IT201800006508A1 - SUSPENSION ARRANGEMENT FOR A VEHICLE CAB - Google Patents

Description

DESCRIPTION

of the patent for industrial invention entitled:

"SUSPENSION ARRANGEMENT FOR A VEHICLE CAB"

TECHNICAL FIELD

The present invention relates to a suspension arrangement, in particular a suspension arrangement for the cab of a vehicle, especially an off-road vehicle such as an agricultural vehicle.

BACKGROUND OF THE INVENTION

Rolling motion of a vehicle's cab relative to its chassis is an annoying movement for the comfort of the vehicle driver. This discomfort is aggravated when the vehicle is an off-road vehicle, such as an agricultural vehicle.

To reduce such troublesome movement, it is known to provide a cab suspension arrangement for decoupling the cab from the frame so as to damp the rolling motion. However, since it is not possible to reduce the excitation frequencies of the roll, the solutions known in the art allow to couple the rolling motion of the cab to the movement of the frame. Thus, no amplification is possible.

By way of example, a known suspension arrangement for an off-road vehicle cabin is described in patent no. US7950727 B2.

That document discloses a spring suspension arrangement which suspends the driver's cab of a heavy vehicle in relation to the vehicle frame. The suspension arrangement includes a pantograph mechanism which is used to reduce the freedom of movement of the cabin by rigidly connecting the vehicle cabin to the vehicle frame. The pantograph mechanism comprises two rigid bars which are hinged at their ends to the cab and frame respectively and which are also hinged together in the central position between those ends.

Another example of a known "pantograph mechanism" aimed at reducing the rolling motion is described in patent no. US2007 / 0056787 A1.

However, such pantograph mechanisms are not capable of significantly reducing the roll motion and must be further coupled to shock absorber spring arrangements in order to effectively reduce the roll motion of the cab.

Therefore, the need is felt to improve the known suspension arrangements to further reduce the cabin roll motion in an optimized and economical way. One of the objectives of the present invention is to satisfy the aforementioned needs.

SUMMARY OF THE INVENTION

The aforementioned objective is achieved through a suspension arrangement as claimed in the series of attached claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention, a preferred embodiment is described below, by way of non-limiting example, with reference to the attached drawings in which:

Figure 1 is a partial sectional view of the rear portion of a tractor, with parts removed for reasons of clarity, comprising a suspension arrangement according to the present invention;

Figure 2 is an enlarged front view of the suspension arrangement according to the present invention in a first operating mode;

Figure 3 is an enlarged front view of the suspension arrangement of figure 2 in a second operating mode; And

Figure 4 is an enlarged perspective view of an element of the suspension arrangement according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Below, by way of example, the invention will be described applied to a tractor cab, however it is understood that the invention can be applied to any type of heavy vehicle. Furthermore, the terms "first", "second" etc. are used merely to improve the clarity of this description.

Figure 1 describes a tractor 1 which comprises a cab 2 supported in a suspended way through a frame 3, which, as known, is connected to traction means 4, for example wheels 5 supported by a transmission shaft 6.

The cab 2 is suspended relative to the frame 3 thanks to a suspension arrangement 10 which connects the cab 2 to the frame 3 as described below.

The suspension arrangement 10 (see Figures 1 and 2) comprises a first connection 11 comprising a first end 11 'connected by a first connection 12 to the frame 3 and a second end 11' 'connected by a second connection 13 to the cabin 2 and a second connection 14 comprising a first end 14 'connected by a third connection 15 to the frame 3 and a second end 14' 'connected by a fourth connection 16 to the cabin 2.

Preferably the first and second connections 11, 14 are structural bars, for example Panhard bars.

The first and second connections 11 and 14 are also connected to each other by a fifth connection 17 which is positioned in an intermediate position between the ends 11 ', 11' 'and 14', 14 '', preferably in a central position with respect to the latter.

In particular, at least the second and fourth connections 13, 16 are connections with variable stiffness; conversely, the first, third and fifth connections 12, 15 and 17 can be rigid connections.

The variable stiffness connections have a stiffness that is different in the direction corresponding to the longitudinal axis A of the connections 11, 14 compared to the remaining part of the connection. In particular, the stiffness in the direction of the longitudinal axis of the connections 11, 14 is lower than the stiffness of the remaining part of the connection.

Advantageously, this different stiffness in the direction of the longitudinal axis of the connections 11, 14 can be variable from a minimum value to a maximum value based on a preset characteristic; the maximum value is, according to the above, lower than the stiffness of the remaining part of the connection.

Since the connections 11, 14 change their position due to the movements of the car 2 / frame 3, their longitudinal axis A will change direction with respect to the second and fourth connections 13, 16. Therefore, the variable stiffness changes in an area comprised in an angle equal to the angular movement of the longitudinal axis A of the connections 11, 14 around the center of the respective connections 13, 16.

According to the above, the vertical deflections of the cab are reduced to a minimum, i.e. the rolling motion is reduced to a minimum.

According to the described embodiment of the present invention, the aforementioned connections can be made as hinges; therefore, according to the above, the second and fourth connections 13, 16 are hinges with variable rigidity and the first, third and fifth connections 12, 15 and 17 are rigid hinges.

The rigid hinges can be made as known in the art, for example the first and third connections 12 and 15 can comprise a pin 12a, 15a supported by the frame 3 housed sliding so as to rotate freely in a housing 12b, 15b supported by the connections 11 , 14. Preferably the housing 12b, 15b is made in a single piece with the ends 11 ', 14'. The fifth connection 17 can be made thanks to a pin 17a slidably housed in such a way as to rotate freely in the coaxial openings 17b made in the respective connection 11, 12. The openings 17b are made with a diameter greater than the diameter of the pin 17a so as to realize a prismatic pin / slot joint between links 11, 14.

The variable stiffness hinges can be made as described below, with reference to Figure 4. This hinge in question can comprise an external rigid layer 20 supported by the respective ends 11 '', 14 '' of the connections 11, 14, preferably made as a single piece with the latter, and a rigid internal layer 21 configured to cooperate in a sliding manner with a pin 13a, 16a supported by the cabin 2.

The hinge further comprises an elastic layer 22 which connects the outer layer and the inner layer 20, 21; this elastic layer can be made of rubber or of any suitable elastic polymer, of the expanded or compact type.

According to the embodiment described, the elastic layer 22 can comprise at least one vacuum area 24; preferably it can comprise two void areas 24 opposite to each other with respect to the X axis, each of which extending circumferentially around the Z axis of the hinge symmetrically with respect to the Y axis of the latter. In particular, at least one vacuum area 24 extends by an angle equal to the angular movement of the longitudinal axis A of the connections 11, 14 around the center of the hinge.

The vacuum area 24 can be formed as through holes in the elastic layer 22; preferably the void areas 24 are larger, ie the hinge is softer, at their ends with respect to the center.

This difference in size is achieved since the position of the connections 11, 14 is usually included in a small angular position and only for considerable displacements of the cab 2 with respect to the frame 3 the longitudinal axis A of each connection 11, 14 could vary considerably the its position with respect to the hinges 12, 16. In this way a variable stiffness is obtained which constantly increases with the relative displacement of the cabin 2 with respect to the frame 3.

The operation of the suspension arrangement 10 as described above is as follows.

In a starting condition (figure 2), i.e. in a nominal zero position in which the connections 11, 14 are symmetrically positioned with respect to each other around the fifth connection 17, the variable rigidity connections 13 and 16 support the car 2 above the frame 3 without substantial deformation as the minimum stiffness in the vertical direction of such connections is designed to support the predetermined weight of the cab 2.

When the frame 3 moves with respect to the cabin 2, or vice versa (figure 3), the connections 11 and 14 can move so that their second ends 11 '', 14 '' follow a circumferential path having the center respectively in the first and in the third connection 12, 15. However, the constraint due to the second and fourth connections 13, 16, does not allow the second ends 11 ', 14' to follow the aforementioned circumferential path, and therefore to the variable stiffness of the second and fourth connections 13, 16 to dampen the motion, thus reducing the roll transmission to the cabin, or by coupling the cabin body to the rolling motion of the chassis body. Since the resistance of the second and fourth connection 13, 16 in the vertical direction is greater than the resistance in the direction corresponding to the longitudinal axis of the connections 11, 14, the rolling motion of the cabin 2 is limited.

In the described embodiments of variable stiffness connections including rubber hinges, an elastic layer 22 will absorb the deformation due to the movement of the links 11, 14. The elastic layer will provide an increase in stiffness as long as it is compressed by the movement of the links 11, 14. The optional presence of the vacuum zone 24 increases the deformability of the elastic layer 22.

Based on the above, the advantages of a suspension arrangement 10 according to the invention are evident. Thanks to the variable stiffness at least of the upper connections 13, 16 of the connections 11, 14, the rolling motion of the cab 2 is reduced; furthermore, the lateral movement of the cab 2 with respect to the frame 3 is further reduced.

The use of an elastic layer 22 made of rubber or any equivalent material guarantees a connection with variable rigidity that is simple to manufacture, assemble and therefore economical.

The presence of a vacuum area 24 increases the deformability of the elastic layer 22, thus providing soft hinges with variable rigidity.

Furthermore, a compression or distension of the cab suspension, due to the mechanical constraints of the illustrated mechanism, requires a deformation of the flexible joint. The greater the vertical travel of the cab suspension, the greater the deformation inside the flexible bushing. This provides, as already mentioned, a sort of stiffness with progressive increase and makes reaching the end of travel of the cab suspension more fluid.

By limiting the deformation after a certain degree of displacement of the flexible bushing, an adequate stroke end characteristic can be obtained. This advantage also helps to designate the cab suspension so that it complies with the restraint devices necessary for ROPS approval.

It is clear that changes may be made to the described suspension arrangement, provided they do not go beyond the scope defined by the claims.

In light of the foregoing description, it is obvious that all connections 12, 13, 15 and 16 can be made as connections with variable stiffness. In that case, 17 should be made as a rigid connection.

Furthermore, the connections with variable stiffness can be made in various ways.

The elastic joints can be made in various ways, for example by means of an elastic joint 22 made of rubber having a different density along the X and Y axes, so as to obtain a variable and distinct stiffness. Furthermore, they can be made by hydraulic means, such as a hydro-bush comprising rubber and oil.

Furthermore, the fifth connection 17 can be replaced by a cylindrical rigid connection and by having a flexible bushing also on the side of the frame.

Claims (15)

CLAIMS 1.- Suspension arrangement (10) for suspending a mass (2) of a heavy vehicle (1) with respect to the chassis (3) of the same, said suspension arrangement (10) comprising: • a first connection (11) comprising a first end (11 ') connectable through a first connection (12) to said frame (3) and a second end (11' ') connectable through a second connection (13) to said suspended mass (2); • a second connection (14) comprising a first end (14 ') connectable through a third connection (15) to said frame (3) and a second end (14' ') connectable through a fourth connection (16) to said suspended mass (2); said first and said second connection (11, 14) being further connected to each other through a fifth connection (17) which is located in an intermediate position constituted by said first and second ends (11 ', 11' '; 14 ', 14' ') of said first and second connections (11, 14), at least said second and fourth connections (13, 16) being connections with variable stiffness. 2.- Suspension arrangement according to Claim 1, wherein said first and second connections (11, 14) are Panhard bars. Suspension arrangement according to claims 1 or 2, wherein the fifth connection (17) is located in the middle of the length of said first and second connections (11, 14). Suspension arrangement according to any preceding claim, wherein said stiffness is variable in a direction about a longitudinal axis of at least one of said links (11, 14) Suspension arrangement according to any preceding claim, wherein said stiffness is variable in a direction substantially coaxial to a longitudinal axis of said links (11, 14). Suspension arrangement according to any one of claims 4 or 5, wherein said variable stiffness is less than the stiffness of the remaining portion of said connection. Suspension arrangement according to any one of the preceding claims, in which said connections (12, 13; 15, 16) are hinges. Suspension arrangement according to any one of the preceding claims, wherein said first and third connections are rigid hinges. Suspension arrangement according to claim 7, wherein each of said at least two variable stiffness hinges comprises an outer layer (20) carried by the respective links (11, 14) and an inner layer (21) configured to cooperate smoothly with a pin (13a, 16a) if carried by said cabin (2) and an elastic layer (22) which connects said outer and inner layers (20, 21), said elastic layer (22) having different stiffness properties in the axial directions and radial. Suspension arrangement according to claim 7, wherein said outer layer (20) is made in one piece with the respective connection (11, 14). Suspension arrangement according to claim 9 or 10, wherein said elastic layer (22) is made of rubber. Suspension arrangement according to any one of claims 9 to 11, wherein said elastic layer (22) comprises at least one vacuum zone (24). 13. Suspension arrangement according to claim 12, in which said at least one vacuum area (24) is a through hole in said elastic layer (22) and is positioned on the longitudinal axis of said connections (11, 14). Suspension arrangement according to claim 12 or 13, wherein said at least one vacuum zone (24) is a through hole in said elastic layer (22) and is positioned coaxially to the longitudinal axis of said connections (11, 14) . Suspension arrangement according to any one of claims 7 to 14, wherein said rigid hinges comprise a housing (12b, 15b) which is made as a single piece with said links (11, 14) and a pin (12a, 15a ) slidably housed in said housing (12b, 15b) and supported by said frame (3).