GB2185088A

GB2185088A - A suspension system for vehicles

Info

Publication number: GB2185088A
Application number: GB08700107A
Authority: GB
Inventors: Kazuo Chishima; Yoshiaki Kurihara
Original assignee: Mitsubishi Steel Mfg Co Ltd
Current assignee: Mitsubishi Steel Mfg Co Ltd
Priority date: 1986-01-07
Filing date: 1987-01-06
Publication date: 1987-07-08
Also published as: GB2185088B; JPH055683B2; JPS62160907A; DE3644803C2; DE3644803A1; GB8700107D0

Abstract

In a suspension system for vehicles utilizing leaf springs each comprising a number of leaves, the first leaf 1 of the leaf spring is arranged on the upper or lower surface of a hollow axle box 3, and a leaf group 2 consisting of the second and following leaves is received within the axle box. The first leaf 1 and axle box 3 are secured to the axle 6 by U-bolts 5. In this manner, the fastening forces applied to the leaf 1 and leaf group 2 can be independently predetermined. <IMAGE>

Description

SPECIFICATION A suspension system for vehicles Technical field The present invention relates to a suspension system for vehicles, and more particularly to a suspension system for vehicles in which leaf springs are utilized as main spring elements.

Background of the invention In a suspension system for vehicles ofthis type as conventionally used in the art each set of leafsprings comprises a number 1 leaf and a group of leaves consisting of the number 2 and following leaves all fixed asa unittothe axlethrough an upper pad by U-bolts. Thus, since the No. 1 leaf is secu rely fixed to the axletogetherwith the leaf group consisting ofthe No. 2 and following leaves strongtorque is required in orderto fasten the respective leaves to the axle. As a consequence strong compressive force is exerted on the mutual fastening portions between the adjoining leaves.

However, in a suspension system for vehicles utilizing leaf springs having such a constitution, when the leaf springs utilized undergo an up and down movement during movement of the vehicles minor displacements are generated at the fastening portions of the leaves. As a result, fretting corrosion phenomena at the side surfaces ofthe respective leaves and the confronting surfaces of the U-bolts where the leaves are fastened by the U-bolts is caused. Once such fretting corrosion phenomena has been generatedfatigue cracks startto develop at the portions attached by the fretting corrosion, which is the principal cause of remarkable decreases in the durability of the respective leaves.In particular, in cases where the leaf group consisting ofthe No. 2 and following leaves is made of reinforced plastic leaves having carbon fibers, glass fibers, etc. as the reinforcing material the decrease in durability of the above leaf group is remarkable.

Summary ofthe invention It is a principal object of the present invention to provide a new suspension system for vehicles. More specifically, it is an object of the present invention to provide a new suspension system for vehicles which can solve such problems inherent in the conventional suspension system forvehicles.

According to one aspect of the present invention there is provided a suspension system for vehicles comprising leaf springs each having a number of leaves and an axle fixed to the leaf springs wherein the No. 1 leaf of each of the leaf springs is arranged on the upper or lower surface of a hollow axle box fixed to the axle, while the leaf group consisting of the No. 2 and following leaves is received within the axleboxundera predetermined fastening force, and the No. 1 leaf is securedtothe axle underan independently predetermined fastening force. Thus No. 2 leaf group may be prevented from directly receiving the clamping force holding the spring to the axle by appropriately relating the depth of the axle box to the depth ofthe No. 2 leaf group and any packings used with it.

Description ofthe drawings Figure 1 is a front elevational view of one embodiment of the present invention as a whole; Figure2 is a bottom view of Figure 1; Figure 3 is a longitudinal sectional view of the portion of the axle box of the embodiment shown in Figures 1 and 2 on a somewhat schematic larger scale; Figure 4 is a plan view of the axle box portion shown in Figure 3; and Figures 5to 8 are views indicating examples of a typical arrangement of various suspension systems forvehicleswith the fundamental constitution according to the present invention being shown in Figures to 4.

Description of the preferred embodiments As shown in Figures 1 and 2, in the present invention the leaves of each ofthe leaf springs are divided into two groups, i.e. onethe No. 1 leaf I,the otherthe leaf group 2 consisting of the No. 2 and following leaves. The No. 1 leaf 1 is, as shown in Figure 3, laid on the outside top 32 of an axle box3 which is in the form of a hollow box-like configuration having substantially a U-shaped cross section with an opening 31 being defined at the lower portion as viewed in the drawing, the axle box 3 having a definite length.An upper pad 4 is laid on the No. 1 leaf 1 and the No. 1 leaf 1 is adapted to be secured to the axle 6through the upper pad 4such that a pair of U-bolts 5 passed through the upper pad 4 from above and th roug h the flan'ge portions of the axle box3formed outside the walls defining the lower opening 31 and then through the axle 6 have their lower end portions secured bythreaded nuts 50 underside the axle 6. Thus, the No. 1 leaf 1 is secured to the axle 6through the axle box 3 and the upper pad 4so that the No. 1 leaf 1 principally supports the front and rear movement ofthe axle 6 due to front and rear loads applied thereto. On the other hand, received within the internal hollow space formed lengthwise inside the axle box3 are, as shown in Figures 3 and 4,the leaf group 2 consisting ofthe No.

2 and following leaves so that even if the axle box 3 is strongly secured to the axle 6 together with the No. 1 leaf 1 through the upper pad 4 by U-bolts Sthe leaf group 2 consisting ofthe No. 2 and following leaves is not subjected to a fastening force overthe appropriately determined force needed for fastening.That is, as shown in Figures3 and 4,the leaf group 2 consisting ofthe No. 2 and following leaves is inserted inside the axle box3 with spacers 7 and 8 being interposed above and below, respectively, and further an axle fastening plate 9 is disposed below the lower spacer 8, and thereafter they are all fastened to the axle 6 by the U-bolts 5.

The axle fastening plate 9 serves then to reveal its original function of giving an appropriate fastening force to the leaf group 2 consisting ofthe No. 2 and following leaves through the spacers 7 and 8when the bolts 5 are fastened, and at the same time it serves also to position the axle box 3 relative to the axle 6 by means of the engagement of the center stud 10 integ rally formed with the fastening plate 9with the identation 11 formed in the upper surface of the axle 6 so as to have a cross section corresponding to that of the center stud 10.

In this case, the appropriate fastening force appliedtothe leaf group 2 consisting ofthe No. 2 and following leaves within the axle box 3 between the inner surface ofthe top ofthe axle box 3 and the upper surface ofthe axle fastening plate 9 when the axle box 3 is fastened to the axle fastening plate 9 by the U-bolts 5 is determined as follows.That is, when it is assumed thatthethickness H ofthe leaf group 2 consisting of the No. and following leaves and the thickness h of the respective spaces 7,8 are previously determined the dimension of the other relating elements are so selected that when the total height Ho ofthespacers7,8 andthe leaf group 2 consisting ofthe No. 2 and following leaves are fastened between the inner bottom surface ofthe axle box 3 and the upper surface of the axle fastening plate 9 by the U-bolts 5, comes to equal the inner height of the axle box 3 a deflection d which gives the predetermined fastening force is given as a value (H+2h)-Ho.

In Figures 1 and 3 the reference numeral 12 indicates the center stud to center the No. 1 leaf 1 relative to the top 32 of the axle box 3.

The typical leaf spring in the suspension system for vehicles in accordance with the present invention has a constitution as described above. The arrangement ofthe various elements therein may be subjected to any modification without departing from the claims ofthe present invention so asto conform to a specific configuration of the frame of the vehicles to which the suspension system is to be provided.

The following descriptions taken in conjunction with Figures 5to 8 arethetypical modesarranging the respective elements: (1 ) Figure 5: The upper pad 4-the leaf group 2 consisting ofthe No. 2 and following leaves-the axle box3 - No. 1 leaf 1 -theaxle6; (2) Figure 6: The upper pad 4 - No. 1 leaf 1 the axle box 3-the leaf group 2 consisting ofthe No. 2 and following leaves - the axle 6; (3) Figure7: The axle 6-No. 1 leaf 1 -the axle box 3-the leaf group 2 consisting ofthe No. 2 and following leaves the upper pad 4; and (4) Figure 8: The axle 6-the leaf group 2 consisting ofthe No. 2 and following leaves - the axle box 3 - No. 1 leaf 1 the upper pad 4.

In the above example the reference numeral 21 represents the supporting portions of the leaf concerned.

From the foregoing it will be appreciated that since the present invention has such constitution and operations as described above the leaf group 2 consisting ofthe No. 2 and following leaves can be adapted to be subjected to an optimal fastening force independent ofthe fastening force to which the No. 1 leaf is subjected owing to their receipt within the inner space of the axle box 3 the generation of fretting corrosion in the leaf group consisting ofthe No. 2 and following leaves attheirsides due to their abutments with the U-bolts 5 is effectiveiy suppressed, and this effect is in particular eminently revealed when these leaves are made of reinforced plastic material reinforced by carbon fibers, glass fibers, etc. Additionally, since the leaf group consisting of the No. 2 and following leaves is not strongly fastened by the axle box 3 the stiffness of the U-bolts 5 due to the fastening force is reduced so that the leaf spring is made to represent a softer spring rate compared with the conventional suspension system.

It is to be understood that although certain forms ofthe present invention have been illustrated and described, it is not to be limited thereto except insofar as such limitations are included in the following claims:

Claims

1. Asuspension system forvehicles having leaf springs each comprising a number of leaves and an axle supported by said leaf spring, wherein the No. 1 leaf of said leaf spring is arranged on the upper or lower surface of a hollow axle box fixed to the axle, the leaf group consisting ofthe No. 2 and following leaves being received within said axle box under a predetermined fastening force, and said No. 1 leaf being fastened to said axle under an independently predetermined fastening force.

2. A suspension system for vehicles as claimed in claim 1 wherein said No. 1 leaf is fastened to said axle with said No. 1 leaf being interposed between an upper pad and said axle box.

3. A suspension system for vehicles as claimed in claim 1 wherein said axle box has substantially a rectangular cross section one of the longitudinal sides ofwhich is open, and fastening plate is disposed between said opened portion and said axle.

4. Asuspension system for vehicles as claimed in claim 3, wherein elastic spacers are disposed on the inner surface ofthe top of said axle box and the upper surface of said fastening plate, respectiveiy.