Note: Descriptions are shown in the official language in which they were submitted.
POWER STEERING OEAR MECHANISM WITH ROTARY
CONTROL VALVE
The present inventlon relates generally to power
steering gear mechanisms for use with automotive vehicles.
It comprises a pressure movable member defining a piston
that is located in a pressure cylinder. The piston and
the cylinder cooperate to define two working pressure cham-
bers, one on each side of the piston. The piston is pro-
vided with rack teeth that engage a pinion that in`turn
is connected operatively to the steering gear linkage for
the dirigible wheels of the vehicle.
A driver controlled torque input member is
journalled in the cylinder housing and is situated in coaxial
alignment with the piston. It is connected to a driven
member of the steering gear mechanism by a torsion bar so
that the input member may deflect angularly with respect
to the driven member. The driven member in turn is connected
to the pinion so that steering torque applied to the input
shaft will be translated into a driving motion of the piston
and the rack teeth in either one direction or the other
depending upon the direction that torque is applied to the
input shaft.
A pressure source, such as an engine driven power
steering pump, not disclosed, distributes working pressure
to the pressure chambers. Pressure distribution to the
chambers is controlled by a rotary valve that comprises
a first valve element connected to or formed in-tegrally
with a torque input shaft. This valve element is rotatably
disposed in a valve sleeve located within a valve housing
at one end of the cylinder housing. The valve sleeve is
ported so that fluid pressure may be admitted to a central
region of the registering valve lands of the valve element
and the sleeve. On either side of the inlet port is a high
pressure distribution port extending to either pressure
chamber. Fluid is circulated continuously through the valve
system, and the outlet for .the circulating fluid is an
outlet port located at the end of the valve spool adjacent
the pinion.
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The invention comprises improvements in a steering
gear valve mechanism of the type that is disclosed in U.S.
Patents Nos. 3r680,~as3; 3,807,456 and 4,063,490 that are
assigned to Ford Motor Company. The valve structure shown
in U.S. Patent No. 4,063,490 includes a valve sleeve within
which is situated a rotary valve element. The sleeve is
provided with porting that establishes communication between
the high pressure inlet port and each of two pressure dis-
tribution chambers in a power steering gear. The outlet
port is located at the rearward end of the valve structure.
The valve sleeve is pinned -to the driven member and axial
thrust forces are transmitted from the driven member to
the case through thrust bearings.
According to the present invention, a pin connection
is provided between the torsion bar and the output member,
and the pin of that pin connection is used also to establish
a driving connection between the output member and the valve
spool. The pin thus serves a double purpose and the axial
length of the valve assembly is reduced because the need
for providing two pin connections is eliminated. This
improved construction also makes it possible to establish
the pin connection at a location that is rela:tively remote
from the bearing point for the output shaft so that the
bearing length can be surface hardened. If the hole for
the pin connection between the output member and the torsion
bar were to be located relatively close to the bearing point
of the output member as in certain prior art designs, drilling
of the hole for the pin connection would be difficult from
a manufacturing standpoint.
The registering valve portions for the sleeve
and the valve element are relatively displaceable, one with
respect to the other, upon deflection of the -torsion that
connects the torque input member with the driven member.
The deflection of the torsion bar is proportional to the
torque applied to the steering gear which, of course, is
directly proportional to the steering effort applied -to
the pinion. The magnitude of the displacement of the
torsion bar, of course, determines the relative displacement
of the valve portions of the sleeve of the valve element.
: - .
As torque is applied in one direction, the degree of commun-
ication between the inlet port and the right turn port
extending to one pressure chamber is increased as correspon~
ding pressure distribution from the inlet port to the left
turn port extending to the opposite pressure chamber is
decreased. The thrust due to pressure forces acting on
the valve sleeve is in the direction of the pinion. No
thrust washer is required to accommodate transfer of thrust
forces from the sleeve to -the housing as in conventional
arrangements. A pin and slot connection is provided between
the driven member and the sleeve so tha-t the driven sleeve
rotates with the driven member with a free floating relative-
ly frictionless movement.
The invention is described further, by way of
illustration, with reference to the accompanying drawings,
wherein:
Figure l is an assembly view of a steering gear
mechanism that includes a ro-tary pressure distribution
valve;
Figure 2 is a cross-sectional view of the rotary
pressure distribution valve for the steering gear of Figure
l as seen from the plane of section line II-II of Figure
1 ;
Figure 3 is an enlarged view of a portion of the
rotary valve mechanism of Figure 2;
Figure 4 is a cross-sectional end view of the
valve of Figure 3 as seen from the plane of section line
4-4 of Figure 3;
Figure 5 is a plan view of the valve s-tructure
of Figure 4 as seen from the plane of section line 5-5 of
Figure 4;
Figure 6 is a cross-sectional view of an alter-
nate rotary valve design for the steering gear of Figure
1 and provided in accordance with this invention; and
Figure 6A is a cross-sectional view of the valve
mechanism of Figure 6 as seen from the plane of section
line 6A-6A of Figure 6.
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5/6
In Figure 1, reference numeral 10 generally des-
ignates a cast housing. It includes a portion 12 that
encloses a rack pinion 14 and a portion 16 that encloses
a valve assembly 18. The pinion 14 engages drivably a rack
20 which extends transversel~ with respect to the axis of
the pinion 14 and is suitabl~ journalled. Reference may
be made to U.S. Patent No. 4,063,490 for a descrip-tion of
one method for enclosing and supporting a rack such as the
rack 20.
Pinion 14 is journalled at the lef-t-hand end,
as seen in Figure 1, by bearing 22 which is capable of
accommodating axial thrust~in either axial direction. The
right-hand end of the pinion, as seen in ~igure 1, is jour-
nalled by bushing 24. Closure member 26 enclosing the left-
hand end of the opening in the housing 10 in which the pinion
14 is journalled.
The rack 20 is adapted -to be connec-ted to the
steering linkage of the clirigible wheels oE a road vehicle.
It is urged into meshing engagement wi-th a pinion 14 by
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yoke 28 slidably positioned in a yoke cavity 30 formed in
the housing portion 12. The yoke 28 is urged into slid-
ing engagement with the rack 20 by means of compression
spring 32.
The valve structure 18 includes a sleeve 34
which is provided with a first high pressure port 36 and
a second high pressure port 38 which communicate respect-
ively with the left turn pressure chamber and the right
turn pressure chamber for the power booster cylinder.
10 Reference may be made to patent No. 4,063,490 for a show-
ing of a power cylinder and piston mechanism capable of
being used with the structure of Figure 1. The rack 20 is
connected to and is formed integrally with the piston in
a steering mechanism so that when pressure is distributed
in the power cylinder to one side of the piston the rac~
20 is urged in one direction. It is urged in the opposite
direction if the pressure build up occurs on the opposike
side of the piston. In this way hydraulic power assist is
achieved. This supplements the steering effort applied to
the rack through the pinion 14.
A torque input shaft 40 is received within the
sleeve 34. The shaft 40 is hollow and i~ receives there-
through a torsion bar 42 which is pinned by means of a pin
and slot connection 44 to the outboard end of the shaft 40.
The inboard end of the torsion rod 42 is pinned by a pin-
and-slot connection to the output member of which the
pinion 14 forms a part. The output member is provided
With an opening 48 through which the pln 46 is received.
The sleeve 34 is positioned in a cylindrical
opening 50 formed in the housing portion 16. A fluld seal
52 is situated on the output member and against a shoulder
formed in the housing portion 16.
A high pressure fluid inlet port 54 formed in
the sleeve 16 extends radially inward toward valve land 56
formed on the input shaft 40. The base of the valve land
7~
.
56 communicates with a central bore 58 in ~he input shaft
40 through a radial passage 60.
! The bore 58 communicates through passage 62,
as seen in Figure ~, with space 64 between the input
shaft 40 and the left-hand end of the sleeve 34. The
slee~e 34 is ported at 66 so that it communicates with
outlet passage 68 formed in ~he housing 16.
Ports 36 and 38 communicate respectively with
left turn pressure passage 70 and right turn pressure
passage 72, respectively.. These pressure passages extend
to opposite sides of the piston for the fluid motor of
which the power cylinder forms a part.
The pinion 14, which also may be referrecl to as
a driven member, is provided with a radial opening 74 in
which is positioned drive pin 76. The radially outward
end of the pin 76 is received in slot 78 formed in the
left-hand end of the sleeve 34 so that the rotary motion
of the pinion 14 will be followed by correspondiny rotary
motion of the sleeve 34.
The left-hand end of the input shaft 40 is
piloted at 80 in a central cylindrical opening formed
in the right-hand end of the pinion 14. The internal
passage 58 in the input member 40 communicates through
radial port 82 at the right hand side of the sleeve 34
so that the high pressure fluid in the inlet port 54 is
transmitted directly to the right-hand end of the sleeve
34.
Fluid seal 84 is situated between the input
shaft 40 and the right-hand end of the housing 16. It is
held in place by snap riny 86. A spacer 88 is located
between the sleeve 34 and the seal 84.
The sleeve 34 is provided with ring seals on
either side of the port 36, on either side of the input
port 54 and on either side of the right turn port 38.
Figure 3 shows an enlargement oE the valve land
54. The land is defined by a cavity ~0 which comprises
,. ...... ~, ............ . ; . , . . . . , . ~
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a milled slot in the input shaft 40. The slots are
angularly disposed about the axis of the shat 40.
The corner of the slots 90 are chamfered as
seen in Fi~ure 4 at 92. The chamfer is defined by a
S crescent surface as in~icated in the plan view of Figure
5. The geometry of the chamfer and the geometry of the
slots 90 are controlled so that sufficient valve clearance
is provided to accommodate the 1OW of fluid through the
valve mechanism and for the distribution of pressure to
each of the pressure ports 36 and 38. A typical valve
opening between the internal valve land 94 formed in the
sleeve 34 and the slot 90 is shown in Figureo4. The
valve lands 94 are in the form of axial flats situated
in angularly disposed relationship about the axis of the
sleeve 34 and these lands register with the lands 54
formed on the member 40.
When torque is applied to the torque input
shaft 40 in one direction, torsion bar 42 yields thereby
decreasing the opening between the lands 94 and 54 that
communicate with one passage while the degree oE communi-
cation through the lands with the other pressure passages
is increased. This effects a turn in either a right
dlrection or a left direction depending upon the direction
of the torque applied to the shaft 40.
A valve mechanism provides a continuously open
~lui~ circuit between the inlet port 54 and the outlet
port 68 as previously described. The pressure that acts
on the right-hand end of the valve sleeve 34 exceecls the
pressure forces acting in a right-hand direction on the
valve sleeve. Thus the valve sleeve is forced normally
toward pinion 14. There is no necessity, therefore~ to
provide a thrust washer at the right-hand end of the
valve sleeve.
The power assist provided by the power cylinder
and piston assembly is in a direction that supplements
the steering effort applied to the input shaft 40. The
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input shaEt 40 is situated as shown in Figure 2 within the
right-hand end of the pinion or driven member 14 to define
a lost motion connection, which is identified by reference
charac-ter g6. If -the torsion rod 42 deflects beyond a
5 certain angular e2~tent, the lost motion connection at 96
will establish a direct driving relationship between the
shaft 40 and the pinion 14.
In Figure 6, there is shown an alterna-te valve
construction that employs a single drive pin for connecting
10 both the torsion rod and the valve sleeve to the driven
member or pinion 14, in accordance with the present
invention. The drive pin that serves this dual purpose
is identified in Figure 6 by reference numeral 100. The
pins in the Figure 2 construction that the drive pin 100
15 replaces are shown at 46 and 76. The pinion 14', which
forms a counterpart for the pinion 14 of the Figure 2 con-
struction, is provided with an opening 102 through which
the pin 100 is received. The radially outward end of the
pin 100 is received in opening 104 in the left hand end
20 of the valve sleeve 34', which forms a counterpart for
the sleeve of Figure 2. Thus the sleeve 34' and the
pinion 14 move in unison although there is no net
hydraulic force acting on -the sleeve 34 in a right-hand
direction. Because of the fact that pressure is dis-
25 tributed to the right-hand end of the sleeve as in the
Figure 2 construction, the pin connection be-tween the
sleeve 34' and the pinion 14' may be a loose fitting
connection; and it functions in a fashion similar
to the pin and slot connection shown at 76 and 78 in
30 Figure 2.
The other elements of the valve structure shown
in Figure 6 have counterpart elements in the Figure 2
structure, and for this reason corresponding elements of
each figure are shown by the same reference numerals although
35 prime notations have been added to the Figure 6 construc-
tion. The lost motion connection between the driving
shaft 40 and the pinion 14 is shown in Figure 6A.
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This connection is similar to the one described in
Figure 2A. For this reason similar numerals have been
used to ~esignate the common elements although prime
notations have been added to the Figure 6A construction.
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