FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, rule 13]
“STEERING SYSTEM FOR A MULTI-AXLE VEHICLE”
NAME AND ADDRESS OF THE APPLICANT:
TATA MOTORS LIMITED, an Indian company having its registered office at Bombay
house, 24 Homi Mody Street, Hutatma Chowk, Mumbai 400 001, Maharashtra, INDIA.
Nationality: Indian
The following specification particularly describes the invention and the manner in which
it is to be performed.
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TECHNICAL FIELD
The present invention generally relates to steering system for automobiles and more
particularly relates to a system for steering multiple axles of a multi-axle automobile.
BACKGROUND OF THE DISCLOSURE
Steering systems of automobiles connects the steering wheel to the wheels of the
automobile. The steering systems are designed to provide steering movement to,
typically, each of the steerable axles for example, front axle (or axles) and/or rear axles
(or axles) of the automobile. The front axle (or axles) and the rear axle (or axles) of the
automobile may be steerable. Typically, for steering the front axle (or axles), the steering
wheel is rotated, and the input from the steering wheel is transmitted to the steering gear
box. From the steering gear box, the movement is transferred to wheels of the front axles
with the help of a front mechanism of pitman arm, idler arm, relay arm and tie rod
mounting arms through drag links, relay rods and tie rods. Frequently, in automobiles
with steerable rear axles, the steering movement from the front mechanism is transferred
to the rear axles through a conventional linkage e.g. a set of elongated linkages disposed
along the chassis. Such conventional linkage poses various problems pertaining to inter
alia, packaging, handling and weight. Further, clearance of such conventional linkages
from a ground or road surface is also an issue that has remained substantially unaddressed
hitherto.
OBJECTS OF THE INVENTION
The objective of invention is to provide a steering system for a multi-axle vehicle which
is simple, accurate and reliable.
Another objective of the preset invention is to provide a steering system for a multi-axle
vehicle which precludes bump/brake steer error.
Further objects and features of the invention will become apparent from the following
detailed description when considered in conjunction with the drawings.
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SUMMARY OF THE INVENTION
The various embodiments of the present invention disclose a steering sensing system for
a multi-axle vehicle having a steering system. The steering system include a steering
wheel; a steering shaft connected to the steering wheel for receiving rotational movement
of the steering wheel; a steering gear box supported on a first long member of a chassis; a
pitman arm associated with the steering gear box and having a top end portion and a
bottom end portion, the pitman arm moving with output from the steering gear box; a
drag link connected to the pitman arm and a first wheel of a first axle; a first relay rod
connected to the top end portion of the pitman arm; an idler arm pivotally mounted on the
first long member of the chassis and connected to the first relay rod; a relay arm
connected to idler arm to provide movement to a second axle with movement of the idler
arm; and a tie rod connecting the first wheel to a second wheel of the second axle, for
transferring movement. The steering sensing system includes a second drag link
connected to a second wheel of the second axle; a second relay arm pivotally mounted on
a second long member of the chassis and having an end portion connected to the second
drag link; a first master cylinder connected to a portion of the second relay arm and the
second long member of the chassis, the second master cylinder is adapted to displace
fluid contained therein, to a predetermined pressure based on the movement of the second
drag link; a second idler rod connected to an end portion of the second relay arm; a
second idler arm pivotally mounted on the second long member of the chassis, and
connected to the second idler rod; and a second master cylinder connected to an end
portion of the second idler arm and the second long member of the chassis, the first
master cylinder is adapted to displace fluid to a predetermined pressure based on the
movement of the second idler arm.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
FIG. 1 illustrates a first front perspective view of a portion of the steering system,
according to an embodiment of the invention,
FIG. 2 illustrates a second front perspective view of a portion of the steering system,
according to an embodiment of the invention,
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FIG. 3 illustrates a perspective view of the steering system, according to an embodiment
of the invention,
FIG. 4 illustrates a top view of the steering system, according to an embodiment of the
invention, and
FIG. 5 illustrates a bottom perspective of a portion of the steering system, according to
an embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings, wherein the showings are for the purpose of illustrating a
preferred embodiment of the invention only, and not for the purpose of limiting the same.
In the multi-axle vehicle 100 the chassis 102 is carried by a plurality of axles such as a
first axle 108, a second axle 110, a third axle 112, and a fourth axle 114. Optionally a
pair of auxiliary axles (not illustrated) may also be present. The pair of auxiliary axles
may not be steerable and may be positioned before the third axle 112 and fourth axle 114.
Alternatively, the pair of auxiliary axles may or may not be steerable, and may be
positioned before or after the third axle 112 and fourth axle 114, without deviating from
the scope of the present invention. Each axle of the plurality of axles includes one or
more wheels.
FIG. 1 illustrates a perspective view of a vehicle 100 having a steering system 200,
according to an embodiment of the invention. The vehicle 100 may be a multi-axle
vehicle. The vehicle 100 may find applications as a commercial or as any other vehicle,
with high load carrying capacity, such as, but not limited to, a dump truck, a ballast truck,
a trailer truck and the like. The chassis 102 has a first long member 104, a second long
member 106 disposed opposite to the first long member 104 and a plurality of horizontal
short members (not numbered) connecting the first long member 104 and the second long
member 106. As would be apparent to those skilled in the art, the cab (not shown) and
the load carrier (not shown) of the vehicle 100 are supported on the chassis 102. As
illustrated in figures, the first axle 108 includes a first wheel 116 on a first, say right, side
of the first axle 108 and a second wheel 118 disposed opposite to the first wheel 116 on a
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second, say left, side of the first axle 108. Likewise, the second axle 110 includes a first
wheel 120 on the first side of the second axle 110 and a second wheel 122 disposed
opposite to the first wheel 120 on the second side of the second axle 110.
Referring again to FIG. 1, the steering system 200 includes a steering wheel 202 and a
steering shaft 204 connected to the steering wheel 202, such that the steering wheel 202 is
positioned within the cab. When the steering wheel 202 is rotated, the steering shaft 204
receives rotational movement thereof. A steering gear box 206 is supported on the first
long member 104 of the chassis102. A pitman arm 208 is associated with the steering
gear box 206 and has a top end portion and a bottom end portion and is configured to
move with output from the steering gear box 206. A drag link 210 is connected to the
pitman arm 208 and the first wheel 116 of the first axle 108. A first relay rod 212 is
connected to the top end portion of the pitman arm 208. An idler arm 214 is pivotally
mounted on the first long member 104 of the chassis 102 and is connected to the first
relay rod 212. A relay arm 216 is connected to the second axle 110, to provide
movement to the first wheel 120 of the second axle 110 with movement of the idler arm
214. As shown in FIG. 4, a tie rod 217 connects the first wheel 116 of the first axle 108
with a second wheel 118 of the first axle 108, for transferring tilting movement of the
first wheel 116 to the second wheel 118. Likewise, a tie rod 218 connects the first wheel
120 to the second wheel 122 of the second axle 110.
Referring now to FIG. 2, which illustrates parts of a steering sensing mechanism 300 for
the multi-axle vehicle 100. The steering sensing mechanism 300 includes a second idler
arm 302 pivotally mounted on the second long member 106 of the chassis 102. A free
end portion of a piston of a second master cylinder 304 is connected to an end portion of
the second idler arm 302. An end of a cylindrical portion of the second master cylinder
304, which telescopically receives the piston, is hingedly connected to the second long
member 106 of the chassis 102. Accordingly, the movement in the second idler arm 302,
about the pivotal point, causes a related displacement of the piston which displaces the
fluid contained therein to a predetermined pressure. In other words, the movement in the
second idler arm 302, about the pivotal point, causes a related displacement of the piston
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with respect to the cylinder, thereby proportionally pressurizing the fluid contained
therein.
Referring again to FIG. 2, the steering sensing mechanism 300 further includes a second
idler rod 306. The second idler rod 306 is connected to an end portion, distal from the
end at which the second master cylinder 304 is connected, of the second idler arm 302. A
second relay arm 308 having a first end portion and a second end portion is connected to
the second idler rod 306. A second drag link 310 is connected to the second end portion
of the second relay arm 308. The second drag link 310 is also connected to the second
wheel 122 of the second axle 110.
Also connected to the second relay arm 308 is a first master cylinder 312. More
specifically, a free end portion of a piston of the first master cylinder 312 is connected to
a portion of the second relay arm 308. An end portion of a cylindrical portion of the first
master cylinder 312, which telescopically receives the piston, is hingedly connected to
the second long member 106 of the chassis 102. Accordingly, movement in the second
relay arm 308, about the pivotal point, causes a related displacement of the piston which
displaces the fluid contained therein to a predetermined pressure. In other words, the
movement in the second relay arm 308, about the pivotal point, causes a related
displacement of the piston with respect to the cylinder, thereby proportionally
pressurizing the fluid contained therein.
Referring now to other figures, the steering sensing mechanism further includes a first
centering cylinder 314 and a second centering cylinder 316. As shown in FIG. 5 the first
centring cylinder 314 is carried by the third axle 112 and the second centering cylinder
316 is carried by the forth axle 114. The first centering cylinder 314 is mounted on the
third axle 112 by a mounting bracket 318 on one side and on other side the first centering
cylinder 314 is connected to a steering arm 320 (also referred to as a tire rod arm 320).
The second centering cylinder 316 is mounted on the fourth axle 114 by a mounting
bracket 322 on one side and on other side the second centering cylinder 316 is connected
to a steering arm 324 (also referred to as a tire rod arm 324) of the fourth axle 114.
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The first centering cylinder 314 is hydraulically coupled with one of the second master
cylinder 304 and the first master cylinder 312, and the second centering cylinder 316 is
hydraulically coupled with the other of the second master cylinder 304 and the first
master cylinder 312. A first hydraulic piping 326 hydraulically couples the first centering
cylinder 314 with one of the second master cylinder 304 and the first master cylinder 312.
Likewise, a second hydraulic piping 328 hydraulically couples the second centering
cylinder 316 with other of the second master cylinder 304 and the first master cylinder
312. In one embodiment of the present invention, the first centering cylinder 314 is
hydraulically coupled with the second master cylinder 304, through the first hydraulic
piping 326 and the second centering cylinder 316 is hydraulically coupled with the first
master cylinder 312, through the second hydraulic piping 328.
At least one hydraulic accumulator, such as hydraulic accumulator 330, or 332, is
provided on at least one of the first hydraulic piping 326 and the second hydraulic piping
328. The hydraulic accumulators adapted to resist a flow of pressurized fluid from one or
more of the first centering cylinder 326 and the second centering cylinder 316 to one or
more of the second master cylinder 304 and the first master cylinder 312. In an
embodiment of the present invention, the hydraulic accumulator 330 is provided on the
first hydraulic piping 326 and resists flow of pressurized fluid from the first centering
cylinder 326 to the second master cylinder 304, when the pressure of the pressurized fluid
is beyond predefined threshold, for example 3 Bar. Likewise, the hydraulic accumulator
332 is provided on the second hydraulic piping 328 and resists flow of pressurized fluid
from the second centering cylinder 316 to the first master cylinder 312, when the pressure
of the pressurized fluid is beyond predefined threshold, for example 3 Bar.
During operation of the vehicle 100, when it is desired that the vehicle 100 takes a turn,
whether right or left, the steering wheel 202 is rotated in a clockwise or anticlockwise
direction. The steering shaft 204 receives rotational movement thereof. Resultantly, the
drag link 210 connected to the pitman arm 208 moves the first wheel 116 of the first axle
108. Simultaneously, the relay arm 216 connected to the second axle 110, provides
movement to the first wheel 120 of the second axle 110 with movement of the idler arm
214. The tie rod 217 transfers tilting motion of the first wheel 116 to the second wheel
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118 and the tie rod 218 transfers tilting motion of the first wheel 120 of the second axle
110 to the second wheel 122 of the second axle 110.
In an embodiment of the present invention when vehicle 100 is taking a left turn, when
the first wheel 116 of the first axle 108 turns by 28 degrees, the second wheel 118 of the
first axle 108, turns by 34 degrees and when the first wheel 120 of the second axle 110
turns by 24 degrees the second wheel 122 of the second axle 110 turns by 28 degrees.
Further, it may herein be noted that in case the vehicle is a left hand drive (LHD), the
steering system 200 and the elements thereof, may be towards the left side of the chassis
102 i.e. towards the second long member 106 of the chassis102, without deviating from
the spirit of the invention.
The movement of the second wheel 122 moves the second drag link 310. The second
drag link 310, being connected to the second relay arm 308, tilts the second relay arm 308
which telescopically moves the piston of the first master cylinder 312. The telescopic
movement of the piston of the first master cylinder creates a hydraulic signal, which is
communicated to the centering cylinders; say the second centering cylinder 316.
Simultaneously, also connected to the second relay arm 308, the second idler rod 306
moves, thereby moving the second idler arm 308. The second relay arm 308 of the
steering sensing mechanism 300, telescopically moves the piston of the second master
cylinder 304. The movement of the piston changes the pressure of the fluid contained in
the second master cylinder 304, which is communicated to the first centering cylinder
314.
The first centering cylinder 314 and the second centering cylinder 316, based on the
hydraulic input, turn the wheels of the third axle 112, a fourth axle 114, respectively. In
an embodiment of the present invention when the first wheel 116 (outer wheel) of the
first axle 108 turns by 28 degrees and the second wheel 118 (inner wheel ) turns by 34
degrees, first wheel (outer wheel) of the third axle 112 turns by 15.5 degrees and second
wheel of the third axle 112 turns by 14 degrees. Simultaneously, first wheel (outer
wheel) of the fourth axle 114 turns by 17 degrees and second wheel 118 turns by 15.5
degrees.
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The foregoing description provides specific embodiments of the present invention. It
should be appreciated that these embodiment are described for purpose of illustration
only, and that numerous other alterations and modifications may be practiced by those
skilled in the art without departing from the spirit and scope of the invention. It is
intended that all such modifications and alterations be included insofar as they come
within the scope of the invention as claimed or the equivalents thereof.
REFERRAL NUMERALS
Reference Numbers Description
100 Vehicle
102 Chassis
108 First axle
110 Second axle
112 Third axle
114 Fourth axle
200 Steering system
104 First long member
106 Second long member
116 First wheel
118 Second wheel
120 First wheel
122 Second wheel
202 Steering wheel
204 Steering shaft
206 Steering gear box
208 Pitman arm
210 Drag link
212 First relay rod
214 Idler arm
216 Relay arm
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217 Tie rod
218 Tie rod
300 Steering sensing mechanism
302 Second idler arm
304 Second master cylinder
306 Second idler rod
308 Second relay arm
110 Second axle
312 First master cylinder
314 First centering cylinder
316 Second centering cylinder
318 Mounting bracket
320 Tie rod arm
322 Mounting bracket
324 Tie rod arm
326 First hydraulic piping
328 Second hydraulic piping
330, 332 Hydraulic accumulator
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We claim:
1. A steering sensing system for a multi-axle vehicle having a steering system
having a steering wheel; a steering shaft connected to the steering wheel for
receiving rotational movement of the steering wheel; a steering gear box
supported on a first long member of a chassis; a pitman arm associated with the
steering gear box and having a top end portion and a bottom end portion, the
pitman arm moving with output from the steering gear box; a drag link connected
to the pitman arm and a first wheel of a first axle; a first relay rod connected to the
top end portion of the pitman arm; an idler arm pivotally mounted on the first
long member of the chassis and connected to the first relay rod; a relay arm
connected to idler arm to provide movement to a second axle with movement of
the idler arm; and a tie rod connecting the first wheel to a second wheel of the
second axle, for transferring movement; the steering sensing mechanism
comprising:
a second drag link connected to a second wheel of the second axle;
a second relay arm pivotally mounted on a second long member of the
chassis and having an end portion connected to the second drag link;
a first master cylinder connected to a portion of the second relay arm and
the second long member of the chassis, the second master cylinder is adapted to
displace fluid contained therein, to a predetermined pressure based on the
movement of the second drag link,
a second idler rod connected to an end portion of the second relay arm;
a second idler arm pivotally mounted on the second long member of the
chassis, and connected to the second idler rod; and
a second master cylinder connected to an end portion of the second idler
arm and the second long member of the chassis, the first master cylinder is
adapted to displace fluid to a predetermined pressure based on the movement of
the second idler arm.
2. The steering sensing system as claimed in claim 1, further comprising,
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a first centering cylinder carried by a third axle of the vehicle, the first
centering cylinder being hydraulically coupled with one of the first master
cylinder and the second master cylinder to get hydraulic input therefrom, for
proportionally tilting wheels of the third axle.
3. The steering sensing system as claimed in claim 1, wherein the first centering
cylinder is mounted on the third axle by a mounting bracket and on other side,
connected to a steering arm of the third axle.
4. The steering sensing system as claimed in claim 1, further comprising,
a second centering cylinder carried by a fourth axle of the vehicle, the
second centering cylinder being hydraulically coupled with one of the first master
cylinder and the second master cylinder to get hydraulic input therefrom, for
proportionally tilting wheels of the fourth axle.
5. The steering sensing system as claimed in claim 1, wherein the second centering
cylinder is mounted on the fourth axle by a mounting bracket and on other side,
connected to a steering arm of the fourth axle.
6. The steering sensing system as claimed in claim 1, further comprising,
a first hydraulic piping hydraulically coupling the first centering cylinder
with one of the first master cylinder and the second master cylinder, and
a second hydraulic piping hydraulically coupling the second centering
cylinder with other of the first master cylinder and the second master cylinder.
7. The steering sensing system as claimed in claim 4, further comprising,
at least one hydraulic accumulator provided on at least one of the first
hydraulic piping and the second hydraulic piping, the at least one hydraulic
accumulator adapted to resist a flow of pressurized fluid from one or more of the
first centering cylinder and the second centering cylinder to one or more of the
first master cylinder and the second master cylinder.
8. A multi-axle steering system for a vehicle having a chassis, the multi-axle steering
system comprising:
a drag link connected to a second wheel of a second axle of the vehicle;
a relay arm pivotally mounted on the chassis and having an end portion
connected to the drag link;
a first master cylinder connected to a portion of the relay arm and the
chassis, the second master cylinder is adapted to displace fluid contained therein,
based on the movement of the drag link;
an idler rod connected to an end portion of the relay arm;
an idler arm pivotally mounted on the chassis, and connected to the idler
rod; and
a second master cylinder connected to an end portion of the idler arm and
the chassis, the first master cylinder is adapted to displace fluid based on the
movement of the second idler arm;
a first centering cylinder carried by a third axle of the vehicle, the first
centering cylinder being hydraulically coupled with one of the first master
cylinder and the second master cylinder to get hydraulic input therefrom, for
proportionally tilting wheels of the third axle; and
a second centering cylinder carried by a fourth axle of the vehicle, the
second centering cylinder being hydraulically coupled with one of the first master
cylinder and the second master cylinder to get hydraulic input therefrom, for
proportionally tilting wheels of the fourth axle.