BOGIE AIR SUSPENSION SYSTEM Field of invention

The present invention relates to suspension system for multi axle vehicles, and more particularly to bogie air spring suspension system having air springs integrated with the bogie leaf spring suspension system.

Background of invention

Suspension systems have been designed and developed for supporting the weight of the trucks and tractors which are operated in off-road sites. Various suspension systems include non-reactive suspension such as bell crank ended suspension, reactive suspension such as slipper ended suspension and bogie spring suspension such as inverted leaf spring suspension. The suspension systems are used in tandem axles of trucks and tractors. The Non-reactive suspension and reactive suspension are used in trucks, especially in haulage application for many decades. The construction of the bogie spring suspension is usual and simple which is compared to non-reactive suspension and reactive suspension. The non reactive suspension system has less mass compared to other two suspension systems. However the bogie spring suspension is more preferable for off-road and overload applications.

FIG. 1 shows the conventional bogie spring suspension (1) in particular, bogie spring suspension for the vehicles having tandem rear axles having two rear axles. The suspension consists of bogie brackets (2), leaf springs (3), spring seats (4), V rod (5), lower control arms (6), U bolts (7), and trunnions (8). The bogie brackets (2) are attached with bottom side of the cross member (not shown) connected in between the chassis side frames. The trunnions (8) are pivotally connected with the bogie brackets (2) and the center portion of the leaf springs (3) is clamped with the trunnion (8) using the U bolts (7). Both the ends of leaf springs (3) are placed on the spring seats (4) which are attached to the rear axles (10) by conventional means.

The conventional bogie spring suspension (1) is usually used in the vehicles operated in off-road sites. In these vehicles, many failures are observed in the conventional bogie spring suspension (1). Especially, many cracks are observed in the chassis frame (9) and cross member where the bogie brackets (2) are attached. It is mainly due to entire load that acts on the rear axles (10) is transferred to the chassis frame (9) through the two pivot pins of the trunnions (8). That is, the entire load leads a high stress concentration in a small portion, bogie bracket's attached area of the chassis frame (9) and cross member of the vehicle. Moreover, the lower control arms (6) are subjected to a severe load in braking and articulation conditions. During braking, the lower control arms (6) are subjected to an enormous compression load, thus they are failed by buckle very often In addition, and the lower control arms (6) are subjected to a severe twisting load, torsional load during vehicle's articulation condition.

Therefore, crimping provided in the lower control arms (6) is failed frequently. Similarly, V rod (5) is also failed in a frequent manner. In the V rod (5), a pair of circlips provided to hold the rubber bushing and bar pin. The circlips are failed due to a sever articulation load. Especially, the circlips pop out from the located position, locked position, thus restricting the bogie spring suspension system (1) to perform the required suspension. The pivot pin of the trunnion is acted as fulcrum in the conventional bogie spring suspension (1). The load which acts on the rear axles (10) is held by the two pivot pins only. Therefore, aluminum bronze bushing provided in the trunnion (8) is worn-out frequently due to repeated high impact loads. Various mechanisms and methods are employed in the vehicle for solving above said problems in the bogie spring suspension system (1). Despite the many designs, only a few mechanisms are commercially viable due to important factors such as easy manufacturability, simple function, low maintenance, high reliability, easy assembly and serviceability. Further the conventional bogie spring suspensions are quite expensive and very difficult to solve the issues. Therefore, it is desirable to provide a reliable bogie spring suspension system with wide load distribution to the chassis frame for the trucks and tractors having tandem rear axles.

Object of the invention:

The main object of the present invention is to provide a simple and cost effective bogie air suspension system which withstands dynamic loads and shocks in the vehicle. Another object of the present invention is to provide a bogie air suspension system, which distributes load to chassis frame widely to minimize frame and cross member failures. Further object of the invention is to equally distribute the load acting on the chassis frame through combination of air spring and leaf spring suspension mechanism. Another object of the present invention is to provide a bogie air suspension system, without much change in the conventional bogie spring suspension system and having adapted to replace the existing the suspension systems. Yet another object of the present invention is to provide a bogie air suspension system, which is highly reliable and retrofittably mountable in the vehicle. Further object of the present invention is to provide a bogie air suspension system, which improves ride and handling of the vehicle. Still further object of the invention is to provide a bogie suspension system having mechanisms which is commercially viable and easy manufacture. Further object of the invention is to provide as suspension system which has simple function, low maintenance, high reliability, easy assembly and serviceability.

Summary of the invention

The present invention which achieves the objectives relates to a bogie air spring suspension system having a pair of tandem rear axles assembled with the chassis of the vehicle, and a pair of leaf springs pivotally mounted to the chassis through hanger brackets and turnnion pivot pins assemblies. The hanger brackets are rigidly attached to a vehicle chassis frame with inside of the chassis frame. The hanger brackets attached to the chassis frame and a cross member is attached in between the hanger brackets. The center of leaf spring is clamped with turnnion which is pivotally connected with the hanger bracket and its ends are placed on spring seat assemblies. A pair of V rods is connected in between the hanger bracket and axles and four lower control arms are connected in between the hanger brackets and axles.

Four air springs are respectively interposed vertically between top air spring mounting brackets attached with the chassis frame and lower air spring mounting brackets welded with the axle. A pneumatic control system supplies compressed air to the air springs to expand the air springs, and thereby enabling sharing the load acting on the rear axle to the leaf springs and air springs. The air springs are inflated and maintained with a required pressure and a constant ride height by the pneumatic control system. The air springs are integrated with the bogie leaf spring suspension system, and the load experiences in the tandem axles are distributed widely to the chassis frame. As the air springs share the load, the load is widely distributed to the chassis frame, this bogie suspension improves the life of cross member, bogie bracket, chassis frame, V rod, lower cross member and the turnnion bushings.

The leaf spring is a parabolic type which is clamped with the turnnion using said U bolts. The spring seats are securely connected with the axles by mean of a plurality of fasteners. The spring seat assemblies clamped with the axles and a pair of cotter pins inserted in the holes provided in the pivot pin and hanger bogie bracket. U bolts are clamped with the leaf springs and the air springs securely connected between the top air springs mounting brackets and bottom air springs mounting brackets attached to the axles. The lower control arm is a rectangular solid section rod and has bar pin type rubber bushings in both the ends. A pair of metal disc covers with fasteners is used to hold all the rubber bushings provided in the lower control arms. As the air springs share a partial the load of the tandem rear axles, the load is widely distributed to the chassis frame and load experiences in the pivot pin is also reduced substantially. Further the life of the pivot pins, radial bushes and spring seats are considerably extended. In addition, it minimizes the failure rate of the cross member and chassis frame in the vehicle.

Brief description of the drawings

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.l shows an assembled model of a bogie suspension system fitted in a chassis frame and tandem axles of a multi axle vehicle, in accordance to the prior art.

FIG.2 shows an assembled model of a bogie air suspension system fitted in a chassis frame of a multi axle vehicle, in accordance with an exemplary embodiment of the present invention.

FIG.3 illustrates the details of the bogie air suspension system, in accordance with an exemplary embodiment of the present invention.

FIG.4 illustrates the hanger bracket for the bogie air suspension system, in accordance with the embodiment of the present invention.

FIG.5 illustrates the cross member for the bogie air suspension system, in accordance with an exemplary embodiment of the present invention.

FIG. 6 illustrates the center C member and side L member of the cross member, in accordance with an exemplary embodiment of the present invention.

FIG. 7 illustrates an assembled model of a V rod for the bogie air suspension system, in accordance with an exemplary embodiment of the present invention.

FIG. 8 illustrates the spring turnnion for the bogie air suspension system, in accordance with the embodiment of the present invention.

FIG.9 illustrates the spring turnnion bracket for the suspension system, in accordance with the embodiment of the present invention.

FIG. 10 illustrates the leaf springs for the suspension system, in accordance with the embodiment of the present invention.

FIG. 11 illustrates lower control arm for the suspension system, in accordance with an exemplary embodiment of the present invention.

FIG. 12 illustrates the spring seats for the suspension system, in accordance with the embodiment of the present invention.

FIG. 13 illustrates the top air springs bracket for the suspension system, in accordance with the embodiment of the present invention;

FIG. 14 illustrates the bottom air springs bracket for the bogie air suspension system, in accordance with the embodiment of the present invention;

FIG. 15 illustrates U bolt assembly for the bogie air suspension system, in accordance with an exemplary embodiment of the present invention.

FIG. 16 illustrates frame flitch for the bogie air suspension system, in accordance with an exemplary embodiment of the present invention.

Detailed description of the invention:

The present invention relates to suspension system for multi axle vehicles, and more particularly to bogie air spring suspension system having air springs integrated with the bogie leaf spring suspension system. The air spring suspension interposed between the chassis frame and the tandem rear axles, such that the load acting on the rear axle is shared to the leaf springs and air springs. The leaf springs are pivotally mounted to hanger brackets through turnnion pivot pins assemblies and pair of V rods are respectively connected in between the hanger bracket and axles and four lower control arms are connected in between the hanger brackets and axles. A set of air springs are interposed vertically between top air spring mounting brackets attached with the chassis frame and lower air spring mounting brackets welded with the axle.

FIG. 2 & 3 shows an assembled view of a bogie air suspension system fitted in a chassis frame of a multi axle vehicle, in accordance with an exemplary embodiment of the present invention. The bogie air suspension system (11) is a simple parallelogram type inverted leaf spring with air spring mechanism. The bogie air suspension system (11) consists of a pair of set of leaf springs (12) and air springs (21) which are attached to the vehicle's chassis frame (23) and vehicle's rear axles (24). The suspension system (11) has a cross member (13), a pair of hanger brackets (14) and a pair of turnnion (15). A set of leaf spring seats (18) is provided with the tandem rear axles. Both the ends of the leaf springs (12) are placed on the leaf spring seats (18), which are securely connected with the rear axles (24). The cross member (13) is connected in between the hanger brackets (14) which are attached with inside of the chassis frame (23).

A pair of V rods (16) and four lower control arms (17) is connected with the leaf spring such that one end of the V rod (16) is pivotally connected with the hanger bracket (14) and other end is pivotally connected with the rear axles (24) of the vehicle. Similarly, one end of the lower control arm (17) is connected to the hanger bracket (14) and other end is pivotally connected to the rear axle (24). The V rod (16) and lower control arm (17) make a parallelogram and ensure a vertical movement of the axles (24) without rolling when the vehicle is operated in undulated roads. And the angle between propeller shaft of the vehicle and the rear axle (24) is maintained a required constant angle. It is mainly to minimize the pinion gear failure of differential gear box which is used in the rear axle (24).

The leaf springs (12) are attached to the chassis frame (23) through the hanger bracket (14) which is securely attached with inside of the chassis frame (23) by usual fasteners such as bolts and nuts. The cross member (13) and the turnnion (15) are pivotally connected with the hanger bracket (14) and the leaf springs (12) are clamped with the turnnion (15) through U bolts (22). The hanger brackets (14) are made of conventional casting process, as it holds the rear axles (24) loads of the vehicle. It has multiples of holes (27) which are used to connect the hanger brackets (14) to the chassis. In order to distribute the load which acts on the pivot pins (25), four air springs (21) are used. The air springs (21) are interposed between the top air springs mounting bracket (19) and bottom air springs bracket (20) which are attached to the chassis frame (23) and rear axles (24), respectively. The air springs (21) are inflated and maintained a required pressure and a constant ride height by the pneumatic control system. As the air springs (21) are integrated with the bogie leaf spring suspension system, the load experiences in the tandem axles are distributed widely to the chassis frame.

This bogie air suspension system (11) is constructed for the vehicle having tandem rear axles (24), such that the load which acts on the rear side of the vehicle is shared to both the tandem rear axles (24). FIG.4 illustrates the hanger bracket for the bogie air suspension system, in accordance with the embodiment of the present invention. A pivot hole (28) is provided in the hanger bracket (14) which is provided for inserting the pivot pin (25) of the trunnion (15) of the bogie air suspension system (11). In order to connect the V rod (16) to the hanger bracket (14), a pair of internal threaded holes (29) is provided at the upper end. Similarly, two holes (30) are provided at the lower end of the hanger bracket (14) which is used to connect the lower control arms (20) by conventional bolts and nuts. The V rod (16) and lower control arm (20) jointly ensure a parallelogram linkage mechanism. It ensures the rear axles (24) in vertical motion without much twist (rolling) when the bogie air suspension system (11) experiences undulated road.

FIG.5 illustrates the cross member for the bogie air suspension system, in accordance with an exemplary embodiment of the present invention. The cross member (13) consists of a pair of center C shape members (31) and a pair of side L shapes members (32). FIG.6 illustrates the center C member and side L member of the cross member, in accordance with an exemplary embodiment of the present invention. The center C shape members (31) and side L shape member (32) are connected by means of conventional rivet joints. FIG.7 illustrates an assembled model of a V rod for the bogie air suspension system, in accordance with an exemplary embodiment of the present invention. The V rod (16) consists of a pair of cylindrical tubular rods (33) and a pair of top cast heads (34), a lower cast head (35), three rubber bushings (36), three bar pins (37) and six metal discs covers (38). One end of the cylindrical tubular rods (33) is crimped with the top cast head (34) and other end is crimped with the lower cast head (35) to make V shape. The rubber bushing (36) and bar pins (37) are housed in both the top cast heads (34) and lower cast head (35).

In order to hold the rubber bushing (36) with both the top cast heads (34) and lower cast head (35), a pair of metal disc covers (38) are bolted within; so that rubber bushing (36) and bar pins (37) are rigidly connected with the cast heads (34,35). FIG.8 illustrates the spring turnnion for the bogie air suspension system, in accordance with the embodiment of the present invention. The turnnion (15), consists of a turnnion bracket (39), a pivot pin (25), a pair of radial bushes (40), a pair of thrust bushes (41), a pair of lock plates (i.e., stopper) (42) and a cover plate (43). FIG.9 illustrates the spring turnnion bracket for the suspension system, in accordance with the embodiment of the present invention. The turnnion bracket (39) has a center hole (44), in which the radial bushes (41) are tightly inserted. In addition, the turnnion bracket (39) has a rectangular slot (45) with four holes (46), where the leaf springs are placed and clamped using U bolts (22). The pivot pin (25) is made of high strength steel and attached to the hanger brackets (14). In order to hold the turnnion (15) rigidly with the hanger brackets (14), a cylindrical cotter pin is inserted into the hole (47) provided in the pivot pin (25) of the turnnion (15) and the hanger bracket (14). The cotter pin (not shown) prevents the rotational movement and translation movement of the pivot pin (25).

Therefore, the pivot pin (25) acts as a fulcrum; about which the leaf springs (12) are rotated when the suspension system experiences pot holes and bumps. A pair of side thrust bushes (41) and a pair of lock plates (42), are provided at both the ends of the pivot pin (25). The lock plates (42) are clamed with the pivot pin (25) by conventional screws. The side thrust bushes (41) and the lock plates (42) are mainly used for clamping the turnnion (15) pivotally the hanger bracket (14). The side thrust bushes (41) are provided especially for reducing friction between the trunnion (15) and the lock plates (42). The lock plates (42) prevent the translation movement of the turnnion (15) (i.e., from the pivot pin (25). A cover plate (43) is attached with the turnnion (15) by conventional screws. FIG. 10 illustrates the leaf springs for the suspension system, in accordance with the embodiment of the present invention. The leaf springs (12) consists of variable thickness of leafs which are laminated (i.e., placed one over another). The leaf spring (12) is made of conventional spring material. The leaf springs (12) are properly designed such that it has two stage stiffness curves. It assists for maintaining a good ride quality in the unladen condition and a good load carrying capacity in laden conditions.

FIG. 11 illustrates lower control arm for the suspension system, in accordance with an exemplary embodiment of the present invention. The lower control arm (20) consists of a solid rectangular section arm (48); a pair of rubber bushings (36), a pair of bar pins (37) and four metal discs covers (38). In general, control rod's bend and rod's crimping failure are observed in the lower control arms (20). These are normally due to sever braking load and cornering load, respectively. In order to prevent the common failures, the lower control arm (20) is made of solid rectangle cross section (48), so that, the both the failures observed in the lower control arms (20) are minimized. The rubber bushing (36) is bonded with the bar pin (37). The lower control arm (20) has two holes (49) at both ends, in which the rubber bushing (36) and the bar pin (37) are inserted tightly. The bar pin (37) has two holes (50) which are provided for connecting the lower control arm (20) with the hanger bracket (14) and the rear axles (24) by conventional bolts and nuts. FIG. 12 illustrates the spring seats for the suspension system, in accordance with the embodiment of the present invention.

The spring seat (18) consists of a spring seat bracket (51), a spring seat wear pad (52), a side wear pad (53) and a spring limiting bracket (54). The spring seat bracket (51) is made of conventional casting. It is attached with the rear axle (24) by conventional mechanical means. The spring seat wear pads (52) are subjected to enormous load. In addition, the leaf spring (12) slides over the spring seat wear pads (52) when the bogie air suspension (11) experiences undulated roads. It leads a rubbing action and wear in the leaf springs (12) and spring seat wear pad (52). In order to minimize the wear in the spring seat wear pad (52), it is made of austenite ductile iron (ADI) material. Similarly, the side wear pad (53) is also made of austenite ductile iron (ADI) material. The spring seat wear pad (52) and side wear pad (53) are attached with the spring seat bracket (51) by conventional screws. The spring limiting bracket (54) is made of casting or ADI which is securely attached with the spring seat bracket (54) by conventional mechanical means. The spring limiting bracket (54) limits the downward movement (i.e., rebound) of the rear axle (24) when the rear axle experiences a pot hole.

FIG. 13 illustrates the top air springs bracket for the suspension system, in accordance with the embodiment of the present invention. The top air springs bracket (19) consists of lower flat plate (55) and U shaped plates (56).The lower flat plate (55) is welded with the U shaped plate (56). Two holes are provided in the U shape plate. The holes are used to connect the top air springs bracket (19) with the chassis frame (23). Similarly, lower flat plate (20) has two holes which are used to connect with the air springs (21) by mechanical means. FIG. 14 illustrates the bottom air springs bracket for the bogie air suspension system, in accordance with the embodiment of the present invention. The air springs (21) are securely attached in between the top air springs bracket (19) and the bottom air springs bracket (20). The bottom air springs bracket (20) is illustrated in FIG. 14. It is made of steel and welded with the rear axle (24). FIG. 15 illustrates U bolt assembly for the bogie air suspension system, in accordance with an exemplary embodiment of the present invention. The U bolts assembly consists of a pairs of U bolts (22) and a clamp plate (57). The clamp plate (57) is a flat plate, and has four holes where the U bolts are inserted and tightened the leaf springs (12) with trunnion bracket (39).

FIG. 16 illustrates frame flitch for the bogie air suspension system, in accordance with an exemplary embodiment of the present invention. The frame flitch (26) is made of steel plate. A pair of frame flitchs (26) is placed in between the hanger brackets (14) and the chassis frame (23). It reduce stress occurs in the chassis frame (23) where the hanger bracket (14) is attached. The bogie air spring suspension (11) is assembled with the vehicle chassis frame (23), and compressed air is supplied to the air springs (21) using the pneumatic control system. The pneumatic control system (not shown) maintains a required constant height and a constant pressure in the air springs (21). When compressed air supplied to the air springs, the air springs expands, and thereby sharing the load acting on the rear axle to the leaf springs and air springs. As the air springs (21) share a partial load of the tandem rear axles (24), the load is widely distributed to the chassis frame (23) and load experiences in the pivot pin (25) is also reduced substantially, and thus the life of the pivot pins (25), radial bushes (40) and spring seats (18) are considerably extended. In addition this minimizes the cross member (13) and chassis frame (23) failure.

The suspension system according to the present invention has integration of four air springs with the conventional bogie spring suspension system, and the air springs (21) are positioned such that to avoid accordion effect, i.e., angular expansion of the air springs. Precisely, the angle should not exceed 30 degree due to restriction in the air springs construction. Further in the present invention is the rectangle solid rod design of the lower control arm (17). This rectangle solid rod design of the lower control arm has high strength in bending as well as buckling. The V rod (16) has a pair of metal disc covers (38) used to hold the rubber bushing (36). The metal disc covers (38) are screwed with the top cast heads (34) and lower cast head (35). This prevents the failure of pop out of rubber bushing (36) when the bogie air spring suspension system (11) experiences a high articulation load. In order to reduce failures in the chassis frame (23), hanger bracket (14) and cross member (13), the present hanger bracket (14) is carefully designed such that it is attached with inside of the chassis frame (13); thereby accessibility of the clamping bolts of hanger bracket (14) and U bolts (22) is improved compared to the conventional bogie spring suspension (1).

The suspension system according to the present invention provides a simple and cost effective bogie air suspension system which withstands dynamic loads and shocks. This system can be adopted without much change in the conventional bogie spring suspension system and replace the existing the suspension systems. This suspension system equally distributes the load acting on the chassis frame through combination of air spring and leaf spring suspension mechanism, and widely minimizes frame and cross member failures. The suspension system of present invention is highly reliable and retrofittably mountable in the vehicle, and improves ride and handling of the vehicle. This improved suspension system has simple function, low maintenance, high reliability, easy assembly and serviceability. The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous 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.

We claim:

1. A bogie air suspension system for an automotive vehicle, said system comprises, a pair of tandem rear axles (24) assembled with the chassis frame (23) of vehicle, and a pair of leaf springs (12) pivotally mounted to said chassis frame (23) through a set of hanger brackets (14) and turnnion pivot pins (15); a set of air springs (21) interposed between top air spring mounting brackets (19) attached with said chassis frame (23) and lower air spring mounting brackets (20) attached with said axles (24), wherein compressed air is supplied to said air springs (21) to expand said the air springs (21), such that the load acting on the rear axles (24) is shared to the leaf springs (12) and the air springs (21).

2. The bogie suspension system as claimed in claim 1, wherein a pair of V rods (16) is connected in between the hanger bracket (14) and the axles (24) and lower control arms (17) are connected in between the hanger brackets (14) and axles (24).

3. The bogie suspension system as claimed in claim 1, wherein said air springs (21) are inflated and maintained with a required pressure and a constant ride height by a pneumatic control system.

4. The bogie suspension system as claimed in claim 1, wherein the air springs (21) are integrated with the bogie leaf spring suspension system, and the load in the tandem axles (24) are distributed to the chassis frame (23).

5. The bogie suspension system as claimed in claim 1, wherein the hanger brackets (14) are rigidly attached to a vehicle chassis frame (23) with inside of the chassis frame (23) and a cross member (13) is attached in between the hanger brackets (14).

6. The bogie suspension system as claimed in claim 1, wherein the top air springs mounting brackets (19) are attached to the chassis frame (23) and the bottom air springs mounting brackets (20) welded with the axles (24).

7. The bogie suspension system as claimed in claim 1, wherein spring seat assemblies (18) are clamped with the axles (24) and a pair of cotter pins is inserted in the holes provided in the pivot pin and hanger bracket (14).

8. The bogie suspension system as claimed in claim 1, wherein said lower control arm (17) is a rectangular solid section rod and said arm (17) has bar pin type rubber bushings at its ends which are held by a pair of metal discs.

9. The bogie suspension system as claimed in claim 1, wherein said V rod (16) has bar pin type rubber bushings at its all ends.

10. The bogie suspension system as claimed in claim 1, wherein said turnnion (15) is pivotally connected with the hanger brackets (14).

11. The bogie suspension system as claimed in claim 1, wherein said leaf spring (12) is a parabolic type spring and is clamped with turnnion (15) using said U bolts (22).