SE542599C2

SE542599C2 - A method of controlling a synchronizing arrangement for a retarder, a retarder and a vehicle

Info

Publication number: SE542599C2
Application number: SE1551059A
Authority: SE
Inventors: Daniel Häggström; Peer Norberg
Original assignee: Scania Cv Ab
Priority date: 2015-08-05
Filing date: 2015-08-05
Publication date: 2020-06-09
Also published as: SE1551059A1; WO2017023198A1; DE112016002953T5; CN107848498B; CN107848498A

Abstract

The invention relates to a method of controlling a synchronizing arrangement (12) for a retarder (6). The method comprises the steps of: a) displacing the sleeve (50) from the first position (A1) to the second position (A3) for connecting the first transmission element (40) to the first shaft (14), b) measuring the synchronizing time (TS) for synchronizing the rotational speed between the first transmission element (40) and the first shaft (14), c) comparing the measured synchronizing time (TS) to an expected time (TE) for synchronizing the rotational speed between the first transmission element (40) and the first shaft (14) using the synchronizing arrangement (8), and d) generating a failure mode if the measured synchronizing time (TS) is substantially shorter than the expected time (TE). The invention also relates to a retarder (6), which is controlled by such a method. The invention also relates to a vehicle (1) comprising such a retarder (6).

Description

A method of controlling a synchronizing arrangement for a retarder, aretarder and a vehicle BACKGROUND AND PRIOR ART The invention relates to a method of controlling a synchronizing arrangementfor a retarder. The invention also relates to a retarder provided with such asynchronizing arrangement. The invention also relates to a vehicle comprising such a retarder.

A hydrodynamic retarder device may be connected to a powertrain in a vehiclein order to brake the vehicle. Often the retarder is used as an auxiliary brake,which complements the wheel brakes of the vehicle. Thus excessive wear of the wheel brakes is avoided.

The retarder comprises a rotor and a stator, which together form a workspacehaving a toroidal geometrical form. The workspace must be filled with a fluid,such as water, coolant or oil as quickly as possible when a braking torque fromthe retarder is requested. When water or coolant is used as fluid in the work-space the braking torque is controlled by means of the volume of water orcoolant filled in the workspace. High braking torques exerted by the retarderare achieved when the workspace is completely or substantially completelyfilled with water or coolant. The volume of fluid in the workspace is controlledby means of one or a number of restriction valves arranged in a fluid circuitconnected to the workspace. The pressure within the workspace increaseswhen the flow of fluid is restricted from the workspace. When the restrictionvalve in an outlet channel from the workspace is opened the volume of fluidwithin the workspace will decrease, which in turn results in a reduced pressurewithin the workspace. The fluid or a part of the volume of fluid in the workspacewill then evaporate, due to the decrease of the static pressure in the work-space to a level which coincides with the evaporation point for fluid. However,the pressure will not reach the evaporation point for the fluid in all parts of the workspace and therefore a small volume of fluid may be left in the workspacedespite the preferred evacuation. This small volume of fluid left in the work-space will contribute to a considerable braking torque on the vehicle.

The fluid is evacuated from the workspace when no braking torque should beprovided. However, when fluid has been evacuated from the workspace thepowertrain of the vehicle still rotates the rotor, which results in a residualtorque acting on the powertrain. The residual torque results in an increasedfuel consumption of the vehicle. ln order to reduce the fuel consumption the rotor is disconnected from thepowertrain by means of a coupling element when the retarder is deactivatedand should not brake the vehicle. Thus, the rotor will substantially stand still and not rotate when the rotor is disconnected from the powertrain.

Next time, when connecting the retarder to a powertrain, a gear wheel whichdrives the retarder is engaged and locked on a shaft of the powertrain bymeans of the coupling element. The coupling element may be an axially dis-placeable sleeve provided with internal teeth, which connects the gear wheeland the shaft. However, the sleeve, gear wheel and the shaft of the powertrainhave different rotational speeds when the gear wheel should be locked on theshaft of the powertrain. Therefore, a synchronizing arrangement is used tosynchronize the rotational speed between the sleeve, gear wheel and the shaftof the powertrain before the gear wheel is locked on the shaft. The synchroniz-ing arrangement comprises a latch cone ring and an inner cone ring arrangedon the side of the gear wheel. The shaft of the powertrain may be a shaft in a gearbox. ln order to obtain good synchronization, the surface of peripheral latch teeth onthe latch cone ring, which face the sleeve and are designed to engage internalteeth in the sleeve during synchronization, must be angled relative to the axis of rotation of the latch cone ring, said angle being balanced against the braking torque that the latch cone ring transmits to the sleeve in order to achievesynchronous speed. This means that said angle must be designed so that thelatch teeth on the latch cone ring engage with that portion of the internal teethin the sleeve that are at said angle and act on the sleeve sufficiently to achievesynchronous speed and then disengage from the portion of the internal teeth inthe sleeve at said angle when the sleeve is to engage with the inner cone ringwhen synchronous speed has been obtained. ln the engaged position betweenthe sleeve and the inner cone ring, the internal teeth in the sleeve engage withperipheral coupling teeth of inner cone ring. The inner cone ring is attached tothe gear wheel. To ensure that synchronous speed is reached before thesleeve passes the latch cone ring axially, the teeth of the latch cone ring mustdisengage from internal teeth at the right moment. This is achieved by a torquebalance where the friction torque, also defined as the synchronizing torque,seeks to increase the overlap between the latch cone teeth and the inner coneteeth, while the torque arising from the teeth-teeth contact seeks to reduce theoverlap between the teeth. When the peripheral latch teeth on the latch conering have disengaged from the internal teeth in the sleeve when synchronousspeed has been obtained between the sleeve and the inner cone ring, thesleeve will be axially displaced so that the latch cone ring is moved inwardsinto the sleeve and stops in an axial position relative to the sleeve, said axialposition being determined by the position at which the sleeve meets andengages with the inner cone ring on the gear wheel.

Pre-synchronization occurs before synchronous speed occurs. During pre-synchronization, the oil present between the conical surfaces must be evacu-ated so that a sufficiently high friction torque is developed, effectively blocking the engagement of the gear wheel during asynchronous speed.

During the pre-synchronization and the following synchronization process theaxial position of the latch cone ring is defined because of the axial force fromthe sleeve acting on the latch cone ring. After the synchronization process thesleeve is coupled to the inner cone ring and also the gear wheel. ln this position the s|eeve, the latch cone ring, the inner cone ring and the gear wheel rotate together with the shaft of the powertrain as one unit.

When deactivating the retarder after braking the s|eeve is returned to an initialposition by means of a shifter fork, so that the rotor of the retarder is discon-nected from the powertrain. Since no axia| force from the s|eeve is acting onthe latch cone ring, it will be retracted from the inner cone and be ready forsynchronization the next time the retarder should be activated. However, insome cases the the conical surface of the latch cone ring will stick to the coni-cal surface of the inner cone ring. This may happen during the first cycles ofuse, if incorrect oil is used or at the end of the life time of the synchronizingarrangement. Also, this problem may arise under other circumstances, espe-cially if the coefficient of friction between the conical surfaces is larger than thetangent of the cone angle. lf the conical surfaces of the latch cone ring and theinner cone ring have stunt: together, the retarder Witt not be disconnected fremthe powertrain as intended. Ttterefere, the rotor of the retarder will rotate whenthe retarder is deactivated, which results in an increased fuel consumption.Also, if the conical surfaces of the latch cone ring and the inner cone ring havesteak together, the next time the retarder eheteid be connected nesynchronization process will take place between the gear wheel and the shaftof the powertrain.

The document EP1251050 A1 shows a retarder for vehicles with a rotor andstator, wherein the rotor is arranged to be connected and disconnected to andfrom the propeller shaft of the vehicle by a clutch device which is pneumaticallycontrolled.

The document DE102012007732 discloses a powertrain for vehicle, providedwith a retarder, which is connected by means of a synchronizing arrangementto the output shaft of a gearbox in the vehicle. A sensor unit is provided to monitor the connection of the retarder to the output shaft of a gearbox.

SUMMARY OF THE INVENTION Despite prior art, there is a need to develop a method of controlling a synchro-nizing arrangement for a retarder, which detects a malfunction in the synchro-nizing arrangement and restores the synchronizing arrangement, so that Et »works properly.

The object of the invention is thus to provide a method of controlling a syn-chronizing arrangement for a retarder, which detects a malfunction in the syn-chronizing arrangement and restores the synchronizing arrangement, so that it works properly.

These objectives are achieved with a method of controlling a synchronizingarrangement for a retarder; a retarder; a vehicle; a computer program and a computer program product as set out in the appended claims.

According to the invention, an advantageously method of controlling a syn-chronizing arrangement for a retarder is achieved. The synchronizing ar-rangement comprises a sleeve, which is axially displaceable between a firstand second position, a |atch cone ring with a substantially circu|ar first frictionsurface, an inner cone ring with a substantially circu|ar second friction surface,which inner cone ring is attached to a transmission element, and a hub, whichis attached to a first shaft. A first transmission element is connectable to thefirst shaft by means of the synchronizing arrangement and the first transmis-sion element is engaged with a second transmission element attached to the retarder.

The method comprises the step of: a) displacing the sleeve from the first position to the second position forconnecting the first transmission element to the first shaft, b) measuring the time for synchronizing the rotational speed between thetransmission element and the first shaft, c) comparing the measured time to an expected time for synchronizing the ro-tational speed between transmission element and the first shaft using the syn-chronizing arrangement, and d) generating a failure mode if the measured time is substantially shorter thanthe expected time.

When knowing the expected time for synchronizing the rotationa| speed be-tween transmission element and the first shaft, a possible failure due to lack ofsynchronization may be detected if the measured time is substantially shorterthan the expected time. The reason why a lack of synchronization occures isthat the friction surfaces of the latch cone ring and the inner cone ring hasbeen stuck together. Thus, a malfunction in the synchronizing arrangementmay be detected.

According to an embodiment of the invention, the time for synchronizing therotationa| speed between the transmission element and the first shaft in step b)is measured by monitoring the axial position of the sleeve during synchroniza- tion.

Synchronization occurs when there is substantial no change in the axial posi-tion of the sleeve, but when there is a substantial change in rotationa| speed ofthe transmission element. However, a rapid displacement of the sleeve fromthe first position to the second position during no change in rotationa| speed ofthe transmission element indicates that no synchronization occurs. Thus, amalfunction in the synchronizing arrangement may be detected.

According to an embodiment of the invention, the expected time for synchro-nizing the rotationa| speed between transmission element and the first shaft isdetermined from synchronization torque, the rotationa| speed of the transmis-sion element and the first shaft, and inertia of the transmission element, the first shaft and the synchronizing arrangement.

The expected time for synchronizing the rotational speed between transmis-sion element and the first shaft using a specific synchronizing arrangementmay be determined by calculating synchronization torque needed at the actualrotational speed of the transmission element and the first shaft, and also takenotice of the inertia of the transmission element, the first shaft and the syn- chronizing arrangement.

According to an embodiment of the invention, the expected time is determinedfrom a table of synchronization times for different rotational speeds of the first shaft stored in an electronic control unit.

As an alternative, a table may be created for a specific synchronizing ar-rangement. Each specific rotational speed of the first shaft has a specific syn- chronization time corresponding to the expected time.

According to an embodiment of the invention, the generated failure mode instep d) is indicated by means of a sound or visual signal. lf the retarder is arranged in a vehicle, the driver may receive a sound or visualsignal if there is a synchronizing failure in the synchronizing arrangement.

Thus, a malfunction in the synchronizing arrangement may be detected.

According to an embodiment of the invention, the method comprises the fur-ther steps of: e) displacing the sleeve from the second position to the first position; and f) requesting a torque from the retarder if failure mode in step d) has been generated.

When requesting a torque from the retarder, fluid is supplied to the workspace.Since the sleeve and the latch cone ring rotates with the same rotational speedand torque is transferred between the sleeve and the latch cone ring, the re-quested torque from the retarder will act on the transmission element. The magnitude of the requested torque from the retarder is essentially the same asthe synchronization torque, which leads to that the friction surfaces of the latchcone ring and the inner cone ring, which has been stuck together, will be re- leased from each other. Thus the synchronizing arrangement may be restored, so that Et vvorks properly.

According to an embodiment of the invention, the method comprises the fur-ther step of: g) measuring the ambient temperature, and requesting the torque from the re-tarder if failure mode in step d) has been generated and only if the ambient temperature is higher than a pre-determined temperature.

Since the retarder acts on the driving wheels in a vehicle, a sudden torquespike may cause a slip between the wheels and the road in slippery road con-ditions. Therefore, if the ambient temperature is low, as an example below thefreezing point for water, it is preferable to perform the steps e) and f) right after start-up or launch of the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS Below is a description of, as examples, preferred embodiments of the invention with reference to the enclosed drawings, in which: Fig. 1 shows schematically a vehicle in a side view, with a retarder according to the invention, Fig. 2 shows schematically a retarder provided with a synchronizing arrange-ment, which is controlled by the method according to the invention, Fig. 3 shows a sectional view of a synchronizing arrangement for a retarder, which is controlled by the method according to the invention, Fig. 4 shows a sectional view along line l - l in Fig. 3 of the latch cone ring in asynchronizing arrangement for a retarder, which is controlled by the method according to the invention, Fig. 5 shows a sectional view of a synchronizing arrangement in Fig. 3 in a pre-synchronizing position, Fig. 6 shows a sectional view of a synchronizing arrangement in Fig. 3 in a synchronizing position, Fig. 7 shows a sectional view of a synchronizing arrangement in Fig. 3 in aposition when the synchronizing process has ended, Fig. 8a shows a graph over the axial position of the sleeve and the rotationalspeed of the inner cone ring in relation to time where a correct synchronization process has been detected, Fig. 8b shows a graph over the axial position of the sleeve and the rotationalspeed of the inner cone ring in relation to time where a malfunction in the synchronization process has been detected, and Fig. 9 shows a flow chart of a method of controlling a synchronizing arrange- ment for a retarder according to the invention.

DETAILED DESCRIPTION OF PREFERRED E|\/|BOD||\/IENTS OF THEINVENTION Fig. 1 shows a side view of a vehicle 1, e.g. a truck, which comprises anengine 2 and a gearbox 4 provided with a retarder 6 and a synchronizing ar-rangement 8, which is controlled by the method according to the invention. Theengine 2 is connected to the gearbox 4 and the gearbox 4 is further connectedto driving wheels 10 of the vehicle 1 via a propeller shaft 12. Preferably, the engine 2 is an internal combustion engine but another type of engine 2 is alsoapplicable, such as an electrical engine. The gearbox 4 may be a manualtransmission, an automated transmission, an automated manual transmission,or a continuously variable transmission. The gearbox may be a single or a dual-clutch transmission.

Fig. 2 shows schematically a retarder 6 provided with a synchronizing ar-rangement 8, which is controlled by the method according to the invention. Afirst shaft 14 is adapted to be connected to a powertrain 18 and a second shaft16 is connected to a rotor 20 of the retarder 6. According to Fig. 2 thepowertrain 18 is arranged in the vehicle 1, where the connection of the retarder6 to the vehicle 1 is performed through the gearbox 4, which thus constitutes apart of the powertrain 18. ln Fig. 2, the gearbox 4 is schematically presented.The first shaft 14 may therefore be a propeller shaft 12, which is bothconnected to the gearbox 4, and to the driving wheels 10 of the vehicle 1.

A transmission 26 comprising a second transmission element such as asecond gear wheel 24 arranged on the second shaft 16 engages with firsttransmission element such as a first gear wheel 40, which is releasablyarranged on the first shaft 14. Preferably, there is an upshift through thetransmission 26 in the order of 3:1, but other ratios are possible such as 1:1.The second shaft 16 is preferably, by means of bearings, mounted in aretarder housing 22 and possibly also in a gearbox house 38. The rotor 20 isprovided on the second shaft 16, which in an engaged state of the retarder 6rotates at a speed proportional to the speed of the first shaft 14. A stator 28 isconnected to the retarder housing 22 and will therefore not rotate.

The rotor 20 and stator 28 together form a workspace 30 having the form of atoroidai hoiiow space. The workapace 30 is fiiied with a fiuid 32 auch as vtfateror oooiartt through en iriiei; opening 34 when tiie retarder 6 is reqtiested toexercise a brakihg toroiie on the first shaft 14 connected to the gearbox 4 iriorder to brake the veiticie t and thus cieorease or rnaintairi the vehicle i 11 speed. The braking torque is generated hy the rotor 26 and stater 28 tiirhich ereprovided with htades or vanes 36, which creates e tiuid ticw in the worhsoace3G when the rotor 2G rotates. The tteid tiow *torrns, in conjonctien vvith thevanes 36 ot the rotor 26 and the stator 28, a reaction torce, which restiits in thebraking torque. The higher the rotationai speed ot the retor 20 and the greaterthe ainoiirtt ot tiuid in the worksoace 36, the iarger is the reaction torce andthus the braking toretie. (En occasicns when the retarder 6 sitetitd net hrakethe vehicte t the tivoritspace 3G is drained corneieteiy ot the titiid 32 end thetieid is reeiaced in part hy stearn, eaesiitg the vanes 36 ot the rotor 20 andstater 28 to create a steam tiovif in the trvortrsoace Se. tiotrvever, the steam tiowotters a reaction tcrce on the second shett i6, which generates an tindesiraoiebraking rtoretie on the tirst shatt 14. The braking torque trorn the retarder 6causes an increased teei consumption ot the vehicte t. Aiso, trioticn trorneearings and seais in the retarder 6 generates a reactien toree, which restittsin an increased toei consumption. For this reason, the second shatt 16 can hedisoonneoted trern the tirst sitatt tft when the retarder 6 is net used te hrairethe vehicte t. Thtrs, the tiiei consumption ot the vehicie t is reduced. Fiiting and drainirtg the worhsoece 36 with the tttiid 32 is done via a titiid circuit 38. ln order to reduce the fuel consumption a first gear wheel 40 of thetransmission 26 can be disconnected from the first shaft 14 so that the secondshaft 16 and thus the rotor 20 in the retarder 6 can be disconnected from thepowertrain 18. As a result, the retarder 6 will not affect the vehicle 1 with abraking torque when the retarder 6 is deactivated. When the retarder 6 is to beactivated, the retarder 6 must in a fast and efficient way be mechanicallyconnected to the outgoing first shaft 14 from the gearbox 4. To accomplishthis, a coupling element 42 is arranged between the second gear wheel 28 andthe second shaft 22. The coupling element 42 comprises a synchronizing arrangement 8.

When the retarder 6 is activated to hrai-te the vehicie t the synchronizing arrangement 8 is thus ectivated so that the tirst gear wheei 46 is connected to 12 the first sheft 14 by means of the synohronizing arrangement 8. Since the firstshaft 14 rotates during engagernent and the second shaft 16 ie stationary, thesynohronizing arrangement 8 wiii cause the second shaft 16 to rotate via thetransmission 26. The synohronizing arrangement 8 is dirnensioned to be abieto transmit the Earge braking torque exerted by the retarder 6 on the first shaft14.

Fig. 3 shows a seotional view of the synohronizing arrangement 8 for a retarder6, whioh is controlled by the method according to the invention. The synohro-nizing arrangement 8 oomprises a latoh oone ring 46, an inner oone ring 48arranged on the side of the first gear wheel 40 and a sleeve 50, whioh is axiallydisplaoeable by means of a shifter fork 52. The shifter fork 52 is axiallydisplaoeable by means of an aotuating means 54. The latoh oone ring 46 andthe inner oone ring 48 are provided with interaoting friotion surfaoes 56, 56”,whioh preferably are of a oonioal design. The shifter fork 52 transmit axial forcefrom the sleeve 50 to the latoh oone ring 46 in order to bring about contactbetween the friotion surfaoes 56 on the latoh oone ring 46 and the inner oonering 48 during gear shifting. This means that an oil film formed between thefriotion surfaoes 56 is displaoed and an initial torque between latoh oone ring46 and the inner oone ring 48 builds up.

When oonneoting the retarder 6 to the powertrain 18 the first gear wheel 40 isengaged and looked on the first shaft 14 by means of the axially displaoeablesleeve 50. A hub 58 provided with splines 60 on the periphery is attached tothe first shaft 14 and allows the sleeve 50 to move axially. The hub 58transmits torque between the first shaft 14 and the sleeve 50. However, thesleeve 50, first gear wheel 40 and first shaft 14 may have different rotationalspeeds when the gear should be shifted and when the first gear wheel 40should be looked on the first shaft 14 by means of the sleeve 50. The synohro-nizing arrangement 8 is therefore used to synohronize the rotational speed be-tween the sleeve 50, first gear wheel 40 and first shaft 14 before the first gearwheel 40 is looked on the first shaft 14. 13 The shifter fork 52 transmits axial force from the sleeve 50 to the latch conering 46 in order to bring about contact between the friction surfaces 56, 56” onthe latch cone ring 46 and the inner cone ring 48 during gear shifting. Thismeans that an oil film formed between the friction surfaces 56, 56” is displacedand an initial torque between latch cone ring 46 and the inner cone ring 48 builds up. ln order to obtain good synchronization in the gearbox 4, the surface of latchteeth 62 on the latch cone ring 46, which face the sleeve 50 and are designedto engage internal teeth 64 in the sleeve 50 during synchronization, must beangled relative to the axis of rotation of the latch cone ring 46, said angle beingbalanced against the braking torque that the latch cone ring 46 transmits to the sleeve 50 in order to achieve synchronous speed.

A number of balls 66, each loaded with a spring 68, are arranged in the sleeve50, the purpose of these is to ensure that pre-synchronization occurs. Thespring-loaded balls 66 act on abutment means 70 arranged on the latch conering 46 to ensure that the latch teeth 62 of the latch cone ring 46 are in thecorrect axial position relative to the internal teeth 64 of the sleeve 50 duringpre-synchronization and the abutment means 70 press the spring-loaded balls66 radially outwards when the sleeve 50 moves axially in relation to the latchcone ring 46 when the pre-synchronization has ended and when thesynchronization or main synchronization should start. ln fig. 3 the sleeve 50,latch cone ring 46 and the inner cone ring 48 are depicted on a distance toeach other for clarity reason. ln Fig. 3 the first gear wheel 40, first shaft 14 andhub 58 are schematically disclosed. The latch teeth 62 extend in a directionparallel to the centre line of the latch cone ring 46 and in a peripheral direction.The abutment means 70 extend in a direction parallel to the centre line of thelatch cone ring 46 and in a peripheral direction. The abutment means 70 have a larger extension than the latch teeth 62 in the direction parallel to the centre 14 line. A circumferential groove 49 is arranged in the peripheral surface of the latch cone ring 46 adjacent to the abutment means 70.

Fig. 4 shows a sectional view along line l - l of the latch cone ring 46. ln thedisclosed embodiment four abutment means 70 are arranged on a substan-tially equally distance on the periphery 72 of the latch cone ring 46. Also, thelatch teeth 62 are arranged on a substantially equally distance on the periph-ery 72 of the latch cone ring 46.

Fig. 5 shows a sectional view of the synchronizing arrangement 8 in a pre-synchronizing position. The shifter fork 52 acts with an axial force on thesleeve 50 and displaces the sleeve 50 and also the latch cone ring 46 axially inrelation to the hub 58 in direction towards the inner cone ring 48. The spring-loaded balls 66 are pressed into the direction of the circumferential groove 49so that the axial position of the latch cone ring 46 in relation to the sleeve 50 isdefined. For this reason the groove 49 has a design which interacts with thespring-loaded ball 40. As mentioned above, the spring-loaded balls 66 also acton the abutment means 70 arranged on the latch cone ring 46, so that thelatch cone ring 46 will be displaced axially by the force from the spring-loadedballs 66 when the sleeve 50 is displaced by means of the shifter fork 52. Asthe sleeve 50 and the latch cone ring 46 are displaced axially the frictionsurfaces 56, 56” on the latch cone ring 46 and the inner cone ring 48 will bebrought to an adjacent position to each other. However, as the gearbox 4 isfilled with oil a thin film 29 of oil is created between the friction surfaces 56, 56”on the latch cone ring 46 and the inner cone ring 48. The axial force from thelatch cone ring 46 acting on the inner cone ring 48 means result in that the oil film formed between the friction surfaces 56, 56” is displaced.

The latch teeth 62 and the abutment means 70 are preferably situated at theside of each latch cone ring 46 that is closest to the inner cone ring 48 to allowthe movement of the latch cone ring 46 in the sleeve 50 during the synchronization process. The abutment means 70 have a smaller radial extension than that of distance between the internal teeth 64 in the sleeve 50.This allows the movement of the latch cone ring 46 in the sleeve 50 during the synchronization process.

Fig. 6 shows a sectional view of the synchronizing arrangement 8 in asynchronizing position in which the oil film formed between the friction surfaces56, 56” has been displaced during pre-synchronization, the friction surfaces 56,56” have contact with each other and an initial torque between latch cone ring46 and the inner cone ring 48 is building up. The latch teeth 62 on the latchcone ring 46 engage with and rest against internal teeth 64 in the sleeve 50during synchronization. Therefore, the surface of the latch teeth 62 on the latchcone ring 46 which engage with and rest against the surface of the internalteeth 64 in the sleeve 50 must be angled relative to the axis of rotation of thelatch cone ring 46, and said angle must balance against the braking torquethat the latch cone ring 46 transmits to the sleeve 50 in order to achievesynchronous speed. During the synchronization the sleeve 50, first gear wheel40 and first shaft 14 have different rotational speeds. However, when asynchronous speed has been reached between the sleeve 50, first gear wheel40 and first shaft 14 the angled surface of the latch teeth 62 on the latch conering 46 disengage from the angled surface of the internal teeth 64 in the sleeve50, so that the sleeve 50 passes the latch cone ring 46 axially. To ensure thatsynchronous speed is reached before the sleeve 50 passes the latch cone ring46 axially, the teeth 62 of the latch cone ring 46 must disengage from internalteeth 64 at the right time. This is achieved by a torque balance where the fric-tion torque, also defined as the synchronizing torque, seeks to increase theoverlap between the latch cone teeth 62 and the inner cone teeth, while thetorque arising from the teeth-teeth contact seeks to reduce the overlap be-tween the teeth. When the sleeve 50 moves axially in relation to the latchcone ring 46, the spring-loaded balls 66 are pushed radially outwards due toan radially directed force from an inclined surface on the abutment means 70.

Since the surface on the abutment means 70 is inclined the spring-loaded balls 16 66 are gradually pushed radially outwards when the s|eeve 50 moves in the axial direction.

Fig. 7 shows a sectional view of the synchronizing arrangement 8 in a positionwhen the synchronizing process has ended and when the peripheral latchteeth 62 on the latch cone ring 46 have disengaged from the internal teeth 64in the s|eeve 50 when the rotationa| speed is synchronous between the s|eeve50 and the inner cone ring 48. ln this position the s|eeve 50 has been axiallydisplaced, so that the latch cone ring 46 has been moved inwards into thes|eeve 50 and stopped in an axial position relative to the s|eeve 50, said axialposition being determined by the position at which the s|eeve 50 meets andengages with the inner cone ring 48 on the first gear wheel 40. ln this positionthe gear shifting operation has ended and the first gear wheel 40 is engagedon the first shaft 14. Also, in this position the spring-loaded balls 66 has beenpushed even more radially outwards and rest on an outer surface of theabutment means 70, depicted as a forth surface 76 of the abutment means 70.

When deactivating the retarder 6 after braking, the s|eeve 50 is displaced tothe first, initial position by means of the shifter fork 52, so that the rotor 20 ofthe retarder 6 is disconnected from the powertrain 18. Since no axial forcefrom the s|eeve 50 is acting on the latch cone ring 46, it will be retracted fromthe inner cone ring 48 and be ready for synchronization the next time the re- tarder 6 should be activated.

However, in some cases the conical friction surface 56, 56” of the latch conering 46 will stick to the conical friction surface 56 of the inner cone ring 48. Therisk of this happening is greater during the first cycles of use, if incorrect oil atthe synchronizing arrangement 8 is used or at the end of the life time of thesynchronizing arrangement 8. Also, this problem may arise under other cir-cumstances, especially if the coefficient of friction between the conical friction surfaces 56 is larger than the tangent of the cone angle. 17 lf the conical friction surfaces 56, 56” of the latch cone ring 46 and the innercone ring 48 have etuok together, the retarder 6 will not be disconnected fromthe powertrain 18 as intended. Therefore, the rotor 20 of the retarder 6 will ro-tate when the retarder 6 is deactivated, which results in an increased fuel con-sumption. Also, if the conical friction surfaces 56 of the latch cone ring 46 andthe inner cone ring 48 have stuck together, the next time the retarder 6 shouldbe connected no synchronization process will take place between the first gearwheel 40 and the first shaft 14 of the powertrain 18.

Fig. 8a shows a graph over the axial position of the sleeve 50, the rotationalspeed of the inner cone ring 48 and the rotational speed of the first gear wheel40 in relation to time where a correct synchronization process has beendetected. The graph over the axial position of the sleeve 50 is shown with anunbroken line, the graph over the rotational speed of the inner cone ring 48 isshown with a broken line and the graph over the rotational speed of the firstgear wheel 40 is shown with dots. ln order to connect the the first gear wheel40 to the first shaft 14 the sleeve is displaced from a first axial position, at A1 infig. 8a, to a direction of a second axial position A3. lf the retarder 6 has beendeactivated for some time, the rotational speed of the first shaft 14 is zerowhen the sleeve 50 is in the first position A1. The synchronizing process startsat a second point of time t2, when the sleeve 50 has been displaced to an in-termediate axial position A2. The first shaft 14 starts to rotate at the secondpoint of time t2 since the torque and the rotational motion of the first gearwheel 40 are transferred to the first shaft 14 by means of the synchronizingarrangement 8. When the synchronizing process starts at the time t2 the axialdisplacement of the sleeve 50 stops so that the synchronizing process maytake place under a certain synchronizing time TS. At a third point of time t3 thesynchronizing process is completed and the first shaft 14 and the first gearwheel 40 have the same rotational speed n1. Finally, the sleeve 50 is dis-placed to the second axial position A3, so that the internal teeth 64 in thesleeve 50 engage with external teeth 74 of the inner cone ring 48 at the pointof time t4. Thus, fig. 8a represents a functional synchronizing process. 18 However, after the synchronizing process, the conical friction surfaces 56, 56”of the latch cone ring and the inner cone ring may stick rtogetlter, so that nosynchronization occurs the next time the retarder 6 should be activated.

The synchronizing time TS, for synchronizing the rotational speed between firstgear wheel 40 and the first shaft 14 is measured and compared to an expectedsynchronizing time TE for synchronizing the rotational speed between first gearwheel 40 and the first shaft 14 using the synchronizing arrangement 8. A fail-ure mode is generated if the measured synchronizing time TS is substantiallyshorter than the expected synchronizing time TE, since a possible ma|functionin the synchronization process has been detected.

Fig. 8b shows a graph over the axia| position of the sleeve 50 and therotational speed of the inner cone ring 48 in relation to time where ama|function in the synchronization process has been detected. The friction sur-faces 56, 56” of the latch cone ring 46 the inner cone ring 48 has been stucktogether, and therefore the retarder 6 is already connected to the powertrain18. For this reason the first shaft 14 and the first gear wheel 40 have the samerotational speed n1 from the beginning. When the sleeve 50 is displaced froma first axia| position, at A1 in Fig. 8a, to a direction of a second axia| positionA3 the internal teeth 64 of the sleeve 50 will engage with the external teeth 62of the latch cone ring 46 at the point of time t2 and at the intermediate axia|position A2 of the sleeve 50. At this point small indications in the axia|movement of the sleeve 50 will occur. Thereafter the sleeve 50 is displaced tothe second axia| position A3, so that the internal teeth 64 in the sleeve 50engage with the external teeth 74 of the inner cone ring 48 at the point of timet3. From the graph in Fig. 8 it is evident that no synchronization between thefirst shaft 14 and the first gear wheel 40 has been detected, because the syn-chronizing time TS is substantially zero. Thus a failure mode is generated be-cause the measured synchronizing time TS is substantially shorter than theexpected synchronizing time TE. 19 The generated failure mode may be indicated by means of a sound or visualsignal. Alternatively, the generated failure mode may be used to solve theproblem with the stucked friction surfaces 56 of the latch cone ring 46 and theinner cone ring 48. This may be done by displacing the sleeve 50 from thesecond position A3 to the first position A1 and requesting a torque from theretarder 6. The torque from the powertrain 18 will be transferred through thefriction surfaces 56, 56” of the latch cone ring 46 and the inner cone ring 48and further to the retarder 6. However, the latch cone ring 46 and the innercone ring 48 cannot transfer the high braking torque from the retarder 6 on thepowertrain 18 and therefore the latch cone ring 46 and the inner cone ring 48 will be released from each other.

Fig. 9 shows a flow chart of the method for controlling the synchronizing ar-rangement 8 for the retarder, which synchronizing arrangement 8 comprisesa sleeve 50, which is axially displaceable between a first and second positionA1 , A3, a latch cone ring 46 with a substantially circular first friction surface 56, an inner cone ring 48 with a substantially circular second friction surface 56”,which inner cone ring 46 is attached to a transmission element 40, and a hub 58, which is attached to a first shaft 14; the first transmission element 40 is connectable to the first shaft 14 by meansof the synchronizing arrangement 8; and the first transmission element 40 is engaged with a second transmission ele-ment 24 attached to the retarder 6.

The method comprises the step of: a) displacing the sleeve 50 from the first position A1 to the second position A3for connecting the first transmission element 40 to the first shaft 14, b) measuring the synchronizing time TS for synchronizing the rotational speed between the first transmission element 40 and the first shaft 14, c) comparing the measured synchronizing time TS to an expected time TE forsynchronizing the rotational speed between first transmission element 40 andthe first shaft 14 using the synchronizing arrangement 8, and d) generating a failure mode if the measured synchronizing time TS is substan-tially shorter than the expected time TE.

When knowing the expected time TE for synchronizing the rotational speedbetween the first transmission element 40 and the first shaft 14, a possiblefailure due to lack of synchronization may be detected if the measured syn-chronizing time TS is substantially shorter than the expected time TE. The rea-son why a lack of synchronization occurs is that the friction surfaces 56, 56” ofthe latch cone ring 46 and the inner cone ring 48 has been stuck together.

Preferably, the synchronizing time TS for synchronizing the rotational speedbetween the first transmission element 40 and the first shaft 14 in step b) ismeasured by monitoring the axial position of the sleeve 50 during synchroniza- tion.

When the axial position of the sleeve 50 does not change or change very slowduring a substantial change in rotational speed of the first transmission ele-ment 40, the synchronization occurs. However, a rapid displacement of thesleeve 50 from the first position A1 to the second position A3 during no changein rotational speed of the first transmission element 40 indicates that no syn- chronization occurs.

Preferably, the expected time TE is determined from synchronization torque,the rotational speed of the first transmission element 40 and the first shaft 14,and the reflected inertia of the first transmission element 40, the first shaft 14 and the synchronizing arrangement 8.

The expected time TE for synchronizing the rotational speed between the first transmission element 40 and the first shaft 14 using a specific synchronizing 21 arrangement 8 may be determined by calculating synchronization torqueneeded at the actual rotational speed of the first transmission element 40 andthe first shaft 14, and also take notice of the inertia of the first transmissionelement 40, the first shaft 14 and the synchronizing arrangement 8.

Preferably, the expected time TE is determined from a table of synchronizationtimes for different rotational speeds of the first shaft 14 stored in an electroniccontrol unit 76.

As an alternative, a table may be created for a specific synchronizing ar-rangement 8. Each specific rotational speeds of the first shaft 14 has a specificsynchronization time corresponding to the expected time TE.

Preferably, the generated failure mode in step d) is indicated by means of a sound or visual signal. lf the retarder 6 is arranged in a vehicle 1, the driver may receive a sound orvisual signal if there is a synchronizing failure in the synchronizing arrange- ment 8. 22 Preferably, the method comprises the further steps of: e) displacing the sleeve 50 from the second position A3 to the first position A1 ;and f) requesting a torque from the retarder 6 if a failure mode in step d) has been generated.

When requesting a torque from the retarder 6, fluid is supplied to the work-space 30. Since the sleeve 50 and the latch cone ring 46 rotates with the samerotationa| speed and torque is transferred between the sleeve 50 and the latchcone ring 46, the requested torque from the retarder 6 will act on the firsttransmission element 40. The magnitude of the requested torque from the re-tarder 6 is essentially the same as the synchronization torque, which leads tothat the friction surfaces 56 of the latch cone ring 46 and the inner cone ring48, which has been stuck together, will be released from each other.

Preferably, the method comprises the further step of:g) measuring the ambient temperature c1, and requesting the torque from theretarder 6 if failure mode in step d) has been generated and only if the ambient temperature c1 is higher than a predetermined temperature c2.

Since the retarder 6 acts on the driving wheels 10 in a vehicle 1, a suddentorque spike may cause a slip between the wheels 10 and the road in slipperyroad conditions. Therefore, if the ambient temperature c1 is low, as an exam-ple below the frozen point for water, it is preferable to perform the steps e) andf) right after start-up or launch of the vehicle 1.

The present invention also relates to a computer program P and a computerprogram product for performing the method steps. The computer program Pcontrols the method of controlling a the synchronizing arrangement 8 for theretarder 6, wherein said computer program P comprises program code formaking the electronic control unit 76 or a computer 78 connected to the elec- 23 tronic control unit 16 to performing the method steps according to the inventionas mentioned herein, when said computer program P is run on the electronic control unit 76 or computer 78 connected to the electronic control unit 76.

The computer program product comprises a program code stored on the elec-tronic control unit 76 or computer 78 connected to the electronic control unit 76readable, media for performing the method steps according to the invention asmentioned herein, when said computer program P is run on the electronic con-trol unit 76 or the computer 78 connected to the electronic control unit 76. Al-ternatively, the computer program product is directly storable in the internalmemory l\/I into the electronic control unit 76 or the computer 78 connected tothe electronic control unit 76, comprising a computer program P for performingthe method steps according to the present invention, when said computer pro-gram P is run on the electronic control unit 76 or the computer 78 connected tothe electronic control unit 76.

The components and features specified above may within the framework of the invention be combined between the different embodiments specified.

Claims

1. A method of controlling a synchronizing arrangement (8) for a retarder (6),which synchronizing arrangement (8) comprises a sleeve (50), which is axially displaceable between a first and second position(A1, A3), a latch cone ring (46) with a substantially circular first friction surface (56), an inner cone ring (48) with a substantially circular second friction surface(56'), which inner cone ring (48) is attached to a first transmission element(40), and a hub (58), which is attached to a first shaft (14); the first transmission element (40) is connectable to the first shaft (14) bymeans of the synchronizing arrangement (8); and the first transmission element (40) is engaged with a second transmissionelement (24) attached to the retarder (6), characterized in the steps: a) displacing the sleeve (50) from the first position (A1) to the second position(A3) for connecting the first transmission element (40) to the first shaft (14),b) measuring the synchronizing time (TS) for synchronizing the rotationalspeed between the first transmission element (40) and the first shaft (14), c) comparing the measured synchronizing time (TS) to an expected time (TE)for synchronizing the rotational speed between the first transmission element(40) and the first shaft (14) using the synchronizing arrangement (8), and d) generating a failure mode if the measured synchronizing time (TS) issubstantially shorter than the expected time (TE).

2. A method according to claim 1, characterized in that the synchronizing time(TS) for synchronizing the rotational speed between the first transmissionelement (40) and the first shaft (14) in step b) is measured by monitoring theaxial position of the sleeve (50) during synchronization.

3. A method according to any of claims 1 - 2, characterized in that theexpected time (TE) is determined from synchronization torque, the rotationalspeed of the first transmission element (40) and the first shaft (14), and inertiaof the first transmission element (40), the first shaft (14) and the synchronizingarrangement (8).

4. A method according to any of claims 1 - 2, characterized in that theexpected time (TE) is determined from a table of synchronization times fordifferent rotational speeds of the first shaft (14) stored in an electronic controlunit (76).

5. A method according to any of any of the preceding claims, characterized inthat the generated failure mode in step d) is indicated by means of a sound or visual signal.

6. A method according to any of claims 1 - 4, characterized in the furthersteps: e) displacing the sleeve (50) from the second position (A3) to the first position(A1); and f) requesting a torque from the retarder (6) if a failure mode in step d) has beengenerated.

7. A method according to claim 6, characterized in that after step e), thefurther step: g) measuring the ambient temperature (c1), and requesting the torque from theretarder (6) if a failure mode in step d) has been generated and only if theambient temperature (c1) is higher than a predetermined temperature (c2).

8. Retarder (6) comprising a synchronizing arrangement (8), whichsynchronizing arrangement (8) comprises: a sleeve (50), which is axially displaceable between a first and second position(A1, A3), a latch cone ring (46) with a substantially circular first friction surface (56), an inner cone ring (48) with a substantially circular second friction surface(56'), which inner cone ring (48) is attached to a first transmission element(40), characterized in that the synchronizing arrangement (8) furthercomprises: a hub (58), which is attached to a first shaft (14); the first transmission element (40) is connectable to the first shaft (14) bymeans of the synchronizing arrangement (8); and the first transmission element (40) is engaged with a second transmissionelement (24) attached to the retarder (6), wherein the synchronizingarrangement (8) is configured to be controlled to displace the sleeve (50) fromthe first position (A1) to the second position (A3) for connecting the firsttransmission element (40) to the first shaft (14); measure the synchronizingtime (TS) for synchronizing the rotational speed between the first transmissionelement (40) and the first shaft (14); compare the measured synchronizingtime (TS) to an expected time (TE) for synchronizing the rotational speedbetween the first transmission element (40) and the first shaft (14) using thesynchronizing arrangement (8); and generate a failure mode if the measuredsynchronizing time (TS) is substantially shorter than the expected time (TE).

9. Vehicle (1 ), characterized in that the vehicle (1) comprises a powertrain (18) connected to the retarder (6) according to claim 8 through a gearbox (4).

10. A computer program (P) for controlling a hydrodynamic retarder device (8),wherein said computer program (P) comprises program code for making anelectronic control unit (76) or computer (78) connected to the electronic control unit (76) to performing the steps according to any of the claims 1 - 7.

11. A computer program product comprising a program code stored on amedia readable by a computer (78) for performing the method steps accordingto any of the claims 1 - 7, when said program code runs on an electroniccontrol unit (76) or computer (78) connected to the electronic control unit (76).