Planetary gear unit

Details Planetary gear unit Planetary gear unit

2002-11-04

2004-11-30

Ho, Ha (Department: 3681)

Planetary gear transmission systems or components

With means to vary drive ratio or disconnect drive

Carrier braked

C475S315000, C475S321000

Reexamination Certificate

active

06824494

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a planetary gear unit used in an automatic transmission. In particular, the present invention relates to a structure for positioning and supporting a clutch member coupled with one element of a planetary gear and engaging a clutch drum, and to friction disks for frictionally engaging a clutch drum.
2. Description of Related Art
Planetary gear units are commonly used in automatic transmissions. For example, a planetary gear unit is used as a forward-reverse switching mechanism for switching between forward travel and travel in reverse using a belt type continuously variable transmission (hereinafter referred to as “CVT”).
FIG. 6
shows in cross-sectional view, a conventional planetary gear unit
100
as including planetary gearing
200
, a clutch for forward (hereinafter referred to as “forward clutch C
1
”) and a brake B
1
for reverse (hereinafter referred to as “reverse brake B
1
”). The planetary gearing
200
includes a sun gear S, a ring gear R, a carrier CR, and a pinion P supported by the carrier CR and meshing with both the ring gear R and the sun gear S, all of which members are disposed around an input shaft
103
.
A hydraulic actuator
111
for operation of the forward clutch C
1
has a clutch drum
109
, a piston member
112
, a return spring
113
, and the like. Furthermore, a hydraulic actuator
123
for operation of the reverse brake B
1
is formed in a partition wall portion of a case
106
, and further includes a piston member
124
, a return spring
125
, and the like.
The aforementioned input shaft
103
is coupled both to an output portion of a torque converter (not shown) and to the clutch drum
109
. The ring gear R is axially positioned and supported (in the direction indicated by the arrows A-B in
FIG. 6
) by being sandwiched between two snap rings
240
and
241
and is splined to an end hub portion of the clutch drum
109
. A pressure receiving member
244
of the outer friction disks
116
of the forward clutch C
1
is axially positioned and supported (in the direction indicated by the arrows A-B in
FIG. 6
) (sandwiched) by a snap ring
242
and splining with the interior surface of an end hub portion of the clutch drum
109
.
Inner friction disks
117
of the forward clutch C
1
are splined to an end hub portion of disk member
114
. The disk member
114
has its inner peripheral portion fixed to the sun gear S. In addition, the sun gear S is splined to the primary pulley
105
.
Outer friction disks
118
of the reverse brake B
1
are splined to the aforementioned case
106
. Furthermore, inner friction disks
119
of the reverse brake B
1
are splined to the outer surface of an end hub portion of a side disk
230
which is one portion of the planetary carrier CR.
With a planetary gear unit as described above, if working pressure is applied to the hydraulic actuator
111
of the forward clutch C
1
, the piston member
112
slides in the direction indicated by the arrow A in
FIG. 6
, against the force of the return spring
113
. Thus, the outer friction disks
116
and the inner friction disks
117
of the forward clutch C
1
are forced together so that they become engaged by frictional force. As a result, the input rotation of the clutch drum
109
engaged with the aforementioned input shaft
103
is transmitted to the primary pulley
105
via the forward clutch C
1
, the disk member
114
and the sun gear S. Accordingly, if the forward clutch C
1
is engaged and the reverse brake B
1
is released, the torque of the input shaft
103
is output as normal (forward) rotation of the primary pulley
105
.
Furthermore, if working pressure is applied to the hydraulic actuator
123
of the reverse brake B
1
, piston member
124
is forced to slide in the direction indicated by the arrow A in
FIG. 6
, against the force of a return spring
125
. Thus, the outer friction disks
118
and the inner friction disks
119
of the reverse brake B
1
are forced together so that they become engaged by frictional force. As a result, the carrier CR is fixed with respect to the case
106
via the reverse brake B
1
. The input rotation of the clutch drum
109
, engaged with the input shaft
103
, is transmitted as reverse rotation to the primary pulley
105
, via the ring gear R, the carrier CR fixed with respect to the case
106
, and the sun gear S. Accordingly, if the reverse brake B
1
is engaged and the forward clutch C
1
is released, the torque of the input shaft
103
is output as reverse rotation to the primary pulley
105
.
However, with the aforementioned planetary gear unit
100
, in order to axially position and support the ring gear R and the pressure receiving member
244
relative to the clutch drum
109
, three snap rings
240
,
241
and
242
are utilized. This configuration does not allow for cost savings which might otherwise be attainable through reduction of parts. Moreover, a configuration in which the snap rings
241
and
242
are disposed between the ring gear R and the forward clutch C
1
, leads to design problems related to strength and assembly. In other words, space is required for receiving the snap rings
241
and
242
, which impedes making the overall planetary gear unit
100
more axially compact.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a planetary gear unit that can solve the problems mentioned above. This is accomplished by axially positioning and supporting the friction disks of the clutch relative to the clutch drum using a first stopper member. Furthermore, an engaging member coupled with one element of the planetary gear is axially positioned and supported by being sandwiched between the first stopper member and a second stopper member.
A planetary gear unit according to one embodiment of the present invention is provided with planetary gearing and a clutch having a clutch drum disposed adjacent to the planetary gearing. The planetary gearing includes: an engaging member which is coupled with one element of the planetary gearing and is engaged with an interior surface of the clutch drum; a first stopper member axially positioning and supporting friction disks of the clutch and disposed on the interior surface of the clutch drum; and a second stopper member axially positioning and supporting the aforementioned engaging member and also disposed on the internal surface of the clutch drum. The planetary gear unit has the engaging member sandwiched between the first stopper member and the second stopper member, thus axially positioning and supporting the engaging member.
In the first embodiment of the present invention, the friction disks are axially positioned and supported by the first stopper member and the engaging member is axially positioned and supported by being sandwiched between the first stopper member and the second stopper member. Accordingly, it is possible to save cost by reducing the number of parts. Furthermore, since the friction disks (in particular, a pressure receiving portion thereof) are axially positioned and supported by the first stopper member, and the engaging member is axially positioned and supported by being sandwiched between the first stopper member and the second stopper member, the spacing between the friction disks and the engaging member is only that which is necessary for provision of the first stopper member. Accordingly, the space between the engaging member and the friction disks (in particular, the pressure receiving portion thereof) is small, and it is possible to make the entire planetary gear unit more axially compact.
Preferably, the aforementioned clutch drum has a toroidal recess in its internal peripheral surface, and the first stopper member is a tapered snap ring having a tapered surface abutting against a corner portion of the recess and an abutting surface that abuts against an inner surface of the recess.
The tapered snap ring (“first stopper member”) fits into the toroidal recess formed in the internal surface of the clutch drum without any cleara

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