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European Patent Office

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(11) EP 1 688 334 A1

(12) EUROPEAN PATENT APPLICATION

(43) Date of publication: 09.08.2006 Bulletin 2006/32

(21) Application number: 06100946.0

(22) Date of filing: 27.01.2006

(51) Int Cl.:B60W 30/18 (2006.01) B60W 10/06 (2006.01)

B60W 10/12 (2006.01)

(84) Designated Contracting States: AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LI LT LU LV MC NL PL PT RO SE SI SK TRDesignated Extension States: AL BA HR MK YU

(30) Priority: 03.02.2005 US 50122

(71) Applicant: DANA CORPORATIONToledo, OH 43615 (US)

(72) Inventors: • Claussen, Stephen P.

49083, RICHLAND (US)• Wenstrup, Leo J.

Portage, Michigan 49024 (US)

(74) Representative: Franzolin, Luigi et alSTUDIO TORTA S.r.l., Via Viotti, 910121 Torino (IT)

(54) Automated inter-axle differential locking system

(57) The present invention relates to an actuation en-hancement for an automated vehicle inter-axle differen-tial (IAD) locking system. The vehicle having an engineand a tandem drive axle. The IAD actuation enhance-ment locking system comprises a rotating sliding clutchand a rotating side helical gear, which are capable of anengagement mode and a disengagement mode, a mi-croprocessor, and an electrical connection between the

microprocessor and an engine electronic control unit.When the sliding clutch and the helical gear are placedin the engagement mode or are placed in the disengage-ment mode, the microprocessor momentarily communi-cates a data link message to the engine electronic controlunit to break engine torque, which has been found tofacilitate engagement or disengagement of the slidingclutch and the helical gear.

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Description

FIELD OF THE INVENTION

[0001] The present invention relates to an actuationenhancement for an automated vehicle inter-axle differ-ential locking system.

BACKGROUND OF THE INVENTION

[0002] Tandem drive axle assemblies having a forwardrear axle and a rearward rear axle in proximity with eachother are well known. Such tandem drive assemblies arewidely used on heavy duty trucks and other over-the-road vehicles, such as busses, which have a high vehicleweight and/or a high load carrying capacity. In such as-semblies, both rear axles may be power driven.[0003] An inter-axle differential (IAD) is commonly em-ployed in such vehicles to split the input shaft torque be-tween the front and rear axle of the tandem. It is commonfor a vehicle operator to engage and disengage a lockout that overrides or disables the IAD through the use ofa pneumatic switch, which typically is mounted on thevehicle dash. The pneumatic switch, in turn, applies airto an axle mounted actuator, which engages a slidingdog clutch to "lock" the inter-axle differential.[0004] However, there are several shortcomings to theabove-described manual methods of engaging/disen-gaging the IAD. First, failure of the vehicle operator tonotice that wheel end slip is occurring and then to engagethe IAD, can result in spin out failures. Second, engage-ment of the IAD, while significant slipping is in process,can result in damage to either or both of the drive axles.Third, leaving the IAD engaged for an extended lengthof time can result in "drive line wind-up" and a resultinginability to disengage the IAD without reversing the ve-hicle. Fourth, since the actuation of the engagement anddisengagement of the IAD are typically switched on orswitched off by the operator, the IAD does not smoothlytransition from one mode to the other. As a result of theseshortcomings, extended wear can occur and the operatormay not notice the wear, as actual, engagement and dis-engagement of the IAD is not typically indicated to theoperator.[0005] More recently, automatic differential lockoutmechanisms have come into use that attempt to minimizewear from engaging or disengaging of the differentials.U.S. Patent No. 4,671,373 to Sigl discloses a locking-type differential being automatically prevented from en-gaging upon certain vehicle operating conditions. For ex-ample, if the steering wheel is deflected or transverseacceleration is sensed, the differential will not be allowedto be locked. The differential is likewise unlocked or pre-vented from locking if, for example, the brakes are appliedor the engine is operating under an idle condition. On theother hand, for example, if a kick-down signal from theaccelerator is sensed, or if the difference in speed of driv-en and rolling wheels exceeds a predetermined amount,

the differential is controlled to lock.[0006] U.S. Patent No. 5,071,392 to Stall et al. disclos-es a process of continuously controlling the degree oflocking of open differential drives in a driven axle of amulti-axle vehicle where the differential speed of the driv-en wheels is compared to the vehicle speed of the non-driven wheels.[0007] U.S. Patent No. 5,130,928 to Petersen providesan anti-lock and/or anti-slip apparatus for commercialtype vehicles where an electronic system determineswhether the rotational speed of the cardan shaft variesfrom the average speed of the monitored wheels. Uponreceipt of a variance, the electronic system controls thelocking of a longitudinal differential.[0008] U.S. Patent No. 5,989,147 to Forrest et al. dis-closes an electronically controllable differential whichtransfers a predetermined amount of torque through arotatable differential based upon, in part, a predeter-mined rotational condition of the side gear.[0009] U.S. Patent No. 6,174,255 to Porter et al. teach-es a differential lock control system that employs speedsensors and an articulation angle sensor that communi-cate speed signals and an articulation angle signal to amicroprocessor for controlling the locks on front and reardifferentials for an articulated work vehicle. In an auto-matic mode, the microprocessor controls the locking ofthe differentials by comparing predicted axle speeds toactual speeds received from the speed sensors and anarticulation angle from the articulation sensor.[0010] U.S. Patent No. 6,487,486 to Anderson disclos-es a process for continuously controlling the transfer oftorque within a differential while utilizing control logicmethodology. Changes in torque values are determinedfrom output shafts speeds and vehicle speeds.[0011] U.S. Patent No. 6,579,204 to Brown et al. gen-erally discloses a full-time power transfer system for con-trolling speed differentiation and torque biasing acrossan interaxle differential in response to changes in sensorsthat monitor dynamic and operational characteristics ofthe vehicle.[0012] Even with the above-described current auto-matic means for controlling the engagement and disen-gagment of the inter-axle differential, optimization of con-ditions, for example, minimizing damage and excessivewear of IAD components, improving the engagement/disengagement timing of the inter-axle differential lockingmechanism, and enhancing the actuation of the engage-ment/disengagement, can still be made.

SUMMARY OF THE INVENTION

[0013] The present invention relates to an actuationenhancement for a vehicle inter-axle differential (IAD)locking system that is used in a vehicle having an engineand a tandem drive axle. The automated IAD lock systemcomprises a single inter-axle differential having a clutchlocking mechanism, the clutch locking mechanism beingcapable of an engagement mode and a disengagement

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mode, and at least one microprocessor. When the clutchlocking mechanism is placed in the engagement modeor placed in the disengagement mode, the microproces-sor momentarily communicates a data link message toan engine electronic control unit (ECU) so as to breakengine torque, thus facilitating engagement or disen-gagement of the clutch locking mechanism.[0014] Further advantages of the present invention willbe apparent from the following description and appendedclaims, reference being made to the accompanying draw-ings forming a part of a specification, wherein like refer-ence characters designate corresponding parts of sev-eral views.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]

Fig. 1 is a mechanical schematic of a top-plan viewof a vehicle in accordance with the present invention;Fig. 2 is a three dimensional view of an inter-axledifferential in accordance with the present invention;Fig. 3 is a partial cut-away of the three dimensionalview of the inter-axle differential of Fig. 2;Fig. 4 is a partial cut-away of a three dimensionalside view of the inter-axle differential of Fig. 2;Fig. 5 is a flow chart of the logic in accordance withthe present invention;Fig. 6 is an electrical connector diagram in accord-ance with the present invention;Fig. 7 is an electrical schematic of a microprocessorin accordance with the present invention;Fig. 8 is a side view of an engaged inter-axle differ-ential in accordance with the present invention; andFig. 9 is a side view of a disengaged inter-axle dif-ferential in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EM-BODIMENTS

[0016] It is to be understood that the invention mayassume various alternative orientations and step se-quences, except where expressly specified to the con-trary. It is also to be understood that the specific devicesand processes illustrated in the attached drawings, anddescribed in the following specification are simply exem-plary embodiments of the inventive concepts defined inthe appended claims. Hence, specific dimensions, direc-tions or other physical characteristics relating to the em-bodiments disclosed are not to be considered as limiting,unless the claims expressly state otherwise.[0017] Preferably, the present invention uses an auto-matic inter-axle differential (IAD) locking system 10 for avehicle 11 having a tandem drive axle assembly 15, asgenerally illustrated in Fig. 1. The vehicle 11 has an en-gine 12, which is drivingly connected to a transmission14. A main drive shaft 16 extends longitudinally from thetransmission 14 to the tandem drive axle assembly 15,

and may be coupled at one end via a conventional cou-pling 17, such as a yoke or a universal joint, to the trans-mission 14, and at the other end by another conventionalcoupling 18 to an input shaft 30 of the tandem drive axleassembly 15.[0018] Vehicle 11 may be any vehicle having a tandemdrive axle assembly, such as a truck, bus or other over-the-road vehicle which has a tandem drive axle assemblycomprising two axially spaced axles. The tandem driveaxle assembly 15 is usually located near the rear of avehicle and may, therefore, be referred to herein as atandem drive rear axle assembly. The tandem drive rearaxle assembly 15 comprises a rearward rear axle 22,which in turn comprises axially aligned right and left axleshafts (not shown), which are driven through an axle dif-ferential 23. In addition, a forward rear axle 24 also com-prises axially aligned right and left axle shafts (notshown), which are driven through an axle differential 25.The axles 22 and 24 of the tandem rear axle assembly15 herein are axially spaced apart but are in proximitywith each other toward the rear of the vehicle 11.[0019] All parts of both the vehicle 11 as a whole andthe tandem drive rear axle assembly 15 described so farmay be conventional. Thus, the two axle differentials 23and 25 (which are to be distinguished from an inter-axledifferential to be subsequently described) may be con-ventional.[0020] Turning to Fig. 2, a tandem inter-axle assembly20 of the preferred embodiment has a housing 26 at itsforward end to rotatably support the longitudinally ex-tending input shaft 30, which may be axially aligned withthe vehicle drive shaft 16. The forward end of input shaft30 is coupled to vehicle main drive shaft 16 in direct driverelationship by means of the coupling 18. The input shaft30 is received in the inter-axle differential 20 for trans-mitting input torque from the vehicle main drive shaft 16to the inter-axle differential 20. Also shown in Fig. 2 arean inter-axle output shaft 31 that transmits torque to therearward rear axle 22 (via an output drive shaft 50 anda rearward coupling 62, as shown in Fig. 1), a rotatingside helical gear speed sensor 27, and a rotating slidingclutch lock speed sensor 28. The sensors 27, 28 may beconventionally available sensors, for example, DanaCorporation part number 673425 or Wabash part number9184.[0021] As illustrated in Fig. 3, the vehide IAD 20 furthercomprises a clutch locking mechanism 32 that includesa rotating side helical gear 33 and a rotating sliding clutch34. As shown in Fig. 3, the sliding clutch lock mechanism32 is engaged and subsequently locked, where lockedis defined as helical gear teeth 33a and sliding clutchteeth 34a being in a meshing relationship. Helical gearteeth 33a are preferably in a fixed position.[0022] On the other hand, Fig. 4, which is a partial,side view, cut-away of the cover 26 of the inter-axle dif-ferential 20 of Fig. 2, taken near to the sliding clutch sen-sor 28, illustrates the sliding clutch lock mechanism 32being disengaged, where the helical gear teeth 33a of

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the rotating side helical gear 33 and the teeth 34a of thesliding clutch 34 are separated.[0023] Also illustrated in Fig. 4 is the alignment of thesliding clutch speed sensor 28 over the teeth 34a of thesliding clutch 34. When the sliding clutch lock mechanism32 is disengaged, the sliding clutch speed sensor 28measures a speed of the sliding clutch 34 by sensing apresence and then an absence of the rotating teeth 34aof the clutch 34 passing below the sliding clutch speedsensor 28. Thus, the sliding clutch speed sensor 28 (viafirst electrical means 66 shown in Fig. 1) provides a slid-ing clutch signal to a microprocessor 35 (see Fig. 6, forexample, Motorola MC9S12D64 or equivalent and POLESENSOR INPUT #1/#2 in Fig. 6) for determining thespeed of the sliding clutch 34, when the gear 33 and theclutch 34 are disengaged. However, when the clutchmechanism 32 is fully engaged (as in Fig. 3), the sensor28 measures zero sliding clutch speed even though thesliding dutch 34 continues to rotate.[0024] The helical gear speed sensor 27, shown in Fig.3, determines the speed of the helical gear 33 by sensingthe presence and absence of second helical gear teeth33b, which provides a helical gear signal to the micro-processor 35 (see POLE SENSOR INPUT #1/#2 in Fig.6).[0025] When the gear 33 and the clutch 34 are locked,the sliding clutch speed sensor 28 no longer senses thepresence and then the absence of the teeth 34a. It is adiscovery of the instant invention that when the clutchmechanism 32 is locked, the sliding clutch speed sensor28 does not provide a signal to the microprocessor 35,even though the sliding clutch 34 continues to rotate,which is due to the specific placement of the clutch sensor28. The absence of a signal is determined by the micro-processor 35 to mean that the clutch mechanism 32 islocked. Thus, the microprocessor 35 is informed of thelocked or unlocked state (or mode) of the clutch mecha-nism 32, without requiring a separate sensor in additionto the two speed sensors 27, 28.[0026] A general overview of the IAD system 10 termi-nology and functions includes the following modes. Inauto lock mode, no driver interaction is required and thesystem automatically detects slipping and locks, for ex-ample, for up to 15 seconds. In manual lock mode, theoperator presses the lock switch (for example, see Fig.6) in the vehicle cab and then the IAD 20 locks, for ex-ample, for 60 seconds. In manual lock and hold mode,the operator presses and holds the lock switch, for ex-ample, for 5 seconds, and then the IAD 20 remains lockeduntil the unlock switch (see, for example, Fig. 6) ispressed or power to the IAD 20 is recycled. In manualunlock and hold mode the operator presses and holdsthe unlock switch in, for example, for 5 seconds, and thenthe IAD 20 remains unlocked until the lock switch ispressed or power to the IAD 20 is recycled.[0027] Display lamp functions utilized within the IAD20 are unlocked lamp solidly lit (IAD lock is disengaged),locked lamp flashing (IAD 20 is attempting to engage the

IAD lock), locked lamp solidly lit (IAD 20 has beenlocked), locked lamp flashing quickly (IAD 20 is in manuallock and hold mode), and unlocked lamp flashing (IAD20 is attempting to disengage the lock). Note that in theunlocked lamp flashing mode, if the unlocked lamp doesnot turn solid, which indicates lock disengagement, thenthe operator is instructed to remove pressure from thethrottle momentarily to allow the lock to disengage.[0028] Referring to Fig. 5, there is shown a flow chartof logic in accordance with the present invention. Uponstart up or returning from an IAD disengagement mode,the automatic IAD lock system 10 is in an IAD unlockedmode where an engage solenoid 37 (as shown in Fig. 1)is turned off. The solenoid may be, for example, a KIPIncorporated part number 2P2108. Also, an unlock lamp(see Fig. 6) is preferably turned on solidly in the vehiclecompartment to indicate to the operator of the vehicle 11that the clutch mechanism 32 is unlocked.[0029] In addition, a relock timer is set for a short delaythat allows the sliding clutch speed to be established bythe system 10 following disengagement that could beconfigured from milliseconds to seconds, where a pre-ferred implementation would be approximately one sec-ond. Note that when the clutch mechanism 32 is en-gaged, there is no speed signal received from the slidingclutch teeth 34a because the teeth 34a are meshed withthe helical teeth 33a, thus providing no gaps therebe-tween. Therefore, initially fallowing disengagement, thesensor 28 needs this short relock time period before be-ginning to sense the gaps between the gear teeth 33a,34a, so as to prevent immediate re-engaging of the IADclutch mechanism 32.[0030] To change from the IAD unlocked mode to theIAD engaged mode the system 10, through the aid of themicroprocessor 35, determines if the following conditionsprevail: is the mathematical absolute difference betweenthe sliding clutch 34 revolutions per minute and the sidehelical gear 33 revolutions per minute greater than a min-imum limit (or has a manual lock request or has a manuallock and hold request been initiated), and is the mathe-matical absolute difference between the sliding clutch 34revolutions per minute and the side helical gear 33 rev-olutions per minute less than a maximum limit, and is thespeed of the vehicle less than a third limit, and has therelock timer expired, and has no manual unlock and holdbeen requested.[0031] It can be appreciated by one skilled in the artthat the speed of the vehicle 11 may be obtained fromthe vehicle communication data link, for example, J1587COMM LINK or J1939 COMM LINK (see Figs. 6 and 7),which follow the standards set by the Society of Automo-tive Engineers (SAE). It can further be appreciated thatthe instant application is not limited by the first electricalmeans 66 and a second electrical means 69 (for example,wires, connectors, or cables, which could include anypresent or future SAE COMM LINKS), solenoid 37, thesensors 27, 28, the micorprocessor 35, or an engine elec-tronic control unit (ECU) 29 (see Fig. 1), which electrically

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communicates with the microprocessor 35 via the secondelectrical means 69.[0032] If, however, the above conditions are met, thenthe system 10 causes the inter-axle differential clutchmechanism 32 to commence the IAD engage mode bysetting an engage timer, by turning on the engage sole-noid 37, and by causing the "lock" lamp to flash on andoff. The engage timer could be configured to run fromseconds to minutes, but a preferred implementationwould be approximately fifteen seconds.[0033] While in the IAD engage mode, the system 10monitors the vehicle speed to determine if the vehiclespeed is greater than the third limit and the system 10monitors the engage timer to see if the engage timer hasexpired. If either of these two conditions are met then thesystem 10 places the IAD 20 into the disengaged modethat is described below.[0034] A further discovery of the present invention isthat, optionally, when the IAD 20 is in the process of en-gaging, as discussed above, the system 10 may com-municate a vehicle communication data link message(such as a signal to COMM LINK J1939 or the like) tothe electronic controls 29 in the engine 12 to momentarily(for example, for a few milliseconds to approximately onesecond) break engine torque. This discovery has beenfound to smooth the engagement of the IAD 20.[0035] Although not wishing to be bound by any theory,it is believed that this smooth engagement results fromreducing the speed differential and torque between theteeth 33a, 34a as the teeth 33a, 34a engage. The amountof clearance (known as backlash) sets the maximumRPM differential that the two sets of teeth 33a, 34a canbe rotating at and still engage properly. It appears thatthe higher the RPM differential between the two gears33, 34 makes engagement easier, but this higher RPMdifferential increases the potential for shock loading whenthe RPM differential becomes too high. If the two sets ofteeth 33a, 34a cannot engage, then they will ratchet(known as "bumping faces") until they meet the maximumengagement RPM differential, which can result in dam-aging the gear 33 and clutch 34.[0036] Note that the amount of time that the enginetorque is disrupted may not be a fixed amount of time.Instead, the amount of time that the engine torque is dis-rupted for engagement may vary depending upon thespeed and/or an acceleration of the vehicle 11, or themechanical performance of the sliding clutch 34, the hel-ical gear 33, or other parts of the present invention.[0037] Otherwise, following IAD engagement, the sys-tem 10 monitors the sliding clutch RPM to see if it is ap-proximately equal to zero (via the sliding clutch speedsensor 28, see, for example, Fig. 6 connections POLESENSOR SPEED INPUT #1 A-B or #2 A-B). If the slidingclutch RPM is approximately equal to zero, then the sys-tem 10 places the IAD 20 into the locked mode via theengage solenoid 37 (see, for example, Fig. 6 connectionsDIFF LOCK SOLENOID A-B), solidly lights the lock lamp(see, for example, Fig. 6 connection DIFF LOCK

SWITCH/LAMPS S10), and initiates a lock timer, whichcould be configured to run from seconds to minutes, buta preferred implementation would be approximately fif-teen seconds.[0038] While in the IAD locked mode, the system 10monitors the vehicle speed to determine if the vehiclespeed is greater than the third limit, or the system 10monitors the lock timer to see if the lock timer has expiredand that the operator has not requested the system 10to be placed in a manual lock and hold mode, or thesystem monitors that the operator has not requestedmanual unlock mode. If any of these conditions has beenmet, then the system 10 places the IAD 20 into the dis-engaged mode, which includes turning off the engagesolenoid 37, and causing the unlock lamp to flash on andoff. Also, the relock timer, as mentioned above, is set fora short delay that allows the sliding clutch speed to beestablished by the system 10 following disengagementthat could be configured from milliseconds to seconds,where a preferred implementation would be approxi-mately one second.[0039] Note that the engage solenoid 37 may be dis-posed anywhere in/on the vehicle where it will not bedamaged. By way of example only, Fig. 1 schematicallydepicts the solenoid 37 adjacent the engine 12, wherethe solenoid 37 controls pressurized air flow through theport 38 (see Figs. 2 and 3).[0040] As conventionally shown in Figs. 8 and 9, theair causes the inter-axle differential clutch mechanism32, which may also include various other elements (suchas, for example, a push rod 42, a piston 43, a shift cylinder44, a shift fork 45, a selector switch 46 (used in a con-ventional manual control versus the microprocessor 35control of the present invention), and a spring 47) to en-gage (Fig. 8) or disengage (Fig. 9). In these illustrations,the air flow is controlled by the selector switch 46, but inthe present invention the separate solenoid 37 may beutilized to allow pressurized air to enter or not to enterport 38, which subsequently causes the fork 45 to shiftthe sliding clutch 34.[0041] Note, however, that it is within the scope andspirit of the present invention that if road conditions resultin wheel slip, the system may choose to return to theengage mode. If the wheels do not slip, the system 10will continue to monitor for any future slip. This procedureassures that the IAD 20 will not stay engaged for longerthan necessary. In addition, the manual lock and holdrequest overrides the lock timer, which allows the system10 to remain in the locked condition if the operator sochooses.[0042] Another discovery of the present invention isthat, optionally, when the IAD 20 is in this process ofdisengaging, the system 10 may communicate a vehiclecommunication data link message to the electronic con-trols 29 in the engine 12 to momentarily (for example, fora few milliseconds to approximately one second) breakengine torque. This discovery has been found to smooththe disengagement of the IAD 20.

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[0043] Although not wishing to be bound by any theory,it is believed that this smooth disengagement results fromreducing the torque between the teeth 33a, 34a.[0044] It should be appreciated that the amount of timethat the engine torque is disrupted may not be a fixedamount of time. Instead, the amount of time that the en-gine torque is disrupted for disengagement may vary de-pending upon the speed and acceleration of the vehicle11, the sliding clutch 34, the helical gear 33, or other partsof the present invention.[0045] While in the IAD disengage mode, the system10 monitors the sliding clutch RPM so as to determine ifthe sliding clutch 34 is greater than zero (i.e., the teeth33a, 34a are no longer meshed). If the sliding clutch RPMis greater than zero, then the system 10 returns the IAD20 to the unlocked mode, as discussed above, where theengage solenoid 37 remains off and the "unlock lamp" isturned on solid in the vehicle compartment to indicate tothe operator of the vehicle 11 that the clutch mechanism32 is unlocked. The relock timer is also initiated at thistime.[0046] Returning to Fig. 1, there is illustrated the inter-connection of various electrical and pneumatic parts thatare described above. The microprocessor 35 is electri-cally connected to the sensors 27, 28 by the first electricalmeans 66, and the microprocessor 35 is electrically con-nected to the solenoid 37 by third electrical means 67.Although shown located within the engine 12, the micro-processor 35 could be located elsewhere. A source ofcompressed air 63 is pneumatically connected to the so-lenoid 37 by first pneumatic means 64, while the solenoid37 would also be pneumatically connected by secondpneumatic means 65 to the compressed air port 38, forcontrolling the engagement/disengagement of the clutchmechanism 32. The source of compressed air 63 couldbe a separate source or a part of the engine 12.[0047] Figs. 6 and 7 illustrate various embodiments ofelectrical connects between the microprocessor 35 theinputs and outputs (for example, 27, 28, 37 (via the firstelectrical means 66) and various conventional lamps/LEDs) for the system 10. It may be appreciated that thesystem 10 is not limited by the lamps, LEDs, solenoids,and/or the pneumatic means to cause air to flow to theshift fork 45 that causes engagement, disengagement,and locking of the locking mechanism 32.[0048] - In accordance with the provisions of the patentstatutes, the principles and modes of operation of thisinvention have been described and illustrated in its pre-ferred embodiments. However, it must be understoodthat the invention may be practiced otherwise than spe-cifically explained and illustrated without departing fromits spirit or scope.

Claims

1. An inter-axle differential locking system for a vehiclehaving an engine and a tandem drive axle, compris-

ing:

a single inter-axle differential having a clutchlocking mechanism, said clutch locking mecha-nism being capable of an engagement modeand a disengagement mode; andat least one microprocessor;

wherein when said clutch locking mechanism isplaced in said engagement mode or placed in saiddisengagement mode, said microprocessor momen-tarily communicates a data link message to an en-gine electronic control unit to break engine torque tofacilitate an engagement or a disengagement of saidclutch locking mechanism.

2. The inter-axle differential locking system of claim 1,wherein said clutch mechanism includes a rotatingside helical gear that has helical gear teeth and arotating sliding clutch that has sliding clutch teeth,and when said clutch mechanism is placed in saidengagement mode, said engine torque is disruptedfor an amount of time in a range of a few millisecondsto approximately one second, thus reducing thespeed differential and torque between said helicalgear teeth and said sliding clutch teeth.

3. The inter-axle differential locking system of claim 1,wherein said clutch mechanism includes a rotatingside helical gear that has helical gear teeth and arotating sliding clutch that has sliding clutch teeth,and when said dutch mechanism is placed in saiddisengagement mode, said engine torque is disrupt-ed for an amount of time in a range of a few millisec-onds to approximately one second, thus reducingthe torque between said helical gear teeth and saidsliding clutch teeth.

4. The inter-axle differential locking system of claim 1,wherein an amount of time that said engine torqueis disrupted is dependent upon the speed and/or ac-celeration of said vehicle and/or said clutch lockingmechanism.

5. The inter-axle differential locking system of claim 1,further comprising a solenoid, which is in communi-cation with said microprocessor for controlling saidengagement or said disengagement of said inter-axle differential.

6. The inter-axle differential locking system of claim 1,wherein said inter-axle differential further comprisesa pneumatic port, a shift fork, a push rod, a piston,and a shift cylinder.

7. An inter-axle differential locking system for a vehiclehaving an engine and a tandem drive axle, compris-ing:

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an inter-axle differential of a vehicle having arotating sliding clutch and a rotating side helicalgear, said sliding clutch and said helical gearbeing capable of an engagement mode and adisengagement mode;a microprocessor; andan electrical connection between said micro-processor and an engine electronic control;

wherein when said sliding clutch and said helicalgear are placed in said engagement mode or placedin said disengagement mode, said microprocessormomentarily communicates a communication datalink message over said electrical connection to saidengine electronic control unit to break engine torque,in order to facilitate engagement or disengagementof said sliding clutch and said helical gear.

8. The inter-axle differential locking system of claim 7,wherein said side helical gear has helical gear teethand said sliding clutch has sliding clutch teeth, andwhen said side helical gear and said sliding clutchare placed in said engagement mode, said enginetorque is disrupted for an amount of time in a rangeof a few milliseconds to approximately one second,thus reducing the speed differential and torque be-tween said helical gear teeth and said sliding clutchteeth.

9. The inter-axle differential locking system of claim 7,wherein said side helical gear has helical gear teethand said sliding clutch has sliding clutch teeth, andwhen said side helical gear and said sliding clutchare placed in said disengagement mode, said enginetorque is disrupted for an amount of time in a rangeof a few milliseconds to approximately one second,thus reducing the torque between said helical gearteeth and said sliding clutch teeth.

10. The inter-axle differential locking system of claim 7,wherein an amount of time that said engine torqueis disrupted is dependent upon the speed and/or ac-celeration of said vehicle, and/or said sliding clutch,and/or said helical gear.

11. An inter-axle differential lock actuation enhancementmethod for an automated inter-axle differential lock-ing system for a vehicle having a tandem drive axle,comprising:

providing a single inter-axle differential havinga clutch locking mechanism for a vehicle, saidclutch locking mechanism being capable of anengagement mode and a disengagement mode;providing at least one microprocessor;placing said clutch locking mechanism in saidengagement mode or placing said clutch lockingmechanism in said disengagement mode; and

momentarily communicating a data link mes-sage to an engine electronic control unit to breakengine torque, thus facilitating said engagementor said disengagement of said clutch lockingmechanism.

12. The inter-axle differential lock actuation enhance-ment method of claim 11, further comprising provid-ing a signal within an operator’s compartment of saidvehicle that said inter-axle differential is engaged ordisengaged.

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