto the chassis, or onto mounting brackets provided on the chassis. This mounting member 6 functions as a torque absorbing structure, absorbing torques applied to the gearbox. If instead the gearbox is mounted at a front flange attached to the engine, the entire gearbox will deform under torque. A gearbox housing 7, here comprising a front housing 8, a rear housing 9, and a rearmost bearing housing 10, surrounds mechanical components, such as shafts, gear wheels and bearings, provided 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, a processing unit 12 attached onto the gearbox housing 7 by means of e.g. gluing, taping, screwing, or similar. In the shown embodiment, the processing unit 12 is attached to the rear housing 9, but it can of course be attached to any external part of the gearbox 1. On the other hand, the system comprises a set of sensors 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 integrated temperature sensor and tachometer 16. All sensors 13-16 are configured to collect and send data to the processing unit 12. Further strain gauges and/or accelerometers may also be provided on 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 triaxial accelerometer configured to sense rigid body motion of the gearbox 1 in three directions, predominantly at relatively low frequencies. For this purpose, it is externally positioned on a portion of the gearbox 1 which is relatively rigid in comparison with an average outer wall of the gearbox housing 7. In this case, the first 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 a position where an output torque from the gearbox 1 is detectable, such that it can be used to detect a torque applied to the gearbox. Thus, the strain gauge 15 cannot be positioned rear of the mounting member 6, since no torque is detectable at that position.

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

The integrated temperature sensor and tachometer 16 is mounted on the gearbox housing 7 in the vicinity of the processing unit 12. An opening is made in the gearbox housing 7 to accommodate the sensor 16, so that it can be used to measure the temperature of lubricating 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 internal storage means for data storage. The processing unit 12 is configured to receive signals sensed by and communicated by the sensors 13-16 and, based thereon, generate health and performance information of the gearbox. Such health and performance information is related to loads affecting the gearbox, such as applied torque, sudden accelerations, vibrations, temperature, etc. The processing unit 12 uses the input signals from the sensors13-16 to determine those loads and to estimate a component life expectancy of the gearbox 1. Damage and load and movement histories may be stored in the means for data storage.

Data from the first accelerometer 13 can be used to determine high frequency and low frequency rigid body motion of the gearbox 1. Data from the strain gauge 15 can be used to determine an output torque from the gearbox, and thereby also to calculate an input torque. Data from the second accelerometer 14, possibly in combination with data from the first accelerometer 13 and with data from the strain gauge 15, can be used to determine rotational speed and engine orders of the engine as well as to identify and log gear shifts and to determine which gear is engaged. Data from the tachometer 16 simplifies an evaluation of the current rotational speed, and can also be used to detect rattle or noise from the gearbox. Temperature data from the integrated temperature sensor 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 more data reduction algorithm(s) to reduce the amount of data to be stored. For example, rainflow count and/or cycle count can be used to log damage arising from applied torques, accelerations, or vibrations, and data can be arranged into matrices, etc. Order analysis and FFT (Fast Fourier Transform) signal analysis can also be 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 an embodiment of the invention, wherein data reduction algorithms have been used to extract the relevant information.

In (a), the accumulated time that a specific torque has been applied to the gearbox is shown, based on the signal from the strain gauge 15. From the diagram, it is possible to identify whether a particular torque has been over-represented, for example if the vehicle has been driven at unnecessarily high torques, which causes wear on the gearbox.

In (b), the number of cycles that the gearbox has been subjected to a specific acceleration, leading to rigid body motion of the gearbox, is shown. The data is primarily obtained from the signal from the first accelerometer 13.

In (c), accumulated damage to a component (here a bracket fixing an electrical unit) is shown for acceleration of the gearbox as a function of frequency. Any components attached to the gearbox 1 are subjected to e.g. engine- and road-induced vibrations causing structural fatigue. The processing unit 12 processes received vibration data and outputs calculated damage to the component.

In (d), the accumulated time that a particular gear has been engaged is shown. Data relating to this are best derived from the signals from the second accelerometer 14 in combination with the first accelerometer 13. Combined with input from e.g. the strain gauge 15 one can also log the above data as a function of torque.

This data helps to understand which bearings and gears in the gearbox 1 are likely to fail.

In (e) and (f) respectively, the number of times that successful and unsuccessful gear shifts from and to particular gears have been performed is shown. The precision can be improved by also logging the time that a gear shift takes for certain up- and downshifts. For high-precision evaluation, a specific sensor that retrieves axial position of manoeuvring axles of the gearbox may be added to the system.

Similar diagrams can be obtained for accumulated time per amount of oil particles detected and/or temperature, angular acceleration as a function of engaged gear, etc. Furthermore, data relating to different parameters can be combined to get an overview of loads and movements affecting the gearbox.

In a method according to an embodiment of the invention, illustrated in fig. 3, a system according to the invention as described above is provided on a gearbox S1 in a first step S1. In a second step S2, rigid body motion of the gearbox 1 is sensed using the first accelerometer 13, and torques applied to the gearbox are sensed using the strain gauge 15. Other mounted sensors sense in this step e.g. rotational speed, temperature, a number of particles in the lubricating oil, vibrations, etc. Local strain gauges attached close to critical positions may be used to sense torque locally. In a third step S3, signals relating to the sensed physical quantities are sent to the processing unit 12. In a fourth step S4, the signals are received in the processing unit.

Based thereon, in a fifth step S5, health and performance information of the gearbox 1 is generated in the processing unit 12. In the fifth step, data reduction algorithms and signal processing is used to generate the requested information from the incoming signals.

The invention is of course not in any way restricted to the embodiments described above, but many possibilities to modifications thereof would be apparent to a person with skill in the art without departing from the scope of the invention as defined in the appended claims. For example, further sensors can be added to the system, such as additional strain gauges mounted at positions which have been found to be vulnerable, or additional accelerometers, e.g. an accelerometer positioned on the bearing housing for obtaining information relating to bearing orders and to be able to predict and prevent bearing failures. Also a GPS receiver can be provided, depending on which information is desired.

Claims

1. A system for monitoring a gearbox (1) in a powertrain of a vehicle, said gearbox having a front end (2) which via a clutch or a corresponding device is arranged to be connected to an engine, a rear end (4) arranged to be connected to drive wheels, and a gearbox housing (7), wherein the system comprises a processing unit (12) and a set of sensors (13, 14, 15, 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 (1) in at least one direction, positioned on a portion of the gearbox which is more rigid than an average outer wall of the gearbox housing (7), and - a first strain gauge (15) configured to sense a torque applied to the gearbox (1) , characterised in that said first strain gauge (15) is positioned on the gearbox (1) in a position where an output torque from the gearbox is detectable, wherein the gearbox comprises a torque absorbing structure (6) between the front end (2) and the rear end (4), and wherein said first strain gauge (15) is positioned on or in front of the torque absorbing structure (6), and that said processing unit (12) is configured to receive said signals and, based thereon, generate health and performance information of the gearbox (1) using signal processing and at least one data reduction algorithm, wherein the health and performance information generated by the processing unit (12) includes at least a torque applied to the gearbox (1) and a rigid body motion 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 health and 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 processing unit (12) comprises storage means for storing said health and performance information.

4. The system according to claim 3, wherein the processing unit (12) is configured to generate and store health and performance information relating to at least one of a load history, a movement history, a gear history, a gear shifting history, and damage caused to a component within the gearbox (1).

5. The system according to any one of the preceding claims, wherein said first accelerometer (13) is positioned between the torque absorbing structure (6) and the rear end (4).

6. The system according to any one of the preceding claims, wherein said set of sensors (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).

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

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

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

10. 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).

11. A motor vehicle comprising a powertrain including a gearbox (1) and a system for monitoring said gearbox (1) according to any one of claims 1-10.

12. A method for monitoring a gearbox (1) in a powertrain of a vehicle, said gearbox (1) having a front end (2) which via a clutch or a corresponding device is arranged to be connected to an engine, a rear end (4) arranged to be connected to drive wheels, and a gearbox housing (7), characterised in that the method comprises the steps of: - providing a system according to any one of claims 1-10, - sensing rigid body motion of the gearbox (1) in at least one direction using said first accelerometer (13) and sending signals relating thereto to the processing unit (12), - sensing torques applied to the gearbox (1) using said first strain gauge (15) and sending signals relating thereto to the processing unit (12), and - in the processing unit (12), receiving said signals and, based thereon, generating health and performance information of the gearbox (1) using signal processing and at least one data reduction algorithm, wherein the health and performance information generated by the processing unit (12) includes at least a torque applied to the gearbox (1) and a rigid body motion of the gearbox (1).

13. The method according to claim 12, further comprising the step of: - based on said signals and/or said health and performance information of the gearbox (1) , estimating a component life expectancy of the gearbox (1).