Machine element or mechanism – Gearing – Follow-up mechanism
Reexamination Certificate
2001-04-20
2004-05-18
Fenstermacher, David (Department: 3682)
Machine element or mechanism
Gearing
Follow-up mechanism
C074S409000
Reexamination Certificate
active
06736021
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a rack and pinion steering gear and, more particularly, to a rack and pinion steering gear having a low friction yoke assembly.
BACKGROUND OF THE INVENTION
A known rack and pinion steering gear includes a pinion gear that is rotatably mounted in a housing and is connected with a steering wheel of a vehicle. A rack bar extends axially through the housing and has opposite end portions connected with steerable vehicle wheels. Gear teeth formed on the rack bar are disposed in meshing engagement with gear teeth on the pinion gear. A yoke assembly, including a yoke and a spring, is disposed in the housing to support and guide movement of the rack bar relative to the housing.
The yoke
210
of the known rack and pinion steering gear is shown in FIG.
6
. An axially extending cavity
212
extends through the yoke
210
and intersects an upper surface
214
of the yoke
210
. The axially extending cavity
212
forms diametrically opposite first and second support walls
216
and
218
. The first and second support walls
216
and
218
support a spindle
220
that extends across the axially extending cavity
212
of the yoke
210
. The length of the spindle
220
is approximately equal to the diameter of the yoke
210
. The spindle
220
supports first and second roller assemblies
222
and
224
within the axially extending cavity
212
. The first roller assembly
222
is near the first support wall
216
and the second roller assembly
224
is near the second support wall
218
. Each of the first and second roller assemblies
222
and
224
include a roller
226
that is fixed to a bushing
228
. Each roller
226
has a concave bearing surface
230
for contacting and supporting the rack bar
232
. The first and second roller assemblies
222
and
224
rotate relative to the yoke
210
and the spindle
220
during axial movement of the rack bar
232
.
During operation of this known rack and pinion steering gear, the yoke assembly may be subjected to both heat and high loads. The heat is produced by friction, generally between the rack bar
232
and the bearing surfaces
230
of the rollers
226
as the rack bar
232
moves over the rollers
226
. A high load may occur, for example, when a vehicle hits a pothole in the road surface. The impact load of the vehicle tire with the pothole is transferred to the rack bar
232
through the vehicle tie rods. The rack bar
232
, in turn, transfers a portion of the load to the yoke assembly. The load transferred to the yoke assembly should be absorbed by the spring that biases the yoke
210
against the rack bar
232
. However, in the yoke assembly of the known rack and pinion steering gear, the load of the rack bar
232
on the rollers
226
creates a significant bending moment on the spindle
220
. As a result, the load may cause the spindle
220
to bend in a location between the roller assemblies
222
and
224
. When the spindle
220
bends, rotation of the first and second roller assemblies
222
and
224
may be impaired and increased friction and heat may develop between the rack bar
232
and the yoke assembly.
SUMMARY OF THE INVENTION
The present invention is a rack and pinion steering gear. The rack and pinion steering gear comprises a housing having an axially extending passage and a yoke bore that extends perpendicular to the axially extending passage and connects with the axially extending passage within the housing. A pinion gear having teeth is rotatably mounted in the housing. A rack bar extends through the axially extending passage of the housing and is movable relative to the pinion gear. The rack bar has teeth in meshing engagement with the teeth of the pinion gear. A yoke assembly is located in the yoke bore of the housing for at least partially supporting and guiding axial movement of the rack bar relative to the pinion gear. The yoke assembly comprises a yoke having first and second roller assemblies for contacting the rack bar and rotating during axial movement of the rack bar. A first spindle is fixed to the yoke and supports the first roller assembly and a second spindle is fixed to the yoke and supports the second roller assembly.
REFERENCES:
patent: 2509161 (1950-05-01), Meyers
patent: 3908479 (1975-09-01), MacDuff
patent: 4215591 (1980-08-01), Bishop
patent: 4271716 (1981-06-01), Carduner
patent: 5117705 (1992-06-01), Guasch
patent: 5983742 (1999-11-01), Morris et al.
patent: 6408708 (2002-06-01), Sahr
patent: 05147542 (1993-06-01), None
patent: 11034886 (1999-02-01), None
Adams Bobby Joe
Little Scott C.
LandOfFree
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