Power transfer device for automotive vehicles

In a power transfer device including an input shaft rotatably mounted within a housing, a first output shaft rotatably supported on the housing for connecting the input shaft to a pair of front wheel drive axles, and a second output shaft arranged in parallel with the first output shaft and rotatably supported on the housing for drive connection to a pair of rear wheel drive axles, a shift mechanism includes a sleeve member axially slidable on the first output shaft between respective positions in which it effects a drive connection or disconnection between the output shafts, a shift rod arranged in parallel with the output shafts and axially movably supported on the housing, a shift fork mounted on the shift rod and coupled with the sleeve member, an operation rod extending through the peripheral wall of the housing and rotatably supported therethrough, the operation rod having an outer end operatively connected to a manual operation lever, and a swing arm secured to the inner end of the operation rod for rotation therewith and engaged at one end portion thereof with a recessed portion formed on the shift rod to restrict axial movement of the operation rod outwardly with respect to the housing and to restrict rotation of the shift rod.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a power transfer device adapted for use in 
combination with a power transmission for a four wheel drive vehicle to 
transfer output drive torque of the power transmission to a pair of front 
road wheels and a pair of rear road wheels, and more particularly to a 
power transfer device capable of selectively providing either a two wheel 
drive or a four wheel drive. 
2. Description of the Prior Art 
There has been proposed a power transfer device of this kind which 
comprises a housing secured to one end of a transmission casing, an input 
shaft rotatably mounted within the housing and drivingly connected to an 
output shaft of the power transmission for the vehicle, a first output 
shaft arranged in parallel or coaxially with the input shaft for drive 
connection of the input shaft with front wheel or rear wheel drive axles, 
a second output shaft arranged coaxially or in parallel with the first 
output shaft for drive connection with rear wheel or front wheel drive 
axles, and a shift mechanism for selective connection or disconnection of 
the first output shaft to or from the second output shaft thereby to 
provide a four wheel drive or a two wheel drive. 
In a Japanese Patent Publication No. 57-54333, for example, there has been 
proposed a shift mechanism in a power transfer device of this kind which 
shift mechanism includes a sleeve member axially slidably mounted on one 
of the first and second output shafts for connection or disconnection of 
the one output shaft to or from the other output shaft, a shift rod 
arranged in parallel with both the output shafts and axially movably 
supported on the peripheral wall of the housing, a shift fork mounted on 
the shift rod and coupled with the sleeve member for shifting the sleeve 
member in response to axial movement of the shift rod, an operation rod in 
the form of a cross-rod arranged perpendicularly to the shift rod and 
rotatably supported on the peripheral wall of the housing to be rotated by 
means of a manual operation lever, and a shift lever fixedly mounted on 
the operation rod for rotation therewith and being integrally provided 
with a swing arm which is engaged with the shift fork to effect axial 
movement of the shift rod in response to rotation of the operation rod. 
In such a conventional shift mechanism as described above, there is 
provided a detent mechanism which cooperates with an interlock mechanism 
for selectively restricting the axial movement of the shift rod. The 
detent mechanism includes a spring loaded check ball selectively 
engageable with a pair of axially spaced recesses formed on the shift rod, 
and the interlock mechanism includes an interlock pin engageable with a 
recess formed on the shift rod. In the detent and interlock mechanisms, it 
is necessary to restrict rotation of the shift rod thereby to ensure 
selective engagement of the check ball and interlock pin with the 
respective recesses of the shift rod. For this reason, an additional arm 
is fixed to an intermediate portion of the shift rod and engaged with a 
stationary member in the transfer device to restrict the rotation of the 
shift rod. This inevitably causes the shift rod to be complicated in 
structure. Furthermore, axial movement of the operation rod outwardly with 
respect to the housing should be avoided to retain it in position. For 
this reason, the peripheral wall of the housing is formed to extend 
between boss portions respectively provided on the manual operation lever 
and on the shift lever so as to retain the operation rod in position. As a 
result of such arrangement as described above, both the side faces of the 
housing and each contact face of the boss portions should be machined with 
a required precision. 
SUMMARY OF THE INVENTION 
It is, therefore, a primary object of the present invention to provide an 
improved power transfer device wherein the shift rod is formed in such a 
manner that the rotation thereof and the aforesaid outward axial movement 
of the operation rod can be readily retained in position without requiring 
any special ancillary provisions therefor so as to make the shift rod 
simple in structure and minimizing the portions of the power transfer 
device parts needing to be precision machined. 
According to the present invention, the primary object is accomplished by 
providing a power transfer device adapted for use in combination with a 
power transmission for an automotive vehicle, the shift mechanism of which 
transfer device includes a sleeve member axially slidably mounted on one 
of the output shafts between respective positions in which it effects a 
drive connection or disconnection between the first and second output 
shafts, a shift rod arranged in parallel with both the output shafts and 
axially movably supported on the peripheral wall of the housing, and a 
shift fork mounted on the shift rod for axial movement therewith and 
coupled with the sleeve member for shifting the sleeve member in response 
to the axial movement of the shift. The shift mechanism further comprises 
an operation rod extending through the peripheral wall of the housing and 
rotatably supported therethrough, the operation rod having an outer end 
operatively connected to a manual operation lever and an inner end located 
in the interior of the housing, and a swing arm secured to the inner end 
of the operation rod for rotation therewith. The shift rod is formed with 
a recessed portion which receives therein one end portion of the swing arm 
to restrict axial movement of the operation rod in a direction outwardly 
with respect to the housing and to restrict rotation of the shift rod. 
In a practical embodiment of the present invention, the first output shaft 
is arranged coaxially with the input shaft and in parallel with the second 
output shaft, the sleeve member is mounted on the first output shaft, the 
shift mechanism further comprises a second sleeve member axially slidably 
mounted on the first output shaft between respective positions in which it 
effects a drive connection or disconnection between the input shaft and 
the first output shaft, a second shift rod arranged in parallel with the 
first-named shift rod and axially movably supported on the peripheral wall 
of the housing, and a second shift fork fixedly mounted on the second 
shift rod and coupled with the second sleeve member for shifting the 
second sleeve member in response to axial movement of the second shift 
rod. In such an arrangement as described above, the second shift fork is 
formed at a base portion thereof with a recessed portion which receives 
therein another end portion of the swing arm to restrict rotation of the 
second shift rod. Preferably, a change-speed mechanism is mounted on the 
input shaft to selectively provide a low speed drive power train or a high 
speed drive power train between the input shaft and the first output 
shaft, and the second sleeve member is arranged to effect a drive 
connection between the input shaft and the first output shaft through the 
change-speed mechanism.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In FIG. 1 of the drawings, there is illustrated a power transfer device for 
a four wheel drive vehicle in accordance with the present invention, which 
transfer device includes a housing 17 to be secured to a right-hand end of 
a transmission casing, an input shaft 11, a first output shaft 12, a 
second output shaft 13, a drive sprocket 14, a driven sprocket 15, a drive 
chain 16, a planetary gear unit 20, a first shift mechanism 30 for 
selective provision of a high speed drive or a low speed drive, and a 
second shift mechanism 40 for selective provision of a two wheel drive or 
a four wheel drive. 
The input shaft 11 is rotatably supported on a left-hand side wall 17a of 
housing 17 through a needle bearing 18a, a carrier 24 of planetary gear 
unit 20, and a ball bearing 18b. The input shaft 11 has an internally 
splined portion 11a for connection to an output shaft of a power 
transmission (not shown) in the transmission casing, and an externally 
splined portion 11b for mounting thereon the planetary gear unit 20. An 
oil pump 18c is mounted on the outer end portion of input shaft 11 and 
enclosed with a bearing retainer 17b fitted in a fluid-tight manner to the 
side wall 17a of housing 17 to supply lubricating oil to bearing portions 
and intermeshed portions in the transfer device. 
The first output shaft 12 is arranged coaxially with input shaft 11 and 
rotatably supported within the right-hand end portion of input shaft 11 
through a needle bearing 18d for relative rotation and on a right-hand 
side wall 17c of housing 17 through a ball bearing 18e. The first output 
shaft 12 is formed with an externally splined hub portion 12a and a 
journal portion 12b and is connected at the right-hand end thereof to rear 
wheel drive alxes (not shown). A drive gear 18h for a speedometer is 
fixedly mounted on the outer end portion of first output shaft 12. 
The second output shaft 13 is arranged in parallel with input and first 
output shafts 11 and 12 and is rotatably supported by a pair of axially 
spaced ball bearings 18f and 18g mounted respectively on both side walls 
17a and 17c of housing 17. The second output shaft 13 has an externally 
splined portion 13a at the left-hand end thereof for connection to front 
wheel drive axles (not shown). The drive sprocket 14 is rotatably 
supported on the journal portion 12b of first output shaft 12 through a 
needle bearing 18i, the driven sprocket 15 on second output shaft 13 being 
similarly supported through a needle bearing 18j. Both the drive sprocket 
14 and driven sprocket 15 are drivingly connected to each other by means 
of the drive chain 16. 
The planetary gear unit 20 is adapted as a change-speed mechanism for the 
transfer device, which comprises a sun gear 21 mounted in place on the 
externally splined portion 11b of input shaft 11 for rotation therewith, a 
stationary ring gear 22 arranged concentrically with sun gear 21 and 
secured to an internal cylindrical wall of housing 17, the carrier 24 
rotatably arranged between sun gear 21 and ring gear 22, and a plurality 
of planetary gears rotatably supported by carrier 24 and in mesh with sun 
gear 21 and ring gear 22. An annular side gear 25 is integrally fixed to 
the right end of carrier 24 for rotation therewith and is formed with an 
internal spline 25a which is arranged to be engaged with a sleeve member 
31 of the first shift mechanism 30. When the sleeve member 31 of first 
shift mechanism 30 is axially moved to engage the internal spline 25a of 
side gear 25 at its external spline 31b, the planetary gear unit 20 acts 
to transfer drive torque from the input shaft 11 to the first output shaft 
12 therethrough at a predetermined reduction speed ratio. 
As is illustrated in FIGS. 1 to 4, the first shift mechanism 30 includes a 
shift rod 32 arranged in parallel with input and output shafts 11, 12, and 
a shift fork 33 fixed at a base portion thereof to an intermediate portion 
of shift rod 32 and coupled with the sleeve member 31. The sleeve member 
31 has an internal spline 31a axially slidably engaged with the externally 
splined hub portion 12a of first output shaft 12 and engageable with the 
externally splined portion 11b of input shaft 11 when shifted rightward. 
As shown in FIG. 3, the shift rod 32 is axially slidably supported on both 
side walls 17a and 17c of housing 17 to be shifted by engagement with a 
swing arm 45 of the second shift mechanism 40. When the shift rod 32 is 
positioned to retain the shift fork 33 in a first position I, the sleeve 
member 31 is disengaged from the internal spline 25a of side gear 25 and 
engaged with the externally splined portion 11b of input shaft 11 to 
effect direct connection between input and output shafts 11 and 12. When 
the shift rod 32 is moved to shift the shift fork 33 to a second position 
II and retain it in the same position, the sleeve member 31 is disengaged 
from the externally splined portion 11b of input shaft 11 and engaged with 
the internal spline 25a of side gear 25 to drivingly connect the input 
shaft 11 to the first output shaft 12 through planetary gear unit 20. 
As is illustrated in FIGS. 1 to 4, the second shift mechanism 40 includes a 
pair of sleeve members 41, 42, a shift rod 43 arranged between the output 
shafts 12, 13 and in parallel with the shift rod 32, a shift fork 44 
axially slidably mounted on an intermediate portion of shift rod 43 and 
coupled with the sleeve members 41, 42, and an operation rod 46 integrally 
provided at its lower end with the swing arm 45. The first sleeve member 
41 has an internal spline 41a axially slidably engaged with the externally 
splined hub portion 12a of first output shaft 12 and engageable with an 
external spline 14a formed on the left-hand end of drive sprocket 14. When 
the shift rod 43 is positioned to retain the shift fork 44 in a first 
position I, the first sleeve member 41 is engaged with the external spline 
14a of drive sprocket 14 to rotate the drive sprocket 14 together with the 
first output shaft 12. When the shift rod 43 is moved to shift the shift 
fork 44 to a second position II and retain it in the same position, the 
first sleeve member 41 is disengaged from the external spline 14a of drive 
sprocket 14 to disconnect the drive sprocket 14 from the first output 
shaft 12. 
The second sleeve member 42 has an internal spline 42a axially slidably 
engaged with an external spline of a clutch hub 18k which is fixedly 
mounted on the second output shaft 13. The internal spline 42a of sleeve 
member 42 is arranged to be engageable with an external spline 15a formed 
on the left-hand end of driven sprocket 15. When the shift rod 43 is 
positioned to retain the shift fork 44 in the first position I, the second 
sleeve member 42 is engaged with the external spline 15a of driven 
sprocket 15 to rotate the second output shaft 13 together with the driven 
sprocket 15. When the shift rod 43 is moved to shift the shift fork 44 to 
the second position II, the second sleeve member 42 is disengaged from the 
external spline 15a of driven sprocket 15 to disconnect the second output 
shaft 13 from the driven sprocket 15. Arranged at the inner circumference 
of second sleeve member 42 is a synchronizer assembly of well-known type, 
which includes a conical hub portion 15b integrally formed on the 
left-hand end of driven sprocket 15, a synchronizer ring 18 mounted on the 
conical portion 15b of driven sprocket 15, a strut key 18m, and a pair of 
retaining springs 18n. When the second sleeve member 42 is moved from the 
second position II to the first position I, the synchronizer assembly acts 
to establish a speed synchronization between the sprockets 14, 15, drive 
chain 16 and second output shaft 13. 
As shown in FIG. 3, the shift rod 43 is axially slidably supported on both 
the side walls 17a, 17c of housing 17. The shift fork 44 is biased 
leftward by a compression coil spring 44c arranged about the shift rod 43 
to resiliently abut against a stepped portion 43a formed on the shift rod 
43 for its positioning. As shown in FIG. 2, the shift fork 44 is 
integrally formed with a pair of fork portions 44a, 44b which are engaged 
with respective sleeve members 41 and 42 to move them as a unit. The shift 
rod 43 is formed at the underside of stepped portion 43a thereof with a 
recessed portion 43b which is engaged one end portion 45a of swing arm 45. 
As shown in FIG. 4, the swing arm 45 is secured to an arm portion 46a 
formed at the lower end of operation rod 46 to be swung therewith, which 
operation rod 46 is inserted in a fluid-tight manner through a boss 
portion 17d of housing 17 and rotatably supported therethrough. In 
operation, the one end portion 45a of swing arm 45 is pressed into contact 
with a side face of recessed portion 43b of shift rod to cause axial 
movement of the shift rod 43, while another end portion 45b of swing arm 
45 is engaged with a recessed portion 33a formed on the base portion of 
shift fork 33 to cause axial movement of the shift rod 32. 
As shown in FIG. 3, a pair of opposed detent mechanisms 51, 52 and an 
interlock mechanism 53 are provided to selectively retain both the shift 
rods 32 and 43 in their shifted positions. The first detent mechanism 51 
includes a check ball 51c loaded by a compression coil spring 51d toward 
the shift rod 43 and selectively engageable with a pair of axially spaced 
recesses 51a, 51b formed on the shift rod 43. The second detent mechanism 
52 includes a check ball 52c loaded by a compression coil spring 52d 
toward the shift rod 32 and selectively engageable with a pair of axially 
spaced recesses 52a, 52b formed on the shift rod 32. The interlock 
mechanism 53 includes an interlock pin 53c selectively engageable with a 
pair of recesses 53a, 53b respectively formed on the shift rods 43 and 32. 
As shown in FIGS. 2 and 4, a connecting lever 47 is keyed to the outer end 
of operation rod 46 and is operatively connected to a manual operation 
lever 49 through a push-pull cable 48 in such a manner that the operation 
rod 46 is rotated by shifting operation of the manual operation lever 49 
to swing the swing arm 45. 
Assuming that the manual operation lever 49 is retained in a position H4 in 
FIG. 2 to provide a high speed four wheel drive, the sleeve member 31 is 
retained in the first position I to directly connect the input shaft 11 to 
the first output shaft 12, and both the sleeve members 41, 42 are 
respectively retained in the first position I to connect the first output 
shaft 12 to the drive sprocket 14 and to connect the second output shaft 
13 to the driven sprocket 15. In such a condition, as shown in FIG. 5(a), 
the base portion of shift fork 33 is in abutment with an internal surface 
of the side wall 17a of housing 17 to restrict leftward movement of the 
shift rod 32, while an annular spring retainer fixed to the shift rod 43 
is in abutment with an internal surface of the side wall 17c of housing 17 
to restrict rightward movement of the shift rod 43. In FIG. 5(a), the 
reference character C indicates a center of the axis of operation rod 46. 
When the manual operation lever 49 is shifted from the position H4 to a 
position H2 in FIG. 2 to provide a high speed two wheel drive, the 
operation rod 46 is rotated in a direction shown by an arrow A.sub.1 in 
FIG. 5(a) through the push-pull cable 48 and connecting lever 47. This 
causes a center of swing arm 45 to rotate in a direction shown by an arrow 
A.sub.2 in FIG. 5(a). In this instance, as shown in FIG. 5(b), the one end 
portion 45a of swing arm 45 swings to move the shift rod 43 leftward, 
while the other end portion 45b of swing arm 45 acts as a fulcrum to 
effect the leftward movement of shift rod 43. Thus, the shift fork 44 is 
shifted to move both the sleeve members 41, 42 from the first position I 
to the second position II thereby to disengage the first output shaft 12 
from the drive sprocket 14 as well as the second output shaft 13 from the 
driven sprocket 15. In such a condition as shown in FIG. 5(b), the 
interlock mechanism 53 acts to retain the shift rod 32 in place, and the 
detent mechanism 51 acts to retain the shift rod 43 in its shifted 
position. When the manual operation lever 49 is shifted from the position 
H2 to the position H4, the swing arm 45 is caused to swing in a reverse 
direction about the other end portion 45b to move the shift rod 43 
rightward. PG,17 
When the manual operation lever 49 is shifted from the position H4 to a 
position L4 in FIG. 2 to provide a low speed four wheel drive, the 
operation rod 46 is rotated in a direction shown by an arrow B.sub.1 in 
FIG. 5(a) through the push-pull cable 48 and connecting lever 47. This 
causes the center of swing arm 45 to rotate in a direction shown by an 
arrow B.sub.2. In this instance, as shown in FIG. 5(c), the other end 
portion 45b of swing arm 45 swings to move the shift fork 33 rightward, 
while the one end portion 45a of swing arm 45 acts as a fulcrum to effect 
the rightward movement of shift fork 33. Thus, the sleeve member 31 is 
caused to move to the second position II in FIG. 1 to connect the input 
shaft 11 to the first output shaft 12 through the planetary gear unit 20. 
In such a condition as shown in FIG. 5(c), the interlock mechanism 53 acts 
to retain the shift rod 43 in place, and the detent mechanism 52 acts to 
retain the shift rod 32 in its shifted position. When the manual operation 
lever 49 is shifted from the position L4 to the position H4, the swing arm 
45 is caused to swing in a reverse direction about the one end portion 45a 
thereof to move the shift rod 32 leftward. 
From the above description, it will be understood that the engagement of 
swing arm 45 at the one end portion thereof 45a with the recessed portion 
43b of shift rod 43 and at the other end portion 45b thereof with the 
recessed portion 33a of shift fork 33 is effective to restrict rotation of 
the respective shift rods 43, 32 and to restrict axial movement of the 
operation rod 46 in a direction outwardly with respect to the housing 17. 
This enables the simplification of the construction of the shift mechanism 
30, 40 and the reduction of portions of the component parts to be 
machined. 
In FIG. 6 there is illustrated a modification of the power transfer device, 
wherein the driven sprocket 15 is replaced with a driven sprocket 15A 
which is integrally mounted on the second output shaft 13 without 
provision of the sleeve member 42 and the synchronizer assembly, and 
wherein the shift fork 44 is replaced with a shift fork 44A which is 
axially slidably mounted on the shift rod 43 without provision of the 
other fork portion 46b. The other construction of the modification is 
substantially the same as that of the above-described embodiment. Thus, 
the modification has the same advantages as those of the above-described 
embodiment. In addition, it is noted that the present invention can be 
applied to a power transfer device of well-known type, which includes a 
first output shaft arranged in parallel with an input shaft for connecting 
the input shaft to a pair of front wheel or rear wheel drive axles, a 
second output shaft coaxially with the first output shaft for drive 
connection to a pair of rear wheel or front wheel drive axles, and a shift 
mechanism for selective connection or disconnection of the first output 
shaft to or from the second output shaft. 
Having now fully set forth both structure and operation of certain 
preferred embodiments of the concept underlying the present invention, 
various other embodiments as well as certain variations and modifications 
of the embodiments herein shown and described will obviously occur to 
those skilled in the art upon becoming familiar with said underlying 
concept. It is to be understood, therefore, that within the scope of the 
appended claims, the invention may be practiced otherwise than as 
specifically set forth herein.