FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, rule 13]
“AIR SUSPENSION AND AXLE LIFT CONTROL SYSTEM OF A
VEHICLE”
NAME AND ADDRESS OF THE APPLICANT:
TATA MOTORS LIMITED, 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.

TECHNICAL FIELD
The present invention generally relates to suspension systems of vehicles and more particularly relates to an air suspension and axle lift control system of a vehicle.
BACKGROUND OF THE INVENTION
Heavy load carrying vehicles, such as commercial vehicles, large trailers and the like, typically have a vehicle body supported on a vehicle frame (also referred to as a chassis). The vehicle frame is supported on two or more axles and a suspension system is installed therebetween, in order to minimize transmission of forces from the axles to the vehicle frame. Particularly, a pair of air-springs may be provided at distal ends of each of the axles such that the air-springs connect the axles to the vehicle frame.
When the vehicle negotiates a turn, the center of gravity of the vehicle changes and the vehicle tends to roll about its centre of gravity. Because of this, additional pressure is applied on one air-spring, while some pressure is relieved from the other air-springs on the opposite of the same axle. Conventionally, the pressurized air from one air-spring is allowed to be transferred to the other air-spring.
Further, the axles, such as a pusher lift axle, of the vehicles may also be configured to be raised and lowered during decreased load operation, in order to improves fuel economy, decreases tire wear, improves tire life and hence decrease in operation cost of the vehicle. Such axles utilize a pair of lift air-springs. Such lift air-springs, when expended raise the axle and when compressed lower the axle.
Specifically, when there is no load on the vehicle, the lift axle is always in lifted condition. The height of the chassis is sensed by a lever operated 3/2 valve. Typically, the lever operated 3/2 valve is assembled on chassis and a sensing link of the lever operated 3/2 valve is connected to the axle. Variation of distance between the chassis and the axle after addition or removal of load on the vehicle is sensed by the lever operated 3/2 valve and a corresponding pneumatic signal is sent to a Solenoid operated 5/2 control valve with hysteresis. When the lever operated 3/2 valve pressure reaches a threshold, say Two (2) Bar, the LACV starts filling the main air-spring, and punctures lift the air-springs.

When the load is extracted from load body, the lever operated 3/2 valve starts decreasing pressure signals to the Solenoid operated 5/2 control valve with hysteresis; which makes the Solenoid operated 5/2 control valve with hysteresis decrease pressure supply to the main air-spring. Once the lever operated 3/2 valve pressure reaches a lower threshold, say Half (0.5) bar, the Solenoid operated 5/2 control valve with hysteresis gives signal to a Relay Valve (RV) to start air pressure supply to lift air-springs, and deplete the main air-spring, to eventually lift the lift axle.
When the vehicle is not loaded and the ignition is turned-off, the axle comes down. However, when the axle comes down in such a condition of the main air-spring, the main air-springs tend to get damages, as there is no pressure therein. Furthermore, since the air-springs are smaller in size than the main air-spring, the air-springs conventionally get depleted in comparatively lesser time.
OBJECTS OF THE INVENTION
The objective of invention is to provide a reliable, simple and economical air suspension and axle lift control system for a vehicle.
Another object of the invention is to improve dynamic behavior and handling of the vehicle.
Yet another embodiment of the present invention is to reduce damage to various air-springs.
Further objects and features of the invention will become apparent from the following detailed description when considered in conjunction with the drawings.
SUMMARY OF THE INVENTION
The various embodiments of the present invention disclose an air-suspension and axle-lift control system for a vehicle having a vehicle body and one or more axles supporting the vehicle body. The system includes a suspension air spring RH side provided on a first side of the axle between the axle and the vehicle body. The suspension air spring RH side is configured to contain pressurized air. A air connection pipe-1 having a first end portion

and a second end portion is connected to the suspension air spring RH side for communicating pressurized air to and from the suspension air spring RH side. A suspension air spring LH side is provided on a second side of the axle between the axle and the vehicle body. The suspension air spring LH side is configured to contain pressurized air. The system further includes an air connection pipe-2 having a first end portion and a second end portion is connected to the suspension air spring LH side for communicating pressurized air to and from the suspension air spring LH side. An spring loaded 3/2 sliding float valve is connected to the second end portion of the air connection pipe-1 and the second end portion of the air connection pipe-2 such that the spring loaded 3/2 sliding float valve selectively allows exchange of pressurized air between the suspension air spring RH side and the suspension air spring LH side.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a pneumatic diagram of an air suspension and axle lift control system for a vehicle, according to an embodiment of the present invention,
FIG. 2A, 2B illustrate a rear views of the vehicles taking a turn in different directions,
FIG. 3 illustrates a view of an spring loaded 3/2 sliding float valve of the air suspension and axle lift control system for a vehicle, according to an embodiment of the invention,
FIG. 4 illustrates a pneumatic diagram of the air suspension and axle lift control system for an vehicle, according to an embodiment of the present invention, and
FIG. 5 illustrates another pneumatic diagram of the air suspension and axle lift control system for a vehicle, according to yet another embodiment of the present 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.
FIG. 1 illustrates a pneumatic diagram of an air suspension and axle lift control system 100 (hereinafter referred to as “system 100”) for a vehicle (not shown). The vehicle may be a truck, a bus or any other heavy commercial vehicle, without deviating from the spirit

of the invention. The vehicle includes a vehicle body and multiple axles, such as a lift axle 102 (shown in FIG. 2). The vehicle body may be mounted on a chassis, which is connected to the axles. Alternatively, the vehicle body may be integral to the chassis. As would be apparent to those skilled in the art, wheels (not numbered) are disposed on opposite ends of the axle, for transferring weight of the vehicle on a surface and enabling movement of the vehicle thereon.
As per one embodiment of the present invention, the system 100 includes a suspension air spring RH side 104 provided on a first side (right hand side, when seen from behind the vehicle) of the axle 102. The suspension air spring RH side 104 is installed between the axle 102 and the vehicle body. The suspension air spring RH side 104, also referred to as bellows, is configured to contain pressurized air and get compressed upon application of pressure. An air connection pipe-1 106 is connected to the suspension air spring RH side 104. Particularly, the air connection pipe-1 106 has a first end portion and a second end portion opposite to the first end portion. The first end portion of the air connection pipe-1 106 is connected to the suspension air spring RH side 104. The air connection pipe-1 106, when required, communicates the air to and extracts the same from the suspension air spring RH side 104.
A suspension air spring LH side 108, similar to the suspension air spring RH side 104, is provided on a second side (left hand side, when seen from behind the vehicle) of the axle 102. The suspension air spring LH side 108 is installed between the axle 102 and the vehicle body. The suspension air spring LH side 108 may also be configured to contain pressurized air. An air connection pipe-2 110 is connected to the suspension air spring LH side 108. Particularly, the air connection pipe-2 110 has a first end portion and a second end portion. The first end portion of the air connection pipe-2 110 is connected to the suspension air spring LH side 108. The air connection pipe-2 110, when required, communicates the air to and extracts the same from the suspension air spring LH side 108.
Referring now to 1 through 3, the system 100 further includes a spring loaded 3/2 sliding float valve 112. The spring loaded 3/2 sliding float valve 112 is connected to the second

end portion of the air connection pipe-1 106 and the second end portion of the air connection pipe-2 110. Therefore, the spring loaded 3/2 sliding float valve 112 is at the junction of the air connection pipe-1 106 and the air connection pipe-2 110, best shown in FIG. 1. The spring loaded 3/2 sliding float valve 112 selectively restricts exchange of pressurized air between the air connection pipe-1 106 and the air connection pipe-2 106, thereby restricting pressure exchange between the suspension air spring RH side 104 and the suspension air spring LH side 108.
In one embodiment of the present invention, the spring loaded 3/2 sliding float valve 112 restricts exchange of pressurized air between the air connection pipe-1 106 and the air connection pipe-2 106 when there is a predetermined threshold pressure difference between the suspension air spring RH side 104 and the suspension air spring LH side 108. Such threshold pressure difference may be equal to or more than two (2) bar or 2±0.5 bar. The pressure difference between air contained within the suspension air spring RH side 104 and the suspension air spring LH side 108 tends to arise when the vehicle is taking a turn. While taking turn, the vehicle often tends to roll about its centre of gravity, as shown in FIGS. 2A and 2B. More the rolling stiffness of the vehicle, lesser is the rolling of the chassis and vise versa. Rolling of chassis and higher roll stiffness of lift axle rubber bush pivots, lifts tag axle tires thereby pressurizing air-springs from one side of the vehicle.
As best shown in FIG. 3, the spring loaded 3/2 sliding float valve 112 may be a Spring Loaded 3/2 Sliding float valve (SCDV). The spring loaded 3/2 sliding float valve 112 is connected to an air connection pipe-3 113 coming from an air tank 114, through Solenoid operated 5/2 control valve with hysteresis 115 (shown in FIG. 1). The spring loaded 3/2 sliding float valve 112 further includes a cylindrical valve housing 116 connected to the air connection pipe-3 113. The cylindrical valve housing 116 has two opposite ends fluidically connected to the second end portion of the air connection pipe-1 106 and the second end portion of the air connection pipe-2 110, respectively.
A float 118 is positioned within the cylindrical valve housing 116 and may move therewithin. The float 118 has concave surfaces facing the end portions of the cylindrical

valve housing 116. The float 118 allows equal distribution of air from the air connection pipe-3 113 to each of the air connection pipe-1 106 and the air connection pipe-2 106 through the cylindrical valve housing 116. Further, the float 118 allows flow of the pressurized air from one air-supply line to the other air-supply line, unless is positioned at an extreme end portions of the cylindrical valve housing 116.
The float 118 is spring biased and tends to come to a central position. The float 118 further remains in any position other at the extreme end portions of the cylindrical valve housing 116, unless the pressure difference between the suspension air spring RH side 104 and the suspension air spring LH side 108 is less than a predetermined threshold. However, when the pressure difference between the suspension air spring RH side 104 and the suspension air spring LH side 108 is beyond a predetermined threshold, say beyond two (2) bar or 2±0.5 bar, the float 18 tends to slide towards an end of the cylindrical valve housing 116, against the spring and closes end portion of the cylindrical valve housing 116. In this way transfer of pressurized air from one supply line to the other supply line is stopped, when pressure in any one air-spring raises beyond a certain level.
Referring now to FIG. 4, the system 100 further includes a pressure operated 3/2 valve 200 disposed on the air connection pipe-3 113 and is fluidically connected to the spring loaded 3/2 sliding float valve 112(not shown in FIG. 4). A 3/2 Sliding float valve 202 is also fluidically connected to the pressure operated 3/2 valve 200. The 3/2 Sliding float valve 202 is configured to give a pressure signal to the pressure operated 3/2 valve 200. Based on the pressure signal to the pressure operated 3/2 valve 200, it initiates supply of pressurized air from the air connection pipe-3 113 to the suspension air spring RH side 104 and the suspension air spring LH side 108, through the spring loaded 3/2 sliding float valve 112.
More specifically, when the vehicle is loaded, a Height Leveling Valve (HLV) 204 sends a pneumatic signal to a Solenoid operated 5/2 control valve with hysteresis 206. When the Height Leveling Valve pressure reaches a threshold, say Two (2) Bar or 2±0.5 bar, the Solenoid operated 5/2 control valve with hysteresis starts supplying pressurized air to

the pressure operated 3/2 valve 200. The pressurized air is eventually supplied to the suspension air spring RH side 104 and the suspension air spring LH side 108, through the spring loaded 3/2 sliding float valve 112. When the vehicle is not loaded and the engine ignition turned on, the Solenoid operated 5/2 control valve with hysteresis 206 supplies the pressurized air the to the 3/2 Sliding float valve 202. The 3/2 Sliding float valve 202 supplies the pressurized air to the pressure operated 3/2 valve 200.
However, when the vehicle is unloaded and the engine ignition is turned off, the 3/2 Sliding float valve 202 also does not supply pressurized air to the pressure operated 3/2 valve 200. Under this condition, i.e. when the pressure operated 3/2 valve 200 is not able sense pressure, the pressure operated 3/2 valve 200 connects the air connection pipe-3 113 to a valve such as a Pressure limiting valve (PLV) 208. Therefore, the pressurized air from the Pressure limiting valve (PLV) 208 gets supplied to the suspension air spring RH side 104 and the suspension air spring LH side 108, through the spring loaded 3/2 sliding float valve 112, shown with arrow headed lined on FIG. 4. In one embodiment, the Pressure limiting valve (PLV) supplies one (1) bar of air pressure to the suspension air spring RH side 104 and the suspension air spring LH side 108. Such pressure in the first air-spring 104 and the second air-spring 108 is particularly advantageous, as it may prevent membrane folding/squeezing and hence failure of the air-springs.
Now referring to FIG. 5, which illustrates a pneumatic diagram of the system 100 in accordance with another embodiment of the present invention, the system 100 further includes a lift air spring RH side 210 the first side of the axle 102 between the axle 102 and the vehicle body. As will be apparent to those skilled in that art, the lift air spring RH side 210 is configured contract and expands to lift the axle 102 of the vehicle, with respect to the ground surface. A lift air spring LH side 302 is provided on a second side of the axle 102 between the axle 102 and the vehicle body. The lift air spring LH side 212 is also configured to contract and expand to lift the axle 102 of the vehicle, with respect to the ground surface.
An air connection pipe-4 214 is connected to the lift air spring RH side 210. The air connection pipe-4 214 communicates the pressurized air to and from the lift air spring

RH side 210. An air connection pipe-5 216 is connected to the suspension air spring LH side 212. Like the air connection pipe-4 214, the air connection pipe-5 216 communicates pressurized air to and from the suspension air spring LH side 212. The air connection pipe-4 214 and the air connection pipe-5 216 is associated to each other at a relay valve 218. The relay valve 218 is configured to regulate the entry and exhaust of pressurized air front the lift air spring RH side 210 and the lift air spring LH side 212. Further, a one way flow control valve 220 is fluidically associated with the relay valve 218 to allow passage of pressurized air to the lift air spring RH side 210 and the lift air spring LH side 212. Likewise, the pressurized air to the lift air spring RH side 210 and the lift air spring LH side 212 may be released from the Solenoid operated 5/2 control valve with hysteresis 206, through air connection pipe-6 217 coming from the one way flow control valve 220.
Furthermore, the one way flow control valve 220 restricts the passage of pressurized air coming from the lift air spring RH side 210 and the suspension air spring LH side 212. Resultantly, a slow exhaust takes from the lift air spring RH side 210 and the lift air spring LH side 212, to the Solenoid operated 5/2 control valve with hysteresis 206, through the air connection pipe-6 217. Therefore, the suspension air spring RH side 104 and the suspension air spring LH side 108 get time to fill. In an embodiment of the present invention, the Lever operated 3/2 valve 204 has a restricted (smaller) exit. The restricted exit of Lever operated 3/2 valve 204 avoids quick exhaust from the lift air spring RH side 210 and the suspension air spring LH side 212.
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
Description
100 Air suspension and axle lift control system, system
104 Suspension air spring RH side
106 Air connection pipe-1
108 Suspension air spring LH side
110 Air connection pipe-2
112 Spring loaded 3/2 sliding float valve
113 Air connection pipe-3
114 Air tank
115 Solenoid operated 5/2 control valve with hysteresis
116 Cylindrical valve housing
118 float
200 Pressure operated 3/2 valve
202 3/2 Sliding float valve
204 Lever operated 3/2 valve
206 Solenoid operated 5/2 control valve with hysteresis
208 Pressure limiting valve (PLV)
210 Lift air spring RH side
212 Lift air spring LH side
214 Air connection pipe-4
216 Air connection pipe-5
217 Air connection pipe-6
218 Relay valve
220 One way flow control valve

We claim:
1. An air-suspension and axle-lift control system for a vehicle having a vehicle body
and one or more axles supporting the vehicle body, the system comprising:
a suspension air spring RH side provided on a first side of the axle between the axle and the vehicle body, the suspension air spring RH side being configured to contain pressurized air;
a air connection pipe-1 having a first end portion and a second end portion, the first end portion of the air connection pipe-1 being connected to the suspension air spring RH side for communicating pressurized air to and from the suspension air spring RH side,
a suspension air spring LH side provided on a second side of the axle between the axle and the vehicle body, the suspension air spring LH side being configured to contain pressurized air;
a air connection pipe-2 having a first end portion and a second end portion, the first end portion of the air connection pipe-2 being connected to the suspension air spring LH side for communicating pressurized air to and from the suspension air spring LH side;
characterized in that,
an spring loaded 3/2 sliding float valve connected to the second end portion of the air connection pipe-1 and the second end portion of the air connection pipe-2 such that the spring loaded 3/2 sliding float valve selectively allows exchange of pressurized air between the suspension air spring RH side and the suspension air spring LH side.
2. The air suspension and axle lift control system for an vehicle as claimed in claim
1, wherein the spring loaded 3/2 sliding float valve restricts exchange of pressurized air
between the air connection pipe-1 and the air connection pipe-2 when there is a
predetermined threshold pressure difference between the suspension air spring RH side
and the suspension air spring LH side.

3. The air suspension and axle lift control system for a vehicle as claimed in claim 2, wherein the predetermined threshold pressure difference between the suspension air spring RH side and the suspension air spring LH side is more than 2±0.5 bar.
4. The air suspension and axle lift control system for a vehicle as claimed in claim 1, wherein the anti-roll comprises,
a cylindrical valve housing connected to a main air line, the cylindrical valve housing having opposite ends fluidically connected to the second end portion of the air connection pipe-1 and the second end portion of the air connection pipe-2 respectively, and
a float positioned within the cylindrical valve housing, the float allows equal distribution of air from the main air line to each of the air connection pipe-1 and the air connection pipe-2 through the cylindrical valve housing.
5. The air suspension and axle lift control system for an vehicle as claimed in claim 4, wherein the float is spring biased to come to a central position when the pressure difference between the suspension air spring RH side and the suspension air spring LH side is less than a predetermined threshold.
6. The air suspension and axle lift control system for an vehicle as claimed in claim 4, wherein the float is configured to slide towards an end of the cylindrical valve housing against the spring, to stop flow of pressurized air therethrough.
7. The air suspension and axle lift control system for an vehicle as claimed in claim 4 further comprising,
a pressure operated 3/2 valve disposed on the main air line and is fluidically connected to the spring loaded 3/2 sliding float valve, and
a 3/2 Sliding float valve fluidically connected to the pressure operated 3/2 valve, the 3/2 Sliding float valve configured to give a signal to the pressure operated 3/2 valve to initiate supply of pressurized air from the main air line to the suspension air spring RH

side and the suspension air spring LH side, through the spring loaded 3/2 sliding float valve.
8. The air suspension and axle lift control system for a vehicle as claimed in claim 1, wherein the double check valve gives no pressure signal to the pressure operated 3/2 valve pilot port when vehicle is unloaded and ignition is turned-off.
9. An air suspension and axle lift control system of a vehicle having a vehicle body and one or more axles, the system comprising:
a lift air spring RH side provided on a first side of the axle between the axle and the vehicle body, the lift air spring RH side being configured contract and expand to lift the axle of the vehicle;
a lift air spring LH side provided on a second side of the axle between the axle and the vehicle body, the lift air spring LH side being configured to contract and expand to lift the axle of the vehicle;
an air connection pipe-4 connected to the suspension air spring RH side for communicating pressurized air to and from the lift air spring RH side;
an air connection pipe-5 connected to the suspension air spring LH side for communicating pressurized air to and from the suspension air spring LH side;
characterized in that
a relay valve associated with the air connection pipe-4 and the air connection pipe-5 for regulating entry and exhaust of pressurized air from the lift air spring RH side and the lift air spring LH sides; and
a one way flow control valve associated with the relay valve to allow passage of pressurized air to the lift air spring RH side and the lift air spring LH sides and restrict the passage of pressurized air from the lift air spring RH side and the suspension air spring LH sides.

10. The air suspension and axle lift control system for an vehicle as claimed in claim 9, wherein the restricted passage of pressurized air from the lift air spring RH side and the lift air spring LH sides causing slow exhaust from the lift air spring RH side and the lift air spring LH sides.