# (12) United States Patent Morscheck et a1. US008523738B2



# US 8,523,738 B2 Sep. 3, 2013 (10) Patent N0.: 

## (45) Date of Patent:

(54)

(75)

(73)

(21) (22) (65)

(60)

(51)
(52)

(58) METHOD OF SHIFTINGA TANDEM DRIVE AXLE HAVING AN INTER-AXLE DIFFERENTIAL



### Inventors: Timothy J. Morscheck, Portage, MI 

### (US); Kenneth E. Cooper, Toledo, OH (US); James F. Ziech, Kalamazoo, MI 

### (US); RichardA. Nellums, Maumee, OH (US); Steven J. WesoloWski, 

### Waterville, OH (US); Donald J. 

### Remboski,AnnArbor, MI (US) Assignee: Dana HeavyVehicle Systems Group, LLC, Maumee, OH (US)

Notice: Subject to any disclaimer, the term ofthis patent is extended or adjusted under 35 

### U.S.C. 154(b) by 55 days. Appl. N0.: 13/353,944

Filed: Jan. 19, 2012

Prior Publication Data
US 2013/0017927 A1 Jan. 17,2013



### Related U.S. Application Data
Provisional application No. 61/435,007, ?led on Jan. 

### 21, 2011.

Int. Cl. 

### B60W10/00 (2006.01) U.S. Cl.
USPC

............. .. 477/77; 477/36; 477/110; 475/221; 475/332 Field of Classi?cation Search USPC

............... 477/35, 36, 77, 107, 110; 475/221, 

### 475/223, 332, 343 See application ?le for complete searchhistory. (56) References Cited

U.S. PATENT DOCUMENTS 2,166,099 A 12/1937 Quartullo 2,291,174 A 3/1939 Stewart 2,290,089 A 7/1942 Bock 2,574,986 A 10/1947 Schou 2,936,036 A 5/1960 Norelius 3,146,842 A 9/1964 Nelson et a1. 3,221,832 A 12/1965 Holmstrom 3,324,965 A 6/1967 Koch et :11. 3,388,760 A 6/1968 Christie 3,577,804 A 5/1971 Ohno 3,657,935 A 4/1972 O’Brien 3,706,350 A 12/1972 Bokovoy 3,792,628 A 2/1974 Stieg 3,827,520 A 8/1974 Mueller 

## (Continued)

FOREIGN PATENT DOCUMENTS
CN 201346995 Y 1/2009 EP 1 527 938 A2 5/2005 

## (Continued)
Primary Examiner * Justin Holmes (74) Attorney, Agent, or Firm * Marshall & Melhom LLC 

### (57) ABSTRACT

A method of shifting a poWer distribution unit for a vehicle from a ?rst operating state to a second operating state is 

### provided. The method includes the step of adjusting a rota tional speed of a portion of a second axle assembly using a clutching device to impart energy to a lubricant Within the second axle assembly. A controller in communication With a poWer source ofthe vehicle adjusts an operating condition of the poWer source to facilitate moving the clutching device. ThepoWer distributionunit includes an inter-axle differential 

### capable being placed in a locked condition by the clutching device and ofaccommodating arotational differencebetWeen

a ?rst output gear and a second output gearWiththe inter-axle differential.



### 44 Claims, 4 Drawing Sheets

## US 8,523,738 B2 Page 2

References Cited 6,840,880 B2 1/2005 Glassner 6,863,634 B2 3/2005 Holman et al. 6,877,573 B2 4/2005 Hasegawa U'S' PATENT DOCUMENTS 6,918,851 B2 7/2005 Ziech et al. 3,915,032 A 10/1975 Ottemann 6,926,634 B2 8/2005 Haka 3,916,728 A 11/1975 Behar et al. 6,932,734 B2* 8/2005 HWa et a1.

................... .. 475/221 3,976,154 A 8/1976 Clark et a1. 6,953,411 B2 10/2005 Burns et al. 4,046,210 A 9/1977 Nelson 6,964,310 B2 11/2005 Hasegawa 4,050,534 A 9/1977 Nelson et al. 7,044,880 B2* 5/2006 Bowen

........................ .. 475/205 4,194,586 A 3/1980 Hicks 7,093,681 B2 8/2006 Strain 4,263,824 A 4/1981 Mueller 7,096,990 B2 8/2006 Borgen etal. 4,432,431 A 2/1984 Russell 7,163,483 B2 1/2007 Haka 4,462,271 A 7/1984 Stieg 7,195,579 B2 3/2007 Claussen et a1. 4,560,018 A 12/1985 Satzler 7,291,083 B2 11/2007 Almaguer 4,677,873 A 7/1987 Eastman er :11 7,306,536 B2 12/2007 Ziech 4,754,847 A 7/1988 GlaZe et 61. 7,399,251 B2 7/2008 Mueller et al. 4,779,699 A 10/1988 Hatano

....................... .. 180/248 7,410,440 B2 8/2008 Garcia et a1. 4,887,487 A 12/1989 May?eld 7,491,145 B2 2/2009 Mizon et al. 5,176,590 A 1/1993 HaydOCk 7,611,414 B2 11/2009 Mueller et al. 5,267,489 A 12/1993 Ziech 7,686,728 B2 3/2010 Imbert 5,370,018 A 12/1994 Kwasniewski 2006/0172852 A1* 8/2006 Claussen et a1.

.............. .. 477/35 5,435,790 A 7/1995 Kota et al. 2006/0272866 A1 12/2006 Ziech 5,641,044 A 6/1997 Morscheck 2008/0210508 A1 9/2008 Heisey et al. 5,651,748 A 7/1997 Adarn et a1. 2010/0206654 A1 8/2010 Cimattiet al. 5,711,389 A 1/1998 Schlosser 2010/0248888 A1 9/2010 Hamperlet al. 5,860,889 A 1/1999 Schlosser et al. 5,876,301 A 3/1999 Tabata et a1.

................ .. 477/109 FOREIGN PATENT DOCUMENTS 5,950,750 A 9/1999 Dong et a1.

_ 6,085,853 A 7 Wernick 58 2 6,154,700 11/2000 Jones JP 337125 A 12/1996 6,258,009 B1 7/2001 Thomas et al. KR 20030000505 A H2003 6,327,935 B1 12/2001 Joslin et al. W0 WO 2008019779 A2 2/200g 6,517,462 B2 2/2003 Borgan eta1~ W0 WO 2008113484 A1 9/2008 6,530,861 B1 3/2003 Nakashima 6,659,249 B2 12/2003 Borgen et al. * cited by examiner

# US. Patent



# ROTATIONAL SPEED

TIME 

## Sep. 3, 2013 Sheet 2 of4 US 8,523,738 B2

A


# :7"

I ‘1/,

w I: / 

# (‘,5 / / PowerSource g / _---TransferShaft 

# .% / —------SecondOutputGear

E II/ | I | 

## g): / l ------F|rstDrrvrngGear

Z----I-/L ------------- -_ 

# 1/,’ 1/‘ 

# lI/I
0 >

A B C D ' — 

# TIME M

It 

# ,/ 

# //

‘r

-_ -Power Source


### /' - - - -Transfer Shaft 

## / ---—--—SecondOutputGear 

# /' ------FirstDn'vingGear __\_\__ 

# \ / \

A B D E 

# [Fig-3

# US. Patent Sep. 3, 2013 Sheet 3 of4 US 8,523,738 B2

__--PowerSource

_ - - -Transfer Shaft 

## _--_---SecondOutputGear -___--FirstDrivingGear It



## TIME



## _--_--—SecondOutputGear _____-FrrstDrrvrng Gear w ? 

## m m



## a m 5 W m

_



### _ i 

# D:

r

_ > _


# \ \ _ \\ 

## "\ 

# \\\ \ u

\

_ C 

# \\ ‘t \ u

\

_

_ 

# \ u 

# \t\\ n \

_ R u 

## \\ n B _

m

M

. A 

# EEZEEEE

0

TIME

## US 8,523,738 B2 1
METHOD OF SHIFTING A TANDEM DRIVE AXLE HAVINGAN INTER-AXLE DIFFERENTIAL

CLAIM OF PRIORITY



### Thepresentapplication claimspriority to and incorporates by reference US. Provisional Application No. 61/435,007 ?led Jan. 21, 2011, entitled “TWo Speed Tandem DriveAxle Having an Inter-Axle Differential.”

FIELD OF THE INVENTION

The present invention relates to a vehicle drive train and to
a method of shifting a tandem drive axle for the vehicle drive train having an inter-axle differential from a ?rst operating state to a second operating state.

BACKGROUND OF THE INVENTION

Vehicles incorporating tandem drive axles bene?t inmany Ways over vehicles having a single driven axle. Inter-axle differentials in such vehicles may be con?gured to distribute 

### torque proportionately or disproportionately betWeen the axles. Additionally, shift mechanisms may be provided to such vehicles to permit the disengagement of one of the driven axles or to transition from single axle operation to 

### tandem axle operation, among otherbene?ts. HoWever, such 

### versatility typically requires the incorporation of additional drive train components into the vehicle at added expense and Weight. Such added Weight results in a decreased fuel e?i 

### ciency ofthe vehicle.

Components ofthe tandem drive axlemay also be selected based on a gear reduction ratio present in an axle. Axle ratios may be ofa tWo-speed con?guration to permit the vehicle to operate in a loW speed and high torque manner or in a high speed and loW torque manner. It is preferred to drive both 

### axles When the loW speed and high torque manner of opera 

### tion is desired (to distribute the higher torque amongst a greaternumber ofWheels) and it is advantageous to operate a 

### single axle When the high speed and loW torque manner of 

### operationisdesired (todecreaseWindageandfrictional losses When torque distribution is of loWer concern). HoWever, incorporation of both the tWo-speed con?guration, an axle disconnect function, and the inter axle differential may be 

### prohibitive With respect to cost and Weight. Such added 

### Weight, Windage losses, and frictional losses result in a decreased fuel e?iciency ofthe vehicle.



### Additionally, When components areprovidedto permit the disengagement ofone ofthe driven axles orto transition from 

### the vehicle from single axle operation to tandem axle opera tion, a complexity of the tandem drive axle is increased. 

### Typically, such operations may require manual engagement by an operator When speci?c conditions are present or may 

### require the operator to stop the vehicle to engage speci?c 

### components. Such features, Whileproviding additional func 

### tionality to the vehicle, may not beproperly implementedby the operator or may not be used at all by the operator. When such features are not properly implemented, a shift from one operating state to anothermayresult indamage to the tandem drive axle or a rough shift, either ofWhich typically result in

a dissatisfaction ofthe operator.

ItWouldbe advantageous to develop amethod ofshifting a 

### tandem drive axle system from a loW speed and high torque tandem axle manner of operation to a high speed and loW 

### torque single axlemanner ofoperation that reduces Windage and frictional losses and facilitates improved shifting from 20

25

30

35

40

45

50

55

60

65 

## 2

one operating state to anotherWithout excessively increasing

a cost and a Weight ofthe tandem drive axle.

SUMMARY OF THE INVENTION


### Presentlyprovidedby the invention, amethod ofshifting a tandem drive axle system from a loW speed and high torque tandem axle manner of operation to a high speed and loW 

### torque single axlemanner ofoperation that reduces Windage and frictional losses and facilitates improved shifting from
one operating state to anotherWithout excessively increasing

a cost and a Weight ofthe tandem drive axle, has surprisingly been discovered.

In one embodiment, the present invention is directed to a method ofshifting apoWerdistributionunit foravehicle from

a ?rst operating state to a second operating state. The method 

### includes the steps ofdrivingly engaging a ?rst axle assembly With a ?rst output ofthepoWerdistributionunit and drivingly engaging a second axle assembly With a second output ofthe poWerdistributionunit. Next, themethod includes the step of 

### drivingly engaging an input of the poWer distribution unit With an output ofa poWer source, the poWer distribution unit 

### includinganinter-axledifferential, the ?rstoutput, the second output, and a ?rst clutching devicehaving a ?rstposition and


### a second position, the ?rst clutching device in the ?rst posi 

### tion locking the inter-axle differential, engaging the ?rst out put With the input of the poWer distribution unit, and disen 

### gaging the second output from the inter-axle differential, the 

### ?rst clutching device in the second position unlocking the inter-axle differential and engaging the ?rst output and the second output With the inter-axle differential. Next, the 

### method includes the steps ofplacingthe ?rst clutchingdevice in one ofthe ?rstposition and the secondposition and apply ing a rotational force to the input of the poWer distribution 

### unit. Next, the method includes the steps of adjusting the rotational force transferred to the poWer distribution unit to 

### facilitate moving the ?rst clutching device and moving the ?rst clutching device from one of the ?rst position and the 

### secondpositionto a thirdposition, the ?rst clutchingdevice in 

### the third position neither locking the inter-axle differential

nor engaging the second output With the inter-axle differen tial. Lastly, the method includes the steps ofadjusting a rota 

### tional speed of the input of the poWer distribution unit to 

### facilitate moving the ?rst clutching device from the third 

### position, moving the ?rst clutching device from the third positionto one ofthe ?rst and secondpositions, andadjusting the rotational force transferred to thepoWer distribution unit.

Various aspects ofthis invention Will become apparent to 

### those skilled inthe art fromthe folloWingdetaileddescription ofthepreferredembodiment,Whenreadinlight oftheaccom 

## panying draWings.

BRIEF DESCRIPTION OF THE DRAWINGS

The above, as Well as other advantages of the present 

### invention, Willbecomereadily apparentto those skilled inthe 

### art from the folloWing detailed description When considered 

### in the light ofthe accompanying draWings in Which:

FIG. 1 is a schematic vieW of a tandem drive axle system including a poWer distribution unit according to an embodi 

### ment ofthe present invention;

FIG. 2 is a chart illustrating a ?rst example of shifting the poWerdistributionunit from a ?rst operating state to a second 

### operating state;

FIG. 3 is a chart illustrating a second example of shifting thepoWerdistributionunit from the ?rst operating state to the 

### second operating state;

## US 8,523,738 B2 3
FIG. 4 is a chart illustrating a third example ofshifting the power distribution unit from the ?rst operating state to the 

### second operating state;

FIG. 5 is a chart illustrating a ?rst example of shifting the poWer distribution unit from the second operating state to the 

### ?rst operating state; and

FIG. 6 is a schematic vieW of a tandem drive axle system including a poWer distribution unit according to another embodiment ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

It is to beunderstoodthat the inventionmay assumevarious 

### alternative orientations and step sequences, except Where expressly speci?ed to the contrary. It is also to be understood that the speci?c devices and processes illustrated in the 

### attached draWings, and described in the folloWing speci?ca tionare simply exemplary embodiments ofthe inventive con 

### cepts de?ned inthe appended claims. Hence, speci?c dimen sions, directions or other physical characteristics relating to the embodiments disclosed are not to be considered as limit 

### ing, unless the claims expressly state otherWise.

FIG. 1 illustrates a drive axle system 10 foravehiclehaving

a poWer source 11. The drive axle system 10 preferably includes apoWerdistributionunit 12, a ?rst axle assembly 14, and a second axle assembly 16. The drive axle system 10 is drivingly engaged With a poWer source 11. As shoWn, the 

### drive axle system 10 includes the three assemblies 12, 14, 16, but it is understood the drive axle system 10 may include feWer or more assemblies or components.

The poWer source 11 is drivingly engaged With an input 

### shaft 18 ofthe poWer distribution unit 12, and applies poWer thereto. The poWer source 11 is, for example, an internal 

### combustion engine; hoWever, it is understood that the poWer

source 11 may include an electric motor or another source of rotational output. It is understood that the poWer source 11 may be a hybrid poWer source including both an internal combustion engine and an electric motor. Further, it is under stood that the poWer source 11 may include a transmission (not shoWn) as knoWn in the art. Further, it is understood that the poWer source 11 may include a clutch (not shoWn) as knoWn in the art, for one of reducing and interrupting a rotational force transferred to the poWer distribution unit 12.

The poWer distribution unit 12 includes an input shaft 18,

an inter-axle differential 19, a ?rst output gear 20, aplurality 

### ofdrivingpinions 21, a transfer shaft 22, a second output gear 

### 24, anda clutch 28. Preferably, thecomponents 18, 19, 20, 21, 22, 24, 28 are formed from a hardened steel, hoWever the 

### components 18, 19, 20, 21, 22, 24, 28 may be formed from any otherrigidmaterial.As shoWn, poWerdistributionunit 12 

### includes the seven components 18, 19, 20, 21, 22, 24, 28 disposed in a housing 30 but it is understood the poWer distribution unit 12 may include feWer or more components.



### The input shaft 18 is at least partially disposed in the 

### housing 30. Preferably, the input shaft 18 is an elongate member, hoWever the input shaft 18 may be any other shape. 

### Bearings 32 disposed betWeen the input shaft 18 and the housing 30 permit the input shaft 18 to rotate about an axis of 

### the input shaft 18. The input shaft 18has a ?rstendportion 33,

a middle portion 34, and a second end portion 35.

The middle portion 34 has a diameter greater than a diam eter of the ?rst end portion 33. The middle portion 34 is a 

### substantiallydisc shapedbody drivingly coupledto the input shaft 18.Altemately, themiddleportion 34 may be integrally formed With the input shaft 18.



### The second end portion 35 is a substantially holloW body having a diameter greater than a diameter of the ?rst end 20

25

30

35

40

45

50

55

60

65 

## 4 portion 33 andthemiddleportion 34. The second endportion 

### 35 is drivingly coupled to themiddleportion 34.Alternately, the second endportion 35 may be integrally formedWith the input shaft 18 and the middle portion 34. The second end portion 35 has apinion carrier 36, a ?rst set ofclutch teeth 37, and an engagement portion 38 formed thereon.



### The pinion carrier 36 is a substantially disc shaped body 

### drivingly coupled to the second end portion 35 ofthe input shaft 18. The pinion carrier 36 includes a plurality ofpinion supports 39 protruding from a ?rst side of the pinion carrier 

### 36 into the second end portion 35 of the input shaft 18. The engagement portion 38 is formed on a second side of the 

### pinion carrier 36.As is knoWn in the art, thepinion carrier 36 is also knoWn as a planet carrier.

The engagement portion 38 is a conical surface oblique to 

### the input shaft 18, hoWever, the engagement portion 38 may have any other shape. The ?rst set of clutch teeth 37 are formed on the pinion carrier 36 radially inWard from the 

### engagement portion 38.

The inter-axledifferential 19 includes thepinioncarrier36, 

### thepluralityofdrivingpinions 21, the ?rstoutputgear20, and the transfer shaft 22. The inter-axle differential 19 is a plan etary differential as knoWn in the art; hoWever, it is under stood that the inter-axle differential 19 may be a bevel gear differential or any other type ofdifferential.



### The plurality ofdriving pinions 21 are rotatably disposed

on thepinion supports 39 ofthepinion carrier 36. Each ofthe driving pinions 21 have gearteeth formed on an outer surface 

### thereof.As is knoWn in the art, each ofthe driving pinions 21 is also knoWn as a planet gear. Preferably, bearings are dis 

### posedbetWeen each ofthe driving pinions 21 and thepinion supports 39, hoWever, the drivingpinions 21 maybe directly mounted on the pinion supports 39.

The ?rst output gear 20 is a gear concentrically disposed 

### Within the second end portion 35 of the input shaft 18. The 

### ?rst output gear 20 is a substantially cup shapedbody having

an inner surface having gear teeth 40 formed on. As is knoWn in the art, the ?rst output gear 20 is knoWn as a ring gear. The gear teeth 40 are engaged With the gear teeth formed on the 

### outer surface ofeach ofthe driving pinions 21.

The ?rst output gear 20 includes an output shaft 41 driv 

### inglycoupledthereto.Altemately, the ?rstoutputgear20may be integrally formedWith the output shaft 41. The ?rst output 

### gear 20 is drivingly engaged With the ?rst axle assembly 14 through the output shaft 41. The output shaft 41 is collinear 

### With the input shaft 18. Bearings 32 disposed betWeen the output shaft 41 andthehousing 30 support the output shaft 41 and permit the output shaft 41 to rotate about an axis ofthe 

### output shaft 41.



### A bevel gear pinion 42 is drivingly coupled to the output shaft 41 opposite the ?rst output gear 20. Altemately, the bevel gearpinion 42maybe integrally formedWiththeoutput shaft 41. As is knoWn in the art, the bevel gearpinion 42 has
gear teeth formed on an outer surface thereof. The bevel gear pinion 42 may be one of a hypoid gear, a spiral bevel gear, a straightbevel gear, or any othergearknoWnto those skilled in the art.

The transfer shaft 22 is aholloW shaft rotatably disposed in the housing 30 andhaving an axis ofrotation concurrent With 

### the axis of rotation of the input shaft 18. Preferably, the transfer shaft 22 is a holloW elongate cylindrical member, hoWever the transfer shaft 22 may be any other shape. Bear 

### ingsmaybedisposedbetWeenthetransfershaft 22 andpinion carrier 36 topermitthe transfer shaft 22 to rotate about an axis of the transfer shaft 22. The transfer shaft 22 has a ?rst end portion 43 having a ?rst set of clutch teeth 44 formed on an

## US 8,523,738 B2 5
outer surface thereof, and a second end portion 45, having a second set ofgearteeth 46 formed on anouter surface thereof.

The ?rst endportion 43 and the second end portion 45 are integrally formed With the transfer shaft 22. The ?rst set of clutch teeth 44 and the second set ofgear teeth 46 are formed 

### in the transfer shaft 22. Altemately, the ?rst end portion 43 and the second end portion 45 may be formed separate from and drivingly coupled to the transfer shaft 22.As is knoWn in 

### the art, the second endportion 45 having the gear teeth 46 is knoWn as a sun gear. The second set of gear teeth 46 are 

### engaged With the plurality ofdrivingpinions 21 and the ?rst set of clutch teeth 44 are disposed adjacent the ?rst set of 

### clutch teeth 37 ofthepinion carrier 36. The ?rstportion 43 of 

### the transfer shaft 22 may be selectively engaged With the second output gear 24 or the pinion carrier 36

The secondoutput gear 24 is agear concentricallydisposed about a portion of the transfer shaft 22. The second output gear 24 has a central perforation having a diameter greater than a diameter of the transfer shaft 22. The second output 

### gear 24 is a substantially disc shapedbody having a ?rst end portion 47, a secondendportion 48 de?ning anouterdiameter 

### ofthe second output gear 24, and an engagement portion 49. 

### Bearings 32 disposedbetWeen the second output gear 24 and the housing 30 permit the second output gear 24 to rotate about an axis of the second output gear 24. The axis of the second output gear 24 is concurrentWith the axis ofthe input shaft 18. A ?rst set of clutch teeth 50 are formed on the ?rst end portion 47 adjacent the ?rst set of clutch teeth 44 of the transfer shaft 22. A second set ofgear teeth 51 are formed on the second end portion 48. The second output gear 24 is 

### drivingly engagedWith the second axle assembly 16.

The engagementportion 49 is formed in the second output gear 24 intermediate the ?rst end portion 47 and the second 

### end portion 48. As shoWn, the engagement portion 49 is a 

### conical surface oblique to the input shaft 18; hoWever, the engagement portion 49 may have any other shape.

The clutch 28 is a shift collarconcentrically disposedabout the transfer shaft 22. The clutch 28 includes a set of inner clutch collar teeth 52 formed on an inner surface thereof, a ?rst synchroniZer 53, and a second synchroniZer 54. The set ofinner clutch collar teeth 52 are engagedWith the ?rst set of clutch teeth 44 ofthe transfer shaft 22. The clutch 28 can be 

### slidablymoved along the axis ofthe input shaft 18 as directed 

### automatically by a controller 55 While maintaining engage ment of the inner clutch collar teeth 52 and the ?rst set of clutch teeth 44. A shift fork 56 disposed in an annular recess formed in the clutch 28 moves the clutch 28 along the axis of the input shaft 18 into a ?rst position, a second position, or a 

### thirdposition.A ?rst actuator 57, Which is drivingly engaged With the shift fork 56, is engaged to position the shift fork 56
as directed by the controller 55. Consequently, the shift fork 

### 56 positions the clutch 28 into the ?rst position, the second position, or the third position. In the ?rst position, the inner clutch collar teeth 52 of the clutch 28 are drivingly engaged With the ?rst set ofclutch teeth 44 ofthe transfer shaft 22 and the ?rst set of clutch teeth 37 ofthe pinion carrier 36. In the second position, inner clutch collar teeth 52 of clutch 28 are 

### drivingly engaged With the ?rst set of clutch teeth 44 of the transfer shaft 22 and the ?rst set of clutch teeth 50 of the second output gear 24. In the third position, the inner clutch 

### collar teeth 52 of the clutch 28 are only drivingly engaged With the ?rst set ofclutch teeth 44 ofthe transfer shaft 22. It 

### is understoodthe clutch 28, the clutchteeth 37, 44, 50, 52, the 

### synchroniZers 53, 54, and the engagement portions 38, 49 may be substituted With any clutching device that permits selective engagement ofa driving and a driven part. 5

20

25

30

35

40

45

50

55

60

65 

## 6 The ?rst synchroniZer 53 is an annularbody coupled to the 

### clutch 28 adjacent the engagement portion 38 of the pinion carrier 36. The ?rst synchroniZer 53 has a ?rst conical engage 

### ment surface 58. Altemately, the ?rst synchroniZer 53 may 

### have an engagement surface having any other shape. When the clutch 28 ismoved from thethirdpositiontoWards the ?rst position, the ?rst conical engagement surface 58 contacts the 

### engagement portion 38 ofthe pinion carrier 36, causing the clutch 28 to actuponthepinioncarrier 36. Whenthe clutch 28 is moved further toWards the ?rst set ofclutch teeth 37 ofthe 

### input shaft 18, the clutch continues to act upon the pinion carrier 36 as the inner clutch collarteeth 52 become drivingly engaged With the ?rst set of clutch teeth 44 of the transfer shaft 22 andthe ?rst set ofclutchteeth 37 ofthepinion carrier 36.



### The second synchroniZer 54 is an annularbody coupled to 

### the clutch 28 adjacent the ?rst end portion 47 of the second output gear 24. The second synchroniZer 54 has a second 

### conical engagement surface 59. Alternately, the second syn chroniZer 54 may have an engagement surface having any other shape. When the clutch 28 is moved from the third 

### position into the secondposition, the second conical engage ment surface 59 contacts the engagement portion 49 of the second output gear 24, causing the clutch 28 to act upon the second output gear 24. When the clutch 28 is moved further toWards the ?rst set of clutch teeth 50 of the second output gear 24, the clutch 28 continues to actupon the second output gear 24 as the inner clutch collar teeth 52 become drivingly engaged With the ?rst set of clutch teeth 44 of the transfer shaft 22 andthe ?rst set ofclutchteeth 50 ofthe secondoutput gear 24.



### The ?rst axle assembly 14 includes the bevel gear pinion 42, a ?rst driving gear 60, a ?rst Wheel differential 61, and a 

### ?rstpair ofoutput axle shafts 62. Preferably, the components 42, 60, 61, 62 are formed from a hardened steel, hoWever the 

### components 42, 60, 61, 62 may be formed from any other 

### rigidmaterial. As shoWn, the ?rst axle assembly 14 includes the four components 42, 60, 61, 62 disposed in a ?rst axle housing 63 but it is understoodthe ?rst axle assembly 14 may include feWer or more components.

The ?rst driving gear 60 is coupled to ahousing ofthe ?rst Wheel differential 61 by a plurality offasteners or a Weld and is rotatable about an axis ofthe ?rstpair ofoutput axle shafts 

### 62 Within the ?rst axle housing 63. Alternately, the ?rst driv ing gear 60 may be integrally formed With the ?rst Wheel differential 61

.As is knoWn in the art, the ?rst driving gear 60 has gear teeth formed on an outer surface thereof. The ?rst driving gear 60 may be one of a hypoid gear, a spiral bevel gear, a straight bevel gear, or any other gear knoWn to those 

### skilled intheart. The ?rstdrivinggear 60 is drivingly engaged With the bevel gear pinion 42 and has a ?rst gear ratio. As a non-limiting example, the ?rst gear ratio may be a 2.26:1 ratio, but it is understood that other ratios may be used. The 

### output shaft 41 is drivingly engagedWiththe ?rstdrivinggear 60 ofthe ?rst axle assembly 14 through a single gear mesh.

The ?rst Wheel differential 61 is a bevel gear style differ ential as is knoWn in the art having a plurality of driving 

### pinions and a pair of side gears drivingly engaged With the ?rst pair ofoutput axle shafts 62. The ?rst Wheel differential 

### 61 is rotatably disposedWithinthe ?rst axlehousing 63 about the axis ofthe ?rst pair ofoutput axle shafts 62. Alternately, other styles ofdifferentials may be used in place of the ?rst Wheel differential 61.



### The ?rst pair of output axle shafts 62 are elongate cylin drical members having a common axis rotatably mounted 

### Within the ?rst axle housing 63. Bearings 32 disposed betWeenthe ?rstpairofoutput axle shafts 62 andthe ?rst axle

## US 8,523,738 B2 7 housing 63 permit the ?rst pair of output axle shafts 62 to rotate therein. The side gears ofthe ?rst Wheel differential 61
are disposed on ?rst ends ofeach ofthe ?rst output axle shafts 62 and Wheels (not shoWn) are disposed on second ends of each ofthe ?rst output axle shafts 62.

The second axle assembly 16 includes an inter-axle shaft 64, a second driving gear 65, a second Wheel differential 66,
a secondpair ofoutput axle shafts 67, and an axle clutch 68. 

### Preferably, thecomponents 64, 65, 66, 67, 68 are formed from
a hardened steel, hoWever the components 64, 65, 66, 67, 68 may be formed from any other rigid material. As shoWn, the 

### secondaxle assembly 16 includesthe ?ve components 64, 65, 66, 67, 68 disposed in a second axle housing 69 but it is understoodthe secondaxle assembly 16may include feWeror
more components.

The inter-axle shaft 64 comprises at least one elongate 

### cylindricalmemberdrivingly engagedWiththe secondoutput gear 24 through a driven gear 70 coupled to the inter-axle shaft 64. As illustrated, the inter-axle shaft 64 comprises a 

### plurality of elongate cylindrical members connected by joints. Bearings 32 disposed betWeen the inter-axle shaft 64 and the housing 30 permit the inter-axle shaft 64 to rotate therein.



### Abevelgearpinion 71 isdrivinglycoupledto the inter-axle shaft 64 oppositethedrivengear 70.As is knoWninthe art, the bevel gearpinion 71 has gearteeth formed on an outer surface thereof. Thebevel gearpinion 71maybe one ofahypoidgear,
a spiral bevel gear, a straight bevel gear, or any other gear knoWn to those skilled in the art.

The second driving gear 65 is a ring style bevel gear as is knoWn in the art having a set ofgear teeth engaged With the gear teeth formed on the bevel gear pinion 71. The second driving gear 65 is coupled to a housing of the second Wheel differential 66 by a plurality of fasteners or a Weld and is rotatable about anaxis ofthe secondpair ofoutput axle shafts 

### 67Within the second axlehousing 69.Alternately, the second driving gear 65 may be integrally formed With the second Wheel differential 66. The seconddriving gear 65 is drivingly engaged With the bevel gearpinion 71 andhas a second gear ratio.As anon-limiting example, the secondgearratiomaybe

a 4.88:1 ratio, Which is a loWer gear ratio than the ?rst gear ratio, but it is understood that other ratios or a ratio equal to the ?rst gear ratio may be used.

The second Wheel differential 66 is a bevel gear style differential as is knoWn inthe art having aplurality ofdriving 

### pinions and a pair of side gears drivingly engaged With the second pair of output axle shafts 67. The second Wheel dif 

### ferential 66 is rotatablydisposedWithinthe secondaxlehous ing 69 about the axis ofthe second pair ofoutput axle shafts 67. Alternately, other styles of differentials may be used in place ofthe second Wheel differential 66.



### The secondpairofoutput axle shafts 67 are elongate cylin drical members having a common axis rotatably mounted 

### Within the second axle housing 69. Bearings 32 disposed betWeen the pair of second output axle shafts 67 and the 

### second axle housing 69 permit the secondpair ofoutput axle shafts 67 to rotate therein. The side gears ofthe secondWheel differential 66 are disposed on ?rst ends ofeach ofthe second output axle shafts 67 andWheels (not shoWn) are disposed on second ends of each ofthe second output axle shafts 67.

The axle clutch 68 is a dog style clutch that divides one of 

### the secondoutputaxle shafts 67 into ?rstand secondportions. Alternately, the axle clutch 68 may be a component of the secondWheel differential 66 Which engages a side gear ofthe second Wheel differential 66 and one of the second output axle shafts 67 or any other clutching device as knoWn in the art. The axle clutch 68 may also be a plate style clutch or any 20

25

30

35

40

45

50

55

60

65 

## 8 other style ofclutch. Theaxle clutch 68has aplurality ofteeth 

### formed thereon for selectively engaging corresponding teeth formed on the ?rst portion and the second portion of the second output axle shafts 67. The axle clutch 68 is urged into

an engaged position or a disengaged position by a shift fork 

### 73.A secondactuator 74, Whichis drivingly engagedWiththe 

### shift fork 73, is engagedto positionthe shift fork 73, and thus the axle clutch 68, as directed by the controller 55. When the 

### axle clutch 68 is in the engaged position, the ?rst portion of

one ofthe second output axle shafts 67 is drivingly engaged Withthe secondportionofone ofthe secondoutputaxle shafts

67

.

The controller 55 is in communication With the poWer
source 11, the ?rst actuator 57, the second actuator 74, and at least one sensor 75. Preferably, the controller 55 is in electri cal communication With the poWer source 11, the ?rst actua tor 57, the second actuator 74, and the at least one sensor 75. Alternately, the controller 55 may be in communicationWith the poWer source 11, the ?rst actuator 57, the second actuator 74, and the at least one sensor 75 using pneumatics, hydrau lics, or a Wireless communication medium.

The controller 55 is con?gured to accept an input contain ing information regarding at least one ofan operating condi tion ofthe poWer source 11, a temperature ofthe second axle assembly 16, a speed of a portion of the transfer shaft 22, a 

### speed ofthe second output gear 24, a speedofaportionofthe second axle assembly 16, an amount of the rotational force transferred to thepoWer distributionunit 12, aposition ofthe clutch 28, and a position ofthe axle clutch 68. The controller 55 uses the input to adjust the at least one of the operating 

### condition of the poWer source 11, the position of the clutch 28, theposition ofthe axle clutch 68, and a durationbetWeen successive positions ofthe clutch 28. The controller 55 per 

### forms the adjustment to the operating condition ofthe poWer


### source 11, the position of the clutch 28, the position of the 

### axle clutch 68, and the durationbetWeen successivepositions ofthe clutch 28 based on at least one ofthe operating condi tion of the poWer source 11, the temperature of the second 

### axle assembly 16, the speed ofthe second output gear 24, the speedofaportionofthe secondaxle assembly 16, the amount of the rotational force transferred to the poWer distribution 

### unit 12, the position ofthe clutch 28, and the position ofthe axle clutch 68. The controller 55 references at least one of a series of instructions and conditions, an operator input, at least one data table, and at least one algorithm to determine 

### the adjustment made to the operating condition ofthe poWer


### source 11, the position of the clutch 28, the position of the 

### axle clutch 68, and the durationbetWeen successivepositions ofthe clutch 28.

The at least one sensor 75 may be disposed Within the 

### housing 30, the ?rst axle housing 63, and the second axle housing 69. Further, it is understood that the at least one
sensor 75 may be disposed on an outer surface of one of the housings 30, 63, 69 ormounted elseWhere onthevehicle. The at least one sensor 75 is con?gured as knoWn in the art to monitor at least one of the operating condition of the poWer


### source 11, the temperature of the second axle assembly 16, 

### the speed ofaportionofthe transfer shaft 22, the speed ofthe second output gear 24, the speed of a portion of the second axle assembly 16, the amount ofarotational force transferred 

### to thepoWerdistributionunit 12, thepositionofthe clutch 28, 

### andthepositionoftheaxle clutch 68. Theoperating condition of the poWer source 11 may be at least one of an indication that thepoWer source 11 is operating, arotational speed ofthe poWer source 11, a state ofa transmission forming aportionof the poWer source 11, and a speed ofthe vehicle.

## US 8,523,738 B2

In use, a method for use With the drive axle system 10 facilitates shifting the power distribution unit 12 from a ?rst operating state to a second operating state.

When the poWer distribution unit 12 is placed in the ?rst 

### operating state, only the ?rst axle assembly 14 is driven in a 

### high speed and loW torque manner of operation. The ?rst operating state is employedWhenthevehiclereaches a “cruis 

### ing” speed, Which typically requires a reduced amount of 

### torque to maintain the “cruising” speed. In the ?rst operating state, the clutch 28 is placed in a ?rst position. In the ?rst position, the inter-axle differential 19 is locked and the ?rst 

### output gear 20 is drivingly engaged With the input shaft 18 through the inter-axle differential 19 in the locked condition. When the inter-axle differential 19 is locked, the pinion car 

### rier36, theplurality ofdrivingpinions 21, the ?rstoutputgear 20, andthe transfer shaft 22 rotate concurrentlybecause inner clutch collar teeth 52 of the clutch 28 are drivingly engaged With the ?rst set ofclutch teeth 37 ofthepinion carrier 36 and the ?rst set ofclutch teeth 44 ofthe transfer shaft 22. Further, 

### in the ?rst position, the second output gear 24 is disengaged from the clutch 28 and the transfer shaft 22, and thus the inter-axle differential 19 and the input shaft 18. When the 

### poWerdistributionunit 12 isplaced inthe ?rst operating state, the axle clutch 68 may be disengaged, permitting the second 

### output gear 24, the driven gear 70, the inter-axle shaft 64, the second driving gear 65, and the secondWheel differential 66
to coast to an idle condition.

WhenthepoWerdistributionunit 12 isplaced inthe second 

### operating state, the ?rst axle assembly 14 andthe second axle assembly 16 are simultaneously driven in a loW speed and 

### high torque manner ofoperation. The second operating state 

### is employed When the vehicle is operated at loWer speeds or Whenthevehicleis accelerating.Whenthevehicle is operated at loWer speeds or When the vehicle is accelerating, an increased amount oftorque is typically required. In the sec 

### ond operating state, the clutch 28 is placed in a secondposi tion. In the second position, the inter-axle differential 19 is unlockedandthe output shaft 41 ofthe ?rst outputgear 20 and 

### the second output gear 24 are drivingly engaged With the 

### input shaft 18 through the inter-axle differential 19. The pin ion carrier 36 simultaneously drives the ?rst output gear 20 

### and the transfer shaft 22 through the plurality of driving pinions 21. When the inter-axle differential 19 is unlocked, 

### the pinion carrier 36, the plurality ofdriving pinions 21, the ?rst output gear 20, and the transfer shaft 22 are free to rotate With respect to one another. Further, in the second position, the ?rst set ofclutch teeth 50 ofthe second output gear 24 and the ?rst set of clutch teeth 44 of the transfer shaft 22 are engagedWith the inner clutch collar teeth 52 ofthe clutch 28. When the poWer distribution unit 12 is placed in the second 

### operating state, the axle clutch 68 is engaged, permitting the second output gear 24 to drive the secondpair ofoutput axle 

### shafts 67 through the driven gear 70, the inter-axle shaft 64, the second driving gear 65, and the secondWheel differential 66.

FIGS. 2-4 are three charts illustrating three non-limiting examples ofshifting thepoWerdistributionunit 12 froma ?rst operating state to a second operating state.



### The shiftingprocedure as illustrated in FIG. 2 is employed by the controller 55 When the temperature ofthe second axle 

### assembly 16 is above the predeterminedvalue priorto initia 

### tionofthe shiftingprocedure. Further, itisunderstoodthatthe example illustrated in FIG. 2 may be selectedby the control ler 55 on the basis that the shifting procedure illustrated in 

### FIG. 2 is advantageous When the temperature of the second 

### axle assembly 16 is Within a predetermined temperature range. A horiZontal axis shoWn in FIG. 2 indicates a duration 20

25

30

35

40

45

50

55

60

65 

## 10 of time from a ?rst chronological reference point, A, to a 

### fourth chronologicalreferencepoint, D. Chronological refer

encepoints B and C respectively occurbetWeenpointsA and D.Avertical axis shoWn in FIG. 2 indicates a rotational speed 

### of the ?rst output gear 20, the transfer shaft 22, the second output gear 24, and the poWer source 11. The vertical axis begins at a rotational speed of Zero and increases as the vertical axis extends aWay from the horiZontal axis. A rota tional speed of the poWer source 11 depicted in FIG. 2 is 

### merely forpurposes ofexample, andthe shiftingprocedure is not limited to the depicted speeds.



### PointA indicates a starting time ofthe shifting procedure. At pointA, the poWer distribution unit 12 is in the ?rst oper 

### ating state. In the ?rst operating state, the clutch 28 is in the ?rst position. When directed by the controller 55 or by an 

### operator ofthe vehicle, the shifting procedure is initiated by verifying disengagement ofthe axle clutch 68 andby adjust ing the rotational force transferred to the poWer distribution unit 12.

The step ofadjusting the rotational force transferred to the 

### poWerdistributionunit 12maybeperformedby oneofadjust ing an operating condition ofthepoWer source 11 andat least 

### partially disengaging a clutch (not shoWn) forming aportion ofthe poWer source 11. When the step ofadjusting the rota tional force transferred to the poWer distribution unit 12 is 

### performed by adjusting the operating condition ofthe poWer

source 11, the operating conditionofthepoWer source 11 may 

### be adjustedby one ofincreasing ordecreasing a fuel supplied to thepoWer source 11. Whenthe rotational force is apositive rotational force (meaning the poWer source 11 is applying a 

### rotational force to the poWer distribution unit 12) the fuel supplied to the poWer source 11 is decreased to reduce the rotational force. When the rotational force is a negative rota 

### tional force (meaning the poWerdistributionunit 12 is apply ing arotational forceto thepoWer source 11) the fuel supplied to the poWer source 11 is increased to increase the rotational 

### force. When the step of one ofreducing and interrupting the rotational force transferredto thepoWerdistributionunit 12 is 

### performed by at least partially disengaging a clutch or other device (neither are shoWn) associated With the poWer source 11, an amount of engagement of the clutch or other device (neither are shoWn) associated With the poWer source 11 is decreased to reduce the rotational force. Adjusting the rota tional force transferred to the poWer distribution unit 12 as 

### mentionedhereinabove isperformeduntil therotational force transferred to the poWer distribution unit 12 is about equal to
an amount ofrotational force applied by the poWer distribu tion unit 12 to the poWer source 11.

When the rotational force transferred to the poWer distri bution unit 12 is about equal to an amount ofrotational force 

### applied by the poWer distribution unit 12, the controller 55 engages the ?rst actuator 57 to move the clutch 28 from the ?rstposition to the thirdposition. Point B ofFIG. 2 indicates


### a time in the shifting procedure When the clutch 28 is placed 

### in the third position. As mentioned hereinabove, When the clutch 28 is placed in the thirdposition, the inter-axle differ ential 19 is unlocked and the second output gear 24 is disen 

### gaged from the transfer shaft 22, and thus the inter-axle dif ferential 19. Once the clutch 28 is placed inthe thirdposition, the controller 55 further engages the ?rst actuator 57 to move 

### the clutch 28 from the third position to the second position 

### While simultaneously adjusting the rotational speed of the poWer source 11.

As shoWn in FIG. 2, the duration oftimebetWeenpoints B and Crepresents a durationoftimeWherethe clutch 28, Which 

### is drivingly engagedWiththe transfer shaft 22, is actingupon

## US 8,523,738 B2 11 the second output gear 24 but before the inner clutch collar teeth 52 engage the ?rst set of clutch teeth 50 ofthe second output gear 24. When the clutch 28 acts upon the second output gear 24, a rotational force is applied to the second output gear 24. The rotational force applied to the second output gear 24 causes the second output gear 24, the driven 

### gear 70, the inter-axle shaft 64, the second driving gear 65, and the second Wheel differential 66 to adjust the rotational speed from the idle condition to one ofapredetermined speed and a target speed.



### The predetermined speed is obtained by the controller 55 by referencing information stored in the at least one data 

### table. Thetarget speedis calculatedbythe controller 55using the at least one algorithm and a speed of the vehicle. To 

### facilitate adjusting the rotational speed to one of the prede 

### termined speed and the target speed, the rotational speed of the poWer source 11 is adjusted. As a non-limiting example, the rotational speed ofthe poWer source 11 may be adjusted by one of increasing or decreasing a fuel supplied to the poWer source 11. A shoWn in FIG. 2, the rotational speed of the poWer source 11 is increased betWeen points B and C. A
near constant rotational speed ofthe ?rst pair of output axle 

### shafts 62 (as thevehicle coasts during the shiftingprocedure) backdrives the ?rst output gear 20. The ?rst output gear 20, backdriven at the near constant rotational speed, permits increases in the rotational speed ofthe poWer source 11 to be 

### directly re?ected in the rotational speed ofthe transfer shaft 22 through the inter-axle differential 19. The concurrent rota 

### tion ofthe pinion carrier 36 (as driven by the input shaft 18) andthe ?rstoutput gear 20 drives thetransfer shaft 22 through 

### the plurality of driving pinions 21 to adjust the rotational speed of the second output gear 24, the driven gear 70, the inter-axle shaft 64, the seconddriving gear 65, andthe second Wheel differential 66 through the clutch 28.

A shoWn in FIG. 2, the one ofthepredetermined speed and 

### the target speed are obtainedWhen the rotational speed ofthe transfer shaft 22 and the second output gear 24 are about 

### equal. Further, the one of the predetermined speed and the target speedpermits ameshing engagementbetWeen the sec ondoutput gear 24 andthetransfer shaft 22Withthe clutch 28.



### When the one of the predetermined speed and the target speed are obtained, the controller 55 further engages the ?rst actuator 57 tomove the clutch 28 fromthe thirdpositionto the second position. Point C of FIG. 2 indicates a time in the 

### shiftingprocedureWhenthe clutch 28 is placed in the second position. As mentioned hereinabove, When the clutch 28 is 

### placed in the secondposition, the inter-axle differential 19 is unlocked and the second output gear 24 is engaged With the transfer shaft 22, and thus the inter-axle differential 19.



### When the one of the predetermined speed and the target speed are obtained, the controller 55 commands the second actuator 74 to move the axle clutch 68 to an engagedposition. 

### Point C ofFIG. 2 indicates the time ofthe shifting procedure When the controller 55 commands the second actuator 74 to
move the axle clutch 68 to an engaged position. Point D of 

### FIG. 2 indicates the time ofthe shifting procedure When the axle clutch 68 is engaged.As shoWn in FIG. 2, the duration of time betWeen points C and D represents a duration of time after the controller 55 commands the second actuator 74 to engage the axle clutch 68 but before the axle clutch 68 is 

### engaged. The axle clutch 68maynot immediately engage due to a misalignment betWeen the ?rst portion and the second portion of one of the second pair of output axle shafts, a 

### slipping condition ofone ofthe Wheels (not shoWn) coupled to the second pair of output axle shafts 67, or due to both conditions.As shoWn in FIG. 2, once the one ofthe predeter 

### mined speedandthetarget speedare obtained, a substantially 20

25

30

35

40

45

50

55

60

65 

## 12
constant rotational speed of the poWer source 11 is main tained by the controller 55. When the axle clutch 68 is 

### engaged, the secondpair ofoutput axle shafts 67 is drivingly engaged With the second output gear 24 through the driven 

### gear 70, the inter-axle shaft 64, the second driving gear 65, and the second Wheel differential 66.



### Followingpoint D, the step ofone ofincreasing andresum ing the rotational force transferred to the poWer distribution 

### unit 12 may be performed by one of adjusting an operating condition ofthe poWer source 11 and by engaging the clutch 

### (not shoWn) forming a portion ofthepoWer source 11. When the step of increasing the rotational force transferred to the 

### poWerdistributionunit 12 isperformedby adjusting the oper ating condition ofthe poWer source 11, the operating condi tion ofthepoWer source 11 maybe adjustedby increasing the fuel supplied to the poWer source 11. When the step of 

### increasing andresuming therotational forcetransferredto the 

### poWer distribution unit 12 is performed by engaging the clutch (not shoWn), the amount ofengagement ofthe clutch (not shoWn) associatedWith the poWer source 11 is increased to increase the rotational force.Adjusting the rotational force transferred to the poWer distribution unit 12 as mentioned 

### hereinabove completes the shiftingprocedure as illustrated in FIG. 2, and the controller 55 returns control of one of the operating conditions of the poWer source 11 and the clutch 

### (not shoWn) to the operator.

Once the drive axle system 10 is placed in the second 

### operating state, the rotational force applied to the poWer dis tribution unit 12 by the poWer source 11 is distributed betWeenthe ?rst output gear 20 andthe second output gear 24 through the inter-axle differential 19. A rotational difference 

### of the ?rst output gear 20 and the second output gear 24 caused by a difference betWeen the ?rst gear ratio and the second gear ratio is accommodated by the inter-axle differ ential 19. Because the inter-axle differential 19 accommo dates the rotational difference betWeen the ?rst gearratio and the secondgearratio, a cumulative gearratio isprovided. The cumulative gear ratio is intermediate the ?rst gear ratio and the second gear ratio.



### The shiftingprocedure as illustrated in FIG. 3 is employed by the controller 55 When the temperature ofthe second axle 

### assembly 16 is beloW thepredeterminedvalue prior to initia 

### tionofthe shiftingprocedure. Further, itisunderstoodthatthe example illustrated in FIG. 3 may be selectedby the control ler 55 on the basis that the shifting procedure illustrated in 

### FIG. 3 is advantageous When the temperature of the second 

### axle assembly 16 is Within a predetermined temperature range. The shifting procedure illustrated in FIG. 3 may be selectedWhenthe temperatureofthe secondaxle assembly 16 is loW enough to substantially reduce an effectiveness ofthe 

### synchroniZer 54 of the clutch 28 in acting upon the second output gear 24 due to an increase inviscosity ofthe lubricant 

### disposed in the second axle assembly 16. A horiZontal axis shoWn in FIG. 3 indicates a duration of time from a ?rst 

### chronological reference point,A, to a ?fth chronological ref


### erence point, E. Chronological reference points B, C, and D respectively occur betWeen points A and E.

A vertical axis shoWn in FIG. 3 indicates the rotational 

### speed of the ?rst output gear 20, the transfer shaft 22, the second output gear 24, and thepoWer source 11. The vertical axis begins at a rotational speed of Zero and increases as the vertical axis extends aWay from the horizontal axis. The rota tional speed of the poWer source 11 depicted in FIG. 3 is 

### merely forpurposes ofexample, andthe shiftingprocedure is not limited to the depicted speeds.



### PointA indicates a starting time ofthe shifting procedure. At pointA, the poWer distribution unit 12 is in the ?rst oper

## US 8,523,738 B2 13 ating state. In the ?rst operating state, the clutch 28 is in the ?rst position. When directed by the controller 55 or by an 

### operator ofthe vehicle, the shifting procedure is initiated by verifying disengagement ofthe axle clutch 68 and by adjust ing the rotational force transferred to the poWer distribution unit 12.

The step ofadjusting the rotational force transferred to the 

### poWerdistributionunit 12maybeperformedby oneofadjust ing an operating condition ofthepoWer source 11 and at least 

### partially disengaging a clutch (not shoWn) forming aportion ofthe poWer source 11. When the step ofadjusting the rota tional force transferred to the poWer distribution unit 12 is 

### performed by adjusting the operating condition ofthe poWer

source 11, the operating conditionofthepoWer source 11 may 

### be adjustedby one ofincreasing ordecreasing a fuel supplied to thepoWer source 11. Whenthe rotational force is apositive rotational force (meaning the poWer source 11 is applying a rotational force to the poWer distribution unit 12) the fuel supplied to the poWer source 11 is decreased to reduce the rotational force. When the rotational force is a negative rota 

### tional force (meaning the poWerdistributionunit 12 is apply ing arotational forceto thepoWer source 11) the fuel supplied to the poWer source 11 is increased to increase the rotational 

### force. When the step of one ofreducing and interrupting the rotational force transferredto thepoWerdistributionunit 12 is 

### performed by at least partially disengaging a clutch or other device (neither are shoWn) associated With the poWer source 11, an amount of engagement of the clutch or other device (neither are shoWn) associated With the poWer source 11 is decreased to reduce the rotational force. Adjusting the rota tional force transferred to the poWer distribution unit 12 as 

### mentionedhereinabove isperformeduntiltherotational force transferred to the poWer distribution unit 12 is about equal to
an amount ofrotational force applied by the poWer distribu tion unit 12 to the poWer source 11.

When the rotational force transferred to the poWer distri bution unit 12 is about equal to an amount ofrotational force 

### applied by the poWer distribution unit 12, the controller 55 engages the ?rst actuator 57 to move the clutch 28 from the ?rstposition to the thirdposition. Point B ofFIG. 3 indicates


### a time in the shifting procedure When the clutch 28 is placed 

### in the third position. As mentioned hereinabove, When the clutch 28 is placed in the thirdposition, the inter-axle differ ential 19 is unlocked and the second output gear 24 is disen 

### gaged from the transfer shaft 22, and thus the inter-axle dif ferential 19.



### Once the clutch 28 is placed in the third position, the controller 55 decreases a rotational speed ofthepoWer source 

### 11. As a non-limiting example, the rotational speed of the poWer source 11 may be decreased by decreasing a fuel supplied to the poWer source 11. A shoWn in FIG. 3, the rotational speed ofthepoWer source 11 is decreased betWeen points B and C. A near constant rotational speed of the ?rst 

### pair ofoutput axle shafts 62 (as the vehicle coasts during the 

### shifting procedure) backdrives the ?rst output gear 20. The ?rst output gear 20, backdriven at the near constant rotational 

### speed, permits decreases in the rotational speed ofthe poWer
source 11 to be directlyre?ected in therotational speed ofthe transfer shaft 22 through the inter-axle differential 19. The 

### concurrent rotation ofthe pinion carrier 36 (as driven by the input shaft 18) and the ?rst output gear 20 retards the transfer 

### shaft 22 through the plurality ofdriving pinions 21 to adjust the rotational speed of the transfer shaft 22. The rotational speed ofthe transfer shaft 22 is adjustedto facilitate a smooth engagement of the clutch 28 With the second output gear 24 When the clutch 28 is moved from the third position to the 

### second position. As a non-limiting example, the rotational 5

10

20

25

30

35

40

45

50

55

60

65 

## 14 speed of the poWer source 11 may be decreased betWeen points B and C to decrease the rotational speed ofthe transfer shaft 22 to about Zero. Point C ofFIG. 3 indicates a time in the 

### shiftingprocedureWhenthe clutch 28 is placed in the second 

## position.

When the rotational speed of the transfer shaft 22 is adjusted to facilitate a smooth engagement of the clutch 28 With the second output gear 24, the controller 55 further engages the ?rst actuator 57 to move the clutch 28 from the 

### third position to the second position While simultaneously adjusting a rotational speed ofthe poWer source 11.

As shoWn in FIG. 3, the duration oftimebetWeenpoints C and D represents a duration of time Where the inner clutch collar teeth 52 are drivingly engaged With the clutch teeth 44 ofthe transfer shaft 22 and the clutch teeth 50 ofthe second output gear 24 but before the controller 55 commands the second actuator 74 to move the axle clutch 68 to an engaged 

## position.

When the clutch 28 is engagedWith the second output gear 

### 24, the second output gear 24 is drivingly engaged With the transfer shaft 22. Whenthe secondoutput gear 24 is drivingly 

### engagedWiththe transfer shaft 22, the rotational speed ofthe second output gear 24, the driven gear 70, the inter-axle shaft 

### 64, the second driving gear 65, and the second Wheel differ ential 66maybe adjustedto one ofapredetermined speedand


### a target speed.



### Further, When the second output gear 24 is drivingly engagedWiththetransfer shaft 22, the seconddriving gear 65 and the second Wheel differential 66 imparts energy to the 

### lubricant disposed Within the second axle assembly 16. The duration oftime betWeenpoints C and D may be determined 

### by the controllerbased on the temperature ofthe second axle assembly 16 as indicated by the sensor 75. The controller 55 may increase ordecrease the duration oftime betWeenpoints C and D until the temperature ofthe second axle assembly 16 

### is above thepredeterminedvalue.As anon-limiting example, the predetermined value may be about 200 Fahrenheit.



### The predetermined speed is obtained by the controller 55 by referencing information stored in the at least one data 

### table. The target speedis calculatedbythe controller 55using the at least one algorithm and a speed of the vehicle. To 

### facilitate adjusting the rotational speed to one of the prede 

### termined speed and the target speed, the rotational speed of the poWer source 11 is adjusted. As a non-limiting example, the rotational speed ofthe poWer source 11 may be adjusted by one of increasing or decreasing a fuel supplied to the poWer source 11. A shoWn in FIG. 3, the rotational speed of the poWer source 11 is increased betWeen points C and D. A
near constant rotational speed ofthe ?rst pair ofoutput axle 

### shafts 62 (as thevehicle coasts during the shiftingprocedure) backdrives the ?rst output gear 20. The ?rst output gear 20, backdriven at the near constant rotational speed, permits increases in the rotational speed ofthe poWer source 11 to be 

### directly re?ected in the rotational speed ofthe transfer shaft 22 through the inter-axle differential 19. The concurrent rota 

### tion ofthe pinion carrier 36 (as driven by the input shaft 18) andthe ?rstoutput gear 20 drives thetransfer shaft 22 through 

### the plurality of driving pinions 21 to adjust the rotational speed of the second output gear 24, the driven gear 70, the inter-axle shaft 64, the seconddriving gear 65, andthe second Wheel differential 66 through the clutch 28 placed in the 

### secondposition.

A shoWn in FIG. 3, the one ofthepredetermined speed and 

### the target speed are obtainedWhen the rotational speed ofthe 

### second output gear 24, the driven gear 70, the inter-axle shaft 

### 64, the second driving gear 65, and the second Wheel differ ential 66 permits a meshing engagement betWeen the ?rst

## US 8,523,738 B2 15 portion ofone ofthe secondpair ofoutput axle shafts 67 and 

### the secondportion ofone the secondpairofoutput axle shafts 67 With the axle clutch 68.



### When the one of the predetermined speed and the target speed are obtained, the controller 55 commands the second actuator 74 tomovethe axle clutch 68 to the engagedposition. 

### Point D ofFIG. 3 indicates the time ofthe shifting procedure When the controller 55 commands the second actuator 74 to
move the axle clutch 68 to the engaged position. Point E of 

### FIG. 3 indicates the time ofthe shifting procedure When the axle clutch 68 is engaged.As shoWn in FIG. 3, the duration of time betWeen points D and E represents a duration of time after the controller 55 commands the second actuator 74 to engage the axle clutch 68 but before the axle clutch 68 is 

### engaged. The axle clutch 68maynot immediately engage due to a misalignment betWeen the ?rst portion and the second portion of one of the second pair of output axle shafts, a 

### slipping condition ofone ofthe Wheels (not shoWn) coupled to the second pair of output axle shafts 67, or due to both conditions.As shoWn in FIG. 3, once the one ofthe predeter 

### mined speedandthetarget speedare obtained, a substantially constant rotational speed of the poWer source 11 is main tained by the controller 55. When the axle clutch 68 is 

### engaged, the secondpair ofoutput axle shafts 67 is drivingly engaged With the second output gear 24 through the driven 

### gear 70, the inter-axle shaft 64, the second driving gear 65, and the second Wheel differential 66.



### Followingpoint E, the step ofone ofincreasing andresum ing the rotational force transferred to the poWer distribution 

### unit 12 may be performed by one of adjusting an operating condition ofthe poWer source 11 and by engaging the clutch 

### (not shown) forming aportion ofthe poWer source 11. When the step of increasing the rotational force transferred to the 

### poWerdistributionunit 12 isperformedby adjustingthe oper ating condition ofthe poWer source 11, the operating condi tionofthepoWer source 11 maybe adjustedby increasing the fuel supplied to the poWer source 11. When the step of 

### increasing andresumingtherotational forcetransferredto the 

### poWer distribution unit 12 is performed by engaging the clutch (not shoWn), the amount ofengagement ofthe clutch (not shoWn) associatedWith thepoWer source 11 is increased to increase the rotational force.Adjusting the rotational force transferred to the poWer distribution unit 12 as mentioned 

### hereinabove completes the shiftingprocedure as illustrated in FIG. 3, and the controller 55 returns control of one of the operating conditions of the poWer source 11 and the clutch 

### (not shoWn) to the operator.

Once the drive axle system 10 is placed in the second 

### operating state, the rotational force applied to the poWer dis tribution unit 12 by the poWer source 11 is distributed betWeenthe ?rst output gear 20 andthe second output gear 24 through the inter-axle differential 19. A rotational difference of the ?rst output gear 20 and the second output gear 24 caused by a difference betWeen the ?rst gear ratio and the second gear ratio is accommodated by the inter-axle differ ential 19. Because the inter-axle differential 19 accommo dates the rotational difference betWeen the ?rst gearratio and the secondgearratio, a cumulative gearratio isprovided. The cumulative gear ratio is intermediate the ?rst gear ratio and the second gear ratio.



### The shiftingprocedure as illustrated in FIG. 4 is employed by the controller 55 When the temperature ofthe second axle 

### assembly 16 is beloW thepredeterminedvalue prior to initia 

### tionofthe shiftingprocedure. Further, itisunderstoodthatthe example illustrated in FIG. 4 may be selectedby the control ler 55 on the basis that the shifting procedure illustrated in 

### FIG. 4 is advantageous When the temperature of the second 20

25

30

35

40

45

50

55

60

65 

## 16 axle assembly 16 is Within a predetermined temperature range. The shifting procedure illustrated in FIG. 3 may be selectedWhenthe temperatureofthe secondaxle assembly 16 is loW enough to reduce an effectiveness ofthe synchroniZer 54 ofthe clutch 28 in acting upon the second output gear 24 due to an increase inviscosity ofthe lubricant disposed in the second axle assembly 16. A horizontal axis shoWn in FIG. 4 indicates a duration of time from a ?rst chronological refer
ence point, A, to a ?fth chronological reference point, E. 

### Chronological reference points B, C, and D respectively

occur betWeen points A and E.

Avertical axis shoWn in FIG. 4 indicates a rotational speed 

### of the ?rst output gear 20, the transfer shaft 22, the second output gear 24, and the poWer source 11. The vertical axis begins at a rotational speed of Zero and increases as the vertical axis extends aWay from the horiZontal axis. The rota tional speed of the poWer source 11 depicted in FIG. 4 is 

### merely forpurposes ofexample, andthe shiftingprocedure is not limited to the depicted speeds.



### PointA indicates a starting time ofthe shifting procedure. At pointA, the poWer distribution unit 12 is in the ?rst oper 

### ating state. In the ?rst operating state, the clutch 28 is in the ?rst position. When directed by the controller 55 or by an 

### operator ofthe vehicle, the shifting procedure is initiated by verifying disengagement ofthe axle clutch 68 andby adjust ing the rotational force transferred to the poWer distribution unit 12.

The step ofadjusting the rotational force transferred to the 

### poWerdistributionunit 12maybeperformedby oneofadjust ing an operating condition ofthepoWer source 11 andat least 

### partially disengaging a clutch (not shoWn) forming aportion ofthe poWer source 11. When the step ofadjusting the rota tional force transferred to the poWer distribution unit 12 is 

### performed by adjusting the operating condition ofthe poWer

source 11, the operating conditionofthepoWer source 11 may 

### be adjustedby one ofincreasing ordecreasing a fuel supplied to thepoWer source 11. Whenthe rotational force is apositive rotational force (meaning the poWer source 11 is applying a rotational force to the poWer distribution unit 12) the fuel supplied to the poWer source 11 is decreased to reduce the rotational force. When the rotational force is a negative rota 

### tional force (meaning the poWerdistributionunit 12 is apply ing arotational forceto thepoWer source 11) the fuel supplied to the poWer source 11 is increased to increase the rotational 

### force. When the step of one ofreducing and interrupting the rotational force transferredto thepoWerdistributionunit 12 is 

### performed by at least partially disengaging a clutch or other device (neither are shoWn) associated With the poWer source 11, an amount of engagement of the clutch or other device (neither are shoWn) associated With the poWer source 11 is decreased to reduce the rotational force. Adjusting the rota tional force transferred to the poWer distribution unit 12 as 

### mentionedhereinabove isperformeduntil therotational force transferred to the poWer distribution unit 12 is about equal to
an amount ofrotational force applied by the poWer distribu tion unit 12 to the poWer source 11.

When the rotational force transferred to the poWer distri bution unit 12 is about equal to an amount ofrotational force 

### applied by the poWer distribution unit 12, the controller 55 engages the ?rst actuator 57 to move the clutch 28 from the ?rstposition to the thirdposition. Point B ofFIG. 4 indicates


### a time in the shifting procedure When the clutch 28 is placed 

### in the third position. As mentioned hereinabove, When the clutch 28 is placed in the thirdposition, the inter-axle differ ential 19 is unlocked and the second output gear 24 is disen 

### gaged from the transfer shaft 22, and thus the inter-axle dif ferential 19.

## US 8,523,738 B2 17 Once the clutch 28 is placed in the third position, the controller 55 further engages the ?rst actuator 57 to move the 

### clutch 28 from the thirdposition to the secondpositionWhile 

### simultaneously adjusting a rotational speed of the poWer
source 11. As shoWn in FIG. 4, the rotational speed of the poWer source 11 is decreased betWeen points B and C as the second synchroniZer 54 ofthe clutch 28 acts upon the second output gear 24butbefore the clutch 28 isplaced in the second 

## position.

As a non-limiting example, the rotational speed of the poWer source 11 may be decreased by decreasing a fuel supplied to the poWer source 11. A shoWn in FIG. 4, the rotational speed ofthepoWer source 11 is decreased betWeen points B and C. A near constant rotational speed of the ?rst 

### pair ofoutput axle shafts 62 (as the vehicle coasts during the 

### shifting procedure) backdrives the ?rst output gear 20. The ?rst output gear 20, backdriven at the near constant rotational 

### speed, permits decreases in the rotational speed ofthe poWer
source 11 to be directlyre?ected in therotational speed ofthe transfer shaft 22 through the inter-axle differential 19. The 

### concurrent rotation ofthe pinion carrier 36 (as driven by the input shaft 18) and the ?rst output gear 20 retards the transfer 

### shaft 22 through the plurality ofdriving pinions 21 to adjust the rotational speed of the transfer shaft 22. The rotational speed ofthe transfer shaft 22 is adjustedto facilitate a smooth engagement of the clutch 28 With the second output gear 24 When the clutch 28 is moved from the third position to the second position. Point C indicates a time in the shifting pro 

### cedure When the clutch 28 is placed in the second position.

When one of the rotational speed of the poWer source 11 andtherotational speed ofthe transfer shaft 22 are adjustedto facilitate a smooth engagement of the clutch 28 With the second output gear 24, the controller 55 further engages the ?rst actuator 57 to engage the clutch 28 With the second output gear 24 then increasing arotational speed ofthepoWer
source 11. BetWeen points C and D, When the clutch 28 is 

### placed in the second position, the rotational speed of the poWer source 11 is increased.

As shoWn in FIG. 4, the duration oftimebetWeenpoints C and D represents a duration of time Where the inner clutch collar teeth 52 are drivingly engaged With the clutch teeth 44 ofthe transfer shaft 22 and the clutch teeth 50 ofthe second output gear 24 butbefore the controllercommands the second actuator 74 to move the axle clutch 68 to an engagedposition.



### When the clutch 28 is engagedWith the second output gear 

### 24, the second output gear 24 is drivingly engaged With the transfer shaft 22. Whenthe secondoutput gear 24 is drivingly 

### engagedWiththe transfer shaft 22, the rotational speed ofthe second output gear 24, the driven gear 70, the inter-axle shaft 

### 64, the second driving gear 65, and the second Wheel differ ential 66maybe adjustedto one ofapredetermined speed and


### a target speed.



### Further, When the second output gear 24 is drivingly engagedWiththe transfer shaft 22, the seconddriving gear 65 and the second Wheel differential 66 imparts energy to the 

### lubricant disposed Within the second axle assembly 16. The duration oftime betWeenpoints C and D may be determined by the controller based on the temperature ofthe second axle assembly 16 as indicated by the sensor 75. The controller 55 may increase or decrease the duration oftime betWeenpoints C andD until the temperature ofthe second axle assembly 16 

### is above thepredeterminedvalue.As anon-limiting example, the predetermined value may be about 200 Fahrenheit.



### The predetermined speed is obtained by the controller 55 by referencing information stored in the at least one data 

### table. Thetarget speedis calculatedbythe controller 55using the at least one algorithm and a speed of the vehicle. To 20

25

30

35

40

50

55

60

65 

## 18 facilitate adjusting the rotational speed to one of the prede 

### termined speed and the target speed, the rotational speed of the poWer source 11 is adjusted. The rotational speed ofthe 

### poWer source 11 is adjustedby adjusting the rotational speed ofthe poWer source 11. As a non-limiting example, the rota 

### tional speed of the poWer source 11 may be adjusted by increasing a fuel supplied to the poWer source 11.A shoWn in FIG. 4, the rotational speed of the poWer source 11 is increasedbetWeenpoints C and D.A near constant rotational 

### speed ofthe ?rst pair ofoutput axle shafts 62 (as the vehicle coasts during the shiftingprocedure) backdrives the ?rst out put gear 20. The ?rst output gear 20, backdriven at the near 

### constant rotational speed, permits increases in the rotational speed of the poWer source 11 to be directly re?ected in the 

### rotational speed ofthe transfer shaft 22 through the inter-axle differential 19. The concurrent rotation of the pinion carrier 

### 36 (as drivenby the input shaft 18) andthe ?rst outputgear 20 drives the transfer shaft 22 through the plurality of driving pinions 21 to adjust the rotational speed ofthe second output gear 24, the drivengear 70, the inter-axle shaft 64, the second 

### driving gear 65, andthe secondWheel differential 66 through the clutch 28 placed in the second position.

A shoWn in FIG. 4, the one ofthepredetermined speed and 

### the target speed are obtainedWhen the rotational speed ofthe 

### second output gear 24, the driven gear 70, the inter-axle shaft 

### 64, the second driving gear 65, and the second Wheel differ ential 66 permits a meshing engagement betWeen the ?rst portion ofone ofthe secondpair ofoutput axle shafts 67 and 

### the secondportion ofone the secondpair ofoutput axle shafts 67 With the axle clutch 68.



### When the one of the predetermined speed and the target 

### speed are obtained, the controller 55 commands the second actuator 74 tomovetheaxle clutch 68 to the engagedposition. 

### Point D ofFIG. 4 indicates the time in the shifting procedure When the controller 55 commands the second actuator 74 to
move the axle clutch 68 to the engaged position. Point E of 

### FIG. 4 indicates the time ofthe shifting procedure When the axle clutch 68 is engaged.As shoWn in FIG. 4, the duration of time betWeen points D and E represents a duration of time after the controller 55 commands the second actuator 74 to engage the axle clutch 68 but before the axle clutch 68 is 

### engaged. The axle clutch 68maynot immediately engage due to a misalignment betWeen the ?rst portion and the second portion of one of the second pair of output axle shafts, a 

### slipping condition ofone ofthe Wheels (not shoWn) coupled to the second pair of output axle shafts 67, or due to both conditions.As shoWn in FIG. 4, once the one ofthe predeter 

### mined speedand thetarget speedare obtained, a substantially constant rotational speed of the poWer source 11 is main tained by the controller 55. When the axle clutch 68 is 

### engaged, the secondpair ofoutput axle shafts 67 is drivingly engaged With the second output gear 24 through the driven 

### gear 70, the inter-axle shaft 64, the second driving gear 65, and the second Wheel differential 66.



### FolloWingpoint E, the step ofone ofincreasing andresum ing the rotational force transferred to the poWer distribution 

### unit 12 may be performed by one of adjusting an operating condition ofthe poWer source 11 and by engaging the clutch 

### (not shoWn) forming a portion ofthepoWer source 11. When the step of increasing the rotational force transferred to the 

### poWerdistributionunit 12 isperformedby adjusting the oper ating condition ofthe poWer source 11, the operating condi tion ofthepoWer source 11 maybe adjustedby increasing the fuel supplied to the poWer source 11. When the step of 

### increasing andresuming therotational forcetransferredto the 

### poWer distribution unit 12 is performed by engaging the clutch (not shoWn), the amount ofengagement ofthe clutch

## US 8,523,738 B2 19 (not shown) associatedWith thepower source 11 is increased to increase the rotational force.Adjusting the rotational force transferred to the poWer distribution unit 12 as mentioned 

### hereinabove completes the shiftingprocedure as illustrated in FIG. 4, and the controller 55 returns control of one of the operating conditions of the poWer source 11 and the clutch 

### (not shoWn) to the operator.

Once the drive axle system 10 is placed in the second 

### operating state, the rotational force applied to the poWer dis tribution unit 12 by the poWer source 11 is distributed betWeenthe ?rst output gear 20 andthe second output gear 24 through the inter-axle differential 19. A rotational difference of the ?rst output gear 20 and the second output gear 24 caused by a difference betWeen the ?rst gear ratio and the second gear ratio is accommodated by the inter-axle differ ential 19. Because the inter-axle differential 19 accommo dates the rotational difference betWeen the ?rst gearratio and the secondgearratio, a cumulative gearratio isprovided. The cumulative gear ratio is intermediate the ?rst gear ratio and the second gear ratio.

FIG. 5 is a chart illustrating an example of shifting the poWer distribution unit 12 from a second operating state to a 

### ?rst operating state. FIG. 5 illustrates anon-limiting example of shifting the poWer distribution unit 12 from the second operating state to the ?rst operating state.

A horiZontal axis shoWn in FIG. 5 indicates a duration of time from a ?rst chronological reference point, A, to a third 

### chronological reference point, C. Chronological reference point B occurs betWeen points A and C.

Avertical axis shoWn in FIG. 5 indicates a rotational speed 

### of the ?rst output gear 20, the transfer shaft 22, the second output gear 24, and the poWer source 11. The vertical axis begins at a rotational speed of Zero and increases as the vertical axis extends aWay from the horiZontal axis. The rota tional speed of the poWer source 11 depicted in FIG. 5 is 

### merely forpurposes ofexample, andthe shiftingprocedure is not limited to the depicted speeds.



### PointA indicates a starting time ofthe shifting procedure. At point A, the poWer distribution unit 12 is in the second 

### operating state. In the second operating state, the clutch 28 is in the secondposition. When directedby the controller 55 or 

### by an operator ofthe vehicle, the shifting procedure is initi 

### ated by disengaging the axle clutch 68 and by adjusting the rotational force transferred to the poWer distribution unit 12.

PointA ofFIG. 5 indicates the time ofthe shifting proce dureWhenthe controller 55 commands the secondactuator 74 to move the axle clutch 68 to a disengaged position. Point B 

### ofFIG. 5 indicates thetime ofthe shiftingprocedureWhenthe axle clutch 68 is disengaged.As shoWn inFIG. 5, the duration oftime betWeenpointsA and B represents a duration oftime after the controller 55 commands the second actuator 74 to disengage the axle clutch 68 but before the axle clutch 68 is 

### disengaged. The axle clutch 68 may not immediately disen gage due to a slipping condition of one of the Wheels (not 

### shoWn) coupledto the secondpairofoutput axle shafts 67.As shoWn inFIG. 5, to facilitatedisengagement ofthe axle clutch 68, a substantially constant rotational speed of the poWer
source 11 is maintained by the controller 55. When the axle 

### clutch 68 is disengaged, the secondpair ofoutput axle shafts 67 is drivingly disengaged from the second output gear 24.

The step ofadjusting the rotational force transferred to the 

### poWerdistributionunit 12maybeperformedby oneofadjust ing an operating condition ofthepoWer source 11 and at least 

### partially disengaging a clutch (not shoWn) forming aportion ofthe poWer source 11. When the step ofadjusting the rota tional force transferred to the poWer distribution unit 12 is 

### performed by adjusting the operating condition ofthe poWer 20

25

30

35

40

45

50

55

60

65 

## 20

source 11, the operating conditionofthepoWer source 11 may 

### be adjustedby one ofincreasing ordecreasing a fuel supplied to thepoWer source 11. Whenthe rotational force is apositive rotational force (meaning the poWer source 11 is applying a rotational force to the poWer distribution unit 12) the fuel supplied to the poWer source 11 is decreased to reduce the rotational force. When the rotational force is a negative rota 

### tional force (meaning the poWerdistributionunit 12 is apply ing arotational forceto thepoWer source 11) the fuel supplied to the poWer source 11 is increased to increase the rotational 

### force. When the step of one ofreducing and interrupting the rotational force transferredto thepoWerdistributionunit 12 is 

### performed by at least partially disengaging a clutch or other device (neither are shoWn) associated With the poWer source 11, an amount of engagement of the clutch or other device (neither are shoWn) associated With the poWer source 11 is decreased to reduce the rotational force. Adjusting the rota tional force transferred to the poWer distribution unit 12 as 

### mentionedhereinabove isperformeduntil therotational force transferred to the poWer distribution unit 12 is about equal to
an amount ofrotational force applied by the poWer distribu tion unit 12 to the poWer source 11.

When the rotational force transferred to the poWer distri bution unit 12 is about equal to an amount ofrotational force 

### applied by the poWer distribution unit 12, the controller 55 engages the ?rst actuator 57 to move the clutch 28 from the second position to the third position. Point B ofFIG. 5 indi cates a time in the shifting procedure When the clutch 28 is 

### placed inthethirdposition.Asmentionedhereinabove, When the clutch 28 is placed in the third position, the inter-axle differential 19 is unlocked and the second output gear 24 is 

### disengaged from the transfer shaft 22, and thus the inter-axle differential 19. As shoWn in FIG. 5, betWeenpoints B and C, When the clutch 28 ismoved to the thirdposition and the axle 

### clutch 68 is disengaged, the second output gear 24, the driven 

### gear 70, the inter-axle shaft 64, the bevel gear pinion 72, the second driving gear 65, and the secondWheel differential 66 coast to the idle condition.



### Once the clutch 28 is placed in the third position, the controller 55 further engages the ?rst actuator 57 to move the 

### clutch 28 from the third position to the ?rst position While 

### simultaneously adjusting a rotational speed of the poWer
source 11. As shoWn in FIG. 5, the rotational speed of the poWer source 11 is decreased as the ?rst synchroniZer 53 of the clutch 28 acts upon the pinion carrier 36 but before the 

### clutch 28 is placed in the ?rst position.

As a non-limiting example, the rotational speed of the poWer source 11 may be decreased by decreasing a fuel supplied to the poWer source 11. A shoWn in FIG. 5, the rotational speed ofthe poWer source 11 is decreasedbetWeen points B and C. A near constant rotational speed of the ?rst 

### pair ofoutput axle shafts 62 (as the vehicle coasts during the 

### shifting procedure) backdrives the ?rst output gear 20. The ?rst output gear 20, backdriven at the near constant rotational 

### speed, permits decreases in the rotational speed ofthe poWer
source 11 to be directly re?ected in therotational speed ofthe transfer shaft 22 through the inter-axle differential 19. The 

### concurrent rotation ofthe pinion carrier 36 (as driven by the input shaft 18) and the ?rst output gear 20 retards the transfer 

### shaft 22 through the plurality ofdriving pinions 21 to adjust the rotational speed of the transfer shaft 22. The rotational speed ofthe transfer shaft 22 is adjustedto facilitate a smooth engagement ofthe clutch 28 Withthe ?rst outputgear 20When the clutch 28 is moved from the third position to the ?rst 

## position.

When one of the rotational speed of the poWer source 11 andtherotational speed ofthe transfer shaft 22 are adjustedto

## US 8,523,738 B2 21 facilitate a smooth engagement ofthe clutch 28 With the ?rst output gear 20, the controller 55 further engages the ?rst actuator 57 tomove the clutch 28 fromthe thirdpositionto the ?rstposition. Point C ofFIG. 5 indicates a time inthe shifting 

### procedureWhenthe clutch 28 isplaced inthe ?rstposition.As mentioned hereinabove, When the clutch 28 is placed in the ?rst position, the inter-axle differential 19 is locked and the 

### ?rst outputgear 20 is engagedWiththe input shaft 18 through the inter-axle differential 19 in the locked condition.



### FolloWingpointC, the step ofoneofincreasing andresum ing the rotational force transferred to the poWer distribution 

### unit 12 may be performed by one of adjusting an operating condition ofthe poWer source 11 and by engaging the clutch 

### (not shoWn) forming aportion ofthe poWer source 11. When the step of increasing the rotational force transferred to the 

### poWerdistributionunit 12 isperformedby adjustingthe oper ating condition ofthe poWer source 11, the operating condi tionofthepoWer source 11 maybe adjustedby increasing the fuel supplied to the poWer source 11. When the step of 

### increasing andresumingtherotational forcetransferredto the 

### poWer distribution unit 12 is performed by engaging the clutch (not shoWn), the amount ofengagement ofthe clutch (not shoWn) associatedWith thepoWer source 11 is increased to increase the rotational force.Adjusting the rotational force transferred to the poWer distribution unit 12 as mentioned 

### hereinabove completes the shiftingprocedure as illustrated in FIG. 5, and the controller 55 returns control of one of the operating conditions of the poWer source 11 and the clutch 

### (not shoWn) to the operator.

FIG. 6 depicts yet another embodiment of the present invention. The embodiment shoWn in FIG. 6 is similar to the embodiment shoWn inFIG. 1. Similar features ofthe embodi ment shoWn in FIG. 6 are numbered similarly in series, With 

### the exception ofthe features described beloW.

FIG. 6 illustrates a drive axle system 10' for a vehicle having a poWer source 11'. The drive axle system 10' prefer ably includes apoWerdistributionunit 612, a ?rst axle assem 

### bly 14', anda secondaxleassembly 16'. Thedrive axle system 10' is drivingly engaged With a poWer source 11'. As shoWn, the drive axle system 10' includes the three assemblies 612, 

### 14', 16', but it is understood the drive axle system 10' may include feWer or more assemblies or components.

The poWer distribution unit 612 includes an input shaft 618, an inter-axle differential 619, a ?rst output gear 620, a 

### plurality ofdrivingpinions 621, atransfer shaft 622, a second output gear 624, and a clutch 628. As shoWn, poWer distribu 

### tion unit 612 includes the seven components 618, 619, 620, 

### 621, 622, 624, 628 disposed in a housing 30' but it is under stood the poWer distribution unit 612 may include feWer or
more components.



### The tandem drive axle system 10' includes the input shaft 

### 618 at least partially disposed in the housing 30'. Preferably, the input shaft 618 is an elongate cylindrical member, hoW
everthe input shaft 618 may be any other shape. Bearings 32' 

### disposedbetWeenthe input shaft 618' andthehousing 30' and the input shaft 618 and the transfer shaft 622 permit the input shaft 618 to rotate about an axis of the input shaft 618. The input shaft 618 has a ?rst endportion 633, having a ?rst set of clutch teeth 637 formed thereon, a middle portion 634, and a 

### second endportion 635, having apinion carrier 636 disposed thereon.

The ?rst end portion 633 has a diameter greater than a 

### diameter ofthe middleportion 634. The ?rst endportion 633 

### is a substantially disc shaped body drivingly coupled to the input shaft 618. Altemately, the ?rst end portion 633 may be integrally formed With the input shaft 618. The ?rst end portion 633 includes an engagement portion 638 formed 20

25

30

35

40

45

50

55

60

65 

## 22 therein adjacent an outer peripheral edge thereof. As shoWn, the engagementportion 638 is a conical surface oblique to the 

### input shaft 618, hoWever, the engagement portion 638 may have any other shape. The ?rst set of clutch teeth 637 are formed on the ?rst end portion 633 intermediate the input 

### shaft 618 and the engagement portion 638.



### The pinion carrier 636 is a substantially disc shaped body 

### having a plurality ofpinion supports 639 protruding there from adjacent a peripheral edge of the pinion carrier 636, hoWever, the pinion carrier 636 may be any other rounded shape and may have a plurality of recesses or perforations formed therein. As is knoWn in the art, the pinion carrier 636 is also knoWn as a planet carrier.



### The plurality ofdriving pinions 621 are rotatably coupled to the pinion supports 639. Each of the driving pinions 621 have gear teeth formed on an outer surface thereof. As is 

### knoWn inthe art, eachofthedrivingpinions 621 is alsoknoWn

as a planet gear. Preferably, bearings are disposed betWeen 

### each ofthe driving pinions 621 and the pinion supports 639, hoWever, the drivingpinions 621 maybe directlymounted on 

### the pinion supports 639.

The transfer shaft 622 is a holloW shaft concentrically 

### disposed about the input shaft 618. Preferably, the transfer shaft 622 is a holloW elongate cylindrical member, hoWever the transfer shaft 622 may be any other shape. Bearings 32' 

### disposed betWeen the transfer shaft 622 and the housing 30' and the input shaft 618 and the transfer shaft 622 permit the transfer shaft 622 to rotate about an axis of the transfer shaft 622. The axis ofthe transfer shaft 622 is concurrent With the axis ofthe input shaft 618. The transfer shaft 622 has a ?rst endportion 643, having a ?rst set ofclutch teeth 644 formed

on an outer surface thereof, and a second end portion 645, having a second set of gear teeth 646 formed on an outer surface thereof.



### The ?rst end portion 643 and the second end portion 645
are substantially disc shapedbodies having an outerdiameter greater than a diameter ofthe transfer shaft 622. The ?rst end 

### portion 643 and the second end portion 645 are drivingly coupled to the transfer shaft 622. Altemately, the ?rst end 

### portion 643 andthe secondendportion 645maybe integrally formed With the transfer shaft 622 and may have a diameter 

### substantially equaltothetransfershaft 622. Similarly, the ?rst set of clutch teeth 644 and the second set of clutch teeth 646 may be formed directly in the transfer shaft 622.As is knoWn 

### in the art, the second endportion 645 having the clutch teeth 646 is knoWn as a sun gear. The second set ofclutch teeth 646 

### are engagedWith the plurality ofdriving pinions 621 and the ?rst set ofclutch teeth 644 are disposed adjacent the ?rst set ofclutch teeth 637 ofthe input shaft 618.

The second output gear 624 is a gear concentrically dis 

### posedaboutthe input shaft 618 andthe transfer shaft 622. The second output gear 624 has a central perforation having a diametergreaterthan a diameter ofthe transfer shaft 622. The 

### second output gear 624 is a substantially disc shaped body having a ?rst end portion 647, a second end portion 648 de?ning an outerdiameter ofthe second output gear 624, and


### an engagement portion 649. Bearings (not shoWn) disposed betWeenthe transfer shaft 622 andthe second output gear 624 permit the second output gear 624 to rotate about an axis of the secondoutputgear 624. The axis ofthe secondoutputgear 624 is concurrent With the axis ofthe input shaft 618. A ?rst set ofclutch teeth 650 are formed on the ?rst endportion 647 adjacent the ?rst set of clutch teeth 644 of the transfer shaft 622. A second set ofgear teeth 651 are formed on the second 

### end portion 648.

The engagement portion 649 is formed in the second out put gear 624 intermediate the ?rst end portion 647 and the

## US 8,523,738 B2 23 second end portion 648. As shown, the engagement portion 649 is a conical surface oblique to the input shaft 618; hoW 

### ever, the engagement portion 649 may have any other shape.

The clutch 628 is a shift collar concentrically disposed aboutthe input shaft 618 andthetransfer shaft 622. The clutch 628 includes a set of inner clutch collar teeth 652 formed on
an inner surface thereof, a ?rst synchroniZer 653, and a sec ond synchroniZer 654. The set ofinner clutch collarteeth 652
are engagedWiththe ?rst set ofclutchteeth 644 ofthe transfer shaft 622. The clutch 628 can be slidably moved along the 

### axis of the input shaft 618 as directed automatically by the 

### controller 55' While maintaining engagement of the inner clutch collar teeth 652 and the ?rst set of clutch teeth 644. A shift fork 56' disposed in an annular recess formed in the clutch 628 moves the clutch 628 along the axis of the input shaft 618 into a ?rst position, a second position, or a third 

### position. The ?rst actuator 57', Which is drivingly engaged With the shift fork 56', is engaged toposition the shift fork 56'


### as directedmanually by the controller 55'. Consequently, the shift fork 56' positions the clutch 628 into the ?rst position, the secondposition, or the thirdposition. In the ?rstposition, the clutch 628 is drivingly engagedWith the ?rst set ofclutch teeth 644 of the transfer shaft 622 and the ?rst set of clutch 

### teeth 637 of the input shaft 618. In the second position, the clutch 628 is drivingly engaged With the ?rst set of clutch teeth 644 of the transfer shaft 622 and the ?rst set of clutch teeth 650 ofthe second output gear 624. In the thirdposition, the inner clutch collar teeth 652 of the clutch 628 are only 

### drivingly engaged With the ?rst set ofclutch teeth 644 ofthe transfer shaft 622. It is understood the clutch 628, the clutch 

### teeth 637, 644, 650, 652, the synchroniZers 653, 654, andthe engagement portions 638, 649 may be substituted With any clutching device thatpermits selective engagement ofa driv ing and a driven part.



### The ?rst synchroniZer 653 is an annular body coupled to 

### the clutch 628 adjacent the ?rst end portion 633 ofthe input shaft 618. The ?rst synchroniZer 653 has a ?rst conical 

### engagement surface 658. Alternately, the ?rst synchroniZer 653 mayhave an engagement surfacehaving any other shape. Whenthe clutch 628 ismoved fromthe thirdpositiontoWards 

### the ?rst position, the ?rst conical engagement surface 658 

### contacts the engagement portion 638 ofthe ?rst end portion 633 ofthe input shaft 618, causing the clutch 628 to act upon the input shaft 618. Whenthe clutch 628 ismovedtoWards the ?rst set of clutch teeth 637 ofthe input shaft 618, the clutch 628 continues to act upon the input shaft 618 as the inner 

### clutch collar teeth 652 become drivingly engaged With the ?rst set of clutch teeth 644 of the transfer shaft 622 and the ?rst set of clutch teeth 637 ofthe input shaft 618.



### The second synchroniZer 654 is anannularbody coupledto 

### the clutch 628 adjacent the ?rst endportion 647 ofthe second output gear 624. The second synchroniZer 654 has a second 

### conical engagement surface 659.Alternately, the second syn chroniZer 654 may have an engagement surface having any other shape. When the clutch 628 is moved from the third 

### position into the secondposition, the second conical engage ment surface 659 contacts the engagementportion 649 ofthe ?rst endportion 647 ofthe second output gear 624. When the clutch 628 ismoved furthertoWards the ?rst set ofclutchteeth 650 ofthe second outputgear 624, the clutch 628 continues to act upon the second output gear 624 as the inner clutch collar 

### teeth 652becomedrivingly engagedWiththe ?rst setofclutch teeth 644 of the transfer shaft 622 and the ?rst set of clutch teeth 650 ofthe second output gear 24.

The ?rst output gear 620 is a gear concentrically disposed 

### about the input shaft 618 and thepinion carrier 636. The ?rst output gear 620 has a central recess having a diametergreater 20

25

30

35

40

45

50

55

60

65 

## 24 than an outer diameter of the pinion carrier 636. The ?rst 

### output gear 620 is a substantially cup shapedbody having an inner surfacehaving gearteeth 640 formed on.As is knoWn in the art, the ?rst output gear 620 is knoWn as a ring gear. The gear teeth 640 are engaged With the gear teeth formed on the 

### outer surface ofeach ofthe driving pinions 621.

The ?rst output gear 620 includes an output shaft 641 

### drivingly coupled thereto. Alternately, the ?rst output gear 620 may be integrally formed With the output shaft 641. The 

### output shaft 641 is collinearWiththe input shaft 618. Bearings 32' disposedbetWeenthe output shaft 641 and thehousing 30' 

### support the ?rst output gear 620 and permit the output shaft 641 to rotate about an axis ofthe output shaft 641.

An axle clutch 668 is a shift collarhaving a conical engage ment surface that divides one ofthe second output axle shafts 

### 67' into ?rst and secondportions.Alternately, the axle clutch 668 may be a plate style clutch or any other style of friction clutch. The axle clutch 668 has a plurality of teeth formed 

### thereon for selectively engaging corresponding teeth formed

on the ?rst portion and the second portion of the second output axle shafts 67'. The axle clutch 668 is urged into an 

### engagedposition or a disengagedpositionby a shift fork 73'. 

### A second actuator 74', Which is drivingly engaged With the 

### shift fork 73', is engagedtopositionthe shift fork 73', andthus the axle clutch 668, as directedby the controller 55'. Whenthe 

### axle clutch 668 is in the engagedposition, the ?rst portion of

one ofthe second output axle shafts 67' is drivingly engaged Withthe secondportionofone ofthe secondoutputaxle shafts 67'.



### The axle clutch 668 may be selectively engaged to impart energy to a lubricant disposedWithinthe secondaxle housing 

### 69'. Preferably, When the axle clutch 668 is used to impart energy to the lubricant disposedWithin the second axle hous 

### ing 69', the axle clutch 668 is a clutch capable ofacting upon

on a connecting component in a variable manner, such as a shift collar having a conical engagement surface. When the axle clutch 668 is used to impart energy to the lubricant 

### disposedWithinthe secondaxlehousing 69', the controller55'

one ofengages andpartially engages the axle clutch 668 until

a temperature of the second axle assembly 16' is above a 

### predetermined value. As a non-limiting example, the prede termined value may be about 200 Fahrenheit.

The axle clutch 668 and the clutch 628 may be simulta 

### neouslyusedto impartenergyto the lubricantdisposedWithin the secondaxlehousing 69'. Whenthe axle clutch 668 andthe clutch 628 are simultaneously used to impart energy to the 

### lubricant disposed Within the second axle housing, the axle clutch 668 cooperates With the clutch 628 to adjust the rota 

### tional speedofthe secondoutput gear 624, thedrivengear 70', the inter-axle shaft 64', the second driving gear 65', and the second Wheel differential 66' to one of the predetermined 

### speed and a target speed.

In use, the method for use of the drive axle system 10' facilitates shifting from the ?rst operating state to the second 

### operating state. Similarly, the shifting procedures described above foruseWiththe drive axle system 10, maybeusedWith 

### the drive axle system 10', accommodating forthe differences ofthe embodiment shoWn in FIG. 6 as describedhereinabove.



### InaccordanceWiththeprovisions ofthepatent statutes, the present invention has been described inWhat is considered to 

### represent its preferred embodiments. HoWever, it should be noted that the invention can be practiced otherWise than as 

### speci?cally illustrated and describedWithout departing from its spirit or scope.

## US 8,523,738 B2 25 What is claimed is: 1. A method of shifting a power distribution unit for a vehicle from a ?rst operating state to a second operating state, 

### the method comprising the steps of:

drivingly engaging a ?rst axle assembly With a ?rst output

ofthe poWer distribution unit; drivingly engaging a second axle assembly With a second



### output ofthe poWer distribution unit; 

### drivingly engaging an input ofthe poWer distribution unit

With an output ofa poWer source, the poWer distribution 

### unit including an inter-axle differential, the ?rst output, the second output, and a ?rst clutching device having a 

### ?rst position and a second position, the ?rst clutching 

### device in the ?rst position locking the inter-axle differ 

### ential, engaging the ?rst output With the input of the poWerdistributionunit, anddisengaging the secondout 

### put from the inter-axle differential, the ?rst clutching device in the second position unlocking the inter-axle differential and engaging the ?rst output and the second 

### output With the inter-axle differential; placing the ?rst clutching device in one ofthe ?rstposition



### and the second position; applying a rotational force to the input ofthe poWer distri



### bution unit; adjusting the rotational force transferred to the poWer dis



### tribution unit to facilitate moving the ?rst clutching 

### device; moving the ?rst clutching device from one of the ?rst



### position and the second position to a third position, the 

### ?rstclutchingdevice inthethirdpositionneitherlocking the inter-axle differential nor engaging the second out 

### put With the inter-axle differential; adjusting a rotational speed of the input ofthe poWer dis



### tribution unit to facilitate moving the ?rst clutching 

### device from the third position; 

### moving the ?rst clutching device fromthe thirdpositionto

one ofthe ?rst and second positions; and adjusting the rotational force transferred to the poWer dis

tribution unit. 2. Themethod according to claim 1, Wherein the inter-axle differential is a planetary differential comprising a carrier 

### drivingly engaged With the input of the poWer distribution 

### unit, a plurality ofdriving pinions rotatably disposed on the carrier, a ring gear drivingly engaged With the ?rst output of the poWer distribution unit, and a sun gear selectively driv 

### ingly engaged With the second output ofthe poWer distribu tion unit.

3. The method according to claim 2, Wherein the ?rst 

### clutching device comprises a shift collar in splined engage ment With a portion ofthe sun gear, a ?rst synchroniZer, and


### a second synchroniZer, the ?rst synchroniZer acting upon the carrier as the ?rst clutching device is moved toWards the ?rst 

### position and the second synchroniZeracting upon the second output as the ?rst clutching device is moved toWards the 

### secondposition.

4. The method according to claim 2, Wherein the ?rst 

### clutching device comprises a shift collar in splined engage ment With a portion of the sun gear and a synchroniZer, the 

### synchroniZeractinguponthe secondoutputas the ?rstclutch 

### ing device is moved toWards the second position.

5. Themethodaccordingto claim 2, furthercomprising the step ofproviding a controller in communication With a ?rst clutching device actuator and at least one sensor, the at least

one sensor for monitoring at least one ofan operating condi tion of the poWer source, a temperature of the second axle assembly, a speed ofthe sungear, a speed ofthe second output gear, a speed of a portion of the second axle assembly, an 20

25

30

35

40

45

50

55

60

65 

## 26
amount ofthe rotational force transferred to the poWer distri bution unit, a position ofa second clutching device for selec 

### tively disengaging a ?rstportion ofthe second axle assembly from a second portion of the second axle assembly, and a position ofthe ?rst clutching device to adjust at least one of 

### the operating condition of the poWer source, the position of 

### the ?rstclutchingdeviceandthe secondclutchingdevice, and

a durationbetWeen successive positions ofthe ?rst clutching device based on at least one ofthe operating condition ofthe 

### poWer source, the temperature of the second axle assembly, the speed ofthe sun gear, a speed ofthe second output gear, a 

### speed ofaportion ofthe second axle assembly, the amount of the rotational force transferred to thepoWer distribution unit, 

### and the position of the ?rst clutching device and the second 

### clutching device.

6. Themethodaccording to claim 1, Whereinthe step ofone of adjusting the rotational force transferred to the poWer 

### distributionunitmaybeperformedby adjusting an operating condition of the poWer source.



### 7. Themethod according to claim 1, Wherein folloWing the step ofmoving the ?rst clutching device from one ofthe ?rst 

### position and the second position, the step of adjusting the rotational speedofthe input ofthepoWer source isperformed by adjusting an operating condition of the poWer source is 

## adjusted.

8. The method according to claim 1, Wherein the ?rst output is a ?rst output gear and the second output is a second 

### output gear.

9. The method according to claim 1, Wherein the ?rst 

### clutching device is selectively engaged to adjust a rotational 

### speed ofa portion ofthe second axle assembly.

10. The method according to claim 1, further comprising 

### the step of moving the ?rst clutching device from the third position to the second position When a temperature of the second axle assembly is above a predetermined value.



### 11. The method according to claim 1, Wherein folloWing the step of moving the ?rst clutching device to the third 

### position, the step ofadjustingtherotational speedofthe input of the poWer distribution unit is performed by adjusting a rotational speed ofthe poWer source.



### 12. The method according to claim 11, further comprising the step of maintaining a substantially constant rotational speed ofthe poWer source once one ofa predetermined speed 

### and a target speed is obtained and moving the ?rst clutching device from the third position to one of the ?rst and second 

## positions.

13. The method according to claim 12, Wherein one ofthe 

### predetermined speed andthe target speedofthepoWer source
causes a sun gear forming a portion of the inter-axle differ ential and the second output to rotate at speeds permitting 

### meshing engagement therebetWeen With the ?rst clutching device.

14. The method according to claim 1, Wherein the second 

### axle assembly further includes a second clutching device, the 

### second clutching device selectively disengaging a ?rst por tion ofthe second axle assembly from a secondportion ofthe 

### second axle assembly.

15. The method according to claim 14, Wherein the step of 

### movingthe ?rst clutchingdevice fromthethirdpositionto the 

### second position partially engages the second output and the ?rstportionofthe second axle assembly to adjust a rotational 

### speed ofthe second output and the ?rst portion ofthe second axle assembly to one ofa target speed and an idle condition, 

### the target speed facilitating engagement betWeen the ?rst portion ofthe secondaxle assembly andthe secondportionof the second axle assembly With the second clutching device.

## US 8,523,738 B2 27 16. Themethod according to claim 14, wherein the second 

### clutching device is selectively engaged to impart energy to a 

### lubricant disposed Within the second axle assembly.

17. The method according to claim 16, further comprising the step of engaging the second clutching device When a temperature ofthe second axle assembly is above a predeter mined value. 18. The method according to claim 14, Wherein the ?rst clutching device and the second clutching device are simul 

### taneously engaged to adjust a rotational speed ofaportion of 

### the second axle assembly.

19. A method of shifting a poWer distribution unit for a vehicle from a ?rst operating state to a second operating state, 

### the method comprising the steps of:

drivingly engaging a ?rst axle assembly With a ?rst output

ofthe poWer distribution unit; drivingly engaging a second axle assembly With a second



### output ofthe poWer distribution unit; 

### drivingly engaging an input ofthe poWer distribution unit

With an output ofa poWer source, the poWer distribution 

### unit including an inter-axle differential, the ?rst output, the second output, and a ?rst clutching device having a 

### ?rst position and a second position, the ?rst clutching 

### device in the ?rst position locking the inter-axle differ 

### ential, engaging the ?rst output With the input of the poWerdistributionunit, anddisengaging the secondout 

### put from the inter-axle differential, the ?rst clutching device in the second position unlocking the inter-axle differential and engaging the ?rst output and the second 

### output With the inter-axle differential; 

### placing the ?rst clutching device in the ?rstposition; applying a rotational force to the input ofthe poWer distri



### bution unit;
one ofreducing and interrupting the rotational force trans

ferred to the poWer distribution unit; 

### moving the ?rst clutching device from the ?rst position to

a third position, the ?rst clutching device in the third 

### positionunlocking the inter-axle differential; adjusting a rotational speed of the input ofthe poWer dis



### tribution unit to facilitate moving the ?rst clutching 

### device from the third position; adjusting a rotational speed ofa ?rstportion ofthe second



### axle assembly to a target speed, the target speed facili tating engagement betWeen the ?rst portion of the sec ond axle assembly and a second portion of the second 

### axle assembly; moving the ?rst clutching device fromthe thirdpositionto

the second position; and
one of increasing and resuming the rotational force trans

ferred to the poWer distribution unit. 20. The method according to claim 19, Wherein the inter axle differential is a planetary differential comprising a car 

### rierdrivingly engagedWiththe input ofthepoWerdistribution 

### unit, a plurality ofdriving pinions rotatably disposed on the carrier, a ring gear drivingly engaged With the ?rst output of the poWer distribution unit, and a sun gear selectively driv 

### ingly engaged With the second output ofthe poWer distribu tion unit.

21. The method according to claim 20, Wherein the ?rst 

### clutching device comprises a shift collar in splined engage ment With a portion ofthe sun gear, a ?rst synchroniZer, and


### a second synchroniZer, the ?rst synchroniZer acting upon the carrier as the ?rst clutching device is moved toWards the ?rst 

### position and the second synchroniZeracting upon the second output as the ?rst clutching device is moved toWards the 

### secondposition. 20

25

30

35

40

45

50

55

60

65 

## 28 22. The method according to claim 20, Wherein the ?rst 

### clutching device comprises a shift collar in splined engage ment With a portion of the sun gear and a synchroniZer, the 

### synchroniZeractinguponthe secondoutputas the ?rstclutch 

### ing device is moved toWards the second position.

23. The method according to claim 20, further comprising the step ofproviding a controller in communication With a ?rst clutching device actuator and at least one sensor, the at least one sensor for monitoring at least one of an operating condition of the poWer source, a temperature of the second axle assembly, a speed ofthe sun gear, a speed ofthe second output gear, a speed ofaportion ofthe second axle assembly,

an amount of the rotational force transferred to the poWer distribution unit, a position of a second clutching device for 

### selectively disengaging the ?rst portion of the second axle assembly from the second portion ofthe second axle assem 

### bly, and a position of the ?rst clutching device to adjust at least one ofthe operating condition ofthe poWer source, the 

### position ofthe ?rst clutching device andthe second clutching device, and a duration betWeen successive positions of the ?rst clutching device based on at least one of the operating condition ofthe poWer source, the temperature ofthe second axle assembly, the speed ofthe sungear, a speed ofthe second output gear, a speed ofaportion ofthe second axle assembly, the amount of the rotational force transferred to the poWer 

### distributionunit, andtheposition ofthe ?rst clutching device and the second clutching device.

24. The method according to claim 19, Wherein the step of
one of reducing and interrupting the rotational force trans 

### ferred to the poWer distribution unit may be performed by adjusting an operating condition ofthe poWer source.



### 25. The method according to claim 19, Wherein folloWing 

### the step of moving the ?rst clutching device from the ?rst position to the third position, the step of adjusting the rota tional speed of the input of the poWer distribution unit is 

### performed by adjusting an operating condition ofthe poWer

source.

26. The method according to claim 19, Wherein the ?rst output is a ?rst output gear and the second output is a second 

### output gear.

27. The method according to claim 19, Wherein the step of adjusting a rotational speed of a ?rst portion of the second 

### axle assembly is performed by selectively engaging the ?rst clutching device.

28. The method according to claim 19, further comprising 

### the step of moving the ?rst clutching device from the third position to the second position When a temperature of the second axle assembly is above a predetermined value.



### 29. The method according to claim 19, Wherein folloWing the step of moving the ?rst clutching device to the third 

### position, the step ofadjustingtherotational speedofthe input of the poWer distribution unit is performed by adjusting a rotational speed ofthe poWer source.



### 30. The method according to claim 29, further comprising the step of maintaining a substantially constant rotational speed ofthe poWer source once one ofa predetermined speed 

### and a target speed is obtained and moving the ?rst clutching device from the third position to the second position.

31. The method according to claim 30, Wherein one ofthe 

### predetermined speed andthe target speedofthepoWer source
causes a sun gear forming a portion of the inter-axle differ ential and the second output to rotate at speeds permitting 

### meshing engagement therebetWeen With the ?rst clutching device.

32. Themethod according to claim 19, Wherein the second 

### axle assembly further includes a second clutching device, the